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NCURSES Programming HOWTO
Pradeep Padala
<ppadala@gmail.com>
v1.9, 2005-06-20
Revision History
Revision 1.9 2005-06-20 Revised by: ppadala
The license has been changed to the MIT-style license used by NCURSES. Note
that the programs are also re-licensed under this.
Revision 1.8 2005-06-17 Revised by: ppadala
Lots of updates. Added references and perl examples. Changes to examples.
Many grammatical and stylistic changes to the content. Changes to NCURSES
history.
Revision 1.7.1 2002-06-25 Revised by: ppadala
Added a README file for building and instructions for building from source.
Revision 1.7 2002-06-25 Revised by: ppadala
Added "Other formats" section and made a lot of fancy changes to the
programs. Inlining of programs is gone.
Revision 1.6.1 2002-02-24 Revised by: ppadala
Removed the old Changelog section, cleaned the makefiles
Revision 1.6 2002-02-16 Revised by: ppadala
Corrected a lot of spelling mistakes, added ACS variables section
Revision 1.5 2002-01-05 Revised by: ppadala
Changed structure to present proper TOC
Revision 1.3.1 2001-07-26 Revised by: ppadala
Corrected maintainers paragraph, Corrected stable release number
Revision 1.3 2001-07-24 Revised by: ppadala
Added copyright notices to main document (LDP license) and programs (GPL),
Corrected printw_example.
Revision 1.2 2001-06-05 Revised by: ppadala
Incorporated ravi's changes. Mainly to introduction, menu, form, justforfun
sections
Revision 1.1 2001-05-22 Revised by: ppadala
Added "a word about window" section, Added scanw_example.
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 [mailto:ppadala@gmail.com] this address
-----------------------------------------------------------------------------
Table of Contents
1. Introduction
1.1. What is NCURSES?
1.2. What we can do with NCURSES
1.3. Where to get it
1.4. Purpose/Scope of the document
1.5. About the Programs
1.6. Other Formats of the document
1.7. Credits
1.8. Wish List
1.9. Copyright
2. Hello World !!!
2.1. Compiling With the NCURSES Library
2.2. Dissection
3. The Gory Details
4. Initialization
4.1. Initialization functions
4.2. raw() and cbreak()
4.3. echo() and noecho()
4.4. keypad()
4.5. halfdelay()
4.6. Miscellaneous Initialization functions
4.7. An Example
5. A Word about Windows
6. Output functions
6.1. addch() class of functions
6.2. mvaddch(), waddch() and mvwaddch()
6.3. printw() class of functions
6.4. addstr() class of functions
6.5. A word of caution
7. Input functions
7.1. getch() class of functions
7.2. scanw() class of functions
7.3. getstr() class of functions
7.4. Some examples
8. Attributes
8.1. The details
8.2. attron() vs attrset()
8.3. attr_get()
8.4. attr_ functions
8.5. wattr functions
8.6. chgat() functions
9. Windows
9.1. The basics
9.2. Let there be a Window !!!
9.3. Explanation
9.4. The other stuff in the example
9.5. Other Border functions
10. Colors
10.1. The basics
10.2. Changing Color Definitions
10.3. Color Content
11. Interfacing with the key board
11.1. The Basics
11.2. A Simple Key Usage example
12. Interfacing with the mouse
12.1. The Basics
12.2. Getting the events
12.3. Putting it all Together
12.4. Miscellaneous Functions
13. Screen Manipulation
13.1. getyx() functions
13.2. Screen Dumping
13.3. Window Dumping
14. Miscellaneous features
14.1. curs_set()
14.2. Temporarily Leaving Curses mode
14.3. ACS_ variables
15. Other libraries
16. Panel Library
16.1. The Basics
16.2. Compiling With the Panels Library
16.3. Panel Window Browsing
16.4. Using User Pointers
16.5. Moving and Resizing Panels
16.6. Hiding and Showing Panels
16.7. panel_above() and panel_below() Functions
17. Menus Library
17.1. The Basics
17.2. Compiling With the Menu Library
17.3. Menu Driver: The work horse of the menu system
17.4. Menu Windows
17.5. Scrolling Menus
17.6. Multi Columnar Menus
17.7. Multi Valued Menus
17.8. Menu Options
17.9. The useful User Pointer
18. Forms Library
18.1. The Basics
18.2. Compiling With the Forms Library
18.3. Playing with Fields
18.4. Form Windows
18.5. Field Validation
18.6. Form Driver: The work horse of the forms system
19. Tools and Widget Libraries
19.1. CDK (Curses Development Kit)
19.2. The dialog
19.3. Perl Curses Modules CURSES::FORM and CURSES::WIDGETS
20. Just For Fun !!!
20.1. The Game of Life
20.2. Magic Square
20.3. Towers of Hanoi
20.4. Queens Puzzle
20.5. Shuffle
20.6. Typing Tutor
21. References
1. Introduction
In the olden days of teletype terminals, terminals were away from computers
and were connected to them through serial cables. The terminals could be
configured by sending a series of bytes. All the capabilities (such as moving
the cursor to a new location, erasing part of the screen, scrolling the
screen, changing modes etc.) of terminals could be accessed through these
series of bytes. These control seeuqnces are usually called escape sequences,
because they start with an escape(0x1B) character. Even today, with proper
emulation, we can send escape sequences to the emulator and achieve the same
effect on a terminal window.
Suppose you wanted to print a line in color. Try typing this on your console.
echo "^[[0;31;40mIn Color"
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.
echo "^[[0;37;40m"
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 termcap. 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 terminfo. 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.
-----------------------------------------------------------------------------
1.1. What is NCURSES?
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.
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.
A detailed history of NCURSES can be found in the NEWS file from the source
distribution. The current package is maintained by [mailto:dickey@his.com]
Thomas Dickey. You can contact the maintainers at [mailto:
bug-ncurses@gnu.org] bug-ncurses@gnu.org.
-----------------------------------------------------------------------------
1.2. What we can do with NCURSES
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.
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.
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.
-----------------------------------------------------------------------------
1.3. Where to get it
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.
Compiling the package
NCURSES can be obtained from [ftp://ftp.gnu.org/pub/gnu/ncurses/
ncurses.tar.gz] ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz or any of
the ftp sites mentioned in [http://www.gnu.org/order/ftp.html] http://
www.gnu.org/order/ftp.html.
Read the README and INSTALL files for details on to how to install it. It
usually involves the following operations.
tar zxvf ncurses<version>.tar.gz # unzip and untar the archive
cd ncurses<version> # cd to the directory
./configure # configure the build according to your
# environment
make # make it
su root # become root
make install # install it
Using the RPM
NCURSES RPM can be found and downloaded from [http://rpmfind.net] http://
rpmfind.net . The RPM can be installed with the following command after
becoming root.
rpm -i <downloaded rpm>
-----------------------------------------------------------------------------
1.4. Purpose/Scope of the document
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.
-----------------------------------------------------------------------------
1.5. About the Programs
All the programs in the document are available in zipped form [http://
www.tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs.tar.gz] here.
Unzip and untar it. The directory structure looks like this.
ncurses
|
|----> JustForFun -- just for fun programs
|----> basics -- basic programs
|----> demo -- output files go into this directory after make
| |
| |----> exe -- exe files of all example programs
|----> forms -- programs related to form library
|----> menus -- programs related to menus library
|----> panels -- programs related to panels library
|----> perl -- perl equivalents of the examples (contributed
| by Anuradha Ratnaweera)
|----> Makefile -- the top level Makefile
|----> README -- the top level README file. contains instructions
|----> COPYING -- copyright notice
The individual directories contain the following files.
Description of files in each directory
--------------------------------------
JustForFun
|
|----> hanoi.c -- The Towers of Hanoi Solver
|----> life.c -- The Game of Life demo
|----> magic.c -- An Odd Order Magic Square builder
|----> queens.c -- The famous N-Queens Solver
|----> shuffle.c -- A fun game, if you have time to kill
|----> tt.c -- A very trivial typing tutor
basics
|
|----> acs_vars.c -- ACS_ variables example
|----> hello_world.c -- Simple "Hello World" Program
|----> init_func_example.c -- Initialization functions example
|----> key_code.c -- Shows the scan code of the key pressed
|----> mouse_menu.c -- A menu accessible by mouse
|----> other_border.c -- Shows usage of other border functions apa
| -- rt from box()
|----> printw_example.c -- A very simple printw() example
|----> scanw_example.c -- A very simple getstr() example
|----> simple_attr.c -- A program that can print a c file with
| -- comments in attribute
|----> simple_color.c -- A simple example demonstrating colors
|----> simple_key.c -- A menu accessible with keyboard UP, DOWN
| -- arrows
|----> temp_leave.c -- Demonstrates temporarily leaving curses mode
|----> win_border.c -- Shows Creation of windows and borders
|----> with_chgat.c -- chgat() usage example
forms
|
|----> form_attrib.c -- Usage of field attributes
|----> form_options.c -- Usage of field options
|----> form_simple.c -- A simple form example
|----> form_win.c -- Demo of windows associated with forms
menus
|
|----> menu_attrib.c -- Usage of menu attributes
|----> menu_item_data.c -- Usage of item_name() etc.. functions
|----> menu_multi_column.c -- Creates multi columnar menus
|----> menu_scroll.c -- Demonstrates scrolling capability of menus
|----> menu_simple.c -- A simple menu accessed by arrow keys
|----> menu_toggle.c -- Creates multi valued menus and explains
| -- REQ_TOGGLE_ITEM
|----> menu_userptr.c -- Usage of user pointer
|----> menu_win.c -- Demo of windows associated with menus
panels
|
|----> panel_browse.c -- Panel browsing through tab. Usage of user
| -- pointer
|----> panel_hide.c -- Hiding and Un hiding of panels
|----> panel_resize.c -- Moving and resizing of panels
|----> panel_simple.c -- A simple panel example
perl
|----> 01-10.pl -- Perl equivalents of first ten example programs
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.
For every example, I have included path name for the file relative to the
examples directory.
If you prefer browsing individual programs, point your browser to [http://
tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/] http://tldp.org/
HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/
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.
-----------------------------------------------------------------------------
1.6. Other Formats of the document
This howto is also availabe in various other formats on the tldp.org site.
Here are the links to other formats of this document.
-----------------------------------------------------------------------------
1.6.1. Readily available formats from tldp.org
<EFBFBD><EFBFBD>*<2A>[http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/pdf/
NCURSES-Programming-HOWTO.pdf] Acrobat PDF Format
<EFBFBD><EFBFBD>*<2A>[http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/ps/
NCURSES-Programming-HOWTO.ps.gz] PostScript Format
<EFBFBD><EFBFBD>*<2A>[http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html/
NCURSES-Programming-HOWTO-html.tar.gz] In Multiple HTML pages
<EFBFBD><EFBFBD>*<2A>[http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/
NCURSES-Programming-HOWTO.html] In One big HTML format
-----------------------------------------------------------------------------
1.6.2. Building from source
If above links are broken or if you want to experiment with sgml read on.
