1 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
3 $Id: ncurses-intro.html,v 1.20 1997/04/26 20:00:29 tom Exp $
7 <TITLE>Writing Programs with NCURSES</TITLE>
8 <link rev="made" href="mailto:dickey@clark.net">
12 <H1>Writing Programs with NCURSES</H1>
15 by Eric S. Raymond and Zeyd M. Ben-Halim<BR>
20 <LI><A HREF="#introduction">Introduction</A>
22 <LI><A HREF="#history">A Brief History of Curses</A>
23 <LI><A HREF="#scope">Scope of This Document</A>
24 <LI><A HREF="#terminology">Terminology</A>
26 <LI><A HREF="#curses">The Curses Library</A>
28 <LI><A HREF="#overview">An Overview of Curses</A>
30 <LI><A HREF="#compiling">Compiling Programs using Curses</A>
31 <LI><A HREF="#updating">Updating the Screen</A>
32 <LI><A HREF="#stdscr">Standard Windows and Function Naming Conventions</A>
33 <LI><A HREF="#variables">Variables</A>
35 <LI><A HREF="#using">Using the Library</A>
37 <LI><A HREF="#starting">Starting up</A>
38 <LI><A HREF="#output">Output</A>
39 <LI><A HREF="#input">Input</A>
40 <LI><A HREF="#formschars">Using Forms Characters</A>
41 <LI><A HREF="#attributes">Character Attributes and Color</A>
42 <LI><A HREF="#mouse">Mouse Interfacing</A>
43 <LI><A HREF="#finishing">Finishing Up</A>
45 <LI><A HREF="#functions">Function Descriptions</A>
47 <LI><A HREF="#init">Initialization and Wrapup</A>
48 <LI><A HREF="#flush">Causing Output to the Terminal</A>
49 <LI><A HREF="#lowlevel">Low-Level Capability Access</A>
50 <LI><A HREF="#debugging">Debugging</A>
52 <LI><A HREF="#hints">Hints, Tips, and Tricks</A>
54 <LI><A HREF="#caution">Some Notes of Caution</A>
55 <LI><A HREF="#leaving">Temporarily Leaving ncurses Mode</A>
56 <LI><A HREF="#xterm">Using <CODE>ncurses</CODE> under <CODE>xterm</CODE></A>
57 <LI><A HREF="#screens">Handling Multiple Terminal Screens</A>
58 <LI><A HREF="#testing">Testing for Terminal Capabilities</A>
59 <LI><A HREF="#tuning">Tuning for Speed</A>
60 <LI><A HREF="#special">Special Features of <CODE>ncurses</CODE></A>
62 <LI><A HREF="#compat">Compatibility with Older Versions</A>
64 <LI><A HREF="#refbug">Refresh of Overlapping Windows</A>
65 <LI><A HREF="#backbug">Background Erase</A>
67 <LI><A HREF="#xsifuncs">XSI Curses Conformance</A>
69 <LI><A HREF="#panels">The Panels Library</A>
71 <LI><A HREF="#pcompile">Compiling With the Panels Library</A>
72 <LI><A HREF="#poverview">Overview of Panels</A>
73 <LI><A HREF="#pstdscr">Panels, Input, and the Standard Screen</A>
74 <LI><A HREF="#hiding">Hiding Panels</A>
75 <LI><A HREF="#pmisc">Miscellaneous Other Facilities</A>
77 <LI><A HREF="#menu">The Menu Library</A>
79 <LI><A HREF="#mcompile">Compiling with the menu Library</A>
80 <LI><A HREF="#moverview">Overview of Menus</A>
81 <LI><A HREF="#mselect">Selecting items</A>
82 <LI><A HREF="#mdisplay">Menu Display</A>
83 <LI><A HREF="#mwindows">Menu Windows</A>
84 <LI><A HREF="#minput">Processing Menu Input</A>
85 <LI><A HREF="#mmisc">Miscellaneous Other Features</A>
87 <LI><A HREF="#form">The Forms Library</A>
89 <LI><A HREF="#fcompile">Compiling with the forms Library</A>
90 <LI><A HREF="#foverview">Overview of Forms</A>
91 <LI><A HREF="#fcreate">Creating and Freeing Fields and Forms</A>
92 <LI><A HREF="#fattributes">Fetching and Changing Field Attributes</A>
94 <LI><A HREF="#fsizes">Fetching Size and Location Data</A>
95 <LI><A HREF="#flocation">Changing the Field Location</A>
96 <LI><A HREF="#fjust">The Justification Attribute</A>
97 <LI><A HREF="#fdispatts">Field Display Attributes</A>
98 <LI><A HREF="#foptions">Field Option Bits</A>
99 <LI><A HREF="#fstatus">Field Status</A>
100 <LI><A HREF="#fuser">Field User Pointer</A>
102 <LI><A HREF="#fdynamic">Variable-Sized Fields</A>
103 <LI><A HREF="#fvalidation">Field Validation</A>
105 <LI><A HREF="#ftype_alpha">TYPE_ALPHA</A>
106 <LI><A HREF="#ftype_alnum">TYPE_ALNUM</A>
107 <LI><A HREF="#ftype_enum">TYPE_ENUM</A>
108 <LI><A HREF="#ftype_integer">TYPE_INTEGER</A>
109 <LI><A HREF="#ftype_numeric">TYPE_NUMERIC</A>
110 <LI><A HREF="#ftype_regexp">TYPE_REGEXP</A>
112 <LI><A HREF="#fbuffer">Direct Field Buffer Manipulation</A>
113 <LI><A HREF="#formattrs">Attributes of Forms</A>
114 <LI><A HREF="#fdisplay">Control of Form Display</A>
115 <LI><A HREF="#fdriver">Input Processing in the Forms Driver</A>
117 <LI><A HREF="#fpage">Page Navigation Requests</A>
118 <LI><A HREF="#ffield">Inter-Field Navigation Requests</A>
119 <LI><A HREF="#fifield">Intra-Field Navigation Requests</A>
120 <LI><A HREF="#fscroll">Scrolling Requests</A>
121 <LI><A HREF="#fedit">Field Editing Requests</A>
122 <LI><A HREF="#forder">Order Requests</A>
123 <LI><A HREF="#fappcmds">Application Commands</A>
125 <LI><A HREF="#fhooks">Field Change Hooks</A>
126 <LI><A HREF="#ffocus">Field Change Commands</A>
127 <LI><A HREF="#frmoptions">Form Options</A>
128 <LI><A HREF="#fcustom">Custom Validation Types</A>
130 <LI><A HREF="#flinktypes">Union Types</A>
131 <LI><A HREF="#fnewtypes">New Field Types</A>
132 <LI><A HREF="#fcheckargs">Validation Function Arguments</A>
133 <LI><A HREF="#fcustorder">Order Functions For Custom Types</A>
134 <LI><A HREF="#fcustprobs">Avoiding Problems</A>
140 <H1><A NAME="introduction">Introduction</A></H1>
142 This document is an introduction to programming with <CODE>curses</CODE>. It is
143 not an exhaustive reference for the curses Application Programming Interface
144 (API); that role is filled by the <CODE>curses</CODE> manual pages. Rather, it
145 is intended to help C programmers ease into using the package. <P>
147 This document is aimed at C applications programmers not yet specifically
148 familiar with ncurses. If you are already an experienced <CODE>curses</CODE>
149 programmer, you should nevertheless read the sections on
150 <A HREF="#mouse">Mouse Interfacing</A>, <A HREF="#debugging">Debugging</A>,
151 <A HREF="compat">Compatibility with Older Versions</A>,
152 and <A HREF="#hints">Hints, Tips, and Tricks</A>. These will bring you up
153 to speed on the special features and quirks of the <CODE>ncurses</CODE>
154 implementation. If you are not so experienced, keep reading. <P>
156 The <CODE>curses</CODE> package is a subroutine library for
157 terminal-independent screen-painting and input-event handling which
158 presents a high level screen model to the programmer, hiding differences
159 between terminal types and doing automatic optimization of output to change
160 one screen full of text into another. <CODE>Curses</CODE> uses terminfo, which
161 is a database format that can describe the capabilities of thousands of
162 different terminals. <P>
164 The <CODE>curses</CODE> API may seem something of an archaism on UNIX desktops
165 increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX still
166 supports tty lines and X supports <EM>xterm(1)</EM>; the <CODE>curses</CODE>
167 API has the advantage of (a) back-portability to character-cell terminals,
168 and (b) simplicity. For an application that does not require bit-mapped
169 graphics and multiple fonts, an interface implementation using <CODE>curses</CODE>
170 will typically be a great deal simpler and less expensive than one using an
173 <H2><A NAME="history">A Brief History of Curses</A></H2>
175 Historically, the first ancestor of <CODE>curses</CODE> was the routines written to
176 provide screen-handling for the game <CODE>rogue</CODE>; these used the
177 already-existing <CODE>termcap</CODE> database facility for describing terminal
178 capabilities. These routines were abstracted into a documented library and
179 first released with the early BSD UNIX versions. <P>
181 System III UNIX from Bell Labs featured a rewritten and much-improved
182 <CODE>curses</CODE> library. It introduced the terminfo format. Terminfo is based
183 on Berkeley's termcap database, but contains a number of improvements and
184 extensions. Parameterized capabilities strings were introduced, making it
185 possible to describe multiple video attributes, and colors and to handle far
186 more unusual terminals than possible with termcap. In the later AT&T
187 System V releases, <CODE>curses</CODE> evolved to use more facilities and offer
188 more capabilities, going far beyond BSD curses in power and flexibility.<P>
190 <H2><A NAME="scope">Scope of This Document</A></H2>
192 This document describes <CODE>ncurses</CODE>, a freeware implementation of
193 the System V <CODE>curses</CODE> API with some clearly marked extensions.
194 It includes the following System V curses features: <P>
196 <LI>Support for multiple screen highlights (BSD curses could only
197 handle one `standout' highlight, usually reverse-video). <P>
198 <LI>Support for line- and box-drawing using forms characters. <P>
199 <LI>Recognition of function keys on input. <P>
200 <LI>Color support. <P>
201 <LI>Support for pads (windows of larger than screen size on which the
202 screen or a subwindow defines a viewport).
205 Also, this package makes use of the insert and delete line and character
206 features of terminals so equipped, and determines how to optimally use these
207 features with no help from the programmer. It allows arbitrary combinations of
208 video attributes to be displayed, even on terminals that leave ``magic
209 cookies'' on the screen to mark changes in attributes. <P>
211 The <CODE>ncurses</CODE> package can also capture and use event reports from a
212 mouse in some environments (notably, xterm under the X window system). This
213 document includes tips for using the mouse. <P>
215 The <CODE>ncurses</CODE> package was originated by Pavel Curtis. The original
216 maintainer of the package is
217 <A HREF="mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</A>
218 <zmbenhal@netcom.com>.
219 <A HREF="mailto:esr@snark.thyrsus.com">Eric S. Raymond</A>
220 <esr@snark.thyrsus.com>
221 wrote many of the new features in versions after 1.8.1
222 and wrote most of this introduction.
223 The current primary maintainers are
224 <A HREF="mailto:dickey@clark.net">Thomas Dickey</A>
225 <dickey@clark.net>
227 <A HREF="mailto:Juergen.Pfeifer@T-Online.de">Juergen Pfeifer</A>.
228 <Juergen.Pfeifer@T-Online.de>
231 This document also describes the <A HREF="panels">panels</A> extension library,
232 similarly modeled on the SVr4 panels facility. This library allows you to
233 associate backing store with each of a stack or deck of overlapping windows,
234 and provides operations for moving windows around in the stack that change
235 their visibility in the natural way (handling window overlaps). <P>
237 Finally, this document describes in detail the <A HREF="#menu">menus</A> and <A
238 HREF="#form">forms</A> extension libraries, also cloned from System V,
239 which support easy construction and sequences of menus and fill-in
240 forms. This code was contributed to the project by
241 <A HREF="mailto:Juergen.Pfeifer@T-Online.de">Jürgen Pfeifer</A>. <P>
244 <H2><A NAME="terminology">Terminology</A></H2>
246 In this document, the following terminology is used with reasonable
252 A data structure describing a sub-rectangle of the screen (possibly the
253 entire screen). You can write to a window as though it were a miniature
254 screen, scrolling independently of other windows on the physical screen. <P>
257 A subset of windows which are as large as the terminal screen, i.e., they start
258 at the upper left hand corner and encompass the lower right hand corner. One
259 of these, <CODE>stdscr</CODE>, is automatically provided for the programmer. <P>
262 The package's idea of what the terminal display currently looks like, i.e.,
263 what the user sees now. This is a special screen.
266 <H1><A NAME="curses">The Curses Library</A></H1>
268 <H2><A NAME="overview">An Overview of Curses</A></H2>
270 <H3><A NAME="compiling">Compiling Programs using Curses</A></H3>
272 In order to use the library, it is necessary to have certain types and
273 variables defined. Therefore, the programmer must have a line:
276 #include <curses.h>
279 at the top of the program source. The screen package uses the Standard I/O
280 library, so <CODE><curses.h></CODE> includes
281 <CODE><stdio.h></CODE>. <CODE><curses.h></CODE> also includes
282 <CODE><termios.h></CODE>, <CODE><termio.h></CODE>, or
283 <CODE><sgtty.h></CODE> depending on your system. It is redundant (but
284 harmless) for the programmer to do these includes, too. In linking with
285 <CODE>curses</CODE> you need to have <CODE>-lncurses</CODE> in your LDFLAGS or on the
286 command line. There is no need for any other libraries.
288 <H3><A NAME="updating">Updating the Screen</A></H3>
290 In order to update the screen optimally, it is necessary for the routines to
291 know what the screen currently looks like and what the programmer wants it to
292 look like next. For this purpose, a data type (structure) named WINDOW is
293 defined which describes a window image to the routines, including its starting
294 position on the screen (the (y, x) coordinates of the upper left hand corner)
295 and its size. One of these (called <CODE>curscr</CODE>, for current screen) is a
296 screen image of what the terminal currently looks like. Another screen (called
297 <CODE>stdscr</CODE>, for standard screen) is provided by default to make changes
300 A window is a purely internal representation. It is used to build and store a
301 potential image of a portion of the terminal. It doesn't bear any necessary
302 relation to what is really on the terminal screen; it's more like a
303 scratchpad or write buffer. <P>
305 To make the section of physical screen corresponding to a window reflect the
306 contents of the window structure, the routine <CODE>refresh()</CODE> (or
307 <CODE>wrefresh()</CODE> if the window is not <CODE>stdscr</CODE>) is called. <P>
309 A given physical screen section may be within the scope of any number of
310 overlapping windows. Also, changes can be made to windows in any order,
311 without regard to motion efficiency. Then, at will, the programmer can
312 effectively say ``make it look like this,'' and let the package implementation
313 determine the most efficient way to repaint the screen. <P>
315 <H3><A NAME="stdscr">Standard Windows and Function Naming Conventions</A></H3>
317 As hinted above, the routines can use several windows, but two are
318 automatically given: <CODE>curscr</CODE>, which knows what the terminal looks like,
319 and <CODE>stdscr</CODE>, which is what the programmer wants the terminal to look
320 like next. The user should never actually access <CODE>curscr</CODE> directly.
