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31 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
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38 <title>Writing Programs with NCURSES</title>
39 <link rel="author" href="mailto:bugs-ncurses@gnu.org">
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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 Characters</a></li>
99 <li><a href="#attributes">Character Attributes and
102 <li><a href="#mouse">Mouse Interfacing</a></li>
104 <li><a href="#finishing">Finishing Up</a></li>
109 <a href="#functions">Function Descriptions</a>
112 <li><a href="#init">Initialization and Wrapup</a></li>
114 <li><a href="#flush">Causing Output to the Terminal</a></li>
116 <li><a href="#lowlevel">Low-Level Capability Access</a></li>
118 <li><a href="#debugging">Debugging</a></li>
123 <a href="#hints">Hints, Tips, and Tricks</a>
126 <li><a href="#caution">Some Notes of Caution</a></li>
128 <li><a href="#leaving">Temporarily Leaving ncurses
131 <li><a href="#xterm">Using <code>ncurses</code> under
132 <code>xterm</code></a></li>
134 <li><a href="#screens">Handling Multiple Terminal
137 <li><a href="#testing">Testing for Terminal
138 Capabilities</a></li>
140 <li><a href="#tuning">Tuning for Speed</a></li>
142 <li><a href="#special">Special Features of
143 <code>ncurses</code></a></li>
148 <a href="#compat">Compatibility with Older Versions</a>
151 <li><a href="#refbug">Refresh of Overlapping
154 <li><a href="#backbug">Background Erase</a></li>
158 <li><a href="#xsifuncs">XSI Curses Conformance</a></li>
163 <a href="#panels">The Panels Library</a>
166 <li><a href="#pcompile">Compiling With the Panels
169 <li><a href="#poverview">Overview of Panels</a></li>
171 <li><a href="#pstdscr">Panels, Input, and the Standard
174 <li><a href="#hiding">Hiding Panels</a></li>
176 <li><a href="#pmisc">Miscellaneous Other Facilities</a></li>
181 <a href="#menu">The Menu Library</a>
184 <li><a href="#mcompile">Compiling with the menu Library</a></li>
186 <li><a href="#moverview">Overview of Menus</a></li>
188 <li><a href="#mselect">Selecting items</a></li>
190 <li><a href="#mdisplay">Menu Display</a></li>
192 <li><a href="#mwindows">Menu Windows</a></li>
194 <li><a href="#minput">Processing Menu Input</a></li>
196 <li><a href="#mmisc">Miscellaneous Other Features</a></li>
201 <a href="#form">The Forms Library</a>
204 <li><a href="#fcompile">Compiling with the forms
207 <li><a href="#foverview">Overview of Forms</a></li>
209 <li><a href="#fcreate">Creating and Freeing Fields and
213 <a href="#fattributes">Fetching and Changing Field
217 <li><a href="#fsizes">Fetching Size and Location
220 <li><a href="#flocation">Changing the Field
223 <li><a href="#fjust">The Justification Attribute</a></li>
225 <li><a href="#fdispatts">Field Display Attributes</a></li>
227 <li><a href="#foptions">Field Option Bits</a></li>
229 <li><a href="#fstatus">Field Status</a></li>
231 <li><a href="#fuser">Field User Pointer</a></li>
235 <li><a href="#fdynamic">Variable-Sized Fields</a></li>
238 <a href="#fvalidation">Field Validation</a>
241 <li><a href="#ftype_alpha">TYPE_ALPHA</a></li>
243 <li><a href="#ftype_alnum">TYPE_ALNUM</a></li>
245 <li><a href="#ftype_enum">TYPE_ENUM</a></li>
247 <li><a href="#ftype_integer">TYPE_INTEGER</a></li>
249 <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li>
251 <li><a href="#ftype_regexp">TYPE_REGEXP</a></li>
255 <li><a href="#fbuffer">Direct Field Buffer Manipulation</a></li>
257 <li><a href="#formattrs">Attributes of Forms</a></li>
259 <li><a href="#fdisplay">Control of Form Display</a></li>
262 <a href="#fdriver">Input Processing in the Forms
266 <li><a href="#fpage">Page Navigation Requests</a></li>
268 <li><a href="#ffield">Inter-Field Navigation
271 <li><a href="#fifield">Intra-Field Navigation
274 <li><a href="#fscroll">Scrolling Requests</a></li>
276 <li><a href="#fedit">Field Editing Requests</a></li>
278 <li><a href="#forder">Order Requests</a></li>
280 <li><a href="#fappcmds">Application Commands</a></li>
284 <li><a href="#fhooks">Field Change Hooks</a></li>
286 <li><a href="#ffocus">Field Change Commands</a></li>
288 <li><a href="#frmoptions">Form Options</a></li>
291 <a href="#fcustom">Custom Validation Types</a>
294 <li><a href="#flinktypes">Union Types</a></li>
296 <li><a href="#fnewtypes">New Field Types</a></li>
298 <li><a href="#fcheckargs">Validation Function
301 <li><a href="#fcustorder">Order Functions For Custom
304 <li><a href="#fcustprobs">Avoiding Problems</a></li>
313 <h1><a name="introduction" id="introduction">Introduction</a></h1>
315 <p>This document is an introduction to programming with
316 <code>curses</code>. It is not an exhaustive reference for the
317 curses Application Programming Interface (API); that role is
318 filled by the <code>curses</code> manual pages. Rather, it is
319 intended to help C programmers ease into using the package.</p>
321 <p>This document is aimed at C applications programmers not yet
322 specifically familiar with ncurses. If you are already an
323 experienced <code>curses</code> programmer, you should
324 nevertheless read the sections on <a href="#mouse">Mouse
325 Interfacing</a>, <a href="#debugging">Debugging</a>, <a href=
326 "#compat">Compatibility with Older Versions</a>, and <a href=
327 "#hints">Hints, Tips, and Tricks</a>. These will bring you up to
328 speed on the special features and quirks of the
329 <code>ncurses</code> implementation. If you are not so
330 experienced, keep reading.</p>
332 <p>The <code>curses</code> package is a subroutine library for
333 terminal-independent screen-painting and input-event handling
334 which presents a high level screen model to the programmer,
335 hiding differences between terminal types and doing automatic
336 optimization of output to change one screen full of text into
337 another. <code>Curses</code> uses terminfo, which is a database
338 format that can describe the capabilities of thousands of
339 different terminals.</p>
341 <p>The <code>curses</code> API may seem something of an archaism
342 on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk.
343 Nevertheless, UNIX still supports tty lines and X supports
344 <em>xterm(1)</em>; the <code>curses</code> API has the advantage
345 of (a) back-portability to character-cell terminals, and (b)
346 simplicity. For an application that does not require bit-mapped
347 graphics and multiple fonts, an interface implementation using
348 <code>curses</code> will typically be a great deal simpler and
349 less expensive than one using an X toolkit.</p>
351 <h2><a name="history" id="history">A Brief History of Curses</a></h2>
353 <p>Historically, the first ancestor of <code>curses</code> was
354 the routines written to provide screen-handling for the
355 <code>vi</code> editor; these used the already-existing
356 <code>termcap</code> database facility for describing terminal
357 capabilities. These routines were abstracted into a documented
358 library and first released with the early BSD UNIX versions. All
359 of this work was done by students at the University of
362 <p>After graduation, one of those students went to work at
363 AT&T Bell Labs, and made an improved <code>termcap</code>
364 library called <code>terminfo</code> (i.e.,
365 “libterm”). That was subsequently released in System
366 V Release 2. Thereafter, other developers added to the terminfo
367 library. For instance, a student at Cornell University wrote an
368 improved terminfo library as well as a tool (<code>tic</code>) to
369 compile the terminal descriptions. As a general rule, AT&T
370 did not identify the developers in the source-code or
371 documentation; the <code>tic</code> and <code>infocmp</code>
372 programs are the exceptions.</p>
374 <p>System V Release 3 (System III UNIX) from Bell Labs featured a
375 rewritten and much-improved <code>curses</code> library,l along
376 with the <code>tic</code> program.</p>
378 <p>To recap, terminfo is based on Berkeley's termcap database,
379 but contains a number of improvements and extensions.
380 Parameterized capabilities strings were introduced, making it
381 possible to describe multiple video attributes, and colors and to
382 handle far more unusual terminals than possible with termcap. In
383 the later AT&T System V releases, <code>curses</code> evolved
384 to use more facilities and offer more capabilities, going far
385 beyond BSD curses in power and flexibility.</p>
387 <h2><a name="scope" id="scope">Scope of This Document</a></h2>
389 <p>This document describes <code>ncurses</code>, a free
390 implementation of the System V <code>curses</code> API with some
391 clearly marked extensions. It includes the following System V
395 <li>Support for multiple screen highlights (BSD curses could
396 only handle one “standout” highlight, usually
399 <li>Support for line- and box-drawing using forms
402 <li>Recognition of function keys on input.</li>
404 <li>Color support.</li>
406 <li>Support for pads (windows of larger than screen size on
407 which the screen or a subwindow defines a viewport).</li>
410 <p>Also, this package makes use of the insert and delete line and
411 character features of terminals so equipped, and determines how
412 to optimally use these features with no help from the programmer.
413 It allows arbitrary combinations of video attributes to be
414 displayed, even on terminals that leave “magic
415 cookies” on the screen to mark changes in attributes.</p>
417 <p>The <code>ncurses</code> package can also capture and use
418 event reports from a mouse in some environments (notably, xterm
419 under the X window system). This document includes tips for using
422 <p>The <code>ncurses</code> package was originated by Pavel
423 Curtis. The original maintainer of this package is <a href=
424 "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a>
425 <zmbenhal@netcom.com>. <a href=
426 "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a>
427 <esr@snark.thyrsus.com> wrote many of the new features in
428 versions after 1.8.1 and wrote most of this introduction.
429 Jürgen Pfeifer wrote all of the menu and forms code as well
430 as the <a href="http://www.adahome.com">Ada95</a> binding.
431 Ongoing work is being done by <a href=
432 "mailto:dickey@invisible-island.net">Thomas Dickey</a>
433 (maintainer). Contact the current maintainers at <a href=
434 "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p>
436 <p>This document also describes the <a href="#panels">panels</a>
437 extension library, similarly modeled on the SVr4 panels facility.
438 This library allows you to associate backing store with each of a
439 stack or deck of overlapping windows, and provides operations for
440 moving windows around in the stack that change their visibility
441 in the natural way (handling window overlaps).</p>
443 <p>Finally, this document describes in detail the <a href=
444 "#menu">menus</a> and <a href="#form">forms</a> extension
445 libraries, also cloned from System V, which support easy
446 construction and sequences of menus and fill-in forms.</p>
448 <h2><a name="terminology" id="terminology">Terminology</a></h2>
450 <p>In this document, the following terminology is used with
451 reasonable consistency:</p>
456 <dd>A data structure describing a sub-rectangle of the screen
457 (possibly the entire screen). You can write to a window as
458 though it were a miniature screen, scrolling independently of
459 other windows on the physical screen.</dd>
463 <dd>A subset of windows which are as large as the terminal
464 screen, i.e., they start at the upper left hand corner and
465 encompass the lower right hand corner. One of these,
466 <code>stdscr</code>, is automatically provided for the
469 <dt>terminal screen</dt>
471 <dd>The package's idea of what the terminal display currently
472 looks like, i.e., what the user sees now. This is a special
476 <h1><a name="curses" id="curses">The Curses Library</a></h1>
478 <h2><a name="overview" id="overview">An Overview of Curses</a></h2>
480 <h3><a name="compiling" id="compiling">Compiling Programs using
483 <p>In order to use the library, it is necessary to have certain
484 types and variables defined. Therefore, the programmer must have
488 #include <curses.h>
491 <p>at the top of the program source. The screen package uses the
492 Standard I/O library, so <code><curses.h></code> includes
493 <code><stdio.h></code>. <code><curses.h></code> also
494 includes <code><termios.h></code>,
495 <code><termio.h></code>, or <code><sgtty.h></code>
496 depending on your system. It is redundant (but harmless) for the
497 programmer to do these includes, too. In linking with
498 <code>curses</code> you need to have <code>-lncurses</code> in
499 your LDFLAGS or on the command line. There is no need for any
502 <h3><a name="updating" id="updating">Updating the Screen</a></h3>
504 <p>In order to update the screen optimally, it is necessary for
505 the routines to know what the screen currently looks like and
506 what the programmer wants it to look like next. For this purpose,
507 a data type (structure) named WINDOW is defined which describes a
508 window image to the routines, including its starting position on
509 the screen (the (y, x) coordinates of the upper left hand corner)
510 and its size. One of these (called <code>curscr</code>, for
511 current screen) is a screen image of what the terminal currently
512 looks like. Another screen (called <code>stdscr</code>, for
513 standard screen) is provided by default to make changes on.</p>
515 <p>A window is a purely internal representation. It is used to
516 build and store a potential image of a portion of the terminal.
517 It does not bear any necessary relation to what is really on the
518 terminal screen; it is more like a scratchpad or write
521 <p>To make the section of physical screen corresponding to a
522 window reflect the contents of the window structure, the routine
523 <code>refresh()</code> (or <code>wrefresh()</code> if the window
524 is not <code>stdscr</code>) is called.</p>
526 <p>A given physical screen section may be within the scope of any
527 number of overlapping windows. Also, changes can be made to
528 windows in any order, without regard to motion efficiency. Then,
529 at will, the programmer can effectively say “make it look
530 like this,” and let the package implementation determine
531 the most efficient way to repaint the screen.</p>
533 <h3><a name="stdscr" id="stdscr">Standard Windows and Function
534 Naming Conventions</a></h3>
536 <p>As hinted above, the routines can use several windows, but two
537 are automatically given: <code>curscr</code>, which knows what
538 the terminal looks like, and <code>stdscr</code>, which is what
539 the programmer wants the terminal to look like next. The user
540 should never actually access <code>curscr</code> directly.
541 Changes should be made to through the API, and then the routine
542 <code>refresh()</code> (or <code>wrefresh()</code>) called.</p>
544 <p>Many functions are defined to use <code>stdscr</code> as a
545 default screen. For example, to add a character to
546 <code>stdscr</code>, one calls <code>addch()</code> with the
547 desired character as argument. To write to a different window.
548 use the routine <code>waddch()</code> (for
549 <strong>w</strong>indow-specific addch()) is provided. This
550 convention of prepending function names with a “w”
551 when they are to be applied to specific windows is consistent.
