downstream
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ncurses


			
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<title>NCURSES Programming HOWTO</title>
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<div class="ARTICLE">
<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">
<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><em>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></em></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>
<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>
</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>
<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>
<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="#ATTR_GET">attr_get()</a></dt>
<dt>8.4. <a href="#ATTR_FUNCS">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>
<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>
</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>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">echo "^[[0;31;40mIn Color"</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">echo "^[[0;37;40m"</font>
</pre></td>
</tr>
</table>
<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 <var class=
"LITERAL">termcap</var>. 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 <var class="LITERAL">terminfo</var>.
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><em>Compiling the package</em></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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">    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</font>
</pre></td>
</tr>
</table>
<p><em>Using the RPM</em></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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    rpm -i &lt;downloaded rpm&gt;</font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">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</font>
</pre></td>
</tr>
</table>
<p>The individual directories contain the following files.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">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</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">&#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</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    #include &lt;ncurses.h&gt;
    .
    .
    .

    compile and link: gcc &lt;program file&gt; -lncurses</font>
</pre></td>
</tr>
</table>
<div class="EXAMPLE"><a name="BHW" id="BHW"></a>
<p><b>Example 1. The Hello World !!! Program</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class=
"LITERAL">stdscr</var>) 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 <var class="LITERAL">cbreak()</var> 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. <var class="LITERAL">noecho()</var> 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 <var class=
"LITERAL">noecho()</var> 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 <var class="LITERAL">keypad(stdscr,
TRUE)</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</div>
<p>This program is self-explanatory. But I used functions which
aren't explained yet. The function <var class=
"LITERAL">getch()</var> is used to get a character from user. It is
equivalent to normal <var class="LITERAL">getchar()</var> except
that we can disable the line buffering to avoid &lt;enter&gt; after
input. Look for more about <var class="LITERAL">getch()</var>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 <var class="LITERAL">stdscr</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    printw("Hi There !!!");
    refresh();</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    wprintw(win, "Hi There !!!");
    wrefresh(win);</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">    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         */</font>
</pre></td>
</tr>
</table>
<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
<var class="LITERAL">ncurses.h</var>. For example, you want to
print a character ch(of type char) bold and underlined, you would
call addch() as below.</p>
<table border="0" bgcolor="#E0E0E0" width="90%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    addch(ch | A_BOLD | A_UNDERLINE);</font>
</pre></td>
</tr>
</table>
</li>
<li>
<p>By using functions like <var class=
"LITERAL">attrset(),attron(),attroff()</var>. 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, <var class="LITERAL">curses</var> 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 <var class=
"LITERAL">ncurses.h</var>. Try looking for macros beginning with
<var class="LITERAL">ACS_</var> 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><var class="LITERAL">mvaddch()</var> is used to move the cursor
to a given point, and then print. Thus, the calls:</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">    move(row,col);    /* moves the cursor to row<em>th</em> row and col<em>th</em> column */
    addch(ch);</font>
</pre></td>
</tr>
</table>
can be replaced by
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    mvaddch(row,col,ch);</font>
</pre></td>
</tr>
</table>
<p><var class="LITERAL">waddch()</var> is similar to <var class=
"LITERAL">addch()</var>, except that it adds a character into the
given window. (Note that <var class="LITERAL">addch()</var> adds a
character into the window <var class="LITERAL">stdscr</var>.)</p>
<p>In a similar fashion <var class="LITERAL">mvwaddch()</var>
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 <var class=
"LITERAL">addch()</var>. But, if we want to print a string, it
would be very annoying to print it character by character.
Fortunately, <var class="LITERAL">ncurses</var> provides
<var class="LITERAL">printf</var><em>-like</em> or <var class=
"LITERAL">puts</var><em>-like</em> 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 <var class=
"LITERAL">printf()</var> 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 <var class=
"LITERAL">printf()</var>. <var class="LITERAL">mvprintw()</var> 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 <var class=
"LITERAL">printw()</var> function, use <var class=
"LITERAL">move()</var> first and then use <var class=
"LITERAL">printw()</var> though I see no point why one should avoid
using <var class="LITERAL">mvprintw()</var>, 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.
