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<div class="TITLEPAGE">
<h1 class="TITLE"><a name="AEN2" id="AEN2">NCURSES Programming
HOWTO</a></h1>
<h3 class="AUTHOR"><a name="AEN4" id="AEN4">Pradeep Padala</a></h3>
<div class="AFFILIATION">
<div class="ADDRESS">
<p class="ADDRESS"><code class="EMAIL">&lt;<a href=
"mailto:ppadala@gmail.com">ppadala@gmail.com</a>&gt;</code></p>
</div>
</div>
<p class="PUBDATE">v1.9, 2005-06-20<br></p>
<div class="REVHISTORY">
<table width="100%" border="0">
<tr>
<th align="left" valign="top" colspan="3"><b>Revision
History</b></th>
</tr>
<tr>
<td align="left">Revision 1.9</td>
<td align="left">2005-06-20</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">The license has been changed to the
MIT-style license used by NCURSES. Note that the programs are also
re-licensed under this.</td>
</tr>
<tr>
<td align="left">Revision 1.8</td>
<td align="left">2005-06-17</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Lots of updates. Added references and
perl examples. Changes to examples. Many grammatical and stylistic
changes to the content. Changes to NCURSES history.</td>
</tr>
<tr>
<td align="left">Revision 1.7.1</td>
<td align="left">2002-06-25</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Added a README file for building and
instructions for building from source.</td>
</tr>
<tr>
<td align="left">Revision 1.7</td>
<td align="left">2002-06-25</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Added "Other formats" section and made
a lot of fancy changes to the programs. Inlining of programs is
gone.</td>
</tr>
<tr>
<td align="left">Revision 1.6.1</td>
<td align="left">2002-02-24</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Removed the old Changelog section,
cleaned the makefiles</td>
</tr>
<tr>
<td align="left">Revision 1.6</td>
<td align="left">2002-02-16</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Corrected a lot of spelling mistakes,
added ACS variables section</td>
</tr>
<tr>
<td align="left">Revision 1.5</td>
<td align="left">2002-01-05</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Changed structure to present proper
TOC</td>
</tr>
<tr>
<td align="left">Revision 1.3.1</td>
<td align="left">2001-07-26</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Corrected maintainers paragraph,
Corrected stable release number</td>
</tr>
<tr>
<td align="left">Revision 1.3</td>
<td align="left">2001-07-24</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Added copyright notices to main
document (LDP license) and programs (GPL), Corrected
printw_example.</td>
</tr>
<tr>
<td align="left">Revision 1.2</td>
<td align="left">2001-06-05</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Incorporated ravi's changes. Mainly to
introduction, menu, form, justforfun sections</td>
</tr>
<tr>
<td align="left">Revision 1.1</td>
<td align="left">2001-05-22</td>
<td align="left">Revised by: ppadala</td>
</tr>
<tr>
<td align="left" colspan="3">Added "a word about window" section,
Added scanw_example.</td>
</tr>
</table>
</div>
<div>
<div class="ABSTRACT"><a name="AEN67" id="AEN67"></a>
<p><em>This document is intended to be an "All in One" guide for
programming with ncurses and its sister libraries. We graduate from
a simple "Hello World" program to more complex form manipulation.
No prior experience in ncurses is assumed. Send comments to
<a href="mailto:ppadala@gmail.com" target="_top">this
address</a></em></p>
</div>
</div>
<hr></div>
<div class="TOC">
<dl>
<dt><b>Table of Contents</b></dt>
<dt>1. <a href="#INTRO">Introduction</a></dt>
<dd>
<dl>
<dt>1.1. <a href="#WHATIS">What is NCURSES?</a></dt>
<dt>1.2. <a href="#WHATCANWEDO">What we can do with
NCURSES</a></dt>
<dt>1.3. <a href="#WHERETOGETIT">Where to get it</a></dt>
<dt>1.4. <a href="#PURPOSE">Purpose/Scope of the document</a></dt>
<dt>1.5. <a href="#ABOUTPROGRAMS">About the Programs</a></dt>
<dt>1.6. <a href="#OTHERFORMATS">Other Formats of the
document</a></dt>
<dt>1.7. <a href="#CREDITS">Credits</a></dt>
<dt>1.8. <a href="#WISHLIST">Wish List</a></dt>
<dt>1.9. <a href="#COPYRIGHT">Copyright</a></dt>
</dl>
</dd>
<dt>2. <a href="#HELLOWORLD">Hello World !!!</a></dt>
<dd>
<dl>
<dt>2.1. <a href="#COMPILECURSES">Compiling With the NCURSES
Library</a></dt>
<dt>2.2. <a href="#DISSECTION">Dissection</a></dt>
</dl>
</dd>
<dt>3. <a href="#GORY">The Gory Details</a></dt>
<dt>4. <a href="#INIT">Initialization</a></dt>
<dd>
<dl>
<dt>4.1. <a href="#ABOUTINIT">Initialization functions</a></dt>
<dt>4.2. <a href="#RAWCBREAK">raw() and cbreak()</a></dt>
<dt>4.3. <a href="#ECHONOECHO">echo() and noecho()</a></dt>
<dt>4.4. <a href="#KEYPAD">keypad()</a></dt>
<dt>4.5. <a href="#HALFDELAY">halfdelay()</a></dt>
<dt>4.6. <a href="#MISCINIT">Miscellaneous Initialization
functions</a></dt>
<dt>4.7. <a href="#INITEX">An Example</a></dt>
</dl>
</dd>
<dt>5. <a href="#AWORDWINDOWS">A Word about Windows</a></dt>
<dt>6. <a href="#PRINTW">Output functions</a></dt>
<dd>
<dl>
<dt>6.1. <a href="#ADDCHCLASS">addch() class of functions</a></dt>
<dt>6.2. <a href="#AEN298">mvaddch(), waddch() and
mvwaddch()</a></dt>
<dt>6.3. <a href="#PRINTWCLASS">printw() class of
functions</a></dt>
<dt>6.4. <a href="#ADDSTRCLASS">addstr() class of
functions</a></dt>
<dt>6.5. <a href="#ACAUTION">A word of caution</a></dt>
</dl>
</dd>
<dt>7. <a href="#SCANW">Input functions</a></dt>
<dd>
<dl>
<dt>7.1. <a href="#GETCHCLASS">getch() class of functions</a></dt>
<dt>7.2. <a href="#SCANWCLASS">scanw() class of functions</a></dt>
<dt>7.3. <a href="#GETSTRCLASS">getstr() class of
functions</a></dt>
<dt>7.4. <a href="#GETSTREX">Some examples</a></dt>
</dl>
</dd>
<dt>8. <a href="#ATTRIB">Attributes</a></dt>
<dd>
<dl>
<dt>8.1. <a href="#ATTRIBDETAILS">The details</a></dt>
<dt>8.2. <a href="#ATTRONVSATTRSET">attron() vs attrset()</a></dt>
<dt>8.3. <a href="#ATTR_GET">attr_get()</a></dt>
<dt>8.4. <a href="#ATTR_FUNCS">attr_ functions</a></dt>
<dt>8.5. <a href="#WATTRFUNCS">wattr functions</a></dt>
<dt>8.6. <a href="#CHGAT">chgat() functions</a></dt>
</dl>
</dd>
<dt>9. <a href="#WINDOWS">Windows</a></dt>
<dd>
<dl>
<dt>9.1. <a href="#WINDOWBASICS">The basics</a></dt>
<dt>9.2. <a href="#LETBEWINDOW">Let there be a Window !!!</a></dt>
<dt>9.3. <a href="#BORDEREXEXPL">Explanation</a></dt>
<dt>9.4. <a href="#OTHERSTUFF">The other stuff in the
example</a></dt>
<dt>9.5. <a href="#OTHERBORDERFUNCS">Other Border
functions</a></dt>
</dl>
</dd>
<dt>10. <a href="#COLOR">Colors</a></dt>
<dd>
<dl>
<dt>10.1. <a href="#COLORBASICS">The basics</a></dt>
<dt>10.2. <a href="#CHANGECOLORDEFS">Changing Color
Definitions</a></dt>
<dt>10.3. <a href="#COLORCONTENT">Color Content</a></dt>
</dl>
</dd>
<dt>11. <a href="#KEYS">Interfacing with the key board</a></dt>
<dd>
<dl>
<dt>11.1. <a href="#KEYSBASICS">The Basics</a></dt>
<dt>11.2. <a href="#SIMPLEKEYEX">A Simple Key Usage
example</a></dt>
</dl>
</dd>
<dt>12. <a href="#MOUSE">Interfacing with the mouse</a></dt>
<dd>
<dl>
<dt>12.1. <a href="#MOUSEBASICS">The Basics</a></dt>
<dt>12.2. <a href="#GETTINGEVENTS">Getting the events</a></dt>
<dt>12.3. <a href="#MOUSETOGETHER">Putting it all Together</a></dt>
<dt>12.4. <a href="#MISCMOUSEFUNCS">Miscellaneous
Functions</a></dt>
</dl>
</dd>
<dt>13. <a href="#SCREEN">Screen Manipulation</a></dt>
<dd>
<dl>
<dt>13.1. <a href="#GETYX">getyx() functions</a></dt>
<dt>13.2. <a href="#SCREENDUMP">Screen Dumping</a></dt>
<dt>13.3. <a href="#WINDOWDUMP">Window Dumping</a></dt>
</dl>
</dd>
<dt>14. <a href="#MISC">Miscellaneous features</a></dt>
<dd>
<dl>
<dt>14.1. <a href="#CURSSET">curs_set()</a></dt>
<dt>14.2. <a href="#TEMPLEAVE">Temporarily Leaving Curses
mode</a></dt>
<dt>14.3. <a href="#ACSVARS">ACS_ variables</a></dt>
</dl>
</dd>
<dt>15. <a href="#OTHERLIB">Other libraries</a></dt>
<dt>16. <a href="#PANELS">Panel Library</a></dt>
<dd>
<dl>
<dt>16.1. <a href="#PANELBASICS">The Basics</a></dt>
<dt>16.2. <a href="#COMPILEPANELS">Compiling With the Panels
Library</a></dt>
<dt>16.3. <a href="#PANELBROWSING">Panel Window Browsing</a></dt>
<dt>16.4. <a href="#USERPTRUSING">Using User Pointers</a></dt>
<dt>16.5. <a href="#PANELMOVERESIZE">Moving and Resizing
Panels</a></dt>
<dt>16.6. <a href="#PANELSHOWHIDE">Hiding and Showing
Panels</a></dt>
<dt>16.7. <a href="#PANELABOVE">panel_above() and panel_below()
Functions</a></dt>
</dl>
</dd>
<dt>17. <a href="#MENUS">Menus Library</a></dt>
<dd>
<dl>
<dt>17.1. <a href="#MENUBASICS">The Basics</a></dt>
<dt>17.2. <a href="#COMPILEMENUS">Compiling With the Menu
Library</a></dt>
<dt>17.3. <a href="#MENUDRIVER">Menu Driver: The work horse of the
menu system</a></dt>
<dt>17.4. <a href="#MENUWINDOWS">Menu Windows</a></dt>
<dt>17.5. <a href="#SCROLLMENUS">Scrolling Menus</a></dt>
<dt>17.6. <a href="#MULTICOLUMN">Multi Columnar Menus</a></dt>
<dt>17.7. <a href="#MULTIVALUEMENUS">Multi Valued Menus</a></dt>
<dt>17.8. <a href="#MENUOPT">Menu Options</a></dt>
<dt>17.9. <a href="#MENUUSERPTR">The useful User Pointer</a></dt>
</dl>
</dd>
<dt>18. <a href="#FORMS">Forms Library</a></dt>
<dd>
<dl>
<dt>18.1. <a href="#FORMBASICS">The Basics</a></dt>
<dt>18.2. <a href="#COMPILEFORMS">Compiling With the Forms
Library</a></dt>
<dt>18.3. <a href="#PLAYFIELDS">Playing with Fields</a></dt>
<dt>18.4. <a href="#FORMWINDOWS">Form Windows</a></dt>
<dt>18.5. <a href="#FILEDVALIDATE">Field Validation</a></dt>
<dt>18.6. <a href="#FORMDRIVER">Form Driver: The work horse of the
forms system</a></dt>
</dl>
</dd>
<dt>19. <a href="#TOOLS">Tools and Widget Libraries</a></dt>
<dd>
<dl>
<dt>19.1. <a href="#CDK">CDK (Curses Development Kit)</a></dt>
<dt>19.2. <a href="#DIALOG">The dialog</a></dt>
<dt>19.3. <a href="#PERLCURSES">Perl Curses Modules CURSES::FORM
and CURSES::WIDGETS</a></dt>
</dl>
</dd>
<dt>20. <a href="#JUSTFORFUN">Just For Fun !!!</a></dt>
<dd>
<dl>
<dt>20.1. <a href="#GAMEOFLIFE">The Game of Life</a></dt>
<dt>20.2. <a href="#MAGIC">Magic Square</a></dt>
<dt>20.3. <a href="#HANOI">Towers of Hanoi</a></dt>
<dt>20.4. <a href="#QUEENS">Queens Puzzle</a></dt>
<dt>20.5. <a href="#SHUFFLE">Shuffle</a></dt>
<dt>20.6. <a href="#TT">Typing Tutor</a></dt>
</dl>
</dd>
<dt>21. <a href="#REF">References</a></dt>
</dl>
</div>
<div class="SECT1">
<h2 class="SECT1"><a name="INTRO" id="INTRO">1.
