2 Writing Programs with NCURSES
4 by Eric S. Raymond and Zeyd M. Ben-Halim
9 + A Brief History of Curses
10 + Scope of This Document
13 + An Overview of Curses
14 o Compiling Programs using Curses
16 o Standard Windows and Function Naming Conventions
22 o Using Forms Characters
23 o Character Attributes and Color
26 + Function Descriptions
27 o Initialization and Wrapup
28 o Causing Output to the Terminal
29 o Low-Level Capability Access
31 + Hints, Tips, and Tricks
32 o Some Notes of Caution
33 o Temporarily Leaving ncurses Mode
34 o Using ncurses under xterm
35 o Handling Multiple Terminal Screens
36 o Testing for Terminal Capabilities
38 o Special Features of ncurses
39 + Compatibility with Older Versions
40 o Refresh of Overlapping Windows
42 + XSI Curses Conformance
44 + Compiling With the Panels Library
46 + Panels, Input, and the Standard Screen
48 + Miscellaneous Other Facilities
50 + Compiling with the menu Library
55 + Processing Menu Input
56 + Miscellaneous Other Features
58 + Compiling with the forms Library
60 + Creating and Freeing Fields and Forms
61 + Fetching and Changing Field Attributes
62 o Fetching Size and Location Data
63 o Changing the Field Location
64 o The Justification Attribute
65 o Field Display Attributes
69 + Variable-Sized Fields
77 + Direct Field Buffer Manipulation
79 + Control of Form Display
80 + Input Processing in the Forms Driver
81 o Page Navigation Requests
82 o Inter-Field Navigation Requests
83 o Intra-Field Navigation Requests
85 o Field Editing Requests
87 o Application Commands
89 + Field Change Commands
91 + Custom Validation Types
94 o Validation Function Arguments
95 o Order Functions For Custom Types
97 _________________________________________________________________
101 This document is an introduction to programming with curses. It is not
102 an exhaustive reference for the curses Application Programming
103 Interface (API); that role is filled by the curses manual pages.
104 Rather, it is intended to help C programmers ease into using the
107 This document is aimed at C applications programmers not yet
108 specifically familiar with ncurses. If you are already an experienced
109 curses programmer, you should nevertheless read the sections on Mouse
110 Interfacing, Debugging, Compatibility with Older Versions, and Hints,
111 Tips, and Tricks. These will bring you up to speed on the special
112 features and quirks of the ncurses implementation. If you are not so
113 experienced, keep reading.
115 The curses package is a subroutine library for terminal-independent
116 screen-painting and input-event handling which presents a high level
117 screen model to the programmer, hiding differences between terminal
118 types and doing automatic optimization of output to change one screen
119 full of text into another. Curses uses terminfo, which is a database
120 format that can describe the capabilities of thousands of different
123 The curses API may seem something of an archaism on UNIX desktops
124 increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX
125 still supports tty lines and X supports xterm(1); the curses API has
126 the advantage of (a) back-portability to character-cell terminals, and
127 (b) simplicity. For an application that does not require bit-mapped
128 graphics and multiple fonts, an interface implementation using curses
129 will typically be a great deal simpler and less expensive than one
132 A Brief History of Curses
134 Historically, the first ancestor of curses was the routines written to
135 provide screen-handling for the game rogue; these used the
136 already-existing termcap database facility for describing terminal
137 capabilities. These routines were abstracted into a documented library
138 and first released with the early BSD UNIX versions.
140 System III UNIX from Bell Labs featured a rewritten and much-improved
141 curses library. It introduced the terminfo format. Terminfo is based
142 on Berkeley's termcap database, but contains a number of improvements
143 and extensions. Parameterized capabilities strings were introduced,
144 making it possible to describe multiple video attributes, and colors
145 and to handle far more unusual terminals than possible with termcap.
146 In the later AT&T System V releases, curses evolved to use more
147 facilities and offer more capabilities, going far beyond BSD curses in
148 power and flexibility.
150 Scope of This Document
152 This document describes ncurses, a freeware implementation of the
153 System V curses API with some clearly marked extensions. It includes
154 the 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 the 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:
342 static void finish(int sig);
344 main(int argc, char *argv[])
346 /* initialize your non-curses data structures here */
348 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
350 (void) initscr(); /* initialize the curses library */
351 keypad(stdscr, TRUE); /* enable keyboard mapping */
352 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
353 (void) cbreak(); /* take input chars one at a time, no wait for \n */
354 (void) noecho(); /* don't echo input */
361 * Simple color assignment, often all we need.
363 init_pair(COLOR_BLACK, COLOR_BLACK, COLOR_BLACK);
364 init_pair(COLOR_GREEN, COLOR_GREEN, COLOR_BLACK);
365 init_pair(COLOR_RED, COLOR_RED, COLOR_BLACK);
366 init_pair(COLOR_CYAN, COLOR_CYAN, COLOR_BLACK);
367 init_pair(COLOR_WHITE, COLOR_WHITE, COLOR_BLACK);
368 init_pair(COLOR_MAGENTA, COLOR_MAGENTA, COLOR_BLACK);
369 init_pair(COLOR_BLUE, COLOR_BLUE, COLOR_BLACK);
370 init_pair(COLOR_YELLOW, COLOR_YELLOW, COLOR_BLACK);
375 int c = getch(); /* refresh, accept single keystroke of input */
377 /* process the command keystroke */
380 finish(0); /* we're done */
383 static void finish(int sig)
387 /* do your non-curses wrapup here */
394 In order to use the screen package, the routines must know about
395 terminal characteristics, and the space for curscr and stdscr must be
396 allocated. These function initscr() does both these things. Since it
397 must allocate space for the windows, it can overflow memory when
398 attempting to do so. On the rare occasions this happens, initscr()
399 will terminate the program with an error message. initscr() must
400 always be called before any of the routines which affect windows are
401 used. If it is not, the program will core dump as soon as either
402 curscr or stdscr are referenced. However, it is usually best to wait
403 to call it until after you are sure you will need it, like after
404 checking for startup errors. Terminal status changing routines like
405 nl() and cbreak() should be called after initscr().
407 Once the screen windows have been allocated, you can set them up for
408 your program. If you want to, say, allow a screen to scroll, use
409 scrollok(). If you want the cursor to be left in place after the last
410 change, use leaveok(). If this isn't done, refresh() will move the
411 cursor to the window's current (y, x) coordinates after updating it.
413 You can create new windows of your own using the functions newwin(),
414 derwin(), and subwin(). The routine delwin() will allow you to get rid
415 of old windows. All the options described above can be applied to any
420 Now that we have set things up, we will want to actually update the
421 terminal. The basic functions used to change what will go on a window
422 are addch() and move(). addch() adds a character at the current (y, x)
423 coordinates. move() changes the current (y, x) coordinates to whatever
424 you want them to be. It returns ERR if you try to move off the window.
425 As mentioned above, you can combine the two into mvaddch() to do both
428 The other output functions, such as addstr() and printw(), all call
429 addch() to add characters to the window.
431 After you have put on the window what you want there, when you want
432 the portion of the terminal covered by the window to be made to look
433 like it, you must call refresh(). In order to optimize finding
434 changes, refresh() assumes that any part of the window not changed
435 since the last refresh() of that window has not been changed on the
436 terminal, i.e., that you have not refreshed a portion of the terminal
437 with an overlapping window. If this is not the case, the routine
438 touchwin() is provided to make it look like the entire window has been
439 changed, thus making refresh() check the whole subsection of the
440 terminal for changes.
442 If you call wrefresh() with curscr as its argument, it will make the
443 screen look like curscr thinks it looks like. This is useful for
444 implementing a command which would redraw the screen in case it get
449 The complementary function to addch() is getch() which, if echo is
450 set, will call addch() to echo the character. Since the screen package
451 needs to know what is on the terminal at all times, if characters are
452 to be echoed, the tty must be in raw or cbreak mode. Since initially
453 the terminal has echoing enabled and is in ordinary ``cooked'' mode,
454 one or the other has to changed before calling getch(); otherwise, the
455 program's output will be unpredictable.
457 When you need to accept line-oriented input in a window, the functions
458 wgetstr() and friends are available. There is even a wscanw() function
459 that can do scanf()(3)-style multi-field parsing on window input.
460 These pseudo-line-oriented functions turn on echoing while they
463 The example code above uses the call keypad(stdscr, TRUE) to enable
464 support for function-key mapping. With this feature, the getch() code
465 watches the input stream for character sequences that correspond to
466 arrow and function keys. These sequences are returned as
467 pseudo-character values. The #define values returned are listed in the
468 curses.h The mapping from sequences to #define values is determined by
469 key_ capabilities in the terminal's terminfo entry.
471 Using Forms Characters
473 The addch() function (and some others, including box() and border())
474 can accept some pseudo-character arguments which are specially defined
475 by ncurses. These are #define values set up in the curses.h header;
476 see there for a complete list (look for the prefix ACS_).
478 The most useful of the ACS defines are the forms-drawing characters.
479 You can use these to draw boxes and simple graphs on the screen. If
480 the terminal does not have such characters, curses.h will map them to
481 a recognizable (though ugly) set of ASCII defaults.
483 Character Attributes and Color
485 The ncurses package supports screen highlights including standout,
486 reverse-video, underline, and blink. It also supports color, which is
487 treated as another kind of highlight.
489 Highlights are encoded, internally, as high bits of the
490 pseudo-character type (chtype) that curses.h uses to represent the
491 contents of a screen cell. See the curses.h header file for a complete
492 list of highlight mask values (look for the prefix A_).
494 There are two ways to make highlights. One is to logical-or the value
495 of the highlights you want into the character argument of an addch()
496 call, or any other output call that takes a chtype argument.