321 Changes should be made to through the API, and then the routine
322 <CODE>refresh()</CODE> (or <CODE>wrefresh()</CODE>) called. <P>
324 Many functions are defined to use <CODE>stdscr</CODE> as a default screen. For
325 example, to add a character to <CODE>stdscr</CODE>, one calls <CODE>addch()</CODE> with
326 the desired character as argument. To write to a different window. use the
327 routine <CODE>waddch()</CODE> (for `w'indow-specific addch()) is provided. This
328 convention of prepending function names with a `w' when they are to be
329 applied to specific windows is consistent. The only routines which do not
330 follow it are those for which a window must always be specified. <P>
332 In order to move the current (y, x) coordinates from one point to another, the
333 routines <CODE>move()</CODE> and <CODE>wmove()</CODE> are provided. However, it is
334 often desirable to first move and then perform some I/O operation. In order to
335 avoid clumsiness, most I/O routines can be preceded by the prefix 'mv' and
336 the desired (y, x) coordinates prepended to the arguments to the function. For
360 mvwaddch(win, y, x, ch);
363 Note that the window description pointer (win) comes before the added (y, x)
364 coordinates. If a function requires a window pointer, it is always the first
365 parameter passed. <P>
367 <H3><A NAME="variables">Variables</A></H3>
369 The <CODE>curses</CODE> library sets some variables describing the terminal
373 type name description
374 ------------------------------------------------------------------
375 int LINES number of lines on the terminal
376 int COLS number of columns on the terminal
379 The <CODE>curses.h</CODE> also introduces some <CODE>#define</CODE> constants and types
380 of general usefulness:
383 <DT> <CODE>bool</CODE>
384 <DD> boolean type, actually a `char' (e.g., <CODE>bool doneit;</CODE>)
385 <DT> <CODE>TRUE</CODE>
386 <DD> boolean `true' flag (1).
387 <DT> <CODE>FALSE</CODE>
388 <DD> boolean `false' flag (0).
389 <DT> <CODE>ERR</CODE>
390 <DD> error flag returned by routines on a failure (-1).
392 <DD> error flag returned by routines when things go right.
395 <H2><A NAME="using">Using the Library</A></H2>
397 Now we describe how to actually use the screen package. In it, we assume all
398 updating, reading, etc. is applied to <CODE>stdscr</CODE>. These instructions will
399 work on any window, providing you change the function names and parameters as
402 Here is a sample program to motivate the discussion: <P>
405 #include <curses.h>
406 #include <signal.h>
408 static void finish(int sig);
410 main(int argc, char *argv[])
412 /* initialize your non-curses data structures here */
414 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
416 (void) initscr(); /* initialize the curses library */
417 keypad(stdscr, TRUE); /* enable keyboard mapping */
418 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
419 (void) cbreak(); /* take input chars one at a time, no wait for \n */
420 (void) noecho(); /* don't echo input */
427 * Simple color assignment, often all we need.
429 init_pair(COLOR_BLACK, COLOR_BLACK, COLOR_BLACK);
430 init_pair(COLOR_GREEN, COLOR_GREEN, COLOR_BLACK);
431 init_pair(COLOR_RED, COLOR_RED, COLOR_BLACK);
432 init_pair(COLOR_CYAN, COLOR_CYAN, COLOR_BLACK);
433 init_pair(COLOR_WHITE, COLOR_WHITE, COLOR_BLACK);
434 init_pair(COLOR_MAGENTA, COLOR_MAGENTA, COLOR_BLACK);
435 init_pair(COLOR_BLUE, COLOR_BLUE, COLOR_BLACK);
436 init_pair(COLOR_YELLOW, COLOR_YELLOW, COLOR_BLACK);
441 int c = getch(); /* refresh, accept single keystroke of input */
443 /* process the command keystroke */
446 finish(0); /* we're done */
449 static void finish(int sig)
453 /* do your non-curses wrapup here */
459 <H3><A NAME="starting">Starting up</A></H3>
461 In order to use the screen package, the routines must know about terminal
462 characteristics, and the space for <CODE>curscr</CODE> and <CODE>stdscr</CODE> must be
463 allocated. These function <CODE>initscr()</CODE> does both these things. Since it
464 must allocate space for the windows, it can overflow memory when attempting to
465 do so. On the rare occasions this happens, <CODE>initscr()</CODE> will terminate
466 the program with an error message. <CODE>initscr()</CODE> must always be called
467 before any of the routines which affect windows are used. If it is not, the
468 program will core dump as soon as either <CODE>curscr</CODE> or <CODE>stdscr</CODE> are
469 referenced. However, it is usually best to wait to call it until after you are
470 sure you will need it, like after checking for startup errors. Terminal status
471 changing routines like <CODE>nl()</CODE> and <CODE>cbreak()</CODE> should be called
472 after <CODE>initscr()</CODE>. <P>
474 Once the screen windows have been allocated, you can set them up for
475 your program. If you want to, say, allow a screen to scroll, use
476 <CODE>scrollok()</CODE>. If you want the cursor to be left in place after
477 the last change, use <CODE>leaveok()</CODE>. If this isn't done,
478 <CODE>refresh()</CODE> will move the cursor to the window's current (y, x)
479 coordinates after updating it. <P>
481 You can create new windows of your own using the functions <CODE>newwin()</CODE>,
482 <CODE>derwin()</CODE>, and <CODE>subwin()</CODE>. The routine <CODE>delwin()</CODE> will
483 allow you to get rid of old windows. All the options described above can be
484 applied to any window. <P>
486 <H3><A NAME="output">Output</A></H3>
488 Now that we have set things up, we will want to actually update the terminal.
489 The basic functions used to change what will go on a window are
490 <CODE>addch()</CODE> and <CODE>move()</CODE>. <CODE>addch()</CODE> adds a character at the
491 current (y, x) coordinates. <CODE>move()</CODE> changes the current (y, x)
492 coordinates to whatever you want them to be. It returns <CODE>ERR</CODE> if you
493 try to move off the window. As mentioned above, you can combine the two into
494 <CODE>mvaddch()</CODE> to do both things at once. <P>
496 The other output functions, such as <CODE>addstr()</CODE> and <CODE>printw()</CODE>,
497 all call <CODE>addch()</CODE> to add characters to the window. <P>
499 After you have put on the window what you want there, when you want the portion
500 of the terminal covered by the window to be made to look like it, you must call
501 <CODE>refresh()</CODE>. In order to optimize finding changes, <CODE>refresh()</CODE>
502 assumes that any part of the window not changed since the last
503 <CODE>refresh()</CODE> of that window has not been changed on the terminal, i.e.,
504 that you have not refreshed a portion of the terminal with an overlapping
505 window. If this is not the case, the routine <CODE>touchwin()</CODE> is provided
506 to make it look like the entire window has been changed, thus making
507 <CODE>refresh()</CODE> check the whole subsection of the terminal for changes. <P>
509 If you call <CODE>wrefresh()</CODE> with <CODE>curscr</CODE> as its argument, it will
510 make the screen look like <CODE>curscr</CODE> thinks it looks like. This is useful
511 for implementing a command which would redraw the screen in case it get messed
514 <H3><A NAME="input">Input</A></H3>
516 The complementary function to <CODE>addch()</CODE> is <CODE>getch()</CODE> which, if
517 echo is set, will call <CODE>addch()</CODE> to echo the character. Since the
518 screen package needs to know what is on the terminal at all times, if
519 characters are to be echoed, the tty must be in raw or cbreak mode. Since
520 initially the terminal has echoing enabled and is in ordinary ``cooked'' mode,
521 one or the other has to changed before calling <CODE>getch()</CODE>; otherwise,
522 the program's output will be unpredictable. <P>
524 When you need to accept line-oriented input in a window, the functions
525 <CODE>wgetstr()</CODE> and friends are available. There is even a <CODE>wscanw()</CODE>
526 function that can do <CODE>scanf()</CODE>(3)-style multi-field parsing on window
527 input. These pseudo-line-oriented functions turn on echoing while they
530 The example code above uses the call <CODE>keypad(stdscr, TRUE)</CODE> to enable
531 support for function-key mapping. With this feature, the <CODE>getch()</CODE> code
532 watches the input stream for character sequences that correspond to arrow and
533 function keys. These sequences are returned as pseudo-character values. The
534 <CODE>#define</CODE> values returned are listed in the <CODE>curses.h</CODE> The
535 mapping from sequences to <CODE>#define</CODE> values is determined by
536 <CODE>key_</CODE> capabilities in the terminal's terminfo entry. <P>
538 <H3><A NAME="formschars">Using Forms Characters</A></H3>
540 The <CODE>addch()</CODE> function (and some others, including <CODE>box()</CODE> and
541 <CODE>border()</CODE>) can accept some pseudo-character arguments which are specially
542 defined by <CODE>ncurses</CODE>. These are <CODE>#define</CODE> values set up in
543 the <CODE>curses.h</CODE> header; see there for a complete list (look for
544 the prefix <CODE>ACS_</CODE>). <P>
546 The most useful of the ACS defines are the forms-drawing characters. You can
547 use these to draw boxes and simple graphs on the screen. If the terminal
548 does not have such characters, <CODE>curses.h</CODE> will map them to a
549 recognizable (though ugly) set of ASCII defaults. <P>
551 <H3><A NAME="attributes">Character Attributes and Color</A></H3>
553 The <CODE>ncurses</CODE> package supports screen highlights including standout,
554 reverse-video, underline, and blink. It also supports color, which is treated
555 as another kind of highlight. <P>
557 Highlights are encoded, internally, as high bits of the pseudo-character type
558 (<CODE>chtype</CODE>) that <CODE>curses.h</CODE> uses to represent the contents of a
559 screen cell. See the <CODE>curses.h</CODE> header file for a complete list of
560 highlight mask values (look for the prefix <CODE>A_</CODE>).<P>
562 There are two ways to make highlights. One is to logical-or the value of the
563 highlights you want into the character argument of an <CODE>addch()</CODE> call,
564 or any other output call that takes a <CODE>chtype</CODE> argument. <P>
566 The other is to set the current-highlight value. This is logical-or'ed with
567 any highlight you specify the first way. You do this with the functions
568 <CODE>attron()</CODE>, <CODE>attroff()</CODE>, and <CODE>attrset()</CODE>; see the manual
571 Color is a special kind of highlight. The package actually thinks in terms
572 of color pairs, combinations of foreground and background colors. The sample
573 code above sets up eight color pairs, all of the guaranteed-available colors
574 on black. Note that each color pair is, in effect, given the name of its
575 foreground color. Any other range of eight non-conflicting values could
576 have been used as the first arguments of the <CODE>init_pair()</CODE> values. <P>
578 Once you've done an <CODE>init_pair()</CODE> that creates color-pair N, you can
579 use <CODE>COLOR_PAIR(N)</CODE> as a highlight that invokes that particular
580 color combination. Note that <CODE>COLOR_PAIR(N)</CODE>, for constant N,
581 is itself a compile-time constant and can be used in initializers. <P>
583 <H3><A NAME="mouse">Mouse Interfacing</A></H3>
585 The <CODE>ncurses</CODE> library also provides a mouse interface. Note:
586 his facility is original to <CODE>ncurses</CODE>, it is not part of either
587 the XSI Curses standard, nor of System V Release 4, nor BSD curses.
588 Thus, we recommend that you wrap mouse-related code in an #ifdef using the
589 feature macro NCURSES_MOUSE_VERSION so it will not be compiled and linked
590 on non-ncurses systems. <P>
592 Presently, mouse event reporting works only under xterm. In the
593 future, ncurses will detect the presence of <CODE>gpm</CODE>(1), Alessandro
594 Rubini's freeware mouse server for Linux systems, and accept mouse
595 reports through it. <P>
597 The mouse interface is very simple. To activate it, you use the function
598 <CODE>mousemask()</CODE>, passing it as first argument a bit-mask that specifies
599 what kinds of events you want your program to be able to see. It will
600 return the bit-mask of events that actually become visible, which may differ
601 from the argument if the mouse device is not capable of reporting some of
602 the event types you specify. <P>
604 Once the mouse is active, your application's command loop should watch
605 for a return value of <CODE>KEY_MOUSE</CODE> from <CODE>wgetch()</CODE>. When
606 you see this, a mouse event report has been queued. To pick it off
607 the queue, use the function <CODE>getmouse()</CODE> (you must do this before
608 the next <CODE>wgetch()</CODE>, otherwise another mouse event might come
609 in and make the first one inaccessible). <P>
611 Each call to <CODE>getmouse()</CODE> fills a structure (the address of which you'll
612 pass it) with mouse event data. The event data includes zero-origin,
613 screen-relative character-cell coordinates of the mouse pointer. It also
614 includes an event mask. Bits in this mask will be set, corresponding
615 to the event type being reported. <P>
617 The mouse structure contains two additional fields which may be
618 significant in the future as ncurses interfaces to new kinds of
619 pointing device. In addition to x and y coordinates, there is a slot
620 for a z coordinate; this might be useful with touch-screens that can
621 return a pressure or duration parameter. There is also a device ID
622 field, which could be used to distinguish between multiple pointing
625 The class of visible events may be changed at any time via <CODE>mousemask()</CODE>.
626 Events that can be reported include presses, releases, single-, double- and
627 triple-clicks (you can set the maximum button-down time for clicks). If
628 you don't make clicks visible, they will be reported as press-release
629 pairs. In some environments, the event mask may include bits reporting
630 the state of shift, alt, and ctrl keys on the keyboard during the event. <P>
632 A function to check whether a mouse event fell within a given window is
633 also supplied. You can use this to see whether a given window should
634 consider a mouse event relevant to it. <P>
636 Because mouse event reporting will not be available in all
637 environments, it would be unwise to build <CODE>ncurses</CODE>
638 applications that <EM>require</EM> the use of a mouse. Rather, you should
639 use the mouse as a shortcut for point-and-shoot commands your application
640 would normally accept from the keyboard. Two of the test games in the
641 <CODE>ncurses</CODE> distribution (<CODE>bs</CODE> and <CODE>knight</CODE>) contain
642 code that illustrates how this can be done. <P>
644 See the manual page <CODE>curs_mouse(3X)</CODE> for full details of the
645 mouse-interface functions. <P>
647 <H3><A NAME="finishing">Finishing Up</A></H3>
649 In order to clean up after the <CODE>ncurses</CODE> routines, the routine
650 <CODE>endwin()</CODE> is provided. It restores tty modes to what they were when
651 <CODE>initscr()</CODE> was first called, and moves the cursor down to the
652 lower-left corner. Thus, anytime after the call to initscr, <CODE>endwin()</CODE>
653 should be called before exiting. <P>
655 <H2><A NAME="functions">Function Descriptions</A></H2>
657 We describe the detailed behavior of some important curses functions here, as a
658 supplement to the manual page descriptions.
