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                  <h1 class="TITLE"><a name="AEN2" id="AEN2">NCURSES

            
                  Programming HOWTO</a></h1>


                  <h3 class="AUTHOR"><a name="AEN4" id="AEN4">Pradeep

            
                  Padala</a></h3>


                  <div class="AFFILIATION">

            
                    <div class="ADDRESS">

            
                      <p class="ADDRESS"><code class="EMAIL">&lt;<a href=

            
                      "mailto:ppadala@gmail.com">ppadala@gmail.com</a>&gt;</code>

            
                      </p>

            
                    </div>

            
                  </div>


                  <p class="PUBDATE">v1.9, 2005-06-20<br></p>


                  <div class="REVHISTORY">

            
                    <table width="100%" border="0" summary="revisions">

            
                      <tr>

            
                        <th align="left" valign="top" colspan="3"><b>Revision

            
                        History</b>

            
                        </th>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 2.0</td>

            
                        <td align="left">2022-12-03</td>

            
                        <td align="left">Revised by: dickey</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Fixes for the sample

            
                        programs, Correct documentation errata.</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.9</td>

            
                        <td align="left">2005-06-20</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">The license has been

            
                        changed to the MIT-style license used by NCURSES. Note

            
                        that the programs are also re-licensed under this.</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.8</td>

            
                        <td align="left">2005-06-17</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Lots of updates. Added

            
                        references and perl examples. Changes to examples. Many

            
                        grammatical and stylistic changes to the content.

            
                        Changes to NCURSES history.</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.7.1</td>

            
                        <td align="left">2002-06-25</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Added a README file for

            
                        building and instructions for building from

            
                        source.</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.7</td>

            
                        <td align="left">2002-06-25</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Added "Other formats"

            
                        section and made a lot of fancy changes to the

            
                        programs. Inlining of programs is gone.</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.6.1</td>

            
                        <td align="left">2002-02-24</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Removed the old Changelog

            
                        section, cleaned the makefiles</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.6</td>

            
                        <td align="left">2002-02-16</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Corrected a lot of

            
                        spelling mistakes, added ACS variables section</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.5</td>

            
                        <td align="left">2002-01-05</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Changed structure to

            
                        present proper TOC</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.3.1</td>

            
                        <td align="left">2001-07-26</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Corrected maintainers

            
                        paragraph, Corrected stable release number</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.3</td>

            
                        <td align="left">2001-07-24</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Added copyright notices to

            
                        main document (LDP license) and programs (GPL),

            
                        Corrected printw_example.</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.2</td>

            
                        <td align="left">2001-06-05</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Incorporated ravi's

            
                        changes. Mainly to introduction, menu, form, justforfun

            
                        sections</td>

            
                      </tr>


                      <tr>

            
                        <td align="left">Revision 1.1</td>

            
                        <td align="left">2001-05-22</td>

            
                        <td align="left">Revised by: ppadala</td>

            
                      </tr>


                      <tr>

            
                        <td align="left" colspan="3">Added "a word about

            
                        window" section, Added scanw_example.</td>

            
                      </tr>

            
                    </table>

            
                  </div>


                  <div>

            
                    <div class="ABSTRACT">

            
                      <a name="AEN72" id="AEN72"></a>

            
                      <p><span class="emphasis"><i class="EMPHASIS">This

            
                      document is intended to be an "All in One" guide for

            
                      programming with ncurses and its sister libraries. We

            
                      graduate from a simple "Hello World" program to more

            
                      complex form manipulation. No prior experience in ncurses

            
                      is assumed. Send comments to <a href=

            
                      "mailto:ppadala@gmail.com" target="_top">this

            
                      address</a></i></span>

            
                      </p>

            
                    </div>

            
                  </div>


                  <hr>

            
                </div>


                <div class="TOC">

            
                  <dl>

            
                    <dt><b>Table of Contents</b>

            
                    </dt>


                    <dt>1. <a href="#INTRO">Introduction</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>1.1. <a href="#WHATIS">What is NCURSES?</a></dt>


                        <dt>1.2. <a href="#WHATCANWEDO">What we can do with

            
                        NCURSES</a></dt>


                        <dt>1.3. <a href="#WHERETOGETIT">Where to get

            
                        it</a></dt>


                        <dt>1.4. <a href="#PURPOSE">Purpose/Scope of the

            
                        document</a></dt>


                        <dt>1.5. <a href="#ABOUTPROGRAMS">About the

            
                        Programs</a></dt>


                        <dt>1.6. <a href="#OTHERFORMATS">Other Formats of the

            
                        document</a></dt>


                        <dd>

            
                          <dl>

            
                            <dt>1.6.1. <a href="#LISTFORMATS">Readily available

            
                            formats from tldp.org</a></dt>


                            <dt>1.6.2. <a href="#BUILDSOURCE">Building from

            
                            source</a></dt>

            
                          </dl>

            
                        </dd>


                        <dt>1.7. <a href="#CREDITS">Credits</a></dt>


                        <dt>1.8. <a href="#WISHLIST">Wish List</a></dt>


                        <dt>1.9. <a href="#COPYRIGHT">Copyright</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>2. <a href="#HELLOWORLD">Hello World !!!</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>2.1. <a href="#COMPILECURSES">Compiling With the

            
                        NCURSES Library</a></dt>


                        <dt>2.2. <a href="#DISSECTION">Dissection</a></dt>


                        <dd>

            
                          <dl>

            
                            <dt>2.2.1. <a href="#ABOUT-INITSCR">About

            
                            initscr()</a></dt>


                            <dt>2.2.2. <a href="#MYST-REFRESH">The mysterious

            
                            refresh()</a></dt>


                            <dt>2.2.3. <a href="#ABOUT-ENDWIN">About

            
                            endwin()</a></dt>

            
                          </dl>

            
                        </dd>

            
                      </dl>

            
                    </dd>


                    <dt>3. <a href="#GORY">The Gory Details</a></dt>


                    <dt>4. <a href="#INIT">Initialization</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>4.1. <a href="#ABOUTINIT">Initialization

            
                        functions</a></dt>


                        <dt>4.2. <a href="#RAWCBREAK">raw() and

            
                        cbreak()</a></dt>


                        <dt>4.3. <a href="#ECHONOECHO">echo() and

            
                        noecho()</a></dt>


                        <dt>4.4. <a href="#KEYPAD">keypad()</a></dt>


                        <dt>4.5. <a href="#HALFDELAY">halfdelay()</a></dt>


                        <dt>4.6. <a href="#MISCINIT">Miscellaneous

            
                        Initialization functions</a></dt>


                        <dt>4.7. <a href="#INITEX">An Example</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>5. <a href="#AWORDWINDOWS">A Word about

            
                    Windows</a></dt>


                    <dt>6. <a href="#PRINTW">Output functions</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>6.1. <a href="#ADDCHCLASS">addch() class of

            
                        functions</a></dt>


                        <dt>6.2. <a href="#AEN303">mvaddch(), waddch() and

            
                        mvwaddch()</a></dt>


                        <dt>6.3. <a href="#PRINTWCLASS">printw() class of

            
                        functions</a></dt>


                        <dd>

            
                          <dl>

            
                            <dt>6.3.1. <a href="#PRINTWMVPRINTW">printw() and

            
                            mvprintw</a></dt>


                            <dt>6.3.2. <a href="#WPRINTWMVWPRINTW">wprintw()

            
                            and mvwprintw</a></dt>


                            <dt>6.3.3. <a href="#VWPRINTW">vw_printw()</a></dt>


                            <dt>6.3.4. <a href="#SIMPLEPRINTWEX">A Simple

            
                            printw example</a></dt>

            
                          </dl>

            
                        </dd>


                        <dt>6.4. <a href="#ADDSTRCLASS">addstr() class of

            
                        functions</a></dt>


                        <dt>6.5. <a href="#ACAUTION">A word of caution</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>7. <a href="#SCANW">Input functions</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>7.1. <a href="#GETCHCLASS">getch() class of

            
                        functions</a></dt>


                        <dt>7.2. <a href="#SCANWCLASS">scanw() class of

            
                        functions</a></dt>


                        <dd>

            
                          <dl>

            
                            <dt>7.2.1. <a href="#SCANWMVSCANW">scanw() and

            
                            mvscanw</a></dt>


                            <dt>7.2.2. <a href="#WSCANWMVWSCANW">wscanw() and

            
                            mvwscanw()</a></dt>


                            <dt>7.2.3. <a href="#VWSCANW">vw_scanw()</a></dt>

            
                          </dl>

            
                        </dd>


                        <dt>7.3. <a href="#GETSTRCLASS">getstr() class of

            
                        functions</a></dt>


                        <dt>7.4. <a href="#GETSTREX">Some examples</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>8. <a href="#ATTRIB">Attributes</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>8.1. <a href="#ATTRIBDETAILS">The details</a></dt>


                        <dt>8.2. <a href="#ATTRONVSATTRSET">attron() vs

            
                        attrset()</a></dt>


                        <dt>8.3. <a href="#ATTRGET">attr_get()</a></dt>


                        <dt>8.4. <a href="#ATTRFUNCS">attr_ functions</a></dt>


                        <dt>8.5. <a href="#WATTRFUNCS">wattr functions</a></dt>


                        <dt>8.6. <a href="#CHGAT">chgat() functions</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>9. <a href="#WINDOWS">Windows</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>9.1. <a href="#WINDOWBASICS">The basics</a></dt>


                        <dt>9.2. <a href="#LETBEWINDOW">Let there be a Window

            
                        !!!</a></dt>


                        <dt>9.3. <a href="#BORDEREXEXPL">Explanation</a></dt>


                        <dt>9.4. <a href="#OTHERSTUFF">The other stuff in the

            
                        example</a></dt>


                        <dt>9.5. <a href="#OTHERBORDERFUNCS">Other Border

            
                        functions</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>10. <a href="#COLOR">Colors</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>10.1. <a href="#COLORBASICS">The basics</a></dt>


                        <dt>10.2. <a href="#CHANGECOLORDEFS">Changing Color

            
                        Definitions</a></dt>


                        <dt>10.3. <a href="#COLORCONTENT">Color

            
                        Content</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>11. <a href="#KEYS">Interfacing with the key

            
                    board</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>11.1. <a href="#KEYSBASICS">The Basics</a></dt>


                        <dt>11.2. <a href="#SIMPLEKEYEX">A Simple Key Usage

            
                        example</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>12. <a href="#MOUSE">Interfacing with the

            
                    mouse</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>12.1. <a href="#MOUSEBASICS">The Basics</a></dt>


                        <dt>12.2. <a href="#GETTINGEVENTS">Getting the

            
                        events</a></dt>


                        <dt>12.3. <a href="#MOUSETOGETHER">Putting it all

            
                        Together</a></dt>


                        <dt>12.4. <a href="#MISCMOUSEFUNCS">Miscellaneous

            
                        Functions</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>13. <a href="#SCREEN">Screen Manipulation</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>13.1. <a href="#GETYX">getyx() functions</a></dt>


                        <dt>13.2. <a href="#SCREENDUMP">Screen Dumping</a></dt>


                        <dt>13.3. <a href="#WINDOWDUMP">Window Dumping</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>14. <a href="#MISC">Miscellaneous features</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>14.1. <a href="#CURSSET">curs_set()</a></dt>


                        <dt>14.2. <a href="#TEMPLEAVE">Temporarily Leaving

            
                        Curses mode</a></dt>


                        <dt>14.3. <a href="#ACSVARS">ACS_ variables</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>15. <a href="#OTHERLIB">Other libraries</a></dt>


                    <dt>16. <a href="#PANELS">Panel Library</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>16.1. <a href="#PANELBASICS">The Basics</a></dt>


                        <dt>16.2. <a href="#COMPILEPANELS">Compiling With the

            
                        Panels Library</a></dt>


                        <dt>16.3. <a href="#PANELBROWSING">Panel Window

            
                        Browsing</a></dt>


                        <dt>16.4. <a href="#USERPTRUSING">Using User

            
                        Pointers</a></dt>


                        <dt>16.5. <a href="#PANELMOVERESIZE">Moving and

            
                        Resizing Panels</a></dt>


                        <dt>16.6. <a href="#PANELSHOWHIDE">Hiding and Showing

            
                        Panels</a></dt>


                        <dt>16.7. <a href="#PANELABOVE">panel_above() and

            
                        panel_below() Functions</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>17. <a href="#MENUS">Menus Library</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>17.1. <a href="#MENUBASICS">The Basics</a></dt>


                        <dt>17.2. <a href="#COMPILEMENUS">Compiling With the

            
                        Menu Library</a></dt>


                        <dt>17.3. <a href="#MENUDRIVER">Menu Driver: The work

            
                        horse of the menu system</a></dt>


                        <dt>17.4. <a href="#MENUWINDOWS">Menu Windows</a></dt>


                        <dt>17.5. <a href="#SCROLLMENUS">Scrolling

            
                        Menus</a></dt>


                        <dt>17.6. <a href="#MULTICOLUMN">Multi Columnar

            
                        Menus</a></dt>


                        <dt>17.7. <a href="#MULTIVALUEMENUS">Multi Valued

            
                        Menus</a></dt>


                        <dt>17.8. <a href="#MENUOPT">Menu Options</a></dt>


                        <dt>17.9. <a href="#MENUUSERPTR">The useful User

            
                        Pointer</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>18. <a href="#FORMS">Forms Library</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>18.1. <a href="#FORMBASICS">The Basics</a></dt>


                        <dt>18.2. <a href="#COMPILEFORMS">Compiling With the

            
                        Forms Library</a></dt>


                        <dt>18.3. <a href="#PLAYFIELDS">Playing with

            
                        Fields</a></dt>


                        <dd>

            
                          <dl>

            
                            <dt>18.3.1. <a href="#FETCHINFO">Fetching Size and

            
                            Location of Field</a></dt>


                            <dt>18.3.2. <a href="#MOVEFIELD">Moving the

            
                            field</a></dt>


                            <dt>18.3.3. <a href="#JUSTIFYFIELD">Field

            
                            Justification</a></dt>


                            <dt>18.3.4. <a href="#FIELDDISPATTRIB">Field

            
                            Display Attributes</a></dt>


                            <dt>18.3.5. <a href="#FIELDOPTIONBITS">Field Option

            
                            Bits</a></dt>


                            <dt>18.3.6. <a href="#FIELDSTATUS">Field

            
                            Status</a></dt>


                            <dt>18.3.7. <a href="#FIELDUSERPTR">Field User

            
                            Pointer</a></dt>


                            <dt>18.3.8. <a href=

            
                            "#VARIABLESIZEFIELDS">Variable-Sized

            
                            Fields</a></dt>

            
                          </dl>

            
                        </dd>


                        <dt>18.4. <a href="#FORMWINDOWS">Form Windows</a></dt>


                        <dt>18.5. <a href="#FILEDVALIDATE">Field

            
                        Validation</a></dt>


                        <dt>18.6. <a href="#FORMDRIVER">Form Driver: The work

            
                        horse of the forms system</a></dt>


                        <dd>

            
                          <dl>

            
                            <dt>18.6.1. <a href="#PAGENAVREQ">Page Navigation

            
                            Requests</a></dt>


                            <dt>18.6.2. <a href="#INTERFIELDNAVREQ">Inter-Field

            
                            Navigation Requests</a></dt>


                            <dt>18.6.3. <a href="#INTRAFIELDNAVREQ">Intra-Field

            
                            Navigation Requests</a></dt>


                            <dt>18.6.4. <a href="#SCROLLREQ">Scrolling

            
                            Requests</a></dt>


                            <dt>18.6.5. <a href="#EDITREQ">Editing

            
                            Requests</a></dt>


                            <dt>18.6.6. <a href="#ORDERREQ">Order

            
                            Requests</a></dt>


                            <dt>18.6.7. <a href="#APPLICCOMMANDS">Application

            
                            Commands</a></dt>

            
                          </dl>

            
                        </dd>

            
                      </dl>

            
                    </dd>


                    <dt>19. <a href="#TOOLS">Tools and Widget

            
                    Libraries</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>19.1. <a href="#CDK">CDK (Curses Development

            
                        Kit)</a></dt>


                        <dd>

            
                          <dl>

            
                            <dt>19.1.1. <a href="#WIDGETLIST">Widget

            
                            List</a></dt>


                            <dt>19.1.2. <a href="#CDKATTRACT">Some Attractive

            
                            Features</a></dt>


                            <dt>19.1.3. <a href=

            
                            "#CDKCONCLUSION">Conclusion</a></dt>

            
                          </dl>

            
                        </dd>


                        <dt>19.2. <a href="#DIALOG">The dialog</a></dt>


                        <dt>19.3. <a href="#PERLCURSES">Perl Curses Modules

            
                        CURSES::FORM and CURSES::WIDGETS</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>20. <a href="#JUSTFORFUN">Just For Fun !!!</a></dt>


                    <dd>

            
                      <dl>

            
                        <dt>20.1. <a href="#GAMEOFLIFE">The Game of

            
                        Life</a></dt>


                        <dt>20.2. <a href="#MAGIC">Magic Square</a></dt>


                        <dt>20.3. <a href="#HANOI">Towers of Hanoi</a></dt>


                        <dt>20.4. <a href="#QUEENS">Queens Puzzle</a></dt>


                        <dt>20.5. <a href="#SHUFFLE">Shuffle</a></dt>


                        <dt>20.6. <a href="#TT">Typing Tutor</a></dt>

            
                      </dl>

            
                    </dd>


                    <dt>21. <a href="#REF">References</a></dt>

            
                  </dl>

            
                </div>


                <div class="SECT1">

            
                  <h2 class="SECT1"><a name="INTRO" id="INTRO">1.

            
                  Introduction</a></h2>


                  <p>In the olden days of teletype terminals, terminals were

            
                  away from computers and were connected to them through serial

            
                  cables. The terminals could be configured by sending a series

            
                  of bytes. All the capabilities (such as moving the cursor to

            
                  a new location, erasing part of the screen, scrolling the

            
                  screen, changing modes, etc.) of terminals could be accessed

            
                  through these series of bytes. These control seeuqnces are

            
                  usually called escape sequences, because they start with an

            
                  escape(0x1B) character. Even today, with proper emulation, we

            
                  can send escape sequences to the emulator and achieve the

            
                  same effect on a terminal window.</p>


                  <p>Suppose you wanted to print a line in color. Try typing

            
                  this on your console.</p>


                  <pre class="PROGRAMLISTING">echo "^[[0;31;40mIn Color"</pre>

            
                  <p>The first character is an escape character, which looks

            
                  like two characters ^ and [. To be able to print it, you have

            
                  to press CTRL+V and then the ESC key. All the others are

            
                  normal printable characters. You should be able to see the

            
                  string "In Color" in red. It stays that way and to revert

            
                  back to the original mode type this.</p>


                  <pre class="PROGRAMLISTING">echo "^[[0;37;40m"</pre>

            
                  <p>Now, what do these magic characters mean? Difficult to

            
                  comprehend? They might even be different for different

            
                  terminals. So the designers of UNIX invented a mechanism

            
                  named <tt class="LITERAL">termcap</tt>. It is a file that

            
                  lists all the capabilities of a particular terminal, along

            
                  with the escape sequences needed to achieve a particular

            
                  effect. In the later years, this was replaced by <tt class=

            
                  "LITERAL">terminfo</tt>. Without delving too much into

            
                  details, this mechanism allows application programs to query

            
                  the terminfo database and obtain the control characters to be

            
                  sent to a terminal or terminal emulator.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="WHATIS" id="WHATIS">1.1. What is

            
                    NCURSES?</a></h3>


                    <p>You might be wondering, what the import of all this

            
                    technical gibberish is. In the above scenario, every

            
                    application program is supposed to query the terminfo and

            
                    perform the necessary stuff (sending control characters,

            
                    etc.). It soon became difficult to manage this complexity

            
                    and this gave birth to 'CURSES'. Curses is a pun on the

            
                    name "cursor optimization". The Curses library forms a

            
                    wrapper over working with raw terminal codes, and provides

            
                    highly flexible and efficient API (Application Programming

            
                    Interface). It provides functions to move the cursor,

            
                    create windows, produce colors, play with mouse, etc. The

            
                    application programs need not worry about the underlying

            
                    terminal capabilities.</p>


                    <p>So what is NCURSES? NCURSES is a clone of the original

            
                    System V Release 4.0 (SVr4) curses. It is a freely

            
                    distributable library, fully compatible with older version

            
                    of curses. In short, it is a library of functions that

            
                    manages an application's display on character-cell

            
                    terminals. In the remainder of the document, the terms

            
                    curses and ncurses are used interchangeably.</p>


                    <p>A detailed history of NCURSES can be found in the NEWS

            
                    file from the source distribution. The current package is

            
                    maintained by <a href="mailto:dickey@invisible-island.net"

            
                    target="_top">Thomas Dickey</a>. You can contact the

            
                    maintainers at <a href="mailto:bug-ncurses@gnu.org" target=

            
                    "_top">bug-ncurses@gnu.org</a>.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="WHATCANWEDO" id=

            
                    "WHATCANWEDO">1.2. What we can do with NCURSES</a></h3>


                    <p>NCURSES not only creates a wrapper over terminal

            
                    capabilities, but also gives a robust framework to create

            
                    nice looking UI (User Interface)s in text mode. It provides

            
                    functions to create windows, etc. Its sister libraries

            
                    panel, menu and form provide an extension to the basic

            
                    curses library. These libraries usually come along with

            
                    curses. One can create applications that contain multiple

            
                    windows, menus, panels and forms. Windows can be managed

            
                    independently, can provide 'scrollability' and even can be

            
                    hidden.</p>


                    <p>Menus provide the user with an easy command selection

            
                    option. Forms allow the creation of easy-to-use data entry

            
                    and display windows. Panels extend the capabilities of

            
                    ncurses to deal with overlapping and stacked windows.</p>


                    <p>These are just some of the basic things we can do with

            
                    ncurses. As we move along, We will see all the capabilities

            
                    of these libraries.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="WHERETOGETIT" id=

            
                    "WHERETOGETIT">1.3. Where to get it</a></h3>


                    <p>All right, now that you know what you can do with

            
                    ncurses, you must be rearing to get started. NCURSES is

            
                    usually shipped with your installation. In case you don't

            
                    have the library or want to compile it on your own, read

            
                    on.</p>


                    <p><span class="emphasis"><i class="EMPHASIS">Compiling the

            
                    package</i></span>

            
                    </p>


                    <p>NCURSES can be obtained from <a href=

            
                    "ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz" target=

            
                    "_top">ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz</a>

            
                    or any of the ftp sites mentioned in <a href=

            
                    "https://www.gnu.org/order/ftp.html" target=

            
                    "_top">https://www.gnu.org/order/ftp.html</a>.</p>


                    <p>Read the README and INSTALL files for details on to how

            
                    to install it. It usually involves the following

            
                    operations.</p>


                    <pre class=

            
                    "PROGRAMLISTING">    tar zxvf ncurses&lt;version&gt;.tar.gz  # unzip and untar the archive

            
                cd ncurses&lt;version&gt;               # cd to the directory

            
                ./configure                             # configure the build according to your

            
                                                        # environment

            
                make                                    # make it

            
                su root                                 # become root

            
                make install                            # install it</pre>

            
                    <p><span class="emphasis"><i class="EMPHASIS">Using the

            
                    RPM</i></span>

            
                    </p>


                    <p>NCURSES RPM can be found and downloaded from <a href=

            
                    "https://rpmfind.net" target="_top">https://rpmfind.net</a>

            
                    . The RPM can be installed with the following command after

            
                    becoming root.</p>


                    <pre class=

            
                    "PROGRAMLISTING">    rpm -i &lt;downloaded rpm&gt;</pre>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PURPOSE" id="PURPOSE">1.4.

            
                    Purpose/Scope of the document</a></h3>


                    <p>This document is intended to be a "All in One" guide for

            
                    programming with ncurses and its sister libraries. We

            
                    graduate from a simple "Hello World" program to more

            
                    complex form manipulation. No prior experience in ncurses

            
                    is assumed. The writing is informal, but a lot of detail is

            
                    provided for each of the examples.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ABOUTPROGRAMS" id=

            
                    "ABOUTPROGRAMS">1.5. About the Programs</a></h3>


                    <p>All the programs in the document are available in zipped

            
                    form <a href=

            
                    "https://www.tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs.tar.gz"

            
                    target="_top">here</a>. Unzip and untar it. The directory

            
                    structure looks like this.</p>


                    <pre class="PROGRAMLISTING">ncurses

            
               |

            
               |----&gt; JustForFun     -- just for fun programs

            
               |----&gt; basics         -- basic programs

            
               |----&gt; demo           -- output files go into this directory after make

            
               |          |

            
               |          |----&gt; exe -- exe files of all example programs

            
               |----&gt; forms          -- programs related to form library

            
               |----&gt; menus          -- programs related to menus library

            
               |----&gt; panels         -- programs related to panels library

            
               |----&gt; perl           -- perl equivalents of the examples (contributed

            
               |                            by Anuradha Ratnaweera)

            
               |----&gt; Makefile       -- the top level Makefile

            
               |----&gt; README         -- the top level README file. contains instructions

            
               |----&gt; COPYING        -- copyright notice</pre>

            
                    <p>The individual directories contain the following

            
                    files.</p>


                    <pre class=

            
                    "PROGRAMLISTING">Description of files in each directory

            
            --------------------------------------

            
            JustForFun

            
                |

            
                |----&gt; hanoi.c   -- The Towers of Hanoi Solver

            
                |----&gt; life.c    -- The Game of Life demo

            
                |----&gt; magic.c   -- An Odd Order Magic Square builder

            
                |----&gt; queens.c  -- The famous N-Queens Solver

            
                |----&gt; shuffle.c -- A fun game, if you have time to kill

            
                |----&gt; tt.c      -- A very trivial typing tutor


              basics

            
                |

            
                |----&gt; acs_vars.c            -- ACS_ variables example

            
                |----&gt; hello_world.c         -- Simple "Hello World" Program

            
                |----&gt; init_func_example.c   -- Initialization functions example

            
                |----&gt; key_code.c            -- Shows the scan code of the key pressed

            
                |----&gt; mouse_menu.c          -- A menu accessible by mouse

            
                |----&gt; other_border.c        -- Shows usage of other border functions apa

            
                |                               -- rt from box()

            
                |----&gt; printw_example.c      -- A very simple printw() example

            
                |----&gt; scanw_example.c       -- A very simple getstr() example

            
                |----&gt; simple_attr.c         -- A program that can print a c file with

            
                |                               -- comments in attribute

            
                |----&gt; simple_color.c        -- A simple example demonstrating colors

            
                |----&gt; simple_key.c          -- A menu accessible with keyboard UP, DOWN

            
                |                               -- arrows

            
                |----&gt; temp_leave.c          -- Demonstrates temporarily leaving curses mode

            
                |----&gt; win_border.c          -- Shows Creation of windows and borders

            
                |----&gt; with_chgat.c          -- chgat() usage example


              forms

            
                |

            
                |----&gt; form_attrib.c     -- Usage of field attributes

            
                |----&gt; form_options.c    -- Usage of field options

            
                |----&gt; form_simple.c     -- A simple form example

            
                |----&gt; form_win.c        -- Demo of windows associated with forms


              menus

            
                |

            
                |----&gt; menu_attrib.c     -- Usage of menu attributes

            
                |----&gt; menu_item_data.c  -- Usage of item_name(), etc. functions

            
                |----&gt; menu_multi_column.c    -- Creates multi columnar menus

            
                |----&gt; menu_scroll.c     -- Demonstrates scrolling capability of menus

            
                |----&gt; menu_simple.c     -- A simple menu accessed by arrow keys

            
                |----&gt; menu_toggle.c     -- Creates multi valued menus and explains

            
                |                           -- REQ_TOGGLE_ITEM

            
                |----&gt; menu_userptr.c    -- Usage of user pointer

            
                |----&gt; menu_win.c        -- Demo of windows associated with menus


              panels

            
                |

            
                |----&gt; panel_browse.c    -- Panel browsing through tab. Usage of user

            
                |                           -- pointer

            
                |----&gt; panel_hide.c      -- Hiding and Un hiding of panels

            
                |----&gt; panel_resize.c    -- Moving and resizing of panels

            
                |----&gt; panel_simple.c    -- A simple panel example


              perl

            
                |----&gt; 01-10.pl          -- Perl equivalents of first ten example programs</pre>

            
                    <p>There is a top level Makefile included in the main

            
                    directory. It builds all the files and puts the

            
                    ready-to-use exes in demo/exe directory. You can also do

            
                    selective make by going into the corresponding directory.