498 The other is to set the current-highlight value. This is logical-or'ed
499 with any highlight you specify the first way. You do this with the
500 functions attron(), attroff(), and attrset(); see the manual pages for
501 details. Color is a special kind of highlight. The package actually
502 thinks in terms of color pairs, combinations of foreground and
503 background colors. The sample code above sets up eight color pairs,
504 all of the guaranteed-available colors on black. Note that each color
505 pair is, in effect, given the name of its foreground color. Any other
506 range of eight non-conflicting values could have been used as the
507 first arguments of the init_pair() values.
509 Once you've done an init_pair() that creates color-pair N, you can use
510 COLOR_PAIR(N) as a highlight that invokes that particular color
511 combination. Note that COLOR_PAIR(N), for constant N, is itself a
512 compile-time constant and can be used in initializers.
516 The ncurses library also provides a mouse interface. Note: his
517 facility is original to ncurses, it is not part of either the XSI
518 Curses standard, nor of System V Release 4, nor BSD curses. Thus, we
519 recommend that you wrap mouse-related code in an #ifdef using the
520 feature macro NCURSES_MOUSE_VERSION so it will not be compiled and
521 linked on non-ncurses systems.
523 Presently, mouse event reporting works only under xterm. In the
524 future, ncurses will detect the presence of gpm(1), Alessandro
525 Rubini's freeware mouse server for Linux systems, and accept mouse
528 The mouse interface is very simple. To activate it, you use the
529 function mousemask(), passing it as first argument a bit-mask that
530 specifies what kinds of events you want your program to be able to
531 see. It will return the bit-mask of events that actually become
532 visible, which may differ from the argument if the mouse device is not
533 capable of reporting some of the event types you specify.
535 Once the mouse is active, your application's command loop should watch
536 for a return value of KEY_MOUSE from wgetch(). When you see this, a
537 mouse event report has been queued. To pick it off the queue, use the
538 function getmouse() (you must do this before the next wgetch(),
539 otherwise another mouse event might come in and make the first one
542 Each call to getmouse() fills a structure (the address of which you'll
543 pass it) with mouse event data. The event data includes zero-origin,
544 screen-relative character-cell coordinates of the mouse pointer. It
545 also includes an event mask. Bits in this mask will be set,
546 corresponding to the event type being reported.
548 The mouse structure contains two additional fields which may be
549 significant in the future as ncurses interfaces to new kinds of
550 pointing device. In addition to x and y coordinates, there is a slot
551 for a z coordinate; this might be useful with touch-screens that can
552 return a pressure or duration parameter. There is also a device ID
553 field, which could be used to distinguish between multiple pointing
556 The class of visible events may be changed at any time via
557 mousemask(). Events that can be reported include presses, releases,
558 single-, double- and triple-clicks (you can set the maximum
559 button-down time for clicks). If you don't make clicks visible, they
560 will be reported as press-release pairs. In some environments, the
561 event mask may include bits reporting the state of shift, alt, and
562 ctrl keys on the keyboard during the event.
564 A function to check whether a mouse event fell within a given window
565 is also supplied. You can use this to see whether a given window
566 should consider a mouse event relevant to it.
568 Because mouse event reporting will not be available in all
569 environments, it would be unwise to build ncurses applications that
570 require the use of a mouse. Rather, you should use the mouse as a
571 shortcut for point-and-shoot commands your application would normally
572 accept from the keyboard. Two of the test games in the ncurses
573 distribution (bs and knight) contain code that illustrates how this
576 See the manual page curs_mouse(3X) for full details of the
577 mouse-interface functions.
581 In order to clean up after the ncurses routines, the routine endwin()
582 is provided. It restores tty modes to what they were when initscr()
583 was first called, and moves the cursor down to the lower-left corner.
584 Thus, anytime after the call to initscr, endwin() should be called
587 Function Descriptions
589 We describe the detailed behavior of some important curses functions
590 here, as a supplement to the manual page descriptions.
592 Initialization and Wrapup
595 The first function called should almost always be initscr().
596 This will determine the terminal type and initialize curses
597 data structures. initscr() also arranges that the first call to
598 refresh() will clear the screen. If an error occurs a message
599 is written to standard error and the program exits. Otherwise
600 it returns a pointer to stdscr. A few functions may be called
601 before initscr (slk_init(), filter(), ripofflines(), use_env(),
602 and, if you are using multiple terminals, newterm().)
605 Your program should always call endwin() before exiting or
606 shelling out of the program. This function will restore tty
607 modes, move the cursor to the lower left corner of the screen,
608 reset the terminal into the proper non-visual mode. Calling
609 refresh() or doupdate() after a temporary escape from the
610 program will restore the ncurses screen from before the escape.
612 newterm(type, ofp, ifp)
613 A program which outputs to more than one terminal should use
614 newterm() instead of initscr(). newterm() should be called once
615 for each terminal. It returns a variable of type SCREEN * which
616 should be saved as a reference to that terminal. The arguments
617 are the type of the terminal (a string) and FILE pointers for
618 the output and input of the terminal. If type is NULL then the
619 environment variable $TERM is used. endwin() should called once
620 at wrapup time for each terminal opened using this function.
623 This function is used to switch to a different terminal
624 previously opened by newterm(). The screen reference for the
625 new terminal is passed as the parameter. The previous terminal
626 is returned by the function. All other calls affect only the
630 The inverse of newterm(); deallocates the data structures
631 associated with a given SCREEN reference.
633 Causing Output to the Terminal
635 refresh() and wrefresh(win)
636 These functions must be called to actually get any output on
637 the terminal, as other routines merely manipulate data
638 structures. wrefresh() copies the named window to the physical
639 terminal screen, taking into account what is already there in
640 order to do optimizations. refresh() does a refresh of
641 stdscr(). Unless leaveok() has been enabled, the physical
642 cursor of the terminal is left at the location of the window's
645 doupdate() and wnoutrefresh(win)
646 These two functions allow multiple updates with more efficiency
647 than wrefresh. To use them, it is important to understand how
648 curses works. In addition to all the window structures, curses
649 keeps two data structures representing the terminal screen: a
650 physical screen, describing what is actually on the screen, and
651 a virtual screen, describing what the programmer wants to have
652 on the screen. wrefresh works by first copying the named window
653 to the virtual screen (wnoutrefresh()), and then calling the
654 routine to update the screen (doupdate()). If the programmer
655 wishes to output several windows at once, a series of calls to
656 wrefresh will result in alternating calls to wnoutrefresh() and
657 doupdate(), causing several bursts of output to the screen. By
658 calling wnoutrefresh() for each window, it is then possible to
659 call doupdate() once, resulting in only one burst of output,
660 with fewer total characters transmitted (this also avoids a
661 visually annoying flicker at each update).
663 Low-Level Capability Access
665 setupterm(term, filenum, errret)
666 This routine is called to initialize a terminal's description,
667 without setting up the curses screen structures or changing the
668 tty-driver mode bits. term is the character string representing
669 the name of the terminal being used. filenum is the UNIX file
670 descriptor of the terminal to be used for output. errret is a
671 pointer to an integer, in which a success or failure indication
672 is returned. The values returned can be 1 (all is well), 0 (no
673 such terminal), or -1 (some problem locating the terminfo
676 The value of term can be given as NULL, which will cause the
677 value of TERM in the environment to be used. The errret pointer
678 can also be given as NULL, meaning no error code is wanted. If
679 errret is defaulted, and something goes wrong, setupterm() will
680 print an appropriate error message and exit, rather than
681 returning. Thus, a simple program can call setupterm(0, 1, 0)
682 and not worry about initialization errors.
684 After the call to setupterm(), the global variable cur_term is
685 set to point to the current structure of terminal capabilities.
686 By calling setupterm() for each terminal, and saving and
687 restoring cur_term, it is possible for a program to use two or
688 more terminals at once. Setupterm() also stores the names
689 section of the terminal description in the global character
690 array ttytype[]. Subsequent calls to setupterm() will overwrite
691 this array, so you'll have to save it yourself if need be.
695 NOTE: These functions are not part of the standard curses API!
698 This function can be used to explicitly set a trace level. If
699 the trace level is nonzero, execution of your program will
700 generate a file called `trace' in the current working directory
701 containing a report on the library's actions. Higher trace
702 levels enable more detailed (and verbose) reporting -- see
703 comments attached to TRACE_ defines in the curses.h file for
704 details. (It is also possible to set a trace level by assigning
705 a trace level value to the environment variable NCURSES_TRACE).
708 This function can be used to output your own debugging
709 information. It is only available only if you link with
710 -lncurses_g. It can be used the same way as printf(), only it
711 outputs a newline after the end of arguments. The output goes
712 to a file called trace in the current directory.
714 Trace logs can be difficult to interpret due to the sheer volume of
715 data dumped in them. There is a script called tracemunch included with
716 the ncurses distribution that can alleviate this problem somewhat; it
717 compacts long sequences of similar operations into more succinct
718 single-line pseudo-operations. These pseudo-ops can be distinguished
719 by the fact that they are named in capital letters.
721 Hints, Tips, and Tricks
723 The ncurses manual pages are a complete reference for this library. In
724 the remainder of this document, we discuss various useful methods that
725 may not be obvious from the manual page descriptions.