Get both the source and the tar,gzipped programs, available at
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/NCURSES-Programming-HOWTO.sgml
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/ncurses_programs.tar.gz
Unzip ncurses_programs.tar.gz with
tar zxvf ncurses_programs.tar.gz
Use jade to create various formats. For example if you just want to create
the multiple html files, you would use
jade -t sgml -i html -d <path to docbook html stylesheet>
NCURSES-Programming-HOWTO.sgml
to get pdf, first create a single html file of the HOWTO with
jade -t sgml -i html -d <path to docbook html stylesheet> -V nochunks
NCURSES-Programming-HOWTO.sgml > NCURSES-ONE-BIG-FILE.html
then use htmldoc to get pdf file with
htmldoc --size universal -t pdf --firstpage p1 -f <output file name.pdf>
NCURSES-ONE-BIG-FILE.html
for ps, you would use
htmldoc --size universal -t ps --firstpage p1 -f <output file name.ps>
NCURSES-ONE-BIG-FILE.html
See [http://www.tldp.org/LDP/LDP-Author-Guide/] LDP Author guide for more
details. If all else failes, mail me at [ppadala@gmail.com] ppadala@gmail.com
-----------------------------------------------------------------------------
1.7. Credits
I thank [mailto:sharath_1@usa.net] Sharath 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.
Perl equivalents of the example programs are contributed by [mailto:
Aratnaweera@virtusa.com] Anuradha Ratnaweera.
Then comes [mailto:parimi@ece.arizona.edu] Ravi Parimi, 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.
-----------------------------------------------------------------------------
1.8. Wish List
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 [mailto:ppadala@gmail.com] me.
<EFBFBD><EFBFBD>*<2A>Add examples to last parts of forms section.
<EFBFBD><EFBFBD>*<2A>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.
<EFBFBD><EFBFBD>*<2A>Add debug info. _tracef, _tracemouse stuff.
<EFBFBD><EFBFBD>*<2A>Accessing termcap, terminfo using functions provided by ncurses package.
<EFBFBD><EFBFBD>*<2A>Working on two terminals simultaneously.
<EFBFBD><EFBFBD>*<2A>Add more stuff to miscellaneous section.
-----------------------------------------------------------------------------
1.9. Copyright
Copyright <20> 2001 by Pradeep Padala.
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:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
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.
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.
-----------------------------------------------------------------------------
2. Hello World !!!
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.
-----------------------------------------------------------------------------
2.1. Compiling With the NCURSES Library
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.
#include <ncurses.h>
.
.
.
compile and link: gcc <program file> -lncurses
Example 1. The Hello World !!! Program
#include <ncurses.h>
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}
-----------------------------------------------------------------------------
2.2. Dissection
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.
-----------------------------------------------------------------------------
2.2.1. About initscr()
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 stdscr) 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.
After this is done, we can do a variety of initializations to customize our
curses settings. These details will be explained later .
-----------------------------------------------------------------------------
2.2.2. The mysterious refresh()
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.
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.
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 :-)
-----------------------------------------------------------------------------
2.2.3. About endwin()
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.
-----------------------------------------------------------------------------
3. The Gory Details
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.
Here we go...
-----------------------------------------------------------------------------
4. Initialization
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();
-----------------------------------------------------------------------------
4.1. Initialization functions
-----------------------------------------------------------------------------
4.2. raw() and cbreak()
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 cbreak() 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.
-----------------------------------------------------------------------------
4.3. echo() and noecho()
These functions control the echoing of characters typed by the user to the
terminal. noecho() 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 noecho() 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.
-----------------------------------------------------------------------------
4.4. keypad()
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 keypad
(stdscr, TRUE) to enable this feature for the regular screen (stdscr). You
will learn more about key management in later sections of this document.
-----------------------------------------------------------------------------
4.5. halfdelay()
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.
-----------------------------------------------------------------------------
4.6. Miscellaneous Initialization functions
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.
-----------------------------------------------------------------------------
4.7. An Example
Let's write a program which will clarify the usage of these functions.
Example 2. Initialization Function Usage example
#include <ncurses.h>
int main()
{ int ch;
initscr(); /* Start curses mode */
raw(); /* Line buffering disabled */
keypad(stdscr, TRUE); /* We get F1, F2 etc.. */
noecho(); /* Don't echo() while we do getch */
printw("Type any character to see it in bold\n");
ch = getch(); /* If raw() hadn't been called
* we have to press enter before it
* gets to the program */
if(ch == KEY_F(1)) /* Without keypad enabled this will */
printw("F1 Key pressed");/* not get to us either */
/* Without noecho() some ugly escape
* charachters might have been printed
* on screen */
else
{ printw("The pressed key is ");
attron(A_BOLD);
printw("%c", ch);
attroff(A_BOLD);
}
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}
This program is self-explanatory. But I used functions which aren't explained
yet. The function getch() is used to get a character from user. It is
equivalent to normal getchar() except that we can disable the line buffering
to avoid <enter> after input. Look for more about getch()and reading keys in
the key management section . 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.
-----------------------------------------------------------------------------
5. A Word about Windows
Before we plunge into the myriad ncurses functions, let me clear few things
about windows. Windows are explained in detail in following sections
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 stdscr 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.
For example, if you call
printw("Hi There !!!");
refresh();
It prints the string on stdscr at the present cursor position. Similarly the
call to refresh(), works on stdscr only.
Say you have created windows then you have to call a function with a 'w'
added to the usual function.
wprintw(win, "Hi There !!!");
wrefresh(win);
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.
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 */
Usually the w-less functions are macros which expand to corresponding
w-function with stdscr as the window parameter.
-----------------------------------------------------------------------------
6. Output functions
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.
There are three classes of functions which you can use to do output on
screen.
1. addch() class: Print single character with attributes
2. printw() class: Print formatted output similar to printf()
3. addstr() class: Print strings
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.
-----------------------------------------------------------------------------
6.1. addch() class of functions
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 sections 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.
In order to combine a character with some attributes, you have two options:
<EFBFBD><EFBFBD>*<2A>By OR'ing a single character with the desired attribute macros. These
attribute macros could be found in the header file ncurses.h. For
example, you want to print a character ch(of type char) bold and
underlined, you would call addch() as below.
addch(ch | A_BOLD | A_UNDERLINE);
<EFBFBD><EFBFBD>*<2A>By using functions like attrset(),attron(),attroff(). These functions are
explained in the Attributes 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.
Additionally, curses 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 ncurses.h. Try looking for
macros beginning with ACS_ in this file.
-----------------------------------------------------------------------------
6.2. mvaddch(), waddch() and mvwaddch()
mvaddch() is used to move the cursor to a given point, and then print. Thus,
the calls:
move(row,col); /* moves the cursor to rowth row and colth column */
addch(ch);
can be replaced by
mvaddch(row,col,ch);
waddch() is similar to addch(), except that it adds a character into the
given window. (Note that addch() adds a character into the window stdscr.)
In a similar fashion mvwaddch() function is used to add a character into the
given window at the given coordinates.
Now, we are familiar with the basic output function addch(). But, if we want
to print a string, it would be very annoying to print it character by
character. Fortunately, ncurses provides printf-like or puts-like functions.
-----------------------------------------------------------------------------
6.3. printw() class of functions
These functions are similar to printf() with the added capability of printing
at any position on the screen.
-----------------------------------------------------------------------------
6.3.1. printw() and mvprintw
These two functions work much like printf(). mvprintw() 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 printw() function, use move() first and then use printw
() though I see no point why one should avoid using mvprintw(), you have the
flexibility to manipulate.
-----------------------------------------------------------------------------
6.3.2. wprintw() and mvwprintw
These two functions are similar to above two except that they print in the
corresponding window given as argument.
-----------------------------------------------------------------------------
6.3.3. vwprintw()
This function is similar to vprintf(). This can be used when variable number
of arguments are to be printed.
-----------------------------------------------------------------------------
6.3.4. A Simple printw example
Example 3. A Simple printw example
#include <ncurses.h> /* ncurses.h includes stdio.h */
#include <string.h>
int main()
{
char mesg[]="Just a string"; /* message to be appeared on the screen */
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
mvprintw(row-2,0,"This screen has %d rows and %d columns\n",row,col);
printw("Try resizing your window(if possible) and then run this program again");
refresh();
getch();
endwin();
return 0;
}
Above program demonstrates how easy it is to use printw. You just feed the
coordinates and the message to be appeared on the screen, then it does what
you want.
The above program introduces us to a new function getmaxyx(), a macro defined
in ncurses.h. It gives the number of columns and the number of rows in a
given window. getmaxyx() does this by updating the variables given to it.
Since getmaxyx() is not a function we don't pass pointers to it, we just give
two integer variables.
-----------------------------------------------------------------------------
6.4. addstr() class of functions
addstr() is used to put a character string into a given window. This function
is similar to calling addch() once for each character in a given string. This
is true for all output functions. There are other functions from this family
such as mvaddstr(),mvwaddstr() and waddstr(), 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.
-----------------------------------------------------------------------------
6.5. A word of caution
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
windows section.
-----------------------------------------------------------------------------
7. Input functions
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.
1. getch() class: Get a character
2. scanw() class: Get formatted input
3. getstr() class: Get strings
-----------------------------------------------------------------------------
7.1. getch() class of functions
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 key management section .
-----------------------------------------------------------------------------
7.2. scanw() class of functions
These functions are similar to scanf() with the added capability of getting
the input from any location on the screen.
-----------------------------------------------------------------------------
7.2.1. scanw() and mvscanw
The usage of these functions is similar to that of sscanf(), where the line
to be scanned is provided by wgetstr() function. That is, these functions
call to wgetstr() function(explained below) and uses the resulting line for a
scan.
-----------------------------------------------------------------------------
7.2.2. wscanw() and mvwscanw()
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.
-----------------------------------------------------------------------------
7.2.3. vwscanw()
This function is similar to vscanf(). This can be used when a variable number
of arguments are to be scanned.
-----------------------------------------------------------------------------
7.3. getstr() class of functions
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
getch() until a newline, carriage return, or end-of-file is received. The
resulting string of characters are pointed to by str, which is a character
pointer provided by the user.
-----------------------------------------------------------------------------
7.4. Some examples
Example 4. A Simple scanw example
#include <ncurses.h> /* ncurses.h includes stdio.h */
#include <string.h>
int main()
{
char mesg[]="Enter a string: "; /* message to be appeared on the screen */
char str[80];
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
getstr(str);
mvprintw(LINES - 2, 0, "You Entered: %s", str);
getch();
endwin();
return 0;
}
-----------------------------------------------------------------------------
8. Attributes
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.
Example 5. A Simple Attributes example
/* pager functionality by Joseph Spainhour" <spainhou@bellsouth.net> */
#include <ncurses.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
int ch, prev, row, col;
prev = EOF;
FILE *fp;
int y, x;
if(argc != 2)
{
printf("Usage: %s <a c file name>\n", argv[0]);
exit(1);
}
fp = fopen(argv[1], "r");
if(fp == NULL)
{
perror("Cannot open input file");
exit(1);
}
initscr(); /* Start curses mode */
getmaxyx(stdscr, row, col); /* find the boundaries of the screeen */
while((ch = fgetc(fp)) != EOF) /* read the file till we reach the end */
{
getyx(stdscr, y, x); /* get the current curser position */
if(y == (row - 1)) /* are we are at the end of the screen */
{
printw("<-Press Any Key->"); /* tell the user to press a key */
getch();
clear(); /* clear the screen */
move(0, 0); /* start at the beginning of the screen */
}
if(prev == '/' && ch == '*') /* If it is / and * then only
* switch bold on */
{
attron(A_BOLD); /* cut bold on */
getyx(stdscr, y, x); /* get the current curser position */
move(y, x - 1); /* back up one space */
printw("%c%c", '/', ch); /* The actual printing is done here */
}
else
printw("%c", ch);
refresh();
if(prev == '*' && ch == '/')
attroff(A_BOLD); /* Switch it off once we got *
* and then / */
prev = ch;
}
endwin(); /* End curses mode */
fclose(fp);
return 0;
}
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 attron
() . When we get the pattern */ it is switched off by attroff() .
