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34 <TITLE>Writing Programs with NCURSES</TITLE>
35 <link rev="made" href="mailto:bugs-ncurses@gnu.org">
36 <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
40 <H1>Writing Programs with NCURSES</H1>
43 by Eric S. Raymond and Zeyd M. Ben-Halim<BR>
44 updates since release 1.9.9e by Thomas Dickey
49 <LI><A HREF="#introduction">Introduction</A>
51 <LI><A HREF="#history">A Brief History of Curses</A>
52 <LI><A HREF="#scope">Scope of This Document</A>
53 <LI><A HREF="#terminology">Terminology</A>
55 <LI><A HREF="#curses">The Curses Library</A>
57 <LI><A HREF="#overview">An Overview of Curses</A>
59 <LI><A HREF="#compiling">Compiling Programs using Curses</A>
60 <LI><A HREF="#updating">Updating the Screen</A>
61 <LI><A HREF="#stdscr">Standard Windows and Function Naming Conventions</A>
62 <LI><A HREF="#variables">Variables</A>
64 <LI><A HREF="#using">Using the Library</A>
66 <LI><A HREF="#starting">Starting up</A>
67 <LI><A HREF="#output">Output</A>
68 <LI><A HREF="#input">Input</A>
69 <LI><A HREF="#formschars">Using Forms Characters</A>
70 <LI><A HREF="#attributes">Character Attributes and Color</A>
71 <LI><A HREF="#mouse">Mouse Interfacing</A>
72 <LI><A HREF="#finishing">Finishing Up</A>
74 <LI><A HREF="#functions">Function Descriptions</A>
76 <LI><A HREF="#init">Initialization and Wrapup</A>
77 <LI><A HREF="#flush">Causing Output to the Terminal</A>
78 <LI><A HREF="#lowlevel">Low-Level Capability Access</A>
79 <LI><A HREF="#debugging">Debugging</A>
81 <LI><A HREF="#hints">Hints, Tips, and Tricks</A>
83 <LI><A HREF="#caution">Some Notes of Caution</A>
84 <LI><A HREF="#leaving">Temporarily Leaving ncurses Mode</A>
85 <LI><A HREF="#xterm">Using <CODE>ncurses</CODE> under <CODE>xterm</CODE></A>
86 <LI><A HREF="#screens">Handling Multiple Terminal Screens</A>
87 <LI><A HREF="#testing">Testing for Terminal Capabilities</A>
88 <LI><A HREF="#tuning">Tuning for Speed</A>
89 <LI><A HREF="#special">Special Features of <CODE>ncurses</CODE></A>
91 <LI><A HREF="#compat">Compatibility with Older Versions</A>
93 <LI><A HREF="#refbug">Refresh of Overlapping Windows</A>
94 <LI><A HREF="#backbug">Background Erase</A>
96 <LI><A HREF="#xsifuncs">XSI Curses Conformance</A>
98 <LI><A HREF="#panels">The Panels Library</A>
100 <LI><A HREF="#pcompile">Compiling With the Panels Library</A>
101 <LI><A HREF="#poverview">Overview of Panels</A>
102 <LI><A HREF="#pstdscr">Panels, Input, and the Standard Screen</A>
103 <LI><A HREF="#hiding">Hiding Panels</A>
104 <LI><A HREF="#pmisc">Miscellaneous Other Facilities</A>
106 <LI><A HREF="#menu">The Menu Library</A>
108 <LI><A HREF="#mcompile">Compiling with the menu Library</A>
109 <LI><A HREF="#moverview">Overview of Menus</A>
110 <LI><A HREF="#mselect">Selecting items</A>
111 <LI><A HREF="#mdisplay">Menu Display</A>
112 <LI><A HREF="#mwindows">Menu Windows</A>
113 <LI><A HREF="#minput">Processing Menu Input</A>
114 <LI><A HREF="#mmisc">Miscellaneous Other Features</A>
116 <LI><A HREF="#form">The Forms Library</A>
118 <LI><A HREF="#fcompile">Compiling with the forms Library</A>
119 <LI><A HREF="#foverview">Overview of Forms</A>
120 <LI><A HREF="#fcreate">Creating and Freeing Fields and Forms</A>
121 <LI><A HREF="#fattributes">Fetching and Changing Field Attributes</A>
123 <LI><A HREF="#fsizes">Fetching Size and Location Data</A>
124 <LI><A HREF="#flocation">Changing the Field Location</A>
125 <LI><A HREF="#fjust">The Justification Attribute</A>
126 <LI><A HREF="#fdispatts">Field Display Attributes</A>
127 <LI><A HREF="#foptions">Field Option Bits</A>
128 <LI><A HREF="#fstatus">Field Status</A>
129 <LI><A HREF="#fuser">Field User Pointer</A>
131 <LI><A HREF="#fdynamic">Variable-Sized Fields</A>
132 <LI><A HREF="#fvalidation">Field Validation</A>
134 <LI><A HREF="#ftype_alpha">TYPE_ALPHA</A>
135 <LI><A HREF="#ftype_alnum">TYPE_ALNUM</A>
136 <LI><A HREF="#ftype_enum">TYPE_ENUM</A>
137 <LI><A HREF="#ftype_integer">TYPE_INTEGER</A>
138 <LI><A HREF="#ftype_numeric">TYPE_NUMERIC</A>
139 <LI><A HREF="#ftype_regexp">TYPE_REGEXP</A>
141 <LI><A HREF="#fbuffer">Direct Field Buffer Manipulation</A>
142 <LI><A HREF="#formattrs">Attributes of Forms</A>
143 <LI><A HREF="#fdisplay">Control of Form Display</A>
144 <LI><A HREF="#fdriver">Input Processing in the Forms Driver</A>
146 <LI><A HREF="#fpage">Page Navigation Requests</A>
147 <LI><A HREF="#ffield">Inter-Field Navigation Requests</A>
148 <LI><A HREF="#fifield">Intra-Field Navigation Requests</A>
149 <LI><A HREF="#fscroll">Scrolling Requests</A>
150 <LI><A HREF="#fedit">Field Editing Requests</A>
151 <LI><A HREF="#forder">Order Requests</A>
152 <LI><A HREF="#fappcmds">Application Commands</A>
154 <LI><A HREF="#fhooks">Field Change Hooks</A>
155 <LI><A HREF="#ffocus">Field Change Commands</A>
156 <LI><A HREF="#frmoptions">Form Options</A>
157 <LI><A HREF="#fcustom">Custom Validation Types</A>
159 <LI><A HREF="#flinktypes">Union Types</A>
160 <LI><A HREF="#fnewtypes">New Field Types</A>
161 <LI><A HREF="#fcheckargs">Validation Function Arguments</A>
162 <LI><A HREF="#fcustorder">Order Functions For Custom Types</A>
163 <LI><A HREF="#fcustprobs">Avoiding Problems</A>
169 <H1><A NAME="introduction">Introduction</A></H1>
171 This document is an introduction to programming with <CODE>curses</CODE>. It is
172 not an exhaustive reference for the curses Application Programming Interface
173 (API); that role is filled by the <CODE>curses</CODE> manual pages. Rather, it
174 is intended to help C programmers ease into using the package. <P>
176 This document is aimed at C applications programmers not yet specifically
177 familiar with ncurses. If you are already an experienced <CODE>curses</CODE>
178 programmer, you should nevertheless read the sections on
179 <A HREF="#mouse">Mouse Interfacing</A>, <A HREF="#debugging">Debugging</A>,
180 <A HREF="#compat">Compatibility with Older Versions</A>,
181 and <A HREF="#hints">Hints, Tips, and Tricks</A>. These will bring you up
182 to speed on the special features and quirks of the <CODE>ncurses</CODE>
183 implementation. If you are not so experienced, keep reading. <P>
185 The <CODE>curses</CODE> package is a subroutine library for
186 terminal-independent screen-painting and input-event handling which
187 presents a high level screen model to the programmer, hiding differences
188 between terminal types and doing automatic optimization of output to change
189 one screen full of text into another. <CODE>Curses</CODE> uses terminfo, which
190 is a database format that can describe the capabilities of thousands of
191 different terminals. <P>
193 The <CODE>curses</CODE> API may seem something of an archaism on UNIX desktops
194 increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX still
195 supports tty lines and X supports <EM>xterm(1)</EM>; the <CODE>curses</CODE>
196 API has the advantage of (a) back-portability to character-cell terminals,
197 and (b) simplicity. For an application that does not require bit-mapped
198 graphics and multiple fonts, an interface implementation using <CODE>curses</CODE>
199 will typically be a great deal simpler and less expensive than one using an
202 <H2><A NAME="history">A Brief History of Curses</A></H2>
204 Historically, the first ancestor of <CODE>curses</CODE> was the routines written to
205 provide screen-handling for the game <CODE>rogue</CODE>; these used the
206 already-existing <CODE>termcap</CODE> database facility for describing terminal
207 capabilities. These routines were abstracted into a documented library and
208 first released with the early BSD UNIX versions. <P>
210 System III UNIX from Bell Labs featured a rewritten and much-improved
211 <CODE>curses</CODE> library. It introduced the terminfo format. Terminfo is based
212 on Berkeley's termcap database, but contains a number of improvements and
213 extensions. Parameterized capabilities strings were introduced, making it
214 possible to describe multiple video attributes, and colors and to handle far
215 more unusual terminals than possible with termcap. In the later AT&T
216 System V releases, <CODE>curses</CODE> evolved to use more facilities and offer
217 more capabilities, going far beyond BSD curses in power and flexibility.
219 <H2><A NAME="scope">Scope of This Document</A></H2>
221 This document describes <CODE>ncurses</CODE>, a free implementation of
222 the System V <CODE>curses</CODE> API with some clearly marked extensions.
223 It includes the following System V curses features:
225 <LI>Support for multiple screen highlights (BSD curses could only
226 handle one `standout' highlight, usually reverse-video).
227 <LI>Support for line- and box-drawing using forms characters.
228 <LI>Recognition of function keys on input.
230 <LI>Support for pads (windows of larger than screen size on which the
231 screen or a subwindow defines a viewport).
234 Also, this package makes use of the insert and delete line and character
235 features of terminals so equipped, and determines how to optimally use these
236 features with no help from the programmer. It allows arbitrary combinations of
237 video attributes to be displayed, even on terminals that leave ``magic
238 cookies'' on the screen to mark changes in attributes. <P>
240 The <CODE>ncurses</CODE> package can also capture and use event reports from a
241 mouse in some environments (notably, xterm under the X window system). This
242 document includes tips for using the mouse. <P>
244 The <CODE>ncurses</CODE> package was originated by Pavel Curtis. The original
245 maintainer of this package is
246 <A HREF="mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</A>
247 <zmbenhal@netcom.com>.
248 <A HREF="mailto:esr@snark.thyrsus.com">Eric S. Raymond</A>
249 <esr@snark.thyrsus.com>
250 wrote many of the new features in versions after 1.8.1
251 and wrote most of this introduction.
253 wrote all of the menu and forms code as well as the
254 <A HREF="http://www.adahome.com">Ada95</A> binding.
255 Ongoing work is being done by
256 <A HREF="mailto:dickey@invisible-island.net">Thomas Dickey</A> (maintainer).
257 Contact the current maintainers at
258 <A HREF="mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</A>.
261 This document also describes the <A HREF="#panels">panels</A> extension library,
262 similarly modeled on the SVr4 panels facility. This library allows you to
263 associate backing store with each of a stack or deck of overlapping windows,
264 and provides operations for moving windows around in the stack that change
265 their visibility in the natural way (handling window overlaps). <P>
267 Finally, this document describes in detail the <A HREF="#menu">menus</A> and <A
268 HREF="#form">forms</A> extension libraries, also cloned from System V,
269 which support easy construction and sequences of menus and fill-in
273 <H2><A NAME="terminology">Terminology</A></H2>
275 In this document, the following terminology is used with reasonable
281 A data structure describing a sub-rectangle of the screen (possibly the
282 entire screen). You can write to a window as though it were a miniature
283 screen, scrolling independently of other windows on the physical screen.
286 A subset of windows which are as large as the terminal screen, i.e., they start
287 at the upper left hand corner and encompass the lower right hand corner. One
288 of these, <CODE>stdscr</CODE>, is automatically provided for the programmer.
291 The package's idea of what the terminal display currently looks like, i.e.,
292 what the user sees now. This is a special screen.
295 <H1><A NAME="curses">The Curses Library</A></H1>
297 <H2><A NAME="overview">An Overview of Curses</A></H2>
299 <H3><A NAME="compiling">Compiling Programs using Curses</A></H3>
301 In order to use the library, it is necessary to have certain types and
302 variables defined. Therefore, the programmer must have a line:
305 #include <curses.h>
308 at the top of the program source. The screen package uses the Standard I/O
309 library, so <CODE><curses.h></CODE> includes
310 <CODE><stdio.h></CODE>. <CODE><curses.h></CODE> also includes
311 <CODE><termios.h></CODE>, <CODE><termio.h></CODE>, or
312 <CODE><sgtty.h></CODE> depending on your system. It is redundant (but
313 harmless) for the programmer to do these includes, too. In linking with
314 <CODE>curses</CODE> you need to have <CODE>-lncurses</CODE> in your LDFLAGS or on the
315 command line. There is no need for any other libraries.
317 <H3><A NAME="updating">Updating the Screen</A></H3>
319 In order to update the screen optimally, it is necessary for the routines to
320 know what the screen currently looks like and what the programmer wants it to
321 look like next. For this purpose, a data type (structure) named WINDOW is
322 defined which describes a window image to the routines, including its starting
323 position on the screen (the (y, x) coordinates of the upper left hand corner)
324 and its size. One of these (called <CODE>curscr</CODE>, for current screen) is a
325 screen image of what the terminal currently looks like. Another screen (called
326 <CODE>stdscr</CODE>, for standard screen) is provided by default to make changes
329 A window is a purely internal representation. It is used to build and store a
330 potential image of a portion of the terminal. It doesn't bear any necessary
331 relation to what is really on the terminal screen; it's more like a
332 scratchpad or write buffer. <P>
334 To make the section of physical screen corresponding to a window reflect the
335 contents of the window structure, the routine <CODE>refresh()</CODE> (or
336 <CODE>wrefresh()</CODE> if the window is not <CODE>stdscr</CODE>) is called. <P>
338 A given physical screen section may be within the scope of any number of
339 overlapping windows. Also, changes can be made to windows in any order,
340 without regard to motion efficiency. Then, at will, the programmer can
341 effectively say ``make it look like this,'' and let the package implementation
342 determine the most efficient way to repaint the screen.