            
                    Each directory contains a README file explaining the

            
                    purpose of each c file in the directory.</p>


                    <p>For every example, I have included path name for the

            
                    file relative to the examples directory.</p>


                    <p>If you prefer browsing individual programs, point your

            
                    browser to <a href=

            
                    "https://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/"

            
                    target=

            
                    "_top">https://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/</a></p>


                    <p>All the programs are released under the same license

            
                    that is used by ncurses (MIT-style). This gives you the

            
                    ability to do pretty much anything other than claiming them

            
                    as yours. Feel free to use them in your programs as

            
                    appropriate.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="OTHERFORMATS" id=

            
                    "OTHERFORMATS">1.6. Other Formats of the document</a></h3>


                    <p>This howto is also available in various other formats on

            
                    the tldp.org site. Here are the links to other formats of

            
                    this document.</p>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="LISTFORMATS" id=

            
                      "LISTFORMATS">1.6.1. Readily available formats from

            
                      tldp.org</a></h4>


                      <ul>

            
                        <li>

            
                          <p><a href=

            
                          "https://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/pdf/NCURSES-Programming-HOWTO.pdf"

            
                          target="_top">Acrobat PDF Format</a></p>

            
                        </li>


                        <li>

            
                          <p><a href=

            
                          "https://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/ps/NCURSES-Programming-HOWTO.ps.gz"

            
                          target="_top">PostScript Format</a></p>

            
                        </li>


                        <li>

            
                          <p><a href=

            
                          "https://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html/NCURSES-Programming-HOWTO-html.tar.gz"

            
                          target="_top">In Multiple HTML pages</a></p>

            
                        </li>


                        <li>

            
                          <p><a href=

            
                          "https://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/NCURSES-Programming-HOWTO.html"

            
                          target="_top">In One big HTML format</a></p>

            
                        </li>

            
                      </ul>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="BUILDSOURCE" id=

            
                      "BUILDSOURCE">1.6.2. Building from source</a></h4>


                      <p>If above links are broken or if you want to experiment

            
                      with sgml read on.</p>


                      <pre class=

            
                      "PROGRAMLISTING">&#13;    Get both the source and the tar,gzipped programs, available at

            
                    http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/

            
                    NCURSES-HOWTO/NCURSES-Programming-HOWTO.sgml

            
                    http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/

            
                    NCURSES-HOWTO/ncurses_programs.tar.gz


                Unzip ncurses_programs.tar.gz with

            
                tar zxvf ncurses_programs.tar.gz


                Use jade to create various formats. For example if you just want to create

            
                the multiple html files, you would use

            
                    jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt;

            
                    NCURSES-Programming-HOWTO.sgml

            
                to get pdf, first create a single html file of the HOWTO with

            
                    jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt; -V nochunks

            
                    NCURSES-Programming-HOWTO.sgml &gt; NCURSES-ONE-BIG-FILE.html

            
                then use htmldoc to get pdf file with

            
                    htmldoc --size universal -t pdf --firstpage p1 -f &lt;output file name.pdf&gt;

            
                    NCURSES-ONE-BIG-FILE.html

            
                for ps, you would use

            
                    htmldoc --size universal -t ps --firstpage p1 -f &lt;output file name.ps&gt;

            
                    NCURSES-ONE-BIG-FILE.html</pre>

            
                      <p>See <a href=

            
                      "https://www.tldp.org/LDP/LDP-Author-Guide/" target=

            
                      "_top">LDP Author guide</a> for more details. If all else

            
                      fails, mail me at <a href="ppadala@gmail.com" target=

            
                      "_top">ppadala@gmail.com</a></p>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="CREDITS" id="CREDITS">1.7.

            
                    Credits</a></h3>


                    <p>I thank <a href="mailto:sharath_1@usa.net" target=

            
                    "_top">Sharath</a> and Emre Akbas for helping me with few

            
                    sections. The introduction was initially written by

            
                    sharath. I rewrote it with few excerpts taken from his

            
                    initial work. Emre helped in writing printw and scanw

            
                    sections.</p>


                    <p>Perl equivalents of the example programs are contributed

            
                    by <a href="mailto:Aratnaweera@virtusa.com" target=

            
                    "_top">Anuradha Ratnaweera</a>.</p>


                    <p>Then comes <a href="mailto:parimi@ece.arizona.edu"

            
                    target="_top">Ravi Parimi</a>, my dearest friend, who has

            
                    been on this project before even one line was written. He

            
                    constantly bombarded me with suggestions and patiently

            
                    reviewed the whole text. He also checked each program on

            
                    Linux and Solaris.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="WISHLIST" id="WISHLIST">1.8.

            
                    Wish List</a></h3>


                    <p>This is the wish list, in the order of priority. If you

            
                    have a wish or you want to work on completing the wish,

            
                    mail <a href="mailto:ppadala@gmail.com" target=

            
                    "_top">me</a>.</p>


                    <ul>

            
                      <li>

            
                        <p>Add examples to last parts of forms section.</p>

            
                      </li>


                      <li>

            
                        <p>Prepare a Demo showing all the programs and allow

            
                        the user to browse through description of each program.

            
                        Let the user compile and see the program in action. A

            
                        dialog based interface is preferred.</p>

            
                      </li>


                      <li>

            
                        <p>Add debug info. _tracef, _tracemouse stuff.</p>

            
                      </li>


                      <li>

            
                        <p>Accessing termcap, terminfo using functions provided

            
                        by ncurses package.</p>

            
                      </li>


                      <li>

            
                        <p>Working on two terminals simultaneously.</p>

            
                      </li>


                      <li>

            
                        <p>Add more stuff to miscellaneous section.</p>

            
                      </li>

            
                    </ul>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="COPYRIGHT" id="COPYRIGHT">1.9.

            
                    Copyright</a></h3>


                    <p>Copyright &copy; 2001 by Pradeep Padala.</p>


                    <p>Permission is hereby granted, free of charge, to any

            
                    person obtaining a copy of this software and associated

            
                    documentation files (the "Software"), to deal in the

            
                    Software without restriction, including without limitation

            
                    the rights to use, copy, modify, merge, publish,

            
                    distribute, distribute with modifications, sublicense,

            
                    and/or sell copies of the Software, and to permit persons

            
                    to whom the Software is furnished to do so, subject to the

            
                    following conditions:</p>


                    <p>The above copyright notice and this permission notice

            
                    shall be included in all copies or substantial portions of

            
                    the Software.</p>


                    <p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF

            
                    ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO

            
                    THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR

            
                    PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE ABOVE

            
                    COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

            
                    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR

            
                    OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE

            
                    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.</p>


                    <p>Except as contained in this notice, the name(s) of the

            
                    above copyright holders shall not be used in advertising or

            
                    otherwise to promote the sale, use or other dealings in

            
                    this Software without prior written authorization.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="HELLOWORLD" id="HELLOWORLD">2.

            
                  Hello World !!!</a></h2>


                  <p>Welcome to the world of curses. Before we plunge into the

            
                  library and look into its various features, let's write a

            
                  simple program and say hello to the world.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="COMPILECURSES" id=

            
                    "COMPILECURSES">2.1. Compiling With the NCURSES Library</a></h3>


                    <p>To use ncurses library functions, you have to include

            
                    ncurses.h in your programs. To link the program with

            
                    ncurses the flag -lncurses should be added.</p>


                    <pre class="PROGRAMLISTING">    #include &lt;ncurses.h&gt;

            
                .

            
                .

            
                .


                compile and link: gcc &lt;program file&gt; -lncurses</pre>

            
                    <div class="EXAMPLE">

            
                      <a name="BHW" id="BHW"></a>

            
                      <p><b>Example 1. The Hello World !!! Program</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;


            int main()

            
            {

            
                    initscr();                      /* Start curses mode              */

            
                    printw("Hello World !!!");      /* Print Hello World              */

            
                    refresh();                      /* Print it on to the real screen */

            
                    getch();                        /* Wait for user input */

            
                    endwin();                       /* End curses mode                */


                    return 0;

            
            }</span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="DISSECTION" id="DISSECTION">2.2.

            
                    Dissection</a></h3>


                    <p>The above program prints "Hello World !!!" to the screen

            
                    and exits. This program shows how to initialize curses and

            
                    do screen manipulation and end curses mode. Let's dissect

            
                    it line by line.</p>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="ABOUT-INITSCR" id=

            
                      "ABOUT-INITSCR">2.2.1. About initscr()</a></h4>


                      <p>The function initscr() initializes the terminal in

            
                      curses mode. In some implementations, it clears the

            
                      screen and presents a blank screen. To do any screen

            
                      manipulation using curses package this has to be called

            
                      first. This function initializes the curses system and

            
                      allocates memory for our present window (called

            
                      <tt class="LITERAL">stdscr</tt>) and some other

            
                      data-structures. Under extreme cases this function might

            
                      fail due to insufficient memory to allocate memory for

            
                      curses library's data structures.</p>


                      <p>After this is done, we can do a variety of

            
                      initializations to customize our curses settings. These

            
                      details will be explained <a href="#INIT">later</a> .</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="MYST-REFRESH" id=

            
                      "MYST-REFRESH">2.2.2. The mysterious refresh()</a></h4>


                      <p>The next line printw prints the string "Hello World

            
                      !!!" on to the screen. This function is analogous to

            
                      normal printf in all respects except that it prints the

            
                      data on a window called stdscr at the current (y,x)

            
                      co-ordinates. Since our present co-ordinates are at 0,0

            
                      the string is printed at the left hand corner of the

            
                      window.</p>


                      <p>This brings us to that mysterious refresh(). Well,

            
                      when we called printw the data is actually written to an

            
                      imaginary window, which is not updated on the screen yet.

            
                      The job of printw is to update a few flags and data

            
                      structures and write the data to a buffer corresponding

            
                      to stdscr. In order to show it on the screen, we need to

            
                      call refresh() and tell the curses system to dump the

            
                      contents on the screen.</p>


                      <p>The philosophy behind all this is to allow the

            
                      programmer to do multiple updates on the imaginary screen

            
                      or windows and do a refresh once all his screen update is

            
                      done. refresh() checks the window and updates only the

            
                      portion which has been changed. This improves performance

            
                      and offers greater flexibility too. But, it is sometimes

            
                      frustrating to beginners. A common mistake committed by

            
                      beginners is to forget to call refresh() after they did

            
                      some update through printw() class of functions. I still

            
                      forget to add it sometimes :-)</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="ABOUT-ENDWIN" id=

            
                      "ABOUT-ENDWIN">2.2.3. About endwin()</a></h4>


                      <p>And finally don't forget to end the curses mode.

            
                      Otherwise your terminal might behave strangely after the

            
                      program quits. endwin() frees the memory taken by curses

            
                      sub-system and its data structures and puts the terminal

            
                      in normal mode. This function must be called after you

            
                      are done with the curses mode.</p>

            
                    </div>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="GORY" id="GORY">3. The Gory

            
                  Details</a></h2>


                  <p>Now that we have seen how to write a simple curses program

            
                  let's get into the details. There are many functions that

            
                  help customize what you see on screen and many features which

            
                  can be put to full use.</p>


                  <p>Here we go...</p>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="INIT" id="INIT">4.

            
                  Initialization</a></h2>


                  <p>We now know that to initialize curses system the function

            
                  initscr() has to be called. There are functions which can be

            
                  called after this initialization to customize our curses

            
                  session. We may ask the curses system to set the terminal in

            
                  raw mode or initialize color or initialize the mouse, etc.

            
                  Let's discuss some of the functions that are normally called

            
                  immediately after initscr();</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ABOUTINIT" id="ABOUTINIT">4.1.

            
                    Initialization functions</a></h3>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="RAWCBREAK" id="RAWCBREAK">4.2.

            
                    raw() and cbreak()</a></h3>


                    <p>Normally the terminal driver buffers the characters a

            
                    user types until a new line or carriage return is

            
                    encountered. But most programs require that the characters

            
                    be available as soon as the user types them. The above two

            
                    functions are used to disable line buffering. The

            
                    difference between these two functions is in the way

            
                    control characters like suspend (CTRL-Z), interrupt and

            
                    quit (CTRL-C) are passed to the program. In the raw() mode

            
                    these characters are directly passed to the program without

            
                    generating a signal. In the <tt class=

            
                    "LITERAL">cbreak()</tt> mode these control characters are

            
                    interpreted as any other character by the terminal driver.

            
                    I personally prefer to use raw() as I can exercise greater

            
                    control over what the user does.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ECHONOECHO" id="ECHONOECHO">4.3.

            
                    echo() and noecho()</a></h3>


                    <p>These functions control the echoing of characters typed

            
                    by the user to the terminal. <tt class=

            
                    "LITERAL">noecho()</tt> switches off echoing. The reason

            
                    you might want to do this is to gain more control over

            
                    echoing or to suppress unnecessary echoing while taking

            
                    input from the user through the getch(), etc. functions.

            
                    Most of the interactive programs call <tt class=

            
                    "LITERAL">noecho()</tt> at initialization and do the

            
                    echoing of characters in a controlled manner. It gives the

            
                    programmer the flexibility of echoing characters at any

            
                    place in the window without updating current (y,x)

            
                    co-ordinates.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="KEYPAD" id="KEYPAD">4.4.

            
                    keypad()</a></h3>


                    <p>This is my favorite initialization function. It enables

            
                    the reading of function keys like F1, F2, arrow keys, etc.

            
                    Almost every interactive program enables this, as arrow

            
                    keys are a major part of any User Interface. Do <tt class=

            
                    "LITERAL">keypad(stdscr, TRUE)</tt> to enable this feature

            
                    for the regular screen (stdscr). You will learn more about

            
                    key management in later sections of this document.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="HALFDELAY" id="HALFDELAY">4.5.

            
                    halfdelay()</a></h3>


                    <p>This function, though not used very often, is a useful

            
                    one at times. halfdelay()is called to enable the half-delay

            
                    mode, which is similar to the cbreak() mode in that

            
                    characters typed are immediately available to program.

            
                    However, it waits for 'X' tenths of a second for input and

            
                    then returns ERR, if no input is available. 'X' is the

            
                    timeout value passed to the function halfdelay(). This

            
                    function is useful when you want to ask the user for input,

            
                    and if he doesn't respond with in certain time, we can do

            
                    some thing else. One possible example is a timeout at the

            
                    password prompt.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MISCINIT" id="MISCINIT">4.6.

            
                    Miscellaneous Initialization functions</a></h3>


                    <p>There are few more functions which are called at

            
                    initialization to customize curses behavior. They are not

            
                    used as extensively as those mentioned above. Some of them

            
                    are explained where appropriate.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="INITEX" id="INITEX">4.7. An

            
                    Example</a></h3>


                    <p>Let's write a program which will clarify the usage of

            
                    these functions.</p>


                    <div class="EXAMPLE">

            
                      <a name="BINFU" id="BINFU"></a>

            
                      <p><b>Example 2. Initialization Function Usage

            
                      example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;


            int main()

            
            {       int ch;


                    initscr();                      /* Start curses mode            */

            
                    raw();                          /* Line buffering disabled      */

            
                    keypad(stdscr, TRUE);           /* We get F1, F2 etc..          */

            
                    noecho();                       /* Don't echo() while we do getch */


                    printw("Type any character to see it in bold\n");

            
                    ch = getch();                   /* If raw() hadn't been called

            
                                                     * we have to press enter before it

            
                                                     * gets to the program          */

            
                    if(ch == KEY_F(1))              /* Without keypad enabled this will */

            
                            printw("F1 Key pressed");/*  not get to us either       */

            
                                                    /* Without noecho() some ugly escape

            
                                                     * characters might have been printed

            
                                                     * on screen                    */

            
                    else

            
                    {       printw("The pressed key is ");

            
                            attron(A_BOLD);

            
                            printw("%c", ch);

            
                            attroff(A_BOLD);

            
                    }

            
                    refresh();                      /* Print it on to the real screen */

            
                    getch();                        /* Wait for user input */

            
                    endwin();                       /* End curses mode                */


                    return 0;

            
            }</span></pre>

            
                    </div>


                    <p>This program is self-explanatory. But I used functions

            
                    which aren't explained yet. The function <tt class=

            
                    "LITERAL">getch()</tt> is used to get a character from

            
                    user. It is equivalent to normal <tt class=

            
                    "LITERAL">getchar()</tt> except that we can disable the

            
                    line buffering to avoid &lt;enter&gt; after input. Look for

            
                    more about <tt class="LITERAL">getch()</tt>and reading keys

            
                    in the <a href="#KEYS">key management section</a> . The

            
                    functions attron and attroff are used to switch some

            
                    attributes on and off respectively. In the example I used

            
                    them to print the character in bold. These functions are

            
                    explained in detail later.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="AWORDWINDOWS" id="AWORDWINDOWS">5.

            
                  A Word about Windows</a></h2>


                  <p>Before we plunge into the myriad ncurses functions, let me

            
                  clear few things about windows. Windows are explained in

            
                  detail in following <a href="#WINDOWS">sections</a></p>


                  <p>A Window is an imaginary screen defined by curses system.

            
                  A window does not mean a bordered window which you usually

            
                  see on Win9X platforms. When curses is initialized, it

            
                  creates a default window named <tt class=

            
                  "LITERAL">stdscr</tt> which represents your 80x25 (or the

            
                  size of window in which you are running) screen. If you are

            
                  doing simple tasks like printing few strings, reading input,

            
                  etc., you can safely use this single window for all of your

            
                  purposes. You can also create windows and call functions

            
                  which explicitly work on the specified window.</p>


                  <p>For example, if you call</p>


                  <pre class="PROGRAMLISTING">    printw("Hi There !!!");

            
                refresh();</pre>

            
                  <p>It prints the string on stdscr at the present cursor

            
                  position. Similarly the call to refresh(), works on stdscr

            
                  only.</p>


                  <p>Say you have created <a href="#WINDOWS">windows</a> then

            
                  you have to call a function with a 'w' added to the usual

            
                  function.</p>


                  <pre class="PROGRAMLISTING">    wprintw(win, "Hi There !!!");

            
                wrefresh(win);</pre>

            
                  <p>As you will see in the rest of the document, naming of

            
                  functions follow the same convention. For each function there

            
                  usually are three more functions.</p>


                  <pre class=

            
                  "PROGRAMLISTING">    printw(string);        /* Print on stdscr at present cursor position */

            
                mvprintw(y, x, string);/* Move to (y, x) then print string     */

            
                wprintw(win, string);  /* Print on window win at present cursor position */

            
                                       /* in the window */

            
                mvwprintw(win, y, x, string);   /* Move to (y, x) relative to window */

            
                                                /* co-ordinates and then print         */</pre>

            
                  <p>Usually the w-less functions are macros which expand to

            
                  corresponding w-function with stdscr as the window

            
                  parameter.</p>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="PRINTW" id="PRINTW">6. Output

            
                  functions</a></h2>


                  <p>I guess you can't wait any more to see some action. Back

            
                  to our odyssey of curses functions. Now that curses is

            
                  initialized, let's interact with world.</p>


                  <p>There are three classes of functions which you can use to

            
                  do output on screen.</p>


                  <ol type="1">

            
                    <li>

            
                      <p>addch() class: Print single character with

            
                      attributes</p>

            
                    </li>


                    <li>

            
                      <p>printw() class: Print formatted output similar to

            
                      printf()</p>

            
                    </li>


                    <li>

            
                      <p>addstr() class: Print strings</p>

            
                    </li>

            
                  </ol>


                  <p>These functions can be used interchangeably and it is a

            
                  matter of style as to which class is used. Let's see each one

            
                  in detail.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ADDCHCLASS" id="ADDCHCLASS">6.1.

            
                    addch() class of functions</a></h3>


                    <p>These functions put a single character into the current

            
                    cursor location and advance the position of the cursor. You

            
                    can give the character to be printed but they usually are

            
                    used to print a character with some attributes. Attributes

            
                    are explained in detail in later <a href=

            
                    "#ATTRIB">sections</a> of the document. If a character is

            
                    associated with an attribute(bold, reverse video etc.),

            
                    when curses prints the character, it is printed in that

            
                    attribute.</p>


                    <p>In order to combine a character with some attributes,

            
                    you have two options:</p>


                    <ul>

            
                      <li>

            
                        <p>By OR'ing a single character with the desired

            
                        attribute macros. These attribute macros could be found

            
                        in the header file <tt class="LITERAL">ncurses.h</tt>.

            
                        For example, you want to print a character ch(of type

            
                        char) bold and underlined, you would call addch() as

            
                        below.</p>


                        <pre class=

            
                        "PROGRAMLISTING">    addch(ch | A_BOLD | A_UNDERLINE);</pre>

            
                      </li>


                      <li>

            
                        <p>By using functions like <tt class=

            
                        "LITERAL">attrset(),attron(),attroff()</tt>. These

            
                        functions are explained in the <a href=

            
                        "#ATTRIB">Attributes</a> section. Briefly, they

            
                        manipulate the current attributes of the given window.

            
                        Once set, the character printed in the window are

            
                        associated with the attributes until it is turned

            
                        off.</p>

            
                      </li>

            
                    </ul>


                    <p>Additionally, <tt class="LITERAL">curses</tt> provides

            
                    some special characters for character-based graphics. You

            
                    can draw tables, horizontal or vertical lines, etc. You can

            
                    find all available characters in the header file <tt class=

            
                    "LITERAL">ncurses.h</tt>. Try looking for macros beginning

            
                    with <tt class="LITERAL">ACS_</tt> in this file.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="AEN303" id="AEN303">6.2.

            
                    mvaddch(), waddch() and mvwaddch()</a></h3>


                    <p><tt class="LITERAL">mvaddch()</tt> is used to move the

            
                    cursor to a given point, and then print. Thus, the

            
                    calls:</p>


                    <pre class=

            
                    "PROGRAMLISTING">    move(row,col);    /* moves the cursor to row<span class="emphasis"><i class="EMPHASIS">th</i></span> row and col<span class="emphasis"><i class="EMPHASIS">th</i></span> column */

            
                addch(ch);</pre>can be replaced by


                    <pre class="PROGRAMLISTING">    mvaddch(row,col,ch);</pre>

            
                    <p><tt class="LITERAL">waddch()</tt> is similar to

            
                    <tt class="LITERAL">addch()</tt>, except that it adds a

            
                    character into the given window. (Note that <tt class=

            
                    "LITERAL">addch()</tt> adds a character into the window

            
                    <tt class="LITERAL">stdscr</tt>.)</p>


                    <p>In a similar fashion <tt class="LITERAL">mvwaddch()</tt>

            
                    function is used to add a character into the given window

            
                    at the given coordinates.</p>


                    <p>Now, we are familiar with the basic output function

            
                    <tt class="LITERAL">addch()</tt>. But, if we want to print

            
                    a string, it would be very annoying to print it character

            
                    by character. Fortunately, <tt class="LITERAL">ncurses</tt>

            
                    provides <tt class="LITERAL">printf</tt><span class=

            
                    "emphasis"><i class="EMPHASIS">-like</i></span> or

            
                    <tt class="LITERAL">puts</tt><span class=

            
                    "emphasis"><i class="EMPHASIS">-like</i></span>

            
                    functions.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PRINTWCLASS" id=

            
                    "PRINTWCLASS">6.3. printw() class of functions</a></h3>


                    <p>These functions are similar to <tt class=

            
                    "LITERAL">printf()</tt> with the added capability of

            
                    printing at any position on the screen.</p>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="PRINTWMVPRINTW" id=

            
                      "PRINTWMVPRINTW">6.3.1. printw() and mvprintw</a></h4>


                      <p>These two functions work much like <tt class=

            
                      "LITERAL">printf()</tt>. <tt class=

            
                      "LITERAL">mvprintw()</tt> can be used to move the cursor

            
                      to a position and then print. If you want to move the

            
                      cursor first and then print using <tt class=

            
                      "LITERAL">printw()</tt> function, use <tt class=

            
                      "LITERAL">move()</tt> first and then use <tt class=

            
                      "LITERAL">printw()</tt> though I see no point why one

            
                      should avoid using <tt class="LITERAL">mvprintw()</tt>,

            
                      you have the flexibility to manipulate.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="WPRINTWMVWPRINTW" id=

            
                      "WPRINTWMVWPRINTW">6.3.2. wprintw() and mvwprintw</a></h4>


                      <p>These two functions are similar to above two except

            
                      that they print in the corresponding window given as

            
                      argument.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="VWPRINTW" id="VWPRINTW">6.3.3.

            
                      vw_printw()</a></h4>


                      <p>This function is similar to <tt class=

            
                      "LITERAL">vprintf()</tt>. This can be used when variable

            
                      number of arguments are to be printed.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="SIMPLEPRINTWEX" id=

            
                      "SIMPLEPRINTWEX">6.3.4. A Simple printw example</a></h4>


                      <div class="EXAMPLE">

            
                        <a name="BPREX" id="BPREX"></a>

            
                        <p><b>Example 3. A Simple printw example</b>

            
                        </p>


                        <pre class="PROGRAMLISTING"><span class=

            
                        "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;

            
            #include &lt;string.h&gt;


            int main()

            
            {

            
             char mesg[]="Just a string";           /* message to be appeared on the screen */

            
             int row,col;                           /* to store the number of rows and *

            
                                                     * the number of columns of the screen */

            
             initscr();                             /* start the curses mode */

            
             getmaxyx(stdscr,row,col);              /* get the number of rows and columns */

            
             mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);

            
                                                    /* print the message at the center of the screen */

            
             mvprintw(row-2,0,"This screen has %d rows and %d columns\n",row,col);

            
             printw("Try resizing your window(if possible) and then run this program again");

            
             refresh();

            
             getch();

            
             endwin();


             return 0;

            
            }</span></pre>

            
                      </div>


                      <p>Above program demonstrates how easy it is to use

            
                      <tt class="LITERAL">printw</tt>. You just feed the

            
                      coordinates and the message to be appeared on the screen,

            
                      then it does what you want.</p>


                      <p>The above program introduces us to a new function

            
                      <tt class="LITERAL">getmaxyx()</tt>, a macro defined in

            
                      <tt class="LITERAL">ncurses.h</tt>. It gives the number

            
                      of columns and the number of rows in a given window.

            
                      <tt class="LITERAL">getmaxyx()</tt> does this by updating

            
                      the variables given to it. Since <tt class=

            
                      "LITERAL">getmaxyx()</tt> is not a function we don't pass

            
                      pointers to it, we just give two integer variables.</p>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ADDSTRCLASS" id=

            
                    "ADDSTRCLASS">6.4. addstr() class of functions</a></h3>


                    <p><tt class="LITERAL">addstr()</tt> is used to put a

            
                    character string into a given window. This function is

            
                    similar to calling <tt class="LITERAL">addch()</tt> once

            
                    for each character in a given string. This is true for all

            
                    output functions. There are other functions from this

            
                    family such as <tt class=

            
                    "LITERAL">mvaddstr(),mvwaddstr()</tt> and <tt class=

            
                    "LITERAL">waddstr()</tt>, which obey the naming convention

            
                    of curses.(e.g. mvaddstr() is similar to the respective

            
                    calls move() and then addstr().) Another function of this

            
                    family is addnstr(), which takes an integer parameter(say

            
                    n) additionally. This function puts at most n characters

            
                    into the screen. If n is negative, then the entire string

            
                    will be added.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ACAUTION" id="ACAUTION">6.5. A

            
                    word of caution</a></h3>


                    <p>All these functions take y co-ordinate first and then x

            
                    in their arguments. A common mistake by beginners is to

            
                    pass x,y in that order. If you are doing too many

            
                    manipulations of (y,x) co-ordinates, think of dividing the

            
                    screen into windows and manipulate each one separately.

            
                    Windows are explained in the <a href="#WINDOWS">windows</a>

            
                    section.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="SCANW" id="SCANW">7. Input

            
                  functions</a></h2>


                  <p>Well, printing without taking input, is boring. Let's see

            
                  functions which allow us to get input from user. These

            
                  functions also can be divided into three categories.</p>


                  <ol type="1">

            
                    <li>

            
                      <p>getch() class: Get a character</p>

            
                    </li>


                    <li>

            
                      <p>scanw() class: Get formatted input</p>

            
                    </li>


                    <li>

            
                      <p>getstr() class: Get strings</p>

            
                    </li>

            
                  </ol>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="GETCHCLASS" id="GETCHCLASS">7.1.

            
                    getch() class of functions</a></h3>


                    <p>These functions read a single character from the

            
                    terminal. But there are several subtle facts to consider.

            
                    For example if you don't use the function cbreak(), curses

            
                    will not read your input characters contiguously but will

            
                    begin read them only after a new line or an EOF is

            
                    encountered. In order to avoid this, the cbreak() function

            
                    must used so that characters are immediately available to

            
                    your program. Another widely used function is noecho(). As

            
                    the name suggests, when this function is set (used), the

            
                    characters that are keyed in by the user will not show up

            
                    on the screen. The two functions cbreak() and noecho() are

            
                    typical examples of key management. Functions of this genre

            
                    are explained in the <a href="#KEYS">key management

            
                    section</a> .</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="SCANWCLASS" id="SCANWCLASS">7.2.

            
                    scanw() class of functions</a></h3>


                    <p>These functions are similar to <tt class=

            
                    "LITERAL">scanf()</tt> with the added capability of getting

            
                    the input from any location on the screen.</p>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="SCANWMVSCANW" id=

            
                      "SCANWMVSCANW">7.2.1. scanw() and mvscanw</a></h4>


                      <p>The usage of these functions is similar to that of

            
                      <tt class="LITERAL">sscanf()</tt>, where the line to be

            
                      scanned is provided by <tt class="LITERAL">wgetstr()</tt>

            
                      function. That is, these functions call to <tt class=

            
                      "LITERAL">wgetstr()</tt> function(explained below) and

            
                      uses the resulting line for a scan.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="WSCANWMVWSCANW" id=

            
                      "WSCANWMVWSCANW">7.2.2. wscanw() and mvwscanw()</a></h4>


                      <p>These are similar to above two functions except that

            
                      they read from a window, which is supplied as one of the

            
                      arguments to these functions.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="VWSCANW" id="VWSCANW">7.2.3.

            
                      vw_scanw()</a></h4>


                      <p>This function is similar to <tt class=

            
                      "LITERAL">vscanf()</tt>. This can be used when a variable

            
                      number of arguments are to be scanned.</p>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="GETSTRCLASS" id=

            
                    "GETSTRCLASS">7.3. getstr() class of functions</a></h3>


                    <p>These functions are used to get strings from the

            
                    terminal. In essence, this function performs the same task

            
                    as would be achieved by a series of calls to <tt class=

            
                    "LITERAL">getch()</tt> until a newline, carriage return, or

            
                    end-of-file is received. The resulting string of characters

            
                    are pointed to by <tt class="LITERAL">str</tt>, which is a

            
                    character pointer provided by the user.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="GETSTREX" id="GETSTREX">7.4.

            
                    Some examples</a></h3>


                    <div class="EXAMPLE">

            
                      <a name="BSCEX" id="BSCEX"></a>

            
                      <p><b>Example 4. A Simple scanw example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;

            
            #include &lt;string.h&gt;


            int main()

            
            {

            
             char mesg[]="Enter a string: ";                /* message to be appeared on the screen */

            
             char str[80];

            
             int row,col;                           /* to store the number of rows and *

            
                                                     * the number of columns of the screen */

            
             initscr();                             /* start the curses mode */

            
             getmaxyx(stdscr,row,col);              /* get the number of rows and columns */

            
             mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);

            
                                            /* print the message at the center of the screen */

            
             getstr(str);

            
             mvprintw(LINES - 2, 0, "You Entered: %s", str);

            
             getch();

            
             endwin();


             return 0;

            
            }</span></pre>

            
                    </div>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="ATTRIB" id="ATTRIB">8.

