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31 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
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36 "HTML Tidy for Linux (vers 25 March 2009), see www.w3.org">
38 <title>Writing Programs with NCURSES</title>
39 <link rev="made" href="mailto:bugs-ncurses@gnu.org">
40 <meta http-equiv="Content-Type" content=
41 "text/html; charset=us-ascii">
45 <h1>Writing Programs with NCURSES</h1>
48 by Eric S. Raymond and Zeyd M. Ben-Halim<br>
49 updates since release 1.9.9e by Thomas Dickey
56 <a href="#introduction">Introduction</a>
59 <li><a href="#history">A Brief History of Curses</a></li>
61 <li><a href="#scope">Scope of This Document</a></li>
63 <li><a href="#terminology">Terminology</a></li>
68 <a href="#curses">The Curses Library</a>
72 <a href="#overview">An Overview of Curses</a>
75 <li><a href="#compiling">Compiling Programs using
78 <li><a href="#updating">Updating the Screen</a></li>
80 <li><a href="#stdscr">Standard Windows and Function
81 Naming Conventions</a></li>
83 <li><a href="#variables">Variables</a></li>
88 <a href="#using">Using the Library</a>
91 <li><a href="#starting">Starting up</a></li>
93 <li><a href="#output">Output</a></li>
95 <li><a href="#input">Input</a></li>
97 <li><a href="#formschars">Using Forms
100 <li><a href="#attributes">Character Attributes and
103 <li><a href="#mouse">Mouse Interfacing</a></li>
105 <li><a href="#finishing">Finishing Up</a></li>
110 <a href="#functions">Function Descriptions</a>
113 <li><a href="#init">Initialization and Wrapup</a></li>
115 <li><a href="#flush">Causing Output to the
118 <li><a href="#lowlevel">Low-Level Capability
121 <li><a href="#debugging">Debugging</a></li>
126 <a href="#hints">Hints, Tips, and Tricks</a>
129 <li><a href="#caution">Some Notes of Caution</a></li>
131 <li><a href="#leaving">Temporarily Leaving ncurses
134 <li><a href="#xterm">Using <code>ncurses</code> under
135 <code>xterm</code></a></li>
137 <li><a href="#screens">Handling Multiple Terminal
140 <li><a href="#testing">Testing for Terminal
141 Capabilities</a></li>
143 <li><a href="#tuning">Tuning for Speed</a></li>
145 <li><a href="#special">Special Features of
146 <code>ncurses</code></a></li>
151 <a href="#compat">Compatibility with Older Versions</a>
154 <li><a href="#refbug">Refresh of Overlapping
157 <li><a href="#backbug">Background Erase</a></li>
161 <li><a href="#xsifuncs">XSI Curses Conformance</a></li>
166 <a href="#panels">The Panels Library</a>
169 <li><a href="#pcompile">Compiling With the Panels
172 <li><a href="#poverview">Overview of Panels</a></li>
174 <li><a href="#pstdscr">Panels, Input, and the Standard
177 <li><a href="#hiding">Hiding Panels</a></li>
179 <li><a href="#pmisc">Miscellaneous Other
185 <a href="#menu">The Menu Library</a>
188 <li><a href="#mcompile">Compiling with the menu
191 <li><a href="#moverview">Overview of Menus</a></li>
193 <li><a href="#mselect">Selecting items</a></li>
195 <li><a href="#mdisplay">Menu Display</a></li>
197 <li><a href="#mwindows">Menu Windows</a></li>
199 <li><a href="#minput">Processing Menu Input</a></li>
201 <li><a href="#mmisc">Miscellaneous Other Features</a></li>
206 <a href="#form">The Forms Library</a>
209 <li><a href="#fcompile">Compiling with the forms
212 <li><a href="#foverview">Overview of Forms</a></li>
214 <li><a href="#fcreate">Creating and Freeing Fields and
218 <a href="#fattributes">Fetching and Changing Field
222 <li><a href="#fsizes">Fetching Size and Location
225 <li><a href="#flocation">Changing the Field
228 <li><a href="#fjust">The Justification
231 <li><a href="#fdispatts">Field Display
234 <li><a href="#foptions">Field Option Bits</a></li>
236 <li><a href="#fstatus">Field Status</a></li>
238 <li><a href="#fuser">Field User Pointer</a></li>
242 <li><a href="#fdynamic">Variable-Sized Fields</a></li>
245 <a href="#fvalidation">Field Validation</a>
248 <li><a href="#ftype_alpha">TYPE_ALPHA</a></li>
250 <li><a href="#ftype_alnum">TYPE_ALNUM</a></li>
252 <li><a href="#ftype_enum">TYPE_ENUM</a></li>
254 <li><a href="#ftype_integer">TYPE_INTEGER</a></li>
256 <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li>
258 <li><a href="#ftype_regexp">TYPE_REGEXP</a></li>
262 <li><a href="#fbuffer">Direct Field Buffer
263 Manipulation</a></li>
265 <li><a href="#formattrs">Attributes of Forms</a></li>
267 <li><a href="#fdisplay">Control of Form Display</a></li>
270 <a href="#fdriver">Input Processing in the Forms
274 <li><a href="#fpage">Page Navigation Requests</a></li>
276 <li><a href="#ffield">Inter-Field Navigation
279 <li><a href="#fifield">Intra-Field Navigation
282 <li><a href="#fscroll">Scrolling Requests</a></li>
284 <li><a href="#fedit">Field Editing Requests</a></li>
286 <li><a href="#forder">Order Requests</a></li>
288 <li><a href="#fappcmds">Application Commands</a></li>
292 <li><a href="#fhooks">Field Change Hooks</a></li>
294 <li><a href="#ffocus">Field Change Commands</a></li>
296 <li><a href="#frmoptions">Form Options</a></li>
299 <a href="#fcustom">Custom Validation Types</a>
302 <li><a href="#flinktypes">Union Types</a></li>
304 <li><a href="#fnewtypes">New Field Types</a></li>
306 <li><a href="#fcheckargs">Validation Function
309 <li><a href="#fcustorder">Order Functions For Custom
312 <li><a href="#fcustprobs">Avoiding Problems</a></li>
320 <h1><a name="introduction" id=
321 "introduction">Introduction</a></h1>
323 <p>This document is an introduction to programming with
324 <code>curses</code>. It is not an exhaustive reference for the
325 curses Application Programming Interface (API); that role is
326 filled by the <code>curses</code> manual pages. Rather, it is
327 intended to help C programmers ease into using the package.</p>
329 <p>This document is aimed at C applications programmers not yet
330 specifically familiar with ncurses. If you are already an
331 experienced <code>curses</code> programmer, you should
332 nevertheless read the sections on <a href="#mouse">Mouse
333 Interfacing</a>, <a href="#debugging">Debugging</a>, <a href=
334 "#compat">Compatibility with Older Versions</a>, and <a href=
335 "#hints">Hints, Tips, and Tricks</a>. These will bring you up to
336 speed on the special features and quirks of the
337 <code>ncurses</code> implementation. If you are not so
338 experienced, keep reading.</p>
340 <p>The <code>curses</code> package is a subroutine library for
341 terminal-independent screen-painting and input-event handling
342 which presents a high level screen model to the programmer,
343 hiding differences between terminal types and doing automatic
344 optimization of output to change one screen full of text into
345 another. <code>Curses</code> uses terminfo, which is a database
346 format that can describe the capabilities of thousands of
347 different terminals.</p>
349 <p>The <code>curses</code> API may seem something of an archaism
350 on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk.
351 Nevertheless, UNIX still supports tty lines and X supports
352 <em>xterm(1)</em>; the <code>curses</code> API has the advantage
353 of (a) back-portability to character-cell terminals, and (b)
354 simplicity. For an application that does not require bit-mapped
355 graphics and multiple fonts, an interface implementation using
356 <code>curses</code> will typically be a great deal simpler and
357 less expensive than one using an X toolkit.</p>
359 <h2><a name="history" id="history">A Brief History of
362 <p>Historically, the first ancestor of <code>curses</code> was
363 the routines written to provide screen-handling for the game
364 <code>rogue</code>; these used the already-existing
365 <code>termcap</code> database facility for describing terminal
366 capabilities. These routines were abstracted into a documented
367 library and first released with the early BSD UNIX versions.</p>
369 <p>System III UNIX from Bell Labs featured a rewritten and
370 much-improved <code>curses</code> library. It introduced the
371 terminfo format. Terminfo is based on Berkeley's termcap
372 database, but contains a number of improvements and extensions.
373 Parameterized capabilities strings were introduced, making it
374 possible to describe multiple video attributes, and colors and to
375 handle far more unusual terminals than possible with termcap. In
376 the later AT&T System V releases, <code>curses</code> evolved
377 to use more facilities and offer more capabilities, going far
378 beyond BSD curses in power and flexibility.</p>
380 <h2><a name="scope" id="scope">Scope of This Document</a></h2>
382 <p>This document describes <code>ncurses</code>, a free
383 implementation of the System V <code>curses</code> API with some
384 clearly marked extensions. It includes the following System V
388 <li>Support for multiple screen highlights (BSD curses could
389 only handle one “standout” highlight, usually
392 <li>Support for line- and box-drawing using forms
395 <li>Recognition of function keys on input.</li>
397 <li>Color support.</li>
399 <li>Support for pads (windows of larger than screen size on
400 which the screen or a subwindow defines a viewport).</li>
403 <p>Also, this package makes use of the insert and delete line and
404 character features of terminals so equipped, and determines how
405 to optimally use these features with no help from the programmer.
406 It allows arbitrary combinations of video attributes to be
407 displayed, even on terminals that leave “magic
408 cookies” on the screen to mark changes in attributes.</p>
410 <p>The <code>ncurses</code> package can also capture and use
411 event reports from a mouse in some environments (notably, xterm
412 under the X window system). This document includes tips for using
415 <p>The <code>ncurses</code> package was originated by Pavel
416 Curtis. The original maintainer of this package is <a href=
417 "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a>
418 <zmbenhal@netcom.com>. <a href=
419 "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a>
420 <esr@snark.thyrsus.com> wrote many of the new features in
421 versions after 1.8.1 and wrote most of this introduction.
422 Jürgen Pfeifer wrote all of the menu and forms code as well
423 as the <a href="http://www.adahome.com">Ada95</a> binding.
424 Ongoing work is being done by <a href=
425 "mailto:dickey@invisible-island.net">Thomas Dickey</a>
426 (maintainer). Contact the current maintainers at <a href=
427 "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p>
429 <p>This document also describes the <a href="#panels">panels</a>
430 extension library, similarly modeled on the SVr4 panels facility.
431 This library allows you to associate backing store with each of a
432 stack or deck of overlapping windows, and provides operations for
433 moving windows around in the stack that change their visibility
434 in the natural way (handling window overlaps).</p>
436 <p>Finally, this document describes in detail the <a href=
437 "#menu">menus</a> and <a href="#form">forms</a> extension
438 libraries, also cloned from System V, which support easy
439 construction and sequences of menus and fill-in forms.</p>
441 <h2><a name="terminology" id="terminology">Terminology</a></h2>
443 <p>In this document, the following terminology is used with
444 reasonable consistency:</p>
449 <dd>A data structure describing a sub-rectangle of the screen
450 (possibly the entire screen). You can write to a window as
451 though it were a miniature screen, scrolling independently of
452 other windows on the physical screen.</dd>
456 <dd>A subset of windows which are as large as the terminal
457 screen, i.e., they start at the upper left hand corner and
458 encompass the lower right hand corner. One of these,
459 <code>stdscr</code>, is automatically provided for the
462 <dt>terminal screen</dt>
464 <dd>The package's idea of what the terminal display currently
465 looks like, i.e., what the user sees now. This is a special
469 <h1><a name="curses" id="curses">The Curses Library</a></h1>
471 <h2><a name="overview" id="overview">An Overview of
474 <h3><a name="compiling" id="compiling">Compiling Programs using
477 <p>In order to use the library, it is necessary to have certain
478 types and variables defined. Therefore, the programmer must have
481 #include <curses.h>
484 <p>at the top of the program source. The screen package uses the
485 Standard I/O library, so <code><curses.h></code> includes
486 <code><stdio.h></code>. <code><curses.h></code> also
487 includes <code><termios.h></code>,
488 <code><termio.h></code>, or <code><sgtty.h></code>
489 depending on your system. It is redundant (but harmless) for the
490 programmer to do these includes, too. In linking with
491 <code>curses</code> you need to have <code>-lncurses</code> in
492 your LDFLAGS or on the command line. There is no need for any
495 <h3><a name="updating" id="updating">Updating the Screen</a></h3>
497 <p>In order to update the screen optimally, it is necessary for
498 the routines to know what the screen currently looks like and
499 what the programmer wants it to look like next. For this purpose,
500 a data type (structure) named WINDOW is defined which describes a
501 window image to the routines, including its starting position on
502 the screen (the (y, x) coordinates of the upper left hand corner)
503 and its size. One of these (called <code>curscr</code>, for
504 current screen) is a screen image of what the terminal currently
505 looks like. Another screen (called <code>stdscr</code>, for
506 standard screen) is provided by default to make changes on.</p>
508 <p>A window is a purely internal representation. It is used to
509 build and store a potential image of a portion of the terminal.
510 It does not bear any necessary relation to what is really on the
511 terminal screen; it is more like a scratchpad or write
514 <p>To make the section of physical screen corresponding to a
515 window reflect the contents of the window structure, the routine
516 <code>refresh()</code> (or <code>wrefresh()</code> if the window
517 is not <code>stdscr</code>) is called.</p>
519 <p>A given physical screen section may be within the scope of any
520 number of overlapping windows. Also, changes can be made to
521 windows in any order, without regard to motion efficiency. Then,
522 at will, the programmer can effectively say “make it look
523 like this,” and let the package implementation determine
524 the most efficient way to repaint the screen.</p>
526 <h3><a name="stdscr" id="stdscr">Standard Windows and Function
527 Naming Conventions</a></h3>
529 <p>As hinted above, the routines can use several windows, but two
530 are automatically given: <code>curscr</code>, which knows what
531 the terminal looks like, and <code>stdscr</code>, which is what
532 the programmer wants the terminal to look like next. The user
533 should never actually access <code>curscr</code> directly.
534 Changes should be made to through the API, and then the routine
535 <code>refresh()</code> (or <code>wrefresh()</code>) called.</p>
537 <p>Many functions are defined to use <code>stdscr</code> as a
538 default screen. For example, to add a character to
539 <code>stdscr</code>, one calls <code>addch()</code> with the
540 desired character as argument. To write to a different window.
