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<!--Title : NCURSES Programming Howto"
Author : Pradeep Padala
E-Mail : ppadala@gmail.com
Web-Page : http://www.eecs.umich.edu/~ppadala
-->
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook V4.1//EN">
<article id="index">
<articleinfo>
<title> NCURSES Programming HOWTO </title>
<author>
<firstname> Pradeep </firstname>
<surname> Padala </surname>
<affiliation>
<address><email>ppadala@gmail.com</email></address>
</affiliation>
</author>
<revhistory>
<revision>
<revnumber>1.9</revnumber>
<date>2005-06-20</date>
<authorinitials>ppadala</authorinitials>
<revremark>The license has been changed to the MIT-style license used
by NCURSES. Note that the programs are also re-licensed under this.
</revremark>
</revision>
<revision>
<revnumber>1.8</revnumber>
<date>2005-06-17</date>
<authorinitials>ppadala</authorinitials>
<revremark>Lots of updates. Added references and perl examples.
Changes to examples. Many grammatical and stylistic changes to the
content. Changes to NCURSES history.
</revremark>
</revision>
<revision>
<revnumber>1.7.1</revnumber>
<date>2002-06-25</date>
<authorinitials>ppadala</authorinitials>
<revremark>Added a README file for building and instructions
for building from source.
</revremark>
</revision>
<revision>
<revnumber>1.7</revnumber>
<date>2002-06-25</date>
<authorinitials>ppadala</authorinitials>
<revremark>Added "Other formats" section and made a lot of fancy
changes to the programs. Inlining of programs is gone.
</revremark>
</revision>
<revision>
<revnumber>1.6.1</revnumber>
<date>2002-02-24</date>
<authorinitials>ppadala</authorinitials>
<revremark>Removed the old Changelog section, cleaned the makefiles
</revremark>
</revision>
<revision>
<revnumber>1.6</revnumber>
<date>2002-02-16</date>
<authorinitials>ppadala</authorinitials>
<revremark>Corrected a lot of spelling mistakes, added ACS variables
section </revremark>
</revision>
<revision>
<revnumber>1.5</revnumber>
<date>2002-01-05</date>
<authorinitials>ppadala</authorinitials>
<revremark>Changed structure to present proper TOC</revremark>
</revision>
<revision>
<revnumber>1.3.1</revnumber>
<date>2001-07-26</date>
<authorinitials>ppadala</authorinitials>
<revremark>Corrected maintainers paragraph, Corrected stable release number
</revremark>
</revision>
<revision>
<revnumber>1.3</revnumber>
<date>2001-07-24</date>
<authorinitials>ppadala</authorinitials>
<revremark>Added copyright notices to main document (LDP license)
and programs (GPL), Corrected
printw_example.
</revremark>
</revision>
<revision>
<revnumber>1.2</revnumber>
<date>2001-06-05</date>
<authorinitials>ppadala</authorinitials>
<revremark>Incorporated ravi's changes. Mainly to introduction, menu,
form, justforfun sections
</revremark>
</revision>
<revision>
<revnumber>1.1</revnumber>
<date>2001-05-22</date>
<authorinitials>ppadala</authorinitials>
<revremark>Added "a word about window" section, Added scanw_example.
</revremark>
</revision>
</revhistory>
<pubdate>v1.9, 2005-06-20</pubdate>
<abstract>
<para>
<emphasis>
This document is intended to be an "All in One" guide for programming with
ncurses and its sister libraries. We graduate from a simple "Hello World"
program to more complex form manipulation. No prior experience in ncurses is
assumed. Send comments to <ulink url="mailto:ppadala@gmail.com">this address
</ulink>
</emphasis>
</para>
</abstract>
</articleinfo>
<sect1 id="intro"> <title>Introduction</title>
<para>
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 sequences 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.
</para>
<para>
Suppose you wanted to print a line in color. Try typing this on your console.
</para>
<programlisting>
echo "^[[0;31;40mIn Color"
</programlisting>
<para>
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.
</para>
<programlisting>
echo "^[[0;37;40m"
</programlisting>
<para>
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 <literal remap="tt">termcap</literal>. 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 <literal remap="tt">terminfo</literal>. 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.
</para>
<sect2 id="whatis"> <title> What is NCURSES? </title>
<para>
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.
</para>
<para>
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.
</para>
<para>
A detailed history of NCURSES can be found in the NEWS file from the source
distribution. The current package is maintained by
<ulink url="mailto:dickey@his.com">Thomas Dickey</ulink>.
You can contact the maintainers at <ulink url="mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</ulink>.
</para>
</sect2>
<sect2 id="whatcanwedo"> <title>What we can do with NCURSES</title>
<para>
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.
</para>
<para>
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.
</para>
<para>
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.
</para>
</sect2>
<sect2 id="wheretogetit"><title>Where to get it</title>
<para>
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.
</para>
<para><emphasis>Compiling the package</emphasis> </para>
<para>
NCURSES can be obtained from <ulink url=
"ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz">
ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz</ulink> or any of the ftp
sites mentioned in <ulink url="http://www.gnu.org/order/ftp.html">
http://www.gnu.org/order/ftp.html</ulink>.
</para>
<para>
Read the README and INSTALL files for details on to how to install it. It
usually involves the following operations.
</para>
<programlisting>
tar zxvf ncurses&lt;version&gt;.tar.gz # unzip and untar the archive
cd ncurses&lt;version&gt; # cd to the directory
./configure # configure the build according to your
# environment
make # make it
su root # become root
make install # install it
</programlisting>
<para><emphasis>Using the RPM </emphasis></para>
<para>
NCURSES RPM can be found and downloaded from <ulink url="http://rpmfind.net">
http://rpmfind.net </ulink>. The RPM can be installed with the following
command after becoming root.
</para>
<programlisting>
rpm -i &lt;downloaded rpm&gt;
</programlisting>
</sect2>
<sect2 id="purpose"><title>Purpose/Scope of the document</title>
<para>
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.
</para>
</sect2>
<sect2 id="aboutprograms"><title>About the Programs</title>
<para>
All the programs in the document are available in zipped form
<ulink url="http://www.tldp.org/HOWTO/NCURSES-Programming-HOWTO/resources/ncurses_programs.tar.gz">
here</ulink>. Unzip and untar it. The directory structure looks like this.
</para>
<programlisting>
ncurses
|
|----&gt; JustForFun -- just for fun programs
|----&gt; basics -- basic programs
|----&gt; demo -- output files go into this directory after make
| |
| |----&gt; exe -- exe files of all example programs
|----&gt; forms -- programs related to form library
|----&gt; menus -- programs related to menus library
|----&gt; panels -- programs related to panels library
|----&gt; perl -- perl equivalents of the examples (contributed
| by Anuradha Ratnaweera)
|----&gt; Makefile -- the top level Makefile
|----&gt; README -- the top level README file. contains instructions
|----&gt; COPYING -- copyright notice
</programlisting>
<para>
The individual directories contain the following files.
</para>
<programlisting>
Description of files in each directory
--------------------------------------
JustForFun
|
|----&gt; hanoi.c -- The Towers of Hanoi Solver
|----&gt; life.c -- The Game of Life demo
|----&gt; magic.c -- An Odd Order Magic Square builder
|----&gt; queens.c -- The famous N-Queens Solver
|----&gt; shuffle.c -- A fun game, if you have time to kill
|----&gt; tt.c -- A very trivial typing tutor
basics
|
|----&gt; acs_vars.c -- ACS_ variables example
|----&gt; hello_world.c -- Simple "Hello World" Program
|----&gt; init_func_example.c -- Initialization functions example
|----&gt; key_code.c -- Shows the scan code of the key pressed
|----&gt; mouse_menu.c -- A menu accessible by mouse
|----&gt; other_border.c -- Shows usage of other border functions apa
| -- rt from box()
|----&gt; printw_example.c -- A very simple printw() example
|----&gt; scanw_example.c -- A very simple getstr() example
|----&gt; simple_attr.c -- A program that can print a c file with
| -- comments in attribute
|----&gt; simple_color.c -- A simple example demonstrating colors
|----&gt; simple_key.c -- A menu accessible with keyboard UP, DOWN
| -- arrows
|----&gt; temp_leave.c -- Demonstrates temporarily leaving curses mode
|----&gt; win_border.c -- Shows Creation of windows and borders
|----&gt; with_chgat.c -- chgat() usage example
forms
|
|----&gt; form_attrib.c -- Usage of field attributes
|----&gt; form_options.c -- Usage of field options
|----&gt; form_simple.c -- A simple form example
|----&gt; form_win.c -- Demo of windows associated with forms
menus
|
|----&gt; menu_attrib.c -- Usage of menu attributes
|----&gt; menu_item_data.c -- Usage of item_name() etc.. functions
|----&gt; menu_multi_column.c -- Creates multi columnar menus
|----&gt; menu_scroll.c -- Demonstrates scrolling capability of menus
|----&gt; menu_simple.c -- A simple menu accessed by arrow keys
|----&gt; menu_toggle.c -- Creates multi valued menus and explains
| -- REQ_TOGGLE_ITEM
|----&gt; menu_userptr.c -- Usage of user pointer
|----&gt; menu_win.c -- Demo of windows associated with menus
panels
|
|----&gt; panel_browse.c -- Panel browsing through tab. Usage of user
| -- pointer
|----&gt; panel_hide.c -- Hiding and Un hiding of panels
|----&gt; panel_resize.c -- Moving and resizing of panels
|----&gt; panel_simple.c -- A simple panel example
perl
|----&gt; 01-10.pl -- Perl equivalents of first ten example programs
</programlisting>
<para>
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.
</para>
<para>
For every example, I have included path name for the file relative to the
examples directory.
</para>
<simpara> If you prefer browsing individual programs, point your browser to
<ulink
url="http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/resources/ncurses_programs/">
http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/resources/ncurses_programs/
</ulink></simpara>
<para>
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.
</para>
</sect2>
<sect2 id="otherformats"><title>Other Formats of the document </title>
<para>
This howto is also availabe in various other formats on the tldp.org site.
Here are the links to other formats of this document.
</para>
<sect3 id="listformats"><title>Readily available formats from tldp.org</title>
<itemizedlist>
<listitem>
<para>
<ulink url="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/pdf/NCURSES-Programming-HOWTO.pdf">Acrobat PDF Format</ulink>
</para>
</listitem>
<listitem>
<para>
<ulink url="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/ps/NCURSES-Programming-HOWTO.ps.gz">PostScript Format</ulink>
</para>
</listitem>
<listitem>
<para>
<ulink url="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html/NCURSES-Programming-HOWTO-html.tar.gz">In Multiple HTML pages</ulink>
</para>
</listitem>
<listitem>
<para>
<ulink url="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/NCURSES-Programming-HOWTO.html">In One big HTML format</ulink>
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3 id="buildsource"><title> Building from source </title>
<para>
If above links are broken or if you want to experiment with sgml read on.
<programlisting>
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/resources/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
</programlisting>
</para>
<para>
See <ulink url="http://www.tldp.org/LDP/LDP-Author-Guide/">
LDP Author guide</ulink> for more details. If all else failes, mail me at
<ulink url= "ppadala@gmail.com">ppadala@gmail.com</ulink>
</para>
</sect3>
</sect2>
<sect2 id="credits"><title>Credits </title>
<para>
I thank <ulink url="mailto:sharath_1@usa.net">Sharath</ulink> 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.
</para>
<para>
Perl equivalents of the example programs are contributed by <ulink
url="mailto:Aratnaweera@virtusa.com">Anuradha Ratnaweera</ulink>.
</para>
<para>
Then comes <ulink url="mailto:parimi@ece.arizona.edu">Ravi Parimi</ulink>, 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.
</para>
</sect2>
<sect2 id="wishlist"><title>Wish List</title>
<para>
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 <ulink url="mailto:ppadala@gmail.com">me
</ulink>.
</para>
<itemizedlist>
<listitem>
<para>Add examples to last parts of forms section.</para>
</listitem>
<listitem>
<para>
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.
</para>
</listitem>
<listitem>
<para>Add debug info. _tracef, _tracemouse stuff.</para>
</listitem>
<listitem>
<para>Accessing termcap, terminfo using functions provided by ncurses
package.</para>
</listitem>
<listitem><para>Working on two terminals simultaneously.</para></listitem>
<listitem><para>Add more stuff to miscellaneous section.</para></listitem>
</itemizedlist>
</sect2>
<sect2 id="copyright"><title>Copyright</title>
<para>
Copyright &copy; 2001 by Pradeep Padala. </para>
<para>
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:
</para>
<para>
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
</para>
<para>
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.