            
                  Attributes</a></h2>


                  <p>We have seen an example of how attributes can be used to

            
                  print characters with some special effects. Attributes, when

            
                  set prudently, can present information in an easy,

            
                  understandable manner. The following program takes a C file

            
                  as input and prints the file with comments in bold. Scan

            
                  through the code.</p>


                  <div class="EXAMPLE">

            
                    <a name="BSIAT" id="BSIAT"></a>

            
                    <p><b>Example 5. A Simple Attributes example</b>

            
                    </p>


                    <pre class="PROGRAMLISTING"><span class=

            
                    "INLINEMEDIAOBJECT">/* pager functionality by Joseph Spainhour" &lt;spainhou@bellsouth.net&gt; */

            
            #include &lt;curses.h&gt;

            
            #include &lt;stdlib.h&gt;


            int main(int argc, char *argv[])

            
            {

            
              int ch, prev, row, col;

            
              prev = EOF;

            
              FILE *fp;

            
              int y, x;


              if(argc != 2)

            
              {

            
                printf("Usage: %s &lt;a c file name&gt;\n", argv[0]);

            
                exit(1);

            
              }

            
              fp = fopen(argv[1], "r");

            
              if(fp == NULL)

            
              {

            
                perror("Cannot open input file");

            
                exit(1);

            
              }

            
              initscr();                            /* Start curses mode */

            
              getmaxyx(stdscr, row, col);           /* find the boundaries of the screeen */

            
              while((ch = fgetc(fp)) != EOF)        /* read the file till we reach the end */

            
              {

            
                getyx(stdscr, y, x);                /* get the current cursor position */

            
                if(y == (row - 1))                  /* are we are at the end of the screen */

            
                {

            
                  printw("&lt;-Press Any Key-&gt;");      /* tell the user to press a key */

            
                  getch();

            
                  clear();                          /* clear the screen */

            
                  move(0, 0);                       /* start at the beginning of the screen */

            
                }

            
                if(prev == '/' &amp;&amp; ch == '*')        /* If it is / and * then only

            
                                                     * switch bold on */

            
                {

            
                  attron(A_BOLD);                   /* cut bold on */

            
                  getyx(stdscr, y, x);              /* get the current cursor position */

            
                  move(y, x - 1);                   /* back up one space */

            
                  printw("%c%c", '/', ch);          /* The actual printing is done here */

            
                }

            
                else

            
                  printw("%c", ch);

            
                refresh();

            
                if(prev == '*' &amp;&amp; ch == '/')

            
                  attroff(A_BOLD);                  /* Switch it off once we got *

            
                                                     * and then / */

            
                prev = ch;

            
              }

            
              endwin();                             /* End curses mode */

            
              fclose(fp);

            
              return 0;

            
            }</span></pre>

            
                  </div>


                  <p>Don't worry about all those initialization and other crap.

            
                  Concentrate on the while loop. It reads each character in the

            
                  file and searches for the pattern /*. Once it spots the

            
                  pattern, it switches the BOLD attribute on with <tt class=

            
                  "LITERAL">attron()</tt> . When we get the pattern */ it is

            
                  switched off by <tt class="LITERAL">attroff()</tt> .</p>


                  <p>The above program also introduces us to two useful

            
                  functions <tt class="LITERAL">getyx()</tt> and <tt class=

            
                  "LITERAL">move()</tt>. The first function gets the

            
                  co-ordinates of the present cursor into the variables y, x.

            
                  Since getyx() is a macro we don't have to pass pointers to

            
                  variables. The function <tt class="LITERAL">move()</tt> moves

            
                  the cursor to the co-ordinates given to it.</p>


                  <p>The above program is really a simple one which doesn't do

            
                  much. On these lines one could write a more useful program

            
                  which reads a C file, parses it and prints it in different

            
                  colors. One could even extend it to other languages as

            
                  well.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ATTRIBDETAILS" id=

            
                    "ATTRIBDETAILS">8.1. The details</a></h3>


                    <p>Let's get into more details of attributes. The functions

            
                    <tt class="LITERAL">attron(), attroff(), attrset()</tt> ,

            
                    and their sister functions <tt class=

            
                    "LITERAL">attr_get()</tt>, etc. can be used to switch

            
                    attributes on/off , get attributes and produce a colorful

            
                    display.</p>


                    <p>The functions attron and attroff take a bit-mask of

            
                    attributes and switch them on or off, respectively. The

            
                    following video attributes, which are defined in

            
                    &lt;curses.h&gt; can be passed to these functions.</p>


                    <pre class="PROGRAMLISTING">

            
                A_NORMAL        Normal display (no highlight)

            
                A_STANDOUT      Best highlighting mode of the terminal.

            
                A_UNDERLINE     Underlining

            
                A_REVERSE       Reverse video

            
                A_BLINK         Blinking

            
                A_DIM           Half bright

            
                A_BOLD          Extra bright or bold

            
                A_PROTECT       Protected mode

            
                A_INVIS         Invisible or blank mode

            
                A_ALTCHARSET    Alternate character set

            
                A_CHARTEXT      Bit-mask to extract a character

            
                COLOR_PAIR(n)   Color-pair number n

            
                </pre>

            
                    <p>The last one is the most colorful one :-) Colors are

            
                    explained in the <a href="#color" target="_top">next

            
                    sections</a>.</p>


                    <p>We can OR(|) any number of above attributes to get a

            
                    combined effect. If you wanted reverse video with blinking

            
                    characters you can use</p>


                    <pre class=

            
                    "PROGRAMLISTING">    attron(A_REVERSE | A_BLINK);</pre>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ATTRONVSATTRSET" id=

            
                    "ATTRONVSATTRSET">8.2. attron() vs attrset()</a></h3>


                    <p>Then what is the difference between attron() and

            
                    attrset()? attrset sets the attributes of window whereas

            
                    attron just switches on the attribute given to it. So

            
                    attrset() fully overrides whatever attributes the window

            
                    previously had and sets it to the new attribute(s).

            
                    Similarly attroff() just switches off the attribute(s)

            
                    given to it as an argument. This gives us the flexibility

            
                    of managing attributes easily.But if you use them

            
                    carelessly you may loose track of what attributes the

            
                    window has and garble the display. This is especially true

            
                    while managing menus with colors and highlighting. So

            
                    decide on a consistent policy and stick to it. You can

            
                    always use <tt class="LITERAL">standend()</tt> which is

            
                    equivalent to <tt class="LITERAL">attrset(A_NORMAL)</tt>

            
                    which turns off all attributes and brings you to normal

            
                    mode.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ATTRGET" id="ATTRGET">8.3.

            
                    attr_get()</a></h3>


                    <p>The function attr_get() gets the current attributes and

            
                    color pair of the window. Though we might not use this as

            
                    often as the above functions, this is useful in scanning

            
                    areas of screen. Say we wanted to do some complex update on

            
                    screen and we are not sure what attribute each character is

            
                    associated with. Then this function can be used with either

            
                    attrset or attron to produce the desired effect.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ATTRFUNCS" id="ATTRFUNCS">8.4.

            
                    attr_ functions</a></h3>


                    <p>There are series of functions like attr_set(), attr_on,

            
                    etc. These are similar to above functions except that they

            
                    take parameters of type <tt class=

            
                    "LITERAL">attr_t</tt>.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="WATTRFUNCS" id="WATTRFUNCS">8.5.

            
                    wattr functions</a></h3>


                    <p>For each of the above functions we have a corresponding

            
                    function with 'w' which operates on a particular window.

            
                    The above functions operate on stdscr.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="CHGAT" id="CHGAT">8.6. chgat()

            
                    functions</a></h3>


                    <p>The function chgat() is listed in the end of the man

            
                    page curs_attr. It actually is a useful one. This function

            
                    can be used to set attributes for a group of characters

            
                    without moving. I mean it !!! without moving the cursor :-)

            
                    It changes the attributes of a given number of characters

            
                    starting at the current cursor location.</p>


                    <p>We can give -1 as the character count to update till end

            
                    of line. If you want to change attributes of characters

            
                    from current position to end of line, just use this.</p>


                    <pre class=

            
                    "PROGRAMLISTING">    chgat(-1, A_REVERSE, 0, NULL);</pre>

            
                    <p>This function is useful when changing attributes for

            
                    characters that are already on the screen. Move to the

            
                    character from which you want to change and change the

            
                    attribute.</p>


                    <p>Other functions wchgat(), mvchgat(), wchgat() behave

            
                    similarly except that the w functions operate on the

            
                    particular window. The mv functions first move the cursor

            
                    then perform the work given to them. Actually chgat is a

            
                    macro which is replaced by a wchgat() with stdscr as the

            
                    window. Most of the "w-less" functions are macros.</p>


                    <div class="EXAMPLE">

            
                      <a name="BWICH" id="BWICH"></a>

            
                      <p><b>Example 6. Chgat() Usage example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;


            int main(int argc, char *argv[])

            
            {       initscr();                      /* Start curses mode            */

            
                    start_color();                  /* Start color functionality    */


                    init_pair(1, COLOR_CYAN, COLOR_BLACK);

            
                    printw("A Big string which i didn't care to type fully ");

            
                    mvchgat(0, 0, -1, A_BLINK, 1, NULL);

            
                    /*

            
                     * First two parameters specify the position at which to start

            
                     * Third parameter number of characters to update. -1 means till

            
                     * end of line

            
                     * Forth parameter is the normal attribute you wanted to give

            
                     * to the character

            
                     * Fifth is the color index. It is the index given during init_pair()

            
                     * use 0 if you didn't want color

            
                     * Sixth one is always NULL

            
                     */

            
                    refresh();

            
                    getch();

            
                    endwin();                       /* End curses mode                */

            
                    return 0;

            
            }</span></pre>

            
                    </div>


                    <p>This example also introduces us to the color world of

            
                    curses. Colors will be explained in detail later. Use 0 for

            
                    no color.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="WINDOWS" id="WINDOWS">9.

            
                  Windows</a></h2>


                  <p>Windows form the most important concept in curses. You

            
                  have seen the standard window stdscr above where all the

            
                  functions implicitly operated on this window. Now to make

            
                  design even a simplest GUI, you need to resort to windows.

            
                  The main reason you may want to use windows is to manipulate

            
                  parts of the screen separately, for better efficiency, by

            
                  updating only the windows that need to be changed and for a

            
                  better design. I would say the last reason is the most

            
                  important in going for windows. You should always strive for

            
                  a better and easy-to-manage design in your programs. If you

            
                  are writing big, complex GUIs this is of pivotal importance

            
                  before you start doing anything.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="WINDOWBASICS" id=

            
                    "WINDOWBASICS">9.1. The basics</a></h3>


                    <p>A Window can be created by calling the function

            
                    <tt class="LITERAL">newwin()</tt>. It doesn't create any

            
                    thing on the screen actually. It allocates memory for a

            
                    structure to manipulate the window and updates the

            
                    structure with data regarding the window such as its size,

            
                    beginy, beginx, etc. Hence in curses, a window is just an

            
                    abstraction of an imaginary window, which can be

            
                    manipulated independent of other parts of screen. The

            
                    function newwin() returns a pointer to structure WINDOW,

            
                    which can be passed to window related functions such as

            
                    wprintw(), etc. Finally the window can be destroyed with

            
                    delwin(). It will deallocate the memory associated with the

            
                    window structure.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="LETBEWINDOW" id=

            
                    "LETBEWINDOW">9.2. Let there be a Window !!!</a></h3>


                    <p>What fun is it, if a window is created and we can't see

            
                    it. So the fun part begins by displaying the window. The

            
                    function <tt class="LITERAL">box()</tt> can be used to draw

            
                    a border around the window. Let's explore these functions

            
                    in more detail in this example.</p>


                    <div class="EXAMPLE">

            
                      <a name="BWIBO" id="BWIBO"></a>

            
                      <p><b>Example 7. Window Border example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;


            WINDOW *create_newwin(int height, int width, int starty, int startx);

            
            void destroy_win(WINDOW *local_win);


            int main(int argc, char *argv[])

            
            {       WINDOW *my_win;

            
                    int startx, starty, width, height;

            
                    int ch;


                    initscr();                      /* Start curses mode            */

            
                    cbreak();                       /* Line buffering disabled, Pass on

            
                                                     * everty thing to me           */

            
                    keypad(stdscr, TRUE);           /* I need that nifty F1         */


                    height = 3;

            
                    width = 10;

            
                    starty = (LINES - height) / 2;  /* Calculating for a center placement */

            
                    startx = (COLS - width) / 2;    /* of the window                */

            
                    printw("Press F1 to exit");

            
                    refresh();

            
                    my_win = create_newwin(height, width, starty, startx);


                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case KEY_LEFT:

            
                                            destroy_win(my_win);

            
                                            my_win = create_newwin(height, width, starty,--startx);

            
                                            break;

            
                                    case KEY_RIGHT:

            
                                            destroy_win(my_win);

            
                                            my_win = create_newwin(height, width, starty,++startx);

            
                                            break;

            
                                    case KEY_UP:

            
                                            destroy_win(my_win);

            
                                            my_win = create_newwin(height, width, --starty,startx);

            
                                            break;

            
                                    case KEY_DOWN:

            
                                            destroy_win(my_win);

            
                                            my_win = create_newwin(height, width, ++starty,startx);

            
                                            break;

            
                            }

            
                    }


                    endwin();                       /* End curses mode                */

            
                    return 0;

            
            }


            WINDOW *create_newwin(int height, int width, int starty, int startx)

            
            {       WINDOW *local_win;


                    local_win = newwin(height, width, starty, startx);

            
                    box(local_win, 0 , 0);          /* 0, 0 gives default characters

            
                                                     * for the vertical and horizontal

            
                                                     * lines                        */

            
                    wrefresh(local_win);            /* Show that box                */


                    return local_win;

            
            }


            void destroy_win(WINDOW *local_win)

            
            {

            
                    /* box(local_win, ' ', ' '); : This won't produce the desired

            
                     * result of erasing the window. It will leave its four corners

            
                     * and so an ugly remnant of window.

            
                     */

            
                    wborder(local_win, ' ', ' ', ' ',' ',' ',' ',' ',' ');

            
                    /* The parameters taken are

            
                     * 1. win: the window on which to operate

            
                     * 2. ls: character to be used for the left side of the window

            
                     * 3. rs: character to be used for the right side of the window

            
                     * 4. ts: character to be used for the top side of the window

            
                     * 5. bs: character to be used for the bottom side of the window

            
                     * 6. tl: character to be used for the top left corner of the window

            
                     * 7. tr: character to be used for the top right corner of the window

            
                     * 8. bl: character to be used for the bottom left corner of the window

            
                     * 9. br: character to be used for the bottom right corner of the window

            
                     */

            
                    wrefresh(local_win);

            
                    delwin(local_win);

            
            }</span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="BORDEREXEXPL" id=

            
                    "BORDEREXEXPL">9.3. Explanation</a></h3>


                    <p>Don't scream. I know it is a big example. But I have to

            
                    explain some important things here :-). This program

            
                    creates a rectangular window that can be moved with left,

            
                    right, up, down arrow keys. It repeatedly creates and

            
                    destroys windows as user press a key. Don't go beyond the

            
                    screen limits. Checking for those limits is left as an

            
                    exercise for the reader. Let's dissect it by line by

            
                    line.</p>


                    <p>The <tt class="LITERAL">create_newwin()</tt> function

            
                    creates a window with <tt class="LITERAL">newwin()</tt> and

            
                    displays a border around it with box. The function

            
                    <tt class="LITERAL">destroy_win()</tt> first erases the

            
                    window from screen by painting a border with ' ' character

            
                    and then calling <tt class="LITERAL">delwin()</tt> to

            
                    deallocate memory related to it. Depending on the key the

            
                    user presses, starty or startx is changed and a new window

            
                    is created.</p>


                    <p>In the destroy_win, as you can see, I used wborder

            
                    instead of box. The reason is written in the comments (You

            
                    missed it. I know. Read the code :-)). wborder draws a

            
                    border around the window with the characters given to it as

            
                    the 4 corner points and the 4 lines. To put it clearly, if

            
                    you have called wborder as below:</p>


                    <pre class=

            
                    "PROGRAMLISTING">    wborder(win, '|', '|', '-', '-', '+', '+', '+', '+');</pre>

            
                    <p>it produces something like</p>


                    <pre class="PROGRAMLISTING">    +------------+

            
                |            |

            
                |            |

            
                |            |

            
                |            |

            
                |            |

            
                |            |

            
                +------------+</pre>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="OTHERSTUFF" id="OTHERSTUFF">9.4.

            
                    The other stuff in the example</a></h3>


                    <p>You can also see in the above examples, that I have used

            
                    the variables COLS, LINES which are initialized to the

            
                    screen sizes after initscr(). They can be useful in finding

            
                    screen dimensions and finding the center co-ordinate of the

            
                    screen as above. The function <tt class=

            
                    "LITERAL">getch()</tt> as usual gets the key from keyboard

            
                    and according to the key it does the corresponding work.

            
                    This type of switch- case is very common in any GUI based

            
                    programs.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="OTHERBORDERFUNCS" id=

            
                    "OTHERBORDERFUNCS">9.5. Other Border functions</a></h3>


                    <p>Above program is grossly inefficient in that with each

            
                    press of a key, a window is destroyed and another is

            
                    created. So let's write a more efficient program which uses

            
                    other border related functions.</p>


                    <p>The following program uses <tt class=

            
                    "LITERAL">mvhline()</tt> and <tt class=

            
                    "LITERAL">mvvline()</tt> to achieve similar effect. These

            
                    two functions are simple. They create a horizontal or

            
                    vertical line of the specified length at the specified

            
                    position.</p>


                    <div class="EXAMPLE">

            
                      <a name="BOTBO" id="BOTBO"></a>

            
                      <p><b>Example 8. More border functions</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;


            typedef struct _win_border_struct {

            
                    chtype  ls, rs, ts, bs,

            
                            tl, tr, bl, br;

            
            }WIN_BORDER;


            typedef struct _WIN_struct {


                    int startx, starty;

            
                    int height, width;

            
                    WIN_BORDER border;

            
            }WIN;


            void init_win_params(WIN *p_win);

            
            void print_win_params(WIN *p_win);

            
            void create_box(WIN *win, bool flag);


            int main(int argc, char *argv[])

            
            {       WIN win;

            
                    int ch;


                    initscr();                      /* Start curses mode            */

            
                    start_color();                  /* Start the color functionality */

            
                    cbreak();                       /* Line buffering disabled, Pass on

            
                                                     * everty thing to me           */

            
                    keypad(stdscr, TRUE);           /* I need that nifty F1         */

            
                    noecho();

            
                    init_pair(1, COLOR_CYAN, COLOR_BLACK);


                    /* Initialize the window parameters */

            
                    init_win_params(&amp;win);

            
                    print_win_params(&amp;win);


                    attron(COLOR_PAIR(1));

            
                    printw("Press F1 to exit");

            
                    refresh();

            
                    attroff(COLOR_PAIR(1));


                    create_box(&amp;win, TRUE);

            
                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case KEY_LEFT:

            
                                            create_box(&amp;win, FALSE);

            
                                            --win.startx;

            
                                            create_box(&amp;win, TRUE);

            
                                            break;

            
                                    case KEY_RIGHT:

            
                                            create_box(&amp;win, FALSE);

            
                                            ++win.startx;

            
                                            create_box(&amp;win, TRUE);

            
                                            break;

            
                                    case KEY_UP:

            
                                            create_box(&amp;win, FALSE);

            
                                            --win.starty;

            
                                            create_box(&amp;win, TRUE);

            
                                            break;

            
                                    case KEY_DOWN:

            
                                            create_box(&amp;win, FALSE);

            
                                            ++win.starty;

            
                                            create_box(&amp;win, TRUE);

            
                                            break;

            
                            }

            
                    }

            
                    endwin();                       /* End curses mode                */

            
                    return 0;

            
            }

            
            void init_win_params(WIN *p_win)

            
            {

            
                    p_win-&gt;height = 3;

            
                    p_win-&gt;width = 10;

            
                    p_win-&gt;starty = (LINES - p_win-&gt;height)/2;

            
                    p_win-&gt;startx = (COLS - p_win-&gt;width)/2;


                    p_win-&gt;border.ls = '|';

            
                    p_win-&gt;border.rs = '|';

            
                    p_win-&gt;border.ts = '-';

            
                    p_win-&gt;border.bs = '-';

            
                    p_win-&gt;border.tl = '+';

            
                    p_win-&gt;border.tr = '+';

            
                    p_win-&gt;border.bl = '+';

            
                    p_win-&gt;border.br = '+';


            }

            
            void print_win_params(WIN *p_win)

            
            {

            
            #ifdef _DEBUG

            
                    mvprintw(25, 0, "%d %d %d %d", p_win-&gt;startx, p_win-&gt;starty,

            
                                            p_win-&gt;width, p_win-&gt;height);

            
                    refresh();

            
            #endif

            
            }

            
            void create_box(WIN *p_win, bool flag)

            
            {       int i, j;

            
                    int x, y, w, h;


                    x = p_win-&gt;startx;

            
                    y = p_win-&gt;starty;

            
                    w = p_win-&gt;width;

            
                    h = p_win-&gt;height;


                    if(flag == TRUE)

            
                    {       mvaddch(y, x, p_win-&gt;border.tl);

            
                            mvaddch(y, x + w, p_win-&gt;border.tr);

            
                            mvaddch(y + h, x, p_win-&gt;border.bl);

            
                            mvaddch(y + h, x + w, p_win-&gt;border.br);

            
                            mvhline(y, x + 1, p_win-&gt;border.ts, w - 1);

            
                            mvhline(y + h, x + 1, p_win-&gt;border.bs, w - 1);

            
                            mvvline(y + 1, x, p_win-&gt;border.ls, h - 1);

            
                            mvvline(y + 1, x + w, p_win-&gt;border.rs, h - 1);


                    }

            
                    else

            
                            for(j = y; j &lt;= y + h; ++j)

            
                                    for(i = x; i &lt;= x + w; ++i)

            
                                            mvaddch(j, i, ' ');


                    refresh();


            }</span></pre>

            
                    </div>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="COLOR" id="COLOR">10. Colors</a></h2>


                  <div class="SECT2">

            
                    <h3 class="SECT2"><a name="COLORBASICS" id=

            
                    "COLORBASICS">10.1. The basics</a></h3>


                    <p>Life seems dull with no colors. Curses has a nice

            
                    mechanism to handle colors. Let's get into the thick of the

            
                    things with a small program.</p>


                    <div class="EXAMPLE">

            
                      <a name="BSICO" id="BSICO"></a>

            
                      <p><b>Example 9. A Simple Color example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;string.h&gt;

            
            #include &lt;curses.h&gt;


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string);

            
            int main(int argc, char *argv[])

            
            {       initscr();                      /* Start curses mode            */

            
                    if(has_colors() == FALSE)

            
                    {       endwin();

            
                            printf("Your terminal does not support color\n");

            
                            exit(1);

            
                    }

            
                    start_color();                  /* Start color                  */

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);


                    attron(COLOR_PAIR(1));

            
                    print_in_middle(stdscr, LINES / 2, 0, 0, "Viola !!! In color ...");

            
                    attroff(COLOR_PAIR(1));

            
                    getch();

            
                    endwin();

            
            }

            
            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string)

            
            {       int length, x, y;

            
                    float temp;


                    if(win == NULL)

            
                            win = stdscr;

            
                    getyx(win, y, x);

            
                    if(startx != 0)

            
                            x = startx;

            
                    if(starty != 0)

            
                            y = starty;

            
                    if(width == 0)

            
                            width = 80;


                    length = strlen(string);

            
                    temp = (width - length)/ 2;

            
                    x = startx + (int)temp;

            
                    mvwprintw(win, y, x, "%s", string);

            
                    refresh();

            
            }

            
            </span></pre>

            
                    </div>


                    <p>As you can see, to start using color, you should first

            
                    call the function <tt class="LITERAL">start_color()</tt>.

            
                    After that, you can use color capabilities of your

            
                    terminals using various functions. To find out whether a

            
                    terminal has color capabilities or not, you can use

            
                    <tt class="LITERAL">has_colors()</tt> function, which

            
                    returns FALSE if the terminal does not support color.</p>


                    <p>Curses initializes all the colors supported by terminal

            
                    when start_color() is called. These can be accessed by the

            
                    define constants like <tt class="LITERAL">COLOR_BLACK</tt>

            
                    , etc. Now to actually start using colors, you have to

            
                    define pairs. Colors are always used in pairs. That means

            
                    you have to use the function <tt class=

            
                    "LITERAL">init_pair()</tt> to define the foreground and

            
                    background for the pair number you give. After that that

            
                    pair number can be used as a normal attribute with

            
                    <tt class="LITERAL">COLOR_PAIR()</tt>function. This may

            
                    seem to be cumbersome at first. But this elegant solution

            
                    allows us to manage color pairs very easily. To appreciate

            
                    it, you have to look into the the source code of "dialog",

            
                    a utility for displaying dialog boxes from shell scripts.

            
                    The developers have defined foreground and background

            
                    combinations for all the colors they might need and

            
                    initialized at the beginning. This makes it very easy to

            
                    set attributes just by accessing a pair which we already

            
                    have defined as a constant.</p>


                    <p>The following colors are defined in <tt class=

            
                    "LITERAL">curses.h</tt>. You can use these as parameters

            
                    for various color functions.</p>


                    <pre class="PROGRAMLISTING">        COLOR_BLACK   0

            
                    COLOR_RED     1

            
                    COLOR_GREEN   2

            
                    COLOR_YELLOW  3

            
                    COLOR_BLUE    4

            
                    COLOR_MAGENTA 5

            
                    COLOR_CYAN    6

            
                    COLOR_WHITE   7</pre>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="CHANGECOLORDEFS" id=

            
                    "CHANGECOLORDEFS">10.2. Changing Color Definitions</a></h3>


                    <p>The function <tt class="LITERAL">init_color()</tt>can be

            
                    used to change the rgb values for the colors defined by

            
                    curses initially. Say you wanted to lighten the intensity

            
                    of red color by a minuscule. Then you can use this function

            
                    as</p>


                    <pre class=

            
                    "PROGRAMLISTING">    init_color(COLOR_RED, 700, 0, 0);

            
                /* param 1     : color name

            
                 * param 2, 3, 4 : rgb content min = 0, max = 1000 */</pre>

            
                    <p>If your terminal cannot change the color definitions,

            
                    the function returns ERR. The function <tt class=

            
                    "LITERAL">can_change_color()</tt> can be used to find out

            
                    whether the terminal has the capability of changing color

            
                    content or not. The rgb content is scaled from 0 to 1000.

