ncurses-intro.doc revision 166124
1166124Srafan                         Writing Programs with NCURSES
276726Speter
376726Speter     by Eric S. Raymond and Zeyd M. Ben-Halim
476726Speter     updates since release 1.9.9e by Thomas Dickey
5166124Srafan
676726Speter                                   Contents
7166124Srafan
876726Speter     * Introduction
976726Speter          + A Brief History of Curses
1076726Speter          + Scope of This Document
1176726Speter          + Terminology
1276726Speter     * The Curses Library
1376726Speter          + An Overview of Curses
1476726Speter               o Compiling Programs using Curses
1576726Speter               o Updating the Screen
1676726Speter               o Standard Windows and Function Naming Conventions
1776726Speter               o Variables
1876726Speter          + Using the Library
1976726Speter               o Starting up
2076726Speter               o Output
2176726Speter               o Input
2276726Speter               o Using Forms Characters
2376726Speter               o Character Attributes and Color
2476726Speter               o Mouse Interfacing
2576726Speter               o Finishing Up
2676726Speter          + Function Descriptions
2776726Speter               o Initialization and Wrapup
2876726Speter               o Causing Output to the Terminal
2976726Speter               o Low-Level Capability Access
3076726Speter               o Debugging
3176726Speter          + Hints, Tips, and Tricks
3276726Speter               o Some Notes of Caution
3376726Speter               o Temporarily Leaving ncurses Mode
3476726Speter               o Using ncurses under xterm
3576726Speter               o Handling Multiple Terminal Screens
3676726Speter               o Testing for Terminal Capabilities
3776726Speter               o Tuning for Speed
3876726Speter               o Special Features of ncurses
3976726Speter          + Compatibility with Older Versions
4076726Speter               o Refresh of Overlapping Windows
4176726Speter               o Background Erase
4276726Speter          + XSI Curses Conformance
4376726Speter     * The Panels Library
4476726Speter          + Compiling With the Panels Library
4576726Speter          + Overview of Panels
4676726Speter          + Panels, Input, and the Standard Screen
4776726Speter          + Hiding Panels
4876726Speter          + Miscellaneous Other Facilities
4976726Speter     * The Menu Library
5076726Speter          + Compiling with the menu Library
5176726Speter          + Overview of Menus
5276726Speter          + Selecting items
5376726Speter          + Menu Display
5476726Speter          + Menu Windows
5576726Speter          + Processing Menu Input
5676726Speter          + Miscellaneous Other Features
5776726Speter     * The Forms Library
5876726Speter          + Compiling with the forms Library
5976726Speter          + Overview of Forms
6076726Speter          + Creating and Freeing Fields and Forms
6176726Speter          + Fetching and Changing Field Attributes
6276726Speter               o Fetching Size and Location Data
6376726Speter               o Changing the Field Location
6476726Speter               o The Justification Attribute
6576726Speter               o Field Display Attributes
6676726Speter               o Field Option Bits
6776726Speter               o Field Status
6876726Speter               o Field User Pointer
6976726Speter          + Variable-Sized Fields
7076726Speter          + Field Validation
7176726Speter               o TYPE_ALPHA
7276726Speter               o TYPE_ALNUM
7376726Speter               o TYPE_ENUM
7476726Speter               o TYPE_INTEGER
7576726Speter               o TYPE_NUMERIC
7676726Speter               o TYPE_REGEXP
7776726Speter          + Direct Field Buffer Manipulation
7876726Speter          + Attributes of Forms
7976726Speter          + Control of Form Display
8076726Speter          + Input Processing in the Forms Driver
8176726Speter               o Page Navigation Requests
8276726Speter               o Inter-Field Navigation Requests
8376726Speter               o Intra-Field Navigation Requests
8476726Speter               o Scrolling Requests
8576726Speter               o Field Editing Requests
8676726Speter               o Order Requests
8776726Speter               o Application Commands
8876726Speter          + Field Change Hooks
8976726Speter          + Field Change Commands
9076726Speter          + Form Options
9176726Speter          + Custom Validation Types
9276726Speter               o Union Types
9376726Speter               o New Field Types
9476726Speter               o Validation Function Arguments
9576726Speter               o Order Functions For Custom Types
9676726Speter               o Avoiding Problems
9776726Speter     _________________________________________________________________
98166124Srafan
9976726Speter                                 Introduction
100166124Srafan
10176726Speter   This document is an introduction to programming with curses. It is not
102166124Srafan   an   exhaustive  reference  for  the  curses  Application  Programming
103166124Srafan   Interface  (API);  that  role  is  filled  by the curses manual pages.
104166124Srafan   Rather,  it  is  intended  to  help  C programmers ease into using the
10576726Speter   package.
106166124Srafan
107166124Srafan   This   document  is  aimed  at  C  applications  programmers  not  yet
108166124Srafan   specifically  familiar with ncurses. If you are already an experienced
109166124Srafan   curses  programmer, you should nevertheless read the sections on Mouse
110166124Srafan   Interfacing,  Debugging, Compatibility with Older Versions, and Hints,
111166124Srafan   Tips,  and  Tricks.  These  will  bring you up to speed on the special
112166124Srafan   features  and  quirks of the ncurses implementation. If you are not so
11376726Speter   experienced, keep reading.
114166124Srafan
115166124Srafan   The  curses  package  is a subroutine library for terminal-independent
116166124Srafan   screen-painting  and  input-event handling which presents a high level
117166124Srafan   screen  model  to  the programmer, hiding differences between terminal
118166124Srafan   types  and doing automatic optimization of output to change one screen
119166124Srafan   full  of  text into another. Curses uses terminfo, which is a database
120166124Srafan   format  that  can  describe the capabilities of thousands of different
12176726Speter   terminals.
122166124Srafan
123166124Srafan   The  curses  API  may  seem  something of an archaism on UNIX desktops
124166124Srafan   increasingly  dominated  by  X,  Motif, and Tcl/Tk. Nevertheless, UNIX
125166124Srafan   still  supports  tty lines and X supports xterm(1); the curses API has
12676726Speter   the advantage of (a) back-portability to character-cell terminals, and
127166124Srafan   (b)  simplicity.  For  an application that does not require bit-mapped
128166124Srafan   graphics  and multiple fonts, an interface implementation using curses
129166124Srafan   will  typically  be  a  great deal simpler and less expensive than one
13076726Speter   using an X toolkit.
131166124Srafan
13276726SpeterA Brief History of Curses
13376726Speter
13476726Speter   Historically, the first ancestor of curses was the routines written to
135166124Srafan   provide   screen-handling   for   the   game  rogue;  these  used  the
136166124Srafan   already-existing  termcap  database  facility  for describing terminal
13776726Speter   capabilities. These routines were abstracted into a documented library
13876726Speter   and first released with the early BSD UNIX versions.
139166124Srafan
140166124Srafan   System  III UNIX from Bell Labs featured a rewritten and much-improved
141166124Srafan   curses  library.  It introduced the terminfo format. Terminfo is based
142166124Srafan   on  Berkeley's termcap database, but contains a number of improvements
143166124Srafan   and  extensions.  Parameterized  capabilities strings were introduced,
144166124Srafan   making  it  possible to describe multiple video attributes, and colors
145166124Srafan   and  to  handle far more unusual terminals than possible with termcap.
146166124Srafan   In  the  later  AT&T  System  V  releases,  curses evolved to use more
14776726Speter   facilities and offer more capabilities, going far beyond BSD curses in
14876726Speter   power and flexibility.
149166124Srafan
15076726SpeterScope of This Document
15176726Speter
15276726Speter   This document describes ncurses, a free implementation of the System V
153166124Srafan   curses  API  with  some  clearly  marked  extensions.  It includes the
15476726Speter   following System V curses features:
155166124Srafan     * Support  for  multiple  screen  highlights  (BSD curses could only
15676726Speter       handle one `standout' highlight, usually reverse-video).
15776726Speter     * Support for line- and box-drawing using forms characters.
15876726Speter     * Recognition of function keys on input.
15976726Speter     * Color support.
160166124Srafan     * Support  for pads (windows of larger than screen size on which the
16176726Speter       screen or a subwindow defines a viewport).
162166124Srafan
163166124Srafan   Also,  this  package  makes  use  of  the  insert  and delete line and
164166124Srafan   character  features  of  terminals  so equipped, and determines how to
165166124Srafan   optimally  use  these  features  with  no help from the programmer. It
166166124Srafan   allows  arbitrary  combinations  of  video attributes to be displayed,
167166124Srafan   even  on  terminals that leave ``magic cookies'' on the screen to mark
16876726Speter   changes in attributes.
169166124Srafan
170166124Srafan   The  ncurses  package  can  also  capture and use event reports from a
17176726Speter   mouse in some environments (notably, xterm under the X window system).
17276726Speter   This document includes tips for using the mouse.
173166124Srafan
174166124Srafan   The  ncurses  package  was  originated  by  Pavel Curtis. The original
175166124Srafan   maintainer  of  this  package is Zeyd Ben-Halim <zmbenhal@netcom.com>.
17676726Speter   Eric S. Raymond <esr@snark.thyrsus.com> wrote many of the new features
177166124Srafan   in  versions  after  1.8.1 and wrote most of this introduction. J�rgen
178166124Srafan   Pfeifer  wrote  all  of  the  menu and forms code as well as the Ada95
179166124Srafan   binding.  Ongoing  work  is  being done by Thomas Dickey (maintainer).
180166124Srafan   Contact the current maintainers at bug-ncurses@gnu.org.
181166124Srafan
182166124Srafan   This  document  also describes the panels extension library, similarly
183166124Srafan   modeled  on  the  SVr4  panels  facility.  This  library allows you to
184166124Srafan   associate  backing  store  with each of a stack or deck of overlapping
185166124Srafan   windows,  and  provides  operations  for  moving windows around in the
18676726Speter   stack that change their visibility in the natural way (handling window
18776726Speter   overlaps).
188166124Srafan
189166124Srafan   Finally,  this  document  describes  in  detail  the  menus  and forms
190166124Srafan   extension  libraries,  also  cloned  from System V, which support easy
19176726Speter   construction and sequences of menus and fill-in forms.
192166124Srafan
19376726SpeterTerminology
19476726Speter
195166124Srafan   In  this  document,  the following terminology is used with reasonable
19676726Speter   consistency:
197166124Srafan
19876726Speter   window
199166124Srafan          A  data  structure  describing  a  sub-rectangle  of the screen
200166124Srafan          (possibly  the  entire  screen).  You  can write to a window as
201166124Srafan          though  it  were a miniature screen, scrolling independently of
20276726Speter          other windows on the physical screen.
203166124Srafan
20476726Speter   screens
205166124Srafan          A  subset of windows which are as large as the terminal screen,
206166124Srafan          i.e.,  they  start  at the upper left hand corner and encompass
207166124Srafan          the   lower  right  hand  corner.  One  of  these,  stdscr,  is
20876726Speter          automatically provided for the programmer.
209166124Srafan
21076726Speter   terminal screen
21176726Speter          The package's idea of what the terminal display currently looks
21276726Speter          like, i.e., what the user sees now. This is a special screen.
213166124Srafan
21476726Speter                              The Curses Library
215166124Srafan
21676726SpeterAn Overview of Curses
21776726Speter
21876726Speter  Compiling Programs using Curses
219166124Srafan
22076726Speter   In order to use the library, it is necessary to have certain types and
22176726Speter   variables defined. Therefore, the programmer must have a line:
22276726Speter          #include <curses.h>
22376726Speter
22476726Speter   at the top of the program source. The screen package uses the Standard
225166124Srafan   I/O   library,  so  <curses.h>  includes  <stdio.h>.  <curses.h>  also
226166124Srafan   includes  <termios.h>,  <termio.h>,  or  <sgtty.h>  depending  on your
227166124Srafan   system.  It is redundant (but harmless) for the programmer to do these
228166124Srafan   includes,  too.  In  linking with curses you need to have -lncurses in
229166124Srafan   your  LDFLAGS  or  on the command line. There is no need for any other
23076726Speter   libraries.
231166124Srafan
23276726Speter  Updating the Screen
233166124Srafan
234166124Srafan   In  order  to  update  the  screen  optimally, it is necessary for the
235166124Srafan   routines  to  know  what  the screen currently looks like and what the
236166124Srafan   programmer  wants  it to look like next. For this purpose, a data type
237166124Srafan   (structure)  named WINDOW is defined which describes a window image to
238166124Srafan   the  routines,  including its starting position on the screen (the (y,
239166124Srafan   x)  coordinates  of  the  upper left hand corner) and its size. One of
240166124Srafan   these  (called  curscr,  for current screen) is a screen image of what
241166124Srafan   the  terminal currently looks like. Another screen (called stdscr, for
24276726Speter   standard screen) is provided by default to make changes on.
243166124Srafan
244166124Srafan   A  window is a purely internal representation. It is used to build and
245166124Srafan   store  a potential image of a portion of the terminal. It doesn't bear
246166124Srafan   any  necessary relation to what is really on the terminal screen; it's
24776726Speter   more like a scratchpad or write buffer.
248166124Srafan
249166124Srafan   To  make  the  section  of  physical  screen corresponding to a window
250166124Srafan   reflect  the  contents  of the window structure, the routine refresh()
25176726Speter   (or wrefresh() if the window is not stdscr) is called.
252166124Srafan
253166124Srafan   A  given physical screen section may be within the scope of any number
254166124Srafan   of  overlapping  windows.  Also, changes can be made to windows in any
255166124Srafan   order,  without  regard  to  motion  efficiency.  Then,  at  will, the
25676726Speter   programmer can effectively say ``make it look like this,'' and let the
25776726Speter   package implementation determine the most efficient way to repaint the
25876726Speter   screen.
259166124Srafan
26076726Speter  Standard Windows and Function Naming Conventions
261166124Srafan
262166124Srafan   As  hinted  above,  the  routines can use several windows, but two are
26376726Speter   automatically given: curscr, which knows what the terminal looks like,
264166124Srafan   and  stdscr,  which  is what the programmer wants the terminal to look
265166124Srafan   like  next.  The  user  should  never actually access curscr directly.
266166124Srafan   Changes  should  be  made  to  through  the  API, and then the routine
26776726Speter   refresh() (or wrefresh()) called.
268166124Srafan
269166124Srafan   Many  functions  are  defined  to  use stdscr as a default screen. For
270166124Srafan   example,  to  add  a  character  to stdscr, one calls addch() with the
27176726Speter   desired character as argument. To write to a different window. use the
272166124Srafan   routine  waddch()  (for  `w'indow-specific  addch()) is provided. This
27376726Speter   convention of prepending function names with a `w' when they are to be
274166124Srafan   applied  to specific windows is consistent. The only routines which do
27576726Speter   not follow it are those for which a window must always be specified.
276166124Srafan
277166124Srafan   In  order  to  move  the  current (y, x) coordinates from one point to
278166124Srafan   another,  the routines move() and wmove() are provided. However, it is
279166124Srafan   often  desirable to first move and then perform some I/O operation. In
280166124Srafan   order  to  avoid  clumsiness, most I/O routines can be preceded by the
281166124Srafan   prefix  'mv'  and  the  desired  (y,  x)  coordinates prepended to the
28276726Speter   arguments to the function. For example, the calls
28376726Speter          move(y, x);
28476726Speter          addch(ch);
28576726Speter
28676726Speter   can be replaced by
28776726Speter          mvaddch(y, x, ch);
28876726Speter
28976726Speter   and
29076726Speter          wmove(win, y, x);
29176726Speter          waddch(win, ch);
29276726Speter
29376726Speter   can be replaced by
29476726Speter          mvwaddch(win, y, x, ch);
29576726Speter
296166124Srafan   Note  that the window description pointer (win) comes before the added
297166124Srafan   (y,  x)  coordinates.  If  a function requires a window pointer, it is
29876726Speter   always the first parameter passed.
299166124Srafan
30076726Speter  Variables
301166124Srafan
302166124Srafan   The  curses  library  sets  some  variables  describing  the  terminal
30376726Speter   capabilities.
30476726Speter      type   name      description
30576726Speter      ------------------------------------------------------------------
30676726Speter      int    LINES     number of lines on the terminal
30776726Speter      int    COLS      number of columns on the terminal
30876726Speter
309166124Srafan   The  curses.h  also  introduces  some  #define  constants and types of
31076726Speter   general usefulness:
311166124Srafan
31276726Speter   bool
31376726Speter          boolean type, actually a `char' (e.g., bool doneit;)
314166124Srafan
31576726Speter   TRUE
31676726Speter          boolean `true' flag (1).
317166124Srafan
31876726Speter   FALSE
31976726Speter          boolean `false' flag (0).
320166124Srafan
32176726Speter   ERR
32276726Speter          error flag returned by routines on a failure (-1).
323166124Srafan
32476726Speter   OK
32576726Speter          error flag returned by routines when things go right.
