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38 <title>Writing Programs with NCURSES</title>
39 <link rel="author" href="mailto:bugs-ncurses@gnu.org">
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45 <h1>Writing Programs with NCURSES</h1>
48 by Eric S. Raymond and Zeyd M. Ben-Halim<br>
49 updates since release 1.9.9e by Thomas Dickey
56 <a href="#introduction">Introduction</a>
59 <li><a href="#history">A Brief History of Curses</a></li>
61 <li><a href="#scope">Scope of This Document</a></li>
63 <li><a href="#terminology">Terminology</a></li>
68 <a href="#curses">The Curses Library</a>
72 <a href="#overview">An Overview of Curses</a>
75 <li><a href="#compiling">Compiling Programs using
78 <li><a href="#updating">Updating the Screen</a></li>
80 <li><a href="#stdscr">Standard Windows and Function
81 Naming Conventions</a></li>
83 <li><a href="#variables">Variables</a></li>
88 <a href="#using">Using the Library</a>
91 <li><a href="#starting">Starting up</a></li>
93 <li><a href="#output">Output</a></li>
95 <li><a href="#input">Input</a></li>
97 <li><a href="#formschars">Using Forms Characters</a></li>
99 <li><a href="#attributes">Character Attributes and
102 <li><a href="#mouse">Mouse Interfacing</a></li>
104 <li><a href="#finishing">Finishing Up</a></li>
109 <a href="#functions">Function Descriptions</a>
112 <li><a href="#init">Initialization and Wrapup</a></li>
114 <li><a href="#flush">Causing Output to the Terminal</a></li>
116 <li><a href="#lowlevel">Low-Level Capability Access</a></li>
118 <li><a href="#debugging">Debugging</a></li>
123 <a href="#hints">Hints, Tips, and Tricks</a>
126 <li><a href="#caution">Some Notes of Caution</a></li>
128 <li><a href="#leaving">Temporarily Leaving ncurses
131 <li><a href="#xterm">Using <code>ncurses</code> under
132 <code>xterm</code></a></li>
134 <li><a href="#screens">Handling Multiple Terminal
137 <li><a href="#testing">Testing for Terminal
138 Capabilities</a></li>
140 <li><a href="#tuning">Tuning for Speed</a></li>
142 <li><a href="#special">Special Features of
143 <code>ncurses</code></a></li>
148 <a href="#compat">Compatibility with Older Versions</a>
151 <li><a href="#refbug">Refresh of Overlapping
154 <li><a href="#backbug">Background Erase</a></li>
158 <li><a href="#xsifuncs">XSI Curses Conformance</a></li>
163 <a href="#panels">The Panels Library</a>
166 <li><a href="#pcompile">Compiling With the Panels
169 <li><a href="#poverview">Overview of Panels</a></li>
171 <li><a href="#pstdscr">Panels, Input, and the Standard
174 <li><a href="#hiding">Hiding Panels</a></li>
176 <li><a href="#pmisc">Miscellaneous Other Facilities</a></li>
181 <a href="#menu">The Menu Library</a>
184 <li><a href="#mcompile">Compiling with the menu Library</a></li>
186 <li><a href="#moverview">Overview of Menus</a></li>
188 <li><a href="#mselect">Selecting items</a></li>
190 <li><a href="#mdisplay">Menu Display</a></li>
192 <li><a href="#mwindows">Menu Windows</a></li>
194 <li><a href="#minput">Processing Menu Input</a></li>
196 <li><a href="#mmisc">Miscellaneous Other Features</a></li>
201 <a href="#form">The Forms Library</a>
204 <li><a href="#fcompile">Compiling with the forms
207 <li><a href="#foverview">Overview of Forms</a></li>
209 <li><a href="#fcreate">Creating and Freeing Fields and
213 <a href="#fattributes">Fetching and Changing Field
217 <li><a href="#fsizes">Fetching Size and Location
220 <li><a href="#flocation">Changing the Field
223 <li><a href="#fjust">The Justification Attribute</a></li>
225 <li><a href="#fdispatts">Field Display Attributes</a></li>
227 <li><a href="#foptions">Field Option Bits</a></li>
229 <li><a href="#fstatus">Field Status</a></li>
231 <li><a href="#fuser">Field User Pointer</a></li>
235 <li><a href="#fdynamic">Variable-Sized Fields</a></li>
238 <a href="#fvalidation">Field Validation</a>
241 <li><a href="#ftype_alpha">TYPE_ALPHA</a></li>
243 <li><a href="#ftype_alnum">TYPE_ALNUM</a></li>
245 <li><a href="#ftype_enum">TYPE_ENUM</a></li>
247 <li><a href="#ftype_integer">TYPE_INTEGER</a></li>
249 <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li>
251 <li><a href="#ftype_regexp">TYPE_REGEXP</a></li>
255 <li><a href="#fbuffer">Direct Field Buffer Manipulation</a></li>
257 <li><a href="#formattrs">Attributes of Forms</a></li>
259 <li><a href="#fdisplay">Control of Form Display</a></li>
262 <a href="#fdriver">Input Processing in the Forms
266 <li><a href="#fpage">Page Navigation Requests</a></li>
268 <li><a href="#ffield">Inter-Field Navigation
271 <li><a href="#fifield">Intra-Field Navigation
274 <li><a href="#fscroll">Scrolling Requests</a></li>
276 <li><a href="#fedit">Field Editing Requests</a></li>
278 <li><a href="#forder">Order Requests</a></li>
280 <li><a href="#fappcmds">Application Commands</a></li>
284 <li><a href="#fhooks">Field Change Hooks</a></li>
286 <li><a href="#ffocus">Field Change Commands</a></li>
288 <li><a href="#frmoptions">Form Options</a></li>
291 <a href="#fcustom">Custom Validation Types</a>
294 <li><a href="#flinktypes">Union Types</a></li>
296 <li><a href="#fnewtypes">New Field Types</a></li>
298 <li><a href="#fcheckargs">Validation Function
301 <li><a href="#fcustorder">Order Functions For Custom
304 <li><a href="#fcustprobs">Avoiding Problems</a></li>
313 <h1><a name="introduction" id="introduction">Introduction</a></h1>
315 <p>This document is an introduction to programming with
316 <code>curses</code>. It is not an exhaustive reference for the
317 curses Application Programming Interface (API); that role is
318 filled by the <code>curses</code> manual pages. Rather, it is
319 intended to help C programmers ease into using the package.</p>
321 <p>This document is aimed at C applications programmers not yet
322 specifically familiar with ncurses. If you are already an
323 experienced <code>curses</code> programmer, you should
324 nevertheless read the sections on <a href="#mouse">Mouse
325 Interfacing</a>, <a href="#debugging">Debugging</a>, <a href=
326 "#compat">Compatibility with Older Versions</a>, and <a href=
327 "#hints">Hints, Tips, and Tricks</a>. These will bring you up to
328 speed on the special features and quirks of the
329 <code>ncurses</code> implementation. If you are not so
330 experienced, keep reading.</p>
332 <p>The <code>curses</code> package is a subroutine library for
333 terminal-independent screen-painting and input-event handling
334 which presents a high level screen model to the programmer,
335 hiding differences between terminal types and doing automatic
336 optimization of output to change one screen full of text into
337 another. <code>Curses</code> uses terminfo, which is a database
338 format that can describe the capabilities of thousands of
339 different terminals.</p>
341 <p>The <code>curses</code> API may seem something of an archaism
342 on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk.
343 Nevertheless, UNIX still supports tty lines and X supports
344 <em>xterm(1)</em>; the <code>curses</code> API has the advantage
345 of (a) back-portability to character-cell terminals, and (b)
346 simplicity. For an application that does not require bit-mapped
347 graphics and multiple fonts, an interface implementation using
348 <code>curses</code> will typically be a great deal simpler and
349 less expensive than one using an X toolkit.</p>
351 <h2><a name="history" id="history">A Brief History of Curses</a></h2>
353 <p>Historically, the first ancestor of <code>curses</code> was
354 the routines written to provide screen-handling for the
355 <code>vi</code> editor; these used the <code>termcap</code>
356 database facility (both released in 3BSD) for describing terminal
357 capabilities. These routines were abstracted into a documented
358 library and first released with the early BSD UNIX versions. All
359 of this work was done by students at the University of California
360 (Berkeley campus). The curses library was first published in
361 4.0BSD, a year after 3BSD (i.e., late 1980).</p>
363 <p>After graduation, one of those students went to work at
364 AT&T Bell Labs, and made an improved <code>termcap</code>
365 library called <code>terminfo</code> (i.e.,
366 “libterm”), and adapted the curses library to use
367 this. That was subsequently released in System V Release 2 (early
368 1984). Thereafter, other developers added to the curses and
369 terminfo libraries. For instance, a student at Cornell University
370 wrote an improved terminfo library as well as a tool
371 (<code>tic</code>) to compile the terminal descriptions. As a
372 general rule, AT&T did not identify the developers in the
373 source-code or documentation; the <code>tic</code> and
374 <code>infocmp</code> programs are the exceptions.</p>
376 <p>System V Release 3 (System III UNIX) from Bell Labs featured a
377 rewritten and much-improved <code>curses</code> library, along
378 with the <code>tic</code> program (late 1986).</p>
380 <p>To recap, terminfo is based on Berkeley's termcap database,
381 but contains a number of improvements and extensions.
382 Parameterized capabilities strings were introduced, making it
383 possible to describe multiple video attributes, and colors and to
384 handle far more unusual terminals than possible with termcap. In
385 the later AT&T System V releases, <code>curses</code> evolved
386 to use more facilities and offer more capabilities, going far
387 beyond BSD curses in power and flexibility.</p>
389 <h2><a name="scope" id="scope">Scope of This Document</a></h2>
391 <p>This document describes <code>ncurses</code>, a free
392 implementation of the System V <code>curses</code> API with some
393 clearly marked extensions. It includes the following System V
397 <li>Support for multiple screen highlights (BSD curses could
398 only handle one “standout” highlight, usually
401 <li>Support for line- and box-drawing using forms
404 <li>Recognition of function keys on input.</li>
406 <li>Color support.</li>
408 <li>Support for pads (windows of larger than screen size on
409 which the screen or a subwindow defines a viewport).</li>
412 <p>Also, this package makes use of the insert and delete line and
413 character features of terminals so equipped, and determines how
414 to optimally use these features with no help from the programmer.
415 It allows arbitrary combinations of video attributes to be
416 displayed, even on terminals that leave “magic
417 cookies” on the screen to mark changes in attributes.</p>
419 <p>The <code>ncurses</code> package can also capture and use
420 event reports from a mouse in some environments (notably, xterm
421 under the X window system). This document includes tips for using
424 <p>The <code>ncurses</code> package was originated by Pavel
425 Curtis. The original maintainer of this package is <a href=
426 "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a>
427 <zmbenhal@netcom.com>. <a href=
428 "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a>
429 <esr@snark.thyrsus.com> wrote many of the new features in
430 versions after 1.8.1 and wrote most of this introduction.
431 Jürgen Pfeifer wrote all of the menu and forms code as well
432 as the <a href="http://www.adahome.com">Ada95</a> binding.
433 Ongoing work is being done by <a href=
434 "mailto:dickey@invisible-island.net">Thomas Dickey</a>
435 (maintainer). Contact the current maintainers at <a href=
436 "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p>
438 <p>This document also describes the <a href="#panels">panels</a>
439 extension library, similarly modeled on the SVr4 panels facility.
440 This library allows you to associate backing store with each of a
441 stack or deck of overlapping windows, and provides operations for
442 moving windows around in the stack that change their visibility
443 in the natural way (handling window overlaps).</p>
445 <p>Finally, this document describes in detail the <a href=
446 "#menu">menus</a> and <a href="#form">forms</a> extension
447 libraries, also cloned from System V, which support easy
448 construction and sequences of menus and fill-in forms.</p>
450 <h2><a name="terminology" id="terminology">Terminology</a></h2>
452 <p>In this document, the following terminology is used with
453 reasonable consistency:</p>
458 <dd>A data structure describing a sub-rectangle of the screen
459 (possibly the entire screen). You can write to a window as
460 though it were a miniature screen, scrolling independently of
461 other windows on the physical screen.</dd>
465 <dd>A subset of windows which are as large as the terminal
466 screen, i.e., they start at the upper left hand corner and
467 encompass the lower right hand corner. One of these,
468 <code>stdscr</code>, is automatically provided for the
471 <dt>terminal screen</dt>
473 <dd>The package's idea of what the terminal display currently
474 looks like, i.e., what the user sees now. This is a special
478 <h1><a name="curses" id="curses">The Curses Library</a></h1>
480 <h2><a name="overview" id="overview">An Overview of Curses</a></h2>
482 <h3><a name="compiling" id="compiling">Compiling Programs using
485 <p>In order to use the library, it is necessary to have certain
486 types and variables defined. Therefore, the programmer must have
490 #include <curses.h>
493 <p>at the top of the program source. The screen package uses the
494 Standard I/O library, so <code><curses.h></code> includes
495 <code><stdio.h></code>. <code><curses.h></code> also
496 includes <code><termios.h></code>,
497 <code><termio.h></code>, or <code><sgtty.h></code>
498 depending on your system. It is redundant (but harmless) for the
499 programmer to do these includes, too. In linking with
500 <code>curses</code> you need to have <code>-lncurses</code> in
501 your LDFLAGS or on the command line. There is no need for any
504 <h3><a name="updating" id="updating">Updating the Screen</a></h3>
506 <p>In order to update the screen optimally, it is necessary for
507 the routines to know what the screen currently looks like and
508 what the programmer wants it to look like next. For this purpose,
509 a data type (structure) named WINDOW is defined which describes a
510 window image to the routines, including its starting position on
511 the screen (the (y, x) coordinates of the upper left hand corner)
512 and its size. One of these (called <code>curscr</code>, for
513 current screen) is a screen image of what the terminal currently
514 looks like. Another screen (called <code>stdscr</code>, for
515 standard screen) is provided by default to make changes on.</p>
517 <p>A window is a purely internal representation. It is used to
518 build and store a potential image of a portion of the terminal.