Introduction</a></h2>
<p>In the olden days of teletype terminals, terminals were away
from computers and were connected to them through serial cables.
The terminals could be configured by sending a series of bytes. All
the capabilities (such as moving the cursor to a new location,
erasing part of the screen, scrolling the screen, changing modes
etc.) of terminals could be accessed through these series of bytes.
These control seeuqnces are usually called escape sequences,
because they start with an escape(0x1B) character. Even today, with
proper emulation, we can send escape sequences to the emulator and
achieve the same effect on a terminal window.</p>
<p>Suppose you wanted to print a line in color. Try typing this on
your console.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">echo "^[[0;31;40mIn Color"</font>
</pre></td>
</tr>
</table>
<p>The first character is an escape character, which looks like two
characters ^ and [. To be able to print it, you have to press
CTRL+V and then the ESC key. All the others are normal printable
characters. You should be able to see the string "In Color" in red.
It stays that way and to revert back to the original mode type
this.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">echo "^[[0;37;40m"</font>
</pre></td>
</tr>
</table>
<p>Now, what do these magic characters mean? Difficult to
comprehend? They might even be different for different terminals.
So the designers of UNIX invented a mechanism named <var class=
"LITERAL">termcap</var>. It is a file that lists all the
capabilities of a particular terminal, along with the escape
sequences needed to achieve a particular effect. In the later
years, this was replaced by <var class="LITERAL">terminfo</var>.
Without delving too much into details, this mechanism allows
application programs to query the terminfo database and obtain the
control characters to be sent to a terminal or terminal
emulator.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WHATIS" id="WHATIS">1.1. What is
NCURSES?</a></h3>
<p>You might be wondering, what the import of all this technical
gibberish is. In the above scenario, every application program is
supposed to query the terminfo and perform the necessary stuff
(sending control characters etc.). It soon became difficult to
manage this complexity and this gave birth to 'CURSES'. Curses is a
pun on the name "cursor optimization". The Curses library forms a
wrapper over working with raw terminal codes, and provides highly
flexible and efficient API (Application Programming Interface). It
provides functions to move the cursor, create windows, produce
colors, play with mouse etc. The application programs need not
worry about the underlying terminal capabilities.</p>
<p>So what is NCURSES? NCURSES is a clone of the original System V
Release 4.0 (SVr4) curses. It is a freely distributable library,
fully compatible with older version of curses. In short, it is a
library of functions that manages an application's display on
character-cell terminals. In the remainder of the document, the
terms curses and ncurses are used interchangeably.</p>
<p>A detailed history of NCURSES can be found in the NEWS file from
the source distribution. The current package is maintained by
<a href="mailto:dickey@his.com" target="_top">Thomas Dickey</a>.
You can contact the maintainers at <a href=
"mailto:bug-ncurses@gnu.org" target=
"_top">bug-ncurses@gnu.org</a>.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WHATCANWEDO" id="WHATCANWEDO">1.2. What
we can do with NCURSES</a></h3>
<p>NCURSES not only creates a wrapper over terminal capabilities,
but also gives a robust framework to create nice looking UI (User
Interface)s in text mode. It provides functions to create windows
etc. Its sister libraries panel, menu and form provide an extension
to the basic curses library. These libraries usually come along
with curses. One can create applications that contain multiple
windows, menus, panels and forms. Windows can be managed
independently, can provide 'scrollability' and even can be
hidden.</p>
<p>Menus provide the user with an easy command selection option.
Forms allow the creation of easy-to-use data entry and display
windows. Panels extend the capabilities of ncurses to deal with
overlapping and stacked windows.</p>
<p>These are just some of the basic things we can do with ncurses.
As we move along, We will see all the capabilities of these
libraries.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WHERETOGETIT" id="WHERETOGETIT">1.3.
Where to get it</a></h3>
<p>All right, now that you know what you can do with ncurses, you
must be rearing to get started. NCURSES is usually shipped with
your installation. In case you don't have the library or want to
compile it on your own, read on.</p>
<p><em>Compiling the package</em></p>
<p>NCURSES can be obtained from <a href=
"ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz" target=
"_top">ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz</a> or any
of the ftp sites mentioned in <a href=
"http://www.gnu.org/order/ftp.html" target=
"_top">http://www.gnu.org/order/ftp.html</a>.</p>
<p>Read the README and INSTALL files for details on to how to
install it. It usually involves the following operations.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000"> tar zxvf ncurses&lt;version&gt;.tar.gz # unzip and untar the archive
cd ncurses&lt;version&gt; # cd to the directory
./configure # configure the build according to your
# environment
make # make it
su root # become root
make install # install it</font>
</pre></td>
</tr>
</table>
<p><em>Using the RPM</em></p>
<p>NCURSES RPM can be found and downloaded from <a href=
"http://rpmfind.net" target="_top">http://rpmfind.net</a> . The RPM
can be installed with the following command after becoming
root.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> rpm -i &lt;downloaded rpm&gt;</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PURPOSE" id="PURPOSE">1.4. Purpose/Scope
of the document</a></h3>
<p>This document is intended to be a "All in One" guide for
programming with ncurses and its sister libraries. We graduate from
a simple "Hello World" program to more complex form manipulation.
No prior experience in ncurses is assumed. The writing is informal,
but a lot of detail is provided for each of the examples.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ABOUTPROGRAMS" id="ABOUTPROGRAMS">1.5.
About the Programs</a></h3>
<p>All the programs in the document are available in zipped form
<a href=
"http://www.tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs.tar.gz"
target="_top">here</a>. Unzip and untar it. The directory structure
looks like this.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">ncurses
|
|----&gt; JustForFun -- just for fun programs
|----&gt; basics -- basic programs
|----&gt; demo -- output files go into this directory after make
| |
| |----&gt; exe -- exe files of all example programs
|----&gt; forms -- programs related to form library
|----&gt; menus -- programs related to menus library
|----&gt; panels -- programs related to panels library
|----&gt; perl -- perl equivalents of the examples (contributed
| by Anuradha Ratnaweera)
|----&gt; Makefile -- the top level Makefile
|----&gt; README -- the top level README file. contains instructions
|----&gt; COPYING -- copyright notice</font>
</pre></td>
</tr>
</table>
<p>The individual directories contain the following files.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">Description of files in each directory
--------------------------------------
JustForFun
|
|----&gt; hanoi.c -- The Towers of Hanoi Solver
|----&gt; life.c -- The Game of Life demo
|----&gt; magic.c -- An Odd Order Magic Square builder
|----&gt; queens.c -- The famous N-Queens Solver
|----&gt; shuffle.c -- A fun game, if you have time to kill
|----&gt; tt.c -- A very trivial typing tutor
basics
|
|----&gt; acs_vars.c -- ACS_ variables example
|----&gt; hello_world.c -- Simple "Hello World" Program
|----&gt; init_func_example.c -- Initialization functions example
|----&gt; key_code.c -- Shows the scan code of the key pressed
|----&gt; mouse_menu.c -- A menu accessible by mouse
|----&gt; other_border.c -- Shows usage of other border functions apa
| -- rt from box()
|----&gt; printw_example.c -- A very simple printw() example
|----&gt; scanw_example.c -- A very simple getstr() example
|----&gt; simple_attr.c -- A program that can print a c file with
| -- comments in attribute
|----&gt; simple_color.c -- A simple example demonstrating colors
|----&gt; simple_key.c -- A menu accessible with keyboard UP, DOWN
| -- arrows
|----&gt; temp_leave.c -- Demonstrates temporarily leaving curses mode
|----&gt; win_border.c -- Shows Creation of windows and borders
|----&gt; with_chgat.c -- chgat() usage example
forms
|
|----&gt; form_attrib.c -- Usage of field attributes
|----&gt; form_options.c -- Usage of field options
|----&gt; form_simple.c -- A simple form example
|----&gt; form_win.c -- Demo of windows associated with forms
menus
|
|----&gt; menu_attrib.c -- Usage of menu attributes
|----&gt; menu_item_data.c -- Usage of item_name() etc.. functions
|----&gt; menu_multi_column.c -- Creates multi columnar menus
|----&gt; menu_scroll.c -- Demonstrates scrolling capability of menus
|----&gt; menu_simple.c -- A simple menu accessed by arrow keys
|----&gt; menu_toggle.c -- Creates multi valued menus and explains
| -- REQ_TOGGLE_ITEM
|----&gt; menu_userptr.c -- Usage of user pointer
|----&gt; menu_win.c -- Demo of windows associated with menus
panels
|
|----&gt; panel_browse.c -- Panel browsing through tab. Usage of user
| -- pointer
|----&gt; panel_hide.c -- Hiding and Un hiding of panels
|----&gt; panel_resize.c -- Moving and resizing of panels
|----&gt; panel_simple.c -- A simple panel example
perl
|----&gt; 01-10.pl -- Perl equivalents of first ten example programs</font>
</pre></td>
</tr>
</table>
<p>There is a top level Makefile included in the main directory. It
builds all the files and puts the ready-to-use exes in demo/exe
directory. You can also do selective make by going into the
corresponding directory. Each directory contains a README file
explaining the purpose of each c file in the directory.</p>
<p>For every example, I have included path name for the file
relative to the examples directory.</p>
<p>If you prefer browsing individual programs, point your browser
to <a href=
"http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/"
target=
"_top">http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/</a></p>
<p>All the programs are released under the same license that is
used by ncurses (MIT-style). This gives you the ability to do
pretty much anything other than claiming them as yours. Feel free
to use them in your programs as appropriate.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="OTHERFORMATS" id="OTHERFORMATS">1.6.
Other Formats of the document</a></h3>
<p>This howto is also availabe in various other formats on the
tldp.org site. Here are the links to other formats of this
document.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="LISTFORMATS" id="LISTFORMATS">1.6.1.
Readily available formats from tldp.org</a></h4>
<ul>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/pdf/NCURSES-Programming-HOWTO.pdf"
target="_top">Acrobat PDF Format</a></p>
</li>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/ps/NCURSES-Programming-HOWTO.ps.gz"
target="_top">PostScript Format</a></p>
</li>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html/NCURSES-Programming-HOWTO-html.tar.gz"
target="_top">In Multiple HTML pages</a></p>
</li>
<li>
<p><a href=
"http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/NCURSES-Programming-HOWTO.html"
target="_top">In One big HTML format</a></p>
</li>
</ul>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="BUILDSOURCE" id="BUILDSOURCE">1.6.2.
Building from source</a></h4>
<p>If above links are broken or if you want to experiment with sgml
read on.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000">&#13; Get both the source and the tar,gzipped programs, available at
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/NCURSES-Programming-HOWTO.sgml
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/ncurses_programs.tar.gz
Unzip ncurses_programs.tar.gz with
tar zxvf ncurses_programs.tar.gz
Use jade to create various formats. For example if you just want to create
the multiple html files, you would use
jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt;
NCURSES-Programming-HOWTO.sgml
to get pdf, first create a single html file of the HOWTO with
jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt; -V nochunks
NCURSES-Programming-HOWTO.sgml &gt; NCURSES-ONE-BIG-FILE.html
then use htmldoc to get pdf file with
htmldoc --size universal -t pdf --firstpage p1 -f &lt;output file name.pdf&gt;
NCURSES-ONE-BIG-FILE.html
for ps, you would use
htmldoc --size universal -t ps --firstpage p1 -f &lt;output file name.ps&gt;
NCURSES-ONE-BIG-FILE.html</font>
</pre></td>
</tr>
</table>
<p>See <a href="http://www.tldp.org/LDP/LDP-Author-Guide/" target=
"_top">LDP Author guide</a> for more details. If all else failes,
mail me at <a href="ppadala@gmail.com" target=
"_top">ppadala@gmail.com</a></p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CREDITS" id="CREDITS">1.7.