326166124Srafan
32776726SpeterUsing the Library
32876726Speter
329166124Srafan   Now  we  describe  how  to  actually use the screen package. In it, we
330166124Srafan   assume  all  updating,  reading,  etc.  is  applied  to  stdscr. These
331166124Srafan   instructions  will  work  on  any  window,  providing  you  change the
33276726Speter   function names and parameters as mentioned above.
333166124Srafan
33476726Speter   Here is a sample program to motivate the discussion:
33576726Speter#include <curses.h>
33676726Speter#include <signal.h>
33776726Speter
33876726Speterstatic void finish(int sig);
33976726Speter
34076726Speterint
34176726Spetermain(int argc, char *argv[])
34276726Speter{
34376726Speter    int num = 0;
34476726Speter
34576726Speter    /* initialize your non-curses data structures here */
34676726Speter
34776726Speter    (void) signal(SIGINT, finish);      /* arrange interrupts to terminate */
34876726Speter
34976726Speter    (void) initscr();      /* initialize the curses library */
35076726Speter    keypad(stdscr, TRUE);  /* enable keyboard mapping */
35176726Speter    (void) nonl();         /* tell curses not to do NL->CR/NL on output */
35276726Speter    (void) cbreak();       /* take input chars one at a time, no wait for \n */
35376726Speter    (void) echo();         /* echo input - in color */
35476726Speter
35576726Speter    if (has_colors())
35676726Speter    {
35776726Speter        start_color();
35876726Speter
35976726Speter        /*
36076726Speter         * Simple color assignment, often all we need.  Color pair 0 cannot
36176726Speter         * be redefined.  This example uses the same value for the color
36276726Speter         * pair as for the foreground color, though of course that is not
36376726Speter         * necessary:
36476726Speter         */
36576726Speter        init_pair(1, COLOR_RED,     COLOR_BLACK);
36676726Speter        init_pair(2, COLOR_GREEN,   COLOR_BLACK);
36776726Speter        init_pair(3, COLOR_YELLOW,  COLOR_BLACK);
36876726Speter        init_pair(4, COLOR_BLUE,    COLOR_BLACK);
36976726Speter        init_pair(5, COLOR_CYAN,    COLOR_BLACK);
37076726Speter        init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
37176726Speter        init_pair(7, COLOR_WHITE,   COLOR_BLACK);
37276726Speter    }
37376726Speter
37476726Speter    for (;;)
37576726Speter    {
37676726Speter        int c = getch();     /* refresh, accept single keystroke of input */
37776726Speter        attrset(COLOR_PAIR(num % 8));
37876726Speter        num++;
37976726Speter
38076726Speter        /* process the command keystroke */
38176726Speter    }
38276726Speter
38376726Speter    finish(0);               /* we're done */
38476726Speter}
38576726Speter
38676726Speterstatic void finish(int sig)
38776726Speter{
38876726Speter    endwin();
38976726Speter
39076726Speter    /* do your non-curses wrapup here */
39176726Speter
39276726Speter    exit(0);
39376726Speter}
39476726Speter
39576726Speter  Starting up
396166124Srafan
397166124Srafan   In  order  to  use  the  screen  package, the routines must know about
398166124Srafan   terminal  characteristics, and the space for curscr and stdscr must be
399166124Srafan   allocated.  These  function initscr() does both these things. Since it
400166124Srafan   must  allocate  space  for  the  windows,  it can overflow memory when
401166124Srafan   attempting  to  do  so.  On the rare occasions this happens, initscr()
402166124Srafan   will  terminate  the  program  with  an  error message. initscr() must
403166124Srafan   always  be  called before any of the routines which affect windows are
404166124Srafan   used.  If  it  is  not,  the  program will core dump as soon as either
405166124Srafan   curscr  or  stdscr are referenced. However, it is usually best to wait
406166124Srafan   to  call  it  until  after  you  are sure you will need it, like after
407166124Srafan   checking  for  startup  errors. Terminal status changing routines like
40876726Speter   nl() and cbreak() should be called after initscr().
409166124Srafan
410166124Srafan   Once  the  screen windows have been allocated, you can set them up for
411166124Srafan   your  program.  If  you  want  to,  say, allow a screen to scroll, use
412166124Srafan   scrollok().  If you want the cursor to be left in place after the last
413166124Srafan   change,  use  leaveok().  If  this isn't done, refresh() will move the
41476726Speter   cursor to the window's current (y, x) coordinates after updating it.
415166124Srafan
416166124Srafan   You  can  create new windows of your own using the functions newwin(),
41776726Speter   derwin(), and subwin(). The routine delwin() will allow you to get rid
418166124Srafan   of  old windows. All the options described above can be applied to any
41976726Speter   window.
420166124Srafan
42176726Speter  Output
422166124Srafan
423166124Srafan   Now  that  we  have set things up, we will want to actually update the
424166124Srafan   terminal.  The basic functions used to change what will go on a window
42576726Speter   are addch() and move(). addch() adds a character at the current (y, x)
42676726Speter   coordinates. move() changes the current (y, x) coordinates to whatever
42776726Speter   you want them to be. It returns ERR if you try to move off the window.
428166124Srafan   As  mentioned above, you can combine the two into mvaddch() to do both
42976726Speter   things at once.
430166124Srafan
431166124Srafan   The  other  output  functions, such as addstr() and printw(), all call
43276726Speter   addch() to add characters to the window.
433166124Srafan
434166124Srafan   After  you  have  put on the window what you want there, when you want
435166124Srafan   the  portion  of the terminal covered by the window to be made to look
436166124Srafan   like  it,  you  must  call  refresh().  In  order  to optimize finding
437166124Srafan   changes,  refresh()  assumes  that  any part of the window not changed
438166124Srafan   since  the  last  refresh() of that window has not been changed on the
439166124Srafan   terminal,  i.e., that you have not refreshed a portion of the terminal
440166124Srafan   with  an  overlapping  window.  If  this  is not the case, the routine
44176726Speter   touchwin() is provided to make it look like the entire window has been
442166124Srafan   changed,  thus  making  refresh()  check  the  whole subsection of the
44376726Speter   terminal for changes.
444166124Srafan
445166124Srafan   If  you  call wrefresh() with curscr as its argument, it will make the
446166124Srafan   screen  look  like  curscr  thinks  it  looks like. This is useful for
447166124Srafan   implementing  a  command  which would redraw the screen in case it get
44876726Speter   messed up.
449166124Srafan
45076726Speter  Input
451166124Srafan
452166124Srafan   The  complementary  function  to  addch() is getch() which, if echo is
45376726Speter   set, will call addch() to echo the character. Since the screen package
454166124Srafan   needs  to know what is on the terminal at all times, if characters are
455166124Srafan   to  be  echoed, the tty must be in raw or cbreak mode. Since initially
456166124Srafan   the  terminal  has echoing enabled and is in ordinary ``cooked'' mode,
45776726Speter   one or the other has to changed before calling getch(); otherwise, the
45876726Speter   program's output will be unpredictable.
459166124Srafan
46076726Speter   When you need to accept line-oriented input in a window, the functions
46176726Speter   wgetstr() and friends are available. There is even a wscanw() function
462166124Srafan   that  can  do  scanf()(3)-style  multi-field  parsing on window input.
463166124Srafan   These  pseudo-line-oriented  functions  turn  on  echoing  while  they
46476726Speter   execute.
465166124Srafan
466166124Srafan   The  example  code  above uses the call keypad(stdscr, TRUE) to enable
467166124Srafan   support  for function-key mapping. With this feature, the getch() code
468166124Srafan   watches  the  input  stream for character sequences that correspond to
469166124Srafan   arrow   and   function   keys.   These   sequences   are  returned  as
47076726Speter   pseudo-character values. The #define values returned are listed in the
47176726Speter   curses.h The mapping from sequences to #define values is determined by
47276726Speter   key_ capabilities in the terminal's terminfo entry.
473166124Srafan
47476726Speter  Using Forms Characters
475166124Srafan
476166124Srafan   The  addch()  function (and some others, including box() and border())
47776726Speter   can accept some pseudo-character arguments which are specially defined
478166124Srafan   by  ncurses.  These  are #define values set up in the curses.h header;
47976726Speter   see there for a complete list (look for the prefix ACS_).
480166124Srafan
481166124Srafan   The  most  useful of the ACS defines are the forms-drawing characters.
482166124Srafan   You  can  use  these to draw boxes and simple graphs on the screen. If
483166124Srafan   the  terminal does not have such characters, curses.h will map them to
48476726Speter   a recognizable (though ugly) set of ASCII defaults.
485166124Srafan
48676726Speter  Character Attributes and Color
487166124Srafan
488166124Srafan   The  ncurses  package  supports  screen highlights including standout,
489166124Srafan   reverse-video,  underline, and blink. It also supports color, which is
49076726Speter   treated as another kind of highlight.
491166124Srafan
492166124Srafan   Highlights   are   encoded,   internally,   as   high   bits   of  the
493166124Srafan   pseudo-character  type  (chtype)  that  curses.h uses to represent the
49476726Speter   contents of a screen cell. See the curses.h header file for a complete
49576726Speter   list of highlight mask values (look for the prefix A_).
496166124Srafan
497166124Srafan   There  are two ways to make highlights. One is to logical-or the value
498166124Srafan   of  the  highlights you want into the character argument of an addch()
49976726Speter   call, or any other output call that takes a chtype argument.
500166124Srafan
50176726Speter   The other is to set the current-highlight value. This is logical-or'ed
502166124Srafan   with  any  highlight  you  specify the first way. You do this with the
50376726Speter   functions attron(), attroff(), and attrset(); see the manual pages for
504166124Srafan   details.  Color  is  a special kind of highlight. The package actually
505166124Srafan   thinks  in  terms  of  color  pairs,  combinations  of  foreground and
506166124Srafan   background  colors.  The  sample code above sets up eight color pairs,
507166124Srafan   all  of the guaranteed-available colors on black. Note that each color
508166124Srafan   pair  is, in effect, given the name of its foreground color. Any other
509166124Srafan   range  of  eight  non-conflicting  values  could have been used as the
51076726Speter   first arguments of the init_pair() values.
511166124Srafan
51276726Speter   Once you've done an init_pair() that creates color-pair N, you can use
513166124Srafan   COLOR_PAIR(N)  as  a  highlight  that  invokes  that  particular color
514166124Srafan   combination.  Note  that  COLOR_PAIR(N),  for  constant N, is itself a
51576726Speter   compile-time constant and can be used in initializers.
516166124Srafan
51776726Speter  Mouse Interfacing
518166124Srafan
51976726Speter   The ncurses library also provides a mouse interface.
520166124Srafan
521166124Srafan     NOTE:  this  facility  is  specific  to  ncurses, it is not part of
522166124Srafan     either  the XSI Curses standard, nor of System V Release 4, nor BSD
523166124Srafan     curses.  System  V  Release  4  curses  contains  code with similar
524166124Srafan     interface  definitions, however it is not documented. Other than by
525166124Srafan     disassembling  the library, we have no way to determine exactly how
526166124Srafan     that   mouse   code   works.  Thus,  we  recommend  that  you  wrap
527166124Srafan     mouse-related   code   in   an   #ifdef  using  the  feature  macro
528166124Srafan     NCURSES_MOUSE_VERSION  so  it  will  not  be compiled and linked on
52976726Speter     non-ncurses systems.
530166124Srafan
53176726Speter   Presently, mouse event reporting works in the following environments:
53276726Speter     * xterm and similar programs such as rxvt.
533166124Srafan     * Linux  console,  when  configured with gpm(1), Alessandro Rubini's
53476726Speter       mouse server.
535166124Srafan     * FreeBSD sysmouse (console)
53676726Speter     * OS/2 EMX
537166124Srafan
538166124Srafan   The  mouse  interface  is  very  simple.  To  activate it, you use the
539166124Srafan   function  mousemask(),  passing  it  as first argument a bit-mask that
540166124Srafan   specifies  what  kinds  of  events you want your program to be able to
541166124Srafan   see.  It  will  return  the  bit-mask  of  events that actually become
54276726Speter   visible, which may differ from the argument if the mouse device is not
54376726Speter   capable of reporting some of the event types you specify.
544166124Srafan
54576726Speter   Once the mouse is active, your application's command loop should watch
546166124Srafan   for  a  return  value of KEY_MOUSE from wgetch(). When you see this, a
547166124Srafan   mouse  event report has been queued. To pick it off the queue, use the
548166124Srafan   function  getmouse()  (you  must  do  this  before  the next wgetch(),
549166124Srafan   otherwise  another  mouse  event  might come in and make the first one
55076726Speter   inaccessible).
551166124Srafan
55276726Speter   Each call to getmouse() fills a structure (the address of which you'll
553166124Srafan   pass  it)  with mouse event data. The event data includes zero-origin,
554166124Srafan   screen-relative  character-cell  coordinates  of the mouse pointer. It
555166124Srafan   also  includes  an  event  mask.  Bits  in  this  mask  will  be  set,
55676726Speter   corresponding to the event type being reported.
557166124Srafan
558166124Srafan   The  mouse  structure  contains  two  additional  fields  which may be
559166124Srafan   significant  in  the  future  as  ncurses  interfaces  to new kinds of
560166124Srafan   pointing  device.  In addition to x and y coordinates, there is a slot
561166124Srafan   for  a  z coordinate; this might be useful with touch-screens that can
562166124Srafan   return  a  pressure  or  duration parameter. There is also a device ID
563166124Srafan   field,  which  could  be used to distinguish between multiple pointing
56476726Speter   devices.
565166124Srafan
566166124Srafan   The   class  of  visible  events  may  be  changed  at  any  time  via
567166124Srafan   mousemask().  Events  that  can be reported include presses, releases,
568166124Srafan   single-,   double-   and   triple-clicks  (you  can  set  the  maximum
569166124Srafan   button-down  time  for clicks). If you don't make clicks visible, they
570166124Srafan   will  be  reported  as  press-release pairs. In some environments, the
571166124Srafan   event  mask  may  include  bits reporting the state of shift, alt, and
57276726Speter   ctrl keys on the keyboard during the event.
573166124Srafan
574166124Srafan   A  function  to check whether a mouse event fell within a given window
575166124Srafan   is  also  supplied.  You  can  use  this to see whether a given window
57676726Speter   should consider a mouse event relevant to it.
577166124Srafan
578166124Srafan   Because   mouse   event   reporting  will  not  be  available  in  all
579166124Srafan   environments,  it  would  be unwise to build ncurses applications that
580166124Srafan   require  the  use  of  a  mouse. Rather, you should use the mouse as a
581166124Srafan   shortcut  for point-and-shoot commands your application would normally
582166124Srafan   accept  from  the  keyboard.  Two  of  the  test  games in the ncurses
583166124Srafan   distribution  (bs  and  knight) contain code that illustrates how this
58476726Speter   can be done.
585166124Srafan
586166124Srafan   See   the   manual   page  curs_mouse(3X)  for  full  details  of  the
58776726Speter   mouse-interface functions.
588166124Srafan
58976726Speter  Finishing Up
590166124Srafan
591166124Srafan   In  order to clean up after the ncurses routines, the routine endwin()
592166124Srafan   is  provided.  It  restores tty modes to what they were when initscr()
593166124Srafan   was  first called, and moves the cursor down to the lower-left corner.
594166124Srafan   Thus,  anytime  after  the  call to initscr, endwin() should be called
59576726Speter   before exiting.
596166124Srafan
59776726SpeterFunction Descriptions
59876726Speter
599166124Srafan   We  describe  the detailed behavior of some important curses functions
60076726Speter   here, as a supplement to the manual page descriptions.
601166124Srafan
60276726Speter  Initialization and Wrapup
603166124Srafan
60476726Speter   initscr()
605166124Srafan          The  first  function  called should almost always be initscr().
606166124Srafan          This  will  determine  the  terminal type and initialize curses
60776726Speter          data structures. initscr() also arranges that the first call to
608166124Srafan          refresh()  will  clear the screen. If an error occurs a message
609166124Srafan          is  written  to standard error and the program exits. Otherwise
610166124Srafan          it  returns  a pointer to stdscr. A few functions may be called
611166124Srafan          before  initscr (slk_init(), filter(), ripoffline(), use_env(),
61276726Speter          and, if you are using multiple terminals, newterm().)
613166124Srafan
61476726Speter   endwin()
615166124Srafan          Your  program  should  always  call  endwin() before exiting or
616166124Srafan          shelling  out  of  the  program. This function will restore tty
617166124Srafan          modes,  move the cursor to the lower left corner of the screen,
618166124Srafan          reset  the  terminal  into  the proper non-visual mode. Calling
619166124Srafan          refresh()  or  doupdate()  after  a  temporary  escape from the
62076726Speter          program will restore the ncurses screen from before the escape.
621166124Srafan
62276726Speter   newterm(type, ofp, ifp)
623166124Srafan          A  program  which  outputs to more than one terminal should use
62476726Speter          newterm() instead of initscr(). newterm() should be called once
62576726Speter          for each terminal. It returns a variable of type SCREEN * which
626166124Srafan          should  be  saved  as  a  reference  to that terminal. (NOTE: a
627166124Srafan          SCREEN  variable is not a screen in the sense we are describing
628166124Srafan          in  this  introduction,  but a collection of parameters used to
629166124Srafan          assist  in  optimizing the display.) The arguments are the type
630166124Srafan          of the terminal (a string) and FILE pointers for the output and
631166124Srafan          input  of  the  terminal.  If type is NULL then the environment
632166124Srafan          variable  $TERM  is used. endwin() should called once at wrapup
633166124Srafan          time for each terminal opened using this function.