552 The only routines which do not follow it are those for which a
553 window must always be specified.</p>
555 <p>In order to move the current (y, x) coordinates from one point
556 to another, the routines <code>move()</code> and
557 <code>wmove()</code> are provided. However, it is often desirable
558 to first move and then perform some I/O operation. In order to
559 avoid clumsiness, most I/O routines can be preceded by the prefix
560 “mv” and the desired (y, x) coordinates prepended to
561 the arguments to the function. For example, the calls</p>
568 <p>can be replaced by</p>
581 <p>can be replaced by</p>
584 mvwaddch(win, y, x, ch);
587 <p>Note that the window description pointer (win) comes before
588 the added (y, x) coordinates. If a function requires a window
589 pointer, it is always the first parameter passed.</p>
591 <h3><a name="variables" id="variables">Variables</a></h3>
593 <p>The <code>curses</code> library sets some variables describing
594 the terminal capabilities.</p>
597 type name description
598 ------------------------------------------------------------------
599 int LINES number of lines on the terminal
600 int COLS number of columns on the terminal
603 <p>The <code>curses.h</code> also introduces some
604 <code>#define</code> constants and types of general
608 <dt><code>bool</code>
611 <dd>boolean type, actually a “char” (e.g.,
612 <code>bool doneit;</code>)</dd>
614 <dt><code>TRUE</code>
617 <dd>boolean “true” flag (1).</dd>
619 <dt><code>FALSE</code>
622 <dd>boolean “false” flag (0).</dd>
627 <dd>error flag returned by routines on a failure (-1).</dd>
632 <dd>error flag returned by routines when things go right.</dd>
635 <h2><a name="using" id="using">Using the Library</a></h2>
637 <p>Now we describe how to actually use the screen package. In it,
638 we assume all updating, reading, etc. is applied to
639 <code>stdscr</code>. These instructions will work on any window,
640 providing you change the function names and parameters as
643 <p>Here is a sample program to motivate the discussion:</p>
646 #include <stdlib.h>
647 #include <curses.h>
648 #include <signal.h>
650 static void finish(int sig);
653 main(int argc, char *argv[])
657 /* initialize your non-curses data structures here */
659 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
661 (void) initscr(); /* initialize the curses library */
662 keypad(stdscr, TRUE); /* enable keyboard mapping */
663 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
664 (void) cbreak(); /* take input chars one at a time, no wait for \n */
665 (void) echo(); /* echo input - in color */
672 * Simple color assignment, often all we need. Color pair 0 cannot
673 * be redefined. This example uses the same value for the color
674 * pair as for the foreground color, though of course that is not
677 init_pair(1, COLOR_RED, COLOR_BLACK);
678 init_pair(2, COLOR_GREEN, COLOR_BLACK);
679 init_pair(3, COLOR_YELLOW, COLOR_BLACK);
680 init_pair(4, COLOR_BLUE, COLOR_BLACK);
681 init_pair(5, COLOR_CYAN, COLOR_BLACK);
682 init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
683 init_pair(7, COLOR_WHITE, COLOR_BLACK);
688 int c = getch(); /* refresh, accept single keystroke of input */
689 attrset(COLOR_PAIR(num % 8));
692 /* process the command keystroke */
695 finish(0); /* we are done */
698 static void finish(int sig)
702 /* do your non-curses wrapup here */
708 <h3><a name="starting" id="starting">Starting up</a></h3>
710 <p>In order to use the screen package, the routines must know
711 about terminal characteristics, and the space for
712 <code>curscr</code> and <code>stdscr</code> must be allocated.
713 These function <code>initscr()</code> does both these things.
714 Since it must allocate space for the windows, it can overflow
715 memory when attempting to do so. On the rare occasions this
716 happens, <code>initscr()</code> will terminate the program with
717 an error message. <code>initscr()</code> must always be called
718 before any of the routines which affect windows are used. If it
719 is not, the program will core dump as soon as either
720 <code>curscr</code> or <code>stdscr</code> are referenced.
721 However, it is usually best to wait to call it until after you
722 are sure you will need it, like after checking for startup
723 errors. Terminal status changing routines like <code>nl()</code>
724 and <code>cbreak()</code> should be called after
725 <code>initscr()</code>.</p>
727 <p>Once the screen windows have been allocated, you can set them
728 up for your program. If you want to, say, allow a screen to
729 scroll, use <code>scrollok()</code>. If you want the cursor to be
730 left in place after the last change, use <code>leaveok()</code>.
731 If this is not done, <code>refresh()</code> will move the cursor
732 to the window's current (y, x) coordinates after updating it.</p>
734 <p>You can create new windows of your own using the functions
735 <code>newwin()</code>, <code>derwin()</code>, and
736 <code>subwin()</code>. The routine <code>delwin()</code> will
737 allow you to get rid of old windows. All the options described
738 above can be applied to any window.</p>
740 <h3><a name="output" id="output">Output</a></h3>
742 <p>Now that we have set things up, we will want to actually
743 update the terminal. The basic functions used to change what will
744 go on a window are <code>addch()</code> and <code>move()</code>.
745 <code>addch()</code> adds a character at the current (y, x)
746 coordinates. <code>move()</code> changes the current (y, x)
747 coordinates to whatever you want them to be. It returns
748 <code>ERR</code> if you try to move off the window. As mentioned
749 above, you can combine the two into <code>mvaddch()</code> to do
750 both things at once.</p>
752 <p>The other output functions, such as <code>addstr()</code> and
753 <code>printw()</code>, all call <code>addch()</code> to add
754 characters to the window.</p>
756 <p>After you have put on the window what you want there, when you
757 want the portion of the terminal covered by the window to be made
758 to look like it, you must call <code>refresh()</code>. In order
759 to optimize finding changes, <code>refresh()</code> assumes that
760 any part of the window not changed since the last
761 <code>refresh()</code> of that window has not been changed on the
762 terminal, i.e., that you have not refreshed a portion of the
763 terminal with an overlapping window. If this is not the case, the
764 routine <code>touchwin()</code> is provided to make it look like
765 the entire window has been changed, thus making
766 <code>refresh()</code> check the whole subsection of the terminal
769 <p>If you call <code>wrefresh()</code> with <code>curscr</code>
770 as its argument, it will make the screen look like
771 <code>curscr</code> thinks it looks like. This is useful for
772 implementing a command which would redraw the screen in case it
775 <h3><a name="input" id="input">Input</a></h3>
777 <p>The complementary function to <code>addch()</code> is
778 <code>getch()</code> which, if echo is set, will call
779 <code>addch()</code> to echo the character. Since the screen
780 package needs to know what is on the terminal at all times, if
781 characters are to be echoed, the tty must be in raw or cbreak
782 mode. Since initially the terminal has echoing enabled and is in
783 ordinary “cooked” mode, one or the other has to
784 changed before calling <code>getch()</code>; otherwise, the
785 program's output will be unpredictable.</p>
787 <p>When you need to accept line-oriented input in a window, the
788 functions <code>wgetstr()</code> and friends are available. There
789 is even a <code>wscanw()</code> function that can do
790 <code>scanf()</code>(3)-style multi-field parsing on window
791 input. These pseudo-line-oriented functions turn on echoing while
794 <p>The example code above uses the call <code>keypad(stdscr,
795 TRUE)</code> to enable support for function-key mapping. With
796 this feature, the <code>getch()</code> code watches the input
797 stream for character sequences that correspond to arrow and
798 function keys. These sequences are returned as pseudo-character
799 values. The <code>#define</code> values returned are listed in
800 the <code>curses.h</code> The mapping from sequences to
801 <code>#define</code> values is determined by <code>key_</code>
802 capabilities in the terminal's terminfo entry.</p>
804 <h3><a name="formschars" id="formschars">Using Forms
807 <p>The <code>addch()</code> function (and some others, including
808 <code>box()</code> and <code>border()</code>) can accept some
809 pseudo-character arguments which are specially defined by
810 <code>ncurses</code>. These are <code>#define</code> values set
811 up in the <code>curses.h</code> header; see there for a complete
812 list (look for the prefix <code>ACS_</code>).</p>
814 <p>The most useful of the ACS defines are the forms-drawing
815 characters. You can use these to draw boxes and simple graphs on
816 the screen. If the terminal does not have such characters,
817 <code>curses.h</code> will map them to a recognizable (though
818 ugly) set of ASCII defaults.</p>
820 <h3><a name="attributes" id="attributes">Character Attributes and
823 <p>The <code>ncurses</code> package supports screen highlights
824 including standout, reverse-video, underline, and blink. It also
825 supports color, which is treated as another kind of
828 <p>Highlights are encoded, internally, as high bits of the
829 pseudo-character type (<code>chtype</code>) that
830 <code>curses.h</code> uses to represent the contents of a screen
831 cell. See the <code>curses.h</code> header file for a complete
832 list of highlight mask values (look for the prefix
833 <code>A_</code>).</p>
835 <p>There are two ways to make highlights. One is to logical-or
836 the value of the highlights you want into the character argument
837 of an <code>addch()</code> call, or any other output call that
838 takes a <code>chtype</code> argument.</p>
840 <p>The other is to set the current-highlight value. This is
841 <em>logical-OR</em>ed with any highlight you specify the first
842 way. You do this with the functions <code>attron()</code>,
843 <code>attroff()</code>, and <code>attrset()</code>; see the
844 manual pages for details. Color is a special kind of highlight.
845 The package actually thinks in terms of color pairs, combinations
846 of foreground and background colors. The sample code above sets
847 up eight color pairs, all of the guaranteed-available colors on
848 black. Note that each color pair is, in effect, given the name of
849 its foreground color. Any other range of eight non-conflicting
850 values could have been used as the first arguments of the
851 <code>init_pair()</code> values.</p>
853 <p>Once you have done an <code>init_pair()</code> that creates
854 color-pair N, you can use <code>COLOR_PAIR(N)</code> as a
855 highlight that invokes that particular color combination. Note
856 that <code>COLOR_PAIR(N)</code>, for constant N, is itself a
857 compile-time constant and can be used in initializers.</p>
859 <h3><a name="mouse" id="mouse">Mouse Interfacing</a></h3>
861 <p>The <code>ncurses</code> library also provides a mouse
865 <strong>NOTE:</strong> this facility is specific to
866 <code>ncurses</code>, it is not part of either the XSI Curses
867 standard, nor of System V Release 4, nor BSD curses. System V
868 Release 4 curses contains code with similar interface
869 definitions, however it is not documented. Other than by
870 disassembling the library, we have no way to determine exactly
871 how that mouse code works. Thus, we recommend that you wrap
872 mouse-related code in an #ifdef using the feature macro
873 NCURSES_MOUSE_VERSION so it will not be compiled and linked on
877 <p>Presently, mouse event reporting works in the following
881 <li>xterm and similar programs such as rxvt.</li>
883 <li>Linux console, when configured with <code>gpm</code>(1),
884 Alessandro Rubini's mouse server.</li>
886 <li>FreeBSD sysmouse (console)</li>
891 <p>The mouse interface is very simple. To activate it, you use
892 the function <code>mousemask()</code>, passing it as first
893 argument a bit-mask that specifies what kinds of events you want
894 your program to be able to see. It will return the bit-mask of
895 events that actually become visible, which may differ from the
896 argument if the mouse device is not capable of reporting some of
897 the event types you specify.</p>
899 <p>Once the mouse is active, your application's command loop
900 should watch for a return value of <code>KEY_MOUSE</code> from
901 <code>wgetch()</code>. When you see this, a mouse event report
902 has been queued. To pick it off the queue, use the function
903 <code>getmouse()</code> (you must do this before the next
904 <code>wgetch()</code>, otherwise another mouse event might come
905 in and make the first one inaccessible).</p>
907 <p>Each call to <code>getmouse()</code> fills a structure (the
908 address of which you will pass it) with mouse event data. The
909 event data includes zero-origin, screen-relative character-cell
910 coordinates of the mouse pointer. It also includes an event mask.
911 Bits in this mask will be set, corresponding to the event type
914 <p>The mouse structure contains two additional fields which may
915 be significant in the future as ncurses interfaces to new kinds
916 of pointing device. In addition to x and y coordinates, there is
917 a slot for a z coordinate; this might be useful with
918 touch-screens that can return a pressure or duration parameter.
919 There is also a device ID field, which could be used to
920 distinguish between multiple pointing devices.</p>
922 <p>The class of visible events may be changed at any time via
923 <code>mousemask()</code>. Events that can be reported include
924 presses, releases, single-, double- and triple-clicks (you can
925 set the maximum button-down time for clicks). If you do not make
926 clicks visible, they will be reported as press-release pairs. In
927 some environments, the event mask may include bits reporting the
928 state of shift, alt, and ctrl keys on the keyboard during the
931 <p>A function to check whether a mouse event fell within a given
932 window is also supplied. You can use this to see whether a given
933 window should consider a mouse event relevant to it.</p>
935 <p>Because mouse event reporting will not be available in all
936 environments, it would be unwise to build <code>ncurses</code>
937 applications that <em>require</em> the use of a mouse. Rather,
938 you should use the mouse as a shortcut for point-and-shoot
939 commands your application would normally accept from the
940 keyboard. Two of the test games in the <code>ncurses</code>
941 distribution (<code>bs</code> and <code>knight</code>) contain
942 code that illustrates how this can be done.</p>
944 <p>See the manual page <code>curs_mouse(3X)</code> for full
945 details of the mouse-interface functions.</p>
947 <h3><a name="finishing" id="finishing">Finishing Up</a></h3>
949 <p>In order to clean up after the <code>ncurses</code> routines,
950 the routine <code>endwin()</code> is provided. It restores tty
951 modes to what they were when <code>initscr()</code> was first
952 called, and moves the cursor down to the lower-left corner. Thus,
953 anytime after the call to initscr, <code>endwin()</code> should
954 be called before exiting.</p>
956 <h2><a name="functions" id="functions">Function Descriptions</a></h2>
958 <p>We describe the detailed behavior of some important curses
959 functions here, as a supplement to the manual page
962 <h3><a name="init" id="init">Initialization and Wrapup</a></h3>
965 <dt><code>initscr()</code>
968 <dd>The first function called should almost always be
969 <code>initscr()</code>. This will determine the terminal type
970 and initialize curses data structures. <code>initscr()</code>
971 also arranges that the first call to <code>refresh()</code>
972 will clear the screen. If an error occurs a message is written
973 to standard error and the program exits. Otherwise it returns a
974 pointer to stdscr. A few functions may be called before initscr
975 (<code>slk_init()</code>, <code>filter()</code>,
976 <code>ripoffline()</code>, <code>use_env()</code>, and, if you
977 are using multiple terminals, <code>newterm()</code>.)</dd>
979 <dt><code>endwin()</code>
982 <dd>Your program should always call <code>endwin()</code>
983 before exiting or shelling out of the program. This function
984 will restore tty modes, move the cursor to the lower left
985 corner of the screen, reset the terminal into the proper
986 non-visual mode. Calling <code>refresh()</code> or
987 <code>doupdate()</code> after a temporary escape from the
988 program will restore the ncurses screen from before the
991 <dt><code>newterm(type, ofp, ifp)</code>
994 <dd>A program which outputs to more than one terminal should
995 use <code>newterm()</code> instead of <code>initscr()</code>.