660 <H3><A NAME="init">Initialization and Wrapup</A></H3>
663 <DT> <CODE>initscr()</CODE>
664 <DD> The first function called should almost always be <CODE>initscr()</CODE>.
665 This will determine the terminal type and
666 initialize curses data structures. <CODE>initscr()</CODE> also arranges that
667 the first call to <CODE>refresh()</CODE> will clear the screen. If an error
668 occurs a message is written to standard error and the program
669 exits. Otherwise it returns a pointer to stdscr. A few functions may be
670 called before initscr (<CODE>slk_init()</CODE>, <CODE>filter()</CODE>,
671 <CODE>ripofflines()</CODE>, <CODE>use_env()</CODE>, and, if you are using multiple
672 terminals, <CODE>newterm()</CODE>.) <P>
673 <DT> <CODE>endwin()</CODE>
674 <DD> Your program should always call <CODE>endwin()</CODE> before exiting or
675 shelling out of the program. This function will restore tty modes,
676 move the cursor to the lower left corner of the screen, reset the
677 terminal into the proper non-visual mode. Calling <CODE>refresh()</CODE>
678 or <CODE>doupdate()</CODE> after a temporary escape from the program will
679 restore the ncurses screen from before the escape. <P>
680 <DT> <CODE>newterm(type, ofp, ifp)</CODE>
681 <DD> A program which outputs to more than one terminal should use
682 <CODE>newterm()</CODE> instead of <CODE>initscr()</CODE>. <CODE>newterm()</CODE> should
683 be called once for each terminal. It returns a variable of type
684 <CODE>SCREEN *</CODE> which should be saved as a reference to that
685 terminal. The arguments are the type of the terminal (a string) and
686 <CODE>FILE</CODE> pointers for the output and input of the terminal. If
687 type is NULL then the environment variable <CODE>$TERM</CODE> is used.
688 <CODE>endwin()</CODE> should called once at wrapup time for each terminal
689 opened using this function. <P>
690 <DT> <CODE>set_term(new)</CODE>
691 <DD> This function is used to switch to a different terminal previously
692 opened by <CODE>newterm()</CODE>. The screen reference for the new terminal
693 is passed as the parameter. The previous terminal is returned by the
694 function. All other calls affect only the current terminal. <P>
695 <DT> <CODE>delscreen(sp)</CODE>
696 <DD> The inverse of <CODE>newterm()</CODE>; deallocates the data structures
697 associated with a given <CODE>SCREEN</CODE> reference.
700 <H3><A NAME="flush">Causing Output to the Terminal</A></H3>
703 <DT> <CODE>refresh()</CODE> and <CODE>wrefresh(win)</CODE>
704 <DD> These functions must be called to actually get any output on
705 the terminal, as other routines merely manipulate data
706 structures. <CODE>wrefresh()</CODE> copies the named window to the physical
707 terminal screen, taking into account what is already
708 there in order to do optimizations. <CODE>refresh()</CODE> does a
709 refresh of <CODE>stdscr()</CODE>. Unless <CODE>leaveok()</CODE> has been
710 enabled, the physical cursor of the terminal is left at the
711 location of the window's cursor. <P>
712 <DT> <CODE>doupdate()</CODE> and <CODE>wnoutrefresh(win)</CODE>
713 <DD> These two functions allow multiple updates with more efficiency
714 than wrefresh. To use them, it is important to understand how curses
715 works. In addition to all the window structures, curses keeps two
716 data structures representing the terminal screen: a physical screen,
717 describing what is actually on the screen, and a virtual screen,
718 describing what the programmer wants to have on the screen. wrefresh
719 works by first copying the named window to the virtual screen
720 (<CODE>wnoutrefresh()</CODE>), and then calling the routine to update the
721 screen (<CODE>doupdate()</CODE>). If the programmer wishes to output
722 several windows at once, a series of calls to <CODE>wrefresh</CODE> will result
723 in alternating calls to <CODE>wnoutrefresh()</CODE> and <CODE>doupdate()</CODE>,
724 causing several bursts of output to the screen. By calling
725 <CODE>wnoutrefresh()</CODE> for each window, it is then possible to call
726 <CODE>doupdate()</CODE> once, resulting in only one burst of output, with
727 fewer total characters transmitted (this also avoids a visually annoying
728 flicker at each update).
731 <H3><A NAME="lowlevel">Low-Level Capability Access</A></H3>
734 <DT> <CODE>setupterm(term, filenum, errret)</CODE>
735 <DD> This routine is called to initialize a terminal's description, without setting
736 up the curses screen structures or changing the tty-driver mode bits.
737 <CODE>term</CODE> is the character string representing the name of the terminal
738 being used. <CODE>filenum</CODE> is the UNIX file descriptor of the terminal to
739 be used for output. <CODE>errret</CODE> is a pointer to an integer, in which a
740 success or failure indication is returned. The values returned can be 1 (all
741 is well), 0 (no such terminal), or -1 (some problem locating the terminfo
744 The value of <CODE>term</CODE> can be given as NULL, which will cause the value of
745 <CODE>TERM</CODE> in the environment to be used. The <CODE>errret</CODE> pointer can
746 also be given as NULL, meaning no error code is wanted. If <CODE>errret</CODE> is
747 defaulted, and something goes wrong, <CODE>setupterm()</CODE> will print an
748 appropriate error message and exit, rather than returning. Thus, a simple
749 program can call setupterm(0, 1, 0) and not worry about initialization
752 After the call to <CODE>setupterm()</CODE>, the global variable <CODE>cur_term</CODE> is
753 set to point to the current structure of terminal capabilities. By calling
754 <CODE>setupterm()</CODE> for each terminal, and saving and restoring
755 <CODE>cur_term</CODE>, it is possible for a program to use two or more terminals at
756 once. <CODE>Setupterm()</CODE> also stores the names section of the terminal
757 description in the global character array <CODE>ttytype[]</CODE>. Subsequent calls
758 to <CODE>setupterm()</CODE> will overwrite this array, so you'll have to save it
762 <H3><A NAME="debugging">Debugging</A></H3>
764 NOTE: These functions are not part of the standard curses API! <P>
767 <DT> <CODE>trace()</CODE>
769 This function can be used to explicitly set a trace level. If the
770 trace level is nonzero, execution of your program will generate a file
771 called `trace' in the current working directory containing a report on
772 the library's actions. Higher trace levels enable more detailed (and
773 verbose) reporting -- see comments attached to <CODE>TRACE_</CODE> defines
774 in the <CODE>curses.h</CODE> file for details. (It is also possible to set
775 a trace level by assigning a trace level value to the environment variable
776 <CODE>NCURSES_TRACE</CODE>).
777 <DT> <CODE>_tracef()</CODE>
779 This function can be used to output your own debugging information. It is only
780 available only if you link with -lncurses_g. It can be used the same way as
781 <CODE>printf()</CODE>, only it outputs a newline after the end of arguments.
782 The output goes to a file called <CODE>trace</CODE> in the current directory.
785 Trace logs can be difficult to interpret due to the sheer volume of
786 data dumped in them. There is a script called <STRONG>tracemunch</STRONG>
787 included with the <CODE>ncurses</CODE> distribution that can alleviate
788 this problem somewhat; it compacts long sequences of similar operations into
789 more succinct single-line pseudo-operations. These pseudo-ops can be
790 distinguished by the fact that they are named in capital letters.<P>
792 <H2><A NAME="hints">Hints, Tips, and Tricks</A></H2>
794 The <CODE>ncurses</CODE> manual pages are a complete reference for this library.
795 In the remainder of this document, we discuss various useful methods that
796 may not be obvious from the manual page descriptions. <P>
798 <H3><A NAME="caution">Some Notes of Caution</A></H3>
800 If you find yourself thinking you need to use <CODE>noraw()</CODE> or
801 <CODE>nocbreak()</CODE>, think again and move carefully. It's probably
802 better design to use <CODE>getstr()</CODE> or one of its relatives to
803 simulate cooked mode. The <CODE>noraw()</CODE> and <CODE>nocbreak()</CODE>
804 functions try to restore cooked mode, but they may end up clobbering
805 some control bits set before you started your application. Also, they
806 have always been poorly documented, and are likely to hurt your
807 application's usability with other curses libraries. <P>
809 Bear in mind that <CODE>refresh()</CODE> is a synonym for <CODE>wrefresh(stdscr)</CODE>,
810 and don't try to mix use of <CODE>stdscr</CODE> with use of windows declared
811 by <CODE>newwin()</CODE>; a <CODE>refresh()</CODE> call will blow them off the
812 screen. The right way to handle this is to use <CODE>subwin()</CODE>, or
813 not touch <CODE>stdscr</CODE> at all and tile your screen with declared
814 windows which you then <CODE>wnoutrefresh()</CODE> somewhere in your program
815 event loop, with a single <CODE>doupdate()</CODE> call to trigger actual
818 You are much less likely to run into problems if you design your screen
819 layouts to use tiled rather than overlapping windows. Historically,
820 curses support for overlapping windows has been weak, fragile, and poorly
821 documented. The <CODE>ncurses</CODE> library is not yet an exception to this
824 There is a freeware panels library included in the <CODE>ncurses</CODE>
825 distribution that does a pretty good job of strengthening the
826 overlapping-windows facilities. <P>
828 Try to avoid using the global variables LINES and COLS. Use
829 <CODE>getmaxyx()</CODE> on the <CODE>stdscr</CODE> context instead. Reason:
830 your code may be ported to run in an environment with window resizes,
831 in which case several screens could be open with different sizes. <P>
833 <H3><A NAME="leaving">Temporarily Leaving <CODE>ncurses</CODE> Mode</A></H3>
835 Sometimes you will want to write a program that spends most of its time in
836 screen mode, but occasionally returns to ordinary `cooked' mode. A common
837 reason for this is to support shell-out. This behavior is simple to arrange
838 in <CODE>ncurses</CODE>. <P>
840 To leave <CODE>ncurses</CODE> mode, call <CODE>endwin()</CODE> as you would if you
841 were intending to terminate the program. This will take the screen back to
842 cooked mode; you can do your shell-out. When you want to return to
843 <CODE>ncurses</CODE> mode, simply call <CODE>refresh()</CODE> or <CODE>doupdate()</CODE>.
844 This will repaint the screen. <P>
846 There is a boolean function, <CODE>isendwin()</CODE>, which code can use to
847 test whether <CODE>ncurses</CODE> screen mode is active. It returns <CODE>TRUE</CODE>
848 in the interval between an <CODE>endwin()</CODE> call and the following
849 <CODE>refresh()</CODE>, <CODE>FALSE</CODE> otherwise. <P>
851 Here is some sample code for shellout:
854 addstr("Shelling out...");
855 def_prog_mode(); /* save current tty modes */
856 endwin(); /* restore original tty modes */
857 system("sh"); /* run shell */
858 addstr("returned.\n"); /* prepare return message */
859 refresh(); /* restore save modes, repaint screen */
862 <H3><A NAME="xterm">Using <CODE>ncurses</CODE> Under <CODE>xterm</CODE></A></H3>
864 A resize operation in X sends SIGWINCH to the application running under xterm.
865 The <CODE>ncurses</CODE> library does not catch this signal, because it cannot in
866 general know how you want the screen re-painted. You will have to write the
867 SIGWINCH handler yourself. <P>
869 The easiest way to code your SIGWINCH handler is to have it do an
870 <CODE>endwin</CODE>, followed by an <CODE>refresh</CODE> and a screen repaint you code
871 yourself. The <CODE>refresh</CODE> will pick up the new screen size from the
874 <H3><A NAME="screens">Handling Multiple Terminal Screens</A></H3>
876 The <CODE>initscr()</CODE> function actually calls a function named
877 <CODE>newterm()</CODE> to do most of its work. If you are writing a program that
878 opens multiple terminals, use <CODE>newterm()</CODE> directly. <P>
880 For each call, you will have to specify a terminal type and a pair of file
881 pointers; each call will return a screen reference, and <CODE>stdscr</CODE> will be
882 set to the last one allocated. You will switch between screens with the
883 <CODE>set_term</CODE> call. Note that you will also have to call
884 <CODE>def_shell_mode</CODE> and <CODE>def_prog_mode</CODE> on each tty yourself. <P>
886 <H3><A NAME="testing">Testing for Terminal Capabilities</A></H3>
888 Sometimes you may want to write programs that test for the presence of various
889 capabilities before deciding whether to go into <CODE>ncurses</CODE> mode. An easy
890 way to do this is to call <CODE>setupterm()</CODE>, then use the functions
891 <CODE>tigetflag()</CODE>, <CODE>tigetnum()</CODE>, and <CODE>tigetstr()</CODE> to do your
894 A particularly useful case of this often comes up when you want to
895 test whether a given terminal type should be treated as `smart'
896 (cursor-addressable) or `stupid'. The right way to test this is to see
897 if the return value of <CODE>tigetstr("cup")</CODE> is non-NULL. Alternatively,
898 you can include the <CODE>term.h</CODE> file and test the value of the
899 macro <CODE>cursor_address</CODE>. <P>
901 <H3><A NAME="tuning">Tuning for Speed</A></H3>
903 Use the <CODE>addchstr()</CODE> family of functions for fast
904 screen-painting of text when you know the text doesn't contain any
905 control characters. Try to make attribute changes infrequent on your
906 screens. Don't use the <CODE>immedok()</CODE> option! <P>
908 <H3><A NAME="special">Special Features of <CODE>ncurses</CODE></A></H3>
910 When running on PC-clones, <CODE>ncurses</CODE> has enhanced support for
911 the IBM high-half and ROM characters. The <CODE>A_ALTCHARSET</CODE> highlight,
912 enables display of both high-half ACS graphics and the PC ROM graphics
913 0-31 that are normally interpreted as control characters. <P>
915 The <CODE>wresize()</CODE> function allows you to resize a window in place. <P>
917 <H2><A NAME="compat">Compatibility with Older Versions</A></H2>
919 Despite our best efforts, there are some differences between <CODE>ncurses</CODE>
920 and the (undocumented!) behavior of older curses implementations. These arise
921 from ambiguities or omissions in the documentation of the API.