727 Some Notes of Caution
729 If you find yourself thinking you need to use noraw() or nocbreak(),
730 think again and move carefully. It's probably better design to use
731 getstr() or one of its relatives to simulate cooked mode. The noraw()
732 and nocbreak() functions try to restore cooked mode, but they may end
733 up clobbering some control bits set before you started your
734 application. Also, they have always been poorly documented, and are
735 likely to hurt your application's usability with other curses
738 Bear in mind that refresh() is a synonym for wrefresh(stdscr), and
739 don't try to mix use of stdscr with use of windows declared by
740 newwin(); a refresh() call will blow them off the screen. The right
741 way to handle this is to use subwin(), or not touch stdscr at all and
742 tile your screen with declared windows which you then wnoutrefresh()
743 somewhere in your program event loop, with a single doupdate() call to
744 trigger actual repainting.
746 You are much less likely to run into problems if you design your
747 screen layouts to use tiled rather than overlapping windows.
748 Historically, curses support for overlapping windows has been weak,
749 fragile, and poorly documented. The ncurses library is not yet an
750 exception to this rule.
752 There is a freeware panels library included in the ncurses
753 distribution that does a pretty good job of strengthening the
754 overlapping-windows facilities.
756 Try to avoid using the global variables LINES and COLS. Use getmaxyx()
757 on the stdscr context instead. Reason: your code may be ported to run
758 in an environment with window resizes, in which case several screens
759 could be open with different sizes.
761 Temporarily Leaving ncurses Mode
763 Sometimes you will want to write a program that spends most of its
764 time in screen mode, but occasionally returns to ordinary `cooked'
765 mode. A common reason for this is to support shell-out. This behavior
766 is simple to arrange in ncurses.
768 To leave ncurses mode, call endwin() as you would if you were
769 intending to terminate the program. This will take the screen back to
770 cooked mode; you can do your shell-out. When you want to return to
771 ncurses mode, simply call refresh() or doupdate(). This will repaint
774 There is a boolean function, isendwin(), which code can use to test
775 whether ncurses screen mode is active. It returns TRUE in the interval
776 between an endwin() call and the following refresh(), FALSE otherwise.
778 Here is some sample code for shellout:
779 addstr("Shelling out...");
780 def_prog_mode(); /* save current tty modes */
781 endwin(); /* restore original tty modes */
782 system("sh"); /* run shell */
783 addstr("returned.\n"); /* prepare return message */
784 refresh(); /* restore save modes, repaint screen */
786 Using ncurses Under xterm
788 A resize operation in X sends SIGWINCH to the application running
789 under xterm. The ncurses library does not catch this signal, because
790 it cannot in general know how you want the screen re-painted. You will
791 have to write the SIGWINCH handler yourself.
793 The easiest way to code your SIGWINCH handler is to have it do an
794 endwin, followed by an refresh and a screen repaint you code yourself.
795 The refresh will pick up the new screen size from the xterm's
798 Handling Multiple Terminal Screens
800 The initscr() function actually calls a function named newterm() to do
801 most of its work. If you are writing a program that opens multiple
802 terminals, use newterm() directly.
804 For each call, you will have to specify a terminal type and a pair of
805 file pointers; each call will return a screen reference, and stdscr
806 will be set to the last one allocated. You will switch between screens
807 with the set_term call. Note that you will also have to call
808 def_shell_mode and def_prog_mode on each tty yourself.
810 Testing for Terminal Capabilities
812 Sometimes you may want to write programs that test for the presence of
813 various capabilities before deciding whether to go into ncurses mode.
814 An easy way to do this is to call setupterm(), then use the functions
815 tigetflag(), tigetnum(), and tigetstr() to do your testing.
817 A particularly useful case of this often comes up when you want to
818 test whether a given terminal type should be treated as `smart'
819 (cursor-addressable) or `stupid'. The right way to test this is to see
820 if the return value of tigetstr("cup") is non-NULL. Alternatively, you
821 can include the term.h file and test the value of the macro
826 Use the addchstr() family of functions for fast screen-painting of
827 text when you know the text doesn't contain any control characters.
828 Try to make attribute changes infrequent on your screens. Don't use
829 the immedok() option!
831 Special Features of ncurses
833 When running on PC-clones, ncurses has enhanced support for the IBM
834 high-half and ROM characters. The A_ALTCHARSET highlight, enables
835 display of both high-half ACS graphics and the PC ROM graphics 0-31
836 that are normally interpreted as control characters.
838 The wresize() function allows you to resize a window in place.
840 Compatibility with Older Versions
842 Despite our best efforts, there are some differences between ncurses
843 and the (undocumented!) behavior of older curses implementations.
844 These arise from ambiguities or omissions in the documentation of the
847 Refresh of Overlapping Windows
849 If you define two windows A and B that overlap, and then alternately
850 scribble on and refresh them, the changes made to the overlapping
851 region under historic curses versions were often not documented
854 To understand why this is a problem, remember that screen updates are
855 calculated between two representations of the entire display. The
856 documentation says that when you refresh a window, it is first copied
857 to to the virtual screen, and then changes are calculated to update
858 the physical screen (and applied to the terminal). But "copied to" is
859 not very specific, and subtle differences in how copying works can
860 produce different behaviors in the case where two overlapping windows
861 are each being refreshed at unpredictable intervals.
863 What happens to the overlapping region depends on what wnoutrefresh()
864 does with its argument -- what portions of the argument window it
865 copies to the virtual screen. Some implementations do "change copy",
866 copying down only locations in the window that have changed (or been
867 marked changed with wtouchln() and friends). Some implementations do
868 "entire copy", copying all window locations to the virtual screen
869 whether or not they have changed.
871 The ncurses library itself has not always been consistent on this
872 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy.
873 Versions 1.8.6 and older, and versions 1.9.9 and newer, do change
876 For most commercial curses implementations, it is not documented and
877 not known for sure (at least not to the ncurses maintainers) whether
878 they do change copy or entire copy. We know that System V release 3
879 curses has logic in it that looks like an attempt to do change copy,
880 but the surrounding logic and data representations are sufficiently
881 complex, and our knowledge sufficiently indirect, that it's hard to
882 know whether this is reliable. It is not clear what the SVr4
883 documentation and XSI standard intend. The XSI Curses standard barely
884 mentions wnoutrefresh(); the SVr4 documents seem to be describing
885 entire-copy, but it is possible with some effort and straining to read
888 It might therefore be unwise to rely on either behavior in programs
889 that might have to be linked with other curses implementations.
890 Instead, you can do an explicit touchwin() before the wnoutrefresh()
891 call to guarantee an entire-contents copy anywhere.
893 The really clean way to handle this is to use the panels library. If,
894 when you want a screen update, you do update_panels(), it will do all
895 the necessary wnoutrfresh() calls for whatever panel stacking order
896 you have defined. Then you can do one doupdate() and there will be a
897 single burst of physical I/O that will do all your updates.
901 If you have been using a very old versions of ncurses (1.8.7 or older)
902 you may be surprised by the behavior of the erase functions. In older
903 versions, erased areas of a window were filled with a blank modified
904 by the window's current attribute (as set by wattrset(), wattron(),
905 wattroff() and friends).
907 In newer versions, this is not so. Instead, the attribute of erased
908 blanks is normal unless and until it is modified by the functions
909 bkgdset() or wbkgdset().
911 This change in behavior conforms ncurses to System V Release 4 and the
914 XSI Curses Conformance
916 The ncurses library is intended to be base-level conformant with the
917 XSI Curses standard from X/Open. Many extended-level features (in
918 fact, almost all features not directly concerned with wide characters
919 and internationalization) are also supported.
921 One effect of XSI conformance is the change in behavior described
922 under "Background Erase -- Compatibility with Old Versions".
924 Also, ncurses meets the XSI requirement that every macro entry point
925 have a corresponding function which may be linked (and will be
926 prototype-checked) if the macro definition is disabled with #undef.
930 The ncurses library by itself provides good support for screen
931 displays in which the windows are tiled (non-overlapping). In the more
932 general case that windows may overlap, you have to use a series of
933 wnoutrefresh() calls followed by a doupdate(), and be careful about
934 the order you do the window refreshes in. It has to be bottom-upwards,
935 otherwise parts of windows that should be obscured will show through.
937 When your interface design is such that windows may dive deeper into
938 the visibility stack or pop to the top at runtime, the resulting
939 book-keeping can be tedious and difficult to get right. Hence the
942 The panel library first appeared in AT&T System V. The version
943 documented here is the freeware panel code distributed with ncurses.
945 Compiling With the Panels Library
947 Your panels-using modules must import the panels library declarations
951 and must be linked explicitly with the panels library using an -lpanel
952 argument. Note that they must also link the ncurses library with
953 -lncurses. Many linkers are two-pass and will accept either order, but
954 it is still good practice to put -lpanel first and -lncurses second.
958 A panel object is a window that is implicitly treated as part of a
959 deck including all other panel objects. The deck has an implicit
960 bottom-to-top visibility order. The panels library includes an update
961 function (analogous to refresh()) that displays all panels in the deck
962 in the proper order to resolve overlaps. The standard window, stdscr,
963 is considered below all panels.
965 Details on the panels functions are available in the man pages. We'll
966 just hit the highlights here.
968 You create a panel from a window by calling new_panel() on a window
969 pointer. It then becomes the top of the deck. The panel's window is
970 available as the value of panel_window() called with the panel pointer
973 You can delete a panel (removing it from the deck) with del_panel.
974 This will not deallocate the associated window; you have to do that
975 yourself. You can replace a panel's window with a different window by
976 calling replace_window. The new window may be of different size; the
977 panel code will re-compute all overlaps. This operation doesn't change
978 the panel's position in the deck.
980 To move a panel's window, use move_panel(). The mvwin() function on
981 the panel's window isn't sufficient because it doesn't update the
982 panels library's representation of where the windows are. This
983 operation leaves the panel's depth, contents, and size unchanged.