519 It does not bear any necessary relation to what is really on the
520 terminal screen; it is more like a scratchpad or write
523 <p>To make the section of physical screen corresponding to a
524 window reflect the contents of the window structure, the routine
525 <code>refresh()</code> (or <code>wrefresh()</code> if the window
526 is not <code>stdscr</code>) is called.</p>
528 <p>A given physical screen section may be within the scope of any
529 number of overlapping windows. Also, changes can be made to
530 windows in any order, without regard to motion efficiency. Then,
531 at will, the programmer can effectively say “make it look
532 like this,” and let the package implementation determine
533 the most efficient way to repaint the screen.</p>
535 <h3><a name="stdscr" id="stdscr">Standard Windows and Function
536 Naming Conventions</a></h3>
538 <p>As hinted above, the routines can use several windows, but two
539 are automatically given: <code>curscr</code>, which knows what
540 the terminal looks like, and <code>stdscr</code>, which is what
541 the programmer wants the terminal to look like next. The user
542 should never actually access <code>curscr</code> directly.
543 Changes should be made to through the API, and then the routine
544 <code>refresh()</code> (or <code>wrefresh()</code>) called.</p>
546 <p>Many functions are defined to use <code>stdscr</code> as a
547 default screen. For example, to add a character to
548 <code>stdscr</code>, one calls <code>addch()</code> with the
549 desired character as argument. To write to a different window.
550 use the routine <code>waddch()</code> (for
551 <strong>w</strong>indow-specific addch()) is provided. This
552 convention of prepending function names with a “w”
553 when they are to be applied to specific windows is consistent.
554 The only routines which do not follow it are those for which a
555 window must always be specified.</p>
557 <p>In order to move the current (y, x) coordinates from one point
558 to another, the routines <code>move()</code> and
559 <code>wmove()</code> are provided. However, it is often desirable
560 to first move and then perform some I/O operation. In order to
561 avoid clumsiness, most I/O routines can be preceded by the prefix
562 “mv” and the desired (y, x) coordinates prepended to
563 the arguments to the function. For example, the calls</p>
570 <p>can be replaced by</p>
583 <p>can be replaced by</p>
586 mvwaddch(win, y, x, ch);
589 <p>Note that the window description pointer (win) comes before
590 the added (y, x) coordinates. If a function requires a window
591 pointer, it is always the first parameter passed.</p>
593 <h3><a name="variables" id="variables">Variables</a></h3>
595 <p>The <code>curses</code> library sets some variables describing
596 the terminal capabilities.</p>
599 type name description
600 ------------------------------------------------------------------
601 int LINES number of lines on the terminal
602 int COLS number of columns on the terminal
605 <p>The <code>curses.h</code> also introduces some
606 <code>#define</code> constants and types of general
610 <dt><code>bool</code>
613 <dd>boolean type, actually a “char” (e.g.,
614 <code>bool doneit;</code>)</dd>
616 <dt><code>TRUE</code>
619 <dd>boolean “true” flag (1).</dd>
621 <dt><code>FALSE</code>
624 <dd>boolean “false” flag (0).</dd>
629 <dd>error flag returned by routines on a failure (-1).</dd>
634 <dd>error flag returned by routines when things go right.</dd>
637 <h2><a name="using" id="using">Using the Library</a></h2>
639 <p>Now we describe how to actually use the screen package. In it,
640 we assume all updating, reading, etc. is applied to
641 <code>stdscr</code>. These instructions will work on any window,
642 providing you change the function names and parameters as
645 <p>Here is a sample program to motivate the discussion:</p>
648 #include <stdlib.h>
649 #include <curses.h>
650 #include <signal.h>
652 static void finish(int sig);
655 main(int argc, char *argv[])
659 /* initialize your non-curses data structures here */
661 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
663 (void) initscr(); /* initialize the curses library */
664 keypad(stdscr, TRUE); /* enable keyboard mapping */
665 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
666 (void) cbreak(); /* take input chars one at a time, no wait for \n */
667 (void) echo(); /* echo input - in color */
674 * Simple color assignment, often all we need. Color pair 0 cannot
675 * be redefined. This example uses the same value for the color
676 * pair as for the foreground color, though of course that is not
679 init_pair(1, COLOR_RED, COLOR_BLACK);
680 init_pair(2, COLOR_GREEN, COLOR_BLACK);
681 init_pair(3, COLOR_YELLOW, COLOR_BLACK);
682 init_pair(4, COLOR_BLUE, COLOR_BLACK);
683 init_pair(5, COLOR_CYAN, COLOR_BLACK);
684 init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
685 init_pair(7, COLOR_WHITE, COLOR_BLACK);
690 int c = getch(); /* refresh, accept single keystroke of input */
691 attrset(COLOR_PAIR(num % 8));
694 /* process the command keystroke */
697 finish(0); /* we are done */
700 static void finish(int sig)
704 /* do your non-curses wrapup here */
710 <h3><a name="starting" id="starting">Starting up</a></h3>
712 <p>In order to use the screen package, the routines must know
713 about terminal characteristics, and the space for
714 <code>curscr</code> and <code>stdscr</code> must be allocated.
715 These function <code>initscr()</code> does both these things.
716 Since it must allocate space for the windows, it can overflow
717 memory when attempting to do so. On the rare occasions this
718 happens, <code>initscr()</code> will terminate the program with
719 an error message. <code>initscr()</code> must always be called
720 before any of the routines which affect windows are used. If it
721 is not, the program will core dump as soon as either
722 <code>curscr</code> or <code>stdscr</code> are referenced.
723 However, it is usually best to wait to call it until after you
724 are sure you will need it, like after checking for startup
725 errors. Terminal status changing routines like <code>nl()</code>
726 and <code>cbreak()</code> should be called after
727 <code>initscr()</code>.</p>
729 <p>Once the screen windows have been allocated, you can set them
730 up for your program. If you want to, say, allow a screen to
731 scroll, use <code>scrollok()</code>. If you want the cursor to be
732 left in place after the last change, use <code>leaveok()</code>.
733 If this is not done, <code>refresh()</code> will move the cursor
734 to the window's current (y, x) coordinates after updating it.</p>
736 <p>You can create new windows of your own using the functions
737 <code>newwin()</code>, <code>derwin()</code>, and
738 <code>subwin()</code>. The routine <code>delwin()</code> will
739 allow you to get rid of old windows. All the options described
740 above can be applied to any window.</p>
742 <h3><a name="output" id="output">Output</a></h3>
744 <p>Now that we have set things up, we will want to actually
745 update the terminal. The basic functions used to change what will
746 go on a window are <code>addch()</code> and <code>move()</code>.
747 <code>addch()</code> adds a character at the current (y, x)
748 coordinates. <code>move()</code> changes the current (y, x)
749 coordinates to whatever you want them to be. It returns
750 <code>ERR</code> if you try to move off the window. As mentioned
751 above, you can combine the two into <code>mvaddch()</code> to do
752 both things at once.</p>
754 <p>The other output functions, such as <code>addstr()</code> and
755 <code>printw()</code>, all call <code>addch()</code> to add
756 characters to the window.</p>
758 <p>After you have put on the window what you want there, when you
759 want the portion of the terminal covered by the window to be made
760 to look like it, you must call <code>refresh()</code>. In order
761 to optimize finding changes, <code>refresh()</code> assumes that
762 any part of the window not changed since the last
763 <code>refresh()</code> of that window has not been changed on the
764 terminal, i.e., that you have not refreshed a portion of the
765 terminal with an overlapping window. If this is not the case, the
766 routine <code>touchwin()</code> is provided to make it look like
767 the entire window has been changed, thus making
768 <code>refresh()</code> check the whole subsection of the terminal
771 <p>If you call <code>wrefresh()</code> with <code>curscr</code>
772 as its argument, it will make the screen look like
773 <code>curscr</code> thinks it looks like. This is useful for
774 implementing a command which would redraw the screen in case it
777 <h3><a name="input" id="input">Input</a></h3>
779 <p>The complementary function to <code>addch()</code> is
780 <code>getch()</code> which, if echo is set, will call
781 <code>addch()</code> to echo the character. Since the screen
782 package needs to know what is on the terminal at all times, if
783 characters are to be echoed, the tty must be in raw or cbreak
784 mode. Since initially the terminal has echoing enabled and is in
785 ordinary “cooked” mode, one or the other has to
786 changed before calling <code>getch()</code>; otherwise, the
787 program's output will be unpredictable.</p>
789 <p>When you need to accept line-oriented input in a window, the
790 functions <code>wgetstr()</code> and friends are available. There
791 is even a <code>wscanw()</code> function that can do
792 <code>scanf()</code>(3)-style multi-field parsing on window
793 input. These pseudo-line-oriented functions turn on echoing while
796 <p>The example code above uses the call <code>keypad(stdscr,
797 TRUE)</code> to enable support for function-key mapping. With
798 this feature, the <code>getch()</code> code watches the input
799 stream for character sequences that correspond to arrow and
800 function keys. These sequences are returned as pseudo-character
801 values. The <code>#define</code> values returned are listed in
802 the <code>curses.h</code> The mapping from sequences to
803 <code>#define</code> values is determined by <code>key_</code>
804 capabilities in the terminal's terminfo entry.</p>
806 <h3><a name="formschars" id="formschars">Using Forms
809 <p>The <code>addch()</code> function (and some others, including
810 <code>box()</code> and <code>border()</code>) can accept some
811 pseudo-character arguments which are specially defined by
812 <code>ncurses</code>. These are <code>#define</code> values set
813 up in the <code>curses.h</code> header; see there for a complete
814 list (look for the prefix <code>ACS_</code>).</p>
816 <p>The most useful of the ACS defines are the forms-drawing
817 characters. You can use these to draw boxes and simple graphs on
818 the screen. If the terminal does not have such characters,
819 <code>curses.h</code> will map them to a recognizable (though
820 ugly) set of ASCII defaults.</p>
822 <h3><a name="attributes" id="attributes">Character Attributes and
825 <p>The <code>ncurses</code> package supports screen highlights
826 including standout, reverse-video, underline, and blink. It also
827 supports color, which is treated as another kind of
830 <p>Highlights are encoded, internally, as high bits of the
831 pseudo-character type (<code>chtype</code>) that
832 <code>curses.h</code> uses to represent the contents of a screen
833 cell. See the <code>curses.h</code> header file for a complete
834 list of highlight mask values (look for the prefix
835 <code>A_</code>).</p>
837 <p>There are two ways to make highlights. One is to logical-or
838 the value of the highlights you want into the character argument
839 of an <code>addch()</code> call, or any other output call that
840 takes a <code>chtype</code> argument.</p>
842 <p>The other is to set the current-highlight value. This is
843 <em>logical-OR</em>ed with any highlight you specify the first
844 way. You do this with the functions <code>attron()</code>,
845 <code>attroff()</code>, and <code>attrset()</code>; see the
846 manual pages for details. Color is a special kind of highlight.
847 The package actually thinks in terms of color pairs, combinations
848 of foreground and background colors. The sample code above sets
849 up eight color pairs, all of the guaranteed-available colors on
850 black. Note that each color pair is, in effect, given the name of
851 its foreground color. Any other range of eight non-conflicting
852 values could have been used as the first arguments of the
853 <code>init_pair()</code> values.</p>
855 <p>Once you have done an <code>init_pair()</code> that creates
856 color-pair N, you can use <code>COLOR_PAIR(N)</code> as a
857 highlight that invokes that particular color combination. Note
858 that <code>COLOR_PAIR(N)</code>, for constant N, is itself a
859 compile-time constant and can be used in initializers.</p>
861 <h3><a name="mouse" id="mouse">Mouse Interfacing</a></h3>
863 <p>The <code>ncurses</code> library also provides a mouse
867 <strong>NOTE:</strong> this facility is specific to
868 <code>ncurses</code>, it is not part of either the XSI Curses
869 standard, nor of System V Release 4, nor BSD curses. System V
870 Release 4 curses contains code with similar interface
871 definitions, however it is not documented. Other than by
872 disassembling the library, we have no way to determine exactly
873 how that mouse code works. Thus, we recommend that you wrap
874 mouse-related code in an #ifdef using the feature macro
875 NCURSES_MOUSE_VERSION so it will not be compiled and linked on
879 <p>Presently, mouse event reporting works in the following
883 <li>xterm and similar programs such as rxvt.</li>
885 <li>Linux console, when configured with <code>gpm</code>(1),
886 Alessandro Rubini's mouse server.</li>
888 <li>FreeBSD sysmouse (console)</li>
893 <p>The mouse interface is very simple. To activate it, you use
894 the function <code>mousemask()</code>, passing it as first
895 argument a bit-mask that specifies what kinds of events you want
896 your program to be able to see. It will return the bit-mask of
897 events that actually become visible, which may differ from the
898 argument if the mouse device is not capable of reporting some of
899 the event types you specify.</p>
901 <p>Once the mouse is active, your application's command loop
902 should watch for a return value of <code>KEY_MOUSE</code> from
903 <code>wgetch()</code>. When you see this, a mouse event report
904 has been queued. To pick it off the queue, use the function
905 <code>getmouse()</code> (you must do this before the next
906 <code>wgetch()</code>, otherwise another mouse event might come
907 in and make the first one inaccessible).</p>
909 <p>Each call to <code>getmouse()</code> fills a structure (the
910 address of which you will pass it) with mouse event data. The
911 event data includes zero-origin, screen-relative character-cell
912 coordinates of the mouse pointer. It also includes an event mask.
913 Bits in this mask will be set, corresponding to the event type
916 <p>The mouse structure contains two additional fields which may
917 be significant in the future as ncurses interfaces to new kinds
918 of pointing device. In addition to x and y coordinates, there is
919 a slot for a z coordinate; this might be useful with
920 touch-screens that can return a pressure or duration parameter.