541 use the routine <code>waddch()</code> (for
542 <strong>w</strong>indow-specific addch()) is provided. This
543 convention of prepending function names with a “w”
544 when they are to be applied to specific windows is consistent.
545 The only routines which do not follow it are those for which a
546 window must always be specified.</p>
548 <p>In order to move the current (y, x) coordinates from one point
549 to another, the routines <code>move()</code> and
550 <code>wmove()</code> are provided. However, it is often desirable
551 to first move and then perform some I/O operation. In order to
552 avoid clumsiness, most I/O routines can be preceded by the prefix
553 “mv” and the desired (y, x) coordinates prepended to
554 the arguments to the function. For example, the calls</p>
560 <p>can be replaced by</p>
571 <p>can be replaced by</p>
573 mvwaddch(win, y, x, ch);
576 <p>Note that the window description pointer (win) comes before
577 the added (y, x) coordinates. If a function requires a window
578 pointer, it is always the first parameter passed.</p>
580 <h3><a name="variables" id="variables">Variables</a></h3>
582 <p>The <code>curses</code> library sets some variables describing
583 the terminal capabilities.</p>
585 type name description
586 ------------------------------------------------------------------
587 int LINES number of lines on the terminal
588 int COLS number of columns on the terminal
591 <p>The <code>curses.h</code> also introduces some
592 <code>#define</code> constants and types of general
596 <dt><code>bool</code></dt>
598 <dd>boolean type, actually a “char” (e.g.,
599 <code>bool doneit;</code>)</dd>
601 <dt><code>TRUE</code></dt>
603 <dd>boolean “true” flag (1).</dd>
605 <dt><code>FALSE</code></dt>
607 <dd>boolean “false” flag (0).</dd>
609 <dt><code>ERR</code></dt>
611 <dd>error flag returned by routines on a failure (-1).</dd>
613 <dt><code>OK</code></dt>
615 <dd>error flag returned by routines when things go right.</dd>
618 <h2><a name="using" id="using">Using the Library</a></h2>
620 <p>Now we describe how to actually use the screen package. In it,
621 we assume all updating, reading, etc. is applied to
622 <code>stdscr</code>. These instructions will work on any window,
623 providing you change the function names and parameters as
626 <p>Here is a sample program to motivate the discussion:</p>
628 #include <stdlib.h>
629 #include <curses.h>
630 #include <signal.h>
632 static void finish(int sig);
635 main(int argc, char *argv[])
639 /* initialize your non-curses data structures here */
641 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
643 (void) initscr(); /* initialize the curses library */
644 keypad(stdscr, TRUE); /* enable keyboard mapping */
645 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
646 (void) cbreak(); /* take input chars one at a time, no wait for \n */
647 (void) echo(); /* echo input - in color */
654 * Simple color assignment, often all we need. Color pair 0 cannot
655 * be redefined. This example uses the same value for the color
656 * pair as for the foreground color, though of course that is not
659 init_pair(1, COLOR_RED, COLOR_BLACK);
660 init_pair(2, COLOR_GREEN, COLOR_BLACK);
661 init_pair(3, COLOR_YELLOW, COLOR_BLACK);
662 init_pair(4, COLOR_BLUE, COLOR_BLACK);
663 init_pair(5, COLOR_CYAN, COLOR_BLACK);
664 init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
665 init_pair(7, COLOR_WHITE, COLOR_BLACK);
670 int c = getch(); /* refresh, accept single keystroke of input */
671 attrset(COLOR_PAIR(num % 8));
674 /* process the command keystroke */
677 finish(0); /* we are done */
680 static void finish(int sig)
684 /* do your non-curses wrapup here */
690 <h3><a name="starting" id="starting">Starting up</a></h3>
692 <p>In order to use the screen package, the routines must know
693 about terminal characteristics, and the space for
694 <code>curscr</code> and <code>stdscr</code> must be allocated.
695 These function <code>initscr()</code> does both these things.
696 Since it must allocate space for the windows, it can overflow
697 memory when attempting to do so. On the rare occasions this
698 happens, <code>initscr()</code> will terminate the program with
699 an error message. <code>initscr()</code> must always be called
700 before any of the routines which affect windows are used. If it
701 is not, the program will core dump as soon as either
702 <code>curscr</code> or <code>stdscr</code> are referenced.
703 However, it is usually best to wait to call it until after you
704 are sure you will need it, like after checking for startup
705 errors. Terminal status changing routines like <code>nl()</code>
706 and <code>cbreak()</code> should be called after
707 <code>initscr()</code>.</p>
709 <p>Once the screen windows have been allocated, you can set them
710 up for your program. If you want to, say, allow a screen to
711 scroll, use <code>scrollok()</code>. If you want the cursor to be
712 left in place after the last change, use <code>leaveok()</code>.
713 If this is not done, <code>refresh()</code> will move the cursor
714 to the window's current (y, x) coordinates after updating it.</p>
716 <p>You can create new windows of your own using the functions
717 <code>newwin()</code>, <code>derwin()</code>, and
718 <code>subwin()</code>. The routine <code>delwin()</code> will
719 allow you to get rid of old windows. All the options described
720 above can be applied to any window.</p>
722 <h3><a name="output" id="output">Output</a></h3>
724 <p>Now that we have set things up, we will want to actually
725 update the terminal. The basic functions used to change what will
726 go on a window are <code>addch()</code> and <code>move()</code>.
727 <code>addch()</code> adds a character at the current (y, x)
728 coordinates. <code>move()</code> changes the current (y, x)
729 coordinates to whatever you want them to be. It returns
730 <code>ERR</code> if you try to move off the window. As mentioned
731 above, you can combine the two into <code>mvaddch()</code> to do
732 both things at once.</p>
734 <p>The other output functions, such as <code>addstr()</code> and
735 <code>printw()</code>, all call <code>addch()</code> to add
736 characters to the window.</p>
738 <p>After you have put on the window what you want there, when you
739 want the portion of the terminal covered by the window to be made
740 to look like it, you must call <code>refresh()</code>. In order
741 to optimize finding changes, <code>refresh()</code> assumes that
742 any part of the window not changed since the last
743 <code>refresh()</code> of that window has not been changed on the
744 terminal, i.e., that you have not refreshed a portion of the
745 terminal with an overlapping window. If this is not the case, the
746 routine <code>touchwin()</code> is provided to make it look like
747 the entire window has been changed, thus making
748 <code>refresh()</code> check the whole subsection of the terminal
751 <p>If you call <code>wrefresh()</code> with <code>curscr</code>
752 as its argument, it will make the screen look like
753 <code>curscr</code> thinks it looks like. This is useful for
754 implementing a command which would redraw the screen in case it
757 <h3><a name="input" id="input">Input</a></h3>
759 <p>The complementary function to <code>addch()</code> is
760 <code>getch()</code> which, if echo is set, will call
761 <code>addch()</code> to echo the character. Since the screen
762 package needs to know what is on the terminal at all times, if
763 characters are to be echoed, the tty must be in raw or cbreak
764 mode. Since initially the terminal has echoing enabled and is in
765 ordinary “cooked” mode, one or the other has to
766 changed before calling <code>getch()</code>; otherwise, the
767 program's output will be unpredictable.</p>
769 <p>When you need to accept line-oriented input in a window, the
770 functions <code>wgetstr()</code> and friends are available. There
771 is even a <code>wscanw()</code> function that can do
772 <code>scanf()</code>(3)-style multi-field parsing on window
773 input. These pseudo-line-oriented functions turn on echoing while
776 <p>The example code above uses the call <code>keypad(stdscr,
777 TRUE)</code> to enable support for function-key mapping. With
778 this feature, the <code>getch()</code> code watches the input
779 stream for character sequences that correspond to arrow and
780 function keys. These sequences are returned as pseudo-character
781 values. The <code>#define</code> values returned are listed in
782 the <code>curses.h</code> The mapping from sequences to
783 <code>#define</code> values is determined by <code>key_</code>
784 capabilities in the terminal's terminfo entry.</p>
786 <h3><a name="formschars" id="formschars">Using Forms
789 <p>The <code>addch()</code> function (and some others, including
790 <code>box()</code> and <code>border()</code>) can accept some
791 pseudo-character arguments which are specially defined by
792 <code>ncurses</code>. These are <code>#define</code> values set
793 up in the <code>curses.h</code> header; see there for a complete
794 list (look for the prefix <code>ACS_</code>).</p>
796 <p>The most useful of the ACS defines are the forms-drawing
797 characters. You can use these to draw boxes and simple graphs on
798 the screen. If the terminal does not have such characters,
799 <code>curses.h</code> will map them to a recognizable (though
800 ugly) set of ASCII defaults.</p>
802 <h3><a name="attributes" id="attributes">Character Attributes and
805 <p>The <code>ncurses</code> package supports screen highlights
806 including standout, reverse-video, underline, and blink. It also
807 supports color, which is treated as another kind of
810 <p>Highlights are encoded, internally, as high bits of the
811 pseudo-character type (<code>chtype</code>) that
812 <code>curses.h</code> uses to represent the contents of a screen
813 cell. See the <code>curses.h</code> header file for a complete
814 list of highlight mask values (look for the prefix
815 <code>A_</code>).</p>
817 <p>There are two ways to make highlights. One is to logical-or
818 the value of the highlights you want into the character argument
819 of an <code>addch()</code> call, or any other output call that
820 takes a <code>chtype</code> argument.</p>
822 <p>The other is to set the current-highlight value. This is
823 <em>logical-OR</em>ed with any highlight you specify the first
824 way. You do this with the functions <code>attron()</code>,
825 <code>attroff()</code>, and <code>attrset()</code>; see the
826 manual pages for details. Color is a special kind of highlight.
827 The package actually thinks in terms of color pairs, combinations
828 of foreground and background colors. The sample code above sets
829 up eight color pairs, all of the guaranteed-available colors on
830 black. Note that each color pair is, in effect, given the name of
831 its foreground color. Any other range of eight non-conflicting
832 values could have been used as the first arguments of the
833 <code>init_pair()</code> values.</p>
835 <p>Once you have done an <code>init_pair()</code> that creates
836 color-pair N, you can use <code>COLOR_PAIR(N)</code> as a
837 highlight that invokes that particular color combination. Note
838 that <code>COLOR_PAIR(N)</code>, for constant N, is itself a
839 compile-time constant and can be used in initializers.</p>
841 <h3><a name="mouse" id="mouse">Mouse Interfacing</a></h3>
843 <p>The <code>ncurses</code> library also provides a mouse
847 <strong>NOTE:</strong> this facility is specific to
848 <code>ncurses</code>, it is not part of either the XSI Curses
849 standard, nor of System V Release 4, nor BSD curses. System V
850 Release 4 curses contains code with similar interface
851 definitions, however it is not documented. Other than by
852 disassembling the library, we have no way to determine exactly
853 how that mouse code works. Thus, we recommend that you wrap
854 mouse-related code in an #ifdef using the feature macro
855 NCURSES_MOUSE_VERSION so it will not be compiled and linked on
859 <p>Presently, mouse event reporting works in the following
863 <li>xterm and similar programs such as rxvt.</li>
865 <li>Linux console, when configured with <code>gpm</code>(1),
866 Alessandro Rubini's mouse server.</li>
868 <li>FreeBSD sysmouse (console)</li>
873 <p>The mouse interface is very simple. To activate it, you use
874 the function <code>mousemask()</code>, passing it as first
875 argument a bit-mask that specifies what kinds of events you want
876 your program to be able to see. It will return the bit-mask of
877 events that actually become visible, which may differ from the
878 argument if the mouse device is not capable of reporting some of
879 the event types you specify.</p>
881 <p>Once the mouse is active, your application's command loop
882 should watch for a return value of <code>KEY_MOUSE</code> from
883 <code>wgetch()</code>. When you see this, a mouse event report
884 has been queued. To pick it off the queue, use the function
885 <code>getmouse()</code> (you must do this before the next
886 <code>wgetch()</code>, otherwise another mouse event might come
887 in and make the first one inaccessible).</p>
889 <p>Each call to <code>getmouse()</code> fills a structure (the
890 address of which you will pass it) with mouse event data. The
891 event data includes zero-origin, screen-relative character-cell
892 coordinates of the mouse pointer. It also includes an event mask.
893 Bits in this mask will be set, corresponding to the event type
896 <p>The mouse structure contains two additional fields which may
897 be significant in the future as ncurses interfaces to new kinds
898 of pointing device. In addition to x and y coordinates, there is
899 a slot for a z coordinate; this might be useful with
900 touch-screens that can return a pressure or duration parameter.
901 There is also a device ID field, which could be used to
902 distinguish between multiple pointing devices.</p>
904 <p>The class of visible events may be changed at any time via
905 <code>mousemask()</code>. Events that can be reported include
906 presses, releases, single-, double- and triple-clicks (you can
907 set the maximum button-down time for clicks). If you do not make
908 clicks visible, they will be reported as press-release pairs. In
909 some environments, the event mask may include bits reporting the
910 state of shift, alt, and ctrl keys on the keyboard during the
913 <p>A function to check whether a mouse event fell within a given
914 window is also supplied. You can use this to see whether a given
915 window should consider a mouse event relevant to it.</p>
917 <p>Because mouse event reporting will not be available in all
918 environments, it would be unwise to build <code>ncurses</code>
919 applications that <em>require</em> the use of a mouse. Rather,
920 you should use the mouse as a shortcut for point-and-shoot
921 commands your application would normally accept from the
922 keyboard. Two of the test games in the <code>ncurses</code>
923 distribution (<code>bs</code> and <code>knight</code>) contain
924 code that illustrates how this can be done.</p>
926 <p>See the manual page <code>curs_mouse(3X)</code> for full
927 details of the mouse-interface functions.</p>
929 <h3><a name="finishing" id="finishing">Finishing Up</a></h3>
931 <p>In order to clean up after the <code>ncurses</code> routines,
932 the routine <code>endwin()</code> is provided. It restores tty
933 modes to what they were when <code>initscr()</code> was first
934 called, and moves the cursor down to the lower-left corner. Thus,
935 anytime after the call to initscr, <code>endwin()</code> should
936 be called before exiting.</p>
938 <h2><a name="functions" id="functions">Function
939 Descriptions</a></h2>
941 <p>We describe the detailed behavior of some important curses
942 functions here, as a supplement to the manual page
945 <h3><a name="init" id="init">Initialization and Wrapup</a></h3>
948 <dt><code>initscr()</code></dt>
950 <dd>The first function called should almost always be
951 <code>initscr()</code>. This will determine the terminal type
952 and initialize curses data structures. <code>initscr()</code>
953 also arranges that the first call to <code>refresh()</code>
954 will clear the screen. If an error occurs a message is written
955 to standard error and the program exits. Otherwise it returns a
956 pointer to stdscr. A few functions may be called before initscr
957 (<code>slk_init()</code>, <code>filter()</code>,
958 <code>ripoffline()</code>, <code>use_env()</code>, and, if you
959 are using multiple terminals, <code>newterm()</code>.)</dd>
961 <dt><code>endwin()</code></dt>
963 <dd>Your program should always call <code>endwin()</code>
964 before exiting or shelling out of the program. This function
965 will restore tty modes, move the cursor to the lower left
966 corner of the screen, reset the terminal into the proper
967 non-visual mode. Calling <code>refresh()</code> or
968 <code>doupdate()</code> after a temporary escape from the
969 program will restore the ncurses screen from before the
972 <dt><code>newterm(type, ofp, ifp)</code></dt>
974 <dd>A program which outputs to more than one terminal should
975 use <code>newterm()</code> instead of <code>initscr()</code>.