634166124Srafan
63576726Speter   set_term(new)
636166124Srafan          This  function  is  used  to  switch  to  a  different terminal
637166124Srafan          previously  opened  by  newterm(). The screen reference for the
638166124Srafan          new  terminal is passed as the parameter. The previous terminal
639166124Srafan          is  returned  by  the function. All other calls affect only the
64076726Speter          current terminal.
641166124Srafan
64276726Speter   delscreen(sp)
643166124Srafan          The  inverse  of  newterm();  deallocates  the  data structures
64476726Speter          associated with a given SCREEN reference.
645166124Srafan
64676726Speter  Causing Output to the Terminal
647166124Srafan
64876726Speter   refresh() and wrefresh(win)
649166124Srafan          These  functions  must  be called to actually get any output on
650166124Srafan          the   terminal,   as  other  routines  merely  manipulate  data
651166124Srafan          structures.  wrefresh() copies the named window to the physical
652166124Srafan          terminal  screen,  taking into account what is already there in
653166124Srafan          order  to do optimizations. refresh() does a refresh of stdscr.
654166124Srafan          Unless  leaveok()  has been enabled, the physical cursor of the
655166124Srafan          terminal is left at the location of the window's cursor.
656166124Srafan
65776726Speter   doupdate() and wnoutrefresh(win)
65876726Speter          These two functions allow multiple updates with more efficiency
659166124Srafan          than  wrefresh.  To use them, it is important to understand how
660166124Srafan          curses  works. In addition to all the window structures, curses
661166124Srafan          keeps  two  data structures representing the terminal screen: a
66276726Speter          physical screen, describing what is actually on the screen, and
663166124Srafan          a  virtual screen, describing what the programmer wants to have
66476726Speter          on the screen. wrefresh works by first copying the named window
665166124Srafan          to  the  virtual  screen (wnoutrefresh()), and then calling the
666166124Srafan          routine  to  update  the screen (doupdate()). If the programmer
667166124Srafan          wishes  to output several windows at once, a series of calls to
66876726Speter          wrefresh will result in alternating calls to wnoutrefresh() and
669166124Srafan          doupdate(),  causing several bursts of output to the screen. By
670166124Srafan          calling  wnoutrefresh() for each window, it is then possible to
671166124Srafan          call  doupdate()  once,  resulting in only one burst of output,
672166124Srafan          with  fewer  total  characters  transmitted (this also avoids a
67376726Speter          visually annoying flicker at each update).
674166124Srafan
67576726Speter  Low-Level Capability Access
676166124Srafan
67776726Speter   setupterm(term, filenum, errret)
678166124Srafan          This  routine is called to initialize a terminal's description,
67976726Speter          without setting up the curses screen structures or changing the
68076726Speter          tty-driver mode bits. term is the character string representing
681166124Srafan          the  name  of the terminal being used. filenum is the UNIX file
682166124Srafan          descriptor  of  the terminal to be used for output. errret is a
68376726Speter          pointer to an integer, in which a success or failure indication
684166124Srafan          is  returned. The values returned can be 1 (all is well), 0 (no
685166124Srafan          such  terminal),  or  -1  (some  problem  locating the terminfo
68676726Speter          database).
687166124Srafan
688166124Srafan          The  value  of  term can be given as NULL, which will cause the
68976726Speter          value of TERM in the environment to be used. The errret pointer
690166124Srafan          can  also be given as NULL, meaning no error code is wanted. If
69176726Speter          errret is defaulted, and something goes wrong, setupterm() will
692166124Srafan          print  an  appropriate  error  message  and  exit,  rather than
693166124Srafan          returning.  Thus,  a simple program can call setupterm(0, 1, 0)
69476726Speter          and not worry about initialization errors.
695166124Srafan
696166124Srafan          After  the call to setupterm(), the global variable cur_term is
69776726Speter          set to point to the current structure of terminal capabilities.
698166124Srafan          By  calling  setupterm()  for  each  terminal,  and  saving and
699166124Srafan          restoring  cur_term, it is possible for a program to use two or
700166124Srafan          more  terminals  at  once.  Setupterm()  also  stores the names
701166124Srafan          section  of  the  terminal  description in the global character
70276726Speter          array ttytype[]. Subsequent calls to setupterm() will overwrite
70376726Speter          this array, so you'll have to save it yourself if need be.
704166124Srafan
70576726Speter  Debugging
706166124Srafan
70776726Speter     NOTE: These functions are not part of the standard curses API!
708166124Srafan
70976726Speter   trace()
710166124Srafan          This  function  can be used to explicitly set a trace level. If
711166124Srafan          the  trace  level  is  nonzero,  execution of your program will
71276726Speter          generate a file called `trace' in the current working directory
713166124Srafan          containing  a  report  on  the  library's actions. Higher trace
714166124Srafan          levels  enable  more  detailed  (and  verbose) reporting -- see
715166124Srafan          comments  attached  to  TRACE_ defines in the curses.h file for
71676726Speter          details. (It is also possible to set a trace level by assigning
71776726Speter          a trace level value to the environment variable NCURSES_TRACE).
718166124Srafan
71976726Speter   _tracef()
720166124Srafan          This  function  can  be  used  to  output  your  own  debugging
721166124Srafan          information.  It  is  only  available  only  if  you  link with
722166124Srafan          -lncurses_g.  It  can be used the same way as printf(), only it
723166124Srafan          outputs  a  newline after the end of arguments. The output goes
72476726Speter          to a file called trace in the current directory.
725166124Srafan
726166124Srafan   Trace  logs  can  be difficult to interpret due to the sheer volume of
72776726Speter   data dumped in them. There is a script called tracemunch included with
728166124Srafan   the  ncurses distribution that can alleviate this problem somewhat; it
729166124Srafan   compacts  long  sequences  of  similar  operations  into more succinct
730166124Srafan   single-line  pseudo-operations.  These pseudo-ops can be distinguished
73176726Speter   by the fact that they are named in capital letters.
732166124Srafan
73376726SpeterHints, Tips, and Tricks
73476726Speter
73576726Speter   The ncurses manual pages are a complete reference for this library. In
73676726Speter   the remainder of this document, we discuss various useful methods that
73776726Speter   may not be obvious from the manual page descriptions.
738166124Srafan
73976726Speter  Some Notes of Caution
740166124Srafan
741166124Srafan   If  you  find yourself thinking you need to use noraw() or nocbreak(),
742166124Srafan   think  again  and  move  carefully. It's probably better design to use
743166124Srafan   getstr()  or one of its relatives to simulate cooked mode. The noraw()
744166124Srafan   and  nocbreak() functions try to restore cooked mode, but they may end
745166124Srafan   up   clobbering   some  control  bits  set  before  you  started  your
746166124Srafan   application.  Also,  they  have always been poorly documented, and are
747166124Srafan   likely   to  hurt  your  application's  usability  with  other  curses
74876726Speter   libraries.
749166124Srafan
750166124Srafan   Bear  in  mind that refresh() is a synonym for wrefresh(stdscr). Don't
751166124Srafan   try  to  mix use of stdscr with use of windows declared by newwin(); a
752166124Srafan   refresh()  call will blow them off the screen. The right way to handle
753166124Srafan   this  is  to  use  subwin(),  or not touch stdscr at all and tile your
754166124Srafan   screen  with  declared windows which you then wnoutrefresh() somewhere
755166124Srafan   in  your  program event loop, with a single doupdate() call to trigger
75676726Speter   actual repainting.
757166124Srafan
758166124Srafan   You  are  much  less  likely  to  run into problems if you design your
759166124Srafan   screen   layouts   to  use  tiled  rather  than  overlapping  windows.
760166124Srafan   Historically,  curses  support  for overlapping windows has been weak,
761166124Srafan   fragile,  and  poorly  documented.  The  ncurses library is not yet an
76276726Speter   exception to this rule.
763166124Srafan
764166124Srafan   There  is  a  panels library included in the ncurses distribution that
765166124Srafan   does  a  pretty  good  job  of  strengthening  the overlapping-windows
76676726Speter   facilities.
767166124Srafan
76876726Speter   Try to avoid using the global variables LINES and COLS. Use getmaxyx()
769166124Srafan   on  the stdscr context instead. Reason: your code may be ported to run
770166124Srafan   in  an  environment with window resizes, in which case several screens
77176726Speter   could be open with different sizes.
772166124Srafan
77376726Speter  Temporarily Leaving NCURSES Mode
774166124Srafan
775166124Srafan   Sometimes  you  will  want  to write a program that spends most of its
776166124Srafan   time  in  screen  mode,  but occasionally returns to ordinary `cooked'
777166124Srafan   mode.  A common reason for this is to support shell-out. This behavior
77876726Speter   is simple to arrange in ncurses.
779166124Srafan
780166124Srafan   To  leave  ncurses  mode,  call  endwin()  as  you  would  if you were
781166124Srafan   intending  to terminate the program. This will take the screen back to
782166124Srafan   cooked  mode;  you  can  do your shell-out. When you want to return to
783166124Srafan   ncurses  mode,  simply call refresh() or doupdate(). This will repaint
78476726Speter   the screen.
785166124Srafan
786166124Srafan   There  is  a  boolean function, isendwin(), which code can use to test
78776726Speter   whether ncurses screen mode is active. It returns TRUE in the interval
78876726Speter   between an endwin() call and the following refresh(), FALSE otherwise.
789166124Srafan
79076726Speter   Here is some sample code for shellout:
79176726Speter    addstr("Shelling out...");
79276726Speter    def_prog_mode();           /* save current tty modes */
79376726Speter    endwin();                  /* restore original tty modes */
79476726Speter    system("sh");              /* run shell */
79576726Speter    addstr("returned.\n");     /* prepare return message */
79676726Speter    refresh();                 /* restore save modes, repaint screen */
79776726Speter
79876726Speter  Using NCURSES under XTERM
799166124Srafan
800166124Srafan   A  resize  operation  in  X  sends SIGWINCH to the application running
801166124Srafan   under  xterm.  The  ncurses  library  provides  an experimental signal
802166124Srafan   handler,  but in general does not catch this signal, because it cannot
803166124Srafan   know  how  you  want  the  screen re-painted. You will usually have to
80476726Speter   write the SIGWINCH handler yourself. Ncurses can give you some help.
805166124Srafan
806166124Srafan   The  easiest  way  to  code  your SIGWINCH handler is to have it do an
80776726Speter   endwin, followed by an refresh and a screen repaint you code yourself.
808166124Srafan   The  refresh  will  pick  up  the  new  screen  size  from the xterm's
80976726Speter   environment.
810166124Srafan
811166124Srafan   That  is the standard way, of course (it even works with some vendor's
812166124Srafan   curses  implementations). Its drawback is that it clears the screen to
81376726Speter   reinitialize the display, and does not resize subwindows which must be
814166124Srafan   shrunk.   Ncurses  provides  an  extension  which  works  better,  the
815166124Srafan   resizeterm  function.  That  function  ensures  that  all  windows are
816166124Srafan   limited  to  the new screen dimensions, and pads stdscr with blanks if
81776726Speter   the screen is larger.
818166124Srafan
819166124Srafan   Finally,  ncurses  can  be  configured  to  provide  its  own SIGWINCH
82076726Speter   handler, based on resizeterm.
821166124Srafan
82276726Speter  Handling Multiple Terminal Screens
823166124Srafan
82476726Speter   The initscr() function actually calls a function named newterm() to do
825166124Srafan   most  of  its  work.  If you are writing a program that opens multiple
82676726Speter   terminals, use newterm() directly.
827166124Srafan
828166124Srafan   For  each call, you will have to specify a terminal type and a pair of
829166124Srafan   file  pointers;  each  call will return a screen reference, and stdscr
83076726Speter   will be set to the last one allocated. You will switch between screens
831166124Srafan   with  the  set_term  call.  Note  that  you  will  also  have  to call
83276726Speter   def_shell_mode and def_prog_mode on each tty yourself.
833166124Srafan
83476726Speter  Testing for Terminal Capabilities
835166124Srafan
83676726Speter   Sometimes you may want to write programs that test for the presence of
837166124Srafan   various  capabilities before deciding whether to go into ncurses mode.
838166124Srafan   An  easy way to do this is to call setupterm(), then use the functions
83976726Speter   tigetflag(), tigetnum(), and tigetstr() to do your testing.
840166124Srafan
841166124Srafan   A  particularly  useful  case  of this often comes up when you want to
842166124Srafan   test  whether  a  given  terminal  type  should  be treated as `smart'
84376726Speter   (cursor-addressable) or `stupid'. The right way to test this is to see
84476726Speter   if the return value of tigetstr("cup") is non-NULL. Alternatively, you
845166124Srafan   can  include  the  term.h  file  and  test  the  value  of  the  macro
84676726Speter   cursor_address.
847166124Srafan
84876726Speter  Tuning for Speed
849166124Srafan
850166124Srafan   Use  the  addchstr()  family  of functions for fast screen-painting of
851166124Srafan   text  when  you  know the text doesn't contain any control characters.
852166124Srafan   Try  to  make  attribute changes infrequent on your screens. Don't use
85376726Speter   the immedok() option!
854166124Srafan
85576726Speter  Special Features of NCURSES
856166124Srafan
857166124Srafan   The  wresize()  function  allows  you to resize a window in place. The
858166124Srafan   associated   resizeterm()  function  simplifies  the  construction  of
85976726Speter   SIGWINCH handlers, for resizing all windows.
860166124Srafan
86176726Speter   The define_key() function allows you to define at runtime function-key
862166124Srafan   control  sequences  which  are  not  in  the terminal description. The
863166124Srafan   keyok()   function   allows  you  to  temporarily  enable  or  disable
86476726Speter   interpretation of any function-key control sequence.
865166124Srafan
86676726Speter   The use_default_colors() function allows you to construct applications
867166124Srafan   which  can use the terminal's default foreground and background colors
868166124Srafan   as  an  additional "default" color. Several terminal emulators support
86976726Speter   this feature, which is based on ISO 6429.
870166124Srafan
871166124Srafan   Ncurses  supports  up 16 colors, unlike SVr4 curses which defines only
87276726Speter   8. While most terminals which provide color allow only 8 colors, about
87376726Speter   a quarter (including XFree86 xterm) support 16 colors.
874166124Srafan
87576726SpeterCompatibility with Older Versions
87676726Speter
877166124Srafan   Despite  our  best efforts, there are some differences between ncurses
878166124Srafan   and  the  (undocumented!)  behavior  of  older curses implementations.
879166124Srafan   These  arise from ambiguities or omissions in the documentation of the
88076726Speter   API.
881166124Srafan
88276726Speter  Refresh of Overlapping Windows
883166124Srafan
884166124Srafan   If  you  define two windows A and B that overlap, and then alternately
885166124Srafan   scribble  on  and  refresh  them,  the changes made to the overlapping
886166124Srafan   region  under  historic  curses  versions  were  often  not documented
88776726Speter   precisely.
888166124Srafan
889166124Srafan   To  understand why this is a problem, remember that screen updates are
890166124Srafan   calculated  between  two  representations  of  the entire display. The
891166124Srafan   documentation  says that when you refresh a window, it is first copied
892166124Srafan   to  the  virtual screen,  and  then  changes  are calculated to update
893166124Srafan   the  physical screen (and applied to the terminal). But "copied to" is
894166124Srafan   not  very  specific,  and  subtle differences in how copying works can
895166124Srafan   produce  different behaviors in the case where two overlapping windows
89676726Speter   are each being refreshed at unpredictable intervals.
897166124Srafan
898166124Srafan   What  happens to the overlapping region depends on what wnoutrefresh()
899166124Srafan   does  with  its  argument  --  what portions of the argument window it
900166124Srafan   copies  to  the virtual screen. Some implementations do "change copy",
901166124Srafan   copying  down  only locations in the window that have changed (or been
902166124Srafan   marked  changed  with wtouchln() and friends). Some implementations do
903166124Srafan   "entire  copy",  copying  all  window  locations to the virtual screen
90476726Speter   whether or not they have changed.
905166124Srafan
906166124Srafan   The  ncurses  library  itself  has  not always been consistent on this
907166124Srafan   score.  Due  to  a  bug,  versions  1.8.7  to  1.9.8a did entire copy.
908166124Srafan   Versions  1.8.6  and  older,  and  versions 1.9.9 and newer, do change
90976726Speter   copy.