921 There is also a device ID field, which could be used to
922 distinguish between multiple pointing devices.</p>
924 <p>The class of visible events may be changed at any time via
925 <code>mousemask()</code>. Events that can be reported include
926 presses, releases, single-, double- and triple-clicks (you can
927 set the maximum button-down time for clicks). If you do not make
928 clicks visible, they will be reported as press-release pairs. In
929 some environments, the event mask may include bits reporting the
930 state of shift, alt, and ctrl keys on the keyboard during the
933 <p>A function to check whether a mouse event fell within a given
934 window is also supplied. You can use this to see whether a given
935 window should consider a mouse event relevant to it.</p>
937 <p>Because mouse event reporting will not be available in all
938 environments, it would be unwise to build <code>ncurses</code>
939 applications that <em>require</em> the use of a mouse. Rather,
940 you should use the mouse as a shortcut for point-and-shoot
941 commands your application would normally accept from the
942 keyboard. Two of the test games in the <code>ncurses</code>
943 distribution (<code>bs</code> and <code>knight</code>) contain
944 code that illustrates how this can be done.</p>
946 <p>See the manual page <code>curs_mouse(3X)</code> for full
947 details of the mouse-interface functions.</p>
949 <h3><a name="finishing" id="finishing">Finishing Up</a></h3>
951 <p>In order to clean up after the <code>ncurses</code> routines,
952 the routine <code>endwin()</code> is provided. It restores tty
953 modes to what they were when <code>initscr()</code> was first
954 called, and moves the cursor down to the lower-left corner. Thus,
955 anytime after the call to initscr, <code>endwin()</code> should
956 be called before exiting.</p>
958 <h2><a name="functions" id="functions">Function Descriptions</a></h2>
960 <p>We describe the detailed behavior of some important curses
961 functions here, as a supplement to the manual page
964 <h3><a name="init" id="init">Initialization and Wrapup</a></h3>
967 <dt><code>initscr()</code>
970 <dd>The first function called should almost always be
971 <code>initscr()</code>. This will determine the terminal type
972 and initialize curses data structures. <code>initscr()</code>
973 also arranges that the first call to <code>refresh()</code>
974 will clear the screen. If an error occurs a message is written
975 to standard error and the program exits. Otherwise it returns a
976 pointer to stdscr. A few functions may be called before initscr
977 (<code>slk_init()</code>, <code>filter()</code>,
978 <code>ripoffline()</code>, <code>use_env()</code>, and, if you
979 are using multiple terminals, <code>newterm()</code>.)</dd>
981 <dt><code>endwin()</code>
984 <dd>Your program should always call <code>endwin()</code>
985 before exiting or shelling out of the program. This function
986 will restore tty modes, move the cursor to the lower left
987 corner of the screen, reset the terminal into the proper
988 non-visual mode. Calling <code>refresh()</code> or
989 <code>doupdate()</code> after a temporary escape from the
990 program will restore the ncurses screen from before the
993 <dt><code>newterm(type, ofp, ifp)</code>
996 <dd>A program which outputs to more than one terminal should
997 use <code>newterm()</code> instead of <code>initscr()</code>.
998 <code>newterm()</code> should be called once for each terminal.
999 It returns a variable of type <code>SCREEN *</code> which
1000 should be saved as a reference to that terminal. (NOTE: a
1001 SCREEN variable is not a <em>screen</em> in the sense we are
1002 describing in this introduction, but a collection of parameters
1003 used to assist in optimizing the display.) The arguments are
1004 the type of the terminal (a string) and <code>FILE</code>
1005 pointers for the output and input of the terminal. If type is
1006 NULL then the environment variable <code>$TERM</code> is used.
1007 <code>endwin()</code> should called once at wrapup time for
1008 each terminal opened using this function.</dd>
1010 <dt><code>set_term(new)</code>
1013 <dd>This function is used to switch to a different terminal
1014 previously opened by <code>newterm()</code>. The screen
1015 reference for the new terminal is passed as the parameter. The
1016 previous terminal is returned by the function. All other calls
1017 affect only the current terminal.</dd>
1019 <dt><code>delscreen(sp)</code>
1022 <dd>The inverse of <code>newterm()</code>; deallocates the data
1023 structures associated with a given <code>SCREEN</code>
1027 <h3><a name="flush" id="flush">Causing Output to the Terminal</a></h3>
1030 <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt>
1032 <dd>These functions must be called to actually get any output
1033 on the terminal, as other routines merely manipulate data
1034 structures. <code>wrefresh()</code> copies the named window to
1035 the physical terminal screen, taking into account what is
1036 already there in order to do optimizations.
1037 <code>refresh()</code> does a refresh of <code>stdscr</code>.
1038 Unless <code>leaveok()</code> has been enabled, the physical
1039 cursor of the terminal is left at the location of the window's
1042 <dt><code>doupdate()</code> and
1043 <code>wnoutrefresh(win)</code></dt>
1045 <dd>These two functions allow multiple updates with more
1046 efficiency than wrefresh. To use them, it is important to
1047 understand how curses works. In addition to all the window
1048 structures, curses keeps two data structures representing the
1049 terminal screen: a physical screen, describing what is actually
1050 on the screen, and a virtual screen, describing what the
1051 programmer wants to have on the screen. wrefresh works by first
1052 copying the named window to the virtual screen
1053 (<code>wnoutrefresh()</code>), and then calling the routine to
1054 update the screen (<code>doupdate()</code>). If the programmer
1055 wishes to output several windows at once, a series of calls to
1056 <code>wrefresh</code> will result in alternating calls to
1057 <code>wnoutrefresh()</code> and <code>doupdate()</code>,
1058 causing several bursts of output to the screen. By calling
1059 <code>wnoutrefresh()</code> for each window, it is then
1060 possible to call <code>doupdate()</code> once, resulting in
1061 only one burst of output, with fewer total characters
1062 transmitted (this also avoids a visually annoying flicker at
1066 <h3><a name="lowlevel" id="lowlevel">Low-Level Capability
1070 <dt><code>setupterm(term, filenum, errret)</code>
1074 This routine is called to initialize a terminal's
1075 description, without setting up the curses screen structures
1076 or changing the tty-driver mode bits. <code>term</code> is
1077 the character string representing the name of the terminal
1078 being used. <code>filenum</code> is the UNIX file descriptor
1079 of the terminal to be used for output. <code>errret</code> is
1080 a pointer to an integer, in which a success or failure
1081 indication is returned. The values returned can be 1 (all is
1082 well), 0 (no such terminal), or -1 (some problem locating the
1085 <p>The value of <code>term</code> can be given as NULL, which
1086 will cause the value of <code>TERM</code> in the environment
1087 to be used. The <code>errret</code> pointer can also be given
1088 as NULL, meaning no error code is wanted. If
1089 <code>errret</code> is defaulted, and something goes wrong,
1090 <code>setupterm()</code> will print an appropriate error
1091 message and exit, rather than returning. Thus, a simple
1092 program can call setupterm(0, 1, 0) and not worry about
1093 initialization errors.</p>
1095 <p>After the call to <code>setupterm()</code>, the global
1096 variable <code>cur_term</code> is set to point to the current
1097 structure of terminal capabilities. By calling
1098 <code>setupterm()</code> for each terminal, and saving and
1099 restoring <code>cur_term</code>, it is possible for a program
1100 to use two or more terminals at once.
1101 <code>Setupterm()</code> also stores the names section of the
1102 terminal description in the global character array
1103 <code>ttytype[]</code>. Subsequent calls to
1104 <code>setupterm()</code> will overwrite this array, so you
1105 will have to save it yourself if need be.</p>
1109 <h3><a name="debugging" id="debugging">Debugging</a></h3>
1112 <strong>NOTE:</strong> These functions are not part of the
1113 standard curses API!
1117 <dt><code>trace()</code>
1120 <dd>This function can be used to explicitly set a trace level.
1121 If the trace level is nonzero, execution of your program will
1122 generate a file called “trace” in the current
1123 working directory containing a report on the library's actions.
1124 Higher trace levels enable more detailed (and verbose)
1125 reporting -- see comments attached to <code>TRACE_</code>
1126 defines in the <code>curses.h</code> file for details. (It is
1127 also possible to set a trace level by assigning a trace level
1128 value to the environment variable
1129 <code>NCURSES_TRACE</code>).</dd>
1131 <dt><code>_tracef()</code>
1134 <dd>This function can be used to output your own debugging
1135 information. It is only available only if you link with
1136 -lncurses_g. It can be used the same way as
1137 <code>printf()</code>, only it outputs a newline after the end
1138 of arguments. The output goes to a file called
1139 <code>trace</code> in the current directory.</dd>
1142 <p>Trace logs can be difficult to interpret due to the sheer
1143 volume of data dumped in them. There is a script called
1144 <strong>tracemunch</strong> included with the
1145 <code>ncurses</code> distribution that can alleviate this problem
1146 somewhat; it compacts long sequences of similar operations into
1147 more succinct single-line pseudo-operations. These pseudo-ops can
1148 be distinguished by the fact that they are named in capital
1151 <h2><a name="hints" id="hints">Hints, Tips, and Tricks</a></h2>
1153 <p>The <code>ncurses</code> manual pages are a complete reference
1154 for this library. In the remainder of this document, we discuss
1155 various useful methods that may not be obvious from the manual
1156 page descriptions.</p>
1158 <h3><a name="caution" id="caution">Some Notes of Caution</a></h3>
1160 <p>If you find yourself thinking you need to use
1161 <code>noraw()</code> or <code>nocbreak()</code>, think again and
1162 move carefully. It is probably better design to use
1163 <code>getstr()</code> or one of its relatives to simulate cooked
1164 mode. The <code>noraw()</code> and <code>nocbreak()</code>
1165 functions try to restore cooked mode, but they may end up
1166 clobbering some control bits set before you started your
1167 application. Also, they have always been poorly documented, and
1168 are likely to hurt your application's usability with other curses
1171 <p>Bear in mind that <code>refresh()</code> is a synonym for
1172 <code>wrefresh(stdscr)</code>. Do not try to mix use of
1173 <code>stdscr</code> with use of windows declared by
1174 <code>newwin()</code>; a <code>refresh()</code> call will blow
1175 them off the screen. The right way to handle this is to use
1176 <code>subwin()</code>, or not touch <code>stdscr</code> at all
1177 and tile your screen with declared windows which you then
1178 <code>wnoutrefresh()</code> somewhere in your program event loop,
1179 with a single <code>doupdate()</code> call to trigger actual
1182 <p>You are much less likely to run into problems if you design
1183 your screen layouts to use tiled rather than overlapping windows.
1184 Historically, curses support for overlapping windows has been
1185 weak, fragile, and poorly documented. The <code>ncurses</code>
1186 library is not yet an exception to this rule.</p>
1188 <p>There is a panels library included in the <code>ncurses</code>
1189 distribution that does a pretty good job of strengthening the
1190 overlapping-windows facilities.</p>
1192 <p>Try to avoid using the global variables LINES and COLS. Use
1193 <code>getmaxyx()</code> on the <code>stdscr</code> context
1194 instead. Reason: your code may be ported to run in an environment
1195 with window resizes, in which case several screens could be open
1196 with different sizes.</p>
1198 <h3><a name="leaving" id="leaving">Temporarily Leaving NCURSES
1201 <p>Sometimes you will want to write a program that spends most of
1202 its time in screen mode, but occasionally returns to ordinary
1203 “cooked” mode. A common reason for this is to support
1204 shell-out. This behavior is simple to arrange in
1205 <code>ncurses</code>.</p>
1207 <p>To leave <code>ncurses</code> mode, call <code>endwin()</code>
1208 as you would if you were intending to terminate the program. This
1209 will take the screen back to cooked mode; you can do your
1210 shell-out. When you want to return to <code>ncurses</code> mode,
1211 simply call <code>refresh()</code> or <code>doupdate()</code>.
1212 This will repaint the screen.</p>
1214 <p>There is a boolean function, <code>isendwin()</code>, which
1215 code can use to test whether <code>ncurses</code> screen mode is
1216 active. It returns <code>TRUE</code> in the interval between an
1217 <code>endwin()</code> call and the following
1218 <code>refresh()</code>, <code>FALSE</code> otherwise.</p>
1220 <p>Here is some sample code for shellout:</p>
1223 addstr("Shelling out...");
1224 def_prog_mode(); /* save current tty modes */
1225 endwin(); /* restore original tty modes */
1226 system("sh"); /* run shell */
1227 addstr("returned.\n"); /* prepare return message */
1228 refresh(); /* restore save modes, repaint screen */
1231 <h3><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h3>
1233 <p>A resize operation in X sends <code>SIGWINCH</code> to the
1234 application running under xterm. The easiest way to handle
1235 <code>SIGWINCH</code> is to do an <code>endwin</code>, followed
1236 by an <code>refresh</code> and a screen repaint you code
1237 yourself. The <code>refresh</code> will pick up the new screen
1238 size from the xterm's environment.</p>
1240 <p>That is the standard way, of course (it even works with some
1241 vendor's curses implementations). Its drawback is that it clears
1242 the screen to reinitialize the display, and does not resize
1243 subwindows which must be shrunk. <code>Ncurses</code> provides an
1244 extension which works better, the <code>resizeterm</code>
1245 function. That function ensures that all windows are limited to
1246 the new screen dimensions, and pads <code>stdscr</code> with
1247 blanks if the screen is larger.</p>
1249 <p>The <code>ncurses</code> library provides a SIGWINCH signal
1250 handler, which pushes a <code>KEY_RESIZE</code> via the wgetch()
1251 calls. When <code>ncurses</code> returns that code, it calls
1252 <code>resizeterm</code> to update the size of the standard
1253 screen's window, repainting that (filling with blanks or
1254 truncating as needed). It also resizes other windows, but its
1255 effect may be less satisfactory because it cannot know how you
1256 want the screen re-painted. You will usually have to write
1257 special-purpose code to handle <code>KEY_RESIZE</code>
1260 <h3><a name="screens" id="screens">Handling Multiple Terminal
1263 <p>The <code>initscr()</code> function actually calls a function
1264 named <code>newterm()</code> to do most of its work. If you are
1265 writing a program that opens multiple terminals, use
1266 <code>newterm()</code> directly.</p>
1268 <p>For each call, you will have to specify a terminal type and a
1269 pair of file pointers; each call will return a screen reference,
1270 and <code>stdscr</code> will be set to the last one allocated.
1271 You will switch between screens with the <code>set_term</code>
1272 call. Note that you will also have to call
1273 <code>def_shell_mode</code> and <code>def_prog_mode</code> on
1274 each tty yourself.</p>
1276 <h3><a name="testing" id="testing">Testing for Terminal
1277 Capabilities</a></h3>
1279 <p>Sometimes you may want to write programs that test for the
1280 presence of various capabilities before deciding whether to go
1281 into <code>ncurses</code> mode. An easy way to do this is to call
1282 <code>setupterm()</code>, then use the functions
1283 <code>tigetflag()</code>, <code>tigetnum()</code>, and
1284 <code>tigetstr()</code> to do your testing.</p>
1286 <p>A particularly useful case of this often comes up when you
1287 want to test whether a given terminal type should be treated as
1288 “smart” (cursor-addressable) or “stupid”.
