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ncursesw-morphos/doc/html/NCURSES-Programming-HOWTO.html
Thomas E. Dickey 5461fc336d ncurses 6.0 - patch 20161231 
+ fix errata for ncurses-howto (report by Damien Ruscoe).
+ fix a few places in configure/build scripts where DESTDIR and rpath
  were combined (report by Thomas Klausner).
+ merge current st description (report by Harry Gindi) -TD
+ modify flash capability for linux and wyse entries to put the delay
  between the reverse/normal escapes rather than after -TD
+ modify program tabs to pass the actual tty file descriptor to
  setupterm rather than the standard output, making padding work
  consistently.
+ explain in clear's manual page that it writes to stdout.
+ add special case for verbose debugging traces of command-line
  utilities which write to stderr (cf: 20161126).
+ remove a trace with literal escapes from skip_DECSCNM(), added in
  20161203.
+ update config.guess, config.sub from
	http://git.savannah.gnu.org/cgit/config.git
2016-12-31 23:48:48 +00:00

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta name="generator" content=
"HTML Tidy for Linux (vers 25 March 2009), see www.w3.org">
<title>NCURSES Programming HOWTO</title>
<meta name="GENERATOR" content=
"Modular DocBook HTML Stylesheet Version 1.79">
</head>
<body class="ARTICLE" bgcolor="#FFFFFF" text="#000000" link=
"#0000FF" vlink="#840084" alink="#0000FF">
<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><span class="emphasis"><i class="EMPHASIS">This
document is intended to be an "All in One" guide for
programming with ncurses and its sister libraries. We
graduate from a simple "Hello World" program to more
complex form manipulation. No prior experience in ncurses
is assumed. Send comments to <a href=
"mailto:ppadala@gmail.com" target="_top">this
address</a></i></span></p>
</div>
</div>
<hr>
</div>
<div class="TOC">
<dl>
<dt><b>Table of Contents</b></dt>
<dt>1. <a href="#INTRO">Introduction</a></dt>
<dd>
<dl>
<dt>1.1. <a href="#WHATIS">What is NCURSES?</a></dt>
<dt>1.2. <a href="#WHATCANWEDO">What we can do with
NCURSES</a></dt>
<dt>1.3. <a href="#WHERETOGETIT">Where to get
it</a></dt>
<dt>1.4. <a href="#PURPOSE">Purpose/Scope of the
document</a></dt>
<dt>1.5. <a href="#ABOUTPROGRAMS">About the
Programs</a></dt>
<dt>1.6. <a href="#OTHERFORMATS">Other Formats of the
document</a></dt>
<dd>
<dl>
<dt>1.6.1. <a href="#LISTFORMATS">Readily available
formats from tldp.org</a></dt>
<dt>1.6.2. <a href="#BUILDSOURCE">Building from
source</a></dt>
</dl>
</dd>
<dt>1.7. <a href="#CREDITS">Credits</a></dt>
<dt>1.8. <a href="#WISHLIST">Wish List</a></dt>
<dt>1.9. <a href="#COPYRIGHT">Copyright</a></dt>
</dl>
</dd>
<dt>2. <a href="#HELLOWORLD">Hello World !!!</a></dt>
<dd>
<dl>
<dt>2.1. <a href="#COMPILECURSES">Compiling With the
NCURSES Library</a></dt>
<dt>2.2. <a href="#DISSECTION">Dissection</a></dt>
<dd>
<dl>
<dt>2.2.1. <a href="#ABOUT-INITSCR">About
initscr()</a></dt>
<dt>2.2.2. <a href="#MYST-REFRESH">The mysterious
refresh()</a></dt>
<dt>2.2.3. <a href="#ABOUT-ENDWIN">About
endwin()</a></dt>
</dl>
</dd>
</dl>
</dd>
<dt>3. <a href="#GORY">The Gory Details</a></dt>
<dt>4. <a href="#INIT">Initialization</a></dt>
<dd>
<dl>
<dt>4.1. <a href="#ABOUTINIT">Initialization
functions</a></dt>
<dt>4.2. <a href="#RAWCBREAK">raw() and
cbreak()</a></dt>
<dt>4.3. <a href="#ECHONOECHO">echo() and
noecho()</a></dt>
<dt>4.4. <a href="#KEYPAD">keypad()</a></dt>
<dt>4.5. <a href="#HALFDELAY">halfdelay()</a></dt>
<dt>4.6. <a href="#MISCINIT">Miscellaneous
Initialization functions</a></dt>
<dt>4.7. <a href="#INITEX">An Example</a></dt>
</dl>
</dd>
<dt>5. <a href="#AWORDWINDOWS">A Word about
Windows</a></dt>
<dt>6. <a href="#PRINTW">Output functions</a></dt>
<dd>
<dl>
<dt>6.1. <a href="#ADDCHCLASS">addch() class of
functions</a></dt>
<dt>6.2. <a href="#AEN298">mvaddch(), waddch() and
mvwaddch()</a></dt>
<dt>6.3. <a href="#PRINTWCLASS">printw() class of
functions</a></dt>
<dd>
<dl>
<dt>6.3.1. <a href="#PRINTWMVPRINTW">printw() and
mvprintw</a></dt>
<dt>6.3.2. <a href="#WPRINTWMVWPRINTW">wprintw()
and mvwprintw</a></dt>
<dt>6.3.3. <a href="#VWPRINTW">vwprintw()</a></dt>
<dt>6.3.4. <a href="#SIMPLEPRINTWEX">A Simple
printw example</a></dt>
</dl>
</dd>
<dt>6.4. <a href="#ADDSTRCLASS">addstr() class of
functions</a></dt>
<dt>6.5. <a href="#ACAUTION">A word of caution</a></dt>
</dl>
</dd>
<dt>7. <a href="#SCANW">Input functions</a></dt>
<dd>
<dl>
<dt>7.1. <a href="#GETCHCLASS">getch() class of
functions</a></dt>
<dt>7.2. <a href="#SCANWCLASS">scanw() class of
functions</a></dt>
<dd>
<dl>
<dt>7.2.1. <a href="#SCANWMVSCANW">scanw() and
mvscanw</a></dt>
<dt>7.2.2. <a href="#WSCANWMVWSCANW">wscanw() and
mvwscanw()</a></dt>
<dt>7.2.3. <a href="#VWSCANW">vwscanw()</a></dt>
</dl>
</dd>
<dt>7.3. <a href="#GETSTRCLASS">getstr() class of
functions</a></dt>
<dt>7.4. <a href="#GETSTREX">Some examples</a></dt>
</dl>
</dd>
<dt>8. <a href="#ATTRIB">Attributes</a></dt>
<dd>
<dl>
<dt>8.1. <a href="#ATTRIBDETAILS">The details</a></dt>
<dt>8.2. <a href="#ATTRONVSATTRSET">attron() vs
attrset()</a></dt>
<dt>8.3. <a href="#ATTRGET">attr_get()</a></dt>
<dt>8.4. <a href="#ATTRFUNCS">attr_ functions</a></dt>
<dt>8.5. <a href="#WATTRFUNCS">wattr functions</a></dt>
<dt>8.6. <a href="#CHGAT">chgat() functions</a></dt>
</dl>
</dd>
<dt>9. <a href="#WINDOWS">Windows</a></dt>
<dd>
<dl>
<dt>9.1. <a href="#WINDOWBASICS">The basics</a></dt>
<dt>9.2. <a href="#LETBEWINDOW">Let there be a Window
!!!</a></dt>
<dt>9.3. <a href="#BORDEREXEXPL">Explanation</a></dt>
<dt>9.4. <a href="#OTHERSTUFF">The other stuff in the
example</a></dt>
<dt>9.5. <a href="#OTHERBORDERFUNCS">Other Border
functions</a></dt>
</dl>
</dd>
<dt>10. <a href="#COLOR">Colors</a></dt>
<dd>
<dl>
<dt>10.1. <a href="#COLORBASICS">The basics</a></dt>
<dt>10.2. <a href="#CHANGECOLORDEFS">Changing Color
Definitions</a></dt>
<dt>10.3. <a href="#COLORCONTENT">Color
Content</a></dt>
</dl>
</dd>
<dt>11. <a href="#KEYS">Interfacing with the key
board</a></dt>
<dd>
<dl>
<dt>11.1. <a href="#KEYSBASICS">The Basics</a></dt>
<dt>11.2. <a href="#SIMPLEKEYEX">A Simple Key Usage
example</a></dt>
</dl>
</dd>
<dt>12. <a href="#MOUSE">Interfacing with the
mouse</a></dt>
<dd>
<dl>
<dt>12.1. <a href="#MOUSEBASICS">The Basics</a></dt>
<dt>12.2. <a href="#GETTINGEVENTS">Getting the
events</a></dt>
<dt>12.3. <a href="#MOUSETOGETHER">Putting it all
Together</a></dt>
<dt>12.4. <a href="#MISCMOUSEFUNCS">Miscellaneous
Functions</a></dt>
</dl>
</dd>
<dt>13. <a href="#SCREEN">Screen Manipulation</a></dt>
<dd>
<dl>
<dt>13.1. <a href="#GETYX">getyx() functions</a></dt>
<dt>13.2. <a href="#SCREENDUMP">Screen Dumping</a></dt>
<dt>13.3. <a href="#WINDOWDUMP">Window Dumping</a></dt>
</dl>
</dd>
<dt>14. <a href="#MISC">Miscellaneous features</a></dt>
<dd>
<dl>
<dt>14.1. <a href="#CURSSET">curs_set()</a></dt>
<dt>14.2. <a href="#TEMPLEAVE">Temporarily Leaving
Curses mode</a></dt>
<dt>14.3. <a href="#ACSVARS">ACS_ variables</a></dt>
</dl>
</dd>
<dt>15. <a href="#OTHERLIB">Other libraries</a></dt>
<dt>16. <a href="#PANELS">Panel Library</a></dt>
<dd>
<dl>
<dt>16.1. <a href="#PANELBASICS">The Basics</a></dt>
<dt>16.2. <a href="#COMPILEPANELS">Compiling With the
Panels Library</a></dt>
<dt>16.3. <a href="#PANELBROWSING">Panel Window
Browsing</a></dt>
<dt>16.4. <a href="#USERPTRUSING">Using User
Pointers</a></dt>
<dt>16.5. <a href="#PANELMOVERESIZE">Moving and
Resizing Panels</a></dt>
<dt>16.6. <a href="#PANELSHOWHIDE">Hiding and Showing
Panels</a></dt>
<dt>16.7. <a href="#PANELABOVE">panel_above() and
panel_below() Functions</a></dt>
</dl>
</dd>
<dt>17. <a href="#MENUS">Menus Library</a></dt>
<dd>
<dl>
<dt>17.1. <a href="#MENUBASICS">The Basics</a></dt>
<dt>17.2. <a href="#COMPILEMENUS">Compiling With the
Menu Library</a></dt>
<dt>17.3. <a href="#MENUDRIVER">Menu Driver: The work
horse of the menu system</a></dt>
<dt>17.4. <a href="#MENUWINDOWS">Menu Windows</a></dt>
<dt>17.5. <a href="#SCROLLMENUS">Scrolling
Menus</a></dt>
<dt>17.6. <a href="#MULTICOLUMN">Multi Columnar
Menus</a></dt>
<dt>17.7. <a href="#MULTIVALUEMENUS">Multi Valued
Menus</a></dt>
<dt>17.8. <a href="#MENUOPT">Menu Options</a></dt>
<dt>17.9. <a href="#MENUUSERPTR">The useful User
Pointer</a></dt>
</dl>
</dd>
<dt>18. <a href="#FORMS">Forms Library</a></dt>
<dd>
<dl>
<dt>18.1. <a href="#FORMBASICS">The Basics</a></dt>
<dt>18.2. <a href="#COMPILEFORMS">Compiling With the
Forms Library</a></dt>
<dt>18.3. <a href="#PLAYFIELDS">Playing with
Fields</a></dt>
<dd>
<dl>
<dt>18.3.1. <a href="#FETCHINFO">Fetching Size and
Location of Field</a></dt>
<dt>18.3.2. <a href="#MOVEFIELD">Moving the
field</a></dt>
<dt>18.3.3. <a href="#JUSTIFYFIELD">Field
Justification</a></dt>
<dt>18.3.4. <a href="#FIELDDISPATTRIB">Field
Display Attributes</a></dt>
<dt>18.3.5. <a href="#FIELDOPTIONBITS">Field Option
Bits</a></dt>
<dt>18.3.6. <a href="#FIELDSTATUS">Field
Status</a></dt>
<dt>18.3.7. <a href="#FIELDUSERPTR">Field User
Pointer</a></dt>
<dt>18.3.8. <a href=
"#VARIABLESIZEFIELDS">Variable-Sized
Fields</a></dt>
</dl>
</dd>
<dt>18.4. <a href="#FORMWINDOWS">Form Windows</a></dt>
<dt>18.5. <a href="#FILEDVALIDATE">Field
Validation</a></dt>
<dt>18.6. <a href="#FORMDRIVER">Form Driver: The work
horse of the forms system</a></dt>
<dd>
<dl>
<dt>18.6.1. <a href="#PAGENAVREQ">Page Navigation
Requests</a></dt>
<dt>18.6.2. <a href="#INTERFIELDNAVREQ">Inter-Field
Navigation Requests</a></dt>
<dt>18.6.3. <a href="#INTRAFIELDNAVREQ">Intra-Field
Navigation Requests</a></dt>
<dt>18.6.4. <a href="#SCROLLREQ">Scrolling
Requests</a></dt>
<dt>18.6.5. <a href="#EDITREQ">Editing
Requests</a></dt>
<dt>18.6.6. <a href="#ORDERREQ">Order
Requests</a></dt>
<dt>18.6.7. <a href="#APPLICCOMMANDS">Application
Commands</a></dt>
</dl>
</dd>
</dl>
</dd>
<dt>19. <a href="#TOOLS">Tools and Widget
Libraries</a></dt>
<dd>
<dl>
<dt>19.1. <a href="#CDK">CDK (Curses Development
Kit)</a></dt>
<dd>
<dl>
<dt>19.1.1. <a href="#WIDGETLIST">Widget
List</a></dt>
<dt>19.1.2. <a href="#CDKATTRACT">Some Attractive
Features</a></dt>
<dt>19.1.3. <a href=
"#CDKCONCLUSION">Conclusion</a></dt>
</dl>
</dd>
<dt>19.2. <a href="#DIALOG">The dialog</a></dt>
<dt>19.3. <a href="#PERLCURSES">Perl Curses Modules
CURSES::FORM and CURSES::WIDGETS</a></dt>
</dl>
</dd>
<dt>20. <a href="#JUSTFORFUN">Just For Fun !!!</a></dt>
<dd>
<dl>
<dt>20.1. <a href="#GAMEOFLIFE">The Game of
Life</a></dt>
<dt>20.2. <a href="#MAGIC">Magic Square</a></dt>
<dt>20.3. <a href="#HANOI">Towers of Hanoi</a></dt>
<dt>20.4. <a href="#QUEENS">Queens Puzzle</a></dt>
<dt>20.5. <a href="#SHUFFLE">Shuffle</a></dt>
<dt>20.6. <a href="#TT">Typing Tutor</a></dt>
</dl>
</dd>
<dt>21. <a href="#REF">References</a></dt>
</dl>
</div>
<div class="SECT1">
<h2 class="SECT1"><a name="INTRO" id="INTRO">1.
Introduction</a></h2>
<p>In the olden days of teletype terminals, terminals were
away from computers and were connected to them through serial
cables. The terminals could be configured by sending a series
of bytes. All the capabilities (such as moving the cursor to
a new location, erasing part of the screen, scrolling the
screen, changing modes etc.) of terminals could be accessed
through these series of bytes. These control seeuqnces are
usually called escape sequences, because they start with an
escape(0x1B) character. Even today, with proper emulation, we
can send escape sequences to the emulator and achieve the
same effect on a terminal window.</p>
<p>Suppose you wanted to print a line in color. Try typing
this on your console.</p>
<pre class="PROGRAMLISTING">
echo "^[[0;31;40mIn Color"
</pre>
<p>The first character is an escape character, which looks
like two characters ^ and [. To be able to print it, you have
to press CTRL+V and then the ESC key. All the others are
normal printable characters. You should be able to see the
string "In Color" in red. It stays that way and to revert
back to the original mode type this.</p>
<pre class="PROGRAMLISTING">
echo "^[[0;37;40m"
</pre>
<p>Now, what do these magic characters mean? Difficult to
comprehend? They might even be different for different
terminals. So the designers of UNIX invented a mechanism
named <tt class="LITERAL">termcap</tt>. It is a file that
lists all the capabilities of a particular terminal, along
with the escape sequences needed to achieve a particular
effect. In the later years, this was replaced by <tt class=
"LITERAL">terminfo</tt>. Without delving too much into
details, this mechanism allows application programs to query
the terminfo database and obtain the control characters to be
sent to a terminal or terminal emulator.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WHATIS" id="WHATIS">1.1. What is
NCURSES?</a></h3>
<p>You might be wondering, what the import of all this
technical gibberish is. In the above scenario, every
application program is supposed to query the terminfo and
perform the necessary stuff (sending control characters
etc.). It soon became difficult to manage this complexity
and this gave birth to 'CURSES'. Curses is a pun on the
name "cursor optimization". The Curses library forms a
wrapper over working with raw terminal codes, and provides
highly flexible and efficient API (Application Programming
Interface). It provides functions to move the cursor,
create windows, produce colors, play with mouse etc. The
application programs need not worry about the underlying
terminal capabilities.</p>
<p>So what is NCURSES? NCURSES is a clone of the original
System V Release 4.0 (SVr4) curses. It is a freely
distributable library, fully compatible with older version
of curses. In short, it is a library of functions that
manages an application's display on character-cell
terminals. In the remainder of the document, the terms
curses and ncurses are used interchangeably.</p>
<p>A detailed history of NCURSES can be found in the NEWS
file from the source distribution. The current package is
maintained by <a href="mailto:dickey@his.com" target=
"_top">Thomas Dickey</a>. You can contact the maintainers
at <a href="mailto:bug-ncurses@gnu.org" target=
"_top">bug-ncurses@gnu.org</a>.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WHATCANWEDO" id=
"WHATCANWEDO">1.2. What we can do with NCURSES</a></h3>
<p>NCURSES not only creates a wrapper over terminal
capabilities, but also gives a robust framework to create
nice looking UI (User Interface)s in text mode. It provides
functions to create windows etc. Its sister libraries
panel, menu and form provide an extension to the basic
curses library. These libraries usually come along with
curses. One can create applications that contain multiple
windows, menus, panels and forms. Windows can be managed
independently, can provide 'scrollability' and even can be
hidden.</p>
<p>Menus provide the user with an easy command selection
option. Forms allow the creation of easy-to-use data entry
and display windows. Panels extend the capabilities of
ncurses to deal with overlapping and stacked windows.</p>
<p>These are just some of the basic things we can do with
ncurses. As we move along, We will see all the capabilities
of these libraries.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WHERETOGETIT" id=
"WHERETOGETIT">1.3. Where to get it</a></h3>
<p>All right, now that you know what you can do with
ncurses, you must be rearing to get started. NCURSES is
usually shipped with your installation. In case you don't
have the library or want to compile it on your own, read
on.</p>
<p><span class="emphasis"><i class="EMPHASIS">Compiling the
package</i></span></p>
<p>NCURSES can be obtained from <a href=
"ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz" target=
"_top">ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz</a>
or any of the ftp sites mentioned in <a href=
"http://www.gnu.org/order/ftp.html" target=
"_top">http://www.gnu.org/order/ftp.html</a>.</p>
<p>Read the README and INSTALL files for details on to how
to install it. It usually involves the following
operations.</p>
<pre class="PROGRAMLISTING">
tar zxvf ncurses&lt;version&gt;.tar.gz # unzip and untar the archive
cd ncurses&lt;version&gt; # cd to the directory
./configure # configure the build according to your
# environment
make # make it
su root # become root
make install # install it
</pre>
<p><span class="emphasis"><i class="EMPHASIS">Using the
RPM</i></span></p>
<p>NCURSES RPM can be found and downloaded from <a href=
"http://rpmfind.net" target="_top">http://rpmfind.net</a> .
The RPM can be installed with the following command after
becoming root.</p>
<pre class="PROGRAMLISTING">
rpm -i &lt;downloaded rpm&gt;
</pre>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PURPOSE" id="PURPOSE">1.4.