976 <code>newterm()</code> should be called once for each terminal.
977 It returns a variable of type <code>SCREEN *</code> which
978 should be saved as a reference to that terminal. (NOTE: a
979 SCREEN variable is not a <em>screen</em> in the sense we are
980 describing in this introduction, but a collection of parameters
981 used to assist in optimizing the display.) The arguments are
982 the type of the terminal (a string) and <code>FILE</code>
983 pointers for the output and input of the terminal. If type is
984 NULL then the environment variable <code>$TERM</code> is used.
985 <code>endwin()</code> should called once at wrapup time for
986 each terminal opened using this function.</dd>
988 <dt><code>set_term(new)</code></dt>
990 <dd>This function is used to switch to a different terminal
991 previously opened by <code>newterm()</code>. The screen
992 reference for the new terminal is passed as the parameter. The
993 previous terminal is returned by the function. All other calls
994 affect only the current terminal.</dd>
996 <dt><code>delscreen(sp)</code></dt>
998 <dd>The inverse of <code>newterm()</code>; deallocates the data
999 structures associated with a given <code>SCREEN</code>
1003 <h3><a name="flush" id="flush">Causing Output to the
1007 <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt>
1009 <dd>These functions must be called to actually get any output
1010 on the terminal, as other routines merely manipulate data
1011 structures. <code>wrefresh()</code> copies the named window to
1012 the physical terminal screen, taking into account what is
1013 already there in order to do optimizations.
1014 <code>refresh()</code> does a refresh of <code>stdscr</code>.
1015 Unless <code>leaveok()</code> has been enabled, the physical
1016 cursor of the terminal is left at the location of the window's
1019 <dt><code>doupdate()</code> and
1020 <code>wnoutrefresh(win)</code></dt>
1022 <dd>These two functions allow multiple updates with more
1023 efficiency than wrefresh. To use them, it is important to
1024 understand how curses works. In addition to all the window
1025 structures, curses keeps two data structures representing the
1026 terminal screen: a physical screen, describing what is actually
1027 on the screen, and a virtual screen, describing what the
1028 programmer wants to have on the screen. wrefresh works by first
1029 copying the named window to the virtual screen
1030 (<code>wnoutrefresh()</code>), and then calling the routine to
1031 update the screen (<code>doupdate()</code>). If the programmer
1032 wishes to output several windows at once, a series of calls to
1033 <code>wrefresh</code> will result in alternating calls to
1034 <code>wnoutrefresh()</code> and <code>doupdate()</code>,
1035 causing several bursts of output to the screen. By calling
1036 <code>wnoutrefresh()</code> for each window, it is then
1037 possible to call <code>doupdate()</code> once, resulting in
1038 only one burst of output, with fewer total characters
1039 transmitted (this also avoids a visually annoying flicker at
1043 <h3><a name="lowlevel" id="lowlevel">Low-Level Capability
1047 <dt><code>setupterm(term, filenum, errret)</code></dt>
1050 This routine is called to initialize a terminal's
1051 description, without setting up the curses screen structures
1052 or changing the tty-driver mode bits. <code>term</code> is
1053 the character string representing the name of the terminal
1054 being used. <code>filenum</code> is the UNIX file descriptor
1055 of the terminal to be used for output. <code>errret</code> is
1056 a pointer to an integer, in which a success or failure
1057 indication is returned. The values returned can be 1 (all is
1058 well), 0 (no such terminal), or -1 (some problem locating the
1061 <p>The value of <code>term</code> can be given as NULL, which
1062 will cause the value of <code>TERM</code> in the environment
1063 to be used. The <code>errret</code> pointer can also be given
1064 as NULL, meaning no error code is wanted. If
1065 <code>errret</code> is defaulted, and something goes wrong,
1066 <code>setupterm()</code> will print an appropriate error
1067 message and exit, rather than returning. Thus, a simple
1068 program can call setupterm(0, 1, 0) and not worry about
1069 initialization errors.</p>
1071 <p>After the call to <code>setupterm()</code>, the global
1072 variable <code>cur_term</code> is set to point to the current
1073 structure of terminal capabilities. By calling
1074 <code>setupterm()</code> for each terminal, and saving and
1075 restoring <code>cur_term</code>, it is possible for a program
1076 to use two or more terminals at once.
1077 <code>Setupterm()</code> also stores the names section of the
1078 terminal description in the global character array
1079 <code>ttytype[]</code>. Subsequent calls to
1080 <code>setupterm()</code> will overwrite this array, so you
1081 will have to save it yourself if need be.</p>
1085 <h3><a name="debugging" id="debugging">Debugging</a></h3>
1088 <strong>NOTE:</strong> These functions are not part of the
1089 standard curses API!
1093 <dt><code>trace()</code></dt>
1095 <dd>This function can be used to explicitly set a trace level.
1096 If the trace level is nonzero, execution of your program will
1097 generate a file called “trace” in the current
1098 working directory containing a report on the library's actions.
1099 Higher trace levels enable more detailed (and verbose)
1100 reporting -- see comments attached to <code>TRACE_</code>
1101 defines in the <code>curses.h</code> file for details. (It is
1102 also possible to set a trace level by assigning a trace level
1103 value to the environment variable
1104 <code>NCURSES_TRACE</code>).</dd>
1106 <dt><code>_tracef()</code></dt>
1108 <dd>This function can be used to output your own debugging
1109 information. It is only available only if you link with
1110 -lncurses_g. It can be used the same way as
1111 <code>printf()</code>, only it outputs a newline after the end
1112 of arguments. The output goes to a file called
1113 <code>trace</code> in the current directory.</dd>
1116 <p>Trace logs can be difficult to interpret due to the sheer
1117 volume of data dumped in them. There is a script called
1118 <strong>tracemunch</strong> included with the
1119 <code>ncurses</code> distribution that can alleviate this problem
1120 somewhat; it compacts long sequences of similar operations into
1121 more succinct single-line pseudo-operations. These pseudo-ops can
1122 be distinguished by the fact that they are named in capital
1125 <h2><a name="hints" id="hints">Hints, Tips, and Tricks</a></h2>
1127 <p>The <code>ncurses</code> manual pages are a complete reference
1128 for this library. In the remainder of this document, we discuss
1129 various useful methods that may not be obvious from the manual
1130 page descriptions.</p>
1132 <h3><a name="caution" id="caution">Some Notes of Caution</a></h3>
1134 <p>If you find yourself thinking you need to use
1135 <code>noraw()</code> or <code>nocbreak()</code>, think again and
1136 move carefully. It is probably better design to use
1137 <code>getstr()</code> or one of its relatives to simulate cooked
1138 mode. The <code>noraw()</code> and <code>nocbreak()</code>
1139 functions try to restore cooked mode, but they may end up
1140 clobbering some control bits set before you started your
1141 application. Also, they have always been poorly documented, and
1142 are likely to hurt your application's usability with other curses
1145 <p>Bear in mind that <code>refresh()</code> is a synonym for
1146 <code>wrefresh(stdscr)</code>. Do not try to mix use of
1147 <code>stdscr</code> with use of windows declared by
1148 <code>newwin()</code>; a <code>refresh()</code> call will blow
1149 them off the screen. The right way to handle this is to use
1150 <code>subwin()</code>, or not touch <code>stdscr</code> at all
1151 and tile your screen with declared windows which you then
1152 <code>wnoutrefresh()</code> somewhere in your program event loop,
1153 with a single <code>doupdate()</code> call to trigger actual
1156 <p>You are much less likely to run into problems if you design
1157 your screen layouts to use tiled rather than overlapping windows.
1158 Historically, curses support for overlapping windows has been
1159 weak, fragile, and poorly documented. The <code>ncurses</code>
1160 library is not yet an exception to this rule.</p>
1162 <p>There is a panels library included in the <code>ncurses</code>
1163 distribution that does a pretty good job of strengthening the
1164 overlapping-windows facilities.</p>
1166 <p>Try to avoid using the global variables LINES and COLS. Use
1167 <code>getmaxyx()</code> on the <code>stdscr</code> context
1168 instead. Reason: your code may be ported to run in an environment
1169 with window resizes, in which case several screens could be open
1170 with different sizes.</p>
1172 <h3><a name="leaving" id="leaving">Temporarily Leaving NCURSES
1175 <p>Sometimes you will want to write a program that spends most of
1176 its time in screen mode, but occasionally returns to ordinary
1177 “cooked” mode. A common reason for this is to support
1178 shell-out. This behavior is simple to arrange in
1179 <code>ncurses</code>.</p>
1181 <p>To leave <code>ncurses</code> mode, call <code>endwin()</code>
1182 as you would if you were intending to terminate the program. This
1183 will take the screen back to cooked mode; you can do your
1184 shell-out. When you want to return to <code>ncurses</code> mode,
1185 simply call <code>refresh()</code> or <code>doupdate()</code>.
1186 This will repaint the screen.</p>
1188 <p>There is a boolean function, <code>isendwin()</code>, which
1189 code can use to test whether <code>ncurses</code> screen mode is
1190 active. It returns <code>TRUE</code> in the interval between an
1191 <code>endwin()</code> call and the following
1192 <code>refresh()</code>, <code>FALSE</code> otherwise.</p>
1194 <p>Here is some sample code for shellout:</p>
1196 addstr("Shelling out...");
1197 def_prog_mode(); /* save current tty modes */
1198 endwin(); /* restore original tty modes */
1199 system("sh"); /* run shell */
1200 addstr("returned.\n"); /* prepare return message */
1201 refresh(); /* restore save modes, repaint screen */
1204 <h3><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h3>
1206 <p>A resize operation in X sends <code>SIGWINCH</code> to the
1207 application running under xterm. The easiest way to handle
1208 <code>SIGWINCH</code> is to do an <code>endwin</code>, followed
1209 by an <code>refresh</code> and a screen repaint you code
1210 yourself. The <code>refresh</code> will pick up the new screen
1211 size from the xterm's environment.</p>
1213 <p>That is the standard way, of course (it even works with some
1214 vendor's curses implementations). Its drawback is that it clears
1215 the screen to reinitialize the display, and does not resize
1216 subwindows which must be shrunk. <code>Ncurses</code> provides an
1217 extension which works better, the <code>resizeterm</code>
1218 function. That function ensures that all windows are limited to
1219 the new screen dimensions, and pads <code>stdscr</code> with
1220 blanks if the screen is larger.</p>
1222 <p>The <code>ncurses</code> library provides a SIGWINCH signal
1223 handler, which pushes a <code>KEY_RESIZE</code> via the wgetch()
1224 calls. When <code>ncurses</code> returns that code, it calls
1225 <code>resizeterm</code> to update the size of the standard
1226 screen's window, repainting that (filling with blanks or
1227 truncating as needed). It also resizes other windows, but its
1228 effect may be less satisfactory because it cannot know how you
1229 want the screen re-painted. You will usually have to write
1230 special-purpose code to handle <code>KEY_RESIZE</code>
1233 <h3><a name="screens" id="screens">Handling Multiple Terminal
1236 <p>The <code>initscr()</code> function actually calls a function
1237 named <code>newterm()</code> to do most of its work. If you are
1238 writing a program that opens multiple terminals, use
1239 <code>newterm()</code> directly.</p>
1241 <p>For each call, you will have to specify a terminal type and a
1242 pair of file pointers; each call will return a screen reference,
1243 and <code>stdscr</code> will be set to the last one allocated.
1244 You will switch between screens with the <code>set_term</code>
1245 call. Note that you will also have to call
1246 <code>def_shell_mode</code> and <code>def_prog_mode</code> on
1247 each tty yourself.</p>
1249 <h3><a name="testing" id="testing">Testing for Terminal
1250 Capabilities</a></h3>
1252 <p>Sometimes you may want to write programs that test for the
1253 presence of various capabilities before deciding whether to go
1254 into <code>ncurses</code> mode. An easy way to do this is to call
1255 <code>setupterm()</code>, then use the functions
1256 <code>tigetflag()</code>, <code>tigetnum()</code>, and
1257 <code>tigetstr()</code> to do your testing.</p>
1259 <p>A particularly useful case of this often comes up when you
1260 want to test whether a given terminal type should be treated as
1261 “smart” (cursor-addressable) or “stupid”.