            
                    Initially RED color is defined with content 1000(r), 0(g),

            
                    0(b).</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="COLORCONTENT" id=

            
                    "COLORCONTENT">10.3. Color Content</a></h3>


                    <p>The functions <tt class="LITERAL">color_content()</tt>

            
                    and <tt class="LITERAL">pair_content()</tt> can be used to

            
                    find the color content and foreground, background

            
                    combination for the pair.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="KEYS" id="KEYS">11. Interfacing

            
                  with the key board</a></h2>


                  <div class="SECT2">

            
                    <h3 class="SECT2"><a name="KEYSBASICS" id=

            
                    "KEYSBASICS">11.1. The Basics</a></h3>


                    <p>No GUI is complete without a strong user interface and

            
                    to interact with the user, a curses program should be

            
                    sensitive to key presses or the mouse actions done by the

            
                    user. Let's deal with the keys first.</p>


                    <p>As you have seen in almost all of the above examples, it

            
                    is very easy to get key input from the user. A simple way

            
                    of getting key presses is to use <tt class=

            
                    "LITERAL">getch()</tt> function. The cbreak mode should be

            
                    enabled to read keys when you are interested in reading

            
                    individual key hits rather than complete lines of text

            
                    (which usually end with a carriage return). keypad should

            
                    be enabled to get the Functions keys, arrow keys, etc. See

            
                    the initialization section for details.</p>


                    <p><tt class="LITERAL">getch()</tt> returns an integer

            
                    corresponding to the key pressed. If it is a normal

            
                    character, the integer value will be equivalent to the

            
                    character. Otherwise it returns a number which can be

            
                    matched with the constants defined in <tt class=

            
                    "LITERAL">curses.h</tt>. For example if the user presses

            
                    F1, the integer returned is 265. This can be checked using

            
                    the macro KEY_F() defined in curses.h. This makes reading

            
                    keys portable and easy to manage.</p>


                    <p>For example, if you call getch() like this</p>


                    <pre class="PROGRAMLISTING">    int ch;


                ch = getch();</pre>

            
                    <p>getch() will wait for the user to press a key, (unless

            
                    you specified a timeout) and when user presses a key, the

            
                    corresponding integer is returned. Then you can check the

            
                    value returned with the constants defined in curses.h to

            
                    match against the keys you want.</p>


                    <p>The following code piece will do that job.</p>


                    <pre class="PROGRAMLISTING">    if(ch == KEY_LEFT)

            
                    printw("Left arrow is pressed\n");</pre>

            
                    <p>Let's write a small program which creates a menu which

            
                    can be navigated by up and down arrows.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="SIMPLEKEYEX" id=

            
                    "SIMPLEKEYEX">11.2. A Simple Key Usage example</a></h3>


                    <div class="EXAMPLE">

            
                      <a name="BSIKE" id="BSIKE"></a>

            
                      <p><b>Example 10. A Simple Key Usage example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;


            #define WIDTH 30

            
            #define HEIGHT 10


            int startx = 0;

            
            int starty = 0;


            char *choices[] = {

            
                                    "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Exit",

            
                              };

            
            int n_choices = sizeof(choices) / sizeof(char *);

            
            void print_menu(WINDOW *menu_win, int highlight);


            int main()

            
            {       WINDOW *menu_win;

            
                    int highlight = 1;

            
                    int choice = 0;

            
                    int c;


                    initscr();

            
                    clear();

            
                    noecho();

            
                    cbreak();       /* Line buffering disabled. pass on everything */

            
                    startx = (80 - WIDTH) / 2;

            
                    starty = (24 - HEIGHT) / 2;


                    menu_win = newwin(HEIGHT, WIDTH, starty, startx);

            
                    keypad(menu_win, TRUE);

            
                    mvprintw(0, 0, "Use arrow keys to go up and down, Press enter to select a choice");

            
                    refresh();

            
                    print_menu(menu_win, highlight);

            
                    while(1)

            
                    {       c = wgetch(menu_win);

            
                            switch(c)

            
                            {       case KEY_UP:

            
                                            if(highlight == 1)

            
                                                    highlight = n_choices;

            
                                            else

            
                                                    --highlight;

            
                                            break;

            
                                    case KEY_DOWN:

            
                                            if(highlight == n_choices)

            
                                                    highlight = 1;

            
                                            else

            
                                                    ++highlight;

            
                                            break;

            
                                    case 10:

            
                                            choice = highlight;

            
                                            break;

            
                                    default:

            
                                            mvprintw(24, 0, "Character pressed is = %3d Hopefully it can be printed as '%c'", c, c);

            
                                            refresh();

            
                                            break;

            
                            }

            
                            print_menu(menu_win, highlight);

            
                            if(choice != 0) /* User did a choice come out of the infinite loop */

            
                                    break;

            
                    }

            
                    mvprintw(23, 0, "You chose choice %d with choice string %s\n", choice, choices[choice - 1]);

            
                    clrtoeol();

            
                    refresh();

            
                    endwin();

            
                    return 0;

            
            }


            void print_menu(WINDOW *menu_win, int highlight)

            
            {

            
                    int x, y, i;


                    x = 2;

            
                    y = 2;

            
                    box(menu_win, 0, 0);

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                    {       if(highlight == i + 1) /* High light the present choice */

            
                            {       wattron(menu_win, A_REVERSE);

            
                                    mvwprintw(menu_win, y, x, "%s", choices[i]);

            
                                    wattroff(menu_win, A_REVERSE);

            
                            }

            
                            else

            
                                    mvwprintw(menu_win, y, x, "%s", choices[i]);

            
                            ++y;

            
                    }

            
                    wrefresh(menu_win);

            
            }

            
            </span></pre>

            
                    </div>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="MOUSE" id="MOUSE">12. Interfacing

            
                  with the mouse</a></h2>


                  <p>Now that you have seen how to get keys, lets do the same

            
                  thing from mouse. Usually each UI allows the user to interact

            
                  with both keyboard and mouse.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MOUSEBASICS" id=

            
                    "MOUSEBASICS">12.1. The Basics</a></h3>


                    <p>Before you do any thing else, the events you want to

            
                    receive have to be enabled with <tt class=

            
                    "LITERAL">mousemask()</tt>.</p>


                    <pre class=

            
                    "PROGRAMLISTING">    mousemask(  mmask_t newmask,    /* The events you want to listen to */

            
                            mmask_t *oldmask)    /* The old events mask                */</pre>

            
                    <p>The first parameter to above function is a bit mask of

            
                    events you would like to listen. By default, all the events

            
                    are turned off. The bit mask <tt class=

            
                    "LITERAL">ALL_MOUSE_EVENTS</tt> can be used to get all the

            
                    events.</p>


                    <p>The following are all the event masks:</p>


                    <pre class="PROGRAMLISTING">    Name            Description

            
                   ---------------------------------------------------------------------

            
                   BUTTON1_PRESSED          mouse button 1 down

            
                   BUTTON1_RELEASED         mouse button 1 up

            
                   BUTTON1_CLICKED          mouse button 1 clicked

            
                   BUTTON1_DOUBLE_CLICKED   mouse button 1 double clicked

            
                   BUTTON1_TRIPLE_CLICKED   mouse button 1 triple clicked

            
                   BUTTON2_PRESSED          mouse button 2 down

            
                   BUTTON2_RELEASED         mouse button 2 up

            
                   BUTTON2_CLICKED          mouse button 2 clicked

            
                   BUTTON2_DOUBLE_CLICKED   mouse button 2 double clicked

            
                   BUTTON2_TRIPLE_CLICKED   mouse button 2 triple clicked

            
                   BUTTON3_PRESSED          mouse button 3 down

            
                   BUTTON3_RELEASED         mouse button 3 up

            
                   BUTTON3_CLICKED          mouse button 3 clicked

            
                   BUTTON3_DOUBLE_CLICKED   mouse button 3 double clicked

            
                   BUTTON3_TRIPLE_CLICKED   mouse button 3 triple clicked

            
                   BUTTON4_PRESSED          mouse button 4 down

            
                   BUTTON4_RELEASED         mouse button 4 up

            
                   BUTTON4_CLICKED          mouse button 4 clicked

            
                   BUTTON4_DOUBLE_CLICKED   mouse button 4 double clicked

            
                   BUTTON4_TRIPLE_CLICKED   mouse button 4 triple clicked

            
                   BUTTON_SHIFT             shift was down during button state change

            
                   BUTTON_CTRL              control was down during button state change

            
                   BUTTON_ALT               alt was down during button state change

            
                   ALL_MOUSE_EVENTS         report all button state changes

            
                   REPORT_MOUSE_POSITION    report mouse movement</pre>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="GETTINGEVENTS" id=

            
                    "GETTINGEVENTS">12.2. Getting the events</a></h3>


                    <p>Once a class of mouse events have been enabled, getch()

            
                    class of functions return KEY_MOUSE every time some mouse

            
                    event happens. Then the mouse event can be retrieved with

            
                    <tt class="LITERAL">getmouse()</tt>.</p>


                    <p>The code approximately looks like this:</p>


                    <pre class="PROGRAMLISTING">    MEVENT event;


                ch = getch();

            
                if(ch == KEY_MOUSE)

            
                    if(getmouse(&amp;event) == OK)

            
                        .    /* Do some thing with the event */

            
                        .

            
                        .</pre>

            
                    <p>getmouse() returns the event into the pointer given to

            
                    it. It is a structure which contains</p>


                    <pre class="PROGRAMLISTING">    typedef struct

            
                {

            
                    short id;         /* ID to distinguish multiple devices */

            
                    int x, y, z;      /* event coordinates */

            
                    mmask_t bstate;   /* button state bits */

            
                }    </pre>

            
                    <p>The <tt class="LITERAL">bstate</tt> is the main variable

            
                    we are interested in. It tells the button state of the

            
                    mouse.</p>


                    <p>Then with a code snippet like the following, we can find

            
                    out what happened.</p>


                    <pre class=

            
                    "PROGRAMLISTING">    if(event.bstate &amp; BUTTON1_PRESSED)

            
                    printw("Left Button Pressed");</pre>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MOUSETOGETHER" id=

            
                    "MOUSETOGETHER">12.3. Putting it all Together</a></h3>


                    <p>That's pretty much interfacing with mouse. Let's create

            
                    the same menu and enable mouse interaction. To make things

            
                    simpler, key handling is removed.</p>


                    <div class="EXAMPLE">

            
                      <a name="BMOME" id="BMOME"></a>

            
                      <p><b>Example 11. Access the menu with mouse !!!</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;string.h&gt;

            
            #include &lt;curses.h&gt;


            #define WIDTH 30

            
            #define HEIGHT 10


            int startx = 0;

            
            int starty = 0;


            char *choices[] = {     "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Exit",

            
                              };


            int n_choices = sizeof(choices) / sizeof(char *);


            void print_menu(WINDOW *menu_win, int highlight);

            
            void report_choice(int mouse_x, int mouse_y, int *p_choice);


            int main()

            
            {       int c, choice = 0;

            
                    WINDOW *menu_win;

            
                    MEVENT event;


                    /* Initialize curses */

            
                    initscr();

            
                    clear();

            
                    noecho();

            
                    cbreak();       //Line buffering disabled. pass on everything


                    /* Try to put the window in the middle of screen */

            
                    startx = (80 - WIDTH) / 2;

            
                    starty = (24 - HEIGHT) / 2;


                    attron(A_REVERSE);

            
                    mvprintw(23, 1, "Click on Exit to quit (Works best in a virtual console)");

            
                    refresh();

            
                    attroff(A_REVERSE);


                    /* Print the menu for the first time */

            
                    menu_win = newwin(HEIGHT, WIDTH, starty, startx);

            
                    print_menu(menu_win, 1);

            
                    /* Get all the mouse events */

            
                    mousemask(ALL_MOUSE_EVENTS, NULL);


                    while(1)

            
                    {       c = wgetch(menu_win);

            
                            switch(c)

            
                            {       case KEY_MOUSE:

            
                                    if(getmouse(&amp;event) == OK)

            
                                    {       /* When the user clicks left mouse button */

            
                                            if(event.bstate &amp; BUTTON1_PRESSED)

            
                                            {       report_choice(event.x + 1, event.y + 1, &amp;choice);

            
                                                    if(choice == -1) //Exit chosen

            
                                                            goto end;

            
                                                    mvprintw(22, 1, "Choice made is : %d String Chosen is \"%10s\"", choice, choices[choice - 1]);

            
                                                    refresh();

            
                                            }

            
                                    }

            
                                    print_menu(menu_win, choice);

            
                                    break;

            
                            }

            
                    }

            
            end:

            
                    endwin();

            
                    return 0;

            
            }


            void print_menu(WINDOW *menu_win, int highlight)

            
            {

            
                    int x, y, i;


                    x = 2;

            
                    y = 2;

            
                    box(menu_win, 0, 0);

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                    {       if(highlight == i + 1)

            
                            {       wattron(menu_win, A_REVERSE);

            
                                    mvwprintw(menu_win, y, x, "%s", choices[i]);

            
                                    wattroff(menu_win, A_REVERSE);

            
                            }

            
                            else

            
                                    mvwprintw(menu_win, y, x, "%s", choices[i]);

            
                            ++y;

            
                    }

            
                    wrefresh(menu_win);

            
            }


            /* Report the choice according to mouse position */

            
            void report_choice(int mouse_x, int mouse_y, int *p_choice)

            
            {       int i,j, choice;


                    i = startx + 2;

            
                    j = starty + 3;


                    for(choice = 0; choice &lt; n_choices; ++choice)

            
                            if(mouse_y == j + choice &amp;&amp; mouse_x &gt;= i &amp;&amp; mouse_x &lt;= i + strlen(choices[choice]))

            
                            {       if(choice == n_choices - 1)

            
                                            *p_choice = -1;

            
                                    else

            
                                            *p_choice = choice + 1;

            
                                    break;

            
                            }

            
            }</span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MISCMOUSEFUNCS" id=

            
                    "MISCMOUSEFUNCS">12.4. Miscellaneous Functions</a></h3>


                    <p>The functions mouse_trafo() and wmouse_trafo() can be

            
                    used to convert to mouse co-ordinates to screen relative

            
                    co-ordinates. See curs_mouse(3X) man page for details.</p>


                    <p>The mouseinterval function sets the maximum time (in

            
                    thousands of a second) that can elapse between press and

            
                    release events in order for them to be recognized as a

            
                    click. This function returns the previous interval value.

            
                    The default is one fifth of a second.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="SCREEN" id="SCREEN">13. Screen

            
                  Manipulation</a></h2>


                  <p>In this section, we will look into some functions, which

            
                  allow us to manage the screen efficiently and to write some

            
                  fancy programs. This is especially important in writing

            
                  games.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="GETYX" id="GETYX">13.1. getyx()

            
                    functions</a></h3>


                    <p>The function <tt class="LITERAL">getyx()</tt> can be

            
                    used to find out the present cursor co-ordinates. It will

            
                    fill the values of x and y co-ordinates in the arguments

            
                    given to it. Since getyx() is a macro you don't have to

            
                    pass the address of the variables. It can be called as</p>


                    <pre class="PROGRAMLISTING">    getyx(win, y, x);

            
                /* win: window pointer

            
                 *   y, x: y, x co-ordinates will be put into this variables

            
                 */</pre>

            
                    <p>The function getparyx() gets the beginning co-ordinates

            
                    of the sub window relative to the main window. This is some

            
                    times useful to update a sub window. When designing fancy

            
                    stuff like writing multiple menus, it becomes difficult to

            
                    store the menu positions, their first option co-ordinates,

            
                    etc. A simple solution to this problem, is to create menus

            
                    in sub windows and later find the starting co-ordinates of

            
                    the menus by using getparyx().</p>


                    <p>The functions getbegyx() and getmaxyx() store current

            
                    window's beginning and maximum co-ordinates. These

            
                    functions are useful in the same way as above in managing

            
                    the windows and sub windows effectively.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="SCREENDUMP" id=

            
                    "SCREENDUMP">13.2. Screen Dumping</a></h3>


                    <p>While writing games, some times it becomes necessary to

            
                    store the state of the screen and restore it back to the

            
                    same state. The function scr_dump() can be used to dump the

            
                    screen contents to a file given as an argument. Later it

            
                    can be restored by scr_restore function. These two simple

            
                    functions can be used effectively to maintain a fast moving

            
                    game with changing scenarios.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="WINDOWDUMP" id=

            
                    "WINDOWDUMP">13.3. Window Dumping</a></h3>


                    <p>To store and restore windows, the functions <tt class=

            
                    "LITERAL">putwin()</tt> and <tt class=

            
                    "LITERAL">getwin()</tt> can be used. <tt class=

            
                    "LITERAL">putwin()</tt> puts the present window state into

            
                    a file, which can be later restored by <tt class=

            
                    "LITERAL">getwin()</tt>.</p>


                    <p>The function <tt class="LITERAL">copywin()</tt> can be

            
                    used to copy a window completely onto another window. It

            
                    takes the source and destination windows as parameters and

            
                    according to the rectangle specified, it copies the

            
                    rectangular region from source to destination window. Its

            
                    last parameter specifies whether to overwrite or just

            
                    overlay the contents on to the destination window. If this

            
                    argument is true, then the copying is non-destructive.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="MISC" id="MISC">14. Miscellaneous

            
                  features</a></h2>


                  <p>Now you know enough features to write a good curses

            
                  program, with all bells and whistles. There are some

            
                  miscellaneous functions which are useful in various cases.

            
                  Let's go headlong into some of those.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="CURSSET" id="CURSSET">14.1.

            
                    curs_set()</a></h3>


                    <p>This function can be used to make the cursor invisible.

            
                    The parameter to this function should be</p>


                    <pre class="PROGRAMLISTING">    0 : invisible      or

            
                1 : normal    or

            
                2 : very visible.</pre>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="TEMPLEAVE" id="TEMPLEAVE">14.2.

            
                    Temporarily Leaving Curses mode</a></h3>


                    <p>Some times you may want to get back to cooked mode

            
                    (normal line buffering mode) temporarily. In such a case

            
                    you will first need to save the tty modes with a call to

            
                    <tt class="LITERAL">def_prog_mode()</tt> and then call

            
                    <tt class="LITERAL">endwin()</tt> to end the curses mode.

            
                    This will leave you in the original tty mode. To get back

            
                    to curses once you are done, call <tt class=

            
                    "LITERAL">reset_prog_mode()</tt> . This function returns

            
                    the tty to the state stored by <tt class=

            
                    "LITERAL">def_prog_mode()</tt>. Then do refresh(), and you

            
                    are back to the curses mode. Here is an example showing the

            
                    sequence of things to be done.</p>


                    <div class="EXAMPLE">

            
                      <a name="BTELE" id="BTELE"></a>

            
                      <p><b>Example 12. Temporarily Leaving Curses Mode</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;curses.h&gt;


            int main()

            
            {

            
                    initscr();                      /* Start curses mode              */

            
                    printw("Hello World !!!\n");    /* Print Hello World              */

            
                    refresh();                      /* Print it on to the real screen */

            
                    def_prog_mode();                /* Save the tty modes             */

            
                    endwin();                       /* End curses mode temporarily    */

            
                    system("/bin/sh");              /* Do whatever you like in cooked mode */

            
                    reset_prog_mode();              /* Return to the previous tty mode*/

            
                                                    /* stored by def_prog_mode()      */

            
                    refresh();                      /* Do refresh() to restore the    */

            
                                                    /* Screen contents                */

            
                    printw("Another String\n");     /* Back to curses use the full    */

            
                    refresh();                      /* capabilities of curses         */

            
                    endwin();                       /* End curses mode                */


                    return 0;

            
            }</span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="ACSVARS" id="ACSVARS">14.3. ACS_

            
                    variables</a></h3>


                    <p>If you have ever programmed in DOS, you know about those

            
                    nifty characters in extended character set. They are

            
                    printable only on some terminals. NCURSES functions like

            
                    <tt class="LITERAL">box()</tt> use these characters. All

            
                    these variables start with ACS meaning alternative

            
                    character set. You might have noticed me using these

            
                    characters in some of the programs above. Here is an

            
                    example showing all the characters.</p>


                    <div class="EXAMPLE">

            
                      <a name="BACSVARS" id="BACSVARS"></a>

            
                      <p><b>Example 13. ACS Variables Example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;curses.h&gt;


            int main()

            
            {

            
                    initscr();


                    printw("Upper left corner           "); addch(ACS_ULCORNER); printw("\n");

            
                    printw("Lower left corner           "); addch(ACS_LLCORNER); printw("\n");

            
                    printw("Lower right corner          "); addch(ACS_LRCORNER); printw("\n");

            
                    printw("Tee pointing right          "); addch(ACS_LTEE); printw("\n");

            
                    printw("Tee pointing left           "); addch(ACS_RTEE); printw("\n");

            
                    printw("Tee pointing up             "); addch(ACS_BTEE); printw("\n");

            
                    printw("Tee pointing down           "); addch(ACS_TTEE); printw("\n");

            
                    printw("Horizontal line             "); addch(ACS_HLINE); printw("\n");

            
                    printw("Vertical line               "); addch(ACS_VLINE); printw("\n");

            
                    printw("Large Plus or cross over    "); addch(ACS_PLUS); printw("\n");

            
                    printw("Scan Line 1                 "); addch(ACS_S1); printw("\n");

            
                    printw("Scan Line 3                 "); addch(ACS_S3); printw("\n");

            
                    printw("Scan Line 7                 "); addch(ACS_S7); printw("\n");

            
                    printw("Scan Line 9                 "); addch(ACS_S9); printw("\n");

            
                    printw("Diamond                     "); addch(ACS_DIAMOND); printw("\n");

            
                    printw("Checker board (stipple)     "); addch(ACS_CKBOARD); printw("\n");

            
                    printw("Degree Symbol               "); addch(ACS_DEGREE); printw("\n");

            
                    printw("Plus/Minus Symbol           "); addch(ACS_PLMINUS); printw("\n");

            
                    printw("Bullet                      "); addch(ACS_BULLET); printw("\n");

            
                    printw("Arrow Pointing Left         "); addch(ACS_LARROW); printw("\n");

            
                    printw("Arrow Pointing Right        "); addch(ACS_RARROW); printw("\n");

            
                    printw("Arrow Pointing Down         "); addch(ACS_DARROW); printw("\n");

            
                    printw("Arrow Pointing Up           "); addch(ACS_UARROW); printw("\n");

            
                    printw("Board of squares            "); addch(ACS_BOARD); printw("\n");

            
                    printw("Lantern Symbol              "); addch(ACS_LANTERN); printw("\n");

            
                    printw("Solid Square Block          "); addch(ACS_BLOCK); printw("\n");

            
                    printw("Less/Equal sign             "); addch(ACS_LEQUAL); printw("\n");

            
                    printw("Greater/Equal sign          "); addch(ACS_GEQUAL); printw("\n");

            
                    printw("Pi                          "); addch(ACS_PI); printw("\n");

            
                    printw("Not equal                   "); addch(ACS_NEQUAL); printw("\n");

            
                    printw("UK pound sign               "); addch(ACS_STERLING); printw("\n");


                    refresh();

            
                    getch();

            
                    endwin();


                    return 0;

            
            }</span></pre>

            
                    </div>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="OTHERLIB" id="OTHERLIB">15. Other

            
                  libraries</a></h2>


                  <p>Apart from the curses library, there are few text mode

            
                  libraries, which provide more functionality and a lot of

            
                  features. The following sections explain three standard

            
                  libraries which are usually distributed along with

            
                  curses.</p>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="PANELS" id="PANELS">16. Panel

            
                  Library</a></h2>


                  <p>Now that you are proficient in curses, you wanted to do

            
                  some thing big. You created a lot of overlapping windows to

            
                  give a professional windows-type look. Unfortunately, it soon

            
                  becomes difficult to manage these. The multiple refreshes,

            
                  updates plunge you into a nightmare. The overlapping windows

            
                  create blotches, whenever you forget to refresh the windows

            
                  in the proper order.</p>


                  <p>Don't despair. There is an elegant solution provided in

            
                  panels library. In the words of developers of ncurses</p>


                  <p><span class="emphasis"><i class="EMPHASIS">When your

            
                  interface design is such that windows may dive deeper into

            
                  the visibility stack or pop to the top at runtime, the

            
                  resulting book-keeping can be tedious and difficult to get

            
                  right. Hence the panels library.</i></span>

            
                  </p>


                  <p>If you have lot of overlapping windows, then panels

            
                  library is the way to go. It obviates the need of doing

            
                  series of wnoutrefresh(), doupdate() and relieves the burden

            
                  of doing it correctly(bottom up). The library maintains

            
                  information about the order of windows, their overlapping and

            
                  update the screen properly. So why wait? Let's take a close

            
                  peek into panels.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PANELBASICS" id=

            
                    "PANELBASICS">16.1. The Basics</a></h3>


                    <p>Panel object is a window that is implicitly treated as

            
                    part of a deck including all other panel objects. The deck

            
                    is treated as a stack with the top panel being completely

            
                    visible and the other panels may or may not be obscured

            
                    according to their positions. So the basic idea is to

            
                    create a stack of overlapping panels and use panels library

            
                    to display them correctly. There is a function similar to

            
                    refresh() which, when called , displays panels in the

            
                    correct order. Functions are provided to hide or show

            
                    panels, move panels, change its size, etc. The overlapping

            
                    problem is managed by the panels library during all the

            
                    calls to these functions.</p>


                    <p>The general flow of a panel program goes like this:</p>


                    <ol type="1">

            
                      <li>

            
                        <p>Create the windows (with newwin()) to be attached to

            
                        the panels.</p>

            
                      </li>


                      <li>

            
                        <p>Create panels with the chosen visibility order.

            
                        Stack them up according to the desired visibility. The

            
                        function new_panel() is used to created panels.</p>

            
                      </li>


                      <li>

            
                        <p>Call update_panels() to write the panels to the

            
                        virtual screen in correct visibility order. Do a

            
                        doupdate() to show it on the screen.</p>

            
                      </li>


                      <li>

            
                        <p>Mainpulate the panels with show_panel(),

            
                        hide_panel(), move_panel(), etc. Make use of helper

            
                        functions like panel_hidden() and panel_window(). Make

            
                        use of user pointer to store custom data for a panel.

            
                        Use the functions set_panel_userptr() and

            
                        panel_userptr() to set and get the user pointer for a

            
                        panel.</p>

            
                      </li>


                      <li>

            
                        <p>When you are done with the panel use del_panel() to

            
                        delete the panel.</p>

            
                      </li>

            
                    </ol>


                    <p>Let's make the concepts clear, with some programs. The

            
                    following is a simple program which creates 3 overlapping

            
                    panels and shows them on the screen.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="COMPILEPANELS" id=

            
                    "COMPILEPANELS">16.2. Compiling With the Panels Library</a></h3>


                    <p>To use panels library functions, you have to include

            
                    panel.h and to link the program with panels library the

            
                    flag -lpanel should be added along with -lncurses in that

            
                    order.</p>


                    <pre class="PROGRAMLISTING">    #include &lt;panel.h&gt;

            
                .

            
                .

            
                .


                compile and link: gcc &lt;program file&gt; -lpanel -lncurses</pre>

            
                    <div class="EXAMPLE">

            
                      <a name="PPASI" id="PPASI"></a>

            
                      <p><b>Example 14. Panel basics</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;panel.h&gt;


            int main()

            
            {       WINDOW *my_wins[3];

            
                    PANEL  *my_panels[3];

            
                    int lines = 10, cols = 40, y = 2, x = 4, i;


                    initscr();

            
                    cbreak();

            
                    noecho();


                    /* Create windows for the panels */

            
                    my_wins[0] = newwin(lines, cols, y, x);

            
                    my_wins[1] = newwin(lines, cols, y + 1, x + 5);

            
                    my_wins[2] = newwin(lines, cols, y + 2, x + 10);


                    /*

            
                     * Create borders around the windows so that you can see the effect

            
                     * of panels

            
                     */

            
                    for(i = 0; i &lt; 3; ++i)

            
                            box(my_wins[i], 0, 0);


                    /* Attach a panel to each window */     /* Order is bottom up */

            
                    my_panels[0] = new_panel(my_wins[0]);   /* Push 0, order: stdscr-0 */

            
                    my_panels[1] = new_panel(my_wins[1]);   /* Push 1, order: stdscr-0-1 */

            
                    my_panels[2] = new_panel(my_wins[2]);   /* Push 2, order: stdscr-0-1-2 */


                    /* Update the stacking order. 2nd panel will be on top */

            
                    update_panels();


                    /* Show it on the screen */

            
                    doupdate();


                    getch();

            
                    endwin();

            
            }

            
            </span></pre>

            
                    </div>


                    <p>As you can see, above program follows a simple flow as

            
                    explained. The windows are created with newwin() and then

            
                    they are attached to panels with new_panel(). As we attach

            
                    one panel after another, the stack of panels gets updated.

            
                    To put them on screen update_panels() and doupdate() are

            
                    called.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PANELBROWSING" id=

            
                    "PANELBROWSING">16.3. Panel Window Browsing</a></h3>


                    <p>A slightly complicated example is given below. This

            
                    program creates 3 windows which can be cycled through using

            
                    tab. Have a look at the code.</p>


                    <div class="EXAMPLE">

            
                      <a name="PPABR" id="PPABR"></a>

            
                      <p><b>Example 15. Panel Window Browsing Example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;string.h&gt;

            
            #include &lt;panel.h&gt;


            #define NLINES 10

            
            #define NCOLS 40


            void init_wins(WINDOW **wins, int n);

            
            void win_show(WINDOW *win, char *label, int label_color);

            
            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);


            int main()

            
            {       WINDOW *my_wins[3];

            
                    PANEL  *my_panels[3];

            
                    PANEL  *top;

            
                    int ch;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize all the colors */

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);

            
                    init_pair(2, COLOR_GREEN, COLOR_BLACK);

            
                    init_pair(3, COLOR_BLUE, COLOR_BLACK);

            
                    init_pair(4, COLOR_CYAN, COLOR_BLACK);


                    init_wins(my_wins, 3);


                    /* Attach a panel to each window */     /* Order is bottom up */

            
                    my_panels[0] = new_panel(my_wins[0]);   /* Push 0, order: stdscr-0 */

            
                    my_panels[1] = new_panel(my_wins[1]);   /* Push 1, order: stdscr-0-1 */

            
                    my_panels[2] = new_panel(my_wins[2]);   /* Push 2, order: stdscr-0-1-2 */


                    /* Set up the user pointers to the next panel */

            
                    set_panel_userptr(my_panels[0], my_panels[1]);

            
                    set_panel_userptr(my_panels[1], my_panels[2]);

            
                    set_panel_userptr(my_panels[2], my_panels[0]);


                    /* Update the stacking order. 2nd panel will be on top */

            
                    update_panels();


                    /* Show it on the screen */

            
                    attron(COLOR_PAIR(4));

            
                    mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");

            
                    attroff(COLOR_PAIR(4));

            
                    doupdate();


                    top = my_panels[2];

            
                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case 9:

            
                                            top = (PANEL *)panel_userptr(top);

            
                                            top_panel(top);

            
                                            break;

            
                            }

            
                            update_panels();

            
                            doupdate();

            
                    }

            
                    endwin();

            
                    return 0;

            
            }


            /* Put all the windows */

            
            void init_wins(WINDOW **wins, int n)

            
            {       int x, y, i;

            
                    char label[80];


                    y = 2;

            
                    x = 10;

            
                    for(i = 0; i &lt; n; ++i)

            
                    {       wins[i] = newwin(NLINES, NCOLS, y, x);

            
                            sprintf(label, "Window Number %d", i + 1);

            
                            win_show(wins[i], label, i + 1);

            
                            y += 3;

            
                            x += 7;

            
                    }

            
            }


            /* Show the window with a border and a label */

            
            void win_show(WINDOW *win, char *label, int label_color)

            
            {       int startx, starty, height, width;


                    getbegyx(win, starty, startx);

            
                    getmaxyx(win, height, width);


                    box(win, 0, 0);

            
                    mvwaddch(win, 2, 0, ACS_LTEE);

            
                    mvwhline(win, 2, 1, ACS_HLINE, width - 2);

            
                    mvwaddch(win, 2, width - 1, ACS_RTEE);


                    print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));

            
            }


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)

            
            {       int length, x, y;

            
                    float temp;


                    if(win == NULL)

            
                            win = stdscr;

            
                    getyx(win, y, x);

            
                    if(startx != 0)

            
                            x = startx;

            
                    if(starty != 0)

            
                            y = starty;

            
                    if(width == 0)

            
                            width = 80;


                    length = strlen(string);

            
                    temp = (width - length)/ 2;

            
                    x = startx + (int)temp;

            
                    wattron(win, color);

            
                    mvwprintw(win, y, x, "%s", string);

            
                    wattroff(win, color);

            
                    refresh();

            
            }</span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="USERPTRUSING" id=

            
                    "USERPTRUSING">16.4. Using User Pointers</a></h3>


                    <p>In the above example I used user pointers to find out

            
                    the next window in the cycle. We can attach custom

            
                    information to the panel by specifying a user pointer,

            
                    which can point to any information you want to store. In

            
                    this case I stored the pointer to the next panel in the

            
                    cycle. User pointer for a panel can be set with the

            
                    function <tt class="LITERAL">set_panel_userptr()</tt>. It

            
                    can be accessed using the function <tt class=

            
                    "LITERAL">panel_userptr()</tt> which will return the user

            
                    pointer for the panel given as argument. After finding the

            
                    next panel in the cycle, it is brought to the top by the

            
                    function top_panel(). This function brings the panel given

            
                    as argument to the top of the panel stack.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PANELMOVERESIZE" id=

            
                    "PANELMOVERESIZE">16.5. Moving and Resizing Panels</a></h3>


                    <p>The function <tt class="LITERAL">move_panel()</tt> can

            
                    be used to move a panel to the desired location. It does

            
                    not change the position of the panel in the stack. Make

            
                    sure that you use move_panel() instead mvwin() on the

            
                    window associated with the panel.</p>


                    <p>Resizing a panel is slightly complex. There is no

            
                    straight forward function just to resize the window

            
                    associated with a panel. A solution to resize a panel is to

            
                    create a new window with the desired sizes, change the

            
                    window associated with the panel using replace_panel().