Purpose/Scope of the document</a></h3>
<p>This document is intended to be a "All in One" guide for
programming with ncurses and its sister libraries. We
graduate from a simple "Hello World" program to more
complex form manipulation. No prior experience in ncurses
is assumed. The writing is informal, but a lot of detail is
provided for each of the examples.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ABOUTPROGRAMS" id=
"ABOUTPROGRAMS">1.5. About the Programs</a></h3>
<p>All the programs in the document are available in zipped
form <a href=
"http://www.tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs.tar.gz"
target="_top">here</a>. Unzip and untar it. The directory
structure looks like this.</p>
<pre class="PROGRAMLISTING">
ncurses
|
|----&gt; JustForFun -- just for fun programs
|----&gt; basics -- basic programs
|----&gt; demo -- output files go into this directory after make
| |
| |----&gt; exe -- exe files of all example programs
|----&gt; forms -- programs related to form library
|----&gt; menus -- programs related to menus library
|----&gt; panels -- programs related to panels library
|----&gt; perl -- perl equivalents of the examples (contributed
| by Anuradha Ratnaweera)
|----&gt; Makefile -- the top level Makefile
|----&gt; README -- the top level README file. contains instructions
|----&gt; COPYING -- copyright notice
</pre>
<p>The individual directories contain the following
files.</p>
<pre class="PROGRAMLISTING">
Description of files in each directory
--------------------------------------
JustForFun
|
|----&gt; hanoi.c -- The Towers of Hanoi Solver
|----&gt; life.c -- The Game of Life demo
|----&gt; magic.c -- An Odd Order Magic Square builder
|----&gt; queens.c -- The famous N-Queens Solver
|----&gt; shuffle.c -- A fun game, if you have time to kill
|----&gt; tt.c -- A very trivial typing tutor
basics
|
|----&gt; acs_vars.c -- ACS_ variables example
|----&gt; hello_world.c -- Simple "Hello World" Program
|----&gt; init_func_example.c -- Initialization functions example
|----&gt; key_code.c -- Shows the scan code of the key pressed
|----&gt; mouse_menu.c -- A menu accessible by mouse
|----&gt; other_border.c -- Shows usage of other border functions apa
| -- rt from box()
|----&gt; printw_example.c -- A very simple printw() example
|----&gt; scanw_example.c -- A very simple getstr() example
|----&gt; simple_attr.c -- A program that can print a c file with
| -- comments in attribute
|----&gt; simple_color.c -- A simple example demonstrating colors
|----&gt; simple_key.c -- A menu accessible with keyboard UP, DOWN
| -- arrows
|----&gt; temp_leave.c -- Demonstrates temporarily leaving curses mode
|----&gt; win_border.c -- Shows Creation of windows and borders
|----&gt; with_chgat.c -- chgat() usage example
forms
|
|----&gt; form_attrib.c -- Usage of field attributes
|----&gt; form_options.c -- Usage of field options
|----&gt; form_simple.c -- A simple form example
|----&gt; form_win.c -- Demo of windows associated with forms
menus
|
|----&gt; menu_attrib.c -- Usage of menu attributes
|----&gt; menu_item_data.c -- Usage of item_name() etc.. functions
|----&gt; menu_multi_column.c -- Creates multi columnar menus
|----&gt; menu_scroll.c -- Demonstrates scrolling capability of menus
|----&gt; menu_simple.c -- A simple menu accessed by arrow keys
|----&gt; menu_toggle.c -- Creates multi valued menus and explains
| -- REQ_TOGGLE_ITEM
|----&gt; menu_userptr.c -- Usage of user pointer
|----&gt; menu_win.c -- Demo of windows associated with menus
panels
|
|----&gt; panel_browse.c -- Panel browsing through tab. Usage of user
| -- pointer
|----&gt; panel_hide.c -- Hiding and Un hiding of panels
|----&gt; panel_resize.c -- Moving and resizing of panels
|----&gt; panel_simple.c -- A simple panel example
perl
|----&gt; 01-10.pl -- Perl equivalents of first ten example programs
</pre>
<p>There is a top level Makefile included in the main
directory. It builds all the files and puts the
ready-to-use exes in demo/exe directory. You can also do
selective make by going into the corresponding directory.
Each directory contains a README file explaining the
purpose of each c file in the directory.</p>
<p>For every example, I have included path name for the
file relative to the examples directory.</p>
<p>If you prefer browsing individual programs, point your
browser to <a href=
"http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/"
target=
"_top">http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/</a></p>
<p>All the programs are released under the same license
that is used by ncurses (MIT-style). This gives you the
ability to do pretty much anything other than claiming them
as yours. Feel free to use them in your programs as
appropriate.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="OTHERFORMATS" id=
"OTHERFORMATS">1.6. Other Formats of the document</a></h3>
<p>This howto is also availabe in various other formats on
the tldp.org site. Here are the links to other formats of
this document.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="LISTFORMATS" id=
"LISTFORMATS">1.6.1. Readily available formats from
tldp.org</a></h4>
<ul>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/pdf/NCURSES-Programming-HOWTO.pdf"
target="_top">Acrobat PDF Format</a></p>
</li>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/ps/NCURSES-Programming-HOWTO.ps.gz"
target="_top">PostScript Format</a></p>
</li>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html/NCURSES-Programming-HOWTO-html.tar.gz"
target="_top">In Multiple HTML pages</a></p>
</li>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/NCURSES-Programming-HOWTO.html"
target="_top">In One big HTML format</a></p>
</li>
</ul>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="BUILDSOURCE" id=
"BUILDSOURCE">1.6.2. Building from source</a></h4>
<p>If above links are broken or if you want to experiment
with sgml read on.</p>
<pre class="PROGRAMLISTING">
&#13; Get both the source and the tar,gzipped programs, available at
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/NCURSES-Programming-HOWTO.sgml
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/ncurses_programs.tar.gz
Unzip ncurses_programs.tar.gz with
tar zxvf ncurses_programs.tar.gz
Use jade to create various formats. For example if you just want to create
the multiple html files, you would use
jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt;
NCURSES-Programming-HOWTO.sgml
to get pdf, first create a single html file of the HOWTO with
jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt; -V nochunks
NCURSES-Programming-HOWTO.sgml &gt; NCURSES-ONE-BIG-FILE.html
then use htmldoc to get pdf file with
htmldoc --size universal -t pdf --firstpage p1 -f &lt;output file name.pdf&gt;
NCURSES-ONE-BIG-FILE.html
for ps, you would use
htmldoc --size universal -t ps --firstpage p1 -f &lt;output file name.ps&gt;
NCURSES-ONE-BIG-FILE.html
</pre>
<p>See <a href=
"http://www.tldp.org/LDP/LDP-Author-Guide/" target=
"_top">LDP Author guide</a> for more details. If all else
failes, mail me at <a href="ppadala@gmail.com" target=
"_top">ppadala@gmail.com</a></p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CREDITS" id="CREDITS">1.7.
Credits</a></h3>
<p>I thank <a href="mailto:sharath_1@usa.net" target=
"_top">Sharath</a> and Emre Akbas for helping me with few
sections. The introduction was initially written by
sharath. I rewrote it with few excerpts taken from his
initial work. Emre helped in writing printw and scanw
sections.</p>
<p>Perl equivalents of the example programs are contributed
by <a href="mailto:Aratnaweera@virtusa.com" target=
"_top">Anuradha Ratnaweera</a>.</p>
<p>Then comes <a href="mailto:parimi@ece.arizona.edu"
target="_top">Ravi Parimi</a>, my dearest friend, who has
been on this project before even one line was written. He
constantly bombarded me with suggestions and patiently
reviewed the whole text. He also checked each program on
Linux and Solaris.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WISHLIST" id="WISHLIST">1.8.
Wish List</a></h3>
<p>This is the wish list, in the order of priority. If you
have a wish or you want to work on completing the wish,
mail <a href="mailto:ppadala@gmail.com" target=
"_top">me</a>.</p>
<ul>
<li>
<p>Add examples to last parts of forms section.</p>
</li>
<li>
<p>Prepare a Demo showing all the programs and allow
the user to browse through description of each program.
Let the user compile and see the program in action. A
dialog based interface is preferred.</p>
</li>
<li>
<p>Add debug info. _tracef, _tracemouse stuff.</p>
</li>
<li>
<p>Accessing termcap, terminfo using functions provided
by ncurses package.</p>
</li>
<li>
<p>Working on two terminals simultaneously.</p>
</li>
<li>
<p>Add more stuff to miscellaneous section.</p>
</li>
</ul>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COPYRIGHT" id="COPYRIGHT">1.9.
Copyright</a></h3>
<p>Copyright &copy; 2001 by Pradeep Padala.</p>
<p>Permission is hereby granted, free of charge, to any
person obtaining a copy of this software and associated
documentation files (the "Software"), to deal in the
Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish,
distribute, distribute with modifications, sublicense,
and/or sell copies of the Software, and to permit persons
to whom the Software is furnished to do so, subject to the
following conditions:</p>
<p>The above copyright notice and this permission notice
shall be included in all copies or substantial portions of
the Software.</p>
<p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO
THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE ABOVE
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.</p>
<p>Except as contained in this notice, the name(s) of the
above copyright holders shall not be used in advertising or
otherwise to promote the sale, use or other dealings in
this Software without prior written authorization.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="HELLOWORLD" id="HELLOWORLD">2.
Hello World !!!</a></h2>
<p>Welcome to the world of curses. Before we plunge into the
library and look into its various features, let's write a
simple program and say hello to the world.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COMPILECURSES" id=
"COMPILECURSES">2.1. Compiling With the NCURSES
Library</a></h3>
<p>To use ncurses library functions, you have to include
ncurses.h in your programs. To link the program with
ncurses the flag -lncurses should be added.</p>
<pre class="PROGRAMLISTING">
#include &lt;ncurses.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lncurses
</pre>
<div class="EXAMPLE">
<a name="BHW" id="BHW"></a>
<p><b>Example 1. The Hello World !!! Program</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="DISSECTION" id="DISSECTION">2.2.
Dissection</a></h3>
<p>The above program prints "Hello World !!!" to the screen
and exits. This program shows how to initialize curses and
do screen manipulation and end curses mode. Let's dissect
it line by line.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="ABOUT-INITSCR" id=
"ABOUT-INITSCR">2.2.1. About initscr()</a></h4>
<p>The function initscr() initializes the terminal in
curses mode. In some implementations, it clears the
screen and presents a blank screen. To do any screen
manipulation using curses package this has to be called
first. This function initializes the curses system and
allocates memory for our present window (called
<tt class="LITERAL">stdscr</tt>) and some other
data-structures. Under extreme cases this function might
fail due to insufficient memory to allocate memory for
curses library's data structures.</p>
<p>After this is done, we can do a variety of
initializations to customize our curses settings. These
details will be explained <a href="#INIT">later</a> .</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="MYST-REFRESH" id=
"MYST-REFRESH">2.2.2. The mysterious refresh()</a></h4>
<p>The next line printw prints the string "Hello World
!!!" on to the screen. This function is analogous to
normal printf in all respects except that it prints the
data on a window called stdscr at the current (y,x)
co-ordinates. Since our present co-ordinates are at 0,0
the string is printed at the left hand corner of the
window.</p>
<p>This brings us to that mysterious refresh(). Well,
when we called printw the data is actually written to an
imaginary window, which is not updated on the screen yet.
The job of printw is to update a few flags and data
structures and write the data to a buffer corresponding
to stdscr. In order to show it on the screen, we need to
call refresh() and tell the curses system to dump the
contents on the screen.</p>
<p>The philosophy behind all this is to allow the
programmer to do multiple updates on the imaginary screen
or windows and do a refresh once all his screen update is
done. refresh() checks the window and updates only the
portion which has been changed. This improves performance
and offers greater flexibility too. But, it is sometimes
frustrating to beginners. A common mistake committed by
beginners is to forget to call refresh() after they did
some update through printw() class of functions. I still
forget to add it sometimes :-)</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="ABOUT-ENDWIN" id=
"ABOUT-ENDWIN">2.2.3. About endwin()</a></h4>
<p>And finally don't forget to end the curses mode.
Otherwise your terminal might behave strangely after the
program quits. endwin() frees the memory taken by curses
sub-system and its data structures and puts the terminal
in normal mode. This function must be called after you
are done with the curses mode.</p>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="GORY" id="GORY">3. The Gory
Details</a></h2>
<p>Now that we have seen how to write a simple curses program
let's get into the details. There are many functions that
help customize what you see on screen and many features which
can be put to full use.</p>
<p>Here we go...</p>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="INIT" id="INIT">4.
Initialization</a></h2>
<p>We now know that to initialize curses system the function
initscr() has to be called. There are functions which can be
called after this initialization to customize our curses
session. We may ask the curses system to set the terminal in
raw mode or initialize color or initialize the mouse etc..
Let's discuss some of the functions that are normally called
immediately after initscr();</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ABOUTINIT" id="ABOUTINIT">4.1.
Initialization functions</a></h3>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="RAWCBREAK" id="RAWCBREAK">4.2.
raw() and cbreak()</a></h3>
<p>Normally the terminal driver buffers the characters a
user types until a new line or carriage return is
encountered. But most programs require that the characters
be available as soon as the user types them. The above two
functions are used to disable line buffering. The
difference between these two functions is in the way
control characters like suspend (CTRL-Z), interrupt and
quit (CTRL-C) are passed to the program. In the raw() mode
these characters are directly passed to the program without
generating a signal. In the <tt class=
"LITERAL">cbreak()</tt> mode these control characters are
interpreted as any other character by the terminal driver.
I personally prefer to use raw() as I can exercise greater
control over what the user does.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ECHONOECHO" id="ECHONOECHO">4.3.
echo() and noecho()</a></h3>
<p>These functions control the echoing of characters typed
by the user to the terminal. <tt class=
"LITERAL">noecho()</tt> switches off echoing. The reason
you might want to do this is to gain more control over
echoing or to suppress unnecessary echoing while taking
input from the user through the getch() etc. functions.
Most of the interactive programs call <tt class=
"LITERAL">noecho()</tt> at initialization and do the
echoing of characters in a controlled manner. It gives the
programmer the flexibility of echoing characters at any
place in the window without updating current (y,x)
co-ordinates.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="KEYPAD" id="KEYPAD">4.4.
keypad()</a></h3>
<p>This is my favorite initialization function. It enables
the reading of function keys like F1, F2, arrow keys etc.
Almost every interactive program enables this, as arrow
keys are a major part of any User Interface. Do <tt class=
"LITERAL">keypad(stdscr, TRUE)</tt> to enable this feature
for the regular screen (stdscr). You will learn more about
key management in later sections of this document.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="HALFDELAY" id="HALFDELAY">4.5.
halfdelay()</a></h3>
<p>This function, though not used very often, is a useful
one at times. halfdelay()is called to enable the half-delay
mode, which is similar to the cbreak() mode in that
characters typed are immediately available to program.
However, it waits for 'X' tenths of a second for input and
then returns ERR, if no input is available. 'X' is the
timeout value passed to the function halfdelay(). This
function is useful when you want to ask the user for input,
and if he doesn't respond with in certain time, we can do
some thing else. One possible example is a timeout at the
password prompt.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MISCINIT" id="MISCINIT">4.6.
Miscellaneous Initialization functions</a></h3>
<p>There are few more functions which are called at
initialization to customize curses behavior. They are not
used as extensively as those mentioned above. Some of them
are explained where appropriate.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="INITEX" id="INITEX">4.7. An
Example</a></h3>
<p>Let's write a program which will clarify the usage of
these functions.</p>
<div class="EXAMPLE">
<a name="BINFU" id="BINFU"></a>
<p><b>Example 2. Initialization Function Usage
example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{ int ch;
initscr(); /* Start curses mode */
raw(); /* Line buffering disabled */
keypad(stdscr, TRUE); /* We get F1, F2 etc.. */
noecho(); /* Don't echo() while we do getch */
printw("Type any character to see it in bold\n");
ch = getch(); /* If raw() hadn't been called
* we have to press enter before it
* gets to the program */
if(ch == KEY_F(1)) /* Without keypad enabled this will */
printw("F1 Key pressed");/* not get to us either */
/* Without noecho() some ugly escape
* charachters might have been printed
* on screen */
else
{ printw("The pressed key is ");
attron(A_BOLD);
printw("%c", ch);
attroff(A_BOLD);
}
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}</span>
</pre>
</div>
<p>This program is self-explanatory. But I used functions
which aren't explained yet. The function <tt class=
"LITERAL">getch()</tt> is used to get a character from
user. It is equivalent to normal <tt class=
"LITERAL">getchar()</tt> except that we can disable the
line buffering to avoid &lt;enter&gt; after input. Look for
more about <tt class="LITERAL">getch()</tt>and reading keys
in the <a href="#KEYS">key management section</a> . The
functions attron and attroff are used to switch some
attributes on and off respectively. In the example I used
them to print the character in bold. These functions are
explained in detail later.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="AWORDWINDOWS" id="AWORDWINDOWS">5.
A Word about Windows</a></h2>
<p>Before we plunge into the myriad ncurses functions, let me
clear few things about windows. Windows are explained in
detail in following <a href="#WINDOWS">sections</a></p>
<p>A Window is an imaginary screen defined by curses system.
A window does not mean a bordered window which you usually
see on Win9X platforms. When curses is initialized, it
creates a default window named <tt class=
"LITERAL">stdscr</tt> which represents your 80x25 (or the
size of window in which you are running) screen. If you are
doing simple tasks like printing few strings, reading input
etc., you can safely use this single window for all of your
purposes. You can also create windows and call functions
which explicitly work on the specified window.</p>
<p>For example, if you call</p>
<pre class="PROGRAMLISTING">
printw("Hi There !!!");
refresh();
</pre>
<p>It prints the string on stdscr at the present cursor
position. Similarly the call to refresh(), works on stdscr
only.</p>
<p>Say you have created <a href="#WINDOWS">windows</a> then
you have to call a function with a 'w' added to the usual
function.</p>
<pre class="PROGRAMLISTING">
wprintw(win, "Hi There !!!");
wrefresh(win);
</pre>
<p>As you will see in the rest of the document, naming of
functions follow the same convention. For each function there
usually are three more functions.</p>
<pre class="PROGRAMLISTING">
printw(string); /* Print on stdscr at present cursor position */
mvprintw(y, x, string);/* Move to (y, x) then print string */
wprintw(win, string); /* Print on window win at present cursor position */
/* in the window */
mvwprintw(win, y, x, string); /* Move to (y, x) relative to window */
/* co-ordinates and then print */
</pre>
<p>Usually the w-less functions are macros which expand to
corresponding w-function with stdscr as the window
parameter.</p>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="PRINTW" id="PRINTW">6. Output
functions</a></h2>
<p>I guess you can't wait any more to see some action. Back
to our odyssey of curses functions. Now that curses is
initialized, let's interact with world.</p>
<p>There are three classes of functions which you can use to
do output on screen.</p>
<ol type="1">
<li>
<p>addch() class: Print single character with
attributes</p>
</li>
<li>
<p>printw() class: Print formatted output similar to
printf()</p>
</li>
<li>
<p>addstr() class: Print strings</p>
</li>
</ol>
<p>These functions can be used interchangeably and it's a
matter of style as to which class is used. Let's see each one
in detail.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ADDCHCLASS" id="ADDCHCLASS">6.1.
addch() class of functions</a></h3>
<p>These functions put a single character into the current
cursor location and advance the position of the cursor. You
can give the character to be printed but they usually are
used to print a character with some attributes. Attributes
are explained in detail in later <a href=
"#ATTRIB">sections</a> of the document. If a character is
associated with an attribute(bold, reverse video etc.),
when curses prints the character, it is printed in that
attribute.</p>
<p>In order to combine a character with some attributes,
you have two options:</p>
<ul>
<li>
<p>By OR'ing a single character with the desired
attribute macros. These attribute macros could be found
in the header file <tt class="LITERAL">ncurses.h</tt>.
For example, you want to print a character ch(of type
char) bold and underlined, you would call addch() as
below.</p>
<pre class="PROGRAMLISTING">
addch(ch | A_BOLD | A_UNDERLINE);
</pre>
</li>
<li>
<p>By using functions like <tt class=
"LITERAL">attrset(),attron(),attroff()</tt>. These
functions are explained in the <a href=
"#ATTRIB">Attributes</a> section. Briefly, they
manipulate the current attributes of the given window.
Once set, the character printed in the window are
associated with the attributes until it is turned
off.</p>
</li>
</ul>
<p>Additionally, <tt class="LITERAL">curses</tt> provides
some special characters for character-based graphics. You
can draw tables, horizontal or vertical lines, etc. You can
find all avaliable characters in the header file <tt class=
"LITERAL">ncurses.h</tt>. Try looking for macros beginning
with <tt class="LITERAL">ACS_</tt> in this file.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="AEN298" id="AEN298">6.2.
mvaddch(), waddch() and mvwaddch()</a></h3>
<p><tt class="LITERAL">mvaddch()</tt> is used to move the
cursor to a given point, and then print. Thus, the
calls:</p>
<pre class="PROGRAMLISTING">
move(row,col); /* moves the cursor to row<span class=
"emphasis"><i class=
"EMPHASIS">th</i></span> row and col<span class="emphasis"><i class="EMPHASIS">th</i></span> column */
addch(ch);
</pre>can be replaced by
<pre class="PROGRAMLISTING">
mvaddch(row,col,ch);
</pre>
<p><tt class="LITERAL">waddch()</tt> is similar to
<tt class="LITERAL">addch()</tt>, except that it adds a
character into the given window. (Note that <tt class=
"LITERAL">addch()</tt> adds a character into the window
<tt class="LITERAL">stdscr</tt>.)</p>
<p>In a similar fashion <tt class="LITERAL">mvwaddch()</tt>
function is used to add a character into the given window
at the given coordinates.</p>
<p>Now, we are familiar with the basic output function
<tt class="LITERAL">addch()</tt>. But, if we want to print
a string, it would be very annoying to print it character
by character. Fortunately, <tt class="LITERAL">ncurses</tt>
provides <tt class="LITERAL">printf</tt><span class=
"emphasis"><i class="EMPHASIS">-like</i></span> or
<tt class="LITERAL">puts</tt><span class=
"emphasis"><i class="EMPHASIS">-like</i></span>
functions.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PRINTWCLASS" id=
"PRINTWCLASS">6.3. printw() class of functions</a></h3>
<p>These functions are similar to <tt class=
"LITERAL">printf()</tt> with the added capability of
printing at any position on the screen.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="PRINTWMVPRINTW" id=
"PRINTWMVPRINTW">6.3.1. printw() and mvprintw</a></h4>
<p>These two functions work much like <tt class=
"LITERAL">printf()</tt>. <tt class=
"LITERAL">mvprintw()</tt> can be used to move the cursor
to a position and then print. If you want to move the
cursor first and then print using <tt class=
"LITERAL">printw()</tt> function, use <tt class=
"LITERAL">move()</tt> first and then use <tt class=
"LITERAL">printw()</tt> though I see no point why one
should avoid using <tt class="LITERAL">mvprintw()</tt>,
you have the flexibility to manipulate.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="WPRINTWMVWPRINTW" id=
"WPRINTWMVWPRINTW">6.3.2. wprintw() and
mvwprintw</a></h4>
<p>These two functions are similar to above two except
that they print in the corresponding window given as
argument.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="VWPRINTW" id="VWPRINTW">6.3.3.
vwprintw()</a></h4>
<p>This function is similar to <tt class=
"LITERAL">vprintf()</tt>. This can be used when variable
number of arguments are to be printed.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="SIMPLEPRINTWEX" id=
"SIMPLEPRINTWEX">6.3.4. A Simple printw example</a></h4>
<div class="EXAMPLE">
<a name="BPREX" id="BPREX"></a>
<p><b>Example 3. A Simple printw example</b></p>
<pre class="PROGRAMLISTING">
<span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt; /* ncurses.h includes stdio.h */
#include &lt;string.h&gt;
int main()
{
char mesg[]="Just a string"; /* message to be appeared on the screen */
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
mvprintw(row-2,0,"This screen has %d rows and %d columns\n",row,col);
printw("Try resizing your window(if possible) and then run this program again");
refresh();
getch();
endwin();
return 0;
}</span>
</pre>
</div>
<p>Above program demonstrates how easy it is to use
<tt class="LITERAL">printw</tt>. You just feed the
coordinates and the message to be appeared on the screen,
then it does what you want.</p>
<p>The above program introduces us to a new function
<tt class="LITERAL">getmaxyx()</tt>, a macro defined in
<tt class="LITERAL">ncurses.h</tt>. It gives the number
of columns and the number of rows in a given window.