985 Two functions (top_panel(), bottom_panel()) are provided for
986 rearranging the deck. The first pops its argument window to the top of
987 the deck; the second sends it to the bottom. Either operation leaves
988 the panel's screen location, contents, and size unchanged.
990 The function update_panels() does all the wnoutrefresh() calls needed
991 to prepare for doupdate() (which you must call yourself, afterwards).
993 Typically, you will want to call update_panels() and doupdate() just
994 before accepting command input, once in each cycle of interaction with
995 the user. If you call update_panels() after each and every panel
996 write, you'll generate a lot of unnecessary refresh activity and
999 Panels, Input, and the Standard Screen
1001 You shouldn't mix wnoutrefresh() or wrefresh() operations with panels
1002 code; this will work only if the argument window is either in the top
1003 panel or unobscured by any other panels.
1005 The stsdcr window is a special case. It is considered below all
1006 panels. Because changes to panels may obscure parts of stdscr, though,
1007 you should call update_panels() before doupdate() even when you only
1010 Note that wgetch automatically calls wrefresh. Therefore, before
1011 requesting input from a panel window, you need to be sure that the
1012 panel is totally unobscured.
1014 There is presently no way to display changes to one obscured panel
1015 without repainting all panels.
1019 It's possible to remove a panel from the deck temporarily; use
1020 hide_panel for this. Use show_panel() to render it visible again. The
1021 predicate function panel_hidden tests whether or not a panel is
1024 The panel_update code ignores hidden panels. You cannot do top_panel()
1025 or bottom_panel on a hidden panel(). Other panels operations are
1028 Miscellaneous Other Facilities
1030 It's possible to navigate the deck using the functions panel_above()
1031 and panel_below. Handed a panel pointer, they return the panel above
1032 or below that panel. Handed NULL, they return the bottom-most or
1035 Every panel has an associated user pointer, not used by the panel
1036 code, to which you can attach application data. See the man page
1037 documentation of set_panel_userptr() and panel_userptr for details.
1041 A menu is a screen display that assists the user to choose some subset
1042 of a given set of items. The menu library is a curses extension that
1043 supports easy programming of menu hierarchies with a uniform but
1046 The menu library first appeared in AT&T System V. The version
1047 documented here is the freeware menu code distributed with ncurses.
1049 Compiling With the menu Library
1051 Your menu-using modules must import the menu library declarations with
1054 and must be linked explicitly with the menus library using an -lmenu
1055 argument. Note that they must also link the ncurses library with
1056 -lncurses. Many linkers are two-pass and will accept either order, but
1057 it is still good practice to put -lmenu first and -lncurses second.
1061 The menus created by this library consist of collections of items
1062 including a name string part and a description string part. To make
1063 menus, you create groups of these items and connect them with menu
1066 The menu can then by posted, that is written to an associated window.
1067 Actually, each menu has two associated windows; a containing window in
1068 which the programmer can scribble titles or borders, and a subwindow
1069 in which the menu items proper are displayed. If this subwindow is too
1070 small to display all the items, it will be a scrollable viewport on
1071 the collection of items.
1073 A menu may also be unposted (that is, undisplayed), and finally freed
1074 to make the storage associated with it and its items available for
1077 The general flow of control of a menu program looks like this:
1078 1. Initialize curses.
1079 2. Create the menu items, using new_item().
1080 3. Create the menu using new_menu().
1081 4. Post the menu using menu_post().
1082 5. Refresh the screen.
1083 6. Process user requests via an input loop.
1084 7. Unpost the menu using menu_unpost().
1085 8. Free the menu, using free_menu().
1086 9. Free the items using free_item().
1087 10. Terminate curses.
1091 Menus may be multi-valued or (the default) single-valued (see the
1092 manual page menu_opts(3x) to see how to change the default). Both
1093 types always have a current item.
1095 From a single-valued menu you can read the selected value simply by
1096 looking at the current item. From a multi-valued menu, you get the
1097 selected set by looping through the items applying the item_value()
1098 predicate function. Your menu-processing code can use the function
1099 set_item_value() to flag the items in the select set.
1101 Menu items can be made unselectable using set_item_opts() or
1102 item_opts_off() with the O_SELECTABLE argument. This is the only
1103 option so far defined for menus, but it is good practice to code as
1104 though other option bits might be on.
1108 The menu library calculates a minimum display size for your window,
1109 based on the following variables:
1111 * The number and maximum length of the menu items
1112 * Whether the O_ROWMAJOR option is enabled
1113 * Whether display of descriptions is enabled
1114 * Whatever menu format may have been set by the programmer
1115 * The length of the menu mark string used for highlighting selected
1118 The function set_menu_format() allows you to set the maximum size of
1119 the viewport or menu page that will be used to display menu items. You
1120 can retrieve any format associated with a menu with menu_format(). The
1121 default format is rows=16, columns=1.
1123 The actual menu page may be smaller than the format size. This depends
1124 on the item number and size and whether O_ROWMAJOR is on. This option
1125 (on by default) causes menu items to be displayed in a `raster-scan'
1126 pattern, so that if more than one item will fit horizontally the first
1127 couple of items are side-by-side in the top row. The alternative is
1128 column-major display, which tries to put the first several items in
1131 As mentioned above, a menu format not large enough to allow all items
1132 to fit on-screen will result in a menu display that is vertically
1135 You can scroll it with requests to the menu driver, which will be
1136 described in the section on menu input handling.
1138 Each menu has a mark string used to visually tag selected items; see
1139 the menu_mark(3x) manual page for details. The mark string length also
1140 influences the menu page size.
1142 The function scale_menu() returns the minimum display size that the
1143 menu code computes from all these factors. There are other menu
1144 display attributes including a select attribute, an attribute for
1145 selectable items, an attribute for unselectable items, and a pad
1146 character used to separate item name text from description text. These
1147 have reasonable defaults which the library allows you to change (see
1148 the menu_attribs(3x) manual page.
1152 Each menu has, as mentioned previously, a pair of associated windows.
1153 Both these windows are painted when the menu is posted and erased when
1154 the menu is unposted.
1156 The outer or frame window is not otherwise touched by the menu
1157 routines. It exists so the programmer can associate a title, a border,
1158 or perhaps help text with the menu and have it properly refreshed or
1159 erased at post/unpost time. The inner window or subwindow is where the
1160 current menu page is displayed.
1162 By default, both windows are stdscr. You can set them with the
1163 functions in menu_win(3x).
1165 When you call menu_post(), you write the menu to its subwindow. When
1166 you call menu_unpost(), you erase the subwindow, However, neither of
1167 these actually modifies the screen. To do that, call wrefresh() or
1170 Processing Menu Input
1172 The main loop of your menu-processing code should call menu_driver()
1173 repeatedly. The first argument of this routine is a menu pointer; the
1174 second is a menu command code. You should write an input-fetching
1175 routine that maps input characters to menu command codes, and pass its
1176 output to menu_driver(). The menu command codes are fully documented
1179 The simplest group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM,
1180 REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_UP_ITEM, REQ_DOWN_ITEM,
1181 REQ_LEFT_ITEM, REQ_RIGHT_ITEM. These change the currently selected
1182 item. These requests may cause scrolling of the menu page if it only
1183 partially displayed.
1185 There are explicit requests for scrolling which also change the
1186 current item (because the select location does not change, but the
1187 item there does). These are REQ_SCR_DLINE, REQ_SCR_ULINE,
1188 REQ_SCR_DPAGE, and REQ_SCR_UPAGE.
1190 The REQ_TOGGLE_ITEM selects or deselects the current item. It is for
1191 use in multi-valued menus; if you use it with O_ONEVALUE on, you'll
1192 get an error return (E_REQUEST_DENIED).
1194 Each menu has an associated pattern buffer. The menu_driver() logic
1195 tries to accumulate printable ASCII characters passed in in that
1196 buffer; when it matches a prefix of an item name, that item (or the
1197 next matching item) is selected. If appending a character yields no
1198 new match, that character is deleted from the pattern buffer, and
1199 menu_driver() returns E_NO_MATCH.
1201 Some requests change the pattern buffer directly: REQ_CLEAR_PATTERN,
1202 REQ_BACK_PATTERN, REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter two are
1203 useful when pattern buffer input matches more than one item in a
1206 Each successful scroll or item navigation request clears the pattern
1207 buffer. It is also possible to set the pattern buffer explicitly with
1210 Finally, menu driver requests above the constant MAX_COMMAND are
1211 considered application-specific commands. The menu_driver() code
1212 ignores them and returns E_UNKNOWN_COMMAND.
1214 Miscellaneous Other Features
1216 Various menu options can affect the processing and visual appearance
1217 and input processing of menus. See menu_opts(3x) for details.
1219 It is possible to change the current item from application code; this
1220 is useful if you want to write your own navigation requests. It is
1221 also possible to explicitly set the top row of the menu display. See
1222 mitem_current(3x). If your application needs to change the menu
1223 subwindow cursor for any reason, pos_menu_cursor() will restore it to
1224 the correct location for continuing menu driver processing.
1226 It is possible to set hooks to be called at menu initialization and
1227 wrapup time, and whenever the selected item changes. See
1230 Each item, and each menu, has an associated user pointer on which you
1231 can hang application data. See mitem_userptr(3x) and menu_userptr(3x).
1235 The form library is a curses extension that supports easy programming
1236 of on-screen forms for data entry and program control.
1238 The form library first appeared in AT&T System V. The version
1239 documented here is the freeware form code distributed with ncurses.
1241 Compiling With the form Library
1243 Your form-using modules must import the form library declarations with
1246 and must be linked explicitly with the forms library using an -lform
1247 argument. Note that they must also link the ncurses library with
1248 -lncurses. Many linkers are two-pass and will accept either order, but
1249 it is still good practice to put -lform first and -lncurses second.
