2 Writing Programs with NCURSES
4 by Eric S. Raymond and Zeyd M. Ben-Halim
5 updates since release 1.9.9e by Thomas Dickey
10 + A Brief History of Curses
11 + Scope of This Document
14 + An Overview of Curses
15 o Compiling Programs using Curses
17 o Standard Windows and Function Naming Conventions
23 o Using Forms Characters
24 o Character Attributes and Color
27 + Function Descriptions
28 o Initialization and Wrapup
29 o Causing Output to the Terminal
30 o Low-Level Capability Access
32 + Hints, Tips, and Tricks
33 o Some Notes of Caution
34 o Temporarily Leaving ncurses Mode
35 o Using ncurses under xterm
36 o Handling Multiple Terminal Screens
37 o Testing for Terminal Capabilities
39 o Special Features of ncurses
40 + Compatibility with Older Versions
41 o Refresh of Overlapping Windows
43 + XSI Curses Conformance
45 + Compiling With the Panels Library
47 + Panels, Input, and the Standard Screen
49 + Miscellaneous Other Facilities
51 + Compiling with the menu Library
56 + Processing Menu Input
57 + Miscellaneous Other Features
59 + Compiling with the forms Library
61 + Creating and Freeing Fields and Forms
62 + Fetching and Changing Field Attributes
63 o Fetching Size and Location Data
64 o Changing the Field Location
65 o The Justification Attribute
66 o Field Display Attributes
70 + Variable-Sized Fields
78 + Direct Field Buffer Manipulation
80 + Control of Form Display
81 + Input Processing in the Forms Driver
82 o Page Navigation Requests
83 o Inter-Field Navigation Requests
84 o Intra-Field Navigation Requests
86 o Field Editing Requests
88 o Application Commands
90 + Field Change Commands
92 + Custom Validation Types
95 o Validation Function Arguments
96 o Order Functions For Custom Types
98 _________________________________________________________________
102 This document is an introduction to programming with curses. It is not
103 an exhaustive reference for the curses Application Programming
104 Interface (API); that role is filled by the curses manual pages.
105 Rather, it is intended to help C programmers ease into using the
108 This document is aimed at C applications programmers not yet
109 specifically familiar with ncurses. If you are already an experienced
110 curses programmer, you should nevertheless read the sections on Mouse
111 Interfacing, Debugging, Compatibility with Older Versions, and Hints,
112 Tips, and Tricks. These will bring you up to speed on the special
113 features and quirks of the ncurses implementation. If you are not so
114 experienced, keep reading.
116 The curses package is a subroutine library for terminal-independent
117 screen-painting and input-event handling which presents a high level
118 screen model to the programmer, hiding differences between terminal
119 types and doing automatic optimization of output to change one screen
120 full of text into another. Curses uses terminfo, which is a database
121 format that can describe the capabilities of thousands of different
124 The curses API may seem something of an archaism on UNIX desktops
125 increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX
126 still supports tty lines and X supports xterm(1); the curses API has
127 the advantage of (a) back-portability to character-cell terminals, and
128 (b) simplicity. For an application that does not require bit-mapped
129 graphics and multiple fonts, an interface implementation using curses
130 will typically be a great deal simpler and less expensive than one
133 A Brief History of Curses
135 Historically, the first ancestor of curses was the routines written to
136 provide screen-handling for the game rogue; these used the
137 already-existing termcap database facility for describing terminal
138 capabilities. These routines were abstracted into a documented library
139 and first released with the early BSD UNIX versions.
141 System III UNIX from Bell Labs featured a rewritten and much-improved
142 curses library. It introduced the terminfo format. Terminfo is based
143 on Berkeley's termcap database, but contains a number of improvements
144 and extensions. Parameterized capabilities strings were introduced,
145 making it possible to describe multiple video attributes, and colors
146 and to handle far more unusual terminals than possible with termcap.
147 In the later AT&T System V releases, curses evolved to use more
148 facilities and offer more capabilities, going far beyond BSD curses in
149 power and flexibility.
151 Scope of This Document
153 This document describes ncurses, a free implementation of the System V
154 curses API with some clearly marked extensions. It includes the
155 following System V curses features:
156 * Support for multiple screen highlights (BSD curses could only
157 handle one `standout' highlight, usually reverse-video).
158 * Support for line- and box-drawing using forms characters.
159 * Recognition of function keys on input.
161 * Support for pads (windows of larger than screen size on which the
162 screen or a subwindow defines a viewport).
164 Also, this package makes use of the insert and delete line and
165 character features of terminals so equipped, and determines how to
166 optimally use these features with no help from the programmer. It
167 allows arbitrary combinations of video attributes to be displayed,
168 even on terminals that leave ``magic cookies'' on the screen to mark
169 changes in attributes.
171 The ncurses package can also capture and use event reports from a
172 mouse in some environments (notably, xterm under the X window system).
173 This document includes tips for using the mouse.
175 The ncurses package was originated by Pavel Curtis. The original
176 maintainer of this package is Zeyd Ben-Halim <zmbenhal@netcom.com>.
177 Eric S. Raymond <esr@snark.thyrsus.com> wrote many of the new features
178 in versions after 1.8.1 and wrote most of this introduction. Jürgen
179 Pfeifer wrote all of the menu and forms code as well as the Ada95
180 binding. Ongoing work is being done by Thomas Dickey and Jürgen
181 Pfeifer. Florian La Roche acts as the maintainer for the Free Software
182 Foundation, which holds the copyright on ncurses. Contact the current
183 maintainers at bug-ncurses@gnu.org.
185 This document also describes the panels extension library, similarly
186 modeled on the SVr4 panels facility. This library allows you to
187 associate backing store with each of a stack or deck of overlapping
188 windows, and provides operations for moving windows around in the
189 stack that change their visibility in the natural way (handling window
192 Finally, this document describes in detail the menus and forms
193 extension libraries, also cloned from System V, which support easy
194 construction and sequences of menus and fill-in forms.
198 In this document, the following terminology is used with reasonable
202 A data structure describing a sub-rectangle of the screen
203 (possibly the entire screen). You can write to a window as
204 though it were a miniature screen, scrolling independently of
205 other windows on the physical screen.
208 A subset of windows which are as large as the terminal screen,
209 i.e., they start at the upper left hand corner and encompass
210 the lower right hand corner. One of these, stdscr, is
211 automatically provided for the programmer.
214 The package's idea of what the terminal display currently looks
215 like, i.e., what the user sees now. This is a special screen.
219 An Overview of Curses
221 Compiling Programs using Curses
223 In order to use the library, it is necessary to have certain types and
224 variables defined. Therefore, the programmer must have a line:
227 at the top of the program source. The screen package uses the Standard
228 I/O library, so <curses.h> includes <stdio.h>. <curses.h> also
229 includes <termios.h>, <termio.h>, or <sgtty.h> depending on your
230 system. It is redundant (but harmless) for the programmer to do these
231 includes, too. In linking with curses you need to have -lncurses in
232 your LDFLAGS or on the command line. There is no need for any other
237 In order to update the screen optimally, it is necessary for the
238 routines to know what the screen currently looks like and what the
239 programmer wants it to look like next. For this purpose, a data type
240 (structure) named WINDOW is defined which describes a window image to
241 the routines, including its starting position on the screen (the (y,
242 x) coordinates of the upper left hand corner) and its size. One of
243 these (called curscr, for current screen) is a screen image of what
244 the terminal currently looks like. Another screen (called stdscr, for
245 standard screen) is provided by default to make changes on.
247 A window is a purely internal representation. It is used to build and
248 store a potential image of a portion of the terminal. It doesn't bear
249 any necessary relation to what is really on the terminal screen; it's
250 more like a scratchpad or write buffer.
252 To make the section of physical screen corresponding to a window
253 reflect the contents of the window structure, the routine refresh()
254 (or wrefresh() if the window is not stdscr) is called.
256 A given physical screen section may be within the scope of any number
257 of overlapping windows. Also, changes can be made to windows in any
258 order, without regard to motion efficiency. Then, at will, the
259 programmer can effectively say ``make it look like this,'' and let the
260 package implementation determine the most efficient way to repaint the
263 Standard Windows and Function Naming Conventions
265 As hinted above, the routines can use several windows, but two are
266 automatically given: curscr, which knows what the terminal looks like,
267 and stdscr, which is what the programmer wants the terminal to look
268 like next. The user should never actually access curscr directly.
269 Changes should be made to through the API, and then the routine
270 refresh() (or wrefresh()) called.
272 Many functions are defined to use stdscr as a default screen. For
273 example, to add a character to stdscr, one calls addch() with the
274 desired character as argument. To write to a different window. use the
275 routine waddch() (for `w'indow-specific addch()) is provided. This
276 convention of prepending function names with a `w' when they are to be
277 applied to specific windows is consistent. The only routines which do
278 not follow it are those for which a window must always be specified.
280 In order to move the current (y, x) coordinates from one point to
281 another, the routines move() and wmove() are provided. However, it is
282 often desirable to first move and then perform some I/O operation. In
283 order to avoid clumsiness, most I/O routines can be preceded by the
284 prefix 'mv' and the desired (y, x) coordinates prepended to the
285 arguments to the function. For example, the calls
297 mvwaddch(win, y, x, ch);
299 Note that the window description pointer (win) comes before the added
300 (y, x) coordinates. If a function requires a window pointer, it is
301 always the first parameter passed.
305 The curses library sets some variables describing the terminal
307 type name description
308 ------------------------------------------------------------------
309 int LINES number of lines on the terminal
310 int COLS number of columns on the terminal
312 The curses.h also introduces some #define constants and types of
316 boolean type, actually a `char' (e.g., bool doneit;)
319 boolean `true' flag (1).
322 boolean `false' flag (0).
325 error flag returned by routines on a failure (-1).
328 error flag returned by routines when things go right.
332 Now we describe how to actually use the screen package. In it, we
333 assume all updating, reading, etc. is applied to stdscr. These
334 instructions will work on any window, providing you change the
335 function names and parameters as mentioned above.