The above program also introduces us to two useful functions getyx() and move
(). 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 move() moves the cursor to the co-ordinates given to
it.
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.
-----------------------------------------------------------------------------
8.1. The details
Let's get into more details of attributes. The functions attron(), attroff(),
attrset() , and their sister functions attr_get() etc.. can be used to switch
attributes on/off , get attributes and produce a colorful display.
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 <curses.h> can be passed to these functions.
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
The last one is the most colorful one :-) Colors are explained in the [#
color] next sections.
We can OR(|) any number of above attributes to get a combined effect. If you
wanted reverse video with blinking characters you can use
attron(A_REVERSE | A_BLINK);
-----------------------------------------------------------------------------
8.2. attron() vs attrset()
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 standend()
which is equivalent to attrset(A_NORMAL) which turns off all attributes and
brings you to normal mode.
-----------------------------------------------------------------------------
8.3. attr_get()
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.
-----------------------------------------------------------------------------
8.4. attr_ functions
There are series of functions like attr_set(), attr_on etc.. These are
similar to above functions except that they take parameters of type attr_t.
-----------------------------------------------------------------------------
8.5. wattr functions
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.
-----------------------------------------------------------------------------
8.6. chgat() functions
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.
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.
chgat(-1, A_REVERSE, 0, NULL);
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.
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.
Example 6. Chgat() Usage example
#include <ncurses.h>
int main(int argc, char *argv[])
{ initscr(); /* Start curses mode */
start_color(); /* Start color functionality */
init_pair(1, COLOR_CYAN, COLOR_BLACK);
printw("A Big string which i didn't care to type fully ");
mvchgat(0, 0, -1, A_BLINK, 1, NULL);
/*
* First two parameters specify the position at which to start
* Third parameter number of characters to update. -1 means till
* end of line
* Forth parameter is the normal attribute you wanted to give
* to the charcter
* Fifth is the color index. It is the index given during init_pair()
* use 0 if you didn't want color
* Sixth one is always NULL
*/
refresh();
getch();
endwin(); /* End curses mode */
return 0;
}
This example also introduces us to the color world of curses. Colors will be
explained in detail later. Use 0 for no color.
-----------------------------------------------------------------------------
9. Windows
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.
-----------------------------------------------------------------------------
9.1. The basics
A Window can be created by calling the function newwin(). 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.
-----------------------------------------------------------------------------
9.2. Let there be a Window !!!
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 box() can be used to draw a
border around the window. Let's explore these functions in more detail in
this example.
Example 7. Window Border example
#include <ncurses.h>
WINDOW *create_newwin(int height, int width, int starty, int startx);
void destroy_win(WINDOW *local_win);
int main(int argc, char *argv[])
{ WINDOW *my_win;
int startx, starty, width, height;
int ch;
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
height = 3;
width = 10;
starty = (LINES - height) / 2; /* Calculating for a center placement */
startx = (COLS - width) / 2; /* of the window */
printw("Press F1 to exit");
refresh();
my_win = create_newwin(height, width, starty, startx);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,--startx);
break;
case KEY_RIGHT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,++startx);
break;
case KEY_UP:
destroy_win(my_win);
my_win = create_newwin(height, width, --starty,startx);
break;
case KEY_DOWN:
destroy_win(my_win);
my_win = create_newwin(height, width, ++starty,startx);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
WINDOW *create_newwin(int height, int width, int starty, int startx)
{ WINDOW *local_win;
local_win = newwin(height, width, starty, startx);
box(local_win, 0 , 0); /* 0, 0 gives default characters
* for the vertical and horizontal
* lines */
wrefresh(local_win); /* Show that box */
return local_win;
}
void destroy_win(WINDOW *local_win)
{
/* box(local_win, ' ', ' '); : This won't produce the desired
* result of erasing the window. It will leave it's four corners
* and so an ugly remnant of window.
*/
wborder(local_win, ' ', ' ', ' ',' ',' ',' ',' ',' ');
/* The parameters taken are
* 1. win: the window on which to operate
* 2. ls: character to be used for the left side of the window
* 3. rs: character to be used for the right side of the window
* 4. ts: character to be used for the top side of the window
* 5. bs: character to be used for the bottom side of the window
* 6. tl: character to be used for the top left corner of the window
* 7. tr: character to be used for the top right corner of the window
* 8. bl: character to be used for the bottom left corner of the window
* 9. br: character to be used for the bottom right corner of the window
*/
wrefresh(local_win);
delwin(local_win);
}
-----------------------------------------------------------------------------
9.3. Explanation
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.
The create_newwin() function creates a window with newwin() and displays a
border around it with box. The function destroy_win() first erases the window
from screen by painting a border with ' ' character and then calling delwin()
to deallocate memory related to it. Depending on the key the user presses,
starty or startx is changed and a new window is created.
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:
wborder(win, '|', '|', '-', '-', '+', '+', '+', '+');
it produces some thing like
+------------+
| |
| |
| |
| |
| |
| |
+------------+
-----------------------------------------------------------------------------
9.4. The other stuff in the example
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 getch() 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.
-----------------------------------------------------------------------------
9.5. Other Border functions
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.
The following program uses mvhline() and mvvline() to achieve similar effect.
These two functions are simple. They create a horizontal or vertical line of
the specified length at the specified position.
Example 8. More border functions
#include <ncurses.h>
typedef struct _win_border_struct {
chtype ls, rs, ts, bs,
tl, tr, bl, br;
}WIN_BORDER;
typedef struct _WIN_struct {
int startx, starty;
int height, width;
WIN_BORDER border;
}WIN;
void init_win_params(WIN *p_win);
void print_win_params(WIN *p_win);
void create_box(WIN *win, bool flag);
int main(int argc, char *argv[])
{ WIN win;
int ch;
initscr(); /* Start curses mode */
start_color(); /* Start the color functionality */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
noecho();
init_pair(1, COLOR_CYAN, COLOR_BLACK);
/* Initialize the window parameters */
init_win_params(&win);
print_win_params(&win);
attron(COLOR_PAIR(1));
printw("Press F1 to exit");
refresh();
attroff(COLOR_PAIR(1));
create_box(&win, TRUE);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
create_box(&win, FALSE);
--win.startx;
create_box(&win, TRUE);
break;
case KEY_RIGHT:
create_box(&win, FALSE);
++win.startx;
create_box(&win, TRUE);
break;
case KEY_UP:
create_box(&win, FALSE);
--win.starty;
create_box(&win, TRUE);
break;
case KEY_DOWN:
create_box(&win, FALSE);
++win.starty;
create_box(&win, TRUE);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
void init_win_params(WIN *p_win)
{
p_win->height = 3;
p_win->width = 10;
p_win->starty = (LINES - p_win->height)/2;
p_win->startx = (COLS - p_win->width)/2;
p_win->border.ls = '|';
p_win->border.rs = '|';
p_win->border.ts = '-';
p_win->border.bs = '-';
p_win->border.tl = '+';
p_win->border.tr = '+';
p_win->border.bl = '+';
p_win->border.br = '+';
}
void print_win_params(WIN *p_win)
{
#ifdef _DEBUG
mvprintw(25, 0, "%d %d %d %d", p_win->startx, p_win->starty,
p_win->width, p_win->height);
refresh();
#endif
}
void create_box(WIN *p_win, bool flag)
{ int i, j;
int x, y, w, h;
x = p_win->startx;
y = p_win->starty;
w = p_win->width;
h = p_win->height;
if(flag == TRUE)
{ mvaddch(y, x, p_win->border.tl);
mvaddch(y, x + w, p_win->border.tr);
mvaddch(y + h, x, p_win->border.bl);
mvaddch(y + h, x + w, p_win->border.br);
mvhline(y, x + 1, p_win->border.ts, w - 1);
mvhline(y + h, x + 1, p_win->border.bs, w - 1);
mvvline(y + 1, x, p_win->border.ls, h - 1);
mvvline(y + 1, x + w, p_win->border.rs, h - 1);
}
else
for(j = y; j <= y + h; ++j)
for(i = x; i <= x + w; ++i)
mvaddch(j, i, ' ');
refresh();
}
-----------------------------------------------------------------------------
10. Colors
10.1. The basics
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.
Example 9. A Simple Color example
#include <ncurses.h>
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string);
int main(int argc, char *argv[])
{ initscr(); /* Start curses mode */
if(has_colors() == FALSE)
{ endwin();
printf("Your terminal does not support color\n");
exit(1);
}
start_color(); /* Start color */
init_pair(1, COLOR_RED, COLOR_BLACK);
attron(COLOR_PAIR(1));
print_in_middle(stdscr, LINES / 2, 0, 0, "Viola !!! In color ...");
attroff(COLOR_PAIR(1));
getch();
endwin();
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
mvwprintw(win, y, x, "%s", string);
refresh();
}
As you can see, to start using color, you should first call the function
start_color(). 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 has_colors() function, which returns FALSE
if the terminal does not support color.
Curses initializes all the colors supported by terminal when start_color() is
called. These can be accessed by the define constants like COLOR_BLACK 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 init_pair() 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 COLOR_PAIR()function.
This may seem to be cumbersome at first. But this elegant solution allows us
to manage color pairs very easily. To appreciate it, you have to look into
the the source code of "dialog", a utility for displaying dialog boxes from
shell scripts. The developers have defined foreground and background
combinations for all the colors they might need and initialized at the
beginning. This makes it very easy to set attributes just by accessing a pair
which we already have defined as a constant.
The following colors are defined in curses.h. You can use these as parameters
for various color functions.
COLOR_BLACK 0
COLOR_RED 1
COLOR_GREEN 2
COLOR_YELLOW 3
COLOR_BLUE 4
COLOR_MAGENTA 5
COLOR_CYAN 6
COLOR_WHITE 7
-----------------------------------------------------------------------------
10.2. Changing Color Definitions
The function init_color()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
init_color(COLOR_RED, 700, 0, 0);
/* param 1 : color name
* param 2, 3, 4 : rgb content min = 0, max = 1000 */
If your terminal cannot change the color definitions, the function returns
ERR. The function can_change_color() 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).
-----------------------------------------------------------------------------
10.3. Color Content
The functions color_content() and pair_content() can be used to find the
color content and foreground, background combination for the pair.
-----------------------------------------------------------------------------
11. Interfacing with the key board
11.1. The Basics
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.
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 getch
() 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.
getch() 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 curses.h. 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.
For example, if you call getch() like this
int ch;
ch = getch();
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.
The following code piece will do that job.
if(ch == KEY_LEFT)
printw("Left arrow is pressed\n");
Let's write a small program which creates a menu which can be navigated by up
and down arrows.