344 <H3><A NAME="stdscr">Standard Windows and Function Naming Conventions</A></H3>
346 As hinted above, the routines can use several windows, but two are
347 automatically given: <CODE>curscr</CODE>, which knows what the terminal looks like,
348 and <CODE>stdscr</CODE>, which is what the programmer wants the terminal to look
349 like next. The user should never actually access <CODE>curscr</CODE> directly.
350 Changes should be made to through the API, and then the routine
351 <CODE>refresh()</CODE> (or <CODE>wrefresh()</CODE>) called. <P>
353 Many functions are defined to use <CODE>stdscr</CODE> as a default screen. For
354 example, to add a character to <CODE>stdscr</CODE>, one calls <CODE>addch()</CODE> with
355 the desired character as argument. To write to a different window. use the
356 routine <CODE>waddch()</CODE> (for `w'indow-specific addch()) is provided. This
357 convention of prepending function names with a `w' when they are to be
358 applied to specific windows is consistent. The only routines which do not
359 follow it are those for which a window must always be specified. <P>
361 In order to move the current (y, x) coordinates from one point to another, the
362 routines <CODE>move()</CODE> and <CODE>wmove()</CODE> are provided. However, it is
363 often desirable to first move and then perform some I/O operation. In order to
364 avoid clumsiness, most I/O routines can be preceded by the prefix 'mv' and
365 the desired (y, x) coordinates prepended to the arguments to the function. For
389 mvwaddch(win, y, x, ch);
392 Note that the window description pointer (win) comes before the added (y, x)
393 coordinates. If a function requires a window pointer, it is always the first
396 <H3><A NAME="variables">Variables</A></H3>
398 The <CODE>curses</CODE> library sets some variables describing the terminal
402 type name description
403 ------------------------------------------------------------------
404 int LINES number of lines on the terminal
405 int COLS number of columns on the terminal
408 The <CODE>curses.h</CODE> also introduces some <CODE>#define</CODE> constants and types
409 of general usefulness:
412 <DT> <CODE>bool</CODE>
413 <DD> boolean type, actually a `char' (e.g., <CODE>bool doneit;</CODE>)
414 <DT> <CODE>TRUE</CODE>
415 <DD> boolean `true' flag (1).
416 <DT> <CODE>FALSE</CODE>
417 <DD> boolean `false' flag (0).
418 <DT> <CODE>ERR</CODE>
419 <DD> error flag returned by routines on a failure (-1).
421 <DD> error flag returned by routines when things go right.
424 <H2><A NAME="using">Using the Library</A></H2>
426 Now we describe how to actually use the screen package. In it, we assume all
427 updating, reading, etc. is applied to <CODE>stdscr</CODE>. These instructions will
428 work on any window, providing you change the function names and parameters as
431 Here is a sample program to motivate the discussion:
434 #include <stdlib.h>
435 #include <curses.h>
436 #include <signal.h>
438 static void finish(int sig);
441 main(int argc, char *argv[])
445 /* initialize your non-curses data structures here */
447 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
449 (void) initscr(); /* initialize the curses library */
450 keypad(stdscr, TRUE); /* enable keyboard mapping */
451 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
452 (void) cbreak(); /* take input chars one at a time, no wait for \n */
453 (void) echo(); /* echo input - in color */
460 * Simple color assignment, often all we need. Color pair 0 cannot
461 * be redefined. This example uses the same value for the color
462 * pair as for the foreground color, though of course that is not
465 init_pair(1, COLOR_RED, COLOR_BLACK);
466 init_pair(2, COLOR_GREEN, COLOR_BLACK);
467 init_pair(3, COLOR_YELLOW, COLOR_BLACK);
468 init_pair(4, COLOR_BLUE, COLOR_BLACK);
469 init_pair(5, COLOR_CYAN, COLOR_BLACK);
470 init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
471 init_pair(7, COLOR_WHITE, COLOR_BLACK);
476 int c = getch(); /* refresh, accept single keystroke of input */
477 attrset(COLOR_PAIR(num % 8));
480 /* process the command keystroke */
483 finish(0); /* we're done */
486 static void finish(int sig)
490 /* do your non-curses wrapup here */
496 <H3><A NAME="starting">Starting up</A></H3>
498 In order to use the screen package, the routines must know about terminal
499 characteristics, and the space for <CODE>curscr</CODE> and <CODE>stdscr</CODE> must be
500 allocated. These function <CODE>initscr()</CODE> does both these things. Since it
501 must allocate space for the windows, it can overflow memory when attempting to
502 do so. On the rare occasions this happens, <CODE>initscr()</CODE> will terminate
503 the program with an error message. <CODE>initscr()</CODE> must always be called
504 before any of the routines which affect windows are used. If it is not, the
505 program will core dump as soon as either <CODE>curscr</CODE> or <CODE>stdscr</CODE> are
506 referenced. However, it is usually best to wait to call it until after you are
507 sure you will need it, like after checking for startup errors. Terminal status
508 changing routines like <CODE>nl()</CODE> and <CODE>cbreak()</CODE> should be called
509 after <CODE>initscr()</CODE>. <P>
511 Once the screen windows have been allocated, you can set them up for
512 your program. If you want to, say, allow a screen to scroll, use
513 <CODE>scrollok()</CODE>. If you want the cursor to be left in place after
514 the last change, use <CODE>leaveok()</CODE>. If this isn't done,
515 <CODE>refresh()</CODE> will move the cursor to the window's current (y, x)
516 coordinates after updating it. <P>
518 You can create new windows of your own using the functions <CODE>newwin()</CODE>,
519 <CODE>derwin()</CODE>, and <CODE>subwin()</CODE>. The routine <CODE>delwin()</CODE> will
520 allow you to get rid of old windows. All the options described above can be
521 applied to any window.
523 <H3><A NAME="output">Output</A></H3>
525 Now that we have set things up, we will want to actually update the terminal.
526 The basic functions used to change what will go on a window are
527 <CODE>addch()</CODE> and <CODE>move()</CODE>. <CODE>addch()</CODE> adds a character at the
528 current (y, x) coordinates. <CODE>move()</CODE> changes the current (y, x)
529 coordinates to whatever you want them to be. It returns <CODE>ERR</CODE> if you
530 try to move off the window. As mentioned above, you can combine the two into
531 <CODE>mvaddch()</CODE> to do both things at once. <P>
533 The other output functions, such as <CODE>addstr()</CODE> and <CODE>printw()</CODE>,
534 all call <CODE>addch()</CODE> to add characters to the window. <P>
536 After you have put on the window what you want there, when you want the portion
537 of the terminal covered by the window to be made to look like it, you must call
538 <CODE>refresh()</CODE>. In order to optimize finding changes, <CODE>refresh()</CODE>
539 assumes that any part of the window not changed since the last
540 <CODE>refresh()</CODE> of that window has not been changed on the terminal, i.e.,
541 that you have not refreshed a portion of the terminal with an overlapping
542 window. If this is not the case, the routine <CODE>touchwin()</CODE> is provided
543 to make it look like the entire window has been changed, thus making
544 <CODE>refresh()</CODE> check the whole subsection of the terminal for changes. <P>
546 If you call <CODE>wrefresh()</CODE> with <CODE>curscr</CODE> as its argument, it will
547 make the screen look like <CODE>curscr</CODE> thinks it looks like. This is useful
548 for implementing a command which would redraw the screen in case it get messed
551 <H3><A NAME="input">Input</A></H3>
553 The complementary function to <CODE>addch()</CODE> is <CODE>getch()</CODE> which, if
554 echo is set, will call <CODE>addch()</CODE> to echo the character. Since the
555 screen package needs to know what is on the terminal at all times, if
556 characters are to be echoed, the tty must be in raw or cbreak mode. Since
557 initially the terminal has echoing enabled and is in ordinary ``cooked'' mode,
558 one or the other has to changed before calling <CODE>getch()</CODE>; otherwise,
559 the program's output will be unpredictable. <P>
561 When you need to accept line-oriented input in a window, the functions
562 <CODE>wgetstr()</CODE> and friends are available. There is even a <CODE>wscanw()</CODE>
563 function that can do <CODE>scanf()</CODE>(3)-style multi-field parsing on window
564 input. These pseudo-line-oriented functions turn on echoing while they
567 The example code above uses the call <CODE>keypad(stdscr, TRUE)</CODE> to enable
568 support for function-key mapping. With this feature, the <CODE>getch()</CODE> code
569 watches the input stream for character sequences that correspond to arrow and
570 function keys. These sequences are returned as pseudo-character values. The
571 <CODE>#define</CODE> values returned are listed in the <CODE>curses.h</CODE> The
572 mapping from sequences to <CODE>#define</CODE> values is determined by
573 <CODE>key_</CODE> capabilities in the terminal's terminfo entry.
575 <H3><A NAME="formschars">Using Forms Characters</A></H3>
577 The <CODE>addch()</CODE> function (and some others, including <CODE>box()</CODE> and
578 <CODE>border()</CODE>) can accept some pseudo-character arguments which are specially
579 defined by <CODE>ncurses</CODE>. These are <CODE>#define</CODE> values set up in
580 the <CODE>curses.h</CODE> header; see there for a complete list (look for
581 the prefix <CODE>ACS_</CODE>). <P>
583 The most useful of the ACS defines are the forms-drawing characters. You can
584 use these to draw boxes and simple graphs on the screen. If the terminal
585 does not have such characters, <CODE>curses.h</CODE> will map them to a
586 recognizable (though ugly) set of ASCII defaults.
588 <H3><A NAME="attributes">Character Attributes and Color</A></H3>
590 The <CODE>ncurses</CODE> package supports screen highlights including standout,
591 reverse-video, underline, and blink. It also supports color, which is treated
592 as another kind of highlight. <P>
594 Highlights are encoded, internally, as high bits of the pseudo-character type
595 (<CODE>chtype</CODE>) that <CODE>curses.h</CODE> uses to represent the contents of a
596 screen cell. See the <CODE>curses.h</CODE> header file for a complete list of
597 highlight mask values (look for the prefix <CODE>A_</CODE>).<P>
599 There are two ways to make highlights. One is to logical-or the value of the
600 highlights you want into the character argument of an <CODE>addch()</CODE> call,
601 or any other output call that takes a <CODE>chtype</CODE> argument. <P>
603 The other is to set the current-highlight value. This is logical-or'ed with
604 any highlight you specify the first way. You do this with the functions
605 <CODE>attron()</CODE>, <CODE>attroff()</CODE>, and <CODE>attrset()</CODE>; see the manual
608 Color is a special kind of highlight. The package actually thinks in terms
609 of color pairs, combinations of foreground and background colors. The sample
610 code above sets up eight color pairs, all of the guaranteed-available colors
611 on black. Note that each color pair is, in effect, given the name of its
612 foreground color. Any other range of eight non-conflicting values could
613 have been used as the first arguments of the <CODE>init_pair()</CODE> values. <P>
615 Once you've done an <CODE>init_pair()</CODE> that creates color-pair N, you can
616 use <CODE>COLOR_PAIR(N)</CODE> as a highlight that invokes that particular
617 color combination. Note that <CODE>COLOR_PAIR(N)</CODE>, for constant N,
618 is itself a compile-time constant and can be used in initializers.
620 <H3><A NAME="mouse">Mouse Interfacing</A></H3>
622 The <CODE>ncurses</CODE> library also provides a mouse interface.
623 <!-- The 'note' tag is not portable enough -->
625 <strong>NOTE:</strong> this facility is specific to <CODE>ncurses</CODE>, it is not part of either
626 the XSI Curses standard, nor of System V Release 4, nor BSD curses.
627 System V Release 4 curses contains code with similar interface definitions,
628 however it is not documented. Other than by disassembling the library, we
629 have no way to determine exactly how that mouse code works.
630 Thus, we recommend that you wrap mouse-related code in an #ifdef using the
631 feature macro NCURSES_MOUSE_VERSION so it will not be compiled and linked
632 on non-ncurses systems.
635 Presently, mouse event reporting works in the following environments:
637 <li>xterm and similar programs such as rxvt.
638 <li>Linux console, when configured with <CODE>gpm</CODE>(1), Alessandro
639 Rubini's mouse server.
640 <li>FreeBSD sysmouse (console)
644 The mouse interface is very simple. To activate it, you use the function
645 <CODE>mousemask()</CODE>, passing it as first argument a bit-mask that specifies
646 what kinds of events you want your program to be able to see. It will
647 return the bit-mask of events that actually become visible, which may differ
648 from the argument if the mouse device is not capable of reporting some of
649 the event types you specify. <P>
651 Once the mouse is active, your application's command loop should watch
652 for a return value of <CODE>KEY_MOUSE</CODE> from <CODE>wgetch()</CODE>. When
653 you see this, a mouse event report has been queued. To pick it off
654 the queue, use the function <CODE>getmouse()</CODE> (you must do this before
655 the next <CODE>wgetch()</CODE>, otherwise another mouse event might come
656 in and make the first one inaccessible). <P>
658 Each call to <CODE>getmouse()</CODE> fills a structure (the address of which you'll
659 pass it) with mouse event data. The event data includes zero-origin,
660 screen-relative character-cell coordinates of the mouse pointer. It also
661 includes an event mask. Bits in this mask will be set, corresponding
662 to the event type being reported. <P>
664 The mouse structure contains two additional fields which may be
665 significant in the future as ncurses interfaces to new kinds of
666 pointing device. In addition to x and y coordinates, there is a slot
667 for a z coordinate; this might be useful with touch-screens that can
668 return a pressure or duration parameter. There is also a device ID
669 field, which could be used to distinguish between multiple pointing
672 The class of visible events may be changed at any time via <CODE>mousemask()</CODE>.
673 Events that can be reported include presses, releases, single-, double- and
674 triple-clicks (you can set the maximum button-down time for clicks). If
675 you don't make clicks visible, they will be reported as press-release
676 pairs. In some environments, the event mask may include bits reporting
677 the state of shift, alt, and ctrl keys on the keyboard during the event. <P>
679 A function to check whether a mouse event fell within a given window is
680 also supplied. You can use this to see whether a given window should
681 consider a mouse event relevant to it. <P>
683 Because mouse event reporting will not be available in all
684 environments, it would be unwise to build <CODE>ncurses</CODE>
685 applications that <EM>require</EM> the use of a mouse. Rather, you should
686 use the mouse as a shortcut for point-and-shoot commands your application
687 would normally accept from the keyboard. Two of the test games in the
688 <CODE>ncurses</CODE> distribution (<CODE>bs</CODE> and <CODE>knight</CODE>) contain
689 code that illustrates how this can be done. <P>
691 See the manual page <CODE>curs_mouse(3X)</CODE> for full details of the
692 mouse-interface functions.
694 <H3><A NAME="finishing">Finishing Up</A></H3>
696 In order to clean up after the <CODE>ncurses</CODE> routines, the routine
697 <CODE>endwin()</CODE> is provided. It restores tty modes to what they were when
698 <CODE>initscr()</CODE> was first called, and moves the cursor down to the
699 lower-left corner. Thus, anytime after the call to initscr, <CODE>endwin()</CODE>
700 should be called before exiting.
