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 -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 -Thomas Dickey. -You can contact the maintainers at 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 or any -of the ftp sites mentioned in 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 . 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 -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/

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

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 LDP Author guide for more details. If all else failes, -mail me at ppadala@gmail.com

1.7. -Credits

I thank 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 -Anuradha -Ratnaweera.

Then comes 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 me.

-
Add examples to last parts of forms section.
-
-
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.
-
-
Add debug info. _tracef, _tracemouse stuff.
-
-
Accessing termcap, terminfo using functions provided by ncurses -package.
-
-
Working on two terminals simultaneously.
-
-
Add more stuff to miscellaneous section.
-

1.9. -Copyright

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.

-
addch() class: Print single character with attributes
-
-
printw() class: Print formatted output similar to printf()
-
-
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:

-
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); -
-
-
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.

-
getch() class: Get a character
-
-
scanw() class: Get formatted input
-
-
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 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:

-
Create the windows (with newwin()) to be attached to the -panels.
-
-
Create panels with the chosen visibility order. Stack them up -according to the desired visibility. The function new_panel() is -used to created panels.
-
-
Call update_panels() to write the panels to the virtual screen -in correct visibility order. Do a doupdate() to show it on the -screen.
-
-
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.
-
-
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 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.

-
Initialize curses
-
-
Create items using new_item(). You can specify a name and -description for the items.
-
-
Create the menu with new_menu() by specifying the items to be -attached with.
-
-
Post the menu with menu_post() and refresh the screen.
-
-
Process the user requests with a loop and do necessary updates -to menu with menu_driver.
-
-
Unpost the menu with menu_unpost()
-
-
Free the memory allocated to menu by free_menu()
-
-
Free the memory allocated to the items with free_item()
-
-
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.

-
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.
-
-
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.
-
-
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.
-
-
REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_NEXT_ITEM and -REQ_PREV_ITEM
-
These requests are self explanatory.
-
-
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().
-
-
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.
-

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
-       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
-            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 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.

-
Initialize curses
-
-
Create fields using new_field(). You can specify the height and -width of the field, and its position on the form.
-
-
Create the forms with new_form() by specifying the fields to be -attached with.
-
-
Post the form with form_post() and refresh the screen.
-
-
Process the user requests with a loop and do necessary updates -to form with form_driver.
-
-
Unpost the menu with form_unpost()
-
-
Free the memory allocated to menu by free_form()
-
-
Free the memory allocated to the items with free_field()
-
-
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:

-
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.
-
-
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.
-
-
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.
-
-
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.
-
-
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.
-
-
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

-
the application program changes the field value by calling -set_field_buffer.
-
-
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

-
REQ_NEXT_PAGE Move to the next form page.
-
-
REQ_PREV_PAGE Move to the previous form page.
-
-
REQ_FIRST_PAGE Move to the first form page.
-
-
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.

-
REQ_NEXT_FIELD Move to next field.
-
-
REQ_PREV_FIELD Move to previous field.
-
-
REQ_FIRST_FIELD Move to the first field.
-
-
REQ_LAST_FIELD Move to the last field.
-
-
REQ_SNEXT_FIELD Move to sorted next field.
-
-
REQ_SPREV_FIELD Move to sorted previous field.
-
-
REQ_SFIRST_FIELD Move to the sorted first field.
-
-
REQ_SLAST_FIELD Move to the sorted last field.
-
-
REQ_LEFT_FIELD Move left to field.
-
-
REQ_RIGHT_FIELD Move right to field.
-
-
REQ_UP_FIELD Move up to field.
-
-
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.

-
REQ_NEXT_CHAR Move to next character.
-
-
REQ_PREV_CHAR Move to previous character.
-
-
REQ_NEXT_LINE Move to next line.
-
-
REQ_PREV_LINE Move to previous line.
-
-
REQ_NEXT_WORD Move to next word.
-
-
REQ_PREV_WORD Move to previous word.
-
-
REQ_BEG_FIELD Move to beginning of field.
-
-
REQ_END_FIELD Move to end of field.
-
-
REQ_BEG_LINE Move to beginning of line.
-
-
REQ_END_LINE Move to end of line.
-
-
REQ_LEFT_CHAR Move left in field.
-
-
REQ_RIGHT_CHAR Move right in field.
-
-
REQ_UP_CHAR Move up in field.
-
-
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:

-
REQ_SCR_FLINE Scroll vertically forward a line.
-
-
REQ_SCR_BLINE Scroll vertically backward a line.
-
-
REQ_SCR_FPAGE Scroll vertically forward a page.
-
-
REQ_SCR_BPAGE Scroll vertically backward a page.
-
-
REQ_SCR_FHPAGE Scroll vertically forward half a -page.
-
-
REQ_SCR_BHPAGE Scroll vertically backward half a -page.
-
-
REQ_SCR_FCHAR Scroll horizontally forward a -character.
-
-
REQ_SCR_BCHAR Scroll horizontally backward a -character.
-
-
REQ_SCR_HFLINE Scroll horizontally one field width -forward.
-
-
REQ_SCR_HBLINE Scroll horizontally one field width -backward.
-
-
REQ_SCR_HFHALF Scroll horizontally one half field width -forward.
-
-
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:

-
REQ_INS_MODE Set insertion mode.
-
-
REQ_OVL_MODE Set overlay mode.
-
-
REQ_NEW_LINE New line request (see below for -explanation).
-
-
REQ_INS_CHAR Insert space at character location.
-
-
REQ_INS_LINE Insert blank line at character -location.
-
-
REQ_DEL_CHAR Delete character at cursor.
-
-
REQ_DEL_PREV Delete previous word at cursor.
-
-
REQ_DEL_LINE Delete line at cursor.
-
-
REQ_DEL_WORD Delete word at cursor.
-
-
REQ_CLR_EOL Clear to end of line.
-
-
REQ_CLR_EOF Clear to end of field.
-
-
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:

-
REQ_NEXT_CHOICE Place the successor value of the -current value in the buffer.
-
-
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/ . 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 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 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 me.

20.1. The -Game of Life

Game of life is a wonder of math. In 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 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

-
NCURSES man pages
-
-
NCURSES FAQ at http://invisible-island.net/ncurses/ncurses.faq.html
-
-
Writing programs with NCURSES by Eric Raymond and Zeyd M. -Ben-Halim at 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
-

Announcing ncurses 5.6

- -In mid-June 1995, the maintainer of 4.4BSD curses declared that he -considered 4.4BSD curses obsolete, and encouraged the keepers of -Unix releases such as BSD/OS, FreeBSD and NetBSD to switch over to -ncurses.

