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32 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
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39 <title>Writing Programs with NCURSES</title>
40 <link rel="author" href="mailto:bugs-ncurses@gnu.org">
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42 "text/html; charset=us-ascii">
46 <h1>Writing Programs with NCURSES</h1>
49 by Eric S. Raymond and Zeyd M. Ben-Halim<br>
50 updates since release 1.9.9e by Thomas Dickey
57 <a href="#introduction">Introduction</a>
60 <li><a href="#history">A Brief History of Curses</a></li>
62 <li><a href="#scope">Scope of This Document</a></li>
64 <li><a href="#terminology">Terminology</a></li>
69 <a href="#curses">The Curses Library</a>
73 <a href="#overview">An Overview of Curses</a>
76 <li><a href="#compiling">Compiling Programs using
79 <li><a href="#updating">Updating the Screen</a></li>
81 <li><a href="#stdscr">Standard Windows and Function
82 Naming Conventions</a></li>
84 <li><a href="#variables">Variables</a></li>
89 <a href="#using">Using the Library</a>
92 <li><a href="#starting">Starting up</a></li>
94 <li><a href="#output">Output</a></li>
96 <li><a href="#input">Input</a></li>
98 <li><a href="#formschars">Using Forms Characters</a></li>
100 <li><a href="#attributes">Character Attributes and
103 <li><a href="#mouse">Mouse Interfacing</a></li>
105 <li><a href="#finishing">Finishing Up</a></li>
110 <a href="#functions">Function Descriptions</a>
113 <li><a href="#init">Initialization and Wrapup</a></li>
115 <li><a href="#flush">Causing Output to the Terminal</a></li>
117 <li><a href="#lowlevel">Low-Level Capability Access</a></li>
119 <li><a href="#debugging">Debugging</a></li>
124 <a href="#hints">Hints, Tips, and Tricks</a>
127 <li><a href="#caution">Some Notes of Caution</a></li>
129 <li><a href="#leaving">Temporarily Leaving ncurses
132 <li><a href="#xterm">Using <code>ncurses</code> under
133 <code>xterm</code></a></li>
135 <li><a href="#screens">Handling Multiple Terminal
138 <li><a href="#testing">Testing for Terminal
139 Capabilities</a></li>
141 <li><a href="#tuning">Tuning for Speed</a></li>
143 <li><a href="#special">Special Features of
144 <code>ncurses</code></a></li>
149 <a href="#compat">Compatibility with Older Versions</a>
152 <li><a href="#refbug">Refresh of Overlapping
155 <li><a href="#backbug">Background Erase</a></li>
159 <li><a href="#xsifuncs">XSI Curses Conformance</a></li>
164 <a href="#panels">The Panels Library</a>
167 <li><a href="#pcompile">Compiling With the Panels
170 <li><a href="#poverview">Overview of Panels</a></li>
172 <li><a href="#pstdscr">Panels, Input, and the Standard
175 <li><a href="#hiding">Hiding Panels</a></li>
177 <li><a href="#pmisc">Miscellaneous Other Facilities</a></li>
182 <a href="#menu">The Menu Library</a>
185 <li><a href="#mcompile">Compiling with the menu Library</a></li>
187 <li><a href="#moverview">Overview of Menus</a></li>
189 <li><a href="#mselect">Selecting items</a></li>
191 <li><a href="#mdisplay">Menu Display</a></li>
193 <li><a href="#mwindows">Menu Windows</a></li>
195 <li><a href="#minput">Processing Menu Input</a></li>
197 <li><a href="#mmisc">Miscellaneous Other Features</a></li>
202 <a href="#form">The Forms Library</a>
205 <li><a href="#fcompile">Compiling with the forms
208 <li><a href="#foverview">Overview of Forms</a></li>
210 <li><a href="#fcreate">Creating and Freeing Fields and
214 <a href="#fattributes">Fetching and Changing Field
218 <li><a href="#fsizes">Fetching Size and Location
221 <li><a href="#flocation">Changing the Field
224 <li><a href="#fjust">The Justification Attribute</a></li>
226 <li><a href="#fdispatts">Field Display Attributes</a></li>
228 <li><a href="#foptions">Field Option Bits</a></li>
230 <li><a href="#fstatus">Field Status</a></li>
232 <li><a href="#fuser">Field User Pointer</a></li>
236 <li><a href="#fdynamic">Variable-Sized Fields</a></li>
239 <a href="#fvalidation">Field Validation</a>
242 <li><a href="#ftype_alpha">TYPE_ALPHA</a></li>
244 <li><a href="#ftype_alnum">TYPE_ALNUM</a></li>
246 <li><a href="#ftype_enum">TYPE_ENUM</a></li>
248 <li><a href="#ftype_integer">TYPE_INTEGER</a></li>
250 <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li>
252 <li><a href="#ftype_regexp">TYPE_REGEXP</a></li>
256 <li><a href="#fbuffer">Direct Field Buffer Manipulation</a></li>
258 <li><a href="#formattrs">Attributes of Forms</a></li>
260 <li><a href="#fdisplay">Control of Form Display</a></li>
263 <a href="#fdriver">Input Processing in the Forms
267 <li><a href="#fpage">Page Navigation Requests</a></li>
269 <li><a href="#ffield">Inter-Field Navigation
272 <li><a href="#fifield">Intra-Field Navigation
275 <li><a href="#fscroll">Scrolling Requests</a></li>
277 <li><a href="#fedit">Field Editing Requests</a></li>
279 <li><a href="#forder">Order Requests</a></li>
281 <li><a href="#fappcmds">Application Commands</a></li>
285 <li><a href="#fhooks">Field Change Hooks</a></li>
287 <li><a href="#ffocus">Field Change Commands</a></li>
289 <li><a href="#frmoptions">Form Options</a></li>
292 <a href="#fcustom">Custom Validation Types</a>
295 <li><a href="#flinktypes">Union Types</a></li>
297 <li><a href="#fnewtypes">New Field Types</a></li>
299 <li><a href="#fcheckargs">Validation Function
302 <li><a href="#fcustorder">Order Functions For Custom
305 <li><a href="#fcustprobs">Avoiding Problems</a></li>
314 <h1><a name="introduction" id="introduction">Introduction</a></h1>
316 <p>This document is an introduction to programming with
317 <code>curses</code>. It is not an exhaustive reference for the
318 curses Application Programming Interface (API); that role is
319 filled by the <code>curses</code> manual pages. Rather, it is
320 intended to help C programmers ease into using the package.</p>
322 <p>This document is aimed at C applications programmers not yet
323 specifically familiar with ncurses. If you are already an
324 experienced <code>curses</code> programmer, you should
325 nevertheless read the sections on <a href="#mouse">Mouse
326 Interfacing</a>, <a href="#debugging">Debugging</a>, <a href=
327 "#compat">Compatibility with Older Versions</a>, and <a href=
328 "#hints">Hints, Tips, and Tricks</a>. These will bring you up to
329 speed on the special features and quirks of the
330 <code>ncurses</code> implementation. If you are not so
331 experienced, keep reading.</p>
333 <p>The <code>curses</code> package is a subroutine library for
334 terminal-independent screen-painting and input-event handling
335 which presents a high level screen model to the programmer,
336 hiding differences between terminal types and doing automatic
337 optimization of output to change one screen full of text into
338 another. <code>Curses</code> uses terminfo, which is a database
339 format that can describe the capabilities of thousands of
340 different terminals.</p>
342 <p>The <code>curses</code> API may seem something of an archaism
343 on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk.
344 Nevertheless, UNIX still supports tty lines and X supports
345 <em>xterm(1)</em>; the <code>curses</code> API has the advantage
346 of (a) back-portability to character-cell terminals, and (b)
347 simplicity. For an application that does not require bit-mapped
348 graphics and multiple fonts, an interface implementation using
349 <code>curses</code> will typically be a great deal simpler and
350 less expensive than one using an X toolkit.</p>
352 <h2><a name="history" id="history">A Brief History of Curses</a></h2>
354 <p>Historically, the first ancestor of <code>curses</code> was
355 the routines written to provide screen-handling for the
356 <code>vi</code> editor; these used the <code>termcap</code>
357 database facility (both released in 3BSD) for describing terminal
358 capabilities. These routines were abstracted into a documented
359 library and first released with the early BSD UNIX versions. All
360 of this work was done by students at the University of California
361 (Berkeley campus). The curses library was first published in
362 4.0BSD, a year after 3BSD (i.e., late 1980).</p>
364 <p>After graduation, one of those students went to work at
365 AT&T Bell Labs, and made an improved <code>termcap</code>
366 library called <code>terminfo</code> (i.e.,
367 “libterm”), and adapted the curses library to use
368 this. That was subsequently released in System V Release 2 (early
369 1984). Thereafter, other developers added to the curses and
370 terminfo libraries. For instance, a student at Cornell University
371 wrote an improved terminfo library as well as a tool
372 (<code>tic</code>) to compile the terminal descriptions. As a
373 general rule, AT&T did not identify the developers in the
374 source-code or documentation; the <code>tic</code> and
375 <code>infocmp</code> programs are the exceptions.</p>
377 <p>System V Release 3 (System III UNIX) from Bell Labs featured a
378 rewritten and much-improved <code>curses</code> library, along
379 with the <code>tic</code> program (late 1986).</p>
381 <p>To recap, terminfo is based on Berkeley's termcap database,
382 but contains a number of improvements and extensions.
383 Parameterized capabilities strings were introduced, making it
384 possible to describe multiple video attributes, and colors and to
385 handle far more unusual terminals than possible with termcap. In
386 the later AT&T System V releases, <code>curses</code> evolved
387 to use more facilities and offer more capabilities, going far
388 beyond BSD curses in power and flexibility.</p>
390 <h2><a name="scope" id="scope">Scope of This Document</a></h2>
392 <p>This document describes <code>ncurses</code>, a free
393 implementation of the System V <code>curses</code> API with some
394 clearly marked extensions. It includes the following System V
398 <li>Support for multiple screen highlights (BSD curses could
399 only handle one “standout” highlight, usually
402 <li>Support for line- and box-drawing using forms
405 <li>Recognition of function keys on input.</li>
407 <li>Color support.</li>
409 <li>Support for pads (windows of larger than screen size on
410 which the screen or a subwindow defines a viewport).</li>
413 <p>Also, this package makes use of the insert and delete line and
414 character features of terminals so equipped, and determines how
415 to optimally use these features with no help from the programmer.
416 It allows arbitrary combinations of video attributes to be
417 displayed, even on terminals that leave “magic
418 cookies” on the screen to mark changes in attributes.</p>
420 <p>The <code>ncurses</code> package can also capture and use
421 event reports from a mouse in some environments (notably, xterm
422 under the X window system). This document includes tips for using
425 <p>The <code>ncurses</code> package was originated by Pavel
426 Curtis. The original maintainer of this package is <a href=
427 "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a>
428 <zmbenhal@netcom.com>. <a href=
429 "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a>
430 <esr@snark.thyrsus.com> wrote many of the new features in
431 versions after 1.8.1 and wrote most of this introduction.
432 Jürgen Pfeifer wrote all of the menu and forms code as well
433 as the <a href="http://www.adahome.com">Ada95</a> binding.
434 Ongoing work is being done by <a href=
435 "mailto:dickey@invisible-island.net">Thomas Dickey</a>
436 (maintainer). Contact the current maintainers at <a href=
437 "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p>
439 <p>This document also describes the <a href="#panels">panels</a>
440 extension library, similarly modeled on the SVr4 panels facility.
441 This library allows you to associate backing store with each of a
442 stack or deck of overlapping windows, and provides operations for
443 moving windows around in the stack that change their visibility
444 in the natural way (handling window overlaps).</p>
446 <p>Finally, this document describes in detail the <a href=
447 "#menu">menus</a> and <a href="#form">forms</a> extension
448 libraries, also cloned from System V, which support easy
449 construction and sequences of menus and fill-in forms.</p>
451 <h2><a name="terminology" id="terminology">Terminology</a></h2>
453 <p>In this document, the following terminology is used with
454 reasonable consistency:</p>
459 <dd>A data structure describing a sub-rectangle of the screen
460 (possibly the entire screen). You can write to a window as
461 though it were a miniature screen, scrolling independently of
462 other windows on the physical screen.</dd>
466 <dd>A subset of windows which are as large as the terminal
467 screen, i.e., they start at the upper left hand corner and
468 encompass the lower right hand corner. One of these,
469 <code>stdscr</code>, is automatically provided for the
472 <dt>terminal screen</dt>
474 <dd>The package's idea of what the terminal display currently
475 looks like, i.e., what the user sees now. This is a special
479 <h1><a name="curses" id="curses">The Curses Library</a></h1>
481 <h2><a name="overview" id="overview">An Overview of Curses</a></h2>
483 <h3><a name="compiling" id="compiling">Compiling Programs using
486 <p>In order to use the library, it is necessary to have certain
487 types and variables defined. Therefore, the programmer must have
491 #include <curses.h>
494 <p>at the top of the program source. The screen package uses the
495 Standard I/O library, so <code><curses.h></code> includes
496 <code><stdio.h></code>. <code><curses.h></code> also
497 includes <code><termios.h></code>,
498 <code><termio.h></code>, or <code><sgtty.h></code>
499 depending on your system. It is redundant (but harmless) for the
500 programmer to do these includes, too. In linking with
501 <code>curses</code> you need to have <code>-lncurses</code> in
502 your LDFLAGS or on the command line. There is no need for any
505 <h3><a name="updating" id="updating">Updating the Screen</a></h3>
507 <p>In order to update the screen optimally, it is necessary for
508 the routines to know what the screen currently looks like and
509 what the programmer wants it to look like next. For this purpose,
510 a data type (structure) named WINDOW is defined which describes a
511 window image to the routines, including its starting position on
512 the screen (the (y, x) coordinates of the upper left hand corner)
513 and its size. One of these (called <code>curscr</code>, for
514 current screen) is a screen image of what the terminal currently
515 looks like. Another screen (called <code>stdscr</code>, for
516 standard screen) is provided by default to make changes on.</p>
518 <p>A window is a purely internal representation. It is used to
519 build and store a potential image of a portion of the terminal.