910166124Srafan
911166124Srafan   For  most  commercial curses implementations, it is not documented and
912166124Srafan   not  known  for sure (at least not to the ncurses maintainers) whether
913166124Srafan   they  do  change  copy or entire copy. We know that System V release 3
914166124Srafan   curses  has  logic in it that looks like an attempt to do change copy,
915166124Srafan   but  the  surrounding  logic and data representations are sufficiently
916166124Srafan   complex,  and  our  knowledge sufficiently indirect, that it's hard to
917166124Srafan   know  whether  this  is  reliable.  It  is  not  clear  what  the SVr4
918166124Srafan   documentation  and XSI standard intend. The XSI Curses standard barely
919166124Srafan   mentions  wnoutrefresh();  the  SVr4  documents  seem to be describing
92076726Speter   entire-copy, but it is possible with some effort and straining to read
92176726Speter   them the other way.
922166124Srafan
923166124Srafan   It  might  therefore  be unwise to rely on either behavior in programs
924166124Srafan   that  might  have  to  be  linked  with  other curses implementations.
925166124Srafan   Instead,  you  can do an explicit touchwin() before the wnoutrefresh()
92676726Speter   call to guarantee an entire-contents copy anywhere.
927166124Srafan
928166124Srafan   The  really clean way to handle this is to use the panels library. If,
929166124Srafan   when  you want a screen update, you do update_panels(), it will do all
930166124Srafan   the  necessary  wnoutrefresh() calls for whatever panel stacking order
931166124Srafan   you  have  defined. Then you can do one doupdate() and there will be a
93276726Speter   single burst of physical I/O that will do all your updates.
933166124Srafan
93476726Speter  Background Erase
935166124Srafan
93676726Speter   If you have been using a very old versions of ncurses (1.8.7 or older)
937166124Srafan   you  may be surprised by the behavior of the erase functions. In older
938166124Srafan   versions,  erased  areas of a window were filled with a blank modified
939166124Srafan   by  the  window's  current attribute (as set by wattrset(), wattron(),
94076726Speter   wattroff() and friends).
941166124Srafan
942166124Srafan   In  newer  versions,  this is not so. Instead, the attribute of erased
943166124Srafan   blanks  is  normal  unless  and  until it is modified by the functions
94476726Speter   bkgdset() or wbkgdset().
945166124Srafan
94676726Speter   This change in behavior conforms ncurses to System V Release 4 and the
94776726Speter   XSI Curses standard.
948166124Srafan
94976726SpeterXSI Curses Conformance
95076726Speter
951166124Srafan   The  ncurses  library is intended to be base-level conformant with the
952166124Srafan   XSI  Curses  standard  from  X/Open.  Many extended-level features (in
953166124Srafan   fact,  almost all features not directly concerned with wide characters
95476726Speter   and internationalization) are also supported.
955166124Srafan
956166124Srafan   One  effect  of  XSI  conformance  is the change in behavior described
95776726Speter   under "Background Erase -- Compatibility with Old Versions".
958166124Srafan
959166124Srafan   Also,  ncurses  meets the XSI requirement that every macro entry point
960166124Srafan   have  a  corresponding  function  which  may  be  linked  (and will be
96176726Speter   prototype-checked) if the macro definition is disabled with #undef.
962166124Srafan
96376726Speter                              The Panels Library
964166124Srafan
965166124Srafan   The  ncurses  library  by  itself  provides  good  support  for screen
96676726Speter   displays in which the windows are tiled (non-overlapping). In the more
967166124Srafan   general  case  that  windows  may overlap, you have to use a series of
968166124Srafan   wnoutrefresh()  calls  followed  by a doupdate(), and be careful about
96976726Speter   the order you do the window refreshes in. It has to be bottom-upwards,
97076726Speter   otherwise parts of windows that should be obscured will show through.
971166124Srafan
972166124Srafan   When  your  interface design is such that windows may dive deeper into
973166124Srafan   the  visibility  stack  or  pop  to  the top at runtime, the resulting
974166124Srafan   book-keeping  can  be  tedious  and  difficult to get right. Hence the
97576726Speter   panels library.
976166124Srafan
977166124Srafan   The  panel  library  first  appeared  in  AT&T  System  V. The version
97876726Speter   documented here is the panel code distributed with ncurses.
979166124Srafan
98076726SpeterCompiling With the Panels Library
98176726Speter
982166124Srafan   Your  panels-using modules must import the panels library declarations
98376726Speter   with
98476726Speter          #include <panel.h>
98576726Speter
98676726Speter   and must be linked explicitly with the panels library using an -lpanel
987166124Srafan   argument.  Note  that  they  must  also  link the ncurses library with
98876726Speter   -lncurses. Many linkers are two-pass and will accept either order, but
98976726Speter   it is still good practice to put -lpanel first and -lncurses second.
990166124Srafan
99176726SpeterOverview of Panels
99276726Speter
993166124Srafan   A  panel  object  is  a window that is implicitly treated as part of a
994166124Srafan   deck  including  all  other  panel  objects.  The deck has an implicit
995166124Srafan   bottom-to-top  visibility order. The panels library includes an update
99676726Speter   function (analogous to refresh()) that displays all panels in the deck
997166124Srafan   in  the proper order to resolve overlaps. The standard window, stdscr,
99876726Speter   is considered below all panels.
999166124Srafan
1000166124Srafan   Details  on the panels functions are available in the man pages. We'll
100176726Speter   just hit the highlights here.
1002166124Srafan
1003166124Srafan   You  create  a  panel from a window by calling new_panel() on a window
1004166124Srafan   pointer.  It  then  becomes the top of the deck. The panel's window is
100576726Speter   available as the value of panel_window() called with the panel pointer
100676726Speter   as argument.
1007166124Srafan
1008166124Srafan   You  can  delete  a  panel (removing it from the deck) with del_panel.
1009166124Srafan   This  will  not  deallocate the associated window; you have to do that
1010166124Srafan   yourself.  You can replace a panel's window with a different window by
1011166124Srafan   calling  replace_window.  The new window may be of different size; the
101276726Speter   panel code will re-compute all overlaps. This operation doesn't change
101376726Speter   the panel's position in the deck.
1014166124Srafan
1015166124Srafan   To  move  a  panel's window, use move_panel(). The mvwin() function on
1016166124Srafan   the  panel's  window  isn't  sufficient  because it doesn't update the
1017166124Srafan   panels  library's  representation  of  where  the  windows  are.  This
101876726Speter   operation leaves the panel's depth, contents, and size unchanged.
1019166124Srafan
1020166124Srafan   Two   functions   (top_panel(),   bottom_panel())   are  provided  for
102176726Speter   rearranging the deck. The first pops its argument window to the top of
1022166124Srafan   the  deck;  the second sends it to the bottom. Either operation leaves
102376726Speter   the panel's screen location, contents, and size unchanged.
1024166124Srafan
1025166124Srafan   The  function update_panels() does all the wnoutrefresh() calls needed
102676726Speter   to prepare for doupdate() (which you must call yourself, afterwards).
1027166124Srafan
1028166124Srafan   Typically,  you  will want to call update_panels() and doupdate() just
102976726Speter   before accepting command input, once in each cycle of interaction with
1030166124Srafan   the  user.  If  you  call  update_panels()  after each and every panel
1031166124Srafan   write,  you'll  generate  a  lot  of  unnecessary refresh activity and
103276726Speter   screen flicker.
1033166124Srafan
103476726SpeterPanels, Input, and the Standard Screen
103576726Speter
1036166124Srafan   You  shouldn't mix wnoutrefresh() or wrefresh() operations with panels
1037166124Srafan   code;  this will work only if the argument window is either in the top
103876726Speter   panel or unobscured by any other panels.
1039166124Srafan
1040166124Srafan   The  stsdcr  window  is  a  special  case.  It is considered below all
104176726Speter   panels. Because changes to panels may obscure parts of stdscr, though,
1042166124Srafan   you  should  call update_panels() before doupdate() even when you only
104376726Speter   change stdscr.
1044166124Srafan
1045166124Srafan   Note  that  wgetch  automatically  calls  wrefresh.  Therefore, before
1046166124Srafan   requesting  input  from  a  panel window, you need to be sure that the
104776726Speter   panel is totally unobscured.
1048166124Srafan
1049166124Srafan   There  is  presently  no  way to display changes to one obscured panel
105076726Speter   without repainting all panels.
1051166124Srafan
105276726SpeterHiding Panels
105376726Speter
1054166124Srafan   It's  possible  to  remove  a  panel  from  the  deck temporarily; use
1055166124Srafan   hide_panel  for this. Use show_panel() to render it visible again. The
1056166124Srafan   predicate  function  panel_hidden  tests  whether  or  not  a panel is
105776726Speter   hidden.
1058166124Srafan
105976726Speter   The panel_update code ignores hidden panels. You cannot do top_panel()
1060166124Srafan   or  bottom_panel  on  a  hidden  panel().  Other panels operations are
106176726Speter   applicable.
1062166124Srafan
106376726SpeterMiscellaneous Other Facilities
106476726Speter
1065166124Srafan   It's  possible  to navigate the deck using the functions panel_above()
1066166124Srafan   and  panel_below.  Handed a panel pointer, they return the panel above
1067166124Srafan   or  below  that  panel.  Handed  NULL,  they return the bottom-most or
106876726Speter   top-most panel.
1069166124Srafan
1070166124Srafan   Every  panel  has  an  associated  user pointer, not used by the panel
1071166124Srafan   code,  to  which  you  can  attach  application data. See the man page
107276726Speter   documentation of set_panel_userptr() and panel_userptr for details.
1073166124Srafan
107476726Speter                               The Menu Library
1075166124Srafan
107676726Speter   A menu is a screen display that assists the user to choose some subset
1077166124Srafan   of  a  given set of items. The menu library is a curses extension that
1078166124Srafan   supports  easy  programming  of  menu  hierarchies  with a uniform but
107976726Speter   flexible interface.
1080166124Srafan
1081166124Srafan   The  menu  library  first  appeared  in  AT&T  System  V.  The version
108276726Speter   documented here is the menu code distributed with ncurses.
1083166124Srafan
108476726SpeterCompiling With the menu Library
108576726Speter
108676726Speter   Your menu-using modules must import the menu library declarations with
108776726Speter          #include <menu.h>
108876726Speter
1089166124Srafan   and  must  be linked explicitly with the menus library using an -lmenu
1090166124Srafan   argument.  Note  that  they  must  also  link the ncurses library with
109176726Speter   -lncurses. Many linkers are two-pass and will accept either order, but
109276726Speter   it is still good practice to put -lmenu first and -lncurses second.
1093166124Srafan
109476726SpeterOverview of Menus
109576726Speter
1096166124Srafan   The  menus  created  by  this  library consist of collections of items
1097166124Srafan   including  a  name  string part and a description string part. To make
1098166124Srafan   menus,  you  create  groups  of these items and connect them with menu
109976726Speter   frame objects.
1100166124Srafan
1101166124Srafan   The  menu can then by posted, that is written to an associated window.
110276726Speter   Actually, each menu has two associated windows; a containing window in
1103166124Srafan   which  the  programmer can scribble titles or borders, and a subwindow
110476726Speter   in which the menu items proper are displayed. If this subwindow is too
1105166124Srafan   small  to  display  all the items, it will be a scrollable viewport on
110676726Speter   the collection of items.
1107166124Srafan
1108166124Srafan   A  menu may also be unposted (that is, undisplayed), and finally freed
1109166124Srafan   to  make  the  storage  associated with it and its items available for
111076726Speter   re-use.
1111166124Srafan
111276726Speter   The general flow of control of a menu program looks like this:
111376726Speter    1. Initialize curses.
111476726Speter    2. Create the menu items, using new_item().
111576726Speter    3. Create the menu using new_menu().
1116166124Srafan    4. Post the menu using post_menu().
111776726Speter    5. Refresh the screen.
111876726Speter    6. Process user requests via an input loop.
1119166124Srafan    7. Unpost the menu using unpost_menu().
112076726Speter    8. Free the menu, using free_menu().
112176726Speter    9. Free the items using free_item().
112276726Speter   10. Terminate curses.
1123166124Srafan
112476726SpeterSelecting items
112576726Speter
1126166124Srafan   Menus  may  be  multi-valued  or  (the default) single-valued (see the
1127166124Srafan   manual  page  menu_opts(3x)  to  see  how to change the default). Both
112876726Speter   types always have a current item.
1129166124Srafan
1130166124Srafan   From  a  single-valued  menu you can read the selected value simply by
1131166124Srafan   looking  at  the  current  item. From a multi-valued menu, you get the
1132166124Srafan   selected  set  by  looping through the items applying the item_value()
1133166124Srafan   predicate  function.  Your  menu-processing  code can use the function
113476726Speter   set_item_value() to flag the items in the select set.
1135166124Srafan
1136166124Srafan   Menu   items   can  be  made  unselectable  using  set_item_opts()  or
1137166124Srafan   item_opts_off()  with  the  O_SELECTABLE  argument.  This  is the only
1138166124Srafan   option  so  far  defined for menus, but it is good practice to code as
113976726Speter   though other option bits might be on.
1140166124Srafan
114176726SpeterMenu Display
114276726Speter
1143166124Srafan   The  menu  library  calculates a minimum display size for your window,
114476726Speter   based on the following variables:
114576726Speter     * The number and maximum length of the menu items
114676726Speter     * Whether the O_ROWMAJOR option is enabled
114776726Speter     * Whether display of descriptions is enabled
114876726Speter     * Whatever menu format may have been set by the programmer
1149166124Srafan     * The  length of the menu mark string used for highlighting selected
115076726Speter       items
1151166124Srafan
1152166124Srafan   The  function  set_menu_format() allows you to set the maximum size of
115376726Speter   the viewport or menu page that will be used to display menu items. You
115476726Speter   can retrieve any format associated with a menu with menu_format(). The
115576726Speter   default format is rows=16, columns=1.
1156166124Srafan
115776726Speter   The actual menu page may be smaller than the format size. This depends
1158166124Srafan   on  the item number and size and whether O_ROWMAJOR is on. This option
1159166124Srafan   (on  by  default) causes menu items to be displayed in a `raster-scan'
116076726Speter   pattern, so that if more than one item will fit horizontally the first
1161166124Srafan   couple  of  items  are side-by-side in the top row. The alternative is
1162166124Srafan   column-major  display,  which  tries to put the first several items in
116376726Speter   the first column.
1164166124Srafan
1165166124Srafan   As  mentioned above, a menu format not large enough to allow all items
1166166124Srafan   to  fit  on-screen  will  result  in a menu display that is vertically
116776726Speter   scrollable.
1168166124Srafan
1169166124Srafan   You  can  scroll  it  with  requests to the menu driver, which will be
117076726Speter   described in the section on menu input handling.
1171166124Srafan
1172166124Srafan   Each  menu  has a mark string used to visually tag selected items; see
117376726Speter   the menu_mark(3x) manual page for details. The mark string length also
117476726Speter   influences the menu page size.
1175166124Srafan
1176166124Srafan   The  function  scale_menu()  returns the minimum display size that the
1177166124Srafan   menu  code  computes  from  all  these  factors.  There are other menu
1178166124Srafan   display  attributes  including  a  select  attribute, an attribute for
1179166124Srafan   selectable  items,  an  attribute  for  unselectable  items, and a pad
118076726Speter   character used to separate item name text from description text. These
1181166124Srafan   have  reasonable  defaults which the library allows you to change (see
118276726Speter   the menu_attribs(3x) manual page.
1183166124Srafan
118476726SpeterMenu Windows
118576726Speter
1186166124Srafan   Each  menu has, as mentioned previously, a pair of associated windows.
118776726Speter   Both these windows are painted when the menu is posted and erased when
118876726Speter   the menu is unposted.
1189166124Srafan
1190166124Srafan   The  outer  or  frame  window  is  not  otherwise  touched by the menu
119176726Speter   routines. It exists so the programmer can associate a title, a border,
1192166124Srafan   or  perhaps  help text with the menu and have it properly refreshed or
119376726Speter   erased at post/unpost time. The inner window or subwindow is where the
119476726Speter   current menu page is displayed.
1195166124Srafan
1196166124Srafan   By  default,  both  windows  are  stdscr.  You  can  set them with the
119776726Speter   functions in menu_win(3x).
1198166124Srafan
1199166124Srafan   When  you  call post_menu(), you write the menu to its subwindow. When
1200166124Srafan   you  call  unpost_menu(), you erase the subwindow, However, neither of
1201166124Srafan   these  actually  modifies  the  screen. To do that, call wrefresh() or
120276726Speter   some equivalent.
1203166124Srafan
120476726SpeterProcessing Menu Input
120576726Speter
1206166124Srafan   The  main  loop of your menu-processing code should call menu_driver()
1207166124Srafan   repeatedly.  The first argument of this routine is a menu pointer; the
1208166124Srafan   second  is  a  menu  command  code. You should write an input-fetching
120976726Speter   routine that maps input characters to menu command codes, and pass its
1210166124Srafan   output  to  menu_driver(). The menu command codes are fully documented
121176726Speter   in menu_driver(3x).