<tt class="LITERAL">getmaxyx()</tt> does this by updating
the variables given to it. Since <tt class=
"LITERAL">getmaxyx()</tt> is not a function we don't pass
pointers to it, we just give two integer variables.</p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ADDSTRCLASS" id=
"ADDSTRCLASS">6.4. addstr() class of functions</a></h3>
<p><tt class="LITERAL">addstr()</tt> is used to put a
character string into a given window. This function is
similar to calling <tt class="LITERAL">addch()</tt> once
for each character in a given string. This is true for all
output functions. There are other functions from this
family such as <tt class=
"LITERAL">mvaddstr(),mvwaddstr()</tt> and <tt class=
"LITERAL">waddstr()</tt>, which obey the naming convention
of curses.(e.g. mvaddstr() is similar to the respective
calls move() and then addstr().) Another function of this
family is addnstr(), which takes an integer parameter(say
n) additionally. This function puts at most n characters
into the screen. If n is negative, then the entire string
will be added.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ACAUTION" id="ACAUTION">6.5. A
word of caution</a></h3>
<p>All these functions take y co-ordinate first and then x
in their arguments. A common mistake by beginners is to
pass x,y in that order. If you are doing too many
manipulations of (y,x) co-ordinates, think of dividing the
screen into windows and manipulate each one separately.
Windows are explained in the <a href="#WINDOWS">windows</a>
section.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="SCANW" id="SCANW">7. Input
functions</a></h2>
<p>Well, printing without taking input, is boring. Let's see
functions which allow us to get input from user. These
functions also can be divided into three categories.</p>
<ol type="1">
<li>
<p>getch() class: Get a character</p>
</li>
<li>
<p>scanw() class: Get formatted input</p>
</li>
<li>
<p>getstr() class: Get strings</p>
</li>
</ol>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETCHCLASS" id="GETCHCLASS">7.1.
getch() class of functions</a></h3>
<p>These functions read a single character from the
terminal. But there are several subtle facts to consider.
For example if you don't use the function cbreak(), curses
will not read your input characters contiguously but will
begin read them only after a new line or an EOF is
encountered. In order to avoid this, the cbreak() function
must used so that characters are immediately available to
your program. Another widely used function is noecho(). As
the name suggests, when this function is set (used), the
characters that are keyed in by the user will not show up
on the screen. The two functions cbreak() and noecho() are
typical examples of key management. Functions of this genre
are explained in the <a href="#KEYS">key management
section</a> .</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SCANWCLASS" id="SCANWCLASS">7.2.
scanw() class of functions</a></h3>
<p>These functions are similar to <tt class=
"LITERAL">scanf()</tt> with the added capability of getting
the input from any location on the screen.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="SCANWMVSCANW" id=
"SCANWMVSCANW">7.2.1. scanw() and mvscanw</a></h4>
<p>The usage of these functions is similar to that of
<tt class="LITERAL">sscanf()</tt>, where the line to be
scanned is provided by <tt class="LITERAL">wgetstr()</tt>
function. That is, these functions call to <tt class=
"LITERAL">wgetstr()</tt> function(explained below) and
uses the resulting line for a scan.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="WSCANWMVWSCANW" id=
"WSCANWMVWSCANW">7.2.2. wscanw() and mvwscanw()</a></h4>
<p>These are similar to above two functions except that
they read from a window, which is supplied as one of the
arguments to these functions.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="VWSCANW" id="VWSCANW">7.2.3.
vwscanw()</a></h4>
<p>This function is similar to <tt class=
"LITERAL">vscanf()</tt>. This can be used when a variable
number of arguments are to be scanned.</p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETSTRCLASS" id=
"GETSTRCLASS">7.3. getstr() class of functions</a></h3>
<p>These functions are used to get strings from the
terminal. In essence, this function performs the same task
as would be achieved by a series of calls to <tt class=
"LITERAL">getch()</tt> until a newline, carriage return, or
end-of-file is received. The resulting string of characters
are pointed to by <tt class="LITERAL">str</tt>, which is a
character pointer provided by the user.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETSTREX" id="GETSTREX">7.4.
Some examples</a></h3>
<div class="EXAMPLE">
<a name="BSCEX" id="BSCEX"></a>
<p><b>Example 4. A Simple scanw example</b></p>
<pre class="PROGRAMLISTING">
<span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt; /* ncurses.h includes stdio.h */
#include &lt;string.h&gt;
int main()
{
char mesg[]="Enter a string: "; /* message to be appeared on the screen */
char str[80];
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
getstr(str);
mvprintw(LINES - 2, 0, "You Entered: %s", str);
getch();
endwin();
return 0;
}</span>
</pre>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="ATTRIB" id="ATTRIB">8.
Attributes</a></h2>
<p>We have seen an example of how attributes can be used to
print characters with some special effects. Attributes, when
set prudently, can present information in an easy,
understandable manner. The following program takes a C file
as input and prints the file with comments in bold. Scan
through the code.</p>
<div class="EXAMPLE">
<a name="BSIAT" id="BSIAT"></a>
<p><b>Example 5. A Simple Attributes example</b></p>
<pre class="PROGRAMLISTING">
<span class=
"INLINEMEDIAOBJECT">/* pager functionality by Joseph Spainhour" &lt;spainhou@bellsouth.net&gt; */
#include &lt;ncurses.h&gt;
#include &lt;stdlib.h&gt;
int main(int argc, char *argv[])
{
int ch, prev, row, col;
prev = EOF;
FILE *fp;
int y, x;
if(argc != 2)
{
printf("Usage: %s &lt;a c file name&gt;\n", argv[0]);
exit(1);
}
fp = fopen(argv[1], "r");
if(fp == NULL)
{
perror("Cannot open input file");
exit(1);
}
initscr(); /* Start curses mode */
getmaxyx(stdscr, row, col); /* find the boundaries of the screeen */
while((ch = fgetc(fp)) != EOF) /* read the file till we reach the end */
{
getyx(stdscr, y, x); /* get the current curser position */
if(y == (row - 1)) /* are we are at the end of the screen */
{
printw("&lt;-Press Any Key-&gt;"); /* tell the user to press a key */
getch();
clear(); /* clear the screen */
move(0, 0); /* start at the beginning of the screen */
}
if(prev == '/' &amp;&amp; ch == '*') /* If it is / and * then only
* switch bold on */
{
attron(A_BOLD); /* cut bold on */
getyx(stdscr, y, x); /* get the current curser position */
move(y, x - 1); /* back up one space */
printw("%c%c", '/', ch); /* The actual printing is done here */
}
else
printw("%c", ch);
refresh();
if(prev == '*' &amp;&amp; ch == '/')
attroff(A_BOLD); /* Switch it off once we got *
* and then / */
prev = ch;
}
endwin(); /* End curses mode */
fclose(fp);
return 0;
}</span>
</pre>
</div>
<p>Don't worry about all those initialization and other crap.
Concentrate on the while loop. It reads each character in the
file and searches for the pattern /*. Once it spots the
pattern, it switches the BOLD attribute on with <tt class=
"LITERAL">attron()</tt> . When we get the pattern */ it is
switched off by <tt class="LITERAL">attroff()</tt> .</p>
<p>The above program also introduces us to two useful
functions <tt class="LITERAL">getyx()</tt> and <tt class=
"LITERAL">move()</tt>. The first function gets the
co-ordinates of the present cursor into the variables y, x.
Since getyx() is a macro we don't have to pass pointers to
variables. The function <tt class="LITERAL">move()</tt> moves
the cursor to the co-ordinates given to it.</p>
<p>The above program is really a simple one which doesn't do
much. On these lines one could write a more useful program
which reads a C file, parses it and prints it in different
colors. One could even extend it to other languages as
well.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTRIBDETAILS" id=
"ATTRIBDETAILS">8.1. The details</a></h3>
<p>Let's get into more details of attributes. The functions
<tt class="LITERAL">attron(), attroff(), attrset()</tt> ,
and their sister functions <tt class=
"LITERAL">attr_get()</tt> etc.. can be used to switch
attributes on/off , get attributes and produce a colorful
display.</p>
<p>The functions attron and attroff take a bit-mask of
attributes and switch them on or off, respectively. The
following video attributes, which are defined in
&lt;curses.h&gt; can be passed to these functions.</p>
<pre class="PROGRAMLISTING">
A_NORMAL Normal display (no highlight)
A_STANDOUT Best highlighting mode of the terminal.
A_UNDERLINE Underlining
A_REVERSE Reverse video
A_BLINK Blinking
A_DIM Half bright
A_BOLD Extra bright or bold
A_PROTECT Protected mode
A_INVIS Invisible or blank mode
A_ALTCHARSET Alternate character set
A_CHARTEXT Bit-mask to extract a character
COLOR_PAIR(n) Color-pair number n
</pre>
<p>The last one is the most colorful one :-) Colors are
explained in the <a href="#color" target="_top">next
sections</a>.</p>
<p>We can OR(|) any number of above attributes to get a
combined effect. If you wanted reverse video with blinking
characters you can use</p>
<pre class="PROGRAMLISTING">
attron(A_REVERSE | A_BLINK);
</pre>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTRONVSATTRSET" id=
"ATTRONVSATTRSET">8.2. attron() vs attrset()</a></h3>
<p>Then what is the difference between attron() and
attrset()? attrset sets the attributes of window whereas
attron just switches on the attribute given to it. So
attrset() fully overrides whatever attributes the window
previously had and sets it to the new attribute(s).
Similarly attroff() just switches off the attribute(s)
given to it as an argument. This gives us the flexibility
of managing attributes easily.But if you use them
carelessly you may loose track of what attributes the
window has and garble the display. This is especially true
while managing menus with colors and highlighting. So
decide on a consistent policy and stick to it. You can
always use <tt class="LITERAL">standend()</tt> which is
equivalent to <tt class="LITERAL">attrset(A_NORMAL)</tt>
which turns off all attributes and brings you to normal
mode.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTRGET" id="ATTRGET">8.3.
attr_get()</a></h3>
<p>The function attr_get() gets the current attributes and
color pair of the window. Though we might not use this as
often as the above functions, this is useful in scanning
areas of screen. Say we wanted to do some complex update on
screen and we are not sure what attribute each character is
associated with. Then this function can be used with either
attrset or attron to produce the desired effect.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTRFUNCS" id="ATTRFUNCS">8.4.
attr_ functions</a></h3>
<p>There are series of functions like attr_set(), attr_on
etc.. These are similar to above functions except that they
take parameters of type <tt class=
"LITERAL">attr_t</tt>.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WATTRFUNCS" id="WATTRFUNCS">8.5.
wattr functions</a></h3>
<p>For each of the above functions we have a corresponding
function with 'w' which operates on a particular window.
The above functions operate on stdscr.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CHGAT" id="CHGAT">8.6. chgat()
functions</a></h3>
<p>The function chgat() is listed in the end of the man
page curs_attr. It actually is a useful one. This function
can be used to set attributes for a group of characters
without moving. I mean it !!! without moving the cursor :-)
It changes the attributes of a given number of characters
starting at the current cursor location.</p>
<p>We can give -1 as the character count to update till end
of line. If you want to change attributes of characters
from current position to end of line, just use this.</p>
<pre class="PROGRAMLISTING">
chgat(-1, A_REVERSE, 0, NULL);
</pre>
<p>This function is useful when changing attributes for
characters that are already on the screen. Move to the
character from which you want to change and change the
attribute.</p>
<p>Other functions wchgat(), mvchgat(), wchgat() behave
similarly except that the w functions operate on the
particular window. The mv functions first move the cursor
then perform the work given to them. Actually chgat is a
macro which is replaced by a wchgat() with stdscr as the
window. Most of the "w-less" functions are macros.</p>
<div class="EXAMPLE">
<a name="BWICH" id="BWICH"></a>
<p><b>Example 6. Chgat() Usage example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main(int argc, char *argv[])
{ initscr(); /* Start curses mode */
start_color(); /* Start color functionality */
init_pair(1, COLOR_CYAN, COLOR_BLACK);
printw("A Big string which i didn't care to type fully ");
mvchgat(0, 0, -1, A_BLINK, 1, NULL);
/*
* First two parameters specify the position at which to start
* Third parameter number of characters to update. -1 means till
* end of line
* Forth parameter is the normal attribute you wanted to give
* to the charcter
* Fifth is the color index. It is the index given during init_pair()
* use 0 if you didn't want color
* Sixth one is always NULL
*/
refresh();
getch();
endwin(); /* End curses mode */
return 0;
}</span>
</pre>
</div>
<p>This example also introduces us to the color world of
curses. Colors will be explained in detail later. Use 0 for
no color.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="WINDOWS" id="WINDOWS">9.
Windows</a></h2>
<p>Windows form the most important concept in curses. You
have seen the standard window stdscr above where all the
functions implicitly operated on this window. Now to make
design even a simplest GUI, you need to resort to windows.
The main reason you may want to use windows is to manipulate
parts of the screen separately, for better efficiency, by
updating only the windows that need to be changed and for a
better design. I would say the last reason is the most
important in going for windows. You should always strive for
a better and easy-to-manage design in your programs. If you
are writing big, complex GUIs this is of pivotal importance
before you start doing anything.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WINDOWBASICS" id=
"WINDOWBASICS">9.1. The basics</a></h3>
<p>A Window can be created by calling the function
<tt class="LITERAL">newwin()</tt>. It doesn't create any
thing on the screen actually. It allocates memory for a
structure to manipulate the window and updates the
structure with data regarding the window like it's size,
beginy, beginx etc.. Hence in curses, a window is just an
abstraction of an imaginary window, which can be
manipulated independent of other parts of screen. The
function newwin() returns a pointer to structure WINDOW,
which can be passed to window related functions like
wprintw() etc.. Finally the window can be destroyed with
delwin(). It will deallocate the memory associated with the
window structure.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="LETBEWINDOW" id=
"LETBEWINDOW">9.2. Let there be a Window !!!</a></h3>
<p>What fun is it, if a window is created and we can't see
it. So the fun part begins by displaying the window. The
function <tt class="LITERAL">box()</tt> can be used to draw
a border around the window. Let's explore these functions
in more detail in this example.</p>
<div class="EXAMPLE">
<a name="BWIBO" id="BWIBO"></a>
<p><b>Example 7. Window Border example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
WINDOW *create_newwin(int height, int width, int starty, int startx);
void destroy_win(WINDOW *local_win);
int main(int argc, char *argv[])
{ WINDOW *my_win;
int startx, starty, width, height;
int ch;
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
height = 3;
width = 10;
starty = (LINES - height) / 2; /* Calculating for a center placement */
startx = (COLS - width) / 2; /* of the window */
printw("Press F1 to exit");
refresh();
my_win = create_newwin(height, width, starty, startx);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,--startx);
break;
case KEY_RIGHT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,++startx);
break;
case KEY_UP:
destroy_win(my_win);
my_win = create_newwin(height, width, --starty,startx);
break;
case KEY_DOWN:
destroy_win(my_win);
my_win = create_newwin(height, width, ++starty,startx);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
WINDOW *create_newwin(int height, int width, int starty, int startx)
{ WINDOW *local_win;
local_win = newwin(height, width, starty, startx);
box(local_win, 0 , 0); /* 0, 0 gives default characters
* for the vertical and horizontal
* lines */
wrefresh(local_win); /* Show that box */
return local_win;
}
void destroy_win(WINDOW *local_win)
{
/* box(local_win, ' ', ' '); : This won't produce the desired
* result of erasing the window. It will leave it's four corners
* and so an ugly remnant of window.
*/
wborder(local_win, ' ', ' ', ' ',' ',' ',' ',' ',' ');
/* The parameters taken are
* 1. win: the window on which to operate
* 2. ls: character to be used for the left side of the window
* 3. rs: character to be used for the right side of the window
* 4. ts: character to be used for the top side of the window
* 5. bs: character to be used for the bottom side of the window
* 6. tl: character to be used for the top left corner of the window
* 7. tr: character to be used for the top right corner of the window
* 8. bl: character to be used for the bottom left corner of the window
* 9. br: character to be used for the bottom right corner of the window
*/
wrefresh(local_win);
delwin(local_win);
}</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="BORDEREXEXPL" id=
"BORDEREXEXPL">9.3. Explanation</a></h3>
<p>Don't scream. I know it's a big example. But I have to
explain some important things here :-). This program
creates a rectangular window that can be moved with left,
right, up, down arrow keys. It repeatedly creates and
destroys windows as user press a key. Don't go beyond the
screen limits. Checking for those limits is left as an
exercise for the reader. Let's dissect it by line by
line.</p>
<p>The <tt class="LITERAL">create_newwin()</tt> function
creates a window with <tt class="LITERAL">newwin()</tt> and
displays a border around it with box. The function
<tt class="LITERAL">destroy_win()</tt> first erases the
window from screen by painting a border with ' ' character
and then calling <tt class="LITERAL">delwin()</tt> to
deallocate memory related to it. Depending on the key the
user presses, starty or startx is changed and a new window
is created.</p>
<p>In the destroy_win, as you can see, I used wborder
instead of box. The reason is written in the comments (You
missed it. I know. Read the code :-)). wborder draws a
border around the window with the characters given to it as
the 4 corner points and the 4 lines. To put it clearly, if
you have called wborder as below:</p>
<pre class="PROGRAMLISTING">
wborder(win, '|', '|', '-', '-', '+', '+', '+', '+');
</pre>
<p>it produces some thing like</p>
<pre class="PROGRAMLISTING">
+------------+
| |
| |
| |
| |
| |
| |
+------------+
</pre>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="OTHERSTUFF" id="OTHERSTUFF">9.4.
The other stuff in the example</a></h3>
<p>You can also see in the above examples, that I have used
the variables COLS, LINES which are initialized to the
screen sizes after initscr(). They can be useful in finding
screen dimensions and finding the center co-ordinate of the
screen as above. The function <tt class=
"LITERAL">getch()</tt> as usual gets the key from keyboard
and according to the key it does the corresponding work.
This type of switch- case is very common in any GUI based
programs.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="OTHERBORDERFUNCS" id=
"OTHERBORDERFUNCS">9.5. Other Border functions</a></h3>
<p>Above program is grossly inefficient in that with each
press of a key, a window is destroyed and another is
created. So let's write a more efficient program which uses
other border related functions.</p>
<p>The following program uses <tt class=
"LITERAL">mvhline()</tt> and <tt class=
"LITERAL">mvvline()</tt> to achieve similar effect. These
two functions are simple. They create a horizontal or
vertical line of the specified length at the specified
position.</p>
<div class="EXAMPLE">
<a name="BOTBO" id="BOTBO"></a>
<p><b>Example 8. More border functions</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
typedef struct _win_border_struct {
chtype ls, rs, ts, bs,
tl, tr, bl, br;
}WIN_BORDER;
typedef struct _WIN_struct {
int startx, starty;
int height, width;
WIN_BORDER border;
}WIN;
void init_win_params(WIN *p_win);
void print_win_params(WIN *p_win);
void create_box(WIN *win, bool flag);
int main(int argc, char *argv[])
{ WIN win;
int ch;
initscr(); /* Start curses mode */
start_color(); /* Start the color functionality */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
noecho();
init_pair(1, COLOR_CYAN, COLOR_BLACK);
/* Initialize the window parameters */
init_win_params(&amp;win);
print_win_params(&amp;win);
attron(COLOR_PAIR(1));
printw("Press F1 to exit");
refresh();
attroff(COLOR_PAIR(1));
create_box(&amp;win, TRUE);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
create_box(&amp;win, FALSE);
--win.startx;
create_box(&amp;win, TRUE);
break;
case KEY_RIGHT:
create_box(&amp;win, FALSE);
++win.startx;
create_box(&amp;win, TRUE);
break;
case KEY_UP:
create_box(&amp;win, FALSE);
--win.starty;
create_box(&amp;win, TRUE);
break;
case KEY_DOWN:
create_box(&amp;win, FALSE);
++win.starty;
create_box(&amp;win, TRUE);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
void init_win_params(WIN *p_win)
{
p_win-&gt;height = 3;
p_win-&gt;width = 10;
p_win-&gt;starty = (LINES - p_win-&gt;height)/2;
p_win-&gt;startx = (COLS - p_win-&gt;width)/2;
p_win-&gt;border.ls = '|';
p_win-&gt;border.rs = '|';
p_win-&gt;border.ts = '-';
p_win-&gt;border.bs = '-';
p_win-&gt;border.tl = '+';
p_win-&gt;border.tr = '+';
p_win-&gt;border.bl = '+';
p_win-&gt;border.br = '+';
}
void print_win_params(WIN *p_win)
{
#ifdef _DEBUG
mvprintw(25, 0, "%d %d %d %d", p_win-&gt;startx, p_win-&gt;starty,
p_win-&gt;width, p_win-&gt;height);
refresh();
#endif
}
void create_box(WIN *p_win, bool flag)
{ int i, j;
int x, y, w, h;
x = p_win-&gt;startx;
y = p_win-&gt;starty;
w = p_win-&gt;width;
h = p_win-&gt;height;
if(flag == TRUE)
{ mvaddch(y, x, p_win-&gt;border.tl);
mvaddch(y, x + w, p_win-&gt;border.tr);
mvaddch(y + h, x, p_win-&gt;border.bl);
mvaddch(y + h, x + w, p_win-&gt;border.br);
mvhline(y, x + 1, p_win-&gt;border.ts, w - 1);
mvhline(y + h, x + 1, p_win-&gt;border.bs, w - 1);
mvvline(y + 1, x, p_win-&gt;border.ls, h - 1);
mvvline(y + 1, x + w, p_win-&gt;border.rs, h - 1);
}
else
for(j = y; j &lt;= y + h; ++j)
for(i = x; i &lt;= x + w; ++i)
mvaddch(j, i, ' ');
refresh();
}</span>
</pre>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="COLOR" id="COLOR">10.