            
                    Don't forget to delete the old window. The window

            
                    associated with a panel can be found by using the function

            
                    panel_window().</p>


                    <p>The following program shows these concepts, in

            
                    supposedly simple program. You can cycle through the window

            
                    with &lt;TAB&gt; as usual. To resize or move the active

            
                    panel press 'r' for resize 'm' for moving. Then use arrow

            
                    keys to resize or move it to the desired way and press

            
                    enter to end your resizing or moving. This example makes

            
                    use of user data to get the required data to do the

            
                    operations.</p>


                    <div class="EXAMPLE">

            
                      <a name="PPARE" id="PPARE"></a>

            
                      <p><b>Example 16. Panel Moving and Resizing example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;string.h&gt;

            
            #include &lt;panel.h&gt;


            typedef struct _PANEL_DATA {

            
                    int x, y, w, h;

            
                    char label[80];

            
                    int label_color;

            
                    PANEL *next;

            
            }PANEL_DATA;


            #define NLINES 10

            
            #define NCOLS 40


            void init_wins(WINDOW **wins, int n);

            
            void win_show(WINDOW *win, char *label, int label_color);

            
            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);

            
            void set_user_ptrs(PANEL **panels, int n);


            int main()

            
            {       WINDOW *my_wins[3];

            
                    PANEL  *my_panels[3];

            
                    PANEL_DATA  *top;

            
                    PANEL *stack_top;

            
                    WINDOW *temp_win, *old_win;

            
                    int ch;

            
                    int newx, newy, neww, newh;

            
                    int size = FALSE, move = FALSE;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize all the colors */

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);

            
                    init_pair(2, COLOR_GREEN, COLOR_BLACK);

            
                    init_pair(3, COLOR_BLUE, COLOR_BLACK);

            
                    init_pair(4, COLOR_CYAN, COLOR_BLACK);


                    init_wins(my_wins, 3);


                    /* Attach a panel to each window */     /* Order is bottom up */

            
                    my_panels[0] = new_panel(my_wins[0]);   /* Push 0, order: stdscr-0 */

            
                    my_panels[1] = new_panel(my_wins[1]);   /* Push 1, order: stdscr-0-1 */

            
                    my_panels[2] = new_panel(my_wins[2]);   /* Push 2, order: stdscr-0-1-2 */


                    set_user_ptrs(my_panels, 3);

            
                    /* Update the stacking order. 2nd panel will be on top */

            
                    update_panels();


                    /* Show it on the screen */

            
                    attron(COLOR_PAIR(4));

            
                    mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");

            
                    mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");

            
                    attroff(COLOR_PAIR(4));

            
                    doupdate();


                    stack_top = my_panels[2];

            
                    top = (PANEL_DATA *)panel_userptr(stack_top);

            
                    newx = top-&gt;x;

            
                    newy = top-&gt;y;

            
                    neww = top-&gt;w;

            
                    newh = top-&gt;h;

            
                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case 9:         /* Tab */

            
                                            top = (PANEL_DATA *)panel_userptr(stack_top);

            
                                            top_panel(top-&gt;next);

            
                                            stack_top = top-&gt;next;

            
                                            top = (PANEL_DATA *)panel_userptr(stack_top);

            
                                            newx = top-&gt;x;

            
                                            newy = top-&gt;y;

            
                                            neww = top-&gt;w;

            
                                            newh = top-&gt;h;

            
                                            break;

            
                                    case 'r':       /* Re-Size*/

            
                                            size = TRUE;

            
                                            attron(COLOR_PAIR(4));

            
                                            mvprintw(LINES - 4, 0, "Entered Resizing :Use Arrow Keys to resize and press &lt;ENTER&gt; to end resizing");

            
                                            refresh();

            
                                            attroff(COLOR_PAIR(4));

            
                                            break;

            
                                    case 'm':       /* Move */

            
                                            attron(COLOR_PAIR(4));

            
                                            mvprintw(LINES - 4, 0, "Entered Moving: Use Arrow Keys to Move and press &lt;ENTER&gt; to end moving");

            
                                            refresh();

            
                                            attroff(COLOR_PAIR(4));

            
                                            move = TRUE;

            
                                            break;

            
                                    case KEY_LEFT:

            
                                            if(size == TRUE)

            
                                            {       --newx;

            
                                                    ++neww;

            
                                            }

            
                                            if(move == TRUE)

            
                                                    --newx;

            
                                            break;

            
                                    case KEY_RIGHT:

            
                                            if(size == TRUE)

            
                                            {       ++newx;

            
                                                    --neww;

            
                                            }

            
                                            if(move == TRUE)

            
                                                    ++newx;

            
                                            break;

            
                                    case KEY_UP:

            
                                            if(size == TRUE)

            
                                            {       --newy;

            
                                                    ++newh;

            
                                            }

            
                                            if(move == TRUE)

            
                                                    --newy;

            
                                            break;

            
                                    case KEY_DOWN:

            
                                            if(size == TRUE)

            
                                            {       ++newy;

            
                                                    --newh;

            
                                            }

            
                                            if(move == TRUE)

            
                                                    ++newy;

            
                                            break;

            
                                    case 10:        /* Enter */

            
                                            move(LINES - 4, 0);

            
                                            clrtoeol();

            
                                            refresh();

            
                                            if(size == TRUE)

            
                                            {       old_win = panel_window(stack_top);

            
                                                    temp_win = newwin(newh, neww, newy, newx);

            
                                                    replace_panel(stack_top, temp_win);

            
                                                    win_show(temp_win, top-&gt;label, top-&gt;label_color);

            
                                                    delwin(old_win);

            
                                                    size = FALSE;

            
                                            }

            
                                            if(move == TRUE)

            
                                            {       move_panel(stack_top, newy, newx);

            
                                                    move = FALSE;

            
                                            }

            
                                            break;


                            }

            
                            attron(COLOR_PAIR(4));

            
                            mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");

            
                            mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");

            
                            attroff(COLOR_PAIR(4));

            
                            refresh();

            
                            update_panels();

            
                            doupdate();

            
                    }

            
                    endwin();

            
                    return 0;

            
            }


            /* Put all the windows */

            
            void init_wins(WINDOW **wins, int n)

            
            {       int x, y, i;

            
                    char label[80];


                    y = 2;

            
                    x = 10;

            
                    for(i = 0; i &lt; n; ++i)

            
                    {       wins[i] = newwin(NLINES, NCOLS, y, x);

            
                            sprintf(label, "Window Number %d", i + 1);

            
                            win_show(wins[i], label, i + 1);

            
                            y += 3;

            
                            x += 7;

            
                    }

            
            }


            /* Set the PANEL_DATA structures for individual panels */

            
            void set_user_ptrs(PANEL **panels, int n)

            
            {       PANEL_DATA *ptrs;

            
                    WINDOW *win;

            
                    int x, y, w, h, i;

            
                    char temp[80];


                    ptrs = (PANEL_DATA *)calloc(n, sizeof(PANEL_DATA));


                    for(i = 0;i &lt; n; ++i)

            
                    {       win = panel_window(panels[i]);

            
                            getbegyx(win, y, x);

            
                            getmaxyx(win, h, w);

            
                            ptrs[i].x = x;

            
                            ptrs[i].y = y;

            
                            ptrs[i].w = w;

            
                            ptrs[i].h = h;

            
                            sprintf(temp, "Window Number %d", i + 1);

            
                            strcpy(ptrs[i].label, temp);

            
                            ptrs[i].label_color = i + 1;

            
                            if(i + 1 == n)

            
                                    ptrs[i].next = panels[0];

            
                            else

            
                                    ptrs[i].next = panels[i + 1];

            
                            set_panel_userptr(panels[i], &amp;ptrs[i]);

            
                    }

            
            }


            /* Show the window with a border and a label */

            
            void win_show(WINDOW *win, char *label, int label_color)

            
            {       int startx, starty, height, width;


                    getbegyx(win, starty, startx);

            
                    getmaxyx(win, height, width);


                    box(win, 0, 0);

            
                    mvwaddch(win, 2, 0, ACS_LTEE);

            
                    mvwhline(win, 2, 1, ACS_HLINE, width - 2);

            
                    mvwaddch(win, 2, width - 1, ACS_RTEE);


                    print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));

            
            }


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)

            
            {       int length, x, y;

            
                    float temp;


                    if(win == NULL)

            
                            win = stdscr;

            
                    getyx(win, y, x);

            
                    if(startx != 0)

            
                            x = startx;

            
                    if(starty != 0)

            
                            y = starty;

            
                    if(width == 0)

            
                            width = 80;


                    length = strlen(string);

            
                    temp = (width - length)/ 2;

            
                    x = startx + (int)temp;

            
                    wattron(win, color);

            
                    mvwprintw(win, y, x, "%s", string);

            
                    wattroff(win, color);

            
                    refresh();

            
            }</span></pre>

            
                    </div>


                    <p>Concentrate on the main while loop. Once it finds out

            
                    the type of key pressed, it takes appropriate action. If

            
                    'r' is pressed resizing mode is started. After this the new

            
                    sizes are updated as the user presses the arrow keys. When

            
                    the user presses &lt;ENTER&gt; present selection ends and

            
                    panel is resized by using the concept explained. While in

            
                    resizing mode the program doesn't show how the window is

            
                    getting resized. It is left as an exercise to the reader to

            
                    print a dotted border while it gets resized to a new

            
                    position.</p>


                    <p>When the user presses 'm' the move mode starts. This is

            
                    a bit simpler than resizing. As the arrow keys are pressed

            
                    the new position is updated and pressing of &lt;ENTER&gt;

            
                    causes the panel to be moved by calling the function

            
                    move_panel().</p>


                    <p>In this program the user data which is represented as

            
                    PANEL_DATA, plays very important role in finding the

            
                    associated information with a panel. As written in the

            
                    comments, the PANEL_DATA stores the panel sizes, label,

            
                    label color and a pointer to the next panel in the

            
                    cycle.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PANELSHOWHIDE" id=

            
                    "PANELSHOWHIDE">16.6. Hiding and Showing Panels</a></h3>


                    <p>A Panel can be hidden by using the function

            
                    hide_panel(). This function merely removes it form the

            
                    stack of panels, thus hiding it on the screen once you do

            
                    update_panels() and doupdate(). It doesn't destroy the

            
                    PANEL structure associated with the hidden panel. It can be

            
                    shown again by using the show_panel() function.</p>


                    <p>The following program shows the hiding of panels. Press

            
                    'a' or 'b' or 'c' to show or hide first, second and third

            
                    windows respectively. It uses a user data with a small

            
                    variable hide, which keeps track of whether the window is

            
                    hidden or not. For some reason the function <tt class=

            
                    "LITERAL">panel_hidden()</tt> which tells whether a panel

            
                    is hidden or not is not working. A bug report was also

            
                    presented by Michael Andres <a href=

            
                    "http://www.geocrawler.com/archives/3/344/1999/9/0/2643549/"

            
                    target="_top">here</a></p>


                    <div class="EXAMPLE">

            
                      <a name="PPAHI" id="PPAHI"></a>

            
                      <p><b>Example 17. Panel Hiding and Showing example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;string.h&gt;

            
            #include &lt;panel.h&gt;


            typedef struct _PANEL_DATA {

            
                    int hide;       /* TRUE if panel is hidden */

            
            }PANEL_DATA;


            #define NLINES 10

            
            #define NCOLS 40


            void init_wins(WINDOW **wins, int n);

            
            void win_show(WINDOW *win, char *label, int label_color);

            
            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);


            int main()

            
            {       WINDOW *my_wins[3];

            
                    PANEL  *my_panels[3];

            
                    PANEL_DATA panel_datas[3];

            
                    PANEL_DATA *temp;

            
                    int ch;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize all the colors */

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);

            
                    init_pair(2, COLOR_GREEN, COLOR_BLACK);

            
                    init_pair(3, COLOR_BLUE, COLOR_BLACK);

            
                    init_pair(4, COLOR_CYAN, COLOR_BLACK);


                    init_wins(my_wins, 3);


                    /* Attach a panel to each window */     /* Order is bottom up */

            
                    my_panels[0] = new_panel(my_wins[0]);   /* Push 0, order: stdscr-0 */

            
                    my_panels[1] = new_panel(my_wins[1]);   /* Push 1, order: stdscr-0-1 */

            
                    my_panels[2] = new_panel(my_wins[2]);   /* Push 2, order: stdscr-0-1-2 */


                    /* Initialize panel data saying that nothing is hidden */

            
                    panel_datas[0].hide = FALSE;

            
                    panel_datas[1].hide = FALSE;

            
                    panel_datas[2].hide = FALSE;


                    set_panel_userptr(my_panels[0], &amp;panel_datas[0]);

            
                    set_panel_userptr(my_panels[1], &amp;panel_datas[1]);

            
                    set_panel_userptr(my_panels[2], &amp;panel_datas[2]);


                    /* Update the stacking order. 2nd panel will be on top */

            
                    update_panels();


                    /* Show it on the screen */

            
                    attron(COLOR_PAIR(4));

            
                    mvprintw(LINES - 3, 0, "Show or Hide a window with 'a'(first window)  'b'(Second Window)  'c'(Third Window)");

            
                    mvprintw(LINES - 2, 0, "F1 to Exit");


                    attroff(COLOR_PAIR(4));

            
                    doupdate();


                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case 'a':

            
                                            temp = (PANEL_DATA *)panel_userptr(my_panels[0]);

            
                                            if(temp-&gt;hide == FALSE)

            
                                            {       hide_panel(my_panels[0]);

            
                                                    temp-&gt;hide = TRUE;

            
                                            }

            
                                            else

            
                                            {       show_panel(my_panels[0]);

            
                                                    temp-&gt;hide = FALSE;

            
                                            }

            
                                            break;

            
                                    case 'b':

            
                                            temp = (PANEL_DATA *)panel_userptr(my_panels[1]);

            
                                            if(temp-&gt;hide == FALSE)

            
                                            {       hide_panel(my_panels[1]);

            
                                                    temp-&gt;hide = TRUE;

            
                                            }

            
                                            else

            
                                            {       show_panel(my_panels[1]);

            
                                                    temp-&gt;hide = FALSE;

            
                                            }

            
                                            break;

            
                                    case 'c':

            
                                            temp = (PANEL_DATA *)panel_userptr(my_panels[2]);

            
                                            if(temp-&gt;hide == FALSE)

            
                                            {       hide_panel(my_panels[2]);

            
                                                    temp-&gt;hide = TRUE;

            
                                            }

            
                                            else

            
                                            {       show_panel(my_panels[2]);

            
                                                    temp-&gt;hide = FALSE;

            
                                            }

            
                                            break;

            
                            }

            
                            update_panels();

            
                            doupdate();

            
                    }

            
                    endwin();

            
                    return 0;

            
            }


            /* Put all the windows */

            
            void init_wins(WINDOW **wins, int n)

            
            {       int x, y, i;

            
                    char label[80];


                    y = 2;

            
                    x = 10;

            
                    for(i = 0; i &lt; n; ++i)

            
                    {       wins[i] = newwin(NLINES, NCOLS, y, x);

            
                            sprintf(label, "Window Number %d", i + 1);

            
                            win_show(wins[i], label, i + 1);

            
                            y += 3;

            
                            x += 7;

            
                    }

            
            }


            /* Show the window with a border and a label */

            
            void win_show(WINDOW *win, char *label, int label_color)

            
            {       int startx, starty, height, width;


                    getbegyx(win, starty, startx);

            
                    getmaxyx(win, height, width);


                    box(win, 0, 0);

            
                    mvwaddch(win, 2, 0, ACS_LTEE);

            
                    mvwhline(win, 2, 1, ACS_HLINE, width - 2);

            
                    mvwaddch(win, 2, width - 1, ACS_RTEE);


                    print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));

            
            }


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)

            
            {       int length, x, y;

            
                    float temp;


                    if(win == NULL)

            
                            win = stdscr;

            
                    getyx(win, y, x);

            
                    if(startx != 0)

            
                            x = startx;

            
                    if(starty != 0)

            
                            y = starty;

            
                    if(width == 0)

            
                            width = 80;


                    length = strlen(string);

            
                    temp = (width - length)/ 2;

            
                    x = startx + (int)temp;

            
                    wattron(win, color);

            
                    mvwprintw(win, y, x, "%s", string);

            
                    wattroff(win, color);

            
                    refresh();

            
            }</span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PANELABOVE" id=

            
                    "PANELABOVE">16.7. panel_above() and panel_below()

            
                    Functions</a></h3>


                    <p>The functions <tt class="LITERAL">panel_above()</tt> and

            
                    <tt class="LITERAL">panel_below()</tt> can be used to find

            
                    out the panel above and below a panel. If the argument to

            
                    these functions is NULL, then they return a pointer to

            
                    bottom panel and top panel respectively.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="MENUS" id="MENUS">17. Menus

            
                  Library</a></h2>


                  <p>The menus library provides a nice extension to basic

            
                  curses, through which you can create menus. It provides a set

            
                  of functions to create menus. But they have to be customized

            
                  to give a nicer look, with colors, etc. Let's get into the

            
                  details.</p>


                  <p>A menu is a screen display that assists the user to choose

            
                  some subset of a given set of items. To put it simple, a menu

            
                  is a collection of items from which one or more items can be

            
                  chosen. Some readers might not be aware of multiple item

            
                  selection capability. Menu library provides functionality to

            
                  write menus from which the user can chose more than one item

            
                  as the preferred choice. This is dealt with in a later

            
                  section. Now it is time for some rudiments.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MENUBASICS" id=

            
                    "MENUBASICS">17.1. The Basics</a></h3>


                    <p>To create menus, you first create items, and then post

            
                    the menu to the display. After that, all the processing of

            
                    user responses is done in an elegant function menu_driver()

            
                    which is the work horse of any menu program.</p>


                    <p>The general flow of control of a menu program looks like

            
                    this.</p>


                    <ol type="1">

            
                      <li>

            
                        <p>Initialize curses</p>

            
                      </li>


                      <li>

            
                        <p>Create items using new_item(). You can specify a

            
                        name and description for the items.</p>

            
                      </li>


                      <li>

            
                        <p>Create the menu with new_menu() by specifying the

            
                        items to be attached with.</p>

            
                      </li>


                      <li>

            
                        <p>Post the menu with menu_post() and refresh the

            
                        screen.</p>

            
                      </li>


                      <li>

            
                        <p>Process the user requests with a loop and do

            
                        necessary updates to menu with menu_driver.</p>

            
                      </li>


                      <li>

            
                        <p>Unpost the menu with menu_unpost()</p>

            
                      </li>


                      <li>

            
                        <p>Free the memory allocated to menu by free_menu()</p>

            
                      </li>


                      <li>

            
                        <p>Free the memory allocated to the items with

            
                        free_item()</p>

            
                      </li>


                      <li>

            
                        <p>End curses</p>

            
                      </li>

            
                    </ol>


                    <p>Let's see a program which prints a simple menu and

            
                    updates the current selection with up, down arrows.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="COMPILEMENUS" id=

            
                    "COMPILEMENUS">17.2. Compiling With the Menu Library</a></h3>


                    <p>To use menu library functions, you have to include

            
                    menu.h and to link the program with menu library the flag

            
                    -lmenu should be added along with -lncurses in that

            
                    order.</p>


                    <pre class="PROGRAMLISTING">    #include &lt;menu.h&gt;

            
                .

            
                .

            
                .


                compile and link: gcc &lt;program file&gt; -lmenu -lncurses</pre>

            
                    <div class="EXAMPLE">

            
                      <a name="MMESI" id="MMESI"></a>

            
                      <p><b>Example 18. Menu Basics</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;curses.h&gt;

            
            #include &lt;menu.h&gt;


            #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

            
            #define CTRLD   4


            char *choices[] = {

            
                                    "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Exit",

            
                              };


            int main()

            
            {       ITEM **my_items;

            
                    int c;

            
                    MENU *my_menu;

            
                    int n_choices, i;

            
                    ITEM *cur_item;


                    initscr();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    n_choices = ARRAY_SIZE(choices);

            
                    my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));


                    for(i = 0; i &lt; n_choices; ++i)

            
                            my_items[i] = new_item(choices[i], choices[i]);

            
                    my_items[n_choices] = (ITEM *)NULL;


                    my_menu = new_menu((ITEM **)my_items);

            
                    mvprintw(LINES - 2, 0, "F1 to Exit");

            
                    post_menu(my_menu);

            
                    refresh();


                    while((c = getch()) != KEY_F(1))

            
                    {   switch(c)

            
                        {   case KEY_DOWN:

            
                                    menu_driver(my_menu, REQ_DOWN_ITEM);

            
                                            break;

            
                                    case KEY_UP:

            
                                            menu_driver(my_menu, REQ_UP_ITEM);

            
                                            break;

            
                            }

            
                    }


                    free_item(my_items[0]);

            
                    free_item(my_items[1]);

            
                    free_menu(my_menu);

            
                    endwin();

            
            }

            
                    </span></pre>

            
                    </div>


                    <p>This program demonstrates the basic concepts involved in

            
                    creating a menu using menus library. First we create the

            
                    items using new_item() and then attach them to the menu

            
                    with new_menu() function. After posting the menu and

            
                    refreshing the screen, the main processing loop starts. It

            
                    reads user input and takes corresponding action. The

            
                    function menu_driver() is the main work horse of the menu

            
                    system. The second parameter to this function tells what's

            
                    to be done with the menu. According to the parameter,

            
                    menu_driver() does the corresponding task. The value can be

            
                    either a menu navigational request, an ascii character, or

            
                    a KEY_MOUSE special key associated with a mouse event.</p>


                    <p>The menu_driver accepts following navigational

            
                    requests.</p>


                    <pre class=

            
                    "PROGRAMLISTING">&#13;     REQ_LEFT_ITEM         Move left to an item.

            
                 REQ_RIGHT_ITEM      Move right to an item.

            
                 REQ_UP_ITEM         Move up to an item.

            
                 REQ_DOWN_ITEM       Move down to an item.

            
                 REQ_SCR_ULINE       Scroll up a line.

            
                 REQ_SCR_DLINE          Scroll down a line.

            
                 REQ_SCR_DPAGE          Scroll down a page.

            
                 REQ_SCR_UPAGE         Scroll up a page.

            
                 REQ_FIRST_ITEM     Move to the first item.

            
                 REQ_LAST_ITEM         Move to the last item.

            
                 REQ_NEXT_ITEM         Move to the next item.

            
                 REQ_PREV_ITEM         Move to the previous item.

            
                 REQ_TOGGLE_ITEM     Select/deselect an item.

            
                 REQ_CLEAR_PATTERN     Clear the menu pattern buffer.

            
                 REQ_BACK_PATTERN      Delete the previous character from the pattern buffer.

            
                 REQ_NEXT_MATCH     Move to the next item matching the pattern match.

            
                 REQ_PREV_MATCH     Move to the previous item matching the pattern match.&#13;</pre>

            
                    <p>Don't get overwhelmed by the number of options. We will

            
                    see them slowly one after another. The options of interest

            
                    in this example are REQ_UP_ITEM and REQ_DOWN_ITEM. These

            
                    two options when passed to menu_driver, menu driver updates

            
                    the current item to one item up or down respectively.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MENUDRIVER" id=

            
                    "MENUDRIVER">17.3. Menu Driver: The work horse of the menu

            
                    system</a></h3>


                    <p>As you have seen in the above example, menu_driver plays

            
                    an important role in updating the menu. It is very

            
                    important to understand various options it takes and what

            
                    they do. As explained above, the second parameter to

            
                    menu_driver() can be either a navigational request, a

            
                    printable character or a KEY_MOUSE key. Let's dissect the

            
                    different navigational requests.</p>


                    <ul>

            
                      <li>

            
                        <p><span class="emphasis"><i class=

            
                        "EMPHASIS">REQ_LEFT_ITEM and REQ_RIGHT_ITEM</i></span>

            
                        </p>


                        <p>A Menu can be displayed with multiple columns for

            
                        more than one item. This can be done by using the

            
                        <tt class="LITERAL">menu_format()</tt>function. When a

            
                        multi columnar menu is displayed these requests cause

            
                        the menu driver to move the current selection to left

            
                        or right.</p>

            
                      </li>


                      <li>

            
                        <p><span class="emphasis"><i class=

            
                        "EMPHASIS">REQ_UP_ITEM and REQ_DOWN_ITEM</i></span>

            
                        </p>


                        <p>These two options you have seen in the above

            
                        example. These options when given, makes the

            
                        menu_driver to move the current selection to an item up

            
                        or down.</p>

            
                      </li>


                      <li>

            
                        <p><span class="emphasis"><i class="EMPHASIS">REQ_SCR_*

            
                        options</i></span>

            
                        </p>


                        <p>The four options REQ_SCR_ULINE, REQ_SCR_DLINE,

            
                        REQ_SCR_DPAGE, REQ_SCR_UPAGE are related to scrolling.

            
                        If all the items in the menu cannot be displayed in the

            
                        menu sub window, then the menu is scrollable. These

            
                        requests can be given to the menu_driver to do the

            
                        scrolling either one line up, down or one page down or

            
                        up respectively.</p>

            
                      </li>


                      <li>

            
                        <p><span class="emphasis"><i class=

            
                        "EMPHASIS">REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_NEXT_ITEM

            
                        and REQ_PREV_ITEM</i></span>

            
                        </p>


                        <p>These requests are self explanatory.</p>

            
                      </li>


                      <li>

            
                        <p><span class="emphasis"><i class=

            
                        "EMPHASIS">REQ_TOGGLE_ITEM</i></span>

            
                        </p>


                        <p>This request when given, toggles the present

            
                        selection. This option is to be used only in a multi

            
                        valued menu. So to use this request the option

            
                        O_ONEVALUE must be off. This option can be made off or

            
                        on with set_menu_opts().</p>

            
                      </li>


                      <li>

            
                        <p><span class="emphasis"><i class="EMPHASIS">Pattern

            
                        Requests</i></span>

            
                        </p>


                        <p>Every menu has an associated pattern buffer, which

            
                        is used to find the nearest match to the ascii

            
                        characters entered by the user. Whenever ascii

            
                        characters are given to menu_driver, it puts in to the

            
                        pattern buffer. It also tries to find the nearest match

            
                        to the pattern in the items list and moves current

            
                        selection to that item. The request REQ_CLEAR_PATTERN

            
                        clears the pattern buffer. The request REQ_BACK_PATTERN

            
                        deletes the previous character in the pattern buffer.

            
                        In case the pattern matches more than one item then the

            
                        matched items can be cycled through REQ_NEXT_MATCH and

            
                        REQ_PREV_MATCH which move the current selection to the

            
                        next and previous matches respectively.</p>

            
                      </li>


                      <li>

            
                        <p><span class="emphasis"><i class="EMPHASIS">Mouse

            
                        Requests</i></span>

            
                        </p>


                        <p>In case of KEY_MOUSE requests, according to the

            
                        mouse position an action is taken accordingly. The

            
                        action to be taken is explained in the man page as,</p>


                        <pre class="PROGRAMLISTING"><span class=

            
                        "emphasis"><i class=

            
                        "EMPHASIS">       If  the  second argument is the KEY_MOUSE special key, the

            
                   associated mouse event is translated into one of the above

            
                   pre-defined  requests.   Currently only clicks in the user

            
                   window (e.g. inside the menu display area or  the  decora&shy;

            
                   tion  window)  are handled. If you click above the display

            
                   region of the menu, a REQ_SCR_ULINE is generated,  if  you

            
                   doubleclick  a  REQ_SCR_UPAGE  is  generated  and  if  you

            
                   tripleclick a REQ_FIRST_ITEM is generated.  If  you  click

            
                   below  the  display region of the menu, a REQ_SCR_DLINE is

            
                   generated, if you doubleclick a REQ_SCR_DPAGE is generated

            
                   and  if  you  tripleclick a REQ_LAST_ITEM is generated. If

            
                   you click at an item inside the display area of the  menu,

            
                   the menu cursor is positioned to that item.</i></span></pre>

            
                      </li>

            
                    </ul>


                    <p>Each of the above requests will be explained in the

            
                    following lines with several examples whenever

            
                    appropriate.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MENUWINDOWS" id=

            
                    "MENUWINDOWS">17.4. Menu Windows</a></h3>


                    <p>Every menu created is associated with a window and a sub

            
                    window. The menu window displays any title or border

            
                    associated with the menu. The menu sub window displays the

            
                    menu items currently available for selection. But we didn't

            
                    specify any window or sub window in the simple example.