</para>
<para>
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.
</para>
</sect2>
</sect1>
<sect1 id="helloworld"><title>Hello World !!!</title>
<para>
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.
</para>
<sect2 id="compilecurses"><title> Compiling With the NCURSES Library </title>
<para>
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.
</para>
<programlisting>
#include &lt;ncurses.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lncurses
</programlisting>
<example id="bhw"> <title> The Hello World !!! Program </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/hello_world.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="dissection"><title>Dissection</title>
<para>
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.
</para>
<sect3 id="about-initscr"><title>About initscr()</title>
<para>
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 <literal remap="tt">stdscr</literal>) 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.
</para>
<para>
After this is done, we can do a variety of initializations to customize
our curses settings. These details will be explained <link linkend="init">
later </link>.
</para>
</sect3>
<sect3 id="myst-refresh"><title>The mysterious refresh()</title>
<para>
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.
</para>
<para>
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.
</para>
<para>
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 :-)
</para>
</sect3>
<sect3 id="about-endwin"><title>About endwin()</title>
<para>
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.
</para>
</sect3>
</sect2>
</sect1>
<sect1 id="gory"><title>The Gory Details </title>
<para>
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.
</para>
<simpara>Here we go...</simpara>
</sect1>
<sect1 id="init"> <title>Initialization </title>
<para>
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();
</para>
<sect2 id="aboutinit"><title>Initialization functions</title>
<para> </para>
</sect2>
<sect2 id="rawcbreak"><title>raw() and cbreak()</title>
<para>
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
<literal remap="tt">cbreak()</literal> 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.
</para>
</sect2>
<sect2 id="echonoecho"><title>echo() and noecho() </title>
<para>
These functions control the echoing of characters typed by the user to the
terminal. <literal remap="tt">noecho()</literal> 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
<literal remap="tt">noecho()</literal> 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.
</para>
</sect2>
<sect2 id="keypad"><title>keypad()</title>
<para>
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
<literal remap="tt">keypad(stdscr, TRUE) </literal> to enable this feature
for the regular screen (stdscr). You will learn more about key management in
later sections of this document.
</para>
</sect2>
<sect2 id="halfdelay"><title>halfdelay()</title>
<para>
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.
</para>
</sect2>
<sect2 id="miscinit"><title>Miscellaneous Initialization functions</title>
<para>
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.
</para>
</sect2>
<sect2 id="initex"><title>An Example</title>
<simpara>
Let's write a program which will clarify the usage of these functions.
</simpara>
<example id="binfu"> <title> Initialization Function Usage example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/init_func_example.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
This program is self-explanatory. But I used functions which aren't explained
yet. The function <literal remap="tt">getch()</literal> is used to get a
character from user. It is equivalent to normal
<literal remap="tt">getchar()</literal> except that we can disable the line
buffering to avoid &lt;enter&gt; after input. Look for more about
<literal remap ="tt">getch()</literal>and reading keys in the <link
linkend="keys"> key management section </link>. 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.
</para>
</sect2>
</sect1>
<sect1 id="awordwindows"><title>A Word about Windows</title>
<para>
Before we plunge into the myriad ncurses functions, let me clear few things
about windows. Windows are explained in detail in following <link
linkend="windows"> sections </link>
</para>
<para>
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
<literal remap="tt">stdscr</literal> 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.
</para>
<para>
For example, if you call
</para>
<programlisting>
printw("Hi There !!!");
refresh();
</programlisting>
<para>
It prints the string on stdscr at the present cursor position. Similarly the
call to refresh(), works on stdscr only.
</para>
<para>
Say you have created <link linkend="windows">windows</link> then you have to
call a function with a 'w' added to the usual function.
</para>
<programlisting>
wprintw(win, "Hi There !!!");
wrefresh(win);
</programlisting>
<para>
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.
</para>
<programlisting>
printw(string); /* Print on stdscr at present cursor position */
mvprintw(y, x, string);/* Move to (y, x) then print string */
wprintw(win, string); /* Print on window win at present cursor position */
/* in the window */
mvwprintw(win, y, x, string); /* Move to (y, x) relative to window */
/* co-ordinates and then print */
</programlisting>
<para>
Usually the w-less functions are macros which expand to corresponding w-function
with stdscr as the window parameter.
</para>
</sect1>
<sect1 id="printw"><title>Output functions</title>
<para>
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.
</para>
<para>
There are three classes of functions which you can use to do output on screen.
<orderedlist>
<listitem><para>addch() class: Print single character with attributes </para>
</listitem>
<listitem><para>printw() class: Print formatted output similar to printf()
</para> </listitem>
<listitem><para>addstr() class: Print strings</para></listitem>
</orderedlist>
</para>
<para>
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.
</para>
<sect2 id="addchclass"> <title> addch() class of functions </title>
<para>
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 <link linkend="attrib"> sections </link> 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.
</para>
<para>
In order to combine a character with some attributes, you have two options:
</para>
<itemizedlist>
<listitem>
<para>
By OR'ing a single character with the desired attribute macros. These attribute
macros could be found in the header file
<literal remap="tt">ncurses.h</literal>. For example, you want to print a
character ch(of type char) bold and underlined, you would call addch() as below.
<programlisting>
addch(ch | A_BOLD | A_UNDERLINE);
</programlisting>
</para>
</listitem>
<listitem>
<para>
By using functions like <literal remap="tt">attrset(),attron(),attroff()
</literal>. These functions are explained in the <link linkend="attrib">
Attributes</link> 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.
</para>
</listitem>
</itemizedlist>
<para>
Additionally, <literal remap="tt">curses</literal> 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
<literal remap="tt">ncurses.h</literal>. Try looking for macros beginning
with <literal remap="tt">ACS_</literal> in this file.
</para>
</sect2>
<sect2><title>mvaddch(), waddch() and mvwaddch() </title>
<para>
<literal remap="tt">mvaddch()</literal> is used to move the cursor to a
given point, and then print. Thus, the calls:
<programlisting>
move(row,col); /* moves the cursor to row<emphasis>th</emphasis> row and col<emphasis>th</emphasis> column */
addch(ch);
</programlisting>
can be replaced by
<programlisting>
mvaddch(row,col,ch);
</programlisting>
</para>
<para>
<literal remap="tt">waddch()</literal> is similar to
<literal remap="tt">addch()</literal>, except that it adds a character into
the given window. (Note that <literal remap="tt">addch()</literal> adds a
character into the window <literal remap="tt">stdscr</literal>.)
</para>
<para>
In a similar fashion <literal remap="tt">mvwaddch()</literal> function is
used to add a character into the given window at the given coordinates.
</para>
<para>
Now, we are familiar with the basic output function
<literal remap="tt">addch()</literal>. But, if we want to print a string, it
would be very annoying to print it character by character. Fortunately,
<literal remap="tt">ncurses</literal> provides <literal remap="tt">
printf</literal><emphasis>-like</emphasis> or
<literal remap="tt">puts</literal><emphasis>-like</emphasis> functions.
</para>
</sect2>
<sect2 id="printwclass"><title>printw() class of functions </title>
<para>
These functions are similar to <literal remap="tt">printf()</literal> with
the added capability of printing at any position on the screen.
</para>
<sect3 id="printwmvprintw"> <title>printw() and mvprintw </title>
<para>
These two functions work much like <literal remap="tt">printf()</literal>.
<literal remap="tt">mvprintw()</literal> 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 <literal remap="tt">printw()</literal> function, use
<literal remap="tt">move() </literal> first and then use
<literal remap="tt">printw()</literal> though I see no point why one should
avoid using <literal remap="tt">mvprintw()</literal>, you have the
flexibility to manipulate.
</para>
</sect3>
<sect3 id="wprintwmvwprintw"><title>wprintw() and mvwprintw </title>
<para>
These two functions are similar to above two except that they print in the
corresponding window given as argument.
</para>
</sect3>
<sect3 id="vwprintw"><title>vwprintw()</title>
<para>
This function is similar to <literal remap="tt">vprintf()</literal>. This can
be used when variable number of arguments are to be printed.
</para>
</sect3>
<sect3 id="simpleprintwex"> <title> A Simple printw example </title>
<example id="bprex"> <title> A Simple printw example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/printw_example.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
Above program demonstrates how easy it is to use <literal remap="tt">printw
</literal>. You just feed the coordinates and the message to be appeared
on the screen, then it does what you want.
</para>
<para>
The above program introduces us to a new function
<literal remap="tt">getmaxyx()</literal>, a macro defined in
<literal remap="tt">ncurses.h</literal>. It gives the number of columns and
the number of rows in a given window.
<literal remap="tt">getmaxyx()</literal> does this by updating the variables
given to it. Since <literal remap="tt">getmaxyx()</literal> is not a function
we don't pass pointers to it, we just give two integer variables.
</para>
</sect3>
</sect2>
<sect2 id="addstrclass"><title>addstr() class of functions </title>
<para>
<literal remap="tt">addstr()</literal> is used to put a character string into
a given window. This function is similar to calling
<literal remap="tt">addch()</literal> once for each character in a given
string. This is true for all output functions. There are other functions from
this family such as <literal remap="tt">mvaddstr(),mvwaddstr()</literal> and
<literal remap="tt">waddstr()</literal>, 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.
</para>
</sect2>
<sect2 id="acaution"><title>A word of caution</title>
<para>
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 <link linkend="windows"> windows </link> section.
</para>
</sect2>
</sect1>
<sect1 id="scanw"><title>Input functions</title>
<para>
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.
</para>
<orderedlist>
<listitem><para>getch() class: Get a character</para></listitem>
<listitem><para>scanw() class: Get formatted input</para></listitem>
<listitem><para>getstr() class: Get strings</para></listitem>
</orderedlist>
<sect2 id="getchclass"><title>getch() class of functions</title>
<para>
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
<link linkend="keys">key management section </link>.
</para>
</sect2>
<sect2 id="scanwclass"><title>scanw() class of functions</title>
<para>
These functions are similar to <literal remap="tt">scanf()</literal> with the
added capability of getting the input from any location on the screen.
</para>
<sect3 id="scanwmvscanw"><title>scanw() and mvscanw </title>
<para>
The usage of these functions is similar to that of
<literal remap="tt">sscanf()</literal>, where the line to be scanned is
provided by <literal remap="tt">wgetstr()</literal> function. That is, these
functions call to <literal remap="tt">wgetstr()</literal> function(explained
below) and uses the resulting line for a scan.
</para>
</sect3>
<sect3 id="wscanwmvwscanw"><title>wscanw() and mvwscanw()</title>
<para>
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.
</para>
</sect3>
<sect3 id="vwscanw"><title>vwscanw()</title>
<para>
This function is similar to <literal remap="tt">vscanf()</literal>. This can
be used when a variable number of arguments are to be scanned.
</para>
</sect3>
</sect2>
<sect2 id="getstrclass"><title>getstr() class of functions </title>
<para>
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
<literal remap="tt">getch()</literal> until a newline, carriage return, or
end-of-file is received. The resulting string of characters are pointed to by
<literal remap="tt">str</literal>, which is a character pointer provided by
the user.
</para>
</sect2>
<sect2 id="getstrex"><title>Some examples</title>
<example id="bscex"> <title> A Simple scanw example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/scanw_example.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
</sect1>
<sect1 id="attrib"><title>Attributes</title>
<para>
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.
</para>
<example id="bsiat"> <title> A Simple Attributes example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/simple_attr.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
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
<literal remap="tt"> attron()</literal> . When we get the pattern */ it is
switched off by <literal remap="tt"> attroff()</literal> .
</para>
<para>
The above program also introduces us to two useful functions
<literal remap="tt">getyx() </literal> and
<literal remap="tt">move()</literal>. 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
<literal remap="tt">move()</literal> moves the cursor to the co-ordinates
given to it.
</para>
<para>
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.
</para>
<sect2 id="attribdetails"><title>The details</title>
<para>
Let's get into more details of attributes. The functions <literal remap="tt">
attron(), attroff(), attrset() </literal>, and their sister functions
<literal remap="tt"> attr_get()</literal> etc.. can be used to switch
attributes on/off , get attributes and produce a colorful display.
</para>
<para>
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.
</para>
<programlisting>
A_NORMAL Normal display (no highlight)
A_STANDOUT Best highlighting mode of the terminal.
