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. The
179 current primary maintainers are Thomas Dickey <dickey@clark.net> and
180 Juergen Pfeifer. <Juergen.Pfeifer@T-Online.de>
182 This document also describes the panels extension library, similarly
183 modeled on the SVr4 panels facility. This library allows you to
184 associate backing store with each of a stack or deck of overlapping
185 windows, and provides operations for moving windows around in the
186 stack that change their visibility in the natural way (handling window
189 Finally, this document describes in detail the menus and forms
190 extension libraries, also cloned from System V, which support easy
191 construction and sequences of menus and fill-in forms. This code was
192 contributed to the project by Jürgen Pfeifer.
196 In this document, the following terminology is used with reasonable
200 A data structure describing a sub-rectangle of the screen
201 (possibly the entire screen). You can write to a window as
202 though it were a miniature screen, scrolling independently of
203 other windows on the physical screen.
206 A subset of windows which are as large as the terminal screen,
207 i.e., they start at the upper left hand corner and encompass
208 the lower right hand corner. One of these, stdscr, is
209 automatically provided for the programmer.
212 The package's idea of what the terminal display currently looks
213 like, i.e., what the user sees now. This is a special screen.
217 An Overview of Curses
219 Compiling Programs using Curses
221 In order to use the library, it is necessary to have certain types and
222 variables defined. Therefore, the programmer must have a line:
226 at the top of the program source. The screen package uses the Standard
227 I/O library, so <curses.h> includes <stdio.h>. <curses.h> also
228 includes <termios.h>, <termio.h>, or <sgtty.h> depending on your
229 system. It is redundant (but harmless) for the programmer to do these
230 includes, too. In linking with curses you need to have -lncurses in
231 your LDFLAGS or on the command line. There is no need for any other
236 In order to update the screen optimally, it is necessary for the
237 routines to know what the screen currently looks like and what the
238 programmer wants it to look like next. For this purpose, a data type
239 (structure) named WINDOW is defined which describes a window image to
240 the routines, including its starting position on the screen (the (y,
241 x) coordinates of the upper left hand corner) and its size. One of
242 these (called curscr, for current screen) is a screen image of what
243 the terminal currently looks like. Another screen (called stdscr, for
244 standard screen) is provided by default to make changes on.
246 A window is a purely internal representation. It is used to build and
247 store a potential image of a portion of the terminal. It doesn't bear
248 any necessary relation to what is really on the terminal screen; it's
249 more like a scratchpad or write buffer.
251 To make the section of physical screen corresponding to a window
252 reflect the contents of the window structure, the routine refresh()
253 (or wrefresh() if the window is not stdscr) is called.
255 A given physical screen section may be within the scope of any number
256 of overlapping windows. Also, changes can be made to windows in any
257 order, without regard to motion efficiency. Then, at will, the
258 programmer can effectively say ``make it look like this,'' and let the
259 package implementation determine the most efficient way to repaint the
262 Standard Windows and Function Naming Conventions
264 As hinted above, the routines can use several windows, but two are
265 automatically given: curscr, which knows what the terminal looks like,
266 and stdscr, which is what the programmer wants the terminal to look
267 like next. The user should never actually access curscr directly.
268 Changes should be made to through the API, and then the routine
269 refresh() (or wrefresh()) called.
271 Many functions are defined to use stdscr as a default screen. For
272 example, to add a character to stdscr, one calls addch() with the
273 desired character as argument. To write to a different window. use the
274 routine waddch() (for `w'indow-specific addch()) is provided. This
275 convention of prepending function names with a `w' when they are to be
276 applied to specific windows is consistent. The only routines which do
277 not follow it are those for which a window must always be specified.
279 In order to move the current (y, x) coordinates from one point to
280 another, the routines move() and wmove() are provided. However, it is
281 often desirable to first move and then perform some I/O operation. In
282 order to avoid clumsiness, most I/O routines can be preceded by the
283 prefix 'mv' and the desired (y, x) coordinates prepended to the
284 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
308 type name description
309 ------------------------------------------------------------------
310 int LINES number of lines on the terminal
311 int COLS number of columns on the terminal
313 The curses.h also introduces some #define constants and types of
317 boolean type, actually a `char' (e.g., bool doneit;)
320 boolean `true' flag (1).
323 boolean `false' flag (0).
326 error flag returned by routines on a failure (-1).
329 error flag returned by routines when things go right.
333 Now we describe how to actually use the screen package. In it, we
334 assume all updating, reading, etc. is applied to stdscr. These
335 instructions will work on any window, providing you change the
336 function names and parameters as mentioned above.
338 Here is a sample program to motivate the discussion:
343 static void finish(int sig);
345 main(int argc, char *argv[])
347 /* initialize your non-curses data structures here */
349 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
351 (void) initscr(); /* initialize the curses library */
352 keypad(stdscr, TRUE); /* enable keyboard mapping */
353 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
354 (void) cbreak(); /* take input chars one at a time, no wait for \n */
355 (void) noecho(); /* don't echo input */
362 * Simple color assignment, often all we need.
364 init_pair(COLOR_BLACK, COLOR_BLACK, COLOR_BLACK);
365 init_pair(COLOR_GREEN, COLOR_GREEN, COLOR_BLACK);
366 init_pair(COLOR_RED, COLOR_RED, COLOR_BLACK);
367 init_pair(COLOR_CYAN, COLOR_CYAN, COLOR_BLACK);
368 init_pair(COLOR_WHITE, COLOR_WHITE, COLOR_BLACK);
369 init_pair(COLOR_MAGENTA, COLOR_MAGENTA, COLOR_BLACK);
370 init_pair(COLOR_BLUE, COLOR_BLUE, COLOR_BLACK);
371 init_pair(COLOR_YELLOW, COLOR_YELLOW, COLOR_BLACK);
376 int c = getch(); /* refresh, accept single keystroke of input */
378 /* process the command keystroke */
381 finish(0); /* we're done */
384 static void finish(int sig)
388 /* do your non-curses wrapup here */
395 In order to use the screen package, the routines must know about
396 terminal characteristics, and the space for curscr and stdscr must be
397 allocated. These function initscr() does both these things. Since it
398 must allocate space for the windows, it can overflow memory when
399 attempting to do so. On the rare occasions this happens, initscr()
400 will terminate the program with an error message. initscr() must
401 always be called before any of the routines which affect windows are
402 used. If it is not, the program will core dump as soon as either
403 curscr or stdscr are referenced. However, it is usually best to wait
404 to call it until after you are sure you will need it, like after
405 checking for startup errors. Terminal status changing routines like
406 nl() and cbreak() should be called after initscr().
408 Once the screen windows have been allocated, you can set them up for
409 your program. If you want to, say, allow a screen to scroll, use
410 scrollok(). If you want the cursor to be left in place after the last
411 change, use leaveok(). If this isn't done, refresh() will move the
412 cursor to the window's current (y, x) coordinates after updating it.
414 You can create new windows of your own using the functions newwin(),
415 derwin(), and subwin(). The routine delwin() will allow you to get rid
416 of old windows. All the options described above can be applied to any
421 Now that we have set things up, we will want to actually update the
422 terminal. The basic functions used to change what will go on a window
423 are addch() and move(). addch() adds a character at the current (y, x)
424 coordinates. move() changes the current (y, x) coordinates to whatever
425 you want them to be. It returns ERR if you try to move off the window.
426 As mentioned above, you can combine the two into mvaddch() to do both
429 The other output functions, such as addstr() and printw(), all call
430 addch() to add characters to the window.
432 After you have put on the window what you want there, when you want
433 the portion of the terminal covered by the window to be made to look
434 like it, you must call refresh(). In order to optimize finding
435 changes, refresh() assumes that any part of the window not changed
436 since the last refresh() of that window has not been changed on the
437 terminal, i.e., that you have not refreshed a portion of the terminal
438 with an overlapping window. If this is not the case, the routine
439 touchwin() is provided to make it look like the entire window has been
440 changed, thus making refresh() check the whole subsection of the
441 terminal for changes.