996 <code>newterm()</code> should be called once for each terminal.
997 It returns a variable of type <code>SCREEN *</code> which
998 should be saved as a reference to that terminal. (NOTE: a
999 SCREEN variable is not a <em>screen</em> in the sense we are
1000 describing in this introduction, but a collection of parameters
1001 used to assist in optimizing the display.) The arguments are
1002 the type of the terminal (a string) and <code>FILE</code>
1003 pointers for the output and input of the terminal. If type is
1004 NULL then the environment variable <code>$TERM</code> is used.
1005 <code>endwin()</code> should called once at wrapup time for
1006 each terminal opened using this function.</dd>
1008 <dt><code>set_term(new)</code>
1011 <dd>This function is used to switch to a different terminal
1012 previously opened by <code>newterm()</code>. The screen
1013 reference for the new terminal is passed as the parameter. The
1014 previous terminal is returned by the function. All other calls
1015 affect only the current terminal.</dd>
1017 <dt><code>delscreen(sp)</code>
1020 <dd>The inverse of <code>newterm()</code>; deallocates the data
1021 structures associated with a given <code>SCREEN</code>
1025 <h3><a name="flush" id="flush">Causing Output to the Terminal</a></h3>
1028 <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt>
1030 <dd>These functions must be called to actually get any output
1031 on the terminal, as other routines merely manipulate data
1032 structures. <code>wrefresh()</code> copies the named window to
1033 the physical terminal screen, taking into account what is
1034 already there in order to do optimizations.
1035 <code>refresh()</code> does a refresh of <code>stdscr</code>.
1036 Unless <code>leaveok()</code> has been enabled, the physical
1037 cursor of the terminal is left at the location of the window's
1040 <dt><code>doupdate()</code> and
1041 <code>wnoutrefresh(win)</code></dt>
1043 <dd>These two functions allow multiple updates with more
1044 efficiency than wrefresh. To use them, it is important to
1045 understand how curses works. In addition to all the window
1046 structures, curses keeps two data structures representing the
1047 terminal screen: a physical screen, describing what is actually
1048 on the screen, and a virtual screen, describing what the
1049 programmer wants to have on the screen. wrefresh works by first
1050 copying the named window to the virtual screen
1051 (<code>wnoutrefresh()</code>), and then calling the routine to
1052 update the screen (<code>doupdate()</code>). If the programmer
1053 wishes to output several windows at once, a series of calls to
1054 <code>wrefresh</code> will result in alternating calls to
1055 <code>wnoutrefresh()</code> and <code>doupdate()</code>,
1056 causing several bursts of output to the screen. By calling
1057 <code>wnoutrefresh()</code> for each window, it is then
1058 possible to call <code>doupdate()</code> once, resulting in
1059 only one burst of output, with fewer total characters
1060 transmitted (this also avoids a visually annoying flicker at
1064 <h3><a name="lowlevel" id="lowlevel">Low-Level Capability
1068 <dt><code>setupterm(term, filenum, errret)</code>
1072 This routine is called to initialize a terminal's
1073 description, without setting up the curses screen structures
1074 or changing the tty-driver mode bits. <code>term</code> is
1075 the character string representing the name of the terminal
1076 being used. <code>filenum</code> is the UNIX file descriptor
1077 of the terminal to be used for output. <code>errret</code> is
1078 a pointer to an integer, in which a success or failure
1079 indication is returned. The values returned can be 1 (all is
1080 well), 0 (no such terminal), or -1 (some problem locating the
1083 <p>The value of <code>term</code> can be given as NULL, which
1084 will cause the value of <code>TERM</code> in the environment
1085 to be used. The <code>errret</code> pointer can also be given
1086 as NULL, meaning no error code is wanted. If
1087 <code>errret</code> is defaulted, and something goes wrong,
1088 <code>setupterm()</code> will print an appropriate error
1089 message and exit, rather than returning. Thus, a simple
1090 program can call setupterm(0, 1, 0) and not worry about
1091 initialization errors.</p>
1093 <p>After the call to <code>setupterm()</code>, the global
1094 variable <code>cur_term</code> is set to point to the current
1095 structure of terminal capabilities. By calling
1096 <code>setupterm()</code> for each terminal, and saving and
1097 restoring <code>cur_term</code>, it is possible for a program
1098 to use two or more terminals at once.
1099 <code>Setupterm()</code> also stores the names section of the
1100 terminal description in the global character array
1101 <code>ttytype[]</code>. Subsequent calls to
1102 <code>setupterm()</code> will overwrite this array, so you
1103 will have to save it yourself if need be.</p>
1107 <h3><a name="debugging" id="debugging">Debugging</a></h3>
1110 <strong>NOTE:</strong> These functions are not part of the
1111 standard curses API!
1115 <dt><code>trace()</code>
1118 <dd>This function can be used to explicitly set a trace level.
1119 If the trace level is nonzero, execution of your program will
1120 generate a file called “trace” in the current
1121 working directory containing a report on the library's actions.
1122 Higher trace levels enable more detailed (and verbose)
1123 reporting -- see comments attached to <code>TRACE_</code>
1124 defines in the <code>curses.h</code> file for details. (It is
1125 also possible to set a trace level by assigning a trace level
1126 value to the environment variable
1127 <code>NCURSES_TRACE</code>).</dd>
1129 <dt><code>_tracef()</code>
1132 <dd>This function can be used to output your own debugging
1133 information. It is only available only if you link with
1134 -lncurses_g. It can be used the same way as
1135 <code>printf()</code>, only it outputs a newline after the end
1136 of arguments. The output goes to a file called
1137 <code>trace</code> in the current directory.</dd>
1140 <p>Trace logs can be difficult to interpret due to the sheer
1141 volume of data dumped in them. There is a script called
1142 <strong>tracemunch</strong> included with the
1143 <code>ncurses</code> distribution that can alleviate this problem
1144 somewhat; it compacts long sequences of similar operations into
1145 more succinct single-line pseudo-operations. These pseudo-ops can
1146 be distinguished by the fact that they are named in capital
1149 <h2><a name="hints" id="hints">Hints, Tips, and Tricks</a></h2>
1151 <p>The <code>ncurses</code> manual pages are a complete reference
1152 for this library. In the remainder of this document, we discuss
1153 various useful methods that may not be obvious from the manual
1154 page descriptions.</p>
1156 <h3><a name="caution" id="caution">Some Notes of Caution</a></h3>
1158 <p>If you find yourself thinking you need to use
1159 <code>noraw()</code> or <code>nocbreak()</code>, think again and
1160 move carefully. It is probably better design to use
1161 <code>getstr()</code> or one of its relatives to simulate cooked
1162 mode. The <code>noraw()</code> and <code>nocbreak()</code>
1163 functions try to restore cooked mode, but they may end up
1164 clobbering some control bits set before you started your
1165 application. Also, they have always been poorly documented, and
1166 are likely to hurt your application's usability with other curses
1169 <p>Bear in mind that <code>refresh()</code> is a synonym for
1170 <code>wrefresh(stdscr)</code>. Do not try to mix use of
1171 <code>stdscr</code> with use of windows declared by
1172 <code>newwin()</code>; a <code>refresh()</code> call will blow
1173 them off the screen. The right way to handle this is to use
1174 <code>subwin()</code>, or not touch <code>stdscr</code> at all
1175 and tile your screen with declared windows which you then
1176 <code>wnoutrefresh()</code> somewhere in your program event loop,
1177 with a single <code>doupdate()</code> call to trigger actual
1180 <p>You are much less likely to run into problems if you design
1181 your screen layouts to use tiled rather than overlapping windows.
1182 Historically, curses support for overlapping windows has been
1183 weak, fragile, and poorly documented. The <code>ncurses</code>
1184 library is not yet an exception to this rule.</p>
1186 <p>There is a panels library included in the <code>ncurses</code>
1187 distribution that does a pretty good job of strengthening the
1188 overlapping-windows facilities.</p>
1190 <p>Try to avoid using the global variables LINES and COLS. Use
1191 <code>getmaxyx()</code> on the <code>stdscr</code> context
1192 instead. Reason: your code may be ported to run in an environment
1193 with window resizes, in which case several screens could be open
1194 with different sizes.</p>
1196 <h3><a name="leaving" id="leaving">Temporarily Leaving NCURSES
1199 <p>Sometimes you will want to write a program that spends most of
1200 its time in screen mode, but occasionally returns to ordinary
1201 “cooked” mode. A common reason for this is to support
1202 shell-out. This behavior is simple to arrange in
1203 <code>ncurses</code>.</p>
1205 <p>To leave <code>ncurses</code> mode, call <code>endwin()</code>
1206 as you would if you were intending to terminate the program. This
1207 will take the screen back to cooked mode; you can do your
1208 shell-out. When you want to return to <code>ncurses</code> mode,
1209 simply call <code>refresh()</code> or <code>doupdate()</code>.
1210 This will repaint the screen.</p>
1212 <p>There is a boolean function, <code>isendwin()</code>, which
1213 code can use to test whether <code>ncurses</code> screen mode is
1214 active. It returns <code>TRUE</code> in the interval between an
1215 <code>endwin()</code> call and the following
1216 <code>refresh()</code>, <code>FALSE</code> otherwise.</p>
1218 <p>Here is some sample code for shellout:</p>
1221 addstr("Shelling out...");
1222 def_prog_mode(); /* save current tty modes */
1223 endwin(); /* restore original tty modes */
1224 system("sh"); /* run shell */
1225 addstr("returned.\n"); /* prepare return message */
1226 refresh(); /* restore save modes, repaint screen */
1229 <h3><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h3>
1231 <p>A resize operation in X sends <code>SIGWINCH</code> to the
1232 application running under xterm. The easiest way to handle
1233 <code>SIGWINCH</code> is to do an <code>endwin</code>, followed
1234 by an <code>refresh</code> and a screen repaint you code
1235 yourself. The <code>refresh</code> will pick up the new screen
1236 size from the xterm's environment.</p>
1238 <p>That is the standard way, of course (it even works with some
1239 vendor's curses implementations). Its drawback is that it clears
1240 the screen to reinitialize the display, and does not resize
1241 subwindows which must be shrunk. <code>Ncurses</code> provides an
1242 extension which works better, the <code>resizeterm</code>
1243 function. That function ensures that all windows are limited to
1244 the new screen dimensions, and pads <code>stdscr</code> with
1245 blanks if the screen is larger.</p>
1247 <p>The <code>ncurses</code> library provides a SIGWINCH signal
1248 handler, which pushes a <code>KEY_RESIZE</code> via the wgetch()
1249 calls. When <code>ncurses</code> returns that code, it calls
1250 <code>resizeterm</code> to update the size of the standard
1251 screen's window, repainting that (filling with blanks or
1252 truncating as needed). It also resizes other windows, but its
1253 effect may be less satisfactory because it cannot know how you
1254 want the screen re-painted. You will usually have to write
1255 special-purpose code to handle <code>KEY_RESIZE</code>
1258 <h3><a name="screens" id="screens">Handling Multiple Terminal
1261 <p>The <code>initscr()</code> function actually calls a function
1262 named <code>newterm()</code> to do most of its work. If you are
1263 writing a program that opens multiple terminals, use
1264 <code>newterm()</code> directly.</p>
1266 <p>For each call, you will have to specify a terminal type and a
1267 pair of file pointers; each call will return a screen reference,
1268 and <code>stdscr</code> will be set to the last one allocated.
1269 You will switch between screens with the <code>set_term</code>
1270 call. Note that you will also have to call
1271 <code>def_shell_mode</code> and <code>def_prog_mode</code> on
1272 each tty yourself.</p>
1274 <h3><a name="testing" id="testing">Testing for Terminal
1275 Capabilities</a></h3>
1277 <p>Sometimes you may want to write programs that test for the
1278 presence of various capabilities before deciding whether to go
1279 into <code>ncurses</code> mode. An easy way to do this is to call
1280 <code>setupterm()</code>, then use the functions
1281 <code>tigetflag()</code>, <code>tigetnum()</code>, and
1282 <code>tigetstr()</code> to do your testing.</p>
1284 <p>A particularly useful case of this often comes up when you
1285 want to test whether a given terminal type should be treated as
1286 “smart” (cursor-addressable) or “stupid”.
1287 The right way to test this is to see if the return value of
1288 <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can
1289 include the <code>term.h</code> file and test the value of the
1290 macro <code>cursor_address</code>.</p>
1292 <h3><a name="tuning" id="tuning">Tuning for Speed</a></h3>
1294 <p>Use the <code>addchstr()</code> family of functions for fast
1295 screen-painting of text when you know the text does not contain
1296 any control characters. Try to make attribute changes infrequent
1297 on your screens. Do not use the <code>immedok()</code>
1300 <h3><a name="special" id="special">Special Features of
1303 <p>The <code>wresize()</code> function allows you to resize a
1304 window in place. The associated <code>resizeterm()</code>
1305 function simplifies the construction of <a href=
1306 "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p>
1308 <p>The <code>define_key()</code> function allows you to define at
1309 runtime function-key control sequences which are not in the
1310 terminal description. The <code>keyok()</code> function allows
1311 you to temporarily enable or disable interpretation of any
1312 function-key control sequence.</p>
1314 <p>The <code>use_default_colors()</code> function allows you to
1315 construct applications which can use the terminal's default
1316 foreground and background colors as an additional "default"
1317 color. Several terminal emulators support this feature, which is
1318 based on ISO 6429.</p>
1320 <p>Ncurses supports up 16 colors, unlike SVr4 curses which
1321 defines only 8. While most terminals which provide color allow
1322 only 8 colors, about a quarter (including XFree86 xterm) support
1325 <h2><a name="compat" id="compat">Compatibility with Older
1328 <p>Despite our best efforts, there are some differences between
1329 <code>ncurses</code> and the (undocumented!) behavior of older
1330 curses implementations. These arise from ambiguities or omissions
1331 in the documentation of the API.</p>
1333 <h3><a name="refbug" id="refbug">Refresh of Overlapping
1336 <p>If you define two windows A and B that overlap, and then
1337 alternately scribble on and refresh them, the changes made to the
1338 overlapping region under historic <code>curses</code> versions
1339 were often not documented precisely.</p>
1341 <p>To understand why this is a problem, remember that screen
1342 updates are calculated between two representations of the
1343 <em>entire</em> display. The documentation says that when you
1344 refresh a window, it is first copied to the virtual screen, and
1345 then changes are calculated to update the physical screen (and
1346 applied to the terminal). But "copied to" is not very specific,
1347 and subtle differences in how copying works can produce different
1348 behaviors in the case where two overlapping windows are each
1349 being refreshed at unpredictable intervals.</p>
1351 <p>What happens to the overlapping region depends on what
1352 <code>wnoutrefresh()</code> does with its argument -- what
1353 portions of the argument window it copies to the virtual screen.