Credits</a></h3>
<p>I thank <a href="mailto:sharath_1@usa.net" target=
"_top">Sharath</a> and Emre Akbas for helping me with few sections.
The introduction was initially written by sharath. I rewrote it
with few excerpts taken from his initial work. Emre helped in
writing printw and scanw sections.</p>
<p>Perl equivalents of the example programs are contributed by
<a href="mailto:Aratnaweera@virtusa.com" target="_top">Anuradha
Ratnaweera</a>.</p>
<p>Then comes <a href="mailto:parimi@ece.arizona.edu" target=
"_top">Ravi Parimi</a>, my dearest friend, who has been on this
project before even one line was written. He constantly bombarded
me with suggestions and patiently reviewed the whole text. He also
checked each program on Linux and Solaris.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WISHLIST" id="WISHLIST">1.8. Wish
List</a></h3>
<p>This is the wish list, in the order of priority. If you have a
wish or you want to work on completing the wish, mail <a href=
"mailto:ppadala@gmail.com" target="_top">me</a>.</p>
<ul>
<li>
<p>Add examples to last parts of forms section.</p>
</li>
<li>
<p>Prepare a Demo showing all the programs and allow the user to
browse through description of each program. Let the user compile
and see the program in action. A dialog based interface is
preferred.</p>
</li>
<li>
<p>Add debug info. _tracef, _tracemouse stuff.</p>
</li>
<li>
<p>Accessing termcap, terminfo using functions provided by ncurses
package.</p>
</li>
<li>
<p>Working on two terminals simultaneously.</p>
</li>
<li>
<p>Add more stuff to miscellaneous section.</p>
</li>
</ul>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COPYRIGHT" id="COPYRIGHT">1.9.
Copyright</a></h3>
<p>Copyright &copy; 2001 by Pradeep Padala.</p>
<p>Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy,
modify, merge, publish, distribute, distribute with modifications,
sublicense, and/or sell copies of the Software, and to permit
persons to whom the Software is furnished to do so, subject to the
following conditions:</p>
<p>The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.</p>
<p>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.</p>
<p>Except as contained in this notice, the name(s) of the above
copyright holders shall not be used in advertising or otherwise to
promote the sale, use or other dealings in this Software without
prior written authorization.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="HELLOWORLD" id="HELLOWORLD">2. Hello
World !!!</a></h2>
<p>Welcome to the world of curses. Before we plunge into the
library and look into its various features, let's write a simple
program and say hello to the world.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COMPILECURSES" id="COMPILECURSES">2.1.
Compiling With the NCURSES Library</a></h3>
<p>To use ncurses library functions, you have to include ncurses.h
in your programs. To link the program with ncurses the flag
-lncurses should be added.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> #include &lt;ncurses.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lncurses</font>
</pre></td>
</tr>
</table>
<div class="EXAMPLE"><a name="BHW" id="BHW"></a>
<p><b>Example 1. The Hello World !!! Program</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="DISSECTION" id="DISSECTION">2.2.
Dissection</a></h3>
<p>The above program prints "Hello World !!!" to the screen and
exits. This program shows how to initialize curses and do screen
manipulation and end curses mode. Let's dissect it line by
line.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="ABOUT-INITSCR" id="ABOUT-INITSCR">2.2.1.
About initscr()</a></h4>
<p>The function initscr() initializes the terminal in curses mode.
In some implementations, it clears the screen and presents a blank
screen. To do any screen manipulation using curses package this has
to be called first. This function initializes the curses system and
allocates memory for our present window (called <var class=
"LITERAL">stdscr</var>) and some other data-structures. Under
extreme cases this function might fail due to insufficient memory
to allocate memory for curses library's data structures.</p>
<p>After this is done, we can do a variety of initializations to
customize our curses settings. These details will be explained
<a href="#INIT">later</a> .</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="MYST-REFRESH" id="MYST-REFRESH">2.2.2.
The mysterious refresh()</a></h4>
<p>The next line printw prints the string "Hello World !!!" on to
the screen. This function is analogous to normal printf in all
respects except that it prints the data on a window called stdscr
at the current (y,x) co-ordinates. Since our present co-ordinates
are at 0,0 the string is printed at the left hand corner of the
window.</p>
<p>This brings us to that mysterious refresh(). Well, when we
called printw the data is actually written to an imaginary window,
which is not updated on the screen yet. The job of printw is to
update a few flags and data structures and write the data to a
buffer corresponding to stdscr. In order to show it on the screen,
we need to call refresh() and tell the curses system to dump the
contents on the screen.</p>
<p>The philosophy behind all this is to allow the programmer to do
multiple updates on the imaginary screen or windows and do a
refresh once all his screen update is done. refresh() checks the
window and updates only the portion which has been changed. This
improves performance and offers greater flexibility too. But, it is
sometimes frustrating to beginners. A common mistake committed by
beginners is to forget to call refresh() after they did some update
through printw() class of functions. I still forget to add it
sometimes :-)</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="ABOUT-ENDWIN" id="ABOUT-ENDWIN">2.2.3.
About endwin()</a></h4>
<p>And finally don't forget to end the curses mode. Otherwise your
terminal might behave strangely after the program quits. endwin()
frees the memory taken by curses sub-system and its data structures
and puts the terminal in normal mode. This function must be called
after you are done with the curses mode.</p>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="GORY" id="GORY">3. The Gory
Details</a></h2>
<p>Now that we have seen how to write a simple curses program let's
get into the details. There are many functions that help customize
what you see on screen and many features which can be put to full
use.</p>
<p>Here we go...</p>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="INIT" id="INIT">4.
Initialization</a></h2>
<p>We now know that to initialize curses system the function
initscr() has to be called. There are functions which can be called
after this initialization to customize our curses session. We may
ask the curses system to set the terminal in raw mode or initialize
color or initialize the mouse etc.. Let's discuss some of the
functions that are normally called immediately after initscr();</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ABOUTINIT" id="ABOUTINIT">4.1.
Initialization functions</a></h3>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="RAWCBREAK" id="RAWCBREAK">4.2. raw() and
cbreak()</a></h3>
<p>Normally the terminal driver buffers the characters a user types
until a new line or carriage return is encountered. But most
programs require that the characters be available as soon as the
user types them. The above two functions are used to disable line
buffering. The difference between these two functions is in the way
control characters like suspend (CTRL-Z), interrupt and quit
(CTRL-C) are passed to the program. In the raw() mode these
characters are directly passed to the program without generating a
signal. In the <var class="LITERAL">cbreak()</var> mode these
control characters are interpreted as any other character by the
terminal driver. I personally prefer to use raw() as I can exercise
greater control over what the user does.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ECHONOECHO" id="ECHONOECHO">4.3. echo()
and noecho()</a></h3>
<p>These functions control the echoing of characters typed by the
user to the terminal. <var class="LITERAL">noecho()</var> switches
off echoing. The reason you might want to do this is to gain more
control over echoing or to suppress unnecessary echoing while
taking input from the user through the getch() etc. functions. Most
of the interactive programs call <var class=
"LITERAL">noecho()</var> at initialization and do the echoing of
characters in a controlled manner. It gives the programmer the
flexibility of echoing characters at any place in the window
without updating current (y,x) co-ordinates.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="KEYPAD" id="KEYPAD">4.4.
keypad()</a></h3>
<p>This is my favorite initialization function. It enables the
reading of function keys like F1, F2, arrow keys etc. Almost every
interactive program enables this, as arrow keys are a major part of
any User Interface. Do <var class="LITERAL">keypad(stdscr,
TRUE)</var> to enable this feature for the regular screen (stdscr).
You will learn more about key management in later sections of this
document.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="HALFDELAY" id="HALFDELAY">4.5.
halfdelay()</a></h3>
<p>This function, though not used very often, is a useful one at
times. halfdelay()is called to enable the half-delay mode, which is
similar to the cbreak() mode in that characters typed are
immediately available to program. However, it waits for 'X' tenths
of a second for input and then returns ERR, if no input is
available. 'X' is the timeout value passed to the function
halfdelay(). This function is useful when you want to ask the user
for input, and if he doesn't respond with in certain time, we can
do some thing else. One possible example is a timeout at the
password prompt.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MISCINIT" id="MISCINIT">4.6.
Miscellaneous Initialization functions</a></h3>
<p>There are few more functions which are called at initialization
to customize curses behavior. They are not used as extensively as
those mentioned above. Some of them are explained where
appropriate.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="INITEX" id="INITEX">4.7. An
Example</a></h3>
<p>Let's write a program which will clarify the usage of these
functions.</p>
<div class="EXAMPLE"><a name="BINFU" id="BINFU"></a>
<p><b>Example 2. Initialization Function Usage example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{ int ch;
initscr(); /* Start curses mode */
raw(); /* Line buffering disabled */
keypad(stdscr, TRUE); /* We get F1, F2 etc.. */
noecho(); /* Don't echo() while we do getch */
printw("Type any character to see it in bold\n");
ch = getch(); /* If raw() hadn't been called
* we have to press enter before it
* gets to the program */
if(ch == KEY_F(1)) /* Without keypad enabled this will */
printw("F1 Key pressed");/* not get to us either */
/* Without noecho() some ugly escape
* charachters might have been printed
* on screen */
else
{ printw("The pressed key is ");
attron(A_BOLD);
printw("%c", ch);
attroff(A_BOLD);
}
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
<p>This program is self-explanatory. But I used functions which
aren't explained yet. The function <var class=
"LITERAL">getch()</var> is used to get a character from user. It is
equivalent to normal <var class="LITERAL">getchar()</var> except
that we can disable the line buffering to avoid &lt;enter&gt; after
input. Look for more about <var class="LITERAL">getch()</var>and
reading keys in the <a href="#KEYS">key management section</a> .
The functions attron and attroff are used to switch some attributes
on and off respectively. In the example I used them to print the
character in bold. These functions are explained in detail
later.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="AWORDWINDOWS" id="AWORDWINDOWS">5. A
Word about Windows</a></h2>
<p>Before we plunge into the myriad ncurses functions, let me clear
few things about windows. Windows are explained in detail in
following <a href="#WINDOWS">sections</a></p>
<p>A Window is an imaginary screen defined by curses system. A
window does not mean a bordered window which you usually see on
Win9X platforms. When curses is initialized, it creates a default
window named <var class="LITERAL">stdscr</var> which represents
your 80x25 (or the size of window in which you are running) screen.
If you are doing simple tasks like printing few strings, reading
input etc., you can safely use this single window for all of your
purposes. You can also create windows and call functions which
explicitly work on the specified window.</p>
<p>For example, if you call</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> printw("Hi There !!!");
refresh();</font>
</pre></td>
</tr>
</table>
<p>It prints the string on stdscr at the present cursor position.