443 If you call wrefresh() with curscr as its argument, it will make the
444 screen look like curscr thinks it looks like. This is useful for
445 implementing a command which would redraw the screen in case it get
450 The complementary function to addch() is getch() which, if echo is
451 set, will call addch() to echo the character. Since the screen package
452 needs to know what is on the terminal at all times, if characters are
453 to be echoed, the tty must be in raw or cbreak mode. Since initially
454 the terminal has echoing enabled and is in ordinary ``cooked'' mode,
455 one or the other has to changed before calling getch(); otherwise, the
456 program's output will be unpredictable.
458 When you need to accept line-oriented input in a window, the functions
459 wgetstr() and friends are available. There is even a wscanw() function
460 that can do scanf()(3)-style multi-field parsing on window input.
461 These pseudo-line-oriented functions turn on echoing while they
464 The example code above uses the call keypad(stdscr, TRUE) to enable
465 support for function-key mapping. With this feature, the getch() code
466 watches the input stream for character sequences that correspond to
467 arrow and function keys. These sequences are returned as
468 pseudo-character values. The #define values returned are listed in the
469 curses.h The mapping from sequences to #define values is determined by
470 key_ capabilities in the terminal's terminfo entry.
472 Using Forms Characters
474 The addch() function (and some others, including box() and border())
475 can accept some pseudo-character arguments which are specially defined
476 by ncurses. These are #define values set up in the curses.h header;
477 see there for a complete list (look for the prefix ACS_).
479 The most useful of the ACS defines are the forms-drawing characters.
480 You can use these to draw boxes and simple graphs on the screen. If
481 the terminal does not have such characters, curses.h will map them to
482 a recognizable (though ugly) set of ASCII defaults.
484 Character Attributes and Color
486 The ncurses package supports screen highlights including standout,
487 reverse-video, underline, and blink. It also supports color, which is
488 treated as another kind of highlight.
490 Highlights are encoded, internally, as high bits of the
491 pseudo-character type (chtype) that curses.h uses to represent the
492 contents of a screen cell. See the curses.h header file for a complete
493 list of highlight mask values (look for the prefix A_).
495 There are two ways to make highlights. One is to logical-or the value
496 of the highlights you want into the character argument of an addch()
497 call, or any other output call that takes a chtype argument.
499 The other is to set the current-highlight value. This is logical-or'ed
500 with any highlight you specify the first way. You do this with the
501 functions attron(), attroff(), and attrset(); see the manual pages for
502 details. Color is a special kind of highlight. The package actually
503 thinks in terms of color pairs, combinations of foreground and
504 background colors. The sample code above sets up eight color pairs,
505 all of the guaranteed-available colors on black. Note that each color
506 pair is, in effect, given the name of its foreground color. Any other
507 range of eight non-conflicting values could have been used as the
508 first arguments of the init_pair() values.
510 Once you've done an init_pair() that creates color-pair N, you can use
511 COLOR_PAIR(N) as a highlight that invokes that particular color
512 combination. Note that COLOR_PAIR(N), for constant N, is itself a
513 compile-time constant and can be used in initializers.
517 The ncurses library also provides a mouse interface. Note: his
518 facility is original to ncurses, it is not part of either the XSI
519 Curses standard, nor of System V Release 4, nor BSD curses. Thus, we
520 recommend that you wrap mouse-related code in an #ifdef using the
521 feature macro NCURSES_MOUSE_VERSION so it will not be compiled and
522 linked on non-ncurses systems.
524 Presently, mouse event reporting works only under xterm. In the
525 future, ncurses will detect the presence of gpm(1), Alessandro
526 Rubini's freeware mouse server for Linux systems, and accept mouse
529 The mouse interface is very simple. To activate it, you use the
530 function mousemask(), passing it as first argument a bit-mask that
531 specifies what kinds of events you want your program to be able to
532 see. It will return the bit-mask of events that actually become
533 visible, which may differ from the argument if the mouse device is not
534 capable of reporting some of the event types you specify.
536 Once the mouse is active, your application's command loop should watch
537 for a return value of KEY_MOUSE from wgetch(). When you see this, a
538 mouse event report has been queued. To pick it off the queue, use the
539 function getmouse() (you must do this before the next wgetch(),
540 otherwise another mouse event might come in and make the first one
543 Each call to getmouse() fills a structure (the address of which you'll
544 pass it) with mouse event data. The event data includes zero-origin,
545 screen-relative character-cell coordinates of the mouse pointer. It
546 also includes an event mask. Bits in this mask will be set,
547 corresponding to the event type being reported.
549 The mouse structure contains two additional fields which may be
550 significant in the future as ncurses interfaces to new kinds of
551 pointing device. In addition to x and y coordinates, there is a slot
552 for a z coordinate; this might be useful with touch-screens that can
553 return a pressure or duration parameter. There is also a device ID
554 field, which could be used to distinguish between multiple pointing
557 The class of visible events may be changed at any time via
558 mousemask(). Events that can be reported include presses, releases,
559 single-, double- and triple-clicks (you can set the maximum
560 button-down time for clicks). If you don't make clicks visible, they
561 will be reported as press-release pairs. In some environments, the
562 event mask may include bits reporting the state of shift, alt, and
563 ctrl keys on the keyboard during the event.
565 A function to check whether a mouse event fell within a given window
566 is also supplied. You can use this to see whether a given window
567 should consider a mouse event relevant to it.
569 Because mouse event reporting will not be available in all
570 environments, it would be unwise to build ncurses applications that
571 require the use of a mouse. Rather, you should use the mouse as a
572 shortcut for point-and-shoot commands your application would normally
573 accept from the keyboard. Two of the test games in the ncurses
574 distribution (bs and knight) contain code that illustrates how this
577 See the manual page curs_mouse(3X) for full details of the
578 mouse-interface functions.
582 In order to clean up after the ncurses routines, the routine endwin()
583 is provided. It restores tty modes to what they were when initscr()
584 was first called, and moves the cursor down to the lower-left corner.
585 Thus, anytime after the call to initscr, endwin() should be called
588 Function Descriptions
590 We describe the detailed behavior of some important curses functions
591 here, as a supplement to the manual page descriptions.
593 Initialization and Wrapup
596 The first function called should almost always be initscr().
597 This will determine the terminal type and initialize curses
598 data structures. initscr() also arranges that the first call to
599 refresh() will clear the screen. If an error occurs a message
600 is written to standard error and the program exits. Otherwise
601 it returns a pointer to stdscr. A few functions may be called
602 before initscr (slk_init(), filter(), ripofflines(), use_env(),
603 and, if you are using multiple terminals, newterm().)
606 Your program should always call endwin() before exiting or
607 shelling out of the program. This function will restore tty
608 modes, move the cursor to the lower left corner of the screen,
609 reset the terminal into the proper non-visual mode. Calling
610 refresh() or doupdate() after a temporary escape from the
611 program will restore the ncurses screen from before the escape.
613 newterm(type, ofp, ifp)
614 A program which outputs to more than one terminal should use
615 newterm() instead of initscr(). newterm() should be called once
616 for each terminal. It returns a variable of type SCREEN * which
617 should be saved as a reference to that terminal. The arguments
618 are the type of the terminal (a string) and FILE pointers for
619 the output and input of the terminal. If type is NULL then the
620 environment variable $TERM is used. endwin() should called once
621 at wrapup time for each terminal opened using this function.
624 This function is used to switch to a different terminal
625 previously opened by newterm(). The screen reference for the
626 new terminal is passed as the parameter. The previous terminal
627 is returned by the function. All other calls affect only the
631 The inverse of newterm(); deallocates the data structures
632 associated with a given SCREEN reference.