1354 Some implementations do "change copy", copying down only
1355 locations in the window that have changed (or been marked changed
1356 with <code>wtouchln()</code> and friends). Some implementations
1357 do "entire copy", copying <em>all</em> window locations to the
1358 virtual screen whether or not they have changed.</p>
1360 <p>The <code>ncurses</code> library itself has not always been
1361 consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a
1362 did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and
1363 newer, do change copy.</p>
1365 <p>For most commercial curses implementations, it is not
1366 documented and not known for sure (at least not to the
1367 <code>ncurses</code> maintainers) whether they do change copy or
1368 entire copy. We know that System V release 3 curses has logic in
1369 it that looks like an attempt to do change copy, but the
1370 surrounding logic and data representations are sufficiently
1371 complex, and our knowledge sufficiently indirect, that it is hard
1372 to know whether this is reliable. It is not clear what the SVr4
1373 documentation and XSI standard intend. The XSI Curses standard
1374 barely mentions wnoutrefresh(); the SVr4 documents seem to be
1375 describing entire-copy, but it is possible with some effort and
1376 straining to read them the other way.</p>
1378 <p>It might therefore be unwise to rely on either behavior in
1379 programs that might have to be linked with other curses
1380 implementations. Instead, you can do an explicit
1381 <code>touchwin()</code> before the <code>wnoutrefresh()</code>
1382 call to guarantee an entire-contents copy anywhere.</p>
1384 <p>The really clean way to handle this is to use the panels
1385 library. If, when you want a screen update, you do
1386 <code>update_panels()</code>, it will do all the necessary
1387 <code>wnoutrefresh()</code> calls for whatever panel stacking
1388 order you have defined. Then you can do one
1389 <code>doupdate()</code> and there will be a <em>single</em> burst
1390 of physical I/O that will do all your updates.</p>
1392 <h3><a name="backbug" id="backbug">Background Erase</a></h3>
1394 <p>If you have been using a very old versions of
1395 <code>ncurses</code> (1.8.7 or older) you may be surprised by the
1396 behavior of the erase functions. In older versions, erased areas
1397 of a window were filled with a blank modified by the window's
1398 current attribute (as set by <strong>wattrset()</strong>,
1399 <strong>wattron()</strong>, <strong>wattroff()</strong> and
1402 <p>In newer versions, this is not so. Instead, the attribute of
1403 erased blanks is normal unless and until it is modified by the
1404 functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p>
1406 <p>This change in behavior conforms <code>ncurses</code> to
1407 System V Release 4 and the XSI Curses standard.</p>
1409 <h2><a name="xsifuncs" id="xsifuncs">XSI Curses Conformance</a></h2>
1411 <p>The <code>ncurses</code> library is intended to be base-level
1412 conformant with the XSI Curses standard from X/Open. Many
1413 extended-level features (in fact, almost all features not
1414 directly concerned with wide characters and internationalization)
1415 are also supported.</p>
1417 <p>One effect of XSI conformance is the change in behavior
1418 described under <a href="#backbug">"Background Erase --
1419 Compatibility with Old Versions"</a>.</p>
1421 <p>Also, <code>ncurses</code> meets the XSI requirement that
1422 every macro entry point have a corresponding function which may
1423 be linked (and will be prototype-checked) if the macro definition
1424 is disabled with <code>#undef</code>.</p>
1426 <h1><a name="panels" id="panels">The Panels Library</a></h1>
1428 <p>The <code>ncurses</code> library by itself provides good
1429 support for screen displays in which the windows are tiled
1430 (non-overlapping). In the more general case that windows may
1431 overlap, you have to use a series of <code>wnoutrefresh()</code>
1432 calls followed by a <code>doupdate()</code>, and be careful about
1433 the order you do the window refreshes in. It has to be
1434 bottom-upwards, otherwise parts of windows that should be
1435 obscured will show through.</p>
1437 <p>When your interface design is such that windows may dive
1438 deeper into the visibility stack or pop to the top at runtime,
1439 the resulting book-keeping can be tedious and difficult to get
1440 right. Hence the panels library.</p>
1442 <p>The <code>panel</code> library first appeared in AT&T
1443 System V. The version documented here is the <code>panel</code>
1444 code distributed with <code>ncurses</code>.</p>
1446 <h2><a name="pcompile" id="pcompile">Compiling With the Panels
1449 <p>Your panels-using modules must import the panels library
1450 declarations with</p>
1453 #include <panel.h>
1456 <p>and must be linked explicitly with the panels library using an
1457 <code>-lpanel</code> argument. Note that they must also link the
1458 <code>ncurses</code> library with <code>-lncurses</code>. Many
1459 linkers are two-pass and will accept either order, but it is
1460 still good practice to put <code>-lpanel</code> first and
1461 <code>-lncurses</code> second.</p>
1463 <h2><a name="poverview" id="poverview">Overview of Panels</a></h2>
1465 <p>A panel object is a window that is implicitly treated as part
1466 of a <dfn>deck</dfn> including all other panel objects. The deck
1467 has an implicit bottom-to-top visibility order. The panels
1468 library includes an update function (analogous to
1469 <code>refresh()</code>) that displays all panels in the deck in
1470 the proper order to resolve overlaps. The standard window,
1471 <code>stdscr</code>, is considered below all panels.</p>
1473 <p>Details on the panels functions are available in the man
1474 pages. We will just hit the highlights here.</p>
1476 <p>You create a panel from a window by calling
1477 <code>new_panel()</code> on a window pointer. It then becomes the
1478 top of the deck. The panel's window is available as the value of
1479 <code>panel_window()</code> called with the panel pointer as
1482 <p>You can delete a panel (removing it from the deck) with
1483 <code>del_panel</code>. This will not deallocate the associated
1484 window; you have to do that yourself. You can replace a panel's
1485 window with a different window by calling
1486 <code>replace_window</code>. The new window may be of different
1487 size; the panel code will re-compute all overlaps. This operation
1488 does not change the panel's position in the deck.</p>
1490 <p>To move a panel's window, use <code>move_panel()</code>. The
1491 <code>mvwin()</code> function on the panel's window is not
1492 sufficient because it does not update the panels library's
1493 representation of where the windows are. This operation leaves
1494 the panel's depth, contents, and size unchanged.</p>
1496 <p>Two functions (<code>top_panel()</code>,
1497 <code>bottom_panel()</code>) are provided for rearranging the
1498 deck. The first pops its argument window to the top of the deck;
1499 the second sends it to the bottom. Either operation leaves the
1500 panel's screen location, contents, and size unchanged.</p>
1502 <p>The function <code>update_panels()</code> does all the
1503 <code>wnoutrefresh()</code> calls needed to prepare for
1504 <code>doupdate()</code> (which you must call yourself,
1507 <p>Typically, you will want to call <code>update_panels()</code>
1508 and <code>doupdate()</code> just before accepting command input,
1509 once in each cycle of interaction with the user. If you call
1510 <code>update_panels()</code> after each and every panel write,
1511 you will generate a lot of unnecessary refresh activity and
1514 <h2><a name="pstdscr" id="pstdscr">Panels, Input, and the
1515 Standard Screen</a></h2>
1517 <p>You should not mix <code>wnoutrefresh()</code> or
1518 <code>wrefresh()</code> operations with panels code; this will
1519 work only if the argument window is either in the top panel or
1520 unobscured by any other panels.</p>
1522 <p>The <code>stsdcr</code> window is a special case. It is
1523 considered below all panels. Because changes to panels may
1524 obscure parts of <code>stdscr</code>, though, you should call
1525 <code>update_panels()</code> before <code>doupdate()</code> even
1526 when you only change <code>stdscr</code>.</p>
1528 <p>Note that <code>wgetch</code> automatically calls
1529 <code>wrefresh</code>. Therefore, before requesting input from a
1530 panel window, you need to be sure that the panel is totally
1533 <p>There is presently no way to display changes to one obscured
1534 panel without repainting all panels.</p>
1536 <h2><a name="hiding" id="hiding">Hiding Panels</a></h2>
1538 <p>It is possible to remove a panel from the deck temporarily;
1539 use <code>hide_panel</code> for this. Use
1540 <code>show_panel()</code> to render it visible again. The
1541 predicate function <code>panel_hidden</code> tests whether or not
1542 a panel is hidden.</p>
1544 <p>The <code>panel_update</code> code ignores hidden panels. You
1545 cannot do <code>top_panel()</code> or <code>bottom_panel</code>
1546 on a hidden panel(). Other panels operations are applicable.</p>
1548 <h2><a name="pmisc" id="pmisc">Miscellaneous Other Facilities</a></h2>
1550 <p>It is possible to navigate the deck using the functions
1551 <code>panel_above()</code> and <code>panel_below</code>. Handed a
1552 panel pointer, they return the panel above or below that panel.
1553 Handed <code>NULL</code>, they return the bottom-most or top-most
1556 <p>Every panel has an associated user pointer, not used by the
1557 panel code, to which you can attach application data. See the man
1558 page documentation of <code>set_panel_userptr()</code> and
1559 <code>panel_userptr</code> for details.</p>
1561 <h1><a name="menu" id="menu">The Menu Library</a></h1>
1563 <p>A menu is a screen display that assists the user to choose
1564 some subset of a given set of items. The <code>menu</code>
1565 library is a curses extension that supports easy programming of
1566 menu hierarchies with a uniform but flexible interface.</p>
1568 <p>The <code>menu</code> library first appeared in AT&T
1569 System V. The version documented here is the <code>menu</code>
1570 code distributed with <code>ncurses</code>.</p>
1572 <h2><a name="mcompile" id="mcompile">Compiling With the menu
1575 <p>Your menu-using modules must import the menu library
1576 declarations with</p>
1579 #include <menu.h>
1582 <p>and must be linked explicitly with the menus library using an
1583 <code>-lmenu</code> argument. Note that they must also link the
1584 <code>ncurses</code> library with <code>-lncurses</code>. Many
1585 linkers are two-pass and will accept either order, but it is
1586 still good practice to put <code>-lmenu</code> first and
1587 <code>-lncurses</code> second.</p>
1589 <h2><a name="moverview" id="moverview">Overview of Menus</a></h2>
1591 <p>The menus created by this library consist of collections of
1592 <dfn>items</dfn> including a name string part and a description
1593 string part. To make menus, you create groups of these items and
1594 connect them with menu frame objects.</p>
1596 <p>The menu can then by <dfn>posted</dfn>, that is written to an
1597 associated window. Actually, each menu has two associated
1598 windows; a containing window in which the programmer can scribble
1599 titles or borders, and a subwindow in which the menu items proper
1600 are displayed. If this subwindow is too small to display all the
1601 items, it will be a scrollable viewport on the collection of
1604 <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed),
1605 and finally freed to make the storage associated with it and its
1606 items available for re-use.</p>
1608 <p>The general flow of control of a menu program looks like
1612 <li>Initialize <code>curses</code>.</li>
1614 <li>Create the menu items, using <code>new_item()</code>.</li>
1616 <li>Create the menu using <code>new_menu()</code>.</li>
1618 <li>Post the menu using <code>post_menu()</code>.</li>
1620 <li>Refresh the screen.</li>
1622 <li>Process user requests via an input loop.</li>
1624 <li>Unpost the menu using <code>unpost_menu()</code>.</li>
1626 <li>Free the menu, using <code>free_menu()</code>.</li>
1628 <li>Free the items using <code>free_item()</code>.</li>
1630 <li>Terminate <code>curses</code>.</li>
1633 <h2><a name="mselect" id="mselect">Selecting items</a></h2>
1635 <p>Menus may be multi-valued or (the default) single-valued (see
1636 the manual page <code>menu_opts(3x)</code> to see how to change
1637 the default). Both types always have a <dfn>current
1640 <p>From a single-valued menu you can read the selected value
1641 simply by looking at the current item. From a multi-valued menu,
1642 you get the selected set by looping through the items applying
1643 the <code>item_value()</code> predicate function. Your
1644 menu-processing code can use the function
1645 <code>set_item_value()</code> to flag the items in the select
1648 <p>Menu items can be made unselectable using
1649 <code>set_item_opts()</code> or <code>item_opts_off()</code> with
1650 the <code>O_SELECTABLE</code> argument. This is the only option
1651 so far defined for menus, but it is good practice to code as
1652 though other option bits might be on.</p>
1654 <h2><a name="mdisplay" id="mdisplay">Menu Display</a></h2>
1656 <p>The menu library calculates a minimum display size for your
1657 window, based on the following variables:</p>
1660 <li>The number and maximum length of the menu items</li>
1662 <li>Whether the O_ROWMAJOR option is enabled</li>
1664 <li>Whether display of descriptions is enabled</li>
1666 <li>Whatever menu format may have been set by the
1669 <li>The length of the menu mark string used for highlighting
1673 <p>The function <code>set_menu_format()</code> allows you to set
1674 the maximum size of the viewport or <dfn>menu page</dfn> that
1675 will be used to display menu items. You can retrieve any format
1676 associated with a menu with <code>menu_format()</code>. The
1677 default format is rows=16, columns=1.</p>
1679 <p>The actual menu page may be smaller than the format size. This
1680 depends on the item number and size and whether O_ROWMAJOR is on.