A_UNDERLINE Underlining
A_REVERSE Reverse video
A_BLINK Blinking
A_DIM Half bright
A_BOLD Extra bright or bold
A_PROTECT Protected mode
A_INVIS Invisible or blank mode
A_ALTCHARSET Alternate character set
A_CHARTEXT Bit-mask to extract a character
COLOR_PAIR(n) Color-pair number n
</programlisting>
<para>
The last one is the most colorful one :-) Colors are explained in the
<ulink url="#color">next sections</ulink>.
</para>
<para>
We can OR(|) any number of above attributes to get a combined effect. If you
wanted reverse video with blinking characters you can use
</para>
<programlisting>
attron(A_REVERSE | A_BLINK);
</programlisting>
</sect2>
<sect2 id="attronvsattrset"><title>attron() vs attrset() </title>
<para>
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 <literal remap="tt"> standend()
</literal> which is equivalent to <literal remap="tt"> attrset(A_NORMAL)
</literal> which turns off all attributes and brings you to normal mode.
</para>
</sect2>
<!-- jade forbids underscore in id="" attribute; thus attr-get -->
<sect2 id="attr-get"><title>attr_get()</title>
<para>
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.
</para>
</sect2>
<!-- jade forbids underscore in id="" attribute; thus attr-funcs -->
<sect2 id="attr-funcs"><title>attr_ functions</title>
<para>
There are series of functions like attr_set(), attr_on etc.. These are similar
to above functions except that they take parameters of type
<literal remap="tt">attr_t</literal>.
</para>
</sect2>
<sect2 id="wattrfuncs"><title>wattr functions</title>
<para>
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.
</para>
</sect2>
<sect2 id="chgat"><title>chgat() functions</title>
<para>
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.
</para>
<para>
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.
</para>
<programlisting>
chgat(-1, A_REVERSE, 0, NULL);
</programlisting>
<para>
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.
</para>
<para>
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.
</para>
<example id="bwich"> <title> Chgat() Usage example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/with_chgat.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
This example also introduces us to the color world of curses. Colors will be
explained in detail later. Use 0 for no color.
</para>
</sect2>
</sect1>
<sect1 id="windows"><title>Windows</title>
<para>
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.
</para>
<sect2 id="windowbasics"><title>The basics</title>
<para>
A Window can be created by calling the function
<literal remap="tt">newwin()</literal>. 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.
</para>
</sect2>
<sect2 id="letbewindow"><title>Let there be a Window !!!</title>
<para>
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
<literal remap="tt">box()</literal> can be used to draw a border around the
window. Let's explore these functions in more detail in this example.
</para>
<example id="bwibo"> <title>Window Border example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/win_border.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="borderexexpl"><title>Explanation</title>
<para>
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.
</para>
<para>
The <literal remap="tt">create_newwin()</literal> function creates a window
with <literal remap="tt">newwin() </literal> and displays a border around it
with box. The function <literal remap="tt"> destroy_win()</literal> first
erases the window from screen by painting a border with ' ' character and then
calling <literal remap="tt">delwin()</literal> to deallocate memory related
to it. Depending on the key the user presses, starty or startx is changed and a
new window is created.
</para>
<para>
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:
<programlisting>
wborder(win, '|', '|', '-', '-', '+', '+', '+', '+');
</programlisting>
</para>
<para>
it produces some thing like
</para>
<programlisting>
+------------+
| |
| |
| |
| |
| |
| |
+------------+
</programlisting>
</sect2>
<sect2 id="otherstuff"><title>The other stuff in the example</title>
<para>
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 <literal remap="tt">getch()</literal> 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.
</para>
</sect2>
<sect2 id="otherborderfuncs"><title>Other Border functions</title>
<para>
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.
</para>
<para>
The following program uses <literal remap="tt">mvhline()</literal> and
<literal remap="tt">mvvline()</literal> to achieve similar effect. These two
functions are simple. They create a horizontal or vertical line of the specified
length at the specified position.
</para>
<example id="botbo"><title> More border functions</title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/other_border.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
</sect1>
<sect1 id="color"><title>Colors</title>
<sect2 id="colorbasics"><title> The basics </title>
<para>
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.
</para>
<example id="bsico"> <title> A Simple Color example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/simple_color.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
As you can see, to start using color, you should first call the function
<literal remap="tt"> start_color()</literal>. 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
<literal remap="tt">has_colors()</literal> function, which returns FALSE if
the terminal does not support color.
</para>
<para>
Curses initializes all the colors supported by terminal when start_color() is
called. These can be accessed by the define constants like
<literal remap="tt">COLOR_BLACK </literal> 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 <literal remap="tt">init_pair() </literal> 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 <literal remap="tt">
COLOR_PAIR()</literal>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 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.
</para>
<para>
The following colors are defined in <literal remap="tt">curses.h</literal>.
You can use these as parameters for various color functions.
<programlisting>
COLOR_BLACK 0
COLOR_RED 1
COLOR_GREEN 2
COLOR_YELLOW 3
COLOR_BLUE 4
COLOR_MAGENTA 5
COLOR_CYAN 6
COLOR_WHITE 7
</programlisting>
</para>
</sect2>
<sect2 id="changecolordefs"><title>Changing Color Definitions </title>
<para>
The function <literal remap="tt">init_color()</literal>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
</para>
<programlisting>
init_color(COLOR_RED, 700, 0, 0);
/* param 1 : color name
* param 2, 3, 4 : rgb content min = 0, max = 1000 */
</programlisting>
<para>
If your terminal cannot change the color definitions, the function returns ERR.
The function <literal remap="tt">can_change_color()</literal> 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).
</para>
</sect2>
<sect2 id="colorcontent"><title>Color Content </title>
<para>
The functions <literal remap="tt">color_content()</literal> and
<literal remap="tt">pair_content()</literal> can be used to find the color
content and foreground, background combination for the pair.
</para>
</sect2>
</sect1>
<sect1 id="keys"> <title>Interfacing with the key board</title>
<sect2 id="keysbasics"><title>The Basics </title>
<para>
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.
</para>
<para>
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
<literal remap="tt">getch()</literal> 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.
</para>
<para>
<literal remap="tt">getch()</literal> 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 <literal remap="tt">curses.h</literal>. 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.
</para>
<para>
For example, if you call getch() like this
</para>
<programlisting>
int ch;
ch = getch();
</programlisting>
<para>
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.
</para>
<para>
The following code piece will do that job.
</para>
<programlisting>
if(ch == KEY_LEFT)
printw("Left arrow is pressed\n");
</programlisting>
<para>
Let's write a small program which creates a menu which can be navigated by up
and down arrows.
</para>
</sect2>
<sect2 id="simplekeyex"> <title>A Simple Key Usage example </title>
<example id="bsike"><title> A Simple Key Usage example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/simple_key.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
</sect1>
<sect1 id="mouse"> <title>Interfacing with the mouse </title>
<para>
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.
</para>
<sect2 id="mousebasics"> <title> The Basics </title>
<para>
Before you do any thing else, the events you want to receive have to be enabled
with <literal remap="tt">mousemask()</literal>.
</para>
<programlisting>
mousemask( mmask_t newmask, /* The events you want to listen to */
mmask_t *oldmask) /* The old events mask */
</programlisting>
<para>
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 <literal
remap="tt"> ALL_MOUSE_EVENTS</literal> can be used to get all the events.
</para>
<para>
The following are all the event masks:
</para>
<programlisting>
Name Description
---------------------------------------------------------------------
BUTTON1_PRESSED mouse button 1 down
BUTTON1_RELEASED mouse button 1 up
BUTTON1_CLICKED mouse button 1 clicked
BUTTON1_DOUBLE_CLICKED mouse button 1 double clicked
BUTTON1_TRIPLE_CLICKED mouse button 1 triple clicked
BUTTON2_PRESSED mouse button 2 down
BUTTON2_RELEASED mouse button 2 up
BUTTON2_CLICKED mouse button 2 clicked
BUTTON2_DOUBLE_CLICKED mouse button 2 double clicked
BUTTON2_TRIPLE_CLICKED mouse button 2 triple clicked
BUTTON3_PRESSED mouse button 3 down
BUTTON3_RELEASED mouse button 3 up
BUTTON3_CLICKED mouse button 3 clicked
BUTTON3_DOUBLE_CLICKED mouse button 3 double clicked
BUTTON3_TRIPLE_CLICKED mouse button 3 triple clicked
BUTTON4_PRESSED mouse button 4 down
BUTTON4_RELEASED mouse button 4 up
BUTTON4_CLICKED mouse button 4 clicked
BUTTON4_DOUBLE_CLICKED mouse button 4 double clicked
BUTTON4_TRIPLE_CLICKED mouse button 4 triple clicked
BUTTON_SHIFT shift was down during button state change
BUTTON_CTRL control was down during button state change
BUTTON_ALT alt was down during button state change
ALL_MOUSE_EVENTS report all button state changes
REPORT_MOUSE_POSITION report mouse movement
</programlisting>
</sect2>
<sect2 id="gettingevents"> <title> Getting the events </title>
<para>
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 <literal remap="tt">getmouse()</literal>.
</para>
<para>
The code approximately looks like this:
</para>
<programlisting>
MEVENT event;
ch = getch();
if(ch == KEY_MOUSE)
if(getmouse(&amp;event) == OK)
. /* Do some thing with the event */
.
.
</programlisting>
<para>
getmouse() returns the event into the pointer given to it. It's a structure
which contains
</para>
<programlisting>
typedef struct
{
short id; /* ID to distinguish multiple devices */
int x, y, z; /* event coordinates */
mmask_t bstate; /* button state bits */
}
</programlisting>
<para>
The <literal remap="tt">bstate</literal> is the main variable we are
interested in. It tells the button state of the mouse.
</para>
<para>
Then with a code snippet like the following, we can find out what happened.
</para>
<programlisting>
if(event.bstate &amp; BUTTON1_PRESSED)
printw("Left Button Pressed");
</programlisting>
</sect2>
<sect2 id="mousetogether"> <title> Putting it all Together </title>
<para>
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.
</para>
<example id="bmome"> <title> Access the menu with mouse !!! </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/mouse_menu.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="miscmousefuncs"> <title> Miscellaneous Functions </title>
<para>
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.
</para>
<para>
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.
</para>
</sect2>
</sect1>
<sect1 id="screen"><title>Screen Manipulation</title>
<para>
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.
</para>
<sect2 id="getyx"><title>getyx() functions </title>
<para>
The function <literal remap="tt">getyx()</literal> 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
</para>
<programlisting>
getyx(win, y, x);
/* win: window pointer
* y, x: y, x co-ordinates will be put into this variables
*/
</programlisting>
<para>
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().
</para>
<para>
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.
</para>
</sect2>
<sect2 id="screendump"><title>Screen Dumping </title>
<para>
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.
</para>
</sect2>
<sect2 id="windowdump"><title>Window Dumping </title>
<para>
To store and restore windows, the functions
<literal remap="tt">putwin()</literal> and <literal remap="tt">getwin()
</literal> can be used. <literal remap="tt">putwin()</literal> puts
the present window state into a file, which can be later restored by
<literal remap="tt">getwin()</literal>.
</para>
<para>
The function <literal remap="tt">copywin()</literal> 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.
</para>
</sect2>
</sect1>
<sect1 id="misc"><title>Miscellaneous features</title>
<para>
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.
</para>
<sect2 id="cursset"><title>curs_set() </title>
<para>
This function can be used to make the cursor invisible. The parameter to this
function should be
</para>
<programlisting>
0 : invisible or
1 : normal or
2 : very visible.
</programlisting>
</sect2>
<sect2 id="templeave"><title>Temporarily Leaving Curses mode </title>
<para>
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 <literal remap="tt">def_prog_mode()</literal> and then call
<literal remap="tt">endwin()</literal> to end the curses mode. This will
leave you in the original tty mode. To get back to curses once you are done,
call <literal remap="tt">reset_prog_mode() </literal>. This function returns
the tty to the state stored by <literal remap="tt">def_prog_mode()
</literal>. Then do refresh(), and you are back to the curses mode. Here
is an example showing the sequence of things to be done.
</para>
<example id="btele"> <title> Temporarily Leaving Curses Mode </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/temp_leave.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="acsvars"><title>ACS_ variables </title>
<para>
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 <literal remap="tt">box()</literal> 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.