634 Causing Output to the Terminal
636 refresh() and wrefresh(win)
637 These functions must be called to actually get any output on
638 the terminal, as other routines merely manipulate data
639 structures. wrefresh() copies the named window to the physical
640 terminal screen, taking into account what is already there in
641 order to do optimizations. refresh() does a refresh of
642 stdscr(). Unless leaveok() has been enabled, the physical
643 cursor of the terminal is left at the location of the window's
646 doupdate() and wnoutrefresh(win)
647 These two functions allow multiple updates with more efficiency
648 than wrefresh. To use them, it is important to understand how
649 curses works. In addition to all the window structures, curses
650 keeps two data structures representing the terminal screen: a
651 physical screen, describing what is actually on the screen, and
652 a virtual screen, describing what the programmer wants to have
653 on the screen. wrefresh works by first copying the named window
654 to the virtual screen (wnoutrefresh()), and then calling the
655 routine to update the screen (doupdate()). If the programmer
656 wishes to output several windows at once, a series of calls to
657 wrefresh will result in alternating calls to wnoutrefresh() and
658 doupdate(), causing several bursts of output to the screen. By
659 calling wnoutrefresh() for each window, it is then possible to
660 call doupdate() once, resulting in only one burst of output,
661 with fewer total characters transmitted (this also avoids a
662 visually annoying flicker at each update).
664 Low-Level Capability Access
666 setupterm(term, filenum, errret)
667 This routine is called to initialize a terminal's description,
668 without setting up the curses screen structures or changing the
669 tty-driver mode bits. term is the character string representing
670 the name of the terminal being used. filenum is the UNIX file
671 descriptor of the terminal to be used for output. errret is a
672 pointer to an integer, in which a success or failure indication
673 is returned. The values returned can be 1 (all is well), 0 (no
674 such terminal), or -1 (some problem locating the terminfo
677 The value of term can be given as NULL, which will cause the
678 value of TERM in the environment to be used. The errret pointer
679 can also be given as NULL, meaning no error code is wanted. If
680 errret is defaulted, and something goes wrong, setupterm() will
681 print an appropriate error message and exit, rather than
682 returning. Thus, a simple program can call setupterm(0, 1, 0)
683 and not worry about initialization errors.
685 After the call to setupterm(), the global variable cur_term is
686 set to point to the current structure of terminal capabilities.
687 By calling setupterm() for each terminal, and saving and
688 restoring cur_term, it is possible for a program to use two or
689 more terminals at once. Setupterm() also stores the names
690 section of the terminal description in the global character
691 array ttytype[]. Subsequent calls to setupterm() will overwrite
692 this array, so you'll have to save it yourself if need be.
696 NOTE: These functions are not part of the standard curses API!
699 This function can be used to explicitly set a trace level. If
700 the trace level is nonzero, execution of your program will
701 generate a file called `trace' in the current working directory
702 containing a report on the library's actions. Higher trace
703 levels enable more detailed (and verbose) reporting -- see
704 comments attached to TRACE_ defines in the curses.h file for
705 details. (It is also possible to set a trace level by assigning
706 a trace level value to the environment variable NCURSES_TRACE).
709 This function can be used to output your own debugging
710 information. It is only available only if you link with
711 -lncurses_g. It can be used the same way as printf(), only it
712 outputs a newline after the end of arguments. The output goes
713 to a file called trace in the current directory.
715 Trace logs can be difficult to interpret due to the sheer volume of
716 data dumped in them. There is a script called tracemunch included with
717 the ncurses distribution that can alleviate this problem somewhat; it
718 compacts long sequences of similar operations into more succinct
719 single-line pseudo-operations. These pseudo-ops can be distinguished
720 by the fact that they are named in capital letters.
722 Hints, Tips, and Tricks
724 The ncurses manual pages are a complete reference for this library. In
725 the remainder of this document, we discuss various useful methods that
726 may not be obvious from the manual page descriptions.
728 Some Notes of Caution
730 If you find yourself thinking you need to use noraw() or nocbreak(),
731 think again and move carefully. It's probably better design to use
732 getstr() or one of its relatives to simulate cooked mode. The noraw()
733 and nocbreak() functions try to restore cooked mode, but they may end
734 up clobbering some control bits set before you started your
735 application. Also, they have always been poorly documented, and are
736 likely to hurt your application's usability with other curses
739 Bear in mind that refresh() is a synonym for wrefresh(stdscr), and
740 don't try to mix use of stdscr with use of windows declared by
741 newwin(); a refresh() call will blow them off the screen. The right
742 way to handle this is to use subwin(), or not touch stdscr at all and
743 tile your screen with declared windows which you then wnoutrefresh()
744 somewhere in your program event loop, with a single doupdate() call to
745 trigger actual repainting.
747 You are much less likely to run into problems if you design your
748 screen layouts to use tiled rather than overlapping windows.
749 Historically, curses support for overlapping windows has been weak,
750 fragile, and poorly documented. The ncurses library is not yet an
751 exception to this rule.
753 There is a freeware panels library included in the ncurses
754 distribution that does a pretty good job of strengthening the
755 overlapping-windows facilities.
757 Try to avoid using the global variables LINES and COLS. Use getmaxyx()
758 on the stdscr context instead. Reason: your code may be ported to run
759 in an environment with window resizes, in which case several screens
760 could be open with different sizes.
762 Temporarily Leaving ncurses Mode
764 Sometimes you will want to write a program that spends most of its
765 time in screen mode, but occasionally returns to ordinary `cooked'
766 mode. A common reason for this is to support shell-out. This behavior
767 is simple to arrange in ncurses.
769 To leave ncurses mode, call endwin() as you would if you were
770 intending to terminate the program. This will take the screen back to
771 cooked mode; you can do your shell-out. When you want to return to
772 ncurses mode, simply call refresh() or doupdate(). This will repaint
775 There is a boolean function, isendwin(), which code can use to test
776 whether ncurses screen mode is active. It returns TRUE in the interval
777 between an endwin() call and the following refresh(), FALSE otherwise.
779 Here is some sample code for shellout:
780 addstr("Shelling out...");
781 def_prog_mode(); /* save current tty modes */
782 endwin(); /* restore original tty modes */
783 system("sh"); /* run shell */
784 addstr("returned.\n"); /* prepare return message */
785 refresh(); /* restore save modes, repaint screen */
787 Using ncurses Under xterm
789 A resize operation in X sends SIGWINCH to the application running
790 under xterm. The ncurses library does not catch this signal, because
791 it cannot in general know how you want the screen re-painted. You will
792 have to write the SIGWINCH handler yourself.
794 The easiest way to code your SIGWINCH handler is to have it do an
795 endwin, followed by an refresh and a screen repaint you code yourself.
796 The refresh will pick up the new screen size from the xterm's
799 Handling Multiple Terminal Screens
801 The initscr() function actually calls a function named newterm() to do
802 most of its work. If you are writing a program that opens multiple
803 terminals, use newterm() directly.
805 For each call, you will have to specify a terminal type and a pair of
806 file pointers; each call will return a screen reference, and stdscr
807 will be set to the last one allocated. You will switch between screens
808 with the set_term call. Note that you will also have to call
809 def_shell_mode and def_prog_mode on each tty yourself.
811 Testing for Terminal Capabilities
813 Sometimes you may want to write programs that test for the presence of
814 various capabilities before deciding whether to go into ncurses mode.
815 An easy way to do this is to call setupterm(), then use the functions
816 tigetflag(), tigetnum(), and tigetstr() to do your testing.
818 A particularly useful case of this often comes up when you want to
819 test whether a given terminal type should be treated as `smart'
820 (cursor-addressable) or `stupid'. The right way to test this is to see
821 if the return value of tigetstr("cup") is non-NULL. Alternatively, you
822 can include the term.h file and test the value of the macro
827 Use the addchstr() family of functions for fast screen-painting of
828 text when you know the text doesn't contain any control characters.