-----------------------------------------------------------------------------
11.2. A Simple Key Usage example
Example 10. A Simple Key Usage example
#include <stdio.h>
#include <ncurses.h>
#define WIDTH 30
#define HEIGHT 10
int startx = 0;
int starty = 0;
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int n_choices = sizeof(choices) / sizeof(char *);
void print_menu(WINDOW *menu_win, int highlight);
int main()
{ WINDOW *menu_win;
int highlight = 1;
int choice = 0;
int c;
initscr();
clear();
noecho();
cbreak(); /* Line buffering disabled. pass on everything */
startx = (80 - WIDTH) / 2;
starty = (24 - HEIGHT) / 2;
menu_win = newwin(HEIGHT, WIDTH, starty, startx);
keypad(menu_win, TRUE);
mvprintw(0, 0, "Use arrow keys to go up and down, Press enter to select a choice");
refresh();
print_menu(menu_win, highlight);
while(1)
{ c = wgetch(menu_win);
switch(c)
{ case KEY_UP:
if(highlight == 1)
highlight = n_choices;
else
--highlight;
break;
case KEY_DOWN:
if(highlight == n_choices)
highlight = 1;
else
++highlight;
break;
case 10:
choice = highlight;
break;
default:
mvprintw(24, 0, "Charcter pressed is = %3d Hopefully it can be printed as '%c'", c, c);
refresh();
break;
}
print_menu(menu_win, highlight);
if(choice != 0) /* User did a choice come out of the infinite loop */
break;
}
mvprintw(23, 0, "You chose choice %d with choice string %s\n", choice, choices[choice - 1]);
clrtoeol();
refresh();
endwin();
return 0;
}
void print_menu(WINDOW *menu_win, int highlight)
{
int x, y, i;
x = 2;
y = 2;
box(menu_win, 0, 0);
for(i = 0; i < n_choices; ++i)
{ if(highlight == i + 1) /* High light the present choice */
{ wattron(menu_win, A_REVERSE);
mvwprintw(menu_win, y, x, "%s", choices[i]);
wattroff(menu_win, A_REVERSE);
}
else
mvwprintw(menu_win, y, x, "%s", choices[i]);
++y;
}
wrefresh(menu_win);
}
-----------------------------------------------------------------------------
12. Interfacing with the mouse
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.
-----------------------------------------------------------------------------
12.1. The Basics
Before you do any thing else, the events you want to receive have to be
enabled with mousemask().
mousemask( mmask_t newmask, /* The events you want to listen to */
mmask_t *oldmask) /* The old events mask */
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
ALL_MOUSE_EVENTS can be used to get all the events.
The following are all the event masks:
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
-----------------------------------------------------------------------------
12.2. Getting the events
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 getmouse().
The code approximately looks like this:
MEVENT event;
ch = getch();
if(ch == KEY_MOUSE)
if(getmouse(&event) == OK)
. /* Do some thing with the event */
.
.
getmouse() returns the event into the pointer given to it. It's a structure
which contains
typedef struct
{
short id; /* ID to distinguish multiple devices */
int x, y, z; /* event coordinates */
mmask_t bstate; /* button state bits */
}
The bstate is the main variable we are interested in. It tells the button
state of the mouse.
Then with a code snippet like the following, we can find out what happened.
if(event.bstate & BUTTON1_PRESSED)
printw("Left Button Pressed");
-----------------------------------------------------------------------------
12.3. Putting it all Together
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.
Example 11. Access the menu with mouse !!!
#include <ncurses.h>
#define WIDTH 30
#define HEIGHT 10
int startx = 0;
int starty = 0;
char *choices[] = { "Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int n_choices = sizeof(choices) / sizeof(char *);
void print_menu(WINDOW *menu_win, int highlight);
void report_choice(int mouse_x, int mouse_y, int *p_choice);
int main()
{ int c, choice = 0;
WINDOW *menu_win;
MEVENT event;
/* Initialize curses */
initscr();
clear();
noecho();
cbreak(); //Line buffering disabled. pass on everything
/* Try to put the window in the middle of screen */
startx = (80 - WIDTH) / 2;
starty = (24 - HEIGHT) / 2;
attron(A_REVERSE);
mvprintw(23, 1, "Click on Exit to quit (Works best in a virtual console)");
refresh();
attroff(A_REVERSE);
/* Print the menu for the first time */
menu_win = newwin(HEIGHT, WIDTH, starty, startx);
print_menu(menu_win, 1);
/* Get all the mouse events */
mousemask(ALL_MOUSE_EVENTS, NULL);
while(1)
{ c = wgetch(menu_win);
switch(c)
{ case KEY_MOUSE:
if(getmouse(&event) == OK)
{ /* When the user clicks left mouse button */
if(event.bstate & BUTTON1_PRESSED)
{ report_choice(event.x + 1, event.y + 1, &choice);
if(choice == -1) //Exit chosen
goto end;
mvprintw(22, 1, "Choice made is : %d String Chosen is \"%10s\"", choice, choices[choice - 1]);
refresh();
}
}
print_menu(menu_win, choice);
break;
}
}
end:
endwin();
return 0;
}
void print_menu(WINDOW *menu_win, int highlight)
{
int x, y, i;
x = 2;
y = 2;
box(menu_win, 0, 0);
for(i = 0; i < n_choices; ++i)
{ if(highlight == i + 1)
{ wattron(menu_win, A_REVERSE);
mvwprintw(menu_win, y, x, "%s", choices[i]);
wattroff(menu_win, A_REVERSE);
}
else
mvwprintw(menu_win, y, x, "%s", choices[i]);
++y;
}
wrefresh(menu_win);
}
/* Report the choice according to mouse position */
void report_choice(int mouse_x, int mouse_y, int *p_choice)
{ int i,j, choice;
i = startx + 2;
j = starty + 3;
for(choice = 0; choice < n_choices; ++choice)
if(mouse_y == j + choice && mouse_x >= i && mouse_x <= i + strlen(choices[choice]))
{ if(choice == n_choices - 1)
*p_choice = -1;
else
*p_choice = choice + 1;
break;
}
}
-----------------------------------------------------------------------------
12.4. Miscellaneous Functions
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.
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.
-----------------------------------------------------------------------------
13. Screen Manipulation
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.
-----------------------------------------------------------------------------
13.1. getyx() functions
The function getyx() 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
getyx(win, y, x);
/* win: window pointer
* y, x: y, x co-ordinates will be put into this variables
*/
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().
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.
-----------------------------------------------------------------------------
13.2. Screen Dumping
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.
-----------------------------------------------------------------------------
13.3. Window Dumping
To store and restore windows, the functions putwin() and getwin() can be
used. putwin() puts the present window state into a file, which can be later
restored by getwin().
The function copywin() 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.
-----------------------------------------------------------------------------
14. Miscellaneous features
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.
-----------------------------------------------------------------------------
14.1. curs_set()
This function can be used to make the cursor invisible. The parameter to this
function should be
0 : invisible or
1 : normal or
2 : very visible.
-----------------------------------------------------------------------------
14.2. Temporarily Leaving Curses mode
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 def_prog_mode() and then call endwin() to end the curses mode.
This will leave you in the original tty mode. To get back to curses once you
are done, call reset_prog_mode() . This function returns the tty to the state
stored by def_prog_mode(). Then do refresh(), and you are back to the curses
mode. Here is an example showing the sequence of things to be done.
Example 12. Temporarily Leaving Curses Mode
#include <ncurses.h>
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!\n"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
def_prog_mode(); /* Save the tty modes */
endwin(); /* End curses mode temporarily */
system("/bin/sh"); /* Do whatever you like in cooked mode */
reset_prog_mode(); /* Return to the previous tty mode*/
/* stored by def_prog_mode() */
refresh(); /* Do refresh() to restore the */
/* Screen contents */
printw("Another String\n"); /* Back to curses use the full */
refresh(); /* capabilities of curses */
endwin(); /* End curses mode */
return 0;
}
-----------------------------------------------------------------------------
14.3. ACS_ variables
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 box() 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.
Example 13. ACS Variables Example
#include <ncurses.h>
int main()
{
initscr();
printw("Upper left corner "); addch(ACS_ULCORNER); printw("\n");
printw("Lower left corner "); addch(ACS_LLCORNER); printw("\n");
printw("Lower right corner "); addch(ACS_LRCORNER); printw("\n");
printw("Tee pointing right "); addch(ACS_LTEE); printw("\n");
printw("Tee pointing left "); addch(ACS_RTEE); printw("\n");
printw("Tee pointing up "); addch(ACS_BTEE); printw("\n");
printw("Tee pointing down "); addch(ACS_TTEE); printw("\n");
printw("Horizontal line "); addch(ACS_HLINE); printw("\n");
printw("Vertical line "); addch(ACS_VLINE); printw("\n");
printw("Large Plus or cross over "); addch(ACS_PLUS); printw("\n");
printw("Scan Line 1 "); addch(ACS_S1); printw("\n");
printw("Scan Line 3 "); addch(ACS_S3); printw("\n");
printw("Scan Line 7 "); addch(ACS_S7); printw("\n");
printw("Scan Line 9 "); addch(ACS_S9); printw("\n");
printw("Diamond "); addch(ACS_DIAMOND); printw("\n");
printw("Checker board (stipple) "); addch(ACS_CKBOARD); printw("\n");
printw("Degree Symbol "); addch(ACS_DEGREE); printw("\n");
printw("Plus/Minus Symbol "); addch(ACS_PLMINUS); printw("\n");
printw("Bullet "); addch(ACS_BULLET); printw("\n");
printw("Arrow Pointing Left "); addch(ACS_LARROW); printw("\n");
printw("Arrow Pointing Right "); addch(ACS_RARROW); printw("\n");
printw("Arrow Pointing Down "); addch(ACS_DARROW); printw("\n");
printw("Arrow Pointing Up "); addch(ACS_UARROW); printw("\n");
printw("Board of squares "); addch(ACS_BOARD); printw("\n");
printw("Lantern Symbol "); addch(ACS_LANTERN); printw("\n");
printw("Solid Square Block "); addch(ACS_BLOCK); printw("\n");
printw("Less/Equal sign "); addch(ACS_LEQUAL); printw("\n");
printw("Greater/Equal sign "); addch(ACS_GEQUAL); printw("\n");
printw("Pi "); addch(ACS_PI); printw("\n");
printw("Not equal "); addch(ACS_NEQUAL); printw("\n");
printw("UK pound sign "); addch(ACS_STERLING); printw("\n");
refresh();
getch();
endwin();
return 0;
}
-----------------------------------------------------------------------------
15. Other libraries
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.
-----------------------------------------------------------------------------
16. Panel Library
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.
Don't despair. There's an elegant solution provided in panels library. In the
words of developers of ncurses
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.
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.
-----------------------------------------------------------------------------
16.1. The Basics
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.
The general flow of a panel program goes like this:
1. Create the windows (with newwin()) to be attached to the panels.
2. Create panels with the chosen visibility order. Stack them up according
to the desired visibility. The function new_panel() is used to created
panels.
3. Call update_panels() to write the panels to the virtual screen in correct
visibility order. Do a doupdate() to show it on the screen.
4. 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.
5. When you are done with the panel use del_panel() to delete the panel.
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.
-----------------------------------------------------------------------------
16.2. Compiling With the Panels Library
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.
#include <panel.h>
.
.