Similarly the call to refresh(), works on stdscr only.</p>
<p>Say you have created <a href="#WINDOWS">windows</a> then you
have to call a function with a 'w' added to the usual function.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> wprintw(win, "Hi There !!!");
wrefresh(win);</font>
</pre></td>
</tr>
</table>
<p>As you will see in the rest of the document, naming of functions
follow the same convention. For each function there usually are
three more functions.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000"> printw(string); /* Print on stdscr at present cursor position */
mvprintw(y, x, string);/* Move to (y, x) then print string */
wprintw(win, string); /* Print on window win at present cursor position */
/* in the window */
mvwprintw(win, y, x, string); /* Move to (y, x) relative to window */
/* co-ordinates and then print */</font>
</pre></td>
</tr>
</table>
<p>Usually the w-less functions are macros which expand to
corresponding w-function with stdscr as the window parameter.</p>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="PRINTW" id="PRINTW">6. Output
functions</a></h2>
<p>I guess you can't wait any more to see some action. Back to our
odyssey of curses functions. Now that curses is initialized, let's
interact with world.</p>
<p>There are three classes of functions which you can use to do
output on screen.</p>
<ol type="1">
<li>
<p>addch() class: Print single character with attributes</p>
</li>
<li>
<p>printw() class: Print formatted output similar to printf()</p>
</li>
<li>
<p>addstr() class: Print strings</p>
</li>
</ol>
<p>These functions can be used interchangeably and it's a matter of
style as to which class is used. Let's see each one in detail.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ADDCHCLASS" id="ADDCHCLASS">6.1. addch()
class of functions</a></h3>
<p>These functions put a single character into the current cursor
location and advance the position of the cursor. You can give the
character to be printed but they usually are used to print a
character with some attributes. Attributes are explained in detail
in later <a href="#ATTRIB">sections</a> of the document. If a
character is associated with an attribute(bold, reverse video
etc.), when curses prints the character, it is printed in that
attribute.</p>
<p>In order to combine a character with some attributes, you have
two options:</p>
<ul>
<li>
<p>By OR'ing a single character with the desired attribute macros.
These attribute macros could be found in the header file
<var class="LITERAL">ncurses.h</var>. For example, you want to
print a character ch(of type char) bold and underlined, you would
call addch() as below.</p>
<table border="0" bgcolor="#E0E0E0" width="90%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> addch(ch | A_BOLD | A_UNDERLINE);</font>
</pre></td>
</tr>
</table>
</li>
<li>
<p>By using functions like <var class=
"LITERAL">attrset(),attron(),attroff()</var>. These functions are
explained in the <a href="#ATTRIB">Attributes</a> section. Briefly,
they manipulate the current attributes of the given window. Once
set, the character printed in the window are associated with the
attributes until it is turned off.</p>
</li>
</ul>
<p>Additionally, <var class="LITERAL">curses</var> provides some
special characters for character-based graphics. You can draw
tables, horizontal or vertical lines, etc. You can find all
avaliable characters in the header file <var class=
"LITERAL">ncurses.h</var>. Try looking for macros beginning with
<var class="LITERAL">ACS_</var> in this file.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="AEN298" id="AEN298">6.2. mvaddch(),
waddch() and mvwaddch()</a></h3>
<p><var class="LITERAL">mvaddch()</var> is used to move the cursor
to a given point, and then print. Thus, the calls:</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000"> move(row,col); /* moves the cursor to row<em>th</em> row and col<em>th</em> column */
addch(ch);</font>
</pre></td>
</tr>
</table>
can be replaced by
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> mvaddch(row,col,ch);</font>
</pre></td>
</tr>
</table>
<p><var class="LITERAL">waddch()</var> is similar to <var class=
"LITERAL">addch()</var>, except that it adds a character into the
given window. (Note that <var class="LITERAL">addch()</var> adds a
character into the window <var class="LITERAL">stdscr</var>.)</p>
<p>In a similar fashion <var class="LITERAL">mvwaddch()</var>
function is used to add a character into the given window at the
given coordinates.</p>
<p>Now, we are familiar with the basic output function <var class=
"LITERAL">addch()</var>. But, if we want to print a string, it
would be very annoying to print it character by character.
Fortunately, <var class="LITERAL">ncurses</var> provides
<var class="LITERAL">printf</var><em>-like</em> or <var class=
"LITERAL">puts</var><em>-like</em> functions.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PRINTWCLASS" id="PRINTWCLASS">6.3.
printw() class of functions</a></h3>
<p>These functions are similar to <var class=
"LITERAL">printf()</var> with the added capability of printing at
any position on the screen.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="PRINTWMVPRINTW" id=
"PRINTWMVPRINTW">6.3.1. printw() and mvprintw</a></h4>
<p>These two functions work much like <var class=
"LITERAL">printf()</var>. <var class="LITERAL">mvprintw()</var> can
be used to move the cursor to a position and then print. If you
want to move the cursor first and then print using <var class=
"LITERAL">printw()</var> function, use <var class=
"LITERAL">move()</var> first and then use <var class=
"LITERAL">printw()</var> though I see no point why one should avoid
using <var class="LITERAL">mvprintw()</var>, you have the
flexibility to manipulate.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="WPRINTWMVWPRINTW" id=
"WPRINTWMVWPRINTW">6.3.2. wprintw() and mvwprintw</a></h4>
<p>These two functions are similar to above two except that they
print in the corresponding window given as argument.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="VWPRINTW" id="VWPRINTW">6.3.3.
vwprintw()</a></h4>
<p>This function is similar to <var class=
"LITERAL">vprintf()</var>. This can be used when variable number of
arguments are to be printed.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="SIMPLEPRINTWEX" id=
"SIMPLEPRINTWEX">6.3.4. A Simple printw example</a></h4>
<div class="EXAMPLE"><a name="BPREX" id="BPREX"></a>
<p><b>Example 3. A Simple printw example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt; /* ncurses.h includes stdio.h */
#include &lt;string.h&gt;
int main()
{
char mesg[]="Just a string"; /* message to be appeared on the screen */
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
mvprintw(row-2,0,"This screen has %d rows and %d columns\n",row,col);
printw("Try resizing your window(if possible) and then run this program again");
refresh();
getch();
endwin();
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
<p>Above program demonstrates how easy it is to use <var class=
"LITERAL">printw</var>. You just feed the coordinates and the
message to be appeared on the screen, then it does what you
want.</p>
<p>The above program introduces us to a new function <var class=
"LITERAL">getmaxyx()</var>, a macro defined in <var class=
"LITERAL">ncurses.h</var>. It gives the number of columns and the
number of rows in a given window. <var class=
"LITERAL">getmaxyx()</var> does this by updating the variables
given to it. Since <var class="LITERAL">getmaxyx()</var> is not a
function we don't pass pointers to it, we just give two integer
variables.</p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ADDSTRCLASS" id="ADDSTRCLASS">6.4.
addstr() class of functions</a></h3>
<p><var class="LITERAL">addstr()</var> is used to put a character
string into a given window. This function is similar to calling
<var class="LITERAL">addch()</var> once for each character in a
given string. This is true for all output functions. There are
other functions from this family such as <var class=
"LITERAL">mvaddstr(),mvwaddstr()</var> and <var class=
"LITERAL">waddstr()</var>, which obey the naming convention of
curses.(e.g. mvaddstr() is similar to the respective calls move()
and then addstr().) Another function of this family is addnstr(),
which takes an integer parameter(say n) additionally. This function
puts at most n characters into the screen. If n is negative, then
the entire string will be added.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ACAUTION" id="ACAUTION">6.5. A word of
caution</a></h3>
<p>All these functions take y co-ordinate first and then x in their
arguments. A common mistake by beginners is to pass x,y in that
order. If you are doing too many manipulations of (y,x)
co-ordinates, think of dividing the screen into windows and
manipulate each one separately. Windows are explained in the
<a href="#WINDOWS">windows</a> section.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="SCANW" id="SCANW">7. Input
functions</a></h2>
<p>Well, printing without taking input, is boring. Let's see
functions which allow us to get input from user. These functions
also can be divided into three categories.</p>
<ol type="1">
<li>
<p>getch() class: Get a character</p>
</li>
<li>
<p>scanw() class: Get formatted input</p>
</li>
<li>
<p>getstr() class: Get strings</p>
</li>
</ol>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETCHCLASS" id="GETCHCLASS">7.1. getch()
class of functions</a></h3>
<p>These functions read a single character from the terminal. But
there are several subtle facts to consider. For example if you
don't use the function cbreak(), curses will not read your input
characters contiguously but will begin read them only after a new
line or an EOF is encountered. In order to avoid this, the cbreak()
function must used so that characters are immediately available to
your program. Another widely used function is noecho(). As the name
suggests, when this function is set (used), the characters that are
keyed in by the user will not show up on the screen. The two
functions cbreak() and noecho() are typical examples of key
management. Functions of this genre are explained in the <a href=
"#KEYS">key management section</a> .</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SCANWCLASS" id="SCANWCLASS">7.2. scanw()
class of functions</a></h3>
<p>These functions are similar to <var class=
"LITERAL">scanf()</var> with the added capability of getting the
input from any location on the screen.</p>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="SCANWMVSCANW" id="SCANWMVSCANW">7.2.1.
scanw() and mvscanw</a></h4>
<p>The usage of these functions is similar to that of <var class=
"LITERAL">sscanf()</var>, where the line to be scanned is provided
by <var class="LITERAL">wgetstr()</var> function. That is, these
functions call to <var class="LITERAL">wgetstr()</var>
function(explained below) and uses the resulting line for a
scan.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="WSCANWMVWSCANW" id=
"WSCANWMVWSCANW">7.2.2. wscanw() and mvwscanw()</a></h4>
<p>These are similar to above two functions except that they read
from a window, which is supplied as one of the arguments to these
functions.</p>
</div>
<div class="SECT3">
<hr>
<h4 class="SECT3"><a name="VWSCANW" id="VWSCANW">7.2.3.
vwscanw()</a></h4>
<p>This function is similar to <var class="LITERAL">vscanf()</var>.
This can be used when a variable number of arguments are to be
scanned.</p>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETSTRCLASS" id="GETSTRCLASS">7.3.
getstr() class of functions</a></h3>
<p>These functions are used to get strings from the terminal. In
essence, this function performs the same task as would be achieved
by a series of calls to <var class="LITERAL">getch()</var> until a
newline, carriage return, or end-of-file is received. The resulting
string of characters are pointed to by <var class=
"LITERAL">str</var>, which is a character pointer provided by the
user.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETSTREX" id="GETSTREX">7.4. Some
examples</a></h3>
<div class="EXAMPLE"><a name="BSCEX" id="BSCEX"></a>
<p><b>Example 4. A Simple scanw example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt; /* ncurses.h includes stdio.h */
#include &lt;string.h&gt;
int main()
{
char mesg[]="Enter a string: "; /* message to be appeared on the screen */
char str[80];
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
getstr(str);
mvprintw(LINES - 2, 0, "You Entered: %s", str);
getch();
endwin();
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="ATTRIB" id="ATTRIB">8.
Attributes</a></h2>
<p>We have seen an example of how attributes can be used to print
characters with some special effects. Attributes, when set
prudently, can present information in an easy, understandable
manner. The following program takes a C file as input and prints
the file with comments in bold. Scan through the code.</p>
<div class="EXAMPLE"><a name="BSIAT" id="BSIAT"></a>
<p><b>Example 5. A Simple Attributes example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">/* pager functionality by Joseph Spainhour" &lt;spainhou@bellsouth.net&gt; */
#include &lt;ncurses.h&gt;
#include &lt;stdlib.h&gt;
int main(int argc, char *argv[])
{
int ch, prev, row, col;
prev = EOF;
FILE *fp;
int y, x;
if(argc != 2)
{
printf("Usage: %s &lt;a c file name&gt;\n", argv[0]);
exit(1);
}
fp = fopen(argv[1], "r");
if(fp == NULL)
{
perror("Cannot open input file");
exit(1);
}
initscr(); /* Start curses mode */
getmaxyx(stdscr, row, col); /* find the boundaries of the screeen */
while((ch = fgetc(fp)) != EOF) /* read the file till we reach the end */
{
getyx(stdscr, y, x); /* get the current curser position */
if(y == (row - 1)) /* are we are at the end of the screen */
{
printw("&lt;-Press Any Key-&gt;"); /* tell the user to press a key */
getch();
clear(); /* clear the screen */
move(0, 0); /* start at the beginning of the screen */
}
if(prev == '/' &amp;&amp; ch == '*') /* If it is / and * then only
* switch bold on */
{
attron(A_BOLD); /* cut bold on */
getyx(stdscr, y, x); /* get the current curser position */
move(y, x - 1); /* back up one space */
printw("%c%c", '/', ch); /* The actual printing is done here */
}
else
printw("%c", ch);
refresh();
if(prev == '*' &amp;&amp; ch == '/')
attroff(A_BOLD); /* Switch it off once we got *
* and then / */
prev = ch;
}
endwin(); /* End curses mode */
fclose(fp);
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
<p>Don't worry about all those initialization and other crap.