829 Try to make attribute changes infrequent on your screens. Don't use
830 the immedok() option!
832 Special Features of ncurses
834 When running on PC-clones, ncurses has enhanced support for the IBM
835 high-half and ROM characters. The A_ALTCHARSET highlight, enables
836 display of both high-half ACS graphics and the PC ROM graphics 0-31
837 that are normally interpreted as control characters.
839 The wresize() function allows you to resize a window in place.
841 Compatibility with Older Versions
843 Despite our best efforts, there are some differences between ncurses
844 and the (undocumented!) behavior of older curses implementations.
845 These arise from ambiguities or omissions in the documentation of the
848 Refresh of Overlapping Windows
850 If you define two windows A and B that overlap, and then alternately
851 scribble on and refresh them, the changes made to the overlapping
852 region under historic curses versions were often not documented
855 To understand why this is a problem, remember that screen updates are
856 calculated between two representations of the entire display. The
857 documentation says that when you refresh a window, it is first copied
858 to to the virtual screen, and then changes are calculated to update
859 the physical screen (and applied to the terminal). But "copied to" is
860 not very specific, and subtle differences in how copying works can
861 produce different behaviors in the case where two overlapping windows
862 are each being refreshed at unpredictable intervals.
864 What happens to the overlapping region depends on what wnoutrefresh()
865 does with its argument -- what portions of the argument window it
866 copies to the virtual screen. Some implementations do "change copy",
867 copying down only locations in the window that have changed (or been
868 marked changed with wtouchln() and friends). Some implementations do
869 "entire copy", copying all window locations to the virtual screen
870 whether or not they have changed.
872 The ncurses library itself has not always been consistent on this
873 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy.
874 Versions 1.8.6 and older, and versions 1.9.9 and newer, do change
877 For most commercial curses implementations, it is not documented and
878 not known for sure (at least not to the ncurses maintainers) whether
879 they do change copy or entire copy. We know that System V release 3
880 curses has logic in it that looks like an attempt to do change copy,
881 but the surrounding logic and data representations are sufficiently
882 complex, and our knowledge sufficiently indirect, that it's hard to
883 know whether this is reliable. It is not clear what the SVr4
884 documentation and XSI standard intend. The XSI Curses standard barely
885 mentions wnoutrefresh(); the SVr4 documents seem to be describing
886 entire-copy, but it is possible with some effort and straining to read
889 It might therefore be unwise to rely on either behavior in programs
890 that might have to be linked with other curses implementations.
891 Instead, you can do an explicit touchwin() before the wnoutrefresh()
892 call to guarantee an entire-contents copy anywhere.
894 The really clean way to handle this is to use the panels library. If,
895 when you want a screen update, you do update_panels(), it will do all
896 the necessary wnoutrfresh() calls for whatever panel stacking order
897 you have defined. Then you can do one doupdate() and there will be a
898 single burst of physical I/O that will do all your updates.
902 If you have been using a very old versions of ncurses (1.8.7 or older)
903 you may be surprised by the behavior of the erase functions. In older
904 versions, erased areas of a window were filled with a blank modified
905 by the window's current attribute (as set by wattrset(), wattron(),
906 wattroff() and friends).
908 In newer versions, this is not so. Instead, the attribute of erased
909 blanks is normal unless and until it is modified by the functions
910 bkgdset() or wbkgdset().
912 This change in behavior conforms ncurses to System V Release 4 and the
915 XSI Curses Conformance
917 The ncurses library is intended to be base-level conformant with the
918 XSI Curses standard from X/Open. Many extended-level features (in
919 fact, almost all features not directly concerned with wide characters
920 and internationalization) are also supported.
922 One effect of XSI conformance is the change in behavior described
923 under "Background Erase -- Compatibility with Old Versions".
925 Also, ncurses meets the XSI requirement that every macro entry point
926 have a corresponding function which may be linked (and will be
927 prototype-checked) if the macro definition is disabled with #undef.
931 The ncurses library by itself provides good support for screen
932 displays in which the windows are tiled (non-overlapping). In the more
933 general case that windows may overlap, you have to use a series of
934 wnoutrefresh() calls followed by a doupdate(), and be careful about
935 the order you do the window refreshes in. It has to be bottom-upwards,
936 otherwise parts of windows that should be obscured will show through.
938 When your interface design is such that windows may dive deeper into
939 the visibility stack or pop to the top at runtime, the resulting
940 book-keeping can be tedious and difficult to get right. Hence the
943 The panel library first appeared in AT&T System V. The version
944 documented here is the freeware panel code distributed with ncurses.
946 Compiling With the Panels Library
948 Your panels-using modules must import the panels library declarations
953 and must be linked explicitly with the panels library using an -lpanel
954 argument. Note that they must also link the ncurses library with
955 -lncurses. Many linkers are two-pass and will accept either order, but
956 it is still good practice to put -lpanel first and -lncurses second.
960 A panel object is a window that is implicitly treated as part of a
961 deck including all other panel objects. The deck has an implicit
962 bottom-to-top visibility order. The panels library includes an update
963 function (analogous to refresh()) that displays all panels in the deck
964 in the proper order to resolve overlaps. The standard window, stdscr,
965 is considered below all panels.
967 Details on the panels functions are available in the man pages. We'll
968 just hit the highlights here.
970 You create a panel from a window by calling new_panel() on a window
971 pointer. It then becomes the top of the deck. The panel's window is
972 available as the value of panel_window() called with the panel pointer
975 You can delete a panel (removing it from the deck) with del_panel.
976 This will not deallocate the associated window; you have to do that
977 yourself. You can replace a panel's window with a different window by
978 calling replace_window. The new window may be of different size; the
979 panel code will re-compute all overlaps. This operation doesn't change
980 the panel's position in the deck.
982 To move a panel's window, use move_panel(). The mvwin() function on
983 the panel's window isn't sufficient because it doesn't update the
984 panels library's representation of where the windows are. This
985 operation leaves the panel's depth, contents, and size unchanged.
987 Two functions (top_panel(), bottom_panel()) are provided for
988 rearranging the deck. The first pops its argument window to the top of
989 the deck; the second sends it to the bottom. Either operation leaves
990 the panel's screen location, contents, and size unchanged.
992 The function update_panels() does all the wnoutrefresh() calls needed
993 to prepare for doupdate() (which you must call yourself, afterwards).
995 Typically, you will want to call update_panels() and doupdate() just
996 before accepting command input, once in each cycle of interaction with
997 the user. If you call update_panels() after each and every panel
998 write, you'll generate a lot of unnecessary refresh activity and
1001 Panels, Input, and the Standard Screen
1003 You shouldn't mix wnoutrefresh() or wrefresh() operations with panels
1004 code; this will work only if the argument window is either in the top
1005 panel or unobscured by any other panels.
1007 The stsdcr window is a special case. It is considered below all
1008 panels. Because changes to panels may obscure parts of stdscr, though,
1009 you should call update_panels() before doupdate() even when you only
1012 Note that wgetch automatically calls wrefresh. Therefore, before
1013 requesting input from a panel window, you need to be sure that the
1014 panel is totally unobscured.
1016 There is presently no way to display changes to one obscured panel
1017 without repainting all panels.
1021 It's possible to remove a panel from the deck temporarily; use
1022 hide_panel for this. Use show_panel() to render it visible again. The
1023 predicate function panel_hidden tests whether or not a panel is
1026 The panel_update code ignores hidden panels. You cannot do top_panel()
1027 or bottom_panel on a hidden panel(). Other panels operations are
1030 Miscellaneous Other Facilities
1032 It's possible to navigate the deck using the functions panel_above()
1033 and panel_below. Handed a panel pointer, they return the panel above
1034 or below that panel. Handed NULL, they return the bottom-most or
1037 Every panel has an associated user pointer, not used by the panel
1038 code, to which you can attach application data. See the man page
1039 documentation of set_panel_userptr() and panel_userptr for details.