337 Here is a sample program to motivate the discussion:
341 static void finish(int sig);
344 main(int argc, char *argv[])
348 /* initialize your non-curses data structures here */
350 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
352 (void) initscr(); /* initialize the curses library */
353 keypad(stdscr, TRUE); /* enable keyboard mapping */
354 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
355 (void) cbreak(); /* take input chars one at a time, no wait for \n */
356 (void) echo(); /* echo input - in color */
363 * Simple color assignment, often all we need. Color pair 0 cannot
364 * be redefined. This example uses the same value for the color
365 * pair as for the foreground color, though of course that is not
368 init_pair(1, COLOR_RED, COLOR_BLACK);
369 init_pair(2, COLOR_GREEN, COLOR_BLACK);
370 init_pair(3, COLOR_YELLOW, COLOR_BLACK);
371 init_pair(4, COLOR_BLUE, COLOR_BLACK);
372 init_pair(5, COLOR_CYAN, COLOR_BLACK);
373 init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
374 init_pair(7, COLOR_WHITE, COLOR_BLACK);
379 int c = getch(); /* refresh, accept single keystroke of input */
380 attrset(COLOR_PAIR(num % 8));
383 /* process the command keystroke */
386 finish(0); /* we're done */
389 static void finish(int sig)
393 /* do your non-curses wrapup here */
400 In order to use the screen package, the routines must know about
401 terminal characteristics, and the space for curscr and stdscr must be
402 allocated. These function initscr() does both these things. Since it
403 must allocate space for the windows, it can overflow memory when
404 attempting to do so. On the rare occasions this happens, initscr()
405 will terminate the program with an error message. initscr() must
406 always be called before any of the routines which affect windows are
407 used. If it is not, the program will core dump as soon as either
408 curscr or stdscr are referenced. However, it is usually best to wait
409 to call it until after you are sure you will need it, like after
410 checking for startup errors. Terminal status changing routines like
411 nl() and cbreak() should be called after initscr().
413 Once the screen windows have been allocated, you can set them up for
414 your program. If you want to, say, allow a screen to scroll, use
415 scrollok(). If you want the cursor to be left in place after the last
416 change, use leaveok(). If this isn't done, refresh() will move the
417 cursor to the window's current (y, x) coordinates after updating it.
419 You can create new windows of your own using the functions newwin(),
420 derwin(), and subwin(). The routine delwin() will allow you to get rid
421 of old windows. All the options described above can be applied to any
426 Now that we have set things up, we will want to actually update the
427 terminal. The basic functions used to change what will go on a window
428 are addch() and move(). addch() adds a character at the current (y, x)
429 coordinates. move() changes the current (y, x) coordinates to whatever
430 you want them to be. It returns ERR if you try to move off the window.
431 As mentioned above, you can combine the two into mvaddch() to do both
434 The other output functions, such as addstr() and printw(), all call
435 addch() to add characters to the window.
437 After you have put on the window what you want there, when you want
438 the portion of the terminal covered by the window to be made to look
439 like it, you must call refresh(). In order to optimize finding
440 changes, refresh() assumes that any part of the window not changed
441 since the last refresh() of that window has not been changed on the
442 terminal, i.e., that you have not refreshed a portion of the terminal
443 with an overlapping window. If this is not the case, the routine
444 touchwin() is provided to make it look like the entire window has been
445 changed, thus making refresh() check the whole subsection of the
446 terminal for changes.
448 If you call wrefresh() with curscr as its argument, it will make the
449 screen look like curscr thinks it looks like. This is useful for
450 implementing a command which would redraw the screen in case it get
455 The complementary function to addch() is getch() which, if echo is
456 set, will call addch() to echo the character. Since the screen package
457 needs to know what is on the terminal at all times, if characters are
458 to be echoed, the tty must be in raw or cbreak mode. Since initially
459 the terminal has echoing enabled and is in ordinary ``cooked'' mode,
460 one or the other has to changed before calling getch(); otherwise, the
461 program's output will be unpredictable.
463 When you need to accept line-oriented input in a window, the functions
464 wgetstr() and friends are available. There is even a wscanw() function
465 that can do scanf()(3)-style multi-field parsing on window input.
466 These pseudo-line-oriented functions turn on echoing while they
469 The example code above uses the call keypad(stdscr, TRUE) to enable
470 support for function-key mapping. With this feature, the getch() code
471 watches the input stream for character sequences that correspond to
472 arrow and function keys. These sequences are returned as
473 pseudo-character values. The #define values returned are listed in the
474 curses.h The mapping from sequences to #define values is determined by
475 key_ capabilities in the terminal's terminfo entry.
477 Using Forms Characters
479 The addch() function (and some others, including box() and border())
480 can accept some pseudo-character arguments which are specially defined
481 by ncurses. These are #define values set up in the curses.h header;
482 see there for a complete list (look for the prefix ACS_).
484 The most useful of the ACS defines are the forms-drawing characters.
485 You can use these to draw boxes and simple graphs on the screen. If
486 the terminal does not have such characters, curses.h will map them to
487 a recognizable (though ugly) set of ASCII defaults.
489 Character Attributes and Color
491 The ncurses package supports screen highlights including standout,
492 reverse-video, underline, and blink. It also supports color, which is
493 treated as another kind of highlight.
495 Highlights are encoded, internally, as high bits of the
496 pseudo-character type (chtype) that curses.h uses to represent the
497 contents of a screen cell. See the curses.h header file for a complete
498 list of highlight mask values (look for the prefix A_).
500 There are two ways to make highlights. One is to logical-or the value
501 of the highlights you want into the character argument of an addch()
502 call, or any other output call that takes a chtype argument.
504 The other is to set the current-highlight value. This is logical-or'ed
505 with any highlight you specify the first way. You do this with the
506 functions attron(), attroff(), and attrset(); see the manual pages for
507 details. Color is a special kind of highlight. The package actually
508 thinks in terms of color pairs, combinations of foreground and
509 background colors. The sample code above sets up eight color pairs,
510 all of the guaranteed-available colors on black. Note that each color
511 pair is, in effect, given the name of its foreground color. Any other
512 range of eight non-conflicting values could have been used as the
513 first arguments of the init_pair() values.
515 Once you've done an init_pair() that creates color-pair N, you can use
516 COLOR_PAIR(N) as a highlight that invokes that particular color
517 combination. Note that COLOR_PAIR(N), for constant N, is itself a
518 compile-time constant and can be used in initializers.
522 The ncurses library also provides a mouse interface.
524 NOTE: this facility is specific to ncurses, it is not part of
525 either the XSI Curses standard, nor of System V Release 4, nor BSD
526 curses. System V Release 4 curses contains code with similar
527 interface definitions, however it is not documented. Other than by
528 disassembling the library, we have no way to determine exactly how
529 that mouse code works. Thus, we recommend that you wrap
530 mouse-related code in an #ifdef using the feature macro
531 NCURSES_MOUSE_VERSION so it will not be compiled and linked on
534 Presently, mouse event reporting works in the following environments:
535 * xterm and similar programs such as rxvt.
536 * Linux console, when configured with gpm(1), Alessandro Rubini's
540 The mouse interface is very simple. To activate it, you use the
541 function mousemask(), passing it as first argument a bit-mask that
542 specifies what kinds of events you want your program to be able to
543 see. It will return the bit-mask of events that actually become
544 visible, which may differ from the argument if the mouse device is not
545 capable of reporting some of the event types you specify.
547 Once the mouse is active, your application's command loop should watch
548 for a return value of KEY_MOUSE from wgetch(). When you see this, a
549 mouse event report has been queued. To pick it off the queue, use the
550 function getmouse() (you must do this before the next wgetch(),
551 otherwise another mouse event might come in and make the first one
554 Each call to getmouse() fills a structure (the address of which you'll
555 pass it) with mouse event data. The event data includes zero-origin,
556 screen-relative character-cell coordinates of the mouse pointer. It
557 also includes an event mask. Bits in this mask will be set,
558 corresponding to the event type being reported.
560 The mouse structure contains two additional fields which may be
561 significant in the future as ncurses interfaces to new kinds of
562 pointing device. In addition to x and y coordinates, there is a slot
563 for a z coordinate; this might be useful with touch-screens that can
564 return a pressure or duration parameter. There is also a device ID
565 field, which could be used to distinguish between multiple pointing
568 The class of visible events may be changed at any time via
569 mousemask(). Events that can be reported include presses, releases,
570 single-, double- and triple-clicks (you can set the maximum
571 button-down time for clicks). If you don't make clicks visible, they
572 will be reported as press-release pairs. In some environments, the
573 event mask may include bits reporting the state of shift, alt, and
574 ctrl keys on the keyboard during the event.
576 A function to check whether a mouse event fell within a given window
577 is also supplied. You can use this to see whether a given window
578 should consider a mouse event relevant to it.
580 Because mouse event reporting will not be available in all
581 environments, it would be unwise to build ncurses applications that
582 require the use of a mouse. Rather, you should use the mouse as a
583 shortcut for point-and-shoot commands your application would normally
584 accept from the keyboard. Two of the test games in the ncurses
585 distribution (bs and knight) contain code that illustrates how this
588 See the manual page curs_mouse(3X) for full details of the
589 mouse-interface functions.
593 In order to clean up after the ncurses routines, the routine endwin()
594 is provided. It restores tty modes to what they were when initscr()
595 was first called, and moves the cursor down to the lower-left corner.
596 Thus, anytime after the call to initscr, endwin() should be called
599 Function Descriptions
601 We describe the detailed behavior of some important curses functions
602 here, as a supplement to the manual page descriptions.
604 Initialization and Wrapup
607 The first function called should almost always be initscr().
608 This will determine the terminal type and initialize curses
609 data structures. initscr() also arranges that the first call to
610 refresh() will clear the screen. If an error occurs a message
611 is written to standard error and the program exits. Otherwise
612 it returns a pointer to stdscr. A few functions may be called
613 before initscr (slk_init(), filter(), ripofflines(), use_env(),
614 and, if you are using multiple terminals, newterm().)
617 Your program should always call endwin() before exiting or
618 shelling out of the program. This function will restore tty
619 modes, move the cursor to the lower left corner of the screen,
620 reset the terminal into the proper non-visual mode. Calling
621 refresh() or doupdate() after a temporary escape from the
622 program will restore the ncurses screen from before the escape.
624 newterm(type, ofp, ifp)
625 A program which outputs to more than one terminal should use
626 newterm() instead of initscr(). newterm() should be called once
627 for each terminal. It returns a variable of type SCREEN * which
628 should be saved as a reference to that terminal. (NOTE: a
629 SCREEN variable is not a screen in the sense we are describing
630 in this introduction, but a collection of parameters used to
631 assist in optimizing the display.) The arguments are the type
632 of the terminal (a string) and FILE pointers for the output and
633 input of the terminal. If type is NULL then the environment
634 variable $TERM is used. endwin() should called once at wrapup
635 time for each terminal opened using this function.