702 <H2><A NAME="functions">Function Descriptions</A></H2>
704 We describe the detailed behavior of some important curses functions here, as a
705 supplement to the manual page descriptions.
707 <H3><A NAME="init">Initialization and Wrapup</A></H3>
710 <DT> <CODE>initscr()</CODE>
711 <DD> The first function called should almost always be <CODE>initscr()</CODE>.
712 This will determine the terminal type and
713 initialize curses data structures. <CODE>initscr()</CODE> also arranges that
714 the first call to <CODE>refresh()</CODE> will clear the screen. If an error
715 occurs a message is written to standard error and the program
716 exits. Otherwise it returns a pointer to stdscr. A few functions may be
717 called before initscr (<CODE>slk_init()</CODE>, <CODE>filter()</CODE>,
718 <CODE>ripoffline()</CODE>, <CODE>use_env()</CODE>, and, if you are using multiple
719 terminals, <CODE>newterm()</CODE>.)
720 <DT> <CODE>endwin()</CODE>
721 <DD> Your program should always call <CODE>endwin()</CODE> before exiting or
722 shelling out of the program. This function will restore tty modes,
723 move the cursor to the lower left corner of the screen, reset the
724 terminal into the proper non-visual mode. Calling <CODE>refresh()</CODE>
725 or <CODE>doupdate()</CODE> after a temporary escape from the program will
726 restore the ncurses screen from before the escape.
727 <DT> <CODE>newterm(type, ofp, ifp)</CODE>
728 <DD> A program which outputs to more than one terminal should use
729 <CODE>newterm()</CODE> instead of <CODE>initscr()</CODE>. <CODE>newterm()</CODE> should
730 be called once for each terminal. It returns a variable of type
731 <CODE>SCREEN *</CODE> which should be saved as a reference to that
733 (NOTE: a SCREEN variable is not a <em>screen</em> in the sense we
734 are describing in this introduction, but a collection of
735 parameters used to assist in optimizing the display.)
736 The arguments are the type of the terminal (a string) and
737 <CODE>FILE</CODE> pointers for the output and input of the terminal. If
738 type is NULL then the environment variable <CODE>$TERM</CODE> is used.
739 <CODE>endwin()</CODE> should called once at wrapup time for each terminal
740 opened using this function.
741 <DT> <CODE>set_term(new)</CODE>
742 <DD> This function is used to switch to a different terminal previously
743 opened by <CODE>newterm()</CODE>. The screen reference for the new terminal
744 is passed as the parameter. The previous terminal is returned by the
745 function. All other calls affect only the current terminal.
746 <DT> <CODE>delscreen(sp)</CODE>
747 <DD> The inverse of <CODE>newterm()</CODE>; deallocates the data structures
748 associated with a given <CODE>SCREEN</CODE> reference.
751 <H3><A NAME="flush">Causing Output to the Terminal</A></H3>
754 <DT> <CODE>refresh()</CODE> and <CODE>wrefresh(win)</CODE>
755 <DD> These functions must be called to actually get any output on
756 the terminal, as other routines merely manipulate data
757 structures. <CODE>wrefresh()</CODE> copies the named window to the physical
758 terminal screen, taking into account what is already
759 there in order to do optimizations. <CODE>refresh()</CODE> does a
760 refresh of <CODE>stdscr</CODE>. Unless <CODE>leaveok()</CODE> has been
761 enabled, the physical cursor of the terminal is left at the
762 location of the window's cursor.
763 <DT> <CODE>doupdate()</CODE> and <CODE>wnoutrefresh(win)</CODE>
764 <DD> These two functions allow multiple updates with more efficiency
765 than wrefresh. To use them, it is important to understand how curses
766 works. In addition to all the window structures, curses keeps two
767 data structures representing the terminal screen: a physical screen,
768 describing what is actually on the screen, and a virtual screen,
769 describing what the programmer wants to have on the screen. wrefresh
770 works by first copying the named window to the virtual screen
771 (<CODE>wnoutrefresh()</CODE>), and then calling the routine to update the
772 screen (<CODE>doupdate()</CODE>). If the programmer wishes to output
773 several windows at once, a series of calls to <CODE>wrefresh</CODE> will result
774 in alternating calls to <CODE>wnoutrefresh()</CODE> and <CODE>doupdate()</CODE>,
775 causing several bursts of output to the screen. By calling
776 <CODE>wnoutrefresh()</CODE> for each window, it is then possible to call
777 <CODE>doupdate()</CODE> once, resulting in only one burst of output, with
778 fewer total characters transmitted (this also avoids a visually annoying
779 flicker at each update).
782 <H3><A NAME="lowlevel">Low-Level Capability Access</A></H3>
785 <DT> <CODE>setupterm(term, filenum, errret)</CODE>
786 <DD> This routine is called to initialize a terminal's description, without setting
787 up the curses screen structures or changing the tty-driver mode bits.
788 <CODE>term</CODE> is the character string representing the name of the terminal
789 being used. <CODE>filenum</CODE> is the UNIX file descriptor of the terminal to
790 be used for output. <CODE>errret</CODE> is a pointer to an integer, in which a
791 success or failure indication is returned. The values returned can be 1 (all
792 is well), 0 (no such terminal), or -1 (some problem locating the terminfo
795 The value of <CODE>term</CODE> can be given as NULL, which will cause the value of
796 <CODE>TERM</CODE> in the environment to be used. The <CODE>errret</CODE> pointer can
797 also be given as NULL, meaning no error code is wanted. If <CODE>errret</CODE> is
798 defaulted, and something goes wrong, <CODE>setupterm()</CODE> will print an
799 appropriate error message and exit, rather than returning. Thus, a simple
800 program can call setupterm(0, 1, 0) and not worry about initialization
803 After the call to <CODE>setupterm()</CODE>, the global variable <CODE>cur_term</CODE> is
804 set to point to the current structure of terminal capabilities. By calling
805 <CODE>setupterm()</CODE> for each terminal, and saving and restoring
806 <CODE>cur_term</CODE>, it is possible for a program to use two or more terminals at
807 once. <CODE>Setupterm()</CODE> also stores the names section of the terminal
808 description in the global character array <CODE>ttytype[]</CODE>. Subsequent calls
809 to <CODE>setupterm()</CODE> will overwrite this array, so you'll have to save it
813 <H3><A NAME="debugging">Debugging</A></H3>
815 <!-- The 'note' tag is not portable enough -->
817 <strong>NOTE:</strong> These functions are not part of the standard curses API!
821 <DT> <CODE>trace()</CODE>
823 This function can be used to explicitly set a trace level. If the
824 trace level is nonzero, execution of your program will generate a file
825 called `trace' in the current working directory containing a report on
826 the library's actions. Higher trace levels enable more detailed (and
827 verbose) reporting -- see comments attached to <CODE>TRACE_</CODE> defines
828 in the <CODE>curses.h</CODE> file for details. (It is also possible to set
829 a trace level by assigning a trace level value to the environment variable
830 <CODE>NCURSES_TRACE</CODE>).
831 <DT> <CODE>_tracef()</CODE>
833 This function can be used to output your own debugging information. It is only
834 available only if you link with -lncurses_g. It can be used the same way as
835 <CODE>printf()</CODE>, only it outputs a newline after the end of arguments.
836 The output goes to a file called <CODE>trace</CODE> in the current directory.
839 Trace logs can be difficult to interpret due to the sheer volume of
840 data dumped in them. There is a script called <STRONG>tracemunch</STRONG>
841 included with the <CODE>ncurses</CODE> distribution that can alleviate
842 this problem somewhat; it compacts long sequences of similar operations into
843 more succinct single-line pseudo-operations. These pseudo-ops can be
844 distinguished by the fact that they are named in capital letters.
846 <H2><A NAME="hints">Hints, Tips, and Tricks</A></H2>
848 The <CODE>ncurses</CODE> manual pages are a complete reference for this library.
849 In the remainder of this document, we discuss various useful methods that
850 may not be obvious from the manual page descriptions.
852 <H3><A NAME="caution">Some Notes of Caution</A></H3>
854 If you find yourself thinking you need to use <CODE>noraw()</CODE> or
855 <CODE>nocbreak()</CODE>, think again and move carefully. It's probably
856 better design to use <CODE>getstr()</CODE> or one of its relatives to
857 simulate cooked mode. The <CODE>noraw()</CODE> and <CODE>nocbreak()</CODE>
858 functions try to restore cooked mode, but they may end up clobbering
859 some control bits set before you started your application. Also, they
860 have always been poorly documented, and are likely to hurt your
861 application's usability with other curses libraries. <P>
863 Bear in mind that <CODE>refresh()</CODE> is a synonym for <CODE>wrefresh(stdscr)</CODE>.
864 Don't try to mix use of <CODE>stdscr</CODE> with use of windows declared
865 by <CODE>newwin()</CODE>; a <CODE>refresh()</CODE> call will blow them off the
866 screen. The right way to handle this is to use <CODE>subwin()</CODE>, or
867 not touch <CODE>stdscr</CODE> at all and tile your screen with declared
868 windows which you then <CODE>wnoutrefresh()</CODE> somewhere in your program
869 event loop, with a single <CODE>doupdate()</CODE> call to trigger actual
872 You are much less likely to run into problems if you design your screen
873 layouts to use tiled rather than overlapping windows. Historically,
874 curses support for overlapping windows has been weak, fragile, and poorly
875 documented. The <CODE>ncurses</CODE> library is not yet an exception to this
878 There is a panels library included in the <CODE>ncurses</CODE>
879 distribution that does a pretty good job of strengthening the
880 overlapping-windows facilities. <P>
882 Try to avoid using the global variables LINES and COLS. Use
883 <CODE>getmaxyx()</CODE> on the <CODE>stdscr</CODE> context instead. Reason:
884 your code may be ported to run in an environment with window resizes,
885 in which case several screens could be open with different sizes.
887 <H3><A NAME="leaving">Temporarily Leaving NCURSES Mode</A></H3>
889 Sometimes you will want to write a program that spends most of its time in
890 screen mode, but occasionally returns to ordinary `cooked' mode. A common
891 reason for this is to support shell-out. This behavior is simple to arrange
892 in <CODE>ncurses</CODE>. <P>
894 To leave <CODE>ncurses</CODE> mode, call <CODE>endwin()</CODE> as you would if you
895 were intending to terminate the program. This will take the screen back to
896 cooked mode; you can do your shell-out. When you want to return to
897 <CODE>ncurses</CODE> mode, simply call <CODE>refresh()</CODE> or <CODE>doupdate()</CODE>.
898 This will repaint the screen. <P>
900 There is a boolean function, <CODE>isendwin()</CODE>, which code can use to
901 test whether <CODE>ncurses</CODE> screen mode is active. It returns <CODE>TRUE</CODE>
902 in the interval between an <CODE>endwin()</CODE> call and the following
903 <CODE>refresh()</CODE>, <CODE>FALSE</CODE> otherwise. <P>
905 Here is some sample code for shellout:
908 addstr("Shelling out...");
909 def_prog_mode(); /* save current tty modes */
910 endwin(); /* restore original tty modes */
911 system("sh"); /* run shell */
912 addstr("returned.\n"); /* prepare return message */
913 refresh(); /* restore save modes, repaint screen */
916 <H3><A NAME="xterm">Using NCURSES under XTERM</A></H3>
918 A resize operation in X sends <CODE>SIGWINCH</CODE> to the application running
921 The easiest way to handle <CODE>SIGWINCH</CODE>
922 is to do an <CODE>endwin</CODE>,
923 followed by an <CODE>refresh</CODE> and a screen repaint you code
925 The <CODE>refresh</CODE> will pick up the new screen size from the
926 xterm's environment. <P>
928 That is the standard way, of course (it even works with some vendor's curses
930 Its drawback is that it clears the screen to reinitialize the display, and does
931 not resize subwindows which must be shrunk.
932 <CODE>Ncurses</CODE> provides an extension which works better, the
933 <CODE>resizeterm</CODE> function. That function ensures that all windows
934 are limited to the new screen dimensions, and pads <CODE>stdscr</CODE>
935 with blanks if the screen is larger. <P>
937 The <CODE>ncurses</CODE> library provides a SIGWINCH signal handler,
938 which pushes a <CODE>KEY_RESIZE</CODE> via the wgetch() calls.
939 When <CODE>ncurses</CODE> returns that code,
940 it calls <code>resizeterm</CODE>
941 to update the size of the standard screen's window, repainting that
942 (filling with blanks or truncating as needed).
943 It also resizes other windows,
944 but its effect may be less satisfactory because it cannot
945 know how you want the screen re-painted.
946 You will usually have to write special-purpose code to handle
947 <CODE>KEY_RESIZE</CODE> yourself.
949 <H3><A NAME="screens">Handling Multiple Terminal Screens</A></H3>
951 The <CODE>initscr()</CODE> function actually calls a function named
952 <CODE>newterm()</CODE> to do most of its work. If you are writing a program that
953 opens multiple terminals, use <CODE>newterm()</CODE> directly. <P>
955 For each call, you will have to specify a terminal type and a pair of file
956 pointers; each call will return a screen reference, and <CODE>stdscr</CODE> will be
957 set to the last one allocated. You will switch between screens with the
958 <CODE>set_term</CODE> call. Note that you will also have to call
959 <CODE>def_shell_mode</CODE> and <CODE>def_prog_mode</CODE> on each tty yourself.
961 <H3><A NAME="testing">Testing for Terminal Capabilities</A></H3>
963 Sometimes you may want to write programs that test for the presence of various
964 capabilities before deciding whether to go into <CODE>ncurses</CODE> mode. An easy
965 way to do this is to call <CODE>setupterm()</CODE>, then use the functions
966 <CODE>tigetflag()</CODE>, <CODE>tigetnum()</CODE>, and <CODE>tigetstr()</CODE> to do your
969 A particularly useful case of this often comes up when you want to
970 test whether a given terminal type should be treated as `smart'
971 (cursor-addressable) or `stupid'. The right way to test this is to see
972 if the return value of <CODE>tigetstr("cup")</CODE> is non-NULL. Alternatively,
973 you can include the <CODE>term.h</CODE> file and test the value of the
974 macro <CODE>cursor_address</CODE>.
976 <H3><A NAME="tuning">Tuning for Speed</A></H3>
978 Use the <CODE>addchstr()</CODE> family of functions for fast
979 screen-painting of text when you know the text doesn't contain any
980 control characters. Try to make attribute changes infrequent on your
981 screens. Don't use the <CODE>immedok()</CODE> option!