1289 The right way to test this is to see if the return value of
1290 <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can
1291 include the <code>term.h</code> file and test the value of the
1292 macro <code>cursor_address</code>.</p>
1294 <h3><a name="tuning" id="tuning">Tuning for Speed</a></h3>
1296 <p>Use the <code>addchstr()</code> family of functions for fast
1297 screen-painting of text when you know the text does not contain
1298 any control characters. Try to make attribute changes infrequent
1299 on your screens. Do not use the <code>immedok()</code>
1302 <h3><a name="special" id="special">Special Features of
1305 <p>The <code>wresize()</code> function allows you to resize a
1306 window in place. The associated <code>resizeterm()</code>
1307 function simplifies the construction of <a href=
1308 "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p>
1310 <p>The <code>define_key()</code> function allows you to define at
1311 runtime function-key control sequences which are not in the
1312 terminal description. The <code>keyok()</code> function allows
1313 you to temporarily enable or disable interpretation of any
1314 function-key control sequence.</p>
1316 <p>The <code>use_default_colors()</code> function allows you to
1317 construct applications which can use the terminal's default
1318 foreground and background colors as an additional "default"
1319 color. Several terminal emulators support this feature, which is
1320 based on ISO 6429.</p>
1322 <p>Ncurses supports up 16 colors, unlike SVr4 curses which
1323 defines only 8. While most terminals which provide color allow
1324 only 8 colors, about a quarter (including XFree86 xterm) support
1327 <h2><a name="compat" id="compat">Compatibility with Older
1330 <p>Despite our best efforts, there are some differences between
1331 <code>ncurses</code> and the (undocumented!) behavior of older
1332 curses implementations. These arise from ambiguities or omissions
1333 in the documentation of the API.</p>
1335 <h3><a name="refbug" id="refbug">Refresh of Overlapping
1338 <p>If you define two windows A and B that overlap, and then
1339 alternately scribble on and refresh them, the changes made to the
1340 overlapping region under historic <code>curses</code> versions
1341 were often not documented precisely.</p>
1343 <p>To understand why this is a problem, remember that screen
1344 updates are calculated between two representations of the
1345 <em>entire</em> display. The documentation says that when you
1346 refresh a window, it is first copied to the virtual screen, and
1347 then changes are calculated to update the physical screen (and
1348 applied to the terminal). But "copied to" is not very specific,
1349 and subtle differences in how copying works can produce different
1350 behaviors in the case where two overlapping windows are each
1351 being refreshed at unpredictable intervals.</p>
1353 <p>What happens to the overlapping region depends on what
1354 <code>wnoutrefresh()</code> does with its argument -- what
1355 portions of the argument window it copies to the virtual screen.
1356 Some implementations do "change copy", copying down only
1357 locations in the window that have changed (or been marked changed
1358 with <code>wtouchln()</code> and friends). Some implementations
1359 do "entire copy", copying <em>all</em> window locations to the
1360 virtual screen whether or not they have changed.</p>
1362 <p>The <code>ncurses</code> library itself has not always been
1363 consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a
1364 did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and
1365 newer, do change copy.</p>
1367 <p>For most commercial curses implementations, it is not
1368 documented and not known for sure (at least not to the
1369 <code>ncurses</code> maintainers) whether they do change copy or
1370 entire copy. We know that System V release 3 curses has logic in
1371 it that looks like an attempt to do change copy, but the
1372 surrounding logic and data representations are sufficiently
1373 complex, and our knowledge sufficiently indirect, that it is hard
1374 to know whether this is reliable. It is not clear what the SVr4
1375 documentation and XSI standard intend. The XSI Curses standard
1376 barely mentions wnoutrefresh(); the SVr4 documents seem to be
1377 describing entire-copy, but it is possible with some effort and
1378 straining to read them the other way.</p>
1380 <p>It might therefore be unwise to rely on either behavior in
1381 programs that might have to be linked with other curses
1382 implementations. Instead, you can do an explicit
1383 <code>touchwin()</code> before the <code>wnoutrefresh()</code>
1384 call to guarantee an entire-contents copy anywhere.</p>
1386 <p>The really clean way to handle this is to use the panels
1387 library. If, when you want a screen update, you do
1388 <code>update_panels()</code>, it will do all the necessary
1389 <code>wnoutrefresh()</code> calls for whatever panel stacking
1390 order you have defined. Then you can do one
1391 <code>doupdate()</code> and there will be a <em>single</em> burst
1392 of physical I/O that will do all your updates.</p>
1394 <h3><a name="backbug" id="backbug">Background Erase</a></h3>
1396 <p>If you have been using a very old versions of
1397 <code>ncurses</code> (1.8.7 or older) you may be surprised by the
1398 behavior of the erase functions. In older versions, erased areas
1399 of a window were filled with a blank modified by the window's
1400 current attribute (as set by <strong>wattrset()</strong>,
1401 <strong>wattron()</strong>, <strong>wattroff()</strong> and
1404 <p>In newer versions, this is not so. Instead, the attribute of
1405 erased blanks is normal unless and until it is modified by the
1406 functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p>
1408 <p>This change in behavior conforms <code>ncurses</code> to
1409 System V Release 4 and the XSI Curses standard.</p>
1411 <h2><a name="xsifuncs" id="xsifuncs">XSI Curses Conformance</a></h2>
1413 <p>The <code>ncurses</code> library is intended to be base-level
1414 conformant with the XSI Curses standard from X/Open. Many
1415 extended-level features (in fact, almost all features not
1416 directly concerned with wide characters and internationalization)
1417 are also supported.</p>
1419 <p>One effect of XSI conformance is the change in behavior
1420 described under <a href="#backbug">"Background Erase --
1421 Compatibility with Old Versions"</a>.</p>
1423 <p>Also, <code>ncurses</code> meets the XSI requirement that
1424 every macro entry point have a corresponding function which may
1425 be linked (and will be prototype-checked) if the macro definition
1426 is disabled with <code>#undef</code>.</p>
1428 <h1><a name="panels" id="panels">The Panels Library</a></h1>
1430 <p>The <code>ncurses</code> library by itself provides good
1431 support for screen displays in which the windows are tiled
1432 (non-overlapping). In the more general case that windows may
1433 overlap, you have to use a series of <code>wnoutrefresh()</code>
1434 calls followed by a <code>doupdate()</code>, and be careful about
1435 the order you do the window refreshes in. It has to be
1436 bottom-upwards, otherwise parts of windows that should be
1437 obscured will show through.</p>
1439 <p>When your interface design is such that windows may dive
1440 deeper into the visibility stack or pop to the top at runtime,
1441 the resulting book-keeping can be tedious and difficult to get
1442 right. Hence the panels library.</p>
1444 <p>The <code>panel</code> library first appeared in AT&T
1445 System V. The version documented here is the <code>panel</code>
1446 code distributed with <code>ncurses</code>.</p>
1448 <h2><a name="pcompile" id="pcompile">Compiling With the Panels
1451 <p>Your panels-using modules must import the panels library
1452 declarations with</p>
1455 #include <panel.h>
1458 <p>and must be linked explicitly with the panels library using an
1459 <code>-lpanel</code> argument. Note that they must also link the
1460 <code>ncurses</code> library with <code>-lncurses</code>. Many
1461 linkers are two-pass and will accept either order, but it is
1462 still good practice to put <code>-lpanel</code> first and
1463 <code>-lncurses</code> second.</p>
1465 <h2><a name="poverview" id="poverview">Overview of Panels</a></h2>
1467 <p>A panel object is a window that is implicitly treated as part
1468 of a <dfn>deck</dfn> including all other panel objects. The deck
1469 has an implicit bottom-to-top visibility order. The panels
1470 library includes an update function (analogous to
1471 <code>refresh()</code>) that displays all panels in the deck in
1472 the proper order to resolve overlaps. The standard window,
1473 <code>stdscr</code>, is considered below all panels.</p>
1475 <p>Details on the panels functions are available in the man
1476 pages. We will just hit the highlights here.</p>
1478 <p>You create a panel from a window by calling
1479 <code>new_panel()</code> on a window pointer. It then becomes the
1480 top of the deck. The panel's window is available as the value of
1481 <code>panel_window()</code> called with the panel pointer as
1484 <p>You can delete a panel (removing it from the deck) with
1485 <code>del_panel</code>. This will not deallocate the associated
1486 window; you have to do that yourself. You can replace a panel's
1487 window with a different window by calling
1488 <code>replace_window</code>. The new window may be of different
1489 size; the panel code will re-compute all overlaps. This operation
1490 does not change the panel's position in the deck.</p>
1492 <p>To move a panel's window, use <code>move_panel()</code>. The
1493 <code>mvwin()</code> function on the panel's window is not
1494 sufficient because it does not update the panels library's
1495 representation of where the windows are. This operation leaves
1496 the panel's depth, contents, and size unchanged.</p>
1498 <p>Two functions (<code>top_panel()</code>,
1499 <code>bottom_panel()</code>) are provided for rearranging the
1500 deck. The first pops its argument window to the top of the deck;
1501 the second sends it to the bottom. Either operation leaves the
1502 panel's screen location, contents, and size unchanged.</p>
1504 <p>The function <code>update_panels()</code> does all the
1505 <code>wnoutrefresh()</code> calls needed to prepare for
1506 <code>doupdate()</code> (which you must call yourself,
1509 <p>Typically, you will want to call <code>update_panels()</code>
1510 and <code>doupdate()</code> just before accepting command input,
1511 once in each cycle of interaction with the user. If you call
1512 <code>update_panels()</code> after each and every panel write,
1513 you will generate a lot of unnecessary refresh activity and
1516 <h2><a name="pstdscr" id="pstdscr">Panels, Input, and the
1517 Standard Screen</a></h2>
1519 <p>You should not mix <code>wnoutrefresh()</code> or
1520 <code>wrefresh()</code> operations with panels code; this will
1521 work only if the argument window is either in the top panel or
1522 unobscured by any other panels.</p>
1524 <p>The <code>stsdcr</code> window is a special case. It is
1525 considered below all panels. Because changes to panels may
1526 obscure parts of <code>stdscr</code>, though, you should call
1527 <code>update_panels()</code> before <code>doupdate()</code> even
1528 when you only change <code>stdscr</code>.</p>
1530 <p>Note that <code>wgetch</code> automatically calls
1531 <code>wrefresh</code>. Therefore, before requesting input from a
1532 panel window, you need to be sure that the panel is totally
1535 <p>There is presently no way to display changes to one obscured
1536 panel without repainting all panels.</p>
1538 <h2><a name="hiding" id="hiding">Hiding Panels</a></h2>
1540 <p>It is possible to remove a panel from the deck temporarily;
1541 use <code>hide_panel</code> for this. Use
1542 <code>show_panel()</code> to render it visible again. The
1543 predicate function <code>panel_hidden</code> tests whether or not
1544 a panel is hidden.</p>
1546 <p>The <code>panel_update</code> code ignores hidden panels. You
1547 cannot do <code>top_panel()</code> or <code>bottom_panel</code>
1548 on a hidden panel(). Other panels operations are applicable.</p>
1550 <h2><a name="pmisc" id="pmisc">Miscellaneous Other Facilities</a></h2>
1552 <p>It is possible to navigate the deck using the functions
1553 <code>panel_above()</code> and <code>panel_below</code>. Handed a
1554 panel pointer, they return the panel above or below that panel.
1555 Handed <code>NULL</code>, they return the bottom-most or top-most
1558 <p>Every panel has an associated user pointer, not used by the
1559 panel code, to which you can attach application data. See the man
1560 page documentation of <code>set_panel_userptr()</code> and
1561 <code>panel_userptr</code> for details.</p>
1563 <h1><a name="menu" id="menu">The Menu Library</a></h1>
1565 <p>A menu is a screen display that assists the user to choose
1566 some subset of a given set of items. The <code>menu</code>
1567 library is a curses extension that supports easy programming of
1568 menu hierarchies with a uniform but flexible interface.</p>
1570 <p>The <code>menu</code> library first appeared in AT&T
1571 System V. The version documented here is the <code>menu</code>
1572 code distributed with <code>ncurses</code>.</p>
1574 <h2><a name="mcompile" id="mcompile">Compiling With the menu
1577 <p>Your menu-using modules must import the menu library
1578 declarations with</p>
1581 #include <menu.h>
1584 <p>and must be linked explicitly with the menus library using an
1585 <code>-lmenu</code> argument. Note that they must also link the
1586 <code>ncurses</code> library with <code>-lncurses</code>. Many
1587 linkers are two-pass and will accept either order, but it is
1588 still good practice to put <code>-lmenu</code> first and
1589 <code>-lncurses</code> second.</p>
1591 <h2><a name="moverview" id="moverview">Overview of Menus</a></h2>
1593 <p>The menus created by this library consist of collections of
1594 <dfn>items</dfn> including a name string part and a description
1595 string part. To make menus, you create groups of these items and
1596 connect them with menu frame objects.</p>
1598 <p>The menu can then by <dfn>posted</dfn>, that is written to an
1599 associated window. Actually, each menu has two associated
1600 windows; a containing window in which the programmer can scribble
1601 titles or borders, and a subwindow in which the menu items proper
1602 are displayed. If this subwindow is too small to display all the
1603 items, it will be a scrollable viewport on the collection of
1606 <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed),
1607 and finally freed to make the storage associated with it and its
1608 items available for re-use.</p>
1610 <p>The general flow of control of a menu program looks like
1614 <li>Initialize <code>curses</code>.</li>
1616 <li>Create the menu items, using <code>new_item()</code>.</li>
1618 <li>Create the menu using <code>new_menu()</code>.</li>
1620 <li>Post the menu using <code>post_menu()</code>.</li>
1622 <li>Refresh the screen.</li>
1624 <li>Process user requests via an input loop.</li>
1626 <li>Unpost the menu using <code>unpost_menu()</code>.</li>
1628 <li>Free the menu, using <code>free_menu()</code>.</li>
1630 <li>Free the items using <code>free_item()</code>.</li>
1632 <li>Terminate <code>curses</code>.</li>
1635 <h2><a name="mselect" id="mselect">Selecting items</a></h2>
1637 <p>Menus may be multi-valued or (the default) single-valued (see
1638 the manual page <code>menu_opts(3x)</code> to see how to change
1639 the default). Both types always have a <dfn>current
1642 <p>From a single-valued menu you can read the selected value
1643 simply by looking at the current item. From a multi-valued menu,
1644 you get the selected set by looping through the items applying
1645 the <code>item_value()</code> predicate function. Your
1646 menu-processing code can use the function
1647 <code>set_item_value()</code> to flag the items in the select
1650 <p>Menu items can be made unselectable using
1651 <code>set_item_opts()</code> or <code>item_opts_off()</code> with
1652 the <code>O_SELECTABLE</code> argument. This is the only option
1653 so far defined for menus, but it is good practice to code as
1654 though other option bits might be on.</p>
1656 <h2><a name="mdisplay" id="mdisplay">Menu Display</a></h2>
1658 <p>The menu library calculates a minimum display size for your
1659 window, based on the following variables:</p>
1662 <li>The number and maximum length of the menu items</li>
1664 <li>Whether the O_ROWMAJOR option is enabled</li>
1666 <li>Whether display of descriptions is enabled</li>
1668 <li>Whatever menu format may have been set by the
1671 <li>The length of the menu mark string used for highlighting
1675 <p>The function <code>set_menu_format()</code> allows you to set
1676 the maximum size of the viewport or <dfn>menu page</dfn> that
1677 will be used to display menu items. You can retrieve any format
1678 associated with a menu with <code>menu_format()</code>. The
1679 default format is rows=16, columns=1.</p>
1681 <p>The actual menu page may be smaller than the format size. This
1682 depends on the item number and size and whether O_ROWMAJOR is on.