            
                    When a window is not specified, stdscr is taken as the main

            
                    window, and then menu system calculates the sub window size

            
                    required for the display of items. Then items are displayed

            
                    in the calculated sub window. So let's play with these

            
                    windows and display a menu with a border and a title.</p>


                    <div class="EXAMPLE">

            
                      <a name="MMEWI" id="MMEWI"></a>

            
                      <p><b>Example 19. Menu Windows Usage example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;string.h&gt;

            
            #include &lt;menu.h&gt;


            #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

            
            #define CTRLD   4


            char *choices[] = {

            
                                    "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Exit",

            
                                    (char *)NULL,

            
                              };

            
            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);


            int main()

            
            {       ITEM **my_items;

            
                    int c;

            
                    MENU *my_menu;

            
                    WINDOW *my_menu_win;

            
                    int n_choices, i;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);


                    /* Create items */

            
                    n_choices = ARRAY_SIZE(choices);

            
                    my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            my_items[i] = new_item(choices[i], choices[i]);


                    /* Crate menu */

            
                    my_menu = new_menu((ITEM **)my_items);


                    /* Create the window to be associated with the menu */

            
                    my_menu_win = newwin(10, 40, 4, 4);

            
                    keypad(my_menu_win, TRUE);


                    /* Set main window and sub window */

            
                    set_menu_win(my_menu, my_menu_win);

            
                    set_menu_sub(my_menu, derwin(my_menu_win, 6, 38, 3, 1));


                    /* Set menu mark to the string " * " */

            
                    set_menu_mark(my_menu, " * ");


                    /* Print a border around the main window and print a title */

            
                    box(my_menu_win, 0, 0);

            
                    print_in_middle(my_menu_win, 1, 0, 40, "My Menu", COLOR_PAIR(1));

            
                    mvwaddch(my_menu_win, 2, 0, ACS_LTEE);

            
                    mvwhline(my_menu_win, 2, 1, ACS_HLINE, 38);

            
                    mvwaddch(my_menu_win, 2, 39, ACS_RTEE);

            
                    mvprintw(LINES - 2, 0, "F1 to exit");

            
                    refresh();


                    /* Post the menu */

            
                    post_menu(my_menu);

            
                    wrefresh(my_menu_win);


                    while((c = wgetch(my_menu_win)) != KEY_F(1))

            
                    {       switch(c)

            
                            {       case KEY_DOWN:

            
                                            menu_driver(my_menu, REQ_DOWN_ITEM);

            
                                            break;

            
                                    case KEY_UP:

            
                                            menu_driver(my_menu, REQ_UP_ITEM);

            
                                            break;

            
                            }

            
                            wrefresh(my_menu_win);

            
                    }


                    /* Unpost and free all the memory taken up */

            
                    unpost_menu(my_menu);

            
                    free_menu(my_menu);

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            free_item(my_items[i]);

            
                    endwin();

            
            }


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)

            
            {       int length, x, y;

            
                    float temp;


                    if(win == NULL)

            
                            win = stdscr;

            
                    getyx(win, y, x);

            
                    if(startx != 0)

            
                            x = startx;

            
                    if(starty != 0)

            
                            y = starty;

            
                    if(width == 0)

            
                            width = 80;


                    length = strlen(string);

            
                    temp = (width - length)/ 2;

            
                    x = startx + (int)temp;

            
                    wattron(win, color);

            
                    mvwprintw(win, y, x, "%s", string);

            
                    wattroff(win, color);

            
                    refresh();

            
            }</span></pre>

            
                    </div>


                    <p>This example creates a menu with a title, border, a

            
                    fancy line separating title and the items. As you can see,

            
                    in order to attach a window to a menu the function

            
                    set_menu_win() has to be used. Then we attach the sub

            
                    window also. This displays the items in the sub window. You

            
                    can also set the mark string which gets displayed to the

            
                    left of the selected item with set_menu_mark().</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="SCROLLMENUS" id=

            
                    "SCROLLMENUS">17.5. Scrolling Menus</a></h3>


                    <p>If the sub window given for a window is not big enough

            
                    to show all the items, then the menu will be scrollable.

            
                    When you are on the last item in the present list, if you

            
                    send REQ_DOWN_ITEM, it gets translated into REQ_SCR_DLINE

            
                    and the menu scrolls by one item. You can manually give

            
                    REQ_SCR_ operations to do scrolling. Let's see how it can

            
                    be done.</p>


                    <div class="EXAMPLE">

            
                      <a name="MMESC" id="MMESC"></a>

            
                      <p><b>Example 20. Scrolling Menus example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;string.h&gt;

            
            #include &lt;curses.h&gt;

            
            #include &lt;menu.h&gt;


            #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

            
            #define CTRLD   4


            char *choices[] = {

            
                                    "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Choice 5",

            
                                    "Choice 6",

            
                                    "Choice 7",

            
                                    "Choice 8",

            
                                    "Choice 9",

            
                                    "Choice 10",

            
                                    "Exit",

            
                                    (char *)NULL,

            
                              };

            
            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);


            int main()

            
            {       ITEM **my_items;

            
                    int c;

            
                    MENU *my_menu;

            
                    WINDOW *my_menu_win;

            
                    int n_choices, i;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);

            
                    init_pair(2, COLOR_CYAN, COLOR_BLACK);


                    /* Create items */

            
                    n_choices = ARRAY_SIZE(choices);

            
                    my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            my_items[i] = new_item(choices[i], choices[i]);


                    /* Crate menu */

            
                    my_menu = new_menu((ITEM **)my_items);


                    /* Create the window to be associated with the menu */

            
                    my_menu_win = newwin(10, 40, 4, 4);

            
                    keypad(my_menu_win, TRUE);


                    /* Set main window and sub window */

            
                    set_menu_win(my_menu, my_menu_win);

            
                    set_menu_sub(my_menu, derwin(my_menu_win, 6, 38, 3, 1));

            
                    set_menu_format(my_menu, 5, 1);


                    /* Set menu mark to the string " * " */

            
                    set_menu_mark(my_menu, " * ");


                    /* Print a border around the main window and print a title */

            
                    box(my_menu_win, 0, 0);

            
                    print_in_middle(my_menu_win, 1, 0, 40, "My Menu", COLOR_PAIR(1));

            
                    mvwaddch(my_menu_win, 2, 0, ACS_LTEE);

            
                    mvwhline(my_menu_win, 2, 1, ACS_HLINE, 38);

            
                    mvwaddch(my_menu_win, 2, 39, ACS_RTEE);


                    /* Post the menu */

            
                    post_menu(my_menu);

            
                    wrefresh(my_menu_win);


                    attron(COLOR_PAIR(2));

            
                    mvprintw(LINES - 2, 0, "Use PageUp and PageDown to scroll down or up a page of items");

            
                    mvprintw(LINES - 1, 0, "Arrow Keys to navigate (F1 to Exit)");

            
                    attroff(COLOR_PAIR(2));

            
                    refresh();


                    while((c = wgetch(my_menu_win)) != KEY_F(1))

            
                    {       switch(c)

            
                            {       case KEY_DOWN:

            
                                            menu_driver(my_menu, REQ_DOWN_ITEM);

            
                                            break;

            
                                    case KEY_UP:

            
                                            menu_driver(my_menu, REQ_UP_ITEM);

            
                                            break;

            
                                    case KEY_NPAGE:

            
                                            menu_driver(my_menu, REQ_SCR_DPAGE);

            
                                            break;

            
                                    case KEY_PPAGE:

            
                                            menu_driver(my_menu, REQ_SCR_UPAGE);

            
                                            break;

            
                            }

            
                            wrefresh(my_menu_win);

            
                    }


                    /* Unpost and free all the memory taken up */

            
                    unpost_menu(my_menu);

            
                    free_menu(my_menu);

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            free_item(my_items[i]);

            
                    endwin();

            
            }


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)

            
            {       int length, x, y;

            
                    float temp;


                    if(win == NULL)

            
                            win = stdscr;

            
                    getyx(win, y, x);

            
                    if(startx != 0)

            
                            x = startx;

            
                    if(starty != 0)

            
                            y = starty;

            
                    if(width == 0)

            
                            width = 80;


                    length = strlen(string);

            
                    temp = (width - length)/ 2;

            
                    x = startx + (int)temp;

            
                    wattron(win, color);

            
                    mvwprintw(win, y, x, "%s", string);

            
                    wattroff(win, color);

            
                    refresh();

            
            }</span></pre>

            
                    </div>


                    <p>This program is self-explanatory. In this example the

            
                    number of choices has been increased to ten, which is

            
                    larger than our sub window size which can hold 6 items.

            
                    This message has to be explicitly conveyed to the menu

            
                    system with the function set_menu_format(). In here we

            
                    specify the number of rows and columns we want to be

            
                    displayed for a single page. We can specify any number of

            
                    items to be shown, in the rows variables, if it is less

            
                    than the height of the sub window. If the key pressed by

            
                    the user is a PAGE UP or PAGE DOWN, the menu is scrolled a

            
                    page due to the requests (REQ_SCR_DPAGE and REQ_SCR_UPAGE)

            
                    given to menu_driver().</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MULTICOLUMN" id=

            
                    "MULTICOLUMN">17.6. Multi Columnar Menus</a></h3>


                    <p>In the above example you have seen how to use the

            
                    function set_menu_format(). I didn't mention what the cols

            
                    variable (third parameter) does. Well, If your sub window

            
                    is wide enough, you can opt to display more than one item

            
                    per row. This can be specified in the cols variable. To

            
                    make things simpler, the following example doesn't show

            
                    descriptions for the items.</p>


                    <div class="EXAMPLE">

            
                      <a name="MMEMUCO" id="MMEMUCO"></a>

            
                      <p><b>Example 21. Milt Columnar Menus Example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;curses.h&gt;

            
            #include &lt;menu.h&gt;


            #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

            
            #define CTRLD   4


            char *choices[] = {

            
                                    "Choice 1", "Choice 2", "Choice 3", "Choice 4", "Choice 5",

            
                                    "Choice 6", "Choice 7", "Choice 8", "Choice 9", "Choice 10",

            
                                    "Choice 11", "Choice 12", "Choice 13", "Choice 14", "Choice 15",

            
                                    "Choice 16", "Choice 17", "Choice 18", "Choice 19", "Choice 20",

            
                                    "Exit",

            
                                    (char *)NULL,

            
                              };


            int main()

            
            {       ITEM **my_items;

            
                    int c;

            
                    MENU *my_menu;

            
                    WINDOW *my_menu_win;

            
                    int n_choices, i;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);

            
                    init_pair(2, COLOR_CYAN, COLOR_BLACK);


                    /* Create items */

            
                    n_choices = ARRAY_SIZE(choices);

            
                    my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            my_items[i] = new_item(choices[i], choices[i]);


                    /* Crate menu */

            
                    my_menu = new_menu((ITEM **)my_items);


                    /* Set menu option not to show the description */

            
                    menu_opts_off(my_menu, O_SHOWDESC);


                    /* Create the window to be associated with the menu */

            
                    my_menu_win = newwin(10, 70, 4, 4);

            
                    keypad(my_menu_win, TRUE);


                    /* Set main window and sub window */

            
                    set_menu_win(my_menu, my_menu_win);

            
                    set_menu_sub(my_menu, derwin(my_menu_win, 6, 68, 3, 1));

            
                    set_menu_format(my_menu, 5, 3);

            
                    set_menu_mark(my_menu, " * ");


                    /* Print a border around the main window and print a title */

            
                    box(my_menu_win, 0, 0);


                    attron(COLOR_PAIR(2));

            
                    mvprintw(LINES - 3, 0, "Use PageUp and PageDown to scroll");

            
                    mvprintw(LINES - 2, 0, "Use Arrow Keys to navigate (F1 to Exit)");

            
                    attroff(COLOR_PAIR(2));

            
                    refresh();


                    /* Post the menu */

            
                    post_menu(my_menu);

            
                    wrefresh(my_menu_win);


                    while((c = wgetch(my_menu_win)) != KEY_F(1))

            
                    {       switch(c)

            
                            {       case KEY_DOWN:

            
                                            menu_driver(my_menu, REQ_DOWN_ITEM);

            
                                            break;

            
                                    case KEY_UP:

            
                                            menu_driver(my_menu, REQ_UP_ITEM);

            
                                            break;

            
                                    case KEY_LEFT:

            
                                            menu_driver(my_menu, REQ_LEFT_ITEM);

            
                                            break;

            
                                    case KEY_RIGHT:

            
                                            menu_driver(my_menu, REQ_RIGHT_ITEM);

            
                                            break;

            
                                    case KEY_NPAGE:

            
                                            menu_driver(my_menu, REQ_SCR_DPAGE);

            
                                            break;

            
                                    case KEY_PPAGE:

            
                                            menu_driver(my_menu, REQ_SCR_UPAGE);

            
                                            break;

            
                            }

            
                            wrefresh(my_menu_win);

            
                    }


                    /* Unpost and free all the memory taken up */

            
                    unpost_menu(my_menu);

            
                    free_menu(my_menu);

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            free_item(my_items[i]);

            
                    endwin();

            
            }</span></pre>

            
                    </div>


                    <p>Watch the function call to set_menu_format(). It

            
                    specifies the number of columns to be 3, thus displaying 3

            
                    items per row. We have also switched off the showing

            
                    descriptions with the function menu_opts_off(). There are

            
                    couple of functions set_menu_opts(), menu_opts_on() and

            
                    menu_opts() which can be used to manipulate menu options.

            
                    The following menu options can be specified.</p>


                    <pre class="PROGRAMLISTING">       O_ONEVALUE

            
                        Only one item can be selected for this menu.


                   O_SHOWDESC

            
                        Display  the  item  descriptions  when  the  menu  is

            
                        posted.


                   O_ROWMAJOR

            
                        Display the menu in row-major order.


                   O_IGNORECASE

            
                        Ignore the case when pattern-matching.


                   O_SHOWMATCH

            
                        Move the cursor to within the item  name  while  pat&shy;

            
                        tern-matching.


                   O_NONCYCLIC

            
                        Don't   wrap   around  next-item  and  previous-item,

            
                        requests to the other end of the menu.</pre>

            
                    <p>All options are on by default. You can switch specific

            
                    attributes on or off with menu_opts_on() and

            
                    menu_opts_off() functions. You can also use set_menu_opts()

            
                    to directly specify the options. The argument to this

            
                    function should be a OR ed value of some of those above

            
                    constants. The function menu_opts() can be used to find out

            
                    a menu's present options.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MULTIVALUEMENUS" id=

            
                    "MULTIVALUEMENUS">17.7. Multi Valued Menus</a></h3>


                    <p>You might be wondering what if you switch off the option

            
                    O_ONEVALUE. Then the menu becomes multi-valued. That means

            
                    you can select more than one item. This brings us to the

            
                    request REQ_TOGGLE_ITEM. Let's see it in action.</p>


                    <div class="EXAMPLE">

            
                      <a name="MMETO" id="MMETO"></a>

            
                      <p><b>Example 22. Multi Valued Menus example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;string.h&gt;

            
            #include &lt;curses.h&gt;

            
            #include &lt;menu.h&gt;


            #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

            
            #define CTRLD   4


            char *choices[] = {

            
                                    "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Choice 5",

            
                                    "Choice 6",

            
                                    "Choice 7",

            
                                    "Exit",

            
                              };


            int main()

            
            {       ITEM **my_items;

            
                    int c;

            
                    MENU *my_menu;

            
                    int n_choices, i;

            
                    ITEM *cur_item;


                    /* Initialize curses */

            
                    initscr();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize items */

            
                    n_choices = ARRAY_SIZE(choices);

            
                    my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            my_items[i] = new_item(choices[i], choices[i]);

            
                    my_items[n_choices] = (ITEM *)NULL;


                    my_menu = new_menu((ITEM **)my_items);


                    /* Make the menu multi valued */

            
                    menu_opts_off(my_menu, O_ONEVALUE);


                    mvprintw(LINES - 3, 0, "Use &lt;SPACE&gt; to select or unselect an item.");

            
                    mvprintw(LINES - 2, 0, "&lt;ENTER&gt; to see presently selected items(F1 to Exit)");

            
                    post_menu(my_menu);

            
                    refresh();


                    while((c = getch()) != KEY_F(1))

            
                    {       switch(c)

            
                            {       case KEY_DOWN:

            
                                            menu_driver(my_menu, REQ_DOWN_ITEM);

            
                                            break;

            
                                    case KEY_UP:

            
                                            menu_driver(my_menu, REQ_UP_ITEM);

            
                                            break;

            
                                    case ' ':

            
                                            menu_driver(my_menu, REQ_TOGGLE_ITEM);

            
                                            break;

            
                                    case 10:        /* Enter */

            
                                    {       char temp[200];

            
                                            ITEM **items;


                                            items = menu_items(my_menu);

            
                                            temp[0] = '\0';

            
                                            for(i = 0; i &lt; item_count(my_menu); ++i)

            
                                                    if(item_value(items[i]) == TRUE)

            
                                                    {       strcat(temp, item_name(items[i]));

            
                                                            strcat(temp, " ");

            
                                                    }

            
                                            move(20, 0);

            
                                            clrtoeol();

            
                                            mvprintw(20, 0, temp);

            
                                            refresh();

            
                                    }

            
                                    break;

            
                            }

            
                    }


                    free_item(my_items[0]);

            
                    free_item(my_items[1]);

            
                    free_menu(my_menu);

            
                    endwin();

            
            }

            
                    </span></pre>

            
                    </div>


                    <p>Whew, A lot of new functions. Let's take them one after

            
                    another. Firstly, the REQ_TOGGLE_ITEM. In a multi-valued

            
                    menu, the user should be allowed to select or un select

            
                    more than one item. The request REQ_TOGGLE_ITEM toggles the

            
                    present selection. In this case when space is pressed

            
                    REQ_TOGGLE_ITEM request is sent to menu_driver to achieve

            
                    the result.</p>


                    <p>Now when the user presses &lt;ENTER&gt; we show the

            
                    items he presently selected. First we find out the items

            
                    associated with the menu using the function menu_items().

            
                    Then we loop through the items to find out if the item is

            
                    selected or not. The function item_value() returns TRUE if

            
                    an item is selected. The function item_count() returns the

            
                    number of items in the menu. The item name can be found

            
                    with item_name(). You can also find the description

            
                    associated with an item using item_description().</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MENUOPT" id="MENUOPT">17.8. Menu

            
                    Options</a></h3>


                    <p>Well, by this time you must be itching for some

            
                    difference in your menu, with lots of functionality. I

            
                    know. You want Colors !!!. You want to create nice menus

            
                    similar to those text mode <a href=

            
                    "http://www.jersey.net/~debinjoe/games/" target="_top">dos

            
                    games</a>. The functions set_menu_fore() and

            
                    set_menu_back() can be used to change the attribute of the

            
                    selected item and unselected item. The names are

            
                    misleading. They don't change menu's foreground or

            
                    background which would have been useless.</p>


                    <p>The function set_menu_grey() can be used to set the

            
                    display attribute for the non-selectable items in the menu.

            
                    This brings us to the interesting option for an item the

            
                    one and only O_SELECTABLE. We can turn it off by the

            
                    function item_opts_off() and after that that item is not

            
                    selectable. It is like a grayed item in those fancy windows

            
                    menus. Let's put these concepts in practice with this

            
                    example</p>


                    <div class="EXAMPLE">

            
                      <a name="MMEAT" id="MMEAT"></a>

            
                      <p><b>Example 23. Menu Options example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;menu.h&gt;


            #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

            
            #define CTRLD   4


            char *choices[] = {

            
                                    "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Choice 5",

            
                                    "Choice 6",

            
                                    "Choice 7",

            
                                    "Exit",

            
                              };


            int main()

            
            {       ITEM **my_items;

            
                    int c;

            
                    MENU *my_menu;

            
                    int n_choices, i;

            
                    ITEM *cur_item;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);

            
                    init_pair(2, COLOR_GREEN, COLOR_BLACK);

            
                    init_pair(3, COLOR_MAGENTA, COLOR_BLACK);


                    /* Initialize items */

            
                    n_choices = ARRAY_SIZE(choices);

            
                    my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            my_items[i] = new_item(choices[i], choices[i]);

            
                    my_items[n_choices] = (ITEM *)NULL;

            
                    item_opts_off(my_items[3], O_SELECTABLE);

            
                    item_opts_off(my_items[6], O_SELECTABLE);


                    /* Create menu */

            
                    my_menu = new_menu((ITEM **)my_items);


                    /* Set fore ground and back ground of the menu */

            
                    set_menu_fore(my_menu, COLOR_PAIR(1) | A_REVERSE);

            
                    set_menu_back(my_menu, COLOR_PAIR(2));

            
                    set_menu_grey(my_menu, COLOR_PAIR(3));


                    /* Post the menu */

            
                    mvprintw(LINES - 3, 0, "Press &lt;ENTER&gt; to see the option selected");

            
                    mvprintw(LINES - 2, 0, "Up and Down arrow keys to naviage (F1 to Exit)");

            
                    post_menu(my_menu);

            
                    refresh();


                    while((c = getch()) != KEY_F(1))

            
                    {       switch(c)

            
                            {       case KEY_DOWN:

            
                                            menu_driver(my_menu, REQ_DOWN_ITEM);

            
                                            break;

            
                                    case KEY_UP:

            
                                            menu_driver(my_menu, REQ_UP_ITEM);

            
                                            break;

            
                                    case 10: /* Enter */

            
                                            move(20, 0);

            
                                            clrtoeol();

            
                                            mvprintw(20, 0, "Item selected is : %s",

            
                                                            item_name(current_item(my_menu)));

            
                                            pos_menu_cursor(my_menu);

            
                                            break;

            
                            }

            
                    }

            
                    unpost_menu(my_menu);

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            free_item(my_items[i]);

            
                    free_menu(my_menu);

            
                    endwin();

            
            }

            
                    </span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MENUUSERPTR" id=

            
                    "MENUUSERPTR">17.9. The useful User Pointer</a></h3>


                    <p>We can associate a user pointer with each item in the

            
                    menu. It works the same way as user pointer in panels. It

            
                    is not touched by menu system. You can store any thing you

            
                    like in that. I usually use it to store the function to be

            
                    executed when the menu option is chosen (It is selected and

            
                    may be the user pressed &lt;ENTER&gt;);</p>


                    <div class="EXAMPLE">

            
                      <a name="MMEUS" id="MMEUS"></a>

            
                      <p><b>Example 24. Menu User Pointer Usage</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;stdlib.h&gt;

            
            #include &lt;curses.h&gt;

            
            #include &lt;menu.h&gt;


            #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))

            
            #define CTRLD   4


            char *choices[] = {

            
                                    "Choice 1",

            
                                    "Choice 2",

            
                                    "Choice 3",

            
                                    "Choice 4",

            
                                    "Choice 5",

            
                                    "Choice 6",

            
                                    "Choice 7",

            
                                    "Exit",

            
                              };

            
            void func(char *name);


            int main()

            
            {       ITEM **my_items;

            
                    int c;

            
                    MENU *my_menu;

            
                    int n_choices, i;

            
                    ITEM *cur_item;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);

            
                    init_pair(2, COLOR_GREEN, COLOR_BLACK);

            
                    init_pair(3, COLOR_MAGENTA, COLOR_BLACK);


                    /* Initialize items */

            
                    n_choices = ARRAY_SIZE(choices);

            
                    my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                    {       my_items[i] = new_item(choices[i], choices[i]);

            
                            /* Set the user pointer */

            
                            set_item_userptr(my_items[i], func);

            
                    }

            
                    my_items[n_choices] = (ITEM *)NULL;


                    /* Create menu */

            
                    my_menu = new_menu((ITEM **)my_items);


                    /* Post the menu */

            
                    mvprintw(LINES - 3, 0, "Press &lt;ENTER&gt; to see the option selected");

            
                    mvprintw(LINES - 2, 0, "Up and Down arrow keys to naviage (F1 to Exit)");

            
                    post_menu(my_menu);

            
                    refresh();


                    while((c = getch()) != KEY_F(1))

            
                    {       switch(c)

            
                            {       case KEY_DOWN:

            
                                            menu_driver(my_menu, REQ_DOWN_ITEM);

            
                                            break;

            
                                    case KEY_UP:

            
                                            menu_driver(my_menu, REQ_UP_ITEM);

            
                                            break;

            
                                    case 10: /* Enter */

            
                                    {       ITEM *cur;

            
                                            void (*p)(char *);


                                            cur = current_item(my_menu);

            
                                            p = item_userptr(cur);

            
                                            p((char *)item_name(cur));

            
                                            pos_menu_cursor(my_menu);

            
                                            break;

            
                                    }

            
                                    break;

            
                            }

            
                    }

            
                    unpost_menu(my_menu);

            
                    for(i = 0; i &lt; n_choices; ++i)

            
                            free_item(my_items[i]);

            
                    free_menu(my_menu);

            
                    endwin();

            
            }


            void func(char *name)

            
            {       move(20, 0);

            
                    clrtoeol();

            
                    mvprintw(20, 0, "Item selected is : %s", name);

            
            }       </span></pre>

            
                    </div>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="FORMS" id="FORMS">18. Forms

            
                  Library</a></h2>


                  <p>Well. If you have seen those forms on web pages which take

            
                  input from users and do various kinds of things, you might be

            
                  wondering how would any one create such forms in text mode

            
                  display. It is quite difficult to write those nifty forms in

            
                  plain ncurses. Forms library tries to provide a basic frame

            
                  work to build and maintain forms with ease. It has lot of

            
                  features(functions) which manage validation, dynamic

            
                  expansion of fields, etc. Let's see it in full flow.</p>


                  <p>A form is a collection of fields; each field can be either

            
                  a label(static text) or a data-entry location. The forms also

            
                  library provides functions to divide forms into multiple

            
                  pages.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="FORMBASICS" id=

            
                    "FORMBASICS">18.1. The Basics</a></h3>


                    <p>Forms are created in much the same way as menus. First

            
                    the fields related to the form are created with

            
                    new_field(). You can set options for the fields, so that

            
                    they can be displayed with some fancy attributes, validated

            
                    before the field looses focus, etc. Then the fields are

            
                    attached to form. After this, the form can be posted to

            
                    display and is ready to receive inputs. On the similar

            
                    lines to menu_driver(), the form is manipulated with

            
                    form_driver(). We can send requests to form_driver to move

            
                    focus to a certain field, move cursor to end of the field

            
                    etc. After the user enters values in the fields and

            
                    validation done, form can be unposted and memory allocated

            
                    can be freed.</p>


                    <p>The general flow of control of a forms program looks

            
                    like this.</p>


                    <ol type="1">

            
                      <li>

            
                        <p>Initialize curses</p>

            
                      </li>


                      <li>

            
                        <p>Create fields using new_field(). You can specify the

            
                        height and width of the field, and its position on the

            
                        form.</p>

            
                      </li>


                      <li>

            
                        <p>Create the forms with new_form() by specifying the

            
                        fields to be attached with.</p>

            
                      </li>


                      <li>

            
                        <p>Post the form with form_post() and refresh the

            
                        screen.</p>

            
                      </li>


                      <li>

            
                        <p>Process the user requests with a loop and do

            
                        necessary updates to form with form_driver.</p>

            
                      </li>


                      <li>

            
                        <p>Unpost the menu with form_unpost()</p>

            
                      </li>


                      <li>

            
                        <p>Free the memory allocated to menu by free_form()</p>

            
                      </li>


                      <li>

            
                        <p>Free the memory allocated to the items with

            
                        free_field()</p>

            
                      </li>


                      <li>

            
                        <p>End curses</p>

            
                      </li>

            
                    </ol>


                    <p>As you can see, working with forms library is much

            
                    similar to handling menu library. The following examples

            
                    will explore various aspects of form processing. Let's

            
                    start the journey with a simple example. first.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="COMPILEFORMS" id=

            
                    "COMPILEFORMS">18.2. Compiling With the Forms Library</a></h3>


                    <p>To use forms library functions, you have to include

            
                    form.h and to link the program with forms library the flag

            
                    -lform should be added along with -lncurses in that

            
                    order.</p>


                    <pre class="PROGRAMLISTING">    #include &lt;form.h&gt;

            
                .

            
                .

            
                .


                compile and link: gcc &lt;program file&gt; -lform -lncurses</pre>

            
                    <div class="EXAMPLE">

            
                      <a name="FFOSI" id="FFOSI"></a>

            
                      <p><b>Example 25. Forms Basics</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;form.h&gt;


            int main()

            
            {       FIELD *field[3];

            
                    FORM  *my_form;

            
                    int ch;


                    /* Initialize curses */

            
                    initscr();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize the fields */

            
                    field[0] = new_field(1, 10, 4, 18, 0, 0);

            
                    field[1] = new_field(1, 10, 6, 18, 0, 0);

            
                    field[2] = NULL;


                    /* Set field options */

            
                    set_field_back(field[0], A_UNDERLINE);  /* Print a line for the option  */

            
                    field_opts_off(field[0], O_AUTOSKIP);   /* Don't go to next field when this */

            
                                                            /* Field is filled up           */

            
                    set_field_back(field[1], A_UNDERLINE);

            
                    field_opts_off(field[1], O_AUTOSKIP);


                    /* Create the form and post it */

            
                    my_form = new_form(field);

            
                    post_form(my_form);

            
                    refresh();


                    mvprintw(4, 10, "Value 1:");

            
                    mvprintw(6, 10, "Value 2:");

            
                    refresh();


                    /* Loop through to get user requests */

            
                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case KEY_DOWN:

            
                                            /* Go to next field */

            
                                            form_driver(my_form, REQ_NEXT_FIELD);

            
                                            /* Go to the end of the present buffer */

            
                                            /* Leaves nicely at the last character */

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    case KEY_UP:

            
                                            /* Go to previous field */

            
                                            form_driver(my_form, REQ_PREV_FIELD);

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    default:

            
                                            /* If this is a normal character, it gets */

            
                                            /* Printed                                */

            
                                            form_driver(my_form, ch);

            
                                            break;

            
                            }

            
                    }


                    /* Un post form and free the memory */

            
                    unpost_form(my_form);

            
                    free_form(my_form);

            
                    free_field(field[0]);

            
                    free_field(field[1]);


                    endwin();

            
                    return 0;

            
            }</span></pre>

            
                    </div>


                    <p>Above example is pretty straight forward. It creates two

            
                    fields with <tt class="LITERAL">new_field()</tt>.