Colors</a></h2>
<div class="SECT2">
<h3 class="SECT2"><a name="COLORBASICS" id=
"COLORBASICS">10.1. The basics</a></h3>
<p>Life seems dull with no colors. Curses has a nice
mechanism to handle colors. Let's get into the thick of the
things with a small program.</p>
<div class="EXAMPLE">
<a name="BSICO" id="BSICO"></a>
<p><b>Example 9. A Simple Color example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string);
int main(int argc, char *argv[])
{ initscr(); /* Start curses mode */
if(has_colors() == FALSE)
{ endwin();
printf("Your terminal does not support color\n");
exit(1);
}
start_color(); /* Start color */
init_pair(1, COLOR_RED, COLOR_BLACK);
attron(COLOR_PAIR(1));
print_in_middle(stdscr, LINES / 2, 0, 0, "Viola !!! In color ...");
attroff(COLOR_PAIR(1));
getch();
endwin();
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
mvwprintw(win, y, x, "%s", string);
refresh();
}
</span>
</pre>
</div>
<p>As you can see, to start using color, you should first
call the function <tt class="LITERAL">start_color()</tt>.
After that, you can use color capabilities of your
terminals using various functions. To find out whether a
terminal has color capabilities or not, you can use
<tt class="LITERAL">has_colors()</tt> function, which
returns FALSE if the terminal does not support color.</p>
<p>Curses initializes all the colors supported by terminal
when start_color() is called. These can be accessed by the
define constants like <tt class="LITERAL">COLOR_BLACK</tt>
etc. Now to actually start using colors, you have to define
pairs. Colors are always used in pairs. That means you have
to use the function <tt class="LITERAL">init_pair()</tt> to
define the foreground and background for the pair number
you give. After that that pair number can be used as a
normal attribute with <tt class=
"LITERAL">COLOR_PAIR()</tt>function. This may seem to be
cumbersome at first. But this elegant solution allows us to
manage color pairs very easily. To appreciate it, you have
to look into the the source code of "dialog", a utility for
displaying dialog boxes from shell scripts. The developers
have defined foreground and background combinations for all
the colors they might need and initialized at the
beginning. This makes it very easy to set attributes just
by accessing a pair which we already have defined as a
constant.</p>
<p>The following colors are defined in <tt class=
"LITERAL">curses.h</tt>. You can use these as parameters
for various color functions.</p>
<pre class="PROGRAMLISTING">
COLOR_BLACK 0
COLOR_RED 1
COLOR_GREEN 2
COLOR_YELLOW 3
COLOR_BLUE 4
COLOR_MAGENTA 5
COLOR_CYAN 6
COLOR_WHITE 7
</pre>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CHANGECOLORDEFS" id=
"CHANGECOLORDEFS">10.2. Changing Color Definitions</a></h3>
<p>The function <tt class="LITERAL">init_color()</tt>can be
used to change the rgb values for the colors defined by
curses initially. Say you wanted to lighten the intensity
of red color by a minuscule. Then you can use this function
as</p>
<pre class="PROGRAMLISTING">
init_color(COLOR_RED, 700, 0, 0);
/* param 1 : color name
* param 2, 3, 4 : rgb content min = 0, max = 1000 */
</pre>
<p>If your terminal cannot change the color definitions,
the function returns ERR. The function <tt class=
"LITERAL">can_change_color()</tt> can be used to find out
whether the terminal has the capability of changing color
content or not. The rgb content is scaled from 0 to 1000.
Initially RED color is defined with content 1000(r), 0(g),
0(b).</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COLORCONTENT" id=
"COLORCONTENT">10.3. Color Content</a></h3>
<p>The functions <tt class="LITERAL">color_content()</tt>
and <tt class="LITERAL">pair_content()</tt> can be used to
find the color content and foreground, background
combination for the pair.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="KEYS" id="KEYS">11. Interfacing
with the key board</a></h2>
<div class="SECT2">
<h3 class="SECT2"><a name="KEYSBASICS" id=
"KEYSBASICS">11.1. The Basics</a></h3>
<p>No GUI is complete without a strong user interface and
to interact with the user, a curses program should be
sensitive to key presses or the mouse actions done by the
user. Let's deal with the keys first.</p>
<p>As you have seen in almost all of the above examples,
it's very easy to get key input from the user. A simple way
of getting key presses is to use <tt class=
"LITERAL">getch()</tt> function. The cbreak mode should be
enabled to read keys when you are interested in reading
individual key hits rather than complete lines of text
(which usually end with a carriage return). keypad should
be enabled to get the Functions keys, arrow keys etc. See
the initialization section for details.</p>
<p><tt class="LITERAL">getch()</tt> returns an integer
corresponding to the key pressed. If it is a normal
character, the integer value will be equivalent to the
character. Otherwise it returns a number which can be
matched with the constants defined in <tt class=
"LITERAL">curses.h</tt>. For example if the user presses
F1, the integer returned is 265. This can be checked using
the macro KEY_F() defined in curses.h. This makes reading
keys portable and easy to manage.</p>
<p>For example, if you call getch() like this</p>
<pre class="PROGRAMLISTING">
int ch;
ch = getch();
</pre>
<p>getch() will wait for the user to press a key, (unless
you specified a timeout) and when user presses a key, the
corresponding integer is returned. Then you can check the
value returned with the constants defined in curses.h to
match against the keys you want.</p>
<p>The following code piece will do that job.</p>
<pre class="PROGRAMLISTING">
if(ch == KEY_LEFT)
printw("Left arrow is pressed\n");
</pre>
<p>Let's write a small program which creates a menu which
can be navigated by up and down arrows.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SIMPLEKEYEX" id=
"SIMPLEKEYEX">11.2. A Simple Key Usage example</a></h3>
<div class="EXAMPLE">
<a name="BSIKE" id="BSIKE"></a>
<p><b>Example 10. A Simple Key Usage example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;stdio.h&gt;
#include &lt;ncurses.h&gt;
#define WIDTH 30
#define HEIGHT 10
int startx = 0;
int starty = 0;
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int n_choices = sizeof(choices) / sizeof(char *);
void print_menu(WINDOW *menu_win, int highlight);
int main()
{ WINDOW *menu_win;
int highlight = 1;
int choice = 0;
int c;
initscr();
clear();
noecho();
cbreak(); /* Line buffering disabled. pass on everything */
startx = (80 - WIDTH) / 2;
starty = (24 - HEIGHT) / 2;
menu_win = newwin(HEIGHT, WIDTH, starty, startx);
keypad(menu_win, TRUE);
mvprintw(0, 0, "Use arrow keys to go up and down, Press enter to select a choice");
refresh();
print_menu(menu_win, highlight);
while(1)
{ c = wgetch(menu_win);
switch(c)
{ case KEY_UP:
if(highlight == 1)
highlight = n_choices;
else
--highlight;
break;
case KEY_DOWN:
if(highlight == n_choices)
highlight = 1;
else
++highlight;
break;
case 10:
choice = highlight;
break;
default:
mvprintw(24, 0, "Charcter pressed is = %3d Hopefully it can be printed as '%c'", c, c);
refresh();
break;
}
print_menu(menu_win, highlight);
if(choice != 0) /* User did a choice come out of the infinite loop */
break;
}
mvprintw(23, 0, "You chose choice %d with choice string %s\n", choice, choices[choice - 1]);
clrtoeol();
refresh();
endwin();
return 0;
}
void print_menu(WINDOW *menu_win, int highlight)
{
int x, y, i;
x = 2;
y = 2;
box(menu_win, 0, 0);
for(i = 0; i &lt; n_choices; ++i)
{ if(highlight == i + 1) /* High light the present choice */
{ wattron(menu_win, A_REVERSE);
mvwprintw(menu_win, y, x, "%s", choices[i]);
wattroff(menu_win, A_REVERSE);
}
else
mvwprintw(menu_win, y, x, "%s", choices[i]);
++y;
}
wrefresh(menu_win);
}
</span>
</pre>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="MOUSE" id="MOUSE">12. Interfacing
with the mouse</a></h2>
<p>Now that you have seen how to get keys, lets do the same
thing from mouse. Usually each UI allows the user to interact
with both keyboard and mouse.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MOUSEBASICS" id=
"MOUSEBASICS">12.1. The Basics</a></h3>
<p>Before you do any thing else, the events you want to
receive have to be enabled with <tt class=
"LITERAL">mousemask()</tt>.</p>
<pre class="PROGRAMLISTING">
mousemask( mmask_t newmask, /* The events you want to listen to */
mmask_t *oldmask) /* The old events mask */
</pre>
<p>The first parameter to above function is a bit mask of
events you would like to listen. By default, all the events
are turned off. The bit mask <tt class=
"LITERAL">ALL_MOUSE_EVENTS</tt> can be used to get all the
events.</p>
<p>The following are all the event masks:</p>
<pre class="PROGRAMLISTING">
Name Description
---------------------------------------------------------------------
BUTTON1_PRESSED mouse button 1 down
BUTTON1_RELEASED mouse button 1 up
BUTTON1_CLICKED mouse button 1 clicked
BUTTON1_DOUBLE_CLICKED mouse button 1 double clicked
BUTTON1_TRIPLE_CLICKED mouse button 1 triple clicked
BUTTON2_PRESSED mouse button 2 down
BUTTON2_RELEASED mouse button 2 up
BUTTON2_CLICKED mouse button 2 clicked
BUTTON2_DOUBLE_CLICKED mouse button 2 double clicked
BUTTON2_TRIPLE_CLICKED mouse button 2 triple clicked
BUTTON3_PRESSED mouse button 3 down
BUTTON3_RELEASED mouse button 3 up
BUTTON3_CLICKED mouse button 3 clicked
BUTTON3_DOUBLE_CLICKED mouse button 3 double clicked
BUTTON3_TRIPLE_CLICKED mouse button 3 triple clicked
BUTTON4_PRESSED mouse button 4 down
BUTTON4_RELEASED mouse button 4 up
BUTTON4_CLICKED mouse button 4 clicked
BUTTON4_DOUBLE_CLICKED mouse button 4 double clicked
BUTTON4_TRIPLE_CLICKED mouse button 4 triple clicked
BUTTON_SHIFT shift was down during button state change
BUTTON_CTRL control was down during button state change
BUTTON_ALT alt was down during button state change
ALL_MOUSE_EVENTS report all button state changes
REPORT_MOUSE_POSITION report mouse movement
</pre>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETTINGEVENTS" id=
"GETTINGEVENTS">12.2. Getting the events</a></h3>
<p>Once a class of mouse events have been enabled, getch()
class of functions return KEY_MOUSE every time some mouse
event happens. Then the mouse event can be retrieved with
<tt class="LITERAL">getmouse()</tt>.</p>
<p>The code approximately looks like this:</p>
<pre class="PROGRAMLISTING">
MEVENT event;
ch = getch();
if(ch == KEY_MOUSE)
if(getmouse(&amp;event) == OK)
. /* Do some thing with the event */
.
.
</pre>
<p>getmouse() returns the event into the pointer given to
it. It's a structure which contains</p>
<pre class="PROGRAMLISTING">
typedef struct
{
short id; /* ID to distinguish multiple devices */
int x, y, z; /* event coordinates */
mmask_t bstate; /* button state bits */
}
</pre>
<p>The <tt class="LITERAL">bstate</tt> is the main variable
we are interested in. It tells the button state of the
mouse.</p>
<p>Then with a code snippet like the following, we can find
out what happened.</p>
<pre class="PROGRAMLISTING">
if(event.bstate &amp; BUTTON1_PRESSED)
printw("Left Button Pressed");
</pre>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MOUSETOGETHER" id=
"MOUSETOGETHER">12.3. Putting it all Together</a></h3>
<p>That's pretty much interfacing with mouse. Let's create
the same menu and enable mouse interaction. To make things
simpler, key handling is removed.</p>
<div class="EXAMPLE">
<a name="BMOME" id="BMOME"></a>
<p><b>Example 11. Access the menu with mouse !!!</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
#define WIDTH 30
#define HEIGHT 10
int startx = 0;
int starty = 0;
char *choices[] = { "Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int n_choices = sizeof(choices) / sizeof(char *);
void print_menu(WINDOW *menu_win, int highlight);
void report_choice(int mouse_x, int mouse_y, int *p_choice);
int main()
{ int c, choice = 0;
WINDOW *menu_win;
MEVENT event;
/* Initialize curses */
initscr();
clear();
noecho();
cbreak(); //Line buffering disabled. pass on everything
/* Try to put the window in the middle of screen */
startx = (80 - WIDTH) / 2;
starty = (24 - HEIGHT) / 2;
attron(A_REVERSE);
mvprintw(23, 1, "Click on Exit to quit (Works best in a virtual console)");
refresh();
attroff(A_REVERSE);
/* Print the menu for the first time */
menu_win = newwin(HEIGHT, WIDTH, starty, startx);
print_menu(menu_win, 1);
/* Get all the mouse events */
mousemask(ALL_MOUSE_EVENTS, NULL);
while(1)
{ c = wgetch(menu_win);
switch(c)
{ case KEY_MOUSE:
if(getmouse(&amp;event) == OK)
{ /* When the user clicks left mouse button */
if(event.bstate &amp; BUTTON1_PRESSED)
{ report_choice(event.x + 1, event.y + 1, &amp;choice);
if(choice == -1) //Exit chosen
goto end;
mvprintw(22, 1, "Choice made is : %d String Chosen is \"%10s\"", choice, choices[choice - 1]);
refresh();
}
}
print_menu(menu_win, choice);
break;
}
}
end:
endwin();
return 0;
}
void print_menu(WINDOW *menu_win, int highlight)
{
int x, y, i;
x = 2;
y = 2;
box(menu_win, 0, 0);
for(i = 0; i &lt; n_choices; ++i)
{ if(highlight == i + 1)
{ wattron(menu_win, A_REVERSE);
mvwprintw(menu_win, y, x, "%s", choices[i]);
wattroff(menu_win, A_REVERSE);
}
else
mvwprintw(menu_win, y, x, "%s", choices[i]);
++y;
}
wrefresh(menu_win);
}
/* Report the choice according to mouse position */
void report_choice(int mouse_x, int mouse_y, int *p_choice)
{ int i,j, choice;
i = startx + 2;
j = starty + 3;
for(choice = 0; choice &lt; n_choices; ++choice)
if(mouse_y == j + choice &amp;&amp; mouse_x &gt;= i &amp;&amp; mouse_x &lt;= i + strlen(choices[choice]))
{ if(choice == n_choices - 1)
*p_choice = -1;
else
*p_choice = choice + 1;
break;
}
}</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MISCMOUSEFUNCS" id=
"MISCMOUSEFUNCS">12.4. Miscellaneous Functions</a></h3>
<p>The functions mouse_trafo() and wmouse_trafo() can be
used to convert to mouse co-ordinates to screen relative
co-ordinates. See curs_mouse(3X) man page for details.</p>
<p>The mouseinterval function sets the maximum time (in
thousands of a second) that can elapse between press and
release events in order for them to be recognized as a
click. This function returns the previous interval value.
The default is one fifth of a second.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="SCREEN" id="SCREEN">13. Screen
Manipulation</a></h2>
<p>In this section, we will look into some functions, which
allow us to manage the screen efficiently and to write some
fancy programs. This is especially important in writing
games.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETYX" id="GETYX">13.1. getyx()
functions</a></h3>
<p>The function <tt class="LITERAL">getyx()</tt> can be
used to find out the present cursor co-ordinates. It will
fill the values of x and y co-ordinates in the arguments
given to it. Since getyx() is a macro you don't have to
pass the address of the variables. It can be called as</p>
<pre class="PROGRAMLISTING">
getyx(win, y, x);
/* win: window pointer
* y, x: y, x co-ordinates will be put into this variables
*/
</pre>
<p>The function getparyx() gets the beginning co-ordinates
of the sub window relative to the main window. This is some
times useful to update a sub window. When designing fancy
stuff like writing multiple menus, it becomes difficult to
store the menu positions, their first option co-ordinates
etc. A simple solution to this problem, is to create menus
in sub windows and later find the starting co-ordinates of
the menus by using getparyx().</p>
<p>The functions getbegyx() and getmaxyx() store current
window's beginning and maximum co-ordinates. These
functions are useful in the same way as above in managing
the windows and sub windows effectively.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SCREENDUMP" id=
"SCREENDUMP">13.2. Screen Dumping</a></h3>
<p>While writing games, some times it becomes necessary to
store the state of the screen and restore it back to the
same state. The function scr_dump() can be used to dump the
screen contents to a file given as an argument. Later it
can be restored by scr_restore function. These two simple
functions can be used effectively to maintain a fast moving
game with changing scenarios.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WINDOWDUMP" id=
"WINDOWDUMP">13.3. Window Dumping</a></h3>
<p>To store and restore windows, the functions <tt class=
"LITERAL">putwin()</tt> and <tt class=
"LITERAL">getwin()</tt> can be used. <tt class=
"LITERAL">putwin()</tt> puts the present window state into
a file, which can be later restored by <tt class=
"LITERAL">getwin()</tt>.</p>
<p>The function <tt class="LITERAL">copywin()</tt> can be
used to copy a window completely onto another window. It
takes the source and destination windows as parameters and
according to the rectangle specified, it copies the
rectangular region from source to destination window. It's
last parameter specifies whether to overwrite or just
overlay the contents on to the destination window. If this
argument is true, then the copying is non-destructive.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="MISC" id="MISC">14. Miscellaneous
features</a></h2>
<p>Now you know enough features to write a good curses
program, with all bells and whistles. There are some
miscellaneous functions which are useful in various cases.
Let's go headlong into some of those.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CURSSET" id="CURSSET">14.1.
curs_set()</a></h3>
<p>This function can be used to make the cursor invisible.
The parameter to this function should be</p>
<pre class="PROGRAMLISTING">
0 : invisible or
1 : normal or
2 : very visible.
</pre>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="TEMPLEAVE" id="TEMPLEAVE">14.2.
Temporarily Leaving Curses mode</a></h3>
<p>Some times you may want to get back to cooked mode
(normal line buffering mode) temporarily. In such a case
you will first need to save the tty modes with a call to
<tt class="LITERAL">def_prog_mode()</tt> and then call
<tt class="LITERAL">endwin()</tt> to end the curses mode.