520 It does not bear any necessary relation to what is really on the
521 terminal screen; it is more like a scratchpad or write
524 <p>To make the section of physical screen corresponding to a
525 window reflect the contents of the window structure, the routine
526 <code>refresh()</code> (or <code>wrefresh()</code> if the window
527 is not <code>stdscr</code>) is called.</p>
529 <p>A given physical screen section may be within the scope of any
530 number of overlapping windows. Also, changes can be made to
531 windows in any order, without regard to motion efficiency. Then,
532 at will, the programmer can effectively say “make it look
533 like this,” and let the package implementation determine
534 the most efficient way to repaint the screen.</p>
536 <h3><a name="stdscr" id="stdscr">Standard Windows and Function
537 Naming Conventions</a></h3>
539 <p>As hinted above, the routines can use several windows, but two
540 are automatically given: <code>curscr</code>, which knows what
541 the terminal looks like, and <code>stdscr</code>, which is what
542 the programmer wants the terminal to look like next. The user
543 should never actually access <code>curscr</code> directly.
544 Changes should be made to through the API, and then the routine
545 <code>refresh()</code> (or <code>wrefresh()</code>) called.</p>
547 <p>Many functions are defined to use <code>stdscr</code> as a
548 default screen. For example, to add a character to
549 <code>stdscr</code>, one calls <code>addch()</code> with the
550 desired character as argument. To write to a different window.
551 use the routine <code>waddch()</code> (for
552 <strong>w</strong>indow-specific addch()) is provided. This
553 convention of prepending function names with a “w”
554 when they are to be applied to specific windows is consistent.
555 The only routines which do not follow it are those for which a
556 window must always be specified.</p>
558 <p>In order to move the current (y, x) coordinates from one point
559 to another, the routines <code>move()</code> and
560 <code>wmove()</code> are provided. However, it is often desirable
561 to first move and then perform some I/O operation. In order to
562 avoid clumsiness, most I/O routines can be preceded by the prefix
563 “mv” and the desired (y, x) coordinates prepended to
564 the arguments to the function. For example, the calls</p>
571 <p>can be replaced by</p>
584 <p>can be replaced by</p>
587 mvwaddch(win, y, x, ch);
590 <p>Note that the window description pointer (win) comes before
591 the added (y, x) coordinates. If a function requires a window
592 pointer, it is always the first parameter passed.</p>
594 <h3><a name="variables" id="variables">Variables</a></h3>
596 <p>The <code>curses</code> library sets some variables describing
597 the terminal capabilities.</p>
600 type name description
601 ------------------------------------------------------------------
602 int LINES number of lines on the terminal
603 int COLS number of columns on the terminal
606 <p>The <code>curses.h</code> also introduces some
607 <code>#define</code> constants and types of general
611 <dt><code>bool</code>
614 <dd>boolean type, actually a “char” (e.g.,
615 <code>bool doneit;</code>)</dd>
617 <dt><code>TRUE</code>
620 <dd>boolean “true” flag (1).</dd>
622 <dt><code>FALSE</code>
625 <dd>boolean “false” flag (0).</dd>
630 <dd>error flag returned by routines on a failure (-1).</dd>
635 <dd>error flag returned by routines when things go right.</dd>
638 <h2><a name="using" id="using">Using the Library</a></h2>
640 <p>Now we describe how to actually use the screen package. In it,
641 we assume all updating, reading, etc. is applied to
642 <code>stdscr</code>. These instructions will work on any window,
643 providing you change the function names and parameters as
646 <p>Here is a sample program to motivate the discussion:</p>
649 #include <stdlib.h>
650 #include <curses.h>
651 #include <signal.h>
653 static void finish(int sig);
656 main(int argc, char *argv[])
660 /* initialize your non-curses data structures here */
662 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
664 (void) initscr(); /* initialize the curses library */
665 keypad(stdscr, TRUE); /* enable keyboard mapping */
666 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
667 (void) cbreak(); /* take input chars one at a time, no wait for \n */
668 (void) echo(); /* echo input - in color */
675 * Simple color assignment, often all we need. Color pair 0 cannot
676 * be redefined. This example uses the same value for the color
677 * pair as for the foreground color, though of course that is not
680 init_pair(1, COLOR_RED, COLOR_BLACK);
681 init_pair(2, COLOR_GREEN, COLOR_BLACK);
682 init_pair(3, COLOR_YELLOW, COLOR_BLACK);
683 init_pair(4, COLOR_BLUE, COLOR_BLACK);
684 init_pair(5, COLOR_CYAN, COLOR_BLACK);
685 init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
686 init_pair(7, COLOR_WHITE, COLOR_BLACK);
691 int c = getch(); /* refresh, accept single keystroke of input */
692 attrset(COLOR_PAIR(num % 8));
695 /* process the command keystroke */
698 finish(0); /* we are done */
701 static void finish(int sig)
705 /* do your non-curses wrapup here */
711 <h3><a name="starting" id="starting">Starting up</a></h3>
713 <p>In order to use the screen package, the routines must know
714 about terminal characteristics, and the space for
715 <code>curscr</code> and <code>stdscr</code> must be allocated.
716 These function <code>initscr()</code> does both these things.
717 Since it must allocate space for the windows, it can overflow
718 memory when attempting to do so. On the rare occasions this
719 happens, <code>initscr()</code> will terminate the program with
720 an error message. <code>initscr()</code> must always be called
721 before any of the routines which affect windows are used. If it
722 is not, the program will core dump as soon as either
723 <code>curscr</code> or <code>stdscr</code> are referenced.
724 However, it is usually best to wait to call it until after you
725 are sure you will need it, like after checking for startup
726 errors. Terminal status changing routines like <code>nl()</code>
727 and <code>cbreak()</code> should be called after
728 <code>initscr()</code>.</p>
730 <p>Once the screen windows have been allocated, you can set them
731 up for your program. If you want to, say, allow a screen to
732 scroll, use <code>scrollok()</code>. If you want the cursor to be
733 left in place after the last change, use <code>leaveok()</code>.
734 If this is not done, <code>refresh()</code> will move the cursor
735 to the window's current (y, x) coordinates after updating it.</p>
737 <p>You can create new windows of your own using the functions
738 <code>newwin()</code>, <code>derwin()</code>, and
739 <code>subwin()</code>. The routine <code>delwin()</code> will
740 allow you to get rid of old windows. All the options described
741 above can be applied to any window.</p>
743 <h3><a name="output" id="output">Output</a></h3>
745 <p>Now that we have set things up, we will want to actually
746 update the terminal. The basic functions used to change what will
747 go on a window are <code>addch()</code> and <code>move()</code>.
748 <code>addch()</code> adds a character at the current (y, x)
749 coordinates. <code>move()</code> changes the current (y, x)
750 coordinates to whatever you want them to be. It returns
751 <code>ERR</code> if you try to move off the window. As mentioned
752 above, you can combine the two into <code>mvaddch()</code> to do
753 both things at once.</p>
755 <p>The other output functions, such as <code>addstr()</code> and
756 <code>printw()</code>, all call <code>addch()</code> to add
757 characters to the window.</p>
759 <p>After you have put on the window what you want there, when you
760 want the portion of the terminal covered by the window to be made
761 to look like it, you must call <code>refresh()</code>. In order
762 to optimize finding changes, <code>refresh()</code> assumes that
763 any part of the window not changed since the last
764 <code>refresh()</code> of that window has not been changed on the
765 terminal, i.e., that you have not refreshed a portion of the
766 terminal with an overlapping window. If this is not the case, the
767 routine <code>touchwin()</code> is provided to make it look like
768 the entire window has been changed, thus making
769 <code>refresh()</code> check the whole subsection of the terminal
772 <p>If you call <code>wrefresh()</code> with <code>curscr</code>
773 as its argument, it will make the screen look like
774 <code>curscr</code> thinks it looks like. This is useful for
775 implementing a command which would redraw the screen in case it
778 <h3><a name="input" id="input">Input</a></h3>
780 <p>The complementary function to <code>addch()</code> is
781 <code>getch()</code> which, if echo is set, will call
782 <code>addch()</code> to echo the character. Since the screen
783 package needs to know what is on the terminal at all times, if
784 characters are to be echoed, the tty must be in raw or cbreak
785 mode. Since initially the terminal has echoing enabled and is in
786 ordinary “cooked” mode, one or the other has to
787 changed before calling <code>getch()</code>; otherwise, the
788 program's output will be unpredictable.</p>
790 <p>When you need to accept line-oriented input in a window, the
791 functions <code>wgetstr()</code> and friends are available. There
792 is even a <code>wscanw()</code> function that can do
793 <code>scanf()</code>(3)-style multi-field parsing on window
794 input. These pseudo-line-oriented functions turn on echoing while
797 <p>The example code above uses the call <code>keypad(stdscr,
798 TRUE)</code> to enable support for function-key mapping. With
799 this feature, the <code>getch()</code> code watches the input
800 stream for character sequences that correspond to arrow and
801 function keys. These sequences are returned as pseudo-character
802 values. The <code>#define</code> values returned are listed in
803 the <code>curses.h</code> The mapping from sequences to
804 <code>#define</code> values is determined by <code>key_</code>
805 capabilities in the terminal's terminfo entry.</p>
807 <h3><a name="formschars" id="formschars">Using Forms
810 <p>The <code>addch()</code> function (and some others, including
811 <code>box()</code> and <code>border()</code>) can accept some
812 pseudo-character arguments which are specially defined by
813 <code>ncurses</code>. These are <code>#define</code> values set
814 up in the <code>curses.h</code> header; see there for a complete
815 list (look for the prefix <code>ACS_</code>).</p>
817 <p>The most useful of the ACS defines are the forms-drawing
818 characters. You can use these to draw boxes and simple graphs on
819 the screen. If the terminal does not have such characters,
820 <code>curses.h</code> will map them to a recognizable (though
821 ugly) set of ASCII defaults.</p>
823 <h3><a name="attributes" id="attributes">Character Attributes and
826 <p>The <code>ncurses</code> package supports screen highlights
827 including standout, reverse-video, underline, and blink. It also
828 supports color, which is treated as another kind of
831 <p>Highlights are encoded, internally, as high bits of the
832 pseudo-character type (<code>chtype</code>) that
833 <code>curses.h</code> uses to represent the contents of a screen
834 cell. See the <code>curses.h</code> header file for a complete
835 list of highlight mask values (look for the prefix
836 <code>A_</code>).</p>
838 <p>There are two ways to make highlights. One is to logical-or
839 the value of the highlights you want into the character argument
840 of an <code>addch()</code> call, or any other output call that
841 takes a <code>chtype</code> argument.</p>
843 <p>The other is to set the current-highlight value. This is
844 <em>logical-OR</em>ed with any highlight you specify the first
845 way. You do this with the functions <code>attron()</code>,
846 <code>attroff()</code>, and <code>attrset()</code>; see the
847 manual pages for details. Color is a special kind of highlight.
848 The package actually thinks in terms of color pairs, combinations
849 of foreground and background colors. The sample code above sets
850 up eight color pairs, all of the guaranteed-available colors on
851 black. Note that each color pair is, in effect, given the name of
852 its foreground color. Any other range of eight non-conflicting
853 values could have been used as the first arguments of the
854 <code>init_pair()</code> values.</p>
856 <p>Once you have done an <code>init_pair()</code> that creates
857 color-pair N, you can use <code>COLOR_PAIR(N)</code> as a
858 highlight that invokes that particular color combination. Note
859 that <code>COLOR_PAIR(N)</code>, for constant N, is itself a
860 compile-time constant and can be used in initializers.</p>
862 <h3><a name="mouse" id="mouse">Mouse Interfacing</a></h3>
864 <p>The <code>ncurses</code> library also provides a mouse
868 <strong>NOTE:</strong> this facility is specific to
869 <code>ncurses</code>, it is not part of either the XSI Curses
870 standard, nor of System V Release 4, nor BSD curses. System V
871 Release 4 curses contains code with similar interface
872 definitions, however it is not documented. Other than by
873 disassembling the library, we have no way to determine exactly
874 how that mouse code works. Thus, we recommend that you wrap
875 mouse-related code in an #ifdef using the feature macro
876 NCURSES_MOUSE_VERSION so it will not be compiled and linked on
880 <p>Presently, mouse event reporting works in the following
884 <li>xterm and similar programs such as rxvt.</li>
886 <li>Linux console, when configured with <code>gpm</code>(1),
887 Alessandro Rubini's mouse server.</li>
889 <li>FreeBSD sysmouse (console)</li>
894 <p>The mouse interface is very simple. To activate it, you use
895 the function <code>mousemask()</code>, passing it as first
896 argument a bit-mask that specifies what kinds of events you want
897 your program to be able to see. It will return the bit-mask of
898 events that actually become visible, which may differ from the
899 argument if the mouse device is not capable of reporting some of
900 the event types you specify.</p>
902 <p>Once the mouse is active, your application's command loop
903 should watch for a return value of <code>KEY_MOUSE</code> from
904 <code>wgetch()</code>. When you see this, a mouse event report
905 has been queued. To pick it off the queue, use the function
906 <code>getmouse()</code> (you must do this before the next
907 <code>wgetch()</code>, otherwise another mouse event might come
908 in and make the first one inaccessible).</p>
910 <p>Each call to <code>getmouse()</code> fills a structure (the
911 address of which you will pass it) with mouse event data. The
912 event data includes zero-origin, screen-relative character-cell
913 coordinates of the mouse pointer. It also includes an event mask.
914 Bits in this mask will be set, corresponding to the event type
917 <p>The mouse structure contains two additional fields which may
918 be significant in the future as ncurses interfaces to new kinds
919 of pointing device. In addition to x and y coordinates, there is
920 a slot for a z coordinate; this might be useful with
921 touch-screens that can return a pressure or duration parameter.