923 <H3><A NAME="refbug">Refresh of Overlapping Windows</A></H3>
925 If you define two windows A and B that overlap, and then alternately scribble
926 on and refresh them, the changes made to the overlapping region under historic
927 <CODE>curses</CODE> versions were often not documented precisely. <P>
929 To understand why this is a problem, remember that screen updates are
930 calculated between two representations of the <EM>entire</EM> display. The
931 documentation says that when you refresh a window, it is first copied to to the
932 virtual screen, and then changes are calculated to update the physical screen
933 (and applied to the terminal). But "copied to" is not very specific, and
934 subtle differences in how copying works can produce different behaviors in the
935 case where two overlapping windows are each being refreshed at unpredictable
938 What happens to the overlapping region depends on what <CODE>wnoutrefresh()</CODE>
939 does with its argument -- what portions of the argument window it copies to the
940 virtual screen. Some implementations do "change copy", copying down only
941 locations in the window that have changed (or been marked changed with
942 <CODE>wtouchln()</CODE> and friends). Some implementations do "entire copy",
943 copying <EM>all</EM> window locations to the virtual screen whether or not
944 they have changed. <P>
946 The <CODE>ncurses</CODE> library itself has not always been consistent on this
947 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy. Versions
948 1.8.6 and older, and versions 1.9.9 and newer, do change copy. <P>
950 For most commercial curses implementations, it is not documented and not known
951 for sure (at least not to the <CODE>ncurses</CODE> maintainers) whether they do
952 change copy or entire copy. We know that System V release 3 curses has logic
953 in it that looks like an attempt to do change copy, but the surrounding logic
954 and data representations are sufficiently complex, and our knowledge
955 sufficiently indirect, that it's hard to know whether this is reliable.
957 It is not clear what the SVr4 documentation and XSI standard intend. The XSI
958 Curses standard barely mentions wnoutrefresh(); the SVr4 documents seem to be
959 describing entire-copy, but it is possible with some effort and straining to
960 read them the other way. <P>
962 It might therefore be unwise to rely on either behavior in programs that might
963 have to be linked with other curses implementations. Instead, you can do an
964 explicit <CODE>touchwin()</CODE> before the <CODE>wnoutrefresh()</CODE> call to
965 guarantee an entire-contents copy anywhere. <P>
967 The really clean way to handle this is to use the panels library. If,
968 when you want a screen update, you do <CODE>update_panels()</CODE>, it will
969 do all the necessary <CODE>wnoutrfresh()</CODE> calls for whatever panel
970 stacking order you have defined. Then you can do one <CODE>doupdate()</CODE>
971 and there will be a <EM>single</EM> burst of physical I/O that will do
972 all your updates. <P>
974 <H3><A NAME="backbug">Background Erase</A></H3>
976 If you have been using a very old versions of <CODE>ncurses</CODE> (1.8.7 or
977 older) you may be surprised by the behavior of the erase functions. In older
978 versions, erased areas of a window were filled with a blank modified by the
979 window's current attribute (as set by <STRONG>wattrset()</STRONG>, <STRONG>wattron()</STRONG>,
980 <STRONG>wattroff()</STRONG> and friends). <P>
982 In newer versions, this is not so. Instead, the attribute of erased blanks
983 is normal unless and until it is modified by the functions <CODE>bkgdset()</CODE>
984 or <CODE>wbkgdset()</CODE>. <P>
986 This change in behavior conforms <CODE>ncurses</CODE> to System V Release 4 and
987 the XSI Curses standard. <P>
989 <H2><A NAME="xsifuncs">XSI Curses Conformance</A></H2>
991 The <CODE>ncurses</CODE> library is intended to be base-level conformant with the
992 XSI Curses standard from X/Open. Many extended-level features (in fact, almost
993 all features not directly concerned with wide characters and
994 internationalization) are also supported. <P>
996 One effect of XSI conformance is the change in behavior described under
997 <A HREF="#backbug">"Background Erase -- Compatibility with Old Versions"</A>. <P>
999 Also, <CODE>ncurses</CODE> meets the XSI requirement that every macro
1000 entry point have a corresponding function which may be linked (and
1001 will be prototype-checked) if the macro definition is disabled with
1002 <CODE>#undef</CODE>. <P>
1004 <H1><A NAME="panels">The Panels Library</A></H1>
1006 The <CODE>ncurses</CODE> library by itself provides good support for screen
1007 displays in which the windows are tiled (non-overlapping). In the more
1008 general case that windows may overlap, you have to use a series of
1009 <CODE>wnoutrefresh()</CODE> calls followed by a <CODE>doupdate()</CODE>, and be
1010 careful about the order you do the window refreshes in. It has to be
1011 bottom-upwards, otherwise parts of windows that should be obscured will
1014 When your interface design is such that windows may dive deeper into the
1015 visibility stack or pop to the top at runtime, the resulting book-keeping
1016 can be tedious and difficult to get right. Hence the panels library. <P>
1018 The <CODE>panel</CODE> library first appeared in AT&T System V. The
1019 version documented here is the freeware <CODE>panel</CODE> code distributed
1020 with <CODE>ncurses</CODE>.
1022 <H2><A NAME="pcompile">Compiling With the Panels Library</A></H2>
1024 Your panels-using modules must import the panels library declarations with
1027 #include <panel.h>
1030 and must be linked explicitly with the panels library using an
1031 <CODE>-lpanel</CODE> argument. Note that they must also link the
1032 <CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
1033 are two-pass and will accept either order, but it is still good practice
1034 to put <CODE>-lpanel</CODE> first and <CODE>-lncurses</CODE> second.
1036 <H2><A NAME="poverview">Overview of Panels</A></H2>
1038 A panel object is a window that is implicitly treated as part of a
1039 <DFN>deck</DFN> including all other panel objects. The deck has an implicit
1040 bottom-to-top visibility order. The panels library includes an update
1041 function (analogous to <CODE>refresh()</CODE>) that displays all panels in the
1042 deck in the proper order to resolve overlaps. The standard window,
1043 <CODE>stdscr</CODE>, is considered below all panels. <P>
1045 Details on the panels functions are available in the man pages. We'll just
1046 hit the highlights here. <P>
1048 You create a panel from a window by calling <CODE>new_panel()</CODE> on a
1049 window pointer. It then becomes the top of the deck. The panel's window
1050 is available as the value of <CODE>panel_window()</CODE> called with the
1051 panel pointer as argument.<P>
1053 You can delete a panel (removing it from the deck) with <CODE>del_panel</CODE>.
1054 This will not deallocate the associated window; you have to do that yourself.
1056 You can replace a panel's window with a different window by calling
1057 <CODE>replace_window</CODE>. The new window may be of different size;
1058 the panel code will re-compute all overlaps. This operation doesn't
1059 change the panel's position in the deck. <P>
1061 To move a panel's window, use <CODE>move_panel()</CODE>. The
1062 <CODE>mvwin()</CODE> function on the panel's window isn't sufficient because it
1063 doesn't update the panels library's representation of where the windows are.
1064 This operation leaves the panel's depth, contents, and size unchanged. <P>
1066 Two functions (<CODE>top_panel()</CODE>, <CODE>bottom_panel()</CODE>) are
1067 provided for rearranging the deck. The first pops its argument window to the
1068 top of the deck; the second sends it to the bottom. Either operation leaves
1069 the panel's screen location, contents, and size unchanged. <P>
1071 The function <CODE>update_panels()</CODE> does all the
1072 <CODE>wnoutrefresh()</CODE> calls needed to prepare for
1073 <CODE>doupdate()</CODE> (which you must call yourself, afterwards). <P>
1075 Typically, you will want to call <CODE>update_panels()</CODE> and
1076 <CODE>doupdate()</CODE> just before accepting command input, once in each cycle
1077 of interaction with the user. If you call <CODE>update_panels()</CODE> after
1078 each and every panel write, you'll generate a lot of unnecessary refresh
1079 activity and screen flicker. <P>
1081 <H2><A NAME="pstdscr">Panels, Input, and the Standard Screen</A></H2>
1083 You shouldn't mix <CODE>wnoutrefresh()</CODE> or <CODE>wrefresh()</CODE>
1084 operations with panels code; this will work only if the argument window
1085 is either in the top panel or unobscured by any other panels. <P>
1087 The <CODE>stsdcr</CODE> window is a special case. It is considered below all
1088 panels. Because changes to panels may obscure parts of <CODE>stdscr</CODE>,
1089 though, you should call <CODE>update_panels()</CODE> before
1090 <CODE>doupdate()</CODE> even when you only change <CODE>stdscr</CODE>. <P>
1092 Note that <CODE>wgetch</CODE> automatically calls <CODE>wrefresh</CODE>.
1093 Therefore, before requesting input from a panel window, you need to be sure
1094 that the panel is totally unobscured. <P>
1096 There is presently no way to display changes to one obscured panel without
1097 repainting all panels. <P>
1099 <H2><A NAME="hiding">Hiding Panels</A></H2>
1101 It's possible to remove a panel from the deck temporarily; use
1102 <CODE>hide_panel</CODE> for this. Use <CODE>show_panel()</CODE> to render it
1103 visible again. The predicate function <CODE>panel_hidden</CODE>
1104 tests whether or not a panel is hidden. <P>
1106 The <CODE>panel_update</CODE> code ignores hidden panels. You cannot do
1107 <CODE>top_panel()</CODE> or <CODE>bottom_panel</CODE> on a hidden panel().
1108 Other panels operations are applicable. <P>
1110 <H2><A NAME="pmisc">Miscellaneous Other Facilities</A></H2>
1112 It's possible to navigate the deck using the functions
1113 <CODE>panel_above()</CODE> and <CODE>panel_below</CODE>. Handed a panel
1114 pointer, they return the panel above or below that panel. Handed
1115 <CODE>NULL</CODE>, they return the bottom-most or top-most panel. <P>
1117 Every panel has an associated user pointer, not used by the panel code, to
1118 which you can attach application data. See the man page documentation
1119 of <CODE>set_panel_userptr()</CODE> and <CODE>panel_userptr</CODE> for
1122 <H1><A NAME="menu">The Menu Library</A></H1>
1124 A menu is a screen display that assists the user to choose some subset
1125 of a given set of items. The <CODE>menu</CODE> library is a curses
1126 extension that supports easy programming of menu hierarchies with a
1127 uniform but flexible interface. <P>
1129 The <CODE>menu</CODE> library first appeared in AT&T System V. The
1130 version documented here is the freeware <CODE>menu</CODE> code distributed
1131 with <CODE>ncurses</CODE>. <P>
1133 <H2><A NAME="mcompile">Compiling With the menu Library</A></H2>
1135 Your menu-using modules must import the menu library declarations with
1138 #include <menu.h>
1141 and must be linked explicitly with the menus library using an
1142 <CODE>-lmenu</CODE> argument. Note that they must also link the
1143 <CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
1144 are two-pass and will accept either order, but it is still good practice
1145 to put <CODE>-lmenu</CODE> first and <CODE>-lncurses</CODE> second.
1147 <H2><A NAME="moverview">Overview of Menus</A></H2>
1149 The menus created by this library consist of collections of
1150 <DFN>items</DFN> including a name string part and a description string
1151 part. To make menus, you create groups of these items and connect
1152 them with menu frame objects. <P>
1154 The menu can then by <DFN>posted</DFN>, that is written to an
1155 associated window. Actually, each menu has two associated windows; a
1156 containing window in which the programmer can scribble titles or
1157 borders, and a subwindow in which the menu items proper are displayed.
1158 If this subwindow is too small to display all the items, it will be a
1159 scrollable viewport on the collection of items. <P>
1161 A menu may also be <DFN>unposted</DFN> (that is, undisplayed), and finally
1162 freed to make the storage associated with it and its items available for
1165 The general flow of control of a menu program looks like this:
1168 <LI>Initialize <CODE>curses</CODE>.
1169 <LI>Create the menu items, using <CODE>new_item()</CODE>.
1170 <LI>Create the menu using <CODE>new_menu()</CODE>.
1171 <LI>Post the menu using <CODE>menu_post()</CODE>.
1172 <LI>Refresh the screen.
1173 <LI>Process user requests via an input loop.
1174 <LI>Unpost the menu using <CODE>menu_unpost()</CODE>.
1175 <LI>Free the menu, using <CODE>free_menu()</CODE>.
1176 <LI>Free the items using <CODE>free_item()</CODE>.
1177 <LI>Terminate <CODE>curses</CODE>.
1180 <H2><A NAME="mselect">Selecting items</A></H2>
1182 Menus may be multi-valued or (the default) single-valued (see the manual
1183 page <CODE>menu_opts(3x)</CODE> to see how to change the default).
1184 Both types always have a <DFN>current item</DFN>. <P>
1186 From a single-valued menu you can read the selected value simply by looking
1187 at the current item. From a multi-valued menu, you get the selected set
1188 by looping through the items applying the <CODE>item_value()</CODE>
1189 predicate function. Your menu-processing code can use the function
1190 <CODE>set_item_value()</CODE> to flag the items in the select set. <P>
1192 Menu items can be made unselectable using <CODE>set_item_opts()</CODE>
1193 or <CODE>item_opts_off()</CODE> with the <CODE>O_SELECTABLE</CODE>
1194 argument. This is the only option so far defined for menus, but it
1195 is good practice to code as though other option bits might be on. <P>
1197 <H2><A NAME="mdisplay">Menu Display</A></H2>
1199 The menu library calculates a minimum display size for your window, based
1200 on the following variables: <P>
1203 <LI>The number and maximum length of the menu items
1204 <LI>Whether the O_ROWMAJOR option is enabled
1205 <LI>Whether display of descriptions is enabled
1206 <LI>Whatever menu format may have been set by the programmer
1207 <LI>The length of the menu mark string used for highlighting selected items
1210 The function <CODE>set_menu_format()</CODE> allows you to set the
1211 maximum size of the viewport or <DFN>menu page</DFN> that will be used
1212 to display menu items. You can retrieve any format associated with a
1213 menu with <CODE>menu_format()</CODE>. The default format is rows=16,
1216 The actual menu page may be smaller than the format size. This depends
1217 on the item number and size and whether O_ROWMAJOR is on. This option
1218 (on by default) causes menu items to be displayed in a `raster-scan'
1219 pattern, so that if more than one item will fit horizontally the first
1220 couple of items are side-by-side in the top row. The alternative is
1221 column-major display, which tries to put the first several items in
1222 the first column. <P>
1224 As mentioned above, a menu format not large enough to allow all items to fit
1225 on-screen will result in a menu display that is vertically scrollable. <P>
1226 You can scroll it with requests to the menu driver, which will be described
1227 in the section on <A HREF="#minput">menu input handling</A>. <P>
1229 Each menu has a <DFN>mark string</DFN> used to visually tag selected items;
1230 see the <CODE>menu_mark(3x)</CODE> manual page for details. The mark
1231 string length also influences the menu page size. <P>
1233 The function <CODE>scale_menu()</CODE> returns the minimum display size
1234 that the menu code computes from all these factors.