Concentrate on the while loop. It reads each character in the file
and searches for the pattern /*. Once it spots the pattern, it
switches the BOLD attribute on with <var class=
"LITERAL">attron()</var> . When we get the pattern */ it is
switched off by <var class="LITERAL">attroff()</var> .</p>
<p>The above program also introduces us to two useful functions
<var class="LITERAL">getyx()</var> and <var class=
"LITERAL">move()</var>. The first function gets the co-ordinates of
the present cursor into the variables y, x. Since getyx() is a
macro we don't have to pass pointers to variables. The function
<var class="LITERAL">move()</var> moves the cursor to the
co-ordinates given to it.</p>
<p>The above program is really a simple one which doesn't do much.
On these lines one could write a more useful program which reads a
C file, parses it and prints it in different colors. One could even
extend it to other languages as well.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTRIBDETAILS" id="ATTRIBDETAILS">8.1.
The details</a></h3>
<p>Let's get into more details of attributes. The functions
<var class="LITERAL">attron(), attroff(), attrset()</var> , and
their sister functions <var class="LITERAL">attr_get()</var> etc..
can be used to switch attributes on/off , get attributes and
produce a colorful display.</p>
<p>The functions attron and attroff take a bit-mask of attributes
and switch them on or off, respectively. The following video
attributes, which are defined in &lt;curses.h&gt; can be passed to
these functions.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000">
A_NORMAL Normal display (no highlight)
A_STANDOUT Best highlighting mode of the terminal.
A_UNDERLINE Underlining
A_REVERSE Reverse video
A_BLINK Blinking
A_DIM Half bright
A_BOLD Extra bright or bold
A_PROTECT Protected mode
A_INVIS Invisible or blank mode
A_ALTCHARSET Alternate character set
A_CHARTEXT Bit-mask to extract a character
COLOR_PAIR(n) Color-pair number n
</font>
</pre></td>
</tr>
</table>
<p>The last one is the most colorful one :-) Colors are explained
in the <a href="#color" target="_top">next sections</a>.</p>
<p>We can OR(|) any number of above attributes to get a combined
effect. If you wanted reverse video with blinking characters you
can use</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> attron(A_REVERSE | A_BLINK);</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTRONVSATTRSET" id=
"ATTRONVSATTRSET">8.2. attron() vs attrset()</a></h3>
<p>Then what is the difference between attron() and attrset()?
attrset sets the attributes of window whereas attron just switches
on the attribute given to it. So attrset() fully overrides whatever
attributes the window previously had and sets it to the new
attribute(s). Similarly attroff() just switches off the
attribute(s) given to it as an argument. This gives us the
flexibility of managing attributes easily.But if you use them
carelessly you may loose track of what attributes the window has
and garble the display. This is especially true while managing
menus with colors and highlighting. So decide on a consistent
policy and stick to it. You can always use <var class=
"LITERAL">standend()</var> which is equivalent to <var class=
"LITERAL">attrset(A_NORMAL)</var> which turns off all attributes
and brings you to normal mode.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTR_GET" id="ATTR_GET">8.3.
attr_get()</a></h3>
<p>The function attr_get() gets the current attributes and color
pair of the window. Though we might not use this as often as the
above functions, this is useful in scanning areas of screen. Say we
wanted to do some complex update on screen and we are not sure what
attribute each character is associated with. Then this function can
be used with either attrset or attron to produce the desired
effect.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ATTR_FUNCS" id="ATTR_FUNCS">8.4. attr_
functions</a></h3>
<p>There are series of functions like attr_set(), attr_on etc..
These are similar to above functions except that they take
parameters of type <var class="LITERAL">attr_t</var>.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WATTRFUNCS" id="WATTRFUNCS">8.5. wattr
functions</a></h3>
<p>For each of the above functions we have a corresponding function
with 'w' which operates on a particular window. The above functions
operate on stdscr.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CHGAT" id="CHGAT">8.6. chgat()
functions</a></h3>
<p>The function chgat() is listed in the end of the man page
curs_attr. It actually is a useful one. This function can be used
to set attributes for a group of characters without moving. I mean
it !!! without moving the cursor :-) It changes the attributes of a
given number of characters starting at the current cursor
location.</p>
<p>We can give -1 as the character count to update till end of
line. If you want to change attributes of characters from current
position to end of line, just use this.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> chgat(-1, A_REVERSE, 0, NULL);</font>
</pre></td>
</tr>
</table>
<p>This function is useful when changing attributes for characters
that are already on the screen. Move to the character from which
you want to change and change the attribute.</p>
<p>Other functions wchgat(), mvchgat(), wchgat() behave similarly
except that the w functions operate on the particular window. The
mv functions first move the cursor then perform the work given to
them. Actually chgat is a macro which is replaced by a wchgat()
with stdscr as the window. Most of the "w-less" functions are
macros.</p>
<div class="EXAMPLE"><a name="BWICH" id="BWICH"></a>
<p><b>Example 6. Chgat() Usage example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main(int argc, char *argv[])
{ initscr(); /* Start curses mode */
start_color(); /* Start color functionality */
init_pair(1, COLOR_CYAN, COLOR_BLACK);
printw("A Big string which i didn't care to type fully ");
mvchgat(0, 0, -1, A_BLINK, 1, NULL);
/*
* First two parameters specify the position at which to start
* Third parameter number of characters to update. -1 means till
* end of line
* Forth parameter is the normal attribute you wanted to give
* to the charcter
* Fifth is the color index. It is the index given during init_pair()
* use 0 if you didn't want color
* Sixth one is always NULL
*/
refresh();
getch();
endwin(); /* End curses mode */
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
<p>This example also introduces us to the color world of curses.
Colors will be explained in detail later. Use 0 for no color.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="WINDOWS" id="WINDOWS">9.
Windows</a></h2>
<p>Windows form the most important concept in curses. You have seen
the standard window stdscr above where all the functions implicitly
operated on this window. Now to make design even a simplest GUI,
you need to resort to windows. The main reason you may want to use
windows is to manipulate parts of the screen separately, for better
efficiency, by updating only the windows that need to be changed
and for a better design. I would say the last reason is the most
important in going for windows. You should always strive for a
better and easy-to-manage design in your programs. If you are
writing big, complex GUIs this is of pivotal importance before you
start doing anything.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WINDOWBASICS" id="WINDOWBASICS">9.1. The
basics</a></h3>
<p>A Window can be created by calling the function <var class=
"LITERAL">newwin()</var>. It doesn't create any thing on the screen
actually. It allocates memory for a structure to manipulate the
window and updates the structure with data regarding the window
like it's size, beginy, beginx etc.. Hence in curses, a window is
just an abstraction of an imaginary window, which can be
manipulated independent of other parts of screen. The function
newwin() returns a pointer to structure WINDOW, which can be passed
to window related functions like wprintw() etc.. Finally the window
can be destroyed with delwin(). It will deallocate the memory
associated with the window structure.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="LETBEWINDOW" id="LETBEWINDOW">9.2. Let
there be a Window !!!</a></h3>
<p>What fun is it, if a window is created and we can't see it. So
the fun part begins by displaying the window. The function
<var class="LITERAL">box()</var> can be used to draw a border
around the window. Let's explore these functions in more detail in
this example.</p>
<div class="EXAMPLE"><a name="BWIBO" id="BWIBO"></a>
<p><b>Example 7. Window Border example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
WINDOW *create_newwin(int height, int width, int starty, int startx);
void destroy_win(WINDOW *local_win);
int main(int argc, char *argv[])
{ WINDOW *my_win;
int startx, starty, width, height;
int ch;
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
height = 3;
width = 10;
starty = (LINES - height) / 2; /* Calculating for a center placement */
startx = (COLS - width) / 2; /* of the window */
printw("Press F1 to exit");
refresh();
my_win = create_newwin(height, width, starty, startx);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,--startx);
break;
case KEY_RIGHT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,++startx);
break;
case KEY_UP:
destroy_win(my_win);
my_win = create_newwin(height, width, --starty,startx);
break;
case KEY_DOWN:
destroy_win(my_win);
my_win = create_newwin(height, width, ++starty,startx);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
WINDOW *create_newwin(int height, int width, int starty, int startx)
{ WINDOW *local_win;
local_win = newwin(height, width, starty, startx);
box(local_win, 0 , 0); /* 0, 0 gives default characters
* for the vertical and horizontal
* lines */
wrefresh(local_win); /* Show that box */
return local_win;
}
void destroy_win(WINDOW *local_win)
{
/* box(local_win, ' ', ' '); : This won't produce the desired
* result of erasing the window. It will leave it's four corners
* and so an ugly remnant of window.
*/
wborder(local_win, ' ', ' ', ' ',' ',' ',' ',' ',' ');
/* The parameters taken are
* 1. win: the window on which to operate
* 2. ls: character to be used for the left side of the window
* 3. rs: character to be used for the right side of the window
* 4. ts: character to be used for the top side of the window
* 5. bs: character to be used for the bottom side of the window
* 6. tl: character to be used for the top left corner of the window
* 7. tr: character to be used for the top right corner of the window
* 8. bl: character to be used for the bottom left corner of the window
* 9. br: character to be used for the bottom right corner of the window
*/
wrefresh(local_win);
delwin(local_win);
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="BORDEREXEXPL" id="BORDEREXEXPL">9.3.
Explanation</a></h3>
<p>Don't scream. I know it's a big example. But I have to explain
some important things here :-). This program creates a rectangular
window that can be moved with left, right, up, down arrow keys. It
repeatedly creates and destroys windows as user press a key. Don't
go beyond the screen limits. Checking for those limits is left as
an exercise for the reader. Let's dissect it by line by line.</p>
<p>The <var class="LITERAL">create_newwin()</var> function creates
a window with <var class="LITERAL">newwin()</var> and displays a
border around it with box. The function <var class=
"LITERAL">destroy_win()</var> first erases the window from screen
by painting a border with ' ' character and then calling
<var class="LITERAL">delwin()</var> to deallocate memory related to
it. Depending on the key the user presses, starty or startx is
changed and a new window is created.</p>
<p>In the destroy_win, as you can see, I used wborder instead of
box. The reason is written in the comments (You missed it. I know.
Read the code :-)). wborder draws a border around the window with
the characters given to it as the 4 corner points and the 4 lines.
To put it clearly, if you have called wborder as below:</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000"> wborder(win, '|', '|', '-', '-', '+', '+', '+', '+');</font>
</pre></td>
</tr>
</table>
<p>it produces some thing like</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> +------------+
| |
| |
| |
| |
| |
| |
+------------+</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="OTHERSTUFF" id="OTHERSTUFF">9.4. The
other stuff in the example</a></h3>
<p>You can also see in the above examples, that I have used the
variables COLS, LINES which are initialized to the screen sizes
after initscr(). They can be useful in finding screen dimensions
and finding the center co-ordinate of the screen as above. The
function <var class="LITERAL">getch()</var> as usual gets the key
from keyboard and according to the key it does the corresponding
work. This type of switch- case is very common in any GUI based
programs.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="OTHERBORDERFUNCS" id=
"OTHERBORDERFUNCS">9.5. Other Border functions</a></h3>
<p>Above program is grossly inefficient in that with each press of
a key, a window is destroyed and another is created. So let's write
a more efficient program which uses other border related
functions.</p>
<p>The following program uses <var class="LITERAL">mvhline()</var>
and <var class="LITERAL">mvvline()</var> to achieve similar effect.