1683 This option (on by default) causes menu items to be displayed in
1684 a “raster-scan” pattern, so that if more than one
1685 item will fit horizontally the first couple of items are
1686 side-by-side in the top row. The alternative is column-major
1687 display, which tries to put the first several items in the first
1690 <p>As mentioned above, a menu format not large enough to allow
1691 all items to fit on-screen will result in a menu display that is
1692 vertically scrollable.</p>
1694 <p>You can scroll it with requests to the menu driver, which will
1695 be described in the section on <a href="#minput">menu input
1698 <p>Each menu has a <dfn>mark string</dfn> used to visually tag
1699 selected items; see the <code>menu_mark(3x)</code> manual page
1700 for details. The mark string length also influences the menu page
1703 <p>The function <code>scale_menu()</code> returns the minimum
1704 display size that the menu code computes from all these factors.
1705 There are other menu display attributes including a select
1706 attribute, an attribute for selectable items, an attribute for
1707 unselectable items, and a pad character used to separate item
1708 name text from description text. These have reasonable defaults
1709 which the library allows you to change (see the
1710 <code>menu_attribs(3x)</code> manual page.</p>
1712 <h2><a name="mwindows" id="mwindows">Menu Windows</a></h2>
1714 <p>Each menu has, as mentioned previously, a pair of associated
1715 windows. Both these windows are painted when the menu is posted
1716 and erased when the menu is unposted.</p>
1718 <p>The outer or frame window is not otherwise touched by the menu
1719 routines. It exists so the programmer can associate a title, a
1720 border, or perhaps help text with the menu and have it properly
1721 refreshed or erased at post/unpost time. The inner window or
1722 <dfn>subwindow</dfn> is where the current menu page is
1725 <p>By default, both windows are <code>stdscr</code>. You can set
1726 them with the functions in <code>menu_win(3x)</code>.</p>
1728 <p>When you call <code>post_menu()</code>, you write the menu to
1729 its subwindow. When you call <code>unpost_menu()</code>, you
1730 erase the subwindow, However, neither of these actually modifies
1731 the screen. To do that, call <code>wrefresh()</code> or some
1734 <h2><a name="minput" id="minput">Processing Menu Input</a></h2>
1736 <p>The main loop of your menu-processing code should call
1737 <code>menu_driver()</code> repeatedly. The first argument of this
1738 routine is a menu pointer; the second is a menu command code. You
1739 should write an input-fetching routine that maps input characters
1740 to menu command codes, and pass its output to
1741 <code>menu_driver()</code>. The menu command codes are fully
1742 documented in <code>menu_driver(3x)</code>.</p>
1744 <p>The simplest group of command codes is
1745 <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>,
1746 <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>,
1747 <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>,
1748 <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These
1749 change the currently selected item. These requests may cause
1750 scrolling of the menu page if it only partially displayed.</p>
1752 <p>There are explicit requests for scrolling which also change
1753 the current item (because the select location does not change,
1754 but the item there does). These are <code>REQ_SCR_DLINE</code>,
1755 <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and
1756 <code>REQ_SCR_UPAGE</code>.</p>
1758 <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the
1759 current item. It is for use in multi-valued menus; if you use it
1760 with <code>O_ONEVALUE</code> on, you will get an error return
1761 (<code>E_REQUEST_DENIED</code>).</p>
1763 <p>Each menu has an associated pattern buffer. The
1764 <code>menu_driver()</code> logic tries to accumulate printable
1765 ASCII characters passed in in that buffer; when it matches a
1766 prefix of an item name, that item (or the next matching item) is
1767 selected. If appending a character yields no new match, that
1768 character is deleted from the pattern buffer, and
1769 <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p>
1771 <p>Some requests change the pattern buffer directly:
1772 <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>,
1773 <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The
1774 latter two are useful when pattern buffer input matches more than
1775 one item in a multi-valued menu.</p>
1777 <p>Each successful scroll or item navigation request clears the
1778 pattern buffer. It is also possible to set the pattern buffer
1779 explicitly with <code>set_menu_pattern()</code>.</p>
1781 <p>Finally, menu driver requests above the constant
1782 <code>MAX_COMMAND</code> are considered application-specific
1783 commands. The <code>menu_driver()</code> code ignores them and
1784 returns <code>E_UNKNOWN_COMMAND</code>.</p>
1786 <h2><a name="mmisc" id="mmisc">Miscellaneous Other Features</a></h2>
1788 <p>Various menu options can affect the processing and visual
1789 appearance and input processing of menus. See <code>menu_opts(3x)
1790 for details.</code></p>
1792 <p>It is possible to change the current item from application
1793 code; this is useful if you want to write your own navigation
1794 requests. It is also possible to explicitly set the top row of
1795 the menu display. See <code>mitem_current(3x)</code>. If your
1796 application needs to change the menu subwindow cursor for any
1797 reason, <code>pos_menu_cursor()</code> will restore it to the
1798 correct location for continuing menu driver processing.</p>
1800 <p>It is possible to set hooks to be called at menu
1801 initialization and wrapup time, and whenever the selected item
1802 changes. See <code>menu_hook(3x)</code>.</p>
1804 <p>Each item, and each menu, has an associated user pointer on
1805 which you can hang application data. See
1806 <code>mitem_userptr(3x)</code> and
1807 <code>menu_userptr(3x)</code>.</p>
1809 <h1><a name="form" id="form">The Forms Library</a></h1>
1811 <p>The <code>form</code> library is a curses extension that
1812 supports easy programming of on-screen forms for data entry and
1813 program control.</p>
1815 <p>The <code>form</code> library first appeared in AT&T
1816 System V. The version documented here is the <code>form</code>
1817 code distributed with <code>ncurses</code>.</p>
1819 <h2><a name="fcompile" id="fcompile">Compiling With the form
1822 <p>Your form-using modules must import the form library
1823 declarations with</p>
1826 #include <form.h>
1829 <p>and must be linked explicitly with the forms library using an
1830 <code>-lform</code> argument. Note that they must also link the
1831 <code>ncurses</code> library with <code>-lncurses</code>. Many
1832 linkers are two-pass and will accept either order, but it is
1833 still good practice to put <code>-lform</code> first and
1834 <code>-lncurses</code> second.</p>
1836 <h2><a name="foverview" id="foverview">Overview of Forms</a></h2>
1838 <p>A form is a collection of fields; each field may be either a
1839 label (explanatory text) or a data-entry location. Long forms may
1840 be segmented into pages; each entry to a new page clears the
1843 <p>To make forms, you create groups of fields and connect them
1844 with form frame objects; the form library makes this relatively
1847 <p>Once defined, a form can be <dfn>posted</dfn>, that is written
1848 to an associated window. Actually, each form has two associated
1849 windows; a containing window in which the programmer can scribble
1850 titles or borders, and a subwindow in which the form fields
1851 proper are displayed.</p>
1853 <p>As the form user fills out the posted form, navigation and
1854 editing keys support movement between fields, editing keys
1855 support modifying field, and plain text adds to or changes data
1856 in a current field. The form library allows you (the forms
1857 designer) to bind each navigation and editing key to any
1858 keystroke accepted by <code>curses</code> Fields may have
1859 validation conditions on them, so that they check input data for
1860 type and value. The form library supplies a rich set of
1861 pre-defined field types, and makes it relatively easy to define
1864 <p>Once its transaction is completed (or aborted), a form may be
1865 <dfn>unposted</dfn> (that is, undisplayed), and finally freed to
1866 make the storage associated with it and its items available for
1869 <p>The general flow of control of a form program looks like
1873 <li>Initialize <code>curses</code>.</li>
1875 <li>Create the form fields, using
1876 <code>new_field()</code>.</li>
1878 <li>Create the form using <code>new_form()</code>.</li>
1880 <li>Post the form using <code>post_form()</code>.</li>
1882 <li>Refresh the screen.</li>
1884 <li>Process user requests via an input loop.</li>
1886 <li>Unpost the form using <code>unpost_form()</code>.</li>
1888 <li>Free the form, using <code>free_form()</code>.</li>
1890 <li>Free the fields using <code>free_field()</code>.</li>
1892 <li>Terminate <code>curses</code>.</li>
1895 <p>Note that this looks much like a menu program; the form
1896 library handles tasks which are in many ways similar, and its
1897 interface was obviously designed to resemble that of the <a href=
1898 "#menu">menu library</a> wherever possible.</p>
1900 <p>In forms programs, however, the “process user
1901 requests” is somewhat more complicated than for menus.
1902 Besides menu-like navigation operations, the menu driver loop has
1903 to support field editing and data validation.</p>
1905 <h2><a name="fcreate" id="fcreate">Creating and Freeing Fields
1908 <p>The basic function for creating fields is
1909 <code>new_field()</code>:</p>
1912 FIELD *new_field(int height, int width, /* new field size */
1913 int top, int left, /* upper left corner */
1914 int offscreen, /* number of offscreen rows */
1915 int nbuf); /* number of working buffers */
1918 <p>Menu items always occupy a single row, but forms fields may
1919 have multiple rows. So <code>new_field()</code> requires you to
1920 specify a width and height (the first two arguments, which mist
1921 both be greater than zero).</p>
1923 <p>You must also specify the location of the field's upper left
1924 corner on the screen (the third and fourth arguments, which must
1925 be zero or greater). Note that these coordinates are relative to
1926 the form subwindow, which will coincide with <code>stdscr</code>
1927 by default but need not be <code>stdscr</code> if you have done
1928 an explicit <code>set_form_win()</code> call.</p>
1930 <p>The fifth argument allows you to specify a number of
1931 off-screen rows. If this is zero, the entire field will always be
1932 displayed. If it is nonzero, the form will be scrollable, with
1933 only one screen-full (initially the top part) displayed at any
1934 given time. If you make a field dynamic and grow it so it will no
1935 longer fit on the screen, the form will become scrollable even if
1936 the <code>offscreen</code> argument was initially zero.</p>
1938 <p>The forms library allocates one working buffer per field; the
1939 size of each buffer is <code>((height + offscreen)*width +
1940 1</code>, one character for each position in the field plus a NUL
1941 terminator. The sixth argument is the number of additional data
1942 buffers to allocate for the field; your application can use them
1943 for its own purposes.</p>
1946 FIELD *dup_field(FIELD *field, /* field to copy */
1947 int top, int left); /* location of new copy */
1950 <p>The function <code>dup_field()</code> duplicates an existing
1951 field at a new location. Size and buffering information are
1952 copied; some attribute flags and status bits are not (see the
1953 <code>form_field_new(3X)</code> for details).</p>
1956 FIELD *link_field(FIELD *field, /* field to copy */
1957 int top, int left); /* location of new copy */
1960 <p>The function <code>link_field()</code> also duplicates an
1961 existing field at a new location. The difference from
1962 <code>dup_field()</code> is that it arranges for the new field's
1963 buffer to be shared with the old one.</p>
1965 <p>Besides the obvious use in making a field editable from two
1966 different form pages, linked fields give you a way to hack in
1967 dynamic labels. If you declare several fields linked to an
1968 original, and then make them inactive, changes from the original
1969 will still be propagated to the linked fields.</p>
1971 <p>As with duplicated fields, linked fields have attribute bits
1972 separate from the original.</p>
1974 <p>As you might guess, all these field-allocations return
1975 <code>NULL</code> if the field allocation is not possible due to
1976 an out-of-memory error or out-of-bounds arguments.</p>
1978 <p>To connect fields to a form, use</p>
1981 FORM *new_form(FIELD **fields);
1984 <p>This function expects to see a NULL-terminated array of field
1985 pointers. Said fields are connected to a newly-allocated form
1986 object; its address is returned (or else NULL if the allocation
1989 <p>Note that <code>new_field()</code> does <em>not</em> copy the
1990 pointer array into private storage; if you modify the contents of
1991 the pointer array during forms processing, all manner of bizarre
1992 things might happen. Also note that any given field may only be
1993 connected to one form.</p>
1995 <p>The functions <code>free_field()</code> and
1996 <code>free_form</code> are available to free field and form
1997 objects. It is an error to attempt to free a field connected to a
1998 form, but not vice-versa; thus, you will generally free your form
2001 <h2><a name="fattributes" id="fattributes">Fetching and Changing
2002 Field Attributes</a></h2>
2004 <p>Each form field has a number of location and size attributes
2005 associated with it. There are other field attributes used to
2006 control display and editing of the field. Some (for example, the
2007 <code>O_STATIC</code> bit) involve sufficient complications to be
2008 covered in sections of their own later on. We cover the functions
2009 used to get and set several basic attributes here.</p>
2011 <p>When a field is created, the attributes not specified by the
2012 <code>new_field</code> function are copied from an invisible
2013 system default field. In attribute-setting and -fetching
2014 functions, the argument NULL is taken to mean this field. Changes
2015 to it persist as defaults until your forms application
2018 <h3><a name="fsizes" id="fsizes">Fetching Size and Location
2021 <p>You can retrieve field sizes and locations through:</p>
2024 int field_info(FIELD *field, /* field from which to fetch */
2025 int *height, *int width, /* field size */
2026 int *top, int *left, /* upper left corner */
2027 int *offscreen, /* number of offscreen rows */
2028 int *nbuf); /* number of working buffers */
2031 <p>This function is a sort of inverse of
2032 <code>new_field()</code>; instead of setting size and location
2033 attributes of a new field, it fetches them from an existing
2036 <h3><a name="flocation" id="flocation">Changing the Field
2039 <p>It is possible to move a field's location on the screen:</p>
2042 int move_field(FIELD *field, /* field to alter */
2043 int top, int left); /* new upper-left corner */
2046 <p>You can, of course. query the current location through
2047 <code>field_info()</code>.</p>
2049 <h3><a name="fjust" id="fjust">The Justification Attribute</a></h3>
2051 <p>One-line fields may be unjustified, justified right, justified
2052 left, or centered. Here is how you manipulate this attribute:</p>
2055 int set_field_just(FIELD *field, /* field to alter */
2056 int justmode); /* mode to set */
2058 int field_just(FIELD *field); /* fetch mode of field */
2061 <p>The mode values accepted and returned by this functions are
2062 preprocessor macros <code>NO_JUSTIFICATION</code>,
2063 <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or
2064 <code>JUSTIFY_CENTER</code>.</p>
2066 <h3><a name="fdispatts" id="fdispatts">Field Display
2069 <p>For each field, you can set a foreground attribute for entered
2070 characters, a background attribute for the entire field, and a
2071 pad character for the unfilled portion of the field. You can also
2072 control pagination of the form.</p>
2074 <p>This group of four field attributes controls the visual
2075 appearance of the field on the screen, without affecting in any
2076 way the data in the field buffer.</p>
2079 int set_field_fore(FIELD *field, /* field to alter */
2080 chtype attr); /* attribute to set */
2082 chtype field_fore(FIELD *field); /* field to query */
2084 int set_field_back(FIELD *field, /* field to alter */
2085 chtype attr); /* attribute to set */
2087 chtype field_back(FIELD *field); /* field to query */
2089 int set_field_pad(FIELD *field, /* field to alter */
2090 int pad); /* pad character to set */
2092 chtype field_pad(FIELD *field);
2094 int set_new_page(FIELD *field, /* field to alter */
2095 int flag); /* TRUE to force new page */
2097 chtype new_page(FIELD *field); /* field to query */
2100 <p>The attributes set and returned by the first four functions
2101 are normal <code>curses(3x)</code> display attribute values
2102 (<code>A_STANDOUT</code>, <code>A_BOLD</code>,
2103 <code>A_REVERSE</code> etc). The page bit of a field controls
2104 whether it is displayed at the start of a new form screen.</p>
2106 <h3><a name="foptions" id="foptions">Field Option Bits</a></h3>
2108 <p>There is also a large collection of field option bits you can
2109 set to control various aspects of forms processing. You can
2110 manipulate them with these functions:</p>
2113 int set_field_opts(FIELD *field, /* field to alter */
2114 int attr); /* attribute to set */
2116 int field_opts_on(FIELD *field, /* field to alter */
2117 int attr); /* attributes to turn on */
2119 int field_opts_off(FIELD *field, /* field to alter */
2120 int attr); /* attributes to turn off */
2122 int field_opts(FIELD *field); /* field to query */
2125 <p>By default, all options are on. Here are the available option
2131 <dd>Controls whether the field is visible on the screen. Can be
2132 used during form processing to hide or pop up fields depending
2133 on the value of parent fields.</dd>
2137 <dd>Controls whether the field is active during forms
2138 processing (i.e. visited by form navigation keys). Can be used
2139 to make labels or derived fields with buffer values alterable
2140 by the forms application, not the user.</dd>
2144 <dd>Controls whether data is displayed during field entry. If
2145 this option is turned off on a field, the library will accept
2146 and edit data in that field, but it will not be displayed and
2147 the visible field cursor will not move. You can turn off the
2148 O_PUBLIC bit to define password fields.</dd>
2152 <dd>Controls whether the field's data can be modified. When
2153 this option is off, all editing requests except
2154 <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code>
2155 will fail. Such read-only fields may be useful for help
2160 <dd>Controls word-wrapping in multi-line fields. Normally, when
2161 any character of a (blank-separated) word reaches the end of
2162 the current line, the entire word is wrapped to the next line
2163 (assuming there is one). When this option is off, the word will
2164 be split across the line break.</dd>
2168 <dd>Controls field blanking. When this option is on, entering a
2169 character at the first field position erases the entire field
2170 (except for the just-entered character).</dd>
2174 <dd>Controls automatic skip to next field when this one fills.