.
compile and link: gcc <program file> -lpanel -lncurses
Example 14. Panel basics
#include <panel.h>
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
int lines = 10, cols = 40, y = 2, x = 4, i;
initscr();
cbreak();
noecho();
/* Create windows for the panels */
my_wins[0] = newwin(lines, cols, y, x);
my_wins[1] = newwin(lines, cols, y + 1, x + 5);
my_wins[2] = newwin(lines, cols, y + 2, x + 10);
/*
* Create borders around the windows so that you can see the effect
* of panels
*/
for(i = 0; i < 3; ++i)
box(my_wins[i], 0, 0);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
doupdate();
getch();
endwin();
}
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.
-----------------------------------------------------------------------------
16.3. Panel Window Browsing
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.
Example 15. Panel Window Browsing Example
#include <panel.h>
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL *top;
int ch;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Set up the user pointers to the next panel */
set_panel_userptr(my_panels[0], my_panels[1]);
set_panel_userptr(my_panels[1], my_panels[2]);
set_panel_userptr(my_panels[2], my_panels[0]);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
doupdate();
top = my_panels[2];
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 9:
top = (PANEL *)panel_userptr(top);
top_panel(top);
break;
}
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i < n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}
-----------------------------------------------------------------------------
16.4. Using User Pointers
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 set_panel_userptr(). It can be accessed using
the function panel_userptr() 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.
-----------------------------------------------------------------------------
16.5. Moving and Resizing Panels
The function move_panel() 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.
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().
The following program shows these concepts, in supposedly simple program. You
can cycle through the window with <TAB> 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.
Example 16. Panel Moving and Resizing example
#include <panel.h>
typedef struct _PANEL_DATA {
int x, y, w, h;
char label[80];
int label_color;
PANEL *next;
}PANEL_DATA;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
void set_user_ptrs(PANEL **panels, int n);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL_DATA *top;
PANEL *stack_top;
WINDOW *temp_win, *old_win;
int ch;
int newx, newy, neww, newh;
int size = FALSE, move = FALSE;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
set_user_ptrs(my_panels, 3);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
doupdate();
stack_top = my_panels[2];
top = (PANEL_DATA *)panel_userptr(stack_top);
newx = top->x;
newy = top->y;
neww = top->w;
newh = top->h;
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 9: /* Tab */
top = (PANEL_DATA *)panel_userptr(stack_top);
top_panel(top->next);
stack_top = top->next;
top = (PANEL_DATA *)panel_userptr(stack_top);
newx = top->x;
newy = top->y;
neww = top->w;
newh = top->h;
break;
case 'r': /* Re-Size*/
size = TRUE;
attron(COLOR_PAIR(4));
mvprintw(LINES - 4, 0, "Entered Resizing :Use Arrow Keys to resize and press <ENTER> to end resizing");
refresh();
attroff(COLOR_PAIR(4));
break;
case 'm': /* Move */
attron(COLOR_PAIR(4));
mvprintw(LINES - 4, 0, "Entered Moving: Use Arrow Keys to Move and press <ENTER> to end moving");
refresh();
attroff(COLOR_PAIR(4));
move = TRUE;
break;
case KEY_LEFT:
if(size == TRUE)
{ --newx;
++neww;
}
if(move == TRUE)
--newx;
break;
case KEY_RIGHT:
if(size == TRUE)
{ ++newx;
--neww;
}
if(move == TRUE)
++newx;
break;
case KEY_UP:
if(size == TRUE)
{ --newy;
++newh;
}
if(move == TRUE)
--newy;
break;
case KEY_DOWN:
if(size == TRUE)
{ ++newy;
--newh;
}
if(move == TRUE)
++newy;
break;
case 10: /* Enter */
move(LINES - 4, 0);
clrtoeol();
refresh();
if(size == TRUE)
{ old_win = panel_window(stack_top);
temp_win = newwin(newh, neww, newy, newx);
replace_panel(stack_top, temp_win);
win_show(temp_win, top->label, top->label_color);
delwin(old_win);
size = FALSE;
}
if(move == TRUE)
{ move_panel(stack_top, newy, newx);
move = FALSE;
}
break;
}
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Use 'm' for moving, 'r' for resizing");
mvprintw(LINES - 2, 0, "Use tab to browse through the windows (F1 to Exit)");
attroff(COLOR_PAIR(4));
refresh();
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i < n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Set the PANEL_DATA structures for individual panels */
void set_user_ptrs(PANEL **panels, int n)
{ PANEL_DATA *ptrs;
WINDOW *win;
int x, y, w, h, i;
char temp[80];
ptrs = (PANEL_DATA *)calloc(n, sizeof(PANEL_DATA));
for(i = 0;i < n; ++i)
{ win = panel_window(panels[i]);
getbegyx(win, y, x);
getmaxyx(win, h, w);
ptrs[i].x = x;
ptrs[i].y = y;
ptrs[i].w = w;
ptrs[i].h = h;
sprintf(temp, "Window Number %d", i + 1);
strcpy(ptrs[i].label, temp);
ptrs[i].label_color = i + 1;
if(i + 1 == n)
ptrs[i].next = panels[0];
else
ptrs[i].next = panels[i + 1];
set_panel_userptr(panels[i], &ptrs[i]);
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}
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 <ENTER> 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.
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 <ENTER> causes the panel to be moved by calling the function
move_panel().
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.
-----------------------------------------------------------------------------
16.6. Hiding and Showing Panels
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.
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 panel_hidden() which tells
whether a panel is hidden or not is not working. A bug report was also
presented by Michael Andres [http://www.geocrawler.com/archives/3/344/1999/9/
0/2643549/] here
Example 17. Panel Hiding and Showing example
#include <panel.h>
typedef struct _PANEL_DATA {
int hide; /* TRUE if panel is hidden */
}PANEL_DATA;
#define NLINES 10
#define NCOLS 40
void init_wins(WINDOW **wins, int n);
void win_show(WINDOW *win, char *label, int label_color);
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ WINDOW *my_wins[3];
PANEL *my_panels[3];
PANEL_DATA panel_datas[3];
PANEL_DATA *temp;
int ch;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize all the colors */
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_BLUE, COLOR_BLACK);
init_pair(4, COLOR_CYAN, COLOR_BLACK);
init_wins(my_wins, 3);
/* Attach a panel to each window */ /* Order is bottom up */
my_panels[0] = new_panel(my_wins[0]); /* Push 0, order: stdscr-0 */
my_panels[1] = new_panel(my_wins[1]); /* Push 1, order: stdscr-0-1 */
my_panels[2] = new_panel(my_wins[2]); /* Push 2, order: stdscr-0-1-2 */
/* Initialize panel datas saying that nothing is hidden */
panel_datas[0].hide = FALSE;
panel_datas[1].hide = FALSE;
panel_datas[2].hide = FALSE;
set_panel_userptr(my_panels[0], &panel_datas[0]);
set_panel_userptr(my_panels[1], &panel_datas[1]);
set_panel_userptr(my_panels[2], &panel_datas[2]);
/* Update the stacking order. 2nd panel will be on top */
update_panels();
/* Show it on the screen */
attron(COLOR_PAIR(4));
mvprintw(LINES - 3, 0, "Show or Hide a window with 'a'(first window) 'b'(Second Window) 'c'(Third Window)");
mvprintw(LINES - 2, 0, "F1 to Exit");
attroff(COLOR_PAIR(4));
doupdate();
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case 'a':
temp = (PANEL_DATA *)panel_userptr(my_panels[0]);
if(temp->hide == FALSE)
{ hide_panel(my_panels[0]);
temp->hide = TRUE;
}
else
{ show_panel(my_panels[0]);
temp->hide = FALSE;
}
break;
case 'b':
temp = (PANEL_DATA *)panel_userptr(my_panels[1]);
if(temp->hide == FALSE)
{ hide_panel(my_panels[1]);
temp->hide = TRUE;
}
else
{ show_panel(my_panels[1]);
temp->hide = FALSE;
}
break;
case 'c':
temp = (PANEL_DATA *)panel_userptr(my_panels[2]);
if(temp->hide == FALSE)
{ hide_panel(my_panels[2]);
temp->hide = TRUE;
}
else
{ show_panel(my_panels[2]);
temp->hide = FALSE;
}
break;
}
update_panels();
doupdate();
}
endwin();
return 0;
}
/* Put all the windows */
void init_wins(WINDOW **wins, int n)
{ int x, y, i;
char label[80];
y = 2;
x = 10;
for(i = 0; i < n; ++i)
{ wins[i] = newwin(NLINES, NCOLS, y, x);
sprintf(label, "Window Number %d", i + 1);
win_show(wins[i], label, i + 1);
y += 3;
x += 7;
}
}
/* Show the window with a border and a label */
void win_show(WINDOW *win, char *label, int label_color)
{ int startx, starty, height, width;
getbegyx(win, starty, startx);
getmaxyx(win, height, width);
box(win, 0, 0);
mvwaddch(win, 2, 0, ACS_LTEE);
mvwhline(win, 2, 1, ACS_HLINE, width - 2);
mvwaddch(win, 2, width - 1, ACS_RTEE);
print_in_middle(win, 1, 0, width, label, COLOR_PAIR(label_color));
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}
-----------------------------------------------------------------------------
16.7. panel_above() and panel_below() Functions
The functions panel_above() and panel_below() 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.
-----------------------------------------------------------------------------
17. Menus Library
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.
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.
-----------------------------------------------------------------------------
17.1. The Basics
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.
The general flow of control of a menu program looks like this.
1. Initialize curses
2. Create items using new_item(). You can specify a name and description for
the items.
3. Create the menu with new_menu() by specifying the items to be attached
with.
4. Post the menu with menu_post() and refresh the screen.
5. Process the user requests with a loop and do necessary updates to menu
with menu_driver.
6. Unpost the menu with menu_unpost()
7. Free the memory allocated to menu by free_menu()
8. Free the memory allocated to the items with free_item()
9. End curses
Let's see a program which prints a simple menu and updates the current
selection with up, down arrows.
-----------------------------------------------------------------------------
17.2. Compiling With the Menu Library
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.
#include <menu.h>
.
.
.
compile and link: gcc <program file> -lmenu -lncurses
Example 18. Menu Basics
#include <curses.h>
#include <menu.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i < n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
my_items[n_choices] = (ITEM *)NULL;
my_menu = new_menu((ITEM **)my_items);
mvprintw(LINES - 2, 0, "F1 to Exit");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
}
}
free_item(my_items[0]);
free_item(my_items[1]);
free_menu(my_menu);
endwin();
}
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.
The menu_driver accepts following navigational requests.
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.
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.
-----------------------------------------------------------------------------
17.3. Menu Driver: The work horse of the menu system
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.
<EFBFBD><EFBFBD>*<2A>REQ_LEFT_ITEM and REQ_RIGHT_ITEM
A Menu can be displayed with multiple columns for more than one item.
This can be done by using the menu_format()function. When a multi
columnar menu is displayed these requests cause the menu driver to move
the current selection to left or right.
<EFBFBD><EFBFBD>*<2A>REQ_UP_ITEM and REQ_DOWN_ITEM
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.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_* options
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.
<EFBFBD><EFBFBD>*<2A>REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_NEXT_ITEM and REQ_PREV_ITEM
These requests are self explanatory.
<EFBFBD><EFBFBD>*<2A>REQ_TOGGLE_ITEM
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().