1681 This option (on by default) causes menu items to be displayed in
1682 a “raster-scan” pattern, so that if more than one
1683 item will fit horizontally the first couple of items are
1684 side-by-side in the top row. The alternative is column-major
1685 display, which tries to put the first several items in the first
1688 <p>As mentioned above, a menu format not large enough to allow
1689 all items to fit on-screen will result in a menu display that is
1690 vertically scrollable.</p>
1692 <p>You can scroll it with requests to the menu driver, which will
1693 be described in the section on <a href="#minput">menu input
1696 <p>Each menu has a <dfn>mark string</dfn> used to visually tag
1697 selected items; see the <code>menu_mark(3x)</code> manual page
1698 for details. The mark string length also influences the menu page
1701 <p>The function <code>scale_menu()</code> returns the minimum
1702 display size that the menu code computes from all these factors.
1703 There are other menu display attributes including a select
1704 attribute, an attribute for selectable items, an attribute for
1705 unselectable items, and a pad character used to separate item
1706 name text from description text. These have reasonable defaults
1707 which the library allows you to change (see the
1708 <code>menu_attribs(3x)</code> manual page.</p>
1710 <h2><a name="mwindows" id="mwindows">Menu Windows</a></h2>
1712 <p>Each menu has, as mentioned previously, a pair of associated
1713 windows. Both these windows are painted when the menu is posted
1714 and erased when the menu is unposted.</p>
1716 <p>The outer or frame window is not otherwise touched by the menu
1717 routines. It exists so the programmer can associate a title, a
1718 border, or perhaps help text with the menu and have it properly
1719 refreshed or erased at post/unpost time. The inner window or
1720 <dfn>subwindow</dfn> is where the current menu page is
1723 <p>By default, both windows are <code>stdscr</code>. You can set
1724 them with the functions in <code>menu_win(3x)</code>.</p>
1726 <p>When you call <code>post_menu()</code>, you write the menu to
1727 its subwindow. When you call <code>unpost_menu()</code>, you
1728 erase the subwindow, However, neither of these actually modifies
1729 the screen. To do that, call <code>wrefresh()</code> or some
1732 <h2><a name="minput" id="minput">Processing Menu Input</a></h2>
1734 <p>The main loop of your menu-processing code should call
1735 <code>menu_driver()</code> repeatedly. The first argument of this
1736 routine is a menu pointer; the second is a menu command code. You
1737 should write an input-fetching routine that maps input characters
1738 to menu command codes, and pass its output to
1739 <code>menu_driver()</code>. The menu command codes are fully
1740 documented in <code>menu_driver(3x)</code>.</p>
1742 <p>The simplest group of command codes is
1743 <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>,
1744 <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>,
1745 <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>,
1746 <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These
1747 change the currently selected item. These requests may cause
1748 scrolling of the menu page if it only partially displayed.</p>
1750 <p>There are explicit requests for scrolling which also change
1751 the current item (because the select location does not change,
1752 but the item there does). These are <code>REQ_SCR_DLINE</code>,
1753 <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and
1754 <code>REQ_SCR_UPAGE</code>.</p>
1756 <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the
1757 current item. It is for use in multi-valued menus; if you use it
1758 with <code>O_ONEVALUE</code> on, you will get an error return
1759 (<code>E_REQUEST_DENIED</code>).</p>
1761 <p>Each menu has an associated pattern buffer. The
1762 <code>menu_driver()</code> logic tries to accumulate printable
1763 ASCII characters passed in in that buffer; when it matches a
1764 prefix of an item name, that item (or the next matching item) is
1765 selected. If appending a character yields no new match, that
1766 character is deleted from the pattern buffer, and
1767 <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p>
1769 <p>Some requests change the pattern buffer directly:
1770 <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>,
1771 <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The
1772 latter two are useful when pattern buffer input matches more than
1773 one item in a multi-valued menu.</p>
1775 <p>Each successful scroll or item navigation request clears the
1776 pattern buffer. It is also possible to set the pattern buffer
1777 explicitly with <code>set_menu_pattern()</code>.</p>
1779 <p>Finally, menu driver requests above the constant
1780 <code>MAX_COMMAND</code> are considered application-specific
1781 commands. The <code>menu_driver()</code> code ignores them and
1782 returns <code>E_UNKNOWN_COMMAND</code>.</p>
1784 <h2><a name="mmisc" id="mmisc">Miscellaneous Other Features</a></h2>
1786 <p>Various menu options can affect the processing and visual
1787 appearance and input processing of menus. See <code>menu_opts(3x)
1788 for details.</code></p>
1790 <p>It is possible to change the current item from application
1791 code; this is useful if you want to write your own navigation
1792 requests. It is also possible to explicitly set the top row of
1793 the menu display. See <code>mitem_current(3x)</code>. If your
1794 application needs to change the menu subwindow cursor for any
1795 reason, <code>pos_menu_cursor()</code> will restore it to the
1796 correct location for continuing menu driver processing.</p>
1798 <p>It is possible to set hooks to be called at menu
1799 initialization and wrapup time, and whenever the selected item
1800 changes. See <code>menu_hook(3x)</code>.</p>
1802 <p>Each item, and each menu, has an associated user pointer on
1803 which you can hang application data. See
1804 <code>mitem_userptr(3x)</code> and
1805 <code>menu_userptr(3x)</code>.</p>
1807 <h1><a name="form" id="form">The Forms Library</a></h1>
1809 <p>The <code>form</code> library is a curses extension that
1810 supports easy programming of on-screen forms for data entry and
1811 program control.</p>
1813 <p>The <code>form</code> library first appeared in AT&T
1814 System V. The version documented here is the <code>form</code>
1815 code distributed with <code>ncurses</code>.</p>
1817 <h2><a name="fcompile" id="fcompile">Compiling With the form
1820 <p>Your form-using modules must import the form library
1821 declarations with</p>
1824 #include <form.h>
1827 <p>and must be linked explicitly with the forms library using an
1828 <code>-lform</code> argument. Note that they must also link the
1829 <code>ncurses</code> library with <code>-lncurses</code>. Many
1830 linkers are two-pass and will accept either order, but it is
1831 still good practice to put <code>-lform</code> first and
1832 <code>-lncurses</code> second.</p>
1834 <h2><a name="foverview" id="foverview">Overview of Forms</a></h2>
1836 <p>A form is a collection of fields; each field may be either a
1837 label (explanatory text) or a data-entry location. Long forms may
1838 be segmented into pages; each entry to a new page clears the
1841 <p>To make forms, you create groups of fields and connect them
1842 with form frame objects; the form library makes this relatively
1845 <p>Once defined, a form can be <dfn>posted</dfn>, that is written
1846 to an associated window. Actually, each form has two associated
1847 windows; a containing window in which the programmer can scribble
1848 titles or borders, and a subwindow in which the form fields
1849 proper are displayed.</p>
1851 <p>As the form user fills out the posted form, navigation and
1852 editing keys support movement between fields, editing keys
1853 support modifying field, and plain text adds to or changes data
1854 in a current field. The form library allows you (the forms
1855 designer) to bind each navigation and editing key to any
1856 keystroke accepted by <code>curses</code> Fields may have
1857 validation conditions on them, so that they check input data for
1858 type and value. The form library supplies a rich set of
1859 pre-defined field types, and makes it relatively easy to define
1862 <p>Once its transaction is completed (or aborted), a form may be
1863 <dfn>unposted</dfn> (that is, undisplayed), and finally freed to
1864 make the storage associated with it and its items available for
1867 <p>The general flow of control of a form program looks like
1871 <li>Initialize <code>curses</code>.</li>
1873 <li>Create the form fields, using
1874 <code>new_field()</code>.</li>
1876 <li>Create the form using <code>new_form()</code>.</li>
1878 <li>Post the form using <code>post_form()</code>.</li>
1880 <li>Refresh the screen.</li>
1882 <li>Process user requests via an input loop.</li>
1884 <li>Unpost the form using <code>unpost_form()</code>.</li>
1886 <li>Free the form, using <code>free_form()</code>.</li>
1888 <li>Free the fields using <code>free_field()</code>.</li>
1890 <li>Terminate <code>curses</code>.</li>
1893 <p>Note that this looks much like a menu program; the form
1894 library handles tasks which are in many ways similar, and its
1895 interface was obviously designed to resemble that of the <a href=
1896 "#menu">menu library</a> wherever possible.</p>
1898 <p>In forms programs, however, the “process user
1899 requests” is somewhat more complicated than for menus.
1900 Besides menu-like navigation operations, the menu driver loop has
1901 to support field editing and data validation.</p>
1903 <h2><a name="fcreate" id="fcreate">Creating and Freeing Fields
1906 <p>The basic function for creating fields is
1907 <code>new_field()</code>:</p>
1910 FIELD *new_field(int height, int width, /* new field size */
1911 int top, int left, /* upper left corner */
1912 int offscreen, /* number of offscreen rows */
1913 int nbuf); /* number of working buffers */
1916 <p>Menu items always occupy a single row, but forms fields may
1917 have multiple rows. So <code>new_field()</code> requires you to
1918 specify a width and height (the first two arguments, which mist
1919 both be greater than zero).</p>
1921 <p>You must also specify the location of the field's upper left
1922 corner on the screen (the third and fourth arguments, which must
1923 be zero or greater). Note that these coordinates are relative to
1924 the form subwindow, which will coincide with <code>stdscr</code>
1925 by default but need not be <code>stdscr</code> if you have done
1926 an explicit <code>set_form_win()</code> call.</p>
1928 <p>The fifth argument allows you to specify a number of
1929 off-screen rows. If this is zero, the entire field will always be
1930 displayed. If it is nonzero, the form will be scrollable, with
1931 only one screen-full (initially the top part) displayed at any
1932 given time. If you make a field dynamic and grow it so it will no
1933 longer fit on the screen, the form will become scrollable even if
1934 the <code>offscreen</code> argument was initially zero.</p>
1936 <p>The forms library allocates one working buffer per field; the
1937 size of each buffer is <code>((height + offscreen)*width +
1938 1</code>, one character for each position in the field plus a NUL
1939 terminator. The sixth argument is the number of additional data
1940 buffers to allocate for the field; your application can use them
1941 for its own purposes.</p>
1944 FIELD *dup_field(FIELD *field, /* field to copy */
1945 int top, int left); /* location of new copy */
1948 <p>The function <code>dup_field()</code> duplicates an existing
1949 field at a new location. Size and buffering information are
1950 copied; some attribute flags and status bits are not (see the
1951 <code>form_field_new(3X)</code> for details).</p>
1954 FIELD *link_field(FIELD *field, /* field to copy */
1955 int top, int left); /* location of new copy */
1958 <p>The function <code>link_field()</code> also duplicates an
1959 existing field at a new location. The difference from
1960 <code>dup_field()</code> is that it arranges for the new field's
1961 buffer to be shared with the old one.</p>
1963 <p>Besides the obvious use in making a field editable from two
1964 different form pages, linked fields give you a way to hack in
1965 dynamic labels. If you declare several fields linked to an
1966 original, and then make them inactive, changes from the original
1967 will still be propagated to the linked fields.</p>
1969 <p>As with duplicated fields, linked fields have attribute bits
1970 separate from the original.</p>
1972 <p>As you might guess, all these field-allocations return
1973 <code>NULL</code> if the field allocation is not possible due to
1974 an out-of-memory error or out-of-bounds arguments.</p>
1976 <p>To connect fields to a form, use</p>
1979 FORM *new_form(FIELD **fields);
1982 <p>This function expects to see a NULL-terminated array of field
1983 pointers. Said fields are connected to a newly-allocated form
1984 object; its address is returned (or else NULL if the allocation
1987 <p>Note that <code>new_field()</code> does <em>not</em> copy the
1988 pointer array into private storage; if you modify the contents of
1989 the pointer array during forms processing, all manner of bizarre
1990 things might happen. Also note that any given field may only be
1991 connected to one form.</p>
1993 <p>The functions <code>free_field()</code> and
1994 <code>free_form</code> are available to free field and form
1995 objects. It is an error to attempt to free a field connected to a
1996 form, but not vice-versa; thus, you will generally free your form
1999 <h2><a name="fattributes" id="fattributes">Fetching and Changing
2000 Field Attributes</a></h2>
2002 <p>Each form field has a number of location and size attributes
2003 associated with it. There are other field attributes used to
2004 control display and editing of the field. Some (for example, the
2005 <code>O_STATIC</code> bit) involve sufficient complications to be
2006 covered in sections of their own later on. We cover the functions
2007 used to get and set several basic attributes here.</p>
2009 <p>When a field is created, the attributes not specified by the
2010 <code>new_field</code> function are copied from an invisible
2011 system default field. In attribute-setting and -fetching
2012 functions, the argument NULL is taken to mean this field. Changes
2013 to it persist as defaults until your forms application
2016 <h3><a name="fsizes" id="fsizes">Fetching Size and Location
2019 <p>You can retrieve field sizes and locations through:</p>
2022 int field_info(FIELD *field, /* field from which to fetch */
2023 int *height, *int width, /* field size */
2024 int *top, int *left, /* upper left corner */
2025 int *offscreen, /* number of offscreen rows */
2026 int *nbuf); /* number of working buffers */
2029 <p>This function is a sort of inverse of
2030 <code>new_field()</code>; instead of setting size and location
2031 attributes of a new field, it fetches them from an existing
2034 <h3><a name="flocation" id="flocation">Changing the Field
2037 <p>It is possible to move a field's location on the screen:</p>
2040 int move_field(FIELD *field, /* field to alter */
2041 int top, int left); /* new upper-left corner */
2044 <p>You can, of course. query the current location through
2045 <code>field_info()</code>.</p>
2047 <h3><a name="fjust" id="fjust">The Justification Attribute</a></h3>
2049 <p>One-line fields may be unjustified, justified right, justified
2050 left, or centered. Here is how you manipulate this attribute:</p>
2053 int set_field_just(FIELD *field, /* field to alter */
2054 int justmode); /* mode to set */
2056 int field_just(FIELD *field); /* fetch mode of field */
2059 <p>The mode values accepted and returned by this functions are
2060 preprocessor macros <code>NO_JUSTIFICATION</code>,
2061 <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or
2062 <code>JUSTIFY_CENTER</code>.</p>
2064 <h3><a name="fdispatts" id="fdispatts">Field Display
2067 <p>For each field, you can set a foreground attribute for entered
2068 characters, a background attribute for the entire field, and a
2069 pad character for the unfilled portion of the field. You can also
2070 control pagination of the form.</p>
2072 <p>This group of four field attributes controls the visual
2073 appearance of the field on the screen, without affecting in any
2074 way the data in the field buffer.</p>
2077 int set_field_fore(FIELD *field, /* field to alter */
2078 chtype attr); /* attribute to set */
2080 chtype field_fore(FIELD *field); /* field to query */
2082 int set_field_back(FIELD *field, /* field to alter */
2083 chtype attr); /* attribute to set */
2085 chtype field_back(FIELD *field); /* field to query */
2087 int set_field_pad(FIELD *field, /* field to alter */
2088 int pad); /* pad character to set */
2090 chtype field_pad(FIELD *field);
2092 int set_new_page(FIELD *field, /* field to alter */
2093 int flag); /* TRUE to force new page */
2095 chtype new_page(FIELD *field); /* field to query */
2098 <p>The attributes set and returned by the first four functions
2099 are normal <code>curses(3x)</code> display attribute values
2100 (<code>A_STANDOUT</code>, <code>A_BOLD</code>,
2101 <code>A_REVERSE</code> etc). The page bit of a field controls
2102 whether it is displayed at the start of a new form screen.</p>
2104 <h3><a name="foptions" id="foptions">Field Option Bits</a></h3>
2106 <p>There is also a large collection of field option bits you can
2107 set to control various aspects of forms processing. You can
2108 manipulate them with these functions:</p>
2111 int set_field_opts(FIELD *field, /* field to alter */
2112 int attr); /* attribute to set */
2114 int field_opts_on(FIELD *field, /* field to alter */
2115 int attr); /* attributes to turn on */
2117 int field_opts_off(FIELD *field, /* field to alter */
2118 int attr); /* attributes to turn off */
2120 int field_opts(FIELD *field); /* field to query */
2123 <p>By default, all options are on. Here are the available option
2129 <dd>Controls whether the field is visible on the screen. Can be
2130 used during form processing to hide or pop up fields depending
2131 on the value of parent fields.</dd>
2135 <dd>Controls whether the field is active during forms
2136 processing (i.e. visited by form navigation keys). Can be used
2137 to make labels or derived fields with buffer values alterable
2138 by the forms application, not the user.</dd>
2142 <dd>Controls whether data is displayed during field entry. If
2143 this option is turned off on a field, the library will accept
2144 and edit data in that field, but it will not be displayed and
2145 the visible field cursor will not move. You can turn off the
2146 O_PUBLIC bit to define password fields.</dd>
2150 <dd>Controls whether the field's data can be modified. When
2151 this option is off, all editing requests except
2152 <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code>
2153 will fail. Such read-only fields may be useful for help
2158 <dd>Controls word-wrapping in multi-line fields. Normally, when
2159 any character of a (blank-separated) word reaches the end of
2160 the current line, the entire word is wrapped to the next line
2161 (assuming there is one). When this option is off, the word will
2162 be split across the line break.</dd>
2166 <dd>Controls field blanking. When this option is on, entering a
2167 character at the first field position erases the entire field
2168 (except for the just-entered character).</dd>
2172 <dd>Controls automatic skip to next field when this one fills.