1236 There are other menu display attributes including a select attribute,
1237 an attribute for selectable items, an attribute for unselectable items,
1238 and a pad character used to separate item name text from description
1239 text. These have reasonable defaults which the library allows you to
1240 change (see the <CODE>menu_attribs(3x)</CODE> manual page. <P>
1242 <H2><A NAME="mwindows">Menu Windows</A></H2>
1244 Each menu has, as mentioned previously, a pair of associated windows.
1245 Both these windows are painted when the menu is posted and erased when
1246 the menu is unposted. <P>
1248 The outer or frame window is not otherwise touched by the menu
1249 routines. It exists so the programmer can associate a title, a
1250 border, or perhaps help text with the menu and have it properly
1251 refreshed or erased at post/unpost time. The inner window or
1252 <DFN>subwindow</DFN> is where the current menu page is displayed. <P>
1254 By default, both windows are <CODE>stdscr</CODE>. You can set them with the
1255 functions in <CODE>menu_win(3x)</CODE>. <P>
1257 When you call <CODE>menu_post()</CODE>, you write the menu to its
1258 subwindow. When you call <CODE>menu_unpost()</CODE>, you erase the
1259 subwindow, However, neither of these actually modifies the screen. To
1260 do that, call <CODE>wrefresh()</CODE> or some equivalent. <P>
1262 <H2><A NAME="minput">Processing Menu Input</A></H2>
1264 The main loop of your menu-processing code should call
1265 <CODE>menu_driver()</CODE> repeatedly. The first argument of this routine
1266 is a menu pointer; the second is a menu command code. You should write an
1267 input-fetching routine that maps input characters to menu command codes, and
1268 pass its output to <CODE>menu_driver()</CODE>. The menu command codes are
1269 fully documented in <CODE>menu_driver(3x)</CODE>. <P>
1271 The simplest group of command codes is <CODE>REQ_NEXT_ITEM</CODE>,
1272 <CODE>REQ_PREV_ITEM</CODE>, <CODE>REQ_FIRST_ITEM</CODE>,
1273 <CODE>REQ_LAST_ITEM</CODE>, <CODE>REQ_UP_ITEM</CODE>,
1274 <CODE>REQ_DOWN_ITEM</CODE>, <CODE>REQ_LEFT_ITEM</CODE>,
1275 <CODE>REQ_RIGHT_ITEM</CODE>. These change the currently selected
1276 item. These requests may cause scrolling of the menu page if it only
1277 partially displayed. <P>
1279 There are explicit requests for scrolling which also change the
1280 current item (because the select location does not change, but the
1281 item there does). These are <CODE>REQ_SCR_DLINE</CODE>,
1282 <CODE>REQ_SCR_ULINE</CODE>, <CODE>REQ_SCR_DPAGE</CODE>, and
1283 <CODE>REQ_SCR_UPAGE</CODE>. <P>
1285 The <CODE>REQ_TOGGLE_ITEM</CODE> selects or deselects the current item.
1286 It is for use in multi-valued menus; if you use it with <CODE>O_ONEVALUE</CODE>
1287 on, you'll get an error return (<CODE>E_REQUEST_DENIED</CODE>). <P>
1289 Each menu has an associated pattern buffer. The
1290 <CODE>menu_driver()</CODE> logic tries to accumulate printable ASCII
1291 characters passed in in that buffer; when it matches a prefix of an
1292 item name, that item (or the next matching item) is selected. If
1293 appending a character yields no new match, that character is deleted
1294 from the pattern buffer, and <CODE>menu_driver()</CODE> returns
1295 <CODE>E_NO_MATCH</CODE>. <P>
1297 Some requests change the pattern buffer directly:
1298 <CODE>REQ_CLEAR_PATTERN</CODE>, <CODE>REQ_BACK_PATTERN</CODE>,
1299 <CODE>REQ_NEXT_MATCH</CODE>, <CODE>REQ_PREV_MATCH</CODE>. The latter
1300 two are useful when pattern buffer input matches more than one item
1301 in a multi-valued menu. <P>
1303 Each successful scroll or item navigation request clears the pattern
1304 buffer. It is also possible to set the pattern buffer explicitly
1305 with <CODE>set_menu_pattern()</CODE>. <P>
1307 Finally, menu driver requests above the constant <CODE>MAX_COMMAND</CODE>
1308 are considered application-specific commands. The <CODE>menu_driver()</CODE>
1309 code ignores them and returns <CODE>E_UNKNOWN_COMMAND</CODE>.
1311 <H2><A NAME="mmisc">Miscellaneous Other Features</A></H2>
1313 Various menu options can affect the processing and visual appearance
1314 and input processing of menus. See <CODE>menu_opts(3x) for
1317 It is possible to change the current item from application code; this
1318 is useful if you want to write your own navigation requests. It is
1319 also possible to explicitly set the top row of the menu display. See
1320 <CODE>mitem_current(3x)</CODE>.
1322 If your application needs to change the menu subwindow cursor for
1323 any reason, <CODE>pos_menu_cursor()</CODE> will restore it to the
1324 correct location for continuing menu driver processing. <P>
1326 It is possible to set hooks to be called at menu initialization and
1327 wrapup time, and whenever the selected item changes. See
1328 <CODE>menu_hook(3x)</CODE>. <P>
1330 Each item, and each menu, has an associated user pointer on which you
1331 can hang application data. See <CODE>mitem_userptr(3x)</CODE> and
1332 <CODE>menu_userptr(3x)</CODE>. <P>
1334 <H1><A NAME="form">The Forms Library</A></H1>
1336 The <CODE>form</CODE> library is a curses extension that supports easy
1337 programming of on-screen forms for data entry and program control. <P>
1339 The <CODE>form</CODE> library first appeared in AT&T System V. The
1340 version documented here is the freeware <CODE>form</CODE> code distributed
1341 with <CODE>ncurses</CODE>. <P>
1343 <H2><A NAME="fcompile">Compiling With the form Library</A></H2>
1345 Your form-using modules must import the form library declarations with
1348 #include <form.h>
1351 and must be linked explicitly with the forms library using an
1352 <CODE>-lform</CODE> argument. Note that they must also link the
1353 <CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
1354 are two-pass and will accept either order, but it is still good practice
1355 to put <CODE>-lform</CODE> first and <CODE>-lncurses</CODE> second. <P>
1357 <H2><A NAME="foverview">Overview of Forms</A></H2>
1359 A form is a collection of fields; each field may be either a label
1360 (explanatory text) or a data-entry location. Long forms may be
1361 segmented into pages; each entry to a new page clears the screen. <P>
1362 To make forms, you create groups of fields and connect them with form
1363 frame objects; the form library makes this relatively simple. <P>
1365 Once defined, a form can be <DFN>posted</DFN>, that is written to an
1366 associated window. Actually, each form has two associated windows; a
1367 containing window in which the programmer can scribble titles or
1368 borders, and a subwindow in which the form fields proper are displayed. <P>
1370 As the form user fills out the posted form, navigation and editing
1371 keys support movement between fields, editing keys support modifying
1372 field, and plain text adds to or changes data in a current field. The
1373 form library allows you (the forms designer) to bind each navigation
1374 and editing key to any keystroke accepted by <CODE>curses</CODE>
1376 Fields may have validation conditions on them, so that they check input
1377 data for type and value. The form library supplies a rich set of
1378 pre-defined field types, and makes it relatively easy to define new ones. <P>
1380 Once its transaction is completed (or aborted), a form may be
1381 <DFN>unposted</DFN> (that is, undisplayed), and finally freed to make
1382 the storage associated with it and its items available for re-use. <P>
1384 The general flow of control of a form program looks like this:
1387 <LI>Initialize <CODE>curses</CODE>.
1388 <LI>Create the form fields, using <CODE>new_field()</CODE>.
1389 <LI>Create the form using <CODE>new_form()</CODE>.
1390 <LI>Post the form using <CODE>form_post()</CODE>.
1391 <LI>Refresh the screen.
1392 <LI>Process user requests via an input loop.
1393 <LI>Unpost the form using <CODE>form_unpost()</CODE>.
1394 <LI>Free the form, using <CODE>free_form()</CODE>.
1395 <LI>Free the fields using <CODE>free_field()</CODE>.
1396 <LI>Terminate <CODE>curses</CODE>.
1399 Note that this looks much like a menu program; the form library handles
1400 tasks which are in many ways similar, and its interface was obviously
1401 designed to resemble that of the <A HREF="#menu">menu library</A>
1402 wherever possible. <P>
1404 In forms programs, however, the `process user requests' is somewhat more
1405 complicated than for menus. Besides menu-like navigation operations,
1406 the menu driver loop has to support field editing and data validation. <P>
1408 <H2><A NAME="fcreate">Creating and Freeing Fields and Forms</A></H2>
1410 The basic function for creating fields is <CODE>new_field()</CODE>: <P>
1413 FIELD *new_field(int height, int width, /* new field size */
1414 int top, int left, /* upper left corner */
1415 int offscreen, /* number of offscreen rows */
1416 int nbuf); /* number of working buffers */
1419 Menu items always occupy a single row, but forms fields may have
1420 multiple rows. So <CODE>new_field()</CODE> requires you to specify a
1421 width and height (the first two arguments, which mist both be greater
1424 You must also specify the location of the field's upper left corner on
1425 the screen (the third and fourth arguments, which must be zero or
1426 greater). Note that these coordinates are relative to the form
1427 subwindow, which will coincide with <CODE>stdscr</CODE> by default but
1428 need not be <CODE>stdscr</CODE> if you've done an explicit
1429 <CODE>set_form_window()</CODE> call. <P>
1431 The fifth argument allows you to specify a number of off-screen rows. If
1432 this is zero, the entire field will always be displayed. If it is
1433 nonzero, the form will be scrollable, with only one screen-full (initially
1434 the top part) displayed at any given time. If you make a field dynamic
1435 and grow it so it will no longer fit on the screen, the form will become
1436 scrollable even if the <CODE>offscreen</CODE> argument was initially zero. <P>
1438 The forms library allocates one working buffer per field; the size of
1439 each buffer is <CODE>((height + offscreen)*width + 1</CODE>, one character
1440 for each position in the field plus a NUL terminator. The sixth
1441 argument is the number of additional data buffers to allocate for the
1442 field; your application can use them for its own purposes. <P>
1445 FIELD *dup_field(FIELD *field, /* field to copy */
1446 int top, int left); /* location of new copy */
1449 The function <CODE>dup_field()</CODE> duplicates an existing field at a
1450 new location. Size and buffering information are copied; some
1451 attribute flags and status bits are not (see the
1452 <CODE>form_field_new(3X)</CODE> for details). <P>
1455 FIELD *link_field(FIELD *field, /* field to copy */
1456 int top, int left); /* location of new copy */
1459 The function <CODE>link_field()</CODE> also duplicates an existing field
1460 at a new location. The difference from <CODE>dup_field()</CODE> is that
1461 it arranges for the new field's buffer to be shared with the old one. <P>
1463 Besides the obvious use in making a field editable from two different
1464 form pages, linked fields give you a way to hack in dynamic labels. If
1465 you declare several fields linked to an original, and then make them
1466 inactive, changes from the original will still be propagated to the
1469 As with duplicated fields, linked fields have attribute bits separate
1470 from the original. <P>
1472 As you might guess, all these field-allocations return <CODE>NULL</CODE> if
1473 the field allocation is not possible due to an out-of-memory error or
1474 out-of-bounds arguments. <P>
1476 To connect fields to a form, use <P>
1479 FORM *new_form(FIELD **fields);
1482 This function expects to see a NULL-terminated array of field pointers.
1483 Said fields are connected to a newly-allocated form object; its address
1484 is returned (or else NULL if the allocation fails). <P>
1486 Note that <CODE>new_field()</CODE> does <EM>not</EM> copy the pointer array
1487 into private storage; if you modify the contents of the pointer array
1488 during forms processing, all manner of bizarre things might happen. Also
1489 note that any given field may only be connected to one form. <P>
1491 The functions <CODE>free_field()</CODE> and <CODE>free_form</CODE> are available
1492 to free field and form objects. It is an error to attempt to free a field
1493 connected to a form, but not vice-versa; thus, you will generally free
1494 your form objects first. <P>
1496 <H2><A NAME="fattributes">Fetching and Changing Field Attributes</A></H2>
1498 Each form field has a number of location and size attributes
1499 associated with it. There are other field attributes used to control
1500 display and editing of the field. Some (for example, the <CODE>O_STATIC</CODE> bit)
1501 involve sufficient complications to be covered in sections of their own
1502 later on. We cover the functions used to get and set several basic
1503 attributes here. <P>
1505 When a field is created, the attributes not specified by the
1506 <CODE>new_field</CODE> function are copied from an invisible system
1507 default field. In attribute-setting and -fetching functions, the
1508 argument NULL is taken to mean this field. Changes to it persist
1509 as defaults until your forms application terminates. <P>
1511 <H3><A NAME="fsizes">Fetching Size and Location Data</A></H3>
1513 You can retrieve field sizes and locations through: <P>
1516 int field_info(FIELD *field, /* field from which to fetch */
1517 int *height, *int width, /* field size */
1518 int *top, int *left, /* upper left corner */
1519 int *offscreen, /* number of offscreen rows */
1520 int *nbuf); /* number of working buffers */
1523 This function is a sort of inverse of <CODE>new_field()</CODE>; instead of
1524 setting size and location attributes of a new field, it fetches them
1525 from an existing one. <P>
1527 <H3><A NAME="flocation">Changing the Field Location</A></H3>
1529 If is possible to move a field's location on the screen: <P>
1532 int move_field(FIELD *field, /* field to alter */
1533 int top, int left); /* new upper-left corner */
1536 You can, of course. query the current location through <CODE>field_info()</CODE>.
1538 <H3><A NAME="fjust">The Justification Attribute</A></H3>
1540 One-line fields may be unjustified, justified right, justified left,
1541 or centered. Here is how you manipulate this attribute: <P>
1544 int set_field_just(FIELD *field, /* field to alter */
1545 int justmode); /* mode to set */
1547 int field_just(FIELD *field); /* fetch mode of field */
1550 The mode values accepted and returned by this functions are
1551 preprocessor macros <CODE>NO_JUSTIFICATION</CODE>, <CODE>JUSTIFY_RIGHT</CODE>,
1552 <CODE>JUSTIFY_LEFT</CODE>, or <CODE>JUSTIFY_CENTER</CODE>. <P>
1554 <H3><A NAME="fdispatts">Field Display Attributes</A></H3>
1556 For each field, you can set a foreground attribute for entered
1557 characters, a background attribute for the entire field, and a pad
1558 character for the unfilled portion of the field. You can also
1559 control pagination of the form. <P>
1561 This group of four field attributes controls the visual appearance
1562 of the field on the screen, without affecting in any way the data
1563 in the field buffer. <P>
1566 int set_field_fore(FIELD *field, /* field to alter */
1567 chtype attr); /* attribute to set */
1569 chtype field_fore(FIELD *field); /* field to query */
1571 int set_field_back(FIELD *field, /* field to alter */
1572 chtype attr); /* attribute to set */
1574 chtype field_back(FIELD *field); /* field to query */
1576 int set_field_pad(FIELD *field, /* field to alter */
1577 int pad); /* pad character to set */
1579 chtype field_pad(FIELD *field);
1581 int set_new_page(FIELD *field, /* field to alter */
1582 int flag); /* TRUE to force new page */
1584 chtype new_page(FIELD *field); /* field to query */
1587 The attributes set and returned by the first four functions are normal
1588 <CODE>curses(3x)</CODE> display attribute values (<CODE>A_STANDOUT</CODE>,
1589 <CODE>A_BOLD</CODE>, <CODE>A_REVERSE</CODE> etc).