1262 The right way to test this is to see if the return value of
1263 <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can
1264 include the <code>term.h</code> file and test the value of the
1265 macro <code>cursor_address</code>.</p>
1267 <h3><a name="tuning" id="tuning">Tuning for Speed</a></h3>
1269 <p>Use the <code>addchstr()</code> family of functions for fast
1270 screen-painting of text when you know the text does not contain
1271 any control characters. Try to make attribute changes infrequent
1272 on your screens. Do not use the <code>immedok()</code>
1275 <h3><a name="special" id="special">Special Features of
1278 <p>The <code>wresize()</code> function allows you to resize a
1279 window in place. The associated <code>resizeterm()</code>
1280 function simplifies the construction of <a href=
1281 "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p>
1283 <p>The <code>define_key()</code> function allows you to define at
1284 runtime function-key control sequences which are not in the
1285 terminal description. The <code>keyok()</code> function allows
1286 you to temporarily enable or disable interpretation of any
1287 function-key control sequence.</p>
1289 <p>The <code>use_default_colors()</code> function allows you to
1290 construct applications which can use the terminal's default
1291 foreground and background colors as an additional "default"
1292 color. Several terminal emulators support this feature, which is
1293 based on ISO 6429.</p>
1295 <p>Ncurses supports up 16 colors, unlike SVr4 curses which
1296 defines only 8. While most terminals which provide color allow
1297 only 8 colors, about a quarter (including XFree86 xterm) support
1300 <h2><a name="compat" id="compat">Compatibility with Older
1303 <p>Despite our best efforts, there are some differences between
1304 <code>ncurses</code> and the (undocumented!) behavior of older
1305 curses implementations. These arise from ambiguities or omissions
1306 in the documentation of the API.</p>
1308 <h3><a name="refbug" id="refbug">Refresh of Overlapping
1311 <p>If you define two windows A and B that overlap, and then
1312 alternately scribble on and refresh them, the changes made to the
1313 overlapping region under historic <code>curses</code> versions
1314 were often not documented precisely.</p>
1316 <p>To understand why this is a problem, remember that screen
1317 updates are calculated between two representations of the
1318 <em>entire</em> display. The documentation says that when you
1319 refresh a window, it is first copied to the virtual screen, and
1320 then changes are calculated to update the physical screen (and
1321 applied to the terminal). But "copied to" is not very specific,
1322 and subtle differences in how copying works can produce different
1323 behaviors in the case where two overlapping windows are each
1324 being refreshed at unpredictable intervals.</p>
1326 <p>What happens to the overlapping region depends on what
1327 <code>wnoutrefresh()</code> does with its argument -- what
1328 portions of the argument window it copies to the virtual screen.
1329 Some implementations do "change copy", copying down only
1330 locations in the window that have changed (or been marked changed
1331 with <code>wtouchln()</code> and friends). Some implementations
1332 do "entire copy", copying <em>all</em> window locations to the
1333 virtual screen whether or not they have changed.</p>
1335 <p>The <code>ncurses</code> library itself has not always been
1336 consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a
1337 did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and
1338 newer, do change copy.</p>
1340 <p>For most commercial curses implementations, it is not
1341 documented and not known for sure (at least not to the
1342 <code>ncurses</code> maintainers) whether they do change copy or
1343 entire copy. We know that System V release 3 curses has logic in
1344 it that looks like an attempt to do change copy, but the
1345 surrounding logic and data representations are sufficiently
1346 complex, and our knowledge sufficiently indirect, that it is hard
1347 to know whether this is reliable. It is not clear what the SVr4
1348 documentation and XSI standard intend. The XSI Curses standard
1349 barely mentions wnoutrefresh(); the SVr4 documents seem to be
1350 describing entire-copy, but it is possible with some effort and
1351 straining to read them the other way.</p>
1353 <p>It might therefore be unwise to rely on either behavior in
1354 programs that might have to be linked with other curses
1355 implementations. Instead, you can do an explicit
1356 <code>touchwin()</code> before the <code>wnoutrefresh()</code>
1357 call to guarantee an entire-contents copy anywhere.</p>
1359 <p>The really clean way to handle this is to use the panels
1360 library. If, when you want a screen update, you do
1361 <code>update_panels()</code>, it will do all the necessary
1362 <code>wnoutrefresh()</code> calls for whatever panel stacking
1363 order you have defined. Then you can do one
1364 <code>doupdate()</code> and there will be a <em>single</em> burst
1365 of physical I/O that will do all your updates.</p>
1367 <h3><a name="backbug" id="backbug">Background Erase</a></h3>
1369 <p>If you have been using a very old versions of
1370 <code>ncurses</code> (1.8.7 or older) you may be surprised by the
1371 behavior of the erase functions. In older versions, erased areas
1372 of a window were filled with a blank modified by the window's
1373 current attribute (as set by <strong>wattrset()</strong>,
1374 <strong>wattron()</strong>, <strong>wattroff()</strong> and
1377 <p>In newer versions, this is not so. Instead, the attribute of
1378 erased blanks is normal unless and until it is modified by the
1379 functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p>
1381 <p>This change in behavior conforms <code>ncurses</code> to
1382 System V Release 4 and the XSI Curses standard.</p>
1384 <h2><a name="xsifuncs" id="xsifuncs">XSI Curses
1385 Conformance</a></h2>
1387 <p>The <code>ncurses</code> library is intended to be base-level
1388 conformant with the XSI Curses standard from X/Open. Many
1389 extended-level features (in fact, almost all features not
1390 directly concerned with wide characters and internationalization)
1391 are also supported.</p>
1393 <p>One effect of XSI conformance is the change in behavior
1394 described under <a href="#backbug">"Background Erase --
1395 Compatibility with Old Versions"</a>.</p>
1397 <p>Also, <code>ncurses</code> meets the XSI requirement that
1398 every macro entry point have a corresponding function which may
1399 be linked (and will be prototype-checked) if the macro definition
1400 is disabled with <code>#undef</code>.</p>
1402 <h1><a name="panels" id="panels">The Panels Library</a></h1>
1404 <p>The <code>ncurses</code> library by itself provides good
1405 support for screen displays in which the windows are tiled
1406 (non-overlapping). In the more general case that windows may
1407 overlap, you have to use a series of <code>wnoutrefresh()</code>
1408 calls followed by a <code>doupdate()</code>, and be careful about
1409 the order you do the window refreshes in. It has to be
1410 bottom-upwards, otherwise parts of windows that should be
1411 obscured will show through.</p>
1413 <p>When your interface design is such that windows may dive
1414 deeper into the visibility stack or pop to the top at runtime,
1415 the resulting book-keeping can be tedious and difficult to get
1416 right. Hence the panels library.</p>
1418 <p>The <code>panel</code> library first appeared in AT&T
1419 System V. The version documented here is the <code>panel</code>
1420 code distributed with <code>ncurses</code>.</p>
1422 <h2><a name="pcompile" id="pcompile">Compiling With the Panels
1425 <p>Your panels-using modules must import the panels library
1426 declarations with</p>
1428 #include <panel.h>
1431 <p>and must be linked explicitly with the panels library using an
1432 <code>-lpanel</code> argument. Note that they must also link the
1433 <code>ncurses</code> library with <code>-lncurses</code>. Many
1434 linkers are two-pass and will accept either order, but it is
1435 still good practice to put <code>-lpanel</code> first and
1436 <code>-lncurses</code> second.</p>
1438 <h2><a name="poverview" id="poverview">Overview of
1441 <p>A panel object is a window that is implicitly treated as part
1442 of a <dfn>deck</dfn> including all other panel objects. The deck
1443 has an implicit bottom-to-top visibility order. The panels
1444 library includes an update function (analogous to
1445 <code>refresh()</code>) that displays all panels in the deck in
1446 the proper order to resolve overlaps. The standard window,
1447 <code>stdscr</code>, is considered below all panels.</p>
1449 <p>Details on the panels functions are available in the man
1450 pages. We will just hit the highlights here.</p>
1452 <p>You create a panel from a window by calling
1453 <code>new_panel()</code> on a window pointer. It then becomes the
1454 top of the deck. The panel's window is available as the value of
1455 <code>panel_window()</code> called with the panel pointer as
1458 <p>You can delete a panel (removing it from the deck) with
1459 <code>del_panel</code>. This will not deallocate the associated
1460 window; you have to do that yourself. You can replace a panel's
1461 window with a different window by calling
1462 <code>replace_window</code>. The new window may be of different
1463 size; the panel code will re-compute all overlaps. This operation
1464 does not change the panel's position in the deck.</p>
1466 <p>To move a panel's window, use <code>move_panel()</code>. The
1467 <code>mvwin()</code> function on the panel's window is not
1468 sufficient because it does not update the panels library's
1469 representation of where the windows are. This operation leaves
1470 the panel's depth, contents, and size unchanged.</p>
1472 <p>Two functions (<code>top_panel()</code>,
1473 <code>bottom_panel()</code>) are provided for rearranging the
1474 deck. The first pops its argument window to the top of the deck;
1475 the second sends it to the bottom. Either operation leaves the
1476 panel's screen location, contents, and size unchanged.</p>
1478 <p>The function <code>update_panels()</code> does all the
1479 <code>wnoutrefresh()</code> calls needed to prepare for
1480 <code>doupdate()</code> (which you must call yourself,
1483 <p>Typically, you will want to call <code>update_panels()</code>
1484 and <code>doupdate()</code> just before accepting command input,
1485 once in each cycle of interaction with the user. If you call
1486 <code>update_panels()</code> after each and every panel write,
1487 you will generate a lot of unnecessary refresh activity and
1490 <h2><a name="pstdscr" id="pstdscr">Panels, Input, and the
1491 Standard Screen</a></h2>
1493 <p>You should not mix <code>wnoutrefresh()</code> or
1494 <code>wrefresh()</code> operations with panels code; this will
1495 work only if the argument window is either in the top panel or
1496 unobscured by any other panels.</p>
1498 <p>The <code>stsdcr</code> window is a special case. It is
1499 considered below all panels. Because changes to panels may
1500 obscure parts of <code>stdscr</code>, though, you should call
1501 <code>update_panels()</code> before <code>doupdate()</code> even
1502 when you only change <code>stdscr</code>.</p>
1504 <p>Note that <code>wgetch</code> automatically calls
1505 <code>wrefresh</code>. Therefore, before requesting input from a
1506 panel window, you need to be sure that the panel is totally
1509 <p>There is presently no way to display changes to one obscured
1510 panel without repainting all panels.</p>
1512 <h2><a name="hiding" id="hiding">Hiding Panels</a></h2>
1514 <p>It is possible to remove a panel from the deck temporarily;
1515 use <code>hide_panel</code> for this. Use
1516 <code>show_panel()</code> to render it visible again. The
1517 predicate function <code>panel_hidden</code> tests whether or not
1518 a panel is hidden.</p>
1520 <p>The <code>panel_update</code> code ignores hidden panels. You
1521 cannot do <code>top_panel()</code> or <code>bottom_panel</code>
1522 on a hidden panel(). Other panels operations are applicable.</p>
1524 <h2><a name="pmisc" id="pmisc">Miscellaneous Other
1527 <p>It is possible to navigate the deck using the functions
1528 <code>panel_above()</code> and <code>panel_below</code>. Handed a
1529 panel pointer, they return the panel above or below that panel.
1530 Handed <code>NULL</code>, they return the bottom-most or top-most
1533 <p>Every panel has an associated user pointer, not used by the
1534 panel code, to which you can attach application data. See the man
1535 page documentation of <code>set_panel_userptr()</code> and
1536 <code>panel_userptr</code> for details.</p>
1538 <h1><a name="menu" id="menu">The Menu Library</a></h1>
1540 <p>A menu is a screen display that assists the user to choose
1541 some subset of a given set of items. The <code>menu</code>
1542 library is a curses extension that supports easy programming of
1543 menu hierarchies with a uniform but flexible interface.</p>
1545 <p>The <code>menu</code> library first appeared in AT&T
1546 System V. The version documented here is the <code>menu</code>
1547 code distributed with <code>ncurses</code>.</p>
1549 <h2><a name="mcompile" id="mcompile">Compiling With the menu
1552 <p>Your menu-using modules must import the menu library
1553 declarations with</p>
1555 #include <menu.h>
1558 <p>and must be linked explicitly with the menus library using an
1559 <code>-lmenu</code> argument. Note that they must also link the
1560 <code>ncurses</code> library with <code>-lncurses</code>. Many
1561 linkers are two-pass and will accept either order, but it is
1562 still good practice to put <code>-lmenu</code> first and
1563 <code>-lncurses</code> second.</p>
1565 <h2><a name="moverview" id="moverview">Overview of Menus</a></h2>
1567 <p>The menus created by this library consist of collections of
1568 <dfn>items</dfn> including a name string part and a description
1569 string part. To make menus, you create groups of these items and
1570 connect them with menu frame objects.</p>
1572 <p>The menu can then by <dfn>posted</dfn>, that is written to an
1573 associated window. Actually, each menu has two associated
1574 windows; a containing window in which the programmer can scribble
1575 titles or borders, and a subwindow in which the menu items proper
1576 are displayed. If this subwindow is too small to display all the
1577 items, it will be a scrollable viewport on the collection of
1580 <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed),
1581 and finally freed to make the storage associated with it and its
1582 items available for re-use.</p>
1584 <p>The general flow of control of a menu program looks like
1588 <li>Initialize <code>curses</code>.</li>
1590 <li>Create the menu items, using <code>new_item()</code>.</li>
1592 <li>Create the menu using <code>new_menu()</code>.</li>
1594 <li>Post the menu using <code>post_menu()</code>.</li>
1596 <li>Refresh the screen.</li>
1598 <li>Process user requests via an input loop.</li>
1600 <li>Unpost the menu using <code>unpost_menu()</code>.</li>
1602 <li>Free the menu, using <code>free_menu()</code>.</li>
1604 <li>Free the items using <code>free_item()</code>.</li>
1606 <li>Terminate <code>curses</code>.</li>
1609 <h2><a name="mselect" id="mselect">Selecting items</a></h2>
1611 <p>Menus may be multi-valued or (the default) single-valued (see
1612 the manual page <code>menu_opts(3x)</code> to see how to change
1613 the default). Both types always have a <dfn>current
1616 <p>From a single-valued menu you can read the selected value
1617 simply by looking at the current item. From a multi-valued menu,
1618 you get the selected set by looping through the items applying
1619 the <code>item_value()</code> predicate function. Your
1620 menu-processing code can use the function
1621 <code>set_item_value()</code> to flag the items in the select
1624 <p>Menu items can be made unselectable using
1625 <code>set_item_opts()</code> or <code>item_opts_off()</code> with
1626 the <code>O_SELECTABLE</code> argument. This is the only option
1627 so far defined for menus, but it is good practice to code as
1628 though other option bits might be on.</p>
1630 <h2><a name="mdisplay" id="mdisplay">Menu Display</a></h2>
1632 <p>The menu library calculates a minimum display size for your
1633 window, based on the following variables:</p>
1636 <li>The number and maximum length of the menu items</li>
1638 <li>Whether the O_ROWMAJOR option is enabled</li>
1640 <li>Whether display of descriptions is enabled</li>
1642 <li>Whatever menu format may have been set by the
1645 <li>The length of the menu mark string used for highlighting
1649 <p>The function <code>set_menu_format()</code> allows you to set
1650 the maximum size of the viewport or <dfn>menu page</dfn> that
1651 will be used to display menu items. You can retrieve any format
1652 associated with a menu with <code>menu_format()</code>. The
1653 default format is rows=16, columns=1.</p>
1655 <p>The actual menu page may be smaller than the format size. This
1656 depends on the item number and size and whether O_ROWMAJOR is on.