922 There is also a device ID field, which could be used to
923 distinguish between multiple pointing devices.</p>
925 <p>The class of visible events may be changed at any time via
926 <code>mousemask()</code>. Events that can be reported include
927 presses, releases, single-, double- and triple-clicks (you can
928 set the maximum button-down time for clicks). If you do not make
929 clicks visible, they will be reported as press-release pairs. In
930 some environments, the event mask may include bits reporting the
931 state of shift, alt, and ctrl keys on the keyboard during the
934 <p>A function to check whether a mouse event fell within a given
935 window is also supplied. You can use this to see whether a given
936 window should consider a mouse event relevant to it.</p>
938 <p>Because mouse event reporting will not be available in all
939 environments, it would be unwise to build <code>ncurses</code>
940 applications that <em>require</em> the use of a mouse. Rather,
941 you should use the mouse as a shortcut for point-and-shoot
942 commands your application would normally accept from the
943 keyboard. Two of the test games in the <code>ncurses</code>
944 distribution (<code>bs</code> and <code>knight</code>) contain
945 code that illustrates how this can be done.</p>
947 <p>See the manual page <code>curs_mouse(3X)</code> for full
948 details of the mouse-interface functions.</p>
950 <h3><a name="finishing" id="finishing">Finishing Up</a></h3>
952 <p>In order to clean up after the <code>ncurses</code> routines,
953 the routine <code>endwin()</code> is provided. It restores tty
954 modes to what they were when <code>initscr()</code> was first
955 called, and moves the cursor down to the lower-left corner. Thus,
956 anytime after the call to initscr, <code>endwin()</code> should
957 be called before exiting.</p>
959 <h2><a name="functions" id="functions">Function Descriptions</a></h2>
961 <p>We describe the detailed behavior of some important curses
962 functions here, as a supplement to the manual page
965 <h3><a name="init" id="init">Initialization and Wrapup</a></h3>
968 <dt><code>initscr()</code>
971 <dd>The first function called should almost always be
972 <code>initscr()</code>. This will determine the terminal type
973 and initialize curses data structures. <code>initscr()</code>
974 also arranges that the first call to <code>refresh()</code>
975 will clear the screen. If an error occurs a message is written
976 to standard error and the program exits. Otherwise it returns a
977 pointer to stdscr. A few functions may be called before initscr
978 (<code>slk_init()</code>, <code>filter()</code>,
979 <code>ripoffline()</code>, <code>use_env()</code>, and, if you
980 are using multiple terminals, <code>newterm()</code>.)</dd>
982 <dt><code>endwin()</code>
985 <dd>Your program should always call <code>endwin()</code>
986 before exiting or shelling out of the program. This function
987 will restore tty modes, move the cursor to the lower left
988 corner of the screen, reset the terminal into the proper
989 non-visual mode. Calling <code>refresh()</code> or
990 <code>doupdate()</code> after a temporary escape from the
991 program will restore the ncurses screen from before the
994 <dt><code>newterm(type, ofp, ifp)</code>
997 <dd>A program which outputs to more than one terminal should
998 use <code>newterm()</code> instead of <code>initscr()</code>.
999 <code>newterm()</code> should be called once for each terminal.
1000 It returns a variable of type <code>SCREEN *</code> which
1001 should be saved as a reference to that terminal. (NOTE: a
1002 SCREEN variable is not a <em>screen</em> in the sense we are
1003 describing in this introduction, but a collection of parameters
1004 used to assist in optimizing the display.) The arguments are
1005 the type of the terminal (a string) and <code>FILE</code>
1006 pointers for the output and input of the terminal. If type is
1007 NULL then the environment variable <code>$TERM</code> is used.
1008 <code>endwin()</code> should called once at wrapup time for
1009 each terminal opened using this function.</dd>
1011 <dt><code>set_term(new)</code>
1014 <dd>This function is used to switch to a different terminal
1015 previously opened by <code>newterm()</code>. The screen
1016 reference for the new terminal is passed as the parameter. The
1017 previous terminal is returned by the function. All other calls
1018 affect only the current terminal.</dd>
1020 <dt><code>delscreen(sp)</code>
1023 <dd>The inverse of <code>newterm()</code>; deallocates the data
1024 structures associated with a given <code>SCREEN</code>
1028 <h3><a name="flush" id="flush">Causing Output to the Terminal</a></h3>
1031 <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt>
1033 <dd>These functions must be called to actually get any output
1034 on the terminal, as other routines merely manipulate data
1035 structures. <code>wrefresh()</code> copies the named window to
1036 the physical terminal screen, taking into account what is
1037 already there in order to do optimizations.
1038 <code>refresh()</code> does a refresh of <code>stdscr</code>.
1039 Unless <code>leaveok()</code> has been enabled, the physical
1040 cursor of the terminal is left at the location of the window's
1043 <dt><code>doupdate()</code> and
1044 <code>wnoutrefresh(win)</code></dt>
1046 <dd>These two functions allow multiple updates with more
1047 efficiency than wrefresh. To use them, it is important to
1048 understand how curses works. In addition to all the window
1049 structures, curses keeps two data structures representing the
1050 terminal screen: a physical screen, describing what is actually
1051 on the screen, and a virtual screen, describing what the
1052 programmer wants to have on the screen. wrefresh works by first
1053 copying the named window to the virtual screen
1054 (<code>wnoutrefresh()</code>), and then calling the routine to
1055 update the screen (<code>doupdate()</code>). If the programmer
1056 wishes to output several windows at once, a series of calls to
1057 <code>wrefresh</code> will result in alternating calls to
1058 <code>wnoutrefresh()</code> and <code>doupdate()</code>,
1059 causing several bursts of output to the screen. By calling
1060 <code>wnoutrefresh()</code> for each window, it is then
1061 possible to call <code>doupdate()</code> once, resulting in
1062 only one burst of output, with fewer total characters
1063 transmitted (this also avoids a visually annoying flicker at
1067 <h3><a name="lowlevel" id="lowlevel">Low-Level Capability
1071 <dt><code>setupterm(term, filenum, errret)</code>
1075 This routine is called to initialize a terminal's
1076 description, without setting up the curses screen structures
1077 or changing the tty-driver mode bits. <code>term</code> is
1078 the character string representing the name of the terminal
1079 being used. <code>filenum</code> is the UNIX file descriptor
1080 of the terminal to be used for output. <code>errret</code> is
1081 a pointer to an integer, in which a success or failure
1082 indication is returned. The values returned can be 1 (all is
1083 well), 0 (no such terminal), or -1 (some problem locating the
1086 <p>The value of <code>term</code> can be given as NULL, which
1087 will cause the value of <code>TERM</code> in the environment
1088 to be used. The <code>errret</code> pointer can also be given
1089 as NULL, meaning no error code is wanted. If
1090 <code>errret</code> is defaulted, and something goes wrong,
1091 <code>setupterm()</code> will print an appropriate error
1092 message and exit, rather than returning. Thus, a simple
1093 program can call setupterm(0, 1, 0) and not worry about
1094 initialization errors.</p>
1096 <p>After the call to <code>setupterm()</code>, the global
1097 variable <code>cur_term</code> is set to point to the current
1098 structure of terminal capabilities. By calling
1099 <code>setupterm()</code> for each terminal, and saving and
1100 restoring <code>cur_term</code>, it is possible for a program
1101 to use two or more terminals at once.
1102 <code>Setupterm()</code> also stores the names section of the
1103 terminal description in the global character array
1104 <code>ttytype[]</code>. Subsequent calls to
1105 <code>setupterm()</code> will overwrite this array, so you
1106 will have to save it yourself if need be.</p>
1110 <h3><a name="debugging" id="debugging">Debugging</a></h3>
1113 <strong>NOTE:</strong> These functions are not part of the
1114 standard curses API!
1118 <dt><code>trace()</code>
1121 <dd>This function can be used to explicitly set a trace level.
1122 If the trace level is nonzero, execution of your program will
1123 generate a file called “trace” in the current
1124 working directory containing a report on the library's actions.
1125 Higher trace levels enable more detailed (and verbose)
1126 reporting -- see comments attached to <code>TRACE_</code>
1127 defines in the <code>curses.h</code> file for details. (It is
1128 also possible to set a trace level by assigning a trace level
1129 value to the environment variable
1130 <code>NCURSES_TRACE</code>).</dd>
1132 <dt><code>_tracef()</code>
1135 <dd>This function can be used to output your own debugging
1136 information. It is only available only if you link with
1137 -lncurses_g. It can be used the same way as
1138 <code>printf()</code>, only it outputs a newline after the end
1139 of arguments. The output goes to a file called
1140 <code>trace</code> in the current directory.</dd>
1143 <p>Trace logs can be difficult to interpret due to the sheer
1144 volume of data dumped in them. There is a script called
1145 <strong>tracemunch</strong> included with the
1146 <code>ncurses</code> distribution that can alleviate this problem
1147 somewhat; it compacts long sequences of similar operations into
1148 more succinct single-line pseudo-operations. These pseudo-ops can
1149 be distinguished by the fact that they are named in capital
1152 <h2><a name="hints" id="hints">Hints, Tips, and Tricks</a></h2>
1154 <p>The <code>ncurses</code> manual pages are a complete reference
1155 for this library. In the remainder of this document, we discuss
1156 various useful methods that may not be obvious from the manual
1157 page descriptions.</p>
1159 <h3><a name="caution" id="caution">Some Notes of Caution</a></h3>
1161 <p>If you find yourself thinking you need to use
1162 <code>noraw()</code> or <code>nocbreak()</code>, think again and
1163 move carefully. It is probably better design to use
1164 <code>getstr()</code> or one of its relatives to simulate cooked
1165 mode. The <code>noraw()</code> and <code>nocbreak()</code>
1166 functions try to restore cooked mode, but they may end up
1167 clobbering some control bits set before you started your
1168 application. Also, they have always been poorly documented, and
1169 are likely to hurt your application's usability with other curses
1172 <p>Bear in mind that <code>refresh()</code> is a synonym for
1173 <code>wrefresh(stdscr)</code>. Do not try to mix use of
1174 <code>stdscr</code> with use of windows declared by
1175 <code>newwin()</code>; a <code>refresh()</code> call will blow
1176 them off the screen. The right way to handle this is to use
1177 <code>subwin()</code>, or not touch <code>stdscr</code> at all
1178 and tile your screen with declared windows which you then
1179 <code>wnoutrefresh()</code> somewhere in your program event loop,
1180 with a single <code>doupdate()</code> call to trigger actual
1183 <p>You are much less likely to run into problems if you design
1184 your screen layouts to use tiled rather than overlapping windows.
1185 Historically, curses support for overlapping windows has been
1186 weak, fragile, and poorly documented. The <code>ncurses</code>
1187 library is not yet an exception to this rule.</p>
1189 <p>There is a panels library included in the <code>ncurses</code>
1190 distribution that does a pretty good job of strengthening the
1191 overlapping-windows facilities.</p>
1193 <p>Try to avoid using the global variables LINES and COLS. Use
1194 <code>getmaxyx()</code> on the <code>stdscr</code> context
1195 instead. Reason: your code may be ported to run in an environment
1196 with window resizes, in which case several screens could be open
1197 with different sizes.</p>
1199 <h3><a name="leaving" id="leaving">Temporarily Leaving NCURSES
1202 <p>Sometimes you will want to write a program that spends most of
1203 its time in screen mode, but occasionally returns to ordinary
1204 “cooked” mode. A common reason for this is to support
1205 shell-out. This behavior is simple to arrange in
1206 <code>ncurses</code>.</p>
1208 <p>To leave <code>ncurses</code> mode, call <code>endwin()</code>
1209 as you would if you were intending to terminate the program. This
1210 will take the screen back to cooked mode; you can do your
1211 shell-out. When you want to return to <code>ncurses</code> mode,
1212 simply call <code>refresh()</code> or <code>doupdate()</code>.
1213 This will repaint the screen.</p>
1215 <p>There is a boolean function, <code>isendwin()</code>, which
1216 code can use to test whether <code>ncurses</code> screen mode is
1217 active. It returns <code>TRUE</code> in the interval between an
1218 <code>endwin()</code> call and the following
1219 <code>refresh()</code>, <code>FALSE</code> otherwise.</p>
1221 <p>Here is some sample code for shellout:</p>
1224 addstr("Shelling out...");
1225 def_prog_mode(); /* save current tty modes */
1226 endwin(); /* restore original tty modes */
1227 system("sh"); /* run shell */
1228 addstr("returned.\n"); /* prepare return message */
1229 refresh(); /* restore save modes, repaint screen */
1232 <h3><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h3>
1234 <p>A resize operation in X sends <code>SIGWINCH</code> to the
1235 application running under xterm. The easiest way to handle
1236 <code>SIGWINCH</code> is to do an <code>endwin</code>, followed
1237 by an <code>refresh</code> and a screen repaint you code
1238 yourself. The <code>refresh</code> will pick up the new screen
1239 size from the xterm's environment.</p>
1241 <p>That is the standard way, of course (it even works with some
1242 vendor's curses implementations). Its drawback is that it clears
1243 the screen to reinitialize the display, and does not resize
1244 subwindows which must be shrunk. <code>Ncurses</code> provides an
1245 extension which works better, the <code>resizeterm</code>
1246 function. That function ensures that all windows are limited to
1247 the new screen dimensions, and pads <code>stdscr</code> with
1248 blanks if the screen is larger.</p>
1250 <p>The <code>ncurses</code> library provides a SIGWINCH signal
1251 handler, which pushes a <code>KEY_RESIZE</code> via the wgetch()
1252 calls. When <code>ncurses</code> returns that code, it calls
1253 <code>resizeterm</code> to update the size of the standard
1254 screen's window, repainting that (filling with blanks or
1255 truncating as needed). It also resizes other windows, but its
1256 effect may be less satisfactory because it cannot know how you
1257 want the screen re-painted. You will usually have to write
1258 special-purpose code to handle <code>KEY_RESIZE</code>
1261 <h3><a name="screens" id="screens">Handling Multiple Terminal
1264 <p>The <code>initscr()</code> function actually calls a function
1265 named <code>newterm()</code> to do most of its work. If you are
1266 writing a program that opens multiple terminals, use
1267 <code>newterm()</code> directly.</p>
1269 <p>For each call, you will have to specify a terminal type and a
1270 pair of file pointers; each call will return a screen reference,
1271 and <code>stdscr</code> will be set to the last one allocated.
1272 You will switch between screens with the <code>set_term</code>
1273 call. Note that you will also have to call
1274 <code>def_shell_mode</code> and <code>def_prog_mode</code> on
1275 each tty yourself.</p>
1277 <h3><a name="testing" id="testing">Testing for Terminal
1278 Capabilities</a></h3>
1280 <p>Sometimes you may want to write programs that test for the
1281 presence of various capabilities before deciding whether to go
1282 into <code>ncurses</code> mode. An easy way to do this is to call
1283 <code>setupterm()</code>, then use the functions
1284 <code>tigetflag()</code>, <code>tigetnum()</code>, and
1285 <code>tigetstr()</code> to do your testing.</p>
1287 <p>A particularly useful case of this often comes up when you
1288 want to test whether a given terminal type should be treated as
1289 “smart” (cursor-addressable) or “stupid”.