This will leave you in the original tty mode. To get back
to curses once you are done, call <tt class=
"LITERAL">reset_prog_mode()</tt> . This function returns
the tty to the state stored by <tt class=
"LITERAL">def_prog_mode()</tt>. Then do refresh(), and you
are back to the curses mode. Here is an example showing the
sequence of things to be done.</p>
<div class="EXAMPLE">
<a name="BTELE" id="BTELE"></a>
<p><b>Example 12. Temporarily Leaving Curses Mode</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!\n"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
def_prog_mode(); /* Save the tty modes */
endwin(); /* End curses mode temporarily */
system("/bin/sh"); /* Do whatever you like in cooked mode */
reset_prog_mode(); /* Return to the previous tty mode*/
/* stored by def_prog_mode() */
refresh(); /* Do refresh() to restore the */
/* Screen contents */
printw("Another String\n"); /* Back to curses use the full */
refresh(); /* capabilities of curses */
endwin(); /* End curses mode */
return 0;
}</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ACSVARS" id="ACSVARS">14.3. ACS_
variables</a></h3>
<p>If you have ever programmed in DOS, you know about those
nifty characters in extended character set. They are
printable only on some terminals. NCURSES functions like
<tt class="LITERAL">box()</tt> use these characters. All
these variables start with ACS meaning alternative
character set. You might have noticed me using these
characters in some of the programs above. Here's an example
showing all the characters.</p>
<div class="EXAMPLE">
<a name="BACSVARS" id="BACSVARS"></a>
<p><b>Example 13. ACS Variables Example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{
initscr();
printw("Upper left corner "); addch(ACS_ULCORNER); printw("\n");
printw("Lower left corner "); addch(ACS_LLCORNER); printw("\n");
printw("Lower right corner "); addch(ACS_LRCORNER); printw("\n");
printw("Tee pointing right "); addch(ACS_LTEE); printw("\n");
printw("Tee pointing left "); addch(ACS_RTEE); printw("\n");
printw("Tee pointing up "); addch(ACS_BTEE); printw("\n");
printw("Tee pointing down "); addch(ACS_TTEE); printw("\n");
printw("Horizontal line "); addch(ACS_HLINE); printw("\n");
printw("Vertical line "); addch(ACS_VLINE); printw("\n");
printw("Large Plus or cross over "); addch(ACS_PLUS); printw("\n");
printw("Scan Line 1 "); addch(ACS_S1); printw("\n");
printw("Scan Line 3 "); addch(ACS_S3); printw("\n");
printw("Scan Line 7 "); addch(ACS_S7); printw("\n");
printw("Scan Line 9 "); addch(ACS_S9); printw("\n");
printw("Diamond "); addch(ACS_DIAMOND); printw("\n");
printw("Checker board (stipple) "); addch(ACS_CKBOARD); printw("\n");
printw("Degree Symbol "); addch(ACS_DEGREE); printw("\n");
printw("Plus/Minus Symbol "); addch(ACS_PLMINUS); printw("\n");
printw("Bullet "); addch(ACS_BULLET); printw("\n");
printw("Arrow Pointing Left "); addch(ACS_LARROW); printw("\n");
printw("Arrow Pointing Right "); addch(ACS_RARROW); printw("\n");
printw("Arrow Pointing Down "); addch(ACS_DARROW); printw("\n");
printw("Arrow Pointing Up "); addch(ACS_UARROW); printw("\n");
printw("Board of squares "); addch(ACS_BOARD); printw("\n");
printw("Lantern Symbol "); addch(ACS_LANTERN); printw("\n");
printw("Solid Square Block "); addch(ACS_BLOCK); printw("\n");
printw("Less/Equal sign "); addch(ACS_LEQUAL); printw("\n");
printw("Greater/Equal sign "); addch(ACS_GEQUAL); printw("\n");
printw("Pi "); addch(ACS_PI); printw("\n");
printw("Not equal "); addch(ACS_NEQUAL); printw("\n");
printw("UK pound sign "); addch(ACS_STERLING); printw("\n");
refresh();
getch();
endwin();
return 0;
}</span>
</pre>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="OTHERLIB" id="OTHERLIB">15. Other
libraries</a></h2>
<p>Apart from the curses library, there are few text mode
libraries, which provide more functionality and a lot of
features. The following sections explain three standard
libraries which are usually distributed along with
curses.</p>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="PANELS" id="PANELS">16. Panel
Library</a></h2>
<p>Now that you are proficient in curses, you wanted to do
some thing big. You created a lot of overlapping windows to
give a professional windows-type look. Unfortunately, it soon
becomes difficult to manage these. The multiple refreshes,
updates plunge you into a nightmare. The overlapping windows
create blotches, whenever you forget to refresh the windows
in the proper order.</p>
<p>Don't despair. There's an elegant solution provided in
panels library. In the words of developers of ncurses</p>
<p><span class="emphasis"><i class="EMPHASIS">When your
interface design is such that windows may dive deeper into
the visibility stack or pop to the top at runtime, the
resulting book-keeping can be tedious and difficult to get
right. Hence the panels library.</i></span></p>
<p>If you have lot of overlapping windows, then panels
library is the way to go. It obviates the need of doing
series of wnoutrefresh(), doupdate() and relieves the burden
of doing it correctly(bottom up). The library maintains
information about the order of windows, their overlapping and
update the screen properly. So why wait? Let's take a close
peek into panels.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELBASICS" id=
"PANELBASICS">16.1. The Basics</a></h3>
<p>Panel object is a window that is implicitly treated as
part of a deck including all other panel objects. The deck
is treated as a stack with the top panel being completely
visible and the other panels may or may not be obscured
according to their positions. So the basic idea is to
create a stack of overlapping panels and use panels library
to display them correctly. There is a function similar to
refresh() which, when called , displays panels in the
correct order. Functions are provided to hide or show
panels, move panels, change its size etc.. The overlapping
problem is managed by the panels library during all the
calls to these functions.</p>
<p>The general flow of a panel program goes like this:</p>
<ol type="1">
<li>
<p>Create the windows (with newwin()) to be attached to
the panels.</p>
</li>
<li>
<p>Create panels with the chosen visibility order.
Stack them up according to the desired visibility. The
function new_panel() is used to created panels.</p>
</li>
<li>
<p>Call update_panels() to write the panels to the
virtual screen in correct visibility order. Do a
doupdate() to show it on the screen.</p>
</li>
<li>
<p>Mainpulate the panels with show_panel(),
hide_panel(), move_panel() etc. Make use of helper
functions like panel_hidden() and panel_window(). Make
use of user pointer to store custom data for a panel.
Use the functions set_panel_userptr() and
panel_userptr() to set and get the user pointer for a
panel.</p>
</li>
<li>
<p>When you are done with the panel use del_panel() to
delete the panel.</p>
</li>
</ol>
<p>Let's make the concepts clear, with some programs. The
following is a simple program which creates 3 overlapping
panels and shows them on the screen.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COMPILEPANELS" id=
"COMPILEPANELS">16.2. Compiling With the Panels
Library</a></h3>
<p>To use panels library functions, you have to include
panel.h and to link the program with panels library the
flag -lpanel should be added along with -lncurses in that
order.</p>
<pre class="PROGRAMLISTING">
#include &lt;panel.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lpanel -lncurses
</pre>
<div class="EXAMPLE">
<a name="PPASI" id="PPASI"></a>
<p><b>Example 14. Panel basics</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
int lines = 10, cols = 40, y = 2, x = 4, i;
initscr();
cbreak();
noecho();
/* Create windows for the panels */
my_wins[0] = newwin(lines, cols, y, x);
my_wins[1] = newwin(lines, cols, y + 1, x + 5);
my_wins[2] = newwin(lines, cols, y + 2, x + 10);
/*
* Create borders around the windows so that you can see the effect
* of panels
*/
for(i = 0; i &lt; 3; ++i)
box(my_wins[i], 0, 0);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
doupdate();
getch();
endwin();
}
</span>
</pre>
</div>
<p>As you can see, above program follows a simple flow as
explained. The windows are created with newwin() and then
they are attached to panels with new_panel(). As we attach
one panel after another, the stack of panels gets updated.
To put them on screen update_panels() and doupdate() are
called.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELBROWSING" id=
"PANELBROWSING">16.3. Panel Window Browsing</a></h3>
<p>A slightly complicated example is given below. This
program creates 3 windows which can be cycled through using
tab. Have a look at the code.</p>
<div class="EXAMPLE">
<a name="PPABR" id="PPABR"></a>
<p><b>Example 15. Panel Window Browsing Example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL *top;
int ch;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Set up the user pointers to the next panel */
set_panel_userptr(my_panels[0], my_panels[1]);
set_panel_userptr(my_panels[1], my_panels[2]);
set_panel_userptr(my_panels[2], my_panels[0]);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
doupdate();
top = my_panels[2];
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 9:
top = (PANEL *)panel_userptr(top);
top_panel(top);
break;
}
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i &lt; n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="USERPTRUSING" id=
"USERPTRUSING">16.4. Using User Pointers</a></h3>
<p>In the above example I used user pointers to find out
the next window in the cycle. We can attach custom
information to the panel by specifying a user pointer,
which can point to any information you want to store. In
this case I stored the pointer to the next panel in the
cycle. User pointer for a panel can be set with the
function <tt class="LITERAL">set_panel_userptr()</tt>. It
can be accessed using the function <tt class=
"LITERAL">panel_userptr()</tt> which will return the user
pointer for the panel given as argument. After finding the
next panel in the cycle It's brought to the top by the
function top_panel(). This function brings the panel given
as argument to the top of the panel stack.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELMOVERESIZE" id=
"PANELMOVERESIZE">16.5. Moving and Resizing Panels</a></h3>
<p>The function <tt class="LITERAL">move_panel()</tt> can
be used to move a panel to the desired location. It does
not change the position of the panel in the stack. Make
sure that you use move_panel() instead mvwin() on the
window associated with the panel.</p>
<p>Resizing a panel is slightly complex. There is no
straight forward function just to resize the window
associated with a panel. A solution to resize a panel is to
create a new window with the desired sizes, change the
window associated with the panel using replace_panel().
Don't forget to delete the old window. The window
associated with a panel can be found by using the function
panel_window().</p>
<p>The following program shows these concepts, in
supposedly simple program. You can cycle through the window
with &lt;TAB&gt; as usual. To resize or move the active
panel press 'r' for resize 'm' for moving. Then use arrow
keys to resize or move it to the desired way and press
enter to end your resizing or moving. This example makes
use of user data to get the required data to do the
operations.</p>
<div class="EXAMPLE">
<a name="PPARE" id="PPARE"></a>
<p><b>Example 16. Panel Moving and Resizing
example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
typedef struct _PANEL_DATA {
int x, y, w, h;
char label[80];
int label_color;
PANEL *next;
}PANEL_DATA;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
void set_user_ptrs(PANEL **panels, int n);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL_DATA *top;
PANEL *stack_top;
WINDOW *temp_win, *old_win;
int ch;
int newx, newy, neww, newh;
int size = FALSE, move = FALSE;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
set_user_ptrs(my_panels, 3);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
doupdate();
stack_top = my_panels[2];
top = (PANEL_DATA *)panel_userptr(stack_top);
newx = top-&gt;x;
newy = top-&gt;y;
neww = top-&gt;w;
newh = top-&gt;h;
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 9: /* Tab */
top = (PANEL_DATA *)panel_userptr(stack_top);
top_panel(top-&gt;next);
stack_top = top-&gt;next;
top = (PANEL_DATA *)panel_userptr(stack_top);
newx = top-&gt;x;
newy = top-&gt;y;
neww = top-&gt;w;
newh = top-&gt;h;
break;
case 'r': /* Re-Size*/
size = TRUE;
attron(COLOR_PAIR(4));
mvprintw(LINES - 4, 0, "Entered Resizing :Use Arrow Keys to resize and press &lt;ENTER&gt; to end resizing");
refresh();
attroff(COLOR_PAIR(4));
break;
case 'm': /* Move */
attron(COLOR_PAIR(4));
mvprintw(LINES - 4, 0, "Entered Moving: Use Arrow Keys to Move and press &lt;ENTER&gt; to end moving");
refresh();
attroff(COLOR_PAIR(4));
move = TRUE;
break;
case KEY_LEFT:
if(size == TRUE)
{ --newx;
++neww;
}
if(move == TRUE)
--newx;
break;
case KEY_RIGHT:
if(size == TRUE)
{ ++newx;
--neww;
}
if(move == TRUE)
++newx;
break;
case KEY_UP:
if(size == TRUE)
{ --newy;
++newh;
}
if(move == TRUE)
--newy;
break;
case KEY_DOWN:
if(size == TRUE)
{ ++newy;
--newh;
}
if(move == TRUE)
++newy;
break;
case 10: /* Enter */
move(LINES - 4, 0);
clrtoeol();
refresh();
if(size == TRUE)
{ old_win = panel_window(stack_top);
temp_win = newwin(newh, neww, newy, newx);
replace_panel(stack_top, temp_win);
win_show(temp_win, top-&gt;label, top-&gt;label_color);
delwin(old_win);
size = FALSE;
}
if(move == TRUE)
{ move_panel(stack_top, newy, newx);
move = FALSE;
}
break;
}
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
refresh();
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i &lt; n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Set the PANEL_DATA structures for individual panels */
void set_user_ptrs(PANEL **panels, int n)
{ PANEL_DATA *ptrs;
WINDOW *win;
int x, y, w, h, i;
char temp[80];
ptrs = (PANEL_DATA *)calloc(n, sizeof(PANEL_DATA));
for(i = 0;i &lt; n; ++i)
{ win = panel_window(panels[i]);
getbegyx(win, y, x);
getmaxyx(win, h, w);
ptrs[i].x = x;
ptrs[i].y = y;
ptrs[i].w = w;
ptrs[i].h = h;
sprintf(temp, "Window Number %d", i + 1);
strcpy(ptrs[i].label, temp);
ptrs[i].label_color = i + 1;
if(i + 1 == n)
ptrs[i].next = panels[0];
else
ptrs[i].next = panels[i + 1];
set_panel_userptr(panels[i], &amp;ptrs[i]);
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span>
</pre>
</div>
<p>Concentrate on the main while loop. Once it finds out
the type of key pressed, it takes appropriate action. If
'r' is pressed resizing mode is started. After this the new
sizes are updated as the user presses the arrow keys. When
the user presses &lt;ENTER&gt; present selection ends and
panel is resized by using the concept explained. While in
resizing mode the program doesn't show how the window is
getting resized. It's left as an exercise to the reader to
print a dotted border while it gets resized to a new
position.</p>
<p>When the user presses 'm' the move mode starts. This is
a bit simpler than resizing. As the arrow keys are pressed
the new position is updated and pressing of &lt;ENTER&gt;
causes the panel to be moved by calling the function
move_panel().</p>
<p>In this program the user data which is represented as
PANEL_DATA, plays very important role in finding the
associated information with a panel. As written in the
comments, the PANEL_DATA stores the panel sizes, label,
label color and a pointer to the next panel in the
cycle.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELSHOWHIDE" id=
"PANELSHOWHIDE">16.6. Hiding and Showing Panels</a></h3>
<p>A Panel can be hidden by using the function
hide_panel(). This function merely removes it form the
stack of panels, thus hiding it on the screen once you do
update_panels() and doupdate(). It doesn't destroy the
PANEL structure associated with the hidden panel. It can be
shown again by using the show_panel() function.</p>
<p>The following program shows the hiding of panels. Press
'a' or 'b' or 'c' to show or hide first, second and third
windows respectively. It uses a user data with a small
variable hide, which keeps track of whether the window is
hidden or not. For some reason the function <tt class=
"LITERAL">panel_hidden()</tt> which tells whether a panel
is hidden or not is not working. A bug report was also
presented by Michael Andres <a href=
"http://www.geocrawler.com/archives/3/344/1999/9/0/2643549/"
target="_top">here</a></p>
<div class="EXAMPLE">
<a name="PPAHI" id="PPAHI"></a>
<p><b>Example 17. Panel Hiding and Showing
example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
typedef struct _PANEL_DATA {
int hide; /* TRUE if panel is hidden */
}PANEL_DATA;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL_DATA panel_datas[3];
PANEL_DATA *temp;
int ch;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Initialize panel datas saying that nothing is hidden */
panel_datas[0].hide = FALSE;
panel_datas[1].hide = FALSE;
panel_datas[2].hide = FALSE;
set_panel_userptr(my_panels[0], &amp;panel_datas[0]);
set_panel_userptr(my_panels[1], &amp;panel_datas[1]);
set_panel_userptr(my_panels[2], &amp;panel_datas[2]);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Show or Hide a window with 'a'(first window) 'b'(Second Window) 'c'(Third Window)");
mvprintw(LINES - 2, 0, "F1 to Exit");
attroff(COLOR_PAIR(4));
doupdate();
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 'a':
temp = (PANEL_DATA *)panel_userptr(my_panels[0]);
if(temp-&gt;hide == FALSE)
{ hide_panel(my_panels[0]);
temp-&gt;hide = TRUE;
}
else
{ show_panel(my_panels[0]);
temp-&gt;hide = FALSE;
}
break;
case 'b':
temp = (PANEL_DATA *)panel_userptr(my_panels[1]);
if(temp-&gt;hide == FALSE)
{ hide_panel(my_panels[1]);
temp-&gt;hide = TRUE;
}
else
{ show_panel(my_panels[1]);
temp-&gt;hide = FALSE;
}
break;
case 'c':
temp = (PANEL_DATA *)panel_userptr(my_panels[2]);
if(temp-&gt;hide == FALSE)
{ hide_panel(my_panels[2]);
temp-&gt;hide = TRUE;
}
else
{ show_panel(my_panels[2]);
temp-&gt;hide = FALSE;
}
break;
}
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i &lt; n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELABOVE" id=
"PANELABOVE">16.7. panel_above() and panel_below()
Functions</a></h3>
<p>The functions <tt class="LITERAL">panel_above()</tt> and
<tt class="LITERAL">panel_below()</tt> can be used to find
out the panel above and below a panel. If the argument to
these functions is NULL, then they return a pointer to
bottom panel and top panel respectively.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="MENUS" id="MENUS">17. Menus
Library</a></h2>
<p>The menus library provides a nice extension to basic
curses, through which you can create menus. It provides a set
of functions to create menus. But they have to be customized
to give a nicer look, with colors etc. Let's get into the
details.</p>
<p>A menu is a screen display that assists the user to choose
some subset of a given set of items. To put it simple, a menu
is a collection of items from which one or more items can be
chosen. Some readers might not be aware of multiple item
selection capability. Menu library provides functionality to
write menus from which the user can chose more than one item
as the preferred choice. This is dealt with in a later
section. Now it is time for some rudiments.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MENUBASICS" id=
"MENUBASICS">17.1. The Basics</a></h3>
<p>To create menus, you first create items, and then post
the menu to the display. After that, all the processing of
user responses is done in an elegant function menu_driver()
which is the work horse of any menu program.</p>
<p>The general flow of control of a menu program looks like
this.</p>
<ol type="1">
<li>
<p>Initialize curses</p>
</li>
<li>
<p>Create items using new_item(). You can specify a
name and description for the items.</p>
</li>
<li>
<p>Create the menu with new_menu() by specifying the
items to be attached with.</p>
</li>
<li>
<p>Post the menu with menu_post() and refresh the
screen.</p>
</li>
<li>
<p>Process the user requests with a loop and do
necessary updates to menu with menu_driver.</p>
</li>
<li>
<p>Unpost the menu with menu_unpost()</p>
</li>
<li>
<p>Free the memory allocated to menu by free_menu()</p>
</li>
<li>
<p>Free the memory allocated to the items with
free_item()</p>
</li>
<li>
<p>End curses</p>
</li>
</ol>
<p>Let's see a program which prints a simple menu and
updates the current selection with up, down arrows.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COMPILEMENUS" id=
"COMPILEMENUS">17.2. Compiling With the Menu
Library</a></h3>
<p>To use menu library functions, you have to include
menu.h and to link the program with menu library the flag
-lmenu should be added along with -lncurses in that
order.</p>
<pre class="PROGRAMLISTING">
#include &lt;menu.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lmenu -lncurses
</pre>
<div class="EXAMPLE">
<a name="MMESI" id="MMESI"></a>
<p><b>Example 18. Menu Basics</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;curses.h&gt;
#include &lt;menu.h&gt;
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i &lt; n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
my_items[n_choices] = (ITEM *)NULL;
my_menu = new_menu((ITEM **)my_items);
mvprintw(LINES - 2, 0, "F1 to Exit");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
}
}
free_item(my_items[0]);
free_item(my_items[1]);
free_menu(my_menu);
endwin();
}
</span>
</pre>
</div>
<p>This program demonstrates the basic concepts involved in
creating a menu using menus library. First we create the
items using new_item() and then attach them to the menu
with new_menu() function. After posting the menu and
refreshing the screen, the main processing loop starts. It
reads user input and takes corresponding action. The
function menu_driver() is the main work horse of the menu
system. The second parameter to this function tells what's
to be done with the menu. According to the parameter,
menu_driver() does the corresponding task. The value can be
either a menu navigational request, an ascii character, or
a KEY_MOUSE special key associated with a mouse event.</p>
<p>The menu_driver accepts following navigational
requests.</p>
<pre class="PROGRAMLISTING">
&#13; REQ_LEFT_ITEM Move left to an item.
REQ_RIGHT_ITEM Move right to an item.
REQ_UP_ITEM Move up to an item.
REQ_DOWN_ITEM Move down to an item.
REQ_SCR_ULINE Scroll up a line.
REQ_SCR_DLINE Scroll down a line.
REQ_SCR_DPAGE Scroll down a page.
REQ_SCR_UPAGE Scroll up a page.
REQ_FIRST_ITEM Move to the first item.
REQ_LAST_ITEM Move to the last item.
REQ_NEXT_ITEM Move to the next item.
REQ_PREV_ITEM Move to the previous item.
REQ_TOGGLE_ITEM Select/deselect an item.
REQ_CLEAR_PATTERN Clear the menu pattern buffer.
REQ_BACK_PATTERN Delete the previous character from the pattern buffer.
REQ_NEXT_MATCH Move to the next item matching the pattern match.
REQ_PREV_MATCH Move to the previous item matching the pattern match.&#13;
</pre>
<p>Don't get overwhelmed by the number of options. We will
see them slowly one after another. The options of interest
in this example are REQ_UP_ITEM and REQ_DOWN_ITEM. These
two options when passed to menu_driver, menu driver updates
the current item to one item up or down respectively.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MENUDRIVER" id=
"MENUDRIVER">17.3. Menu Driver: The work horse of the menu
system</a></h3>
<p>As you have seen in the above example, menu_driver plays
an important role in updating the menu. It is very
important to understand various options it takes and what
they do. As explained above, the second parameter to
menu_driver() can be either a navigational request, a
printable character or a KEY_MOUSE key. Let's dissect the
different navigational requests.</p>
<ul>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_LEFT_ITEM and
REQ_RIGHT_ITEM</i></span></p>
<p>A Menu can be displayed with multiple columns for
more than one item. This can be done by using the
<tt class="LITERAL">menu_format()</tt>function. When a
multi columnar menu is displayed these requests cause
the menu driver to move the current selection to left
or right.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_UP_ITEM and REQ_DOWN_ITEM</i></span></p>
<p>These two options you have seen in the above
example. These options when given, makes the
menu_driver to move the current selection to an item up
or down.</p>
</li>
<li>
<p><span class="emphasis"><i class="EMPHASIS">REQ_SCR_*
options</i></span></p>
<p>The four options REQ_SCR_ULINE, REQ_SCR_DLINE,
REQ_SCR_DPAGE, REQ_SCR_UPAGE are related to scrolling.