638 This function is used to switch to a different terminal
639 previously opened by newterm(). The screen reference for the
640 new terminal is passed as the parameter. The previous terminal
641 is returned by the function. All other calls affect only the
645 The inverse of newterm(); deallocates the data structures
646 associated with a given SCREEN reference.
648 Causing Output to the Terminal
650 refresh() and wrefresh(win)
651 These functions must be called to actually get any output on
652 the terminal, as other routines merely manipulate data
653 structures. wrefresh() copies the named window to the physical
654 terminal screen, taking into account what is already there in
655 order to do optimizations. refresh() does a refresh of
656 stdscr(). Unless leaveok() has been enabled, the physical
657 cursor of the terminal is left at the location of the window's
660 doupdate() and wnoutrefresh(win)
661 These two functions allow multiple updates with more efficiency
662 than wrefresh. To use them, it is important to understand how
663 curses works. In addition to all the window structures, curses
664 keeps two data structures representing the terminal screen: a
665 physical screen, describing what is actually on the screen, and
666 a virtual screen, describing what the programmer wants to have
667 on the screen. wrefresh works by first copying the named window
668 to the virtual screen (wnoutrefresh()), and then calling the
669 routine to update the screen (doupdate()). If the programmer
670 wishes to output several windows at once, a series of calls to
671 wrefresh will result in alternating calls to wnoutrefresh() and
672 doupdate(), causing several bursts of output to the screen. By
673 calling wnoutrefresh() for each window, it is then possible to
674 call doupdate() once, resulting in only one burst of output,
675 with fewer total characters transmitted (this also avoids a
676 visually annoying flicker at each update).
678 Low-Level Capability Access
680 setupterm(term, filenum, errret)
681 This routine is called to initialize a terminal's description,
682 without setting up the curses screen structures or changing the
683 tty-driver mode bits. term is the character string representing
684 the name of the terminal being used. filenum is the UNIX file
685 descriptor of the terminal to be used for output. errret is a
686 pointer to an integer, in which a success or failure indication
687 is returned. The values returned can be 1 (all is well), 0 (no
688 such terminal), or -1 (some problem locating the terminfo
691 The value of term can be given as NULL, which will cause the
692 value of TERM in the environment to be used. The errret pointer
693 can also be given as NULL, meaning no error code is wanted. If
694 errret is defaulted, and something goes wrong, setupterm() will
695 print an appropriate error message and exit, rather than
696 returning. Thus, a simple program can call setupterm(0, 1, 0)
697 and not worry about initialization errors.
699 After the call to setupterm(), the global variable cur_term is
700 set to point to the current structure of terminal capabilities.
701 By calling setupterm() for each terminal, and saving and
702 restoring cur_term, it is possible for a program to use two or
703 more terminals at once. Setupterm() also stores the names
704 section of the terminal description in the global character
705 array ttytype[]. Subsequent calls to setupterm() will overwrite
706 this array, so you'll have to save it yourself if need be.
710 NOTE: These functions are not part of the standard curses API!
713 This function can be used to explicitly set a trace level. If
714 the trace level is nonzero, execution of your program will
715 generate a file called `trace' in the current working directory
716 containing a report on the library's actions. Higher trace
717 levels enable more detailed (and verbose) reporting -- see
718 comments attached to TRACE_ defines in the curses.h file for
719 details. (It is also possible to set a trace level by assigning
720 a trace level value to the environment variable NCURSES_TRACE).
723 This function can be used to output your own debugging
724 information. It is only available only if you link with
725 -lncurses_g. It can be used the same way as printf(), only it
726 outputs a newline after the end of arguments. The output goes
727 to a file called trace in the current directory.
729 Trace logs can be difficult to interpret due to the sheer volume of
730 data dumped in them. There is a script called tracemunch included with
731 the ncurses distribution that can alleviate this problem somewhat; it
732 compacts long sequences of similar operations into more succinct
733 single-line pseudo-operations. These pseudo-ops can be distinguished
734 by the fact that they are named in capital letters.
736 Hints, Tips, and Tricks
738 The ncurses manual pages are a complete reference for this library. In
739 the remainder of this document, we discuss various useful methods that
740 may not be obvious from the manual page descriptions.
742 Some Notes of Caution
744 If you find yourself thinking you need to use noraw() or nocbreak(),
745 think again and move carefully. It's probably better design to use
746 getstr() or one of its relatives to simulate cooked mode. The noraw()
747 and nocbreak() functions try to restore cooked mode, but they may end
748 up clobbering some control bits set before you started your
749 application. Also, they have always been poorly documented, and are
750 likely to hurt your application's usability with other curses
753 Bear in mind that refresh() is a synonym for wrefresh(stdscr). Don't
754 try to mix use of stdscr with use of windows declared by newwin(); a
755 refresh() call will blow them off the screen. The right way to handle
756 this is to use subwin(), or not touch stdscr at all and tile your
757 screen with declared windows which you then wnoutrefresh() somewhere
758 in your program event loop, with a single doupdate() call to trigger
761 You are much less likely to run into problems if you design your
762 screen layouts to use tiled rather than overlapping windows.
763 Historically, curses support for overlapping windows has been weak,
764 fragile, and poorly documented. The ncurses library is not yet an
765 exception to this rule.
767 There is a panels library included in the ncurses distribution that
768 does a pretty good job of strengthening the overlapping-windows
771 Try to avoid using the global variables LINES and COLS. Use getmaxyx()
772 on the stdscr context instead. Reason: your code may be ported to run
773 in an environment with window resizes, in which case several screens
774 could be open with different sizes.
776 Temporarily Leaving NCURSES Mode
778 Sometimes you will want to write a program that spends most of its
779 time in screen mode, but occasionally returns to ordinary `cooked'
780 mode. A common reason for this is to support shell-out. This behavior
781 is simple to arrange in ncurses.
783 To leave ncurses mode, call endwin() as you would if you were
784 intending to terminate the program. This will take the screen back to
785 cooked mode; you can do your shell-out. When you want to return to
786 ncurses mode, simply call refresh() or doupdate(). This will repaint
789 There is a boolean function, isendwin(), which code can use to test
790 whether ncurses screen mode is active. It returns TRUE in the interval
791 between an endwin() call and the following refresh(), FALSE otherwise.
793 Here is some sample code for shellout:
794 addstr("Shelling out...");
795 def_prog_mode(); /* save current tty modes */
796 endwin(); /* restore original tty modes */
797 system("sh"); /* run shell */
798 addstr("returned.\n"); /* prepare return message */
799 refresh(); /* restore save modes, repaint screen */
801 Using NCURSES under XTERM
803 A resize operation in X sends SIGWINCH to the application running
804 under xterm. The ncurses library provides an experimental signal
805 handler, but in general does not catch this signal, because it cannot
806 know how you want the screen re-painted. You will usually have to
807 write the SIGWINCH handler yourself. Ncurses can give you some help.
809 The easiest way to code your SIGWINCH handler is to have it do an
810 endwin, followed by an refresh and a screen repaint you code yourself.
811 The refresh will pick up the new screen size from the xterm's
814 That is the standard way, of course (it even works with some vendor's
815 curses implementations). Its drawback is that it clears the screen to
816 reinitialize the display, and does not resize subwindows which must be
817 shrunk. Ncurses provides an extension which works better, the
818 resizeterm function. That function ensures that all windows are
819 limited to the new screen dimensions, and pads stdscr with blanks if
820 the screen is larger.
822 Finally, ncurses can be configured to provide its own SIGWINCH
823 handler, based on resizeterm.
825 Handling Multiple Terminal Screens
827 The initscr() function actually calls a function named newterm() to do
828 most of its work. If you are writing a program that opens multiple
829 terminals, use newterm() directly.
831 For each call, you will have to specify a terminal type and a pair of
832 file pointers; each call will return a screen reference, and stdscr
833 will be set to the last one allocated. You will switch between screens
834 with the set_term call. Note that you will also have to call
835 def_shell_mode and def_prog_mode on each tty yourself.
837 Testing for Terminal Capabilities
839 Sometimes you may want to write programs that test for the presence of
840 various capabilities before deciding whether to go into ncurses mode.
841 An easy way to do this is to call setupterm(), then use the functions
842 tigetflag(), tigetnum(), and tigetstr() to do your testing.
844 A particularly useful case of this often comes up when you want to
845 test whether a given terminal type should be treated as `smart'
846 (cursor-addressable) or `stupid'. The right way to test this is to see
847 if the return value of tigetstr("cup") is non-NULL. Alternatively, you
848 can include the term.h file and test the value of the macro
853 Use the addchstr() family of functions for fast screen-painting of
854 text when you know the text doesn't contain any control characters.
855 Try to make attribute changes infrequent on your screens. Don't use
856 the immedok() option!
858 Special Features of NCURSES
860 The wresize() function allows you to resize a window in place. The
861 associated resizeterm() function simplifies the construction of
862 SIGWINCH handlers, for resizing all windows.
864 The define_key() function allows you to define at runtime function-key
865 control sequences which are not in the terminal description. The
866 keyok() function allows you to temporarily enable or disable
867 interpretation of any function-key control sequence.
869 The use_default_colors() function allows you to construct applications
870 which can use the terminal's default foreground and background colors
871 as an additional "default" color. Several terminal emulators support
872 this feature, which is based on ISO 6429.
874 Ncurses supports up 16 colors, unlike SVr4 curses which defines only
875 8. While most terminals which provide color allow only 8 colors, about
876 a quarter (including XFree86 xterm) support 16 colors.
878 Compatibility with Older Versions
880 Despite our best efforts, there are some differences between ncurses
881 and the (undocumented!) behavior of older curses implementations.
882 These arise from ambiguities or omissions in the documentation of the
885 Refresh of Overlapping Windows
887 If you define two windows A and B that overlap, and then alternately
888 scribble on and refresh them, the changes made to the overlapping
889 region under historic curses versions were often not documented
892 To understand why this is a problem, remember that screen updates are
893 calculated between two representations of the entire display. The
894 documentation says that when you refresh a window, it is first copied
895 to to the virtual screen, and then changes are calculated to update
896 the physical screen (and applied to the terminal). But "copied to" is
897 not very specific, and subtle differences in how copying works can
898 produce different behaviors in the case where two overlapping windows
899 are each being refreshed at unpredictable intervals.
901 What happens to the overlapping region depends on what wnoutrefresh()
902 does with its argument -- what portions of the argument window it
903 copies to the virtual screen. Some implementations do "change copy",
904 copying down only locations in the window that have changed (or been
905 marked changed with wtouchln() and friends). Some implementations do
906 "entire copy", copying all window locations to the virtual screen
907 whether or not they have changed.