1657 This option (on by default) causes menu items to be displayed in
1658 a “raster-scan” pattern, so that if more than one
1659 item will fit horizontally the first couple of items are
1660 side-by-side in the top row. The alternative is column-major
1661 display, which tries to put the first several items in the first
1664 <p>As mentioned above, a menu format not large enough to allow
1665 all items to fit on-screen will result in a menu display that is
1666 vertically scrollable.</p>
1668 <p>You can scroll it with requests to the menu driver, which will
1669 be described in the section on <a href="#minput">menu input
1672 <p>Each menu has a <dfn>mark string</dfn> used to visually tag
1673 selected items; see the <code>menu_mark(3x)</code> manual page
1674 for details. The mark string length also influences the menu page
1677 <p>The function <code>scale_menu()</code> returns the minimum
1678 display size that the menu code computes from all these factors.
1679 There are other menu display attributes including a select
1680 attribute, an attribute for selectable items, an attribute for
1681 unselectable items, and a pad character used to separate item
1682 name text from description text. These have reasonable defaults
1683 which the library allows you to change (see the
1684 <code>menu_attribs(3x)</code> manual page.</p>
1686 <h2><a name="mwindows" id="mwindows">Menu Windows</a></h2>
1688 <p>Each menu has, as mentioned previously, a pair of associated
1689 windows. Both these windows are painted when the menu is posted
1690 and erased when the menu is unposted.</p>
1692 <p>The outer or frame window is not otherwise touched by the menu
1693 routines. It exists so the programmer can associate a title, a
1694 border, or perhaps help text with the menu and have it properly
1695 refreshed or erased at post/unpost time. The inner window or
1696 <dfn>subwindow</dfn> is where the current menu page is
1699 <p>By default, both windows are <code>stdscr</code>. You can set
1700 them with the functions in <code>menu_win(3x)</code>.</p>
1702 <p>When you call <code>post_menu()</code>, you write the menu to
1703 its subwindow. When you call <code>unpost_menu()</code>, you
1704 erase the subwindow, However, neither of these actually modifies
1705 the screen. To do that, call <code>wrefresh()</code> or some
1708 <h2><a name="minput" id="minput">Processing Menu Input</a></h2>
1710 <p>The main loop of your menu-processing code should call
1711 <code>menu_driver()</code> repeatedly. The first argument of this
1712 routine is a menu pointer; the second is a menu command code. You
1713 should write an input-fetching routine that maps input characters
1714 to menu command codes, and pass its output to
1715 <code>menu_driver()</code>. The menu command codes are fully
1716 documented in <code>menu_driver(3x)</code>.</p>
1718 <p>The simplest group of command codes is
1719 <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>,
1720 <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>,
1721 <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>,
1722 <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These
1723 change the currently selected item. These requests may cause
1724 scrolling of the menu page if it only partially displayed.</p>
1726 <p>There are explicit requests for scrolling which also change
1727 the current item (because the select location does not change,
1728 but the item there does). These are <code>REQ_SCR_DLINE</code>,
1729 <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and
1730 <code>REQ_SCR_UPAGE</code>.</p>
1732 <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the
1733 current item. It is for use in multi-valued menus; if you use it
1734 with <code>O_ONEVALUE</code> on, you will get an error return
1735 (<code>E_REQUEST_DENIED</code>).</p>
1737 <p>Each menu has an associated pattern buffer. The
1738 <code>menu_driver()</code> logic tries to accumulate printable
1739 ASCII characters passed in in that buffer; when it matches a
1740 prefix of an item name, that item (or the next matching item) is
1741 selected. If appending a character yields no new match, that
1742 character is deleted from the pattern buffer, and
1743 <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p>
1745 <p>Some requests change the pattern buffer directly:
1746 <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>,
1747 <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The
1748 latter two are useful when pattern buffer input matches more than
1749 one item in a multi-valued menu.</p>
1751 <p>Each successful scroll or item navigation request clears the
1752 pattern buffer. It is also possible to set the pattern buffer
1753 explicitly with <code>set_menu_pattern()</code>.</p>
1755 <p>Finally, menu driver requests above the constant
1756 <code>MAX_COMMAND</code> are considered application-specific
1757 commands. The <code>menu_driver()</code> code ignores them and
1758 returns <code>E_UNKNOWN_COMMAND</code>.</p>
1760 <h2><a name="mmisc" id="mmisc">Miscellaneous Other
1763 <p>Various menu options can affect the processing and visual
1764 appearance and input processing of menus. See <code>menu_opts(3x)
1765 for details.</code></p>
1767 <p>It is possible to change the current item from application
1768 code; this is useful if you want to write your own navigation
1769 requests. It is also possible to explicitly set the top row of
1770 the menu display. See <code>mitem_current(3x)</code>. If your
1771 application needs to change the menu subwindow cursor for any
1772 reason, <code>pos_menu_cursor()</code> will restore it to the
1773 correct location for continuing menu driver processing.</p>
1775 <p>It is possible to set hooks to be called at menu
1776 initialization and wrapup time, and whenever the selected item
1777 changes. See <code>menu_hook(3x)</code>.</p>
1779 <p>Each item, and each menu, has an associated user pointer on
1780 which you can hang application data. See
1781 <code>mitem_userptr(3x)</code> and
1782 <code>menu_userptr(3x)</code>.</p>
1784 <h1><a name="form" id="form">The Forms Library</a></h1>
1786 <p>The <code>form</code> library is a curses extension that
1787 supports easy programming of on-screen forms for data entry and
1788 program control.</p>
1790 <p>The <code>form</code> library first appeared in AT&T
1791 System V. The version documented here is the <code>form</code>
1792 code distributed with <code>ncurses</code>.</p>
1794 <h2><a name="fcompile" id="fcompile">Compiling With the form
1797 <p>Your form-using modules must import the form library
1798 declarations with</p>
1800 #include <form.h>
1803 <p>and must be linked explicitly with the forms library using an
1804 <code>-lform</code> argument. Note that they must also link the
1805 <code>ncurses</code> library with <code>-lncurses</code>. Many
1806 linkers are two-pass and will accept either order, but it is
1807 still good practice to put <code>-lform</code> first and
1808 <code>-lncurses</code> second.</p>
1810 <h2><a name="foverview" id="foverview">Overview of Forms</a></h2>
1812 <p>A form is a collection of fields; each field may be either a
1813 label (explanatory text) or a data-entry location. Long forms may
1814 be segmented into pages; each entry to a new page clears the
1817 <p>To make forms, you create groups of fields and connect them
1818 with form frame objects; the form library makes this relatively
1821 <p>Once defined, a form can be <dfn>posted</dfn>, that is written
1822 to an associated window. Actually, each form has two associated
1823 windows; a containing window in which the programmer can scribble
1824 titles or borders, and a subwindow in which the form fields
1825 proper are displayed.</p>
1827 <p>As the form user fills out the posted form, navigation and
1828 editing keys support movement between fields, editing keys
1829 support modifying field, and plain text adds to or changes data
1830 in a current field. The form library allows you (the forms
1831 designer) to bind each navigation and editing key to any
1832 keystroke accepted by <code>curses</code> Fields may have
1833 validation conditions on them, so that they check input data for
1834 type and value. The form library supplies a rich set of
1835 pre-defined field types, and makes it relatively easy to define
1838 <p>Once its transaction is completed (or aborted), a form may be
1839 <dfn>unposted</dfn> (that is, undisplayed), and finally freed to
1840 make the storage associated with it and its items available for
1843 <p>The general flow of control of a form program looks like
1847 <li>Initialize <code>curses</code>.</li>
1849 <li>Create the form fields, using
1850 <code>new_field()</code>.</li>
1852 <li>Create the form using <code>new_form()</code>.</li>
1854 <li>Post the form using <code>post_form()</code>.</li>
1856 <li>Refresh the screen.</li>
1858 <li>Process user requests via an input loop.</li>
1860 <li>Unpost the form using <code>unpost_form()</code>.</li>
1862 <li>Free the form, using <code>free_form()</code>.</li>
1864 <li>Free the fields using <code>free_field()</code>.</li>
1866 <li>Terminate <code>curses</code>.</li>
1869 <p>Note that this looks much like a menu program; the form
1870 library handles tasks which are in many ways similar, and its
1871 interface was obviously designed to resemble that of the <a href=
1872 "#menu">menu library</a> wherever possible.</p>
1874 <p>In forms programs, however, the “process user
1875 requests” is somewhat more complicated than for menus.
1876 Besides menu-like navigation operations, the menu driver loop has
1877 to support field editing and data validation.</p>
1879 <h2><a name="fcreate" id="fcreate">Creating and Freeing Fields
1882 <p>The basic function for creating fields is
1883 <code>new_field()</code>:</p>
1885 FIELD *new_field(int height, int width, /* new field size */
1886 int top, int left, /* upper left corner */
1887 int offscreen, /* number of offscreen rows */
1888 int nbuf); /* number of working buffers */
1891 <p>Menu items always occupy a single row, but forms fields may
1892 have multiple rows. So <code>new_field()</code> requires you to
1893 specify a width and height (the first two arguments, which mist
1894 both be greater than zero).</p>
1896 <p>You must also specify the location of the field's upper left
1897 corner on the screen (the third and fourth arguments, which must
1898 be zero or greater). Note that these coordinates are relative to
1899 the form subwindow, which will coincide with <code>stdscr</code>
1900 by default but need not be <code>stdscr</code> if you have done
1901 an explicit <code>set_form_win()</code> call.</p>
1903 <p>The fifth argument allows you to specify a number of
1904 off-screen rows. If this is zero, the entire field will always be
1905 displayed. If it is nonzero, the form will be scrollable, with
1906 only one screen-full (initially the top part) displayed at any
1907 given time. If you make a field dynamic and grow it so it will no
1908 longer fit on the screen, the form will become scrollable even if
1909 the <code>offscreen</code> argument was initially zero.</p>
1911 <p>The forms library allocates one working buffer per field; the
1912 size of each buffer is <code>((height + offscreen)*width +
1913 1</code>, one character for each position in the field plus a NUL
1914 terminator. The sixth argument is the number of additional data
1915 buffers to allocate for the field; your application can use them
1916 for its own purposes.</p>
1918 FIELD *dup_field(FIELD *field, /* field to copy */
1919 int top, int left); /* location of new copy */
1922 <p>The function <code>dup_field()</code> duplicates an existing
1923 field at a new location. Size and buffering information are
1924 copied; some attribute flags and status bits are not (see the
1925 <code>form_field_new(3X)</code> for details).</p>
1927 FIELD *link_field(FIELD *field, /* field to copy */
1928 int top, int left); /* location of new copy */
1931 <p>The function <code>link_field()</code> also duplicates an
1932 existing field at a new location. The difference from
1933 <code>dup_field()</code> is that it arranges for the new field's
1934 buffer to be shared with the old one.</p>
1936 <p>Besides the obvious use in making a field editable from two
1937 different form pages, linked fields give you a way to hack in
1938 dynamic labels. If you declare several fields linked to an
1939 original, and then make them inactive, changes from the original
1940 will still be propagated to the linked fields.</p>
1942 <p>As with duplicated fields, linked fields have attribute bits
1943 separate from the original.</p>
1945 <p>As you might guess, all these field-allocations return
1946 <code>NULL</code> if the field allocation is not possible due to
1947 an out-of-memory error or out-of-bounds arguments.</p>
1949 <p>To connect fields to a form, use</p>
1951 FORM *new_form(FIELD **fields);
1954 <p>This function expects to see a NULL-terminated array of field
1955 pointers. Said fields are connected to a newly-allocated form
1956 object; its address is returned (or else NULL if the allocation
1959 <p>Note that <code>new_field()</code> does <em>not</em> copy the
1960 pointer array into private storage; if you modify the contents of
1961 the pointer array during forms processing, all manner of bizarre
1962 things might happen. Also note that any given field may only be
1963 connected to one form.</p>
1965 <p>The functions <code>free_field()</code> and
1966 <code>free_form</code> are available to free field and form
1967 objects. It is an error to attempt to free a field connected to a
1968 form, but not vice-versa; thus, you will generally free your form
1971 <h2><a name="fattributes" id="fattributes">Fetching and Changing
1972 Field Attributes</a></h2>
1974 <p>Each form field has a number of location and size attributes
1975 associated with it. There are other field attributes used to
1976 control display and editing of the field. Some (for example, the
1977 <code>O_STATIC</code> bit) involve sufficient complications to be
1978 covered in sections of their own later on. We cover the functions
1979 used to get and set several basic attributes here.</p>
1981 <p>When a field is created, the attributes not specified by the
1982 <code>new_field</code> function are copied from an invisible
1983 system default field. In attribute-setting and -fetching
1984 functions, the argument NULL is taken to mean this field. Changes
1985 to it persist as defaults until your forms application
1988 <h3><a name="fsizes" id="fsizes">Fetching Size and Location
1991 <p>You can retrieve field sizes and locations through:</p>
1993 int field_info(FIELD *field, /* field from which to fetch */
1994 int *height, *int width, /* field size */
1995 int *top, int *left, /* upper left corner */
1996 int *offscreen, /* number of offscreen rows */
1997 int *nbuf); /* number of working buffers */
2000 <p>This function is a sort of inverse of
2001 <code>new_field()</code>; instead of setting size and location
2002 attributes of a new field, it fetches them from an existing
2005 <h3><a name="flocation" id="flocation">Changing the Field
2008 <p>It is possible to move a field's location on the screen:</p>
2010 int move_field(FIELD *field, /* field to alter */
2011 int top, int left); /* new upper-left corner */
2014 <p>You can, of course. query the current location through
2015 <code>field_info()</code>.</p>
2017 <h3><a name="fjust" id="fjust">The Justification
2020 <p>One-line fields may be unjustified, justified right, justified
2021 left, or centered. Here is how you manipulate this attribute:</p>
2023 int set_field_just(FIELD *field, /* field to alter */
2024 int justmode); /* mode to set */
2026 int field_just(FIELD *field); /* fetch mode of field */
2029 <p>The mode values accepted and returned by this functions are
2030 preprocessor macros <code>NO_JUSTIFICATION</code>,
2031 <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or
2032 <code>JUSTIFY_CENTER</code>.</p>
2034 <h3><a name="fdispatts" id="fdispatts">Field Display
2037 <p>For each field, you can set a foreground attribute for entered
2038 characters, a background attribute for the entire field, and a
2039 pad character for the unfilled portion of the field. You can also
2040 control pagination of the form.</p>
2042 <p>This group of four field attributes controls the visual
2043 appearance of the field on the screen, without affecting in any
2044 way the data in the field buffer.</p>
2046 int set_field_fore(FIELD *field, /* field to alter */
2047 chtype attr); /* attribute to set */
2049 chtype field_fore(FIELD *field); /* field to query */
2051 int set_field_back(FIELD *field, /* field to alter */
2052 chtype attr); /* attribute to set */
2054 chtype field_back(FIELD *field); /* field to query */
2056 int set_field_pad(FIELD *field, /* field to alter */
2057 int pad); /* pad character to set */
2059 chtype field_pad(FIELD *field);
2061 int set_new_page(FIELD *field, /* field to alter */
2062 int flag); /* TRUE to force new page */
2064 chtype new_page(FIELD *field); /* field to query */
2067 <p>The attributes set and returned by the first four functions
2068 are normal <code>curses(3x)</code> display attribute values
2069 (<code>A_STANDOUT</code>, <code>A_BOLD</code>,
2070 <code>A_REVERSE</code> etc). The page bit of a field controls
2071 whether it is displayed at the start of a new form screen.</p>
2073 <h3><a name="foptions" id="foptions">Field Option Bits</a></h3>
2075 <p>There is also a large collection of field option bits you can
2076 set to control various aspects of forms processing. You can
2077 manipulate them with these functions:</p>
2079 int set_field_opts(FIELD *field, /* field to alter */
2080 int attr); /* attribute to set */
2082 int field_opts_on(FIELD *field, /* field to alter */
2083 int attr); /* attributes to turn on */
2085 int field_opts_off(FIELD *field, /* field to alter */
2086 int attr); /* attributes to turn off */
2088 int field_opts(FIELD *field); /* field to query */
2091 <p>By default, all options are on. Here are the available option
2097 <dd>Controls whether the field is visible on the screen. Can be
2098 used during form processing to hide or pop up fields depending
2099 on the value of parent fields.</dd>
2103 <dd>Controls whether the field is active during forms
2104 processing (i.e. visited by form navigation keys). Can be used
2105 to make labels or derived fields with buffer values alterable
2106 by the forms application, not the user.</dd>
2110 <dd>Controls whether data is displayed during field entry. If
2111 this option is turned off on a field, the library will accept
2112 and edit data in that field, but it will not be displayed and
2113 the visible field cursor will not move. You can turn off the
2114 O_PUBLIC bit to define password fields.</dd>
2118 <dd>Controls whether the field's data can be modified. When
2119 this option is off, all editing requests except
2120 <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code>
2121 will fail. Such read-only fields may be useful for help
2126 <dd>Controls word-wrapping in multi-line fields. Normally, when
2127 any character of a (blank-separated) word reaches the end of
2128 the current line, the entire word is wrapped to the next line
2129 (assuming there is one). When this option is off, the word will
2130 be split across the line break.</dd>
2134 <dd>Controls field blanking. When this option is on, entering a
2135 character at the first field position erases the entire field
2136 (except for the just-entered character).</dd>
2140 <dd>Controls automatic skip to next field when this one fills.