983 <H3><A NAME="special">Special Features of NCURSES</A></H3>
985 The <CODE>wresize()</CODE> function allows you to resize a window in place.
986 The associated <CODE>resizeterm()</CODE> function simplifies the construction
987 of <a HREF="#xterm">SIGWINCH</a> handlers, for resizing all windows. <P>
989 The <CODE>define_key()</CODE> function allows you
990 to define at runtime function-key control sequences which are not in the
991 terminal description.
992 The <CODE>keyok()</CODE> function allows you to temporarily
993 enable or disable interpretation of any function-key control sequence. <P>
995 The <CODE>use_default_colors()</CODE> function allows you to construct
996 applications which can use the terminal's default foreground and
997 background colors as an additional "default" color.
998 Several terminal emulators support this feature, which is based on ISO 6429. <P>
1000 Ncurses supports up 16 colors, unlike SVr4 curses which defines only 8.
1001 While most terminals which provide color allow only 8 colors, about
1002 a quarter (including XFree86 xterm) support 16 colors.
1004 <H2><A NAME="compat">Compatibility with Older Versions</A></H2>
1006 Despite our best efforts, there are some differences between <CODE>ncurses</CODE>
1007 and the (undocumented!) behavior of older curses implementations. These arise
1008 from ambiguities or omissions in the documentation of the API.
1010 <H3><A NAME="refbug">Refresh of Overlapping Windows</A></H3>
1012 If you define two windows A and B that overlap, and then alternately scribble
1013 on and refresh them, the changes made to the overlapping region under historic
1014 <CODE>curses</CODE> versions were often not documented precisely. <P>
1016 To understand why this is a problem, remember that screen updates are
1017 calculated between two representations of the <EM>entire</EM> display. The
1018 documentation says that when you refresh a window, it is first copied to the
1019 virtual screen, and then changes are calculated to update the physical screen
1020 (and applied to the terminal). But "copied to" is not very specific, and
1021 subtle differences in how copying works can produce different behaviors in the
1022 case where two overlapping windows are each being refreshed at unpredictable
1025 What happens to the overlapping region depends on what <CODE>wnoutrefresh()</CODE>
1026 does with its argument -- what portions of the argument window it copies to the
1027 virtual screen. Some implementations do "change copy", copying down only
1028 locations in the window that have changed (or been marked changed with
1029 <CODE>wtouchln()</CODE> and friends). Some implementations do "entire copy",
1030 copying <EM>all</EM> window locations to the virtual screen whether or not
1031 they have changed. <P>
1033 The <CODE>ncurses</CODE> library itself has not always been consistent on this
1034 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy. Versions
1035 1.8.6 and older, and versions 1.9.9 and newer, do change copy. <P>
1037 For most commercial curses implementations, it is not documented and not known
1038 for sure (at least not to the <CODE>ncurses</CODE> maintainers) whether they do
1039 change copy or entire copy. We know that System V release 3 curses has logic
1040 in it that looks like an attempt to do change copy, but the surrounding logic
1041 and data representations are sufficiently complex, and our knowledge
1042 sufficiently indirect, that it's hard to know whether this is reliable.
1044 It is not clear what the SVr4 documentation and XSI standard intend. The XSI
1045 Curses standard barely mentions wnoutrefresh(); the SVr4 documents seem to be
1046 describing entire-copy, but it is possible with some effort and straining to
1047 read them the other way. <P>
1049 It might therefore be unwise to rely on either behavior in programs that might
1050 have to be linked with other curses implementations. Instead, you can do an
1051 explicit <CODE>touchwin()</CODE> before the <CODE>wnoutrefresh()</CODE> call to
1052 guarantee an entire-contents copy anywhere. <P>
1054 The really clean way to handle this is to use the panels library. If,
1055 when you want a screen update, you do <CODE>update_panels()</CODE>, it will
1056 do all the necessary <CODE>wnoutrefresh()</CODE> calls for whatever panel
1057 stacking order you have defined. Then you can do one <CODE>doupdate()</CODE>
1058 and there will be a <EM>single</EM> burst of physical I/O that will do
1061 <H3><A NAME="backbug">Background Erase</A></H3>
1063 If you have been using a very old versions of <CODE>ncurses</CODE> (1.8.7 or
1064 older) you may be surprised by the behavior of the erase functions. In older
1065 versions, erased areas of a window were filled with a blank modified by the
1066 window's current attribute (as set by <STRONG>wattrset()</STRONG>, <STRONG>wattron()</STRONG>,
1067 <STRONG>wattroff()</STRONG> and friends). <P>
1069 In newer versions, this is not so. Instead, the attribute of erased blanks
1070 is normal unless and until it is modified by the functions <CODE>bkgdset()</CODE>
1071 or <CODE>wbkgdset()</CODE>. <P>
1073 This change in behavior conforms <CODE>ncurses</CODE> to System V Release 4 and
1074 the XSI Curses standard.
1076 <H2><A NAME="xsifuncs">XSI Curses Conformance</A></H2>
1078 The <CODE>ncurses</CODE> library is intended to be base-level conformant with the
1079 XSI Curses standard from X/Open. Many extended-level features (in fact, almost
1080 all features not directly concerned with wide characters and
1081 internationalization) are also supported. <P>
1083 One effect of XSI conformance is the change in behavior described under
1084 <A HREF="#backbug">"Background Erase -- Compatibility with Old Versions"</A>. <P>
1086 Also, <CODE>ncurses</CODE> meets the XSI requirement that every macro
1087 entry point have a corresponding function which may be linked (and
1088 will be prototype-checked) if the macro definition is disabled with
1089 <CODE>#undef</CODE>.
1091 <H1><A NAME="panels">The Panels Library</A></H1>
1093 The <CODE>ncurses</CODE> library by itself provides good support for screen
1094 displays in which the windows are tiled (non-overlapping). In the more
1095 general case that windows may overlap, you have to use a series of
1096 <CODE>wnoutrefresh()</CODE> calls followed by a <CODE>doupdate()</CODE>, and be
1097 careful about the order you do the window refreshes in. It has to be
1098 bottom-upwards, otherwise parts of windows that should be obscured will
1101 When your interface design is such that windows may dive deeper into the
1102 visibility stack or pop to the top at runtime, the resulting book-keeping
1103 can be tedious and difficult to get right. Hence the panels library. <P>
1105 The <CODE>panel</CODE> library first appeared in AT&T System V. The
1106 version documented here is the <CODE>panel</CODE> code distributed
1107 with <CODE>ncurses</CODE>.
1109 <H2><A NAME="pcompile">Compiling With the Panels Library</A></H2>
1111 Your panels-using modules must import the panels library declarations with
1114 #include <panel.h>
1117 and must be linked explicitly with the panels library using an
1118 <CODE>-lpanel</CODE> argument. Note that they must also link the
1119 <CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
1120 are two-pass and will accept either order, but it is still good practice
1121 to put <CODE>-lpanel</CODE> first and <CODE>-lncurses</CODE> second.
1123 <H2><A NAME="poverview">Overview of Panels</A></H2>
1125 A panel object is a window that is implicitly treated as part of a
1126 <DFN>deck</DFN> including all other panel objects. The deck has an implicit
1127 bottom-to-top visibility order. The panels library includes an update
1128 function (analogous to <CODE>refresh()</CODE>) that displays all panels in the
1129 deck in the proper order to resolve overlaps. The standard window,
1130 <CODE>stdscr</CODE>, is considered below all panels. <P>
1132 Details on the panels functions are available in the man pages. We'll just
1133 hit the highlights here. <P>
1135 You create a panel from a window by calling <CODE>new_panel()</CODE> on a
1136 window pointer. It then becomes the top of the deck. The panel's window
1137 is available as the value of <CODE>panel_window()</CODE> called with the
1138 panel pointer as argument.<P>
1140 You can delete a panel (removing it from the deck) with <CODE>del_panel</CODE>.
1141 This will not deallocate the associated window; you have to do that yourself.
1143 You can replace a panel's window with a different window by calling
1144 <CODE>replace_window</CODE>. The new window may be of different size;
1145 the panel code will re-compute all overlaps. This operation doesn't
1146 change the panel's position in the deck. <P>
1148 To move a panel's window, use <CODE>move_panel()</CODE>. The
1149 <CODE>mvwin()</CODE> function on the panel's window isn't sufficient because it
1150 doesn't update the panels library's representation of where the windows are.
1151 This operation leaves the panel's depth, contents, and size unchanged. <P>
1153 Two functions (<CODE>top_panel()</CODE>, <CODE>bottom_panel()</CODE>) are
1154 provided for rearranging the deck. The first pops its argument window to the
1155 top of the deck; the second sends it to the bottom. Either operation leaves
1156 the panel's screen location, contents, and size unchanged. <P>
1158 The function <CODE>update_panels()</CODE> does all the
1159 <CODE>wnoutrefresh()</CODE> calls needed to prepare for
1160 <CODE>doupdate()</CODE> (which you must call yourself, afterwards). <P>
1162 Typically, you will want to call <CODE>update_panels()</CODE> and
1163 <CODE>doupdate()</CODE> just before accepting command input, once in each cycle
1164 of interaction with the user. If you call <CODE>update_panels()</CODE> after
1165 each and every panel write, you'll generate a lot of unnecessary refresh
1166 activity and screen flicker.
1168 <H2><A NAME="pstdscr">Panels, Input, and the Standard Screen</A></H2>
1170 You shouldn't mix <CODE>wnoutrefresh()</CODE> or <CODE>wrefresh()</CODE>
1171 operations with panels code; this will work only if the argument window
1172 is either in the top panel or unobscured by any other panels. <P>
1174 The <CODE>stsdcr</CODE> window is a special case. It is considered below all
1175 panels. Because changes to panels may obscure parts of <CODE>stdscr</CODE>,
1176 though, you should call <CODE>update_panels()</CODE> before
1177 <CODE>doupdate()</CODE> even when you only change <CODE>stdscr</CODE>. <P>
1179 Note that <CODE>wgetch</CODE> automatically calls <CODE>wrefresh</CODE>.
1180 Therefore, before requesting input from a panel window, you need to be sure
1181 that the panel is totally unobscured. <P>
1183 There is presently no way to display changes to one obscured panel without
1184 repainting all panels.
1186 <H2><A NAME="hiding">Hiding Panels</A></H2>
1188 It's possible to remove a panel from the deck temporarily; use
1189 <CODE>hide_panel</CODE> for this. Use <CODE>show_panel()</CODE> to render it
1190 visible again. The predicate function <CODE>panel_hidden</CODE>
1191 tests whether or not a panel is hidden. <P>
1193 The <CODE>panel_update</CODE> code ignores hidden panels. You cannot do
1194 <CODE>top_panel()</CODE> or <CODE>bottom_panel</CODE> on a hidden panel().
1195 Other panels operations are applicable.
1197 <H2><A NAME="pmisc">Miscellaneous Other Facilities</A></H2>
1199 It's possible to navigate the deck using the functions
1200 <CODE>panel_above()</CODE> and <CODE>panel_below</CODE>. Handed a panel
1201 pointer, they return the panel above or below that panel. Handed
1202 <CODE>NULL</CODE>, they return the bottom-most or top-most panel. <P>
1204 Every panel has an associated user pointer, not used by the panel code, to
1205 which you can attach application data. See the man page documentation
1206 of <CODE>set_panel_userptr()</CODE> and <CODE>panel_userptr</CODE> for
1209 <H1><A NAME="menu">The Menu Library</A></H1>
1211 A menu is a screen display that assists the user to choose some subset
1212 of a given set of items. The <CODE>menu</CODE> library is a curses
1213 extension that supports easy programming of menu hierarchies with a
1214 uniform but flexible interface. <P>
1216 The <CODE>menu</CODE> library first appeared in AT&T System V. The
1217 version documented here is the <CODE>menu</CODE> code distributed
1218 with <CODE>ncurses</CODE>.
1220 <H2><A NAME="mcompile">Compiling With the menu Library</A></H2>
1222 Your menu-using modules must import the menu library declarations with
1225 #include <menu.h>
1228 and must be linked explicitly with the menus library using an
1229 <CODE>-lmenu</CODE> argument. Note that they must also link the
1230 <CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
1231 are two-pass and will accept either order, but it is still good practice
1232 to put <CODE>-lmenu</CODE> first and <CODE>-lncurses</CODE> second.
1234 <H2><A NAME="moverview">Overview of Menus</A></H2>
1236 The menus created by this library consist of collections of
1237 <DFN>items</DFN> including a name string part and a description string
1238 part. To make menus, you create groups of these items and connect
1239 them with menu frame objects. <P>
1241 The menu can then by <DFN>posted</DFN>, that is written to an
1242 associated window. Actually, each menu has two associated windows; a
1243 containing window in which the programmer can scribble titles or
1244 borders, and a subwindow in which the menu items proper are displayed.
1245 If this subwindow is too small to display all the items, it will be a
1246 scrollable viewport on the collection of items. <P>
1248 A menu may also be <DFN>unposted</DFN> (that is, undisplayed), and finally
1249 freed to make the storage associated with it and its items available for
1252 The general flow of control of a menu program looks like this:
1255 <LI>Initialize <CODE>curses</CODE>.
1256 <LI>Create the menu items, using <CODE>new_item()</CODE>.
1257 <LI>Create the menu using <CODE>new_menu()</CODE>.
1258 <LI>Post the menu using <CODE>post_menu()</CODE>.
1259 <LI>Refresh the screen.
1260 <LI>Process user requests via an input loop.
1261 <LI>Unpost the menu using <CODE>unpost_menu()</CODE>.
1262 <LI>Free the menu, using <CODE>free_menu()</CODE>.
1263 <LI>Free the items using <CODE>free_item()</CODE>.
1264 <LI>Terminate <CODE>curses</CODE>.
1267 <H2><A NAME="mselect">Selecting items</A></H2>
1269 Menus may be multi-valued or (the default) single-valued (see the manual
1270 page <CODE>menu_opts(3x)</CODE> to see how to change the default).
1271 Both types always have a <DFN>current item</DFN>. <P>
1273 From a single-valued menu you can read the selected value simply by looking
1274 at the current item. From a multi-valued menu, you get the selected set
1275 by looping through the items applying the <CODE>item_value()</CODE>
1276 predicate function. Your menu-processing code can use the function
1277 <CODE>set_item_value()</CODE> to flag the items in the select set. <P>
1279 Menu items can be made unselectable using <CODE>set_item_opts()</CODE>
1280 or <CODE>item_opts_off()</CODE> with the <CODE>O_SELECTABLE</CODE>
1281 argument. This is the only option so far defined for menus, but it
1282 is good practice to code as though other option bits might be on.
