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Thomas E. Dickey
ncurses 6.1 - patch 20180609
10 июн 2018, 02:57
10 июн 2018, 02:57e23d7db
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    <div class="TITLEPAGE">
      <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 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="AEN67" id="AEN67"></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="#AEN298">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@his.com" 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=
        "http://www.gnu.org/order/ftp.html" target=
        "_top">http://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=
        "http://rpmfind.net" target="_top">http://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=
        "http://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=
        "http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/"
        target=
        "_top">http://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 availabe 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=
              "http://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=
              "http://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=
              "http://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=
              "http://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=
          "http://www.tldp.org/LDP/LDP-Author-Guide/" target=
          "_top">LDP Author guide</a> for more details. If all else
          failes, 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;ncurses.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;ncurses.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
                                         * charachters 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's 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 avaliable 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="AEN298" id="AEN298">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;ncurses.h&gt;                   /* ncurses.h includes stdio.h */  
#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 colums 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;ncurses.h&gt;                   /* ncurses.h includes stdio.h */  
#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 colums 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;ncurses.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 curser 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 curser 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;ncurses.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 charcter
         * 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 like it's 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 like
        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;ncurses.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 it's 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's 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 some thing 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;ncurses.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;ncurses.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's 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;stdio.h&gt;
#include &lt;ncurses.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, "Charcter 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's 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;ncurses.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. It's
        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;ncurses.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's 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;ncurses.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's 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;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's 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;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's 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;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 datas 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;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;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;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 scoll 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;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;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's 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;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's
        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's 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;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's 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's 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's 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;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's a bit
        tricky and cumbersome.</p>

        <h1 class="BRIDGEHEAD"><a name="AEN1069" id=
        "AEN1069"></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's 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="AEN1073" id=
        "AEN1073"></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's 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="AEN1077" id=
        "AEN1077"></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="AEN1084" id=
        "AEN1084"></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="AEN1090" id=
        "AEN1090"></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="AEN1096" id=
        "AEN1096"></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's 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's 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 capabilites. 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="http://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
        diagnol 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>
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