2141 Normally, when the forms user tries to type more data into a
2142 field than will fit, the editing location jumps to next field.
2143 When this option is off, the user's cursor will hang at the end
2144 of the field. This option is ignored in dynamic fields that
2145 have not reached their size limit.</dd>
2149 <dd>Controls whether <a href="#fvalidation">validation</a> is
2150 applied to blank fields. Normally, it is not; the user can
2151 leave a field blank without invoking the usual validation check
2152 on exit. If this option is off on a field, exit from it will
2153 invoke a validation check.</dd>
2157 <dd>Controls whether validation occurs on every exit, or only
2158 after the field is modified. Normally the latter is true.
2159 Setting O_PASSOK may be useful if your field's validation
2160 function may change during forms processing.</dd>
2164 <dd>Controls whether the field is fixed to its initial
2165 dimensions. If you turn this off, the field becomes <a href=
2166 "#fdynamic">dynamic</a> and will stretch to fit entered
2170 <p>A field's options cannot be changed while the field is
2171 currently selected. However, options may be changed on posted
2172 fields that are not current.</p>
2174 <p>The option values are bit-masks and can be composed with
2175 logical-or in the obvious way.</p>
2177 <h2><a name="fstatus" id="fstatus">Field Status</a></h2>
2179 <p>Every field has a status flag, which is set to FALSE when the
2180 field is created and TRUE when the value in field buffer 0
2181 changes. This flag can be queried and set directly:</p>
2183 int set_field_status(FIELD *field, /* field to alter */
2184 int status); /* mode to set */
2186 int field_status(FIELD *field); /* fetch mode of field */
2189 <p>Setting this flag under program control can be useful if you
2190 use the same form repeatedly, looking for modified fields each
2193 <p>Calling <code>field_status()</code> on a field not currently
2194 selected for input will return a correct value. Calling
2195 <code>field_status()</code> on a field that is currently selected
2196 for input may not necessarily give a correct field status value,
2197 because entered data is not necessarily copied to buffer zero
2198 before the exit validation check. To guarantee that the returned
2199 status value reflects reality, call <code>field_status()</code>
2200 either (1) in the field's exit validation check routine, (2) from
2201 the field's or form's initialization or termination hooks, or (3)
2202 just after a <code>REQ_VALIDATION</code> request has been
2203 processed by the forms driver.</p>
2205 <h2><a name="fuser" id="fuser">Field User Pointer</a></h2>
2207 <p>Each field structure contains one character pointer slot that
2208 is not used by the forms library. It is intended to be used by
2209 applications to store private per-field data. You can manipulate
2212 int set_field_userptr(FIELD *field, /* field to alter */
2213 char *userptr); /* mode to set */
2215 char *field_userptr(FIELD *field); /* fetch mode of field */
2216 </pre>(Properly, this user pointer field ought to have <code>(void
2217 *)</code> type. The <code>(char *)</code> type is retained for
2218 System V compatibility.)
2220 <p>It is valid to set the user pointer of the default field (with
2221 a <code>set_field_userptr()</code> call passed a NULL field
2222 pointer.) When a new field is created, the default-field user
2223 pointer is copied to initialize the new field's user pointer.</p>
2225 <h2><a name="fdynamic" id="fdynamic">Variable-Sized
2228 <p>Normally, a field is fixed at the size specified for it at
2229 creation time. If, however, you turn off its O_STATIC bit, it
2230 becomes <dfn>dynamic</dfn> and will automatically resize itself
2231 to accommodate data as it is entered. If the field has extra
2232 buffers associated with it, they will grow right along with the
2233 main input buffer.</p>
2235 <p>A one-line dynamic field will have a fixed height (1) but
2236 variable width, scrolling horizontally to display data within the
2237 field area as originally dimensioned and located. A multi-line
2238 dynamic field will have a fixed width, but variable height
2239 (number of rows), scrolling vertically to display data within the
2240 field area as originally dimensioned and located.</p>
2242 <p>Normally, a dynamic field is allowed to grow without limit.
2243 But it is possible to set an upper limit on the size of a dynamic
2244 field. You do it with this function:</p>
2246 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
2247 int max_size); /* upper limit on field size */
2250 <p>If the field is one-line, <code>max_size</code> is taken to be
2251 a column size limit; if it is multi-line, it is taken to be a
2252 line size limit. To disable any limit, use an argument of zero.
2253 The growth limit can be changed whether or not the O_STATIC bit
2254 is on, but has no effect until it is.</p>
2256 <p>The following properties of a field change when it becomes
2260 <li>If there is no growth limit, there is no final position of
2261 the field; therefore <code>O_AUTOSKIP</code> and
2262 <code>O_NL_OVERLOAD</code> are ignored.</li>
2264 <li>Field justification will be ignored (though whatever
2265 justification is set up will be retained internally and can be
2268 <li>The <code>dup_field()</code> and <code>link_field()</code>
2269 calls copy dynamic-buffer sizes. If the <code>O_STATIC</code>
2270 option is set on one of a collection of links, buffer resizing
2271 will occur only when the field is edited through that
2274 <li>The call <code>field_info()</code> will retrieve the
2275 original static size of the field; use
2276 <code>dynamic_field_info()</code> to get the actual dynamic
2280 <h2><a name="fvalidation" id="fvalidation">Field
2283 <p>By default, a field will accept any data that will fit in its
2284 input buffer. However, it is possible to attach a validation type
2285 to a field. If you do this, any attempt to leave the field while
2286 it contains data that does not match the validation type will
2287 fail. Some validation types also have a character-validity check
2288 for each time a character is entered in the field.</p>
2290 <p>A field's validation check (if any) is not called when
2291 <code>set_field_buffer()</code> modifies the input buffer, nor
2292 when that buffer is changed through a linked field.</p>
2294 <p>The <code>form</code> library provides a rich set of
2295 pre-defined validation types, and gives you the capability to
2296 define custom ones of your own. You can examine and change field
2297 validation attributes with the following functions:</p>
2299 int set_field_type(FIELD *field, /* field to alter */
2300 FIELDTYPE *ftype, /* type to associate */
2301 ...); /* additional arguments*/
2303 FIELDTYPE *field_type(FIELD *field); /* field to query */
2306 <p>The validation type of a field is considered an attribute of
2307 the field. As with other field attributes, Also, doing
2308 <code>set_field_type()</code> with a <code>NULL</code> field
2309 default will change the system default for validation of
2310 newly-created fields.</p>
2312 <p>Here are the pre-defined validation types:</p>
2314 <h3><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h3>
2316 <p>This field type accepts alphabetic data; no blanks, no digits,
2317 no special characters (this is checked at character-entry time).
2318 It is set up with:</p>
2320 int set_field_type(FIELD *field, /* field to alter */
2321 TYPE_ALPHA, /* type to associate */
2322 int width); /* maximum width of field */
2325 <p>The <code>width</code> argument sets a minimum width of data.
2326 Typically you will want to set this to the field width; if it is
2327 greater than the field width, the validation check will always
2328 fail. A minimum width of zero makes field completion
2331 <h3><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h3>
2333 <p>This field type accepts alphabetic data and digits; no blanks,
2334 no special characters (this is checked at character-entry time).
2335 It is set up with:</p>
2337 int set_field_type(FIELD *field, /* field to alter */
2338 TYPE_ALNUM, /* type to associate */
2339 int width); /* maximum width of field */
2342 <p>The <code>width</code> argument sets a minimum width of data.
2343 As with TYPE_ALPHA, typically you will want to set this to the
2344 field width; if it is greater than the field width, the
2345 validation check will always fail. A minimum width of zero makes
2346 field completion optional.</p>
2348 <h3><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h3>
2350 <p>This type allows you to restrict a field's values to be among
2351 a specified set of string values (for example, the two-letter
2352 postal codes for U.S. states). It is set up with:</p>
2354 int set_field_type(FIELD *field, /* field to alter */
2355 TYPE_ENUM, /* type to associate */
2356 char **valuelist; /* list of possible values */
2357 int checkcase; /* case-sensitive? */
2358 int checkunique); /* must specify uniquely? */
2361 <p>The <code>valuelist</code> parameter must point at a
2362 NULL-terminated list of valid strings. The <code>checkcase</code>
2363 argument, if true, makes comparison with the string
2366 <p>When the user exits a TYPE_ENUM field, the validation
2367 procedure tries to complete the data in the buffer to a valid
2368 entry. If a complete choice string has been entered, it is of
2369 course valid. But it is also possible to enter a prefix of a
2370 valid string and have it completed for you.</p>
2372 <p>By default, if you enter such a prefix and it matches more
2373 than one value in the string list, the prefix will be completed
2374 to the first matching value. But the <code>checkunique</code>
2375 argument, if true, requires prefix matches to be unique in order
2378 <p>The <code>REQ_NEXT_CHOICE</code> and
2379 <code>REQ_PREV_CHOICE</code> input requests can be particularly
2380 useful with these fields.</p>
2382 <h3><a name="ftype_integer" id=
2383 "ftype_integer">TYPE_INTEGER</a></h3>
2385 <p>This field type accepts an integer. It is set up as
2388 int set_field_type(FIELD *field, /* field to alter */
2389 TYPE_INTEGER, /* type to associate */
2390 int padding, /* # places to zero-pad to */
2391 int vmin, int vmax); /* valid range */
2394 <p>Valid characters consist of an optional leading minus and
2395 digits. The range check is performed on exit. If the range
2396 maximum is less than or equal to the minimum, the range is
2399 <p>If the value passes its range check, it is padded with as many
2400 leading zero digits as necessary to meet the padding
2403 <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be
2404 interpreted with the C library function <code>atoi(3)</code>.</p>
2406 <h3><a name="ftype_numeric" id=
2407 "ftype_numeric">TYPE_NUMERIC</a></h3>
2409 <p>This field type accepts a decimal number. It is set up as
2412 int set_field_type(FIELD *field, /* field to alter */
2413 TYPE_NUMERIC, /* type to associate */
2414 int padding, /* # places of precision */
2415 double vmin, double vmax); /* valid range */
2418 <p>Valid characters consist of an optional leading minus and
2419 digits. possibly including a decimal point. If your system
2420 supports locale's, the decimal point character used must be the
2421 one defined by your locale. The range check is performed on exit.