2173 Normally, when the forms user tries to type more data into a
2174 field than will fit, the editing location jumps to next field.
2175 When this option is off, the user's cursor will hang at the end
2176 of the field. This option is ignored in dynamic fields that
2177 have not reached their size limit.</dd>
2181 <dd>Controls whether <a href="#fvalidation">validation</a> is
2182 applied to blank fields. Normally, it is not; the user can
2183 leave a field blank without invoking the usual validation check
2184 on exit. If this option is off on a field, exit from it will
2185 invoke a validation check.</dd>
2189 <dd>Controls whether validation occurs on every exit, or only
2190 after the field is modified. Normally the latter is true.
2191 Setting O_PASSOK may be useful if your field's validation
2192 function may change during forms processing.</dd>
2196 <dd>Controls whether the field is fixed to its initial
2197 dimensions. If you turn this off, the field becomes <a href=
2198 "#fdynamic">dynamic</a> and will stretch to fit entered
2202 <p>A field's options cannot be changed while the field is
2203 currently selected. However, options may be changed on posted
2204 fields that are not current.</p>
2206 <p>The option values are bit-masks and can be composed with
2207 logical-or in the obvious way.</p>
2209 <h2><a name="fstatus" id="fstatus">Field Status</a></h2>
2211 <p>Every field has a status flag, which is set to FALSE when the
2212 field is created and TRUE when the value in field buffer 0
2213 changes. This flag can be queried and set directly:</p>
2216 int set_field_status(FIELD *field, /* field to alter */
2217 int status); /* mode to set */
2219 int field_status(FIELD *field); /* fetch mode of field */
2222 <p>Setting this flag under program control can be useful if you
2223 use the same form repeatedly, looking for modified fields each
2226 <p>Calling <code>field_status()</code> on a field not currently
2227 selected for input will return a correct value. Calling
2228 <code>field_status()</code> on a field that is currently selected
2229 for input may not necessarily give a correct field status value,
2230 because entered data is not necessarily copied to buffer zero
2231 before the exit validation check. To guarantee that the returned
2232 status value reflects reality, call <code>field_status()</code>
2233 either (1) in the field's exit validation check routine, (2) from
2234 the field's or form's initialization or termination hooks, or (3)
2235 just after a <code>REQ_VALIDATION</code> request has been
2236 processed by the forms driver.</p>
2238 <h2><a name="fuser" id="fuser">Field User Pointer</a></h2>
2240 <p>Each field structure contains one character pointer slot that
2241 is not used by the forms library. It is intended to be used by
2242 applications to store private per-field data. You can manipulate
2246 int set_field_userptr(FIELD *field, /* field to alter */
2247 char *userptr); /* mode to set */
2249 char *field_userptr(FIELD *field); /* fetch mode of field */
2250 </pre>(Properly, this user pointer field ought to have <code>(void
2251 *)</code> type. The <code>(char *)</code> type is retained for
2252 System V compatibility.)
2254 <p>It is valid to set the user pointer of the default field (with
2255 a <code>set_field_userptr()</code> call passed a NULL field
2256 pointer.) When a new field is created, the default-field user
2257 pointer is copied to initialize the new field's user pointer.</p>
2259 <h2><a name="fdynamic" id="fdynamic">Variable-Sized Fields</a></h2>
2261 <p>Normally, a field is fixed at the size specified for it at
2262 creation time. If, however, you turn off its O_STATIC bit, it
2263 becomes <dfn>dynamic</dfn> and will automatically resize itself
2264 to accommodate data as it is entered. If the field has extra
2265 buffers associated with it, they will grow right along with the
2266 main input buffer.</p>
2268 <p>A one-line dynamic field will have a fixed height (1) but
2269 variable width, scrolling horizontally to display data within the
2270 field area as originally dimensioned and located. A multi-line
2271 dynamic field will have a fixed width, but variable height
2272 (number of rows), scrolling vertically to display data within the
2273 field area as originally dimensioned and located.</p>
2275 <p>Normally, a dynamic field is allowed to grow without limit.
2276 But it is possible to set an upper limit on the size of a dynamic
2277 field. You do it with this function:</p>
2280 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
2281 int max_size); /* upper limit on field size */
2284 <p>If the field is one-line, <code>max_size</code> is taken to be
2285 a column size limit; if it is multi-line, it is taken to be a
2286 line size limit. To disable any limit, use an argument of zero.
2287 The growth limit can be changed whether or not the O_STATIC bit
2288 is on, but has no effect until it is.</p>
2290 <p>The following properties of a field change when it becomes
2294 <li>If there is no growth limit, there is no final position of
2295 the field; therefore <code>O_AUTOSKIP</code> and
2296 <code>O_NL_OVERLOAD</code> are ignored.</li>
2298 <li>Field justification will be ignored (though whatever
2299 justification is set up will be retained internally and can be
2302 <li>The <code>dup_field()</code> and <code>link_field()</code>
2303 calls copy dynamic-buffer sizes. If the <code>O_STATIC</code>
2304 option is set on one of a collection of links, buffer resizing
2305 will occur only when the field is edited through that
2308 <li>The call <code>field_info()</code> will retrieve the
2309 original static size of the field; use
2310 <code>dynamic_field_info()</code> to get the actual dynamic
2314 <h2><a name="fvalidation" id="fvalidation">Field Validation</a></h2>
2316 <p>By default, a field will accept any data that will fit in its
2317 input buffer. However, it is possible to attach a validation type
2318 to a field. If you do this, any attempt to leave the field while
2319 it contains data that does not match the validation type will
2320 fail. Some validation types also have a character-validity check
2321 for each time a character is entered in the field.</p>
2323 <p>A field's validation check (if any) is not called when
2324 <code>set_field_buffer()</code> modifies the input buffer, nor
2325 when that buffer is changed through a linked field.</p>
2327 <p>The <code>form</code> library provides a rich set of
2328 pre-defined validation types, and gives you the capability to
2329 define custom ones of your own. You can examine and change field
2330 validation attributes with the following functions:</p>
2333 int set_field_type(FIELD *field, /* field to alter */
2334 FIELDTYPE *ftype, /* type to associate */
2335 ...); /* additional arguments*/
2337 FIELDTYPE *field_type(FIELD *field); /* field to query */
2340 <p>The validation type of a field is considered an attribute of
2341 the field. As with other field attributes, Also, doing
2342 <code>set_field_type()</code> with a <code>NULL</code> field
2343 default will change the system default for validation of
2344 newly-created fields.</p>
2346 <p>Here are the pre-defined validation types:</p>
2348 <h3><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h3>
2350 <p>This field type accepts alphabetic data; no blanks, no digits,
2351 no special characters (this is checked at character-entry time).
2352 It is set up with:</p>
2355 int set_field_type(FIELD *field, /* field to alter */
2356 TYPE_ALPHA, /* type to associate */
2357 int width); /* maximum width of field */
2360 <p>The <code>width</code> argument sets a minimum width of data.
2361 Typically you will want to set this to the field width; if it is
2362 greater than the field width, the validation check will always
2363 fail. A minimum width of zero makes field completion
2366 <h3><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h3>
2368 <p>This field type accepts alphabetic data and digits; no blanks,
2369 no special characters (this is checked at character-entry time).
2370 It is set up with:</p>
2373 int set_field_type(FIELD *field, /* field to alter */
2374 TYPE_ALNUM, /* type to associate */
2375 int width); /* maximum width of field */
2378 <p>The <code>width</code> argument sets a minimum width of data.
2379 As with TYPE_ALPHA, typically you will want to set this to the
2380 field width; if it is greater than the field width, the
2381 validation check will always fail. A minimum width of zero makes
2382 field completion optional.</p>
2384 <h3><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h3>
2386 <p>This type allows you to restrict a field's values to be among
2387 a specified set of string values (for example, the two-letter
2388 postal codes for U.S. states). It is set up with:</p>
2391 int set_field_type(FIELD *field, /* field to alter */
2392 TYPE_ENUM, /* type to associate */
2393 char **valuelist; /* list of possible values */
2394 int checkcase; /* case-sensitive? */
2395 int checkunique); /* must specify uniquely? */
2398 <p>The <code>valuelist</code> parameter must point at a
2399 NULL-terminated list of valid strings. The <code>checkcase</code>
2400 argument, if true, makes comparison with the string
2403 <p>When the user exits a TYPE_ENUM field, the validation
2404 procedure tries to complete the data in the buffer to a valid
2405 entry. If a complete choice string has been entered, it is of
2406 course valid. But it is also possible to enter a prefix of a
2407 valid string and have it completed for you.</p>
2409 <p>By default, if you enter such a prefix and it matches more
2410 than one value in the string list, the prefix will be completed
2411 to the first matching value. But the <code>checkunique</code>
2412 argument, if true, requires prefix matches to be unique in order
2415 <p>The <code>REQ_NEXT_CHOICE</code> and
2416 <code>REQ_PREV_CHOICE</code> input requests can be particularly
2417 useful with these fields.</p>
2419 <h3><a name="ftype_integer" id="ftype_integer">TYPE_INTEGER</a></h3>
2421 <p>This field type accepts an integer. It is set up as
2425 int set_field_type(FIELD *field, /* field to alter */
2426 TYPE_INTEGER, /* type to associate */
2427 int padding, /* # places to zero-pad to */
2428 int vmin, int vmax); /* valid range */
2431 <p>Valid characters consist of an optional leading minus and
2432 digits. The range check is performed on exit. If the range
2433 maximum is less than or equal to the minimum, the range is
2436 <p>If the value passes its range check, it is padded with as many
2437 leading zero digits as necessary to meet the padding
2440 <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be
2441 interpreted with the C library function <code>atoi(3)</code>.</p>
2443 <h3><a name="ftype_numeric" id="ftype_numeric">TYPE_NUMERIC</a></h3>
2445 <p>This field type accepts a decimal number. It is set up as
2449 int set_field_type(FIELD *field, /* field to alter */
2450 TYPE_NUMERIC, /* type to associate */
2451 int padding, /* # places of precision */
2452 double vmin, double vmax); /* valid range */
2455 <p>Valid characters consist of an optional leading minus and
2456 digits. possibly including a decimal point. If your system
2457 supports locale's, the decimal point character used must be the
2458 one defined by your locale. The range check is performed on exit.