vwprintw()</a></h4>
<p>This function is similar to <var class=
"LITERAL">vprintf()</var>. 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</div>
<p>Above program demonstrates how easy it is to use <var class=
"LITERAL">printw</var>. 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 <var class=
"LITERAL">getmaxyx()</var>, a macro defined in <var class=
"LITERAL">ncurses.h</var>. It gives the number of columns and the
number of rows in a given window. <var class=
"LITERAL">getmaxyx()</var> does this by updating the variables
given to it. Since <var class="LITERAL">getmaxyx()</var> 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><var class="LITERAL">addstr()</var> is used to put a character
string into a given window. This function is similar to calling
<var class="LITERAL">addch()</var> once for each character in a
given string. This is true for all output functions. There are
other functions from this family such as <var class=
"LITERAL">mvaddstr(),mvwaddstr()</var> and <var class=
"LITERAL">waddstr()</var>, 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 <var class=
"LITERAL">scanf()</var> 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 <var class=
"LITERAL">sscanf()</var>, where the line to be scanned is provided
by <var class="LITERAL">wgetstr()</var> function. That is, these
functions call to <var class="LITERAL">wgetstr()</var>
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.
vwscanw()</a></h4>
<p>This function is similar to <var class="LITERAL">vscanf()</var>.
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 <var class="LITERAL">getch()</var> until a
newline, carriage return, or end-of-file is received. The resulting
string of characters are pointed to by <var class=
"LITERAL">str</var>, 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class=
"LITERAL">attron()</var> . When we get the pattern */ it is
switched off by <var class="LITERAL">attroff()</var> .</p>
<p>The above program also introduces us to two useful functions
<var class="LITERAL">getyx()</var> and <var class=
"LITERAL">move()</var>. 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
<var class="LITERAL">move()</var> 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
<var class="LITERAL">attron(), attroff(), attrset()</var> , and
their sister functions <var class="LITERAL">attr_get()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    
    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 
    </font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    attron(A_REVERSE | A_BLINK);</font>
</pre></td>
</tr>
</table>
</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 <var class=
"LITERAL">standend()</var> which is equivalent to <var class=
"LITERAL">attrset(A_NORMAL)</var> which turns off all attributes
and brings you to normal mode.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTR_GET" id="ATTR_GET">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="ATTR_FUNCS" id="ATTR_FUNCS">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 <var class="LITERAL">attr_t</var>.</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    chgat(-1, A_REVERSE, 0, NULL);</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class=
"LITERAL">newwin()</var>. 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
<var class="LITERAL">box()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class="LITERAL">create_newwin()</var> function creates
a window with <var class="LITERAL">newwin()</var> and displays a
border around it with box. The function <var class=
"LITERAL">destroy_win()</var> first erases the window from screen
by painting a border with ' ' character and then calling
<var class="LITERAL">delwin()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">    wborder(win, '|', '|', '-', '-', '+', '+', '+', '+');</font>
</pre></td>
</tr>
</table>
<p>it produces some thing like</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    +------------+
    |            |
    |            |
    |            |
    |            |
    |            |
    |            |
    +------------+</font>
</pre></td>
</tr>
</table>
</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 <var class="LITERAL">getch()</var> 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 <var class="LITERAL">mvhline()</var>
and <var class="LITERAL">mvvline()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</div>
<p>As you can see, to start using color, you should first call the
function <var class="LITERAL">start_color()</var>. 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 <var class="LITERAL">has_colors()</var> 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 <var class="LITERAL">COLOR_BLACK</var> 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
<var class="LITERAL">init_pair()</var> 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 <var class=
"LITERAL">COLOR_PAIR()</var>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 <var class=
"LITERAL">curses.h</var>. You can use these as parameters for
various color functions.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">        COLOR_BLACK   0
        COLOR_RED     1
        COLOR_GREEN   2
        COLOR_YELLOW  3
        COLOR_BLUE    4
        COLOR_MAGENTA 5
        COLOR_CYAN    6
        COLOR_WHITE   7</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CHANGECOLORDEFS" id=
"CHANGECOLORDEFS">10.2. Changing Color Definitions</a></h3>
<p>The function <var class="LITERAL">init_color()</var>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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    init_color(COLOR_RED, 700, 0, 0);
    /* param 1     : color name
     * param 2, 3, 4 : rgb content min = 0, max = 1000 */</font>
</pre></td>
</tr>
</table>
<p>If your terminal cannot change the color definitions, the
function returns ERR. The function <var class=
"LITERAL">can_change_color()</var> 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 <var class="LITERAL">color_content()</var> and
<var class="LITERAL">pair_content()</var> 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 <var class="LITERAL">getch()</var> 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><var class="LITERAL">getch()</var> 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
<var class="LITERAL">curses.h</var>. 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    int ch;

    ch = getch();</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    if(ch == KEY_LEFT)
        printw("Left arrow is pressed\n");</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class="LITERAL">mousemask()</var>.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">    mousemask(  mmask_t newmask,    /* The events you want to listen to */
                mmask_t *oldmask)    /* The old events mask                */</font>
</pre></td>
</tr>
</table>
<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 <var class="LITERAL">ALL_MOUSE_EVENTS</var> can
be used to get all the events.</p>
<p>The following are all the event masks:</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    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</font>
</pre></td>
</tr>
</table>
</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 <var class=
"LITERAL">getmouse()</var>.</p>
<p>The code approximately looks like this:</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    MEVENT event;

    ch = getch();
    if(ch == KEY_MOUSE)
        if(getmouse(&amp;event) == OK)
            .    /* Do some thing with the event */
            .