            
                    new_field() takes height, width, starty, startx, number of

            
                    offscreen rows and number of additional working buffers.

            
                    The fifth argument number of offscreen rows specifies how

            
                    much of the field to be shown. If it is zero, the entire

            
                    field is always displayed otherwise the form will be

            
                    scrollable when the user accesses not displayed parts of

            
                    the field. The forms library allocates one buffer per field

            
                    to store the data user enters. Using the last parameter to

            
                    new_field() we can specify it to allocate some additional

            
                    buffers. These can be used for any purpose you like.</p>


                    <p>After creating the fields, back ground attribute of both

            
                    of them is set to an underscore with set_field_back(). The

            
                    AUTOSKIP option is turned off using field_opts_off(). If

            
                    this option is turned on, focus will move to the next field

            
                    in the form once the active field is filled up

            
                    completely.</p>


                    <p>After attaching the fields to the form, it is posted.

            
                    Here on, user inputs are processed in the while loop, by

            
                    making corresponding requests to form_driver. The details

            
                    of all the requests to the form_driver() are explained

            
                    later.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PLAYFIELDS" id=

            
                    "PLAYFIELDS">18.3. Playing with Fields</a></h3>


                    <p>Each form field is associated with a lot of attributes.

            
                    They can be manipulated to get the required effect and to

            
                    have fun !!!. So why wait?</p>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="FETCHINFO" id=

            
                      "FETCHINFO">18.3.1. Fetching Size and Location of

            
                      Field</a></h4>


                      <p>The parameters we have given at the time of creation

            
                      of a field can be retrieved with field_info(). It returns

            
                      height, width, starty, startx, number of offscreen rows,

            
                      and number of additional buffers into the parameters

            
                      given to it. It is a sort of inverse of new_field().</p>


                      <pre class=

            
                      "PROGRAMLISTING">int field_info(     FIELD *field,              /* field from which to fetch */

            
                                int *height, *int width,   /* field size */

            
                                int *top, int *left,       /* upper left corner */

            
                                int *offscreen,            /* number of offscreen rows */

            
                                int *nbuf);                /* number of working buffers */</pre>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="MOVEFIELD" id=

            
                      "MOVEFIELD">18.3.2. Moving the field</a></h4>


                      <p>The location of the field can be moved to a different

            
                      position with move_field().</p>


                      <pre class=

            
                      "PROGRAMLISTING">int move_field(    FIELD *field,              /* field to alter */

            
                               int top, int left);        /* new upper-left corner */</pre>

            
                      <p>As usual, the changed position can be queried with

            
                      field_infor().</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="JUSTIFYFIELD" id=

            
                      "JUSTIFYFIELD">18.3.3. Field Justification</a></h4>


                      <p>The justification to be done for the field can be

            
                      fixed using the function set_field_just().</p>


                      <pre class=

            
                      "PROGRAMLISTING">    int set_field_just(FIELD *field,          /* field to alter */

            
                           int justmode);         /* mode to set */

            
                int field_just(FIELD *field);          /* fetch justify mode of field */</pre>

            
                      <p>The justification mode valued accepted and returned by

            
                      these functions are NO_JUSTIFICATION, JUSTIFY_RIGHT,

            
                      JUSTIFY_LEFT, or JUSTIFY_CENTER.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="FIELDDISPATTRIB" id=

            
                      "FIELDDISPATTRIB">18.3.4. Field Display Attributes</a></h4>


                      <p>As you have seen, in the above example, display

            
                      attribute for the fields can be set with set_field_fore()

            
                      and setfield_back(). These functions set foreground and

            
                      background attribute of the fields. You can also specify

            
                      a pad character which will be filled in the unfilled

            
                      portion of the field. The pad character is set with a

            
                      call to set_field_pad(). Default pad value is a space.

            
                      The functions field_fore(), field_back, field_pad() can

            
                      be used to query the present foreground, background

            
                      attributes and pad character for the field. The following

            
                      list gives the usage of functions.</p>


                      <pre class=

            
                      "PROGRAMLISTING">&#13;int set_field_fore(FIELD *field,        /* field to alter */

            
                               chtype attr);        /* attribute to set */


            chtype field_fore(FIELD *field);        /* field to query */

            
                                                    /* returns foreground attribute */


            int set_field_back(FIELD *field,        /* field to alter */

            
                               chtype attr);        /* attribute to set */


            chtype field_back(FIELD *field);        /* field to query */

            
                                                    /* returns background attribute */


            int set_field_pad(FIELD *field,         /* field to alter */

            
                              int pad);             /* pad character to set */


            chtype field_pad(FIELD *field);         /* field to query */

            
                                                    /* returns present pad character */&#13;</pre>

            
                      <p>Though above functions seem quite simple, using colors

            
                      with set_field_fore() may be frustrating in the

            
                      beginning. Let me first explain about foreground and

            
                      background attributes of a field. The foreground

            
                      attribute is associated with the character. That means a

            
                      character in the field is printed with the attribute you

            
                      have set with set_field_fore(). Background attribute is

            
                      the attribute used to fill background of field, whether

            
                      any character is there or not. So what about colors?

            
                      Since colors are always defined in pairs, what is the

            
                      right way to display colored fields? Here's an example

            
                      clarifying color attributes.</p>


                      <div class="EXAMPLE">

            
                        <a name="FFOAT" id="FFOAT"></a>

            
                        <p><b>Example 26. Form Attributes example</b>

            
                        </p>


                        <pre class="PROGRAMLISTING"><span class=

            
                        "INLINEMEDIAOBJECT">#include &lt;form.h&gt;


            int main()

            
            {       FIELD *field[3];

            
                    FORM  *my_form;

            
                    int ch;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize few color pairs */

            
                    init_pair(1, COLOR_WHITE, COLOR_BLUE);

            
                    init_pair(2, COLOR_WHITE, COLOR_BLUE);


                    /* Initialize the fields */

            
                    field[0] = new_field(1, 10, 4, 18, 0, 0);

            
                    field[1] = new_field(1, 10, 6, 18, 0, 0);

            
                    field[2] = NULL;


                    /* Set field options */

            
                    set_field_fore(field[0], COLOR_PAIR(1));/* Put the field with blue background */

            
                    set_field_back(field[0], COLOR_PAIR(2));/* and white foreground (characters */

            
                                                            /* are printed in white         */

            
                    field_opts_off(field[0], O_AUTOSKIP);   /* Don't go to next field when this */

            
                                                            /* Field is filled up           */

            
                    set_field_back(field[1], A_UNDERLINE);

            
                    field_opts_off(field[1], O_AUTOSKIP);


                    /* Create the form and post it */

            
                    my_form = new_form(field);

            
                    post_form(my_form);

            
                    refresh();


                    set_current_field(my_form, field[0]); /* Set focus to the colored field */

            
                    mvprintw(4, 10, "Value 1:");

            
                    mvprintw(6, 10, "Value 2:");

            
                    mvprintw(LINES - 2, 0, "Use UP, DOWN arrow keys to switch between fields");

            
                    refresh();


                    /* Loop through to get user requests */

            
                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case KEY_DOWN:

            
                                            /* Go to next field */

            
                                            form_driver(my_form, REQ_NEXT_FIELD);

            
                                            /* Go to the end of the present buffer */

            
                                            /* Leaves nicely at the last character */

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    case KEY_UP:

            
                                            /* Go to previous field */

            
                                            form_driver(my_form, REQ_PREV_FIELD);

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    default:

            
                                            /* If this is a normal character, it gets */

            
                                            /* Printed                                */

            
                                            form_driver(my_form, ch);

            
                                            break;

            
                            }

            
                    }


                    /* Un post form and free the memory */

            
                    unpost_form(my_form);

            
                    free_form(my_form);

            
                    free_field(field[0]);

            
                    free_field(field[1]);


                    endwin();

            
                    return 0;

            
            }</span></pre>

            
                      </div>


                      <p>Play with the color pairs and try to understand the

            
                      foreground and background attributes. In my programs

            
                      using color attributes, I usually set only the background

            
                      with set_field_back(). Curses simply doesn't allow

            
                      defining individual color attributes.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="FIELDOPTIONBITS" id=

            
                      "FIELDOPTIONBITS">18.3.5. Field Option Bits</a></h4>


                      <p>There is also a large collection of field option bits

            
                      you can set to control various aspects of forms

            
                      processing. You can manipulate them with these

            
                      functions:</p>


                      <pre class=

            
                      "PROGRAMLISTING">int set_field_opts(FIELD *field,          /* field to alter */

            
                               int attr);             /* attribute to set */


            int field_opts_on(FIELD *field,           /* field to alter */

            
                              int attr);              /* attributes to turn on */


            int field_opts_off(FIELD *field,          /* field to alter */

            
                              int attr);              /* attributes to turn off */


            int field_opts(FIELD *field);             /* field to query */ </pre>

            
                      <p>The function set_field_opts() can be used to directly

            
                      set attributes of a field or you can choose to switch a

            
                      few attributes on and off with field_opts_on() and

            
                      field_opts_off() selectively. Anytime you can query the

            
                      attributes of a field with field_opts(). The following is

            
                      the list of available options. By default, all options

            
                      are on.</p>


                      <div class="VARIABLELIST">

            
                        <dl>

            
                          <dt>O_VISIBLE</dt>


                          <dd>

            
                            <p>Controls whether the field is visible on the

            
                            screen. Can be used during form processing to hide

            
                            or pop up fields depending on the value of parent

            
                            fields.</p>

            
                          </dd>


                          <dt>O_ACTIVE</dt>


                          <dd>

            
                            <p>Controls whether the field is active during

            
                            forms processing (i.e. visited by form navigation

            
                            keys). Can be used to make labels or derived fields

            
                            with buffer values alterable by the forms

            
                            application, not the user.</p>

            
                          </dd>


                          <dt>O_PUBLIC</dt>


                          <dd>

            
                            <p>Controls whether data is displayed during field

            
                            entry. If this option is turned off on a field, the

            
                            library will accept and edit data in that field,

            
                            but it will not be displayed and the visible field

            
                            cursor will not move. You can turn off the O_PUBLIC

            
                            bit to define password fields.</p>

            
                          </dd>


                          <dt>O_EDIT</dt>


                          <dd>

            
                            <p>Controls whether the field's data can be

            
                            modified. When this option is off, all editing

            
                            requests except <tt class=

            
                            "LITERAL">REQ_PREV_CHOICE</tt> and <tt class=

            
                            "LITERAL">REQ_NEXT_CHOICE</tt>will fail. Such

            
                            read-only fields may be useful for help

            
                            messages.</p>

            
                          </dd>


                          <dt>O_WRAP</dt>


                          <dd>

            
                            <p>Controls word-wrapping in multi-line fields.

            
                            Normally, when any character of a (blank-separated)

            
                            word reaches the end of the current line, the

            
                            entire word is wrapped to the next line (assuming

            
                            there is one). When this option is off, the word

            
                            will be split across the line break.</p>

            
                          </dd>


                          <dt>O_BLANK</dt>


                          <dd>

            
                            <p>Controls field blanking. When this option is on,

            
                            entering a character at the first field position

            
                            erases the entire field (except for the

            
                            just-entered character).</p>

            
                          </dd>


                          <dt>O_AUTOSKIP</dt>


                          <dd>

            
                            <p>Controls automatic skip to next field when this

            
                            one fills. Normally, when the forms user tries to

            
                            type more data into a field than will fit, the

            
                            editing location jumps to next field. When this

            
                            option is off, the user's cursor will hang at the

            
                            end of the field. This option is ignored in dynamic

            
                            fields that have not reached their size limit.</p>

            
                          </dd>


                          <dt>O_NULLOK</dt>


                          <dd>

            
                            <p>Controls whether validation is applied to blank

            
                            fields. Normally, it is not; the user can leave a

            
                            field blank without invoking the usual validation

            
                            check on exit. If this option is off on a field,

            
                            exit from it will invoke a validation check.</p>

            
                          </dd>


                          <dt>O_PASSOK</dt>


                          <dd>

            
                            <p>Controls whether validation occurs on every

            
                            exit, or only after the field is modified. Normally

            
                            the latter is true. Setting O_PASSOK may be useful

            
                            if your field's validation function may change

            
                            during forms processing.</p>

            
                          </dd>


                          <dt>O_STATIC</dt>


                          <dd>

            
                            <p>Controls whether the field is fixed to its

            
                            initial dimensions. If you turn this off, the field

            
                            becomes dynamic and will stretch to fit entered

            
                            data.</p>

            
                          </dd>

            
                        </dl>

            
                      </div>


                      <p>A field's options cannot be changed while the field is

            
                      currently selected. However, options may be changed on

            
                      posted fields that are not current.</p>


                      <p>The option values are bit-masks and can be composed

            
                      with logical-or in the obvious way. You have seen the

            
                      usage of switching off O_AUTOSKIP option. The following

            
                      example clarifies usage of some more options. Other

            
                      options are explained where appropriate.</p>


                      <div class="EXAMPLE">

            
                        <a name="FFOOP" id="FFOOP"></a>

            
                        <p><b>Example 27. Field Options Usage example</b>

            
                        </p>


                        <pre class="PROGRAMLISTING"><span class=

            
                        "INLINEMEDIAOBJECT">#include &lt;form.h&gt;


            #define STARTX 15

            
            #define STARTY 4

            
            #define WIDTH 25


            #define N_FIELDS 3


            int main()

            
            {       FIELD *field[N_FIELDS];

            
                    FORM  *my_form;

            
                    int ch, i;


                    /* Initialize curses */

            
                    initscr();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize the fields */

            
                    for(i = 0; i &lt; N_FIELDS - 1; ++i)

            
                            field[i] = new_field(1, WIDTH, STARTY + i * 2, STARTX, 0, 0);

            
                    field[N_FIELDS - 1] = NULL;


                    /* Set field options */

            
                    set_field_back(field[1], A_UNDERLINE);  /* Print a line for the option  */


                    field_opts_off(field[0], O_ACTIVE); /* This field is a static label */

            
                    field_opts_off(field[1], O_PUBLIC); /* This filed is like a password field*/

            
                    field_opts_off(field[1], O_AUTOSKIP); /* To avoid entering the same field */

            
                                                          /* after last character is entered */


                    /* Create the form and post it */

            
                    my_form = new_form(field);

            
                    post_form(my_form);

            
                    refresh();


                    set_field_just(field[0], JUSTIFY_CENTER); /* Center Justification */

            
                    set_field_buffer(field[0], 0, "This is a static Field");

            
                                                              /* Initialize the field  */

            
                    mvprintw(STARTY, STARTX - 10, "Field 1:");

            
                    mvprintw(STARTY + 2, STARTX - 10, "Field 2:");

            
                    refresh();


                    /* Loop through to get user requests */

            
                    while((ch = getch()) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case KEY_DOWN:

            
                                            /* Go to next field */

            
                                            form_driver(my_form, REQ_NEXT_FIELD);

            
                                            /* Go to the end of the present buffer */

            
                                            /* Leaves nicely at the last character */

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    case KEY_UP:

            
                                            /* Go to previous field */

            
                                            form_driver(my_form, REQ_PREV_FIELD);

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    default:

            
                                            /* If this is a normal character, it gets */

            
                                            /* Printed                                */

            
                                            form_driver(my_form, ch);

            
                                            break;

            
                            }

            
                    }


                    /* Un post form and free the memory */

            
                    unpost_form(my_form);

            
                    free_form(my_form);

            
                    free_field(field[0]);

            
                    free_field(field[1]);


                    endwin();

            
                    return 0;

            
            }</span></pre>

            
                      </div>


                      <p>This example, though useless, shows the usage of

            
                      options. If used properly, they can present information

            
                      very effectively in a form. The second field being not

            
                      O_PUBLIC, does not show the characters you are

            
                      typing.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="FIELDSTATUS" id=

            
                      "FIELDSTATUS">18.3.6. Field Status</a></h4>


                      <p>The field status specifies whether the field has got

            
                      edited or not. It is initially set to FALSE and when user

            
                      enters something and the data buffer gets modified it

            
                      becomes TRUE. So a field's status can be queried to find

            
                      out whether it has been modified or not. The following

            
                      functions can assist in those operations.</p>


                      <pre class=

            
                      "PROGRAMLISTING">int set_field_status(FIELD *field,      /* field to alter */

            
                               int status);         /* status to set */


            int field_status(FIELD *field);         /* fetch status of field */</pre>

            
                      <p>It is better to check the field's status only after

            
                      after leaving the field, as data buffer might not have

            
                      been updated yet as the validation is still due. To

            
                      guarantee that right status is returned, call

            
                      field_status() either (1) in the field's exit validation

            
                      check routine, (2) from the field's or form's

            
                      initialization or termination hooks, or (3) just after a

            
                      REQ_VALIDATION request has been processed by the forms

            
                      driver</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="FIELDUSERPTR" id=

            
                      "FIELDUSERPTR">18.3.7. Field User Pointer</a></h4>


                      <p>Every field structure contains one pointer that can be

            
                      used by the user for various purposes. It is not touched

            
                      by forms library and can be used for any purpose by the

            
                      user. The following functions set and fetch user

            
                      pointer.</p>


                      <pre class=

            
                      "PROGRAMLISTING">int set_field_userptr(FIELD *field,

            
                       char *userptr);      /* the user pointer you wish to associate */

            
                                            /* with the field    */


            char *field_userptr(FIELD *field);      /* fetch user pointer of the field */</pre>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="VARIABLESIZEFIELDS" id=

            
                      "VARIABLESIZEFIELDS">18.3.8. Variable-Sized Fields</a></h4>


                      <p>If you want a dynamically changing field with variable

            
                      width, this is the feature you want to put to full use.

            
                      This will allow the user to enter more data than the

            
                      original size of the field and let the field grow.

            
                      According to the field orientation it will scroll

            
                      horizontally or vertically to incorporate the new

            
                      data.</p>


                      <p>To make a field dynamically growable, the option

            
                      O_STATIC should be turned off. This can be done with

            
                      a</p>


                      <pre class=

            
                      "PROGRAMLISTING">    field_opts_off(field_pointer, O_STATIC);</pre>

            
                      <p>But it is usually not advisable to allow a field to

            
                      grow infinitely. You can set a maximum limit to the

            
                      growth of the field with</p>


                      <pre class=

            
                      "PROGRAMLISTING">int set_max_field(FIELD *field,    /* Field on which to operate */

            
                              int max_growth); /* maximum growth allowed for the field */</pre>

            
                      <p>The field info for a dynamically growable field can be

            
                      retrieved by</p>


                      <pre class=

            
                      "PROGRAMLISTING">int dynamic_field_info( FIELD *field,     /* Field on which to operate */

            
                        int   *prows,     /* number of rows will be filled in this */

            
                        int   *pcols,     /* number of columns will be filled in this*/

            
                        int   *pmax)      /* maximum allowable growth will be filled */

            
                                          /* in this */</pre>Though field_info

            
            work as usual, it is advisable to use this function to get the

            
            proper attributes of a dynamically growable field.

            
                      <p>Recall the library routine new_field; a new field

            
                      created with height set to one will be defined to be a

            
                      one line field. A new field created with height greater

            
                      than one will be defined to be a multi line field.</p>


                      <p>A one line field with O_STATIC turned off (dynamically

            
                      growable field) will contain a single fixed row, but the

            
                      number of columns can increase if the user enters more

            
                      data than the initial field will hold. The number of

            
                      columns displayed will remain fixed and the additional

            
                      data will scroll horizontally.</p>


                      <p>A multi line field with O_STATIC turned off

            
                      (dynamically growable field) will contain a fixed number

            
                      of columns, but the number of rows can increase if the

            
                      user enters more data than the initial field will hold.

            
                      The number of rows displayed will remain fixed and the

            
                      additional data will scroll vertically.</p>


                      <p>The above two paragraphs pretty much describe a

            
                      dynamically growable field's behavior. The way other

            
                      parts of forms library behaves is described below:</p>


                      <ol type="1">

            
                        <li>

            
                          <p>The field option O_AUTOSKIP will be ignored if the

            
                          option O_STATIC is off and there is no maximum growth

            
                          specified for the field. Currently, O_AUTOSKIP

            
                          generates an automatic REQ_NEXT_FIELD form driver

            
                          request when the user types in the last character

            
                          position of a field. On a growable field with no

            
                          maximum growth specified, there is no last character

            
                          position. If a maximum growth is specified, the

            
                          O_AUTOSKIP option will work as normal if the field

            
                          has grown to its maximum size.</p>

            
                        </li>


                        <li>

            
                          <p>The field justification will be ignored if the

            
                          option O_STATIC is off. Currently, set_field_just can

            
                          be used to JUSTIFY_LEFT, JUSTIFY_RIGHT,

            
                          JUSTIFY_CENTER the contents of a one line field. A

            
                          growable one line field will, by definition, grow and

            
                          scroll horizontally and may contain more data than

            
                          can be justified. The return from field_just will be

            
                          unchanged.</p>

            
                        </li>


                        <li>

            
                          <p>The overloaded form driver request REQ_NEW_LINE

            
                          will operate the same way regardless of the

            
                          O_NL_OVERLOAD form option if the field option

            
                          O_STATIC is off and there is no maximum growth

            
                          specified for the field. Currently, if the form

            
                          option O_NL_OVERLOAD is on, REQ_NEW_LINE implicitly

            
                          generates a REQ_NEXT_FIELD if called from the last

            
                          line of a field. If a field can grow without bound,

            
                          there is no last line, so REQ_NEW_LINE will never

            
                          implicitly generate a REQ_NEXT_FIELD. If a maximum

            
                          growth limit is specified and the O_NL_OVERLOAD form

            
                          option is on, REQ_NEW_LINE will only implicitly

            
                          generate REQ_NEXT_FIELD if the field has grown to its

            
                          maximum size and the user is on the last line.</p>

            
                        </li>


                        <li>

            
                          <p>The library call dup_field will work as usual; it

            
                          will duplicate the field, including the current

            
                          buffer size and contents of the field being

            
                          duplicated. Any specified maximum growth will also be

            
                          duplicated.</p>

            
                        </li>


                        <li>

            
                          <p>The library call link_field will work as usual; it

            
                          will duplicate all field attributes and share buffers

            
                          with the field being linked. If the O_STATIC field

            
                          option is subsequently changed by a field sharing

            
                          buffers, how the system reacts to an attempt to enter

            
                          more data into the field than the buffer will

            
                          currently hold will depend on the setting of the

            
                          option in the current field.</p>

            
                        </li>


                        <li>

            
                          <p>The library call field_info will work as usual;

            
                          the variable nrow will contain the value of the

            
                          original call to new_field. The user should use

            
                          dynamic_field_info, described above, to query the

            
                          current size of the buffer.</p>

            
                        </li>

            
                      </ol>


                      <p>Some of the above points make sense only after

            
                      explaining form driver. We will be looking into that in

            
                      next few sections.</p>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="FORMWINDOWS" id=

            
                    "FORMWINDOWS">18.4. Form Windows</a></h3>


                    <p>The form windows concept is pretty much similar to menu

            
                    windows. Every form is associated with a main window and a

            
                    sub window. The form main window displays any title or

            
                    border associated or whatever the user wishes. Then the sub

            
                    window contains all the fields and displays them according

            
                    to their position. This gives the flexibility of

            
                    manipulating fancy form displaying very easily.</p>


                    <p>Since this is pretty much similar to menu windows, I am

            
                    providing an example with out much explanation. The

            
                    functions are similar and they work the same way.</p>


                    <div class="EXAMPLE">

            
                      <a name="FFOWI" id="FFOWI"></a>

            
                      <p><b>Example 28. Form Windows Example</b>

            
                      </p>


                      <pre class="PROGRAMLISTING"><span class=

            
                      "INLINEMEDIAOBJECT">#include &lt;string.h&gt;

            
            #include &lt;form.h&gt;


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);


            int main()

            
            {

            
                    FIELD *field[3];

            
                    FORM  *my_form;

            
                    WINDOW *my_form_win;

            
                    int ch, rows, cols;


                    /* Initialize curses */

            
                    initscr();

            
                    start_color();

            
                    cbreak();

            
                    noecho();

            
                    keypad(stdscr, TRUE);


                    /* Initialize few color pairs */

            
                    init_pair(1, COLOR_RED, COLOR_BLACK);


                    /* Initialize the fields */

            
                    field[0] = new_field(1, 10, 6, 1, 0, 0);

            
                    field[1] = new_field(1, 10, 8, 1, 0, 0);

            
                    field[2] = NULL;


                    /* Set field options */

            
                    set_field_back(field[0], A_UNDERLINE);

            
                    field_opts_off(field[0], O_AUTOSKIP); /* Don't go to next field when this */

            
                                                          /* Field is filled up             */

            
                    set_field_back(field[1], A_UNDERLINE);

            
                    field_opts_off(field[1], O_AUTOSKIP);


                    /* Create the form and post it */

            
                    my_form = new_form(field);


                    /* Calculate the area required for the form */

            
                    scale_form(my_form, &amp;rows, &amp;cols);


                    /* Create the window to be associated with the form */

            
                    my_form_win = newwin(rows + 4, cols + 4, 4, 4);

            
                    keypad(my_form_win, TRUE);


                    /* Set main window and sub window */

            
                    set_form_win(my_form, my_form_win);

            
                    set_form_sub(my_form, derwin(my_form_win, rows, cols, 2, 2));


                    /* Print a border around the main window and print a title */

            
                    box(my_form_win, 0, 0);

            
                    print_in_middle(my_form_win, 1, 0, cols + 4, "My Form", COLOR_PAIR(1));


                    post_form(my_form);

            
                    wrefresh(my_form_win);


                    mvprintw(LINES - 2, 0, "Use UP, DOWN arrow keys to switch between fields");

            
                    refresh();


                    /* Loop through to get user requests */

            
                    while((ch = wgetch(my_form_win)) != KEY_F(1))

            
                    {       switch(ch)

            
                            {       case KEY_DOWN:

            
                                            /* Go to next field */

            
                                            form_driver(my_form, REQ_NEXT_FIELD);

            
                                            /* Go to the end of the present buffer */

            
                                            /* Leaves nicely at the last character */

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    case KEY_UP:

            
                                            /* Go to previous field */

            
                                            form_driver(my_form, REQ_PREV_FIELD);

            
                                            form_driver(my_form, REQ_END_LINE);

            
                                            break;

            
                                    default:

            
                                            /* If this is a normal character, it gets */

            
                                            /* Printed                                */

            
                                            form_driver(my_form, ch);

            
                                            break;

            
                            }

            
                    }


                    /* Un post form and free the memory */

            
                    unpost_form(my_form);

            
                    free_form(my_form);

            
                    free_field(field[0]);

            
                    free_field(field[1]);


                    endwin();

            
                    return 0;

            
            }


            void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)

            
            {       int length, x, y;

            
                    float temp;


                    if(win == NULL)

            
                            win = stdscr;

            
                    getyx(win, y, x);

            
                    if(startx != 0)

            
                            x = startx;

            
                    if(starty != 0)

            
                            y = starty;

            
                    if(width == 0)

            
                            width = 80;


                    length = strlen(string);

            
                    temp = (width - length)/ 2;

            
                    x = startx + (int)temp;

            
                    wattron(win, color);

            
                    mvwprintw(win, y, x, "%s", string);

            
                    wattroff(win, color);

            
                    refresh();

            
            }</span></pre>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="FILEDVALIDATE" id=

            
                    "FILEDVALIDATE">18.5. Field Validation</a></h3>


                    <p>By default, a field will accept any data input by the

            
                    user. It is possible to attach validation to the field.