1284 <H2><A NAME="mdisplay">Menu Display</A></H2>
1286 The menu library calculates a minimum display size for your window, based
1287 on the following variables:
1290 <LI>The number and maximum length of the menu items
1291 <LI>Whether the O_ROWMAJOR option is enabled
1292 <LI>Whether display of descriptions is enabled
1293 <LI>Whatever menu format may have been set by the programmer
1294 <LI>The length of the menu mark string used for highlighting selected items
1297 The function <CODE>set_menu_format()</CODE> allows you to set the
1298 maximum size of the viewport or <DFN>menu page</DFN> that will be used
1299 to display menu items. You can retrieve any format associated with a
1300 menu with <CODE>menu_format()</CODE>. The default format is rows=16,
1303 The actual menu page may be smaller than the format size. This depends
1304 on the item number and size and whether O_ROWMAJOR is on. This option
1305 (on by default) causes menu items to be displayed in a `raster-scan'
1306 pattern, so that if more than one item will fit horizontally the first
1307 couple of items are side-by-side in the top row. The alternative is
1308 column-major display, which tries to put the first several items in
1309 the first column. <P>
1311 As mentioned above, a menu format not large enough to allow all items to fit
1312 on-screen will result in a menu display that is vertically scrollable. <P>
1313 You can scroll it with requests to the menu driver, which will be described
1314 in the section on <A HREF="#minput">menu input handling</A>. <P>
1316 Each menu has a <DFN>mark string</DFN> used to visually tag selected items;
1317 see the <CODE>menu_mark(3x)</CODE> manual page for details. The mark
1318 string length also influences the menu page size. <P>
1320 The function <CODE>scale_menu()</CODE> returns the minimum display size
1321 that the menu code computes from all these factors.
1323 There are other menu display attributes including a select attribute,
1324 an attribute for selectable items, an attribute for unselectable items,
1325 and a pad character used to separate item name text from description
1326 text. These have reasonable defaults which the library allows you to
1327 change (see the <CODE>menu_attribs(3x)</CODE> manual page.
1329 <H2><A NAME="mwindows">Menu Windows</A></H2>
1331 Each menu has, as mentioned previously, a pair of associated windows.
1332 Both these windows are painted when the menu is posted and erased when
1333 the menu is unposted. <P>
1335 The outer or frame window is not otherwise touched by the menu
1336 routines. It exists so the programmer can associate a title, a
1337 border, or perhaps help text with the menu and have it properly
1338 refreshed or erased at post/unpost time. The inner window or
1339 <DFN>subwindow</DFN> is where the current menu page is displayed. <P>
1341 By default, both windows are <CODE>stdscr</CODE>. You can set them with the
1342 functions in <CODE>menu_win(3x)</CODE>. <P>
1344 When you call <CODE>post_menu()</CODE>, you write the menu to its
1345 subwindow. When you call <CODE>unpost_menu()</CODE>, you erase the
1346 subwindow, However, neither of these actually modifies the screen. To
1347 do that, call <CODE>wrefresh()</CODE> or some equivalent.
1349 <H2><A NAME="minput">Processing Menu Input</A></H2>
1351 The main loop of your menu-processing code should call
1352 <CODE>menu_driver()</CODE> repeatedly. The first argument of this routine
1353 is a menu pointer; the second is a menu command code. You should write an
1354 input-fetching routine that maps input characters to menu command codes, and
1355 pass its output to <CODE>menu_driver()</CODE>. The menu command codes are
1356 fully documented in <CODE>menu_driver(3x)</CODE>. <P>
1358 The simplest group of command codes is <CODE>REQ_NEXT_ITEM</CODE>,
1359 <CODE>REQ_PREV_ITEM</CODE>, <CODE>REQ_FIRST_ITEM</CODE>,
1360 <CODE>REQ_LAST_ITEM</CODE>, <CODE>REQ_UP_ITEM</CODE>,
1361 <CODE>REQ_DOWN_ITEM</CODE>, <CODE>REQ_LEFT_ITEM</CODE>,
1362 <CODE>REQ_RIGHT_ITEM</CODE>. These change the currently selected
1363 item. These requests may cause scrolling of the menu page if it only
1364 partially displayed. <P>
1366 There are explicit requests for scrolling which also change the
1367 current item (because the select location does not change, but the
1368 item there does). These are <CODE>REQ_SCR_DLINE</CODE>,
1369 <CODE>REQ_SCR_ULINE</CODE>, <CODE>REQ_SCR_DPAGE</CODE>, and
1370 <CODE>REQ_SCR_UPAGE</CODE>. <P>
1372 The <CODE>REQ_TOGGLE_ITEM</CODE> selects or deselects the current item.
1373 It is for use in multi-valued menus; if you use it with <CODE>O_ONEVALUE</CODE>
1374 on, you'll get an error return (<CODE>E_REQUEST_DENIED</CODE>). <P>
1376 Each menu has an associated pattern buffer. The
1377 <CODE>menu_driver()</CODE> logic tries to accumulate printable ASCII
1378 characters passed in in that buffer; when it matches a prefix of an
1379 item name, that item (or the next matching item) is selected. If
1380 appending a character yields no new match, that character is deleted
1381 from the pattern buffer, and <CODE>menu_driver()</CODE> returns
1382 <CODE>E_NO_MATCH</CODE>. <P>
1384 Some requests change the pattern buffer directly:
1385 <CODE>REQ_CLEAR_PATTERN</CODE>, <CODE>REQ_BACK_PATTERN</CODE>,
1386 <CODE>REQ_NEXT_MATCH</CODE>, <CODE>REQ_PREV_MATCH</CODE>. The latter
1387 two are useful when pattern buffer input matches more than one item
1388 in a multi-valued menu. <P>
1390 Each successful scroll or item navigation request clears the pattern
1391 buffer. It is also possible to set the pattern buffer explicitly
1392 with <CODE>set_menu_pattern()</CODE>. <P>
1394 Finally, menu driver requests above the constant <CODE>MAX_COMMAND</CODE>
1395 are considered application-specific commands. The <CODE>menu_driver()</CODE>
1396 code ignores them and returns <CODE>E_UNKNOWN_COMMAND</CODE>.
1398 <H2><A NAME="mmisc">Miscellaneous Other Features</A></H2>
1400 Various menu options can affect the processing and visual appearance
1401 and input processing of menus. See <CODE>menu_opts(3x) for
1404 It is possible to change the current item from application code; this
1405 is useful if you want to write your own navigation requests. It is
1406 also possible to explicitly set the top row of the menu display. See
1407 <CODE>mitem_current(3x)</CODE>.
1409 If your application needs to change the menu subwindow cursor for
1410 any reason, <CODE>pos_menu_cursor()</CODE> will restore it to the
1411 correct location for continuing menu driver processing. <P>
1413 It is possible to set hooks to be called at menu initialization and
1414 wrapup time, and whenever the selected item changes. See
1415 <CODE>menu_hook(3x)</CODE>. <P>
1417 Each item, and each menu, has an associated user pointer on which you
1418 can hang application data. See <CODE>mitem_userptr(3x)</CODE> and
1419 <CODE>menu_userptr(3x)</CODE>.
1421 <H1><A NAME="form">The Forms Library</A></H1>
1423 The <CODE>form</CODE> library is a curses extension that supports easy
1424 programming of on-screen forms for data entry and program control. <P>
1426 The <CODE>form</CODE> library first appeared in AT&T System V. The
1427 version documented here is the <CODE>form</CODE> code distributed
1428 with <CODE>ncurses</CODE>.
1430 <H2><A NAME="fcompile">Compiling With the form Library</A></H2>
1432 Your form-using modules must import the form library declarations with
1435 #include <form.h>
1438 and must be linked explicitly with the forms library using an
1439 <CODE>-lform</CODE> argument. Note that they must also link the
1440 <CODE>ncurses</CODE> library with <CODE>-lncurses</CODE>. Many linkers
1441 are two-pass and will accept either order, but it is still good practice
1442 to put <CODE>-lform</CODE> first and <CODE>-lncurses</CODE> second.
1444 <H2><A NAME="foverview">Overview of Forms</A></H2>
1446 A form is a collection of fields; each field may be either a label
1447 (explanatory text) or a data-entry location. Long forms may be
1448 segmented into pages; each entry to a new page clears the screen. <P>
1449 To make forms, you create groups of fields and connect them with form
1450 frame objects; the form library makes this relatively simple. <P>
1452 Once defined, a form can be <DFN>posted</DFN>, that is written to an
1453 associated window. Actually, each form has two associated windows; a
1454 containing window in which the programmer can scribble titles or
1455 borders, and a subwindow in which the form fields proper are displayed. <P>
1457 As the form user fills out the posted form, navigation and editing
1458 keys support movement between fields, editing keys support modifying
1459 field, and plain text adds to or changes data in a current field. The
1460 form library allows you (the forms designer) to bind each navigation
1461 and editing key to any keystroke accepted by <CODE>curses</CODE>
1463 Fields may have validation conditions on them, so that they check input
1464 data for type and value. The form library supplies a rich set of
1465 pre-defined field types, and makes it relatively easy to define new ones. <P>
1467 Once its transaction is completed (or aborted), a form may be
1468 <DFN>unposted</DFN> (that is, undisplayed), and finally freed to make
1469 the storage associated with it and its items available for re-use. <P>
1471 The general flow of control of a form program looks like this:
1474 <LI>Initialize <CODE>curses</CODE>.
1475 <LI>Create the form fields, using <CODE>new_field()</CODE>.
1476 <LI>Create the form using <CODE>new_form()</CODE>.
1477 <LI>Post the form using <CODE>post_form()</CODE>.
1478 <LI>Refresh the screen.
1479 <LI>Process user requests via an input loop.
1480 <LI>Unpost the form using <CODE>unpost_form()</CODE>.
1481 <LI>Free the form, using <CODE>free_form()</CODE>.
1482 <LI>Free the fields using <CODE>free_field()</CODE>.
1483 <LI>Terminate <CODE>curses</CODE>.
1486 Note that this looks much like a menu program; the form library handles
1487 tasks which are in many ways similar, and its interface was obviously
1488 designed to resemble that of the <A HREF="#menu">menu library</A>
1489 wherever possible. <P>
1491 In forms programs, however, the `process user requests' is somewhat more
1492 complicated than for menus. Besides menu-like navigation operations,
1493 the menu driver loop has to support field editing and data validation.
1495 <H2><A NAME="fcreate">Creating and Freeing Fields and Forms</A></H2>
1497 The basic function for creating fields is <CODE>new_field()</CODE>:
1500 FIELD *new_field(int height, int width, /* new field size */
1501 int top, int left, /* upper left corner */
1502 int offscreen, /* number of offscreen rows */
1503 int nbuf); /* number of working buffers */
1506 Menu items always occupy a single row, but forms fields may have
1507 multiple rows. So <CODE>new_field()</CODE> requires you to specify a
1508 width and height (the first two arguments, which mist both be greater
1511 You must also specify the location of the field's upper left corner on
1512 the screen (the third and fourth arguments, which must be zero or
1513 greater). Note that these coordinates are relative to the form
1514 subwindow, which will coincide with <CODE>stdscr</CODE> by default but
1515 need not be <CODE>stdscr</CODE> if you've done an explicit
1516 <CODE>set_form_win()</CODE> call. <P>
1518 The fifth argument allows you to specify a number of off-screen rows. If
1519 this is zero, the entire field will always be displayed. If it is
1520 nonzero, the form will be scrollable, with only one screen-full (initially
1521 the top part) displayed at any given time. If you make a field dynamic
1522 and grow it so it will no longer fit on the screen, the form will become
1523 scrollable even if the <CODE>offscreen</CODE> argument was initially zero. <P>
1525 The forms library allocates one working buffer per field; the size of
1526 each buffer is <CODE>((height + offscreen)*width + 1</CODE>, one character
1527 for each position in the field plus a NUL terminator. The sixth
1528 argument is the number of additional data buffers to allocate for the
1529 field; your application can use them for its own purposes.
1532 FIELD *dup_field(FIELD *field, /* field to copy */
1533 int top, int left); /* location of new copy */
1536 The function <CODE>dup_field()</CODE> duplicates an existing field at a
1537 new location. Size and buffering information are copied; some
1538 attribute flags and status bits are not (see the
1539 <CODE>form_field_new(3X)</CODE> for details).
1542 FIELD *link_field(FIELD *field, /* field to copy */
1543 int top, int left); /* location of new copy */
1546 The function <CODE>link_field()</CODE> also duplicates an existing field
1547 at a new location. The difference from <CODE>dup_field()</CODE> is that
1548 it arranges for the new field's buffer to be shared with the old one. <P>
1550 Besides the obvious use in making a field editable from two different
1551 form pages, linked fields give you a way to hack in dynamic labels. If
1552 you declare several fields linked to an original, and then make them
1553 inactive, changes from the original will still be propagated to the
1556 As with duplicated fields, linked fields have attribute bits separate
1557 from the original. <P>
1559 As you might guess, all these field-allocations return <CODE>NULL</CODE> if
1560 the field allocation is not possible due to an out-of-memory error or
1561 out-of-bounds arguments. <P>
1563 To connect fields to a form, use
1566 FORM *new_form(FIELD **fields);
1569 This function expects to see a NULL-terminated array of field pointers.
1570 Said fields are connected to a newly-allocated form object; its address
1571 is returned (or else NULL if the allocation fails). <P>
1573 Note that <CODE>new_field()</CODE> does <EM>not</EM> copy the pointer array
1574 into private storage; if you modify the contents of the pointer array
1575 during forms processing, all manner of bizarre things might happen. Also
1576 note that any given field may only be connected to one form. <P>
1578 The functions <CODE>free_field()</CODE> and <CODE>free_form</CODE> are available
1579 to free field and form objects. It is an error to attempt to free a field
1580 connected to a form, but not vice-versa; thus, you will generally free
1581 your form objects first.
1583 <H2><A NAME="fattributes">Fetching and Changing Field Attributes</A></H2>
1585 Each form field has a number of location and size attributes
1586 associated with it. There are other field attributes used to control
1587 display and editing of the field. Some (for example, the <CODE>O_STATIC</CODE> bit)
1588 involve sufficient complications to be covered in sections of their own
1589 later on. We cover the functions used to get and set several basic
1590 attributes here. <P>
1592 When a field is created, the attributes not specified by the
1593 <CODE>new_field</CODE> function are copied from an invisible system
1594 default field. In attribute-setting and -fetching functions, the
1595 argument NULL is taken to mean this field. Changes to it persist
1596 as defaults until your forms application terminates.
1598 <H3><A NAME="fsizes">Fetching Size and Location Data</A></H3>
1600 You can retrieve field sizes and locations through:
1603 int field_info(FIELD *field, /* field from which to fetch */
1604 int *height, *int width, /* field size */
1605 int *top, int *left, /* upper left corner */
1606 int *offscreen, /* number of offscreen rows */
1607 int *nbuf); /* number of working buffers */
1610 This function is a sort of inverse of <CODE>new_field()</CODE>; instead of
1611 setting size and location attributes of a new field, it fetches them
1612 from an existing one.