909 The ncurses library itself has not always been consistent on this
910 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy.
911 Versions 1.8.6 and older, and versions 1.9.9 and newer, do change
914 For most commercial curses implementations, it is not documented and
915 not known for sure (at least not to the ncurses maintainers) whether
916 they do change copy or entire copy. We know that System V release 3
917 curses has logic in it that looks like an attempt to do change copy,
918 but the surrounding logic and data representations are sufficiently
919 complex, and our knowledge sufficiently indirect, that it's hard to
920 know whether this is reliable. It is not clear what the SVr4
921 documentation and XSI standard intend. The XSI Curses standard barely
922 mentions wnoutrefresh(); the SVr4 documents seem to be describing
923 entire-copy, but it is possible with some effort and straining to read
926 It might therefore be unwise to rely on either behavior in programs
927 that might have to be linked with other curses implementations.
928 Instead, you can do an explicit touchwin() before the wnoutrefresh()
929 call to guarantee an entire-contents copy anywhere.
931 The really clean way to handle this is to use the panels library. If,
932 when you want a screen update, you do update_panels(), it will do all
933 the necessary wnoutrfresh() calls for whatever panel stacking order
934 you have defined. Then you can do one doupdate() and there will be a
935 single burst of physical I/O that will do all your updates.
939 If you have been using a very old versions of ncurses (1.8.7 or older)
940 you may be surprised by the behavior of the erase functions. In older
941 versions, erased areas of a window were filled with a blank modified
942 by the window's current attribute (as set by wattrset(), wattron(),
943 wattroff() and friends).
945 In newer versions, this is not so. Instead, the attribute of erased
946 blanks is normal unless and until it is modified by the functions
947 bkgdset() or wbkgdset().
949 This change in behavior conforms ncurses to System V Release 4 and the
952 XSI Curses Conformance
954 The ncurses library is intended to be base-level conformant with the
955 XSI Curses standard from X/Open. Many extended-level features (in
956 fact, almost all features not directly concerned with wide characters
957 and internationalization) are also supported.
959 One effect of XSI conformance is the change in behavior described
960 under "Background Erase -- Compatibility with Old Versions".
962 Also, ncurses meets the XSI requirement that every macro entry point
963 have a corresponding function which may be linked (and will be
964 prototype-checked) if the macro definition is disabled with #undef.
968 The ncurses library by itself provides good support for screen
969 displays in which the windows are tiled (non-overlapping). In the more
970 general case that windows may overlap, you have to use a series of
971 wnoutrefresh() calls followed by a doupdate(), and be careful about
972 the order you do the window refreshes in. It has to be bottom-upwards,
973 otherwise parts of windows that should be obscured will show through.
975 When your interface design is such that windows may dive deeper into
976 the visibility stack or pop to the top at runtime, the resulting
977 book-keeping can be tedious and difficult to get right. Hence the
980 The panel library first appeared in AT&T System V. The version
981 documented here is the panel code distributed with ncurses.
983 Compiling With the Panels Library
985 Your panels-using modules must import the panels library declarations
989 and must be linked explicitly with the panels library using an -lpanel
990 argument. Note that they must also link the ncurses library with
991 -lncurses. Many linkers are two-pass and will accept either order, but
992 it is still good practice to put -lpanel first and -lncurses second.
996 A panel object is a window that is implicitly treated as part of a
997 deck including all other panel objects. The deck has an implicit
998 bottom-to-top visibility order. The panels library includes an update
999 function (analogous to refresh()) that displays all panels in the deck
1000 in the proper order to resolve overlaps. The standard window, stdscr,
1001 is considered below all panels.
1003 Details on the panels functions are available in the man pages. We'll
1004 just hit the highlights here.
1006 You create a panel from a window by calling new_panel() on a window
1007 pointer. It then becomes the top of the deck. The panel's window is
1008 available as the value of panel_window() called with the panel pointer
1011 You can delete a panel (removing it from the deck) with del_panel.
1012 This will not deallocate the associated window; you have to do that
1013 yourself. You can replace a panel's window with a different window by
1014 calling replace_window. The new window may be of different size; the
1015 panel code will re-compute all overlaps. This operation doesn't change
1016 the panel's position in the deck.
1018 To move a panel's window, use move_panel(). The mvwin() function on
1019 the panel's window isn't sufficient because it doesn't update the
1020 panels library's representation of where the windows are. This
1021 operation leaves the panel's depth, contents, and size unchanged.
1023 Two functions (top_panel(), bottom_panel()) are provided for
1024 rearranging the deck. The first pops its argument window to the top of
1025 the deck; the second sends it to the bottom. Either operation leaves
1026 the panel's screen location, contents, and size unchanged.
1028 The function update_panels() does all the wnoutrefresh() calls needed
1029 to prepare for doupdate() (which you must call yourself, afterwards).
1031 Typically, you will want to call update_panels() and doupdate() just
1032 before accepting command input, once in each cycle of interaction with
1033 the user. If you call update_panels() after each and every panel
1034 write, you'll generate a lot of unnecessary refresh activity and
1037 Panels, Input, and the Standard Screen
1039 You shouldn't mix wnoutrefresh() or wrefresh() operations with panels
1040 code; this will work only if the argument window is either in the top
1041 panel or unobscured by any other panels.
1043 The stsdcr window is a special case. It is considered below all
1044 panels. Because changes to panels may obscure parts of stdscr, though,
1045 you should call update_panels() before doupdate() even when you only
1048 Note that wgetch automatically calls wrefresh. Therefore, before
1049 requesting input from a panel window, you need to be sure that the
1050 panel is totally unobscured.
1052 There is presently no way to display changes to one obscured panel
1053 without repainting all panels.
1057 It's possible to remove a panel from the deck temporarily; use
1058 hide_panel for this. Use show_panel() to render it visible again. The
1059 predicate function panel_hidden tests whether or not a panel is
1062 The panel_update code ignores hidden panels. You cannot do top_panel()
1063 or bottom_panel on a hidden panel(). Other panels operations are
1066 Miscellaneous Other Facilities
1068 It's possible to navigate the deck using the functions panel_above()
1069 and panel_below. Handed a panel pointer, they return the panel above
1070 or below that panel. Handed NULL, they return the bottom-most or
1073 Every panel has an associated user pointer, not used by the panel
1074 code, to which you can attach application data. See the man page
1075 documentation of set_panel_userptr() and panel_userptr for details.
1079 A menu is a screen display that assists the user to choose some subset
1080 of a given set of items. The menu library is a curses extension that
1081 supports easy programming of menu hierarchies with a uniform but
1084 The menu library first appeared in AT&T System V. The version
1085 documented here is the menu code distributed with ncurses.
1087 Compiling With the menu Library
1089 Your menu-using modules must import the menu library declarations with
1092 and must be linked explicitly with the menus library using an -lmenu
1093 argument. Note that they must also link the ncurses library with
1094 -lncurses. Many linkers are two-pass and will accept either order, but
1095 it is still good practice to put -lmenu first and -lncurses second.
1099 The menus created by this library consist of collections of items
1100 including a name string part and a description string part. To make
1101 menus, you create groups of these items and connect them with menu
1104 The menu can then by posted, that is written to an associated window.
1105 Actually, each menu has two associated windows; a containing window in
1106 which the programmer can scribble titles or borders, and a subwindow
1107 in which the menu items proper are displayed. If this subwindow is too
1108 small to display all the items, it will be a scrollable viewport on
1109 the collection of items.
1111 A menu may also be unposted (that is, undisplayed), and finally freed
1112 to make the storage associated with it and its items available for
1115 The general flow of control of a menu program looks like this:
1116 1. Initialize curses.
1117 2. Create the menu items, using new_item().
1118 3. Create the menu using new_menu().
1119 4. Post the menu using menu_post().
1120 5. Refresh the screen.
1121 6. Process user requests via an input loop.
1122 7. Unpost the menu using menu_unpost().
1123 8. Free the menu, using free_menu().
1124 9. Free the items using free_item().
1125 10. Terminate curses.
1129 Menus may be multi-valued or (the default) single-valued (see the
1130 manual page menu_opts(3x) to see how to change the default). Both
1131 types always have a current item.
1133 From a single-valued menu you can read the selected value simply by
1134 looking at the current item. From a multi-valued menu, you get the
1135 selected set by looping through the items applying the item_value()
1136 predicate function. Your menu-processing code can use the function
1137 set_item_value() to flag the items in the select set.
1139 Menu items can be made unselectable using set_item_opts() or
1140 item_opts_off() with the O_SELECTABLE argument. This is the only
1141 option so far defined for menus, but it is good practice to code as
1142 though other option bits might be on.
1146 The menu library calculates a minimum display size for your window,
1147 based on the following variables:
1148 * The number and maximum length of the menu items
1149 * Whether the O_ROWMAJOR option is enabled
1150 * Whether display of descriptions is enabled
1151 * Whatever menu format may have been set by the programmer
1152 * The length of the menu mark string used for highlighting selected
1155 The function set_menu_format() allows you to set the maximum size of
1156 the viewport or menu page that will be used to display menu items. You
1157 can retrieve any format associated with a menu with menu_format(). The
1158 default format is rows=16, columns=1.
1160 The actual menu page may be smaller than the format size. This depends
1161 on the item number and size and whether O_ROWMAJOR is on. This option
1162 (on by default) causes menu items to be displayed in a `raster-scan'
1163 pattern, so that if more than one item will fit horizontally the first
1164 couple of items are side-by-side in the top row. The alternative is
1165 column-major display, which tries to put the first several items in
1168 As mentioned above, a menu format not large enough to allow all items
1169 to fit on-screen will result in a menu display that is vertically
1172 You can scroll it with requests to the menu driver, which will be
1173 described in the section on menu input handling.
1175 Each menu has a mark string used to visually tag selected items; see
1176 the menu_mark(3x) manual page for details. The mark string length also
1177 influences the menu page size.
1179 The function scale_menu() returns the minimum display size that the
1180 menu code computes from all these factors. There are other menu
1181 display attributes including a select attribute, an attribute for
1182 selectable items, an attribute for unselectable items, and a pad
1183 character used to separate item name text from description text. These
1184 have reasonable defaults which the library allows you to change (see
1185 the menu_attribs(3x) manual page.
1189 Each menu has, as mentioned previously, a pair of associated windows.
1190 Both these windows are painted when the menu is posted and erased when
1191 the menu is unposted.