2422 If the range maximum is less than or equal to the minimum, the
2423 range is ignored.</p>
2425 <p>If the value passes its range check, it is padded with as many
2426 trailing zero digits as necessary to meet the padding
2429 <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be
2430 interpreted with the C library function <code>atof(3)</code>.</p>
2432 <h3><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h3>
2434 <p>This field type accepts data matching a regular expression. It
2435 is set up as follows:</p>
2437 int set_field_type(FIELD *field, /* field to alter */
2438 TYPE_REGEXP, /* type to associate */
2439 char *regexp); /* expression to match */
2442 <p>The syntax for regular expressions is that of
2443 <code>regcomp(3)</code>. The check for regular-expression match
2444 is performed on exit.</p>
2446 <h2><a name="fbuffer" id="fbuffer">Direct Field Buffer
2447 Manipulation</a></h2>
2449 <p>The chief attribute of a field is its buffer contents. When a
2450 form has been completed, your application usually needs to know
2451 the state of each field buffer. You can find this out with:</p>
2453 char *field_buffer(FIELD *field, /* field to query */
2454 int bufindex); /* number of buffer to query */
2457 <p>Normally, the state of the zero-numbered buffer for each field
2458 is set by the user's editing actions on that field. It is
2459 sometimes useful to be able to set the value of the zero-numbered
2460 (or some other) buffer from your application:</p>
2462 int set_field_buffer(FIELD *field, /* field to alter */
2463 int bufindex, /* number of buffer to alter */
2464 char *value); /* string value to set */
2467 <p>If the field is not large enough and cannot be resized to a
2468 sufficiently large size to contain the specified value, the value
2469 will be truncated to fit.</p>
2471 <p>Calling <code>field_buffer()</code> with a null field pointer
2472 will raise an error. Calling <code>field_buffer()</code> on a
2473 field not currently selected for input will return a correct
2474 value. Calling <code>field_buffer()</code> on a field that is
2475 currently selected for input may not necessarily give a correct
2476 field buffer value, because entered data is not necessarily
2477 copied to buffer zero before the exit validation check. To
2478 guarantee that the returned buffer value reflects on-screen
2479 reality, call <code>field_buffer()</code> either (1) in the
2480 field's exit validation check routine, (2) from the field's or
2481 form's initialization or termination hooks, or (3) just after a
2482 <code>REQ_VALIDATION</code> request has been processed by the
2485 <h2><a name="formattrs" id="formattrs">Attributes of
2488 <p>As with field attributes, form attributes inherit a default
2489 from a system default form structure. These defaults can be
2490 queried or set by of these functions using a form-pointer
2491 argument of <code>NULL</code>.</p>
2493 <p>The principal attribute of a form is its field list. You can
2494 query and change this list with:</p>
2496 int set_form_fields(FORM *form, /* form to alter */
2497 FIELD **fields); /* fields to connect */
2499 char *form_fields(FORM *form); /* fetch fields of form */
2501 int field_count(FORM *form); /* count connect fields */
2504 <p>The second argument of <code>set_form_fields()</code> may be a
2505 NULL-terminated field pointer array like the one required by
2506 <code>new_form()</code>. In that case, the old fields of the form
2507 are disconnected but not freed (and eligible to be connected to
2508 other forms), then the new fields are connected.</p>
2510 <p>It may also be null, in which case the old fields are
2511 disconnected (and not freed) but no new ones are connected.</p>
2513 <p>The <code>field_count()</code> function simply counts the
2514 number of fields connected to a given from. It returns -1 if the
2515 form-pointer argument is NULL.</p>
2517 <h2><a name="fdisplay" id="fdisplay">Control of Form
2520 <p>In the overview section, you saw that to display a form you
2521 normally start by defining its size (and fields), posting it, and
2522 refreshing the screen. There is an hidden step before posting,
2523 which is the association of the form with a frame window
2524 (actually, a pair of windows) within which it will be displayed.
2525 By default, the forms library associates every form with the
2526 full-screen window <code>stdscr</code>.</p>
2528 <p>By making this step explicit, you can associate a form with a
2529 declared frame window on your screen display. This can be useful
2530 if you want to adapt the form display to different screen sizes,
2531 dynamically tile forms on the screen, or use a form as part of an
2532 interface layout managed by <a href="#panels">panels</a>.</p>
2534 <p>The two windows associated with each form have the same
2535 functions as their analogues in the <a href="#menu">menu
2536 library</a>. Both these windows are painted when the form is
2537 posted and erased when the form is unposted.</p>
2539 <p>The outer or frame window is not otherwise touched by the form
2540 routines. It exists so the programmer can associate a title, a
2541 border, or perhaps help text with the form and have it properly
2542 refreshed or erased at post/unpost time. The inner window or
2543 subwindow is where the current form page is actually
2546 <p>In order to declare your own frame window for a form, you will
2547 need to know the size of the form's bounding rectangle. You can
2548 get this information with:</p>
2550 int scale_form(FORM *form, /* form to query */
2551 int *rows, /* form rows */
2552 int *cols); /* form cols */
2555 <p>The form dimensions are passed back in the locations pointed
2556 to by the arguments. Once you have this information, you can use
2557 it to declare of windows, then use one of these functions:</p>
2559 int set_form_win(FORM *form, /* form to alter */
2560 WINDOW *win); /* frame window to connect */
2562 WINDOW *form_win(FORM *form); /* fetch frame window of form */
2564 int set_form_sub(FORM *form, /* form to alter */
2565 WINDOW *win); /* form subwindow to connect */
2567 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
2570 <p>Note that curses operations, including <code>refresh()</code>,
2571 on the form, should be done on the frame window, not the form
2574 <p>It is possible to check from your application whether all of a
2575 scrollable field is actually displayed within the menu subwindow.
2576 Use these functions:</p>
2578 int data_ahead(FORM *form); /* form to be queried */
2580 int data_behind(FORM *form); /* form to be queried */
2583 <p>The function <code>data_ahead()</code> returns TRUE if (a) the
2584 current field is one-line and has undisplayed data off to the
2585 right, (b) the current field is multi-line and there is data
2586 off-screen below it.</p>
2588 <p>The function <code>data_behind()</code> returns TRUE if the
2589 first (upper left hand) character position is off-screen (not
2590 being displayed).</p>
2592 <p>Finally, there is a function to restore the form window's
2593 cursor to the value expected by the forms driver:</p>
2595 int pos_form_cursor(FORM *) /* form to be queried */
2598 <p>If your application changes the form window cursor, call this
2599 function before handing control back to the forms driver in order
2600 to re-synchronize it.</p>
2602 <h2><a name="fdriver" id="fdriver">Input Processing in the Forms
2605 <p>The function <code>form_driver()</code> handles virtualized
2606 input requests for form navigation, editing, and validation
2607 requests, just as <code>menu_driver</code> does for menus (see
2608 the section on <a href="#minput">menu input handling</a>).</p>
2610 int form_driver(FORM *form, /* form to pass input to */
2611 int request); /* form request code */
2614 <p>Your input virtualization function needs to take input and
2615 then convert it to either an alphanumeric character (which is
2616 treated as data to be entered in the currently-selected field),
2617 or a forms processing request.</p>
2619 <p>The forms driver provides hooks (through input-validation and
2620 field-termination functions) with which your application code can
2621 check that the input taken by the driver matched what was
2624 <h3><a name="fpage" id="fpage">Page Navigation Requests</a></h3>
2626 <p>These requests cause page-level moves through the form,
2627 triggering display of a new form screen.</p>
2630 <dt><code>REQ_NEXT_PAGE</code></dt>
2632 <dd>Move to the next form page.</dd>
2634 <dt><code>REQ_PREV_PAGE</code></dt>
2636 <dd>Move to the previous form page.</dd>
2638 <dt><code>REQ_FIRST_PAGE</code></dt>
2640 <dd>Move to the first form page.</dd>
2642 <dt><code>REQ_LAST_PAGE</code></dt>
2644 <dd>Move to the last form page.</dd>
2647 <p>These requests treat the list as cyclic; that is,
2648 <code>REQ_NEXT_PAGE</code> from the last page goes to the first,
2649 and <code>REQ_PREV_PAGE</code> from the first page goes to the
2652 <h3><a name="ffield" id="ffield">Inter-Field Navigation
2655 <p>These requests handle navigation between fields on the same
2659 <dt><code>REQ_NEXT_FIELD</code></dt>
2661 <dd>Move to next field.</dd>
2663 <dt><code>REQ_PREV_FIELD</code></dt>
2665 <dd>Move to previous field.</dd>
2667 <dt><code>REQ_FIRST_FIELD</code></dt>
2669 <dd>Move to the first field.</dd>
2671 <dt><code>REQ_LAST_FIELD</code></dt>
2673 <dd>Move to the last field.</dd>
2675 <dt><code>REQ_SNEXT_FIELD</code></dt>
2677 <dd>Move to sorted next field.</dd>
2679 <dt><code>REQ_SPREV_FIELD</code></dt>
2681 <dd>Move to sorted previous field.</dd>
2683 <dt><code>REQ_SFIRST_FIELD</code></dt>
2685 <dd>Move to the sorted first field.</dd>
2687 <dt><code>REQ_SLAST_FIELD</code></dt>
2689 <dd>Move to the sorted last field.</dd>
2691 <dt><code>REQ_LEFT_FIELD</code></dt>
2693 <dd>Move left to field.</dd>
2695 <dt><code>REQ_RIGHT_FIELD</code></dt>
2697 <dd>Move right to field.</dd>
2699 <dt><code>REQ_UP_FIELD</code></dt>
2701 <dd>Move up to field.</dd>
2703 <dt><code>REQ_DOWN_FIELD</code></dt>
2705 <dd>Move down to field.</dd>
2708 <p>These requests treat the list of fields on a page as cyclic;
2709 that is, <code>REQ_NEXT_FIELD</code> from the last field goes to
2710 the first, and <code>REQ_PREV_FIELD</code> from the first field
2711 goes to the last. The order of the fields for these (and the
2712 <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code>
2713 requests) is simply the order of the field pointers in the form
2714 array (as set up by <code>new_form()</code> or
2715 <code>set_form_fields()</code></p>
2717 <p>It is also possible to traverse the fields as if they had been
2718 sorted in screen-position order, so the sequence goes
2719 left-to-right and top-to-bottom. To do this, use the second group
2720 of four sorted-movement requests.</p>
2722 <p>Finally, it is possible to move between fields using visual
2723 directions up, down, right, and left. To accomplish this, use the
2724 third group of four requests. Note, however, that the position of
2725 a form for purposes of these requests is its upper-left
2728 <p>For example, suppose you have a multi-line field B, and two
2729 single-line fields A and C on the same line with B, with A to the
2730 left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code>
2731 from A will go to B only if A, B, and C <em>all</em> share the
2732 same first line; otherwise it will skip over B to C.</p>
2734 <h3><a name="fifield" id="fifield">Intra-Field Navigation
2737 <p>These requests drive movement of the edit cursor within the
2738 currently selected field.</p>
2741 <dt><code>REQ_NEXT_CHAR</code></dt>
2743 <dd>Move to next character.</dd>
2745 <dt><code>REQ_PREV_CHAR</code></dt>
2747 <dd>Move to previous character.</dd>
2749 <dt><code>REQ_NEXT_LINE</code></dt>
2751 <dd>Move to next line.</dd>
2753 <dt><code>REQ_PREV_LINE</code></dt>
2755 <dd>Move to previous line.</dd>
2757 <dt><code>REQ_NEXT_WORD</code></dt>
2759 <dd>Move to next word.</dd>
2761 <dt><code>REQ_PREV_WORD</code></dt>
2763 <dd>Move to previous word.</dd>
2765 <dt><code>REQ_BEG_FIELD</code></dt>
2767 <dd>Move to beginning of field.</dd>
2769 <dt><code>REQ_END_FIELD</code></dt>
2771 <dd>Move to end of field.</dd>
2773 <dt><code>REQ_BEG_LINE</code></dt>
2775 <dd>Move to beginning of line.</dd>
2777 <dt><code>REQ_END_LINE</code></dt>
2779 <dd>Move to end of line.</dd>
2781 <dt><code>REQ_LEFT_CHAR</code></dt>
2783 <dd>Move left in field.</dd>
2785 <dt><code>REQ_RIGHT_CHAR</code></dt>
2787 <dd>Move right in field.</dd>
2789 <dt><code>REQ_UP_CHAR</code></dt>
2791 <dd>Move up in field.</dd>
2793 <dt><code>REQ_DOWN_CHAR</code></dt>
2795 <dd>Move down in field.</dd>
2798 <p>Each <em>word</em> is separated from the previous and next
2799 characters by whitespace. The commands to move to beginning and
2800 end of line or field look for the first or last non-pad character
2801 in their ranges.</p>
2803 <h3><a name="fscroll" id="fscroll">Scrolling Requests</a></h3>
2805 <p>Fields that are dynamic and have grown and fields explicitly
2806 created with offscreen rows are scrollable. One-line fields
2807 scroll horizontally; multi-line fields scroll vertically. Most
2808 scrolling is triggered by editing and intra-field movement (the
2809 library scrolls the field to keep the cursor visible). It is
2810 possible to explicitly request scrolling with the following
2814 <dt><code>REQ_SCR_FLINE</code></dt>
2816 <dd>Scroll vertically forward a line.</dd>
2818 <dt><code>REQ_SCR_BLINE</code></dt>
2820 <dd>Scroll vertically backward a line.</dd>
2822 <dt><code>REQ_SCR_FPAGE</code></dt>
2824 <dd>Scroll vertically forward a page.</dd>
2826 <dt><code>REQ_SCR_BPAGE</code></dt>
2828 <dd>Scroll vertically backward a page.</dd>
2830 <dt><code>REQ_SCR_FHPAGE</code></dt>
2832 <dd>Scroll vertically forward half a page.</dd>
2834 <dt><code>REQ_SCR_BHPAGE</code></dt>
2836 <dd>Scroll vertically backward half a page.</dd>
2838 <dt><code>REQ_SCR_FCHAR</code></dt>
2840 <dd>Scroll horizontally forward a character.</dd>
2842 <dt><code>REQ_SCR_BCHAR</code></dt>
2844 <dd>Scroll horizontally backward a character.</dd>
2846 <dt><code>REQ_SCR_HFLINE</code></dt>
2848 <dd>Scroll horizontally one field width forward.</dd>
2850 <dt><code>REQ_SCR_HBLINE</code></dt>
2852 <dd>Scroll horizontally one field width backward.</dd>
2854 <dt><code>REQ_SCR_HFHALF</code></dt>
2856 <dd>Scroll horizontally one half field width forward.</dd>
2858 <dt><code>REQ_SCR_HBHALF</code></dt>
2860 <dd>Scroll horizontally one half field width backward.</dd>
2863 <p>For scrolling purposes, a <em>page</em> of a field is the
2864 height of its visible part.</p>
2866 <h3><a name="fedit" id="fedit">Editing Requests</a></h3>
2868 <p>When you pass the forms driver an ASCII character, it is
2869 treated as a request to add the character to the field's data
2870 buffer. Whether this is an insertion or a replacement depends on
2871 the field's edit mode (insertion is the default.</p>
2873 <p>The following requests support editing the field and changing
2877 <dt><code>REQ_INS_MODE</code></dt>
2879 <dd>Set insertion mode.</dd>
2881 <dt><code>REQ_OVL_MODE</code></dt>
2883 <dd>Set overlay mode.</dd>
2885 <dt><code>REQ_NEW_LINE</code></dt>
2887 <dd>New line request (see below for explanation).</dd>
2889 <dt><code>REQ_INS_CHAR</code></dt>
2891 <dd>Insert space at character location.</dd>
2893 <dt><code>REQ_INS_LINE</code></dt>
2895 <dd>Insert blank line at character location.</dd>
2897 <dt><code>REQ_DEL_CHAR</code></dt>
2899 <dd>Delete character at cursor.</dd>
2901 <dt><code>REQ_DEL_PREV</code></dt>
2903 <dd>Delete previous word at cursor.</dd>