1591 The page bit of a field controls whether it is displayed at the start of
1592 a new form screen. <P>
1594 <H3><A NAME="foptions">Field Option Bits</A></H3>
1596 There is also a large collection of field option bits you can set to control
1597 various aspects of forms processing. You can manipulate them with these
1601 int set_field_opts(FIELD *field, /* field to alter */
1602 int attr); /* attribute to set */
1604 int field_opts_on(FIELD *field, /* field to alter */
1605 int attr); /* attributes to turn on */
1607 int field_opts_off(FIELD *field, /* field to alter */
1608 int attr); /* attributes to turn off */
1610 int field_opts(FIELD *field); /* field to query */
1613 By default, all options are on. Here are the available option bits:
1616 <DD> Controls whether the field is visible on the screen. Can be used
1617 during form processing to hide or pop up fields depending on the value
1620 <DD> Controls whether the field is active during forms processing (i.e.
1621 visited by form navigation keys). Can be used to make labels or derived
1622 fields with buffer values alterable by the forms application, not the user.
1624 <DD> Controls whether data is displayed during field entry. If this option is
1625 turned off on a field, the library will accept and edit data in that field,
1626 but it will not be displayed and the visible field cursor will not move.
1627 You can turn off the O_PUBLIC bit to define password fields.
1629 <DD> Controls whether the field's data can be modified. When this option is
1630 off, all editing requests except <CODE>REQ_PREV_CHOICE</CODE> and
1631 <CODE>REQ_NEXT_CHOICE</CODE> will fail. Such read-only fields may be useful for
1634 <DD> Controls word-wrapping in multi-line fields. Normally, when any
1635 character of a (blank-separated) word reaches the end of the current line, the
1636 entire word is wrapped to the next line (assuming there is one). When this
1637 option is off, the word will be split across the line break.
1639 <DD> Controls field blanking. When this option is on, entering a character at
1640 the first field position erases the entire field (except for the just-entered
1643 <DD> Controls automatic skip to next field when this one fills. Normally,
1644 when the forms user tries to type more data into a field than will fit,
1645 the editing location jumps to next field. When this option is off, the
1646 user's cursor will hang at the end of the field. This option is ignored
1647 in dynamic fields that have not reached their size limit.
1649 <DD> Controls whether <A HREF="#fvalidation">validation</A> is applied to
1650 blank fields. Normally, it is not; the user can leave a field blank
1651 without invoking the usual validation check on exit. If this option is
1652 off on a field, exit from it will invoke a validation check.
1654 <DD> Controls whether validation occurs on every exit, or only after
1655 the field is modified. Normally the latter is true. Setting O_PASSOK
1656 may be useful if your field's validation function may change during
1659 <DD> Controls whether the field is fixed to its initial dimensions. If you
1660 turn this off, the field becomes <A HREF="#fdynamic">dynamic</A> and will
1661 stretch to fit entered data.
1664 A field's options cannot be changed while the field is currently selected.
1665 However, options may be changed on posted fields that are not current. <P>
1667 The option values are bit-masks and can be composed with logical-or in
1668 the obvious way. <P>
1670 <H2><A NAME="fstatus">Field Status</A></H2>
1672 Every field has a status flag, which is set to FALSE when the field is
1673 created and TRUE when the value in field buffer 0 changes. This flag can
1674 be queried and set directly: <P>
1677 int set_field_status(FIELD *field, /* field to alter */
1678 int status); /* mode to set */
1680 int field_status(FIELD *field); /* fetch mode of field */
1683 Setting this flag under program control can be useful if you use the same
1684 form repeatedly, looking for modified fields each time. <P>
1686 Calling <CODE>field_status()</CODE> on a field not currently selected
1687 for input will return a correct value. Calling <CODE>field_status()</CODE> on a
1688 field that is currently selected for input may not necessarily give a
1689 correct field status value, because entered data isn't necessarily copied to
1690 buffer zero before the exit validation check.
1692 To guarantee that the returned status value reflects reality, call
1693 <CODE>field_status()</CODE> either (1) in the field's exit validation check
1694 routine, (2) from the field's or form's initialization or termination
1695 hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been
1696 processed by the forms driver. <P>
1698 <H2><A NAME="fuser">Field User Pointer</A></H2>
1700 Each field structure contains one character pointer slot that is not used
1701 by the forms library. It is intended to be used by applications to store
1702 private per-field data. You can manipulate it with:
1705 int set_field_userptr(FIELD *field, /* field to alter */
1706 char *userptr); /* mode to set */
1708 char *field_userptr(FIELD *field); /* fetch mode of field */
1711 (Properly, this user pointer field ought to have <CODE>(void *)</CODE> type.
1712 The <CODE>(char *)</CODE> type is retained for System V compatibility.) <P>
1714 It is valid to set the user pointer of the default field (with a
1715 <CODE>set_field_userptr()</CODE> call passed a NULL field pointer.)
1716 When a new field is created, the default-field user pointer is copied
1717 to initialize the new field's user pointer. <P>
1719 <H2><A NAME="fdynamic">Variable-Sized Fields</A></H2>
1721 Normally, a field is fixed at the size specified for it at creation
1722 time. If, however, you turn off its O_STATIC bit, it becomes
1723 <DFN>dynamic</DFN> and will automatically resize itself to accommodate
1724 data as it is entered. If the field has extra buffers associated with it,
1725 they will grow right along with the main input buffer. <P>
1727 A one-line dynamic field will have a fixed height (1) but variable
1728 width, scrolling horizontally to display data within the field area as
1729 originally dimensioned and located. A multi-line dynamic field will
1730 have a fixed width, but variable height (number of rows), scrolling
1731 vertically to display data within the field area as originally
1732 dimensioned and located. <P>
1734 Normally, a dynamic field is allowed to grow without limit. But it is
1735 possible to set an upper limit on the size of a dynamic field. You do
1736 it with this function: <P>
1739 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
1740 int max_size); /* upper limit on field size */
1743 If the field is one-line, <CODE>max_size</CODE> is taken to be a column size
1744 limit; if it is multi-line, it is taken to be a line size limit. To disable
1745 any limit, use an argument of zero. The growth limit can be changed whether
1746 or not the O_STATIC bit is on, but has no effect until it is. <P>
1748 The following properties of a field change when it becomes dynamic:
1751 <LI>If there is no growth limit, there is no final position of the field;
1752 therefore <CODE>O_AUTOSKIP</CODE> and <CODE>O_NL_OVERLOAD</CODE> are ignored.
1753 <LI>Field justification will be ignored (though whatever justification is
1754 set up will be retained internally and can be queried).
1755 <LI>The <CODE>dup_field()</CODE> and <CODE>link_field()</CODE> calls copy
1756 dynamic-buffer sizes. If the <CODE>O_STATIC</CODE> option is set on one of a
1757 collection of links, buffer resizing will occur only when the field is
1758 edited through that link.
1759 <LI>The call <CODE>field_info()</CODE> will retrieve the original static size of
1760 the field; use <CODE>dynamic_field_info()</CODE> to get the actual dynamic size.
1763 <H2><A NAME="fvalidation">Field Validation</A></H2>
1765 By default, a field will accept any data that will fit in its input buffer.
1766 However, it is possible to attach a validation type to a field. If you do
1767 this, any attempt to leave the field while it contains data that doesn't
1768 match the validation type will fail. Some validation types also have a
1769 character-validity check for each time a character is entered in the field. <P>
1771 A field's validation check (if any) is not called when
1772 <CODE>set_field_buffer()</CODE> modifies the input buffer, nor when that buffer
1773 is changed through a linked field. <P>
1775 The <CODE>form</CODE> library provides a rich set of pre-defined validation
1776 types, and gives you the capability to define custom ones of your own. You
1777 can examine and change field validation attributes with the following
1781 int set_field_type(FIELD *field, /* field to alter */
1782 FIELDTYPE *ftype, /* type to associate */
1783 ...); /* additional arguments*/
1785 FIELDTYPE *field_type(FIELD *field); /* field to query */
1788 The validation type of a field is considered an attribute of the field. As
1789 with other field attributes, Also, doing <CODE>set_field_type()</CODE> with a
1790 <CODE>NULL</CODE> field default will change the system default for validation of
1791 newly-created fields. <P>
1793 Here are the pre-defined validation types: <P>
1795 <H3><A NAME="ftype_alpha">TYPE_ALPHA</A></H3>
1797 This field type accepts alphabetic data; no blanks, no digits, no special
1798 characters (this is checked at character-entry time). It is set up with: <P>
1801 int set_field_type(FIELD *field, /* field to alter */
1802 TYPE_ALPHA, /* type to associate */
1803 int width); /* maximum width of field */
1806 The <CODE>width</CODE> argument sets a minimum width of data. Typically
1807 you'll want to set this to the field width; if it's greater than the
1808 field width, the validation check will always fail. A minimum width
1809 of zero makes field completion optional. <P>
1811 <H3><A NAME="ftype_alnum">TYPE_ALNUM</A></H3>
1813 This field type accepts alphabetic data and digits; no blanks, no special
1814 characters (this is checked at character-entry time). It is set up with: <P>
1817 int set_field_type(FIELD *field, /* field to alter */
1818 TYPE_ALNUM, /* type to associate */
1819 int width); /* maximum width of field */
1822 The <CODE>width</CODE> argument sets a minimum width of data. As with
1823 TYPE_ALPHA, typically you'll want to set this to the field width; if it's
1824 greater than the field width, the validation check will always fail. A
1825 minimum width of zero makes field completion optional. <P>
1827 <H3><A NAME="ftype_enum">TYPE_ENUM</A></H3>
1829 This type allows you to restrict a field's values to be among a specified
1830 set of string values (for example, the two-letter postal codes for U.S.
1831 states). It is set up with: <P>
1834 int set_field_type(FIELD *field, /* field to alter */
1835 TYPE_ENUM, /* type to associate */
1836 char **valuelist; /* list of possible values */
1837 int checkcase; /* case-sensitive? */
1838 int checkunique); /* must specify uniquely? */
1841 The <CODE>valuelist</CODE> parameter must point at a NULL-terminated list of
1842 valid strings. The <CODE>checkcase</CODE> argument, if true, makes comparison
1843 with the string case-sensitive. <P>
1845 When the user exits a TYPE_ENUM field, the validation procedure tries to
1846 complete the data in the buffer to a valid entry. If a complete choice string
1847 has been entered, it is of course valid. But it is also possible to enter a
1848 prefix of a valid string and have it completed for you. <P>
1850 By default, if you enter such a prefix and it matches more than one value
1851 in the string list, the prefix will be completed to the first matching
1852 value. But the <CODE>checkunique</CODE> argument, if true, requires prefix
1853 matches to be unique in order to be valid. <P>
1855 The <CODE>REQ_NEXT_CHOICE</CODE> and <CODE>REQ_PREV_CHOICE</CODE> input requests
1856 can be particularly useful with these fields. <P>
1858 <H3><A NAME="ftype_integer">TYPE_INTEGER</A></H3>
1860 This field type accepts an integer. It is set up as follows: <P>
1863 int set_field_type(FIELD *field, /* field to alter */
1864 TYPE_INTEGER, /* type to associate */
1865 int padding, /* # places to zero-pad to */
1866 int vmin, int vmax); /* valid range */
1869 Valid characters consist of an optional leading minus and digits.
1870 The range check is performed on exit. If the range maximum is less
1871 than or equal to the minimum, the range is ignored. <P>
1873 If the value passes its range check, it is padded with as many leading
1874 zero digits as necessary to meet the padding argument. <P>
1876 A <CODE>TYPE_INTEGER</CODE> value buffer can conveniently be interpreted
1877 with the C library function <CODE>atoi(3)</CODE>.
1879 <H3><A NAME="ftype_numeric">TYPE_NUMERIC</A></H3>
1881 This field type accepts a decimal number. It is set up as follows: <P>
1884 int set_field_type(FIELD *field, /* field to alter */
1885 TYPE_NUMERIC, /* type to associate */
1886 int padding, /* # places of precision */
1887 double vmin, double vmax); /* valid range */
1890 Valid characters consist of an optional leading minus and digits. possibly
1891 including a decimal point. If your system supports locale's, the decimal point
1892 character used must be the one defined by your locale. The range check is
1893 performed on exit. If the range maximum is less than or equal to the minimum,
1894 the range is ignored. <P>
1896 If the value passes its range check, it is padded with as many trailing
1897 zero digits as necessary to meet the padding argument. <P>
1899 A <CODE>TYPE_NUMERIC</CODE> value buffer can conveniently be interpreted
1900 with the C library function <CODE>atof(3)</CODE>.