1290 The right way to test this is to see if the return value of
1291 <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can
1292 include the <code>term.h</code> file and test the value of the
1293 macro <code>cursor_address</code>.</p>
1295 <h3><a name="tuning" id="tuning">Tuning for Speed</a></h3>
1297 <p>Use the <code>addchstr()</code> family of functions for fast
1298 screen-painting of text when you know the text does not contain
1299 any control characters. Try to make attribute changes infrequent
1300 on your screens. Do not use the <code>immedok()</code>
1303 <h3><a name="special" id="special">Special Features of
1306 <p>The <code>wresize()</code> function allows you to resize a
1307 window in place. The associated <code>resizeterm()</code>
1308 function simplifies the construction of <a href=
1309 "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p>
1311 <p>The <code>define_key()</code> function allows you to define at
1312 runtime function-key control sequences which are not in the
1313 terminal description. The <code>keyok()</code> function allows
1314 you to temporarily enable or disable interpretation of any
1315 function-key control sequence.</p>
1317 <p>The <code>use_default_colors()</code> function allows you to
1318 construct applications which can use the terminal's default
1319 foreground and background colors as an additional "default"
1320 color. Several terminal emulators support this feature, which is
1321 based on ISO 6429.</p>
1323 <p>Ncurses supports up 16 colors, unlike SVr4 curses which
1324 defines only 8. While most terminals which provide color allow
1325 only 8 colors, about a quarter (including XFree86 xterm) support
1328 <h2><a name="compat" id="compat">Compatibility with Older
1331 <p>Despite our best efforts, there are some differences between
1332 <code>ncurses</code> and the (undocumented!) behavior of older
1333 curses implementations. These arise from ambiguities or omissions
1334 in the documentation of the API.</p>
1336 <h3><a name="refbug" id="refbug">Refresh of Overlapping
1339 <p>If you define two windows A and B that overlap, and then
1340 alternately scribble on and refresh them, the changes made to the
1341 overlapping region under historic <code>curses</code> versions
1342 were often not documented precisely.</p>
1344 <p>To understand why this is a problem, remember that screen
1345 updates are calculated between two representations of the
1346 <em>entire</em> display. The documentation says that when you
1347 refresh a window, it is first copied to the virtual screen, and
1348 then changes are calculated to update the physical screen (and
1349 applied to the terminal). But "copied to" is not very specific,
1350 and subtle differences in how copying works can produce different
1351 behaviors in the case where two overlapping windows are each
1352 being refreshed at unpredictable intervals.</p>
1354 <p>What happens to the overlapping region depends on what
1355 <code>wnoutrefresh()</code> does with its argument -- what
1356 portions of the argument window it copies to the virtual screen.
1357 Some implementations do "change copy", copying down only
1358 locations in the window that have changed (or been marked changed
1359 with <code>wtouchln()</code> and friends). Some implementations
1360 do "entire copy", copying <em>all</em> window locations to the
1361 virtual screen whether or not they have changed.</p>
1363 <p>The <code>ncurses</code> library itself has not always been
1364 consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a
1365 did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and
1366 newer, do change copy.</p>
1368 <p>For most commercial curses implementations, it is not
1369 documented and not known for sure (at least not to the
1370 <code>ncurses</code> maintainers) whether they do change copy or
1371 entire copy. We know that System V release 3 curses has logic in
1372 it that looks like an attempt to do change copy, but the
1373 surrounding logic and data representations are sufficiently
1374 complex, and our knowledge sufficiently indirect, that it is hard
1375 to know whether this is reliable. It is not clear what the SVr4
1376 documentation and XSI standard intend. The XSI Curses standard
1377 barely mentions wnoutrefresh(); the SVr4 documents seem to be
1378 describing entire-copy, but it is possible with some effort and
1379 straining to read them the other way.</p>
1381 <p>It might therefore be unwise to rely on either behavior in
1382 programs that might have to be linked with other curses
1383 implementations. Instead, you can do an explicit
1384 <code>touchwin()</code> before the <code>wnoutrefresh()</code>
1385 call to guarantee an entire-contents copy anywhere.</p>
1387 <p>The really clean way to handle this is to use the panels
1388 library. If, when you want a screen update, you do
1389 <code>update_panels()</code>, it will do all the necessary
1390 <code>wnoutrefresh()</code> calls for whatever panel stacking
1391 order you have defined. Then you can do one
1392 <code>doupdate()</code> and there will be a <em>single</em> burst
1393 of physical I/O that will do all your updates.</p>
1395 <h3><a name="backbug" id="backbug">Background Erase</a></h3>
1397 <p>If you have been using a very old versions of
1398 <code>ncurses</code> (1.8.7 or older) you may be surprised by the
1399 behavior of the erase functions. In older versions, erased areas
1400 of a window were filled with a blank modified by the window's
1401 current attribute (as set by <strong>wattrset()</strong>,
1402 <strong>wattron()</strong>, <strong>wattroff()</strong> and
1405 <p>In newer versions, this is not so. Instead, the attribute of
1406 erased blanks is normal unless and until it is modified by the
1407 functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p>
1409 <p>This change in behavior conforms <code>ncurses</code> to
1410 System V Release 4 and the XSI Curses standard.</p>
1412 <h2><a name="xsifuncs" id="xsifuncs">XSI Curses Conformance</a></h2>
1414 <p>The <code>ncurses</code> library is intended to be base-level
1415 conformant with the XSI Curses standard from X/Open. Many
1416 extended-level features (in fact, almost all features not
1417 directly concerned with wide characters and internationalization)
1418 are also supported.</p>
1420 <p>One effect of XSI conformance is the change in behavior
1421 described under <a href="#backbug">"Background Erase --
1422 Compatibility with Old Versions"</a>.</p>
1424 <p>Also, <code>ncurses</code> meets the XSI requirement that
1425 every macro entry point have a corresponding function which may
1426 be linked (and will be prototype-checked) if the macro definition
1427 is disabled with <code>#undef</code>.</p>
1429 <h1><a name="panels" id="panels">The Panels Library</a></h1>
1431 <p>The <code>ncurses</code> library by itself provides good
1432 support for screen displays in which the windows are tiled
1433 (non-overlapping). In the more general case that windows may
1434 overlap, you have to use a series of <code>wnoutrefresh()</code>
1435 calls followed by a <code>doupdate()</code>, and be careful about
1436 the order you do the window refreshes in. It has to be
1437 bottom-upwards, otherwise parts of windows that should be
1438 obscured will show through.</p>
1440 <p>When your interface design is such that windows may dive
1441 deeper into the visibility stack or pop to the top at runtime,
1442 the resulting book-keeping can be tedious and difficult to get
1443 right. Hence the panels library.</p>
1445 <p>The <code>panel</code> library first appeared in AT&T
1446 System V. The version documented here is the <code>panel</code>
1447 code distributed with <code>ncurses</code>.</p>
1449 <h2><a name="pcompile" id="pcompile">Compiling With the Panels
1452 <p>Your panels-using modules must import the panels library
1453 declarations with</p>
1456 #include <panel.h>
1459 <p>and must be linked explicitly with the panels library using an
1460 <code>-lpanel</code> argument. Note that they must also link the
1461 <code>ncurses</code> library with <code>-lncurses</code>. Many
1462 linkers are two-pass and will accept either order, but it is
1463 still good practice to put <code>-lpanel</code> first and
1464 <code>-lncurses</code> second.</p>
1466 <h2><a name="poverview" id="poverview">Overview of Panels</a></h2>
1468 <p>A panel object is a window that is implicitly treated as part
1469 of a <dfn>deck</dfn> including all other panel objects. The deck
1470 has an implicit bottom-to-top visibility order. The panels
1471 library includes an update function (analogous to
1472 <code>refresh()</code>) that displays all panels in the deck in
1473 the proper order to resolve overlaps. The standard window,
1474 <code>stdscr</code>, is considered below all panels.</p>
1476 <p>Details on the panels functions are available in the man
1477 pages. We will just hit the highlights here.</p>
1479 <p>You create a panel from a window by calling
1480 <code>new_panel()</code> on a window pointer. It then becomes the
1481 top of the deck. The panel's window is available as the value of
1482 <code>panel_window()</code> called with the panel pointer as
1485 <p>You can delete a panel (removing it from the deck) with
1486 <code>del_panel</code>. This will not deallocate the associated
1487 window; you have to do that yourself. You can replace a panel's
1488 window with a different window by calling
1489 <code>replace_window</code>. The new window may be of different
1490 size; the panel code will re-compute all overlaps. This operation
1491 does not change the panel's position in the deck.</p>
1493 <p>To move a panel's window, use <code>move_panel()</code>. The
1494 <code>mvwin()</code> function on the panel's window is not
1495 sufficient because it does not update the panels library's
1496 representation of where the windows are. This operation leaves
1497 the panel's depth, contents, and size unchanged.</p>
1499 <p>Two functions (<code>top_panel()</code>,
1500 <code>bottom_panel()</code>) are provided for rearranging the
1501 deck. The first pops its argument window to the top of the deck;
1502 the second sends it to the bottom. Either operation leaves the
1503 panel's screen location, contents, and size unchanged.</p>
1505 <p>The function <code>update_panels()</code> does all the
1506 <code>wnoutrefresh()</code> calls needed to prepare for
1507 <code>doupdate()</code> (which you must call yourself,
1510 <p>Typically, you will want to call <code>update_panels()</code>
1511 and <code>doupdate()</code> just before accepting command input,
1512 once in each cycle of interaction with the user. If you call
1513 <code>update_panels()</code> after each and every panel write,
1514 you will generate a lot of unnecessary refresh activity and
1517 <h2><a name="pstdscr" id="pstdscr">Panels, Input, and the
1518 Standard Screen</a></h2>
1520 <p>You should not mix <code>wnoutrefresh()</code> or
1521 <code>wrefresh()</code> operations with panels code; this will
1522 work only if the argument window is either in the top panel or
1523 unobscured by any other panels.</p>
1525 <p>The <code>stsdcr</code> window is a special case. It is
1526 considered below all panels. Because changes to panels may
1527 obscure parts of <code>stdscr</code>, though, you should call
1528 <code>update_panels()</code> before <code>doupdate()</code> even
1529 when you only change <code>stdscr</code>.</p>
1531 <p>Note that <code>wgetch</code> automatically calls
1532 <code>wrefresh</code>. Therefore, before requesting input from a
1533 panel window, you need to be sure that the panel is totally
1536 <p>There is presently no way to display changes to one obscured
1537 panel without repainting all panels.</p>
1539 <h2><a name="hiding" id="hiding">Hiding Panels</a></h2>
1541 <p>It is possible to remove a panel from the deck temporarily;
1542 use <code>hide_panel</code> for this. Use
1543 <code>show_panel()</code> to render it visible again. The
1544 predicate function <code>panel_hidden</code> tests whether or not
1545 a panel is hidden.</p>
1547 <p>The <code>panel_update</code> code ignores hidden panels. You
1548 cannot do <code>top_panel()</code> or <code>bottom_panel</code>
1549 on a hidden panel(). Other panels operations are applicable.</p>
1551 <h2><a name="pmisc" id="pmisc">Miscellaneous Other Facilities</a></h2>
1553 <p>It is possible to navigate the deck using the functions
1554 <code>panel_above()</code> and <code>panel_below</code>. Handed a
1555 panel pointer, they return the panel above or below that panel.
1556 Handed <code>NULL</code>, they return the bottom-most or top-most
1559 <p>Every panel has an associated user pointer, not used by the
1560 panel code, to which you can attach application data. See the man
1561 page documentation of <code>set_panel_userptr()</code> and
1562 <code>panel_userptr</code> for details.</p>
1564 <h1><a name="menu" id="menu">The Menu Library</a></h1>
1566 <p>A menu is a screen display that assists the user to choose
1567 some subset of a given set of items. The <code>menu</code>
1568 library is a curses extension that supports easy programming of
1569 menu hierarchies with a uniform but flexible interface.</p>
1571 <p>The <code>menu</code> library first appeared in AT&T
1572 System V. The version documented here is the <code>menu</code>
1573 code distributed with <code>ncurses</code>.</p>
1575 <h2><a name="mcompile" id="mcompile">Compiling With the menu
1578 <p>Your menu-using modules must import the menu library
1579 declarations with</p>
1582 #include <menu.h>
1585 <p>and must be linked explicitly with the menus library using an
1586 <code>-lmenu</code> argument. Note that they must also link the
1587 <code>ncurses</code> library with <code>-lncurses</code>. Many
1588 linkers are two-pass and will accept either order, but it is
1589 still good practice to put <code>-lmenu</code> first and
1590 <code>-lncurses</code> second.</p>
1592 <h2><a name="moverview" id="moverview">Overview of Menus</a></h2>
1594 <p>The menus created by this library consist of collections of
1595 <dfn>items</dfn> including a name string part and a description
1596 string part. To make menus, you create groups of these items and
1597 connect them with menu frame objects.</p>
1599 <p>The menu can then by <dfn>posted</dfn>, that is written to an
1600 associated window. Actually, each menu has two associated
1601 windows; a containing window in which the programmer can scribble
1602 titles or borders, and a subwindow in which the menu items proper
1603 are displayed. If this subwindow is too small to display all the
1604 items, it will be a scrollable viewport on the collection of
1607 <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed),
1608 and finally freed to make the storage associated with it and its
1609 items available for re-use.</p>
1611 <p>The general flow of control of a menu program looks like
1615 <li>Initialize <code>curses</code>.</li>
1617 <li>Create the menu items, using <code>new_item()</code>.</li>
1619 <li>Create the menu using <code>new_menu()</code>.</li>
1621 <li>Post the menu using <code>post_menu()</code>.</li>
1623 <li>Refresh the screen.</li>
1625 <li>Process user requests via an input loop.</li>
1627 <li>Unpost the menu using <code>unpost_menu()</code>.</li>
1629 <li>Free the menu, using <code>free_menu()</code>.</li>
1631 <li>Free the items using <code>free_item()</code>.</li>
1633 <li>Terminate <code>curses</code>.</li>
1636 <h2><a name="mselect" id="mselect">Selecting items</a></h2>
1638 <p>Menus may be multi-valued or (the default) single-valued (see
1639 the manual page <code>menu_opts(3x)</code> to see how to change
1640 the default). Both types always have a <dfn>current
1643 <p>From a single-valued menu you can read the selected value
1644 simply by looking at the current item. From a multi-valued menu,
1645 you get the selected set by looping through the items applying
1646 the <code>item_value()</code> predicate function. Your
1647 menu-processing code can use the function
1648 <code>set_item_value()</code> to flag the items in the select
1651 <p>Menu items can be made unselectable using
1652 <code>set_item_opts()</code> or <code>item_opts_off()</code> with
1653 the <code>O_SELECTABLE</code> argument. This is the only option
1654 so far defined for menus, but it is good practice to code as
1655 though other option bits might be on.</p>
1657 <h2><a name="mdisplay" id="mdisplay">Menu Display</a></h2>
1659 <p>The menu library calculates a minimum display size for your
1660 window, based on the following variables:</p>
1663 <li>The number and maximum length of the menu items</li>
1665 <li>Whether the O_ROWMAJOR option is enabled</li>
1667 <li>Whether display of descriptions is enabled</li>
1669 <li>Whatever menu format may have been set by the
1672 <li>The length of the menu mark string used for highlighting
1676 <p>The function <code>set_menu_format()</code> allows you to set
1677 the maximum size of the viewport or <dfn>menu page</dfn> that
1678 will be used to display menu items. You can retrieve any format
1679 associated with a menu with <code>menu_format()</code>. The
1680 default format is rows=16, columns=1.</p>
1682 <p>The actual menu page may be smaller than the format size. This
1683 depends on the item number and size and whether O_ROWMAJOR is on.