1212166124Srafan
1213166124Srafan   The  simplest  group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM,
1214166124Srafan   REQ_FIRST_ITEM,     REQ_LAST_ITEM,     REQ_UP_ITEM,     REQ_DOWN_ITEM,
1215166124Srafan   REQ_LEFT_ITEM,  REQ_RIGHT_ITEM.  These  change  the currently selected
1216166124Srafan   item.  These  requests may cause scrolling of the menu page if it only
121776726Speter   partially displayed.
1218166124Srafan
1219166124Srafan   There  are  explicit  requests  for  scrolling  which  also change the
1220166124Srafan   current  item  (because  the  select location does not change, but the
1221166124Srafan   item    there   does).   These   are   REQ_SCR_DLINE,   REQ_SCR_ULINE,
122276726Speter   REQ_SCR_DPAGE, and REQ_SCR_UPAGE.
1223166124Srafan
1224166124Srafan   The  REQ_TOGGLE_ITEM  selects or deselects the current item. It is for
1225166124Srafan   use  in  multi-valued  menus; if you use it with O_ONEVALUE on, you'll
122676726Speter   get an error return (E_REQUEST_DENIED).
1227166124Srafan
1228166124Srafan   Each  menu  has  an associated pattern buffer. The menu_driver() logic
1229166124Srafan   tries  to  accumulate  printable  ASCII  characters  passed in in that
1230166124Srafan   buffer;  when  it  matches a prefix of an item name, that item (or the
1231166124Srafan   next  matching  item)  is selected. If appending a character yields no
1232166124Srafan   new  match,  that  character  is  deleted from the pattern buffer, and
123376726Speter   menu_driver() returns E_NO_MATCH.
1234166124Srafan
1235166124Srafan   Some  requests  change the pattern buffer directly: REQ_CLEAR_PATTERN,
1236166124Srafan   REQ_BACK_PATTERN,  REQ_NEXT_MATCH,  REQ_PREV_MATCH. The latter two are
1237166124Srafan   useful  when  pattern  buffer  input  matches  more than one item in a
123876726Speter   multi-valued menu.
1239166124Srafan
1240166124Srafan   Each  successful  scroll or item navigation request clears the pattern
1241166124Srafan   buffer.  It is also possible to set the pattern buffer explicitly with
124276726Speter   set_menu_pattern().
1243166124Srafan
1244166124Srafan   Finally,  menu  driver  requests  above  the  constant MAX_COMMAND are
1245166124Srafan   considered   application-specific  commands.  The  menu_driver()  code
124676726Speter   ignores them and returns E_UNKNOWN_COMMAND.
1247166124Srafan
124876726SpeterMiscellaneous Other Features
124976726Speter
1250166124Srafan   Various  menu  options can affect the processing and visual appearance
125176726Speter   and input processing of menus. See menu_opts(3x) for details.
1252166124Srafan
1253166124Srafan   It  is possible to change the current item from application code; this
1254166124Srafan   is  useful  if  you  want to write your own navigation requests. It is
1255166124Srafan   also  possible  to explicitly set the top row of the menu display. See
1256166124Srafan   mitem_current(3x).  If  your  application  needs  to  change  the menu
1257166124Srafan   subwindow  cursor for any reason, pos_menu_cursor() will restore it to
125876726Speter   the correct location for continuing menu driver processing.
1259166124Srafan
1260166124Srafan   It  is  possible  to set hooks to be called at menu initialization and
1261166124Srafan   wrapup   time,   and   whenever   the   selected   item  changes.  See
126276726Speter   menu_hook(3x).
1263166124Srafan
1264166124Srafan   Each  item, and each menu, has an associated user pointer on which you
126576726Speter   can hang application data. See mitem_userptr(3x) and menu_userptr(3x).
1266166124Srafan
126776726Speter                               The Forms Library
1268166124Srafan
1269166124Srafan   The  form library is a curses extension that supports easy programming
127076726Speter   of on-screen forms for data entry and program control.
1271166124Srafan
1272166124Srafan   The  form  library  first  appeared  in  AT&T  System  V.  The version
127376726Speter   documented here is the form code distributed with ncurses.
1274166124Srafan
127576726SpeterCompiling With the form Library
127676726Speter
127776726Speter   Your form-using modules must import the form library declarations with
127876726Speter          #include <form.h>
127976726Speter
1280166124Srafan   and  must  be linked explicitly with the forms library using an -lform
1281166124Srafan   argument.  Note  that  they  must  also  link the ncurses library with
128276726Speter   -lncurses. Many linkers are two-pass and will accept either order, but
128376726Speter   it is still good practice to put -lform first and -lncurses second.
1284166124Srafan
128576726SpeterOverview of Forms
128676726Speter
1287166124Srafan   A  form  is  a  collection of fields; each field may be either a label
1288166124Srafan   (explanatory  text)  or  a  data-entry  location.  Long  forms  may be
128976726Speter   segmented into pages; each entry to a new page clears the screen.
1290166124Srafan
1291166124Srafan   To  make forms, you create groups of fields and connect them with form
129276726Speter   frame objects; the form library makes this relatively simple.
1293166124Srafan
1294166124Srafan   Once  defined,  a form can be posted, that is written to an associated
1295166124Srafan   window.  Actually,  each form has two associated windows; a containing
1296166124Srafan   window  in  which the programmer can scribble titles or borders, and a
129776726Speter   subwindow in which the form fields proper are displayed.
1298166124Srafan
1299166124Srafan   As  the  form  user  fills out the posted form, navigation and editing
1300166124Srafan   keys  support  movement between fields, editing keys support modifying
1301166124Srafan   field,  and plain text adds to or changes data in a current field. The
1302166124Srafan   form  library  allows you (the forms designer) to bind each navigation
1303166124Srafan   and  editing  key  to any keystroke accepted by curses Fields may have
1304166124Srafan   validation  conditions on them, so that they check input data for type
1305166124Srafan   and  value.  The form library supplies a rich set of pre-defined field
130676726Speter   types, and makes it relatively easy to define new ones.
1307166124Srafan
130876726Speter   Once its transaction is completed (or aborted), a form may be unposted
1309166124Srafan   (that  is,  undisplayed),  and  finally  freed  to  make  the  storage
131076726Speter   associated with it and its items available for re-use.
1311166124Srafan
131276726Speter   The general flow of control of a form program looks like this:
131376726Speter    1. Initialize curses.
131476726Speter    2. Create the form fields, using new_field().
131576726Speter    3. Create the form using new_form().
1316166124Srafan    4. Post the form using post_form().
131776726Speter    5. Refresh the screen.
131876726Speter    6. Process user requests via an input loop.
1319166124Srafan    7. Unpost the form using unpost_form().
132076726Speter    8. Free the form, using free_form().
132176726Speter    9. Free the fields using free_field().
132276726Speter   10. Terminate curses.
1323166124Srafan
1324166124Srafan   Note  that  this  looks  much  like  a  menu program; the form library
1325166124Srafan   handles  tasks  which  are in many ways similar, and its interface was
1326166124Srafan   obviously  designed  to  resemble  that  of  the menu library wherever
132776726Speter   possible.
1328166124Srafan
1329166124Srafan   In  forms  programs,  however, the `process user requests' is somewhat
1330166124Srafan   more   complicated   than  for  menus.  Besides  menu-like  navigation
133176726Speter   operations, the menu driver loop has to support field editing and data
133276726Speter   validation.
1333166124Srafan
133476726SpeterCreating and Freeing Fields and Forms
133576726Speter
133676726Speter   The basic function for creating fields is new_field():
133776726SpeterFIELD *new_field(int height, int width,   /* new field size */
133876726Speter                 int top, int left,       /* upper left corner */
133976726Speter                 int offscreen,           /* number of offscreen rows */
134076726Speter                 int nbuf);               /* number of working buffers */
134176726Speter
1342166124Srafan   Menu  items  always  occupy  a  single  row, but forms fields may have
1343166124Srafan   multiple  rows.  So  new_field()  requires  you to specify a width and
1344166124Srafan   height  (the  first  two  arguments,  which  mist both be greater than
134576726Speter   zero).
1346166124Srafan
134776726Speter   You must also specify the location of the field's upper left corner on
1348166124Srafan   the  screen  (the  third  and  fourth arguments, which must be zero or
1349166124Srafan   greater).  Note  that  these  coordinates  are  relative  to  the form
1350166124Srafan   subwindow,  which will coincide with stdscr by default but need not be
1351166124Srafan   stdscr if you've done an explicit set_form_win() call.
1352166124Srafan
1353166124Srafan   The  fifth argument allows you to specify a number of off-screen rows.
1354166124Srafan   If  this  is zero, the entire field will always be displayed. If it is
1355166124Srafan   nonzero,  the  form  will  be  scrollable,  with  only one screen-full
1356166124Srafan   (initially  the  top  part) displayed at any given time. If you make a
1357166124Srafan   field  dynamic and grow it so it will no longer fit on the screen, the
1358166124Srafan   form  will  become  scrollable  even  if  the  offscreen  argument was
135976726Speter   initially zero.
1360166124Srafan
1361166124Srafan   The  forms library allocates one working buffer per field; the size of
136276726Speter   each buffer is ((height + offscreen)*width + 1, one character for each
136376726Speter   position in the field plus a NUL terminator. The sixth argument is the
1364166124Srafan   number  of  additional  data  buffers  to allocate for the field; your
136576726Speter   application can use them for its own purposes.
136676726SpeterFIELD *dup_field(FIELD *field,            /* field to copy */
136776726Speter                 int top, int left);      /* location of new copy */
136876726Speter
1369166124Srafan   The  function  dup_field()  duplicates  an  existing  field  at  a new
1370166124Srafan   location.  Size  and  buffering information are copied; some attribute
1371166124Srafan   flags  and  status  bits  are  not  (see  the  form_field_new(3X)  for
137276726Speter   details).
137376726SpeterFIELD *link_field(FIELD *field,           /* field to copy */
137476726Speter                  int top, int left);     /* location of new copy */
137576726Speter
1376166124Srafan   The  function  link_field() also duplicates an existing field at a new
1377166124Srafan   location.  The difference from dup_field() is that it arranges for the
137876726Speter   new field's buffer to be shared with the old one.
1379166124Srafan
1380166124Srafan   Besides  the obvious use in making a field editable from two different
138176726Speter   form pages, linked fields give you a way to hack in dynamic labels. If
1382166124Srafan   you  declare  several fields linked to an original, and then make them
1383166124Srafan   inactive,  changes  from  the original will still be propagated to the
138476726Speter   linked fields.
1385166124Srafan
1386166124Srafan   As  with duplicated fields, linked fields have attribute bits separate
138776726Speter   from the original.
1388166124Srafan
1389166124Srafan   As  you  might  guess,  all these field-allocations return NULL if the
1390166124Srafan   field  allocation  is  not  possible  due to an out-of-memory error or
139176726Speter   out-of-bounds arguments.
1392166124Srafan
139376726Speter   To connect fields to a form, use
139476726SpeterFORM *new_form(FIELD **fields);
139576726Speter
1396166124Srafan   This  function  expects  to  see  a  NULL-terminated  array  of  field
1397166124Srafan   pointers.  Said fields are connected to a newly-allocated form object;
139876726Speter   its address is returned (or else NULL if the allocation fails).
1399166124Srafan
1400166124Srafan   Note  that  new_field()  does  not copy the pointer array into private
1401166124Srafan   storage;  if you modify the contents of the pointer array during forms
1402166124Srafan   processing,  all manner of bizarre things might happen. Also note that
140376726Speter   any given field may only be connected to one form.
1404166124Srafan
1405166124Srafan   The  functions  free_field() and free_form are available to free field
1406166124Srafan   and  form objects. It is an error to attempt to free a field connected
140776726Speter   to a form, but not vice-versa; thus, you will generally free your form
140876726Speter   objects first.
1409166124Srafan
141076726SpeterFetching and Changing Field Attributes
141176726Speter
1412166124Srafan   Each  form  field  has  a  number  of  location  and  size  attributes
1413166124Srafan   associated  with  it. There are other field attributes used to control
141476726Speter   display and editing of the field. Some (for example, the O_STATIC bit)
1415166124Srafan   involve  sufficient  complications  to be covered in sections of their
141676726Speter   own later on. We cover the functions used to get and set several basic
141776726Speter   attributes here.
1418166124Srafan
141976726Speter   When a field is created, the attributes not specified by the new_field
1420166124Srafan   function  are  copied  from  an  invisible  system  default  field. In
1421166124Srafan   attribute-setting  and -fetching functions, the argument NULL is taken
142276726Speter   to mean this field. Changes to it persist as defaults until your forms
142376726Speter   application terminates.
1424166124Srafan
142576726Speter  Fetching Size and Location Data
1426166124Srafan
142776726Speter   You can retrieve field sizes and locations through:
142876726Speterint field_info(FIELD *field,              /* field from which to fetch */
142976726Speter               int *height, *int width,   /* field size */
143076726Speter               int *top, int *left,       /* upper left corner */
143176726Speter               int *offscreen,            /* number of offscreen rows */
143276726Speter               int *nbuf);                /* number of working buffers */
143376726Speter
1434166124Srafan   This  function is a sort of inverse of new_field(); instead of setting
1435166124Srafan   size  and  location attributes of a new field, it fetches them from an
143676726Speter   existing one.
1437166124Srafan
143876726Speter  Changing the Field Location
1439166124Srafan
144076726Speter   It is possible to move a field's location on the screen:
144176726Speterint move_field(FIELD *field,              /* field to alter */
144276726Speter               int top, int left);        /* new upper-left corner */
144376726Speter
144476726Speter   You can, of course. query the current location through field_info().
1445166124Srafan
144676726Speter  The Justification Attribute
1447166124Srafan
1448166124Srafan   One-line  fields  may be unjustified, justified right, justified left,
144976726Speter   or centered. Here is how you manipulate this attribute:
145076726Speterint set_field_just(FIELD *field,          /* field to alter */
145176726Speter                   int justmode);         /* mode to set */
145276726Speter
145376726Speterint field_just(FIELD *field);             /* fetch mode of field */
145476726Speter
1455166124Srafan   The   mode   values  accepted  and  returned  by  this  functions  are
1456166124Srafan   preprocessor  macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or
145776726Speter   JUSTIFY_CENTER.
1458166124Srafan
145976726Speter  Field Display Attributes
1460166124Srafan
1461166124Srafan   For  each  field,  you  can  set  a  foreground  attribute for entered
1462166124Srafan   characters,  a  background  attribute  for the entire field, and a pad
1463166124Srafan   character  for the unfilled portion of the field. You can also control
146476726Speter   pagination of the form.
1465166124Srafan
1466166124Srafan   This  group of four field attributes controls the visual appearance of
1467166124Srafan   the  field on the screen, without affecting in any way the data in the
146876726Speter   field buffer.
146976726Speterint set_field_fore(FIELD *field,          /* field to alter */
147076726Speter                   chtype attr);          /* attribute to set */
147176726Speter
147276726Speterchtype field_fore(FIELD *field);          /* field to query */
147376726Speter
147476726Speterint set_field_back(FIELD *field,          /* field to alter */
147576726Speter                   chtype attr);          /* attribute to set */
147676726Speter
147776726Speterchtype field_back(FIELD *field);          /* field to query */
147876726Speter
147976726Speterint set_field_pad(FIELD *field,           /* field to alter */
148076726Speter                 int pad);                /* pad character to set */
148176726Speter
148276726Speterchtype field_pad(FIELD *field);
148376726Speter
148476726Speterint set_new_page(FIELD *field,            /* field to alter */
148576726Speter                 int flag);               /* TRUE to force new page */
148676726Speter
148776726Speterchtype new_page(FIELD *field);            /* field to query */
148876726Speter
148976726Speter   The attributes set and returned by the first four functions are normal
1490166124Srafan   curses(3x)  display  attribute  values  (A_STANDOUT, A_BOLD, A_REVERSE
1491166124Srafan   etc).  The page bit of a field controls whether it is displayed at the
149276726Speter   start of a new form screen.
1493166124Srafan
149476726Speter  Field Option Bits
1495166124Srafan
1496166124Srafan   There  is  also a large collection of field option bits you can set to
1497166124Srafan   control  various  aspects of forms processing. You can manipulate them
149876726Speter   with these functions:
149976726Speterint set_field_opts(FIELD *field,          /* field to alter */
150076726Speter                   int attr);             /* attribute to set */
150176726Speter
150276726Speterint field_opts_on(FIELD *field,           /* field to alter */
150376726Speter                  int attr);              /* attributes to turn on */
150476726Speter
150576726Speterint field_opts_off(FIELD *field,          /* field to alter */
150676726Speter                   int attr);             /* attributes to turn off */
150776726Speter
150876726Speterint field_opts(FIELD *field);             /* field to query */
150976726Speter
151076726Speter   By default, all options are on. Here are the available option bits:
1511166124Srafan
151276726Speter   O_VISIBLE
1513166124Srafan          Controls  whether  the  field  is visible on the screen. Can be
1514166124Srafan          used  during form processing to hide or pop up fields depending
151576726Speter          on the value of parent fields.