- -The ncurses code was developed under GNU/Linux. -It has been in use for some time with OpenBSD as the system curses library, -and on FreeBSD and NetBSD as an external package. -It should port easily to any ANSI/POSIX-conforming UNIX. -It has even been ported to OS/2 Warp!

- -The distribution includes the library and support utilities, including a -terminfo compiler tic(1), a decompiler infocmp(1), clear(1), tput(1), tset(1), -and a termcap conversion tool captoinfo(1). Full manual pages are provided for -the library and tools.

Release Notes

Features of Ncurses

State of the Package

- -The ncurses code has been tested with a wide variety of applications -including (versions starting with those noted): -

- -The ncurses distribution includes a selection of test programs (including -a few games). - -

Who's Who and What's What

- -To join the ncurses mailing list, please write email to -bug-ncurses-request@gnu.org containing the line: -

Future Plans

Other Related Resources

- -You can find lots of information on terminal-related topics -not covered in the terminfo file at -Richard Shuford's -archive . - - - diff --git a/contrib/ncurses/doc/html/hackguide.html b/contrib/ncurses/doc/html/hackguide.html deleted file mode 100644 index 97d1369170c1..000000000000 --- a/contrib/ncurses/doc/html/hackguide.html +++ /dev/null @@ -1,914 +0,0 @@ - - - - -A Hacker's Guide to Ncurses Internals - - - - - - -

A Hacker's Guide to NCURSES

Abstract

Objective of the Package

Why System V Curses?

- -System V curses implementations can support BSD curses programs with -just a recompilation, so by capturing the System V API we also -capture BSD's.

- -More importantly for the future, the XSI Curses standard issued by X/Open -is explicitly and closely modeled on System V. So conformance with -System V took us most of the way to base-level XSI conformance. - -

How to Design Extensions

- -Accordingly, we have a policy of associating with each nonstandard extension -a feature macro, so that ncurses client code can use this macro to condition -in or out the code that requires the ncurses extension.

- -For example, there is a macro NCURSES_MOUSE_VERSION which XSI Curses -does not define, but which is defined in the ncurses library header. -You can use this to condition the calls to the mouse API calls. - -

Portability and Configuration

- -We encourage (but do not require) developers to make the code friendly -to less-capable UNIX environments wherever possible.

- -We encourage developers to support OS-specific optimizations and methods -not available under POSIX/ANSI, provided only that: - -

Documentation Conventions

- -The reason for choosing HTML is that it's (a) well-adapted for on-line -browsing through viewers that are everywhere; (b) more easily readable -as plain text than most other mark-ups, if you don't have a viewer; and (c) -carries enough information that you can generate a nice-looking printed -version from it. Also, of course, it make exporting things like the -announcement document to WWW pretty trivial. - -

How to Report Bugs

- -In order to use our bug-fixing time efficiently, we put people who -show us they've taken these steps at the head of our queue. This -means that if you don't, you'll probably end up at the tail end and -have to wait a while. - -

- -The most important of these is mvcur, a test frame for the -cursor-movement optimization code. With this program, you can see -directly what control sequences will be emitted for any given cursor -movement or scroll/insert/delete operations. If you think you've got -a bad capability identified, you can disable it and test again. The -program is command-driven and has on-line help.

- -If you think the vertical-scroll optimization is broken, or just want to -understand how it works better, build hashmap and read the -header comments of hardscroll.c and hashmap.c; then try -it out. You can also test the hardware-scrolling optimization separately -with hardscroll.

A Tour of the Ncurses Library

Library Overview

- -There is another group of files that do direct I/O via tputs(), -computations on the terminal capabilities, or queries to the OS -environment, but nevertheless have only fairly low complexity. These -include: -

- -These files -have serious hooks into -the tty driver and signal facilities: -

- -Finally, there is a group of files that is actually most of the -terminfo compiler. The reason this code lives in the ncurses -library is to support fallback to /etc/termcap. These files include -

The Engine Room

Keyboard Input

- -The central data structure in this module is a FIFO queue, used to -match multiple-character input sequences against special-key -capabilities; also to implement pushback via ungetch().

- -The wgetch() code distinguishes between function key -sequences and the same sequences typed manually by doing a timed wait -after each input character that could lead a function key sequence. -If the entire sequence takes less than 1 second, it is assumed to have -been generated by a function key press.

- -Hackers bruised by previous encounters with variant select(2) -calls may find the code in lib_twait.c interesting. It deals -with the problem that some BSD selects don't return a reliable -time-left value. The function timed_wait() effectively -simulates a System V select. - -

Mouse Events

- -Under xterm, however, mouse event notifications come in via the keyboard -input stream. They are recognized by having the kmous capability -as a prefix. This is kind of klugey, but trying to wire in recognition of -a mouse key prefix without going through the function-key machinery would -be just too painful, and this turns out to imply having the prefix somewhere -in the function-key capabilities at terminal-type initialization.

- -This kluge only works because kmous isn't actually used by any -historic terminal type or curses implementation we know of. Best -guess is it's a relic of some forgotten experiment in-house at Bell -Labs that didn't leave any traces in the publicly-distributed System V -terminfo files. If System V or XPG4 ever gets serious about using it -again, this kluge may have to change.

- -The lib_mouse()code is logically split into a lower level that -accepts event reports in a device-dependent format and an upper level that -parses mouse gestures and filters events. The mediating data structure is a -circular queue of event structures.

- -Functionally, the lower level's job is to pick up primitive events and -put them on the circular queue. This can happen in one of two ways: -either (a) _nc_mouse_event() detects a series of incoming -mouse reports and queues them, or (b) code in lib_getch.c detects the -kmous prefix in the keyboard input stream and calls _nc_mouse_inline -to queue up a series of adjacent mouse reports.

- -In either case, _nc_mouse_parse() should be called after the -series is accepted to parse the digested mouse reports (low-level -events) into a gesture (a high-level or composite event). - -

Output and Screen Updating

- -The main job is to go from the current state of the screen (as represented -in the curscr window structure) to the desired new state (as -represented in the newscr window structure), while doing as -little I/O as possible.