1193 The outer or frame window is not otherwise touched by the menu
1194 routines. It exists so the programmer can associate a title, a border,
1195 or perhaps help text with the menu and have it properly refreshed or
1196 erased at post/unpost time. The inner window or subwindow is where the
1197 current menu page is displayed.
1199 By default, both windows are stdscr. You can set them with the
1200 functions in menu_win(3x).
1202 When you call menu_post(), you write the menu to its subwindow. When
1203 you call menu_unpost(), you erase the subwindow, However, neither of
1204 these actually modifies the screen. To do that, call wrefresh() or
1207 Processing Menu Input
1209 The main loop of your menu-processing code should call menu_driver()
1210 repeatedly. The first argument of this routine is a menu pointer; the
1211 second is a menu command code. You should write an input-fetching
1212 routine that maps input characters to menu command codes, and pass its
1213 output to menu_driver(). The menu command codes are fully documented
1216 The simplest group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM,
1217 REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_UP_ITEM, REQ_DOWN_ITEM,
1218 REQ_LEFT_ITEM, REQ_RIGHT_ITEM. These change the currently selected
1219 item. These requests may cause scrolling of the menu page if it only
1220 partially displayed.
1222 There are explicit requests for scrolling which also change the
1223 current item (because the select location does not change, but the
1224 item there does). These are REQ_SCR_DLINE, REQ_SCR_ULINE,
1225 REQ_SCR_DPAGE, and REQ_SCR_UPAGE.
1227 The REQ_TOGGLE_ITEM selects or deselects the current item. It is for
1228 use in multi-valued menus; if you use it with O_ONEVALUE on, you'll
1229 get an error return (E_REQUEST_DENIED).
1231 Each menu has an associated pattern buffer. The menu_driver() logic
1232 tries to accumulate printable ASCII characters passed in in that
1233 buffer; when it matches a prefix of an item name, that item (or the
1234 next matching item) is selected. If appending a character yields no
1235 new match, that character is deleted from the pattern buffer, and
1236 menu_driver() returns E_NO_MATCH.
1238 Some requests change the pattern buffer directly: REQ_CLEAR_PATTERN,
1239 REQ_BACK_PATTERN, REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter two are
1240 useful when pattern buffer input matches more than one item in a
1243 Each successful scroll or item navigation request clears the pattern
1244 buffer. It is also possible to set the pattern buffer explicitly with
1247 Finally, menu driver requests above the constant MAX_COMMAND are
1248 considered application-specific commands. The menu_driver() code
1249 ignores them and returns E_UNKNOWN_COMMAND.
1251 Miscellaneous Other Features
1253 Various menu options can affect the processing and visual appearance
1254 and input processing of menus. See menu_opts(3x) for details.
1256 It is possible to change the current item from application code; this
1257 is useful if you want to write your own navigation requests. It is
1258 also possible to explicitly set the top row of the menu display. See
1259 mitem_current(3x). If your application needs to change the menu
1260 subwindow cursor for any reason, pos_menu_cursor() will restore it to
1261 the correct location for continuing menu driver processing.
1263 It is possible to set hooks to be called at menu initialization and
1264 wrapup time, and whenever the selected item changes. See
1267 Each item, and each menu, has an associated user pointer on which you
1268 can hang application data. See mitem_userptr(3x) and menu_userptr(3x).
1272 The form library is a curses extension that supports easy programming
1273 of on-screen forms for data entry and program control.
1275 The form library first appeared in AT&T System V. The version
1276 documented here is the form code distributed with ncurses.
1278 Compiling With the form Library
1280 Your form-using modules must import the form library declarations with
1283 and must be linked explicitly with the forms library using an -lform
1284 argument. Note that they must also link the ncurses library with
1285 -lncurses. Many linkers are two-pass and will accept either order, but
1286 it is still good practice to put -lform first and -lncurses second.
1290 A form is a collection of fields; each field may be either a label
1291 (explanatory text) or a data-entry location. Long forms may be
1292 segmented into pages; each entry to a new page clears the screen.
1294 To make forms, you create groups of fields and connect them with form
1295 frame objects; the form library makes this relatively simple.
1297 Once defined, a form can be posted, that is written to an associated
1298 window. Actually, each form has two associated windows; a containing
1299 window in which the programmer can scribble titles or borders, and a
1300 subwindow in which the form fields proper are displayed.
1302 As the form user fills out the posted form, navigation and editing
1303 keys support movement between fields, editing keys support modifying
1304 field, and plain text adds to or changes data in a current field. The
1305 form library allows you (the forms designer) to bind each navigation
1306 and editing key to any keystroke accepted by curses Fields may have
1307 validation conditions on them, so that they check input data for type
1308 and value. The form library supplies a rich set of pre-defined field
1309 types, and makes it relatively easy to define new ones.
1311 Once its transaction is completed (or aborted), a form may be unposted
1312 (that is, undisplayed), and finally freed to make the storage
1313 associated with it and its items available for re-use.
1315 The general flow of control of a form program looks like this:
1316 1. Initialize curses.
1317 2. Create the form fields, using new_field().
1318 3. Create the form using new_form().
1319 4. Post the form using form_post().
1320 5. Refresh the screen.
1321 6. Process user requests via an input loop.
1322 7. Unpost the form using form_unpost().
1323 8. Free the form, using free_form().
1324 9. Free the fields using free_field().
1325 10. Terminate curses.
1327 Note that this looks much like a menu program; the form library
1328 handles tasks which are in many ways similar, and its interface was
1329 obviously designed to resemble that of the menu library wherever
1332 In forms programs, however, the `process user requests' is somewhat
1333 more complicated than for menus. Besides menu-like navigation
1334 operations, the menu driver loop has to support field editing and data
1337 Creating and Freeing Fields and Forms
1339 The basic function for creating fields is new_field():
1340 FIELD *new_field(int height, int width, /* new field size */
1341 int top, int left, /* upper left corner */
1342 int offscreen, /* number of offscreen rows */
1343 int nbuf); /* number of working buffers */
1345 Menu items always occupy a single row, but forms fields may have
1346 multiple rows. So new_field() requires you to specify a width and
1347 height (the first two arguments, which mist both be greater than
1350 You must also specify the location of the field's upper left corner on
1351 the screen (the third and fourth arguments, which must be zero or
1352 greater). Note that these coordinates are relative to the form
1353 subwindow, which will coincide with stdscr by default but need not be
1354 stdscr if you've done an explicit set_form_window() call.
1356 The fifth argument allows you to specify a number of off-screen rows.
1357 If this is zero, the entire field will always be displayed. If it is
1358 nonzero, the form will be scrollable, with only one screen-full
1359 (initially the top part) displayed at any given time. If you make a
1360 field dynamic and grow it so it will no longer fit on the screen, the
1361 form will become scrollable even if the offscreen argument was
1364 The forms library allocates one working buffer per field; the size of
1365 each buffer is ((height + offscreen)*width + 1, one character for each
1366 position in the field plus a NUL terminator. The sixth argument is the
1367 number of additional data buffers to allocate for the field; your
1368 application can use them for its own purposes.
1369 FIELD *dup_field(FIELD *field, /* field to copy */
1370 int top, int left); /* location of new copy */
1372 The function dup_field() duplicates an existing field at a new
1373 location. Size and buffering information are copied; some attribute
1374 flags and status bits are not (see the form_field_new(3X) for
1376 FIELD *link_field(FIELD *field, /* field to copy */
1377 int top, int left); /* location of new copy */
1379 The function link_field() also duplicates an existing field at a new
1380 location. The difference from dup_field() is that it arranges for the
1381 new field's buffer to be shared with the old one.
1383 Besides the obvious use in making a field editable from two different
1384 form pages, linked fields give you a way to hack in dynamic labels. If
1385 you declare several fields linked to an original, and then make them
1386 inactive, changes from the original will still be propagated to the
1389 As with duplicated fields, linked fields have attribute bits separate
1392 As you might guess, all these field-allocations return NULL if the
1393 field allocation is not possible due to an out-of-memory error or
1394 out-of-bounds arguments.
1396 To connect fields to a form, use
1397 FORM *new_form(FIELD **fields);
1399 This function expects to see a NULL-terminated array of field
1400 pointers. Said fields are connected to a newly-allocated form object;
1401 its address is returned (or else NULL if the allocation fails).
1403 Note that new_field() does not copy the pointer array into private
1404 storage; if you modify the contents of the pointer array during forms
1405 processing, all manner of bizarre things might happen. Also note that
1406 any given field may only be connected to one form.
1408 The functions free_field() and free_form are available to free field
1409 and form objects. It is an error to attempt to free a field connected
1410 to a form, but not vice-versa; thus, you will generally free your form
1413 Fetching and Changing Field Attributes
1415 Each form field has a number of location and size attributes
1416 associated with it. There are other field attributes used to control
1417 display and editing of the field. Some (for example, the O_STATIC bit)
1418 involve sufficient complications to be covered in sections of their
1419 own later on. We cover the functions used to get and set several basic
1422 When a field is created, the attributes not specified by the new_field
1423 function are copied from an invisible system default field. In
1424 attribute-setting and -fetching functions, the argument NULL is taken
1425 to mean this field. Changes to it persist as defaults until your forms
1426 application terminates.
1428 Fetching Size and Location Data
1430 You can retrieve field sizes and locations through:
1431 int field_info(FIELD *field, /* field from which to fetch */
1432 int *height, *int width, /* field size */
1433 int *top, int *left, /* upper left corner */
1434 int *offscreen, /* number of offscreen rows */
1435 int *nbuf); /* number of working buffers */
1437 This function is a sort of inverse of new_field(); instead of setting
1438 size and location attributes of a new field, it fetches them from an
1441 Changing the Field Location
1443 It is possible to move a field's location on the screen:
1444 int move_field(FIELD *field, /* field to alter */
1445 int top, int left); /* new upper-left corner */
1447 You can, of course. query the current location through field_info().
1449 The Justification Attribute
1451 One-line fields may be unjustified, justified right, justified left,
1452 or centered. Here is how you manipulate this attribute:
1453 int set_field_just(FIELD *field, /* field to alter */
1454 int justmode); /* mode to set */
1456 int field_just(FIELD *field); /* fetch mode of field */
1458 The mode values accepted and returned by this functions are
1459 preprocessor macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or
1462 Field Display Attributes
1464 For each field, you can set a foreground attribute for entered
1465 characters, a background attribute for the entire field, and a pad
1466 character for the unfilled portion of the field. You can also control
1467 pagination of the form.