2175 Normally, when the forms user tries to type more data into a
2176 field than will fit, the editing location jumps to next field.
2177 When this option is off, the user's cursor will hang at the end
2178 of the field. This option is ignored in dynamic fields that
2179 have not reached their size limit.</dd>
2183 <dd>Controls whether <a href="#fvalidation">validation</a> is
2184 applied to blank fields. Normally, it is not; the user can
2185 leave a field blank without invoking the usual validation check
2186 on exit. If this option is off on a field, exit from it will
2187 invoke a validation check.</dd>
2191 <dd>Controls whether validation occurs on every exit, or only
2192 after the field is modified. Normally the latter is true.
2193 Setting O_PASSOK may be useful if your field's validation
2194 function may change during forms processing.</dd>
2198 <dd>Controls whether the field is fixed to its initial
2199 dimensions. If you turn this off, the field becomes <a href=
2200 "#fdynamic">dynamic</a> and will stretch to fit entered
2204 <p>A field's options cannot be changed while the field is
2205 currently selected. However, options may be changed on posted
2206 fields that are not current.</p>
2208 <p>The option values are bit-masks and can be composed with
2209 logical-or in the obvious way.</p>
2211 <h2><a name="fstatus" id="fstatus">Field Status</a></h2>
2213 <p>Every field has a status flag, which is set to FALSE when the
2214 field is created and TRUE when the value in field buffer 0
2215 changes. This flag can be queried and set directly:</p>
2218 int set_field_status(FIELD *field, /* field to alter */
2219 int status); /* mode to set */
2221 int field_status(FIELD *field); /* fetch mode of field */
2224 <p>Setting this flag under program control can be useful if you
2225 use the same form repeatedly, looking for modified fields each
2228 <p>Calling <code>field_status()</code> on a field not currently
2229 selected for input will return a correct value. Calling
2230 <code>field_status()</code> on a field that is currently selected
2231 for input may not necessarily give a correct field status value,
2232 because entered data is not necessarily copied to buffer zero
2233 before the exit validation check. To guarantee that the returned
2234 status value reflects reality, call <code>field_status()</code>
2235 either (1) in the field's exit validation check routine, (2) from
2236 the field's or form's initialization or termination hooks, or (3)
2237 just after a <code>REQ_VALIDATION</code> request has been
2238 processed by the forms driver.</p>
2240 <h2><a name="fuser" id="fuser">Field User Pointer</a></h2>
2242 <p>Each field structure contains one character pointer slot that
2243 is not used by the forms library. It is intended to be used by
2244 applications to store private per-field data. You can manipulate
2248 int set_field_userptr(FIELD *field, /* field to alter */
2249 char *userptr); /* mode to set */
2251 char *field_userptr(FIELD *field); /* fetch mode of field */
2252 </pre>(Properly, this user pointer field ought to have <code>(void
2253 *)</code> type. The <code>(char *)</code> type is retained for
2254 System V compatibility.)
2256 <p>It is valid to set the user pointer of the default field (with
2257 a <code>set_field_userptr()</code> call passed a NULL field
2258 pointer.) When a new field is created, the default-field user
2259 pointer is copied to initialize the new field's user pointer.</p>
2261 <h2><a name="fdynamic" id="fdynamic">Variable-Sized Fields</a></h2>
2263 <p>Normally, a field is fixed at the size specified for it at
2264 creation time. If, however, you turn off its O_STATIC bit, it
2265 becomes <dfn>dynamic</dfn> and will automatically resize itself
2266 to accommodate data as it is entered. If the field has extra
2267 buffers associated with it, they will grow right along with the
2268 main input buffer.</p>
2270 <p>A one-line dynamic field will have a fixed height (1) but
2271 variable width, scrolling horizontally to display data within the
2272 field area as originally dimensioned and located. A multi-line
2273 dynamic field will have a fixed width, but variable height
2274 (number of rows), scrolling vertically to display data within the
2275 field area as originally dimensioned and located.</p>
2277 <p>Normally, a dynamic field is allowed to grow without limit.
2278 But it is possible to set an upper limit on the size of a dynamic
2279 field. You do it with this function:</p>
2282 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
2283 int max_size); /* upper limit on field size */
2286 <p>If the field is one-line, <code>max_size</code> is taken to be
2287 a column size limit; if it is multi-line, it is taken to be a
2288 line size limit. To disable any limit, use an argument of zero.
2289 The growth limit can be changed whether or not the O_STATIC bit
2290 is on, but has no effect until it is.</p>
2292 <p>The following properties of a field change when it becomes
2296 <li>If there is no growth limit, there is no final position of
2297 the field; therefore <code>O_AUTOSKIP</code> and
2298 <code>O_NL_OVERLOAD</code> are ignored.</li>
2300 <li>Field justification will be ignored (though whatever
2301 justification is set up will be retained internally and can be
2304 <li>The <code>dup_field()</code> and <code>link_field()</code>
2305 calls copy dynamic-buffer sizes. If the <code>O_STATIC</code>
2306 option is set on one of a collection of links, buffer resizing
2307 will occur only when the field is edited through that
2310 <li>The call <code>field_info()</code> will retrieve the
2311 original static size of the field; use
2312 <code>dynamic_field_info()</code> to get the actual dynamic
2316 <h2><a name="fvalidation" id="fvalidation">Field Validation</a></h2>
2318 <p>By default, a field will accept any data that will fit in its
2319 input buffer. However, it is possible to attach a validation type
2320 to a field. If you do this, any attempt to leave the field while
2321 it contains data that does not match the validation type will
2322 fail. Some validation types also have a character-validity check
2323 for each time a character is entered in the field.</p>
2325 <p>A field's validation check (if any) is not called when
2326 <code>set_field_buffer()</code> modifies the input buffer, nor
2327 when that buffer is changed through a linked field.</p>
2329 <p>The <code>form</code> library provides a rich set of
2330 pre-defined validation types, and gives you the capability to
2331 define custom ones of your own. You can examine and change field
2332 validation attributes with the following functions:</p>
2335 int set_field_type(FIELD *field, /* field to alter */
2336 FIELDTYPE *ftype, /* type to associate */
2337 ...); /* additional arguments*/
2339 FIELDTYPE *field_type(FIELD *field); /* field to query */
2342 <p>The validation type of a field is considered an attribute of
2343 the field. As with other field attributes, Also, doing
2344 <code>set_field_type()</code> with a <code>NULL</code> field
2345 default will change the system default for validation of
2346 newly-created fields.</p>
2348 <p>Here are the pre-defined validation types:</p>
2350 <h3><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h3>
2352 <p>This field type accepts alphabetic data; no blanks, no digits,
2353 no special characters (this is checked at character-entry time).
2354 It is set up with:</p>
2357 int set_field_type(FIELD *field, /* field to alter */
2358 TYPE_ALPHA, /* type to associate */
2359 int width); /* maximum width of field */
2362 <p>The <code>width</code> argument sets a minimum width of data.
2363 Typically you will want to set this to the field width; if it is
2364 greater than the field width, the validation check will always
2365 fail. A minimum width of zero makes field completion
2368 <h3><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h3>
2370 <p>This field type accepts alphabetic data and digits; no blanks,
2371 no special characters (this is checked at character-entry time).
2372 It is set up with:</p>
2375 int set_field_type(FIELD *field, /* field to alter */
2376 TYPE_ALNUM, /* type to associate */
2377 int width); /* maximum width of field */
2380 <p>The <code>width</code> argument sets a minimum width of data.
2381 As with TYPE_ALPHA, typically you will want to set this to the
2382 field width; if it is greater than the field width, the
2383 validation check will always fail. A minimum width of zero makes
2384 field completion optional.</p>
2386 <h3><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h3>
2388 <p>This type allows you to restrict a field's values to be among
2389 a specified set of string values (for example, the two-letter
2390 postal codes for U.S. states). It is set up with:</p>
2393 int set_field_type(FIELD *field, /* field to alter */
2394 TYPE_ENUM, /* type to associate */
2395 char **valuelist; /* list of possible values */
2396 int checkcase; /* case-sensitive? */
2397 int checkunique); /* must specify uniquely? */
2400 <p>The <code>valuelist</code> parameter must point at a
2401 NULL-terminated list of valid strings. The <code>checkcase</code>
2402 argument, if true, makes comparison with the string
2405 <p>When the user exits a TYPE_ENUM field, the validation
2406 procedure tries to complete the data in the buffer to a valid
2407 entry. If a complete choice string has been entered, it is of
2408 course valid. But it is also possible to enter a prefix of a
2409 valid string and have it completed for you.</p>
2411 <p>By default, if you enter such a prefix and it matches more
2412 than one value in the string list, the prefix will be completed
2413 to the first matching value. But the <code>checkunique</code>
2414 argument, if true, requires prefix matches to be unique in order
2417 <p>The <code>REQ_NEXT_CHOICE</code> and
2418 <code>REQ_PREV_CHOICE</code> input requests can be particularly
2419 useful with these fields.</p>
2421 <h3><a name="ftype_integer" id="ftype_integer">TYPE_INTEGER</a></h3>
2423 <p>This field type accepts an integer. It is set up as
2427 int set_field_type(FIELD *field, /* field to alter */
2428 TYPE_INTEGER, /* type to associate */
2429 int padding, /* # places to zero-pad to */
2430 int vmin, int vmax); /* valid range */
2433 <p>Valid characters consist of an optional leading minus and
2434 digits. The range check is performed on exit. If the range
2435 maximum is less than or equal to the minimum, the range is
2438 <p>If the value passes its range check, it is padded with as many
2439 leading zero digits as necessary to meet the padding
2442 <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be
2443 interpreted with the C library function <code>atoi(3)</code>.</p>
2445 <h3><a name="ftype_numeric" id="ftype_numeric">TYPE_NUMERIC</a></h3>
2447 <p>This field type accepts a decimal number. It is set up as
2451 int set_field_type(FIELD *field, /* field to alter */
2452 TYPE_NUMERIC, /* type to associate */
2453 int padding, /* # places of precision */
2454 double vmin, double vmax); /* valid range */
2457 <p>Valid characters consist of an optional leading minus and
2458 digits. possibly including a decimal point. If your system
2459 supports locale's, the decimal point character used must be the
2460 one defined by your locale. The range check is performed on exit.