            
                    Then any attempt by the user to leave the field, while it

            
                    contains data that doesn't match the validation type will

            
                    fail. Some validation types also have a character-validity

            
                    check for each time a character is entered in the

            
                    field.</p>


                    <p>Validation can be attached to a field with the following

            
                    function.</p>


                    <pre class=

            
                    "PROGRAMLISTING">int set_field_type(FIELD *field,          /* field to alter */

            
                               FIELDTYPE *ftype,      /* type to associate */

            
                               ...);                  /* additional arguments*/</pre>Once

            
            set, the validation type for a field can be queried with


                    <pre class=

            
                    "PROGRAMLISTING">FIELDTYPE *field_type(FIELD *field);      /* field to query */</pre>

            
                    <p>The form driver validates the data in a field only when

            
                    data is entered by the end-user. Validation does not occur

            
                    when</p>


                    <ul>

            
                      <li>

            
                        <p>the application program changes the field value by

            
                        calling set_field_buffer.</p>

            
                      </li>


                      <li>

            
                        <p>linked field values are changed indirectly -- by

            
                        changing the field to which they are linked</p>

            
                      </li>

            
                    </ul>


                    <p>The following are the pre-defined validation types. You

            
                    can also specify custom validation, though it is a bit

            
                    tricky and cumbersome.</p>


                    <h1 class="BRIDGEHEAD"><a name="AEN1074" id=

            
                    "AEN1074"></a>TYPE_ALPHA</h1>


                    <p>This field type accepts alphabetic data; no blanks, no

            
                    digits, no special characters (this is checked at

            
                    character-entry time). It is set up with:</p>


                    <pre class=

            
                    "PROGRAMLISTING">int set_field_type(FIELD *field,          /* field to alter */

            
                               TYPE_ALPHA,            /* type to associate */

            
                               int width);            /* minimum width of field */</pre>

            
                    <p>The width argument sets a minimum width of data. The

            
                    user has to enter at-least width number of characters

            
                    before he can leave the field. Typically you'll want to set

            
                    this to the field width; if it is greater than the field

            
                    width, the validation check will always fail. A minimum

            
                    width of zero makes field completion optional.</p>


                    <h1 class="BRIDGEHEAD"><a name="AEN1078" id=

            
                    "AEN1078"></a>TYPE_ALNUM</h1>


                    <p>This field type accepts alphabetic data and digits; no

            
                    blanks, no special characters (this is checked at

            
                    character-entry time). It is set up with:</p>


                    <pre class=

            
                    "PROGRAMLISTING">int set_field_type(FIELD *field,          /* field to alter */

            
                               TYPE_ALNUM,            /* type to associate */

            
                               int width);            /* minimum width of field */</pre>

            
                    <p>The width argument sets a minimum width of data. As with

            
                    TYPE_ALPHA, typically you'll want to set this to the field

            
                    width; if it is greater than the field width, the

            
                    validation check will always fail. A minimum width of zero

            
                    makes field completion optional.</p>


                    <h1 class="BRIDGEHEAD"><a name="AEN1082" id=

            
                    "AEN1082"></a>TYPE_ENUM</h1>


                    <p>This type allows you to restrict a field's values to be

            
                    among a specified set of string values (for example, the

            
                    two-letter postal codes for U.S. states). It is set up

            
                    with:</p>


                    <pre class=

            
                    "PROGRAMLISTING">int set_field_type(FIELD *field,          /* field to alter */

            
                               TYPE_ENUM,             /* type to associate */

            
                               char **valuelist;      /* list of possible values */

            
                               int checkcase;         /* case-sensitive? */

            
                               int checkunique);      /* must specify uniquely? */</pre>

            
                    <p>The valuelist parameter must point at a NULL-terminated

            
                    list of valid strings. The checkcase argument, if true,

            
                    makes comparison with the string case-sensitive.</p>


                    <p>When the user exits a TYPE_ENUM field, the validation

            
                    procedure tries to complete the data in the buffer to a

            
                    valid entry. If a complete choice string has been entered,

            
                    it is of course valid. But it is also possible to enter a

            
                    prefix of a valid string and have it completed for you.</p>


                    <p>By default, if you enter such a prefix and it matches

            
                    more than one value in the string list, the prefix will be

            
                    completed to the first matching value. But the checkunique

            
                    argument, if true, requires prefix matches to be unique in

            
                    order to be valid.</p>


                    <p>The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests

            
                    can be particularly useful with these fields.</p>


                    <h1 class="BRIDGEHEAD"><a name="AEN1089" id=

            
                    "AEN1089"></a>TYPE_INTEGER</h1>


                    <p>This field type accepts an integer. It is set up as

            
                    follows:</p>


                    <pre class=

            
                    "PROGRAMLISTING">int set_field_type(FIELD *field,          /* field to alter */

            
                               TYPE_INTEGER,          /* type to associate */

            
                               int padding,           /* # places to zero-pad to */

            
                               int vmin, int vmax);   /* valid range */</pre>

            
                    <p>Valid characters consist of an optional leading minus

            
                    and digits. The range check is performed on exit. If the

            
                    range maximum is less than or equal to the minimum, the

            
                    range is ignored.</p>


                    <p>If the value passes its range check, it is padded with

            
                    as many leading zero digits as necessary to meet the

            
                    padding argument.</p>


                    <p>A TYPE_INTEGER value buffer can conveniently be

            
                    interpreted with the C library function atoi(3).</p>


                    <h1 class="BRIDGEHEAD"><a name="AEN1095" id=

            
                    "AEN1095"></a>TYPE_NUMERIC</h1>


                    <p>This field type accepts a decimal number. It is set up

            
                    as follows:</p>


                    <pre class=

            
                    "PROGRAMLISTING">int set_field_type(FIELD *field,          /* field to alter */

            
                               TYPE_NUMERIC,          /* type to associate */

            
                               int padding,           /* # places of precision */

            
                               int vmin, int vmax);   /* valid range */</pre>

            
                    <p>Valid characters consist of an optional leading minus

            
                    and digits. possibly including a decimal point. The range

            
                    check is performed on exit. If the range maximum is less

            
                    than or equal to the minimum, the range is ignored.</p>


                    <p>If the value passes its range check, it is padded with

            
                    as many trailing zero digits as necessary to meet the

            
                    padding argument.</p>


                    <p>A TYPE_NUMERIC value buffer can conveniently be

            
                    interpreted with the C library function atof(3).</p>


                    <h1 class="BRIDGEHEAD"><a name="AEN1101" id=

            
                    "AEN1101"></a>TYPE_REGEXP</h1>


                    <p>This field type accepts data matching a regular

            
                    expression. It is set up as follows:</p>


                    <pre class=

            
                    "PROGRAMLISTING">int set_field_type(FIELD *field,          /* field to alter */

            
                               TYPE_REGEXP,           /* type to associate */

            
                               char *regexp);         /* expression to match */</pre>

            
                    <p>The syntax for regular expressions is that of

            
                    regcomp(3). The check for regular-expression match is

            
                    performed on exit.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="FORMDRIVER" id=

            
                    "FORMDRIVER">18.6. Form Driver: The work horse of the forms

            
                    system</a></h3>


                    <p>As in the menu system, form_driver() plays a very

            
                    important role in forms system. All types of requests to

            
                    forms system should be funneled through form_driver().</p>


                    <pre class=

            
                    "PROGRAMLISTING">int form_driver(FORM *form,     /* form on which to operate     */

            
                            int request)    /* form request code         */</pre>

            
                    <p>As you have seen some of the examples above, you have to

            
                    be in a loop looking for user input and then decide whether

            
                    it is a field data or a form request. The form requests are

            
                    then passed to form_driver() to do the work.</p>


                    <p>The requests roughly can be divided into following

            
                    categories. Different requests and their usage is explained

            
                    below:</p>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="PAGENAVREQ" id=

            
                      "PAGENAVREQ">18.6.1. Page Navigation Requests</a></h4>


                      <p>These requests cause page-level moves through the

            
                      form, triggering display of a new form screen. A form can

            
                      be made of multiple pages. If you have a big form with

            
                      lot of fields and logical sections, then you can divide

            
                      the form into pages. The function set_new_page() to set a

            
                      new page at the field specified.</p>


                      <pre class=

            
                      "PROGRAMLISTING">int set_new_page(FIELD *field,/* Field at which page break to be set or unset */

            
                     bool new_page_flag); /* should be TRUE to put a break */</pre>

            
                      <p>The following requests allow you to move to different

            
                      pages</p>


                      <ul>

            
                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_NEXT_PAGE</i></span> Move to the next

            
                          form page.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_PREV_PAGE</i></span> Move to the

            
                          previous form page.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_FIRST_PAGE</i></span> Move to the

            
                          first form page.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_LAST_PAGE</i></span> Move to the last

            
                          form page.</p>

            
                        </li>

            
                      </ul>


                      <p>These requests treat the list as cyclic; that is,

            
                      REQ_NEXT_PAGE from the last page goes to the first, and

            
                      REQ_PREV_PAGE from the first page goes to the last.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="INTERFIELDNAVREQ" id=

            
                      "INTERFIELDNAVREQ">18.6.2. Inter-Field Navigation

            
                      Requests</a></h4>


                      <p>These requests handle navigation between fields on the

            
                      same page.</p>


                      <ul>

            
                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_NEXT_FIELD</i></span> Move to next

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_PREV_FIELD</i></span> Move to previous

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_FIRST_FIELD</i></span> Move to the

            
                          first field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_LAST_FIELD</i></span> Move to the last

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SNEXT_FIELD</i></span> Move to sorted

            
                          next field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SPREV_FIELD</i></span> Move to sorted

            
                          previous field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SFIRST_FIELD</i></span> Move to the

            
                          sorted first field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SLAST_FIELD</i></span> Move to the

            
                          sorted last field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_LEFT_FIELD</i></span> Move left to

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_RIGHT_FIELD</i></span> Move right to

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_UP_FIELD</i></span> Move up to

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_DOWN_FIELD</i></span> Move down to

            
                          field.</p>

            
                        </li>

            
                      </ul>


                      <p>These requests treat the list of fields on a page as

            
                      cyclic; that is, REQ_NEXT_FIELD from the last field goes

            
                      to the first, and REQ_PREV_FIELD from the first field

            
                      goes to the last. The order of the fields for these (and

            
                      the REQ_FIRST_FIELD and REQ_LAST_FIELD requests) is

            
                      simply the order of the field pointers in the form array

            
                      (as set up by new_form() or set_form_fields()</p>


                      <p>It is also possible to traverse the fields as if they

            
                      had been sorted in screen-position order, so the sequence

            
                      goes left-to-right and top-to-bottom. To do this, use the

            
                      second group of four sorted-movement requests.</p>


                      <p>Finally, it is possible to move between fields using

            
                      visual directions up, down, right, and left. To

            
                      accomplish this, use the third group of four requests.

            
                      Note, however, that the position of a form for purposes

            
                      of these requests is its upper-left corner.</p>


                      <p>For example, suppose you have a multi-line field B,

            
                      and two single-line fields A and C on the same line with

            
                      B, with A to the left of B and C to the right of B. A

            
                      REQ_MOVE_RIGHT from A will go to B only if A, B, and C

            
                      all share the same first line; otherwise it will skip

            
                      over B to C.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="INTRAFIELDNAVREQ" id=

            
                      "INTRAFIELDNAVREQ">18.6.3. Intra-Field Navigation

            
                      Requests</a></h4>


                      <p>These requests drive movement of the edit cursor

            
                      within the currently selected field.</p>


                      <ul>

            
                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_NEXT_CHAR</i></span> Move to next

            
                          character.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_PREV_CHAR</i></span> Move to previous

            
                          character.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_NEXT_LINE</i></span> Move to next

            
                          line.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_PREV_LINE</i></span> Move to previous

            
                          line.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_NEXT_WORD</i></span> Move to next

            
                          word.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_PREV_WORD</i></span> Move to previous

            
                          word.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_BEG_FIELD</i></span> Move to beginning

            
                          of field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_END_FIELD</i></span> Move to end of

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_BEG_LINE</i></span> Move to beginning

            
                          of line.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_END_LINE</i></span> Move to end of

            
                          line.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_LEFT_CHAR</i></span> Move left in

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_RIGHT_CHAR</i></span> Move right in

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_UP_CHAR</i></span> Move up in

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_DOWN_CHAR</i></span> Move down in

            
                          field.</p>

            
                        </li>

            
                      </ul>


                      <p>Each word is separated from the previous and next

            
                      characters by whitespace. The commands to move to

            
                      beginning and end of line or field look for the first or

            
                      last non-pad character in their ranges.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="SCROLLREQ" id=

            
                      "SCROLLREQ">18.6.4. Scrolling Requests</a></h4>


                      <p>Fields that are dynamic and have grown and fields

            
                      explicitly created with offscreen rows are scrollable.

            
                      One-line fields scroll horizontally; multi-line fields

            
                      scroll vertically. Most scrolling is triggered by editing

            
                      and intra-field movement (the library scrolls the field

            
                      to keep the cursor visible). It is possible to explicitly

            
                      request scrolling with the following requests:</p>


                      <ul>

            
                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_FLINE</i></span> Scroll vertically

            
                          forward a line.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_BLINE</i></span> Scroll vertically

            
                          backward a line.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_FPAGE</i></span> Scroll vertically

            
                          forward a page.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_BPAGE</i></span> Scroll vertically

            
                          backward a page.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_FHPAGE</i></span> Scroll

            
                          vertically forward half a page.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_BHPAGE</i></span> Scroll

            
                          vertically backward half a page.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_FCHAR</i></span> Scroll

            
                          horizontally forward a character.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_BCHAR</i></span> Scroll

            
                          horizontally backward a character.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_HFLINE</i></span> Scroll

            
                          horizontally one field width forward.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_HBLINE</i></span> Scroll

            
                          horizontally one field width backward.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_HFHALF</i></span> Scroll

            
                          horizontally one half field width forward.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_SCR_HBHALF</i></span> Scroll

            
                          horizontally one half field width backward.</p>

            
                        </li>

            
                      </ul>


                      <p>For scrolling purposes, a page of a field is the

            
                      height of its visible part.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="EDITREQ" id="EDITREQ">18.6.5.

            
                      Editing Requests</a></h4>


                      <p>When you pass the forms driver an ASCII character, it

            
                      is treated as a request to add the character to the

            
                      field's data buffer. Whether this is an insertion or a

            
                      replacement depends on the field's edit mode (insertion

            
                      is the default.</p>


                      <p>The following requests support editing the field and

            
                      changing the edit mode:</p>


                      <ul>

            
                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_INS_MODE</i></span> Set insertion

            
                          mode.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_OVL_MODE</i></span> Set overlay

            
                          mode.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_NEW_LINE</i></span> New line request

            
                          (see below for explanation).</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_INS_CHAR</i></span> Insert space at

            
                          character location.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_INS_LINE</i></span> Insert blank line

            
                          at character location.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_DEL_CHAR</i></span> Delete character

            
                          at cursor.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_DEL_PREV</i></span> Delete previous

            
                          word at cursor.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_DEL_LINE</i></span> Delete line at

            
                          cursor.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_DEL_WORD</i></span> Delete word at

            
                          cursor.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_CLR_EOL</i></span> Clear to end of

            
                          line.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_CLR_EOF</i></span> Clear to end of

            
                          field.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_CLR_FIELD</i></span> Clear entire

            
                          field.</p>

            
                        </li>

            
                      </ul>


                      <p>The behavior of the REQ_NEW_LINE and REQ_DEL_PREV

            
                      requests is complicated and partly controlled by a pair

            
                      of forms options. The special cases are triggered when

            
                      the cursor is at the beginning of a field, or on the last

            
                      line of the field.</p>


                      <p>First, we consider REQ_NEW_LINE:</p>


                      <p>The normal behavior of REQ_NEW_LINE in insert mode is

            
                      to break the current line at the position of the edit

            
                      cursor, inserting the portion of the current line after

            
                      the cursor as a new line following the current and moving

            
                      the cursor to the beginning of that new line (you may

            
                      think of this as inserting a newline in the field

            
                      buffer).</p>


                      <p>The normal behavior of REQ_NEW_LINE in overlay mode is

            
                      to clear the current line from the position of the edit

            
                      cursor to end of line. The cursor is then moved to the

            
                      beginning of the next line.</p>


                      <p>However, REQ_NEW_LINE at the beginning of a field, or

            
                      on the last line of a field, instead does a

            
                      REQ_NEXT_FIELD. O_NL_OVERLOAD option is off, this special

            
                      action is disabled.</p>


                      <p>Now, let us consider REQ_DEL_PREV:</p>


                      <p>The normal behavior of REQ_DEL_PREV is to delete the

            
                      previous character. If insert mode is on, and the cursor

            
                      is at the start of a line, and the text on that line will

            
                      fit on the previous one, it instead appends the contents

            
                      of the current line to the previous one and deletes the

            
                      current line (you may think of this as deleting a newline

            
                      from the field buffer).</p>


                      <p>However, REQ_DEL_PREV at the beginning of a field is

            
                      instead treated as a REQ_PREV_FIELD.</p>


                      <p>If the O_BS_OVERLOAD option is off, this special

            
                      action is disabled and the forms driver just returns

            
                      E_REQUEST_DENIED.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="ORDERREQ" id=

            
                      "ORDERREQ">18.6.6. Order Requests</a></h4>


                      <p>If the type of your field is ordered, and has

            
                      associated functions for getting the next and previous

            
                      values of the type from a given value, there are requests

            
                      that can fetch that value into the field buffer:</p>


                      <ul>

            
                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_NEXT_CHOICE</i></span> Place the

            
                          successor value of the current value in the

            
                          buffer.</p>

            
                        </li>


                        <li>

            
                          <p><span class="emphasis"><i class=

            
                          "EMPHASIS">REQ_PREV_CHOICE</i></span> Place the

            
                          predecessor value of the current value in the

            
                          buffer.</p>

            
                        </li>

            
                      </ul>


                      <p>Of the built-in field types, only TYPE_ENUM has

            
                      built-in successor and predecessor functions. When you

            
                      define a field type of your own (see Custom Validation

            
                      Types), you can associate our own ordering functions.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="APPLICCOMMANDS" id=

            
                      "APPLICCOMMANDS">18.6.7. Application Commands</a></h4>


                      <p>Form requests are represented as integers above the

            
                      curses value greater than KEY_MAX and less than or equal

            
                      to the constant MAX_COMMAND. A value within this range

            
                      gets ignored by form_driver(). So this can be used for

            
                      any purpose by the application. It can be treated as an

            
                      application specific action and take corresponding

            
                      action.</p>

            
                    </div>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="TOOLS" id="TOOLS">19. Tools and

            
                  Widget Libraries</a></h2>


                  <p>Now that you have seen the capabilities of ncurses and its

            
                  sister libraries, you are rolling your sleeves up and gearing

            
                  for a project that heavily manipulates screen. But wait.. It

            
                  can be pretty difficult to write and maintain complex GUI

            
                  widgets in plain ncurses or even with the additional

            
                  libraries. There are some ready-to-use tools and widget

            
                  libraries that can be used instead of writing your own

            
                  widgets. You can use some of them, get ideas from the code,

            
                  or even extend them.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="CDK" id="CDK">19.1. CDK (Curses

            
                    Development Kit)</a></h3>


                    <p>In the author's words</p>


                    <p><span class="emphasis"><i class="EMPHASIS">CDK stands

            
                    for 'Curses Development Kit' and it currently contains 21

            
                    ready to use widgets which facilitate the speedy

            
                    development of full screen curses programs.</i></span>

            
                    </p>


                    <p>The kit provides some useful widgets, which can be used

            
                    in your programs directly. It is pretty well written and

            
                    the documentation is very good. The examples in the

            
                    examples directory can be a good place to start for

            
                    beginners. The CDK can be downloaded from <a href=

            
                    "https://invisible-island.net/cdk/" target=

            
                    "_top">https://invisible-island.net/cdk/</a> . Follow the

            
                    instructions in README file to install it.</p>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="WIDGETLIST" id=

            
                      "WIDGETLIST">19.1.1. Widget List</a></h4>


                      <p>The following is the list of widgets provided with cdk

            
                      and their description.</p>


                      <pre class=

            
                      "PROGRAMLISTING">Widget Type           Quick Description

            
            ===========================================================================

            
            Alphalist             Allows a user to select from a list of words, with

            
                                  the ability to narrow the search list by typing in a

            
                                  few characters of the desired word.

            
            Buttonbox             This creates a multiple button widget.

            
            Calendar              Creates a little simple calendar widget.

            
            Dialog                Prompts the user with a message, and the user

            
                                  can pick an answer from the buttons provided.

            
            Entry                 Allows the user to enter various types of information.

            
            File Selector         A file selector built from Cdk base widgets. This

            
                                  example shows how to create more complicated widgets

            
                                  using the Cdk widget library.

            
            Graph                 Draws a graph.

            
            Histogram             Draws a histogram.

            
            Item List             Creates a pop up field which allows the user to select

            
                                  one of several choices in a small field. Very useful

            
                                  for things like days of the week or month names.

            
            Label                 Displays messages in a pop up box, or the label can be

            
                                  considered part of the screen.

            
            Marquee               Displays a message in a scrolling marquee.

            
            Matrix                Creates a complex matrix with lots of options.

            
            Menu                  Creates a pull-down menu interface.

            
            Multiple Line Entry   A multiple line entry field. Very useful

            
                                  for long fields. (like a description

            
                                  field)

            
            Radio List            Creates a radio button list.

            
            Scale                 Creates a numeric scale. Used for allowing a user to

            
                                  pick a numeric value and restrict them to a range of

            
                                  values.

            
            Scrolling List        Creates a scrolling list/menu list.

            
            Scrolling Window      Creates a scrolling log file viewer. Can add

            
                                  information into the window while its running.

            
                                  A good widget for displaying the progress of

            
                                  something. (akin to a console window)

            
            Selection List        Creates a multiple option selection list.

            
            Slider                Akin to the scale widget, this widget provides a

            
                                  visual slide bar to represent the numeric value.

            
            Template              Creates a entry field with character sensitive

            
                                  positions. Used for pre-formatted fields like

            
                                  dates and phone numbers.

            
            Viewer                This is a file/information viewer. Very useful

            
                                  when you need to display loads of information.

            
            ===========================================================================</pre>

            
                      <p>A few of the widgets are modified by Thomas Dickey in

            
                      recent versions.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="CDKATTRACT" id=

            
                      "CDKATTRACT">19.1.2. Some Attractive Features</a></h4>


                      <p>Apart from making our life easier with readily usable

            
                      widgets, cdk solves one frustrating problem with printing

            
                      multi colored strings, justified strings elegantly.

            
                      Special formatting tags can be embedded in the strings

            
                      which are passed to CDK functions. For Example</p>


                      <p>If the string</p>


                      <pre class=

            
                      "PROGRAMLISTING">"&lt;/B/1&gt;This line should have a yellow foreground and a blue

            
            background.&lt;!1&gt;"</pre>

            
                      <p>given as a parameter to newCDKLabel(), it prints the

            
                      line with yellow foreground and blue background. There

            
                      are other tags available for justifying string, embedding

            
                      special drawing characters, etc. Please refer to the man

            
                      page cdk_display(3X) for details. The man page explains

            
                      the usage with nice examples.</p>

            
                    </div>


                    <div class="SECT3">

            
                      <hr>


                      <h4 class="SECT3"><a name="CDKCONCLUSION" id=

            
                      "CDKCONCLUSION">19.1.3. Conclusion</a></h4>


                      <p>All in all, CDK is a well-written package of widgets,

            
                      which if used properly can form a strong frame work for

            
                      developing complex GUI.</p>

            
                    </div>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="DIALOG" id="DIALOG">19.2. The

            
                    dialog</a></h3>


                    <p>Long long ago, in September 1994, when few people knew

            
                    linux, Jeff Tranter wrote an <a href=

            
                    "http://www2.linuxjournal.com/lj-issues/issue5/2807.html"

            
                    target="_top">article</a> on dialog in Linux Journal. He

            
                    starts the article with these words..</p>


                    <p><span class="emphasis"><i class="EMPHASIS">Linux is

            
                    based on the Unix operating system, but also features a

            
                    number of unique and useful kernel features and application

            
                    programs that often go beyond what is available under Unix.

            
                    One little-known gem is "dialog", a utility for creating

            
                    professional-looking dialog boxes from within shell

            
                    scripts. This article presents a tutorial introduction to

            
                    the dialog utility, and shows examples of how and where it

            
                    can be used</i></span>

            
                    </p>


                    <p>As he explains, dialog is a real gem in making

            
                    professional-looking dialog boxes with ease. It creates a

            
                    variety of dialog boxes, menus, check lists, etc. It is

            
                    usually installed by default. If not, you can download it

            
                    from <a href="https://invisible-island.net/dialog/" target=

            
                    "_top">Thomas Dickey</a>'s site.</p>


                    <p>The above-mentioned article gives a very good overview

            
                    of its uses and capabilities. The man page has more

            
                    details. It can be used in variety of situations. One good

            
                    example is building of linux kernel in text mode. Linux

            
                    kernel uses a modified version of dialog tailored for its

            
                    needs.</p>


                    <p>dialog was initially designed to be used with shell

            
                    scripts. If you want to use its functionality in a c

            
                    program, then you can use libdialog. The documentation

            
                    regarding this is sparse. Definitive reference is the

            
                    dialog.h header file which comes with the library. You may

            
                    need to hack here and there to get the required output. The

            
                    source is easily customizable. I have used it on a number

            
                    of occasions by modifying the code.</p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="PERLCURSES" id=

            
                    "PERLCURSES">19.3. Perl Curses Modules CURSES::FORM and

            
                    CURSES::WIDGETS</a></h3>


                    <p>The perl module Curses, Curses::Form and Curses::Widgets

            
                    give access to curses from perl. If you have curses and

            
                    basic perl is installed, you can get these modules from

            
                    <a href="http://www.cpan.org/modules/01modules.index.html"

            
                    target="_top">CPAN All Modules page</a>. Get the three

            
                    zipped modules in the Curses category. Once installed you

            
                    can use these modules from perl scripts like any other

            
                    module. For more information on perl modules see perlmod

            
                    man page. The above modules come with good documentation

            
                    and they have some demo scripts to test the functionality.

            
                    Though the widgets provided are very rudimentary, these

            
                    modules provide good access to curses library from

            
                    perl.</p>


                    <p>Some of my code examples are converted to perl by

            
                    Anuradha Ratnaweera and they are available in the

            
                    <tt class="LITERAL">perl</tt> directory.</p>


                    <p>For more information see man pages Curses(3) ,

            
                    Curses::Form(3) and Curses::Widgets(3). These pages are

            
                    installed only when the above modules are acquired and

            
                    installed.</p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="JUSTFORFUN" id="JUSTFORFUN">20.

            
                  Just For Fun !!!</a></h2>


                  <p>This section contains few programs written by me just for

            
                  fun. They don't signify a better programming practice or the

            
                  best way of using ncurses. They are provided here so as to

            
                  allow beginners to get ideas and add more programs to this

            
                  section. If you have written a couple of nice, simple

            
                  programs in curses and want them to included here, contact

            
                  <a href="mailto:ppadala@gmail.com" target="_top">me</a>.</p>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="GAMEOFLIFE" id=

            
                    "GAMEOFLIFE">20.1. The Game of Life</a></h3>


                    <p>Game of life is a wonder of math. In <a href=

            
                    "http://www.math.com/students/wonders/life/life.html"

            
                    target="_top">Paul Callahan</a>'s words</p>


                    <pre class="PROGRAMLISTING"><span class="emphasis"><i class=

            
                    "EMPHASIS">The Game of Life (or simply Life) is not a game in the conventional sense. There

            
            are no players, and no winning or losing. Once the "pieces" are placed in the

            
            starting position, the rules determine everything that happens later.

            
            Nevertheless, Life is full of surprises! In most cases, it is impossible to look

            
            at a starting position (or pattern) and see what will happen in the future. The

            
            only way to find out is to follow the rules of the game.</i></span></pre>

            
                    <p>This program starts with a simple inverted U pattern and

            
                    shows how wonderful life works. There is a lot of room for

            
                    improvement in the program. You can let the user enter

            
                    pattern of his choice or even take input from a file. You

            
                    can also change rules and play with a lot of variations.

            
                    Search on <a href="https://www.google.com" target=

            
                    "_top">google</a> for interesting information on game of

            
                    life.</p>


                    <p><span class="emphasis"><i class="EMPHASIS">File Path:

            
                    JustForFun/life.c</i></span>

            
                    </p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="MAGIC" id="MAGIC">20.2. Magic

            
                    Square</a></h3>


                    <p>Magic Square, another wonder of math, is very simple to

            
                    understand but very difficult to make. In a magic square

            
                    sum of the numbers in each row, each column is equal. Even

            
                    diagonal sum can be equal. There are many variations which

            
                    have special properties.</p>


                    <p>This program creates a simple magic square of odd

            
                    order.</p>


                    <p><span class="emphasis"><i class="EMPHASIS">File Path:

            
                    JustForFun/magic.c</i></span>

            
                    </p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="HANOI" id="HANOI">20.3. Towers

            
                    of Hanoi</a></h3>


                    <p>The famous towers of hanoi solver. The aim of the game

            
                    is to move the disks on the first peg to last peg, using

            
                    middle peg as a temporary stay. The catch is not to place a

            
                    larger disk over a small disk at any time.</p>


                    <p><span class="emphasis"><i class="EMPHASIS">File Path:

            
                    JustForFun/hanoi.c</i></span>

            
                    </p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="QUEENS" id="QUEENS">20.4. Queens

            
                    Puzzle</a></h3>


                    <p>The objective of the famous N-Queen puzzle is to put N

            
                    queens on a N X N chess board without attacking each

            
                    other.</p>


                    <p>This program solves it with a simple backtracking

            
                    technique.</p>


                    <p><span class="emphasis"><i class="EMPHASIS">File Path:

            
                    JustForFun/queens.c</i></span>

            
                    </p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="SHUFFLE" id="SHUFFLE">20.5.

            
                    Shuffle</a></h3>


                    <p>A fun game, if you have time to kill.</p>


                    <p><span class="emphasis"><i class="EMPHASIS">File Path:

            
                    JustForFun/shuffle.c</i></span>

            
                    </p>

            
                  </div>


                  <div class="SECT2">

            
                    <hr>


                    <h3 class="SECT2"><a name="TT" id="TT">20.6. Typing

            
                    Tutor</a></h3>


                    <p>A simple typing tutor, I created more out of need than

            
                    for ease of use. If you know how to put your fingers

            
                    correctly on the keyboard, but lack practice, this can be

            
                    helpful.</p>


                    <p><span class="emphasis"><i class="EMPHASIS">File Path:

            
                    JustForFun/tt.c</i></span>

            
                    </p>

            
                  </div>

            
                </div>


                <div class="SECT1">

            
                  <hr>


                  <h2 class="SECT1"><a name="REF" id="REF">21. References</a></h2>


                  <ul>

            
                    <li>

            
                      <p>NCURSES man pages</p>

            
                    </li>


                    <li>

            
                      <p>NCURSES FAQ at <a href=

            
                      "https://invisible-island.net/ncurses/ncurses.faq.html"

            
                      target=

            
                      "_top">https://invisible-island.net/ncurses/ncurses.faq.html</a></p>

            
                    </li>


                    <li>

            
                      <p>Writing programs with NCURSES by Eric Raymond and Zeyd

            
                      M. Ben-Halim at <a href=

            
                      "https://invisible-island.net/ncurses/ncurses-intro.html"

            
                      target=

            
                      "_top">https://invisible-island.net/ncurses/ncurses-intro.html</a>

            
                      - somewhat obsolete. I was inspired by this document and

            
                      the structure of this HOWTO follows from the original

            
                      document</p>

            
                    </li>

            
                  </ul>

            
                </div>

            
              </div>

            
            </body>

            
            </html>