1902 <H3><A NAME="ftype_regexp">TYPE_REGEXP</A></H3>
1904 This field type accepts data matching a regular expression. It is set up
1908 int set_field_type(FIELD *field, /* field to alter */
1909 TYPE_REGEXP, /* type to associate */
1910 char *regexp); /* expression to match */
1913 The syntax for regular expressions is that of <CODE>regcomp(3)</CODE>.
1914 The check for regular-expression match is performed on exit.
1916 <H2><A NAME="fbuffer">Direct Field Buffer Manipulation</A></H2>
1918 The chief attribute of a field is its buffer contents. When a form has
1919 been completed, your application usually needs to know the state of each
1920 field buffer. You can find this out with: <P>
1923 char *field_buffer(FIELD *field, /* field to query */
1924 int bufindex); /* number of buffer to query */
1927 Normally, the state of the zero-numbered buffer for each field is set by
1928 the user's editing actions on that field. It's sometimes useful to be able
1929 to set the value of the zero-numbered (or some other) buffer from your
1933 int set_field_buffer(FIELD *field, /* field to alter */
1934 int bufindex, /* number of buffer to alter */
1935 char *value); /* string value to set */
1938 If the field is not large enough and cannot be resized to a sufficiently
1939 large size to contain the specified value, the value will be truncated
1942 Calling <CODE>field_buffer()</CODE> with a null field pointer will raise an
1943 error. Calling <CODE>field_buffer()</CODE> on a field not currently selected
1944 for input will return a correct value. Calling <CODE>field_buffer()</CODE> on a
1945 field that is currently selected for input may not necessarily give a
1946 correct field buffer value, because entered data isn't necessarily copied to
1947 buffer zero before the exit validation check.
1949 To guarantee that the returned buffer value reflects on-screen reality,
1950 call <CODE>field_buffer()</CODE> either (1) in the field's exit validation
1951 check routine, (2) from the field's or form's initialization or termination
1952 hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been processed
1953 by the forms driver. <P>
1955 <H2><A NAME="formattrs">Attributes of Forms</A></H2>
1957 As with field attributes, form attributes inherit a default from a
1958 system default form structure. These defaults can be queried or set by
1959 of these functions using a form-pointer argument of <CODE>NULL</CODE>. <P>
1961 The principal attribute of a form is its field list. You can query
1962 and change this list with: <P>
1965 int set_form_fields(FORM *form, /* form to alter */
1966 FIELD **fields); /* fields to connect */
1968 char *form_fields(FORM *form); /* fetch fields of form */
1970 int field_count(FORM *form); /* count connect fields */
1973 The second argument of <CODE>set_form_fields()</CODE> may be a
1974 NULL-terminated field pointer array like the one required by
1975 <CODE>new_form()</CODE>. In that case, the old fields of the form are
1976 disconnected but not freed (and eligible to be connected to other
1977 forms), then the new fields are connected. <P>
1979 It may also be null, in which case the old fields are disconnected
1980 (and not freed) but no new ones are connected. <P>
1982 The <CODE>field_count()</CODE> function simply counts the number of fields
1983 connected to a given from. It returns -1 if the form-pointer argument
1986 <H2><A NAME="fdisplay">Control of Form Display</A></H2>
1988 In the overview section, you saw that to display a form you normally
1989 start by defining its size (and fields), posting it, and refreshing
1990 the screen. There is an hidden step before posting, which is the
1991 association of the form with a frame window (actually, a pair of
1992 windows) within which it will be displayed. By default, the forms
1993 library associates every form with the full-screen window
1994 <CODE>stdscr</CODE>. <P>
1996 By making this step explicit, you can associate a form with a declared
1997 frame window on your screen display. This can be useful if you want to
1998 adapt the form display to different screen sizes, dynamically tile
1999 forms on the screen, or use a form as part of an interface layout
2000 managed by <A HREF="#panels">panels</A>. <P>
2002 The two windows associated with each form have the same functions as
2003 their analogues in the <A HREF="#menu">menu library</A>. Both these
2004 windows are painted when the form is posted and erased when the form
2007 The outer or frame window is not otherwise touched by the form
2008 routines. It exists so the programmer can associate a title, a
2009 border, or perhaps help text with the form and have it properly
2010 refreshed or erased at post/unpost time. The inner window or subwindow
2011 is where the current form page is actually displayed. <P>
2013 In order to declare your own frame window for a form, you'll need to
2014 know the size of the form's bounding rectangle. You can get this
2015 information with: <P>
2018 int scale_form(FORM *form, /* form to query */
2019 int *rows, /* form rows */
2020 int *cols); /* form cols */
2023 The form dimensions are passed back in the locations pointed to by
2024 the arguments. Once you have this information, you can use it to
2025 declare of windows, then use one of these functions:
2028 int set_form_win(FORM *form, /* form to alter */
2029 WINDOW *win); /* frame window to connect */
2031 WINDOW *form_win(FORM *form); /* fetch frame window of form */
2033 int set_form_sub(FORM *form, /* form to alter */
2034 WINDOW *win); /* form subwindow to connect */
2036 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
2039 Note that curses operations, including <CODE>refresh()</CODE>, on the form,
2040 should be done on the frame window, not the form subwindow. <P>
2042 It is possible to check from your application whether all of a
2043 scrollable field is actually displayed within the menu subwindow. Use
2044 these functions: <P>
2047 int data_ahead(FORM *form); /* form to be queried */
2049 int data_behind(FORM *form); /* form to be queried */
2052 The function <CODE>data_ahead()</CODE> returns TRUE if (a) the current
2053 field is one-line and has undisplayed data off to the right, (b) the current
2054 field is multi-line and there is data off-screen below it. <P>
2056 The function <CODE>data_behind()</CODE> returns TRUE if the first (upper
2057 left hand) character position is off-screen (not being displayed). <P>
2059 Finally, there is a function to restore the form window's cursor to the
2060 value expected by the forms driver: <P>
2063 int pos_form_cursor(FORM *) /* form to be queried */
2066 If your application changes the form window cursor, call this function before
2067 handing control back to the forms driver in order to re-synchronize it. <P>
2069 <H2><A NAME="fdriver">Input Processing in the Forms Driver</A></H2>
2071 The function <CODE>form_driver()</CODE> handles virtualized input requests
2072 for form navigation, editing, and validation requests, just as
2073 <CODE>menu_driver</CODE> does for menus (see the section on <A
2074 HREF="#minput">menu input handling</A>). <P>
2077 int form_driver(FORM *form, /* form to pass input to */
2078 int request); /* form request code */
2081 Your input virtualization function needs to take input and then convert it
2082 to either an alphanumeric character (which is treated as data to be
2083 entered in the currently-selected field), or a forms processing request. <P>
2085 The forms driver provides hooks (through input-validation and
2086 field-termination functions) with which your application code can check
2087 that the input taken by the driver matched what was expected. <P>
2089 <H3><A NAME="fpage">Page Navigation Requests</A></H3>
2091 These requests cause page-level moves through the form,
2092 triggering display of a new form screen. <P>
2095 <DT> <CODE>REQ_NEXT_PAGE</CODE>
2096 <DD> Move to the next form page.
2097 <DT> <CODE>REQ_PREV_PAGE</CODE>
2098 <DD> Move to the previous form page.
2099 <DT> <CODE>REQ_FIRST_PAGE</CODE>
2100 <DD> Move to the first form page.
2101 <DT> <CODE>REQ_LAST_PAGE</CODE>
2102 <DD> Move to the last form page.
2105 These requests treat the list as cyclic; that is, <CODE>REQ_NEXT_PAGE</CODE>
2106 from the last page goes to the first, and <CODE>REQ_PREV_PAGE</CODE> from
2107 the first page goes to the last. <P>
2109 <H3><A NAME="#ffield">Inter-Field Navigation Requests</A></H3>
2111 These requests handle navigation between fields on the same page. <P>
2114 <DT> <CODE>REQ_NEXT_FIELD</CODE>
2115 <DD> Move to next field.
2116 <DT> <CODE>REQ_PREV_FIELD</CODE>
2117 <DD> Move to previous field.
2118 <DT> <CODE>REQ_FIRST_FIELD</CODE>
2119 <DD> Move to the first field.
2120 <DT> <CODE>REQ_LAST_FIELD</CODE>
2121 <DD> Move to the last field.
2123 <DT> <CODE>REQ_SNEXT_FIELD</CODE>
2124 <DD> Move to sorted next field.
2125 <DT> <CODE>REQ_SPREV_FIELD</CODE>
2126 <DD> Move to sorted previous field.
2127 <DT> <CODE>REQ_SFIRST_FIELD</CODE>
2128 <DD> Move to the sorted first field.
2129 <DT> <CODE>REQ_SLAST_FIELD</CODE>
2130 <DD> Move to the sorted last field.
2132 <DT> <CODE>REQ_LEFT_FIELD</CODE>
2133 <DD> Move left to field.
2134 <DT> <CODE>REQ_RIGHT_FIELD</CODE>
2135 <DD> Move right to field.
2136 <DT> <CODE>REQ_UP_FIELD</CODE>
2137 <DD> Move up to field.
2138 <DT> <CODE>REQ_DOWN_FIELD</CODE>
2139 <DD> Move down to field.
2142 These requests treat the list of fields on a page as cyclic; that is,
2143 <CODE>REQ_NEXT_FIELD</CODE> from the last field goes to the first, and
2144 <CODE>REQ_PREV_FIELD</CODE> from the first field goes to the last. The
2145 order of the fields for these (and the <CODE>REQ_FIRST_FIELD</CODE> and
2146 <CODE>REQ_LAST_FIELD</CODE> requests) is simply the order of the field
2147 pointers in the form array (as set up by <CODE>new_form()</CODE> or
2148 <CODE>set_form_fields()</CODE> <P>
2150 It is also possible to traverse the fields as if they had been sorted in
2151 screen-position order, so the sequence goes left-to-right and top-to-bottom.
2152 To do this, use the second group of four sorted-movement requests. <P>
2154 Finally, it is possible to move between fields using visual directions up,
2155 down, right, and left. To accomplish this, use the third group of four
2156 requests. Note, however, that the position of a form for purposes of these
2157 requests is its upper-left corner. <P>
2159 For example, suppose you have a multi-line field B, and two
2160 single-line fields A and C on the same line with B, with A to the left
2161 of B and C to the right of B. A <CODE>REQ_MOVE_RIGHT</CODE> from A will
2162 go to B only if A, B, and C <EM>all</EM> share the same first line;
2163 otherwise it will skip over B to C. <P>
2165 <H3><A NAME="#fifield">Intra-Field Navigation Requests</A></H3>
2167 These requests drive movement of the edit cursor within the currently
2171 <DT> <CODE>REQ_NEXT_CHAR</CODE>
2172 <DD> Move to next character.
2173 <DT> <CODE>REQ_PREV_CHAR</CODE>
2174 <DD> Move to previous character.
2175 <DT> <CODE>REQ_NEXT_LINE</CODE>
2176 <DD> Move to next line.
2177 <DT> <CODE>REQ_PREV_LINE</CODE>
2178 <DD> Move to previous line.
2179 <DT> <CODE>REQ_NEXT_WORD</CODE>
2180 <DD> Move to next word.
2181 <DT> <CODE>REQ_PREV_WORD</CODE>
2182 <DD> Move to previous word.
2183 <DT> <CODE>REQ_BEG_FIELD</CODE>
2184 <DD> Move to beginning of field.
2185 <DT> <CODE>REQ_END_FIELD</CODE>
2186 <DD> Move to end of field.
2187 <DT> <CODE>REQ_BEG_LINE</CODE>
2188 <DD> Move to beginning of line.
2189 <DT> <CODE>REQ_END_LINE</CODE>
2190 <DD> Move to end of line.
2191 <DT> <CODE>REQ_LEFT_CHAR</CODE>
2192 <DD> Move left in field.
2193 <DT> <CODE>REQ_RIGHT_CHAR</CODE>
2194 <DD> Move right in field.
2195 <DT> <CODE>REQ_UP_CHAR</CODE>
2196 <DD> Move up in field.
2197 <DT> <CODE>REQ_DOWN_CHAR</CODE>
2198 <DD> Move down in field.
2201 Each <EM>word</EM> is separated from the previous and next characters
2202 by whitespace. The commands to move to beginning and end of line or field
2203 look for the first or last non-pad character in their ranges. <P>
2205 <H3><A NAME="fscroll">Scrolling Requests</A></H3>
2207 Fields that are dynamic and have grown and fields explicitly created
2208 with offscreen rows are scrollable. One-line fields scroll horizontally;
2209 multi-line fields scroll vertically. Most scrolling is triggered by
2210 editing and intra-field movement (the library scrolls the field to keep the
2211 cursor visible). It is possible to explicitly request scrolling with the
2216 <DT> <CODE>REQ_SCR_FLINE</CODE>
2217 <DD> Scroll vertically forward a line.
2218 <DT> <CODE>REQ_SCR_BLINE</CODE>
2219 <DD> Scroll vertically backward a line.
2220 <DT> <CODE>REQ_SCR_FPAGE</CODE>
2221 <DD> Scroll vertically forward a page.
2222 <DT> <CODE>REQ_SCR_BPAGE</CODE>
2223 <DD> Scroll vertically backward a page.
2224 <DT> <CODE>REQ_SCR_FHPAGE</CODE>
2225 <DD> Scroll vertically forward half a page.
2226 <DT> <CODE>REQ_SCR_BHPAGE</CODE>
2227 <DD> Scroll vertically backward half a page.
2228 <DT> <CODE>REQ_SCR_FCHAR</CODE>
2229 <DD> Scroll horizontally forward a character.
2230 <DT> <CODE>REQ_SCR_BCHAR</CODE>
2231 <DD> Scroll horizontally backward a character.
2232 <DT> <CODE>REQ_SCR_HFLINE</CODE>
2233 <DD> Scroll horizontally one field width forward.
2234 <DT> <CODE>REQ_SCR_HBLINE</CODE>
2235 <DD> Scroll horizontally one field width backward.
2236 <DT> <CODE>REQ_SCR_HFHALF</CODE>
2237 <DD> Scroll horizontally one half field width forward.
2238 <DT> <CODE>REQ_SCR_HBHALF</CODE>
2239 <DD> Scroll horizontally one half field width backward.
2242 For scrolling purposes, a <EM>page</EM> of a field is the height
2243 of its visible part. <P>
2245 <H3><A NAME="fedit">Editing Requests</A></H3>
2247 When you pass the forms driver an ASCII character, it is treated as a
2248 request to add the character to the field's data buffer. Whether this
2249 is an insertion or a replacement depends on the field's edit mode
2250 (insertion is the default. <P>
2252 The following requests support editing the field and changing the edit
2256 <DT> <CODE>REQ_INS_MODE</CODE>
2257 <DD> Set insertion mode.
2258 <DT> <CODE>REQ_OVL_MODE</CODE>
2259 <DD> Set overlay mode.
2260 <DT> <CODE>REQ_NEW_LINE</CODE>
2261 <DD> New line request (see below for explanation).
2262 <DT> <CODE>REQ_INS_CHAR</CODE>
2263 <DD> Insert space at character location.
2264 <DT> <CODE>REQ_INS_LINE</CODE>
2265 <DD> Insert blank line at character location.