1253 A form is a collection of fields; each field may be either a label
1254 (explanatory text) or a data-entry location. Long forms may be
1255 segmented into pages; each entry to a new page clears the screen.
1257 To make forms, you create groups of fields and connect them with form
1258 frame objects; the form library makes this relatively simple.
1260 Once defined, a form can be posted, that is written to an associated
1261 window. Actually, each form has two associated windows; a containing
1262 window in which the programmer can scribble titles or borders, and a
1263 subwindow in which the form fields proper are displayed.
1265 As the form user fills out the posted form, navigation and editing
1266 keys support movement between fields, editing keys support modifying
1267 field, and plain text adds to or changes data in a current field. The
1268 form library allows you (the forms designer) to bind each navigation
1269 and editing key to any keystroke accepted by curses Fields may have
1270 validation conditions on them, so that they check input data for type
1271 and value. The form library supplies a rich set of pre-defined field
1272 types, and makes it relatively easy to define new ones.
1274 Once its transaction is completed (or aborted), a form may be unposted
1275 (that is, undisplayed), and finally freed to make the storage
1276 associated with it and its items available for re-use.
1278 The general flow of control of a form program looks like this:
1279 1. Initialize curses.
1280 2. Create the form fields, using new_field().
1281 3. Create the form using new_form().
1282 4. Post the form using form_post().
1283 5. Refresh the screen.
1284 6. Process user requests via an input loop.
1285 7. Unpost the form using form_unpost().
1286 8. Free the form, using free_form().
1287 9. Free the fields using free_field().
1288 10. Terminate curses.
1290 Note that this looks much like a menu program; the form library
1291 handles tasks which are in many ways similar, and its interface was
1292 obviously designed to resemble that of the menu library wherever
1295 In forms programs, however, the `process user requests' is somewhat
1296 more complicated than for menus. Besides menu-like navigation
1297 operations, the menu driver loop has to support field editing and data
1300 Creating and Freeing Fields and Forms
1302 The basic function for creating fields is new_field():
1304 FIELD *new_field(int height, int width, /* new field size */
1305 int top, int left, /* upper left corner */
1306 int offscreen, /* number of offscreen rows */
1307 int nbuf); /* number of working buffers */
1309 Menu items always occupy a single row, but forms fields may have
1310 multiple rows. So new_field() requires you to specify a width and
1311 height (the first two arguments, which mist both be greater than
1314 You must also specify the location of the field's upper left corner on
1315 the screen (the third and fourth arguments, which must be zero or
1316 greater). Note that these coordinates are relative to the form
1317 subwindow, which will coincide with stdscr by default but need not be
1318 stdscr if you've done an explicit set_form_window() call.
1320 The fifth argument allows you to specify a number of off-screen rows.
1321 If this is zero, the entire field will always be displayed. If it is
1322 nonzero, the form will be scrollable, with only one screen-full
1323 (initially the top part) displayed at any given time. If you make a
1324 field dynamic and grow it so it will no longer fit on the screen, the
1325 form will become scrollable even if the offscreen argument was
1328 The forms library allocates one working buffer per field; the size of
1329 each buffer is ((height + offscreen)*width + 1, one character for each
1330 position in the field plus a NUL terminator. The sixth argument is the
1331 number of additional data buffers to allocate for the field; your
1332 application can use them for its own purposes.
1334 FIELD *dup_field(FIELD *field, /* field to copy */
1335 int top, int left); /* location of new copy */
1337 The function dup_field() duplicates an existing field at a new
1338 location. Size and buffering information are copied; some attribute
1339 flags and status bits are not (see the form_field_new(3X) for
1342 FIELD *link_field(FIELD *field, /* field to copy */
1343 int top, int left); /* location of new copy */
1345 The function link_field() also duplicates an existing field at a new
1346 location. The difference from dup_field() is that it arranges for the
1347 new field's buffer to be shared with the old one.
1349 Besides the obvious use in making a field editable from two different
1350 form pages, linked fields give you a way to hack in dynamic labels. If
1351 you declare several fields linked to an original, and then make them
1352 inactive, changes from the original will still be propagated to the
1355 As with duplicated fields, linked fields have attribute bits separate
1358 As you might guess, all these field-allocations return NULL if the
1359 field allocation is not possible due to an out-of-memory error or
1360 out-of-bounds arguments.
1362 To connect fields to a form, use
1364 FORM *new_form(FIELD **fields);
1366 This function expects to see a NULL-terminated array of field
1367 pointers. Said fields are connected to a newly-allocated form object;
1368 its address is returned (or else NULL if the allocation fails).
1370 Note that new_field() does not copy the pointer array into private
1371 storage; if you modify the contents of the pointer array during forms
1372 processing, all manner of bizarre things might happen. Also note that
1373 any given field may only be connected to one form.
1375 The functions free_field() and free_form are available to free field
1376 and form objects. It is an error to attempt to free a field connected
1377 to a form, but not vice-versa; thus, you will generally free your form
1380 Fetching and Changing Field Attributes
1382 Each form field has a number of location and size attributes
1383 associated with it. There are other field attributes used to control
1384 display and editing of the field. Some (for example, the O_STATIC bit)
1385 involve sufficient complications to be covered in sections of their
1386 own later on. We cover the functions used to get and set several basic
1389 When a field is created, the attributes not specified by the new_field
1390 function are copied from an invisible system default field. In
1391 attribute-setting and -fetching functions, the argument NULL is taken
1392 to mean this field. Changes to it persist as defaults until your forms
1393 application terminates.
1395 Fetching Size and Location Data
1397 You can retrieve field sizes and locations through:
1399 int field_info(FIELD *field, /* field from which to fetch */
1400 int *height, *int width, /* field size */
1401 int *top, int *left, /* upper left corner */
1402 int *offscreen, /* number of offscreen rows */
1403 int *nbuf); /* number of working buffers */
1405 This function is a sort of inverse of new_field(); instead of setting
1406 size and location attributes of a new field, it fetches them from an
1409 Changing the Field Location
1411 If is possible to move a field's location on the screen:
1413 int move_field(FIELD *field, /* field to alter */
1414 int top, int left); /* new upper-left corner */
1416 You can, of course. query the current location through field_info().
1418 The Justification Attribute
1420 One-line fields may be unjustified, justified right, justified left,
1421 or centered. Here is how you manipulate this attribute:
1423 int set_field_just(FIELD *field, /* field to alter */
1424 int justmode); /* mode to set */
1426 int field_just(FIELD *field); /* fetch mode of field */
1428 The mode values accepted and returned by this functions are
1429 preprocessor macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or
1432 Field Display Attributes
1434 For each field, you can set a foreground attribute for entered
1435 characters, a background attribute for the entire field, and a pad
1436 character for the unfilled portion of the field. You can also control
1437 pagination of the form.
1439 This group of four field attributes controls the visual appearance of
1440 the field on the screen, without affecting in any way the data in the
1443 int set_field_fore(FIELD *field, /* field to alter */
1444 chtype attr); /* attribute to set */
1446 chtype field_fore(FIELD *field); /* field to query */
1448 int set_field_back(FIELD *field, /* field to alter */
1449 chtype attr); /* attribute to set */
1451 chtype field_back(FIELD *field); /* field to query */
1453 int set_field_pad(FIELD *field, /* field to alter */
1454 int pad); /* pad character to set */
1456 chtype field_pad(FIELD *field);
1458 int set_new_page(FIELD *field, /* field to alter */
1459 int flag); /* TRUE to force new page */
1461 chtype new_page(FIELD *field); /* field to query */
1463 The attributes set and returned by the first four functions are normal
1464 curses(3x) display attribute values (A_STANDOUT, A_BOLD, A_REVERSE
1465 etc). The page bit of a field controls whether it is displayed at the
1466 start of a new form screen.
1470 There is also a large collection of field option bits you can set to
1471 control various aspects of forms processing. You can manipulate them
1472 with these functions:
1473 int set_field_opts(FIELD *field, /* field to alter */
1474 int attr); /* attribute to set */
1476 int field_opts_on(FIELD *field, /* field to alter */
1477 int attr); /* attributes to turn on */
1479 int field_opts_off(FIELD *field, /* field to alter */
1480 int attr); /* attributes to turn off */
1482 int field_opts(FIELD *field); /* field to query */
1484 By default, all options are on. Here are the available option bits:
1487 Controls whether the field is visible on the screen. Can be
1488 used during form processing to hide or pop up fields depending
1489 on the value of parent fields.
1492 Controls whether the field is active during forms processing
1493 (i.e. visited by form navigation keys). Can be used to make
1494 labels or derived fields with buffer values alterable by the
1495 forms application, not the user.
1498 Controls whether data is displayed during field entry. If this
1499 option is turned off on a field, the library will accept and
1500 edit data in that field, but it will not be displayed and the
1501 visible field cursor will not move. You can turn off the
1502 O_PUBLIC bit to define password fields.
1505 Controls whether the field's data can be modified. When this
1506 option is off, all editing requests except REQ_PREV_CHOICE and
1507 REQ_NEXT_CHOICE will fail. Such read-only fields may be useful
1511 Controls word-wrapping in multi-line fields. Normally, when any
1512 character of a (blank-separated) word reaches the end of the
1513 current line, the entire word is wrapped to the next line
1514 (assuming there is one). When this option is off, the word will
1515 be split across the line break.
1518 Controls field blanking. When this option is on, entering a
1519 character at the first field position erases the entire field
1520 (except for the just-entered character).