- -The brains of this operation are the modules hashmap.c, -hardscroll.c and lib_doupdate.c; the latter two use -lib_mvcur.c. Essentially, what happens looks like this:

- -The hashmap.c module tries to detect vertical motion -changes between the real and virtual screens. This information -is represented by the oldindex members in the newscr structure. -These are modified by vertical-motion and clear operations, and both are -re-initialized after each update. To this change-journalling -information, the hashmap code adds deductions made using a modified Heckel -algorithm on hash values generated from the line contents.

- -The hardscroll.c module computes an optimum set of scroll, -insertion, and deletion operations to make the indices match. It calls -_nc_mvcur_scrolln() in lib_mvcur.c to do those motions.

- -Then lib_doupdate.c goes to work. Its job is to do line-by-line -transformations of curscr lines to newscr lines. Its main -tool is the routine mvcur() in lib_mvcur.c. This routine -does cursor-movement optimization, attempting to get from given screen -location A to given location B in the fewest output characters possible.

- -If you want to work on screen optimizations, you should use the fact -that (in the trace-enabled version of the library) enabling the -TRACE_TIMES trace level causes a report to be emitted after -each screen update giving the elapsed time and a count of characters -emitted during the update. You can use this to tell when an update -optimization improves efficiency.

- -In the trace-enabled version of the library, it is also possible to disable -and re-enable various optimizations at runtime by tweaking the variable -_nc_optimize_enable. See the file include/curses.h.in -for mask values, near the end. - -

The Forms and Menu Libraries

- -The configuration code prefers the POSIX regex facility, modeled on -System V's, but will settle for BSD regexps if the former isn't available.

- -Historical note: the panels code was written primarily to assist in -porting u386mon 2.0 (comp.sources.misc v14i001-4) to systems lacking -panels support; u386mon 2.10 and beyond use it. This version has been -slightly cleaned up for ncurses. - -

A Tour of the Terminfo Compiler

- -The implementation therefore starts with a table-driven, dual-mode -lexical analyzer (in comp_scan.c). The lexer chooses its -mode (termcap or terminfo) based on the first `,' or `:' it finds in -each entry. The lexer does all the work of recognizing capability -names and values; the grammar above it is trivial, just "parse entries -till you run out of file". - -

Translation of Non-use Capabilities

- -One possibly interesting aspect of the implementation is the way the -compiler tables are initialized. All the tables are generated by various -awk/sed/sh scripts from a master table include/Caps; these -scripts actually write C initializers which are linked to the compiler. -Furthermore, the hash table is generated in the same way, so it doesn't -have to be generated at compiler startup time (another benefit of this -organization is that the hash table can be in shareable text space).

- -Thus, adding a new capability is usually pretty trivial, just a matter -of adding one line to the include/Caps file. We'll have more -to say about this in the section on Source-Form -Translation. - -

Use Capability Resolution

- -This won't do for ncurses. The problem is that that the whole -compilation process has to be embeddable in the ncurses library -so that it can be called by the startup code to translate termcap -entries on the fly. The embedded version can't go promiscuously writing -everything it translates out to disk -- for one thing, it will typically -be running with non-root permissions.

- -So our tic is designed to parse an entire terminfo file into a -doubly-linked circular list of entry structures in-core, and then do -use resolution in-memory before writing everything out. This -design has other advantages: it makes forward and back use-references -equally easy (so we get the latter for free), and it makes checking for -name collisions before they're written out easy to do.

- -And this is exactly how the embedded version works. But the stand-alone -user-accessible version of tic partly reverts to the historical -strategy; it writes to disk (not keeping in core) any entry with no -use references.

- -This is strictly a core-economy kluge, implemented because the -terminfo master file is large enough that some core-poor systems swap -like crazy when you compile it all in memory...there have been reports of -this process taking three hours, rather than the twenty seconds -or less typical on the author's development box.

- -So. The executable tic passes the entry-parser a hook that -immediately writes out the referenced entry if it has no use -capabilities. The compiler main loop refrains from adding the entry -to the in-core list when this hook fires. If some other entry later -needs to reference an entry that got written immediately, that's OK; -the resolution code will fetch it off disk when it can't find it in -core.

- -Name collisions will still be detected, just not as cleanly. The -write_entry() code complains before overwriting an entry that -postdates the time of tic's first call to -write_entry(), Thus it will complain about overwriting -entries newly made during the tic run, but not about -overwriting ones that predate it. - -

Source-Form Translation

- -The translation output code (dump_entry() in -ncurses/dump_entry.c) is shared with the infocmp(1) -utility. It takes the same internal representation used to generate -the binary form and dumps it to standard output in a specified -format.

- -The include/Caps file has a header comment describing ways you -can specify source translations for nonstandard capabilities just by -altering the master table. It's possible to set up capability aliasing -or tell the compiler to plain ignore a given capability without writing -any C code at all.

- -For circumstances where you need to do algorithmic translation, there -are functions in parse_entry.c called after the parse of each -entry that are specifically intended to encapsulate such -translations. This, for example, is where the AIX box1 capability -get translated to an acsc string. - -

Other Utilities

- -The tput and clear utilities just do an entry load -followed by a tputs() of a selected capability. - -

Style Tips for Developers

- -The prefix _nc_ should be used on library public functions that are -not part of the curses API in order to prevent pollution of the -application namespace. - -If you have to add to or modify the function prototypes in curses.h.in, -read ncurses/MKlib_gen.sh first so you can avoid breaking XSI conformance. - -Please join the ncurses mailing list. See the INSTALL file in the -top level of the distribution for details on the list.

- -Look for the string FIXME in source files to tag minor bugs -and potential problems that could use fixing.

- -Don't try to auto-detect OS features in the main body of the C code. -That's the job of the configuration system.

- -To hold down complexity, do make your code data-driven. Especially, -if you can drive logic from a table filtered out of -include/Caps, do it. If you find you need to augment the -data in that file in order to generate the proper table, that's still -preferable to ad-hoc code -- that's why the fifth field (flags) is -there.