2461 If the range maximum is less than or equal to the minimum, the
2462 range is ignored.</p>
2464 <p>If the value passes its range check, it is padded with as many
2465 trailing zero digits as necessary to meet the padding
2468 <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be
2469 interpreted with the C library function <code>atof(3)</code>.</p>
2471 <h3><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h3>
2473 <p>This field type accepts data matching a regular expression. It
2474 is set up as follows:</p>
2477 int set_field_type(FIELD *field, /* field to alter */
2478 TYPE_REGEXP, /* type to associate */
2479 char *regexp); /* expression to match */
2482 <p>The syntax for regular expressions is that of
2483 <code>regcomp(3)</code>. The check for regular-expression match
2484 is performed on exit.</p>
2486 <h2><a name="fbuffer" id="fbuffer">Direct Field Buffer
2487 Manipulation</a></h2>
2489 <p>The chief attribute of a field is its buffer contents. When a
2490 form has been completed, your application usually needs to know
2491 the state of each field buffer. You can find this out with:</p>
2494 char *field_buffer(FIELD *field, /* field to query */
2495 int bufindex); /* number of buffer to query */
2498 <p>Normally, the state of the zero-numbered buffer for each field
2499 is set by the user's editing actions on that field. It is
2500 sometimes useful to be able to set the value of the zero-numbered
2501 (or some other) buffer from your application:</p>
2504 int set_field_buffer(FIELD *field, /* field to alter */
2505 int bufindex, /* number of buffer to alter */
2506 char *value); /* string value to set */
2509 <p>If the field is not large enough and cannot be resized to a
2510 sufficiently large size to contain the specified value, the value
2511 will be truncated to fit.</p>
2513 <p>Calling <code>field_buffer()</code> with a null field pointer
2514 will raise an error. Calling <code>field_buffer()</code> on a
2515 field not currently selected for input will return a correct
2516 value. Calling <code>field_buffer()</code> on a field that is
2517 currently selected for input may not necessarily give a correct
2518 field buffer value, because entered data is not necessarily
2519 copied to buffer zero before the exit validation check. To
2520 guarantee that the returned buffer value reflects on-screen
2521 reality, call <code>field_buffer()</code> either (1) in the
2522 field's exit validation check routine, (2) from the field's or
2523 form's initialization or termination hooks, or (3) just after a
2524 <code>REQ_VALIDATION</code> request has been processed by the
2527 <h2><a name="formattrs" id="formattrs">Attributes of Forms</a></h2>
2529 <p>As with field attributes, form attributes inherit a default
2530 from a system default form structure. These defaults can be
2531 queried or set by of these functions using a form-pointer
2532 argument of <code>NULL</code>.</p>
2534 <p>The principal attribute of a form is its field list. You can
2535 query and change this list with:</p>
2538 int set_form_fields(FORM *form, /* form to alter */
2539 FIELD **fields); /* fields to connect */
2541 char *form_fields(FORM *form); /* fetch fields of form */
2543 int field_count(FORM *form); /* count connect fields */
2546 <p>The second argument of <code>set_form_fields()</code> may be a
2547 NULL-terminated field pointer array like the one required by
2548 <code>new_form()</code>. In that case, the old fields of the form
2549 are disconnected but not freed (and eligible to be connected to
2550 other forms), then the new fields are connected.</p>
2552 <p>It may also be null, in which case the old fields are
2553 disconnected (and not freed) but no new ones are connected.</p>
2555 <p>The <code>field_count()</code> function simply counts the
2556 number of fields connected to a given from. It returns -1 if the
2557 form-pointer argument is NULL.</p>
2559 <h2><a name="fdisplay" id="fdisplay">Control of Form Display</a></h2>
2561 <p>In the overview section, you saw that to display a form you
2562 normally start by defining its size (and fields), posting it, and
2563 refreshing the screen. There is an hidden step before posting,
2564 which is the association of the form with a frame window
2565 (actually, a pair of windows) within which it will be displayed.
2566 By default, the forms library associates every form with the
2567 full-screen window <code>stdscr</code>.</p>
2569 <p>By making this step explicit, you can associate a form with a
2570 declared frame window on your screen display. This can be useful
2571 if you want to adapt the form display to different screen sizes,
2572 dynamically tile forms on the screen, or use a form as part of an
2573 interface layout managed by <a href="#panels">panels</a>.</p>
2575 <p>The two windows associated with each form have the same
2576 functions as their analogues in the <a href="#menu">menu
2577 library</a>. Both these windows are painted when the form is
2578 posted and erased when the form is unposted.</p>
2580 <p>The outer or frame window is not otherwise touched by the form
2581 routines. It exists so the programmer can associate a title, a
2582 border, or perhaps help text with the form and have it properly
2583 refreshed or erased at post/unpost time. The inner window or
2584 subwindow is where the current form page is actually
2587 <p>In order to declare your own frame window for a form, you will
2588 need to know the size of the form's bounding rectangle. You can
2589 get this information with:</p>
2592 int scale_form(FORM *form, /* form to query */
2593 int *rows, /* form rows */
2594 int *cols); /* form cols */
2597 <p>The form dimensions are passed back in the locations pointed
2598 to by the arguments. Once you have this information, you can use
2599 it to declare of windows, then use one of these functions:</p>
2602 int set_form_win(FORM *form, /* form to alter */
2603 WINDOW *win); /* frame window to connect */
2605 WINDOW *form_win(FORM *form); /* fetch frame window of form */
2607 int set_form_sub(FORM *form, /* form to alter */
2608 WINDOW *win); /* form subwindow to connect */
2610 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
2613 <p>Note that curses operations, including <code>refresh()</code>,
2614 on the form, should be done on the frame window, not the form
2617 <p>It is possible to check from your application whether all of a
2618 scrollable field is actually displayed within the menu subwindow.
2619 Use these functions:</p>
2622 int data_ahead(FORM *form); /* form to be queried */
2624 int data_behind(FORM *form); /* form to be queried */
2627 <p>The function <code>data_ahead()</code> returns TRUE if (a) the
2628 current field is one-line and has undisplayed data off to the
2629 right, (b) the current field is multi-line and there is data
2630 off-screen below it.</p>
2632 <p>The function <code>data_behind()</code> returns TRUE if the
2633 first (upper left hand) character position is off-screen (not
2634 being displayed).</p>
2636 <p>Finally, there is a function to restore the form window's
2637 cursor to the value expected by the forms driver:</p>
2640 int pos_form_cursor(FORM *) /* form to be queried */
2643 <p>If your application changes the form window cursor, call this
2644 function before handing control back to the forms driver in order
2645 to re-synchronize it.</p>
2647 <h2><a name="fdriver" id="fdriver">Input Processing in the Forms
2650 <p>The function <code>form_driver()</code> handles virtualized
2651 input requests for form navigation, editing, and validation
2652 requests, just as <code>menu_driver</code> does for menus (see
2653 the section on <a href="#minput">menu input handling</a>).</p>
2656 int form_driver(FORM *form, /* form to pass input to */
2657 int request); /* form request code */
2660 <p>Your input virtualization function needs to take input and
2661 then convert it to either an alphanumeric character (which is
2662 treated as data to be entered in the currently-selected field),
2663 or a forms processing request.</p>
2665 <p>The forms driver provides hooks (through input-validation and
2666 field-termination functions) with which your application code can
2667 check that the input taken by the driver matched what was
2670 <h3><a name="fpage" id="fpage">Page Navigation Requests</a></h3>
2672 <p>These requests cause page-level moves through the form,
2673 triggering display of a new form screen.</p>
2676 <dt><code>REQ_NEXT_PAGE</code>
2679 <dd>Move to the next form page.</dd>
2681 <dt><code>REQ_PREV_PAGE</code>
2684 <dd>Move to the previous form page.</dd>
2686 <dt><code>REQ_FIRST_PAGE</code>
2689 <dd>Move to the first form page.</dd>
2691 <dt><code>REQ_LAST_PAGE</code>
2694 <dd>Move to the last form page.</dd>
2697 <p>These requests treat the list as cyclic; that is,
2698 <code>REQ_NEXT_PAGE</code> from the last page goes to the first,
2699 and <code>REQ_PREV_PAGE</code> from the first page goes to the
2702 <h3><a name="ffield" id="ffield">Inter-Field Navigation
2705 <p>These requests handle navigation between fields on the same
2709 <dt><code>REQ_NEXT_FIELD</code>
2712 <dd>Move to next field.</dd>
2714 <dt><code>REQ_PREV_FIELD</code>
2717 <dd>Move to previous field.</dd>
2719 <dt><code>REQ_FIRST_FIELD</code>
2722 <dd>Move to the first field.</dd>
2724 <dt><code>REQ_LAST_FIELD</code>
2727 <dd>Move to the last field.</dd>
2729 <dt><code>REQ_SNEXT_FIELD</code>
2732 <dd>Move to sorted next field.</dd>
2734 <dt><code>REQ_SPREV_FIELD</code>
2737 <dd>Move to sorted previous field.</dd>
2739 <dt><code>REQ_SFIRST_FIELD</code>
2742 <dd>Move to the sorted first field.</dd>
2744 <dt><code>REQ_SLAST_FIELD</code>
2747 <dd>Move to the sorted last field.</dd>
2749 <dt><code>REQ_LEFT_FIELD</code>
2752 <dd>Move left to field.</dd>
2754 <dt><code>REQ_RIGHT_FIELD</code>
2757 <dd>Move right to field.</dd>
2759 <dt><code>REQ_UP_FIELD</code>
2762 <dd>Move up to field.</dd>
2764 <dt><code>REQ_DOWN_FIELD</code>
2767 <dd>Move down to field.</dd>
2770 <p>These requests treat the list of fields on a page as cyclic;
2771 that is, <code>REQ_NEXT_FIELD</code> from the last field goes to
2772 the first, and <code>REQ_PREV_FIELD</code> from the first field
2773 goes to the last. The order of the fields for these (and the
2774 <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code>
2775 requests) is simply the order of the field pointers in the form
2776 array (as set up by <code>new_form()</code> or
2777 <code>set_form_fields()</code></p>
2779 <p>It is also possible to traverse the fields as if they had been
2780 sorted in screen-position order, so the sequence goes
2781 left-to-right and top-to-bottom. To do this, use the second group
2782 of four sorted-movement requests.</p>
2784 <p>Finally, it is possible to move between fields using visual
2785 directions up, down, right, and left. To accomplish this, use the
2786 third group of four requests. Note, however, that the position of
2787 a form for purposes of these requests is its upper-left
2790 <p>For example, suppose you have a multi-line field B, and two
2791 single-line fields A and C on the same line with B, with A to the
2792 left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code>
2793 from A will go to B only if A, B, and C <em>all</em> share the
2794 same first line; otherwise it will skip over B to C.</p>
2796 <h3><a name="fifield" id="fifield">Intra-Field Navigation
2799 <p>These requests drive movement of the edit cursor within the
2800 currently selected field.</p>
2803 <dt><code>REQ_NEXT_CHAR</code>
2806 <dd>Move to next character.</dd>
2808 <dt><code>REQ_PREV_CHAR</code>
2811 <dd>Move to previous character.</dd>
2813 <dt><code>REQ_NEXT_LINE</code>
2816 <dd>Move to next line.</dd>
2818 <dt><code>REQ_PREV_LINE</code>
2821 <dd>Move to previous line.</dd>
2823 <dt><code>REQ_NEXT_WORD</code>
2826 <dd>Move to next word.</dd>
2828 <dt><code>REQ_PREV_WORD</code>
2831 <dd>Move to previous word.</dd>
2833 <dt><code>REQ_BEG_FIELD</code>
2836 <dd>Move to beginning of field.</dd>
2838 <dt><code>REQ_END_FIELD</code>
2841 <dd>Move to end of field.</dd>
2843 <dt><code>REQ_BEG_LINE</code>
2846 <dd>Move to beginning of line.</dd>
2848 <dt><code>REQ_END_LINE</code>
2851 <dd>Move to end of line.</dd>
2853 <dt><code>REQ_LEFT_CHAR</code>
2856 <dd>Move left in field.</dd>
2858 <dt><code>REQ_RIGHT_CHAR</code>
2861 <dd>Move right in field.</dd>
2863 <dt><code>REQ_UP_CHAR</code>
2866 <dd>Move up in field.</dd>
2868 <dt><code>REQ_DOWN_CHAR</code>
2871 <dd>Move down in field.</dd>
2874 <p>Each <em>word</em> is separated from the previous and next
2875 characters by whitespace. The commands to move to beginning and
2876 end of line or field look for the first or last non-pad character
2877 in their ranges.</p>
2879 <h3><a name="fscroll" id="fscroll">Scrolling Requests</a></h3>
2881 <p>Fields that are dynamic and have grown and fields explicitly
2882 created with offscreen rows are scrollable. One-line fields
2883 scroll horizontally; multi-line fields scroll vertically. Most
2884 scrolling is triggered by editing and intra-field movement (the
2885 library scrolls the field to keep the cursor visible). It is
2886 possible to explicitly request scrolling with the following
2890 <dt><code>REQ_SCR_FLINE</code>
2893 <dd>Scroll vertically forward a line.</dd>
2895 <dt><code>REQ_SCR_BLINE</code>
2898 <dd>Scroll vertically backward a line.</dd>
2900 <dt><code>REQ_SCR_FPAGE</code>
2903 <dd>Scroll vertically forward a page.</dd>
2905 <dt><code>REQ_SCR_BPAGE</code>
2908 <dd>Scroll vertically backward a page.</dd>
2910 <dt><code>REQ_SCR_FHPAGE</code>
2913 <dd>Scroll vertically forward half a page.</dd>
2915 <dt><code>REQ_SCR_BHPAGE</code>
2918 <dd>Scroll vertically backward half a page.</dd>
2920 <dt><code>REQ_SCR_FCHAR</code>
2923 <dd>Scroll horizontally forward a character.</dd>
2925 <dt><code>REQ_SCR_BCHAR</code>
2928 <dd>Scroll horizontally backward a character.</dd>
2930 <dt><code>REQ_SCR_HFLINE</code>
2933 <dd>Scroll horizontally one field width forward.</dd>
2935 <dt><code>REQ_SCR_HBLINE</code>
2938 <dd>Scroll horizontally one field width backward.</dd>
2940 <dt><code>REQ_SCR_HFHALF</code>
2943 <dd>Scroll horizontally one half field width forward.</dd>
2945 <dt><code>REQ_SCR_HBHALF</code>
2948 <dd>Scroll horizontally one half field width backward.</dd>
2951 <p>For scrolling purposes, a <em>page</em> of a field is the
2952 height of its visible part.</p>
2954 <h3><a name="fedit" id="fedit">Editing Requests</a></h3>
2956 <p>When you pass the forms driver an ASCII character, it is
2957 treated as a request to add the character to the field's data
2958 buffer. Whether this is an insertion or a replacement depends on
2959 the field's edit mode (insertion is the default.</p>
2961 <p>The following requests support editing the field and changing
2965 <dt><code>REQ_INS_MODE</code>
2968 <dd>Set insertion mode.</dd>
2970 <dt><code>REQ_OVL_MODE</code>
2973 <dd>Set overlay mode.</dd>
2975 <dt><code>REQ_NEW_LINE</code>
2978 <dd>New line request (see below for explanation).</dd>
2980 <dt><code>REQ_INS_CHAR</code>
2983 <dd>Insert space at character location.</dd>
2985 <dt><code>REQ_INS_LINE</code>
2988 <dd>Insert blank line at character location.</dd>
2990 <dt><code>REQ_DEL_CHAR</code>
2993 <dd>Delete character at cursor.</dd>
2995 <dt><code>REQ_DEL_PREV</code>
2998 <dd>Delete previous word at cursor.</dd>
3000 <dt><code>REQ_DEL_LINE</code>
3003 <dd>Delete line at cursor.</dd>
3005 <dt><code>REQ_DEL_WORD</code>