            .</font>
</pre></td>
</tr>
</table>
<p>getmouse() returns the event into the pointer given to it. It's
a structure which contains</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    typedef struct
    {
        short id;         /* ID to distinguish multiple devices */
        int x, y, z;      /* event coordinates */
        mmask_t bstate;   /* button state bits */
    }    </font>
</pre></td>
</tr>
</table>
<p>The <var class="LITERAL">bstate</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    if(event.bstate &amp; BUTTON1_PRESSED)
        printw("Left Button Pressed");</font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class="LITERAL">getyx()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    getyx(win, y, x);
    /* win: window pointer
     *   y, x: y, x co-ordinates will be put into this variables 
     */</font>
</pre></td>
</tr>
</table>
<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 <var class=
"LITERAL">putwin()</var> and <var class="LITERAL">getwin()</var>
can be used. <var class="LITERAL">putwin()</var> puts the present
window state into a file, which can be later restored by
<var class="LITERAL">getwin()</var>.</p>
<p>The function <var class="LITERAL">copywin()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    0 : invisible      or
    1 : normal    or
    2 : very visible.</font>
</pre></td>
</tr>
</table>
</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 <var class=
"LITERAL">def_prog_mode()</var> and then call <var class=
"LITERAL">endwin()</var> to end the curses mode. This will leave
you in the original tty mode. To get back to curses once you are
done, call <var class="LITERAL">reset_prog_mode()</var> . This
function returns the tty to the state stored by <var class=
"LITERAL">def_prog_mode()</var>. 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class=
"LITERAL">box()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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><em>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.</em></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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    #include &lt;panel.h&gt;
    .
    .
    .

    compile and link: gcc &lt;program file&gt; -lpanel -lncurses</font>
</pre></td>
</tr>
</table>
<div class="EXAMPLE"><a name="PPASI" id="PPASI"></a>
<p><b>Example 14. Panel basics</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class="LITERAL">set_panel_userptr()</var>. It can be
accessed using the function <var class=
"LITERAL">panel_userptr()</var> 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 <var class="LITERAL">move_panel()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class="LITERAL">panel_hidden()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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 <var class="LITERAL">panel_above()</var> and
<var class="LITERAL">panel_below()</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    #include &lt;menu.h&gt;
    .
    .
    .

    compile and link: gcc &lt;program file&gt; -lmenu -lncurses</font>
</pre></td>
</tr>
</table>
<div class="EXAMPLE"><a name="MMESI" id="MMESI"></a>
<p><b>Example 18. Menu Basics</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">&#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;</font>
</pre></td>
</tr>
</table>
<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><em>REQ_LEFT_ITEM and REQ_RIGHT_ITEM</em></p>
<p>A Menu can be displayed with multiple columns for more than one
item. This can be done by using the <var class=
"LITERAL">menu_format()</var>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><em>REQ_UP_ITEM and REQ_DOWN_ITEM</em></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><em>REQ_SCR_* options</em></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><em>REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_NEXT_ITEM and
REQ_PREV_ITEM</em></p>
<p>These requests are self explanatory.</p>
</li>
<li>
<p><em>REQ_TOGGLE_ITEM</em></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><em>Pattern Requests</em></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><em>Mouse Requests</em></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>
<table border="0" bgcolor="#E0E0E0" width="90%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000"><em>       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.</em></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">       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.</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">    #include &lt;form.h&gt;
    .
    .
    .