These two functions are simple. They create a horizontal or
vertical line of the specified length at the specified
position.</p>
<div class="EXAMPLE"><a name="BOTBO" id="BOTBO"></a>
<p><b>Example 8. More border functions</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
typedef struct _win_border_struct {
chtype ls, rs, ts, bs,
tl, tr, bl, br;
}WIN_BORDER;
typedef struct _WIN_struct {
int startx, starty;
int height, width;
WIN_BORDER border;
}WIN;
void init_win_params(WIN *p_win);
void print_win_params(WIN *p_win);
void create_box(WIN *win, bool flag);
int main(int argc, char *argv[])
{ WIN win;
int ch;
initscr(); /* Start curses mode */
start_color(); /* Start the color functionality */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
noecho();
init_pair(1, COLOR_CYAN, COLOR_BLACK);
/* Initialize the window parameters */
init_win_params(&amp;win);
print_win_params(&amp;win);
attron(COLOR_PAIR(1));
printw("Press F1 to exit");
refresh();
attroff(COLOR_PAIR(1));
create_box(&amp;win, TRUE);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
create_box(&amp;win, FALSE);
--win.startx;
create_box(&amp;win, TRUE);
break;
case KEY_RIGHT:
create_box(&amp;win, FALSE);
++win.startx;
create_box(&amp;win, TRUE);
break;
case KEY_UP:
create_box(&amp;win, FALSE);
--win.starty;
create_box(&amp;win, TRUE);
break;
case KEY_DOWN:
create_box(&amp;win, FALSE);
++win.starty;
create_box(&amp;win, TRUE);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
void init_win_params(WIN *p_win)
{
p_win-&gt;height = 3;
p_win-&gt;width = 10;
p_win-&gt;starty = (LINES - p_win-&gt;height)/2;
p_win-&gt;startx = (COLS - p_win-&gt;width)/2;
p_win-&gt;border.ls = '|';
p_win-&gt;border.rs = '|';
p_win-&gt;border.ts = '-';
p_win-&gt;border.bs = '-';
p_win-&gt;border.tl = '+';
p_win-&gt;border.tr = '+';
p_win-&gt;border.bl = '+';
p_win-&gt;border.br = '+';
}
void print_win_params(WIN *p_win)
{
#ifdef _DEBUG
mvprintw(25, 0, "%d %d %d %d", p_win-&gt;startx, p_win-&gt;starty,
p_win-&gt;width, p_win-&gt;height);
refresh();
#endif
}
void create_box(WIN *p_win, bool flag)
{ int i, j;
int x, y, w, h;
x = p_win-&gt;startx;
y = p_win-&gt;starty;
w = p_win-&gt;width;
h = p_win-&gt;height;
if(flag == TRUE)
{ mvaddch(y, x, p_win-&gt;border.tl);
mvaddch(y, x + w, p_win-&gt;border.tr);
mvaddch(y + h, x, p_win-&gt;border.bl);
mvaddch(y + h, x + w, p_win-&gt;border.br);
mvhline(y, x + 1, p_win-&gt;border.ts, w - 1);
mvhline(y + h, x + 1, p_win-&gt;border.bs, w - 1);
mvvline(y + 1, x, p_win-&gt;border.ls, h - 1);
mvvline(y + 1, x + w, p_win-&gt;border.rs, h - 1);
}
else
for(j = y; j &lt;= y + h; ++j)
for(i = x; i &lt;= x + w; ++i)
mvaddch(j, i, ' ');
refresh();
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="COLOR" id="COLOR">10. Colors</a></h2>
<div class="SECT2">
<h3 class="SECT2"><a name="COLORBASICS" id="COLORBASICS">10.1. The
basics</a></h3>
<p>Life seems dull with no colors. Curses has a nice mechanism to
handle colors. Let's get into the thick of the things with a small
program.</p>
<div class="EXAMPLE"><a name="BSICO" id="BSICO"></a>
<p><b>Example 9. A Simple Color example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string);
int main(int argc, char *argv[])
{ initscr(); /* Start curses mode */
if(has_colors() == FALSE)
{ endwin();
printf("Your terminal does not support color\n");
exit(1);
}
start_color(); /* Start color */
init_pair(1, COLOR_RED, COLOR_BLACK);
attron(COLOR_PAIR(1));
print_in_middle(stdscr, LINES / 2, 0, 0, "Viola !!! In color ...");
attroff(COLOR_PAIR(1));
getch();
endwin();
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
mvwprintw(win, y, x, "%s", string);
refresh();
}
</span></font>
</pre></td>
</tr>
</table>
</div>
<p>As you can see, to start using color, you should first call the
function <var class="LITERAL">start_color()</var>. After that, you
can use color capabilities of your terminals using various
functions. To find out whether a terminal has color capabilities or
not, you can use <var class="LITERAL">has_colors()</var> function,
which returns FALSE if the terminal does not support color.</p>
<p>Curses initializes all the colors supported by terminal when
start_color() is called. These can be accessed by the define
constants like <var class="LITERAL">COLOR_BLACK</var> etc. Now to
actually start using colors, you have to define pairs. Colors are
always used in pairs. That means you have to use the function
<var class="LITERAL">init_pair()</var> to define the foreground and
background for the pair number you give. After that that pair
number can be used as a normal attribute with <var class=
"LITERAL">COLOR_PAIR()</var>function. This may seem to be
cumbersome at first. But this elegant solution allows us to manage
color pairs very easily. To appreciate it, you have to look into
the the source code of "dialog", a utility for displaying dialog
boxes from shell scripts. The developers have defined foreground
and background combinations for all the colors they might need and
initialized at the beginning. This makes it very easy to set
attributes just by accessing a pair which we already have defined
as a constant.</p>
<p>The following colors are defined in <var class=
"LITERAL">curses.h</var>. You can use these as parameters for
various color functions.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> COLOR_BLACK 0
COLOR_RED 1
COLOR_GREEN 2
COLOR_YELLOW 3
COLOR_BLUE 4
COLOR_MAGENTA 5
COLOR_CYAN 6
COLOR_WHITE 7</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CHANGECOLORDEFS" id=
"CHANGECOLORDEFS">10.2. Changing Color Definitions</a></h3>
<p>The function <var class="LITERAL">init_color()</var>can be used
to change the rgb values for the colors defined by curses
initially. Say you wanted to lighten the intensity of red color by
a minuscule. Then you can use this function as</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> init_color(COLOR_RED, 700, 0, 0);
/* param 1 : color name
* param 2, 3, 4 : rgb content min = 0, max = 1000 */</font>
</pre></td>
</tr>
</table>
<p>If your terminal cannot change the color definitions, the
function returns ERR. The function <var class=
"LITERAL">can_change_color()</var> can be used to find out whether
the terminal has the capability of changing color content or not.
The rgb content is scaled from 0 to 1000. Initially RED color is
defined with content 1000(r), 0(g), 0(b).</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COLORCONTENT" id="COLORCONTENT">10.3.
Color Content</a></h3>
<p>The functions <var class="LITERAL">color_content()</var> and
<var class="LITERAL">pair_content()</var> can be used to find the
color content and foreground, background combination for the
pair.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="KEYS" id="KEYS">11. Interfacing with the
key board</a></h2>
<div class="SECT2">
<h3 class="SECT2"><a name="KEYSBASICS" id="KEYSBASICS">11.1. The
Basics</a></h3>
<p>No GUI is complete without a strong user interface and to
interact with the user, a curses program should be sensitive to key
presses or the mouse actions done by the user. Let's deal with the
keys first.</p>
<p>As you have seen in almost all of the above examples, it's very
easy to get key input from the user. A simple way of getting key
presses is to use <var class="LITERAL">getch()</var> function. The
cbreak mode should be enabled to read keys when you are interested
in reading individual key hits rather than complete lines of text
(which usually end with a carriage return). keypad should be
enabled to get the Functions keys, arrow keys etc. See the
initialization section for details.</p>
<p><var class="LITERAL">getch()</var> returns an integer
corresponding to the key pressed. If it is a normal character, the
integer value will be equivalent to the character. Otherwise it
returns a number which can be matched with the constants defined in
<var class="LITERAL">curses.h</var>. For example if the user
presses F1, the integer returned is 265. This can be checked using
the macro KEY_F() defined in curses.h. This makes reading keys
portable and easy to manage.</p>
<p>For example, if you call getch() like this</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> int ch;
ch = getch();</font>
</pre></td>
</tr>
</table>
<p>getch() will wait for the user to press a key, (unless you
specified a timeout) and when user presses a key, the corresponding
integer is returned. Then you can check the value returned with the
constants defined in curses.h to match against the keys you
want.</p>
<p>The following code piece will do that job.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> if(ch == KEY_LEFT)
printw("Left arrow is pressed\n");</font>
</pre></td>
</tr>
</table>
<p>Let's write a small program which creates a menu which can be
navigated by up and down arrows.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SIMPLEKEYEX" id="SIMPLEKEYEX">11.2. A
Simple Key Usage example</a></h3>
<div class="EXAMPLE"><a name="BSIKE" id="BSIKE"></a>
<p><b>Example 10. A Simple Key Usage example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;stdio.h&gt;
#include &lt;ncurses.h&gt;
#define WIDTH 30
#define HEIGHT 10
int startx = 0;
int starty = 0;
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int n_choices = sizeof(choices) / sizeof(char *);
void print_menu(WINDOW *menu_win, int highlight);
int main()
{ WINDOW *menu_win;
int highlight = 1;
int choice = 0;
int c;
initscr();
clear();
noecho();
cbreak(); /* Line buffering disabled. pass on everything */
startx = (80 - WIDTH) / 2;
starty = (24 - HEIGHT) / 2;
menu_win = newwin(HEIGHT, WIDTH, starty, startx);
keypad(menu_win, TRUE);
mvprintw(0, 0, "Use arrow keys to go up and down, Press enter to select a choice");
refresh();
print_menu(menu_win, highlight);
while(1)
{ c = wgetch(menu_win);
switch(c)
{ case KEY_UP:
if(highlight == 1)
highlight = n_choices;
else
--highlight;
break;
case KEY_DOWN:
if(highlight == n_choices)
highlight = 1;
else
++highlight;
break;
case 10:
choice = highlight;
break;
default:
mvprintw(24, 0, "Charcter pressed is = %3d Hopefully it can be printed as '%c'", c, c);
refresh();
break;
}
print_menu(menu_win, highlight);
if(choice != 0) /* User did a choice come out of the infinite loop */
break;
}
mvprintw(23, 0, "You chose choice %d with choice string %s\n", choice, choices[choice - 1]);
clrtoeol();
refresh();
endwin();
return 0;
}
void print_menu(WINDOW *menu_win, int highlight)
{
int x, y, i;
x = 2;
y = 2;
box(menu_win, 0, 0);
for(i = 0; i &lt; n_choices; ++i)
{ if(highlight == i + 1) /* High light the present choice */
{ wattron(menu_win, A_REVERSE);
mvwprintw(menu_win, y, x, "%s", choices[i]);
wattroff(menu_win, A_REVERSE);
}
else
mvwprintw(menu_win, y, x, "%s", choices[i]);
++y;
}
wrefresh(menu_win);
}
</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="MOUSE" id="MOUSE">12. Interfacing with
the mouse</a></h2>
<p>Now that you have seen how to get keys, lets do the same thing
from mouse. Usually each UI allows the user to interact with both
keyboard and mouse.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MOUSEBASICS" id="MOUSEBASICS">12.1. The
Basics</a></h3>
<p>Before you do any thing else, the events you want to receive
have to be enabled with <var class="LITERAL">mousemask()</var>.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color=
"#000000"> mousemask( mmask_t newmask, /* The events you want to listen to */
mmask_t *oldmask) /* The old events mask */</font>
</pre></td>
</tr>
</table>
<p>The first parameter to above function is a bit mask of events
you would like to listen. By default, all the events are turned
off. The bit mask <var class="LITERAL">ALL_MOUSE_EVENTS</var> can
be used to get all the events.</p>
<p>The following are all the event masks:</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> Name Description
---------------------------------------------------------------------
BUTTON1_PRESSED mouse button 1 down
BUTTON1_RELEASED mouse button 1 up
BUTTON1_CLICKED mouse button 1 clicked
BUTTON1_DOUBLE_CLICKED mouse button 1 double clicked
BUTTON1_TRIPLE_CLICKED mouse button 1 triple clicked
BUTTON2_PRESSED mouse button 2 down
BUTTON2_RELEASED mouse button 2 up
BUTTON2_CLICKED mouse button 2 clicked
BUTTON2_DOUBLE_CLICKED mouse button 2 double clicked
BUTTON2_TRIPLE_CLICKED mouse button 2 triple clicked
BUTTON3_PRESSED mouse button 3 down
BUTTON3_RELEASED mouse button 3 up
BUTTON3_CLICKED mouse button 3 clicked
BUTTON3_DOUBLE_CLICKED mouse button 3 double clicked
BUTTON3_TRIPLE_CLICKED mouse button 3 triple clicked
BUTTON4_PRESSED mouse button 4 down
BUTTON4_RELEASED mouse button 4 up
BUTTON4_CLICKED mouse button 4 clicked
BUTTON4_DOUBLE_CLICKED mouse button 4 double clicked
BUTTON4_TRIPLE_CLICKED mouse button 4 triple clicked
BUTTON_SHIFT shift was down during button state change
BUTTON_CTRL control was down during button state change
BUTTON_ALT alt was down during button state change
ALL_MOUSE_EVENTS report all button state changes
REPORT_MOUSE_POSITION report mouse movement</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETTINGEVENTS" id="GETTINGEVENTS">12.2.