If all the items in the menu cannot be displayed in the
menu sub window, then the menu is scrollable. These
requests can be given to the menu_driver to do the
scrolling either one line up, down or one page down or
up respectively.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_NEXT_ITEM
and REQ_PREV_ITEM</i></span></p>
<p>These requests are self explanatory.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_TOGGLE_ITEM</i></span></p>
<p>This request when given, toggles the present
selection. This option is to be used only in a multi
valued menu. So to use this request the option
O_ONEVALUE must be off. This option can be made off or
on with set_menu_opts().</p>
</li>
<li>
<p><span class="emphasis"><i class="EMPHASIS">Pattern
Requests</i></span></p>
<p>Every menu has an associated pattern buffer, which
is used to find the nearest match to the ascii
characters entered by the user. Whenever ascii
characters are given to menu_driver, it puts in to the
pattern buffer. It also tries to find the nearest match
to the pattern in the items list and moves current
selection to that item. The request REQ_CLEAR_PATTERN
clears the pattern buffer. The request REQ_BACK_PATTERN
deletes the previous character in the pattern buffer.
In case the pattern matches more than one item then the
matched items can be cycled through REQ_NEXT_MATCH and
REQ_PREV_MATCH which move the current selection to the
next and previous matches respectively.</p>
</li>
<li>
<p><span class="emphasis"><i class="EMPHASIS">Mouse
Requests</i></span></p>
<p>In case of KEY_MOUSE requests, according to the
mouse position an action is taken accordingly. The
action to be taken is explained in the man page as,</p>
<pre class="PROGRAMLISTING">
<span class="emphasis"><i class=
"EMPHASIS"> If the second argument is the KEY_MOUSE special key, the
associated mouse event is translated into one of the above
pre-defined requests. Currently only clicks in the user
window (e.g. inside the menu display area or the decora&shy;
tion window) are handled. If you click above the display
region of the menu, a REQ_SCR_ULINE is generated, if you
doubleclick a REQ_SCR_UPAGE is generated and if you
tripleclick a REQ_FIRST_ITEM is generated. If you click
below the display region of the menu, a REQ_SCR_DLINE is
generated, if you doubleclick a REQ_SCR_DPAGE is generated
and if you tripleclick a REQ_LAST_ITEM is generated. If
you click at an item inside the display area of the menu,
the menu cursor is positioned to that item.</i></span>
</pre>
</li>
</ul>
<p>Each of the above requests will be explained in the
following lines with several examples whenever
appropriate.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MENUWINDOWS" id=
"MENUWINDOWS">17.4. Menu Windows</a></h3>
<p>Every menu created is associated with a window and a sub
window. The menu window displays any title or border
associated with the menu. The menu sub window displays the
menu items currently available for selection. But we didn't
specify any window or sub window in the simple example.
When a window is not specified, stdscr is taken as the main
window, and then menu system calculates the sub window size
required for the display of items. Then items are displayed
in the calculated sub window. So let's play with these
windows and display a menu with a border and a title.</p>
<div class="EXAMPLE">
<a name="MMEWI" id="MMEWI"></a>
<p><b>Example 19. Menu Windows Usage example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;menu.h&gt;
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
(char *)NULL,
};
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
WINDOW *my_menu_win;
int n_choices, i;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
/* Create items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));
for(i = 0; i &lt; n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
/* Crate menu */
my_menu = new_menu((ITEM **)my_items);
/* Create the window to be associated with the menu */
my_menu_win = newwin(10, 40, 4, 4);
keypad(my_menu_win, TRUE);
/* Set main window and sub window */
set_menu_win(my_menu, my_menu_win);
set_menu_sub(my_menu, derwin(my_menu_win, 6, 38, 3, 1));
/* Set menu mark to the string " * " */
set_menu_mark(my_menu, " * ");
/* Print a border around the main window and print a title */
box(my_menu_win, 0, 0);
print_in_middle(my_menu_win, 1, 0, 40, "My Menu", COLOR_PAIR(1));
mvwaddch(my_menu_win, 2, 0, ACS_LTEE);
mvwhline(my_menu_win, 2, 1, ACS_HLINE, 38);
mvwaddch(my_menu_win, 2, 39, ACS_RTEE);
mvprintw(LINES - 2, 0, "F1 to exit");
refresh();
/* Post the menu */
post_menu(my_menu);
wrefresh(my_menu_win);
while((c = wgetch(my_menu_win)) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
}
wrefresh(my_menu_win);
}
/* Unpost and free all the memory taken up */
unpost_menu(my_menu);
free_menu(my_menu);
for(i = 0; i &lt; n_choices; ++i)
free_item(my_items[i]);
endwin();
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span>
</pre>
</div>
<p>This example creates a menu with a title, border, a
fancy line separating title and the items. As you can see,
in order to attach a window to a menu the function
set_menu_win() has to be used. Then we attach the sub
window also. This displays the items in the sub window. You
can also set the mark string which gets displayed to the
left of the selected item with set_menu_mark().</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SCROLLMENUS" id=
"SCROLLMENUS">17.5. Scrolling Menus</a></h3>
<p>If the sub window given for a window is not big enough
to show all the items, then the menu will be scrollable.
When you are on the last item in the present list, if you
send REQ_DOWN_ITEM, it gets translated into REQ_SCR_DLINE
and the menu scrolls by one item. You can manually give
REQ_SCR_ operations to do scrolling. Let's see how it can
be done.</p>
<div class="EXAMPLE">
<a name="MMESC" id="MMESC"></a>
<p><b>Example 20. Scrolling Menus example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;curses.h&gt;
#include &lt;menu.h&gt;
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Choice 8",
"Choice 9",
"Choice 10",
"Exit",
(char *)NULL,
};
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
WINDOW *my_menu_win;
int n_choices, i;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_CYAN, COLOR_BLACK);
/* Create items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));
for(i = 0; i &lt; n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
/* Crate menu */
my_menu = new_menu((ITEM **)my_items);
/* Create the window to be associated with the menu */
my_menu_win = newwin(10, 40, 4, 4);
keypad(my_menu_win, TRUE);
/* Set main window and sub window */
set_menu_win(my_menu, my_menu_win);
set_menu_sub(my_menu, derwin(my_menu_win, 6, 38, 3, 1));
set_menu_format(my_menu, 5, 1);
/* Set menu mark to the string " * " */
set_menu_mark(my_menu, " * ");
/* Print a border around the main window and print a title */
box(my_menu_win, 0, 0);
print_in_middle(my_menu_win, 1, 0, 40, "My Menu", COLOR_PAIR(1));
mvwaddch(my_menu_win, 2, 0, ACS_LTEE);
mvwhline(my_menu_win, 2, 1, ACS_HLINE, 38);
mvwaddch(my_menu_win, 2, 39, ACS_RTEE);
/* Post the menu */
post_menu(my_menu);
wrefresh(my_menu_win);
attron(COLOR_PAIR(2));
mvprintw(LINES - 2, 0, "Use PageUp and PageDown to scoll down or up a page of items");
mvprintw(LINES - 1, 0, "Arrow Keys to navigate (F1 to Exit)");
attroff(COLOR_PAIR(2));
refresh();
while((c = wgetch(my_menu_win)) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case KEY_NPAGE:
menu_driver(my_menu, REQ_SCR_DPAGE);
break;
case KEY_PPAGE:
menu_driver(my_menu, REQ_SCR_UPAGE);
break;
}
wrefresh(my_menu_win);
}
/* Unpost and free all the memory taken up */
unpost_menu(my_menu);
free_menu(my_menu);
for(i = 0; i &lt; n_choices; ++i)
free_item(my_items[i]);
endwin();
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span>
</pre>
</div>
<p>This program is self-explanatory. In this example the
number of choices has been increased to ten, which is
larger than our sub window size which can hold 6 items.
This message has to be explicitly conveyed to the menu
system with the function set_menu_format(). In here we
specify the number of rows and columns we want to be
displayed for a single page. We can specify any number of
items to be shown, in the rows variables, if it is less
than the height of the sub window. If the key pressed by
the user is a PAGE UP or PAGE DOWN, the menu is scrolled a
page due to the requests (REQ_SCR_DPAGE and REQ_SCR_UPAGE)
given to menu_driver().</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MULTICOLUMN" id=
"MULTICOLUMN">17.6. Multi Columnar Menus</a></h3>
<p>In the above example you have seen how to use the
function set_menu_format(). I didn't mention what the cols
variable (third parameter) does. Well, If your sub window
is wide enough, you can opt to display more than one item
per row. This can be specified in the cols variable. To
make things simpler, the following example doesn't show
descriptions for the items.</p>
<div class="EXAMPLE">
<a name="MMEMUCO" id="MMEMUCO"></a>
<p><b>Example 21. Milt Columnar Menus Example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;curses.h&gt;
#include &lt;menu.h&gt;
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1", "Choice 2", "Choice 3", "Choice 4", "Choice 5",
"Choice 6", "Choice 7", "Choice 8", "Choice 9", "Choice 10",
"Choice 11", "Choice 12", "Choice 13", "Choice 14", "Choice 15",
"Choice 16", "Choice 17", "Choice 18", "Choice 19", "Choice 20",
"Exit",
(char *)NULL,
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
WINDOW *my_menu_win;
int n_choices, i;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_CYAN, COLOR_BLACK);
/* Create items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));
for(i = 0; i &lt; n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
/* Crate menu */
my_menu = new_menu((ITEM **)my_items);
/* Set menu option not to show the description */
menu_opts_off(my_menu, O_SHOWDESC);
/* Create the window to be associated with the menu */
my_menu_win = newwin(10, 70, 4, 4);
keypad(my_menu_win, TRUE);
/* Set main window and sub window */
set_menu_win(my_menu, my_menu_win);
set_menu_sub(my_menu, derwin(my_menu_win, 6, 68, 3, 1));
set_menu_format(my_menu, 5, 3);
set_menu_mark(my_menu, " * ");
/* Print a border around the main window and print a title */
box(my_menu_win, 0, 0);
attron(COLOR_PAIR(2));
mvprintw(LINES - 3, 0, "Use PageUp and PageDown to scroll");
mvprintw(LINES - 2, 0, "Use Arrow Keys to navigate (F1 to Exit)");
attroff(COLOR_PAIR(2));
refresh();
/* Post the menu */
post_menu(my_menu);
wrefresh(my_menu_win);
while((c = wgetch(my_menu_win)) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case KEY_LEFT:
menu_driver(my_menu, REQ_LEFT_ITEM);
break;
case KEY_RIGHT:
menu_driver(my_menu, REQ_RIGHT_ITEM);
break;
case KEY_NPAGE:
menu_driver(my_menu, REQ_SCR_DPAGE);
break;
case KEY_PPAGE:
menu_driver(my_menu, REQ_SCR_UPAGE);
break;
}
wrefresh(my_menu_win);
}
/* Unpost and free all the memory taken up */
unpost_menu(my_menu);
free_menu(my_menu);
for(i = 0; i &lt; n_choices; ++i)
free_item(my_items[i]);
endwin();
}</span>
</pre>
</div>
<p>Watch the function call to set_menu_format(). It
specifies the number of columns to be 3, thus displaying 3
items per row. We have also switched off the showing
descriptions with the function menu_opts_off(). There are
couple of functions set_menu_opts(), menu_opts_on() and
menu_opts() which can be used to manipulate menu options.
The following menu options can be specified.</p>
<pre class="PROGRAMLISTING">
O_ONEVALUE
Only one item can be selected for this menu.
O_SHOWDESC
Display the item descriptions when the menu is
posted.
O_ROWMAJOR
Display the menu in row-major order.
O_IGNORECASE
Ignore the case when pattern-matching.
O_SHOWMATCH
Move the cursor to within the item name while pat&shy;
tern-matching.
O_NONCYCLIC
Don't wrap around next-item and previous-item,
requests to the other end of the menu.
</pre>
<p>All options are on by default. You can switch specific
attributes on or off with menu_opts_on() and
menu_opts_off() functions. You can also use set_menu_opts()
to directly specify the options. The argument to this
function should be a OR ed value of some of those above
constants. The function menu_opts() can be used to find out
a menu's present options.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MULTIVALUEMENUS" id=
"MULTIVALUEMENUS">17.7. Multi Valued Menus</a></h3>
<p>You might be wondering what if you switch off the option
O_ONEVALUE. Then the menu becomes multi-valued. That means
you can select more than one item. This brings us to the
request REQ_TOGGLE_ITEM. Let's see it in action.</p>
<div class="EXAMPLE">
<a name="MMETO" id="MMETO"></a>
<p><b>Example 22. Multi Valued Menus example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;curses.h&gt;
#include &lt;menu.h&gt;
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Exit",
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
/* Initialize curses */
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i &lt; n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
my_items[n_choices] = (ITEM *)NULL;
my_menu = new_menu((ITEM **)my_items);
/* Make the menu multi valued */
menu_opts_off(my_menu, O_ONEVALUE);
mvprintw(LINES - 3, 0, "Use &lt;SPACE&gt; to select or unselect an item.");
mvprintw(LINES - 2, 0, "&lt;ENTER&gt; to see presently selected items(F1 to Exit)");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case ' ':
menu_driver(my_menu, REQ_TOGGLE_ITEM);
break;
case 10: /* Enter */
{ char temp[200];
ITEM **items;
items = menu_items(my_menu);
temp[0] = '\0';
for(i = 0; i &lt; item_count(my_menu); ++i)
if(item_value(items[i]) == TRUE)
{ strcat(temp, item_name(items[i]));
strcat(temp, " ");
}
move(20, 0);
clrtoeol();
mvprintw(20, 0, temp);
refresh();
}
break;
}
}
free_item(my_items[0]);
free_item(my_items[1]);
free_menu(my_menu);
endwin();
}
</span>
</pre>
</div>
<p>Whew, A lot of new functions. Let's take them one after
another. Firstly, the REQ_TOGGLE_ITEM. In a multi-valued
menu, the user should be allowed to select or un select
more than one item. The request REQ_TOGGLE_ITEM toggles the
present selection. In this case when space is pressed
REQ_TOGGLE_ITEM request is sent to menu_driver to achieve
the result.</p>
<p>Now when the user presses &lt;ENTER&gt; we show the
items he presently selected. First we find out the items
associated with the menu using the function menu_items().
Then we loop through the items to find out if the item is
selected or not. The function item_value() returns TRUE if
an item is selected. The function item_count() returns the
number of items in the menu. The item name can be found
with item_name(). You can also find the description
associated with an item using item_description().</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MENUOPT" id="MENUOPT">17.8. Menu
Options</a></h3>
<p>Well, by this time you must be itching for some
difference in your menu, with lots of functionality. I
know. You want Colors !!!. You want to create nice menus
similar to those text mode <a href=
"http://www.jersey.net/~debinjoe/games/" target="_top">dos
games</a>. The functions set_menu_fore() and
set_menu_back() can be used to change the attribute of the
selected item and unselected item. The names are
misleading. They don't change menu's foreground or
background which would have been useless.</p>
<p>The function set_menu_grey() can be used to set the
display attribute for the non-selectable items in the menu.
This brings us to the interesting option for an item the
one and only O_SELECTABLE. We can turn it off by the
function item_opts_off() and after that that item is not
selectable. It's like a grayed item in those fancy windows
menus. Let's put these concepts in practice with this
example</p>
<div class="EXAMPLE">
<a name="MMEAT" id="MMEAT"></a>
<p><b>Example 23. Menu Options example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;menu.h&gt;
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Exit",
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_MAGENTA, COLOR_BLACK);
/* Initialize items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i &lt; n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
my_items[n_choices] = (ITEM *)NULL;
item_opts_off(my_items[3], O_SELECTABLE);
item_opts_off(my_items[6], O_SELECTABLE);
/* Create menu */
my_menu = new_menu((ITEM **)my_items);
/* Set fore ground and back ground of the menu */
set_menu_fore(my_menu, COLOR_PAIR(1) | A_REVERSE);
set_menu_back(my_menu, COLOR_PAIR(2));
set_menu_grey(my_menu, COLOR_PAIR(3));
/* Post the menu */
mvprintw(LINES - 3, 0, "Press &lt;ENTER&gt; to see the option selected");
mvprintw(LINES - 2, 0, "Up and Down arrow keys to naviage (F1 to Exit)");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case 10: /* Enter */
move(20, 0);
clrtoeol();
mvprintw(20, 0, "Item selected is : %s",
item_name(current_item(my_menu)));
pos_menu_cursor(my_menu);
break;
}
}
unpost_menu(my_menu);
for(i = 0; i &lt; n_choices; ++i)
free_item(my_items[i]);
free_menu(my_menu);
endwin();
}
</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MENUUSERPTR" id=
"MENUUSERPTR">17.9. The useful User Pointer</a></h3>
<p>We can associate a user pointer with each item in the
menu. It works the same way as user pointer in panels. It's
not touched by menu system. You can store any thing you
like in that. I usually use it to store the function to be
executed when the menu option is chosen (It's selected and
may be the user pressed &lt;ENTER&gt;);</p>
<div class="EXAMPLE">
<a name="MMEUS" id="MMEUS"></a>
<p><b>Example 24. Menu User Pointer Usage</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;curses.h&gt;
#include &lt;menu.h&gt;
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Exit",
};
void func(char *name);
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_MAGENTA, COLOR_BLACK);
/* Initialize items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i &lt; n_choices; ++i)
{ my_items[i] = new_item(choices[i], choices[i]);
/* Set the user pointer */
set_item_userptr(my_items[i], func);
}
my_items[n_choices] = (ITEM *)NULL;
/* Create menu */
my_menu = new_menu((ITEM **)my_items);
/* Post the menu */
mvprintw(LINES - 3, 0, "Press &lt;ENTER&gt; to see the option selected");
mvprintw(LINES - 2, 0, "Up and Down arrow keys to naviage (F1 to Exit)");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case 10: /* Enter */
{ ITEM *cur;
void (*p)(char *);
cur = current_item(my_menu);
p = item_userptr(cur);
p((char *)item_name(cur));
pos_menu_cursor(my_menu);
break;
}
break;
}
}
unpost_menu(my_menu);
for(i = 0; i &lt; n_choices; ++i)
free_item(my_items[i]);
free_menu(my_menu);
endwin();
}
void func(char *name)
{ move(20, 0);
clrtoeol();
mvprintw(20, 0, "Item selected is : %s", name);
} </span>
</pre>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="FORMS" id="FORMS">18. Forms
Library</a></h2>
<p>Well. If you have seen those forms on web pages which take
input from users and do various kinds of things, you might be
wondering how would any one create such forms in text mode
display. It's quite difficult to write those nifty forms in
plain ncurses. Forms library tries to provide a basic frame
work to build and maintain forms with ease. It has lot of
features(functions) which manage validation, dynamic
expansion of fields etc.. Let's see it in full flow.</p>
<p>A form is a collection of fields; each field can be either
a label(static text) or a data-entry location. The forms also
library provides functions to divide forms into multiple
pages.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="FORMBASICS" id=
"FORMBASICS">18.1. The Basics</a></h3>
<p>Forms are created in much the same way as menus. First
the fields related to the form are created with
new_field(). You can set options for the fields, so that
they can be displayed with some fancy attributes, validated
before the field looses focus etc.. Then the fields are
attached to form. After this, the form can be posted to
display and is ready to receive inputs. On the similar
lines to menu_driver(), the form is manipulated with
form_driver(). We can send requests to form_driver to move
focus to a certain field, move cursor to end of the field
etc.. After the user enters values in the fields and
validation done, form can be unposted and memory allocated
can be freed.</p>
<p>The general flow of control of a forms program looks
like this.</p>
<ol type="1">
<li>
<p>Initialize curses</p>
</li>
<li>
<p>Create fields using new_field(). You can specify the
height and width of the field, and its position on the
form.</p>
</li>
<li>
<p>Create the forms with new_form() by specifying the
fields to be attached with.</p>
</li>
<li>
<p>Post the form with form_post() and refresh the
screen.</p>
</li>
<li>
<p>Process the user requests with a loop and do
necessary updates to form with form_driver.</p>
</li>
<li>
<p>Unpost the menu with form_unpost()</p>
</li>
<li>
<p>Free the memory allocated to menu by free_form()</p>
</li>
<li>
<p>Free the memory allocated to the items with
free_field()</p>
</li>
<li>
<p>End curses</p>
</li>
</ol>
<p>As you can see, working with forms library is much
similar to handling menu library. The following examples
will explore various aspects of form processing. Let's
start the journey with a simple example. first.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COMPILEFORMS" id=
"COMPILEFORMS">18.2. Compiling With the Forms
Library</a></h3>
<p>To use forms library functions, you have to include
form.h and to link the program with forms library the flag
-lform should be added along with -lncurses in that
order.</p>
<pre class="PROGRAMLISTING">
#include &lt;form.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lform -lncurses
</pre>
<div class="EXAMPLE">
<a name="FFOSI" id="FFOSI"></a>
<p><b>Example 25. Forms Basics</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;form.h&gt;
int main()
{ FIELD *field[3];
FORM *my_form;
int ch;
/* Initialize curses */
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize the fields */
field[0] = new_field(1, 10, 4, 18, 0, 0);
field[1] = new_field(1, 10, 6, 18, 0, 0);
field[2] = NULL;
/* Set field options */
set_field_back(field[0], A_UNDERLINE); /* Print a line for the option */
field_opts_off(field[0], O_AUTOSKIP); /* Don't go to next field when this */
/* Field is filled up */
set_field_back(field[1], A_UNDERLINE);
field_opts_off(field[1], O_AUTOSKIP);
/* Create the form and post it */
my_form = new_form(field);
post_form(my_form);
refresh();
mvprintw(4, 10, "Value 1:");
mvprintw(6, 10, "Value 2:");
refresh();
/* Loop through to get user requests */
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}</span>
</pre>
</div>
<p>Above example is pretty straight forward. It creates two
fields with <tt class="LITERAL">new_field()</tt>.
new_field() takes height, width, starty, startx, number of
offscreen rows and number of additional working buffers.