1684 This option (on by default) causes menu items to be displayed in
1685 a “raster-scan” pattern, so that if more than one
1686 item will fit horizontally the first couple of items are
1687 side-by-side in the top row. The alternative is column-major
1688 display, which tries to put the first several items in the first
1691 <p>As mentioned above, a menu format not large enough to allow
1692 all items to fit on-screen will result in a menu display that is
1693 vertically scrollable.</p>
1695 <p>You can scroll it with requests to the menu driver, which will
1696 be described in the section on <a href="#minput">menu input
1699 <p>Each menu has a <dfn>mark string</dfn> used to visually tag
1700 selected items; see the <code>menu_mark(3x)</code> manual page
1701 for details. The mark string length also influences the menu page
1704 <p>The function <code>scale_menu()</code> returns the minimum
1705 display size that the menu code computes from all these factors.
1706 There are other menu display attributes including a select
1707 attribute, an attribute for selectable items, an attribute for
1708 unselectable items, and a pad character used to separate item
1709 name text from description text. These have reasonable defaults
1710 which the library allows you to change (see the
1711 <code>menu_attribs(3x)</code> manual page.</p>
1713 <h2><a name="mwindows" id="mwindows">Menu Windows</a></h2>
1715 <p>Each menu has, as mentioned previously, a pair of associated
1716 windows. Both these windows are painted when the menu is posted
1717 and erased when the menu is unposted.</p>
1719 <p>The outer or frame window is not otherwise touched by the menu
1720 routines. It exists so the programmer can associate a title, a
1721 border, or perhaps help text with the menu and have it properly
1722 refreshed or erased at post/unpost time. The inner window or
1723 <dfn>subwindow</dfn> is where the current menu page is
1726 <p>By default, both windows are <code>stdscr</code>. You can set
1727 them with the functions in <code>menu_win(3x)</code>.</p>
1729 <p>When you call <code>post_menu()</code>, you write the menu to
1730 its subwindow. When you call <code>unpost_menu()</code>, you
1731 erase the subwindow, However, neither of these actually modifies
1732 the screen. To do that, call <code>wrefresh()</code> or some
1735 <h2><a name="minput" id="minput">Processing Menu Input</a></h2>
1737 <p>The main loop of your menu-processing code should call
1738 <code>menu_driver()</code> repeatedly. The first argument of this
1739 routine is a menu pointer; the second is a menu command code. You
1740 should write an input-fetching routine that maps input characters
1741 to menu command codes, and pass its output to
1742 <code>menu_driver()</code>. The menu command codes are fully
1743 documented in <code>menu_driver(3x)</code>.</p>
1745 <p>The simplest group of command codes is
1746 <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>,
1747 <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>,
1748 <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>,
1749 <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These
1750 change the currently selected item. These requests may cause
1751 scrolling of the menu page if it only partially displayed.</p>
1753 <p>There are explicit requests for scrolling which also change
1754 the current item (because the select location does not change,
1755 but the item there does). These are <code>REQ_SCR_DLINE</code>,
1756 <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and
1757 <code>REQ_SCR_UPAGE</code>.</p>
1759 <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the
1760 current item. It is for use in multi-valued menus; if you use it
1761 with <code>O_ONEVALUE</code> on, you will get an error return
1762 (<code>E_REQUEST_DENIED</code>).</p>
1764 <p>Each menu has an associated pattern buffer. The
1765 <code>menu_driver()</code> logic tries to accumulate printable
1766 ASCII characters passed in in that buffer; when it matches a
1767 prefix of an item name, that item (or the next matching item) is
1768 selected. If appending a character yields no new match, that
1769 character is deleted from the pattern buffer, and
1770 <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p>
1772 <p>Some requests change the pattern buffer directly:
1773 <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>,
1774 <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The
1775 latter two are useful when pattern buffer input matches more than
1776 one item in a multi-valued menu.</p>
1778 <p>Each successful scroll or item navigation request clears the
1779 pattern buffer. It is also possible to set the pattern buffer
1780 explicitly with <code>set_menu_pattern()</code>.</p>
1782 <p>Finally, menu driver requests above the constant
1783 <code>MAX_COMMAND</code> are considered application-specific
1784 commands. The <code>menu_driver()</code> code ignores them and
1785 returns <code>E_UNKNOWN_COMMAND</code>.</p>
1787 <h2><a name="mmisc" id="mmisc">Miscellaneous Other Features</a></h2>
1789 <p>Various menu options can affect the processing and visual
1790 appearance and input processing of menus. See <code>menu_opts(3x)
1791 for details.</code></p>
1793 <p>It is possible to change the current item from application
1794 code; this is useful if you want to write your own navigation
1795 requests. It is also possible to explicitly set the top row of
1796 the menu display. See <code>mitem_current(3x)</code>. If your
1797 application needs to change the menu subwindow cursor for any
1798 reason, <code>pos_menu_cursor()</code> will restore it to the
1799 correct location for continuing menu driver processing.</p>
1801 <p>It is possible to set hooks to be called at menu
1802 initialization and wrapup time, and whenever the selected item
1803 changes. See <code>menu_hook(3x)</code>.</p>
1805 <p>Each item, and each menu, has an associated user pointer on
1806 which you can hang application data. See
1807 <code>mitem_userptr(3x)</code> and
1808 <code>menu_userptr(3x)</code>.</p>
1810 <h1><a name="form" id="form">The Forms Library</a></h1>
1812 <p>The <code>form</code> library is a curses extension that
1813 supports easy programming of on-screen forms for data entry and
1814 program control.</p>
1816 <p>The <code>form</code> library first appeared in AT&T
1817 System V. The version documented here is the <code>form</code>
1818 code distributed with <code>ncurses</code>.</p>
1820 <h2><a name="fcompile" id="fcompile">Compiling With the form
1823 <p>Your form-using modules must import the form library
1824 declarations with</p>
1827 #include <form.h>
1830 <p>and must be linked explicitly with the forms library using an
1831 <code>-lform</code> argument. Note that they must also link the
1832 <code>ncurses</code> library with <code>-lncurses</code>. Many
1833 linkers are two-pass and will accept either order, but it is
1834 still good practice to put <code>-lform</code> first and
1835 <code>-lncurses</code> second.</p>
1837 <h2><a name="foverview" id="foverview">Overview of Forms</a></h2>
1839 <p>A form is a collection of fields; each field may be either a
1840 label (explanatory text) or a data-entry location. Long forms may
1841 be segmented into pages; each entry to a new page clears the
1844 <p>To make forms, you create groups of fields and connect them
1845 with form frame objects; the form library makes this relatively
1848 <p>Once defined, a form can be <dfn>posted</dfn>, that is written
1849 to an associated window. Actually, each form has two associated
1850 windows; a containing window in which the programmer can scribble
1851 titles or borders, and a subwindow in which the form fields
1852 proper are displayed.</p>
1854 <p>As the form user fills out the posted form, navigation and
1855 editing keys support movement between fields, editing keys
1856 support modifying field, and plain text adds to or changes data
1857 in a current field. The form library allows you (the forms
1858 designer) to bind each navigation and editing key to any
1859 keystroke accepted by <code>curses</code> Fields may have
1860 validation conditions on them, so that they check input data for
1861 type and value. The form library supplies a rich set of
1862 pre-defined field types, and makes it relatively easy to define
1865 <p>Once its transaction is completed (or aborted), a form may be
1866 <dfn>unposted</dfn> (that is, undisplayed), and finally freed to
1867 make the storage associated with it and its items available for
1870 <p>The general flow of control of a form program looks like
1874 <li>Initialize <code>curses</code>.</li>
1876 <li>Create the form fields, using
1877 <code>new_field()</code>.</li>
1879 <li>Create the form using <code>new_form()</code>.</li>
1881 <li>Post the form using <code>post_form()</code>.</li>
1883 <li>Refresh the screen.</li>
1885 <li>Process user requests via an input loop.</li>
1887 <li>Unpost the form using <code>unpost_form()</code>.</li>
1889 <li>Free the form, using <code>free_form()</code>.</li>
1891 <li>Free the fields using <code>free_field()</code>.</li>
1893 <li>Terminate <code>curses</code>.</li>
1896 <p>Note that this looks much like a menu program; the form
1897 library handles tasks which are in many ways similar, and its
1898 interface was obviously designed to resemble that of the <a href=
1899 "#menu">menu library</a> wherever possible.</p>
1901 <p>In forms programs, however, the “process user
1902 requests” is somewhat more complicated than for menus.
1903 Besides menu-like navigation operations, the menu driver loop has
1904 to support field editing and data validation.</p>
1906 <h2><a name="fcreate" id="fcreate">Creating and Freeing Fields
1909 <p>The basic function for creating fields is
1910 <code>new_field()</code>:</p>
1913 FIELD *new_field(int height, int width, /* new field size */
1914 int top, int left, /* upper left corner */
1915 int offscreen, /* number of offscreen rows */
1916 int nbuf); /* number of working buffers */
1919 <p>Menu items always occupy a single row, but forms fields may
1920 have multiple rows. So <code>new_field()</code> requires you to
1921 specify a width and height (the first two arguments, which mist
1922 both be greater than zero).</p>
1924 <p>You must also specify the location of the field's upper left
1925 corner on the screen (the third and fourth arguments, which must
1926 be zero or greater). Note that these coordinates are relative to
1927 the form subwindow, which will coincide with <code>stdscr</code>
1928 by default but need not be <code>stdscr</code> if you have done
1929 an explicit <code>set_form_win()</code> call.</p>
1931 <p>The fifth argument allows you to specify a number of
1932 off-screen rows. If this is zero, the entire field will always be
1933 displayed. If it is nonzero, the form will be scrollable, with
1934 only one screen-full (initially the top part) displayed at any
1935 given time. If you make a field dynamic and grow it so it will no
1936 longer fit on the screen, the form will become scrollable even if
1937 the <code>offscreen</code> argument was initially zero.</p>
1939 <p>The forms library allocates one working buffer per field; the
1940 size of each buffer is <code>((height + offscreen)*width +
1941 1</code>, one character for each position in the field plus a NUL
1942 terminator. The sixth argument is the number of additional data
1943 buffers to allocate for the field; your application can use them
1944 for its own purposes.</p>
1947 FIELD *dup_field(FIELD *field, /* field to copy */
1948 int top, int left); /* location of new copy */
1951 <p>The function <code>dup_field()</code> duplicates an existing
1952 field at a new location. Size and buffering information are
1953 copied; some attribute flags and status bits are not (see the
1954 <code>form_field_new(3X)</code> for details).</p>
1957 FIELD *link_field(FIELD *field, /* field to copy */
1958 int top, int left); /* location of new copy */
1961 <p>The function <code>link_field()</code> also duplicates an
1962 existing field at a new location. The difference from
1963 <code>dup_field()</code> is that it arranges for the new field's
1964 buffer to be shared with the old one.</p>
1966 <p>Besides the obvious use in making a field editable from two
1967 different form pages, linked fields give you a way to hack in
1968 dynamic labels. If you declare several fields linked to an
1969 original, and then make them inactive, changes from the original
1970 will still be propagated to the linked fields.</p>
1972 <p>As with duplicated fields, linked fields have attribute bits
1973 separate from the original.</p>
1975 <p>As you might guess, all these field-allocations return
1976 <code>NULL</code> if the field allocation is not possible due to
1977 an out-of-memory error or out-of-bounds arguments.</p>
1979 <p>To connect fields to a form, use</p>
1982 FORM *new_form(FIELD **fields);
1985 <p>This function expects to see a NULL-terminated array of field
1986 pointers. Said fields are connected to a newly-allocated form
1987 object; its address is returned (or else NULL if the allocation
1990 <p>Note that <code>new_field()</code> does <em>not</em> copy the
1991 pointer array into private storage; if you modify the contents of
1992 the pointer array during forms processing, all manner of bizarre
1993 things might happen. Also note that any given field may only be
1994 connected to one form.</p>
1996 <p>The functions <code>free_field()</code> and
1997 <code>free_form</code> are available to free field and form
1998 objects. It is an error to attempt to free a field connected to a
1999 form, but not vice-versa; thus, you will generally free your form
2002 <h2><a name="fattributes" id="fattributes">Fetching and Changing
2003 Field Attributes</a></h2>
2005 <p>Each form field has a number of location and size attributes
2006 associated with it. There are other field attributes used to
2007 control display and editing of the field. Some (for example, the
2008 <code>O_STATIC</code> bit) involve sufficient complications to be
2009 covered in sections of their own later on. We cover the functions
2010 used to get and set several basic attributes here.</p>
2012 <p>When a field is created, the attributes not specified by the
2013 <code>new_field</code> function are copied from an invisible
2014 system default field. In attribute-setting and -fetching
2015 functions, the argument NULL is taken to mean this field. Changes
2016 to it persist as defaults until your forms application
2019 <h3><a name="fsizes" id="fsizes">Fetching Size and Location
2022 <p>You can retrieve field sizes and locations through:</p>
2025 int field_info(FIELD *field, /* field from which to fetch */
2026 int *height, *int width, /* field size */
2027 int *top, int *left, /* upper left corner */
2028 int *offscreen, /* number of offscreen rows */
2029 int *nbuf); /* number of working buffers */
2032 <p>This function is a sort of inverse of
2033 <code>new_field()</code>; instead of setting size and location
2034 attributes of a new field, it fetches them from an existing
2037 <h3><a name="flocation" id="flocation">Changing the Field
2040 <p>It is possible to move a field's location on the screen:</p>
2043 int move_field(FIELD *field, /* field to alter */
2044 int top, int left); /* new upper-left corner */
2047 <p>You can, of course. query the current location through
2048 <code>field_info()</code>.</p>
2050 <h3><a name="fjust" id="fjust">The Justification Attribute</a></h3>
2052 <p>One-line fields may be unjustified, justified right, justified
2053 left, or centered. Here is how you manipulate this attribute:</p>
2056 int set_field_just(FIELD *field, /* field to alter */
2057 int justmode); /* mode to set */
2059 int field_just(FIELD *field); /* fetch mode of field */
2062 <p>The mode values accepted and returned by this functions are
2063 preprocessor macros <code>NO_JUSTIFICATION</code>,
2064 <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or
2065 <code>JUSTIFY_CENTER</code>.</p>
2067 <h3><a name="fdispatts" id="fdispatts">Field Display
2070 <p>For each field, you can set a foreground attribute for entered
2071 characters, a background attribute for the entire field, and a
2072 pad character for the unfilled portion of the field. You can also
2073 control pagination of the form.</p>
2075 <p>This group of four field attributes controls the visual
2076 appearance of the field on the screen, without affecting in any
2077 way the data in the field buffer.</p>
2080 int set_field_fore(FIELD *field, /* field to alter */
2081 chtype attr); /* attribute to set */
2083 chtype field_fore(FIELD *field); /* field to query */
2085 int set_field_back(FIELD *field, /* field to alter */
2086 chtype attr); /* attribute to set */
2088 chtype field_back(FIELD *field); /* field to query */
2090 int set_field_pad(FIELD *field, /* field to alter */
2091 int pad); /* pad character to set */
2093 chtype field_pad(FIELD *field);
2095 int set_new_page(FIELD *field, /* field to alter */
2096 int flag); /* TRUE to force new page */
2098 chtype new_page(FIELD *field); /* field to query */
2101 <p>The attributes set and returned by the first four functions
2102 are normal <code>curses(3x)</code> display attribute values
2103 (<code>A_STANDOUT</code>, <code>A_BOLD</code>,
2104 <code>A_REVERSE</code> etc). The page bit of a field controls
2105 whether it is displayed at the start of a new form screen.</p>
2107 <h3><a name="foptions" id="foptions">Field Option Bits</a></h3>
2109 <p>There is also a large collection of field option bits you can
2110 set to control various aspects of forms processing. You can
2111 manipulate them with these functions:</p>
2114 int set_field_opts(FIELD *field, /* field to alter */
2115 int attr); /* attribute to set */
2117 int field_opts_on(FIELD *field, /* field to alter */
2118 int attr); /* attributes to turn on */
2120 int field_opts_off(FIELD *field, /* field to alter */
2121 int attr); /* attributes to turn off */
2123 int field_opts(FIELD *field); /* field to query */
2126 <p>By default, all options are on. Here are the available option
2132 <dd>Controls whether the field is visible on the screen. Can be
2133 used during form processing to hide or pop up fields depending
2134 on the value of parent fields.</dd>
2138 <dd>Controls whether the field is active during forms
2139 processing (i.e. visited by form navigation keys). Can be used
2140 to make labels or derived fields with buffer values alterable
2141 by the forms application, not the user.</dd>
2145 <dd>Controls whether data is displayed during field entry. If
2146 this option is turned off on a field, the library will accept
2147 and edit data in that field, but it will not be displayed and
2148 the visible field cursor will not move. You can turn off the
2149 O_PUBLIC bit to define password fields.</dd>
2153 <dd>Controls whether the field's data can be modified. When
2154 this option is off, all editing requests except
2155 <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code>
2156 will fail. Such read-only fields may be useful for help
2161 <dd>Controls word-wrapping in multi-line fields. Normally, when
2162 any character of a (blank-separated) word reaches the end of
2163 the current line, the entire word is wrapped to the next line
2164 (assuming there is one). When this option is off, the word will
2165 be split across the line break.</dd>
2169 <dd>Controls field blanking. When this option is on, entering a
2170 character at the first field position erases the entire field
2171 (except for the just-entered character).</dd>
2175 <dd>Controls automatic skip to next field when this one fills.