1523 Controls automatic skip to next field when this one fills.
1524 Normally, when the forms user tries to type more data into a
1525 field than will fit, the editing location jumps to next field.
1526 When this option is off, the user's cursor will hang at the end
1527 of the field. This option is ignored in dynamic fields that
1528 have not reached their size limit.
1531 Controls whether validation is applied to blank fields.
1532 Normally, it is not; the user can leave a field blank without
1533 invoking the usual validation check on exit. If this option is
1534 off on a field, exit from it will invoke a validation check.
1537 Controls whether validation occurs on every exit, or only after
1538 the field is modified. Normally the latter is true. Setting
1539 O_PASSOK may be useful if your field's validation function may
1540 change during forms processing.
1543 Controls whether the field is fixed to its initial dimensions.
1544 If you turn this off, the field becomes dynamic and will
1545 stretch to fit entered data.
1547 A field's options cannot be changed while the field is currently
1548 selected. However, options may be changed on posted fields that are
1551 The option values are bit-masks and can be composed with logical-or in
1556 Every field has a status flag, which is set to FALSE when the field is
1557 created and TRUE when the value in field buffer 0 changes. This flag
1558 can be queried and set directly:
1560 int set_field_status(FIELD *field, /* field to alter */
1561 int status); /* mode to set */
1563 int field_status(FIELD *field); /* fetch mode of field */
1565 Setting this flag under program control can be useful if you use the
1566 same form repeatedly, looking for modified fields each time.
1568 Calling field_status() on a field not currently selected for input
1569 will return a correct value. Calling field_status() on a field that is
1570 currently selected for input may not necessarily give a correct field
1571 status value, because entered data isn't necessarily copied to buffer
1572 zero before the exit validation check. To guarantee that the returned
1573 status value reflects reality, call field_status() either (1) in the
1574 field's exit validation check routine, (2) from the field's or form's
1575 initialization or termination hooks, or (3) just after a
1576 REQ_VALIDATION request has been processed by the forms driver.
1580 Each field structure contains one character pointer slot that is not
1581 used by the forms library. It is intended to be used by applications
1582 to store private per-field data. You can manipulate it with:
1583 int set_field_userptr(FIELD *field, /* field to alter */
1584 char *userptr); /* mode to set */
1586 char *field_userptr(FIELD *field); /* fetch mode of field */
1588 (Properly, this user pointer field ought to have (void *) type. The
1589 (char *) type is retained for System V compatibility.)
1591 It is valid to set the user pointer of the default field (with a
1592 set_field_userptr() call passed a NULL field pointer.) When a new
1593 field is created, the default-field user pointer is copied to
1594 initialize the new field's user pointer.
1596 Variable-Sized Fields
1598 Normally, a field is fixed at the size specified for it at creation
1599 time. If, however, you turn off its O_STATIC bit, it becomes dynamic
1600 and will automatically resize itself to accommodate data as it is
1601 entered. If the field has extra buffers associated with it, they will
1602 grow right along with the main input buffer.
1604 A one-line dynamic field will have a fixed height (1) but variable
1605 width, scrolling horizontally to display data within the field area as
1606 originally dimensioned and located. A multi-line dynamic field will
1607 have a fixed width, but variable height (number of rows), scrolling
1608 vertically to display data within the field area as originally
1609 dimensioned and located.
1611 Normally, a dynamic field is allowed to grow without limit. But it is
1612 possible to set an upper limit on the size of a dynamic field. You do
1613 it with this function:
1615 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
1616 int max_size); /* upper limit on field size */
1618 If the field is one-line, max_size is taken to be a column size limit;
1619 if it is multi-line, it is taken to be a line size limit. To disable
1620 any limit, use an argument of zero. The growth limit can be changed
1621 whether or not the O_STATIC bit is on, but has no effect until it is.
1623 The following properties of a field change when it becomes dynamic:
1624 * If there is no growth limit, there is no final position of the
1625 field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored.
1626 * Field justification will be ignored (though whatever justification
1627 is set up will be retained internally and can be queried).
1628 * The dup_field() and link_field() calls copy dynamic-buffer sizes.
1629 If the O_STATIC option is set on one of a collection of links,
1630 buffer resizing will occur only when the field is edited through
1632 * The call field_info() will retrieve the original static size of
1633 the field; use dynamic_field_info() to get the actual dynamic
1638 By default, a field will accept any data that will fit in its input
1639 buffer. However, it is possible to attach a validation type to a
1640 field. If you do this, any attempt to leave the field while it
1641 contains data that doesn't match the validation type will fail. Some
1642 validation types also have a character-validity check for each time a
1643 character is entered in the field.
1645 A field's validation check (if any) is not called when
1646 set_field_buffer() modifies the input buffer, nor when that buffer is
1647 changed through a linked field.
1649 The form library provides a rich set of pre-defined validation types,
1650 and gives you the capability to define custom ones of your own. You
1651 can examine and change field validation attributes with the following
1654 int set_field_type(FIELD *field, /* field to alter */
1655 FIELDTYPE *ftype, /* type to associate */
1656 ...); /* additional arguments*/
1658 FIELDTYPE *field_type(FIELD *field); /* field to query */
1660 The validation type of a field is considered an attribute of the
1661 field. As with other field attributes, Also, doing set_field_type()
1662 with a NULL field default will change the system default for
1663 validation of newly-created fields.
1665 Here are the pre-defined validation types:
1669 This field type accepts alphabetic data; no blanks, no digits, no
1670 special characters (this is checked at character-entry time). It is
1673 int set_field_type(FIELD *field, /* field to alter */
1674 TYPE_ALPHA, /* type to associate */
1675 int width); /* maximum width of field */
1677 The width argument sets a minimum width of data. Typically you'll want
1678 to set this to the field width; if it's greater than the field width,
1679 the validation check will always fail. A minimum width of zero makes
1680 field completion optional.
1684 This field type accepts alphabetic data and digits; no blanks, no
1685 special characters (this is checked at character-entry time). It is
1688 int set_field_type(FIELD *field, /* field to alter */
1689 TYPE_ALNUM, /* type to associate */
1690 int width); /* maximum width of field */
1692 The width argument sets a minimum width of data. As with TYPE_ALPHA,
1693 typically you'll want to set this to the field width; if it's greater
1694 than the field width, the validation check will always fail. A minimum
1695 width of zero makes field completion optional.
1699 This type allows you to restrict a field's values to be among a
1700 specified set of string values (for example, the two-letter postal
1701 codes for U.S. states). It is set up with:
1703 int set_field_type(FIELD *field, /* field to alter */
1704 TYPE_ENUM, /* type to associate */
1705 char **valuelist; /* list of possible values */
1706 int checkcase; /* case-sensitive? */
1707 int checkunique); /* must specify uniquely? */
1709 The valuelist parameter must point at a NULL-terminated list of valid
1710 strings. The checkcase argument, if true, makes comparison with the
1711 string case-sensitive.
1713 When the user exits a TYPE_ENUM field, the validation procedure tries
1714 to complete the data in the buffer to a valid entry. If a complete
1715 choice string has been entered, it is of course valid. But it is also
1716 possible to enter a prefix of a valid string and have it completed for
1719 By default, if you enter such a prefix and it matches more than one
1720 value in the string list, the prefix will be completed to the first
1721 matching value. But the checkunique argument, if true, requires prefix
1722 matches to be unique in order to be valid.
1724 The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be
1725 particularly useful with these fields.
1729 This field type accepts an integer. It is set up as follows:
1731 int set_field_type(FIELD *field, /* field to alter */
1732 TYPE_INTEGER, /* type to associate */
1733 int padding, /* # places to zero-pad to */
1734 int vmin, int vmax); /* valid range */
1736 Valid characters consist of an optional leading minus and digits. The
1737 range check is performed on exit. If the range maximum is less than or
1738 equal to the minimum, the range is ignored.
1740 If the value passes its range check, it is padded with as many leading
1741 zero digits as necessary to meet the padding argument.
1743 A TYPE_INTEGER value buffer can conveniently be interpreted with the C
1744 library function atoi(3).
1748 This field type accepts a decimal number. It is set up as follows:
1750 int set_field_type(FIELD *field, /* field to alter */
1751 TYPE_NUMERIC, /* type to associate */
1752 int padding, /* # places of precision */
1753 double vmin, double vmax); /* valid range */
1755 Valid characters consist of an optional leading minus and digits.
1756 possibly including a decimal point. If your system supports locale's,
1757 the decimal point character used must be the one defined by your
1758 locale. The range check is performed on exit. If the range maximum is
1759 less than or equal to the minimum, the range is ignored.
1761 If the value passes its range check, it is padded with as many
1762 trailing zero digits as necessary to meet the padding argument.
1764 A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
1765 library function atof(3).
1769 This field type accepts data matching a regular expression. It is set
1772 int set_field_type(FIELD *field, /* field to alter */
1773 TYPE_REGEXP, /* type to associate */
1774 char *regexp); /* expression to match */
1776 The syntax for regular expressions is that of regcomp(3). The check
1777 for regular-expression match is performed on exit.
1779 Direct Field Buffer Manipulation
1781 The chief attribute of a field is its buffer contents. When a form has
1782 been completed, your application usually needs to know the state of
1783 each field buffer. You can find this out with:
1785 char *field_buffer(FIELD *field, /* field to query */
1786 int bufindex); /* number of buffer to query */
1788 Normally, the state of the zero-numbered buffer for each field is set
1789 by the user's editing actions on that field. It's sometimes useful to
1790 be able to set the value of the zero-numbered (or some other) buffer
1791 from your application:
1792 int set_field_buffer(FIELD *field, /* field to alter */
1793 int bufindex, /* number of buffer to alter */
1794 char *value); /* string value to set */
1796 If the field is not large enough and cannot be resized to a
1797 sufficiently large size to contain the specified value, the value will
1798 be truncated to fit.