</para>
<example id="bacsvars"> <title> ACS Variables Example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/basics/acs_vars.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
</sect1>
<sect1 id="otherlib"><title> Other libraries </title>
<para>
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.
</para>
</sect1>
<sect1 id="panels"><title> Panel Library</title>
<para>
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.
</para>
<para>
Don't despair. There's an elegant solution provided in panels library. In the
words of developers of ncurses
</para>
<para>
<emphasis>
When your interface design is such that windows may dive deeper into the
visibility stack or pop to the top at runtime, the resulting book-keeping can be
tedious and difficult to get right. Hence the panels library.
</emphasis>
</para>
<para>
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.
</para>
<sect2 id="panelbasics"><title> The Basics </title>
<para>
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.
</para>
<para>
The general flow of a panel program goes like this:
<orderedlist>
<listitem>
<para>Create the windows (with newwin()) to be attached to the panels.</para>
</listitem>
<listitem>
<para>
Create panels with the chosen visibility order. Stack them up according to the
desired visibility. The function new_panel() is used to created panels.
</para>
</listitem>
<listitem>
<para>
Call update_panels() to write the panels to the virtual screen in correct
visibility order. Do a doupdate() to show it on the screen.
</para>
</listitem>
<listitem>
<para>
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.
</para>
</listitem>
<listitem>
<para>
When you are done with the panel use del_panel() to delete the panel.
</para>
</listitem>
</orderedlist>
</para>
<para>
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.
</para>
</sect2>
<sect2 id="compilepanels"><title> Compiling With the Panels Library </title>
<para>
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.
</para>
<programlisting>
#include &lt;panel.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lpanel -lncurses
</programlisting>
<example id="ppasi"><title> Panel basics</title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/panels/panel_simple.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
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.
</para>
</sect2>
<sect2 id ="panelbrowsing"> <title> Panel Window Browsing </title>
<para>
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.
</para>
<example id="ppabr"><title> Panel Window Browsing Example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/panels/panel_browse.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="userptrusing"><title> Using User Pointers </title>
<para>
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 <literal remap="tt"> set_panel_userptr()</literal>.
It can be accessed using the function <literal remap="tt">panel_userptr()
</literal> 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.
</para>
</sect2>
<sect2 id="panelmoveresize"><title> Moving and Resizing Panels </title>
<para>
The function <literal remap="tt">move_panel()</literal> 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.
</para>
<para>
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().
</para>
<para>
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.
</para>
<example id="ppare"><title> Panel Moving and Resizing example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/panels/panel_resize.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
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.
</para>
<para>
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().
</para>
<para>
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.
</para>
</sect2>
<sect2 id="panelshowhide"><title> Hiding and Showing Panels </title>
<para>
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.
</para>
<para>
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
<literal remap="tt">panel_hidden()</literal> which tells whether a panel is
hidden or not is not working. A bug report was also presented by Michael Andres
<ulink url="http://www.geocrawler.com/archives/3/344/1999/9/0/2643549/"> here
</ulink>
</para>
<example id="ppahi"><title> Panel Hiding and Showing example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/panels/panel_hide.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="panelabove"><title> panel_above() and panel_below() Functions </title>
<para>
The functions <literal remap="tt">panel_above()</literal> and
<literal remap="tt">panel_below()</literal> can be used to find out the panel
above and below a panel. If the argument to these functions is NULL, then they
return a pointer to bottom panel and top panel respectively.
</para>
</sect2>
</sect1>
<sect1 id="menus"><title> Menus Library </title>
<para>
The menus library provides a nice extension to basic curses, through which you
can create menus. It provides a set of functions to create menus. But they have
to be customized to give a nicer look, with colors etc. Let's get into the
details.
</para>
<para>
A menu is a screen display that assists the user to choose some subset of a
given set of items. To put it simple, a menu is a collection of items from which
one or more items can be chosen. Some readers might not be aware of multiple
item selection capability. Menu library provides functionality to write menus
from which the user can chose more than one item as the preferred choice. This
is dealt with in a later section. Now it is time for some rudiments.
</para>
<sect2 id="menubasics"><title> The Basics </title>
<para>
To create menus, you first create items, and then post the menu to the display.
After that, all the processing of user responses is done in an elegant function
menu_driver() which is the work horse of any menu program.
</para>
<para>
The general flow of control of a menu program looks like this.
<orderedlist>
<listitem><para>Initialize curses</para></listitem>
<listitem>
<para>
Create items using new_item(). You can specify a name and description for the
items.
</para>
</listitem>
<listitem>
<para>
Create the menu with new_menu() by specifying the items to be attached with.
</para>
</listitem>
<listitem>
<para>Post the menu with menu_post() and refresh the screen.</para>
</listitem>
<listitem>
<para>
Process the user requests with a loop and do necessary updates to menu with
menu_driver.
</para>
</listitem>
<listitem><para>Unpost the menu with menu_unpost()</para></listitem>
<listitem><para>Free the memory allocated to menu by free_menu()</para>
</listitem>
<listitem><para>Free the memory allocated to the items with free_item() </para>
</listitem>
<listitem><para>End curses </para> </listitem>
</orderedlist>
</para>
<para>
Let's see a program which prints a simple menu and updates the current selection
with up, down arrows.
</para>
</sect2>
<sect2 id="compilemenus"><title> Compiling With the Menu Library </title>
<para>
To use menu library functions, you have to include menu.h and to link the
program with menu library the flag -lmenu should be added along with -lncurses
in that order.
</para>
<programlisting>
#include &lt;menu.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lmenu -lncurses
</programlisting>
<example id="mmesi"> <title>Menu Basics </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/menus/menu_simple.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
This program demonstrates the basic concepts involved in creating a menu using
menus library. First we create the items using new_item() and then attach them
to the menu with new_menu() function. After posting the menu and refreshing the
screen, the main processing loop starts. It reads user input and takes
corresponding action. The function menu_driver() is the main work horse of the
menu system. The second parameter to this function tells what's to be done with
the menu. According to the parameter, menu_driver() does the corresponding task.
The value can be either a menu navigational request, an ascii character, or a
KEY_MOUSE special key associated with a mouse event.
</para>
<para>
The menu_driver accepts following navigational requests.
<programlisting>
REQ_LEFT_ITEM Move left to an item.
REQ_RIGHT_ITEM Move right to an item.
REQ_UP_ITEM Move up to an item.
REQ_DOWN_ITEM Move down to an item.
REQ_SCR_ULINE Scroll up a line.
REQ_SCR_DLINE Scroll down a line.
REQ_SCR_DPAGE Scroll down a page.
REQ_SCR_UPAGE Scroll up a page.
REQ_FIRST_ITEM Move to the first item.
REQ_LAST_ITEM Move to the last item.
REQ_NEXT_ITEM Move to the next item.
REQ_PREV_ITEM Move to the previous item.
REQ_TOGGLE_ITEM Select/deselect an item.
REQ_CLEAR_PATTERN Clear the menu pattern buffer.
REQ_BACK_PATTERN Delete the previous character from the pattern buffer.
REQ_NEXT_MATCH Move to the next item matching the pattern match.
REQ_PREV_MATCH Move to the previous item matching the pattern match.
</programlisting>
</para>
<para>
Don't get overwhelmed by the number of options. We will see them slowly one
after another. The options of interest in this example are REQ_UP_ITEM and
REQ_DOWN_ITEM. These two options when passed to menu_driver, menu driver
updates the current item to one item up or down respectively.
</para>
</sect2>
<sect2 id="menudriver"><title> Menu Driver: The work horse of the menu system</title>
<para>
As you have seen in the above example, menu_driver plays an important role in
updating the menu. It is very important to understand various options it takes
and what they do. As explained above, the second parameter to menu_driver() can
be either a navigational request, a printable character or a KEY_MOUSE key.
Let's dissect the different navigational requests.
</para>
<itemizedlist>
<listitem><para><emphasis>REQ_LEFT_ITEM and REQ_RIGHT_ITEM</emphasis></para>
<para>
A Menu can be displayed with multiple columns for more than one item. This can
be done by using the <literal remap="tt">menu_format()</literal>function.
When a multi columnar menu is displayed these requests cause the menu driver to
move the current selection to left or right.
</para>
</listitem>
<listitem><para><emphasis>REQ_UP_ITEM and REQ_DOWN_ITEM </emphasis> </para>
<para>
These two options you have seen in the above example. These options when given,
makes the menu_driver to move the current selection to an item up or down.
</para>
</listitem>
<listitem><para> <emphasis>REQ_SCR_* options</emphasis> </para>
<para>
The four options REQ_SCR_ULINE, REQ_SCR_DLINE, REQ_SCR_DPAGE, REQ_SCR_UPAGE are
related to scrolling. If all the items in the menu cannot be displayed in the
menu sub window, then the menu is scrollable. These requests can be given to the
menu_driver to do the scrolling either one line up, down or one page down or up
respectively.
</para>
</listitem>
<listitem><para><emphasis>REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_NEXT_ITEM and
REQ_PREV_ITEM </emphasis> </para>
<para>
These requests are self explanatory.
</para>
</listitem>
<listitem><para> <emphasis>REQ_TOGGLE_ITEM</emphasis> </para>
<para>
This request when given, toggles the present selection. This option is to be
used only in a multi valued menu. So to use this request the option O_ONEVALUE
must be off. This option can be made off or on with set_menu_opts().
</para>
</listitem>
<listitem><para> <emphasis>Pattern Requests </emphasis></para>
<para>
Every menu has an associated pattern buffer, which is used to find the nearest
match to the ascii characters entered by the user. Whenever ascii characters are
given to menu_driver, it puts in to the pattern buffer. It also tries to find
the nearest match to the pattern in the items list and moves current selection
to that item. The request REQ_CLEAR_PATTERN clears the pattern buffer. The
request REQ_BACK_PATTERN deletes the previous character in the pattern buffer.
In case the pattern matches more than one item then the matched items can be
cycled through REQ_NEXT_MATCH and REQ_PREV_MATCH which move the current
selection to the next and previous matches respectively.
</para>
</listitem>
<listitem><para> <emphasis>Mouse Requests</emphasis></para>
<para>
In case of KEY_MOUSE requests, according to the mouse position an action is
taken accordingly. The action to be taken is explained in the man page as,
</para>
<programlisting>
<emphasis>
If the second argument is the KEY_MOUSE special key, the
associated mouse event is translated into one of the above
pre-defined requests. Currently only clicks in the user
window (e.g. inside the menu display area or the decora&shy;
tion window) are handled. If you click above the display
region of the menu, a REQ_SCR_ULINE is generated, if you
doubleclick a REQ_SCR_UPAGE is generated and if you
tripleclick a REQ_FIRST_ITEM is generated. If you click
below the display region of the menu, a REQ_SCR_DLINE is
generated, if you doubleclick a REQ_SCR_DPAGE is generated
and if you tripleclick a REQ_LAST_ITEM is generated. If
you click at an item inside the display area of the menu,
the menu cursor is positioned to that item.
</emphasis>
</programlisting>
</listitem>
</itemizedlist>
<para>
Each of the above requests will be explained in the following lines with several
examples whenever appropriate.
</para>
</sect2>
<sect2 id="menuwindows"><title> Menu Windows </title>
<para>
Every menu created is associated with a window and a sub window. The menu window
displays any title or border associated with the menu. The menu sub window
displays the menu items currently available for selection. But we didn't specify
any window or sub window in the simple example. When a window is not specified,
stdscr is taken as the main window, and then menu system calculates the sub
window size required for the display of items. Then items are displayed in the
calculated sub window. So let's play with these windows and display a menu with
a border and a title.
</para>
<example id="mmewi"><title> Menu Windows Usage example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/menus/menu_win.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
This example creates a menu with a title, border, a fancy line separating title
and the items. As you can see, in order to attach a window to a menu the
function set_menu_win() has to be used. Then we attach the sub window also. This
displays the items in the sub window. You can also set the mark string which
gets displayed to the left of the selected item with set_menu_mark().
</para>
</sect2>
<sect2 id="scrollmenus"><title> Scrolling Menus </title>
<para>
If the sub window given for a window is not big enough to show all the items,
then the menu will be scrollable. When you are on the last item in the present
list, if you send REQ_DOWN_ITEM, it gets translated into REQ_SCR_DLINE and the
menu scrolls by one item. You can manually give REQ_SCR_ operations to do
scrolling. Let's see how it can be done.