1614 <H3><A NAME="flocation">Changing the Field Location</A></H3>
1616 It is possible to move a field's location on the screen:
1619 int move_field(FIELD *field, /* field to alter */
1620 int top, int left); /* new upper-left corner */
1623 You can, of course. query the current location through <CODE>field_info()</CODE>.
1625 <H3><A NAME="fjust">The Justification Attribute</A></H3>
1627 One-line fields may be unjustified, justified right, justified left,
1628 or centered. Here is how you manipulate this attribute:
1631 int set_field_just(FIELD *field, /* field to alter */
1632 int justmode); /* mode to set */
1634 int field_just(FIELD *field); /* fetch mode of field */
1637 The mode values accepted and returned by this functions are
1638 preprocessor macros <CODE>NO_JUSTIFICATION</CODE>, <CODE>JUSTIFY_RIGHT</CODE>,
1639 <CODE>JUSTIFY_LEFT</CODE>, or <CODE>JUSTIFY_CENTER</CODE>.
1641 <H3><A NAME="fdispatts">Field Display Attributes</A></H3>
1643 For each field, you can set a foreground attribute for entered
1644 characters, a background attribute for the entire field, and a pad
1645 character for the unfilled portion of the field. You can also
1646 control pagination of the form. <P>
1648 This group of four field attributes controls the visual appearance
1649 of the field on the screen, without affecting in any way the data
1650 in the field buffer.
1653 int set_field_fore(FIELD *field, /* field to alter */
1654 chtype attr); /* attribute to set */
1656 chtype field_fore(FIELD *field); /* field to query */
1658 int set_field_back(FIELD *field, /* field to alter */
1659 chtype attr); /* attribute to set */
1661 chtype field_back(FIELD *field); /* field to query */
1663 int set_field_pad(FIELD *field, /* field to alter */
1664 int pad); /* pad character to set */
1666 chtype field_pad(FIELD *field);
1668 int set_new_page(FIELD *field, /* field to alter */
1669 int flag); /* TRUE to force new page */
1671 chtype new_page(FIELD *field); /* field to query */
1674 The attributes set and returned by the first four functions are normal
1675 <CODE>curses(3x)</CODE> display attribute values (<CODE>A_STANDOUT</CODE>,
1676 <CODE>A_BOLD</CODE>, <CODE>A_REVERSE</CODE> etc).
1678 The page bit of a field controls whether it is displayed at the start of
1681 <H3><A NAME="foptions">Field Option Bits</A></H3>
1683 There is also a large collection of field option bits you can set to control
1684 various aspects of forms processing. You can manipulate them with these
1688 int set_field_opts(FIELD *field, /* field to alter */
1689 int attr); /* attribute to set */
1691 int field_opts_on(FIELD *field, /* field to alter */
1692 int attr); /* attributes to turn on */
1694 int field_opts_off(FIELD *field, /* field to alter */
1695 int attr); /* attributes to turn off */
1697 int field_opts(FIELD *field); /* field to query */
1700 By default, all options are on. Here are the available option bits:
1703 <DD> Controls whether the field is visible on the screen. Can be used
1704 during form processing to hide or pop up fields depending on the value
1707 <DD> Controls whether the field is active during forms processing (i.e.
1708 visited by form navigation keys). Can be used to make labels or derived
1709 fields with buffer values alterable by the forms application, not the user.
1711 <DD> Controls whether data is displayed during field entry. If this option is
1712 turned off on a field, the library will accept and edit data in that field,
1713 but it will not be displayed and the visible field cursor will not move.
1714 You can turn off the O_PUBLIC bit to define password fields.
1716 <DD> Controls whether the field's data can be modified. When this option is
1717 off, all editing requests except <CODE>REQ_PREV_CHOICE</CODE> and
1718 <CODE>REQ_NEXT_CHOICE</CODE> will fail. Such read-only fields may be useful for
1721 <DD> Controls word-wrapping in multi-line fields. Normally, when any
1722 character of a (blank-separated) word reaches the end of the current line, the
1723 entire word is wrapped to the next line (assuming there is one). When this
1724 option is off, the word will be split across the line break.
1726 <DD> Controls field blanking. When this option is on, entering a character at
1727 the first field position erases the entire field (except for the just-entered
1730 <DD> Controls automatic skip to next field when this one fills. Normally,
1731 when the forms user tries to type more data into a field than will fit,
1732 the editing location jumps to next field. When this option is off, the
1733 user's cursor will hang at the end of the field. This option is ignored
1734 in dynamic fields that have not reached their size limit.
1736 <DD> Controls whether <A HREF="#fvalidation">validation</A> is applied to
1737 blank fields. Normally, it is not; the user can leave a field blank
1738 without invoking the usual validation check on exit. If this option is
1739 off on a field, exit from it will invoke a validation check.
1741 <DD> Controls whether validation occurs on every exit, or only after
1742 the field is modified. Normally the latter is true. Setting O_PASSOK
1743 may be useful if your field's validation function may change during
1746 <DD> Controls whether the field is fixed to its initial dimensions. If you
1747 turn this off, the field becomes <A HREF="#fdynamic">dynamic</A> and will
1748 stretch to fit entered data.
1751 A field's options cannot be changed while the field is currently selected.
1752 However, options may be changed on posted fields that are not current. <P>
1754 The option values are bit-masks and can be composed with logical-or in
1757 <H2><A NAME="fstatus">Field Status</A></H2>
1759 Every field has a status flag, which is set to FALSE when the field is
1760 created and TRUE when the value in field buffer 0 changes. This flag can
1761 be queried and set directly:
1764 int set_field_status(FIELD *field, /* field to alter */
1765 int status); /* mode to set */
1767 int field_status(FIELD *field); /* fetch mode of field */
1770 Setting this flag under program control can be useful if you use the same
1771 form repeatedly, looking for modified fields each time. <P>
1773 Calling <CODE>field_status()</CODE> on a field not currently selected
1774 for input will return a correct value. Calling <CODE>field_status()</CODE> on a
1775 field that is currently selected for input may not necessarily give a
1776 correct field status value, because entered data isn't necessarily copied to
1777 buffer zero before the exit validation check.
1779 To guarantee that the returned status value reflects reality, call
1780 <CODE>field_status()</CODE> either (1) in the field's exit validation check
1781 routine, (2) from the field's or form's initialization or termination
1782 hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been
1783 processed by the forms driver.
1785 <H2><A NAME="fuser">Field User Pointer</A></H2>
1787 Each field structure contains one character pointer slot that is not used
1788 by the forms library. It is intended to be used by applications to store
1789 private per-field data. You can manipulate it with:
1792 int set_field_userptr(FIELD *field, /* field to alter */
1793 char *userptr); /* mode to set */
1795 char *field_userptr(FIELD *field); /* fetch mode of field */
1798 (Properly, this user pointer field ought to have <CODE>(void *)</CODE> type.
1799 The <CODE>(char *)</CODE> type is retained for System V compatibility.) <P>
1801 It is valid to set the user pointer of the default field (with a
1802 <CODE>set_field_userptr()</CODE> call passed a NULL field pointer.)
1803 When a new field is created, the default-field user pointer is copied
1804 to initialize the new field's user pointer.
1806 <H2><A NAME="fdynamic">Variable-Sized Fields</A></H2>
1808 Normally, a field is fixed at the size specified for it at creation
1809 time. If, however, you turn off its O_STATIC bit, it becomes
1810 <DFN>dynamic</DFN> and will automatically resize itself to accommodate
1811 data as it is entered. If the field has extra buffers associated with it,
1812 they will grow right along with the main input buffer. <P>
1814 A one-line dynamic field will have a fixed height (1) but variable
1815 width, scrolling horizontally to display data within the field area as
1816 originally dimensioned and located. A multi-line dynamic field will
1817 have a fixed width, but variable height (number of rows), scrolling
1818 vertically to display data within the field area as originally
1819 dimensioned and located. <P>
1821 Normally, a dynamic field is allowed to grow without limit. But it is
1822 possible to set an upper limit on the size of a dynamic field. You do
1823 it with this function:
1826 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
1827 int max_size); /* upper limit on field size */
1830 If the field is one-line, <CODE>max_size</CODE> is taken to be a column size
1831 limit; if it is multi-line, it is taken to be a line size limit. To disable
1832 any limit, use an argument of zero. The growth limit can be changed whether
1833 or not the O_STATIC bit is on, but has no effect until it is. <P>
1835 The following properties of a field change when it becomes dynamic:
1838 <LI>If there is no growth limit, there is no final position of the field;
1839 therefore <CODE>O_AUTOSKIP</CODE> and <CODE>O_NL_OVERLOAD</CODE> are ignored.
1840 <LI>Field justification will be ignored (though whatever justification is
1841 set up will be retained internally and can be queried).
1842 <LI>The <CODE>dup_field()</CODE> and <CODE>link_field()</CODE> calls copy
1843 dynamic-buffer sizes. If the <CODE>O_STATIC</CODE> option is set on one of a
1844 collection of links, buffer resizing will occur only when the field is
1845 edited through that link.
1846 <LI>The call <CODE>field_info()</CODE> will retrieve the original static size of
1847 the field; use <CODE>dynamic_field_info()</CODE> to get the actual dynamic size.
1850 <H2><A NAME="fvalidation">Field Validation</A></H2>
1852 By default, a field will accept any data that will fit in its input buffer.
1853 However, it is possible to attach a validation type to a field. If you do
1854 this, any attempt to leave the field while it contains data that doesn't
1855 match the validation type will fail. Some validation types also have a
1856 character-validity check for each time a character is entered in the field. <P>
1858 A field's validation check (if any) is not called when
1859 <CODE>set_field_buffer()</CODE> modifies the input buffer, nor when that buffer
1860 is changed through a linked field. <P>
1862 The <CODE>form</CODE> library provides a rich set of pre-defined validation
1863 types, and gives you the capability to define custom ones of your own. You
1864 can examine and change field validation attributes with the following
1868 int set_field_type(FIELD *field, /* field to alter */
1869 FIELDTYPE *ftype, /* type to associate */
1870 ...); /* additional arguments*/
1872 FIELDTYPE *field_type(FIELD *field); /* field to query */
1875 The validation type of a field is considered an attribute of the field. As
1876 with other field attributes, Also, doing <CODE>set_field_type()</CODE> with a
1877 <CODE>NULL</CODE> field default will change the system default for validation of
1878 newly-created fields. <P>
1880 Here are the pre-defined validation types:
1882 <H3><A NAME="ftype_alpha">TYPE_ALPHA</A></H3>
1884 This field type accepts alphabetic data; no blanks, no digits, no special
1885 characters (this is checked at character-entry time). It is set up with:
1888 int set_field_type(FIELD *field, /* field to alter */
1889 TYPE_ALPHA, /* type to associate */
1890 int width); /* maximum width of field */
1893 The <CODE>width</CODE> argument sets a minimum width of data. Typically
1894 you'll want to set this to the field width; if it's greater than the
1895 field width, the validation check will always fail. A minimum width
1896 of zero makes field completion optional.
1898 <H3><A NAME="ftype_alnum">TYPE_ALNUM</A></H3>
1900 This field type accepts alphabetic data and digits; no blanks, no special
1901 characters (this is checked at character-entry time). It is set up with:
1904 int set_field_type(FIELD *field, /* field to alter */
1905 TYPE_ALNUM, /* type to associate */
1906 int width); /* maximum width of field */
1909 The <CODE>width</CODE> argument sets a minimum width of data. As with
1910 TYPE_ALPHA, typically you'll want to set this to the field width; if it's
1911 greater than the field width, the validation check will always fail. A
1912 minimum width of zero makes field completion optional.
1914 <H3><A NAME="ftype_enum">TYPE_ENUM</A></H3>
1916 This type allows you to restrict a field's values to be among a specified
1917 set of string values (for example, the two-letter postal codes for U.S.
1918 states). It is set up with:
1921 int set_field_type(FIELD *field, /* field to alter */
1922 TYPE_ENUM, /* type to associate */
1923 char **valuelist; /* list of possible values */
1924 int checkcase; /* case-sensitive? */
1925 int checkunique); /* must specify uniquely? */
1928 The <CODE>valuelist</CODE> parameter must point at a NULL-terminated list of
1929 valid strings. The <CODE>checkcase</CODE> argument, if true, makes comparison
1930 with the string case-sensitive. <P>
1932 When the user exits a TYPE_ENUM field, the validation procedure tries to
1933 complete the data in the buffer to a valid entry. If a complete choice string
1934 has been entered, it is of course valid. But it is also possible to enter a
1935 prefix of a valid string and have it completed for you. <P>
1937 By default, if you enter such a prefix and it matches more than one value
1938 in the string list, the prefix will be completed to the first matching
1939 value. But the <CODE>checkunique</CODE> argument, if true, requires prefix
1940 matches to be unique in order to be valid. <P>
1942 The <CODE>REQ_NEXT_CHOICE</CODE> and <CODE>REQ_PREV_CHOICE</CODE> input requests
1943 can be particularly useful with these fields.
1945 <H3><A NAME="ftype_integer">TYPE_INTEGER</A></H3>
1947 This field type accepts an integer. It is set up as follows:
1950 int set_field_type(FIELD *field, /* field to alter */
1951 TYPE_INTEGER, /* type to associate */
1952 int padding, /* # places to zero-pad to */
1953 int vmin, int vmax); /* valid range */
1956 Valid characters consist of an optional leading minus and digits.
1957 The range check is performed on exit. If the range maximum is less
1958 than or equal to the minimum, the range is ignored. <P>
1960 If the value passes its range check, it is padded with as many leading
1961 zero digits as necessary to meet the padding argument. <P>
1963 A <CODE>TYPE_INTEGER</CODE> value buffer can conveniently be interpreted
1964 with the C library function <CODE>atoi(3)</CODE>.
1966 <H3><A NAME="ftype_numeric">TYPE_NUMERIC</A></H3>
1968 This field type accepts a decimal number. It is set up as follows:
1971 int set_field_type(FIELD *field, /* field to alter */
1972 TYPE_NUMERIC, /* type to associate */
1973 int padding, /* # places of precision */
1974 double vmin, double vmax); /* valid range */
1977 Valid characters consist of an optional leading minus and digits. possibly
1978 including a decimal point. If your system supports locale's, the decimal point
1979 character used must be the one defined by your locale. The range check is
1980 performed on exit. If the range maximum is less than or equal to the minimum,
1981 the range is ignored. <P>
1983 If the value passes its range check, it is padded with as many trailing
1984 zero digits as necessary to meet the padding argument. <P>
1986 A <CODE>TYPE_NUMERIC</CODE> value buffer can conveniently be interpreted
1987 with the C library function <CODE>atof(3)</CODE>.