1800 Calling field_buffer() with a null field pointer will raise an error.
1801 Calling field_buffer() on a field not currently selected for input
1802 will return a correct value. Calling field_buffer() on a field that is
1803 currently selected for input may not necessarily give a correct field
1804 buffer value, because entered data isn't necessarily copied to buffer
1805 zero before the exit validation check. To guarantee that the returned
1806 buffer value reflects on-screen reality, call field_buffer() either
1807 (1) in the field's exit validation check routine, (2) from the field's
1808 or form's initialization or termination hooks, or (3) just after a
1809 REQ_VALIDATION request has been processed by the forms driver.
1813 As with field attributes, form attributes inherit a default from a
1814 system default form structure. These defaults can be queried or set by
1815 of these functions using a form-pointer argument of NULL.
1817 The principal attribute of a form is its field list. You can query and
1818 change this list with:
1820 int set_form_fields(FORM *form, /* form to alter */
1821 FIELD **fields); /* fields to connect */
1823 char *form_fields(FORM *form); /* fetch fields of form */
1825 int field_count(FORM *form); /* count connect fields */
1827 The second argument of set_form_fields() may be a NULL-terminated
1828 field pointer array like the one required by new_form(). In that case,
1829 the old fields of the form are disconnected but not freed (and
1830 eligible to be connected to other forms), then the new fields are
1833 It may also be null, in which case the old fields are disconnected
1834 (and not freed) but no new ones are connected.
1836 The field_count() function simply counts the number of fields
1837 connected to a given from. It returns -1 if the form-pointer argument
1840 Control of Form Display
1842 In the overview section, you saw that to display a form you normally
1843 start by defining its size (and fields), posting it, and refreshing
1844 the screen. There is an hidden step before posting, which is the
1845 association of the form with a frame window (actually, a pair of
1846 windows) within which it will be displayed. By default, the forms
1847 library associates every form with the full-screen window stdscr.
1849 By making this step explicit, you can associate a form with a declared
1850 frame window on your screen display. This can be useful if you want to
1851 adapt the form display to different screen sizes, dynamically tile
1852 forms on the screen, or use a form as part of an interface layout
1855 The two windows associated with each form have the same functions as
1856 their analogues in the menu library. Both these windows are painted
1857 when the form is posted and erased when the form is unposted.
1859 The outer or frame window is not otherwise touched by the form
1860 routines. It exists so the programmer can associate a title, a border,
1861 or perhaps help text with the form and have it properly refreshed or
1862 erased at post/unpost time. The inner window or subwindow is where the
1863 current form page is actually displayed.
1865 In order to declare your own frame window for a form, you'll need to
1866 know the size of the form's bounding rectangle. You can get this
1869 int scale_form(FORM *form, /* form to query */
1870 int *rows, /* form rows */
1871 int *cols); /* form cols */
1873 The form dimensions are passed back in the locations pointed to by the
1874 arguments. Once you have this information, you can use it to declare
1875 of windows, then use one of these functions:
1876 int set_form_win(FORM *form, /* form to alter */
1877 WINDOW *win); /* frame window to connect */
1879 WINDOW *form_win(FORM *form); /* fetch frame window of form */
1881 int set_form_sub(FORM *form, /* form to alter */
1882 WINDOW *win); /* form subwindow to connect */
1884 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
1886 Note that curses operations, including refresh(), on the form, should
1887 be done on the frame window, not the form subwindow.
1889 It is possible to check from your application whether all of a
1890 scrollable field is actually displayed within the menu subwindow. Use
1893 int data_ahead(FORM *form); /* form to be queried */
1895 int data_behind(FORM *form); /* form to be queried */
1897 The function data_ahead() returns TRUE if (a) the current field is
1898 one-line and has undisplayed data off to the right, (b) the current
1899 field is multi-line and there is data off-screen below it.
1901 The function data_behind() returns TRUE if the first (upper left hand)
1902 character position is off-screen (not being displayed).
1904 Finally, there is a function to restore the form window's cursor to
1905 the value expected by the forms driver:
1907 int pos_form_cursor(FORM *) /* form to be queried */
1909 If your application changes the form window cursor, call this function
1910 before handing control back to the forms driver in order to
1913 Input Processing in the Forms Driver
1915 The function form_driver() handles virtualized input requests for form
1916 navigation, editing, and validation requests, just as menu_driver does
1917 for menus (see the section on menu input handling).
1919 int form_driver(FORM *form, /* form to pass input to */
1920 int request); /* form request code */
1922 Your input virtualization function needs to take input and then
1923 convert it to either an alphanumeric character (which is treated as
1924 data to be entered in the currently-selected field), or a forms
1927 The forms driver provides hooks (through input-validation and
1928 field-termination functions) with which your application code can
1929 check that the input taken by the driver matched what was expected.
1931 Page Navigation Requests
1933 These requests cause page-level moves through the form, triggering
1934 display of a new form screen.
1937 Move to the next form page.
1940 Move to the previous form page.
1943 Move to the first form page.
1946 Move to the last form page.
1948 These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from
1949 the last page goes to the first, and REQ_PREV_PAGE from the first page
1952 Inter-Field Navigation Requests
1954 These requests handle navigation between fields on the same page.
1960 Move to previous field.
1963 Move to the first field.
1966 Move to the last field.
1969 Move to sorted next field.
1972 Move to sorted previous field.
1975 Move to the sorted first field.
1978 Move to the sorted last field.
1984 Move right to field.
1992 These requests treat the list of fields on a page as cyclic; that is,
1993 REQ_NEXT_FIELD from the last field goes to the first, and
1994 REQ_PREV_FIELD from the first field goes to the last. The order of the
1995 fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests)
1996 is simply the order of the field pointers in the form array (as set up
1997 by new_form() or set_form_fields()
1999 It is also possible to traverse the fields as if they had been sorted
2000 in screen-position order, so the sequence goes left-to-right and
2001 top-to-bottom. To do this, use the second group of four
2002 sorted-movement requests.
2004 Finally, it is possible to move between fields using visual directions
2005 up, down, right, and left. To accomplish this, use the third group of
2006 four requests. Note, however, that the position of a form for purposes
2007 of these requests is its upper-left corner.
2009 For example, suppose you have a multi-line field B, and two
2010 single-line fields A and C on the same line with B, with A to the left
2011 of B and C to the right of B. A REQ_MOVE_RIGHT from A will go to B
2012 only if A, B, and C all share the same first line; otherwise it will
2015 Intra-Field Navigation Requests
2017 These requests drive movement of the edit cursor within the currently
2021 Move to next character.
2024 Move to previous character.
2030 Move to previous line.
2036 Move to previous word.
2039 Move to beginning of field.
2042 Move to end of field.
2045 Move to beginning of line.
2048 Move to end of line.
2054 Move right in field.
2062 Each word is separated from the previous and next characters by
2063 whitespace. The commands to move to beginning and end of line or field
2064 look for the first or last non-pad character in their ranges.
2068 Fields that are dynamic and have grown and fields explicitly created
2069 with offscreen rows are scrollable. One-line fields scroll
2070 horizontally; multi-line fields scroll vertically. Most scrolling is
2071 triggered by editing and intra-field movement (the library scrolls the
2072 field to keep the cursor visible). It is possible to explicitly
2073 request scrolling with the following requests:
2076 Scroll vertically forward a line.
2079 Scroll vertically backward a line.
2082 Scroll vertically forward a page.
2085 Scroll vertically backward a page.
2088 Scroll vertically forward half a page.
2091 Scroll vertically backward half a page.
2094 Scroll horizontally forward a character.
2097 Scroll horizontally backward a character.
2100 Scroll horizontally one field width forward.
2103 Scroll horizontally one field width backward.
2106 Scroll horizontally one half field width forward.
2109 Scroll horizontally one half field width backward.
2111 For scrolling purposes, a page of a field is the height of its visible
2116 When you pass the forms driver an ASCII character, it is treated as a
2117 request to add the character to the field's data buffer. Whether this
2118 is an insertion or a replacement depends on the field's edit mode
2119 (insertion is the default.
2121 The following requests support editing the field and changing the edit
2131 New line request (see below for explanation).
2134 Insert space at character location.
2137 Insert blank line at character location.
2140 Delete character at cursor.
2143 Delete previous word at cursor.
2146 Delete line at cursor.
2149 Delete word at cursor.
2152 Clear to end of line.
2155 Clear to end of field.
2160 The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is
2161 complicated and partly controlled by a pair of forms options. The
2162 special cases are triggered when the cursor is at the beginning of a
2163 field, or on the last line of the field.
2165 First, we consider REQ_NEW_LINE:
2167 The normal behavior of REQ_NEW_LINE in insert mode is to break the
2168 current line at the position of the edit cursor, inserting the portion
2169 of the current line after the cursor as a new line following the
2170 current and moving the cursor to the beginning of that new line (you
2171 may think of this as inserting a newline in the field buffer).
2173 The normal behavior of REQ_NEW_LINE in overlay mode is to clear the
2174 current line from the position of the edit cursor to end of line. The
2175 cursor is then moved to the beginning of the next line.
2177 However, REQ_NEW_LINE at the beginning of a field, or on the last line
2178 of a field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is
2179 off, this special action is disabled.
2181 Now, let us consider REQ_DEL_PREV:
2183 The normal behavior of REQ_DEL_PREV is to delete the previous
2184 character. If insert mode is on, and the cursor is at the start of a
2185 line, and the text on that line will fit on the previous one, it
2186 instead appends the contents of the current line to the previous one
2187 and deletes the current line (you may think of this as deleting a
2188 newline from the field buffer).