1043 A menu is a screen display that assists the user to choose some subset
1044 of a given set of items. The menu library is a curses extension that
1045 supports easy programming of menu hierarchies with a uniform but
1048 The menu library first appeared in AT&T System V. The version
1049 documented here is the freeware menu code distributed with ncurses.
1051 Compiling With the menu Library
1053 Your menu-using modules must import the menu library declarations with
1057 and must be linked explicitly with the menus library using an -lmenu
1058 argument. Note that they must also link the ncurses library with
1059 -lncurses. Many linkers are two-pass and will accept either order, but
1060 it is still good practice to put -lmenu first and -lncurses second.
1064 The menus created by this library consist of collections of items
1065 including a name string part and a description string part. To make
1066 menus, you create groups of these items and connect them with menu
1069 The menu can then by posted, that is written to an associated window.
1070 Actually, each menu has two associated windows; a containing window in
1071 which the programmer can scribble titles or borders, and a subwindow
1072 in which the menu items proper are displayed. If this subwindow is too
1073 small to display all the items, it will be a scrollable viewport on
1074 the collection of items.
1076 A menu may also be unposted (that is, undisplayed), and finally freed
1077 to make the storage associated with it and its items available for
1080 The general flow of control of a menu program looks like this:
1081 1. Initialize curses.
1082 2. Create the menu items, using new_item().
1083 3. Create the menu using new_menu().
1084 4. Post the menu using menu_post().
1085 5. Refresh the screen.
1086 6. Process user requests via an input loop.
1087 7. Unpost the menu using menu_unpost().
1088 8. Free the menu, using free_menu().
1089 9. Free the items using free_item().
1090 10. Terminate curses.
1094 Menus may be multi-valued or (the default) single-valued (see the
1095 manual page menu_opts(3x) to see how to change the default). Both
1096 types always have a current item.
1098 From a single-valued menu you can read the selected value simply by
1099 looking at the current item. From a multi-valued menu, you get the
1100 selected set by looping through the items applying the item_value()
1101 predicate function. Your menu-processing code can use the function
1102 set_item_value() to flag the items in the select set.
1104 Menu items can be made unselectable using set_item_opts() or
1105 item_opts_off() with the O_SELECTABLE argument. This is the only
1106 option so far defined for menus, but it is good practice to code as
1107 though other option bits might be on.
1111 The menu library calculates a minimum display size for your window,
1112 based on the following variables:
1114 * The number and maximum length of the menu items
1115 * Whether the O_ROWMAJOR option is enabled
1116 * Whether display of descriptions is enabled
1117 * Whatever menu format may have been set by the programmer
1118 * The length of the menu mark string used for highlighting selected
1121 The function set_menu_format() allows you to set the maximum size of
1122 the viewport or menu page that will be used to display menu items. You
1123 can retrieve any format associated with a menu with menu_format(). The
1124 default format is rows=16, columns=1.
1126 The actual menu page may be smaller than the format size. This depends
1127 on the item number and size and whether O_ROWMAJOR is on. This option
1128 (on by default) causes menu items to be displayed in a `raster-scan'
1129 pattern, so that if more than one item will fit horizontally the first
1130 couple of items are side-by-side in the top row. The alternative is
1131 column-major display, which tries to put the first several items in
1134 As mentioned above, a menu format not large enough to allow all items
1135 to fit on-screen will result in a menu display that is vertically
1138 You can scroll it with requests to the menu driver, which will be
1139 described in the section on menu input handling.
1141 Each menu has a mark string used to visually tag selected items; see
1142 the menu_mark(3x) manual page for details. The mark string length also
1143 influences the menu page size.
1145 The function scale_menu() returns the minimum display size that the
1146 menu code computes from all these factors. There are other menu
1147 display attributes including a select attribute, an attribute for
1148 selectable items, an attribute for unselectable items, and a pad
1149 character used to separate item name text from description text. These
1150 have reasonable defaults which the library allows you to change (see
1151 the menu_attribs(3x) manual page.
1155 Each menu has, as mentioned previously, a pair of associated windows.
1156 Both these windows are painted when the menu is posted and erased when
1157 the menu is unposted.
1159 The outer or frame window is not otherwise touched by the menu
1160 routines. It exists so the programmer can associate a title, a border,
1161 or perhaps help text with the menu and have it properly refreshed or
1162 erased at post/unpost time. The inner window or subwindow is where the
1163 current menu page is displayed.
1165 By default, both windows are stdscr. You can set them with the
1166 functions in menu_win(3x).
1168 When you call menu_post(), you write the menu to its subwindow. When
1169 you call menu_unpost(), you erase the subwindow, However, neither of
1170 these actually modifies the screen. To do that, call wrefresh() or
1173 Processing Menu Input
1175 The main loop of your menu-processing code should call menu_driver()
1176 repeatedly. The first argument of this routine is a menu pointer; the
1177 second is a menu command code. You should write an input-fetching
1178 routine that maps input characters to menu command codes, and pass its
1179 output to menu_driver(). The menu command codes are fully documented
1182 The simplest group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM,
1183 REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_UP_ITEM, REQ_DOWN_ITEM,
1184 REQ_LEFT_ITEM, REQ_RIGHT_ITEM. These change the currently selected
1185 item. These requests may cause scrolling of the menu page if it only
1186 partially displayed.
1188 There are explicit requests for scrolling which also change the
1189 current item (because the select location does not change, but the
1190 item there does). These are REQ_SCR_DLINE, REQ_SCR_ULINE,
1191 REQ_SCR_DPAGE, and REQ_SCR_UPAGE.
1193 The REQ_TOGGLE_ITEM selects or deselects the current item. It is for
1194 use in multi-valued menus; if you use it with O_ONEVALUE on, you'll
1195 get an error return (E_REQUEST_DENIED).
1197 Each menu has an associated pattern buffer. The menu_driver() logic
1198 tries to accumulate printable ASCII characters passed in in that
1199 buffer; when it matches a prefix of an item name, that item (or the
1200 next matching item) is selected. If appending a character yields no
1201 new match, that character is deleted from the pattern buffer, and
1202 menu_driver() returns E_NO_MATCH.
1204 Some requests change the pattern buffer directly: REQ_CLEAR_PATTERN,
1205 REQ_BACK_PATTERN, REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter two are
1206 useful when pattern buffer input matches more than one item in a
1209 Each successful scroll or item navigation request clears the pattern
1210 buffer. It is also possible to set the pattern buffer explicitly with
1213 Finally, menu driver requests above the constant MAX_COMMAND are
1214 considered application-specific commands. The menu_driver() code
1215 ignores them and returns E_UNKNOWN_COMMAND.
1217 Miscellaneous Other Features
1219 Various menu options can affect the processing and visual appearance
1220 and input processing of menus. See menu_opts(3x) for details.
1222 It is possible to change the current item from application code; this
1223 is useful if you want to write your own navigation requests. It is
1224 also possible to explicitly set the top row of the menu display. See
1225 mitem_current(3x). If your application needs to change the menu
1226 subwindow cursor for any reason, pos_menu_cursor() will restore it to
1227 the correct location for continuing menu driver processing.
1229 It is possible to set hooks to be called at menu initialization and
1230 wrapup time, and whenever the selected item changes. See
1233 Each item, and each menu, has an associated user pointer on which you
1234 can hang application data. See mitem_userptr(3x) and menu_userptr(3x).
1238 The form library is a curses extension that supports easy programming
1239 of on-screen forms for data entry and program control.