Porting Hints

- -The following library modules are `pure curses'; they operate only on -the curses internal structures, do all output through other curses -calls (not including tputs() and putp()) and do not -call any other UNIX routines such as signal(2) or the stdio library. -Thus, they should not need to be modified for single-terminal -ports. - -

- -These modules are pure curses, except that they use tputs() -and putp(): - -

- -The following modules will use open()/read()/write()/close()/lseek() on files, -but no other OS calls. - -

- -The following modules are `pure curses' but contain assumptions inappropriate -for a memory-mapped port. - -

Writing Programs with NCURSES

Introduction

- -This document is aimed at C applications programmers not yet specifically -familiar with ncurses. If you are already an experienced curses -programmer, you should nevertheless read the sections on -Mouse Interfacing, Debugging, -Compatibility with Older Versions, -and Hints, Tips, and Tricks. These will bring you up -to speed on the special features and quirks of the ncurses -implementation. If you are not so experienced, keep reading.

- -The curses package is a subroutine library for -terminal-independent screen-painting and input-event handling which -presents a high level screen model to the programmer, hiding differences -between terminal types and doing automatic optimization of output to change -one screen full of text into another. Curses uses terminfo, which -is a database format that can describe the capabilities of thousands of -different terminals.

- -The curses API may seem something of an archaism on UNIX desktops -increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX still -supports tty lines and X supports xterm(1); the curses -API has the advantage of (a) back-portability to character-cell terminals, -and (b) simplicity. For an application that does not require bit-mapped -graphics and multiple fonts, an interface implementation using curses -will typically be a great deal simpler and less expensive than one using an -X toolkit. - -

A Brief History of Curses

- -System III UNIX from Bell Labs featured a rewritten and much-improved -curses library. It introduced the terminfo format. Terminfo is based -on Berkeley's termcap database, but contains a number of improvements and -extensions. Parameterized capabilities strings were introduced, making it -possible to describe multiple video attributes, and colors and to handle far -more unusual terminals than possible with termcap. In the later AT&T -System V releases, curses evolved to use more facilities and offer -more capabilities, going far beyond BSD curses in power and flexibility. - -

Scope of This Document

- -The ncurses package can also capture and use event reports from a -mouse in some environments (notably, xterm under the X window system). This -document includes tips for using the mouse.

- -The ncurses package was originated by Pavel Curtis. The original -maintainer of this package is -Zeyd Ben-Halim -<zmbenhal@netcom.com>. -Eric S. Raymond -<esr@snark.thyrsus.com> -wrote many of the new features in versions after 1.8.1 -and wrote most of this introduction. -Jürgen Pfeifer -wrote all of the menu and forms code as well as the -Ada95 binding. -Ongoing work is being done by -Thomas Dickey (maintainer). -Contact the current maintainers at -bug-ncurses@gnu.org. -

- -This document also describes the panels extension library, -similarly modeled on the SVr4 panels facility. This library allows you to -associate backing store with each of a stack or deck of overlapping windows, -and provides operations for moving windows around in the stack that change -their visibility in the natural way (handling window overlaps).

- -Finally, this document describes in detail the menus and forms extension libraries, also cloned from System V, -which support easy construction and sequences of menus and fill-in -forms. - - -

Terminology

The Curses Library

An Overview of Curses

Compiling Programs using Curses

Updating the Screen

- -A window is a purely internal representation. It is used to build and store a -potential image of a portion of the terminal. It doesn't bear any necessary -relation to what is really on the terminal screen; it's more like a -scratchpad or write buffer.

- -To make the section of physical screen corresponding to a window reflect the -contents of the window structure, the routine refresh() (or -wrefresh() if the window is not stdscr) is called.

- -A given physical screen section may be within the scope of any number of -overlapping windows. Also, changes can be made to windows in any order, -without regard to motion efficiency. Then, at will, the programmer can -effectively say ``make it look like this,'' and let the package implementation -determine the most efficient way to repaint the screen. - -

Standard Windows and Function Naming Conventions

- -Many functions are defined to use stdscr as a default screen. For -example, to add a character to stdscr, one calls addch() with -the desired character as argument. To write to a different window. use the -routine waddch() (for `w'indow-specific addch()) is provided. This -convention of prepending function names with a `w' when they are to be -applied to specific windows is consistent. The only routines which do not -follow it are those for which a window must always be specified.

- -In order to move the current (y, x) coordinates from one point to another, the -routines move() and wmove() are provided. However, it is -often desirable to first move and then perform some I/O operation. In order to -avoid clumsiness, most I/O routines can be preceded by the prefix 'mv' and -the desired (y, x) coordinates prepended to the arguments to the function. For -example, the calls - -

Variables

Using the Library

Starting up

- -Once the screen windows have been allocated, you can set them up for -your program. If you want to, say, allow a screen to scroll, use -scrollok(). If you want the cursor to be left in place after -the last change, use leaveok(). If this isn't done, -refresh() will move the cursor to the window's current (y, x) -coordinates after updating it.

- -You can create new windows of your own using the functions newwin(), -derwin(), and subwin(). The routine delwin() will -allow you to get rid of old windows. All the options described above can be -applied to any window. - -

Output

- -The other output functions, such as addstr() and printw(), -all call addch() to add characters to the window.

- -After you have put on the window what you want there, when you want the portion -of the terminal covered by the window to be made to look like it, you must call -refresh(). In order to optimize finding changes, refresh() -assumes that any part of the window not changed since the last -refresh() of that window has not been changed on the terminal, i.e., -that you have not refreshed a portion of the terminal with an overlapping -window. If this is not the case, the routine touchwin() is provided -to make it look like the entire window has been changed, thus making -refresh() check the whole subsection of the terminal for changes.

- -If you call wrefresh() with curscr as its argument, it will -make the screen look like curscr thinks it looks like. This is useful -for implementing a command which would redraw the screen in case it get messed -up. - -

Input

- -When you need to accept line-oriented input in a window, the functions -wgetstr() and friends are available. There is even a wscanw() -function that can do scanf()(3)-style multi-field parsing on window -input. These pseudo-line-oriented functions turn on echoing while they -execute.

- -The example code above uses the call keypad(stdscr, TRUE) to enable -support for function-key mapping. With this feature, the getch() code -watches the input stream for character sequences that correspond to arrow and -function keys. These sequences are returned as pseudo-character values. The -#define values returned are listed in the curses.h The -mapping from sequences to #define values is determined by -key_ capabilities in the terminal's terminfo entry. - -

Using Forms Characters

- -The most useful of the ACS defines are the forms-drawing characters. You can -use these to draw boxes and simple graphs on the screen. If the terminal -does not have such characters, curses.h will map them to a -recognizable (though ugly) set of ASCII defaults. - -

Character Attributes and Color

- -Highlights are encoded, internally, as high bits of the pseudo-character type -(chtype) that curses.h uses to represent the contents of a -screen cell. See the curses.h header file for a complete list of -highlight mask values (look for the prefix A_).