1516166124Srafan
151776726Speter   O_ACTIVE
1518166124Srafan          Controls  whether  the  field is active during forms processing
1519166124Srafan          (i.e.  visited  by  form  navigation keys). Can be used to make
1520166124Srafan          labels  or  derived  fields with buffer values alterable by the
152176726Speter          forms application, not the user.
1522166124Srafan
152376726Speter   O_PUBLIC
1524166124Srafan          Controls  whether data is displayed during field entry. If this
1525166124Srafan          option  is  turned  off on a field, the library will accept and
1526166124Srafan          edit  data  in that field, but it will not be displayed and the
1527166124Srafan          visible  field  cursor  will  not  move.  You  can turn off the
152876726Speter          O_PUBLIC bit to define password fields.
1529166124Srafan
153076726Speter   O_EDIT
1531166124Srafan          Controls  whether  the  field's data can be modified. When this
1532166124Srafan          option  is off, all editing requests except REQ_PREV_CHOICE and
1533166124Srafan          REQ_NEXT_CHOICE  will fail. Such read-only fields may be useful
153476726Speter          for help messages.
1535166124Srafan
153676726Speter   O_WRAP
153776726Speter          Controls word-wrapping in multi-line fields. Normally, when any
1538166124Srafan          character  of  a  (blank-separated) word reaches the end of the
1539166124Srafan          current  line,  the  entire  word  is  wrapped to the next line
154076726Speter          (assuming there is one). When this option is off, the word will
154176726Speter          be split across the line break.
1542166124Srafan
154376726Speter   O_BLANK
1544166124Srafan          Controls  field  blanking.  When  this option is on, entering a
1545166124Srafan          character  at  the first field position erases the entire field
154676726Speter          (except for the just-entered character).
1547166124Srafan
154876726Speter   O_AUTOSKIP
1549166124Srafan          Controls  automatic  skip  to  next  field when this one fills.
1550166124Srafan          Normally,  when  the  forms user tries to type more data into a
1551166124Srafan          field  than will fit, the editing location jumps to next field.
155276726Speter          When this option is off, the user's cursor will hang at the end
1553166124Srafan          of  the  field.  This  option is ignored in dynamic fields that
155476726Speter          have not reached their size limit.
1555166124Srafan
155676726Speter   O_NULLOK
1557166124Srafan          Controls   whether  validation  is  applied  to  blank  fields.
1558166124Srafan          Normally,  it  is not; the user can leave a field blank without
1559166124Srafan          invoking  the usual validation check on exit. If this option is
156076726Speter          off on a field, exit from it will invoke a validation check.
1561166124Srafan
156276726Speter   O_PASSOK
156376726Speter          Controls whether validation occurs on every exit, or only after
1564166124Srafan          the  field  is  modified.  Normally the latter is true. Setting
1565166124Srafan          O_PASSOK  may be useful if your field's validation function may
156676726Speter          change during forms processing.
1567166124Srafan
156876726Speter   O_STATIC
1569166124Srafan          Controls  whether the field is fixed to its initial dimensions.
1570166124Srafan          If  you  turn  this  off,  the  field  becomes dynamic and will
157176726Speter          stretch to fit entered data.
1572166124Srafan
1573166124Srafan   A  field's  options  cannot  be  changed  while the field is currently
1574166124Srafan   selected.  However,  options  may be changed on posted fields that are
157576726Speter   not current.
1576166124Srafan
157776726Speter   The option values are bit-masks and can be composed with logical-or in
157876726Speter   the obvious way.
1579166124Srafan
158076726SpeterField Status
158176726Speter
158276726Speter   Every field has a status flag, which is set to FALSE when the field is
1583166124Srafan   created  and  TRUE when the value in field buffer 0 changes. This flag
158476726Speter   can be queried and set directly:
158576726Speterint set_field_status(FIELD *field,      /* field to alter */
158676726Speter                   int status);         /* mode to set */
158776726Speter
158876726Speterint field_status(FIELD *field);         /* fetch mode of field */
158976726Speter
1590166124Srafan   Setting  this  flag under program control can be useful if you use the
159176726Speter   same form repeatedly, looking for modified fields each time.
1592166124Srafan
1593166124Srafan   Calling  field_status()  on  a  field not currently selected for input
159476726Speter   will return a correct value. Calling field_status() on a field that is
1595166124Srafan   currently  selected for input may not necessarily give a correct field
1596166124Srafan   status  value, because entered data isn't necessarily copied to buffer
1597166124Srafan   zero  before the exit validation check. To guarantee that the returned
1598166124Srafan   status  value  reflects reality, call field_status() either (1) in the
1599166124Srafan   field's  exit validation check routine, (2) from the field's or form's
1600166124Srafan   initialization   or   termination   hooks,   or   (3)   just  after  a
160176726Speter   REQ_VALIDATION request has been processed by the forms driver.
1602166124Srafan
160376726SpeterField User Pointer
160476726Speter
1605166124Srafan   Each  field  structure contains one character pointer slot that is not
1606166124Srafan   used  by  the forms library. It is intended to be used by applications
160776726Speter   to store private per-field data. You can manipulate it with:
160876726Speterint set_field_userptr(FIELD *field,       /* field to alter */
160976726Speter                   char *userptr);        /* mode to set */
161076726Speter
161176726Speterchar *field_userptr(FIELD *field);        /* fetch mode of field */
161276726Speter
1613166124Srafan   (Properly,  this  user  pointer field ought to have (void *) type. The
161476726Speter   (char *) type is retained for System V compatibility.)
1615166124Srafan
1616166124Srafan   It  is  valid  to  set  the  user pointer of the default field (with a
1617166124Srafan   set_field_userptr()  call  passed  a  NULL  field pointer.) When a new
1618166124Srafan   field  is  created,  the  default-field  user  pointer  is  copied  to
161976726Speter   initialize the new field's user pointer.
1620166124Srafan
162176726SpeterVariable-Sized Fields
162276726Speter
1623166124Srafan   Normally,  a  field  is fixed at the size specified for it at creation
1624166124Srafan   time.  If,  however, you turn off its O_STATIC bit, it becomes dynamic
1625166124Srafan   and  will  automatically  resize  itself  to accommodate data as it is
1626166124Srafan   entered.  If the field has extra buffers associated with it, they will
162776726Speter   grow right along with the main input buffer.
1628166124Srafan
1629166124Srafan   A  one-line  dynamic  field  will have a fixed height (1) but variable
163076726Speter   width, scrolling horizontally to display data within the field area as
1631166124Srafan   originally  dimensioned  and  located. A multi-line dynamic field will
1632166124Srafan   have  a  fixed  width, but variable height (number of rows), scrolling
1633166124Srafan   vertically  to  display  data  within  the  field  area  as originally
163476726Speter   dimensioned and located.
1635166124Srafan
1636166124Srafan   Normally,  a dynamic field is allowed to grow without limit. But it is
1637166124Srafan   possible  to set an upper limit on the size of a dynamic field. You do
163876726Speter   it with this function:
163976726Speterint set_max_field(FIELD *field,     /* field to alter (may not be NULL) */
164076726Speter                   int max_size);   /* upper limit on field size */
164176726Speter
164276726Speter   If the field is one-line, max_size is taken to be a column size limit;
1643166124Srafan   if  it  is multi-line, it is taken to be a line size limit. To disable
1644166124Srafan   any  limit,  use  an argument of zero. The growth limit can be changed
164576726Speter   whether or not the O_STATIC bit is on, but has no effect until it is.
1646166124Srafan
164776726Speter   The following properties of a field change when it becomes dynamic:
1648166124Srafan     * If  there  is  no  growth limit, there is no final position of the
164976726Speter       field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored.
165076726Speter     * Field justification will be ignored (though whatever justification
165176726Speter       is set up will be retained internally and can be queried).
1652166124Srafan     * The  dup_field() and link_field() calls copy dynamic-buffer sizes.
1653166124Srafan       If  the  O_STATIC  option  is set on one of a collection of links,
1654166124Srafan       buffer  resizing  will occur only when the field is edited through
165576726Speter       that link.
1656166124Srafan     * The  call  field_info()  will retrieve the original static size of
1657166124Srafan       the  field;  use  dynamic_field_info()  to  get the actual dynamic
165876726Speter       size.
1659166124Srafan
166076726SpeterField Validation
166176726Speter
1662166124Srafan   By  default,  a  field will accept any data that will fit in its input
1663166124Srafan   buffer.  However,  it  is  possible  to  attach a validation type to a
1664166124Srafan   field.  If  you  do  this,  any  attempt  to  leave the field while it
1665166124Srafan   contains  data  that doesn't match the validation type will fail. Some
1666166124Srafan   validation  types also have a character-validity check for each time a
166776726Speter   character is entered in the field.
1668166124Srafan
1669166124Srafan   A   field's   validation   check   (if   any)   is   not  called  when
1670166124Srafan   set_field_buffer()  modifies the input buffer, nor when that buffer is
167176726Speter   changed through a linked field.
1672166124Srafan
1673166124Srafan   The  form library provides a rich set of pre-defined validation types,
1674166124Srafan   and  gives  you  the capability to define custom ones of your own. You
1675166124Srafan   can  examine and change field validation attributes with the following
167676726Speter   functions:
167776726Speterint set_field_type(FIELD *field,          /* field to alter */
167876726Speter                   FIELDTYPE *ftype,      /* type to associate */
167976726Speter                   ...);                  /* additional arguments*/
168076726Speter
168176726SpeterFIELDTYPE *field_type(FIELD *field);      /* field to query */
168276726Speter
1683166124Srafan   The  validation  type  of  a  field  is considered an attribute of the
1684166124Srafan   field.  As  with  other field attributes, Also, doing set_field_type()
1685166124Srafan   with  a  NULL  field  default  will  change  the  system  default  for
168676726Speter   validation of newly-created fields.
1687166124Srafan
168876726Speter   Here are the pre-defined validation types:
1689166124Srafan
169076726Speter  TYPE_ALPHA
1691166124Srafan
1692166124Srafan   This  field  type  accepts  alphabetic  data; no blanks, no digits, no
1693166124Srafan   special  characters  (this  is checked at character-entry time). It is
169476726Speter   set up with:
169576726Speterint set_field_type(FIELD *field,          /* field to alter */
169676726Speter                   TYPE_ALPHA,            /* type to associate */
169776726Speter                   int width);            /* maximum width of field */
169876726Speter
169976726Speter   The width argument sets a minimum width of data. Typically you'll want
1700166124Srafan   to  set this to the field width; if it's greater than the field width,
1701166124Srafan   the  validation  check will always fail. A minimum width of zero makes
170276726Speter   field completion optional.
1703166124Srafan
170476726Speter  TYPE_ALNUM
1705166124Srafan
1706166124Srafan   This  field  type  accepts  alphabetic  data and digits; no blanks, no
1707166124Srafan   special  characters  (this  is checked at character-entry time). It is
170876726Speter   set up with:
170976726Speterint set_field_type(FIELD *field,          /* field to alter */
171076726Speter                   TYPE_ALNUM,            /* type to associate */
171176726Speter                   int width);            /* maximum width of field */
171276726Speter
1713166124Srafan   The  width  argument sets a minimum width of data. As with TYPE_ALPHA,
1714166124Srafan   typically  you'll want to set this to the field width; if it's greater
171576726Speter   than the field width, the validation check will always fail. A minimum
171676726Speter   width of zero makes field completion optional.
1717166124Srafan
171876726Speter  TYPE_ENUM
1719166124Srafan
1720166124Srafan   This  type  allows  you  to  restrict  a  field's values to be among a
1721166124Srafan   specified  set  of  string  values (for example, the two-letter postal
172276726Speter   codes for U.S. states). It is set up with:
172376726Speterint set_field_type(FIELD *field,          /* field to alter */
172476726Speter                   TYPE_ENUM,             /* type to associate */
172576726Speter                   char **valuelist;      /* list of possible values */
172676726Speter                   int checkcase;         /* case-sensitive? */
172776726Speter                   int checkunique);      /* must specify uniquely? */
172876726Speter
1729166124Srafan   The  valuelist parameter must point at a NULL-terminated list of valid
1730166124Srafan   strings.  The  checkcase  argument, if true, makes comparison with the
173176726Speter   string case-sensitive.
1732166124Srafan
1733166124Srafan   When  the user exits a TYPE_ENUM field, the validation procedure tries
1734166124Srafan   to  complete  the  data  in the buffer to a valid entry. If a complete
1735166124Srafan   choice  string has been entered, it is of course valid. But it is also
173676726Speter   possible to enter a prefix of a valid string and have it completed for
173776726Speter   you.
1738166124Srafan
1739166124Srafan   By  default,  if  you enter such a prefix and it matches more than one
1740166124Srafan   value  in  the  string list, the prefix will be completed to the first
174176726Speter   matching value. But the checkunique argument, if true, requires prefix
174276726Speter   matches to be unique in order to be valid.
1743166124Srafan
1744166124Srafan   The   REQ_NEXT_CHOICE   and  REQ_PREV_CHOICE  input  requests  can  be
174576726Speter   particularly useful with these fields.
1746166124Srafan
174776726Speter  TYPE_INTEGER
1748166124Srafan
174976726Speter   This field type accepts an integer. It is set up as follows:
175076726Speterint set_field_type(FIELD *field,          /* field to alter */
175176726Speter                   TYPE_INTEGER,          /* type to associate */
175276726Speter                   int padding,           /* # places to zero-pad to */
175376726Speter                   int vmin, int vmax);   /* valid range */
175476726Speter
1755166124Srafan   Valid  characters consist of an optional leading minus and digits. The
175676726Speter   range check is performed on exit. If the range maximum is less than or
175776726Speter   equal to the minimum, the range is ignored.
1758166124Srafan
175976726Speter   If the value passes its range check, it is padded with as many leading
176076726Speter   zero digits as necessary to meet the padding argument.
1761166124Srafan
176276726Speter   A TYPE_INTEGER value buffer can conveniently be interpreted with the C
176376726Speter   library function atoi(3).
1764166124Srafan
176576726Speter  TYPE_NUMERIC
1766166124Srafan
176776726Speter   This field type accepts a decimal number. It is set up as follows:
176876726Speterint set_field_type(FIELD *field,              /* field to alter */
176976726Speter                   TYPE_NUMERIC,              /* type to associate */
177076726Speter                   int padding,               /* # places of precision */
177176726Speter                   double vmin, double vmax); /* valid range */
177276726Speter
1773166124Srafan   Valid  characters  consist  of  an  optional leading minus and digits.
1774166124Srafan   possibly  including a decimal point. If your system supports locale's,
1775166124Srafan   the  decimal  point  character  used  must  be the one defined by your
1776166124Srafan   locale.  The range check is performed on exit. If the range maximum is
177776726Speter   less than or equal to the minimum, the range is ignored.
1778166124Srafan
1779166124Srafan   If  the  value  passes  its  range  check,  it  is padded with as many
178076726Speter   trailing zero digits as necessary to meet the padding argument.
1781166124Srafan
178276726Speter   A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
178376726Speter   library function atof(3).
1784166124Srafan
178576726Speter  TYPE_REGEXP
1786166124Srafan
1787166124Srafan   This  field type accepts data matching a regular expression. It is set
178876726Speter   up as follows:
178976726Speterint set_field_type(FIELD *field,          /* field to alter */
179076726Speter                   TYPE_REGEXP,           /* type to associate */
179176726Speter                   char *regexp);         /* expression to match */
179276726Speter
1793166124Srafan   The  syntax  for  regular expressions is that of regcomp(3). The check
179476726Speter   for regular-expression match is performed on exit.
1795166124Srafan
179676726SpeterDirect Field Buffer Manipulation
179776726Speter
179876726Speter   The chief attribute of a field is its buffer contents. When a form has
1799166124Srafan   been  completed,  your  application usually needs to know the state of
180076726Speter   each field buffer. You can find this out with:
180176726Speterchar *field_buffer(FIELD *field,          /* field to query */
180276726Speter                   int bufindex);         /* number of buffer to query */
180376726Speter
1804166124Srafan   Normally,  the state of the zero-numbered buffer for each field is set
1805166124Srafan   by  the user's editing actions on that field. It's sometimes useful to
1806166124Srafan   be  able  to set the value of the zero-numbered (or some other) buffer
180776726Speter   from your application:
180876726Speterint set_field_buffer(FIELD *field,        /* field to alter */
180976726Speter                   int bufindex,          /* number of buffer to alter */
181076726Speter                   char *value);          /* string value to set */
181176726Speter
1812166124Srafan   If  the  field  is  not  large  enough  and  cannot  be  resized  to a
181376726Speter   sufficiently large size to contain the specified value, the value will
181476726Speter   be truncated to fit.
1815166124Srafan
1816166124Srafan   Calling  field_buffer() with a null field pointer will raise an error.