The fifth argument number of offscreen rows specifies how
much of the field to be shown. If it is zero, the entire
field is always displayed otherwise the form will be
scrollable when the user accesses not displayed parts of
the field. The forms library allocates one buffer per field
to store the data user enters. Using the last parameter to
new_field() we can specify it to allocate some additional
buffers. These can be used for any purpose you like.</p>
<p>After creating the fields, back ground attribute of both
of them is set to an underscore with set_field_back(). The
AUTOSKIP option is turned off using field_opts_off(). If
this option is turned on, focus will move to the next field
in the form once the active field is filled up
completely.</p>
<p>After attaching the fields to the form, it is posted.
Here on, user inputs are processed in the while loop, by
making corresponding requests to form_driver. The details
of all the requests to the form_driver() are explained
later.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PLAYFIELDS" id=
"PLAYFIELDS">18.3. Playing with Fields</a></h3>
<p>Each form field is associated with a lot of attributes.
They can be manipulated to get the required effect and to
have fun !!!. So why wait?</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="FETCHINFO" id=
"FETCHINFO">18.3.1. Fetching Size and Location of
Field</a></h4>
<p>The parameters we have given at the time of creation
of a field can be retrieved with field_info(). It returns
height, width, starty, startx, number of offscreen rows,
and number of additional buffers into the parameters
given to it. It is a sort of inverse of new_field().</p>
<pre class="PROGRAMLISTING">
int field_info( FIELD *field, /* field from which to fetch */
int *height, *int width, /* field size */
int *top, int *left, /* upper left corner */
int *offscreen, /* number of offscreen rows */
int *nbuf); /* number of working buffers */
</pre>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="MOVEFIELD" id=
"MOVEFIELD">18.3.2. Moving the field</a></h4>
<p>The location of the field can be moved to a different
position with move_field().</p>
<pre class="PROGRAMLISTING">
int move_field( FIELD *field, /* field to alter */
int top, int left); /* new upper-left corner */
</pre>
<p>As usual, the changed position can be queried with
field_infor().</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="JUSTIFYFIELD" id=
"JUSTIFYFIELD">18.3.3. Field Justification</a></h4>
<p>The justification to be done for the field can be
fixed using the function set_field_just().</p>
<pre class="PROGRAMLISTING">
int set_field_just(FIELD *field, /* field to alter */
int justmode); /* mode to set */
int field_just(FIELD *field); /* fetch justify mode of field */
</pre>
<p>The justification mode valued accepted and returned by
these functions are NO_JUSTIFICATION, JUSTIFY_RIGHT,
JUSTIFY_LEFT, or JUSTIFY_CENTER.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="FIELDDISPATTRIB" id=
"FIELDDISPATTRIB">18.3.4. Field Display
Attributes</a></h4>
<p>As you have seen, in the above example, display
attribute for the fields can be set with set_field_fore()
and setfield_back(). These functions set foreground and
background attribute of the fields. You can also specify
a pad character which will be filled in the unfilled
portion of the field. The pad character is set with a
call to set_field_pad(). Default pad value is a space.
The functions field_fore(), field_back, field_pad() can
be used to query the present foreground, background
attributes and pad character for the field. The following
list gives the usage of functions.</p>
<pre class="PROGRAMLISTING">
&#13;int set_field_fore(FIELD *field, /* field to alter */
chtype attr); /* attribute to set */
chtype field_fore(FIELD *field); /* field to query */
/* returns foreground attribute */
int set_field_back(FIELD *field, /* field to alter */
chtype attr); /* attribute to set */
chtype field_back(FIELD *field); /* field to query */
/* returns background attribute */
int set_field_pad(FIELD *field, /* field to alter */
int pad); /* pad character to set */
chtype field_pad(FIELD *field); /* field to query */
/* returns present pad character */&#13;
</pre>
<p>Though above functions seem quite simple, using colors
with set_field_fore() may be frustrating in the
beginning. Let me first explain about foreground and
background attributes of a field. The foreground
attribute is associated with the character. That means a
character in the field is printed with the attribute you
have set with set_field_fore(). Background attribute is
the attribute used to fill background of field, whether
any character is there or not. So what about colors?
Since colors are always defined in pairs, what is the
right way to display colored fields? Here's an example
clarifying color attributes.</p>
<div class="EXAMPLE">
<a name="FFOAT" id="FFOAT"></a>
<p><b>Example 26. Form Attributes example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;form.h&gt;
int main()
{ FIELD *field[3];
FORM *my_form;
int ch;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize few color pairs */
init_pair(1, COLOR_WHITE, COLOR_BLUE);
init_pair(2, COLOR_WHITE, COLOR_BLUE);
/* Initialize the fields */
field[0] = new_field(1, 10, 4, 18, 0, 0);
field[1] = new_field(1, 10, 6, 18, 0, 0);
field[2] = NULL;
/* Set field options */
set_field_fore(field[0], COLOR_PAIR(1));/* Put the field with blue background */
set_field_back(field[0], COLOR_PAIR(2));/* and white foreground (characters */
/* are printed in white */
field_opts_off(field[0], O_AUTOSKIP); /* Don't go to next field when this */
/* Field is filled up */
set_field_back(field[1], A_UNDERLINE);
field_opts_off(field[1], O_AUTOSKIP);
/* Create the form and post it */
my_form = new_form(field);
post_form(my_form);
refresh();
set_current_field(my_form, field[0]); /* Set focus to the colored field */
mvprintw(4, 10, "Value 1:");
mvprintw(6, 10, "Value 2:");
mvprintw(LINES - 2, 0, "Use UP, DOWN arrow keys to switch between fields");
refresh();
/* Loop through to get user requests */
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}</span>
</pre>
</div>
<p>Play with the color pairs and try to understand the
foreground and background attributes. In my programs
using color attributes, I usually set only the background
with set_field_back(). Curses simply doesn't allow
defining individual color attributes.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="FIELDOPTIONBITS" id=
"FIELDOPTIONBITS">18.3.5. Field Option Bits</a></h4>
<p>There is also a large collection of field option bits
you can set to control various aspects of forms
processing. You can manipulate them with these
functions:</p>
<pre class="PROGRAMLISTING">
int set_field_opts(FIELD *field, /* field to alter */
int attr); /* attribute to set */
int field_opts_on(FIELD *field, /* field to alter */
int attr); /* attributes to turn on */
int field_opts_off(FIELD *field, /* field to alter */
int attr); /* attributes to turn off */
int field_opts(FIELD *field); /* field to query */
</pre>
<p>The function set_field_opts() can be used to directly
set attributes of a field or you can choose to switch a
few attributes on and off with field_opts_on() and
field_opts_off() selectively. Anytime you can query the
attributes of a field with field_opts(). The following is
the list of available options. By default, all options
are on.</p>
<div class="VARIABLELIST">
<dl>
<dt>O_VISIBLE</dt>
<dd>
<p>Controls whether the field is visible on the
screen. Can be used during form processing to hide
or pop up fields depending on the value of parent
fields.</p>
</dd>
<dt>O_ACTIVE</dt>
<dd>
<p>Controls whether the field is active during
forms processing (i.e. visited by form navigation
keys). Can be used to make labels or derived fields
with buffer values alterable by the forms
application, not the user.</p>
</dd>
<dt>O_PUBLIC</dt>
<dd>
<p>Controls whether data is displayed during field
entry. If this option is turned off on a field, the
library will accept and edit data in that field,
but it will not be displayed and the visible field
cursor will not move. You can turn off the O_PUBLIC
bit to define password fields.</p>
</dd>
<dt>O_EDIT</dt>
<dd>
<p>Controls whether the field's data can be
modified. When this option is off, all editing
requests except <tt class=
"LITERAL">REQ_PREV_CHOICE</tt> and <tt class=
"LITERAL">REQ_NEXT_CHOICE</tt>will fail. Such
read-only fields may be useful for help
messages.</p>
</dd>
<dt>O_WRAP</dt>
<dd>
<p>Controls word-wrapping in multi-line fields.
Normally, when any character of a (blank-separated)
word reaches the end of the current line, the
entire word is wrapped to the next line (assuming
there is one). When this option is off, the word
will be split across the line break.</p>
</dd>
<dt>O_BLANK</dt>
<dd>
<p>Controls field blanking. When this option is on,
entering a character at the first field position
erases the entire field (except for the
just-entered character).</p>
</dd>
<dt>O_AUTOSKIP</dt>
<dd>
<p>Controls automatic skip to next field when this
one fills. Normally, when the forms user tries to
type more data into a field than will fit, the
editing location jumps to next field. When this
option is off, the user's cursor will hang at the
end of the field. This option is ignored in dynamic
fields that have not reached their size limit.</p>
</dd>
<dt>O_NULLOK</dt>
<dd>
<p>Controls whether validation is applied to blank
fields. Normally, it is not; the user can leave a
field blank without invoking the usual validation
check on exit. If this option is off on a field,
exit from it will invoke a validation check.</p>
</dd>
<dt>O_PASSOK</dt>
<dd>
<p>Controls whether validation occurs on every
exit, or only after the field is modified. Normally
the latter is true. Setting O_PASSOK may be useful
if your field's validation function may change
during forms processing.</p>
</dd>
<dt>O_STATIC</dt>
<dd>
<p>Controls whether the field is fixed to its
initial dimensions. If you turn this off, the field
becomes dynamic and will stretch to fit entered
data.</p>
</dd>
</dl>
</div>
<p>A field's options cannot be changed while the field is
currently selected. However, options may be changed on
posted fields that are not current.</p>
<p>The option values are bit-masks and can be composed
with logical-or in the obvious way. You have seen the
usage of switching off O_AUTOSKIP option. The following
example clarifies usage of some more options. Other
options are explained where appropriate.</p>
<div class="EXAMPLE">
<a name="FFOOP" id="FFOOP"></a>
<p><b>Example 27. Field Options Usage example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;form.h&gt;
#define STARTX 15
#define STARTY 4
#define WIDTH 25
#define N_FIELDS 3
int main()
{ FIELD *field[N_FIELDS];
FORM *my_form;
int ch, i;
/* Initialize curses */
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize the fields */
for(i = 0; i &lt; N_FIELDS - 1; ++i)
field[i] = new_field(1, WIDTH, STARTY + i * 2, STARTX, 0, 0);
field[N_FIELDS - 1] = NULL;
/* Set field options */
set_field_back(field[1], A_UNDERLINE); /* Print a line for the option */
field_opts_off(field[0], O_ACTIVE); /* This field is a static label */
field_opts_off(field[1], O_PUBLIC); /* This filed is like a password field*/
field_opts_off(field[1], O_AUTOSKIP); /* To avoid entering the same field */
/* after last character is entered */
/* Create the form and post it */
my_form = new_form(field);
post_form(my_form);
refresh();
set_field_just(field[0], JUSTIFY_CENTER); /* Center Justification */
set_field_buffer(field[0], 0, "This is a static Field");
/* Initialize the field */
mvprintw(STARTY, STARTX - 10, "Field 1:");
mvprintw(STARTY + 2, STARTX - 10, "Field 2:");
refresh();
/* Loop through to get user requests */
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}</span>
</pre>
</div>
<p>This example, though useless, shows the usage of
options. If used properly, they can present information
very effectively in a form. The second field being not
O_PUBLIC, does not show the characters you are
typing.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="FIELDSTATUS" id=
"FIELDSTATUS">18.3.6. Field Status</a></h4>
<p>The field status specifies whether the field has got
edited or not. It is initially set to FALSE and when user
enters something and the data buffer gets modified it
becomes TRUE. So a field's status can be queried to find
out whether it has been modified or not. The following
functions can assist in those operations.</p>
<pre class="PROGRAMLISTING">
int set_field_status(FIELD *field, /* field to alter */
int status); /* status to set */
int field_status(FIELD *field); /* fetch status of field */
</pre>
<p>It's better to check the field's status only after
after leaving the field, as data buffer might not have
been updated yet as the validation is still due. To
guarantee that right status is returned, call
field_status() either (1) in the field's exit validation
check routine, (2) from the field's or form's
initialization or termination hooks, or (3) just after a
REQ_VALIDATION request has been processed by the forms
driver</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="FIELDUSERPTR" id=
"FIELDUSERPTR">18.3.7. Field User Pointer</a></h4>
<p>Every field structure contains one pointer that can be
used by the user for various purposes. It is not touched
by forms library and can be used for any purpose by the
user. The following functions set and fetch user
pointer.</p>
<pre class="PROGRAMLISTING">
int set_field_userptr(FIELD *field,
char *userptr); /* the user pointer you wish to associate */
/* with the field */
char *field_userptr(FIELD *field); /* fetch user pointer of the field */
</pre>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="VARIABLESIZEFIELDS" id=
"VARIABLESIZEFIELDS">18.3.8. Variable-Sized
Fields</a></h4>
<p>If you want a dynamically changing field with variable
width, this is the feature you want to put to full use.
This will allow the user to enter more data than the
original size of the field and let the field grow.
According to the field orientation it will scroll
horizontally or vertically to incorporate the new
data.</p>
<p>To make a field dynamically growable, the option
O_STATIC should be turned off. This can be done with
a</p>
<pre class="PROGRAMLISTING">
field_opts_off(field_pointer, O_STATIC);
</pre>
<p>But it's usually not advisable to allow a field to
grow infinitely. You can set a maximum limit to the
growth of the field with</p>
<pre class="PROGRAMLISTING">
int set_max_field(FIELD *field, /* Field on which to operate */
int max_growth); /* maximum growth allowed for the field */
</pre>
<p>The field info for a dynamically growable field can be
retrieved by</p>
<pre class="PROGRAMLISTING">
int dynamic_field_info( FIELD *field, /* Field on which to operate */
int *prows, /* number of rows will be filled in this */
int *pcols, /* number of columns will be filled in this*/
int *pmax) /* maximum allowable growth will be filled */
/* in this */
</pre>Though field_info work as usual, it is advisable to use this
function to get the proper attributes of a dynamically growable
field.
<p>Recall the library routine new_field; a new field
created with height set to one will be defined to be a
one line field. A new field created with height greater
than one will be defined to be a multi line field.</p>
<p>A one line field with O_STATIC turned off (dynamically
growable field) will contain a single fixed row, but the
number of columns can increase if the user enters more
data than the initial field will hold. The number of
columns displayed will remain fixed and the additional
data will scroll horizontally.</p>
<p>A multi line field with O_STATIC turned off
(dynamically growable field) will contain a fixed number
of columns, but the number of rows can increase if the
user enters more data than the initial field will hold.
The number of rows displayed will remain fixed and the
additional data will scroll vertically.</p>
<p>The above two paragraphs pretty much describe a
dynamically growable field's behavior. The way other
parts of forms library behaves is described below:</p>
<ol type="1">
<li>
<p>The field option O_AUTOSKIP will be ignored if the
option O_STATIC is off and there is no maximum growth
specified for the field. Currently, O_AUTOSKIP
generates an automatic REQ_NEXT_FIELD form driver
request when the user types in the last character
position of a field. On a growable field with no
maximum growth specified, there is no last character
position. If a maximum growth is specified, the
O_AUTOSKIP option will work as normal if the field
has grown to its maximum size.</p>
</li>
<li>
<p>The field justification will be ignored if the
option O_STATIC is off. Currently, set_field_just can
be used to JUSTIFY_LEFT, JUSTIFY_RIGHT,
JUSTIFY_CENTER the contents of a one line field. A
growable one line field will, by definition, grow and
scroll horizontally and may contain more data than
can be justified. The return from field_just will be
unchanged.</p>
</li>
<li>
<p>The overloaded form driver request REQ_NEW_LINE
will operate the same way regardless of the
O_NL_OVERLOAD form option if the field option
O_STATIC is off and there is no maximum growth
specified for the field. Currently, if the form
option O_NL_OVERLOAD is on, REQ_NEW_LINE implicitly
generates a REQ_NEXT_FIELD if called from the last
line of a field. If a field can grow without bound,
there is no last line, so REQ_NEW_LINE will never
implicitly generate a REQ_NEXT_FIELD. If a maximum
growth limit is specified and the O_NL_OVERLOAD form
option is on, REQ_NEW_LINE will only implicitly
generate REQ_NEXT_FIELD if the field has grown to its
maximum size and the user is on the last line.</p>
</li>
<li>
<p>The library call dup_field will work as usual; it
will duplicate the field, including the current
buffer size and contents of the field being
duplicated. Any specified maximum growth will also be
duplicated.</p>
</li>
<li>
<p>The library call link_field will work as usual; it
will duplicate all field attributes and share buffers
with the field being linked. If the O_STATIC field
option is subsequently changed by a field sharing
buffers, how the system reacts to an attempt to enter
more data into the field than the buffer will
currently hold will depend on the setting of the
option in the current field.</p>
</li>
<li>
<p>The library call field_info will work as usual;
the variable nrow will contain the value of the
original call to new_field. The user should use
dynamic_field_info, described above, to query the
current size of the buffer.</p>
</li>
</ol>
<p>Some of the above points make sense only after
explaining form driver. We will be looking into that in
next few sections.</p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="FORMWINDOWS" id=
"FORMWINDOWS">18.4. Form Windows</a></h3>
<p>The form windows concept is pretty much similar to menu
windows. Every form is associated with a main window and a
sub window. The form main window displays any title or
border associated or whatever the user wishes. Then the sub
window contains all the fields and displays them according
to their position. This gives the flexibility of
manipulating fancy form displaying very easily.</p>
<p>Since this is pretty much similar to menu windows, I am
providing an example with out much explanation. The
functions are similar and they work the same way.</p>
<div class="EXAMPLE">
<a name="FFOWI" id="FFOWI"></a>
<p><b>Example 28. Form Windows Example</b></p>
<pre class="PROGRAMLISTING">
<span class="INLINEMEDIAOBJECT">#include &lt;form.h&gt;
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{
FIELD *field[3];
FORM *my_form;
WINDOW *my_form_win;
int ch, rows, cols;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize few color pairs */
init_pair(1, COLOR_RED, COLOR_BLACK);
/* Initialize the fields */
field[0] = new_field(1, 10, 6, 1, 0, 0);
field[1] = new_field(1, 10, 8, 1, 0, 0);
field[2] = NULL;
/* Set field options */
set_field_back(field[0], A_UNDERLINE);
field_opts_off(field[0], O_AUTOSKIP); /* Don't go to next field when this */
/* Field is filled up */
set_field_back(field[1], A_UNDERLINE);
field_opts_off(field[1], O_AUTOSKIP);
/* Create the form and post it */
my_form = new_form(field);
/* Calculate the area required for the form */
scale_form(my_form, &amp;rows, &amp;cols);
/* Create the window to be associated with the form */
my_form_win = newwin(rows + 4, cols + 4, 4, 4);
keypad(my_form_win, TRUE);
/* Set main window and sub window */
set_form_win(my_form, my_form_win);
set_form_sub(my_form, derwin(my_form_win, rows, cols, 2, 2));
/* Print a border around the main window and print a title */
box(my_form_win, 0, 0);
print_in_middle(my_form_win, 1, 0, cols + 4, "My Form", COLOR_PAIR(1));
post_form(my_form);
wrefresh(my_form_win);
mvprintw(LINES - 2, 0, "Use UP, DOWN arrow keys to switch between fields");
refresh();
/* Loop through to get user requests */
while((ch = wgetch(my_form_win)) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span>
</pre>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="FILEDVALIDATE" id=
"FILEDVALIDATE">18.5. Field Validation</a></h3>
<p>By default, a field will accept any data input by the
user. It is possible to attach validation to the field.