</para>
<example id="mmesc"><title> Scrolling Menus example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/menus/menu_scroll.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
This program is self-explanatory. In this example the number of choices has been
increased to ten, which is larger than our sub window size which can hold 6
items. This message has to be explicitly conveyed to the menu system with the
function set_menu_format(). In here we specify the number of rows and columns we
want to be displayed for a single page. We can specify any number of items to be
shown, in the rows variables, if it is less than the height of the sub window.
If the key pressed by the user is a PAGE UP or PAGE DOWN, the menu is scrolled a
page due to the requests (REQ_SCR_DPAGE and REQ_SCR_UPAGE) given to
menu_driver().
</para>
</sect2>
<sect2 id="multicolumn"><title> Multi Columnar Menus </title>
<para>
In the above example you have seen how to use the function set_menu_format(). I
didn't mention what the cols variable (third parameter) does. Well, If your sub
window is wide enough, you can opt to display more than one item per row. This
can be specified in the cols variable. To make things simpler, the following
example doesn't show descriptions for the items.
</para>
<example id="mmemuco"> <title> Milt Columnar Menus Example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/menus/menu_multi_column.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
Watch the function call to set_menu_format(). It specifies the number of columns
to be 3, thus displaying 3 items per row. We have also switched off the showing
descriptions with the function menu_opts_off(). There are couple of functions
set_menu_opts(), menu_opts_on() and menu_opts() which can be used to manipulate
menu options. The following menu options can be specified.
</para>
<programlisting>
O_ONEVALUE
Only one item can be selected for this menu.
O_SHOWDESC
Display the item descriptions when the menu is
posted.
O_ROWMAJOR
Display the menu in row-major order.
O_IGNORECASE
Ignore the case when pattern-matching.
O_SHOWMATCH
Move the cursor to within the item name while pat&shy;
tern-matching.
O_NONCYCLIC
Don't wrap around next-item and previous-item,
requests to the other end of the menu.
</programlisting>
<para>
All options are on by default. You can switch specific attributes on or off with
menu_opts_on() and menu_opts_off() functions. You can also use set_menu_opts()
to directly specify the options. The argument to this function should be a OR ed
value of some of those above constants. The function menu_opts() can be used to
find out a menu's present options.
</para>
</sect2>
<sect2 id="multivaluemenus"><title> Multi Valued Menus </title>
<para>
You might be wondering what if you switch off the option O_ONEVALUE. Then the
menu becomes multi-valued. That means you can select more than one item. This
brings us to the request REQ_TOGGLE_ITEM. Let's see it in action.
</para>
<example id="mmeto"><title> Multi Valued Menus example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/menus/menu_toggle.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
Whew, A lot of new functions. Let's take them one after another. Firstly, the
REQ_TOGGLE_ITEM. In a multi-valued menu, the user should be allowed to select
or un select more than one item. The request REQ_TOGGLE_ITEM toggles the present
selection. In this case when space is pressed REQ_TOGGLE_ITEM request is sent to
menu_driver to achieve the result.
</para>
<para>
Now when the user presses &lt;ENTER&gt; we show the items he presently selected.
First we find out the items associated with the menu using the function
menu_items(). Then we loop through the items to find out if the item is selected
or not. The function item_value() returns TRUE if an item is selected. The
function item_count() returns the number of items in the menu. The item name can
be found with item_name(). You can also find the description associated with an
item using item_description().
</para>
</sect2>
<sect2 id="menuopt"><title> Menu Options </title>
<para>
Well, by this time you must be itching for some difference in your menu, with
lots of functionality. I know. You want Colors !!!. You want to create nice
menus similar to those text mode <ulink
url="http://www.jersey.net/~debinjoe/games/">dos games</ulink>. The functions
set_menu_fore() and set_menu_back() can be used to change the attribute of the
selected item and unselected item. The names are misleading. They don't change
menu's foreground or background which would have been useless.
</para>
<para>
The function set_menu_grey() can be used to set the display attribute for the
non-selectable items in the menu. This brings us to the interesting option for
an item the one and only O_SELECTABLE. We can turn it off by the function
item_opts_off() and after that the item is not selectable. It's like a grayed
item in those fancy windows menus. Let's put these concepts in practice with
this example
</para>
<example id="mmeat"><title> Menu Options example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/menus/menu_attrib.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="menuuserptr"><title> The useful User Pointer </title>
<para>
We can associate a user pointer with each item in the menu. It works the same
way as user pointer in panels. It's not touched by menu system. You can store
any thing you like in that. I usually use it to store the function to be
executed when the menu option is chosen (It's selected and may be the user
pressed &lt;ENTER&gt;);
</para>
<example id="mmeus"><title> Menu User Pointer Usage </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/menus/menu_userptr.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
</sect1>
<sect1 id="forms"><title> Forms Library </title>
<para>
Well. If you have seen those forms on web pages which take input from users and
do various kinds of things, you might be wondering how would any one create such
forms in text mode display. It's quite difficult to write those nifty forms in
plain ncurses. Forms library tries to provide a basic frame work to build and
maintain forms with ease. It has lot of features(functions) which manage
validation, dynamic expansion of fields etc.. Let's see it in full flow.
</para>
<para>
A form is a collection of fields; each field can be either a label(static text)
or a data-entry location. The forms also library provides functions to divide
forms into multiple pages.
</para>
<sect2 id="formbasics"><title> The Basics </title>
<para>
Forms are created in much the same way as menus. First the fields related to the
form are created with new_field(). You can set options for the fields, so that
they can be displayed with some fancy attributes, validated before the field
looses focus etc.. Then the fields are attached to form. After this, the form
can be posted to display and is ready to receive inputs. On the similar lines to
menu_driver(), the form is manipulated with form_driver(). We can send requests
to form_driver to move focus to a certain field, move cursor to end of the field
etc.. After the user enters values in the fields and validation done, form can
be unposted and memory allocated can be freed.
</para>
<para>
The general flow of control of a forms program looks like this.
<orderedlist>
<listitem><para>Initialize curses</para> </listitem>
<listitem><para>Create fields using new_field(). You can specify the height and
width of the field, and its position on the form.</para> </listitem>
<listitem><para>Create the forms with new_form() by specifying the fields to be
attached with.</para> </listitem>
<listitem><para>Post the form with form_post() and refresh the screen.</para>
</listitem>
<listitem><para>Process the user requests with a loop and do necessary updates
to form with form_driver.</para> </listitem>
<listitem><para>Unpost the menu with form_unpost()</para> </listitem>
<listitem><para>Free the memory allocated to menu by free_form()</para>
</listitem>
<listitem><para>Free the memory allocated to the items with free_field()</para> </listitem>
<listitem><para>End curses</para> </listitem>
</orderedlist>
</para>
<para>
As you can see, working with forms library is much similar to handling menu
library. The following examples will explore various aspects of form
processing. Let's start the journey with a simple example. first.
</para>
</sect2>
<sect2 id="compileforms"><title> Compiling With the Forms Library </title>
<para>
To use forms library functions, you have to include form.h and to link the
program with forms library the flag -lform should be added along with -lncurses
in that order.
</para>
<programlisting>
#include &lt;form.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lform -lncurses
</programlisting>
<example id="ffosi"><title> Forms Basics </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/forms/form_simple.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
Above example is pretty straight forward. It creates two fields with
<literal remap="tt">new_field()</literal>. new_field() takes height, width,
starty, startx, number of offscreen rows and number of additional working
buffers. The fifth argument number of offscreen rows specifies how much of the
field to be shown. If it is zero, the entire field is always displayed otherwise
the form will be scrollable when the user accesses not displayed parts of the
field. The forms library allocates one buffer per field to store the data user
enters. Using the last parameter to new_field() we can specify it to allocate
some additional buffers. These can be used for any purpose you like.
</para>
<para>
After creating the fields, back ground attribute of both of them is set to an
underscore with set_field_back(). The AUTOSKIP option is turned off using
field_opts_off(). If this option is turned on, focus will move to the next
field in the form once the active field is filled up completely.
</para>
<para>
After attaching the fields to the form, it is posted. Here on, user inputs are
processed in the while loop, by making corresponding requests to form_driver.
The details of all the requests to the form_driver() are explained later.
</para>
</sect2>
<sect2 id="playfields"><title> Playing with Fields </title>
<para>
Each form field is associated with a lot of attributes. They can be manipulated
to get the required effect and to have fun !!!. So why wait?
</para>
<sect3 id="fetchinfo"><title> Fetching Size and Location of Field </title>
<para>
The parameters we have given at the time of creation of a field can be retrieved
with field_info(). It returns height, width, starty, startx, number of offscreen
rows, and number of additional buffers into the parameters given to it. It is a
sort of inverse of new_field().
</para>
<programlisting>
int field_info( FIELD *field, /* field from which to fetch */
int *height, *int width, /* field size */
int *top, int *left, /* upper left corner */
int *offscreen, /* number of offscreen rows */
int *nbuf); /* number of working buffers */
</programlisting>
</sect3>
<sect3 id="movefield"><title> Moving the field </title>
<para>
The location of the field can be moved to a different position with
move_field().
</para>
<programlisting>
int move_field( FIELD *field, /* field to alter */
int top, int left); /* new upper-left corner */
</programlisting>
<para>
As usual, the changed position can be queried with field_infor().
</para>
</sect3>
<sect3 id="justifyfield"><title> Field Justification </title>
<para>
The justification to be done for the field can be fixed using the function
set_field_just().
</para>
<programlisting>
int set_field_just(FIELD *field, /* field to alter */
int justmode); /* mode to set */
int field_just(FIELD *field); /* fetch justify mode of field */
</programlisting>
<para>
The justification mode valued accepted and returned by these functions are
NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or JUSTIFY_CENTER.
</para>
</sect3>
<sect3 id="fielddispattrib"><title> Field Display Attributes </title>
<para>
As you have seen, in the above example, display attribute for the fields can be
set with set_field_fore() and setfield_back(). These functions set foreground
and background attribute of the fields. You can also specify a pad character
which will be filled in the unfilled portion of the field. The pad character is
set with a call to set_field_pad(). Default pad value is a space. The functions
field_fore(), field_back, field_pad() can be used to query the present
foreground, background attributes and pad character for the field. The following
list gives the usage of functions.
</para>
<programlisting>
int set_field_fore(FIELD *field, /* field to alter */
chtype attr); /* attribute to set */
chtype field_fore(FIELD *field); /* field to query */
/* returns foreground attribute */
int set_field_back(FIELD *field, /* field to alter */
chtype attr); /* attribute to set */
chtype field_back(FIELD *field); /* field to query */
/* returns background attribute */
int set_field_pad(FIELD *field, /* field to alter */
int pad); /* pad character to set */
chtype field_pad(FIELD *field); /* field to query */
/* returns present pad character */
</programlisting>
<para>
Though above functions seem quite simple, using colors with set_field_fore() may
be frustrating in the beginning. Let me first explain about foreground and
background attributes of a field. The foreground attribute is associated with
the character. That means a character in the field is printed with the attribute
you have set with set_field_fore(). Background attribute is the attribute used
to fill background of field, whether any character is there or not. So what
about colors? Since colors are always defined in pairs, what is the right way to
display colored fields? Here's an example clarifying color attributes.
</para>
<example id="ffoat"> <title> Form Attributes example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/forms/form_attrib.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
Play with the color pairs and try to understand the foreground and background
attributes. In my programs using color attributes, I usually set only the
background with set_field_back(). Curses simply doesn't allow defining
individual color attributes.
</para>
</sect3>
<sect3 id="fieldoptionbits"><title> Field Option Bits </title>
<para>
There is also a large collection of field option bits you can set to control
various aspects of forms processing. You can manipulate them with these
functions:
</para>
<programlisting>
int set_field_opts(FIELD *field, /* field to alter */
int attr); /* attribute to set */
int field_opts_on(FIELD *field, /* field to alter */
int attr); /* attributes to turn on */
int field_opts_off(FIELD *field, /* field to alter */
int attr); /* attributes to turn off */
int field_opts(FIELD *field); /* field to query */
</programlisting>
<para>
The function set_field_opts() can be used to directly set attributes of a field
or you can choose to switch a few attributes on and off with field_opts_on() and
field_opts_off() selectively. Anytime you can query the attributes of a field
with field_opts(). The following is the list of available options. By default,
all options are on.