    compile and link: gcc &lt;program file&gt; -lform -lncurses</font>
</pre></td>
</tr>
</table>
<div class="EXAMPLE"><a name="FFOSI" id="FFOSI"></a>
<p><b>Example 25. Forms Basics</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</div>
<p>Above example is pretty straight forward. It creates two fields
with <var class="LITERAL">new_field()</var>. 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">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 */</font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int move_field(    FIELD *field,              /* field to alter */
                   int top, int left);        /* new upper-left corner */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">    int set_field_just(FIELD *field,          /* field to alter */
               int justmode);         /* mode to set */
    int field_just(FIELD *field);          /* fetch justify mode of field */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">&#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;</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">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 */ </font>
</pre></td>
</tr>
</table>
<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 <var class=
"LITERAL">REQ_PREV_CHOICE</var> and <var class=
"LITERAL">REQ_NEXT_CHOICE</var>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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int set_field_status(FIELD *field,      /* field to alter */
                   int status);         /* status to set */

int field_status(FIELD *field);         /* fetch status of field */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">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 */</font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">    field_opts_off(field_pointer, O_STATIC);</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int set_max_field(FIELD *field,    /* Field on which to operate */
                  int max_growth); /* maximum growth allowed for the field */</font>
</pre></td>
</tr>
</table>
<p>The field info for a dynamically growable field can be retrieved
by</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">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 */</font>
</pre></td>
</tr>
</table>
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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><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></font>
</pre></td>
</tr>
</table>
</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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int set_field_type(FIELD *field,          /* field to alter */
                   FIELDTYPE *ftype,      /* type to associate */
                   ...);                  /* additional arguments*/</font>
</pre></td>
</tr>
</table>
Once set, the validation type for a field can be queried with
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">FIELDTYPE *field_type(FIELD *field);      /* field to query */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int set_field_type(FIELD *field,          /* field to alter */
                   TYPE_ALPHA,            /* type to associate */
                   int width);            /* maximum width of field */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int set_field_type(FIELD *field,          /* field to alter */
                   TYPE_ALNUM,            /* type to associate */
                   int width);            /* maximum width of field */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">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? */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">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 */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">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 */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int set_field_type(FIELD *field,          /* field to alter */
                   TYPE_REGEXP,           /* type to associate */
                   char *regexp);         /* expression to match */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">int form_driver(FORM *form,     /* form on which to operate     */
                int request)    /* form request code         */</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">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 */</font>
</pre></td>
</tr>
</table>
<p>The following requests allow you to move to different pages</p>
<ul>
<li>
<p><em>REQ_NEXT_PAGE</em> Move to the next form page.</p>
</li>
<li>
<p><em>REQ_PREV_PAGE</em> Move to the previous form page.</p>
</li>
<li>
<p><em>REQ_FIRST_PAGE</em> Move to the first form page.</p>
</li>
<li>
<p><em>REQ_LAST_PAGE</em> 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><em>REQ_NEXT_FIELD</em> Move to next field.</p>
</li>
<li>
<p><em>REQ_PREV_FIELD</em> Move to previous field.</p>
</li>
<li>
<p><em>REQ_FIRST_FIELD</em> Move to the first field.</p>
</li>
<li>
<p><em>REQ_LAST_FIELD</em> Move to the last field.</p>
</li>
<li>
<p><em>REQ_SNEXT_FIELD</em> Move to sorted next field.</p>
</li>
<li>
<p><em>REQ_SPREV_FIELD</em> Move to sorted previous field.</p>
</li>
<li>
<p><em>REQ_SFIRST_FIELD</em> Move to the sorted first field.</p>
</li>
<li>
<p><em>REQ_SLAST_FIELD</em> Move to the sorted last field.</p>
</li>
<li>