Then any attempt by the user to leave the field, while it
contains data that doesn't match the validation type will
fail. Some validation types also have a character-validity
check for each time a character is entered in the
field.</p>
<p>Validation can be attached to a field with the following
function.</p>
<pre class="PROGRAMLISTING">
int set_field_type(FIELD *field, /* field to alter */
FIELDTYPE *ftype, /* type to associate */
...); /* additional arguments*/
</pre>Once set, the validation type for a field can be queried with
<pre class="PROGRAMLISTING">
FIELDTYPE *field_type(FIELD *field); /* field to query */
</pre>
<p>The form driver validates the data in a field only when
data is entered by the end-user. Validation does not occur
when</p>
<ul>
<li>
<p>the application program changes the field value by
calling set_field_buffer.</p>
</li>
<li>
<p>linked field values are changed indirectly -- by
changing the field to which they are linked</p>
</li>
</ul>
<p>The following are the pre-defined validation types. You
can also specify custom validation, though it's a bit
tricky and cumbersome.</p>
<h1 class="BRIDGEHEAD"><a name="AEN1069" id=
"AEN1069"></a>TYPE_ALPHA</h1>
<p>This field type accepts alphabetic data; no blanks, no
digits, no special characters (this is checked at
character-entry time). It is set up with:</p>
<pre class="PROGRAMLISTING">
int set_field_type(FIELD *field, /* field to alter */
TYPE_ALPHA, /* type to associate */
int width); /* minimum width of field */
</pre>
<p>The width argument sets a minimum width of data. The
user has to enter at-least width number of characters
before he can leave the field. Typically you'll want to set
this to the field width; if it's greater than the field
width, the validation check will always fail. A minimum
width of zero makes field completion optional.</p>
<h1 class="BRIDGEHEAD"><a name="AEN1073" id=
"AEN1073"></a>TYPE_ALNUM</h1>
<p>This field type accepts alphabetic data and digits; no
blanks, no special characters (this is checked at
character-entry time). It is set up with:</p>
<pre class="PROGRAMLISTING">
int set_field_type(FIELD *field, /* field to alter */
TYPE_ALNUM, /* type to associate */
int width); /* minimum width of field */
</pre>
<p>The width argument sets a minimum width of data. As with
TYPE_ALPHA, typically you'll want to set this to the field
width; if it's greater than the field width, the validation
check will always fail. A minimum width of zero makes field
completion optional.</p>
<h1 class="BRIDGEHEAD"><a name="AEN1077" id=
"AEN1077"></a>TYPE_ENUM</h1>
<p>This type allows you to restrict a field's values to be
among a specified set of string values (for example, the
two-letter postal codes for U.S. states). It is set up
with:</p>
<pre class="PROGRAMLISTING">
int set_field_type(FIELD *field, /* field to alter */
TYPE_ENUM, /* type to associate */
char **valuelist; /* list of possible values */
int checkcase; /* case-sensitive? */
int checkunique); /* must specify uniquely? */
</pre>
<p>The valuelist parameter must point at a NULL-terminated
list of valid strings. The checkcase argument, if true,
makes comparison with the string case-sensitive.</p>
<p>When the user exits a TYPE_ENUM field, the validation
procedure tries to complete the data in the buffer to a
valid entry. If a complete choice string has been entered,
it is of course valid. But it is also possible to enter a
prefix of a valid string and have it completed for you.</p>
<p>By default, if you enter such a prefix and it matches
more than one value in the string list, the prefix will be
completed to the first matching value. But the checkunique
argument, if true, requires prefix matches to be unique in
order to be valid.</p>
<p>The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests
can be particularly useful with these fields.</p>
<h1 class="BRIDGEHEAD"><a name="AEN1084" id=
"AEN1084"></a>TYPE_INTEGER</h1>
<p>This field type accepts an integer. It is set up as
follows:</p>
<pre class="PROGRAMLISTING">
int set_field_type(FIELD *field, /* field to alter */
TYPE_INTEGER, /* type to associate */
int padding, /* # places to zero-pad to */
int vmin, int vmax); /* valid range */
</pre>
<p>Valid characters consist of an optional leading minus
and digits. The range check is performed on exit. If the
range maximum is less than or equal to the minimum, the
range is ignored.</p>
<p>If the value passes its range check, it is padded with
as many leading zero digits as necessary to meet the
padding argument.</p>
<p>A TYPE_INTEGER value buffer can conveniently be
interpreted with the C library function atoi(3).</p>
<h1 class="BRIDGEHEAD"><a name="AEN1090" id=
"AEN1090"></a>TYPE_NUMERIC</h1>
<p>This field type accepts a decimal number. It is set up
as follows:</p>
<pre class="PROGRAMLISTING">
int set_field_type(FIELD *field, /* field to alter */
TYPE_NUMERIC, /* type to associate */
int padding, /* # places of precision */
int vmin, int vmax); /* valid range */
</pre>
<p>Valid characters consist of an optional leading minus
and digits. possibly including a decimal point. The range
check is performed on exit. If the range maximum is less
than or equal to the minimum, the range is ignored.</p>
<p>If the value passes its range check, it is padded with
as many trailing zero digits as necessary to meet the
padding argument.</p>
<p>A TYPE_NUMERIC value buffer can conveniently be
interpreted with the C library function atof(3).</p>
<h1 class="BRIDGEHEAD"><a name="AEN1096" id=
"AEN1096"></a>TYPE_REGEXP</h1>
<p>This field type accepts data matching a regular
expression. It is set up as follows:</p>
<pre class="PROGRAMLISTING">
int set_field_type(FIELD *field, /* field to alter */
TYPE_REGEXP, /* type to associate */
char *regexp); /* expression to match */
</pre>
<p>The syntax for regular expressions is that of
regcomp(3). The check for regular-expression match is
performed on exit.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="FORMDRIVER" id=
"FORMDRIVER">18.6. Form Driver: The work horse of the forms
system</a></h3>
<p>As in the menu system, form_driver() plays a very
important role in forms system. All types of requests to
forms system should be funneled through form_driver().</p>
<pre class="PROGRAMLISTING">
int form_driver(FORM *form, /* form on which to operate */
int request) /* form request code */
</pre>
<p>As you have seen some of the examples above, you have to
be in a loop looking for user input and then decide whether
it's a field data or a form request. The form requests are
then passed to form_driver() to do the work.</p>
<p>The requests roughly can be divided into following
categories. Different requests and their usage is explained
below:</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="PAGENAVREQ" id=
"PAGENAVREQ">18.6.1. Page Navigation Requests</a></h4>
<p>These requests cause page-level moves through the
form, triggering display of a new form screen. A form can
be made of multiple pages. If you have a big form with
lot of fields and logical sections, then you can divide
the form into pages. The function set_new_page() to set a
new page at the field specified.</p>
<pre class="PROGRAMLISTING">
int set_new_page(FIELD *field,/* Field at which page break to be set or unset */
bool new_page_flag); /* should be TRUE to put a break */
</pre>
<p>The following requests allow you to move to different
pages</p>
<ul>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_NEXT_PAGE</i></span> Move to the next
form page.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_PREV_PAGE</i></span> Move to the
previous form page.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_FIRST_PAGE</i></span> Move to the
first form page.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_LAST_PAGE</i></span> Move to the last
form page.</p>
</li>
</ul>
<p>These requests treat the list as cyclic; that is,
REQ_NEXT_PAGE from the last page goes to the first, and
REQ_PREV_PAGE from the first page goes to the last.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="INTERFIELDNAVREQ" id=
"INTERFIELDNAVREQ">18.6.2. Inter-Field Navigation
Requests</a></h4>
<p>These requests handle navigation between fields on the
same page.</p>
<ul>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_NEXT_FIELD</i></span> Move to next
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_PREV_FIELD</i></span> Move to previous
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_FIRST_FIELD</i></span> Move to the
first field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_LAST_FIELD</i></span> Move to the last
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SNEXT_FIELD</i></span> Move to sorted
next field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SPREV_FIELD</i></span> Move to sorted
previous field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SFIRST_FIELD</i></span> Move to the
sorted first field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SLAST_FIELD</i></span> Move to the
sorted last field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_LEFT_FIELD</i></span> Move left to
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_RIGHT_FIELD</i></span> Move right to
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_UP_FIELD</i></span> Move up to
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_DOWN_FIELD</i></span> Move down to
field.</p>
</li>
</ul>
<p>These requests treat the list of fields on a page as
cyclic; that is, REQ_NEXT_FIELD from the last field goes
to the first, and REQ_PREV_FIELD from the first field
goes to the last. The order of the fields for these (and
the REQ_FIRST_FIELD and REQ_LAST_FIELD requests) is
simply the order of the field pointers in the form array
(as set up by new_form() or set_form_fields()</p>
<p>It is also possible to traverse the fields as if they
had been sorted in screen-position order, so the sequence
goes left-to-right and top-to-bottom. To do this, use the
second group of four sorted-movement requests.</p>
<p>Finally, it is possible to move between fields using
visual directions up, down, right, and left. To
accomplish this, use the third group of four requests.
Note, however, that the position of a form for purposes
of these requests is its upper-left corner.</p>
<p>For example, suppose you have a multi-line field B,
and two single-line fields A and C on the same line with
B, with A to the left of B and C to the right of B. A
REQ_MOVE_RIGHT from A will go to B only if A, B, and C
all share the same first line; otherwise it will skip
over B to C.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="INTRAFIELDNAVREQ" id=
"INTRAFIELDNAVREQ">18.6.3. Intra-Field Navigation
Requests</a></h4>
<p>These requests drive movement of the edit cursor
within the currently selected field.</p>
<ul>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_NEXT_CHAR</i></span> Move to next
character.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_PREV_CHAR</i></span> Move to previous
character.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_NEXT_LINE</i></span> Move to next
line.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_PREV_LINE</i></span> Move to previous
line.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_NEXT_WORD</i></span> Move to next
word.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_PREV_WORD</i></span> Move to previous
word.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_BEG_FIELD</i></span> Move to beginning
of field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_END_FIELD</i></span> Move to end of
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_BEG_LINE</i></span> Move to beginning
of line.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_END_LINE</i></span> Move to end of
line.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_LEFT_CHAR</i></span> Move left in
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_RIGHT_CHAR</i></span> Move right in
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_UP_CHAR</i></span> Move up in
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_DOWN_CHAR</i></span> Move down in
field.</p>
</li>
</ul>
<p>Each word is separated from the previous and next
characters by whitespace. The commands to move to
beginning and end of line or field look for the first or
last non-pad character in their ranges.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="SCROLLREQ" id=
"SCROLLREQ">18.6.4. Scrolling Requests</a></h4>
<p>Fields that are dynamic and have grown and fields
explicitly created with offscreen rows are scrollable.
One-line fields scroll horizontally; multi-line fields
scroll vertically. Most scrolling is triggered by editing
and intra-field movement (the library scrolls the field
to keep the cursor visible). It is possible to explicitly
request scrolling with the following requests:</p>
<ul>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_FLINE</i></span> Scroll vertically
forward a line.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_BLINE</i></span> Scroll vertically
backward a line.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_FPAGE</i></span> Scroll vertically
forward a page.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_BPAGE</i></span> Scroll vertically
backward a page.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_FHPAGE</i></span> Scroll
vertically forward half a page.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_BHPAGE</i></span> Scroll
vertically backward half a page.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_FCHAR</i></span> Scroll
horizontally forward a character.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_BCHAR</i></span> Scroll
horizontally backward a character.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_HFLINE</i></span> Scroll
horizontally one field width forward.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_HBLINE</i></span> Scroll
horizontally one field width backward.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_HFHALF</i></span> Scroll
horizontally one half field width forward.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_SCR_HBHALF</i></span> Scroll
horizontally one half field width backward.</p>
</li>
</ul>
<p>For scrolling purposes, a page of a field is the
height of its visible part.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="EDITREQ" id="EDITREQ">18.6.5.
Editing Requests</a></h4>
<p>When you pass the forms driver an ASCII character, it
is treated as a request to add the character to the
field's data buffer. Whether this is an insertion or a
replacement depends on the field's edit mode (insertion
is the default.</p>
<p>The following requests support editing the field and
changing the edit mode:</p>
<ul>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_INS_MODE</i></span> Set insertion
mode.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_OVL_MODE</i></span> Set overlay
mode.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_NEW_LINE</i></span> New line request
(see below for explanation).</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_INS_CHAR</i></span> Insert space at
character location.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_INS_LINE</i></span> Insert blank line
at character location.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_DEL_CHAR</i></span> Delete character
at cursor.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_DEL_PREV</i></span> Delete previous
word at cursor.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_DEL_LINE</i></span> Delete line at
cursor.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_DEL_WORD</i></span> Delete word at
cursor.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_CLR_EOL</i></span> Clear to end of
line.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_CLR_EOF</i></span> Clear to end of
field.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_CLR_FIELD</i></span> Clear entire
field.</p>
</li>
</ul>
<p>The behavior of the REQ_NEW_LINE and REQ_DEL_PREV
requests is complicated and partly controlled by a pair
of forms options. The special cases are triggered when
the cursor is at the beginning of a field, or on the last
line of the field.</p>
<p>First, we consider REQ_NEW_LINE:</p>
<p>The normal behavior of REQ_NEW_LINE in insert mode is
to break the current line at the position of the edit
cursor, inserting the portion of the current line after
the cursor as a new line following the current and moving
the cursor to the beginning of that new line (you may
think of this as inserting a newline in the field
buffer).</p>
<p>The normal behavior of REQ_NEW_LINE in overlay mode is
to clear the current line from the position of the edit
cursor to end of line. The cursor is then moved to the
beginning of the next line.</p>
<p>However, REQ_NEW_LINE at the beginning of a field, or
on the last line of a field, instead does a
REQ_NEXT_FIELD. O_NL_OVERLOAD option is off, this special
action is disabled.</p>
<p>Now, let us consider REQ_DEL_PREV:</p>
<p>The normal behavior of REQ_DEL_PREV is to delete the
previous character. If insert mode is on, and the cursor
is at the start of a line, and the text on that line will
fit on the previous one, it instead appends the contents
of the current line to the previous one and deletes the
current line (you may think of this as deleting a newline
from the field buffer).</p>
<p>However, REQ_DEL_PREV at the beginning of a field is
instead treated as a REQ_PREV_FIELD.</p>
<p>If the O_BS_OVERLOAD option is off, this special
action is disabled and the forms driver just returns
E_REQUEST_DENIED.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="ORDERREQ" id=
"ORDERREQ">18.6.6. Order Requests</a></h4>
<p>If the type of your field is ordered, and has
associated functions for getting the next and previous
values of the type from a given value, there are requests
that can fetch that value into the field buffer:</p>
<ul>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_NEXT_CHOICE</i></span> Place the
successor value of the current value in the
buffer.</p>
</li>
<li>
<p><span class="emphasis"><i class=
"EMPHASIS">REQ_PREV_CHOICE</i></span> Place the
predecessor value of the current value in the
buffer.</p>
</li>
</ul>
<p>Of the built-in field types, only TYPE_ENUM has
built-in successor and predecessor functions. When you
define a field type of your own (see Custom Validation
Types), you can associate our own ordering functions.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="APPLICCOMMANDS" id=
"APPLICCOMMANDS">18.6.7. Application Commands</a></h4>
<p>Form requests are represented as integers above the
curses value greater than KEY_MAX and less than or equal
to the constant MAX_COMMAND. A value within this range
gets ignored by form_driver(). So this can be used for
any purpose by the application. It can be treated as an
application specific action and take corresponding
action.</p>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="TOOLS" id="TOOLS">19. Tools and
Widget Libraries</a></h2>
<p>Now that you have seen the capabilities of ncurses and its
sister libraries, you are rolling your sleeves up and gearing
for a project that heavily manipulates screen. But wait.. It
can be pretty difficult to write and maintain complex GUI
widgets in plain ncurses or even with the additional
libraries. There are some ready-to-use tools and widget
libraries that can be used instead of writing your own
widgets. You can use some of them, get ideas from the code,
or even extend them.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CDK" id="CDK">19.1. CDK (Curses
Development Kit)</a></h3>
<p>In the author's words</p>
<p><span class="emphasis"><i class="EMPHASIS">CDK stands
for 'Curses Development Kit' and it currently contains 21
ready to use widgets which facilitate the speedy
development of full screen curses programs.</i></span></p>
<p>The kit provides some useful widgets, which can be used
in your programs directly. It's pretty well written and the
documentation is very good. The examples in the examples
directory can be a good place to start for beginners. The
CDK can be downloaded from <a href=
"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>
<pre class="PROGRAMLISTING">
Widget Type Quick Description
===========================================================================
Alphalist Allows a user to select from a list of words, with
the ability to narrow the search list by typing in a
few characters of the desired word.
Buttonbox This creates a multiple button widget.
Calendar Creates a little simple calendar widget.
Dialog Prompts the user with a message, and the user
can pick an answer from the buttons provided.
Entry Allows the user to enter various types of information.
File Selector A file selector built from Cdk base widgets. This
example shows how to create more complicated widgets
using the Cdk widget library.
Graph Draws a graph.
Histogram Draws a histogram.
Item List Creates a pop up field which allows the user to select
one of several choices in a small field. Very useful
for things like days of the week or month names.
Label Displays messages in a pop up box, or the label can be
considered part of the screen.
Marquee Displays a message in a scrolling marquee.
Matrix Creates a complex matrix with lots of options.
Menu Creates a pull-down menu interface.
Multiple Line Entry A multiple line entry field. Very useful
for long fields. (like a description
field)
Radio List Creates a radio button list.
Scale Creates a numeric scale. Used for allowing a user to
pick a numeric value and restrict them to a range of
values.
Scrolling List Creates a scrolling list/menu list.
Scrolling Window Creates a scrolling log file viewer. Can add
information into the window while its running.
A good widget for displaying the progress of
something. (akin to a console window)
Selection List Creates a multiple option selection list.
Slider Akin to the scale widget, this widget provides a
visual slide bar to represent the numeric value.
Template Creates a entry field with character sensitive
positions. Used for pre-formatted fields like
dates and phone numbers.
Viewer This is a file/information viewer. Very useful
when you need to display loads of information.
===========================================================================
</pre>
<p>A few of the widgets are modified by Thomas Dickey in
recent versions.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="CDKATTRACT" id=
"CDKATTRACT">19.1.2. Some Attractive Features</a></h4>
<p>Apart from making our life easier with readily usable
widgets, cdk solves one frustrating problem with printing
multi colored strings, justified strings elegantly.
Special formatting tags can be embedded in the strings
which are passed to CDK functions. For Example</p>
<p>If the string</p>
<pre class="PROGRAMLISTING">
"&lt;/B/1&gt;This line should have a yellow foreground and a blue
background.&lt;!1&gt;"
</pre>
<p>given as a parameter to newCDKLabel(), it prints the
line with yellow foreground and blue background. There
are other tags available for justifying string, embedding
special drawing characters etc.. Please refer to the man
page cdk_display(3X) for details. The man page explains
the usage with nice examples.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="CDKCONCLUSION" id=
"CDKCONCLUSION">19.1.3. Conclusion</a></h4>
<p>All in all, CDK is a well-written package of widgets,
which if used properly can form a strong frame work for
developing complex GUI.</p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="DIALOG" id="DIALOG">19.2. The
dialog</a></h3>
<p>Long long ago, in September 1994, when few people knew
linux, Jeff Tranter wrote an <a href=
"http://www2.linuxjournal.com/lj-issues/issue5/2807.html"
target="_top">article</a> on dialog in Linux Journal. He
starts the article with these words..</p>
<p><span class="emphasis"><i class="EMPHASIS">Linux is
based on the Unix operating system, but also features a
number of unique and useful kernel features and application
programs that often go beyond what is available under Unix.
One little-known gem is "dialog", a utility for creating
professional-looking dialog boxes from within shell
scripts. This article presents a tutorial introduction to
the dialog utility, and shows examples of how and where it
can be used</i></span></p>
<p>As he explains, dialog is a real gem in making
professional-looking dialog boxes with ease. It creates a
variety of dialog boxes, menus, check lists etc.. It is
usually installed by default. If not, you can download it
from <a href="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
<tt class="LITERAL">perl</tt> directory.</p>
<p>For more information see man pages Curses(3) ,
Curses::Form(3) and Curses::Widgets(3). These pages are
installed only when the above modules are acquired and
installed.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="JUSTFORFUN" id="JUSTFORFUN">20.
Just For Fun !!!</a></h2>
<p>This section contains few programs written by me just for
fun. They don't signify a better programming practice or the
best way of using ncurses. They are provided here so as to
allow beginners to get ideas and add more programs to this
section. If you have written a couple of nice, simple
programs in curses and want them to included here, contact
<a href="mailto:ppadala@gmail.com" target="_top">me</a>.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GAMEOFLIFE" id=
"GAMEOFLIFE">20.1. The Game of Life</a></h3>
<p>Game of life is a wonder of math. In <a href=
"http://www.math.com/students/wonders/life/life.html"
target="_top">Paul Callahan</a>'s words</p>
<pre class="PROGRAMLISTING">
<span class="emphasis"><i class=
"EMPHASIS">The Game of Life (or simply Life) is not a game in the conventional sense. There
are no players, and no winning or losing. Once the "pieces" are placed in the
starting position, the rules determine everything that happens later.
Nevertheless, Life is full of surprises! In most cases, it is impossible to look
at a starting position (or pattern) and see what will happen in the future. The
only way to find out is to follow the rules of the game.</i></span>
</pre>
<p>This program starts with a simple inverted U pattern and
shows how wonderful life works. There is a lot of room for
improvement in the program. You can let the user enter
pattern of his choice or even take input from a file. You
can also change rules and play with a lot of variations.
Search on <a href="http://www.google.com" target=
"_top">google</a> for interesting information on game of
life.</p>
<p><span class="emphasis"><i class="EMPHASIS">File Path:
JustForFun/life.c</i></span></p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MAGIC" id="MAGIC">20.2. Magic
Square</a></h3>
<p>Magic Square, another wonder of math, is very simple to
understand but very difficult to make. In a magic square
sum of the numbers in each row, each column is equal. Even
diagnol sum can be equal. There are many variations which
have special properties.</p>
<p>This program creates a simple magic square of odd
order.</p>
<p><span class="emphasis"><i class="EMPHASIS">File Path:
JustForFun/magic.c</i></span></p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="HANOI" id="HANOI">20.3. Towers
of Hanoi</a></h3>
<p>The famous towers of hanoi solver. The aim of the game
is to move the disks on the first peg to last peg, using
middle peg as a temporary stay. The catch is not to place a
larger disk over a small disk at any time.</p>
<p><span class="emphasis"><i class="EMPHASIS">File Path:
JustForFun/hanoi.c</i></span></p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="QUEENS" id="QUEENS">20.4. Queens
Puzzle</a></h3>
<p>The objective of the famous N-Queen puzzle is to put N
queens on a N X N chess board without attacking each
other.</p>
<p>This program solves it with a simple backtracking
technique.</p>
<p><span class="emphasis"><i class="EMPHASIS">File Path:
JustForFun/queens.c</i></span></p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SHUFFLE" id="SHUFFLE">20.5.
Shuffle</a></h3>
<p>A fun game, if you have time to kill.</p>
<p><span class="emphasis"><i class="EMPHASIS">File Path:
JustForFun/shuffle.c</i></span></p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="TT" id="TT">20.6. Typing
Tutor</a></h3>
<p>A simple typing tutor, I created more out of need than
for ease of use. If you know how to put your fingers
correctly on the keyboard, but lack practice, this can be
helpful.</p>
<p><span class="emphasis"><i class="EMPHASIS">File Path:
JustForFun/tt.c</i></span></p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="REF" id="REF">21.
References</a></h2>
<ul>
<li>
<p>NCURSES man pages</p>
</li>
<li>
<p>NCURSES FAQ at <a href=
"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>
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