- -There are two ways to make highlights. One is to logical-or the value of the -highlights you want into the character argument of an addch() call, -or any other output call that takes a chtype argument.

- -The other is to set the current-highlight value. This is logical-or'ed with -any highlight you specify the first way. You do this with the functions -attron(), attroff(), and attrset(); see the manual -pages for details. - -Color is a special kind of highlight. The package actually thinks in terms -of color pairs, combinations of foreground and background colors. The sample -code above sets up eight color pairs, all of the guaranteed-available colors -on black. Note that each color pair is, in effect, given the name of its -foreground color. Any other range of eight non-conflicting values could -have been used as the first arguments of the init_pair() values.

- -Once you've done an init_pair() that creates color-pair N, you can -use COLOR_PAIR(N) as a highlight that invokes that particular -color combination. Note that COLOR_PAIR(N), for constant N, -is itself a compile-time constant and can be used in initializers. - -

Mouse Interfacing

-The mouse interface is very simple. To activate it, you use the function -mousemask(), passing it as first argument a bit-mask that specifies -what kinds of events you want your program to be able to see. It will -return the bit-mask of events that actually become visible, which may differ -from the argument if the mouse device is not capable of reporting some of -the event types you specify.

- -Once the mouse is active, your application's command loop should watch -for a return value of KEY_MOUSE from wgetch(). When -you see this, a mouse event report has been queued. To pick it off -the queue, use the function getmouse() (you must do this before -the next wgetch(), otherwise another mouse event might come -in and make the first one inaccessible).

- -Each call to getmouse() fills a structure (the address of which you'll -pass it) with mouse event data. The event data includes zero-origin, -screen-relative character-cell coordinates of the mouse pointer. It also -includes an event mask. Bits in this mask will be set, corresponding -to the event type being reported.

- -The mouse structure contains two additional fields which may be -significant in the future as ncurses interfaces to new kinds of -pointing device. In addition to x and y coordinates, there is a slot -for a z coordinate; this might be useful with touch-screens that can -return a pressure or duration parameter. There is also a device ID -field, which could be used to distinguish between multiple pointing -devices.

- -The class of visible events may be changed at any time via mousemask(). -Events that can be reported include presses, releases, single-, double- and -triple-clicks (you can set the maximum button-down time for clicks). If -you don't make clicks visible, they will be reported as press-release -pairs. In some environments, the event mask may include bits reporting -the state of shift, alt, and ctrl keys on the keyboard during the event.

- -A function to check whether a mouse event fell within a given window is -also supplied. You can use this to see whether a given window should -consider a mouse event relevant to it.

- -Because mouse event reporting will not be available in all -environments, it would be unwise to build ncurses -applications that require the use of a mouse. Rather, you should -use the mouse as a shortcut for point-and-shoot commands your application -would normally accept from the keyboard. Two of the test games in the -ncurses distribution (bs and knight) contain -code that illustrates how this can be done.

- -See the manual page curs_mouse(3X) for full details of the -mouse-interface functions. - -

Finishing Up

Function Descriptions

Initialization and Wrapup

Causing Output to the Terminal

Low-Level Capability Access

Debugging

Hints, Tips, and Tricks

Some Notes of Caution

- -Bear in mind that refresh() is a synonym for wrefresh(stdscr). -Don't try to mix use of stdscr with use of windows declared -by newwin(); a refresh() call will blow them off the -screen. The right way to handle this is to use subwin(), or -not touch stdscr at all and tile your screen with declared -windows which you then wnoutrefresh() somewhere in your program -event loop, with a single doupdate() call to trigger actual -repainting.

- -You are much less likely to run into problems if you design your screen -layouts to use tiled rather than overlapping windows. Historically, -curses support for overlapping windows has been weak, fragile, and poorly -documented. The ncurses library is not yet an exception to this -rule.

- -There is a panels library included in the ncurses -distribution that does a pretty good job of strengthening the -overlapping-windows facilities.

- -Try to avoid using the global variables LINES and COLS. Use -getmaxyx() on the stdscr context instead. Reason: -your code may be ported to run in an environment with window resizes, -in which case several screens could be open with different sizes. - -

Temporarily Leaving NCURSES Mode

- -To leave ncurses mode, call endwin() as you would if you -were intending to terminate the program. This will take the screen back to -cooked mode; you can do your shell-out. When you want to return to -ncurses mode, simply call refresh() or doupdate(). -This will repaint the screen.

- -There is a boolean function, isendwin(), which code can use to -test whether ncurses screen mode is active. It returns TRUE -in the interval between an endwin() call and the following -refresh(), FALSE otherwise.

Using NCURSES under XTERM

- -That is the standard way, of course (it even works with some vendor's curses -implementations). -Its drawback is that it clears the screen to reinitialize the display, and does -not resize subwindows which must be shrunk. -Ncurses provides an extension which works better, the -resizeterm function. That function ensures that all windows -are limited to the new screen dimensions, and pads stdscr -with blanks if the screen is larger.

- -The ncurses library provides a SIGWINCH signal handler, -which pushes a KEY_RESIZE via the wgetch() calls. -When ncurses returns that code, -it calls resizeterm -to update the size of the standard screen's window, repainting that -(filling with blanks or truncating as needed). -It also resizes other windows, -but its effect may be less satisfactory because it cannot -know how you want the screen re-painted. -You will usually have to write special-purpose code to handle -KEY_RESIZE yourself. - -

Handling Multiple Terminal Screens

- -For each call, you will have to specify a terminal type and a pair of file -pointers; each call will return a screen reference, and stdscr will be -set to the last one allocated. You will switch between screens with the -set_term call. Note that you will also have to call -def_shell_mode and def_prog_mode on each tty yourself. - -

Testing for Terminal Capabilities

- -A particularly useful case of this often comes up when you want to -test whether a given terminal type should be treated as `smart' -(cursor-addressable) or `stupid'. The right way to test this is to see -if the return value of tigetstr("cup") is non-NULL. Alternatively, -you can include the term.h file and test the value of the -macro cursor_address. - -

Tuning for Speed

Special Features of NCURSES

- -The define_key() function allows you -to define at runtime function-key control sequences which are not in the -terminal description. -The keyok() function allows you to temporarily -enable or disable interpretation of any function-key control sequence.