<p><em>REQ_LEFT_FIELD</em> Move left to field.</p>
</li>
<li>
<p><em>REQ_RIGHT_FIELD</em> Move right to field.</p>
</li>
<li>
<p><em>REQ_UP_FIELD</em> Move up to field.</p>
</li>
<li>
<p><em>REQ_DOWN_FIELD</em> 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><em>REQ_NEXT_CHAR</em> Move to next character.</p>
</li>
<li>
<p><em>REQ_PREV_CHAR</em> Move to previous character.</p>
</li>
<li>
<p><em>REQ_NEXT_LINE</em> Move to next line.</p>
</li>
<li>
<p><em>REQ_PREV_LINE</em> Move to previous line.</p>
</li>
<li>
<p><em>REQ_NEXT_WORD</em> Move to next word.</p>
</li>
<li>
<p><em>REQ_PREV_WORD</em> Move to previous word.</p>
</li>
<li>
<p><em>REQ_BEG_FIELD</em> Move to beginning of field.</p>
</li>
<li>
<p><em>REQ_END_FIELD</em> Move to end of field.</p>
</li>
<li>
<p><em>REQ_BEG_LINE</em> Move to beginning of line.</p>
</li>
<li>
<p><em>REQ_END_LINE</em> Move to end of line.</p>
</li>
<li>
<p><em>REQ_LEFT_CHAR</em> Move left in field.</p>
</li>
<li>
<p><em>REQ_RIGHT_CHAR</em> Move right in field.</p>
</li>
<li>
<p><em>REQ_UP_CHAR</em> Move up in field.</p>
</li>
<li>
<p><em>REQ_DOWN_CHAR</em> 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><em>REQ_SCR_FLINE</em> Scroll vertically forward a line.</p>
</li>
<li>
<p><em>REQ_SCR_BLINE</em> Scroll vertically backward a line.</p>
</li>
<li>
<p><em>REQ_SCR_FPAGE</em> Scroll vertically forward a page.</p>
</li>
<li>
<p><em>REQ_SCR_BPAGE</em> Scroll vertically backward a page.</p>
</li>
<li>
<p><em>REQ_SCR_FHPAGE</em> Scroll vertically forward half a
page.</p>
</li>
<li>
<p><em>REQ_SCR_BHPAGE</em> Scroll vertically backward half a
page.</p>
</li>
<li>
<p><em>REQ_SCR_FCHAR</em> Scroll horizontally forward a
character.</p>
</li>
<li>
<p><em>REQ_SCR_BCHAR</em> Scroll horizontally backward a
character.</p>
</li>
<li>
<p><em>REQ_SCR_HFLINE</em> Scroll horizontally one field width
forward.</p>
</li>
<li>
<p><em>REQ_SCR_HBLINE</em> Scroll horizontally one field width
backward.</p>
</li>
<li>
<p><em>REQ_SCR_HFHALF</em> Scroll horizontally one half field width
forward.</p>
</li>
<li>
<p><em>REQ_SCR_HBHALF</em> 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><em>REQ_INS_MODE</em> Set insertion mode.</p>
</li>
<li>
<p><em>REQ_OVL_MODE</em> Set overlay mode.</p>
</li>
<li>
<p><em>REQ_NEW_LINE</em> New line request (see below for
explanation).</p>
</li>
<li>
<p><em>REQ_INS_CHAR</em> Insert space at character location.</p>
</li>
<li>
<p><em>REQ_INS_LINE</em> Insert blank line at character
location.</p>
</li>
<li>
<p><em>REQ_DEL_CHAR</em> Delete character at cursor.</p>
</li>
<li>
<p><em>REQ_DEL_PREV</em> Delete previous word at cursor.</p>
</li>
<li>
<p><em>REQ_DEL_LINE</em> Delete line at cursor.</p>
</li>
<li>
<p><em>REQ_DEL_WORD</em> Delete word at cursor.</p>
</li>
<li>
<p><em>REQ_CLR_EOL</em> Clear to end of line.</p>
</li>
<li>
<p><em>REQ_CLR_EOF</em> Clear to end of field.</p>
</li>
<li>
<p><em>REQ_CLR_FIELD</em> 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><em>REQ_NEXT_CHOICE</em> Place the successor value of the
current value in the buffer.</p>
</li>
<li>
<p><em>REQ_PREV_CHOICE</em> 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><em>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.</em></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="http://invisible-island.net/cdk/" target=
"_top">http://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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">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.
===========================================================================</font>
</pre></td>
</tr>
</table>
<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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">"&lt;/B/1&gt;This line should have a yellow foreground and a blue
background.&lt;!1&gt;"</font>
</pre></td>
</tr>
</table>
<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><em>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</em></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=
"http://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 <var class=
"LITERAL">perl</var> 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>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000"><em>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.</em></font>
</pre></td>
</tr>
</table>
<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><em>File Path: JustForFun/life.c</em></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><em>File Path: JustForFun/magic.c</em></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><em>File Path: JustForFun/hanoi.c</em></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><em>File Path: JustForFun/queens.c</em></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><em>File Path: JustForFun/shuffle.c</em></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><em>File Path: JustForFun/tt.c</em></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=
"http://invisible-island.net/ncurses/ncurses.faq.html" target=
"_top">http://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=
"http://invisible-island.net/ncurses/ncurses-intro.html" target=
"_top">http://invisible-island.net/ncurses/ncurses-intro.html</a> -
somewhat obsolete. I was inspired by this document and the
structure of this HOWTO follows from the original document</p>
</li>
</ul>
</div>
</div>
</body>
</html>