2905 <dt><code>REQ_DEL_LINE</code></dt>
2907 <dd>Delete line at cursor.</dd>
2909 <dt><code>REQ_DEL_WORD</code></dt>
2911 <dd>Delete word at cursor.</dd>
2913 <dt><code>REQ_CLR_EOL</code></dt>
2915 <dd>Clear to end of line.</dd>
2917 <dt><code>REQ_CLR_EOF</code></dt>
2919 <dd>Clear to end of field.</dd>
2921 <dt><code>REQ_CLEAR_FIELD</code></dt>
2923 <dd>Clear entire field.</dd>
2926 <p>The behavior of the <code>REQ_NEW_LINE</code> and
2927 <code>REQ_DEL_PREV</code> requests is complicated and partly
2928 controlled by a pair of forms options. The special cases are
2929 triggered when the cursor is at the beginning of a field, or on
2930 the last line of the field.</p>
2932 <p>First, we consider <code>REQ_NEW_LINE</code>:</p>
2934 <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert
2935 mode is to break the current line at the position of the edit
2936 cursor, inserting the portion of the current line after the
2937 cursor as a new line following the current and moving the cursor
2938 to the beginning of that new line (you may think of this as
2939 inserting a newline in the field buffer).</p>
2941 <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay
2942 mode is to clear the current line from the position of the edit
2943 cursor to end of line. The cursor is then moved to the beginning
2944 of the next line.</p>
2946 <p>However, <code>REQ_NEW_LINE</code> at the beginning of a
2947 field, or on the last line of a field, instead does a
2948 <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is
2949 off, this special action is disabled.</p>
2951 <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p>
2953 <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete
2954 the previous character. If insert mode is on, and the cursor is
2955 at the start of a line, and the text on that line will fit on the
2956 previous one, it instead appends the contents of the current line
2957 to the previous one and deletes the current line (you may think
2958 of this as deleting a newline from the field buffer).</p>
2960 <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field
2961 is instead treated as a <code>REQ_PREV_FIELD</code>.</p>
2963 <p>If the <code>O_BS_OVERLOAD</code> option is off, this special
2964 action is disabled and the forms driver just returns
2965 <code>E_REQUEST_DENIED</code>.</p>
2967 <p>See <a href="#frmoptions">Form Options</a> for discussion of
2968 how to set and clear the overload options.</p>
2970 <h3><a name="forder" id="forder">Order Requests</a></h3>
2972 <p>If the type of your field is ordered, and has associated
2973 functions for getting the next and previous values of the type
2974 from a given value, there are requests that can fetch that value
2975 into the field buffer:</p>
2978 <dt><code>REQ_NEXT_CHOICE</code></dt>
2980 <dd>Place the successor value of the current value in the
2983 <dt><code>REQ_PREV_CHOICE</code></dt>
2985 <dd>Place the predecessor value of the current value in the
2989 <p>Of the built-in field types, only <code>TYPE_ENUM</code> has
2990 built-in successor and predecessor functions. When you define a
2991 field type of your own (see <a href="#fcustom">Custom Validation
2992 Types</a>), you can associate our own ordering functions.</p>
2994 <h3><a name="fappcmds" id="fappcmds">Application
2997 <p>Form requests are represented as integers above the
2998 <code>curses</code> value greater than <code>KEY_MAX</code> and
2999 less than or equal to the constant <code>MAX_COMMAND</code>. If
3000 your input-virtualization routine returns a value above
3001 <code>MAX_COMMAND</code>, the forms driver will ignore it.</p>
3003 <h2><a name="fhooks" id="fhooks">Field Change Hooks</a></h2>
3005 <p>It is possible to set function hooks to be executed whenever
3006 the current field or form changes. Here are the functions that
3009 typedef void (*HOOK)(); /* pointer to function returning void */
3011 int set_form_init(FORM *form, /* form to alter */
3012 HOOK hook); /* initialization hook */
3014 HOOK form_init(FORM *form); /* form to query */
3016 int set_form_term(FORM *form, /* form to alter */
3017 HOOK hook); /* termination hook */
3019 HOOK form_term(FORM *form); /* form to query */
3021 int set_field_init(FORM *form, /* form to alter */
3022 HOOK hook); /* initialization hook */
3024 HOOK field_init(FORM *form); /* form to query */
3026 int set_field_term(FORM *form, /* form to alter */
3027 HOOK hook); /* termination hook */
3029 HOOK field_term(FORM *form); /* form to query */
3032 <p>These functions allow you to either set or query four
3033 different hooks. In each of the set functions, the second
3034 argument should be the address of a hook function. These
3035 functions differ only in the timing of the hook call.</p>
3040 <dd>This hook is called when the form is posted; also, just
3041 after each page change operation.</dd>
3045 <dd>This hook is called when the form is posted; also, just
3046 after each field change</dd>
3050 <dd>This hook is called just after field validation; that is,
3051 just before the field is altered. It is also called when the
3052 form is unposted.</dd>
3056 <dd>This hook is called when the form is unposted; also, just
3057 before each page change operation.</dd>
3060 <p>Calls to these hooks may be triggered</p>
3063 <li>When user editing requests are processed by the forms
3066 <li>When the current page is changed by
3067 <code>set_current_field()</code> call</li>
3069 <li>When the current field is changed by a
3070 <code>set_form_page()</code> call</li>
3073 <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for
3074 discussion of the latter two cases.</p>
3076 <p>You can set a default hook for all fields by passing one of
3077 the set functions a NULL first argument.</p>
3079 <p>You can disable any of these hooks by (re)setting them to
3080 NULL, the default value.</p>
3082 <h2><a href="#ffocus">Field Change Commands</a></h2>
3084 <p>Normally, navigation through the form will be driven by the
3085 user's input requests. But sometimes it is useful to be able to
3086 move the focus for editing and viewing under control of your
3087 application, or ask which field it currently is in. The following
3088 functions help you accomplish this:</p>
3090 int set_current_field(FORM *form, /* form to alter */
3091 FIELD *field); /* field to shift to */
3093 FIELD *current_field(FORM *form); /* form to query */
3095 int field_index(FORM *form, /* form to query */
3096 FIELD *field); /* field to get index of */
3099 <p>The function <code>field_index()</code> returns the index of
3100 the given field in the given form's field array (the array passed
3101 to <code>new_form()</code> or
3102 <code>set_form_fields()</code>).</p>
3104 <p>The initial current field of a form is the first active field
3105 on the first page. The function <code>set_form_fields()</code>
3108 <p>It is also possible to move around by pages.</p>
3110 int set_form_page(FORM *form, /* form to alter */
3111 int page); /* page to go to (0-origin) */
3113 int form_page(FORM *form); /* return form's current page */
3116 <p>The initial page of a newly-created form is 0. The function
3117 <code>set_form_fields()</code> resets this.</p>
3119 <h2><a name="frmoptions" id="frmoptions">Form Options</a></h2>
3121 <p>Like fields, forms may have control option bits. They can be
3122 changed or queried with these functions:</p>
3124 int set_form_opts(FORM *form, /* form to alter */
3125 int attr); /* attribute to set */
3127 int form_opts_on(FORM *form, /* form to alter */
3128 int attr); /* attributes to turn on */
3130 int form_opts_off(FORM *form, /* form to alter */
3131 int attr); /* attributes to turn off */
3133 int form_opts(FORM *form); /* form to query */
3136 <p>By default, all options are on. Here are the available option
3140 <dt>O_NL_OVERLOAD</dt>
3142 <dd>Enable overloading of <code>REQ_NEW_LINE</code> as
3143 described in <a href="#fedit">Editing Requests</a>. The value
3144 of this option is ignored on dynamic fields that have not
3145 reached their size limit; these have no last line, so the
3146 circumstances for triggering a <code>REQ_NEXT_FIELD</code>
3149 <dt>O_BS_OVERLOAD</dt>
3151 <dd>Enable overloading of <code>REQ_DEL_PREV</code> as
3152 described in <a href="#fedit">Editing Requests</a>.</dd>
3155 <p>The option values are bit-masks and can be composed with
3156 logical-or in the obvious way.</p>
3158 <h2><a name="fcustom" id="fcustom">Custom Validation
3161 <p>The <code>form</code> library gives you the capability to
3162 define custom validation types of your own. Further, the optional
3163 additional arguments of <code>set_field_type</code> effectively
3164 allow you to parameterize validation types. Most of the
3165 complications in the validation-type interface have to do with
3166 the handling of the additional arguments within custom validation
3169 <h3><a name="flinktypes" id="flinktypes">Union Types</a></h3>
3171 <p>The simplest way to create a custom data type is to compose it
3172 from two preexisting ones:</p>
3174 FIELD *link_fieldtype(FIELDTYPE *type1,
3178 <p>This function creates a field type that will accept any of the
3179 values legal for either of its argument field types (which may be
3180 either predefined or programmer-defined). If a
3181 <code>set_field_type()</code> call later requires arguments, the
3182 new composite type expects all arguments for the first type, than
3183 all arguments for the second. Order functions (see <a href=
3184 "#forder">Order Requests</a>) associated with the component types
3185 will work on the composite; what it does is check the validation
3186 function for the first type, then for the second, to figure what
3187 type the buffer contents should be treated as.</p>
3189 <h3><a name="fnewtypes" id="fnewtypes">New Field Types</a></h3>
3191 <p>To create a field type from scratch, you need to specify one
3192 or both of the following things:</p>
3195 <li>A character-validation function, to check each character as
3198 <li>A field-validation function to be applied on exit from the
3202 <p>Here is how you do that:</p>
3204 typedef int (*HOOK)(); /* pointer to function returning int */
3206 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
3207 HOOK c_validate) /* character validator */
3210 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
3213 <p>At least one of the arguments of <code>new_fieldtype()</code>
3214 must be non-NULL. The forms driver will automatically call the
3215 new type's validation functions at appropriate points in
3216 processing a field of the new type.</p>
3218 <p>The function <code>free_fieldtype()</code> deallocates the
3219 argument fieldtype, freeing all storage associated with it.</p>
3221 <p>Normally, a field validator is called when the user attempts
3222 to leave the field. Its first argument is a field pointer, from
3223 which it can get to field buffer 0 and test it. If the function
3224 returns TRUE, the operation succeeds; if it returns FALSE, the
3225 edit cursor stays in the field.</p>
3227 <p>A character validator gets the character passed in as a first
3228 argument. It too should return TRUE if the character is valid,
3229 FALSE otherwise.</p>
3231 <h3><a name="fcheckargs" id="fcheckargs">Validation Function
3234 <p>Your field- and character- validation functions will be passed
3235 a second argument as well. This second argument is the address of
3236 a structure (which we will call a <em>pile</em>) built from any
3237 of the field-type-specific arguments passed to
3238 <code>set_field_type()</code>. If no such arguments are defined
3239 for the field type, this pile pointer argument will be NULL.</p>
3241 <p>In order to arrange for such arguments to be passed to your
3242 validation functions, you must associate a small set of
3243 storage-management functions with the type. The forms driver will
3244 use these to synthesize a pile from the trailing arguments of
3245 each <code>set_field_type()</code> argument, and a pointer to the
3246 pile will be passed to the validation functions.</p>
3248 <p>Here is how you make the association:</p>
3250 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
3251 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
3253 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3254 PTRHOOK make_str, /* make structure from args */
3255 PTRHOOK copy_str, /* make copy of structure */
3256 VOIDHOOK free_str); /* free structure storage */
3259 <p>Here is how the storage-management hooks are used:</p>
3262 <dt><code>make_str</code></dt>
3264 <dd>This function is called by <code>set_field_type()</code>.
3265 It gets one argument, a <code>va_list</code> of the
3266 type-specific arguments passed to
3267 <code>set_field_type()</code>. It is expected to return a pile
3268 pointer to a data structure that encapsulates those
3271 <dt><code>copy_str</code></dt>
3273 <dd>This function is called by form library functions that
3274 allocate new field instances. It is expected to take a pile
3275 pointer, copy the pile to allocated storage, and return the
3276 address of the pile copy.</dd>
3278 <dt><code>free_str</code></dt>
3280 <dd>This function is called by field- and type-deallocation
3281 routines in the library. It takes a pile pointer argument, and
3282 is expected to free the storage of that pile.</dd>
3285 <p>The <code>make_str</code> and <code>copy_str</code> functions
3286 may return NULL to signal allocation failure. The library
3287 routines will that call them will return error indication when
3288 this happens. Thus, your validation functions should never see a
3289 NULL file pointer and need not check specially for it.</p>
3291 <h3><a name="fcustorder" id="fcustorder">Order Functions For
3292 Custom Types</a></h3>
3294 <p>Some custom field types are simply ordered in the same
3295 well-defined way that <code>TYPE_ENUM</code> is. For such types,
3296 it is possible to define successor and predecessor functions to
3297 support the <code>REQ_NEXT_CHOICE</code> and
3298 <code>REQ_PREV_CHOICE</code> requests. Here is how:</p>
3300 typedef int (*INTHOOK)(); /* pointer to function returning int */
3302 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3303 INTHOOK succ, /* get successor value */
3304 INTHOOK pred); /* get predecessor value */
3307 <p>The successor and predecessor arguments will each be passed
3308 two arguments; a field pointer, and a pile pointer (as for the
3309 validation functions). They are expected to use the function
3310 <code>field_buffer()</code> to read the current value, and
3311 <code>set_field_buffer()</code> on buffer 0 to set the next or
3312 previous value. Either hook may return TRUE to indicate success
3313 (a legal next or previous value was set) or FALSE to indicate
3316 <h3><a name="fcustprobs" id="fcustprobs">Avoiding
3319 <p>The interface for defining custom types is complicated and
3320 tricky. Rather than attempting to create a custom type entirely
3321 from scratch, you should start by studying the library source
3322 code for whichever of the pre-defined types seems to be closest
3323 to what you want.</p>
3325 <p>Use that code as a model, and evolve it towards what you
3326 really want. You will avoid many problems and annoyances that
3327 way. The code in the <code>ncurses</code> library has been
3328 specifically exempted from the package copyright to support
3331 <p>If your custom type defines order functions, have do something
3332 intuitive with a blank field. A useful convention is to make the
3333 successor of a blank field the types minimum value, and its
3334 predecessor the maximum.</p>