- -The use_default_colors() function allows you to construct -applications which can use the terminal's default foreground and -background colors as an additional "default" color. -Several terminal emulators support this feature, which is based on ISO 6429.

- -Ncurses supports up 16 colors, unlike SVr4 curses which defines only 8. -While most terminals which provide color allow only 8 colors, about -a quarter (including XFree86 xterm) support 16 colors. - -

Compatibility with Older Versions

Refresh of Overlapping Windows

- -To understand why this is a problem, remember that screen updates are -calculated between two representations of the entire display. The -documentation says that when you refresh a window, it is first copied to the -virtual screen, and then changes are calculated to update the physical screen -(and applied to the terminal). But "copied to" is not very specific, and -subtle differences in how copying works can produce different behaviors in the -case where two overlapping windows are each being refreshed at unpredictable -intervals.

- -What happens to the overlapping region depends on what wnoutrefresh() -does with its argument -- what portions of the argument window it copies to the -virtual screen. Some implementations do "change copy", copying down only -locations in the window that have changed (or been marked changed with -wtouchln() and friends). Some implementations do "entire copy", -copying all window locations to the virtual screen whether or not -they have changed.

- -The ncurses library itself has not always been consistent on this -score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy. Versions -1.8.6 and older, and versions 1.9.9 and newer, do change copy.

- -For most commercial curses implementations, it is not documented and not known -for sure (at least not to the ncurses maintainers) whether they do -change copy or entire copy. We know that System V release 3 curses has logic -in it that looks like an attempt to do change copy, but the surrounding logic -and data representations are sufficiently complex, and our knowledge -sufficiently indirect, that it's hard to know whether this is reliable. - -It is not clear what the SVr4 documentation and XSI standard intend. The XSI -Curses standard barely mentions wnoutrefresh(); the SVr4 documents seem to be -describing entire-copy, but it is possible with some effort and straining to -read them the other way.

- -It might therefore be unwise to rely on either behavior in programs that might -have to be linked with other curses implementations. Instead, you can do an -explicit touchwin() before the wnoutrefresh() call to -guarantee an entire-contents copy anywhere.

- -The really clean way to handle this is to use the panels library. If, -when you want a screen update, you do update_panels(), it will -do all the necessary wnoutrefresh() calls for whatever panel -stacking order you have defined. Then you can do one doupdate() -and there will be a single burst of physical I/O that will do -all your updates. - -

Background Erase

- -In newer versions, this is not so. Instead, the attribute of erased blanks -is normal unless and until it is modified by the functions bkgdset() -or wbkgdset().

- -This change in behavior conforms ncurses to System V Release 4 and -the XSI Curses standard. - -

XSI Curses Conformance

- -Also, ncurses meets the XSI requirement that every macro -entry point have a corresponding function which may be linked (and -will be prototype-checked) if the macro definition is disabled with -#undef. - -

The Panels Library

- -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.

- -The panel library first appeared in AT&T System V. The -version documented here is the panel code distributed -with ncurses. - -

Compiling With the Panels Library

Overview of Panels

- -Details on the panels functions are available in the man pages. We'll just -hit the highlights here.

- -You create a panel from a window by calling new_panel() on a -window pointer. It then becomes the top of the deck. The panel's window -is available as the value of panel_window() called with the -panel pointer as argument.

- -You can delete a panel (removing it from the deck) with del_panel. -This will not deallocate the associated window; you have to do that yourself. - -You can replace a panel's window with a different window by calling -replace_window. The new window may be of different size; -the panel code will re-compute all overlaps. This operation doesn't -change the panel's position in the deck.

- -To move a panel's window, use move_panel(). The -mvwin() function on the panel's window isn't sufficient because it -doesn't update the panels library's representation of where the windows are. -This operation leaves the panel's depth, contents, and size unchanged.

- -Two functions (top_panel(), bottom_panel()) are -provided for rearranging the deck. The first pops its argument window to the -top of the deck; the second sends it to the bottom. Either operation leaves -the panel's screen location, contents, and size unchanged.

- -The function update_panels() does all the -wnoutrefresh() calls needed to prepare for -doupdate() (which you must call yourself, afterwards).

- -Typically, you will want to call update_panels() and -doupdate() just before accepting command input, once in each cycle -of interaction with the user. If you call update_panels() after -each and every panel write, you'll generate a lot of unnecessary refresh -activity and screen flicker. - -

Panels, Input, and the Standard Screen

- -The stsdcr window is a special case. It is considered below all -panels. Because changes to panels may obscure parts of stdscr, -though, you should call update_panels() before -doupdate() even when you only change stdscr.

- -Note that wgetch automatically calls wrefresh. -Therefore, before requesting input from a panel window, you need to be sure -that the panel is totally unobscured.

- -There is presently no way to display changes to one obscured panel without -repainting all panels. - -

Hiding Panels

- -The panel_update code ignores hidden panels. You cannot do -top_panel() or bottom_panel on a hidden panel(). -Other panels operations are applicable. - -

Miscellaneous Other Facilities

- -Every panel has an associated user pointer, not used by the panel code, to -which you can attach application data. See the man page documentation -of set_panel_userptr() and panel_userptr for -details. - -

The Menu Library

- -The menu library first appeared in AT&T System V. The -version documented here is the menu code distributed -with ncurses. - -

Compiling With the menu Library

Overview of Menus

- -The menu can then by posted, that is written to an -associated window. Actually, each menu has two associated windows; a -containing window in which the programmer can scribble titles or -borders, and a subwindow in which the menu items proper are displayed. -If this subwindow is too small to display all the items, it will be a -scrollable viewport on the collection of items.

- -A menu may also be unposted (that is, undisplayed), and finally -freed to make the storage associated with it and its items available for -re-use.

Selecting items

- -From a single-valued menu you can read the selected value simply by looking -at the current item. From a multi-valued menu, you get the selected set -by looping through the items applying the item_value() -predicate function. Your menu-processing code can use the function -set_item_value() to flag the items in the select set.