1241 The form library first appeared in AT&T System V. The version
1242 documented here is the freeware form code distributed with ncurses.
1244 Compiling With the form Library
1246 Your form-using modules must import the form library declarations with
1250 and must be linked explicitly with the forms library using an -lform
1251 argument. Note that they must also link the ncurses library with
1252 -lncurses. Many linkers are two-pass and will accept either order, but
1253 it is still good practice to put -lform first and -lncurses second.
1257 A form is a collection of fields; each field may be either a label
1258 (explanatory text) or a data-entry location. Long forms may be
1259 segmented into pages; each entry to a new page clears the screen.
1261 To make forms, you create groups of fields and connect them with form
1262 frame objects; the form library makes this relatively simple.
1264 Once defined, a form can be posted, that is written to an associated
1265 window. Actually, each form has two associated windows; a containing
1266 window in which the programmer can scribble titles or borders, and a
1267 subwindow in which the form fields proper are displayed.
1269 As the form user fills out the posted form, navigation and editing
1270 keys support movement between fields, editing keys support modifying
1271 field, and plain text adds to or changes data in a current field. The
1272 form library allows you (the forms designer) to bind each navigation
1273 and editing key to any keystroke accepted by curses Fields may have
1274 validation conditions on them, so that they check input data for type
1275 and value. The form library supplies a rich set of pre-defined field
1276 types, and makes it relatively easy to define new ones.
1278 Once its transaction is completed (or aborted), a form may be unposted
1279 (that is, undisplayed), and finally freed to make the storage
1280 associated with it and its items available for re-use.
1282 The general flow of control of a form program looks like this:
1283 1. Initialize curses.
1284 2. Create the form fields, using new_field().
1285 3. Create the form using new_form().
1286 4. Post the form using form_post().
1287 5. Refresh the screen.
1288 6. Process user requests via an input loop.
1289 7. Unpost the form using form_unpost().
1290 8. Free the form, using free_form().
1291 9. Free the fields using free_field().
1292 10. Terminate curses.
1294 Note that this looks much like a menu program; the form library
1295 handles tasks which are in many ways similar, and its interface was
1296 obviously designed to resemble that of the menu library wherever
1299 In forms programs, however, the `process user requests' is somewhat
1300 more complicated than for menus. Besides menu-like navigation
1301 operations, the menu driver loop has to support field editing and data
1304 Creating and Freeing Fields and Forms
1306 The basic function for creating fields is new_field():
1308 FIELD *new_field(int height, int width, /* new field size */
1309 int top, int left, /* upper left corner */
1310 int offscreen, /* number of offscreen rows */
1311 int nbuf); /* number of working buffers */
1313 Menu items always occupy a single row, but forms fields may have
1314 multiple rows. So new_field() requires you to specify a width and
1315 height (the first two arguments, which mist both be greater than
1318 You must also specify the location of the field's upper left corner on
1319 the screen (the third and fourth arguments, which must be zero or
1320 greater). Note that these coordinates are relative to the form
1321 subwindow, which will coincide with stdscr by default but need not be
1322 stdscr if you've done an explicit set_form_window() call.
1324 The fifth argument allows you to specify a number of off-screen rows.
1325 If this is zero, the entire field will always be displayed. If it is
1326 nonzero, the form will be scrollable, with only one screen-full
1327 (initially the top part) displayed at any given time. If you make a
1328 field dynamic and grow it so it will no longer fit on the screen, the
1329 form will become scrollable even if the offscreen argument was
1332 The forms library allocates one working buffer per field; the size of
1333 each buffer is ((height + offscreen)*width + 1, one character for each
1334 position in the field plus a NUL terminator. The sixth argument is the
1335 number of additional data buffers to allocate for the field; your
1336 application can use them for its own purposes.
1338 FIELD *dup_field(FIELD *field, /* field to copy */
1339 int top, int left); /* location of new copy */
1341 The function dup_field() duplicates an existing field at a new
1342 location. Size and buffering information are copied; some attribute
1343 flags and status bits are not (see the form_field_new(3X) for
1346 FIELD *link_field(FIELD *field, /* field to copy */
1347 int top, int left); /* location of new copy */
1349 The function link_field() also duplicates an existing field at a new
1350 location. The difference from dup_field() is that it arranges for the
1351 new field's buffer to be shared with the old one.
1353 Besides the obvious use in making a field editable from two different
1354 form pages, linked fields give you a way to hack in dynamic labels. If
1355 you declare several fields linked to an original, and then make them
1356 inactive, changes from the original will still be propagated to the
1359 As with duplicated fields, linked fields have attribute bits separate
1362 As you might guess, all these field-allocations return NULL if the
1363 field allocation is not possible due to an out-of-memory error or
1364 out-of-bounds arguments.
1366 To connect fields to a form, use
1368 FORM *new_form(FIELD **fields);
1370 This function expects to see a NULL-terminated array of field
1371 pointers. Said fields are connected to a newly-allocated form object;
1372 its address is returned (or else NULL if the allocation fails).
1374 Note that new_field() does not copy the pointer array into private
1375 storage; if you modify the contents of the pointer array during forms
1376 processing, all manner of bizarre things might happen. Also note that
1377 any given field may only be connected to one form.
1379 The functions free_field() and free_form are available to free field
1380 and form objects. It is an error to attempt to free a field connected
1381 to a form, but not vice-versa; thus, you will generally free your form
1384 Fetching and Changing Field Attributes
1386 Each form field has a number of location and size attributes
1387 associated with it. There are other field attributes used to control
1388 display and editing of the field. Some (for example, the O_STATIC bit)
1389 involve sufficient complications to be covered in sections of their
1390 own later on. We cover the functions used to get and set several basic
1393 When a field is created, the attributes not specified by the new_field
1394 function are copied from an invisible system default field. In
1395 attribute-setting and -fetching functions, the argument NULL is taken
1396 to mean this field. Changes to it persist as defaults until your forms
1397 application terminates.
1399 Fetching Size and Location Data
1401 You can retrieve field sizes and locations through:
1403 int field_info(FIELD *field, /* field from which to fetch */
1404 int *height, *int width, /* field size */
1405 int *top, int *left, /* upper left corner */
1406 int *offscreen, /* number of offscreen rows */
1407 int *nbuf); /* number of working buffers */
1409 This function is a sort of inverse of new_field(); instead of setting
1410 size and location attributes of a new field, it fetches them from an
1413 Changing the Field Location
1415 If is possible to move a field's location on the screen:
1417 int move_field(FIELD *field, /* field to alter */
1418 int top, int left); /* new upper-left corner */
1420 You can, of course. query the current location through field_info().
1422 The Justification Attribute
1424 One-line fields may be unjustified, justified right, justified left,
1425 or centered. Here is how you manipulate this attribute:
1427 int set_field_just(FIELD *field, /* field to alter */
1428 int justmode); /* mode to set */
1430 int field_just(FIELD *field); /* fetch mode of field */
1432 The mode values accepted and returned by this functions are
1433 preprocessor macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or
1436 Field Display Attributes
1438 For each field, you can set a foreground attribute for entered
1439 characters, a background attribute for the entire field, and a pad
1440 character for the unfilled portion of the field. You can also control
1441 pagination of the form.
1443 This group of four field attributes controls the visual appearance of
1444 the field on the screen, without affecting in any way the data in the
1447 int set_field_fore(FIELD *field, /* field to alter */
1448 chtype attr); /* attribute to set */
1450 chtype field_fore(FIELD *field); /* field to query */
1452 int set_field_back(FIELD *field, /* field to alter */
1453 chtype attr); /* attribute to set */
1455 chtype field_back(FIELD *field); /* field to query */
1457 int set_field_pad(FIELD *field, /* field to alter */
1458 int pad); /* pad character to set */
1460 chtype field_pad(FIELD *field);
1462 int set_new_page(FIELD *field, /* field to alter */
1463 int flag); /* TRUE to force new page */
1465 chtype new_page(FIELD *field); /* field to query */
1467 The attributes set and returned by the first four functions are normal
1468 curses(3x) display attribute values (A_STANDOUT, A_BOLD, A_REVERSE
1469 etc). The page bit of a field controls whether it is displayed at the
1470 start of a new form screen.