2176 Normally, when the forms user tries to type more data into a
2177 field than will fit, the editing location jumps to next field.
2178 When this option is off, the user's cursor will hang at the end
2179 of the field. This option is ignored in dynamic fields that
2180 have not reached their size limit.</dd>
2184 <dd>Controls whether <a href="#fvalidation">validation</a> is
2185 applied to blank fields. Normally, it is not; the user can
2186 leave a field blank without invoking the usual validation check
2187 on exit. If this option is off on a field, exit from it will
2188 invoke a validation check.</dd>
2192 <dd>Controls whether validation occurs on every exit, or only
2193 after the field is modified. Normally the latter is true.
2194 Setting O_PASSOK may be useful if your field's validation
2195 function may change during forms processing.</dd>
2199 <dd>Controls whether the field is fixed to its initial
2200 dimensions. If you turn this off, the field becomes <a href=
2201 "#fdynamic">dynamic</a> and will stretch to fit entered
2205 <p>A field's options cannot be changed while the field is
2206 currently selected. However, options may be changed on posted
2207 fields that are not current.</p>
2209 <p>The option values are bit-masks and can be composed with
2210 logical-or in the obvious way.</p>
2212 <h2><a name="fstatus" id="fstatus">Field Status</a></h2>
2214 <p>Every field has a status flag, which is set to FALSE when the
2215 field is created and TRUE when the value in field buffer 0
2216 changes. This flag can be queried and set directly:</p>
2219 int set_field_status(FIELD *field, /* field to alter */
2220 int status); /* mode to set */
2222 int field_status(FIELD *field); /* fetch mode of field */
2225 <p>Setting this flag under program control can be useful if you
2226 use the same form repeatedly, looking for modified fields each
2229 <p>Calling <code>field_status()</code> on a field not currently
2230 selected for input will return a correct value. Calling
2231 <code>field_status()</code> on a field that is currently selected
2232 for input may not necessarily give a correct field status value,
2233 because entered data is not necessarily copied to buffer zero
2234 before the exit validation check. To guarantee that the returned
2235 status value reflects reality, call <code>field_status()</code>
2236 either (1) in the field's exit validation check routine, (2) from
2237 the field's or form's initialization or termination hooks, or (3)
2238 just after a <code>REQ_VALIDATION</code> request has been
2239 processed by the forms driver.</p>
2241 <h2><a name="fuser" id="fuser">Field User Pointer</a></h2>
2243 <p>Each field structure contains one character pointer slot that
2244 is not used by the forms library. It is intended to be used by
2245 applications to store private per-field data. You can manipulate
2249 int set_field_userptr(FIELD *field, /* field to alter */
2250 char *userptr); /* mode to set */
2252 char *field_userptr(FIELD *field); /* fetch mode of field */
2253 </pre>(Properly, this user pointer field ought to have <code>(void
2254 *)</code> type. The <code>(char *)</code> type is retained for
2255 System V compatibility.)
2257 <p>It is valid to set the user pointer of the default field (with
2258 a <code>set_field_userptr()</code> call passed a NULL field
2259 pointer.) When a new field is created, the default-field user
2260 pointer is copied to initialize the new field's user pointer.</p>
2262 <h2><a name="fdynamic" id="fdynamic">Variable-Sized Fields</a></h2>
2264 <p>Normally, a field is fixed at the size specified for it at
2265 creation time. If, however, you turn off its O_STATIC bit, it
2266 becomes <dfn>dynamic</dfn> and will automatically resize itself
2267 to accommodate data as it is entered. If the field has extra
2268 buffers associated with it, they will grow right along with the
2269 main input buffer.</p>
2271 <p>A one-line dynamic field will have a fixed height (1) but
2272 variable width, scrolling horizontally to display data within the
2273 field area as originally dimensioned and located. A multi-line
2274 dynamic field will have a fixed width, but variable height
2275 (number of rows), scrolling vertically to display data within the
2276 field area as originally dimensioned and located.</p>
2278 <p>Normally, a dynamic field is allowed to grow without limit.
2279 But it is possible to set an upper limit on the size of a dynamic
2280 field. You do it with this function:</p>
2283 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
2284 int max_size); /* upper limit on field size */
2287 <p>If the field is one-line, <code>max_size</code> is taken to be
2288 a column size limit; if it is multi-line, it is taken to be a
2289 line size limit. To disable any limit, use an argument of zero.
2290 The growth limit can be changed whether or not the O_STATIC bit
2291 is on, but has no effect until it is.</p>
2293 <p>The following properties of a field change when it becomes
2297 <li>If there is no growth limit, there is no final position of
2298 the field; therefore <code>O_AUTOSKIP</code> and
2299 <code>O_NL_OVERLOAD</code> are ignored.</li>
2301 <li>Field justification will be ignored (though whatever
2302 justification is set up will be retained internally and can be
2305 <li>The <code>dup_field()</code> and <code>link_field()</code>
2306 calls copy dynamic-buffer sizes. If the <code>O_STATIC</code>
2307 option is set on one of a collection of links, buffer resizing
2308 will occur only when the field is edited through that
2311 <li>The call <code>field_info()</code> will retrieve the
2312 original static size of the field; use
2313 <code>dynamic_field_info()</code> to get the actual dynamic
2317 <h2><a name="fvalidation" id="fvalidation">Field Validation</a></h2>
2319 <p>By default, a field will accept any data that will fit in its
2320 input buffer. However, it is possible to attach a validation type
2321 to a field. If you do this, any attempt to leave the field while
2322 it contains data that does not match the validation type will
2323 fail. Some validation types also have a character-validity check
2324 for each time a character is entered in the field.</p>
2326 <p>A field's validation check (if any) is not called when
2327 <code>set_field_buffer()</code> modifies the input buffer, nor
2328 when that buffer is changed through a linked field.</p>
2330 <p>The <code>form</code> library provides a rich set of
2331 pre-defined validation types, and gives you the capability to
2332 define custom ones of your own. You can examine and change field
2333 validation attributes with the following functions:</p>
2336 int set_field_type(FIELD *field, /* field to alter */
2337 FIELDTYPE *ftype, /* type to associate */
2338 ...); /* additional arguments*/
2340 FIELDTYPE *field_type(FIELD *field); /* field to query */
2343 <p>The validation type of a field is considered an attribute of
2344 the field. As with other field attributes, Also, doing
2345 <code>set_field_type()</code> with a <code>NULL</code> field
2346 default will change the system default for validation of
2347 newly-created fields.</p>
2349 <p>Here are the pre-defined validation types:</p>
2351 <h3><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h3>
2353 <p>This field type accepts alphabetic data; no blanks, no digits,
2354 no special characters (this is checked at character-entry time).
2355 It is set up with:</p>
2358 int set_field_type(FIELD *field, /* field to alter */
2359 TYPE_ALPHA, /* type to associate */
2360 int width); /* maximum width of field */
2363 <p>The <code>width</code> argument sets a minimum width of data.
2364 Typically you will want to set this to the field width; if it is
2365 greater than the field width, the validation check will always
2366 fail. A minimum width of zero makes field completion
2369 <h3><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h3>
2371 <p>This field type accepts alphabetic data and digits; no blanks,
2372 no special characters (this is checked at character-entry time).
2373 It is set up with:</p>
2376 int set_field_type(FIELD *field, /* field to alter */
2377 TYPE_ALNUM, /* type to associate */
2378 int width); /* maximum width of field */
2381 <p>The <code>width</code> argument sets a minimum width of data.
2382 As with TYPE_ALPHA, typically you will want to set this to the
2383 field width; if it is greater than the field width, the
2384 validation check will always fail. A minimum width of zero makes
2385 field completion optional.</p>
2387 <h3><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h3>
2389 <p>This type allows you to restrict a field's values to be among
2390 a specified set of string values (for example, the two-letter
2391 postal codes for U.S. states). It is set up with:</p>
2394 int set_field_type(FIELD *field, /* field to alter */
2395 TYPE_ENUM, /* type to associate */
2396 char **valuelist; /* list of possible values */
2397 int checkcase; /* case-sensitive? */
2398 int checkunique); /* must specify uniquely? */
2401 <p>The <code>valuelist</code> parameter must point at a
2402 NULL-terminated list of valid strings. The <code>checkcase</code>
2403 argument, if true, makes comparison with the string
2406 <p>When the user exits a TYPE_ENUM field, the validation
2407 procedure tries to complete the data in the buffer to a valid
2408 entry. If a complete choice string has been entered, it is of
2409 course valid. But it is also possible to enter a prefix of a
2410 valid string and have it completed for you.</p>
2412 <p>By default, if you enter such a prefix and it matches more
2413 than one value in the string list, the prefix will be completed
2414 to the first matching value. But the <code>checkunique</code>
2415 argument, if true, requires prefix matches to be unique in order
2418 <p>The <code>REQ_NEXT_CHOICE</code> and
2419 <code>REQ_PREV_CHOICE</code> input requests can be particularly
2420 useful with these fields.</p>
2422 <h3><a name="ftype_integer" id="ftype_integer">TYPE_INTEGER</a></h3>
2424 <p>This field type accepts an integer. It is set up as
2428 int set_field_type(FIELD *field, /* field to alter */
2429 TYPE_INTEGER, /* type to associate */
2430 int padding, /* # places to zero-pad to */
2431 int vmin, int vmax); /* valid range */
2434 <p>Valid characters consist of an optional leading minus and
2435 digits. The range check is performed on exit. If the range
2436 maximum is less than or equal to the minimum, the range is
2439 <p>If the value passes its range check, it is padded with as many
2440 leading zero digits as necessary to meet the padding
2443 <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be
2444 interpreted with the C library function <code>atoi(3)</code>.</p>
2446 <h3><a name="ftype_numeric" id="ftype_numeric">TYPE_NUMERIC</a></h3>
2448 <p>This field type accepts a decimal number. It is set up as
2452 int set_field_type(FIELD *field, /* field to alter */
2453 TYPE_NUMERIC, /* type to associate */
2454 int padding, /* # places of precision */
2455 double vmin, double vmax); /* valid range */
2458 <p>Valid characters consist of an optional leading minus and
2459 digits. possibly including a decimal point. If your system
2460 supports locale's, the decimal point character used must be the
2461 one defined by your locale. The range check is performed on exit.