<EFBFBD><EFBFBD>*<2A>Pattern Requests
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.
<EFBFBD><EFBFBD>*<2A>Mouse Requests
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,
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<72>
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.
Each of the above requests will be explained in the following lines with
several examples whenever appropriate.
-----------------------------------------------------------------------------
17.4. Menu Windows
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.
Example 19. Menu Windows Usage example
#include <menu.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Exit",
(char *)NULL,
};
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
WINDOW *my_menu_win;
int n_choices, i;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
/* Create items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));
for(i = 0; i < n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
/* Crate menu */
my_menu = new_menu((ITEM **)my_items);
/* Create the window to be associated with the menu */
my_menu_win = newwin(10, 40, 4, 4);
keypad(my_menu_win, TRUE);
/* Set main window and sub window */
set_menu_win(my_menu, my_menu_win);
set_menu_sub(my_menu, derwin(my_menu_win, 6, 38, 3, 1));
/* Set menu mark to the string " * " */
set_menu_mark(my_menu, " * ");
/* Print a border around the main window and print a title */
box(my_menu_win, 0, 0);
print_in_middle(my_menu_win, 1, 0, 40, "My Menu", COLOR_PAIR(1));
mvwaddch(my_menu_win, 2, 0, ACS_LTEE);
mvwhline(my_menu_win, 2, 1, ACS_HLINE, 38);
mvwaddch(my_menu_win, 2, 39, ACS_RTEE);
mvprintw(LINES - 2, 0, "F1 to exit");
refresh();
/* Post the menu */
post_menu(my_menu);
wrefresh(my_menu_win);
while((c = wgetch(my_menu_win)) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
}
wrefresh(my_menu_win);
}
/* Unpost and free all the memory taken up */
unpost_menu(my_menu);
free_menu(my_menu);
for(i = 0; i < n_choices; ++i)
free_item(my_items[i]);
endwin();
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}
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().
-----------------------------------------------------------------------------
17.5. Scrolling Menus
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.
Example 20. Scrolling Menus example
#include <curses.h>
#include <menu.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Choice 8",
"Choice 9",
"Choice 10",
"Exit",
(char *)NULL,
};
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
WINDOW *my_menu_win;
int n_choices, i;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_CYAN, COLOR_BLACK);
/* Create items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));
for(i = 0; i < n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
/* Crate menu */
my_menu = new_menu((ITEM **)my_items);
/* Create the window to be associated with the menu */
my_menu_win = newwin(10, 40, 4, 4);
keypad(my_menu_win, TRUE);
/* Set main window and sub window */
set_menu_win(my_menu, my_menu_win);
set_menu_sub(my_menu, derwin(my_menu_win, 6, 38, 3, 1));
set_menu_format(my_menu, 5, 1);
/* Set menu mark to the string " * " */
set_menu_mark(my_menu, " * ");
/* Print a border around the main window and print a title */
box(my_menu_win, 0, 0);
print_in_middle(my_menu_win, 1, 0, 40, "My Menu", COLOR_PAIR(1));
mvwaddch(my_menu_win, 2, 0, ACS_LTEE);
mvwhline(my_menu_win, 2, 1, ACS_HLINE, 38);
mvwaddch(my_menu_win, 2, 39, ACS_RTEE);
/* Post the menu */
post_menu(my_menu);
wrefresh(my_menu_win);
attron(COLOR_PAIR(2));
mvprintw(LINES - 2, 0, "Use PageUp and PageDown to scoll down or up a page of items");
mvprintw(LINES - 1, 0, "Arrow Keys to navigate (F1 to Exit)");
attroff(COLOR_PAIR(2));
refresh();
while((c = wgetch(my_menu_win)) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case KEY_NPAGE:
menu_driver(my_menu, REQ_SCR_DPAGE);
break;
case KEY_PPAGE:
menu_driver(my_menu, REQ_SCR_UPAGE);
break;
}
wrefresh(my_menu_win);
}
/* Unpost and free all the memory taken up */
unpost_menu(my_menu);
free_menu(my_menu);
for(i = 0; i < n_choices; ++i)
free_item(my_items[i]);
endwin();
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}
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().
-----------------------------------------------------------------------------
17.6. Multi Columnar Menus
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.
Example 21. Milt Columnar Menus Example
#include <curses.h>
#include <menu.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1", "Choice 2", "Choice 3", "Choice 4", "Choice 5",
"Choice 6", "Choice 7", "Choice 8", "Choice 9", "Choice 10",
"Choice 11", "Choice 12", "Choice 13", "Choice 14", "Choice 15",
"Choice 16", "Choice 17", "Choice 18", "Choice 19", "Choice 20",
"Exit",
(char *)NULL,
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
WINDOW *my_menu_win;
int n_choices, i;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_CYAN, COLOR_BLACK);
/* Create items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices, sizeof(ITEM *));
for(i = 0; i < n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
/* Crate menu */
my_menu = new_menu((ITEM **)my_items);
/* Set menu option not to show the description */
menu_opts_off(my_menu, O_SHOWDESC);
/* Create the window to be associated with the menu */
my_menu_win = newwin(10, 70, 4, 4);
keypad(my_menu_win, TRUE);
/* Set main window and sub window */
set_menu_win(my_menu, my_menu_win);
set_menu_sub(my_menu, derwin(my_menu_win, 6, 68, 3, 1));
set_menu_format(my_menu, 5, 3);
set_menu_mark(my_menu, " * ");
/* Print a border around the main window and print a title */
box(my_menu_win, 0, 0);
attron(COLOR_PAIR(2));
mvprintw(LINES - 3, 0, "Use PageUp and PageDown to scroll");
mvprintw(LINES - 2, 0, "Use Arrow Keys to navigate (F1 to Exit)");
attroff(COLOR_PAIR(2));
refresh();
/* Post the menu */
post_menu(my_menu);
wrefresh(my_menu_win);
while((c = wgetch(my_menu_win)) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case KEY_LEFT:
menu_driver(my_menu, REQ_LEFT_ITEM);
break;
case KEY_RIGHT:
menu_driver(my_menu, REQ_RIGHT_ITEM);
break;
case KEY_NPAGE:
menu_driver(my_menu, REQ_SCR_DPAGE);
break;
case KEY_PPAGE:
menu_driver(my_menu, REQ_SCR_UPAGE);
break;
}
wrefresh(my_menu_win);
}
/* Unpost and free all the memory taken up */
unpost_menu(my_menu);
free_menu(my_menu);
for(i = 0; i < n_choices; ++i)
free_item(my_items[i]);
endwin();
}
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.
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<61>
tern-matching.
O_NONCYCLIC
Don't wrap around next-item and previous-item,
requests to the other end of the menu.
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.
-----------------------------------------------------------------------------
17.7. Multi Valued Menus
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.
Example 22. Multi Valued Menus example
#include <curses.h>
#include <menu.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Exit",
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
/* Initialize curses */
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i < n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
my_items[n_choices] = (ITEM *)NULL;
my_menu = new_menu((ITEM **)my_items);
/* Make the menu multi valued */
menu_opts_off(my_menu, O_ONEVALUE);
mvprintw(LINES - 3, 0, "Use <SPACE> to select or unselect an item.");
mvprintw(LINES - 2, 0, "<ENTER> to see presently selected items(F1 to Exit)");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case ' ':
menu_driver(my_menu, REQ_TOGGLE_ITEM);
break;
case 10: /* Enter */
{ char temp[200];
ITEM **items;
items = menu_items(my_menu);
temp[0] = '\0';
for(i = 0; i < item_count(my_menu); ++i)
if(item_value(items[i]) == TRUE)
{ strcat(temp, item_name(items[i]));
strcat(temp, " ");
}
move(20, 0);
clrtoeol();
mvprintw(20, 0, temp);
refresh();
}
break;
}
}
free_item(my_items[0]);
free_item(my_items[1]);
free_menu(my_menu);
endwin();
}
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.
Now when the user presses <ENTER> 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().
-----------------------------------------------------------------------------
17.8. Menu Options
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 [http://www.jersey.net/~debinjoe/games/] dos
games. 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.
The function set_menu_grey() can be used to set the display attribute for the
non-selectable items in the menu. This brings us to the interesting option
for an item the one and only O_SELECTABLE. We can turn it off by the function
item_opts_off() and after that that item is not selectable. It's like a
grayed item in those fancy windows menus. Let's put these concepts in
practice with this example
Example 23. Menu Options example
#include <menu.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Exit",
};
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_MAGENTA, COLOR_BLACK);
/* Initialize items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i < n_choices; ++i)
my_items[i] = new_item(choices[i], choices[i]);
my_items[n_choices] = (ITEM *)NULL;
item_opts_off(my_items[3], O_SELECTABLE);
item_opts_off(my_items[6], O_SELECTABLE);
/* Create menu */
my_menu = new_menu((ITEM **)my_items);
/* Set fore ground and back ground of the menu */
set_menu_fore(my_menu, COLOR_PAIR(1) | A_REVERSE);
set_menu_back(my_menu, COLOR_PAIR(2));
set_menu_grey(my_menu, COLOR_PAIR(3));
/* Post the menu */
mvprintw(LINES - 3, 0, "Press <ENTER> to see the option selected");
mvprintw(LINES - 2, 0, "Up and Down arrow keys to naviage (F1 to Exit)");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case 10: /* Enter */
move(20, 0);
clrtoeol();
mvprintw(20, 0, "Item selected is : %s",
item_name(current_item(my_menu)));
pos_menu_cursor(my_menu);
break;
}
}
unpost_menu(my_menu);
for(i = 0; i < n_choices; ++i)
free_item(my_items[i]);
free_menu(my_menu);
endwin();
}
-----------------------------------------------------------------------------
17.9. The useful User Pointer
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 <ENTER>);
Example 24. Menu User Pointer Usage
#include <curses.h>
#include <menu.h>
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define CTRLD 4
char *choices[] = {
"Choice 1",
"Choice 2",
"Choice 3",
"Choice 4",
"Choice 5",
"Choice 6",
"Choice 7",
"Exit",
};
void func(char *name);
int main()
{ ITEM **my_items;
int c;
MENU *my_menu;
int n_choices, i;
ITEM *cur_item;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
init_pair(1, COLOR_RED, COLOR_BLACK);
init_pair(2, COLOR_GREEN, COLOR_BLACK);
init_pair(3, COLOR_MAGENTA, COLOR_BLACK);
/* Initialize items */
n_choices = ARRAY_SIZE(choices);
my_items = (ITEM **)calloc(n_choices + 1, sizeof(ITEM *));
for(i = 0; i < n_choices; ++i)
{ my_items[i] = new_item(choices[i], choices[i]);
/* Set the user pointer */
set_item_userptr(my_items[i], func);
}
my_items[n_choices] = (ITEM *)NULL;
/* Create menu */
my_menu = new_menu((ITEM **)my_items);
/* Post the menu */
mvprintw(LINES - 3, 0, "Press <ENTER> to see the option selected");
mvprintw(LINES - 2, 0, "Up and Down arrow keys to naviage (F1 to Exit)");
post_menu(my_menu);
refresh();
while((c = getch()) != KEY_F(1))
{ switch(c)
{ case KEY_DOWN:
menu_driver(my_menu, REQ_DOWN_ITEM);
break;
case KEY_UP:
menu_driver(my_menu, REQ_UP_ITEM);
break;
case 10: /* Enter */
{ ITEM *cur;
void (*p)(char *);
cur = current_item(my_menu);
p = item_userptr(cur);
p((char *)item_name(cur));
pos_menu_cursor(my_menu);
break;
}
break;
}
}
unpost_menu(my_menu);
for(i = 0; i < n_choices; ++i)
free_item(my_items[i]);
free_menu(my_menu);
endwin();
}
void func(char *name)
{ move(20, 0);
clrtoeol();
mvprintw(20, 0, "Item selected is : %s", name);
}
-----------------------------------------------------------------------------
18. Forms Library
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.