1469 This group of four field attributes controls the visual appearance of
1470 the field on the screen, without affecting in any way the data in the
1472 int set_field_fore(FIELD *field, /* field to alter */
1473 chtype attr); /* attribute to set */
1475 chtype field_fore(FIELD *field); /* field to query */
1477 int set_field_back(FIELD *field, /* field to alter */
1478 chtype attr); /* attribute to set */
1480 chtype field_back(FIELD *field); /* field to query */
1482 int set_field_pad(FIELD *field, /* field to alter */
1483 int pad); /* pad character to set */
1485 chtype field_pad(FIELD *field);
1487 int set_new_page(FIELD *field, /* field to alter */
1488 int flag); /* TRUE to force new page */
1490 chtype new_page(FIELD *field); /* field to query */
1492 The attributes set and returned by the first four functions are normal
1493 curses(3x) display attribute values (A_STANDOUT, A_BOLD, A_REVERSE
1494 etc). The page bit of a field controls whether it is displayed at the
1495 start of a new form screen.
1499 There is also a large collection of field option bits you can set to
1500 control various aspects of forms processing. You can manipulate them
1501 with these functions:
1502 int set_field_opts(FIELD *field, /* field to alter */
1503 int attr); /* attribute to set */
1505 int field_opts_on(FIELD *field, /* field to alter */
1506 int attr); /* attributes to turn on */
1508 int field_opts_off(FIELD *field, /* field to alter */
1509 int attr); /* attributes to turn off */
1511 int field_opts(FIELD *field); /* field to query */
1513 By default, all options are on. Here are the available option bits:
1516 Controls whether the field is visible on the screen. Can be
1517 used during form processing to hide or pop up fields depending
1518 on the value of parent fields.
1521 Controls whether the field is active during forms processing
1522 (i.e. visited by form navigation keys). Can be used to make
1523 labels or derived fields with buffer values alterable by the
1524 forms application, not the user.
1527 Controls whether data is displayed during field entry. If this
1528 option is turned off on a field, the library will accept and
1529 edit data in that field, but it will not be displayed and the
1530 visible field cursor will not move. You can turn off the
1531 O_PUBLIC bit to define password fields.
1534 Controls whether the field's data can be modified. When this
1535 option is off, all editing requests except REQ_PREV_CHOICE and
1536 REQ_NEXT_CHOICE will fail. Such read-only fields may be useful
1540 Controls word-wrapping in multi-line fields. Normally, when any
1541 character of a (blank-separated) word reaches the end of the
1542 current line, the entire word is wrapped to the next line
1543 (assuming there is one). When this option is off, the word will
1544 be split across the line break.
1547 Controls field blanking. When this option is on, entering a
1548 character at the first field position erases the entire field
1549 (except for the just-entered character).
1552 Controls automatic skip to next field when this one fills.
1553 Normally, when the forms user tries to type more data into a
1554 field than will fit, the editing location jumps to next field.
1555 When this option is off, the user's cursor will hang at the end
1556 of the field. This option is ignored in dynamic fields that
1557 have not reached their size limit.
1560 Controls whether validation is applied to blank fields.
1561 Normally, it is not; the user can leave a field blank without
1562 invoking the usual validation check on exit. If this option is
1563 off on a field, exit from it will invoke a validation check.
1566 Controls whether validation occurs on every exit, or only after
1567 the field is modified. Normally the latter is true. Setting
1568 O_PASSOK may be useful if your field's validation function may
1569 change during forms processing.
1572 Controls whether the field is fixed to its initial dimensions.
1573 If you turn this off, the field becomes dynamic and will
1574 stretch to fit entered data.
1576 A field's options cannot be changed while the field is currently
1577 selected. However, options may be changed on posted fields that are
1580 The option values are bit-masks and can be composed with logical-or in
1585 Every field has a status flag, which is set to FALSE when the field is
1586 created and TRUE when the value in field buffer 0 changes. This flag
1587 can be queried and set directly:
1588 int set_field_status(FIELD *field, /* field to alter */
1589 int status); /* mode to set */
1591 int field_status(FIELD *field); /* fetch mode of field */
1593 Setting this flag under program control can be useful if you use the
1594 same form repeatedly, looking for modified fields each time.
1596 Calling field_status() on a field not currently selected for input
1597 will return a correct value. Calling field_status() on a field that is
1598 currently selected for input may not necessarily give a correct field
1599 status value, because entered data isn't necessarily copied to buffer
1600 zero before the exit validation check. To guarantee that the returned
1601 status value reflects reality, call field_status() either (1) in the
1602 field's exit validation check routine, (2) from the field's or form's
1603 initialization or termination hooks, or (3) just after a
1604 REQ_VALIDATION request has been processed by the forms driver.
1608 Each field structure contains one character pointer slot that is not
1609 used by the forms library. It is intended to be used by applications
1610 to store private per-field data. You can manipulate it with:
1611 int set_field_userptr(FIELD *field, /* field to alter */
1612 char *userptr); /* mode to set */
1614 char *field_userptr(FIELD *field); /* fetch mode of field */
1616 (Properly, this user pointer field ought to have (void *) type. The
1617 (char *) type is retained for System V compatibility.)
1619 It is valid to set the user pointer of the default field (with a
1620 set_field_userptr() call passed a NULL field pointer.) When a new
1621 field is created, the default-field user pointer is copied to
1622 initialize the new field's user pointer.
1624 Variable-Sized Fields
1626 Normally, a field is fixed at the size specified for it at creation
1627 time. If, however, you turn off its O_STATIC bit, it becomes dynamic
1628 and will automatically resize itself to accommodate data as it is
1629 entered. If the field has extra buffers associated with it, they will
1630 grow right along with the main input buffer.
1632 A one-line dynamic field will have a fixed height (1) but variable
1633 width, scrolling horizontally to display data within the field area as
1634 originally dimensioned and located. A multi-line dynamic field will
1635 have a fixed width, but variable height (number of rows), scrolling
1636 vertically to display data within the field area as originally
1637 dimensioned and located.
1639 Normally, a dynamic field is allowed to grow without limit. But it is
1640 possible to set an upper limit on the size of a dynamic field. You do
1641 it with this function:
1642 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
1643 int max_size); /* upper limit on field size */
1645 If the field is one-line, max_size is taken to be a column size limit;
1646 if it is multi-line, it is taken to be a line size limit. To disable
1647 any limit, use an argument of zero. The growth limit can be changed
1648 whether or not the O_STATIC bit is on, but has no effect until it is.
1650 The following properties of a field change when it becomes dynamic:
1651 * If there is no growth limit, there is no final position of the
1652 field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored.
1653 * Field justification will be ignored (though whatever justification
1654 is set up will be retained internally and can be queried).
1655 * The dup_field() and link_field() calls copy dynamic-buffer sizes.
1656 If the O_STATIC option is set on one of a collection of links,
1657 buffer resizing will occur only when the field is edited through
1659 * The call field_info() will retrieve the original static size of
1660 the field; use dynamic_field_info() to get the actual dynamic
1665 By default, a field will accept any data that will fit in its input
1666 buffer. However, it is possible to attach a validation type to a
1667 field. If you do this, any attempt to leave the field while it
1668 contains data that doesn't match the validation type will fail. Some
1669 validation types also have a character-validity check for each time a
1670 character is entered in the field.
1672 A field's validation check (if any) is not called when
1673 set_field_buffer() modifies the input buffer, nor when that buffer is
1674 changed through a linked field.
1676 The form library provides a rich set of pre-defined validation types,
1677 and gives you the capability to define custom ones of your own. You
1678 can examine and change field validation attributes with the following
1680 int set_field_type(FIELD *field, /* field to alter */
1681 FIELDTYPE *ftype, /* type to associate */
1682 ...); /* additional arguments*/
1684 FIELDTYPE *field_type(FIELD *field); /* field to query */
1686 The validation type of a field is considered an attribute of the
1687 field. As with other field attributes, Also, doing set_field_type()
1688 with a NULL field default will change the system default for
1689 validation of newly-created fields.
1691 Here are the pre-defined validation types:
1695 This field type accepts alphabetic data; no blanks, no digits, no
1696 special characters (this is checked at character-entry time). It is
1698 int set_field_type(FIELD *field, /* field to alter */
1699 TYPE_ALPHA, /* type to associate */
1700 int width); /* maximum width of field */
1702 The width argument sets a minimum width of data. Typically you'll want
1703 to set this to the field width; if it's greater than the field width,
1704 the validation check will always fail. A minimum width of zero makes
1705 field completion optional.
1709 This field type accepts alphabetic data and digits; no blanks, no
1710 special characters (this is checked at character-entry time). It is
1712 int set_field_type(FIELD *field, /* field to alter */
1713 TYPE_ALNUM, /* type to associate */
1714 int width); /* maximum width of field */
1716 The width argument sets a minimum width of data. As with TYPE_ALPHA,
1717 typically you'll want to set this to the field width; if it's greater
1718 than the field width, the validation check will always fail. A minimum
1719 width of zero makes field completion optional.
1723 This type allows you to restrict a field's values to be among a
1724 specified set of string values (for example, the two-letter postal
1725 codes for U.S. states). It is set up with:
1726 int set_field_type(FIELD *field, /* field to alter */
1727 TYPE_ENUM, /* type to associate */
1728 char **valuelist; /* list of possible values */
1729 int checkcase; /* case-sensitive? */
1730 int checkunique); /* must specify uniquely? */
1732 The valuelist parameter must point at a NULL-terminated list of valid
1733 strings. The checkcase argument, if true, makes comparison with the
1734 string case-sensitive.
1736 When the user exits a TYPE_ENUM field, the validation procedure tries
1737 to complete the data in the buffer to a valid entry. If a complete
1738 choice string has been entered, it is of course valid. But it is also
1739 possible to enter a prefix of a valid string and have it completed for
1742 By default, if you enter such a prefix and it matches more than one
1743 value in the string list, the prefix will be completed to the first
1744 matching value. But the checkunique argument, if true, requires prefix
1745 matches to be unique in order to be valid.
1747 The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be
1748 particularly useful with these fields.
1752 This field type accepts an integer. It is set up as follows:
1753 int set_field_type(FIELD *field, /* field to alter */
1754 TYPE_INTEGER, /* type to associate */
1755 int padding, /* # places to zero-pad to */
1756 int vmin, int vmax); /* valid range */
1758 Valid characters consist of an optional leading minus and digits. The
1759 range check is performed on exit. If the range maximum is less than or
1760 equal to the minimum, the range is ignored.
1762 If the value passes its range check, it is padded with as many leading
1763 zero digits as necessary to meet the padding argument.