2190 However, REQ_DEL_PREV at the beginning of a field is instead treated
2191 as a REQ_PREV_FIELD.
2193 If the O_BS_OVERLOAD option is off, this special action is disabled
2194 and the forms driver just returns E_REQUEST_DENIED.
2196 See Form Options for discussion of how to set and clear the overload
2201 If the type of your field is ordered, and has associated functions for
2202 getting the next and previous values of the type from a given value,
2203 there are requests that can fetch that value into the field buffer:
2206 Place the successor value of the current value in the buffer.
2209 Place the predecessor value of the current value in the buffer.
2211 Of the built-in field types, only TYPE_ENUM has built-in successor and
2212 predecessor functions. When you define a field type of your own (see
2213 Custom Validation Types), you can associate our own ordering
2216 Application Commands
2218 Form requests are represented as integers above the curses value
2219 greater than KEY_MAX and less than or equal to the constant
2220 MAX_COMMAND. If your input-virtualization routine returns a value
2221 above MAX_COMMAND, the forms driver will ignore it.
2225 It is possible to set function hooks to be executed whenever the
2226 current field or form changes. Here are the functions that support
2229 typedef void (*HOOK)(); /* pointer to function returning void */
2231 int set_form_init(FORM *form, /* form to alter */
2232 HOOK hook); /* initialization hook */
2234 HOOK form_init(FORM *form); /* form to query */
2236 int set_form_term(FORM *form, /* form to alter */
2237 HOOK hook); /* termination hook */
2239 HOOK form_term(FORM *form); /* form to query */
2241 int set_field_init(FORM *form, /* form to alter */
2242 HOOK hook); /* initialization hook */
2244 HOOK field_init(FORM *form); /* form to query */
2246 int set_field_term(FORM *form, /* form to alter */
2247 HOOK hook); /* termination hook */
2249 HOOK field_term(FORM *form); /* form to query */
2251 These functions allow you to either set or query four different hooks.
2252 In each of the set functions, the second argument should be the
2253 address of a hook function. These functions differ only in the timing
2257 This hook is called when the form is posted; also, just after
2258 each page change operation.
2261 This hook is called when the form is posted; also, just after
2265 This hook is called just after field validation; that is, just
2266 before the field is altered. It is also called when the form is
2270 This hook is called when the form is unposted; also, just
2271 before each page change operation.
2273 Calls to these hooks may be triggered
2274 1. When user editing requests are processed by the forms driver
2275 2. When the current page is changed by set_current_field() call
2276 3. When the current field is changed by a set_form_page() call
2278 See Field Change Commands for discussion of the latter two cases.
2280 You can set a default hook for all fields by passing one of the set
2281 functions a NULL first argument.
2283 You can disable any of these hooks by (re)setting them to NULL, the
2286 Field Change Commands
2288 Normally, navigation through the form will be driven by the user's
2289 input requests. But sometimes it is useful to be able to move the
2290 focus for editing and viewing under control of your application, or
2291 ask which field it currently is in. The following functions help you
2294 int set_current_field(FORM *form, /* form to alter */
2295 FIELD *field); /* field to shift to */
2297 FIELD *current_field(FORM *form); /* form to query */
2299 int field_index(FORM *form, /* form to query */
2300 FIELD *field); /* field to get index of */
2302 The function field_index() returns the index of the given field in the
2303 given form's field array (the array passed to new_form() or
2306 The initial current field of a form is the first active field on the
2307 first page. The function set_form_fields() resets this.
2309 It is also possible to move around by pages.
2311 int set_form_page(FORM *form, /* form to alter */
2312 int page); /* page to go to (0-origin) */
2314 int form_page(FORM *form); /* return form's current page */
2316 The initial page of a newly-created form is 0. The function
2317 set_form_fields() resets this.
2321 Like fields, forms may have control option bits. They can be changed
2322 or queried with these functions:
2324 int set_form_opts(FORM *form, /* form to alter */
2325 int attr); /* attribute to set */
2327 int form_opts_on(FORM *form, /* form to alter */
2328 int attr); /* attributes to turn on */
2330 int form_opts_off(FORM *form, /* form to alter */
2331 int attr); /* attributes to turn off */
2333 int form_opts(FORM *form); /* form to query */
2335 By default, all options are on. Here are the available option bits:
2338 Enable overloading of REQ_NEW_LINE as described in Editing
2339 Requests. The value of this option is ignored on dynamic fields
2340 that have not reached their size limit; these have no last
2341 line, so the circumstances for triggering a REQ_NEXT_FIELD
2345 Enable overloading of REQ_DEL_PREV as described in Editing
2348 The option values are bit-masks and can be composed with logical-or in
2351 Custom Validation Types
2353 The form library gives you the capability to define custom validation
2354 types of your own. Further, the optional additional arguments of
2355 set_field_type effectively allow you to parameterize validation types.
2356 Most of the complications in the validation-type interface have to do
2357 with the handling of the additional arguments within custom validation
2362 The simplest way to create a custom data type is to compose it from
2363 two preexisting ones:
2365 FIELD *link_fieldtype(FIELDTYPE *type1,
2368 This function creates a field type that will accept any of the values
2369 legal for either of its argument field types (which may be either
2370 predefined or programmer-defined). If a set_field_type() call later
2371 requires arguments, the new composite type expects all arguments for
2372 the first type, than all arguments for the second. Order functions
2373 (see Order Requests) associated with the component types will work on
2374 the composite; what it does is check the validation function for the
2375 first type, then for the second, to figure what type the buffer
2376 contents should be treated as.
2380 To create a field type from scratch, you need to specify one or both
2381 of the following things:
2383 * A character-validation function, to check each character as it is
2385 * A field-validation function to be applied on exit from the field.
2387 Here's how you do that:
2389 typedef int (*HOOK)(); /* pointer to function returning int */
2391 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
2392 HOOK c_validate) /* character validator */
2395 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
2397 At least one of the arguments of new_fieldtype() must be non-NULL. The
2398 forms driver will automatically call the new type's validation
2399 functions at appropriate points in processing a field of the new type.
2401 The function free_fieldtype() deallocates the argument fieldtype,
2402 freeing all storage associated with it.
2404 Normally, a field validator is called when the user attempts to leave
2405 the field. Its first argument is a field pointer, from which it can
2406 get to field buffer 0 and test it. If the function returns TRUE, the
2407 operation succeeds; if it returns FALSE, the edit cursor stays in the
2410 A character validator gets the character passed in as a first
2411 argument. It too should return TRUE if the character is valid, FALSE
2414 Validation Function Arguments
2416 Your field- and character- validation functions will be passed a
2417 second argument as well. This second argument is the address of a
2418 structure (which we'll call a pile) built from any of the
2419 field-type-specific arguments passed to set_field_type(). If no such
2420 arguments are defined for the field type, this pile pointer argument
2423 In order to arrange for such arguments to be passed to your validation
2424 functions, you must associate a small set of storage-management
2425 functions with the type. The forms driver will use these to synthesize
2426 a pile from the trailing arguments of each set_field_type() argument,
2427 and a pointer to the pile will be passed to the validation functions.
2429 Here is how you make the association:
2431 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
2432 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
2434 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2435 PTRHOOK make_str, /* make structure from args */
2436 PTRHOOK copy_str, /* make copy of structure */
2437 VOIDHOOK free_str); /* free structure storage */
2439 Here is how the storage-management hooks are used:
2442 This function is called by set_field_type(). It gets one
2443 argument, a va_list of the type-specific arguments passed to
2444 set_field_type(). It is expected to return a pile pointer to a
2445 data structure that encapsulates those arguments.
2448 This function is called by form library functions that allocate
2449 new field instances. It is expected to take a pile pointer,
2450 copy the pile to allocated storage, and return the address of
2454 This function is called by field- and type-deallocation
2455 routines in the library. It takes a pile pointer argument, and
2456 is expected to free the storage of that pile.
2458 The make_str and copy_str functions may return NULL to signal
2459 allocation failure. The library routines will that call them will
2460 return error indication when this happens. Thus, your validation
2461 functions should never see a NULL file pointer and need not check
2464 Order Functions For Custom Types
2466 Some custom field types are simply ordered in the same well-defined
2467 way that TYPE_ENUM is. For such types, it is possible to define
2468 successor and predecessor functions to support the REQ_NEXT_CHOICE and
2469 REQ_PREV_CHOICE requests. Here's how:
2471 typedef int (*INTHOOK)(); /* pointer to function returning int */
2473 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2474 INTHOOK succ, /* get successor value */
2475 INTHOOK pred); /* get predecessor value */
2477 The successor and predecessor arguments will each be passed two
2478 arguments; a field pointer, and a pile pointer (as for the validation
2479 functions). They are expected to use the function field_buffer() to
2480 read the current value, and set_field_buffer() on buffer 0 to set the
2481 next or previous value. Either hook may return TRUE to indicate
2482 success (a legal next or previous value was set) or FALSE to indicate
2487 The interface for defining custom types is complicated and tricky.
2488 Rather than attempting to create a custom type entirely from scratch,
2489 you should start by studying the library source code for whichever of
2490 the pre-defined types seems to be closest to what you want.
2492 Use that code as a model, and evolve it towards what you really want.
2493 You will avoid many problems and annoyances that way. The code in the
2494 ncurses library has been specifically exempted from the package
2495 copyright to support this.
2497 If your custom type defines order functions, have do something
2498 intuitive with a blank field. A useful convention is to make the
2499 successor of a blank field the types minimum value, and its
2500 predecessor the maximum.