2462 If the range maximum is less than or equal to the minimum, the
2463 range is ignored.</p>
2465 <p>If the value passes its range check, it is padded with as many
2466 trailing zero digits as necessary to meet the padding
2469 <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be
2470 interpreted with the C library function <code>atof(3)</code>.</p>
2472 <h3><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h3>
2474 <p>This field type accepts data matching a regular expression. It
2475 is set up as follows:</p>
2478 int set_field_type(FIELD *field, /* field to alter */
2479 TYPE_REGEXP, /* type to associate */
2480 char *regexp); /* expression to match */
2483 <p>The syntax for regular expressions is that of
2484 <code>regcomp(3)</code>. The check for regular-expression match
2485 is performed on exit.</p>
2487 <h2><a name="fbuffer" id="fbuffer">Direct Field Buffer
2488 Manipulation</a></h2>
2490 <p>The chief attribute of a field is its buffer contents. When a
2491 form has been completed, your application usually needs to know
2492 the state of each field buffer. You can find this out with:</p>
2495 char *field_buffer(FIELD *field, /* field to query */
2496 int bufindex); /* number of buffer to query */
2499 <p>Normally, the state of the zero-numbered buffer for each field
2500 is set by the user's editing actions on that field. It is
2501 sometimes useful to be able to set the value of the zero-numbered
2502 (or some other) buffer from your application:</p>
2505 int set_field_buffer(FIELD *field, /* field to alter */
2506 int bufindex, /* number of buffer to alter */
2507 char *value); /* string value to set */
2510 <p>If the field is not large enough and cannot be resized to a
2511 sufficiently large size to contain the specified value, the value
2512 will be truncated to fit.</p>
2514 <p>Calling <code>field_buffer()</code> with a null field pointer
2515 will raise an error. Calling <code>field_buffer()</code> on a
2516 field not currently selected for input will return a correct
2517 value. Calling <code>field_buffer()</code> on a field that is
2518 currently selected for input may not necessarily give a correct
2519 field buffer value, because entered data is not necessarily
2520 copied to buffer zero before the exit validation check. To
2521 guarantee that the returned buffer value reflects on-screen
2522 reality, call <code>field_buffer()</code> either (1) in the
2523 field's exit validation check routine, (2) from the field's or
2524 form's initialization or termination hooks, or (3) just after a
2525 <code>REQ_VALIDATION</code> request has been processed by the
2528 <h2><a name="formattrs" id="formattrs">Attributes of Forms</a></h2>
2530 <p>As with field attributes, form attributes inherit a default
2531 from a system default form structure. These defaults can be
2532 queried or set by of these functions using a form-pointer
2533 argument of <code>NULL</code>.</p>
2535 <p>The principal attribute of a form is its field list. You can
2536 query and change this list with:</p>
2539 int set_form_fields(FORM *form, /* form to alter */
2540 FIELD **fields); /* fields to connect */
2542 char *form_fields(FORM *form); /* fetch fields of form */
2544 int field_count(FORM *form); /* count connect fields */
2547 <p>The second argument of <code>set_form_fields()</code> may be a
2548 NULL-terminated field pointer array like the one required by
2549 <code>new_form()</code>. In that case, the old fields of the form
2550 are disconnected but not freed (and eligible to be connected to
2551 other forms), then the new fields are connected.</p>
2553 <p>It may also be null, in which case the old fields are
2554 disconnected (and not freed) but no new ones are connected.</p>
2556 <p>The <code>field_count()</code> function simply counts the
2557 number of fields connected to a given from. It returns -1 if the
2558 form-pointer argument is NULL.</p>
2560 <h2><a name="fdisplay" id="fdisplay">Control of Form Display</a></h2>
2562 <p>In the overview section, you saw that to display a form you
2563 normally start by defining its size (and fields), posting it, and
2564 refreshing the screen. There is an hidden step before posting,
2565 which is the association of the form with a frame window
2566 (actually, a pair of windows) within which it will be displayed.
2567 By default, the forms library associates every form with the
2568 full-screen window <code>stdscr</code>.</p>
2570 <p>By making this step explicit, you can associate a form with a
2571 declared frame window on your screen display. This can be useful
2572 if you want to adapt the form display to different screen sizes,
2573 dynamically tile forms on the screen, or use a form as part of an
2574 interface layout managed by <a href="#panels">panels</a>.</p>
2576 <p>The two windows associated with each form have the same
2577 functions as their analogues in the <a href="#menu">menu
2578 library</a>. Both these windows are painted when the form is
2579 posted and erased when the form is unposted.</p>
2581 <p>The outer or frame window is not otherwise touched by the form
2582 routines. It exists so the programmer can associate a title, a
2583 border, or perhaps help text with the form and have it properly
2584 refreshed or erased at post/unpost time. The inner window or
2585 subwindow is where the current form page is actually
2588 <p>In order to declare your own frame window for a form, you will
2589 need to know the size of the form's bounding rectangle. You can
2590 get this information with:</p>
2593 int scale_form(FORM *form, /* form to query */
2594 int *rows, /* form rows */
2595 int *cols); /* form cols */
2598 <p>The form dimensions are passed back in the locations pointed
2599 to by the arguments. Once you have this information, you can use
2600 it to declare of windows, then use one of these functions:</p>
2603 int set_form_win(FORM *form, /* form to alter */
2604 WINDOW *win); /* frame window to connect */
2606 WINDOW *form_win(FORM *form); /* fetch frame window of form */
2608 int set_form_sub(FORM *form, /* form to alter */
2609 WINDOW *win); /* form subwindow to connect */
2611 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
2614 <p>Note that curses operations, including <code>refresh()</code>,
2615 on the form, should be done on the frame window, not the form
2618 <p>It is possible to check from your application whether all of a
2619 scrollable field is actually displayed within the menu subwindow.
2620 Use these functions:</p>
2623 int data_ahead(FORM *form); /* form to be queried */
2625 int data_behind(FORM *form); /* form to be queried */
2628 <p>The function <code>data_ahead()</code> returns TRUE if (a) the
2629 current field is one-line and has undisplayed data off to the
2630 right, (b) the current field is multi-line and there is data
2631 off-screen below it.</p>
2633 <p>The function <code>data_behind()</code> returns TRUE if the
2634 first (upper left hand) character position is off-screen (not
2635 being displayed).</p>
2637 <p>Finally, there is a function to restore the form window's
2638 cursor to the value expected by the forms driver:</p>
2641 int pos_form_cursor(FORM *) /* form to be queried */
2644 <p>If your application changes the form window cursor, call this
2645 function before handing control back to the forms driver in order
2646 to re-synchronize it.</p>
2648 <h2><a name="fdriver" id="fdriver">Input Processing in the Forms
2651 <p>The function <code>form_driver()</code> handles virtualized
2652 input requests for form navigation, editing, and validation
2653 requests, just as <code>menu_driver</code> does for menus (see
2654 the section on <a href="#minput">menu input handling</a>).</p>
2657 int form_driver(FORM *form, /* form to pass input to */
2658 int request); /* form request code */
2661 <p>Your input virtualization function needs to take input and
2662 then convert it to either an alphanumeric character (which is
2663 treated as data to be entered in the currently-selected field),
2664 or a forms processing request.</p>
2666 <p>The forms driver provides hooks (through input-validation and
2667 field-termination functions) with which your application code can
2668 check that the input taken by the driver matched what was
2671 <h3><a name="fpage" id="fpage">Page Navigation Requests</a></h3>
2673 <p>These requests cause page-level moves through the form,
2674 triggering display of a new form screen.</p>
2677 <dt><code>REQ_NEXT_PAGE</code>
2680 <dd>Move to the next form page.</dd>
2682 <dt><code>REQ_PREV_PAGE</code>
2685 <dd>Move to the previous form page.</dd>
2687 <dt><code>REQ_FIRST_PAGE</code>
2690 <dd>Move to the first form page.</dd>
2692 <dt><code>REQ_LAST_PAGE</code>
2695 <dd>Move to the last form page.</dd>
2698 <p>These requests treat the list as cyclic; that is,
2699 <code>REQ_NEXT_PAGE</code> from the last page goes to the first,
2700 and <code>REQ_PREV_PAGE</code> from the first page goes to the
2703 <h3><a name="ffield" id="ffield">Inter-Field Navigation
2706 <p>These requests handle navigation between fields on the same
2710 <dt><code>REQ_NEXT_FIELD</code>
2713 <dd>Move to next field.</dd>
2715 <dt><code>REQ_PREV_FIELD</code>
2718 <dd>Move to previous field.</dd>
2720 <dt><code>REQ_FIRST_FIELD</code>
2723 <dd>Move to the first field.</dd>
2725 <dt><code>REQ_LAST_FIELD</code>
2728 <dd>Move to the last field.</dd>
2730 <dt><code>REQ_SNEXT_FIELD</code>
2733 <dd>Move to sorted next field.</dd>
2735 <dt><code>REQ_SPREV_FIELD</code>
2738 <dd>Move to sorted previous field.</dd>
2740 <dt><code>REQ_SFIRST_FIELD</code>
2743 <dd>Move to the sorted first field.</dd>
2745 <dt><code>REQ_SLAST_FIELD</code>
2748 <dd>Move to the sorted last field.</dd>
2750 <dt><code>REQ_LEFT_FIELD</code>
2753 <dd>Move left to field.</dd>
2755 <dt><code>REQ_RIGHT_FIELD</code>
2758 <dd>Move right to field.</dd>
2760 <dt><code>REQ_UP_FIELD</code>
2763 <dd>Move up to field.</dd>
2765 <dt><code>REQ_DOWN_FIELD</code>
2768 <dd>Move down to field.</dd>
2771 <p>These requests treat the list of fields on a page as cyclic;
2772 that is, <code>REQ_NEXT_FIELD</code> from the last field goes to
2773 the first, and <code>REQ_PREV_FIELD</code> from the first field
2774 goes to the last. The order of the fields for these (and the
2775 <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code>
2776 requests) is simply the order of the field pointers in the form
2777 array (as set up by <code>new_form()</code> or
2778 <code>set_form_fields()</code></p>
2780 <p>It is also possible to traverse the fields as if they had been
2781 sorted in screen-position order, so the sequence goes
2782 left-to-right and top-to-bottom. To do this, use the second group
2783 of four sorted-movement requests.</p>
2785 <p>Finally, it is possible to move between fields using visual
2786 directions up, down, right, and left. To accomplish this, use the
2787 third group of four requests. Note, however, that the position of
2788 a form for purposes of these requests is its upper-left
2791 <p>For example, suppose you have a multi-line field B, and two
2792 single-line fields A and C on the same line with B, with A to the
2793 left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code>
2794 from A will go to B only if A, B, and C <em>all</em> share the
2795 same first line; otherwise it will skip over B to C.</p>
2797 <h3><a name="fifield" id="fifield">Intra-Field Navigation
2800 <p>These requests drive movement of the edit cursor within the
2801 currently selected field.</p>
2804 <dt><code>REQ_NEXT_CHAR</code>
2807 <dd>Move to next character.</dd>
2809 <dt><code>REQ_PREV_CHAR</code>
2812 <dd>Move to previous character.</dd>
2814 <dt><code>REQ_NEXT_LINE</code>
2817 <dd>Move to next line.</dd>
2819 <dt><code>REQ_PREV_LINE</code>
2822 <dd>Move to previous line.</dd>
2824 <dt><code>REQ_NEXT_WORD</code>
2827 <dd>Move to next word.</dd>
2829 <dt><code>REQ_PREV_WORD</code>
2832 <dd>Move to previous word.</dd>
2834 <dt><code>REQ_BEG_FIELD</code>
2837 <dd>Move to beginning of field.</dd>
2839 <dt><code>REQ_END_FIELD</code>
2842 <dd>Move to end of field.</dd>
2844 <dt><code>REQ_BEG_LINE</code>
2847 <dd>Move to beginning of line.</dd>
2849 <dt><code>REQ_END_LINE</code>
2852 <dd>Move to end of line.</dd>
2854 <dt><code>REQ_LEFT_CHAR</code>
2857 <dd>Move left in field.</dd>
2859 <dt><code>REQ_RIGHT_CHAR</code>
2862 <dd>Move right in field.</dd>
2864 <dt><code>REQ_UP_CHAR</code>
2867 <dd>Move up in field.</dd>
2869 <dt><code>REQ_DOWN_CHAR</code>
2872 <dd>Move down in field.</dd>
2875 <p>Each <em>word</em> is separated from the previous and next
2876 characters by whitespace. The commands to move to beginning and
2877 end of line or field look for the first or last non-pad character
2878 in their ranges.</p>
2880 <h3><a name="fscroll" id="fscroll">Scrolling Requests</a></h3>
2882 <p>Fields that are dynamic and have grown and fields explicitly
2883 created with offscreen rows are scrollable. One-line fields
2884 scroll horizontally; multi-line fields scroll vertically. Most
2885 scrolling is triggered by editing and intra-field movement (the
2886 library scrolls the field to keep the cursor visible). It is
2887 possible to explicitly request scrolling with the following
2891 <dt><code>REQ_SCR_FLINE</code>
2894 <dd>Scroll vertically forward a line.</dd>
2896 <dt><code>REQ_SCR_BLINE</code>
2899 <dd>Scroll vertically backward a line.</dd>
2901 <dt><code>REQ_SCR_FPAGE</code>
2904 <dd>Scroll vertically forward a page.</dd>
2906 <dt><code>REQ_SCR_BPAGE</code>
2909 <dd>Scroll vertically backward a page.</dd>
2911 <dt><code>REQ_SCR_FHPAGE</code>
2914 <dd>Scroll vertically forward half a page.</dd>
2916 <dt><code>REQ_SCR_BHPAGE</code>
2919 <dd>Scroll vertically backward half a page.</dd>
2921 <dt><code>REQ_SCR_FCHAR</code>
2924 <dd>Scroll horizontally forward a character.</dd>
2926 <dt><code>REQ_SCR_BCHAR</code>
2929 <dd>Scroll horizontally backward a character.</dd>
2931 <dt><code>REQ_SCR_HFLINE</code>
2934 <dd>Scroll horizontally one field width forward.</dd>
2936 <dt><code>REQ_SCR_HBLINE</code>
2939 <dd>Scroll horizontally one field width backward.</dd>
2941 <dt><code>REQ_SCR_HFHALF</code>
2944 <dd>Scroll horizontally one half field width forward.</dd>
2946 <dt><code>REQ_SCR_HBHALF</code>
2949 <dd>Scroll horizontally one half field width backward.</dd>
2952 <p>For scrolling purposes, a <em>page</em> of a field is the
2953 height of its visible part.</p>
2955 <h3><a name="fedit" id="fedit">Editing Requests</a></h3>
2957 <p>When you pass the forms driver an ASCII character, it is
2958 treated as a request to add the character to the field's data
2959 buffer. Whether this is an insertion or a replacement depends on
2960 the field's edit mode (insertion is the default.</p>
2962 <p>The following requests support editing the field and changing
2966 <dt><code>REQ_INS_MODE</code>
2969 <dd>Set insertion mode.</dd>
2971 <dt><code>REQ_OVL_MODE</code>
2974 <dd>Set overlay mode.</dd>
2976 <dt><code>REQ_NEW_LINE</code>
2979 <dd>New line request (see below for explanation).</dd>
2981 <dt><code>REQ_INS_CHAR</code>
2984 <dd>Insert space at character location.</dd>
2986 <dt><code>REQ_INS_LINE</code>
2989 <dd>Insert blank line at character location.</dd>
2991 <dt><code>REQ_DEL_CHAR</code>
2994 <dd>Delete character at cursor.</dd>
2996 <dt><code>REQ_DEL_PREV</code>
2999 <dd>Delete previous word at cursor.</dd>
3001 <dt><code>REQ_DEL_LINE</code>
3004 <dd>Delete line at cursor.</dd>
3006 <dt><code>REQ_DEL_WORD</code>