1989 <H3><A NAME="ftype_regexp">TYPE_REGEXP</A></H3>
1991 This field type accepts data matching a regular expression. It is set up
1995 int set_field_type(FIELD *field, /* field to alter */
1996 TYPE_REGEXP, /* type to associate */
1997 char *regexp); /* expression to match */
2000 The syntax for regular expressions is that of <CODE>regcomp(3)</CODE>.
2001 The check for regular-expression match is performed on exit.
2003 <H2><A NAME="fbuffer">Direct Field Buffer Manipulation</A></H2>
2005 The chief attribute of a field is its buffer contents. When a form has
2006 been completed, your application usually needs to know the state of each
2007 field buffer. You can find this out with:
2010 char *field_buffer(FIELD *field, /* field to query */
2011 int bufindex); /* number of buffer to query */
2014 Normally, the state of the zero-numbered buffer for each field is set by
2015 the user's editing actions on that field. It's sometimes useful to be able
2016 to set the value of the zero-numbered (or some other) buffer from your
2020 int set_field_buffer(FIELD *field, /* field to alter */
2021 int bufindex, /* number of buffer to alter */
2022 char *value); /* string value to set */
2025 If the field is not large enough and cannot be resized to a sufficiently
2026 large size to contain the specified value, the value will be truncated
2029 Calling <CODE>field_buffer()</CODE> with a null field pointer will raise an
2030 error. Calling <CODE>field_buffer()</CODE> on a field not currently selected
2031 for input will return a correct value. Calling <CODE>field_buffer()</CODE> on a
2032 field that is currently selected for input may not necessarily give a
2033 correct field buffer value, because entered data isn't necessarily copied to
2034 buffer zero before the exit validation check.
2036 To guarantee that the returned buffer value reflects on-screen reality,
2037 call <CODE>field_buffer()</CODE> either (1) in the field's exit validation
2038 check routine, (2) from the field's or form's initialization or termination
2039 hooks, or (3) just after a <CODE>REQ_VALIDATION</CODE> request has been processed
2040 by the forms driver.
2042 <H2><A NAME="formattrs">Attributes of Forms</A></H2>
2044 As with field attributes, form attributes inherit a default from a
2045 system default form structure. These defaults can be queried or set by
2046 of these functions using a form-pointer argument of <CODE>NULL</CODE>. <P>
2048 The principal attribute of a form is its field list. You can query
2049 and change this list with:
2052 int set_form_fields(FORM *form, /* form to alter */
2053 FIELD **fields); /* fields to connect */
2055 char *form_fields(FORM *form); /* fetch fields of form */
2057 int field_count(FORM *form); /* count connect fields */
2060 The second argument of <CODE>set_form_fields()</CODE> may be a
2061 NULL-terminated field pointer array like the one required by
2062 <CODE>new_form()</CODE>. In that case, the old fields of the form are
2063 disconnected but not freed (and eligible to be connected to other
2064 forms), then the new fields are connected. <P>
2066 It may also be null, in which case the old fields are disconnected
2067 (and not freed) but no new ones are connected. <P>
2069 The <CODE>field_count()</CODE> function simply counts the number of fields
2070 connected to a given from. It returns -1 if the form-pointer argument
2073 <H2><A NAME="fdisplay">Control of Form Display</A></H2>
2075 In the overview section, you saw that to display a form you normally
2076 start by defining its size (and fields), posting it, and refreshing
2077 the screen. There is an hidden step before posting, which is the
2078 association of the form with a frame window (actually, a pair of
2079 windows) within which it will be displayed. By default, the forms
2080 library associates every form with the full-screen window
2081 <CODE>stdscr</CODE>. <P>
2083 By making this step explicit, you can associate a form with a declared
2084 frame window on your screen display. This can be useful if you want to
2085 adapt the form display to different screen sizes, dynamically tile
2086 forms on the screen, or use a form as part of an interface layout
2087 managed by <A HREF="#panels">panels</A>. <P>
2089 The two windows associated with each form have the same functions as
2090 their analogues in the <A HREF="#menu">menu library</A>. Both these
2091 windows are painted when the form is posted and erased when the form
2094 The outer or frame window is not otherwise touched by the form
2095 routines. It exists so the programmer can associate a title, a
2096 border, or perhaps help text with the form and have it properly
2097 refreshed or erased at post/unpost time. The inner window or subwindow
2098 is where the current form page is actually displayed. <P>
2100 In order to declare your own frame window for a form, you'll need to
2101 know the size of the form's bounding rectangle. You can get this
2105 int scale_form(FORM *form, /* form to query */
2106 int *rows, /* form rows */
2107 int *cols); /* form cols */
2110 The form dimensions are passed back in the locations pointed to by
2111 the arguments. Once you have this information, you can use it to
2112 declare of windows, then use one of these functions:
2115 int set_form_win(FORM *form, /* form to alter */
2116 WINDOW *win); /* frame window to connect */
2118 WINDOW *form_win(FORM *form); /* fetch frame window of form */
2120 int set_form_sub(FORM *form, /* form to alter */
2121 WINDOW *win); /* form subwindow to connect */
2123 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
2126 Note that curses operations, including <CODE>refresh()</CODE>, on the form,
2127 should be done on the frame window, not the form subwindow. <P>
2129 It is possible to check from your application whether all of a
2130 scrollable field is actually displayed within the menu subwindow. Use
2134 int data_ahead(FORM *form); /* form to be queried */
2136 int data_behind(FORM *form); /* form to be queried */
2139 The function <CODE>data_ahead()</CODE> returns TRUE if (a) the current
2140 field is one-line and has undisplayed data off to the right, (b) the current
2141 field is multi-line and there is data off-screen below it. <P>
2143 The function <CODE>data_behind()</CODE> returns TRUE if the first (upper
2144 left hand) character position is off-screen (not being displayed). <P>
2146 Finally, there is a function to restore the form window's cursor to the
2147 value expected by the forms driver:
2150 int pos_form_cursor(FORM *) /* form to be queried */
2153 If your application changes the form window cursor, call this function before
2154 handing control back to the forms driver in order to re-synchronize it.
2156 <H2><A NAME="fdriver">Input Processing in the Forms Driver</A></H2>
2158 The function <CODE>form_driver()</CODE> handles virtualized input requests
2159 for form navigation, editing, and validation requests, just as
2160 <CODE>menu_driver</CODE> does for menus (see the section on <A
2161 HREF="#minput">menu input handling</A>).
2164 int form_driver(FORM *form, /* form to pass input to */
2165 int request); /* form request code */
2168 Your input virtualization function needs to take input and then convert it
2169 to either an alphanumeric character (which is treated as data to be
2170 entered in the currently-selected field), or a forms processing request. <P>
2172 The forms driver provides hooks (through input-validation and
2173 field-termination functions) with which your application code can check
2174 that the input taken by the driver matched what was expected.
2176 <H3><A NAME="fpage">Page Navigation Requests</A></H3>
2178 These requests cause page-level moves through the form,
2179 triggering display of a new form screen.
2182 <DT> <CODE>REQ_NEXT_PAGE</CODE>
2183 <DD> Move to the next form page.
2184 <DT> <CODE>REQ_PREV_PAGE</CODE>
2185 <DD> Move to the previous form page.
2186 <DT> <CODE>REQ_FIRST_PAGE</CODE>
2187 <DD> Move to the first form page.
2188 <DT> <CODE>REQ_LAST_PAGE</CODE>
2189 <DD> Move to the last form page.
2192 These requests treat the list as cyclic; that is, <CODE>REQ_NEXT_PAGE</CODE>
2193 from the last page goes to the first, and <CODE>REQ_PREV_PAGE</CODE> from
2194 the first page goes to the last.
2196 <H3><A NAME="ffield">Inter-Field Navigation Requests</A></H3>
2198 These requests handle navigation between fields on the same page.
2201 <DT> <CODE>REQ_NEXT_FIELD</CODE>
2202 <DD> Move to next field.
2203 <DT> <CODE>REQ_PREV_FIELD</CODE>
2204 <DD> Move to previous field.
2205 <DT> <CODE>REQ_FIRST_FIELD</CODE>
2206 <DD> Move to the first field.
2207 <DT> <CODE>REQ_LAST_FIELD</CODE>
2208 <DD> Move to the last field.
2209 <DT> <CODE>REQ_SNEXT_FIELD</CODE>
2210 <DD> Move to sorted next field.
2211 <DT> <CODE>REQ_SPREV_FIELD</CODE>
2212 <DD> Move to sorted previous field.
2213 <DT> <CODE>REQ_SFIRST_FIELD</CODE>
2214 <DD> Move to the sorted first field.
2215 <DT> <CODE>REQ_SLAST_FIELD</CODE>
2216 <DD> Move to the sorted last field.
2217 <DT> <CODE>REQ_LEFT_FIELD</CODE>
2218 <DD> Move left to field.
2219 <DT> <CODE>REQ_RIGHT_FIELD</CODE>
2220 <DD> Move right to field.
2221 <DT> <CODE>REQ_UP_FIELD</CODE>
2222 <DD> Move up to field.
2223 <DT> <CODE>REQ_DOWN_FIELD</CODE>
2224 <DD> Move down to field.
2227 These requests treat the list of fields on a page as cyclic; that is,
2228 <CODE>REQ_NEXT_FIELD</CODE> from the last field goes to the first, and
2229 <CODE>REQ_PREV_FIELD</CODE> from the first field goes to the last. The
2230 order of the fields for these (and the <CODE>REQ_FIRST_FIELD</CODE> and
2231 <CODE>REQ_LAST_FIELD</CODE> requests) is simply the order of the field
2232 pointers in the form array (as set up by <CODE>new_form()</CODE> or
2233 <CODE>set_form_fields()</CODE> <P>
2235 It is also possible to traverse the fields as if they had been sorted in
2236 screen-position order, so the sequence goes left-to-right and top-to-bottom.
2237 To do this, use the second group of four sorted-movement requests. <P>
2239 Finally, it is possible to move between fields using visual directions up,
2240 down, right, and left. To accomplish this, use the third group of four
2241 requests. Note, however, that the position of a form for purposes of these
2242 requests is its upper-left corner. <P>
2244 For example, suppose you have a multi-line field B, and two
2245 single-line fields A and C on the same line with B, with A to the left
2246 of B and C to the right of B. A <CODE>REQ_MOVE_RIGHT</CODE> from A will
2247 go to B only if A, B, and C <EM>all</EM> share the same first line;
2248 otherwise it will skip over B to C.
2250 <H3><A NAME="fifield">Intra-Field Navigation Requests</A></H3>
2252 These requests drive movement of the edit cursor within the currently
2256 <DT> <CODE>REQ_NEXT_CHAR</CODE>
2257 <DD> Move to next character.
2258 <DT> <CODE>REQ_PREV_CHAR</CODE>
2259 <DD> Move to previous character.
2260 <DT> <CODE>REQ_NEXT_LINE</CODE>
2261 <DD> Move to next line.
2262 <DT> <CODE>REQ_PREV_LINE</CODE>
2263 <DD> Move to previous line.
2264 <DT> <CODE>REQ_NEXT_WORD</CODE>
2265 <DD> Move to next word.
2266 <DT> <CODE>REQ_PREV_WORD</CODE>
2267 <DD> Move to previous word.
2268 <DT> <CODE>REQ_BEG_FIELD</CODE>
2269 <DD> Move to beginning of field.
2270 <DT> <CODE>REQ_END_FIELD</CODE>
2271 <DD> Move to end of field.
2272 <DT> <CODE>REQ_BEG_LINE</CODE>
2273 <DD> Move to beginning of line.
2274 <DT> <CODE>REQ_END_LINE</CODE>
2275 <DD> Move to end of line.
2276 <DT> <CODE>REQ_LEFT_CHAR</CODE>
2277 <DD> Move left in field.
2278 <DT> <CODE>REQ_RIGHT_CHAR</CODE>
2279 <DD> Move right in field.
2280 <DT> <CODE>REQ_UP_CHAR</CODE>
2281 <DD> Move up in field.
2282 <DT> <CODE>REQ_DOWN_CHAR</CODE>
2283 <DD> Move down in field.
2286 Each <EM>word</EM> is separated from the previous and next characters
2287 by whitespace. The commands to move to beginning and end of line or field
2288 look for the first or last non-pad character in their ranges.
2290 <H3><A NAME="fscroll">Scrolling Requests</A></H3>
2292 Fields that are dynamic and have grown and fields explicitly created
2293 with offscreen rows are scrollable. One-line fields scroll horizontally;
2294 multi-line fields scroll vertically. Most scrolling is triggered by
2295 editing and intra-field movement (the library scrolls the field to keep the
2296 cursor visible). It is possible to explicitly request scrolling with the
2300 <DT> <CODE>REQ_SCR_FLINE</CODE>
2301 <DD> Scroll vertically forward a line.
2302 <DT> <CODE>REQ_SCR_BLINE</CODE>
2303 <DD> Scroll vertically backward a line.
2304 <DT> <CODE>REQ_SCR_FPAGE</CODE>
2305 <DD> Scroll vertically forward a page.
2306 <DT> <CODE>REQ_SCR_BPAGE</CODE>
2307 <DD> Scroll vertically backward a page.
2308 <DT> <CODE>REQ_SCR_FHPAGE</CODE>
2309 <DD> Scroll vertically forward half a page.
2310 <DT> <CODE>REQ_SCR_BHPAGE</CODE>
2311 <DD> Scroll vertically backward half a page.
2312 <DT> <CODE>REQ_SCR_FCHAR</CODE>
2313 <DD> Scroll horizontally forward a character.
2314 <DT> <CODE>REQ_SCR_BCHAR</CODE>
2315 <DD> Scroll horizontally backward a character.
2316 <DT> <CODE>REQ_SCR_HFLINE</CODE>
2317 <DD> Scroll horizontally one field width forward.
2318 <DT> <CODE>REQ_SCR_HBLINE</CODE>
2319 <DD> Scroll horizontally one field width backward.
2320 <DT> <CODE>REQ_SCR_HFHALF</CODE>
2321 <DD> Scroll horizontally one half field width forward.
2322 <DT> <CODE>REQ_SCR_HBHALF</CODE>
2323 <DD> Scroll horizontally one half field width backward.
2326 For scrolling purposes, a <EM>page</EM> of a field is the height
2327 of its visible part.
2329 <H3><A NAME="fedit">Editing Requests</A></H3>
2331 When you pass the forms driver an ASCII character, it is treated as a
2332 request to add the character to the field's data buffer. Whether this
2333 is an insertion or a replacement depends on the field's edit mode
2334 (insertion is the default. <P>
2336 The following requests support editing the field and changing the edit
2340 <DT> <CODE>REQ_INS_MODE</CODE>
2341 <DD> Set insertion mode.