2459 If the range maximum is less than or equal to the minimum, the
2460 range is ignored.</p>
2462 <p>If the value passes its range check, it is padded with as many
2463 trailing zero digits as necessary to meet the padding
2466 <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be
2467 interpreted with the C library function <code>atof(3)</code>.</p>
2469 <h3><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h3>
2471 <p>This field type accepts data matching a regular expression. It
2472 is set up as follows:</p>
2475 int set_field_type(FIELD *field, /* field to alter */
2476 TYPE_REGEXP, /* type to associate */
2477 char *regexp); /* expression to match */
2480 <p>The syntax for regular expressions is that of
2481 <code>regcomp(3)</code>. The check for regular-expression match
2482 is performed on exit.</p>
2484 <h2><a name="fbuffer" id="fbuffer">Direct Field Buffer
2485 Manipulation</a></h2>
2487 <p>The chief attribute of a field is its buffer contents. When a
2488 form has been completed, your application usually needs to know
2489 the state of each field buffer. You can find this out with:</p>
2492 char *field_buffer(FIELD *field, /* field to query */
2493 int bufindex); /* number of buffer to query */
2496 <p>Normally, the state of the zero-numbered buffer for each field
2497 is set by the user's editing actions on that field. It is
2498 sometimes useful to be able to set the value of the zero-numbered
2499 (or some other) buffer from your application:</p>
2502 int set_field_buffer(FIELD *field, /* field to alter */
2503 int bufindex, /* number of buffer to alter */
2504 char *value); /* string value to set */
2507 <p>If the field is not large enough and cannot be resized to a
2508 sufficiently large size to contain the specified value, the value
2509 will be truncated to fit.</p>
2511 <p>Calling <code>field_buffer()</code> with a null field pointer
2512 will raise an error. Calling <code>field_buffer()</code> on a
2513 field not currently selected for input will return a correct
2514 value. Calling <code>field_buffer()</code> on a field that is
2515 currently selected for input may not necessarily give a correct
2516 field buffer value, because entered data is not necessarily
2517 copied to buffer zero before the exit validation check. To
2518 guarantee that the returned buffer value reflects on-screen
2519 reality, call <code>field_buffer()</code> either (1) in the
2520 field's exit validation check routine, (2) from the field's or
2521 form's initialization or termination hooks, or (3) just after a
2522 <code>REQ_VALIDATION</code> request has been processed by the
2525 <h2><a name="formattrs" id="formattrs">Attributes of Forms</a></h2>
2527 <p>As with field attributes, form attributes inherit a default
2528 from a system default form structure. These defaults can be
2529 queried or set by of these functions using a form-pointer
2530 argument of <code>NULL</code>.</p>
2532 <p>The principal attribute of a form is its field list. You can
2533 query and change this list with:</p>
2536 int set_form_fields(FORM *form, /* form to alter */
2537 FIELD **fields); /* fields to connect */
2539 char *form_fields(FORM *form); /* fetch fields of form */
2541 int field_count(FORM *form); /* count connect fields */
2544 <p>The second argument of <code>set_form_fields()</code> may be a
2545 NULL-terminated field pointer array like the one required by
2546 <code>new_form()</code>. In that case, the old fields of the form
2547 are disconnected but not freed (and eligible to be connected to
2548 other forms), then the new fields are connected.</p>
2550 <p>It may also be null, in which case the old fields are
2551 disconnected (and not freed) but no new ones are connected.</p>
2553 <p>The <code>field_count()</code> function simply counts the
2554 number of fields connected to a given from. It returns -1 if the
2555 form-pointer argument is NULL.</p>
2557 <h2><a name="fdisplay" id="fdisplay">Control of Form Display</a></h2>
2559 <p>In the overview section, you saw that to display a form you
2560 normally start by defining its size (and fields), posting it, and
2561 refreshing the screen. There is an hidden step before posting,
2562 which is the association of the form with a frame window
2563 (actually, a pair of windows) within which it will be displayed.
2564 By default, the forms library associates every form with the
2565 full-screen window <code>stdscr</code>.</p>
2567 <p>By making this step explicit, you can associate a form with a
2568 declared frame window on your screen display. This can be useful
2569 if you want to adapt the form display to different screen sizes,
2570 dynamically tile forms on the screen, or use a form as part of an
2571 interface layout managed by <a href="#panels">panels</a>.</p>
2573 <p>The two windows associated with each form have the same
2574 functions as their analogues in the <a href="#menu">menu
2575 library</a>. Both these windows are painted when the form is
2576 posted and erased when the form is unposted.</p>
2578 <p>The outer or frame window is not otherwise touched by the form
2579 routines. It exists so the programmer can associate a title, a
2580 border, or perhaps help text with the form and have it properly
2581 refreshed or erased at post/unpost time. The inner window or
2582 subwindow is where the current form page is actually
2585 <p>In order to declare your own frame window for a form, you will
2586 need to know the size of the form's bounding rectangle. You can
2587 get this information with:</p>
2590 int scale_form(FORM *form, /* form to query */
2591 int *rows, /* form rows */
2592 int *cols); /* form cols */
2595 <p>The form dimensions are passed back in the locations pointed
2596 to by the arguments. Once you have this information, you can use
2597 it to declare of windows, then use one of these functions:</p>
2600 int set_form_win(FORM *form, /* form to alter */
2601 WINDOW *win); /* frame window to connect */
2603 WINDOW *form_win(FORM *form); /* fetch frame window of form */
2605 int set_form_sub(FORM *form, /* form to alter */
2606 WINDOW *win); /* form subwindow to connect */
2608 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
2611 <p>Note that curses operations, including <code>refresh()</code>,
2612 on the form, should be done on the frame window, not the form
2615 <p>It is possible to check from your application whether all of a
2616 scrollable field is actually displayed within the menu subwindow.
2617 Use these functions:</p>
2620 int data_ahead(FORM *form); /* form to be queried */
2622 int data_behind(FORM *form); /* form to be queried */
2625 <p>The function <code>data_ahead()</code> returns TRUE if (a) the
2626 current field is one-line and has undisplayed data off to the
2627 right, (b) the current field is multi-line and there is data
2628 off-screen below it.</p>
2630 <p>The function <code>data_behind()</code> returns TRUE if the
2631 first (upper left hand) character position is off-screen (not
2632 being displayed).</p>
2634 <p>Finally, there is a function to restore the form window's
2635 cursor to the value expected by the forms driver:</p>
2638 int pos_form_cursor(FORM *) /* form to be queried */
2641 <p>If your application changes the form window cursor, call this
2642 function before handing control back to the forms driver in order
2643 to re-synchronize it.</p>
2645 <h2><a name="fdriver" id="fdriver">Input Processing in the Forms
2648 <p>The function <code>form_driver()</code> handles virtualized
2649 input requests for form navigation, editing, and validation
2650 requests, just as <code>menu_driver</code> does for menus (see
2651 the section on <a href="#minput">menu input handling</a>).</p>
2654 int form_driver(FORM *form, /* form to pass input to */
2655 int request); /* form request code */
2658 <p>Your input virtualization function needs to take input and
2659 then convert it to either an alphanumeric character (which is
2660 treated as data to be entered in the currently-selected field),
2661 or a forms processing request.</p>
2663 <p>The forms driver provides hooks (through input-validation and
2664 field-termination functions) with which your application code can
2665 check that the input taken by the driver matched what was
2668 <h3><a name="fpage" id="fpage">Page Navigation Requests</a></h3>
2670 <p>These requests cause page-level moves through the form,
2671 triggering display of a new form screen.</p>
2674 <dt><code>REQ_NEXT_PAGE</code>
2677 <dd>Move to the next form page.</dd>
2679 <dt><code>REQ_PREV_PAGE</code>
2682 <dd>Move to the previous form page.</dd>
2684 <dt><code>REQ_FIRST_PAGE</code>
2687 <dd>Move to the first form page.</dd>
2689 <dt><code>REQ_LAST_PAGE</code>
2692 <dd>Move to the last form page.</dd>
2695 <p>These requests treat the list as cyclic; that is,
2696 <code>REQ_NEXT_PAGE</code> from the last page goes to the first,
2697 and <code>REQ_PREV_PAGE</code> from the first page goes to the
2700 <h3><a name="ffield" id="ffield">Inter-Field Navigation
2703 <p>These requests handle navigation between fields on the same
2707 <dt><code>REQ_NEXT_FIELD</code>
2710 <dd>Move to next field.</dd>
2712 <dt><code>REQ_PREV_FIELD</code>
2715 <dd>Move to previous field.</dd>
2717 <dt><code>REQ_FIRST_FIELD</code>
2720 <dd>Move to the first field.</dd>
2722 <dt><code>REQ_LAST_FIELD</code>
2725 <dd>Move to the last field.</dd>
2727 <dt><code>REQ_SNEXT_FIELD</code>
2730 <dd>Move to sorted next field.</dd>
2732 <dt><code>REQ_SPREV_FIELD</code>
2735 <dd>Move to sorted previous field.</dd>
2737 <dt><code>REQ_SFIRST_FIELD</code>
2740 <dd>Move to the sorted first field.</dd>
2742 <dt><code>REQ_SLAST_FIELD</code>
2745 <dd>Move to the sorted last field.</dd>
2747 <dt><code>REQ_LEFT_FIELD</code>
2750 <dd>Move left to field.</dd>
2752 <dt><code>REQ_RIGHT_FIELD</code>
2755 <dd>Move right to field.</dd>
2757 <dt><code>REQ_UP_FIELD</code>
2760 <dd>Move up to field.</dd>
2762 <dt><code>REQ_DOWN_FIELD</code>
2765 <dd>Move down to field.</dd>
2768 <p>These requests treat the list of fields on a page as cyclic;
2769 that is, <code>REQ_NEXT_FIELD</code> from the last field goes to
2770 the first, and <code>REQ_PREV_FIELD</code> from the first field
2771 goes to the last. The order of the fields for these (and the
2772 <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code>
2773 requests) is simply the order of the field pointers in the form
2774 array (as set up by <code>new_form()</code> or
2775 <code>set_form_fields()</code></p>
2777 <p>It is also possible to traverse the fields as if they had been
2778 sorted in screen-position order, so the sequence goes
2779 left-to-right and top-to-bottom. To do this, use the second group
2780 of four sorted-movement requests.</p>
2782 <p>Finally, it is possible to move between fields using visual
2783 directions up, down, right, and left. To accomplish this, use the
2784 third group of four requests. Note, however, that the position of
2785 a form for purposes of these requests is its upper-left
2788 <p>For example, suppose you have a multi-line field B, and two
2789 single-line fields A and C on the same line with B, with A to the
2790 left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code>
2791 from A will go to B only if A, B, and C <em>all</em> share the
2792 same first line; otherwise it will skip over B to C.</p>
2794 <h3><a name="fifield" id="fifield">Intra-Field Navigation
2797 <p>These requests drive movement of the edit cursor within the
2798 currently selected field.</p>
2801 <dt><code>REQ_NEXT_CHAR</code>
2804 <dd>Move to next character.</dd>
2806 <dt><code>REQ_PREV_CHAR</code>
2809 <dd>Move to previous character.</dd>
2811 <dt><code>REQ_NEXT_LINE</code>
2814 <dd>Move to next line.</dd>
2816 <dt><code>REQ_PREV_LINE</code>
2819 <dd>Move to previous line.</dd>
2821 <dt><code>REQ_NEXT_WORD</code>
2824 <dd>Move to next word.</dd>
2826 <dt><code>REQ_PREV_WORD</code>
2829 <dd>Move to previous word.</dd>
2831 <dt><code>REQ_BEG_FIELD</code>
2834 <dd>Move to beginning of field.</dd>
2836 <dt><code>REQ_END_FIELD</code>
2839 <dd>Move to end of field.</dd>
2841 <dt><code>REQ_BEG_LINE</code>
2844 <dd>Move to beginning of line.</dd>
2846 <dt><code>REQ_END_LINE</code>
2849 <dd>Move to end of line.</dd>
2851 <dt><code>REQ_LEFT_CHAR</code>
2854 <dd>Move left in field.</dd>
2856 <dt><code>REQ_RIGHT_CHAR</code>
2859 <dd>Move right in field.</dd>
2861 <dt><code>REQ_UP_CHAR</code>
2864 <dd>Move up in field.</dd>
2866 <dt><code>REQ_DOWN_CHAR</code>
2869 <dd>Move down in field.</dd>
2872 <p>Each <em>word</em> is separated from the previous and next
2873 characters by whitespace. The commands to move to beginning and
2874 end of line or field look for the first or last non-pad character
2875 in their ranges.</p>
2877 <h3><a name="fscroll" id="fscroll">Scrolling Requests</a></h3>
2879 <p>Fields that are dynamic and have grown and fields explicitly
2880 created with offscreen rows are scrollable. One-line fields
2881 scroll horizontally; multi-line fields scroll vertically. Most
2882 scrolling is triggered by editing and intra-field movement (the
2883 library scrolls the field to keep the cursor visible). It is
2884 possible to explicitly request scrolling with the following
2888 <dt><code>REQ_SCR_FLINE</code>
2891 <dd>Scroll vertically forward a line.</dd>
2893 <dt><code>REQ_SCR_BLINE</code>
2896 <dd>Scroll vertically backward a line.</dd>
2898 <dt><code>REQ_SCR_FPAGE</code>
2901 <dd>Scroll vertically forward a page.</dd>
2903 <dt><code>REQ_SCR_BPAGE</code>
2906 <dd>Scroll vertically backward a page.</dd>
2908 <dt><code>REQ_SCR_FHPAGE</code>
2911 <dd>Scroll vertically forward half a page.</dd>
2913 <dt><code>REQ_SCR_BHPAGE</code>
2916 <dd>Scroll vertically backward half a page.</dd>
2918 <dt><code>REQ_SCR_FCHAR</code>
2921 <dd>Scroll horizontally forward a character.</dd>
2923 <dt><code>REQ_SCR_BCHAR</code>
2926 <dd>Scroll horizontally backward a character.</dd>
2928 <dt><code>REQ_SCR_HFLINE</code>
2931 <dd>Scroll horizontally one field width forward.</dd>
2933 <dt><code>REQ_SCR_HBLINE</code>
2936 <dd>Scroll horizontally one field width backward.</dd>
2938 <dt><code>REQ_SCR_HFHALF</code>
2941 <dd>Scroll horizontally one half field width forward.</dd>
2943 <dt><code>REQ_SCR_HBHALF</code>
2946 <dd>Scroll horizontally one half field width backward.</dd>
2949 <p>For scrolling purposes, a <em>page</em> of a field is the
2950 height of its visible part.</p>
2952 <h3><a name="fedit" id="fedit">Editing Requests</a></h3>
2954 <p>When you pass the forms driver an ASCII character, it is
2955 treated as a request to add the character to the field's data
2956 buffer. Whether this is an insertion or a replacement depends on
2957 the field's edit mode (insertion is the default.</p>
2959 <p>The following requests support editing the field and changing
2963 <dt><code>REQ_INS_MODE</code>
2966 <dd>Set insertion mode.</dd>
2968 <dt><code>REQ_OVL_MODE</code>
2971 <dd>Set overlay mode.</dd>
2973 <dt><code>REQ_NEW_LINE</code>
2976 <dd>New line request (see below for explanation).</dd>
2978 <dt><code>REQ_INS_CHAR</code>
2981 <dd>Insert space at character location.</dd>
2983 <dt><code>REQ_INS_LINE</code>
2986 <dd>Insert blank line at character location.</dd>
2988 <dt><code>REQ_DEL_CHAR</code>
2991 <dd>Delete character at cursor.</dd>
2993 <dt><code>REQ_DEL_PREV</code>
2996 <dd>Delete previous word at cursor.</dd>
2998 <dt><code>REQ_DEL_LINE</code>
3001 <dd>Delete line at cursor.</dd>
3003 <dt><code>REQ_DEL_WORD</code>