1765 A TYPE_INTEGER value buffer can conveniently be interpreted with the C
1766 library function atoi(3).
1770 This field type accepts a decimal number. It is set up as follows:
1771 int set_field_type(FIELD *field, /* field to alter */
1772 TYPE_NUMERIC, /* type to associate */
1773 int padding, /* # places of precision */
1774 double vmin, double vmax); /* valid range */
1776 Valid characters consist of an optional leading minus and digits.
1777 possibly including a decimal point. If your system supports locale's,
1778 the decimal point character used must be the one defined by your
1779 locale. The range check is performed on exit. If the range maximum is
1780 less than or equal to the minimum, the range is ignored.
1782 If the value passes its range check, it is padded with as many
1783 trailing zero digits as necessary to meet the padding argument.
1785 A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
1786 library function atof(3).
1790 This field type accepts data matching a regular expression. It is set
1792 int set_field_type(FIELD *field, /* field to alter */
1793 TYPE_REGEXP, /* type to associate */
1794 char *regexp); /* expression to match */
1796 The syntax for regular expressions is that of regcomp(3). The check
1797 for regular-expression match is performed on exit.
1799 Direct Field Buffer Manipulation
1801 The chief attribute of a field is its buffer contents. When a form has
1802 been completed, your application usually needs to know the state of
1803 each field buffer. You can find this out with:
1804 char *field_buffer(FIELD *field, /* field to query */
1805 int bufindex); /* number of buffer to query */
1807 Normally, the state of the zero-numbered buffer for each field is set
1808 by the user's editing actions on that field. It's sometimes useful to
1809 be able to set the value of the zero-numbered (or some other) buffer
1810 from your application:
1811 int set_field_buffer(FIELD *field, /* field to alter */
1812 int bufindex, /* number of buffer to alter */
1813 char *value); /* string value to set */
1815 If the field is not large enough and cannot be resized to a
1816 sufficiently large size to contain the specified value, the value will
1817 be truncated to fit.
1819 Calling field_buffer() with a null field pointer will raise an error.
1820 Calling field_buffer() on a field not currently selected for input
1821 will return a correct value. Calling field_buffer() on a field that is
1822 currently selected for input may not necessarily give a correct field
1823 buffer value, because entered data isn't necessarily copied to buffer
1824 zero before the exit validation check. To guarantee that the returned
1825 buffer value reflects on-screen reality, call field_buffer() either
1826 (1) in the field's exit validation check routine, (2) from the field's
1827 or form's initialization or termination hooks, or (3) just after a
1828 REQ_VALIDATION request has been processed by the forms driver.
1832 As with field attributes, form attributes inherit a default from a
1833 system default form structure. These defaults can be queried or set by
1834 of these functions using a form-pointer argument of NULL.
1836 The principal attribute of a form is its field list. You can query and
1837 change this list with:
1838 int set_form_fields(FORM *form, /* form to alter */
1839 FIELD **fields); /* fields to connect */
1841 char *form_fields(FORM *form); /* fetch fields of form */
1843 int field_count(FORM *form); /* count connect fields */
1845 The second argument of set_form_fields() may be a NULL-terminated
1846 field pointer array like the one required by new_form(). In that case,
1847 the old fields of the form are disconnected but not freed (and
1848 eligible to be connected to other forms), then the new fields are
1851 It may also be null, in which case the old fields are disconnected
1852 (and not freed) but no new ones are connected.
1854 The field_count() function simply counts the number of fields
1855 connected to a given from. It returns -1 if the form-pointer argument
1858 Control of Form Display
1860 In the overview section, you saw that to display a form you normally
1861 start by defining its size (and fields), posting it, and refreshing
1862 the screen. There is an hidden step before posting, which is the
1863 association of the form with a frame window (actually, a pair of
1864 windows) within which it will be displayed. By default, the forms
1865 library associates every form with the full-screen window stdscr.
1867 By making this step explicit, you can associate a form with a declared
1868 frame window on your screen display. This can be useful if you want to
1869 adapt the form display to different screen sizes, dynamically tile
1870 forms on the screen, or use a form as part of an interface layout
1873 The two windows associated with each form have the same functions as
1874 their analogues in the menu library. Both these windows are painted
1875 when the form is posted and erased when the form is unposted.
1877 The outer or frame window is not otherwise touched by the form
1878 routines. It exists so the programmer can associate a title, a border,
1879 or perhaps help text with the form and have it properly refreshed or
1880 erased at post/unpost time. The inner window or subwindow is where the
1881 current form page is actually displayed.
1883 In order to declare your own frame window for a form, you'll need to
1884 know the size of the form's bounding rectangle. You can get this
1886 int scale_form(FORM *form, /* form to query */
1887 int *rows, /* form rows */
1888 int *cols); /* form cols */
1890 The form dimensions are passed back in the locations pointed to by the
1891 arguments. Once you have this information, you can use it to declare
1892 of windows, then use one of these functions:
1893 int set_form_win(FORM *form, /* form to alter */
1894 WINDOW *win); /* frame window to connect */
1896 WINDOW *form_win(FORM *form); /* fetch frame window of form */
1898 int set_form_sub(FORM *form, /* form to alter */
1899 WINDOW *win); /* form subwindow to connect */
1901 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
1903 Note that curses operations, including refresh(), on the form, should
1904 be done on the frame window, not the form subwindow.
1906 It is possible to check from your application whether all of a
1907 scrollable field is actually displayed within the menu subwindow. Use
1909 int data_ahead(FORM *form); /* form to be queried */
1911 int data_behind(FORM *form); /* form to be queried */
1913 The function data_ahead() returns TRUE if (a) the current field is
1914 one-line and has undisplayed data off to the right, (b) the current
1915 field is multi-line and there is data off-screen below it.
1917 The function data_behind() returns TRUE if the first (upper left hand)
1918 character position is off-screen (not being displayed).
1920 Finally, there is a function to restore the form window's cursor to
1921 the value expected by the forms driver:
1922 int pos_form_cursor(FORM *) /* form to be queried */
1924 If your application changes the form window cursor, call this function
1925 before handing control back to the forms driver in order to
1928 Input Processing in the Forms Driver
1930 The function form_driver() handles virtualized input requests for form
1931 navigation, editing, and validation requests, just as menu_driver does
1932 for menus (see the section on menu input handling).
1933 int form_driver(FORM *form, /* form to pass input to */
1934 int request); /* form request code */
1936 Your input virtualization function needs to take input and then
1937 convert it to either an alphanumeric character (which is treated as
1938 data to be entered in the currently-selected field), or a forms
1941 The forms driver provides hooks (through input-validation and
1942 field-termination functions) with which your application code can
1943 check that the input taken by the driver matched what was expected.
1945 Page Navigation Requests
1947 These requests cause page-level moves through the form, triggering
1948 display of a new form screen.
1951 Move to the next form page.
1954 Move to the previous form page.
1957 Move to the first form page.
1960 Move to the last form page.
1962 These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from
1963 the last page goes to the first, and REQ_PREV_PAGE from the first page
1966 Inter-Field Navigation Requests
1968 These requests handle navigation between fields on the same page.
1974 Move to previous field.
1977 Move to the first field.
1980 Move to the last field.
1983 Move to sorted next field.
1986 Move to sorted previous field.
1989 Move to the sorted first field.
1992 Move to the sorted last field.
1998 Move right to field.
2006 These requests treat the list of fields on a page as cyclic; that is,
2007 REQ_NEXT_FIELD from the last field goes to the first, and
2008 REQ_PREV_FIELD from the first field goes to the last. The order of the
2009 fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests)
2010 is simply the order of the field pointers in the form array (as set up
2011 by new_form() or set_form_fields()
2013 It is also possible to traverse the fields as if they had been sorted
2014 in screen-position order, so the sequence goes left-to-right and
2015 top-to-bottom. To do this, use the second group of four
2016 sorted-movement requests.
2018 Finally, it is possible to move between fields using visual directions
2019 up, down, right, and left. To accomplish this, use the third group of
2020 four requests. Note, however, that the position of a form for purposes
2021 of these requests is its upper-left corner.
2023 For example, suppose you have a multi-line field B, and two
2024 single-line fields A and C on the same line with B, with A to the left
2025 of B and C to the right of B. A REQ_MOVE_RIGHT from A will go to B
2026 only if A, B, and C all share the same first line; otherwise it will
2029 Intra-Field Navigation Requests
2031 These requests drive movement of the edit cursor within the currently
2035 Move to next character.
2038 Move to previous character.
2044 Move to previous line.
2050 Move to previous word.
2053 Move to beginning of field.
2056 Move to end of field.
2059 Move to beginning of line.
2062 Move to end of line.
2068 Move right in field.
2076 Each word is separated from the previous and next characters by
2077 whitespace. The commands to move to beginning and end of line or field
2078 look for the first or last non-pad character in their ranges.
2082 Fields that are dynamic and have grown and fields explicitly created
2083 with offscreen rows are scrollable. One-line fields scroll
2084 horizontally; multi-line fields scroll vertically. Most scrolling is
2085 triggered by editing and intra-field movement (the library scrolls the
2086 field to keep the cursor visible). It is possible to explicitly
2087 request scrolling with the following requests:
2090 Scroll vertically forward a line.
2093 Scroll vertically backward a line.
2096 Scroll vertically forward a page.
2099 Scroll vertically backward a page.
2102 Scroll vertically forward half a page.
2105 Scroll vertically backward half a page.
2108 Scroll horizontally forward a character.
2111 Scroll horizontally backward a character.
2114 Scroll horizontally one field width forward.
2117 Scroll horizontally one field width backward.
2120 Scroll horizontally one half field width forward.
2123 Scroll horizontally one half field width backward.
2125 For scrolling purposes, a page of a field is the height of its visible
2130 When you pass the forms driver an ASCII character, it is treated as a
2131 request to add the character to the field's data buffer. Whether this
2132 is an insertion or a replacement depends on the field's edit mode
2133 (insertion is the default.
2135 The following requests support editing the field and changing the edit
2145 New line request (see below for explanation).
2148 Insert space at character location.
2151 Insert blank line at character location.
2154 Delete character at cursor.
2157 Delete previous word at cursor.
2160 Delete line at cursor.
2163 Delete word at cursor.
2166 Clear to end of line.
2169 Clear to end of field.
2174 The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is
2175 complicated and partly controlled by a pair of forms options. The
2176 special cases are triggered when the cursor is at the beginning of a
2177 field, or on the last line of the field.