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.
-----------------------------------------------------------------------------
18.1. The Basics
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.
The general flow of control of a forms program looks like this.
1. Initialize curses
2. Create fields using new_field(). You can specify the height and width of
the field, and its position on the form.
3. Create the forms with new_form() by specifying the fields to be attached
with.
4. Post the form with form_post() and refresh the screen.
5. Process the user requests with a loop and do necessary updates to form
with form_driver.
6. Unpost the menu with form_unpost()
7. Free the memory allocated to menu by free_form()
8. Free the memory allocated to the items with free_field()
9. End curses
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.
-----------------------------------------------------------------------------
18.2. Compiling With the Forms Library
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.
#include <form.h>
.
.
.
compile and link: gcc <program file> -lform -lncurses
Example 25. Forms Basics
#include <form.h>
int main()
{ FIELD *field[3];
FORM *my_form;
int ch;
/* Initialize curses */
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize the fields */
field[0] = new_field(1, 10, 4, 18, 0, 0);
field[1] = new_field(1, 10, 6, 18, 0, 0);
field[2] = NULL;
/* Set field options */
set_field_back(field[0], A_UNDERLINE); /* Print a line for the option */
field_opts_off(field[0], O_AUTOSKIP); /* Don't go to next field when this */
/* Field is filled up */
set_field_back(field[1], A_UNDERLINE);
field_opts_off(field[1], O_AUTOSKIP);
/* Create the form and post it */
my_form = new_form(field);
post_form(my_form);
refresh();
mvprintw(4, 10, "Value 1:");
mvprintw(6, 10, "Value 2:");
refresh();
/* Loop through to get user requests */
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}
Above example is pretty straight forward. It creates two fields with
new_field(). 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.
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.
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.
-----------------------------------------------------------------------------
18.3. Playing with Fields
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?
-----------------------------------------------------------------------------
18.3.1. Fetching Size and Location of Field
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().
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 */
-----------------------------------------------------------------------------
18.3.2. Moving the field
The location of the field can be moved to a different position with
move_field().
int move_field( FIELD *field, /* field to alter */
int top, int left); /* new upper-left corner */
As usual, the changed position can be queried with field_infor().
-----------------------------------------------------------------------------
18.3.3. Field Justification
The justification to be done for the field can be fixed using the function
set_field_just().
int set_field_just(FIELD *field, /* field to alter */
int justmode); /* mode to set */
int field_just(FIELD *field); /* fetch justify mode of field */
The justification mode valued accepted and returned by these functions are
NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or JUSTIFY_CENTER.
-----------------------------------------------------------------------------
18.3.4. Field Display Attributes
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.
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 */
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.
Example 26. Form Attributes example
#include <form.h>
int main()
{ FIELD *field[3];
FORM *my_form;
int ch;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize few color pairs */
init_pair(1, COLOR_WHITE, COLOR_BLUE);
init_pair(2, COLOR_WHITE, COLOR_BLUE);
/* Initialize the fields */
field[0] = new_field(1, 10, 4, 18, 0, 0);
field[1] = new_field(1, 10, 6, 18, 0, 0);
field[2] = NULL;
/* Set field options */
set_field_fore(field[0], COLOR_PAIR(1));/* Put the field with blue background */
set_field_back(field[0], COLOR_PAIR(2));/* and white foreground (characters */
/* are printed in white */
field_opts_off(field[0], O_AUTOSKIP); /* Don't go to next field when this */
/* Field is filled up */
set_field_back(field[1], A_UNDERLINE);
field_opts_off(field[1], O_AUTOSKIP);
/* Create the form and post it */
my_form = new_form(field);
post_form(my_form);
refresh();
set_current_field(my_form, field[0]); /* Set focus to the colored field */
mvprintw(4, 10, "Value 1:");
mvprintw(6, 10, "Value 2:");
mvprintw(LINES - 2, 0, "Use UP, DOWN arrow keys to switch between fields");
refresh();
/* Loop through to get user requests */
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}
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.
-----------------------------------------------------------------------------
18.3.5. Field Option Bits
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:
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 */
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.
O_VISIBLE
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.
O_ACTIVE
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.
O_PUBLIC
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.
O_EDIT
Controls whether the field's data can be modified. When this option is
off, all editing requests except REQ_PREV_CHOICE and REQ_NEXT_CHOICEwill
fail. Such read-only fields may be useful for help messages.
O_WRAP
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.
O_BLANK
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).
O_AUTOSKIP
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.
O_NULLOK
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.
O_PASSOK
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.
O_STATIC
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.
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.
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.
Example 27. Field Options Usage example
#include <form.h>
#define STARTX 15
#define STARTY 4
#define WIDTH 25
#define N_FIELDS 3
int main()
{ FIELD *field[N_FIELDS];
FORM *my_form;
int ch, i;
/* Initialize curses */
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize the fields */
for(i = 0; i < N_FIELDS - 1; ++i)
field[i] = new_field(1, WIDTH, STARTY + i * 2, STARTX, 0, 0);
field[N_FIELDS - 1] = NULL;
/* Set field options */
set_field_back(field[1], A_UNDERLINE); /* Print a line for the option */
field_opts_off(field[0], O_ACTIVE); /* This field is a static label */
field_opts_off(field[1], O_PUBLIC); /* This filed is like a password field*/
field_opts_off(field[1], O_AUTOSKIP); /* To avoid entering the same field */
/* after last character is entered */
/* Create the form and post it */
my_form = new_form(field);
post_form(my_form);
refresh();
set_field_just(field[0], JUSTIFY_CENTER); /* Center Justification */
set_field_buffer(field[0], 0, "This is a static Field");
/* Initialize the field */
mvprintw(STARTY, STARTX - 10, "Field 1:");
mvprintw(STARTY + 2, STARTX - 10, "Field 2:");
refresh();
/* Loop through to get user requests */
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}
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.
-----------------------------------------------------------------------------
18.3.6. Field Status
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.
int set_field_status(FIELD *field, /* field to alter */
int status); /* status to set */
int field_status(FIELD *field); /* fetch status of field */
It's better to check the field's status only after after leaving the field,
as data buffer might not have been updated yet as the validation is still
due. To guarantee that right status is returned, call field_status() either
(1) in the field's exit validation check routine, (2) from the field's or
form's initialization or termination hooks, or (3) just after a
REQ_VALIDATION request has been processed by the forms driver
-----------------------------------------------------------------------------
18.3.7. Field User Pointer
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.
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 */
-----------------------------------------------------------------------------
18.3.8. Variable-Sized Fields
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.
To make a field dynamically growable, the option O_STATIC should be turned
off. This can be done with a
field_opts_off(field_pointer, O_STATIC);
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
int set_max_field(FIELD *field, /* Field on which to operate */
int max_growth); /* maximum growth allowed for the field */
The field info for a dynamically growable field can be retrieved by
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 */
Though field_info work as usual, it is advisable to use this function to get
the proper attributes of a dynamically growable field.
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.
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.
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.
The above two paragraphs pretty much describe a dynamically growable field's
behavior. The way other parts of forms library behaves is described below:
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
Some of the above points make sense only after explaining form driver. We
will be looking into that in next few sections.
-----------------------------------------------------------------------------
18.4. Form Windows
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.
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.
Example 28. Form Windows Example
#include <form.h>
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color);
int main()
{
FIELD *field[3];
FORM *my_form;
WINDOW *my_form_win;
int ch, rows, cols;
/* Initialize curses */
initscr();
start_color();
cbreak();
noecho();
keypad(stdscr, TRUE);
/* Initialize few color pairs */
init_pair(1, COLOR_RED, COLOR_BLACK);
/* Initialize the fields */
field[0] = new_field(1, 10, 6, 1, 0, 0);
field[1] = new_field(1, 10, 8, 1, 0, 0);
field[2] = NULL;
/* Set field options */
set_field_back(field[0], A_UNDERLINE);
field_opts_off(field[0], O_AUTOSKIP); /* Don't go to next field when this */
/* Field is filled up */
set_field_back(field[1], A_UNDERLINE);
field_opts_off(field[1], O_AUTOSKIP);
/* Create the form and post it */
my_form = new_form(field);
/* Calculate the area required for the form */
scale_form(my_form, &rows, &cols);
/* Create the window to be associated with the form */
my_form_win = newwin(rows + 4, cols + 4, 4, 4);
keypad(my_form_win, TRUE);
/* Set main window and sub window */
set_form_win(my_form, my_form_win);
set_form_sub(my_form, derwin(my_form_win, rows, cols, 2, 2));
/* Print a border around the main window and print a title */
box(my_form_win, 0, 0);
print_in_middle(my_form_win, 1, 0, cols + 4, "My Form", COLOR_PAIR(1));
post_form(my_form);
wrefresh(my_form_win);
mvprintw(LINES - 2, 0, "Use UP, DOWN arrow keys to switch between fields");
refresh();
/* Loop through to get user requests */
while((ch = wgetch(my_form_win)) != KEY_F(1))
{ switch(ch)
{ case KEY_DOWN:
/* Go to next field */
form_driver(my_form, REQ_NEXT_FIELD);
/* Go to the end of the present buffer */
/* Leaves nicely at the last character */
form_driver(my_form, REQ_END_LINE);
break;
case KEY_UP:
/* Go to previous field */
form_driver(my_form, REQ_PREV_FIELD);
form_driver(my_form, REQ_END_LINE);
break;
default:
/* If this is a normal character, it gets */
/* Printed */
form_driver(my_form, ch);
break;
}
}
/* Un post form and free the memory */
unpost_form(my_form);
free_form(my_form);
free_field(field[0]);
free_field(field[1]);
endwin();
return 0;
}
void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string, chtype color)
{ int length, x, y;
float temp;
if(win == NULL)
win = stdscr;
getyx(win, y, x);
if(startx != 0)
x = startx;
if(starty != 0)
y = starty;
if(width == 0)
width = 80;
length = strlen(string);
temp = (width - length)/ 2;
x = startx + (int)temp;
wattron(win, color);
mvwprintw(win, y, x, "%s", string);
wattroff(win, color);
refresh();
}
-----------------------------------------------------------------------------
18.5. Field Validation
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.
Validation can be attached to a field with the following function.
int set_field_type(FIELD *field, /* field to alter */
FIELDTYPE *ftype, /* type to associate */
...); /* additional arguments*/
Once set, the validation type for a field can be queried with
FIELDTYPE *field_type(FIELD *field); /* field to query */
The form driver validates the data in a field only when data is entered by
the end-user. Validation does not occur when
<EFBFBD><EFBFBD>*<2A>the application program changes the field value by calling
set_field_buffer.