- -Menu items can be made unselectable using set_item_opts() -or item_opts_off() with the O_SELECTABLE -argument. This is the only option so far defined for menus, but it -is good practice to code as though other option bits might be on. - -

Menu Display

- -The actual menu page may be smaller than the format size. This depends -on the item number and size and whether O_ROWMAJOR is on. This option -(on by default) causes menu items to be displayed in a `raster-scan' -pattern, so that if more than one item will fit horizontally the first -couple of items are side-by-side in the top row. The alternative is -column-major display, which tries to put the first several items in -the first column.

- -As mentioned above, a menu format not large enough to allow all items to fit -on-screen will result in a menu display that is vertically scrollable.

-You can scroll it with requests to the menu driver, which will be described -in the section on menu input handling.

- -Each menu has a mark string used to visually tag selected items; -see the menu_mark(3x) manual page for details. The mark -string length also influences the menu page size.

- -The function scale_menu() returns the minimum display size -that the menu code computes from all these factors. - -There are other menu display attributes including a select attribute, -an attribute for selectable items, an attribute for unselectable items, -and a pad character used to separate item name text from description -text. These have reasonable defaults which the library allows you to -change (see the menu_attribs(3x) manual page. - -

Menu Windows

- -The outer or frame window is not otherwise touched by the menu -routines. It exists so the programmer can associate a title, a -border, or perhaps help text with the menu and have it properly -refreshed or erased at post/unpost time. The inner window or -subwindow is where the current menu page is displayed.

- -By default, both windows are stdscr. You can set them with the -functions in menu_win(3x).

- -When you call post_menu(), you write the menu to its -subwindow. When you call unpost_menu(), you erase the -subwindow, However, neither of these actually modifies the screen. To -do that, call wrefresh() or some equivalent. - -

Processing Menu Input

- -The simplest group of command codes is REQ_NEXT_ITEM, -REQ_PREV_ITEM, REQ_FIRST_ITEM, -REQ_LAST_ITEM, REQ_UP_ITEM, -REQ_DOWN_ITEM, REQ_LEFT_ITEM, -REQ_RIGHT_ITEM. These change the currently selected -item. These requests may cause scrolling of the menu page if it only -partially displayed.

- -There are explicit requests for scrolling which also change the -current item (because the select location does not change, but the -item there does). These are REQ_SCR_DLINE, -REQ_SCR_ULINE, REQ_SCR_DPAGE, and -REQ_SCR_UPAGE.

- -The REQ_TOGGLE_ITEM selects or deselects the current item. -It is for use in multi-valued menus; if you use it with O_ONEVALUE -on, you'll get an error return (E_REQUEST_DENIED).

- -Each menu has an associated pattern buffer. The -menu_driver() logic tries to accumulate printable ASCII -characters passed in in that buffer; when it matches a prefix of an -item name, that item (or the next matching item) is selected. If -appending a character yields no new match, that character is deleted -from the pattern buffer, and menu_driver() returns -E_NO_MATCH.

- -Some requests change the pattern buffer directly: -REQ_CLEAR_PATTERN, REQ_BACK_PATTERN, -REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter -two are useful when pattern buffer input matches more than one item -in a multi-valued menu.

- -Each successful scroll or item navigation request clears the pattern -buffer. It is also possible to set the pattern buffer explicitly -with set_menu_pattern().

- -Finally, menu driver requests above the constant MAX_COMMAND -are considered application-specific commands. The menu_driver() -code ignores them and returns E_UNKNOWN_COMMAND. - -

Miscellaneous Other Features

- -It is possible to change the current item from application code; this -is useful if you want to write your own navigation requests. It is -also possible to explicitly set the top row of the menu display. See -mitem_current(3x). - -If your application needs to change the menu subwindow cursor for -any reason, pos_menu_cursor() will restore it to the -correct location for continuing menu driver processing.

- -It is possible to set hooks to be called at menu initialization and -wrapup time, and whenever the selected item changes. See -menu_hook(3x).

- -Each item, and each menu, has an associated user pointer on which you -can hang application data. See mitem_userptr(3x) and -menu_userptr(3x). - -

The Forms Library

- -The form library first appeared in AT&T System V. The -version documented here is the form code distributed -with ncurses. - -

Compiling With the form Library

Overview of Forms

-To make forms, you create groups of fields and connect them with form -frame objects; the form library makes this relatively simple.

- -Once defined, a form can be posted, that is written to an -associated window. Actually, each form has two associated windows; a -containing window in which the programmer can scribble titles or -borders, and a subwindow in which the form fields proper are displayed.

- -As the form user fills out the posted form, navigation and editing -keys support movement between fields, editing keys support modifying -field, and plain text adds to or changes data in a current field. The -form library allows you (the forms designer) to bind each navigation -and editing key to any keystroke accepted by curses - -Fields may have validation conditions on them, so that they check input -data for type and value. The form library supplies a rich set of -pre-defined field types, and makes it relatively easy to define new ones.

- -Once its transaction is completed (or aborted), a form may be -unposted (that is, undisplayed), and finally freed to make -the storage associated with it and its items available for re-use.

- -In forms programs, however, the `process user requests' is somewhat more -complicated than for menus. Besides menu-like navigation operations, -the menu driver loop has to support field editing and data validation. - -

Creating and Freeing Fields and Forms

- -You must also specify the location of the field's upper left corner on -the screen (the third and fourth arguments, which must be zero or -greater). Note that these coordinates are relative to the form -subwindow, which will coincide with stdscr by default but -need not be stdscr if you've done an explicit -set_form_win() call.

- -The fifth argument allows you to specify a number of off-screen rows. If -this is zero, the entire field will always be displayed. If it is -nonzero, the form will be scrollable, with only one screen-full (initially -the top part) displayed at any given time. If you make a field dynamic -and grow it so it will no longer fit on the screen, the form will become -scrollable even if the offscreen argument was initially zero.

- -The forms library allocates one working buffer per field; the size of -each buffer is ((height + offscreen)*width + 1, one character -for each position in the field plus a NUL terminator. The sixth -argument is the number of additional data buffers to allocate for the -field; your application can use them for its own purposes. - -

- -Besides the obvious use in making a field editable from two different -form pages, linked fields give you a way to hack in dynamic labels. If -you declare several fields linked to an original, and then make them -inactive, changes from the original will still be propagated to the -linked fields.