2266 <DT> <CODE>REQ_DEL_CHAR</CODE>
2267 <DD> Delete character at cursor.
2268 <DT> <CODE>REQ_DEL_PREV</CODE>
2269 <DD> Delete previous word at cursor.
2270 <DT> <CODE>REQ_DEL_LINE</CODE>
2271 <DD> Delete line at cursor.
2272 <DT> <CODE>REQ_DEL_WORD</CODE>
2273 <DD> Delete word at cursor.
2274 <DT> <CODE>REQ_CLR_EOL</CODE>
2275 <DD> Clear to end of line.
2276 <DT> <CODE>REQ_CLR_EOF</CODE>
2277 <DD> Clear to end of field.
2278 <DT> <CODE>REQ_CLEAR_FIELD</CODE>
2279 <DD> Clear entire field.
2282 The behavior of the <CODE>REQ_NEW_LINE</CODE> and <CODE>REQ_DEL_PREV</CODE> requests
2283 is complicated and partly controlled by a pair of forms options.
2284 The special cases are triggered when the cursor is at the beginning of
2285 a field, or on the last line of the field. <P>
2287 First, we consider <CODE>REQ_NEW_LINE</CODE>: <P>
2289 The normal behavior of <CODE>REQ_NEW_LINE</CODE> in insert mode is to break the
2290 current line at the position of the edit cursor, inserting the portion of
2291 the current line after the cursor as a new line following the current
2292 and moving the cursor to the beginning of that new line (you may think
2293 of this as inserting a newline in the field buffer). <P>
2295 The normal behavior of <CODE>REQ_NEW_LINE</CODE> in overlay mode is to clear the
2296 current line from the position of the edit cursor to end of line.
2297 The cursor is then moved to the beginning of the next line. <P>
2299 However, <CODE>REQ_NEW_LINE</CODE> at the beginning of a field, or on the
2300 last line of a field, instead does a <CODE>REQ_NEXT_FIELD</CODE>.
2301 <CODE>O_NL_OVERLOAD</CODE> option is off, this special action is
2304 Now, let us consider <CODE>REQ_DEL_PREV</CODE>: <P>
2306 The normal behavior of <CODE>REQ_DEL_PREV</CODE> is to delete the previous
2307 character. If insert mode is on, and the cursor is at the start of a
2308 line, and the text on that line will fit on the previous one, it
2309 instead appends the contents of the current line to the previous one
2310 and deletes the current line (you may think of this as deleting a
2311 newline from the field buffer). <P>
2313 However, <CODE>REQ_DEL_PREV</CODE> at the beginning of a field is instead
2314 treated as a <CODE>REQ_PREV_FIELD</CODE>. <P> If the
2315 <CODE>O_BS_OVERLOAD</CODE> option is off, this special action is
2316 disabled and the forms driver just returns <CODE>E_REQUEST_DENIED</CODE>. <P>
2318 See <A HREF="#frmoptions">Form Options</A> for discussion of how to set
2319 and clear the overload options. <P>
2321 <H3><A NAME="forder">Order Requests</A></H3>
2323 If the type of your field is ordered, and has associated functions
2324 for getting the next and previous values of the type from a given value,
2325 there are requests that can fetch that value into the field buffer: <P>
2328 <DT> <CODE>REQ_NEXT_CHOICE</CODE>
2329 <DD> Place the successor value of the current value in the buffer.
2330 <DT> <CODE>REQ_PREV_CHOICE</CODE>
2331 <DD> Place the predecessor value of the current value in the buffer.
2334 Of the built-in field types, only <CODE>TYPE_ENUM</CODE> has built-in successor
2335 and predecessor functions. When you define a field type of your own
2336 (see <A HREF="#fcustom">Custom Validation Types</A>), you can associate
2337 our own ordering functions. <P>
2339 <H3><A NAME="fappcmds">Application Commands</A></H3>
2341 Form requests are represented as integers above the <CODE>curses</CODE> value
2342 greater than <CODE>KEY_MAX</CODE> and less than or equal to the constant
2343 <CODE>MAX_COMMAND</CODE>. If your input-virtualization routine returns a
2344 value above <CODE>MAX_COMMAND</CODE>, the forms driver will ignore it. <P>
2346 <H2><A NAME="fhooks">Field Change Hooks</A></H2>
2348 It is possible to set function hooks to be executed whenever the
2349 current field or form changes. Here are the functions that support this: <P>
2352 typedef void (*HOOK)(); /* pointer to function returning void */
2354 int set_form_init(FORM *form, /* form to alter */
2355 HOOK hook); /* initialization hook */
2357 HOOK form_init(FORM *form); /* form to query */
2359 int set_form_term(FORM *form, /* form to alter */
2360 HOOK hook); /* termination hook */
2362 HOOK form_term(FORM *form); /* form to query */
2364 int set_field_init(FORM *form, /* form to alter */
2365 HOOK hook); /* initialization hook */
2367 HOOK field_init(FORM *form); /* form to query */
2369 int set_field_term(FORM *form, /* form to alter */
2370 HOOK hook); /* termination hook */
2372 HOOK field_term(FORM *form); /* form to query */
2375 These functions allow you to either set or query four different hooks.
2376 In each of the set functions, the second argument should be the
2377 address of a hook function. These functions differ only in the timing
2378 of the hook call. <P>
2382 <DD> This hook is called when the form is posted; also, just after
2383 each page change operation.
2385 <DD> This hook is called when the form is posted; also, just after
2388 <DD> This hook is called just after field validation; that is, just before
2389 the field is altered. It is also called when the form is unposted. <P>
2391 <DD> This hook is called when the form is unposted; also, just before
2392 each page change operation.
2395 Calls to these hooks may be triggered
2397 <LI>When user editing requests are processed by the forms driver
2398 <LI>When the current page is changed by <CODE>set_current_field()</CODE> call
2399 <LI>When the current field is changed by a <CODE>set_form_page()</CODE> call
2402 See <A NAME="ffocus">Field Change Commands</A> for discussion of the latter
2405 You can set a default hook for all fields by passing one of the set functions
2406 a NULL first argument. <P>
2408 You can disable any of these hooks by (re)setting them to NULL, the default
2411 <H2><A HREF="#ffocus">Field Change Commands</A></H2>
2413 Normally, navigation through the form will be driven by the user's
2414 input requests. But sometimes it is useful to be able to move the
2415 focus for editing and viewing under control of your application, or
2416 ask which field it currently is in. The following functions help you
2417 accomplish this: <P>
2420 int set_current_field(FORM *form, /* form to alter */
2421 FIELD *field); /* field to shift to */
2423 FIELD *current_field(FORM *form); /* form to query */
2425 int field_index(FORM *form, /* form to query */
2426 FIELD *field); /* field to get index of */
2429 The function <CODE>field_index()</CODE> returns the index of the given field
2430 in the given form's field array (the array passed to <CODE>new_form()</CODE> or
2431 <CODE>set_form_fields()</CODE>). <P>
2433 The initial current field of a form is the first active field on the
2434 first page. The function <CODE>set_form_fields()</CODE> resets this.<P>
2436 It is also possible to move around by pages. <P>
2439 int set_form_page(FORM *form, /* form to alter */
2440 int page); /* page to go to (0-origin) */
2442 int form_page(FORM *form); /* return form's current page */
2445 The initial page of a newly-created form is 0. The function
2446 <CODE>set_form_fields()</CODE> resets this. <P>
2448 <H2><A NAME="frmoptions">Form Options</A></H2>
2450 Like fields, forms may have control option bits. They can be changed
2451 or queried with these functions: <P>
2454 int set_form_opts(FORM *form, /* form to alter */
2455 int attr); /* attribute to set */
2457 int form_opts_on(FORM *form, /* form to alter */
2458 int attr); /* attributes to turn on */
2460 int form_opts_off(FORM *form, /* form to alter */
2461 int attr); /* attributes to turn off */
2463 int form_opts(FORM *form); /* form to query */
2466 By default, all options are on. Here are the available option bits:
2470 <DD> Enable overloading of <CODE>REQ_NEW_LINE</CODE> as described in <A
2471 NAME="fedit">Editing Requests</A>. The value of this option is
2472 ignored on dynamic fields that have not reached their size limit;
2473 these have no last line, so the circumstances for triggering a
2474 <CODE>REQ_NEXT_FIELD</CODE> never arise.
2476 <DD> Enable overloading of <CODE>REQ_DEL_PREV</CODE> as described in
2477 <A NAME="fedit">Editing Requests</A>.
2480 The option values are bit-masks and can be composed with logical-or in
2481 the obvious way. <P>
2483 <H2><A NAME="fcustom">Custom Validation Types</A></H2>
2485 The <CODE>form</CODE> library gives you the capability to define custom
2486 validation types of your own. Further, the optional additional arguments
2487 of <CODE>set_field_type</CODE> effectively allow you to parameterize validation
2488 types. Most of the complications in the validation-type interface have to
2489 do with the handling of the additional arguments within custom validation
2492 <H3><A NAME="flinktypes">Union Types</A></H3>
2494 The simplest way to create a custom data type is to compose it from two
2495 preexisting ones: <P>
2498 FIELD *link_fieldtype(FIELDTYPE *type1,
2502 This function creates a field type that will accept any of the values
2503 legal for either of its argument field types (which may be either
2504 predefined or programmer-defined).
2506 If a <CODE>set_field_type()</CODE> call later requires arguments, the new
2507 composite type expects all arguments for the first type, than all arguments
2508 for the second. Order functions (see <A HREF="#forder">Order Requests</A>)
2509 associated with the component types will work on the composite; what it does
2510 is check the validation function for the first type, then for the second, to
2511 figure what type the buffer contents should be treated as. <P>
2513 <H3><A NAME="fnewtypes">New Field Types</A></H3>
2515 To create a field type from scratch, you need to specify one or both of the
2516 following things: <P>
2519 <LI>A character-validation function, to check each character as it is entered.
2520 <LI>A field-validation function to be applied on exit from the field.
2523 Here's how you do that: <P>
2525 typedef int (*HOOK)(); /* pointer to function returning int */
2527 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
2528 HOOK c_validate) /* character validator */
2531 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
2534 At least one of the arguments of <CODE>new_fieldtype()</CODE> must be
2535 non-NULL. The forms driver will automatically call the new type's
2536 validation functions at appropriate points in processing a field of
2539 The function <CODE>free_fieldtype()</CODE> deallocates the argument
2540 fieldtype, freeing all storage associated with it. <P>
2542 Normally, a field validator is called when the user attempts to
2543 leave the field. Its first argument is a field pointer, from which it
2544 can get to field buffer 0 and test it. If the function returns TRUE,
2545 the operation succeeds; if it returns FALSE, the edit cursor stays in
2548 A character validator gets the character passed in as a first argument.
2549 It too should return TRUE if the character is valid, FALSE otherwise. <P>
2551 <H3><A NAME="fcheckargs">Validation Function Arguments</A></H3>
2553 Your field- and character- validation functions will be passed a
2554 second argument as well. This second argument is the address of a
2555 structure (which we'll call a <EM>pile</EM>) built from any of the
2556 field-type-specific arguments passed to <CODE>set_field_type()</CODE>. If
2557 no such arguments are defined for the field type, this pile pointer
2558 argument will be NULL. <P>
2560 In order to arrange for such arguments to be passed to your validation
2561 functions, you must associate a small set of storage-management functions
2562 with the type. The forms driver will use these to synthesize a pile
2563 from the trailing arguments of each <CODE>set_field_type()</CODE> argument, and
2564 a pointer to the pile will be passed to the validation functions. <P>
2566 Here is how you make the association: <P>
2569 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
2570 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
2572 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2573 PTRHOOK make_str, /* make structure from args */
2574 PTRHOOK copy_str, /* make copy of structure */
2575 VOIDHOOK free_str); /* free structure storage */
2578 Here is how the storage-management hooks are used: <P>
2581 <DT> <CODE>make_str</CODE>
2582 <DD> This function is called by <CODE>set_field_type()</CODE>. It gets one
2583 argument, a <CODE>va_list</CODE> of the type-specific arguments passed to
2584 <CODE>set_field_type()</CODE>. It is expected to return a pile pointer to a data
2585 structure that encapsulates those arguments.
2586 <DT> <CODE>copy_str</CODE>
2587 <DD> This function is called by form library functions that allocate new
2588 field instances. It is expected to take a pile pointer, copy the pile
2589 to allocated storage, and return the address of the pile copy.
2590 <DT> <CODE>free_str</CODE>
2591 <DD> This function is called by field- and type-deallocation routines in the
2592 library. It takes a pile pointer argument, and is expected to free the
2593 storage of that pile.
2596 The <CODE>make_str</CODE> and <CODE>copy_str</CODE> functions may return NULL to
2597 signal allocation failure. The library routines will that call them will
2598 return error indication when this happens. Thus, your validation functions
2599 should never see a NULL file pointer and need not check specially for it. <P>
2601 <H3><A NAME="fcustorder">Order Functions For Custom Types</A></H3>
2603 Some custom field types are simply ordered in the same well-defined way
2604 that <CODE>TYPE_ENUM</CODE> is. For such types, it is possible to define
2605 successor and predecessor functions to support the <CODE>REQ_NEXT_CHOICE</CODE>
2606 and <CODE>REQ_PREV_CHOICE</CODE> requests. Here's how: <P>
2609 typedef int (*INTHOOK)(); /* pointer to function returning int */
2611 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2612 INTHOOK succ, /* get successor value */
2613 INTHOOK pred); /* get predecessor value */
2616 The successor and predecessor arguments will each be passed two arguments;
2617 a field pointer, and a pile pointer (as for the validation functions). They
2618 are expected to use the function <CODE>field_buffer()</CODE> to read the
2619 current value, and <CODE>set_field_buffer()</CODE> on buffer 0 to set the next
2620 or previous value. Either hook may return TRUE to indicate success (a
2621 legal next or previous value was set) or FALSE to indicate failure. <P>
2623 <H3><A NAME="fcustprobs">Avoiding Problems</A></H3>
2625 The interface for defining custom types is complicated and tricky.
2626 Rather than attempting to create a custom type entirely from scratch,
2627 you should start by studying the library source code for whichever of
2628 the pre-defined types seems to be closest to what you want. <P>
2630 Use that code as a model, and evolve it towards what you really want.
2631 You will avoid many problems and annoyances that way. The code
2632 in the <CODE>ncurses</CODE> library has been specifically exempted from
2633 the package copyright to support this. <P>
2635 If your custom type defines order functions, have do something intuitive
2636 with a blank field. A useful convention is to make the successor of a
2637 blank field the types minimum value, and its predecessor the maximum.