1474 There is also a large collection of field option bits you can set to
1475 control various aspects of forms processing. You can manipulate them
1476 with these functions:
1478 int set_field_opts(FIELD *field, /* field to alter */
1479 int attr); /* attribute to set */
1481 int field_opts_on(FIELD *field, /* field to alter */
1482 int attr); /* attributes to turn on */
1484 int field_opts_off(FIELD *field, /* field to alter */
1485 int attr); /* attributes to turn off */
1487 int field_opts(FIELD *field); /* field to query */
1489 By default, all options are on. Here are the available option bits:
1492 Controls whether the field is visible on the screen. Can be
1493 used during form processing to hide or pop up fields depending
1494 on the value of parent fields.
1497 Controls whether the field is active during forms processing
1498 (i.e. visited by form navigation keys). Can be used to make
1499 labels or derived fields with buffer values alterable by the
1500 forms application, not the user.
1503 Controls whether data is displayed during field entry. If this
1504 option is turned off on a field, the library will accept and
1505 edit data in that field, but it will not be displayed and the
1506 visible field cursor will not move. You can turn off the
1507 O_PUBLIC bit to define password fields.
1510 Controls whether the field's data can be modified. When this
1511 option is off, all editing requests except REQ_PREV_CHOICE and
1512 REQ_NEXT_CHOICE will fail. Such read-only fields may be useful
1516 Controls word-wrapping in multi-line fields. Normally, when any
1517 character of a (blank-separated) word reaches the end of the
1518 current line, the entire word is wrapped to the next line
1519 (assuming there is one). When this option is off, the word will
1520 be split across the line break.
1523 Controls field blanking. When this option is on, entering a
1524 character at the first field position erases the entire field
1525 (except for the just-entered character).
1528 Controls automatic skip to next field when this one fills.
1529 Normally, when the forms user tries to type more data into a
1530 field than will fit, the editing location jumps to next field.
1531 When this option is off, the user's cursor will hang at the end
1532 of the field. This option is ignored in dynamic fields that
1533 have not reached their size limit.
1536 Controls whether validation is applied to blank fields.
1537 Normally, it is not; the user can leave a field blank without
1538 invoking the usual validation check on exit. If this option is
1539 off on a field, exit from it will invoke a validation check.
1542 Controls whether validation occurs on every exit, or only after
1543 the field is modified. Normally the latter is true. Setting
1544 O_PASSOK may be useful if your field's validation function may
1545 change during forms processing.
1548 Controls whether the field is fixed to its initial dimensions.
1549 If you turn this off, the field becomes dynamic and will
1550 stretch to fit entered data.
1552 A field's options cannot be changed while the field is currently
1553 selected. However, options may be changed on posted fields that are
1556 The option values are bit-masks and can be composed with logical-or in
1561 Every field has a status flag, which is set to FALSE when the field is
1562 created and TRUE when the value in field buffer 0 changes. This flag
1563 can be queried and set directly:
1565 int set_field_status(FIELD *field, /* field to alter */
1566 int status); /* mode to set */
1568 int field_status(FIELD *field); /* fetch mode of field */
1570 Setting this flag under program control can be useful if you use the
1571 same form repeatedly, looking for modified fields each time.
1573 Calling field_status() on a field not currently selected for input
1574 will return a correct value. Calling field_status() on a field that is
1575 currently selected for input may not necessarily give a correct field
1576 status value, because entered data isn't necessarily copied to buffer
1577 zero before the exit validation check. To guarantee that the returned
1578 status value reflects reality, call field_status() either (1) in the
1579 field's exit validation check routine, (2) from the field's or form's
1580 initialization or termination hooks, or (3) just after a
1581 REQ_VALIDATION request has been processed by the forms driver.
1585 Each field structure contains one character pointer slot that is not
1586 used by the forms library. It is intended to be used by applications
1587 to store private per-field data. You can manipulate it with:
1589 int set_field_userptr(FIELD *field, /* field to alter */
1590 char *userptr); /* mode to set */
1592 char *field_userptr(FIELD *field); /* fetch mode of field */
1594 (Properly, this user pointer field ought to have (void *) type. The
1595 (char *) type is retained for System V compatibility.)
1597 It is valid to set the user pointer of the default field (with a
1598 set_field_userptr() call passed a NULL field pointer.) When a new
1599 field is created, the default-field user pointer is copied to
1600 initialize the new field's user pointer.
1602 Variable-Sized Fields
1604 Normally, a field is fixed at the size specified for it at creation
1605 time. If, however, you turn off its O_STATIC bit, it becomes dynamic
1606 and will automatically resize itself to accommodate data as it is
1607 entered. If the field has extra buffers associated with it, they will
1608 grow right along with the main input buffer.
1610 A one-line dynamic field will have a fixed height (1) but variable
1611 width, scrolling horizontally to display data within the field area as
1612 originally dimensioned and located. A multi-line dynamic field will
1613 have a fixed width, but variable height (number of rows), scrolling
1614 vertically to display data within the field area as originally
1615 dimensioned and located.
1617 Normally, a dynamic field is allowed to grow without limit. But it is
1618 possible to set an upper limit on the size of a dynamic field. You do
1619 it with this function:
1621 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
1622 int max_size); /* upper limit on field size */
1624 If the field is one-line, max_size is taken to be a column size limit;
1625 if it is multi-line, it is taken to be a line size limit. To disable
1626 any limit, use an argument of zero. The growth limit can be changed
1627 whether or not the O_STATIC bit is on, but has no effect until it is.
1629 The following properties of a field change when it becomes dynamic:
1630 * If there is no growth limit, there is no final position of the
1631 field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored.
1632 * Field justification will be ignored (though whatever justification
1633 is set up will be retained internally and can be queried).
1634 * The dup_field() and link_field() calls copy dynamic-buffer sizes.
1635 If the O_STATIC option is set on one of a collection of links,
1636 buffer resizing will occur only when the field is edited through
1638 * The call field_info() will retrieve the original static size of
1639 the field; use dynamic_field_info() to get the actual dynamic
1644 By default, a field will accept any data that will fit in its input
1645 buffer. However, it is possible to attach a validation type to a
1646 field. If you do this, any attempt to leave the field while it
1647 contains data that doesn't match the validation type will fail. Some
1648 validation types also have a character-validity check for each time a
1649 character is entered in the field.
1651 A field's validation check (if any) is not called when
1652 set_field_buffer() modifies the input buffer, nor when that buffer is
1653 changed through a linked field.
1655 The form library provides a rich set of pre-defined validation types,
1656 and gives you the capability to define custom ones of your own. You
1657 can examine and change field validation attributes with the following
1660 int set_field_type(FIELD *field, /* field to alter */
1661 FIELDTYPE *ftype, /* type to associate */
1662 ...); /* additional arguments*/
1664 FIELDTYPE *field_type(FIELD *field); /* field to query */
1666 The validation type of a field is considered an attribute of the
1667 field. As with other field attributes, Also, doing set_field_type()
1668 with a NULL field default will change the system default for
1669 validation of newly-created fields.
1671 Here are the pre-defined validation types:
1675 This field type accepts alphabetic data; no blanks, no digits, no
1676 special characters (this is checked at character-entry time). It is
1679 int set_field_type(FIELD *field, /* field to alter */
1680 TYPE_ALPHA, /* type to associate */
1681 int width); /* maximum width of field */
1683 The width argument sets a minimum width of data. Typically you'll want
1684 to set this to the field width; if it's greater than the field width,
1685 the validation check will always fail. A minimum width of zero makes
1686 field completion optional.