2342 <DT> <CODE>REQ_OVL_MODE</CODE>
2343 <DD> Set overlay mode.
2344 <DT> <CODE>REQ_NEW_LINE</CODE>
2345 <DD> New line request (see below for explanation).
2346 <DT> <CODE>REQ_INS_CHAR</CODE>
2347 <DD> Insert space at character location.
2348 <DT> <CODE>REQ_INS_LINE</CODE>
2349 <DD> Insert blank line at character location.
2350 <DT> <CODE>REQ_DEL_CHAR</CODE>
2351 <DD> Delete character at cursor.
2352 <DT> <CODE>REQ_DEL_PREV</CODE>
2353 <DD> Delete previous word at cursor.
2354 <DT> <CODE>REQ_DEL_LINE</CODE>
2355 <DD> Delete line at cursor.
2356 <DT> <CODE>REQ_DEL_WORD</CODE>
2357 <DD> Delete word at cursor.
2358 <DT> <CODE>REQ_CLR_EOL</CODE>
2359 <DD> Clear to end of line.
2360 <DT> <CODE>REQ_CLR_EOF</CODE>
2361 <DD> Clear to end of field.
2362 <DT> <CODE>REQ_CLEAR_FIELD</CODE>
2363 <DD> Clear entire field.
2366 The behavior of the <CODE>REQ_NEW_LINE</CODE> and <CODE>REQ_DEL_PREV</CODE> requests
2367 is complicated and partly controlled by a pair of forms options.
2368 The special cases are triggered when the cursor is at the beginning of
2369 a field, or on the last line of the field. <P>
2371 First, we consider <CODE>REQ_NEW_LINE</CODE>: <P>
2373 The normal behavior of <CODE>REQ_NEW_LINE</CODE> in insert mode is to break the
2374 current line at the position of the edit cursor, inserting the portion of
2375 the current line after the cursor as a new line following the current
2376 and moving the cursor to the beginning of that new line (you may think
2377 of this as inserting a newline in the field buffer). <P>
2379 The normal behavior of <CODE>REQ_NEW_LINE</CODE> in overlay mode is to clear the
2380 current line from the position of the edit cursor to end of line.
2381 The cursor is then moved to the beginning of the next line. <P>
2383 However, <CODE>REQ_NEW_LINE</CODE> at the beginning of a field, or on the
2384 last line of a field, instead does a <CODE>REQ_NEXT_FIELD</CODE>.
2385 <CODE>O_NL_OVERLOAD</CODE> option is off, this special action is
2388 Now, let us consider <CODE>REQ_DEL_PREV</CODE>: <P>
2390 The normal behavior of <CODE>REQ_DEL_PREV</CODE> is to delete the previous
2391 character. If insert mode is on, and the cursor is at the start of a
2392 line, and the text on that line will fit on the previous one, it
2393 instead appends the contents of the current line to the previous one
2394 and deletes the current line (you may think of this as deleting a
2395 newline from the field buffer). <P>
2397 However, <CODE>REQ_DEL_PREV</CODE> at the beginning of a field is instead
2398 treated as a <CODE>REQ_PREV_FIELD</CODE>. <P> If the
2399 <CODE>O_BS_OVERLOAD</CODE> option is off, this special action is
2400 disabled and the forms driver just returns <CODE>E_REQUEST_DENIED</CODE>. <P>
2402 See <A HREF="#frmoptions">Form Options</A> for discussion of how to set
2403 and clear the overload options.
2405 <H3><A NAME="forder">Order Requests</A></H3>
2407 If the type of your field is ordered, and has associated functions
2408 for getting the next and previous values of the type from a given value,
2409 there are requests that can fetch that value into the field buffer:
2412 <DT> <CODE>REQ_NEXT_CHOICE</CODE>
2413 <DD> Place the successor value of the current value in the buffer.
2414 <DT> <CODE>REQ_PREV_CHOICE</CODE>
2415 <DD> Place the predecessor value of the current value in the buffer.
2418 Of the built-in field types, only <CODE>TYPE_ENUM</CODE> has built-in successor
2419 and predecessor functions. When you define a field type of your own
2420 (see <A HREF="#fcustom">Custom Validation Types</A>), you can associate
2421 our own ordering functions.
2423 <H3><A NAME="fappcmds">Application Commands</A></H3>
2425 Form requests are represented as integers above the <CODE>curses</CODE> value
2426 greater than <CODE>KEY_MAX</CODE> and less than or equal to the constant
2427 <CODE>MAX_COMMAND</CODE>. If your input-virtualization routine returns a
2428 value above <CODE>MAX_COMMAND</CODE>, the forms driver will ignore it.
2430 <H2><A NAME="fhooks">Field Change Hooks</A></H2>
2432 It is possible to set function hooks to be executed whenever the
2433 current field or form changes. Here are the functions that support this:
2436 typedef void (*HOOK)(); /* pointer to function returning void */
2438 int set_form_init(FORM *form, /* form to alter */
2439 HOOK hook); /* initialization hook */
2441 HOOK form_init(FORM *form); /* form to query */
2443 int set_form_term(FORM *form, /* form to alter */
2444 HOOK hook); /* termination hook */
2446 HOOK form_term(FORM *form); /* form to query */
2448 int set_field_init(FORM *form, /* form to alter */
2449 HOOK hook); /* initialization hook */
2451 HOOK field_init(FORM *form); /* form to query */
2453 int set_field_term(FORM *form, /* form to alter */
2454 HOOK hook); /* termination hook */
2456 HOOK field_term(FORM *form); /* form to query */
2459 These functions allow you to either set or query four different hooks.
2460 In each of the set functions, the second argument should be the
2461 address of a hook function. These functions differ only in the timing
2466 <DD> This hook is called when the form is posted; also, just after
2467 each page change operation.
2469 <DD> This hook is called when the form is posted; also, just after
2472 <DD> This hook is called just after field validation; that is, just before
2473 the field is altered. It is also called when the form is unposted.
2475 <DD> This hook is called when the form is unposted; also, just before
2476 each page change operation.
2479 Calls to these hooks may be triggered
2481 <LI>When user editing requests are processed by the forms driver
2482 <LI>When the current page is changed by <CODE>set_current_field()</CODE> call
2483 <LI>When the current field is changed by a <CODE>set_form_page()</CODE> call
2486 See <A NAME="ffocus">Field Change Commands</A> for discussion of the latter
2489 You can set a default hook for all fields by passing one of the set functions
2490 a NULL first argument. <P>
2492 You can disable any of these hooks by (re)setting them to NULL, the default
2495 <H2><A HREF="#ffocus">Field Change Commands</A></H2>
2497 Normally, navigation through the form will be driven by the user's
2498 input requests. But sometimes it is useful to be able to move the
2499 focus for editing and viewing under control of your application, or
2500 ask which field it currently is in. The following functions help you
2504 int set_current_field(FORM *form, /* form to alter */
2505 FIELD *field); /* field to shift to */
2507 FIELD *current_field(FORM *form); /* form to query */
2509 int field_index(FORM *form, /* form to query */
2510 FIELD *field); /* field to get index of */
2513 The function <CODE>field_index()</CODE> returns the index of the given field
2514 in the given form's field array (the array passed to <CODE>new_form()</CODE> or
2515 <CODE>set_form_fields()</CODE>). <P>
2517 The initial current field of a form is the first active field on the
2518 first page. The function <CODE>set_form_fields()</CODE> resets this.<P>
2520 It is also possible to move around by pages.
2523 int set_form_page(FORM *form, /* form to alter */
2524 int page); /* page to go to (0-origin) */
2526 int form_page(FORM *form); /* return form's current page */
2529 The initial page of a newly-created form is 0. The function
2530 <CODE>set_form_fields()</CODE> resets this.
2532 <H2><A NAME="frmoptions">Form Options</A></H2>
2534 Like fields, forms may have control option bits. They can be changed
2535 or queried with these functions:
2538 int set_form_opts(FORM *form, /* form to alter */
2539 int attr); /* attribute to set */
2541 int form_opts_on(FORM *form, /* form to alter */
2542 int attr); /* attributes to turn on */
2544 int form_opts_off(FORM *form, /* form to alter */
2545 int attr); /* attributes to turn off */
2547 int form_opts(FORM *form); /* form to query */
2550 By default, all options are on. Here are the available option bits:
2554 <DD> Enable overloading of <CODE>REQ_NEW_LINE</CODE> as described in <A
2555 href="#fedit">Editing Requests</A>. The value of this option is
2556 ignored on dynamic fields that have not reached their size limit;
2557 these have no last line, so the circumstances for triggering a
2558 <CODE>REQ_NEXT_FIELD</CODE> never arise.
2560 <DD> Enable overloading of <CODE>REQ_DEL_PREV</CODE> as described in
2561 <A href="#fedit">Editing Requests</A>.
2564 The option values are bit-masks and can be composed with logical-or in
2567 <H2><A NAME="fcustom">Custom Validation Types</A></H2>
2569 The <CODE>form</CODE> library gives you the capability to define custom
2570 validation types of your own. Further, the optional additional arguments
2571 of <CODE>set_field_type</CODE> effectively allow you to parameterize validation
2572 types. Most of the complications in the validation-type interface have to
2573 do with the handling of the additional arguments within custom validation
2576 <H3><A NAME="flinktypes">Union Types</A></H3>
2578 The simplest way to create a custom data type is to compose it from two
2582 FIELD *link_fieldtype(FIELDTYPE *type1,
2586 This function creates a field type that will accept any of the values
2587 legal for either of its argument field types (which may be either
2588 predefined or programmer-defined).
2590 If a <CODE>set_field_type()</CODE> call later requires arguments, the new
2591 composite type expects all arguments for the first type, than all arguments
2592 for the second. Order functions (see <A HREF="#forder">Order Requests</A>)
2593 associated with the component types will work on the composite; what it does
2594 is check the validation function for the first type, then for the second, to
2595 figure what type the buffer contents should be treated as.
2597 <H3><A NAME="fnewtypes">New Field Types</A></H3>
2599 To create a field type from scratch, you need to specify one or both of the
2603 <LI>A character-validation function, to check each character as it is entered.
2604 <LI>A field-validation function to be applied on exit from the field.
2607 Here's how you do that:
2609 typedef int (*HOOK)(); /* pointer to function returning int */
2611 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
2612 HOOK c_validate) /* character validator */
2615 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
2618 At least one of the arguments of <CODE>new_fieldtype()</CODE> must be
2619 non-NULL. The forms driver will automatically call the new type's
2620 validation functions at appropriate points in processing a field of
2623 The function <CODE>free_fieldtype()</CODE> deallocates the argument
2624 fieldtype, freeing all storage associated with it. <P>
2626 Normally, a field validator is called when the user attempts to
2627 leave the field. Its first argument is a field pointer, from which it
2628 can get to field buffer 0 and test it. If the function returns TRUE,
2629 the operation succeeds; if it returns FALSE, the edit cursor stays in
2632 A character validator gets the character passed in as a first argument.
2633 It too should return TRUE if the character is valid, FALSE otherwise.
2635 <H3><A NAME="fcheckargs">Validation Function Arguments</A></H3>
2637 Your field- and character- validation functions will be passed a
2638 second argument as well. This second argument is the address of a
2639 structure (which we'll call a <EM>pile</EM>) built from any of the
2640 field-type-specific arguments passed to <CODE>set_field_type()</CODE>. If
2641 no such arguments are defined for the field type, this pile pointer
2642 argument will be NULL. <P>
2644 In order to arrange for such arguments to be passed to your validation
2645 functions, you must associate a small set of storage-management functions
2646 with the type. The forms driver will use these to synthesize a pile
2647 from the trailing arguments of each <CODE>set_field_type()</CODE> argument, and
2648 a pointer to the pile will be passed to the validation functions. <P>
2650 Here is how you make the association:
2653 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
2654 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
2656 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2657 PTRHOOK make_str, /* make structure from args */
2658 PTRHOOK copy_str, /* make copy of structure */
2659 VOIDHOOK free_str); /* free structure storage */
2662 Here is how the storage-management hooks are used:
2665 <DT> <CODE>make_str</CODE>
2666 <DD> This function is called by <CODE>set_field_type()</CODE>. It gets one
2667 argument, a <CODE>va_list</CODE> of the type-specific arguments passed to
2668 <CODE>set_field_type()</CODE>. It is expected to return a pile pointer to a data
2669 structure that encapsulates those arguments.
2670 <DT> <CODE>copy_str</CODE>
2671 <DD> This function is called by form library functions that allocate new
2672 field instances. It is expected to take a pile pointer, copy the pile
2673 to allocated storage, and return the address of the pile copy.
2674 <DT> <CODE>free_str</CODE>
2675 <DD> This function is called by field- and type-deallocation routines in the
2676 library. It takes a pile pointer argument, and is expected to free the
2677 storage of that pile.
2680 The <CODE>make_str</CODE> and <CODE>copy_str</CODE> functions may return NULL to
2681 signal allocation failure. The library routines will that call them will
2682 return error indication when this happens. Thus, your validation functions
2683 should never see a NULL file pointer and need not check specially for it.
2685 <H3><A NAME="fcustorder">Order Functions For Custom Types</A></H3>
2687 Some custom field types are simply ordered in the same well-defined way
2688 that <CODE>TYPE_ENUM</CODE> is. For such types, it is possible to define
2689 successor and predecessor functions to support the <CODE>REQ_NEXT_CHOICE</CODE>
2690 and <CODE>REQ_PREV_CHOICE</CODE> requests. Here's how:
2693 typedef int (*INTHOOK)(); /* pointer to function returning int */
2695 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2696 INTHOOK succ, /* get successor value */
2697 INTHOOK pred); /* get predecessor value */
2700 The successor and predecessor arguments will each be passed two arguments;
2701 a field pointer, and a pile pointer (as for the validation functions). They
2702 are expected to use the function <CODE>field_buffer()</CODE> to read the
2703 current value, and <CODE>set_field_buffer()</CODE> on buffer 0 to set the next
2704 or previous value. Either hook may return TRUE to indicate success (a
2705 legal next or previous value was set) or FALSE to indicate failure.
2707 <H3><A NAME="fcustprobs">Avoiding Problems</A></H3>
2709 The interface for defining custom types is complicated and tricky.
2710 Rather than attempting to create a custom type entirely from scratch,
2711 you should start by studying the library source code for whichever of
2712 the pre-defined types seems to be closest to what you want. <P>
2714 Use that code as a model, and evolve it towards what you really want.
2715 You will avoid many problems and annoyances that way. The code
2716 in the <CODE>ncurses</CODE> library has been specifically exempted from
2717 the package copyright to support this. <P>
2719 If your custom type defines order functions, have do something intuitive
2720 with a blank field. A useful convention is to make the successor of a
2721 blank field the types minimum value, and its predecessor the maximum.