3009 <dd>Delete word at cursor.</dd>
3011 <dt><code>REQ_CLR_EOL</code>
3014 <dd>Clear to end of line.</dd>
3016 <dt><code>REQ_CLR_EOF</code>
3019 <dd>Clear to end of field.</dd>
3021 <dt><code>REQ_CLEAR_FIELD</code>
3024 <dd>Clear entire field.</dd>
3027 <p>The behavior of the <code>REQ_NEW_LINE</code> and
3028 <code>REQ_DEL_PREV</code> requests is complicated and partly
3029 controlled by a pair of forms options. The special cases are
3030 triggered when the cursor is at the beginning of a field, or on
3031 the last line of the field.</p>
3033 <p>First, we consider <code>REQ_NEW_LINE</code>:</p>
3035 <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert
3036 mode is to break the current line at the position of the edit
3037 cursor, inserting the portion of the current line after the
3038 cursor as a new line following the current and moving the cursor
3039 to the beginning of that new line (you may think of this as
3040 inserting a newline in the field buffer).</p>
3042 <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay
3043 mode is to clear the current line from the position of the edit
3044 cursor to end of line. The cursor is then moved to the beginning
3045 of the next line.</p>
3047 <p>However, <code>REQ_NEW_LINE</code> at the beginning of a
3048 field, or on the last line of a field, instead does a
3049 <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is
3050 off, this special action is disabled.</p>
3052 <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p>
3054 <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete
3055 the previous character. If insert mode is on, and the cursor is
3056 at the start of a line, and the text on that line will fit on the
3057 previous one, it instead appends the contents of the current line
3058 to the previous one and deletes the current line (you may think
3059 of this as deleting a newline from the field buffer).</p>
3061 <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field
3062 is instead treated as a <code>REQ_PREV_FIELD</code>.</p>
3064 <p>If the <code>O_BS_OVERLOAD</code> option is off, this special
3065 action is disabled and the forms driver just returns
3066 <code>E_REQUEST_DENIED</code>.</p>
3068 <p>See <a href="#frmoptions">Form Options</a> for discussion of
3069 how to set and clear the overload options.</p>
3071 <h3><a name="forder" id="forder">Order Requests</a></h3>
3073 <p>If the type of your field is ordered, and has associated
3074 functions for getting the next and previous values of the type
3075 from a given value, there are requests that can fetch that value
3076 into the field buffer:</p>
3079 <dt><code>REQ_NEXT_CHOICE</code>
3082 <dd>Place the successor value of the current value in the
3085 <dt><code>REQ_PREV_CHOICE</code>
3088 <dd>Place the predecessor value of the current value in the
3092 <p>Of the built-in field types, only <code>TYPE_ENUM</code> has
3093 built-in successor and predecessor functions. When you define a
3094 field type of your own (see <a href="#fcustom">Custom Validation
3095 Types</a>), you can associate our own ordering functions.</p>
3097 <h3><a name="fappcmds" id="fappcmds">Application Commands</a></h3>
3099 <p>Form requests are represented as integers above the
3100 <code>curses</code> value greater than <code>KEY_MAX</code> and
3101 less than or equal to the constant <code>MAX_COMMAND</code>. If
3102 your input-virtualization routine returns a value above
3103 <code>MAX_COMMAND</code>, the forms driver will ignore it.</p>
3105 <h2><a name="fhooks" id="fhooks">Field Change Hooks</a></h2>
3107 <p>It is possible to set function hooks to be executed whenever
3108 the current field or form changes. Here are the functions that
3112 typedef void (*HOOK)(); /* pointer to function returning void */
3114 int set_form_init(FORM *form, /* form to alter */
3115 HOOK hook); /* initialization hook */
3117 HOOK form_init(FORM *form); /* form to query */
3119 int set_form_term(FORM *form, /* form to alter */
3120 HOOK hook); /* termination hook */
3122 HOOK form_term(FORM *form); /* form to query */
3124 int set_field_init(FORM *form, /* form to alter */
3125 HOOK hook); /* initialization hook */
3127 HOOK field_init(FORM *form); /* form to query */
3129 int set_field_term(FORM *form, /* form to alter */
3130 HOOK hook); /* termination hook */
3132 HOOK field_term(FORM *form); /* form to query */
3135 <p>These functions allow you to either set or query four
3136 different hooks. In each of the set functions, the second
3137 argument should be the address of a hook function. These
3138 functions differ only in the timing of the hook call.</p>
3143 <dd>This hook is called when the form is posted; also, just
3144 after each page change operation.</dd>
3148 <dd>This hook is called when the form is posted; also, just
3149 after each field change</dd>
3153 <dd>This hook is called just after field validation; that is,
3154 just before the field is altered. It is also called when the
3155 form is unposted.</dd>
3159 <dd>This hook is called when the form is unposted; also, just
3160 before each page change operation.</dd>
3163 <p>Calls to these hooks may be triggered</p>
3166 <li>When user editing requests are processed by the forms
3169 <li>When the current page is changed by
3170 <code>set_current_field()</code> call</li>
3172 <li>When the current field is changed by a
3173 <code>set_form_page()</code> call</li>
3176 <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for
3177 discussion of the latter two cases.</p>
3179 <p>You can set a default hook for all fields by passing one of
3180 the set functions a NULL first argument.</p>
3182 <p>You can disable any of these hooks by (re)setting them to
3183 NULL, the default value.</p>
3185 <h2><a href="#ffocus">Field Change Commands</a></h2>
3187 <p>Normally, navigation through the form will be driven by the
3188 user's input requests. But sometimes it is useful to be able to
3189 move the focus for editing and viewing under control of your
3190 application, or ask which field it currently is in. The following
3191 functions help you accomplish this:</p>
3194 int set_current_field(FORM *form, /* form to alter */
3195 FIELD *field); /* field to shift to */
3197 FIELD *current_field(FORM *form); /* form to query */
3199 int field_index(FORM *form, /* form to query */
3200 FIELD *field); /* field to get index of */
3203 <p>The function <code>field_index()</code> returns the index of
3204 the given field in the given form's field array (the array passed
3205 to <code>new_form()</code> or
3206 <code>set_form_fields()</code>).</p>
3208 <p>The initial current field of a form is the first active field
3209 on the first page. The function <code>set_form_fields()</code>
3212 <p>It is also possible to move around by pages.</p>
3215 int set_form_page(FORM *form, /* form to alter */
3216 int page); /* page to go to (0-origin) */
3218 int form_page(FORM *form); /* return form's current page */
3221 <p>The initial page of a newly-created form is 0. The function
3222 <code>set_form_fields()</code> resets this.</p>
3224 <h2><a name="frmoptions" id="frmoptions">Form Options</a></h2>
3226 <p>Like fields, forms may have control option bits. They can be
3227 changed or queried with these functions:</p>
3230 int set_form_opts(FORM *form, /* form to alter */
3231 int attr); /* attribute to set */
3233 int form_opts_on(FORM *form, /* form to alter */
3234 int attr); /* attributes to turn on */
3236 int form_opts_off(FORM *form, /* form to alter */
3237 int attr); /* attributes to turn off */
3239 int form_opts(FORM *form); /* form to query */
3242 <p>By default, all options are on. Here are the available option
3246 <dt>O_NL_OVERLOAD</dt>
3248 <dd>Enable overloading of <code>REQ_NEW_LINE</code> as
3249 described in <a href="#fedit">Editing Requests</a>. The value
3250 of this option is ignored on dynamic fields that have not
3251 reached their size limit; these have no last line, so the
3252 circumstances for triggering a <code>REQ_NEXT_FIELD</code>
3255 <dt>O_BS_OVERLOAD</dt>
3257 <dd>Enable overloading of <code>REQ_DEL_PREV</code> as
3258 described in <a href="#fedit">Editing Requests</a>.</dd>
3261 <p>The option values are bit-masks and can be composed with
3262 logical-or in the obvious way.</p>
3264 <h2><a name="fcustom" id="fcustom">Custom Validation Types</a></h2>
3266 <p>The <code>form</code> library gives you the capability to
3267 define custom validation types of your own. Further, the optional
3268 additional arguments of <code>set_field_type</code> effectively
3269 allow you to parameterize validation types. Most of the
3270 complications in the validation-type interface have to do with
3271 the handling of the additional arguments within custom validation
3274 <h3><a name="flinktypes" id="flinktypes">Union Types</a></h3>
3276 <p>The simplest way to create a custom data type is to compose it
3277 from two preexisting ones:</p>
3280 FIELD *link_fieldtype(FIELDTYPE *type1,
3284 <p>This function creates a field type that will accept any of the
3285 values legal for either of its argument field types (which may be
3286 either predefined or programmer-defined). If a
3287 <code>set_field_type()</code> call later requires arguments, the
3288 new composite type expects all arguments for the first type, than
3289 all arguments for the second. Order functions (see <a href=
3290 "#forder">Order Requests</a>) associated with the component types
3291 will work on the composite; what it does is check the validation
3292 function for the first type, then for the second, to figure what
3293 type the buffer contents should be treated as.</p>
3295 <h3><a name="fnewtypes" id="fnewtypes">New Field Types</a></h3>
3297 <p>To create a field type from scratch, you need to specify one
3298 or both of the following things:</p>
3301 <li>A character-validation function, to check each character as
3304 <li>A field-validation function to be applied on exit from the
3308 <p>Here is how you do that:</p>
3311 typedef int (*HOOK)(); /* pointer to function returning int */
3313 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
3314 HOOK c_validate) /* character validator */
3316 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
3319 <p>At least one of the arguments of <code>new_fieldtype()</code>
3320 must be non-NULL. The forms driver will automatically call the
3321 new type's validation functions at appropriate points in
3322 processing a field of the new type.</p>
3324 <p>The function <code>free_fieldtype()</code> deallocates the
3325 argument fieldtype, freeing all storage associated with it.</p>
3327 <p>Normally, a field validator is called when the user attempts
3328 to leave the field. Its first argument is a field pointer, from
3329 which it can get to field buffer 0 and test it. If the function
3330 returns TRUE, the operation succeeds; if it returns FALSE, the
3331 edit cursor stays in the field.</p>
3333 <p>A character validator gets the character passed in as a first
3334 argument. It too should return TRUE if the character is valid,
3335 FALSE otherwise.</p>
3337 <h3><a name="fcheckargs" id="fcheckargs">Validation Function
3340 <p>Your field- and character- validation functions will be passed
3341 a second argument as well. This second argument is the address of
3342 a structure (which we will call a <em>pile</em>) built from any
3343 of the field-type-specific arguments passed to
3344 <code>set_field_type()</code>. If no such arguments are defined
3345 for the field type, this pile pointer argument will be NULL.</p>
3347 <p>In order to arrange for such arguments to be passed to your
3348 validation functions, you must associate a small set of
3349 storage-management functions with the type. The forms driver will
3350 use these to synthesize a pile from the trailing arguments of
3351 each <code>set_field_type()</code> argument, and a pointer to the
3352 pile will be passed to the validation functions.</p>
3354 <p>Here is how you make the association:</p>
3357 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
3358 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
3360 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3361 PTRHOOK make_str, /* make structure from args */
3362 PTRHOOK copy_str, /* make copy of structure */
3363 VOIDHOOK free_str); /* free structure storage */
3366 <p>Here is how the storage-management hooks are used:</p>
3369 <dt><code>make_str</code>
3372 <dd>This function is called by <code>set_field_type()</code>.
3373 It gets one argument, a <code>va_list</code> of the
3374 type-specific arguments passed to
3375 <code>set_field_type()</code>. It is expected to return a pile
3376 pointer to a data structure that encapsulates those
3379 <dt><code>copy_str</code>
3382 <dd>This function is called by form library functions that
3383 allocate new field instances. It is expected to take a pile
3384 pointer, copy the pile to allocated storage, and return the
3385 address of the pile copy.</dd>
3387 <dt><code>free_str</code>
3390 <dd>This function is called by field- and type-deallocation
3391 routines in the library. It takes a pile pointer argument, and
3392 is expected to free the storage of that pile.</dd>
3395 <p>The <code>make_str</code> and <code>copy_str</code> functions
3396 may return NULL to signal allocation failure. The library
3397 routines will that call them will return error indication when
3398 this happens. Thus, your validation functions should never see a
3399 NULL file pointer and need not check specially for it.</p>
3401 <h3><a name="fcustorder" id="fcustorder">Order Functions For
3402 Custom Types</a></h3>
3404 <p>Some custom field types are simply ordered in the same
3405 well-defined way that <code>TYPE_ENUM</code> is. For such types,
3406 it is possible to define successor and predecessor functions to
3407 support the <code>REQ_NEXT_CHOICE</code> and
3408 <code>REQ_PREV_CHOICE</code> requests. Here is how:</p>
3411 typedef int (*INTHOOK)(); /* pointer to function returning int */
3413 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3414 INTHOOK succ, /* get successor value */
3415 INTHOOK pred); /* get predecessor value */
3418 <p>The successor and predecessor arguments will each be passed
3419 two arguments; a field pointer, and a pile pointer (as for the
3420 validation functions). They are expected to use the function
3421 <code>field_buffer()</code> to read the current value, and
3422 <code>set_field_buffer()</code> on buffer 0 to set the next or
3423 previous value. Either hook may return TRUE to indicate success
3424 (a legal next or previous value was set) or FALSE to indicate
3427 <h3><a name="fcustprobs" id="fcustprobs">Avoiding Problems</a></h3>
3429 <p>The interface for defining custom types is complicated and
3430 tricky. Rather than attempting to create a custom type entirely
3431 from scratch, you should start by studying the library source
3432 code for whichever of the pre-defined types seems to be closest
3433 to what you want.</p>
3435 <p>Use that code as a model, and evolve it towards what you
3436 really want. You will avoid many problems and annoyances that
3437 way. The code in the <code>ncurses</code> library has been
3438 specifically exempted from the package copyright to support
3441 <p>If your custom type defines order functions, have do something
3442 intuitive with a blank field. A useful convention is to make the
3443 successor of a blank field the types minimum value, and its
3444 predecessor the maximum.</p>