1817166124Srafan   Calling  field_buffer()  on  a  field not currently selected for input
181876726Speter   will return a correct value. Calling field_buffer() on a field that is
1819166124Srafan   currently  selected for input may not necessarily give a correct field
1820166124Srafan   buffer  value, because entered data isn't necessarily copied to buffer
1821166124Srafan   zero  before the exit validation check. To guarantee that the returned
1822166124Srafan   buffer  value  reflects  on-screen reality, call field_buffer() either
182376726Speter   (1) in the field's exit validation check routine, (2) from the field's
1824166124Srafan   or  form's  initialization  or  termination hooks, or (3) just after a
182576726Speter   REQ_VALIDATION request has been processed by the forms driver.
1826166124Srafan
182776726SpeterAttributes of Forms
182876726Speter
1829166124Srafan   As  with  field  attributes,  form attributes inherit a default from a
183076726Speter   system default form structure. These defaults can be queried or set by
183176726Speter   of these functions using a form-pointer argument of NULL.
1832166124Srafan
183376726Speter   The principal attribute of a form is its field list. You can query and
183476726Speter   change this list with:
183576726Speterint set_form_fields(FORM *form,           /* form to alter */
183676726Speter                    FIELD **fields);      /* fields to connect */
183776726Speter
183876726Speterchar *form_fields(FORM *form);            /* fetch fields of form */
183976726Speter
184076726Speterint field_count(FORM *form);              /* count connect fields */
184176726Speter
1842166124Srafan   The  second  argument  of  set_form_fields()  may be a NULL-terminated
184376726Speter   field pointer array like the one required by new_form(). In that case,
1844166124Srafan   the  old  fields  of  the  form  are  disconnected  but not freed (and
1845166124Srafan   eligible  to  be  connected  to  other forms), then the new fields are
184676726Speter   connected.
1847166124Srafan
1848166124Srafan   It  may  also  be  null, in which case the old fields are disconnected
184976726Speter   (and not freed) but no new ones are connected.
1850166124Srafan
1851166124Srafan   The   field_count()  function  simply  counts  the  number  of  fields
1852166124Srafan   connected  to a given from. It returns -1 if the form-pointer argument
185376726Speter   is NULL.
1854166124Srafan
185576726SpeterControl of Form Display
185676726Speter
1857166124Srafan   In  the  overview section, you saw that to display a form you normally
1858166124Srafan   start  by  defining  its size (and fields), posting it, and refreshing
1859166124Srafan   the  screen.  There  is  an  hidden  step before posting, which is the
1860166124Srafan   association  of  the  form  with  a  frame window (actually, a pair of
1861166124Srafan   windows)  within  which  it  will  be displayed. By default, the forms
186276726Speter   library associates every form with the full-screen window stdscr.
1863166124Srafan
186476726Speter   By making this step explicit, you can associate a form with a declared
186576726Speter   frame window on your screen display. This can be useful if you want to
1866166124Srafan   adapt  the  form  display  to different screen sizes, dynamically tile
1867166124Srafan   forms  on  the  screen,  or  use a form as part of an interface layout
186876726Speter   managed by panels.
1869166124Srafan
1870166124Srafan   The  two  windows associated with each form have the same functions as
1871166124Srafan   their  analogues  in  the menu library. Both these windows are painted
187276726Speter   when the form is posted and erased when the form is unposted.
1873166124Srafan
1874166124Srafan   The  outer  or  frame  window  is  not  otherwise  touched by the form
187576726Speter   routines. It exists so the programmer can associate a title, a border,
1876166124Srafan   or  perhaps  help text with the form and have it properly refreshed or
187776726Speter   erased at post/unpost time. The inner window or subwindow is where the
187876726Speter   current form page is actually displayed.
1879166124Srafan
1880166124Srafan   In  order  to declare your own frame window for a form, you'll need to
1881166124Srafan   know  the  size  of  the  form's  bounding rectangle. You can get this
188276726Speter   information with:
188376726Speterint scale_form(FORM *form,                /* form to query */
188476726Speter               int *rows,                 /* form rows */
188576726Speter               int *cols);                /* form cols */
188676726Speter
188776726Speter   The form dimensions are passed back in the locations pointed to by the
1888166124Srafan   arguments.  Once  you have this information, you can use it to declare
188976726Speter   of windows, then use one of these functions:
189076726Speterint set_form_win(FORM *form,              /* form to alter */
189176726Speter                 WINDOW *win);            /* frame window to connect */
189276726Speter
189376726SpeterWINDOW *form_win(FORM *form);             /* fetch frame window of form */
189476726Speter
189576726Speterint set_form_sub(FORM *form,              /* form to alter */
189676726Speter                 WINDOW *win);            /* form subwindow to connect */
189776726Speter
189876726SpeterWINDOW *form_sub(FORM *form);             /* fetch form subwindow of form */
189976726Speter
1900166124Srafan   Note  that curses operations, including refresh(), on the form, should
190176726Speter   be done on the frame window, not the form subwindow.
1902166124Srafan
1903166124Srafan   It  is  possible  to  check  from  your  application  whether all of a
1904166124Srafan   scrollable  field is actually displayed within the menu subwindow. Use
190576726Speter   these functions:
190676726Speterint data_ahead(FORM *form);               /* form to be queried */
190776726Speter
190876726Speterint data_behind(FORM *form);              /* form to be queried */
190976726Speter
1910166124Srafan   The  function  data_ahead()  returns  TRUE if (a) the current field is
1911166124Srafan   one-line  and  has  undisplayed data off to the right, (b) the current
191276726Speter   field is multi-line and there is data off-screen below it.
1913166124Srafan
191476726Speter   The function data_behind() returns TRUE if the first (upper left hand)
191576726Speter   character position is off-screen (not being displayed).
1916166124Srafan
1917166124Srafan   Finally,  there  is  a function to restore the form window's cursor to
191876726Speter   the value expected by the forms driver:
191976726Speterint pos_form_cursor(FORM *)               /* form to be queried */
192076726Speter
192176726Speter   If your application changes the form window cursor, call this function
1922166124Srafan   before   handing  control  back  to  the  forms  driver  in  order  to
192376726Speter   re-synchronize it.
1924166124Srafan
192576726SpeterInput Processing in the Forms Driver
192676726Speter
192776726Speter   The function form_driver() handles virtualized input requests for form
192876726Speter   navigation, editing, and validation requests, just as menu_driver does
192976726Speter   for menus (see the section on menu input handling).
193076726Speterint form_driver(FORM *form,               /* form to pass input to */
193176726Speter                int request);             /* form request code */
193276726Speter
1933166124Srafan   Your  input  virtualization  function  needs  to  take  input and then
1934166124Srafan   convert  it  to  either an alphanumeric character (which is treated as
1935166124Srafan   data  to  be  entered  in  the  currently-selected  field), or a forms
193676726Speter   processing request.
1937166124Srafan
1938166124Srafan   The   forms   driver  provides  hooks  (through  input-validation  and
1939166124Srafan   field-termination  functions)  with  which  your  application code can
194076726Speter   check that the input taken by the driver matched what was expected.
1941166124Srafan
194276726Speter  Page Navigation Requests
1943166124Srafan
1944166124Srafan   These  requests  cause  page-level  moves through the form, triggering
194576726Speter   display of a new form screen.
1946166124Srafan
194776726Speter   REQ_NEXT_PAGE
194876726Speter          Move to the next form page.
1949166124Srafan
195076726Speter   REQ_PREV_PAGE
195176726Speter          Move to the previous form page.
1952166124Srafan
195376726Speter   REQ_FIRST_PAGE
195476726Speter          Move to the first form page.
1955166124Srafan
195676726Speter   REQ_LAST_PAGE
195776726Speter          Move to the last form page.
1958166124Srafan
1959166124Srafan   These  requests  treat the list as cyclic; that is, REQ_NEXT_PAGE from
196076726Speter   the last page goes to the first, and REQ_PREV_PAGE from the first page
196176726Speter   goes to the last.
1962166124Srafan
196376726Speter  Inter-Field Navigation Requests
1964166124Srafan
196576726Speter   These requests handle navigation between fields on the same page.
1966166124Srafan
196776726Speter   REQ_NEXT_FIELD
196876726Speter          Move to next field.
1969166124Srafan
197076726Speter   REQ_PREV_FIELD
197176726Speter          Move to previous field.
1972166124Srafan
197376726Speter   REQ_FIRST_FIELD
197476726Speter          Move to the first field.
1975166124Srafan
197676726Speter   REQ_LAST_FIELD
197776726Speter          Move to the last field.
1978166124Srafan
197976726Speter   REQ_SNEXT_FIELD
198076726Speter          Move to sorted next field.
1981166124Srafan
198276726Speter   REQ_SPREV_FIELD
198376726Speter          Move to sorted previous field.
1984166124Srafan
198576726Speter   REQ_SFIRST_FIELD
198676726Speter          Move to the sorted first field.
1987166124Srafan
198876726Speter   REQ_SLAST_FIELD
198976726Speter          Move to the sorted last field.
1990166124Srafan
199176726Speter   REQ_LEFT_FIELD
199276726Speter          Move left to field.
1993166124Srafan
199476726Speter   REQ_RIGHT_FIELD
199576726Speter          Move right to field.
1996166124Srafan
199776726Speter   REQ_UP_FIELD
199876726Speter          Move up to field.
1999166124Srafan
200076726Speter   REQ_DOWN_FIELD
200176726Speter          Move down to field.
2002166124Srafan
2003166124Srafan   These  requests treat the list of fields on a page as cyclic; that is,
2004166124Srafan   REQ_NEXT_FIELD   from   the   last   field  goes  to  the  first,  and
200576726Speter   REQ_PREV_FIELD from the first field goes to the last. The order of the
200676726Speter   fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests)
200776726Speter   is simply the order of the field pointers in the form array (as set up
200876726Speter   by new_form() or set_form_fields()
2009166124Srafan
2010166124Srafan   It  is also possible to traverse the fields as if they had been sorted
2011166124Srafan   in  screen-position  order,  so  the  sequence  goes left-to-right and
2012166124Srafan   top-to-bottom.   To   do   this,   use   the   second  group  of  four
201376726Speter   sorted-movement requests.
2014166124Srafan
201576726Speter   Finally, it is possible to move between fields using visual directions
2016166124Srafan   up,  down, right, and left. To accomplish this, use the third group of
201776726Speter   four requests. Note, however, that the position of a form for purposes
201876726Speter   of these requests is its upper-left corner.
2019166124Srafan
2020166124Srafan   For   example,  suppose  you  have  a  multi-line  field  B,  and  two
202176726Speter   single-line fields A and C on the same line with B, with A to the left
2022166124Srafan   of  B  and  C  to the right of B. A REQ_MOVE_RIGHT from A will go to B
2023166124Srafan   only  if  A, B, and C all share the same first line; otherwise it will
202476726Speter   skip over B to C.
2025166124Srafan
202676726Speter  Intra-Field Navigation Requests
2027166124Srafan
2028166124Srafan   These  requests drive movement of the edit cursor within the currently
202976726Speter   selected field.
2030166124Srafan
203176726Speter   REQ_NEXT_CHAR
203276726Speter          Move to next character.
2033166124Srafan
203476726Speter   REQ_PREV_CHAR
203576726Speter          Move to previous character.
2036166124Srafan
203776726Speter   REQ_NEXT_LINE
203876726Speter          Move to next line.
2039166124Srafan
204076726Speter   REQ_PREV_LINE
204176726Speter          Move to previous line.
2042166124Srafan
204376726Speter   REQ_NEXT_WORD
204476726Speter          Move to next word.
2045166124Srafan
204676726Speter   REQ_PREV_WORD
204776726Speter          Move to previous word.
2048166124Srafan
204976726Speter   REQ_BEG_FIELD
205076726Speter          Move to beginning of field.
2051166124Srafan
205276726Speter   REQ_END_FIELD
205376726Speter          Move to end of field.
2054166124Srafan
205576726Speter   REQ_BEG_LINE
205676726Speter          Move to beginning of line.
2057166124Srafan
205876726Speter   REQ_END_LINE
205976726Speter          Move to end of line.
2060166124Srafan
206176726Speter   REQ_LEFT_CHAR
206276726Speter          Move left in field.
2063166124Srafan
206476726Speter   REQ_RIGHT_CHAR
206576726Speter          Move right in field.
2066166124Srafan
206776726Speter   REQ_UP_CHAR
206876726Speter          Move up in field.
2069166124Srafan
207076726Speter   REQ_DOWN_CHAR
207176726Speter          Move down in field.
2072166124Srafan
2073166124Srafan   Each  word  is  separated  from  the  previous  and next characters by
207476726Speter   whitespace. The commands to move to beginning and end of line or field
207576726Speter   look for the first or last non-pad character in their ranges.
2076166124Srafan
207776726Speter  Scrolling Requests
2078166124Srafan
2079166124Srafan   Fields  that  are dynamic and have grown and fields explicitly created
2080166124Srafan   with   offscreen   rows   are   scrollable.   One-line  fields  scroll
2081166124Srafan   horizontally;  multi-line  fields scroll vertically. Most scrolling is
208276726Speter   triggered by editing and intra-field movement (the library scrolls the
2083166124Srafan   field  to  keep  the  cursor  visible).  It  is possible to explicitly
208476726Speter   request scrolling with the following requests:
2085166124Srafan
208676726Speter   REQ_SCR_FLINE
208776726Speter          Scroll vertically forward a line.
2088166124Srafan
208976726Speter   REQ_SCR_BLINE
209076726Speter          Scroll vertically backward a line.
2091166124Srafan
209276726Speter   REQ_SCR_FPAGE
209376726Speter          Scroll vertically forward a page.
2094166124Srafan
209576726Speter   REQ_SCR_BPAGE
209676726Speter          Scroll vertically backward a page.
2097166124Srafan
209876726Speter   REQ_SCR_FHPAGE
209976726Speter          Scroll vertically forward half a page.
2100166124Srafan
210176726Speter   REQ_SCR_BHPAGE
210276726Speter          Scroll vertically backward half a page.
2103166124Srafan
210476726Speter   REQ_SCR_FCHAR
210576726Speter          Scroll horizontally forward a character.
2106166124Srafan
210776726Speter   REQ_SCR_BCHAR
210876726Speter          Scroll horizontally backward a character.
2109166124Srafan
211076726Speter   REQ_SCR_HFLINE
211176726Speter          Scroll horizontally one field width forward.
2112166124Srafan
211376726Speter   REQ_SCR_HBLINE
211476726Speter          Scroll horizontally one field width backward.
2115166124Srafan
211676726Speter   REQ_SCR_HFHALF
211776726Speter          Scroll horizontally one half field width forward.
2118166124Srafan
211976726Speter   REQ_SCR_HBHALF
212076726Speter          Scroll horizontally one half field width backward.
2121166124Srafan
212276726Speter   For scrolling purposes, a page of a field is the height of its visible
212376726Speter   part.
2124166124Srafan
212576726Speter  Editing Requests
2126166124Srafan
2127166124Srafan   When  you pass the forms driver an ASCII character, it is treated as a
2128166124Srafan   request  to add the character to the field's data buffer. Whether this
2129166124Srafan   is  an  insertion  or  a  replacement depends on the field's edit mode
213076726Speter   (insertion is the default.
2131166124Srafan
213276726Speter   The following requests support editing the field and changing the edit
213376726Speter   mode:
2134166124Srafan
213576726Speter   REQ_INS_MODE
213676726Speter          Set insertion mode.
2137166124Srafan
213876726Speter   REQ_OVL_MODE
213976726Speter          Set overlay mode.
2140166124Srafan
214176726Speter   REQ_NEW_LINE
214276726Speter          New line request (see below for explanation).
2143166124Srafan
214476726Speter   REQ_INS_CHAR
214576726Speter          Insert space at character location.
2146166124Srafan
214776726Speter   REQ_INS_LINE
214876726Speter          Insert blank line at character location.
2149166124Srafan
215076726Speter   REQ_DEL_CHAR
215176726Speter          Delete character at cursor.
2152166124Srafan
215376726Speter   REQ_DEL_PREV
215476726Speter          Delete previous word at cursor.
2155166124Srafan
215676726Speter   REQ_DEL_LINE
215776726Speter          Delete line at cursor.
2158166124Srafan
215976726Speter   REQ_DEL_WORD
216076726Speter          Delete word at cursor.
2161166124Srafan
216276726Speter   REQ_CLR_EOL
216376726Speter          Clear to end of line.
2164166124Srafan
216576726Speter   REQ_CLR_EOF
216676726Speter          Clear to end of field.
2167166124Srafan
216876726Speter   REQ_CLEAR_FIELD
216976726Speter          Clear entire field.
2170166124Srafan
2171166124Srafan   The   behavior  of  the  REQ_NEW_LINE  and  REQ_DEL_PREV  requests  is
2172166124Srafan   complicated  and  partly  controlled  by  a pair of forms options. The
2173166124Srafan   special  cases  are triggered when the cursor is at the beginning of a
217476726Speter   field, or on the last line of the field.
2175166124Srafan
217676726Speter   First, we consider REQ_NEW_LINE:
2177166124Srafan
2178166124Srafan   The  normal  behavior  of  REQ_NEW_LINE in insert mode is to break the
217976726Speter   current line at the position of the edit cursor, inserting the portion
2180166124Srafan   of  the  current  line  after  the  cursor as a new line following the
2181166124Srafan   current  and  moving the cursor to the beginning of that new line (you
218276726Speter   may think of this as inserting a newline in the field buffer).