- -As with duplicated fields, linked fields have attribute bits separate -from the original.

- -As you might guess, all these field-allocations return NULL if -the field allocation is not possible due to an out-of-memory error or -out-of-bounds arguments.

- -Note that new_field() does not copy the pointer array -into private storage; if you modify the contents of the pointer array -during forms processing, all manner of bizarre things might happen. Also -note that any given field may only be connected to one form.

- -The functions free_field() and free_form are available -to free field and form objects. It is an error to attempt to free a field -connected to a form, but not vice-versa; thus, you will generally free -your form objects first. - -

Fetching and Changing Field Attributes

- -When a field is created, the attributes not specified by the -new_field function are copied from an invisible system -default field. In attribute-setting and -fetching functions, the -argument NULL is taken to mean this field. Changes to it persist -as defaults until your forms application terminates. - -

Fetching Size and Location Data

Changing the Field Location

The Justification Attribute

Field Display Attributes

- -This group of four field attributes controls the visual appearance -of the field on the screen, without affecting in any way the data -in the field buffer. - -

Field Option Bits

- -The option values are bit-masks and can be composed with logical-or in -the obvious way. - -

Field Status

- -Calling field_status() on a field not currently selected -for input will return a correct value. Calling field_status() on a -field that is currently selected for input may not necessarily give a -correct field status value, because entered data isn't necessarily copied to -buffer zero before the exit validation check. - -To guarantee that the returned status value reflects reality, 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. - -

Field User Pointer

- -It is valid to set the user pointer of the default field (with a -set_field_userptr() call passed a NULL field pointer.) -When a new field is created, the default-field user pointer is copied -to initialize the new field's user pointer. - -

Variable-Sized Fields

- -A one-line dynamic field will have a fixed height (1) but variable -width, scrolling horizontally to display data within the field area as -originally dimensioned and located. A multi-line dynamic field will -have a fixed width, but variable height (number of rows), scrolling -vertically to display data within the field area as originally -dimensioned and located.

- -Normally, a dynamic field is allowed to grow without limit. But it is -possible to set an upper limit on the size of a dynamic field. You do -it with this function: - -

Field Validation

- -A field's validation check (if any) is not called when -set_field_buffer() modifies the input buffer, nor when that buffer -is changed through a linked field.

- -The form library provides a rich set of pre-defined validation -types, and gives you the capability to define custom ones of your own. You -can examine and change field validation attributes with the following -functions: - -

TYPE_ALPHA

TYPE_ALNUM

TYPE_ENUM

- -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

- -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

- -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

Direct Field Buffer Manipulation

- -Calling field_buffer() with a null field pointer will raise an -error. Calling field_buffer() on a field not currently selected -for input will return a correct value. Calling field_buffer() on a -field that is currently selected for input may not necessarily give a -correct field buffer value, because entered data isn't necessarily copied to -buffer zero before the exit validation check. - -To guarantee that the returned buffer value reflects on-screen reality, -call field_buffer() 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. - -

Attributes of Forms

- -The principal attribute of a form is its field list. You can query -and change this list with: - -

- -It may also be null, in which case the old fields are disconnected -(and not freed) but no new ones are connected.

- -The field_count() function simply counts the number of fields -connected to a given from. It returns -1 if the form-pointer argument -is NULL. - -

Control of Form Display

- -By making this step explicit, you can associate a form with a declared -frame window on your screen display. This can be useful if you want to -adapt the form display to different screen sizes, dynamically tile -forms on the screen, or use a form as part of an interface layout -managed by panels.

- -The two windows associated with each form have the same functions as -their analogues in the menu library. Both these -windows are painted when the form is posted and erased when the form -is unposted.

- -The outer or frame window is not otherwise touched by the form -routines. It exists so the programmer can associate a title, a -border, or perhaps help text with the form and have it properly -refreshed or erased at post/unpost time. The inner window or subwindow -is where the current form page is actually displayed.

- -In order to declare your own frame window for a form, you'll need to -know the size of the form's bounding rectangle. You can get this -information with: - -

- -It is possible to check from your application whether all of a -scrollable field is actually displayed within the menu subwindow. Use -these functions: - -

- -The function data_behind() returns TRUE if the first (upper -left hand) character position is off-screen (not being displayed).

- -Finally, there is a function to restore the form window's cursor to the -value expected by the forms driver: - -

Input Processing in the Forms Driver

- -The forms driver provides hooks (through input-validation and -field-termination functions) with which your application code can check -that the input taken by the driver matched what was expected. - -

Page Navigation Requests

Inter-Field Navigation Requests

- -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. - -

Intra-Field Navigation Requests

Scrolling Requests

Editing Requests

- -The following requests support editing the field and changing the edit -mode: - -

- -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.

- -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.

- -See Form Options for discussion of how to set -and clear the overload options. - -

Order Requests

Application Commands

Field Change Hooks

- -You can set a default hook for all fields by passing one of the set functions -a NULL first argument.

- -You can disable any of these hooks by (re)setting them to NULL, the default -value. - -

Field Change Commands

- -The initial current field of a form is the first active field on the -first page. The function set_form_fields() resets this.

Form Options

Custom Validation Types

Union Types

New Field Types

- -The function free_fieldtype() deallocates the argument -fieldtype, freeing all storage associated with it.

- -Normally, a field validator is called when the user attempts to -leave the field. Its first argument is a field pointer, from which it -can get to field buffer 0 and test it. If the function returns TRUE, -the operation succeeds; if it returns FALSE, the edit cursor stays in -the field.

- -A character validator gets the character passed in as a first argument. -It too should return TRUE if the character is valid, FALSE otherwise. - -

Validation Function Arguments

- -In order to arrange for such arguments to be passed to your validation -functions, you must associate a small set of storage-management functions -with the type. The forms driver will use these to synthesize a pile -from the trailing arguments of each set_field_type() argument, and -a pointer to the pile will be passed to the validation functions.

Order Functions For Custom Types

Avoiding Problems

- -Use that code as a model, and evolve it towards what you really want. -You will avoid many problems and annoyances that way. The code -in the ncurses library has been specifically exempted from -the package copyright to support this.

- -If your custom type defines order functions, have do something intuitive -with a blank field. A useful convention is to make the successor of a -blank field the types minimum value, and its predecessor the maximum. - - -- cgit v1.2.3