</para>
<variablelist>
<varlistentry><term> O_VISIBLE </term>
<listitem>
<para>
Controls whether the field is visible on the screen. Can be used
during form processing to hide or pop up fields depending on the value
of parent fields.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_ACTIVE </term>
<listitem>
<para>
Controls whether the field is active during forms processing (i.e.
visited by form navigation keys). Can be used to make labels or derived
fields with buffer values alterable by the forms application, not the user.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_PUBLIC</term>
<listitem>
<para>
Controls whether data is displayed during field entry. If this option is
turned off on a field, the library will accept and edit data in that field,
but it will not be displayed and the visible field cursor will not move.
You can turn off the O_PUBLIC bit to define password fields.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_EDIT </term>
<listitem>
<para>
Controls whether the field's data can be modified. When this option is
off, all editing requests except <literal remap="tt">REQ_PREV_CHOICE
</literal> and <literal remap="tt">REQ_NEXT_CHOICE</literal>will
fail. Such read-only fields may be useful for help messages.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_WRAP </term>
<listitem>
<para>
Controls word-wrapping in multi-line fields. Normally, when any
character of a (blank-separated) word reaches the end of the current line, the
entire word is wrapped to the next line (assuming there is one). When this
option is off, the word will be split across the line break.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_BLANK </term>
<listitem>
<para>
Controls field blanking. When this option is on, entering a character at
the first field position erases the entire field (except for the just-entered
character).
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_AUTOSKIP </term>
<listitem>
<para>
Controls automatic skip to next field when this one fills. Normally,
when the forms user tries to type more data into a field than will fit,
the editing location jumps to next field. When this option is off, the
user's cursor will hang at the end of the field. This option is ignored
in dynamic fields that have not reached their size limit.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_NULLOK </term>
<listitem>
<para>
Controls whether validation is applied to
blank fields. Normally, it is not; the user can leave a field blank
without invoking the usual validation check on exit. If this option is
off on a field, exit from it will invoke a validation check.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_PASSOK </term>
<listitem>
<para>
Controls whether validation occurs on every exit, or only after
the field is modified. Normally the latter is true. Setting O_PASSOK
may be useful if your field's validation function may change during
forms processing.
</para>
</listitem>
</varlistentry>
<varlistentry><term> O_STATIC </term>
<listitem>
<para>
Controls whether the field is fixed to its initial dimensions. If you
turn this off, the field becomes dynamic and will
stretch to fit entered data.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
A field's options cannot be changed while the field is currently selected.
However, options may be changed on posted fields that are not current.
</para>
<para>
The option values are bit-masks and can be composed with logical-or in
the obvious way. You have seen the usage of switching off O_AUTOSKIP option.
The following example clarifies usage of some more options. Other options
are explained where appropriate.
</para>
<example id="ffoop"> <title> Field Options Usage example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/forms/form_options.c">
</imageobject></inlinemediaobject></programlisting>
</example>
<para>
This example, though useless, shows the usage of options. If used properly, they
can present information very effectively in a form. The second field being not
O_PUBLIC, does not show the characters you are typing.
</para>
</sect3>
<sect3 id="fieldstatus"><title> Field Status </title>
<para>
The field status specifies whether the field has got edited or not. It is
initially set to FALSE and when user enters something and the data buffer gets
modified it becomes TRUE. So a field's status can be queried to find out whether
it has been modified or not. The following functions can assist in those
operations.
</para>
<programlisting>
int set_field_status(FIELD *field, /* field to alter */
int status); /* status to set */
int field_status(FIELD *field); /* fetch status of field */
</programlisting>
<para>
It's better to check the field's status only after leaving the field, as
data buffer might not have been updated yet as the validation is still due. To
guarantee that right status is returned, call field_status() either (1) in the
field's exit validation check routine, (2) from the field's or form's
initialization or termination hooks, or (3) just after a REQ_VALIDATION request
has been processed by the forms driver
</para>
</sect3>
<sect3 id="fielduserptr"><title> Field User Pointer </title>
<para>
Every field structure contains one pointer that can be used by the user for
various purposes. It is not touched by forms library and can be used for any
purpose by the user. The following functions set and fetch user pointer.
</para>
<programlisting>
int set_field_userptr(FIELD *field,
char *userptr); /* the user pointer you wish to associate */
/* with the field */
char *field_userptr(FIELD *field); /* fetch user pointer of the field */
</programlisting>
</sect3>
<sect3 id="variablesizefields"><title> Variable-Sized Fields </title>
<para>
If you want a dynamically changing field with variable width, this is the
feature you want to put to full use. This will allow the user to enter more data
than the original size of the field and let the field grow. According to the
field orientation it will scroll horizontally or vertically to incorporate the
new data.
</para>
<para>
To make a field dynamically growable, the option O_STATIC should be turned off.
This can be done with a
<programlisting>
field_opts_off(field_pointer, O_STATIC);
</programlisting>
</para>
<para>
But it's usually not advisable to allow a field to grow infinitely. You can set
a maximum limit to the growth of the field with
<programlisting>
int set_max_field(FIELD *field, /* Field on which to operate */
int max_growth); /* maximum growth allowed for the field */
</programlisting>
</para>
<para>
The field info for a dynamically growable field can be retrieved by
<programlisting>
int dynamic_field_info( FIELD *field, /* Field on which to operate */
int *prows, /* number of rows will be filled in this */
int *pcols, /* number of columns will be filled in this*/
int *pmax) /* maximum allowable growth will be filled */
/* in this */
</programlisting>
Though field_info work as usual, it is advisable to use this function to get the
proper attributes of a dynamically growable field.
</para>
<para>
Recall the library routine new_field; a new field created with height set to one
will be defined to be a one line field. A new field created with height greater
than one will be defined to be a multi line field.
</para>
<para>
A one line field with O_STATIC turned off (dynamically growable field) will
contain a single fixed row, but the number of columns can increase if the user
enters more data than the initial field will hold. The number of columns
displayed will remain fixed and the additional data will scroll horizontally.
</para>
<para>
A multi line field with O_STATIC turned off (dynamically growable field) will
contain a fixed number of columns, but the number of rows can increase if the
user enters more data than the initial field will hold. The number of rows
displayed will remain fixed and the additional data will scroll vertically.
</para>
<para>
The above two paragraphs pretty much describe a dynamically growable field's
behavior. The way other parts of forms library behaves is described below:
</para>
<orderedlist>
<listitem><para>
The field option O_AUTOSKIP will be ignored if the option O_STATIC is off and
there is no maximum growth specified for the field. Currently, O_AUTOSKIP
generates an automatic REQ_NEXT_FIELD form driver request when the user types in
the last character position of a field. On a growable field with no maximum
growth specified, there is no last character position. If a maximum growth is
specified, the O_AUTOSKIP option will work as normal if the field has grown to
its maximum size.
</para></listitem>
<listitem>
<para>
The field justification will be ignored if the option O_STATIC is off.
Currently, set_field_just can be used to JUSTIFY_LEFT, JUSTIFY_RIGHT,
JUSTIFY_CENTER the contents of a one line field. A growable one line field will,
by definition, grow and scroll horizontally and may contain more data than can
be justified. The return from field_just will be unchanged.
</para></listitem>
<listitem>
<para>
The overloaded form driver request REQ_NEW_LINE will operate the same way
regardless of the O_NL_OVERLOAD form option if the field option O_STATIC is off
and there is no maximum growth specified for the field. Currently, if the form
option O_NL_OVERLOAD is on, REQ_NEW_LINE implicitly generates a REQ_NEXT_FIELD
if called from the last line of a field. If a field can grow without bound,
there is no last line, so REQ_NEW_LINE will never implicitly generate a
REQ_NEXT_FIELD. If a maximum growth limit is specified and the O_NL_OVERLOAD
form option is on, REQ_NEW_LINE will only implicitly generate REQ_NEXT_FIELD if
the field has grown to its maximum size and the user is on the last line.
</para></listitem>
<listitem>
<para>
The library call dup_field will work as usual; it will duplicate the field,
including the current buffer size and contents of the field being duplicated.
Any specified maximum growth will also be duplicated.
</para></listitem>
<listitem><para>
The library call link_field will work as usual; it will duplicate all field
attributes and share buffers with the field being linked. If the O_STATIC field
option is subsequently changed by a field sharing buffers, how the system reacts
to an attempt to enter more data into the field than the buffer will currently
hold will depend on the setting of the option in the current field.
</para></listitem>
<listitem><para>
The library call field_info will work as usual; the variable nrow will contain
the value of the original call to new_field. The user should use
dynamic_field_info, described above, to query the current size of the buffer.
</para></listitem>
</orderedlist>
<para>
Some of the above points make sense only after explaining form driver. We will
be looking into that in next few sections.
</para>
</sect3>
</sect2>
<sect2 id="formwindows"><title> Form Windows </title>
<para>
The form windows concept is pretty much similar to menu windows. Every form is
associated with a main window and a sub window. The form main window displays
any title or border associated or whatever the user wishes. Then the sub window
contains all the fields and displays them according to their position. This
gives the flexibility of manipulating fancy form displaying very easily.
</para>
<para>
Since this is pretty much similar to menu windows, I am providing an example
with out much explanation. The functions are similar and they work the same way.
</para>
<example id="ffowi"><title> Form Windows Example </title>
<programlisting><inlinemediaobject><imageobject>
<imagedata format="linespecific"
fileref="resources/ncurses_programs/forms/form_win.c">
</imageobject></inlinemediaobject></programlisting>
</example>
</sect2>
<sect2 id="filedvalidate"><title> Field Validation </title>
<para>
By default, a field will accept any data input by the user. It is possible to
attach validation to the field. Then any attempt by the user to leave the field,
while it contains data that doesn't match the validation type will fail. Some
validation types also have a character-validity check for each time a character
is entered in the field.
</para>
<para>
Validation can be attached to a field with the following function.
<programlisting>
int set_field_type(FIELD *field, /* field to alter */
FIELDTYPE *ftype, /* type to associate */
...); /* additional arguments*/
</programlisting>
Once set, the validation type for a field can be queried with
<programlisting>
FIELDTYPE *field_type(FIELD *field); /* field to query */
</programlisting>
</para>
<para>
The form driver validates the data in a field only when data is entered by the
end-user. Validation does not occur when
</para>
<itemizedlist>
<listitem><para>
the application program changes the field value by calling set_field_buffer.
</para></listitem>
<listitem><para>
linked field values are changed indirectly -- by changing the field to which
they are linked
</para></listitem>
</itemizedlist>
<para>
The following are the pre-defined validation types. You can also specify custom
validation, though it's a bit tricky and cumbersome.
</para>
<bridgehead>TYPE_ALPHA</bridgehead>
<para>
This field type accepts alphabetic data; no blanks, no digits, no special
characters (this is checked at character-entry time). It is set up with:
</para>
<programlisting>
int set_field_type(FIELD *field, /* field to alter */
TYPE_ALPHA, /* type to associate */
int width); /* maximum width of field */
</programlisting>
<para>
The width argument sets a minimum width of data. The user has to enter at-least
width number of characters before he can leave the field. Typically
you'll want to set this to the field width; if it's greater than the
field width, the validation check will always fail. A minimum width
of zero makes field completion optional.
</para>
<bridgehead>TYPE_ALNUM</bridgehead>
<para>
This field type accepts alphabetic data and digits; no blanks, no special
characters (this is checked at character-entry time). It is set up with:
</para>
<programlisting>
int set_field_type(FIELD *field, /* field to alter */
TYPE_ALNUM, /* type to associate */
int width); /* maximum width of field */
</programlisting>
<para>
The width argument sets a minimum width of data. As with
TYPE_ALPHA, typically you'll want to set this to the field width; if it's
greater than the field width, the validation check will always fail. A
minimum width of zero makes field completion optional.
</para>
<bridgehead>TYPE_ENUM</bridgehead>
<para>
This type allows you to restrict a field's values to be among a specified
set of string values (for example, the two-letter postal codes for U.S.
states). It is set up with:
</para>
<programlisting>
int set_field_type(FIELD *field, /* field to alter */
TYPE_ENUM, /* type to associate */
char **valuelist; /* list of possible values */
int checkcase; /* case-sensitive? */
int checkunique); /* must specify uniquely? */
</programlisting>
<para>
The valuelist parameter must point at a NULL-terminated list of
valid strings. The checkcase argument, if true, makes comparison
with the string case-sensitive.
</para>
<para>
When the user exits a TYPE_ENUM field, the validation procedure tries to
complete the data in the buffer to a valid entry. If a complete choice string
has been entered, it is of course valid. But it is also possible to enter a
prefix of a valid string and have it completed for you.