3008 <dd>Delete word at cursor.</dd>
3010 <dt><code>REQ_CLR_EOL</code>
3013 <dd>Clear to end of line.</dd>
3015 <dt><code>REQ_CLR_EOF</code>
3018 <dd>Clear to end of field.</dd>
3020 <dt><code>REQ_CLEAR_FIELD</code>
3023 <dd>Clear entire field.</dd>
3026 <p>The behavior of the <code>REQ_NEW_LINE</code> and
3027 <code>REQ_DEL_PREV</code> requests is complicated and partly
3028 controlled by a pair of forms options. The special cases are
3029 triggered when the cursor is at the beginning of a field, or on
3030 the last line of the field.</p>
3032 <p>First, we consider <code>REQ_NEW_LINE</code>:</p>
3034 <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert
3035 mode is to break the current line at the position of the edit
3036 cursor, inserting the portion of the current line after the
3037 cursor as a new line following the current and moving the cursor
3038 to the beginning of that new line (you may think of this as
3039 inserting a newline in the field buffer).</p>
3041 <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay
3042 mode is to clear the current line from the position of the edit
3043 cursor to end of line. The cursor is then moved to the beginning
3044 of the next line.</p>
3046 <p>However, <code>REQ_NEW_LINE</code> at the beginning of a
3047 field, or on the last line of a field, instead does a
3048 <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is
3049 off, this special action is disabled.</p>
3051 <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p>
3053 <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete
3054 the previous character. If insert mode is on, and the cursor is
3055 at the start of a line, and the text on that line will fit on the
3056 previous one, it instead appends the contents of the current line
3057 to the previous one and deletes the current line (you may think
3058 of this as deleting a newline from the field buffer).</p>
3060 <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field
3061 is instead treated as a <code>REQ_PREV_FIELD</code>.</p>
3063 <p>If the <code>O_BS_OVERLOAD</code> option is off, this special
3064 action is disabled and the forms driver just returns
3065 <code>E_REQUEST_DENIED</code>.</p>
3067 <p>See <a href="#frmoptions">Form Options</a> for discussion of
3068 how to set and clear the overload options.</p>
3070 <h3><a name="forder" id="forder">Order Requests</a></h3>
3072 <p>If the type of your field is ordered, and has associated
3073 functions for getting the next and previous values of the type
3074 from a given value, there are requests that can fetch that value
3075 into the field buffer:</p>
3078 <dt><code>REQ_NEXT_CHOICE</code>
3081 <dd>Place the successor value of the current value in the
3084 <dt><code>REQ_PREV_CHOICE</code>
3087 <dd>Place the predecessor value of the current value in the
3091 <p>Of the built-in field types, only <code>TYPE_ENUM</code> has
3092 built-in successor and predecessor functions. When you define a
3093 field type of your own (see <a href="#fcustom">Custom Validation
3094 Types</a>), you can associate our own ordering functions.</p>
3096 <h3><a name="fappcmds" id="fappcmds">Application Commands</a></h3>
3098 <p>Form requests are represented as integers above the
3099 <code>curses</code> value greater than <code>KEY_MAX</code> and
3100 less than or equal to the constant <code>MAX_COMMAND</code>. If
3101 your input-virtualization routine returns a value above
3102 <code>MAX_COMMAND</code>, the forms driver will ignore it.</p>
3104 <h2><a name="fhooks" id="fhooks">Field Change Hooks</a></h2>
3106 <p>It is possible to set function hooks to be executed whenever
3107 the current field or form changes. Here are the functions that
3111 typedef void (*HOOK)(); /* pointer to function returning void */
3113 int set_form_init(FORM *form, /* form to alter */
3114 HOOK hook); /* initialization hook */
3116 HOOK form_init(FORM *form); /* form to query */
3118 int set_form_term(FORM *form, /* form to alter */
3119 HOOK hook); /* termination hook */
3121 HOOK form_term(FORM *form); /* form to query */
3123 int set_field_init(FORM *form, /* form to alter */
3124 HOOK hook); /* initialization hook */
3126 HOOK field_init(FORM *form); /* form to query */
3128 int set_field_term(FORM *form, /* form to alter */
3129 HOOK hook); /* termination hook */
3131 HOOK field_term(FORM *form); /* form to query */
3134 <p>These functions allow you to either set or query four
3135 different hooks. In each of the set functions, the second
3136 argument should be the address of a hook function. These
3137 functions differ only in the timing of the hook call.</p>
3142 <dd>This hook is called when the form is posted; also, just
3143 after each page change operation.</dd>
3147 <dd>This hook is called when the form is posted; also, just
3148 after each field change</dd>
3152 <dd>This hook is called just after field validation; that is,
3153 just before the field is altered. It is also called when the
3154 form is unposted.</dd>
3158 <dd>This hook is called when the form is unposted; also, just
3159 before each page change operation.</dd>
3162 <p>Calls to these hooks may be triggered</p>
3165 <li>When user editing requests are processed by the forms
3168 <li>When the current page is changed by
3169 <code>set_current_field()</code> call</li>
3171 <li>When the current field is changed by a
3172 <code>set_form_page()</code> call</li>
3175 <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for
3176 discussion of the latter two cases.</p>
3178 <p>You can set a default hook for all fields by passing one of
3179 the set functions a NULL first argument.</p>
3181 <p>You can disable any of these hooks by (re)setting them to
3182 NULL, the default value.</p>
3184 <h2><a href="#ffocus">Field Change Commands</a></h2>
3186 <p>Normally, navigation through the form will be driven by the
3187 user's input requests. But sometimes it is useful to be able to
3188 move the focus for editing and viewing under control of your
3189 application, or ask which field it currently is in. The following
3190 functions help you accomplish this:</p>
3193 int set_current_field(FORM *form, /* form to alter */
3194 FIELD *field); /* field to shift to */
3196 FIELD *current_field(FORM *form); /* form to query */
3198 int field_index(FORM *form, /* form to query */
3199 FIELD *field); /* field to get index of */
3202 <p>The function <code>field_index()</code> returns the index of
3203 the given field in the given form's field array (the array passed
3204 to <code>new_form()</code> or
3205 <code>set_form_fields()</code>).</p>
3207 <p>The initial current field of a form is the first active field
3208 on the first page. The function <code>set_form_fields()</code>
3211 <p>It is also possible to move around by pages.</p>
3214 int set_form_page(FORM *form, /* form to alter */
3215 int page); /* page to go to (0-origin) */
3217 int form_page(FORM *form); /* return form's current page */
3220 <p>The initial page of a newly-created form is 0. The function
3221 <code>set_form_fields()</code> resets this.</p>
3223 <h2><a name="frmoptions" id="frmoptions">Form Options</a></h2>
3225 <p>Like fields, forms may have control option bits. They can be
3226 changed or queried with these functions:</p>
3229 int set_form_opts(FORM *form, /* form to alter */
3230 int attr); /* attribute to set */
3232 int form_opts_on(FORM *form, /* form to alter */
3233 int attr); /* attributes to turn on */
3235 int form_opts_off(FORM *form, /* form to alter */
3236 int attr); /* attributes to turn off */
3238 int form_opts(FORM *form); /* form to query */
3241 <p>By default, all options are on. Here are the available option
3245 <dt>O_NL_OVERLOAD</dt>
3247 <dd>Enable overloading of <code>REQ_NEW_LINE</code> as
3248 described in <a href="#fedit">Editing Requests</a>. The value
3249 of this option is ignored on dynamic fields that have not
3250 reached their size limit; these have no last line, so the
3251 circumstances for triggering a <code>REQ_NEXT_FIELD</code>
3254 <dt>O_BS_OVERLOAD</dt>
3256 <dd>Enable overloading of <code>REQ_DEL_PREV</code> as
3257 described in <a href="#fedit">Editing Requests</a>.</dd>
3260 <p>The option values are bit-masks and can be composed with
3261 logical-or in the obvious way.</p>
3263 <h2><a name="fcustom" id="fcustom">Custom Validation Types</a></h2>
3265 <p>The <code>form</code> library gives you the capability to
3266 define custom validation types of your own. Further, the optional
3267 additional arguments of <code>set_field_type</code> effectively
3268 allow you to parameterize validation types. Most of the
3269 complications in the validation-type interface have to do with
3270 the handling of the additional arguments within custom validation
3273 <h3><a name="flinktypes" id="flinktypes">Union Types</a></h3>
3275 <p>The simplest way to create a custom data type is to compose it
3276 from two preexisting ones:</p>
3279 FIELD *link_fieldtype(FIELDTYPE *type1,
3283 <p>This function creates a field type that will accept any of the
3284 values legal for either of its argument field types (which may be
3285 either predefined or programmer-defined). If a
3286 <code>set_field_type()</code> call later requires arguments, the
3287 new composite type expects all arguments for the first type, than
3288 all arguments for the second. Order functions (see <a href=
3289 "#forder">Order Requests</a>) associated with the component types
3290 will work on the composite; what it does is check the validation
3291 function for the first type, then for the second, to figure what
3292 type the buffer contents should be treated as.</p>
3294 <h3><a name="fnewtypes" id="fnewtypes">New Field Types</a></h3>
3296 <p>To create a field type from scratch, you need to specify one
3297 or both of the following things:</p>
3300 <li>A character-validation function, to check each character as
3303 <li>A field-validation function to be applied on exit from the
3307 <p>Here is how you do that:</p>
3310 typedef int (*HOOK)(); /* pointer to function returning int */
3312 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
3313 HOOK c_validate) /* character validator */
3315 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
3318 <p>At least one of the arguments of <code>new_fieldtype()</code>
3319 must be non-NULL. The forms driver will automatically call the
3320 new type's validation functions at appropriate points in
3321 processing a field of the new type.</p>
3323 <p>The function <code>free_fieldtype()</code> deallocates the
3324 argument fieldtype, freeing all storage associated with it.</p>
3326 <p>Normally, a field validator is called when the user attempts
3327 to leave the field. Its first argument is a field pointer, from
3328 which it can get to field buffer 0 and test it. If the function
3329 returns TRUE, the operation succeeds; if it returns FALSE, the
3330 edit cursor stays in the field.</p>
3332 <p>A character validator gets the character passed in as a first
3333 argument. It too should return TRUE if the character is valid,
3334 FALSE otherwise.</p>
3336 <h3><a name="fcheckargs" id="fcheckargs">Validation Function
3339 <p>Your field- and character- validation functions will be passed
3340 a second argument as well. This second argument is the address of
3341 a structure (which we will call a <em>pile</em>) built from any
3342 of the field-type-specific arguments passed to
3343 <code>set_field_type()</code>. If no such arguments are defined
3344 for the field type, this pile pointer argument will be NULL.</p>
3346 <p>In order to arrange for such arguments to be passed to your
3347 validation functions, you must associate a small set of
3348 storage-management functions with the type. The forms driver will
3349 use these to synthesize a pile from the trailing arguments of
3350 each <code>set_field_type()</code> argument, and a pointer to the
3351 pile will be passed to the validation functions.</p>
3353 <p>Here is how you make the association:</p>
3356 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
3357 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
3359 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3360 PTRHOOK make_str, /* make structure from args */
3361 PTRHOOK copy_str, /* make copy of structure */
3362 VOIDHOOK free_str); /* free structure storage */
3365 <p>Here is how the storage-management hooks are used:</p>
3368 <dt><code>make_str</code>
3371 <dd>This function is called by <code>set_field_type()</code>.
3372 It gets one argument, a <code>va_list</code> of the
3373 type-specific arguments passed to
3374 <code>set_field_type()</code>. It is expected to return a pile
3375 pointer to a data structure that encapsulates those
3378 <dt><code>copy_str</code>
3381 <dd>This function is called by form library functions that
3382 allocate new field instances. It is expected to take a pile
3383 pointer, copy the pile to allocated storage, and return the
3384 address of the pile copy.</dd>
3386 <dt><code>free_str</code>
3389 <dd>This function is called by field- and type-deallocation
3390 routines in the library. It takes a pile pointer argument, and
3391 is expected to free the storage of that pile.</dd>
3394 <p>The <code>make_str</code> and <code>copy_str</code> functions
3395 may return NULL to signal allocation failure. The library
3396 routines will that call them will return error indication when
3397 this happens. Thus, your validation functions should never see a
3398 NULL file pointer and need not check specially for it.</p>
3400 <h3><a name="fcustorder" id="fcustorder">Order Functions For
3401 Custom Types</a></h3>
3403 <p>Some custom field types are simply ordered in the same
3404 well-defined way that <code>TYPE_ENUM</code> is. For such types,
3405 it is possible to define successor and predecessor functions to
3406 support the <code>REQ_NEXT_CHOICE</code> and
3407 <code>REQ_PREV_CHOICE</code> requests. Here is how:</p>
3410 typedef int (*INTHOOK)(); /* pointer to function returning int */
3412 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
3413 INTHOOK succ, /* get successor value */
3414 INTHOOK pred); /* get predecessor value */
3417 <p>The successor and predecessor arguments will each be passed
3418 two arguments; a field pointer, and a pile pointer (as for the
3419 validation functions). They are expected to use the function
3420 <code>field_buffer()</code> to read the current value, and
3421 <code>set_field_buffer()</code> on buffer 0 to set the next or
3422 previous value. Either hook may return TRUE to indicate success
3423 (a legal next or previous value was set) or FALSE to indicate
3426 <h3><a name="fcustprobs" id="fcustprobs">Avoiding Problems</a></h3>
3428 <p>The interface for defining custom types is complicated and
3429 tricky. Rather than attempting to create a custom type entirely
3430 from scratch, you should start by studying the library source
3431 code for whichever of the pre-defined types seems to be closest
3432 to what you want.</p>
3434 <p>Use that code as a model, and evolve it towards what you
3435 really want. You will avoid many problems and annoyances that
3436 way. The code in the <code>ncurses</code> library has been
3437 specifically exempted from the package copyright to support
3440 <p>If your custom type defines order functions, have do something
3441 intuitive with a blank field. A useful convention is to make the
3442 successor of a blank field the types minimum value, and its
3443 predecessor the maximum.</p>