2179 First, we consider REQ_NEW_LINE:
2181 The normal behavior of REQ_NEW_LINE in insert mode is to break the
2182 current line at the position of the edit cursor, inserting the portion
2183 of the current line after the cursor as a new line following the
2184 current and moving the cursor to the beginning of that new line (you
2185 may think of this as inserting a newline in the field buffer).
2187 The normal behavior of REQ_NEW_LINE in overlay mode is to clear the
2188 current line from the position of the edit cursor to end of line. The
2189 cursor is then moved to the beginning of the next line.
2191 However, REQ_NEW_LINE at the beginning of a field, or on the last line
2192 of a field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is
2193 off, this special action is disabled.
2195 Now, let us consider REQ_DEL_PREV:
2197 The normal behavior of REQ_DEL_PREV is to delete the previous
2198 character. If insert mode is on, and the cursor is at the start of a
2199 line, and the text on that line will fit on the previous one, it
2200 instead appends the contents of the current line to the previous one
2201 and deletes the current line (you may think of this as deleting a
2202 newline from the field buffer).
2204 However, REQ_DEL_PREV at the beginning of a field is instead treated
2205 as a REQ_PREV_FIELD.
2207 If the O_BS_OVERLOAD option is off, this special action is disabled
2208 and the forms driver just returns E_REQUEST_DENIED.
2210 See Form Options for discussion of how to set and clear the overload
2215 If the type of your field is ordered, and has associated functions for
2216 getting the next and previous values of the type from a given value,
2217 there are requests that can fetch that value into the field buffer:
2220 Place the successor value of the current value in the buffer.
2223 Place the predecessor value of the current value in the buffer.
2225 Of the built-in field types, only TYPE_ENUM has built-in successor and
2226 predecessor functions. When you define a field type of your own (see
2227 Custom Validation Types), you can associate our own ordering
2230 Application Commands
2232 Form requests are represented as integers above the curses value
2233 greater than KEY_MAX and less than or equal to the constant
2234 MAX_COMMAND. If your input-virtualization routine returns a value
2235 above MAX_COMMAND, the forms driver will ignore it.
2239 It is possible to set function hooks to be executed whenever the
2240 current field or form changes. Here are the functions that support
2242 typedef void (*HOOK)(); /* pointer to function returning void */
2244 int set_form_init(FORM *form, /* form to alter */
2245 HOOK hook); /* initialization hook */
2247 HOOK form_init(FORM *form); /* form to query */
2249 int set_form_term(FORM *form, /* form to alter */
2250 HOOK hook); /* termination hook */
2252 HOOK form_term(FORM *form); /* form to query */
2254 int set_field_init(FORM *form, /* form to alter */
2255 HOOK hook); /* initialization hook */
2257 HOOK field_init(FORM *form); /* form to query */
2259 int set_field_term(FORM *form, /* form to alter */
2260 HOOK hook); /* termination hook */
2262 HOOK field_term(FORM *form); /* form to query */
2264 These functions allow you to either set or query four different hooks.
2265 In each of the set functions, the second argument should be the
2266 address of a hook function. These functions differ only in the timing
2270 This hook is called when the form is posted; also, just after
2271 each page change operation.
2274 This hook is called when the form is posted; also, just after
2278 This hook is called just after field validation; that is, just
2279 before the field is altered. It is also called when the form is
2283 This hook is called when the form is unposted; also, just
2284 before each page change operation.
2286 Calls to these hooks may be triggered
2287 1. When user editing requests are processed by the forms driver
2288 2. When the current page is changed by set_current_field() call
2289 3. When the current field is changed by a set_form_page() call
2291 See Field Change Commands for discussion of the latter two cases.
2293 You can set a default hook for all fields by passing one of the set
2294 functions a NULL first argument.
2296 You can disable any of these hooks by (re)setting them to NULL, the
2299 Field Change Commands
2301 Normally, navigation through the form will be driven by the user's
2302 input requests. But sometimes it is useful to be able to move the
2303 focus for editing and viewing under control of your application, or
2304 ask which field it currently is in. The following functions help you
2306 int set_current_field(FORM *form, /* form to alter */
2307 FIELD *field); /* field to shift to */
2309 FIELD *current_field(FORM *form); /* form to query */
2311 int field_index(FORM *form, /* form to query */
2312 FIELD *field); /* field to get index of */
2314 The function field_index() returns the index of the given field in the
2315 given form's field array (the array passed to new_form() or
2318 The initial current field of a form is the first active field on the
2319 first page. The function set_form_fields() resets this.
2321 It is also possible to move around by pages.
2322 int set_form_page(FORM *form, /* form to alter */
2323 int page); /* page to go to (0-origin) */
2325 int form_page(FORM *form); /* return form's current page */
2327 The initial page of a newly-created form is 0. The function
2328 set_form_fields() resets this.
2332 Like fields, forms may have control option bits. They can be changed
2333 or queried with these functions:
2334 int set_form_opts(FORM *form, /* form to alter */
2335 int attr); /* attribute to set */
2337 int form_opts_on(FORM *form, /* form to alter */
2338 int attr); /* attributes to turn on */
2340 int form_opts_off(FORM *form, /* form to alter */
2341 int attr); /* attributes to turn off */
2343 int form_opts(FORM *form); /* form to query */
2345 By default, all options are on. Here are the available option bits:
2348 Enable overloading of REQ_NEW_LINE as described in Editing
2349 Requests. The value of this option is ignored on dynamic fields
2350 that have not reached their size limit; these have no last
2351 line, so the circumstances for triggering a REQ_NEXT_FIELD
2355 Enable overloading of REQ_DEL_PREV as described in Editing
2358 The option values are bit-masks and can be composed with logical-or in
2361 Custom Validation Types
2363 The form library gives you the capability to define custom validation
2364 types of your own. Further, the optional additional arguments of
2365 set_field_type effectively allow you to parameterize validation types.
2366 Most of the complications in the validation-type interface have to do
2367 with the handling of the additional arguments within custom validation
2372 The simplest way to create a custom data type is to compose it from
2373 two preexisting ones:
2374 FIELD *link_fieldtype(FIELDTYPE *type1,
2377 This function creates a field type that will accept any of the values
2378 legal for either of its argument field types (which may be either
2379 predefined or programmer-defined). If a set_field_type() call later
2380 requires arguments, the new composite type expects all arguments for
2381 the first type, than all arguments for the second. Order functions
2382 (see Order Requests) associated with the component types will work on
2383 the composite; what it does is check the validation function for the
2384 first type, then for the second, to figure what type the buffer
2385 contents should be treated as.
2389 To create a field type from scratch, you need to specify one or both
2390 of the following things:
2391 * A character-validation function, to check each character as it is
2393 * A field-validation function to be applied on exit from the field.
2395 Here's how you do that:
2396 typedef int (*HOOK)(); /* pointer to function returning int */
2398 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
2399 HOOK c_validate) /* character validator */
2402 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
2404 At least one of the arguments of new_fieldtype() must be non-NULL. The
2405 forms driver will automatically call the new type's validation
2406 functions at appropriate points in processing a field of the new type.
2408 The function free_fieldtype() deallocates the argument fieldtype,
2409 freeing all storage associated with it.
2411 Normally, a field validator is called when the user attempts to leave
2412 the field. Its first argument is a field pointer, from which it can
2413 get to field buffer 0 and test it. If the function returns TRUE, the
2414 operation succeeds; if it returns FALSE, the edit cursor stays in the
2417 A character validator gets the character passed in as a first
2418 argument. It too should return TRUE if the character is valid, FALSE
2421 Validation Function Arguments
2423 Your field- and character- validation functions will be passed a
2424 second argument as well. This second argument is the address of a
2425 structure (which we'll call a pile) built from any of the
2426 field-type-specific arguments passed to set_field_type(). If no such
2427 arguments are defined for the field type, this pile pointer argument
2430 In order to arrange for such arguments to be passed to your validation
2431 functions, you must associate a small set of storage-management
2432 functions with the type. The forms driver will use these to synthesize
2433 a pile from the trailing arguments of each set_field_type() argument,
2434 and a pointer to the pile will be passed to the validation functions.
2436 Here is how you make the association:
2437 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
2438 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
2440 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2441 PTRHOOK make_str, /* make structure from args */
2442 PTRHOOK copy_str, /* make copy of structure */
2443 VOIDHOOK free_str); /* free structure storage */
2445 Here is how the storage-management hooks are used:
2448 This function is called by set_field_type(). It gets one
2449 argument, a va_list of the type-specific arguments passed to
2450 set_field_type(). It is expected to return a pile pointer to a
2451 data structure that encapsulates those arguments.
2454 This function is called by form library functions that allocate
2455 new field instances. It is expected to take a pile pointer,
2456 copy the pile to allocated storage, and return the address of
2460 This function is called by field- and type-deallocation
2461 routines in the library. It takes a pile pointer argument, and
2462 is expected to free the storage of that pile.
2464 The make_str and copy_str functions may return NULL to signal
2465 allocation failure. The library routines will that call them will
2466 return error indication when this happens. Thus, your validation
2467 functions should never see a NULL file pointer and need not check
2470 Order Functions For Custom Types
2472 Some custom field types are simply ordered in the same well-defined
2473 way that TYPE_ENUM is. For such types, it is possible to define
2474 successor and predecessor functions to support the REQ_NEXT_CHOICE and
2475 REQ_PREV_CHOICE requests. Here's how:
2476 typedef int (*INTHOOK)(); /* pointer to function returning int */
2478 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2479 INTHOOK succ, /* get successor value */
2480 INTHOOK pred); /* get predecessor value */
2482 The successor and predecessor arguments will each be passed two
2483 arguments; a field pointer, and a pile pointer (as for the validation
2484 functions). They are expected to use the function field_buffer() to
2485 read the current value, and set_field_buffer() on buffer 0 to set the
2486 next or previous value. Either hook may return TRUE to indicate
2487 success (a legal next or previous value was set) or FALSE to indicate
2492 The interface for defining custom types is complicated and tricky.
2493 Rather than attempting to create a custom type entirely from scratch,
2494 you should start by studying the library source code for whichever of
2495 the pre-defined types seems to be closest to what you want.
2497 Use that code as a model, and evolve it towards what you really want.
2498 You will avoid many problems and annoyances that way. The code in the
2499 ncurses library has been specifically exempted from the package
2500 copyright to support this.
2502 If your custom type defines order functions, have do something
2503 intuitive with a blank field. A useful convention is to make the
2504 successor of a blank field the types minimum value, and its
2505 predecessor the maximum.