3006 <dd>Delete word at cursor.</dd>
3008 <dt><code>REQ_CLR_EOL</code>
3011 <dd>Clear to end of line.</dd>
3013 <dt><code>REQ_CLR_EOF</code>
3016 <dd>Clear to end of field.</dd>
3018 <dt><code>REQ_CLEAR_FIELD</code>
3021 <dd>Clear entire field.</dd>
3024 <p>The behavior of the <code>REQ_NEW_LINE</code> and
3025 <code>REQ_DEL_PREV</code> requests is complicated and partly
3026 controlled by a pair of forms options. The special cases are
3027 triggered when the cursor is at the beginning of a field, or on
3028 the last line of the field.</p>
3030 <p>First, we consider <code>REQ_NEW_LINE</code>:</p>
3032 <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert
3033 mode is to break the current line at the position of the edit
3034 cursor, inserting the portion of the current line after the
3035 cursor as a new line following the current and moving the cursor
3036 to the beginning of that new line (you may think of this as
3037 inserting a newline in the field buffer).</p>
3039 <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay
3040 mode is to clear the current line from the position of the edit
3041 cursor to end of line. The cursor is then moved to the beginning
3042 of the next line.</p>
3044 <p>However, <code>REQ_NEW_LINE</code> at the beginning of a
3045 field, or on the last line of a field, instead does a
3046 <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is
3047 off, this special action is disabled.</p>
3049 <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p>
3051 <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete
3052 the previous character. If insert mode is on, and the cursor is
3053 at the start of a line, and the text on that line will fit on the
3054 previous one, it instead appends the contents of the current line
3055 to the previous one and deletes the current line (you may think
3056 of this as deleting a newline from the field buffer).</p>
3058 <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field
3059 is instead treated as a <code>REQ_PREV_FIELD</code>.</p>
3061 <p>If the <code>O_BS_OVERLOAD</code> option is off, this special
3062 action is disabled and the forms driver just returns
3063 <code>E_REQUEST_DENIED</code>.</p>
3065 <p>See <a href="#frmoptions">Form Options</a> for discussion of
3066 how to set and clear the overload options.</p>
3068 <h3><a name="forder" id="forder">Order Requests</a></h3>
3070 <p>If the type of your field is ordered, and has associated
3071 functions for getting the next and previous values of the type
3072 from a given value, there are requests that can fetch that value
3073 into the field buffer:</p>
3076 <dt><code>REQ_NEXT_CHOICE</code>
3079 <dd>Place the successor value of the current value in the
3082 <dt><code>REQ_PREV_CHOICE</code>
3085 <dd>Place the predecessor value of the current value in the
3089 <p>Of the built-in field types, only <code>TYPE_ENUM</code> has
3090 built-in successor and predecessor functions. When you define a
3091 field type of your own (see <a href="#fcustom">Custom Validation
3092 Types</a>), you can associate our own ordering functions.</p>
3094 <h3><a name="fappcmds" id="fappcmds">Application Commands</a></h3>
3096 <p>Form requests are represented as integers above the
3097 <code>curses</code> value greater than <code>KEY_MAX</code> and
3098 less than or equal to the constant <code>MAX_COMMAND</code>. If
3099 your input-virtualization routine returns a value above
3100 <code>MAX_COMMAND</code>, the forms driver will ignore it.</p>
3102 <h2><a name="fhooks" id="fhooks">Field Change Hooks</a></h2>
3104 <p>It is possible to set function hooks to be executed whenever
3105 the current field or form changes. Here are the functions that
3109 typedef void (*HOOK)(); /* pointer to function returning void */
3111 int set_form_init(FORM *form, /* form to alter */
3112 HOOK hook); /* initialization hook */
3114 HOOK form_init(FORM *form); /* form to query */
3116 int set_form_term(FORM *form, /* form to alter */
3117 HOOK hook); /* termination hook */
3119 HOOK form_term(FORM *form); /* form to query */
3121 int set_field_init(FORM *form, /* form to alter */
3122 HOOK hook); /* initialization hook */
3124 HOOK field_init(FORM *form); /* form to query */
3126 int set_field_term(FORM *form, /* form to alter */
3127 HOOK hook); /* termination hook */
3129 HOOK field_term(FORM *form); /* form to query */
3132 <p>These functions allow you to either set or query four
3133 different hooks. In each of the set functions, the second
3134 argument should be the address of a hook function. These
3135 functions differ only in the timing of the hook call.</p>
3140 <dd>This hook is called when the form is posted; also, just
3141 after each page change operation.</dd>
3145 <dd>This hook is called when the form is posted; also, just
3146 after each field change</dd>
3150 <dd>This hook is called just after field validation; that is,
3151 just before the field is altered. It is also called when the
3152 form is unposted.</dd>
3156 <dd>This hook is called when the form is unposted; also, just
3157 before each page change operation.</dd>
3160 <p>Calls to these hooks may be triggered</p>
3163 <li>When user editing requests are processed by the forms
3166 <li>When the current page is changed by
3167 <code>set_current_field()</code> call</li>
3169 <li>When the current field is changed by a
3170 <code>set_form_page()</code> call</li>
3173 <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for
3174 discussion of the latter two cases.</p>
3176 <p>You can set a default hook for all fields by passing one of
3177 the set functions a NULL first argument.</p>
3179 <p>You can disable any of these hooks by (re)setting them to
3180 NULL, the default value.</p>
3182 <h2><a href="#ffocus">Field Change Commands</a></h2>
3184 <p>Normally, navigation through the form will be driven by the
3185 user's input requests. But sometimes it is useful to be able to
3186 move the focus for editing and viewing under control of your
3187 application, or ask which field it currently is in. The following
3188 functions help you accomplish this:</p>
3191 int set_current_field(FORM *form, /* form to alter */
3192 FIELD *field); /* field to shift to */
3194 FIELD *current_field(FORM *form); /* form to query */
3196 int field_index(FORM *form, /* form to query */
3197 FIELD *field); /* field to get index of */
3200 <p>The function <code>field_index()</code> returns the index of
3201 the given field in the given form's field array (the array passed
3202 to <code>new_form()</code> or
3203 <code>set_form_fields()</code>).</p>
3205 <p>The initial current field of a form is the first active field
3206 on the first page. The function <code>set_form_fields()</code>
3209 <p>It is also possible to move around by pages.</p>
3212 int set_form_page(FORM *form, /* form to alter */
3213 int page); /* page to go to (0-origin) */
3215 int form_page(FORM *form); /* return form's current page */
3218 <p>The initial page of a newly-created form is 0. The function
3219 <code>set_form_fields()</code> resets this.</p>
3221 <h2><a name="frmoptions" id="frmoptions">Form Options</a></h2>
3223 <p>Like fields, forms may have control option bits. They can be
3224 changed or queried with these functions:</p>
3227 int set_form_opts(FORM *form, /* form to alter */
3228 int attr); /* attribute to set */
3230 int form_opts_on(FORM *form, /* form to alter */
3231 int attr); /* attributes to turn on */
3233 int form_opts_off(FORM *form, /* form to alter */
3234 int attr); /* attributes to turn off */
3236 int form_opts(FORM *form); /* form to query */
3239 <p>By default, all options are on. Here are the available option
3243 <dt>O_NL_OVERLOAD</dt>
3245 <dd>Enable overloading of <code>REQ_NEW_LINE</code> as
3246 described in <a href="#fedit">Editing Requests</a>. The value
3247 of this option is ignored on dynamic fields that have not
3248 reached their size limit; these have no last line, so the
3249 circumstances for triggering a <code>REQ_NEXT_FIELD</code>
3252 <dt>O_BS_OVERLOAD</dt>
3254 <dd>Enable overloading of <code>REQ_DEL_PREV</code> as
3255 described in <a href="#fedit">Editing Requests</a>.</dd>
3258 <p>The option values are bit-masks and can be composed with
3259 logical-or in the obvious way.</p>
3261 <h2><a name="fcustom" id="fcustom">Custom Validation Types</a></h2>
3263 <p>The <code>form</code> library gives you the capability to
3264 define custom validation types of your own. Further, the optional
3265 additional arguments of <code>set_field_type</code> effectively
3266 allow you to parameterize validation types. Most of the
3267 complications in the validation-type interface have to do with
3268 the handling of the additional arguments within custom validation
3271 <h3><a name="flinktypes" id="flinktypes">Union Types</a></h3>
3273 <p>The simplest way to create a custom data type is to compose it
3274 from two preexisting ones:</p>
3277 FIELD *link_fieldtype(FIELDTYPE *type1,
3281 <p>This function creates a field type that will accept any of the
3282 values legal for either of its argument field types (which may be
3283 either predefined or programmer-defined). If a
3284 <code>set_field_type()</code> call later requires arguments, the
3285 new composite type expects all arguments for the first type, than
3286 all arguments for the second. Order functions (see <a href=
3287 "#forder">Order Requests</a>) associated with the component types
3288 will work on the composite; what it does is check the validation
3289 function for the first type, then for the second, to figure what
3290 type the buffer contents should be treated as.</p>
3292 <h3><a name="fnewtypes" id="fnewtypes">New Field Types</a></h3>
3294 <p>To create a field type from scratch, you need to specify one
3295 or both of the following things:</p>
3298 <li>A character-validation function, to check each character as
3301 <li>A field-validation function to be applied on exit from the
3305 <p>Here is how you do that:</p>
3308 typedef int (*HOOK)(); /* pointer to function returning int */
3310 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
3311 HOOK c_validate) /* character validator */
3313 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
3316 <p>At least one of the arguments of <code>new_fieldtype()</code>
3317 must be non-NULL. The forms driver will automatically call the
3318 new type's validation functions at appropriate points in
3319 processing a field of the new type.</p>
3321 <p>The function <code>free_fieldtype()</code> deallocates the
3322 argument fieldtype, freeing all storage associated with it.</p>
3324 <p>Normally, a field validator is called when the user attempts
3325 to leave the field. Its first argument is a field pointer, from
3326 which it can get to field buffer 0 and test it. If the function
3327 returns TRUE, the operation succeeds; if it returns FALSE, the
3328 edit cursor stays in the field.</p>
3330 <p>A character validator gets the character passed in as a first
3331 argument. It too should return TRUE if the character is valid,
3332 FALSE otherwise.</p>
3334 <h3><a name="fcheckargs" id="fcheckargs">Validation Function
3337 <p>Your field- and character- validation functions will be passed
3338 a second argument as well. This second argument is the address of
3339 a structure (which we will call a <em>pile</em>) built from any
3340 of the field-type-specific arguments passed to
3341 <code>set_field_type()</code>. If no such arguments are defined
3342 for the field type, this pile pointer argument will be NULL.</p>
3344 <p>In order to arrange for such arguments to be passed to your
3345 validation functions, you must associate a small set of
3346 storage-management functions with the type. The forms driver will
3347 use these to synthesize a pile from the trailing arguments of
3348 each <code>set_field_type()</code> argument, and a pointer to the
3349 pile will be passed to the validation functions.</p>
3351 <p>Here is how you make the association:</p>
3354 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
3355 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
3357 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3358 PTRHOOK make_str, /* make structure from args */
3359 PTRHOOK copy_str, /* make copy of structure */
3360 VOIDHOOK free_str); /* free structure storage */
3363 <p>Here is how the storage-management hooks are used:</p>
3366 <dt><code>make_str</code>
3369 <dd>This function is called by <code>set_field_type()</code>.
3370 It gets one argument, a <code>va_list</code> of the
3371 type-specific arguments passed to
3372 <code>set_field_type()</code>. It is expected to return a pile
3373 pointer to a data structure that encapsulates those
3376 <dt><code>copy_str</code>
3379 <dd>This function is called by form library functions that
3380 allocate new field instances. It is expected to take a pile
3381 pointer, copy the pile to allocated storage, and return the
3382 address of the pile copy.</dd>
3384 <dt><code>free_str</code>
3387 <dd>This function is called by field- and type-deallocation
3388 routines in the library. It takes a pile pointer argument, and
3389 is expected to free the storage of that pile.</dd>
3392 <p>The <code>make_str</code> and <code>copy_str</code> functions
3393 may return NULL to signal allocation failure. The library
3394 routines will that call them will return error indication when
3395 this happens. Thus, your validation functions should never see a
3396 NULL file pointer and need not check specially for it.</p>
3398 <h3><a name="fcustorder" id="fcustorder">Order Functions For
3399 Custom Types</a></h3>
3401 <p>Some custom field types are simply ordered in the same
3402 well-defined way that <code>TYPE_ENUM</code> is. For such types,
3403 it is possible to define successor and predecessor functions to
3404 support the <code>REQ_NEXT_CHOICE</code> and
3405 <code>REQ_PREV_CHOICE</code> requests. Here is how:</p>
3408 typedef int (*INTHOOK)(); /* pointer to function returning int */
3410 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3411 INTHOOK succ, /* get successor value */
3412 INTHOOK pred); /* get predecessor value */
3415 <p>The successor and predecessor arguments will each be passed
3416 two arguments; a field pointer, and a pile pointer (as for the
3417 validation functions). They are expected to use the function
3418 <code>field_buffer()</code> to read the current value, and
3419 <code>set_field_buffer()</code> on buffer 0 to set the next or
3420 previous value. Either hook may return TRUE to indicate success
3421 (a legal next or previous value was set) or FALSE to indicate
3424 <h3><a name="fcustprobs" id="fcustprobs">Avoiding Problems</a></h3>
3426 <p>The interface for defining custom types is complicated and
3427 tricky. Rather than attempting to create a custom type entirely
3428 from scratch, you should start by studying the library source
3429 code for whichever of the pre-defined types seems to be closest
3430 to what you want.</p>
3432 <p>Use that code as a model, and evolve it towards what you
3433 really want. You will avoid many problems and annoyances that
3434 way. The code in the <code>ncurses</code> library has been
3435 specifically exempted from the package copyright to support
3438 <p>If your custom type defines order functions, have do something
3439 intuitive with a blank field. A useful convention is to make the
3440 successor of a blank field the types minimum value, and its
3441 predecessor the maximum.</p>