Getting the events</a></h3>
<p>Once a class of mouse events have been enabled, getch() class of
functions return KEY_MOUSE every time some mouse event happens.
Then the mouse event can be retrieved with <var class=
"LITERAL">getmouse()</var>.</p>
<p>The code approximately looks like this:</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> MEVENT event;
ch = getch();
if(ch == KEY_MOUSE)
if(getmouse(&amp;event) == OK)
. /* Do some thing with the event */
.
.</font>
</pre></td>
</tr>
</table>
<p>getmouse() returns the event into the pointer given to it. It's
a structure which contains</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> typedef struct
{
short id; /* ID to distinguish multiple devices */
int x, y, z; /* event coordinates */
mmask_t bstate; /* button state bits */
} </font>
</pre></td>
</tr>
</table>
<p>The <var class="LITERAL">bstate</var> is the main variable we
are interested in. It tells the button state of the mouse.</p>
<p>Then with a code snippet like the following, we can find out
what happened.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> if(event.bstate &amp; BUTTON1_PRESSED)
printw("Left Button Pressed");</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MOUSETOGETHER" id="MOUSETOGETHER">12.3.
Putting it all Together</a></h3>
<p>That's pretty much interfacing with mouse. Let's create the same
menu and enable mouse interaction. To make things simpler, key
handling is removed.</p>
<div class="EXAMPLE"><a name="BMOME" id="BMOME"></a>
<p><b>Example 11. Access the menu with mouse !!!</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
#define WIDTH 30
#define HEIGHT 10
int startx = 0;
int starty = 0;
char *choices[] = { "Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int n_choices = sizeof(choices) / sizeof(char *);
void print_menu(WINDOW *menu_win, int highlight);
void report_choice(int mouse_x, int mouse_y, int *p_choice);
int main()
{ int c, choice = 0;
WINDOW *menu_win;
MEVENT event;
/* Initialize curses */
initscr();
clear();
noecho();
cbreak(); //Line buffering disabled. pass on everything
/* Try to put the window in the middle of screen */
startx = (80 - WIDTH) / 2;
starty = (24 - HEIGHT) / 2;
attron(A_REVERSE);
mvprintw(23, 1, "Click on Exit to quit (Works best in a virtual console)");
refresh();
attroff(A_REVERSE);
/* Print the menu for the first time */
menu_win = newwin(HEIGHT, WIDTH, starty, startx);
print_menu(menu_win, 1);
/* Get all the mouse events */
mousemask(ALL_MOUSE_EVENTS, NULL);
while(1)
{ c = wgetch(menu_win);
switch(c)
{ case KEY_MOUSE:
if(getmouse(&amp;event) == OK)
{ /* When the user clicks left mouse button */
if(event.bstate &amp; BUTTON1_PRESSED)
{ report_choice(event.x + 1, event.y + 1, &amp;choice);
if(choice == -1) //Exit chosen
goto end;
mvprintw(22, 1, "Choice made is : %d String Chosen is \"%10s\"", choice, choices[choice - 1]);
refresh();
}
}
print_menu(menu_win, choice);
break;
}
}
end:
endwin();
return 0;
}
void print_menu(WINDOW *menu_win, int highlight)
{
int x, y, i;
x = 2;
y = 2;
box(menu_win, 0, 0);
for(i = 0; i &lt; n_choices; ++i)
{ if(highlight == i + 1)
{ wattron(menu_win, A_REVERSE);
mvwprintw(menu_win, y, x, "%s", choices[i]);
wattroff(menu_win, A_REVERSE);
}
else
mvwprintw(menu_win, y, x, "%s", choices[i]);
++y;
}
wrefresh(menu_win);
}
/* Report the choice according to mouse position */
void report_choice(int mouse_x, int mouse_y, int *p_choice)
{ int i,j, choice;
i = startx + 2;
j = starty + 3;
for(choice = 0; choice &lt; n_choices; ++choice)
if(mouse_y == j + choice &amp;&amp; mouse_x &gt;= i &amp;&amp; mouse_x &lt;= i + strlen(choices[choice]))
{ if(choice == n_choices - 1)
*p_choice = -1;
else
*p_choice = choice + 1;
break;
}
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="MISCMOUSEFUNCS" id=
"MISCMOUSEFUNCS">12.4. Miscellaneous Functions</a></h3>
<p>The functions mouse_trafo() and wmouse_trafo() can be used to
convert to mouse co-ordinates to screen relative co-ordinates. See
curs_mouse(3X) man page for details.</p>
<p>The mouseinterval function sets the maximum time (in thousands
of a second) that can elapse between press and release events in
order for them to be recognized as a click. This function returns
the previous interval value. The default is one fifth of a
second.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="SCREEN" id="SCREEN">13. Screen
Manipulation</a></h2>
<p>In this section, we will look into some functions, which allow
us to manage the screen efficiently and to write some fancy
programs. This is especially important in writing games.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="GETYX" id="GETYX">13.1. getyx()
functions</a></h3>
<p>The function <var class="LITERAL">getyx()</var> can be used to
find out the present cursor co-ordinates. It will fill the values
of x and y co-ordinates in the arguments given to it. Since getyx()
is a macro you don't have to pass the address of the variables. It
can be called as</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> getyx(win, y, x);
/* win: window pointer
* y, x: y, x co-ordinates will be put into this variables
*/</font>
</pre></td>
</tr>
</table>
<p>The function getparyx() gets the beginning co-ordinates of the
sub window relative to the main window. This is some times useful
to update a sub window. When designing fancy stuff like writing
multiple menus, it becomes difficult to store the menu positions,
their first option co-ordinates etc. A simple solution to this
problem, is to create menus in sub windows and later find the
starting co-ordinates of the menus by using getparyx().</p>
<p>The functions getbegyx() and getmaxyx() store current window's
beginning and maximum co-ordinates. These functions are useful in
the same way as above in managing the windows and sub windows
effectively.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="SCREENDUMP" id="SCREENDUMP">13.2. Screen
Dumping</a></h3>
<p>While writing games, some times it becomes necessary to store
the state of the screen and restore it back to the same state. The
function scr_dump() can be used to dump the screen contents to a
file given as an argument. Later it can be restored by scr_restore
function. These two simple functions can be used effectively to
maintain a fast moving game with changing scenarios.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="WINDOWDUMP" id="WINDOWDUMP">13.3. Window
Dumping</a></h3>
<p>To store and restore windows, the functions <var class=
"LITERAL">putwin()</var> and <var class="LITERAL">getwin()</var>
can be used. <var class="LITERAL">putwin()</var> puts the present
window state into a file, which can be later restored by
<var class="LITERAL">getwin()</var>.</p>
<p>The function <var class="LITERAL">copywin()</var> can be used to
copy a window completely onto another window. It takes the source
and destination windows as parameters and according to the
rectangle specified, it copies the rectangular region from source
to destination window. It's last parameter specifies whether to
overwrite or just overlay the contents on to the destination
window. If this argument is true, then the copying is
non-destructive.</p>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="MISC" id="MISC">14. Miscellaneous
features</a></h2>
<p>Now you know enough features to write a good curses program,
with all bells and whistles. There are some miscellaneous functions
which are useful in various cases. Let's go headlong into some of
those.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="CURSSET" id="CURSSET">14.1.
curs_set()</a></h3>
<p>This function can be used to make the cursor invisible. The
parameter to this function should be</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> 0 : invisible or
1 : normal or
2 : very visible.</font>
</pre></td>
</tr>
</table>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="TEMPLEAVE" id="TEMPLEAVE">14.2.
Temporarily Leaving Curses mode</a></h3>
<p>Some times you may want to get back to cooked mode (normal line
buffering mode) temporarily. In such a case you will first need to
save the tty modes with a call to <var class=
"LITERAL">def_prog_mode()</var> and then call <var class=
"LITERAL">endwin()</var> to end the curses mode. This will leave
you in the original tty mode. To get back to curses once you are
done, call <var class="LITERAL">reset_prog_mode()</var> . This
function returns the tty to the state stored by <var class=
"LITERAL">def_prog_mode()</var>. Then do refresh(), and you are
back to the curses mode. Here is an example showing the sequence of
things to be done.</p>
<div class="EXAMPLE"><a name="BTELE" id="BTELE"></a>
<p><b>Example 12. Temporarily Leaving Curses Mode</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!\n"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
def_prog_mode(); /* Save the tty modes */
endwin(); /* End curses mode temporarily */
system("/bin/sh"); /* Do whatever you like in cooked mode */
reset_prog_mode(); /* Return to the previous tty mode*/
/* stored by def_prog_mode() */
refresh(); /* Do refresh() to restore the */
/* Screen contents */
printw("Another String\n"); /* Back to curses use the full */
refresh(); /* capabilities of curses */
endwin(); /* End curses mode */
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="ACSVARS" id="ACSVARS">14.3. ACS_
variables</a></h3>
<p>If you have ever programmed in DOS, you know about those nifty
characters in extended character set. They are printable only on
some terminals. NCURSES functions like <var class=
"LITERAL">box()</var> use these characters. All these variables
start with ACS meaning alternative character set. You might have
noticed me using these characters in some of the programs above.
Here's an example showing all the characters.</p>
<div class="EXAMPLE"><a name="BACSVARS" id="BACSVARS"></a>
<p><b>Example 13. ACS Variables Example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;ncurses.h&gt;
int main()
{
initscr();
printw("Upper left corner "); addch(ACS_ULCORNER); printw("\n");
printw("Lower left corner "); addch(ACS_LLCORNER); printw("\n");
printw("Lower right corner "); addch(ACS_LRCORNER); printw("\n");
printw("Tee pointing right "); addch(ACS_LTEE); printw("\n");
printw("Tee pointing left "); addch(ACS_RTEE); printw("\n");
printw("Tee pointing up "); addch(ACS_BTEE); printw("\n");
printw("Tee pointing down "); addch(ACS_TTEE); printw("\n");
printw("Horizontal line "); addch(ACS_HLINE); printw("\n");
printw("Vertical line "); addch(ACS_VLINE); printw("\n");
printw("Large Plus or cross over "); addch(ACS_PLUS); printw("\n");
printw("Scan Line 1 "); addch(ACS_S1); printw("\n");
printw("Scan Line 3 "); addch(ACS_S3); printw("\n");
printw("Scan Line 7 "); addch(ACS_S7); printw("\n");
printw("Scan Line 9 "); addch(ACS_S9); printw("\n");
printw("Diamond "); addch(ACS_DIAMOND); printw("\n");
printw("Checker board (stipple) "); addch(ACS_CKBOARD); printw("\n");
printw("Degree Symbol "); addch(ACS_DEGREE); printw("\n");
printw("Plus/Minus Symbol "); addch(ACS_PLMINUS); printw("\n");
printw("Bullet "); addch(ACS_BULLET); printw("\n");
printw("Arrow Pointing Left "); addch(ACS_LARROW); printw("\n");
printw("Arrow Pointing Right "); addch(ACS_RARROW); printw("\n");
printw("Arrow Pointing Down "); addch(ACS_DARROW); printw("\n");
printw("Arrow Pointing Up "); addch(ACS_UARROW); printw("\n");
printw("Board of squares "); addch(ACS_BOARD); printw("\n");
printw("Lantern Symbol "); addch(ACS_LANTERN); printw("\n");
printw("Solid Square Block "); addch(ACS_BLOCK); printw("\n");
printw("Less/Equal sign "); addch(ACS_LEQUAL); printw("\n");
printw("Greater/Equal sign "); addch(ACS_GEQUAL); printw("\n");
printw("Pi "); addch(ACS_PI); printw("\n");
printw("Not equal "); addch(ACS_NEQUAL); printw("\n");
printw("UK pound sign "); addch(ACS_STERLING); printw("\n");
refresh();
getch();
endwin();
return 0;
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="OTHERLIB" id="OTHERLIB">15. Other
libraries</a></h2>
<p>Apart from the curses library, there are few text mode
libraries, which provide more functionality and a lot of features.