</para>
<para>
By default, if you enter such a prefix and it matches more than one value
in the string list, the prefix will be completed to the first matching
value. But the checkunique argument, if true, requires prefix
matches to be unique in order to be valid.
</para>
<para>
The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be particularly
useful with these fields.
</para>
<bridgehead>TYPE_INTEGER</bridgehead>
<para>
This field type accepts an integer. It is set up as follows:
</para>
<programlisting>
int set_field_type(FIELD *field, /* field to alter */
TYPE_INTEGER, /* type to associate */
int padding, /* # places to zero-pad to */
int vmin, int vmax); /* valid range */
</programlisting>
<para>
Valid characters consist of an optional leading minus and digits.
The range check is performed on exit. If the range maximum is less
than or equal to the minimum, the range is ignored.
</para>
<para>
If the value passes its range check, it is padded with as many leading
zero digits as necessary to meet the padding argument.
</para>
<para>
A TYPE_INTEGER value buffer can conveniently be interpreted with the C library
function atoi(3).
</para>
<bridgehead>TYPE_NUMERIC</bridgehead>
<para>
This field type accepts a decimal number. It is set up as follows:
</para>
<programlisting>
int set_field_type(FIELD *field, /* field to alter */
TYPE_NUMERIC, /* type to associate */
int padding, /* # places of precision */
int vmin, int vmax); /* valid range */
</programlisting>
<para>
Valid characters consist of an optional leading minus and digits. possibly
including a decimal point. The range check is performed on exit. If the
range maximum is less than or equal to the minimum, the range is
ignored.
</para>
<para>
If the value passes its range check, it is padded with as many trailing
zero digits as necessary to meet the padding argument.
</para>
<para>
A TYPE_NUMERIC value buffer can conveniently be interpreted with the C library
function atof(3).
</para>
<bridgehead>TYPE_REGEXP</bridgehead>
<para>
This field type accepts data matching a regular expression. It is set up
as follows:
</para>
<programlisting>
int set_field_type(FIELD *field, /* field to alter */
TYPE_REGEXP, /* type to associate */
char *regexp); /* expression to match */
</programlisting>
<para>
The syntax for regular expressions is that of regcomp(3).
The check for regular-expression match is performed on exit.
</para>
</sect2>
<sect2 id="formdriver"><title> Form Driver: The work horse of the forms system </title>
<para>
As in the menu system, form_driver() plays a very important role in forms
system. All types of requests to forms system should be funneled through
form_driver().
</para>
<programlisting>
int form_driver(FORM *form, /* form on which to operate */
int request) /* form request code */
</programlisting>
<para>
As you have seen some of the examples above, you have to be in a loop looking
for user input and then decide whether it's a field data or a form request. The
form requests are then passed to form_driver() to do the work.
</para>
<para>
The requests roughly can be divided into following categories. Different
requests and their usage is explained below:
</para>
<sect3 id="pagenavreq"><title> Page Navigation Requests </title>
<para>
These requests cause page-level moves through the form, triggering display of a
new form screen. A form can be made of multiple pages. If you have a big form
with lot of fields and logical sections, then you can divide the form into
pages. The function set_new_page() to set a new page at the field specified.
</para>
<programlisting>
int set_new_page(FIELD *field,/* Field at which page break to be set or unset */
bool new_page_flag); /* should be TRUE to put a break */
</programlisting>
<para>
The following requests allow you to move to different pages
</para>
<itemizedlist>
<listitem><para><emphasis>REQ_NEXT_PAGE</emphasis> Move to the next form page.
</para> </listitem>
<listitem><para><emphasis>REQ_PREV_PAGE</emphasis> Move to the previous
form page.</para></listitem>
<listitem><para><emphasis>REQ_FIRST_PAGE</emphasis> Move to the first form page.
</para> </listitem>
<listitem><para><emphasis>REQ_LAST_PAGE</emphasis> Move to the last form page.
</para> </listitem>
</itemizedlist>
<para>
These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from the
last page goes to the first, and REQ_PREV_PAGE from the first page goes to
the last.
</para>
</sect3>
<sect3 id="interfieldnavreq"> <title> Inter-Field Navigation Requests</title>
<para>
These requests handle navigation between fields on the same page.
</para>
<itemizedlist>
<listitem><para><emphasis>REQ_NEXT_FIELD</emphasis>
Move to next field. </para> </listitem>
<listitem><para><emphasis>REQ_PREV_FIELD</emphasis>
Move to previous field. </para></listitem>
<listitem><para><emphasis>REQ_FIRST_FIELD</emphasis>
Move to the first field. </para> </listitem>
<listitem><para><emphasis>REQ_LAST_FIELD</emphasis>
Move to the last field. </para> </listitem>
<listitem><para><emphasis>REQ_SNEXT_FIELD</emphasis>
Move to sorted next field. </para> </listitem>
<listitem><para><emphasis>REQ_SPREV_FIELD</emphasis>
Move to sorted previous field. </para> </listitem>
<listitem><para><emphasis>REQ_SFIRST_FIELD</emphasis>
Move to the sorted first field. </para> </listitem>
<listitem><para><emphasis>REQ_SLAST_FIELD</emphasis>
Move to the sorted last field. </para> </listitem>
<listitem><para><emphasis>REQ_LEFT_FIELD</emphasis>
Move left to field. </para> </listitem>
<listitem><para><emphasis>REQ_RIGHT_FIELD</emphasis>
Move right to field. </para> </listitem>
<listitem><para><emphasis>REQ_UP_FIELD</emphasis>
Move up to field. </para> </listitem>
<listitem><para><emphasis>REQ_DOWN_FIELD</emphasis>
Move down to field. </para> </listitem>
</itemizedlist>
<para>
These requests treat the list of fields on a page as cyclic; that is,
REQ_NEXT_FIELD from the last field goes to the first, and REQ_PREV_FIELD
from the first field goes to the last. The order of the fields for these
(and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests) is simply the order of
the field pointers in the form array (as set up by new_form() or
set_form_fields()
</para>
<para>
It is also possible to traverse the fields as if they had been sorted in
screen-position order, so the sequence goes left-to-right and top-to-bottom.
To do this, use the second group of four sorted-movement requests.
</para>
<para>
Finally, it is possible to move between fields using visual directions up,
down, right, and left. To accomplish this, use the third group of four
requests. Note, however, that the position of a form for purposes of these
requests is its upper-left corner.
</para>
<para>
For example, suppose you have a multi-line field B, and two single-line
fields A and C on the same line with B, with A to the left of B and C to the
right of B. A REQ_MOVE_RIGHT from A will go to B only if A, B, and C all
share the same first line; otherwise it will skip over B to C.
</para>
</sect3>
<sect3 id="intrafieldnavreq"><title> Intra-Field Navigation Requests </title>
<para>
These requests drive movement of the edit cursor within the currently
selected field.
</para>
<itemizedlist>
<listitem><para><emphasis>REQ_NEXT_CHAR</emphasis>
Move to next character. </para> </listitem>
<listitem><para><emphasis>REQ_PREV_CHAR</emphasis>
Move to previous character. </para> </listitem>
<listitem><para><emphasis>REQ_NEXT_LINE</emphasis>
Move to next line. </para> </listitem>
<listitem><para><emphasis>REQ_PREV_LINE</emphasis>
Move to previous line. </para> </listitem>
<listitem><para><emphasis>REQ_NEXT_WORD</emphasis>
Move to next word. </para> </listitem>
<listitem><para><emphasis>REQ_PREV_WORD</emphasis>
Move to previous word. </para> </listitem>
<listitem><para><emphasis>REQ_BEG_FIELD</emphasis>
Move to beginning of field. </para> </listitem>
<listitem><para><emphasis>REQ_END_FIELD</emphasis>
Move to end of field. </para> </listitem>
<listitem><para><emphasis>REQ_BEG_LINE</emphasis>
Move to beginning of line. </para> </listitem>
<listitem><para><emphasis>REQ_END_LINE</emphasis>
Move to end of line. </para> </listitem>
<listitem><para><emphasis>REQ_LEFT_CHAR</emphasis>
Move left in field. </para> </listitem>
<listitem><para><emphasis>REQ_RIGHT_CHAR</emphasis>
Move right in field. </para> </listitem>
<listitem><para><emphasis>REQ_UP_CHAR</emphasis>
Move up in field. </para> </listitem>
<listitem><para><emphasis>REQ_DOWN_CHAR</emphasis>
Move down in field. </para> </listitem>
</itemizedlist>
<para>
Each word is separated from the previous and next characters by whitespace.
The commands to move to beginning and end of line or field look for the
first or last non-pad character in their ranges.
</para>
</sect3>
<sect3 id="scrollreq"><title> Scrolling Requests </title>
<para>
Fields that are dynamic and have grown and fields explicitly created with
offscreen rows are scrollable. One-line fields scroll horizontally;
multi-line fields scroll vertically. Most scrolling is triggered by editing
and intra-field movement (the library scrolls the field to keep the cursor
visible). It is possible to explicitly request scrolling with the following
requests:
</para>
<itemizedlist>
<listitem><para><emphasis>REQ_SCR_FLINE</emphasis>
Scroll vertically forward a line. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_BLINE</emphasis>
Scroll vertically backward a line. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_FPAGE</emphasis>
Scroll vertically forward a page. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_BPAGE</emphasis>
Scroll vertically backward a page. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_FHPAGE</emphasis>
Scroll vertically forward half a page. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_BHPAGE</emphasis>
Scroll vertically backward half a page. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_FCHAR</emphasis>
Scroll horizontally forward a character. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_BCHAR</emphasis>
Scroll horizontally backward a character. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_HFLINE</emphasis>
Scroll horizontally one field width forward. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_HBLINE</emphasis>
Scroll horizontally one field width backward. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_HFHALF</emphasis>
Scroll horizontally one half field width forward. </para> </listitem>
<listitem><para><emphasis>REQ_SCR_HBHALF</emphasis>
Scroll horizontally one half field width backward. </para> </listitem>
</itemizedlist>
<para>
For scrolling purposes, a page of a field is the height of its visible part.
</para>
</sect3>
<sect3 id="editreq"> <title> Editing Requests </title>
<para>
When you pass the forms driver an ASCII character, it is treated as a
request to add the character to the field's data buffer. Whether this is an
insertion or a replacement depends on the field's edit mode (insertion is
the default.
</para>
<para>
The following requests support editing the field and changing the edit mode:
</para>
<itemizedlist>
<listitem><para><emphasis>REQ_INS_MODE</emphasis>
Set insertion mode. </para> </listitem>
<listitem><para><emphasis>REQ_OVL_MODE</emphasis>
Set overlay mode. </para> </listitem>
<listitem><para><emphasis>REQ_NEW_LINE</emphasis>
New line request (see below for explanation). </para> </listitem>
<listitem><para><emphasis>REQ_INS_CHAR</emphasis>
Insert space at character location. </para> </listitem>
<listitem><para><emphasis>REQ_INS_LINE</emphasis>
Insert blank line at character location. </para> </listitem>
<listitem><para><emphasis>REQ_DEL_CHAR</emphasis>
Delete character at cursor. </para> </listitem>
<listitem><para><emphasis>REQ_DEL_PREV</emphasis>
Delete previous word at cursor. </para> </listitem>
<listitem><para><emphasis>REQ_DEL_LINE</emphasis>
Delete line at cursor. </para> </listitem>
<listitem><para><emphasis>REQ_DEL_WORD</emphasis>
Delete word at cursor. </para> </listitem>
<listitem><para><emphasis>REQ_CLR_EOL</emphasis>
Clear to end of line. </para> </listitem>
<listitem><para><emphasis>REQ_CLR_EOF</emphasis>
Clear to end of field. </para> </listitem>
<listitem><para><emphasis>REQ_CLR_FIELD</emphasis>
Clear entire field. </para> </listitem>
</itemizedlist>
<para>
The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is complicated
and partly controlled by a pair of forms options. The special cases are
triggered when the cursor is at the beginning of a field, or on the last
line of the field.
</para>
<para>
First, we consider REQ_NEW_LINE:
</para>
<para>
The normal behavior of REQ_NEW_LINE in insert mode is to break the current
line at the position of the edit cursor, inserting the portion of the
current line after the cursor as a new line following the current and moving
the cursor to the beginning of that new line (you may think of this as
inserting a newline in the field buffer).
</para>
<para>
The normal behavior of REQ_NEW_LINE in overlay mode is to clear the current
line from the position of the edit cursor to end of line. The cursor is then
moved to the beginning of the next line.