2183166124Srafan
2184166124Srafan   The  normal  behavior  of REQ_NEW_LINE in overlay mode is to clear the
2185166124Srafan   current  line from the position of the edit cursor to end of line. The
218676726Speter   cursor is then moved to the beginning of the next line.
2187166124Srafan
218876726Speter   However, REQ_NEW_LINE at the beginning of a field, or on the last line
2189166124Srafan   of  a  field,  instead  does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is
219076726Speter   off, this special action is disabled.
2191166124Srafan
219276726Speter   Now, let us consider REQ_DEL_PREV:
2193166124Srafan
2194166124Srafan   The  normal  behavior  of  REQ_DEL_PREV  is  to  delete  the  previous
2195166124Srafan   character.  If  insert mode is on, and the cursor is at the start of a
2196166124Srafan   line,  and  the  text  on  that  line will fit on the previous one, it
2197166124Srafan   instead  appends  the contents of the current line to the previous one
2198166124Srafan   and  deletes  the  current  line  (you may think of this as deleting a
219976726Speter   newline from the field buffer).
2200166124Srafan
2201166124Srafan   However,  REQ_DEL_PREV  at the beginning of a field is instead treated
220276726Speter   as a REQ_PREV_FIELD.
2203166124Srafan
2204166124Srafan   If  the  O_BS_OVERLOAD  option is off, this special action is disabled
220576726Speter   and the forms driver just returns E_REQUEST_DENIED.
2206166124Srafan
2207166124Srafan   See  Form  Options for discussion of how to set and clear the overload
220876726Speter   options.
2209166124Srafan
221076726Speter  Order Requests
2211166124Srafan
221276726Speter   If the type of your field is ordered, and has associated functions for
2213166124Srafan   getting  the  next and previous values of the type from a given value,
221476726Speter   there are requests that can fetch that value into the field buffer:
2215166124Srafan
221676726Speter   REQ_NEXT_CHOICE
221776726Speter          Place the successor value of the current value in the buffer.
2218166124Srafan
221976726Speter   REQ_PREV_CHOICE
222076726Speter          Place the predecessor value of the current value in the buffer.
2221166124Srafan
222276726Speter   Of the built-in field types, only TYPE_ENUM has built-in successor and
2223166124Srafan   predecessor  functions.  When you define a field type of your own (see
2224166124Srafan   Custom   Validation   Types),  you  can  associate  our  own  ordering
222576726Speter   functions.
2226166124Srafan
222776726Speter  Application Commands
2228166124Srafan
2229166124Srafan   Form  requests  are  represented  as  integers  above the curses value
2230166124Srafan   greater   than  KEY_MAX  and  less  than  or  equal  to  the  constant
2231166124Srafan   MAX_COMMAND.  If  your  input-virtualization  routine  returns a value
223276726Speter   above MAX_COMMAND, the forms driver will ignore it.
2233166124Srafan
223476726SpeterField Change Hooks
223576726Speter
2236166124Srafan   It  is  possible  to  set  function  hooks to be executed whenever the
2237166124Srafan   current  field  or  form  changes. Here are the functions that support
223876726Speter   this:
223976726Spetertypedef void    (*HOOK)();       /* pointer to function returning void */
224076726Speter
224176726Speterint set_form_init(FORM *form,    /* form to alter */
224276726Speter                  HOOK hook);    /* initialization hook */
224376726Speter
224476726SpeterHOOK form_init(FORM *form);      /* form to query */
224576726Speter
224676726Speterint set_form_term(FORM *form,    /* form to alter */
224776726Speter                  HOOK hook);    /* termination hook */
224876726Speter
224976726SpeterHOOK form_term(FORM *form);      /* form to query */
225076726Speter
225176726Speterint set_field_init(FORM *form,   /* form to alter */
225276726Speter                  HOOK hook);    /* initialization hook */
225376726Speter
225476726SpeterHOOK field_init(FORM *form);     /* form to query */
225576726Speter
225676726Speterint set_field_term(FORM *form,   /* form to alter */
225776726Speter                  HOOK hook);    /* termination hook */
225876726Speter
225976726SpeterHOOK field_term(FORM *form);     /* form to query */
226076726Speter
226176726Speter   These functions allow you to either set or query four different hooks.
2262166124Srafan   In  each  of  the  set  functions,  the  second argument should be the
2263166124Srafan   address  of a hook function. These functions differ only in the timing
226476726Speter   of the hook call.
2265166124Srafan
226676726Speter   form_init
2267166124Srafan          This  hook  is called when the form is posted; also, just after
226876726Speter          each page change operation.
2269166124Srafan
227076726Speter   field_init
2271166124Srafan          This  hook  is called when the form is posted; also, just after
227276726Speter          each field change
2273166124Srafan
227476726Speter   field_term
2275166124Srafan          This  hook is called just after field validation; that is, just
227676726Speter          before the field is altered. It is also called when the form is
227776726Speter          unposted.
2278166124Srafan
227976726Speter   form_term
2280166124Srafan          This  hook  is  called  when  the  form is unposted; also, just
228176726Speter          before each page change operation.
2282166124Srafan
228376726Speter   Calls to these hooks may be triggered
228476726Speter    1. When user editing requests are processed by the forms driver
228576726Speter    2. When the current page is changed by set_current_field() call
228676726Speter    3. When the current field is changed by a set_form_page() call
2287166124Srafan
228876726Speter   See Field Change Commands for discussion of the latter two cases.
2289166124Srafan
2290166124Srafan   You  can  set  a default hook for all fields by passing one of the set
229176726Speter   functions a NULL first argument.
2292166124Srafan
2293166124Srafan   You  can  disable  any of these hooks by (re)setting them to NULL, the
229476726Speter   default value.
2295166124Srafan
229676726SpeterField Change Commands
229776726Speter
2298166124Srafan   Normally,  navigation  through  the  form will be driven by the user's
2299166124Srafan   input  requests.  But  sometimes  it  is useful to be able to move the
2300166124Srafan   focus  for  editing  and viewing under control of your application, or
2301166124Srafan   ask  which  field it currently is in. The following functions help you
230276726Speter   accomplish this:
230376726Speterint set_current_field(FORM *form,         /* form to alter */
230476726Speter                      FIELD *field);      /* field to shift to */
230576726Speter
230676726SpeterFIELD *current_field(FORM *form);         /* form to query */
230776726Speter
230876726Speterint field_index(FORM *form,               /* form to query */
230976726Speter                FIELD *field);            /* field to get index of */
231076726Speter
231176726Speter   The function field_index() returns the index of the given field in the
2312166124Srafan   given   form's   field  array  (the  array  passed  to  new_form()  or
231376726Speter   set_form_fields()).
2314166124Srafan
2315166124Srafan   The  initial  current field of a form is the first active field on the
231676726Speter   first page. The function set_form_fields() resets this.
2317166124Srafan
231876726Speter   It is also possible to move around by pages.
231976726Speterint set_form_page(FORM *form,             /* form to alter */
232076726Speter                  int page);              /* page to go to (0-origin) */
232176726Speter
232276726Speterint form_page(FORM *form);                /* return form's current page */
232376726Speter
2324166124Srafan   The   initial  page  of  a  newly-created  form  is  0.  The  function
232576726Speter   set_form_fields() resets this.
2326166124Srafan
232776726SpeterForm Options
232876726Speter
2329166124Srafan   Like  fields,  forms may have control option bits. They can be changed
233076726Speter   or queried with these functions:
233176726Speterint set_form_opts(FORM *form,             /* form to alter */
233276726Speter                  int attr);              /* attribute to set */
233376726Speter
233476726Speterint form_opts_on(FORM *form,              /* form to alter */
233576726Speter                 int attr);               /* attributes to turn on */
233676726Speter
233776726Speterint form_opts_off(FORM *form,             /* form to alter */
233876726Speter                  int attr);              /* attributes to turn off */
233976726Speter
234076726Speterint form_opts(FORM *form);                /* form to query */
234176726Speter
234276726Speter   By default, all options are on. Here are the available option bits:
2343166124Srafan
234476726Speter   O_NL_OVERLOAD
2345166124Srafan          Enable  overloading  of  REQ_NEW_LINE  as  described in Editing
234676726Speter          Requests. The value of this option is ignored on dynamic fields
2347166124Srafan          that  have  not  reached  their  size limit; these have no last
2348166124Srafan          line,  so  the  circumstances  for  triggering a REQ_NEXT_FIELD
234976726Speter          never arise.
2350166124Srafan
235176726Speter   O_BS_OVERLOAD
2352166124Srafan          Enable  overloading  of  REQ_DEL_PREV  as  described in Editing
235376726Speter          Requests.
2354166124Srafan
235576726Speter   The option values are bit-masks and can be composed with logical-or in
235676726Speter   the obvious way.
2357166124Srafan
235876726SpeterCustom Validation Types
235976726Speter
2360166124Srafan   The  form library gives you the capability to define custom validation
2361166124Srafan   types  of  your  own.  Further,  the  optional additional arguments of
236276726Speter   set_field_type effectively allow you to parameterize validation types.
2363166124Srafan   Most  of the complications in the validation-type interface have to do
236476726Speter   with the handling of the additional arguments within custom validation
236576726Speter   functions.
2366166124Srafan
236776726Speter  Union Types
2368166124Srafan
2369166124Srafan   The  simplest  way  to create a custom data type is to compose it from
237076726Speter   two preexisting ones:
237176726SpeterFIELD *link_fieldtype(FIELDTYPE *type1,
237276726Speter                      FIELDTYPE *type2);
237376726Speter
2374166124Srafan   This  function creates a field type that will accept any of the values
2375166124Srafan   legal  for  either  of  its  argument field types (which may be either
2376166124Srafan   predefined  or  programmer-defined).  If a set_field_type() call later
2377166124Srafan   requires  arguments,  the new composite type expects all arguments for
2378166124Srafan   the  first  type,  than  all arguments for the second. Order functions
2379166124Srafan   (see  Order Requests) associated with the component types will work on
2380166124Srafan   the  composite;  what it does is check the validation function for the
2381166124Srafan   first  type,  then  for  the  second,  to  figure what type the buffer
238276726Speter   contents should be treated as.
2383166124Srafan
238476726Speter  New Field Types
2385166124Srafan
2386166124Srafan   To  create  a field type from scratch, you need to specify one or both
238776726Speter   of the following things:
2388166124Srafan     * A  character-validation function, to check each character as it is
238976726Speter       entered.
239076726Speter     * A field-validation function to be applied on exit from the field.
2391166124Srafan
239276726Speter   Here's how you do that:
239376726Spetertypedef int     (*HOOK)();       /* pointer to function returning int */
239476726Speter
239576726SpeterFIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
239676726Speter                         HOOK c_validate) /* character validator */
239776726Speter
239876726Speter
239976726Speterint free_fieldtype(FIELDTYPE *ftype);     /* type to free */
240076726Speter
240176726Speter   At least one of the arguments of new_fieldtype() must be non-NULL. The
2402166124Srafan   forms  driver  will  automatically  call  the  new  type's  validation
240376726Speter   functions at appropriate points in processing a field of the new type.
2404166124Srafan
2405166124Srafan   The  function  free_fieldtype()  deallocates  the  argument fieldtype,
240676726Speter   freeing all storage associated with it.
2407166124Srafan
2408166124Srafan   Normally,  a field validator is called when the user attempts to leave
2409166124Srafan   the  field.  Its  first argument is a field pointer, from which it can
2410166124Srafan   get  to  field buffer 0 and test it. If the function returns TRUE, the
2411166124Srafan   operation  succeeds; if it returns FALSE, the edit cursor stays in the
241276726Speter   field.
2413166124Srafan
2414166124Srafan   A  character  validator  gets  the  character  passed  in  as  a first
2415166124Srafan   argument.  It  too should return TRUE if the character is valid, FALSE
241676726Speter   otherwise.
2417166124Srafan
241876726Speter  Validation Function Arguments
2419166124Srafan
2420166124Srafan   Your  field-  and  character-  validation  functions  will be passed a
2421166124Srafan   second  argument  as  well.  This  second argument is the address of a
2422166124Srafan   structure   (which   we'll   call  a  pile)  built  from  any  of  the
2423166124Srafan   field-type-specific  arguments  passed to set_field_type(). If no such
2424166124Srafan   arguments  are  defined for the field type, this pile pointer argument
242576726Speter   will be NULL.
2426166124Srafan
242776726Speter   In order to arrange for such arguments to be passed to your validation
2428166124Srafan   functions,  you  must  associate  a  small  set  of storage-management
242976726Speter   functions with the type. The forms driver will use these to synthesize
2430166124Srafan   a  pile from the trailing arguments of each set_field_type() argument,
243176726Speter   and a pointer to the pile will be passed to the validation functions.
2432166124Srafan
243376726Speter   Here is how you make the association:
243476726Spetertypedef char    *(*PTRHOOK)();    /* pointer to function returning (char *) */
243576726Spetertypedef void    (*VOIDHOOK)();    /* pointer to function returning void */
243676726Speter
243776726Speterint set_fieldtype_arg(FIELDTYPE *type,    /* type to alter */
243876726Speter                      PTRHOOK make_str,   /* make structure from args */
243976726Speter                      PTRHOOK copy_str,   /* make copy of structure */
244076726Speter                      VOIDHOOK free_str); /* free structure storage */
244176726Speter
244276726Speter   Here is how the storage-management hooks are used:
2443166124Srafan
244476726Speter   make_str
2445166124Srafan          This  function  is  called  by  set_field_type().  It  gets one
2446166124Srafan          argument,  a  va_list  of the type-specific arguments passed to
2447166124Srafan          set_field_type().  It is expected to return a pile pointer to a
244876726Speter          data structure that encapsulates those arguments.
2449166124Srafan
245076726Speter   copy_str
245176726Speter          This function is called by form library functions that allocate
2452166124Srafan          new  field  instances.  It  is expected to take a pile pointer,
2453166124Srafan          copy  the  pile to allocated storage, and return the address of
245476726Speter          the pile copy.
2455166124Srafan
245676726Speter   free_str
2457166124Srafan          This   function  is  called  by  field-  and  type-deallocation
2458166124Srafan          routines  in the library. It takes a pile pointer argument, and
245976726Speter          is expected to free the storage of that pile.
2460166124Srafan
2461166124Srafan   The  make_str  and  copy_str  functions  may  return  NULL  to  signal
2462166124Srafan   allocation  failure.  The  library  routines  will that call them will
2463166124Srafan   return  error  indication  when  this  happens.  Thus, your validation
2464166124Srafan   functions  should  never  see  a  NULL file pointer and need not check
246576726Speter   specially for it.
2466166124Srafan
246776726Speter  Order Functions For Custom Types
2468166124Srafan
2469166124Srafan   Some  custom  field  types are simply ordered in the same well-defined
2470166124Srafan   way  that  TYPE_ENUM  is.  For  such  types,  it is possible to define
247176726Speter   successor and predecessor functions to support the REQ_NEXT_CHOICE and
247276726Speter   REQ_PREV_CHOICE requests. Here's how:
247376726Spetertypedef int     (*INTHOOK)();     /* pointer to function returning int */
247476726Speter
247576726Speterint set_fieldtype_arg(FIELDTYPE *type,    /* type to alter */
247676726Speter                      INTHOOK succ,       /* get successor value */
247776726Speter                      INTHOOK pred);      /* get predecessor value */
247876726Speter
2479166124Srafan   The  successor  and  predecessor  arguments  will  each  be passed two
2480166124Srafan   arguments;  a field pointer, and a pile pointer (as for the validation
2481166124Srafan   functions).  They  are  expected to use the function field_buffer() to
2482166124Srafan   read  the current value, and set_field_buffer() on buffer 0 to set the
2483166124Srafan   next  or  previous  value.  Either  hook  may  return TRUE to indicate
2484166124Srafan   success  (a legal next or previous value was set) or FALSE to indicate
248576726Speter   failure.
2486166124Srafan
248776726Speter  Avoiding Problems
2488166124Srafan
2489166124Srafan   The  interface  for  defining  custom types is complicated and tricky.
2490166124Srafan   Rather  than attempting to create a custom type entirely from scratch,
2491166124Srafan   you  should start by studying the library source code for whichever of
249276726Speter   the pre-defined types seems to be closest to what you want.
2493166124Srafan
2494166124Srafan   Use  that code as a model, and evolve it towards what you really want.
2495166124Srafan   You  will avoid many problems and annoyances that way. The code in the
2496166124Srafan   ncurses  library  has  been  specifically  exempted  from  the package
249776726Speter   copyright to support this.
2498166124Srafan
2499166124Srafan   If  your  custom  type  defines  order  functions,  have  do something
2500166124Srafan   intuitive  with  a  blank  field.  A  useful convention is to make the
2501166124Srafan   successor   of  a  blank  field  the  types  minimum  value,  and  its
250276726Speter   predecessor the maximum.
2503