<EFBFBD><EFBFBD>*<2A>linked field values are changed indirectly -- by changing the field to
which they are linked
The following are the pre-defined validation types. You can also specify
custom validation, though it's a bit tricky and cumbersome.
TYPE_ALPHA
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:
int set_field_type(FIELD *field, /* field to alter */
TYPE_ALPHA, /* type to associate */
int width); /* maximum width of field */
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.
TYPE_ALNUM
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:
int set_field_type(FIELD *field, /* field to alter */
TYPE_ALNUM, /* type to associate */
int width); /* maximum width of field */
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.
TYPE_ENUM
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:
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? */
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.
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.
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.
The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be particularly
useful with these fields.
TYPE_INTEGER
This field type accepts an integer. It is set up as follows:
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 */
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.
If the value passes its range check, it is padded with as many leading zero
digits as necessary to meet the padding argument.
A TYPE_INTEGER value buffer can conveniently be interpreted with the C
library function atoi(3).
TYPE_NUMERIC
This field type accepts a decimal number. It is set up as follows:
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 */
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.
If the value passes its range check, it is padded with as many trailing zero
digits as necessary to meet the padding argument.
A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
library function atof(3).
TYPE_REGEXP
This field type accepts data matching a regular expression. It is set up as
follows:
int set_field_type(FIELD *field, /* field to alter */
TYPE_REGEXP, /* type to associate */
char *regexp); /* expression to match */
The syntax for regular expressions is that of regcomp(3). The check for
regular-expression match is performed on exit.
-----------------------------------------------------------------------------
18.6. Form Driver: The work horse of the forms system
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().
int form_driver(FORM *form, /* form on which to operate */
int request) /* form request code */
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.
The requests roughly can be divided into following categories. Different
requests and their usage is explained below:
-----------------------------------------------------------------------------
18.6.1. Page Navigation Requests
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.
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 */
The following requests allow you to move to different pages
<EFBFBD><EFBFBD>*<2A>REQ_NEXT_PAGE Move to the next form page.
<EFBFBD><EFBFBD>*<2A>REQ_PREV_PAGE Move to the previous form page.
<EFBFBD><EFBFBD>*<2A>REQ_FIRST_PAGE Move to the first form page.
<EFBFBD><EFBFBD>*<2A>REQ_LAST_PAGE Move to the last form page.
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.
-----------------------------------------------------------------------------
18.6.2. Inter-Field Navigation Requests
These requests handle navigation between fields on the same page.
<EFBFBD><EFBFBD>*<2A>REQ_NEXT_FIELD Move to next field.
<EFBFBD><EFBFBD>*<2A>REQ_PREV_FIELD Move to previous field.
<EFBFBD><EFBFBD>*<2A>REQ_FIRST_FIELD Move to the first field.
<EFBFBD><EFBFBD>*<2A>REQ_LAST_FIELD Move to the last field.
<EFBFBD><EFBFBD>*<2A>REQ_SNEXT_FIELD Move to sorted next field.
<EFBFBD><EFBFBD>*<2A>REQ_SPREV_FIELD Move to sorted previous field.
<EFBFBD><EFBFBD>*<2A>REQ_SFIRST_FIELD Move to the sorted first field.
<EFBFBD><EFBFBD>*<2A>REQ_SLAST_FIELD Move to the sorted last field.
<EFBFBD><EFBFBD>*<2A>REQ_LEFT_FIELD Move left to field.
<EFBFBD><EFBFBD>*<2A>REQ_RIGHT_FIELD Move right to field.
<EFBFBD><EFBFBD>*<2A>REQ_UP_FIELD Move up to field.
<EFBFBD><EFBFBD>*<2A>REQ_DOWN_FIELD Move down to field.
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()
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.
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.
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.
-----------------------------------------------------------------------------
18.6.3. Intra-Field Navigation Requests
These requests drive movement of the edit cursor within the currently
selected field.
<EFBFBD><EFBFBD>*<2A>REQ_NEXT_CHAR Move to next character.
<EFBFBD><EFBFBD>*<2A>REQ_PREV_CHAR Move to previous character.
<EFBFBD><EFBFBD>*<2A>REQ_NEXT_LINE Move to next line.
<EFBFBD><EFBFBD>*<2A>REQ_PREV_LINE Move to previous line.
<EFBFBD><EFBFBD>*<2A>REQ_NEXT_WORD Move to next word.
<EFBFBD><EFBFBD>*<2A>REQ_PREV_WORD Move to previous word.
<EFBFBD><EFBFBD>*<2A>REQ_BEG_FIELD Move to beginning of field.
<EFBFBD><EFBFBD>*<2A>REQ_END_FIELD Move to end of field.
<EFBFBD><EFBFBD>*<2A>REQ_BEG_LINE Move to beginning of line.
<EFBFBD><EFBFBD>*<2A>REQ_END_LINE Move to end of line.
<EFBFBD><EFBFBD>*<2A>REQ_LEFT_CHAR Move left in field.
<EFBFBD><EFBFBD>*<2A>REQ_RIGHT_CHAR Move right in field.
<EFBFBD><EFBFBD>*<2A>REQ_UP_CHAR Move up in field.
<EFBFBD><EFBFBD>*<2A>REQ_DOWN_CHAR Move down in field.
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.
-----------------------------------------------------------------------------
18.6.4. Scrolling Requests
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:
<EFBFBD><EFBFBD>*<2A>REQ_SCR_FLINE Scroll vertically forward a line.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_BLINE Scroll vertically backward a line.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_FPAGE Scroll vertically forward a page.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_BPAGE Scroll vertically backward a page.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_FHPAGE Scroll vertically forward half a page.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_BHPAGE Scroll vertically backward half a page.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_FCHAR Scroll horizontally forward a character.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_BCHAR Scroll horizontally backward a character.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_HFLINE Scroll horizontally one field width forward.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_HBLINE Scroll horizontally one field width backward.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_HFHALF Scroll horizontally one half field width forward.
<EFBFBD><EFBFBD>*<2A>REQ_SCR_HBHALF Scroll horizontally one half field width backward.
For scrolling purposes, a page of a field is the height of its visible part.
-----------------------------------------------------------------------------
18.6.5. Editing Requests
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.
The following requests support editing the field and changing the edit mode:
<EFBFBD><EFBFBD>*<2A>REQ_INS_MODE Set insertion mode.
<EFBFBD><EFBFBD>*<2A>REQ_OVL_MODE Set overlay mode.
<EFBFBD><EFBFBD>*<2A>REQ_NEW_LINE New line request (see below for explanation).
<EFBFBD><EFBFBD>*<2A>REQ_INS_CHAR Insert space at character location.
<EFBFBD><EFBFBD>*<2A>REQ_INS_LINE Insert blank line at character location.
<EFBFBD><EFBFBD>*<2A>REQ_DEL_CHAR Delete character at cursor.
<EFBFBD><EFBFBD>*<2A>REQ_DEL_PREV Delete previous word at cursor.
<EFBFBD><EFBFBD>*<2A>REQ_DEL_LINE Delete line at cursor.
<EFBFBD><EFBFBD>*<2A>REQ_DEL_WORD Delete word at cursor.
<EFBFBD><EFBFBD>*<2A>REQ_CLR_EOL Clear to end of line.
<EFBFBD><EFBFBD>*<2A>REQ_CLR_EOF Clear to end of field.
<EFBFBD><EFBFBD>*<2A>REQ_CLR_FIELD Clear entire field.
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.
First, we consider REQ_NEW_LINE:
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).
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.
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.
Now, let us consider REQ_DEL_PREV:
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).
However, REQ_DEL_PREV at the beginning of a field is instead treated as a
REQ_PREV_FIELD.
If the O_BS_OVERLOAD option is off, this special action is disabled and the
forms driver just returns E_REQUEST_DENIED.
-----------------------------------------------------------------------------
18.6.6. Order Requests
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:
<EFBFBD><EFBFBD>*<2A>REQ_NEXT_CHOICE Place the successor value of the current value in the
buffer.
<EFBFBD><EFBFBD>*<2A>REQ_PREV_CHOICE Place the predecessor value of the current value in the
buffer.
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.
-----------------------------------------------------------------------------
18.6.7. Application Commands
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.
-----------------------------------------------------------------------------
19. Tools and Widget Libraries
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.
-----------------------------------------------------------------------------
19.1. CDK (Curses Development Kit)
In the author's words
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.
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 [http://invisible-island.net/cdk/]
http://invisible-island.net/cdk/ . Follow the instructions in README file to
install it.
-----------------------------------------------------------------------------
19.1.1. Widget List
The following is the list of widgets provided with cdk and their description.
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.
===========================================================================
A few of the widgets are modified by Thomas Dickey in recent versions.
-----------------------------------------------------------------------------
19.1.2. Some Attractive Features
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
If the string
"</B/1>This line should have a yellow foreground and a blue
background.<!1>"
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.
-----------------------------------------------------------------------------
19.1.3. Conclusion
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.
-----------------------------------------------------------------------------
19.2. The dialog
Long long ago, in September 1994, when few people knew linux, Jeff Tranter
wrote an [http://www2.linuxjournal.com/lj-issues/issue5/2807.html] article on
dialog in Linux Journal. He starts the article with these words..
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
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
[http://invisible-island.net/dialog/] Thomas Dickey's site.
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.
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.
-----------------------------------------------------------------------------
19.3. Perl Curses Modules CURSES::FORM and CURSES::WIDGETS
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 CPAN All Modules page. 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.
Some of my code examples are converted to perl by Anuradha Ratnaweera and
they are available in the perl directory.
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.
-----------------------------------------------------------------------------
20. Just For Fun !!!
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 [mailto:ppadala@gmail.com] me.
-----------------------------------------------------------------------------
20.1. The Game of Life
Game of life is a wonder of math. In [http://www.math.com/students/wonders/
life/life.html] Paul Callahan's words
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.
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 [http://
www.google.com] google for interesting information on game of life.
File Path: JustForFun/life.c
-----------------------------------------------------------------------------
20.2. Magic Square
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.
This program creates a simple magic square of odd order.
File Path: JustForFun/magic.c
-----------------------------------------------------------------------------
20.3. Towers of Hanoi
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.
File Path: JustForFun/hanoi.c
-----------------------------------------------------------------------------
20.4. Queens Puzzle
The objective of the famous N-Queen puzzle is to put N queens on a N X N
chess board without attacking each other.
This program solves it with a simple backtracking technique.
File Path: JustForFun/queens.c
-----------------------------------------------------------------------------
20.5. Shuffle
A fun game, if you have time to kill.
File Path: JustForFun/shuffle.c
-----------------------------------------------------------------------------
20.6. Typing Tutor
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.
File Path: JustForFun/tt.c
-----------------------------------------------------------------------------
21. References
<EFBFBD><EFBFBD>*<2A>NCURSES man pages
<EFBFBD><EFBFBD>*<2A>NCURSES FAQ at [http://invisible-island.net/ncurses/ncurses.faq.html]
http://invisible-island.net/ncurses/ncurses.faq.html
<EFBFBD><EFBFBD>*<2A>Writing programs with NCURSES by Eric Raymond and Zeyd M. Ben-Halim at
[http://invisible-island.net/ncurses/ncurses-intro.html] http://
invisible-island.net/ncurses/ncurses-intro.html - somewhat obsolete. I
was inspired by this document and the structure of this HOWTO follows
from the original document
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