</para>
<para>
However, REQ_NEW_LINE at the beginning of a field, or on the last line of a
field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is off, this
special action is disabled.
</para>
<para>
Now, let us consider REQ_DEL_PREV:
</para>
<para>
The normal behavior of REQ_DEL_PREV is to delete the previous character. If
insert mode is on, and the cursor is at the start of a line, and the text on
that line will fit on the previous one, it instead appends the contents of
the current line to the previous one and deletes the current line (you may
think of this as deleting a newline from the field buffer).
</para>
<para>
However, REQ_DEL_PREV at the beginning of a field is instead treated as a
REQ_PREV_FIELD.
</para>
<para>
If the O_BS_OVERLOAD option is off, this special action is disabled and the
forms driver just returns E_REQUEST_DENIED.
</para>
</sect3>
<sect3 id="orderreq"> <title> Order Requests </title>
<para>
If the type of your field is ordered, and has associated functions for
getting the next and previous values of the type from a given value, there
are requests that can fetch that value into the field buffer:
</para>
<itemizedlist>
<listitem><para><emphasis>REQ_NEXT_CHOICE</emphasis>
Place the successor value of the current value in the buffer.
</para> </listitem>
<listitem><para><emphasis>REQ_PREV_CHOICE</emphasis>
Place the predecessor value of the current value in the buffer.
</para> </listitem>
</itemizedlist>
<para>
Of the built-in field types, only TYPE_ENUM has built-in successor and
predecessor functions. When you define a field type of your own (see Custom
Validation Types), you can associate our own ordering functions.
</para>
</sect3>
<sect3 id="appliccommands"> <title> Application Commands </title>
<para>
Form requests are represented as integers above the curses value greater than
KEY_MAX and less than or equal to the constant MAX_COMMAND. A value within this
range gets ignored by form_driver(). So this can be used for any purpose by the
application. It can be treated as an application specific action and take
corresponding action.
</para>
</sect3>
</sect2>
</sect1>
<sect1 id="tools"><title> Tools and Widget Libraries</title>
<para>
Now that you have seen the capabilities of ncurses and its sister libraries, you
are rolling your sleeves up and gearing for a project that heavily manipulates
screen. But wait.. It can be pretty difficult to write and maintain complex GUI
widgets in plain ncurses or even with the additional libraries. There are some
ready-to-use tools and widget libraries that can be used instead of writing your
own widgets. You can use some of them, get ideas from the code, or even extend
them.
</para>
<sect2 id="cdk"><title> CDK (Curses Development Kit) </title>
<para>
In the author's words
</para>
<para>
<emphasis>
CDK stands for 'Curses Development Kit' and it currently contains 21 ready
to use widgets which facilitate the speedy development of full screen
curses programs.
</emphasis>
</para>
<para>
The kit provides some useful widgets, which can be used in your programs
directly. It's pretty well written and the documentation is very good. The
examples in the examples directory can be a good place to start for beginners.
The CDK can be downloaded from <ulink
url="http://invisible-island.net/cdk/">http://invisible-island.net/cdk/</ulink>
. Follow the instructions in
README file to install it.
</para>
<sect3 id="widgetlist"><title> Widget List </title>
<para>
The following is the list of widgets provided with cdk and their description.
</para>
<programlisting>
Widget Type Quick Description
===========================================================================
Alphalist Allows a user to select from a list of words, with
the ability to narrow the search list by typing in a
few characters of the desired word.
Buttonbox This creates a multiple button widget.
Calendar Creates a little simple calendar widget.
Dialog Prompts the user with a message, and the user
can pick an answer from the buttons provided.
Entry Allows the user to enter various types of information.
File Selector A file selector built from Cdk base widgets. This
example shows how to create more complicated widgets
using the Cdk widget library.
Graph Draws a graph.
Histogram Draws a histogram.
Item List Creates a pop up field which allows the user to select
one of several choices in a small field. Very useful
for things like days of the week or month names.
Label Displays messages in a pop up box, or the label can be
considered part of the screen.
Marquee Displays a message in a scrolling marquee.
Matrix Creates a complex matrix with lots of options.
Menu Creates a pull-down menu interface.
Multiple Line Entry A multiple line entry field. Very useful
for long fields. (like a description
field)
Radio List Creates a radio button list.
Scale Creates a numeric scale. Used for allowing a user to
pick a numeric value and restrict them to a range of
values.
Scrolling List Creates a scrolling list/menu list.
Scrolling Window Creates a scrolling log file viewer. Can add
information into the window while its running.
A good widget for displaying the progress of
something. (akin to a console window)
Selection List Creates a multiple option selection list.
Slider Akin to the scale widget, this widget provides a
visual slide bar to represent the numeric value.
Template Creates a entry field with character sensitive
positions. Used for pre-formatted fields like
dates and phone numbers.
Viewer This is a file/information viewer. Very useful
when you need to display loads of information.
===========================================================================
</programlisting>
<para>
A few of the widgets are modified by Thomas Dickey in recent versions.
</para>
</sect3>
<sect3 id="cdkattract"><title> Some Attractive Features </title>
<para>
Apart from making our life easier with readily usable widgets, cdk solves one
frustrating problem with printing multi colored strings, justified strings
elegantly. Special formatting tags can be embedded in the strings which are
passed to CDK functions. For Example
</para>
<para>
If the string
</para>
<programlisting>
"&lt;/B/1&gt;This line should have a yellow foreground and a blue
background.&lt;!1&gt;"
</programlisting>
<para>
given as a parameter to newCDKLabel(), it prints the line with yellow foreground
and blue background. There are other tags available for justifying string,
embedding special drawing characters etc.. Please refer to the man page
cdk_display(3X) for details. The man page explains the usage with nice examples.
</para>
</sect3>
<sect3 id="cdkconclusion"><title> Conclusion </title>
<para>
All in all, CDK is a well-written package of widgets, which if used properly can
form a strong frame work for developing complex GUI.
</para>
</sect3>
</sect2>
<sect2 id="dialog"><title> The dialog </title>
<para>
Long long ago, in September 1994, when few people knew linux, Jeff Tranter wrote
an <ulink url="http://www2.linuxjournal.com/lj-issues/issue5/2807.html">article
</ulink> on dialog in Linux Journal. He starts the article with these words..
</para>
<para>
<emphasis>
Linux is based on the Unix operating system, but also features a number of
unique and useful kernel features and application programs that often go beyond
what is available under Unix. One little-known gem is "dialog", a utility for
creating professional-looking dialog boxes from within shell scripts. This
article presents a tutorial introduction to the dialog utility, and shows
examples of how and where it can be used
</emphasis>
</para>
<para>
As he explains, dialog is a real gem in making professional-looking dialog boxes
with ease. It creates a variety of dialog boxes, menus, check lists etc.. It is
usually installed by default. If not, you can download it from <ulink
url="http://invisible-island.net/dialog/">Thomas Dickey</ulink>'s site.
</para>
<para>
The above-mentioned article gives a very good overview of its uses and
capabilites. The man page has more details. It can be used in variety of
situations. One good example is building of linux kernel in text mode. Linux
kernel uses a modified version of dialog tailored for its needs.
</para>
<para>
dialog was initially designed to be used with shell scripts. If you want to use
its functionality in a c program, then you can use libdialog. The documentation
regarding this is sparse. Definitive reference is the dialog.h header file which
comes with the library. You may need to hack here and there to get the required
output. The source is easily customizable. I have used it on a number of
occasions by modifying the code.
</para>
</sect2>
<sect2 id="perlcurses"><title> Perl Curses Modules CURSES::FORM and CURSES::WIDGETS</title>
<para>
The perl module Curses, Curses::Form and Curses::Widgets give access to curses
from perl. If you have curses and basic perl is installed, you can get these
modules from <ulink url="http://www.cpan.org/modules/01modules.index.html"> CPAN
All Modules page</ulink>. Get the three zipped modules in the Curses category.
Once installed you can use these modules from perl scripts like any other
module. For more information on perl modules see perlmod man page. The above
modules come with good documentation and they have some demo scripts to test the
functionality. Though the widgets provided are very rudimentary, these modules
provide good access to curses library from perl.
</para>
<para>
Some of my code examples are converted to perl by Anuradha Ratnaweera and they
are available in the <literal remap="tt">perl</literal> directory.
</para>
<para>
For more information see man pages Curses(3) , Curses::Form(3) and
Curses::Widgets(3). These pages are installed only when the above modules are
acquired and installed.
</para>
</sect2>
</sect1>
<sect1 id="justforfun"> <title>Just For Fun !!!</title>
<para>
This section contains few programs written by me just for fun. They don't
signify a better programming practice or the best way of using ncurses. They are
provided here so as to allow beginners to get ideas and add more programs to
this section. If you have written a couple of nice, simple programs in curses
and want them to included here, contact <ulink url="mailto:ppadala@gmail.com">
me</ulink>.
</para>
<sect2 id="gameoflife"><title>The Game of Life</title>
<para>
Game of life is a wonder of math. In
<ulink url="http://www.math.com/students/wonders/life/life.html">
Paul Callahan</ulink>'s words
</para>
<programlisting>
<emphasis>
The Game of Life (or simply Life) is not a game in the conventional sense. There
are no players, and no winning or losing. Once the "pieces" are placed in the
starting position, the rules determine everything that happens later.
Nevertheless, Life is full of surprises! In most cases, it is impossible to look
at a starting position (or pattern) and see what will happen in the future. The
only way to find out is to follow the rules of the game.
</emphasis>
</programlisting>
<para>
This program starts with a simple inverted U pattern and shows how wonderful
life works. There is a lot of room for improvement in the program. You can let
the user enter pattern of his choice or even take input from a file. You can
also change rules and play with a lot of variations. Search on <ulink
url="http://www.google.com">google</ulink> for interesting information on game
of life.
</para>
<para>
<emphasis>File Path: JustForFun/life.c</emphasis>
</para>
</sect2>
<sect2 id="magic"><title>Magic Square</title>
<para>
Magic Square, another wonder of math, is very simple to understand but very
difficult to make. In a magic square sum of the numbers in each row, each column
is equal. Even diagnol sum can be equal. There are many variations which have
special properties.
</para>
<para>
This program creates a simple magic square of odd order.
</para>
<para>
<emphasis>File Path: JustForFun/magic.c</emphasis>
</para>
</sect2>
<sect2 id="hanoi"> <title> Towers of Hanoi </title>
<para>
The famous towers of hanoi solver. The aim of the game is to move the disks on
the first peg to last peg, using middle peg as a temporary stay. The catch is
not to place a larger disk over a small disk at any time.
</para>
<para>
<emphasis>File Path: JustForFun/hanoi.c</emphasis>
</para>
</sect2>
<sect2 id="queens"> <title> Queens Puzzle </title>
<para>
The objective of the famous N-Queen puzzle is to put N queens on a N X N chess
board without attacking each other.
</para>
<para>
This program solves it with a simple backtracking technique.
</para>
<para>
<emphasis>File Path: JustForFun/queens.c</emphasis>
</para>
</sect2>
<sect2 id="shuffle"> <title>Shuffle </title>
<para>
A fun game, if you have time to kill.
</para>
<para>
<emphasis>File Path: JustForFun/shuffle.c</emphasis>
</para>
</sect2>
<sect2 id="tt"> <title>Typing Tutor </title>
<para>
A simple typing tutor, I created more out of need than for ease of use. If you
know how to put your fingers correctly on the keyboard, but lack practice, this
can be helpful.
</para>
<para>
<emphasis>File Path: JustForFun/tt.c</emphasis>
</para>
</sect2>
</sect1>
<sect1 id="ref"> <title>References</title>
<itemizedlist>
<listitem><para>NCURSES man pages </para> </listitem>
<listitem><para>NCURSES FAQ at <ulink
url="http://invisible-island.net/ncurses/ncurses.faq.html">
http://invisible-island.net/ncurses/ncurses.faq.html</ulink>
</para> </listitem>
<listitem><para>Writing programs with NCURSES by Eric Raymond and Zeyd M.
Ben-Halim at
<ulink
url="http://invisible-island.net/ncurses/ncurses-intro.html">http://invisible-island.net/ncurses/ncurses-intro.html</ulink> - somewhat
obsolete. I was inspired by this document and the structure of this HOWTO
follows from the original document</para></listitem>
</itemizedlist>
</sect1>
</article>
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