The following sections explain three standard libraries which are
usually distributed along with curses.</p>
</div>
<div class="SECT1">
<hr>
<h2 class="SECT1"><a name="PANELS" id="PANELS">16. Panel
Library</a></h2>
<p>Now that you are proficient in curses, you wanted to do some
thing big. You created a lot of overlapping windows to give a
professional windows-type look. Unfortunately, it soon becomes
difficult to manage these. The multiple refreshes, updates plunge
you into a nightmare. The overlapping windows create blotches,
whenever you forget to refresh the windows in the proper order.</p>
<p>Don't despair. There's an elegant solution provided in panels
library. In the words of developers of ncurses</p>
<p><em>When your interface design is such that windows may dive
deeper into the visibility stack or pop to the top at runtime, the
resulting book-keeping can be tedious and difficult to get right.
Hence the panels library.</em></p>
<p>If you have lot of overlapping windows, then panels library is
the way to go. It obviates the need of doing series of
wnoutrefresh(), doupdate() and relieves the burden of doing it
correctly(bottom up). The library maintains information about the
order of windows, their overlapping and update the screen properly.
So why wait? Let's take a close peek into panels.</p>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELBASICS" id="PANELBASICS">16.1. The
Basics</a></h3>
<p>Panel object is a window that is implicitly treated as part of a
deck including all other panel objects. The deck is treated as a
stack with the top panel being completely visible and the other
panels may or may not be obscured according to their positions. So
the basic idea is to create a stack of overlapping panels and use
panels library to display them correctly. There is a function
similar to refresh() which, when called , displays panels in the
correct order. Functions are provided to hide or show panels, move
panels, change its size etc.. The overlapping problem is managed by
the panels library during all the calls to these functions.</p>
<p>The general flow of a panel program goes like this:</p>
<ol type="1">
<li>
<p>Create the windows (with newwin()) to be attached to the
panels.</p>
</li>
<li>
<p>Create panels with the chosen visibility order. Stack them up
according to the desired visibility. The function new_panel() is
used to created panels.</p>
</li>
<li>
<p>Call update_panels() to write the panels to the virtual screen
in correct visibility order. Do a doupdate() to show it on the
screen.</p>
</li>
<li>
<p>Mainpulate the panels with show_panel(), hide_panel(),
move_panel() etc. Make use of helper functions like panel_hidden()
and panel_window(). Make use of user pointer to store custom data
for a panel. Use the functions set_panel_userptr() and
panel_userptr() to set and get the user pointer for a panel.</p>
</li>
<li>
<p>When you are done with the panel use del_panel() to delete the
panel.</p>
</li>
</ol>
<p>Let's make the concepts clear, with some programs. The following
is a simple program which creates 3 overlapping panels and shows
them on the screen.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="COMPILEPANELS" id="COMPILEPANELS">16.2.
Compiling With the Panels Library</a></h3>
<p>To use panels library functions, you have to include panel.h and
to link the program with panels library the flag -lpanel should be
added along with -lncurses in that order.</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"> #include &lt;panel.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lpanel -lncurses</font>
</pre></td>
</tr>
</table>
<div class="EXAMPLE"><a name="PPASI" id="PPASI"></a>
<p><b>Example 14. Panel basics</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
int lines = 10, cols = 40, y = 2, x = 4, i;
initscr();
cbreak();
noecho();
/* Create windows for the panels */
my_wins[0] = newwin(lines, cols, y, x);
my_wins[1] = newwin(lines, cols, y + 1, x + 5);
my_wins[2] = newwin(lines, cols, y + 2, x + 10);
/*
* Create borders around the windows so that you can see the effect
* of panels
*/
for(i = 0; i &lt; 3; ++i)
box(my_wins[i], 0, 0);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
doupdate();
getch();
endwin();
}
</span></font>
</pre></td>
</tr>
</table>
</div>
<p>As you can see, above program follows a simple flow as
explained. The windows are created with newwin() and then they are
attached to panels with new_panel(). As we attach one panel after
another, the stack of panels gets updated. To put them on screen
update_panels() and doupdate() are called.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELBROWSING" id="PANELBROWSING">16.3.
Panel Window Browsing</a></h3>
<p>A slightly complicated example is given below. This program
creates 3 windows which can be cycled through using tab. Have a
look at the code.</p>
<div class="EXAMPLE"><a name="PPABR" id="PPABR"></a>
<p><b>Example 15. Panel Window Browsing Example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL *top;
int ch;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Set up the user pointers to the next panel */
set_panel_userptr(my_panels[0], my_panels[1]);
set_panel_userptr(my_panels[1], my_panels[2]);
set_panel_userptr(my_panels[2], my_panels[0]);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
doupdate();
top = my_panels[2];
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 9:
top = (PANEL *)panel_userptr(top);
top_panel(top);
break;
}
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i &lt; n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span></font>
</pre></td>
</tr>
</table>
</div>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="USERPTRUSING" id="USERPTRUSING">16.4.
Using User Pointers</a></h3>
<p>In the above example I used user pointers to find out the next
window in the cycle. We can attach custom information to the panel
by specifying a user pointer, which can point to any information
you want to store. In this case I stored the pointer to the next
panel in the cycle. User pointer for a panel can be set with the
function <var class="LITERAL">set_panel_userptr()</var>. It can be
accessed using the function <var class=
"LITERAL">panel_userptr()</var> which will return the user pointer
for the panel given as argument. After finding the next panel in
the cycle It's brought to the top by the function top_panel(). This
function brings the panel given as argument to the top of the panel
stack.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELMOVERESIZE" id=
"PANELMOVERESIZE">16.5. Moving and Resizing Panels</a></h3>
<p>The function <var class="LITERAL">move_panel()</var> can be used
to move a panel to the desired location. It does not change the
position of the panel in the stack. Make sure that you use
move_panel() instead mvwin() on the window associated with the
panel.</p>
<p>Resizing a panel is slightly complex. There is no straight
forward function just to resize the window associated with a panel.
A solution to resize a panel is to create a new window with the
desired sizes, change the window associated with the panel using
replace_panel(). Don't forget to delete the old window. The window
associated with a panel can be found by using the function
panel_window().</p>
<p>The following program shows these concepts, in supposedly simple
program. You can cycle through the window with &lt;TAB&gt; as
usual. To resize or move the active panel press 'r' for resize 'm'
for moving. Then use arrow keys to resize or move it to the desired
way and press enter to end your resizing or moving. This example
makes use of user data to get the required data to do the
operations.</p>
<div class="EXAMPLE"><a name="PPARE" id="PPARE"></a>
<p><b>Example 16. Panel Moving and Resizing example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
typedef struct _PANEL_DATA {
int x, y, w, h;
char label[80];
int label_color;
PANEL *next;
}PANEL_DATA;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
void set_user_ptrs(PANEL **panels, int n);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL_DATA *top;
PANEL *stack_top;
WINDOW *temp_win, *old_win;
int ch;
int newx, newy, neww, newh;
int size = FALSE, move = FALSE;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
set_user_ptrs(my_panels, 3);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
doupdate();
stack_top = my_panels[2];
top = (PANEL_DATA *)panel_userptr(stack_top);
newx = top-&gt;x;
newy = top-&gt;y;
neww = top-&gt;w;
newh = top-&gt;h;
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 9: /* Tab */
top = (PANEL_DATA *)panel_userptr(stack_top);
top_panel(top-&gt;next);
stack_top = top-&gt;next;
top = (PANEL_DATA *)panel_userptr(stack_top);
newx = top-&gt;x;
newy = top-&gt;y;
neww = top-&gt;w;
newh = top-&gt;h;
break;
case 'r': /* Re-Size*/
size = TRUE;
attron(COLOR_PAIR(4));
mvprintw(LINES - 4, 0, "Entered Resizing :Use Arrow Keys to resize and press &lt;ENTER&gt; to end resizing");
refresh();
attroff(COLOR_PAIR(4));
break;
case 'm': /* Move */
attron(COLOR_PAIR(4));
mvprintw(LINES - 4, 0, "Entered Moving: Use Arrow Keys to Move and press &lt;ENTER&gt; to end moving");
refresh();
attroff(COLOR_PAIR(4));
move = TRUE;
break;
case KEY_LEFT:
if(size == TRUE)
{ --newx;
++neww;
}
if(move == TRUE)
--newx;
break;
case KEY_RIGHT:
if(size == TRUE)
{ ++newx;
--neww;
}
if(move == TRUE)
++newx;
break;
case KEY_UP:
if(size == TRUE)
{ --newy;
++newh;
}
if(move == TRUE)
--newy;
break;
case KEY_DOWN:
if(size == TRUE)
{ ++newy;
--newh;
}
if(move == TRUE)
++newy;
break;
case 10: /* Enter */
move(LINES - 4, 0);
clrtoeol();
refresh();
if(size == TRUE)
{ old_win = panel_window(stack_top);
temp_win = newwin(newh, neww, newy, newx);
replace_panel(stack_top, temp_win);
win_show(temp_win, top-&gt;label, top-&gt;label_color);
delwin(old_win);
size = FALSE;
}
if(move == TRUE)
{ move_panel(stack_top, newy, newx);
move = FALSE;
}
break;
}
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
refresh();
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i &lt; n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Set the PANEL_DATA structures for individual panels */
void set_user_ptrs(PANEL **panels, int n)
{ PANEL_DATA *ptrs;
WINDOW *win;
int x, y, w, h, i;
char temp[80];
ptrs = (PANEL_DATA *)calloc(n, sizeof(PANEL_DATA));
for(i = 0;i &lt; n; ++i)
{ win = panel_window(panels[i]);
getbegyx(win, y, x);
getmaxyx(win, h, w);
ptrs[i].x = x;
ptrs[i].y = y;
ptrs[i].w = w;
ptrs[i].h = h;
sprintf(temp, "Window Number %d", i + 1);
strcpy(ptrs[i].label, temp);
ptrs[i].label_color = i + 1;
if(i + 1 == n)
ptrs[i].next = panels[0];
else
ptrs[i].next = panels[i + 1];
set_panel_userptr(panels[i], &amp;ptrs[i]);
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}</span></font>
</pre></td>
</tr>
</table>
</div>
<p>Concentrate on the main while loop. Once it finds out the type
of key pressed, it takes appropriate action. If 'r' is pressed
resizing mode is started. After this the new sizes are updated as
the user presses the arrow keys. When the user presses
&lt;ENTER&gt; present selection ends and panel is resized by using
the concept explained. While in resizing mode the program doesn't
show how the window is getting resized. It's left as an exercise to
the reader to print a dotted border while it gets resized to a new
position.</p>
<p>When the user presses 'm' the move mode starts. This is a bit
simpler than resizing. As the arrow keys are pressed the new
position is updated and pressing of &lt;ENTER&gt; causes the panel
to be moved by calling the function move_panel().</p>
<p>In this program the user data which is represented as
PANEL_DATA, plays very important role in finding the associated
information with a panel. As written in the comments, the
PANEL_DATA stores the panel sizes, label, label color and a pointer
to the next panel in the cycle.</p>
</div>
<div class="SECT2">
<hr>
<h3 class="SECT2"><a name="PANELSHOWHIDE" id="PANELSHOWHIDE">16.6.
Hiding and Showing Panels</a></h3>
<p>A Panel can be hidden by using the function hide_panel(). This
function merely removes it form the stack of panels, thus hiding it
on the screen once you do update_panels() and doupdate(). It
doesn't destroy the PANEL structure associated with the hidden
panel. It can be shown again by using the show_panel()
function.</p>
<p>The following program shows the hiding of panels. Press 'a' or
'b' or 'c' to show or hide first, second and third windows
respectively. It uses a user data with a small variable hide, which
keeps track of whether the window is hidden or not. For some reason
the function <var class="LITERAL">panel_hidden()</var> which tells
whether a panel is hidden or not is not working. A bug report was
also presented by Michael Andres <a href=
"http://www.geocrawler.com/archives/3/344/1999/9/0/2643549/"
target="_top">here</a></p>
<div class="EXAMPLE"><a name="PPAHI" id="PPAHI"></a>
<p><b>Example 17. Panel Hiding and Showing example</b></p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
<font color="#000000"><span class=
"INLINEMEDIAOBJECT">#include &lt;panel.h&gt;
typedef struct _PANEL_DATA {
int hide; /* TRUE if panel is hidden */
}PANEL_DATA;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL_DATA panel_datas[3];
PANEL_DATA *temp;
int ch;