1690 This field type accepts alphabetic data and digits; no blanks, no
1691 special characters (this is checked at character-entry time). It is
1694 int set_field_type(FIELD *field, /* field to alter */
1695 TYPE_ALNUM, /* type to associate */
1696 int width); /* maximum width of field */
1698 The width argument sets a minimum width of data. As with TYPE_ALPHA,
1699 typically you'll want to set this to the field width; if it's greater
1700 than the field width, the validation check will always fail. A minimum
1701 width of zero makes field completion optional.
1705 This type allows you to restrict a field's values to be among a
1706 specified set of string values (for example, the two-letter postal
1707 codes for U.S. states). It is set up with:
1709 int set_field_type(FIELD *field, /* field to alter */
1710 TYPE_ENUM, /* type to associate */
1711 char **valuelist; /* list of possible values */
1712 int checkcase; /* case-sensitive? */
1713 int checkunique); /* must specify uniquely? */
1715 The valuelist parameter must point at a NULL-terminated list of valid
1716 strings. The checkcase argument, if true, makes comparison with the
1717 string case-sensitive.
1719 When the user exits a TYPE_ENUM field, the validation procedure tries
1720 to complete the data in the buffer to a valid entry. If a complete
1721 choice string has been entered, it is of course valid. But it is also
1722 possible to enter a prefix of a valid string and have it completed for
1725 By default, if you enter such a prefix and it matches more than one
1726 value in the string list, the prefix will be completed to the first
1727 matching value. But the checkunique argument, if true, requires prefix
1728 matches to be unique in order to be valid.
1730 The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be
1731 particularly useful with these fields.
1735 This field type accepts an integer. It is set up as follows:
1737 int set_field_type(FIELD *field, /* field to alter */
1738 TYPE_INTEGER, /* type to associate */
1739 int padding, /* # places to zero-pad to */
1740 int vmin, int vmax); /* valid range */
1742 Valid characters consist of an optional leading minus and digits. The
1743 range check is performed on exit. If the range maximum is less than or
1744 equal to the minimum, the range is ignored.
1746 If the value passes its range check, it is padded with as many leading
1747 zero digits as necessary to meet the padding argument.
1749 A TYPE_INTEGER value buffer can conveniently be interpreted with the C
1750 library function atoi(3).
1754 This field type accepts a decimal number. It is set up as follows:
1756 int set_field_type(FIELD *field, /* field to alter */
1757 TYPE_NUMERIC, /* type to associate */
1758 int padding, /* # places of precision */
1759 double vmin, double vmax); /* valid range */
1761 Valid characters consist of an optional leading minus and digits.
1762 possibly including a decimal point. If your system supports locale's,
1763 the decimal point character used must be the one defined by your
1764 locale. The range check is performed on exit. If the range maximum is
1765 less than or equal to the minimum, the range is ignored.
1767 If the value passes its range check, it is padded with as many
1768 trailing zero digits as necessary to meet the padding argument.
1770 A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
1771 library function atof(3).
1775 This field type accepts data matching a regular expression. It is set
1778 int set_field_type(FIELD *field, /* field to alter */
1779 TYPE_REGEXP, /* type to associate */
1780 char *regexp); /* expression to match */
1782 The syntax for regular expressions is that of regcomp(3). The check
1783 for regular-expression match is performed on exit.
1785 Direct Field Buffer Manipulation
1787 The chief attribute of a field is its buffer contents. When a form has
1788 been completed, your application usually needs to know the state of
1789 each field buffer. You can find this out with:
1791 char *field_buffer(FIELD *field, /* field to query */
1792 int bufindex); /* number of buffer to query */
1794 Normally, the state of the zero-numbered buffer for each field is set
1795 by the user's editing actions on that field. It's sometimes useful to
1796 be able to set the value of the zero-numbered (or some other) buffer
1797 from your application:
1799 int set_field_buffer(FIELD *field, /* field to alter */
1800 int bufindex, /* number of buffer to alter */
1801 char *value); /* string value to set */
1803 If the field is not large enough and cannot be resized to a
1804 sufficiently large size to contain the specified value, the value will
1805 be truncated to fit.
1807 Calling field_buffer() with a null field pointer will raise an error.
1808 Calling field_buffer() on a field not currently selected for input
1809 will return a correct value. Calling field_buffer() on a field that is
1810 currently selected for input may not necessarily give a correct field
1811 buffer value, because entered data isn't necessarily copied to buffer
1812 zero before the exit validation check. To guarantee that the returned
1813 buffer value reflects on-screen reality, call field_buffer() either
1814 (1) in the field's exit validation check routine, (2) from the field's
1815 or form's initialization or termination hooks, or (3) just after a
1816 REQ_VALIDATION request has been processed by the forms driver.
1820 As with field attributes, form attributes inherit a default from a
1821 system default form structure. These defaults can be queried or set by
1822 of these functions using a form-pointer argument of NULL.
1824 The principal attribute of a form is its field list. You can query and
1825 change this list with:
1827 int set_form_fields(FORM *form, /* form to alter */
1828 FIELD **fields); /* fields to connect */
1830 char *form_fields(FORM *form); /* fetch fields of form */
1832 int field_count(FORM *form); /* count connect fields */
1834 The second argument of set_form_fields() may be a NULL-terminated
1835 field pointer array like the one required by new_form(). In that case,
1836 the old fields of the form are disconnected but not freed (and
1837 eligible to be connected to other forms), then the new fields are
1840 It may also be null, in which case the old fields are disconnected
1841 (and not freed) but no new ones are connected.
1843 The field_count() function simply counts the number of fields
1844 connected to a given from. It returns -1 if the form-pointer argument
1847 Control of Form Display
1849 In the overview section, you saw that to display a form you normally
1850 start by defining its size (and fields), posting it, and refreshing
1851 the screen. There is an hidden step before posting, which is the
1852 association of the form with a frame window (actually, a pair of
1853 windows) within which it will be displayed. By default, the forms
1854 library associates every form with the full-screen window stdscr.
1856 By making this step explicit, you can associate a form with a declared
1857 frame window on your screen display. This can be useful if you want to
1858 adapt the form display to different screen sizes, dynamically tile
1859 forms on the screen, or use a form as part of an interface layout
1862 The two windows associated with each form have the same functions as
1863 their analogues in the menu library. Both these windows are painted
1864 when the form is posted and erased when the form is unposted.
1866 The outer or frame window is not otherwise touched by the form
1867 routines. It exists so the programmer can associate a title, a border,
1868 or perhaps help text with the form and have it properly refreshed or
1869 erased at post/unpost time. The inner window or subwindow is where the
1870 current form page is actually displayed.
1872 In order to declare your own frame window for a form, you'll need to
1873 know the size of the form's bounding rectangle. You can get this
1876 int scale_form(FORM *form, /* form to query */
1877 int *rows, /* form rows */
1878 int *cols); /* form cols */
1880 The form dimensions are passed back in the locations pointed to by the
1881 arguments. Once you have this information, you can use it to declare
1882 of windows, then use one of these functions:
1884 int set_form_win(FORM *form, /* form to alter */
1885 WINDOW *win); /* frame window to connect */
1887 WINDOW *form_win(FORM *form); /* fetch frame window of form */
1889 int set_form_sub(FORM *form, /* form to alter */
1890 WINDOW *win); /* form subwindow to connect */
1892 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
1894 Note that curses operations, including refresh(), on the form, should
1895 be done on the frame window, not the form subwindow.
1897 It is possible to check from your application whether all of a
1898 scrollable field is actually displayed within the menu subwindow. Use
1901 int data_ahead(FORM *form); /* form to be queried */
1903 int data_behind(FORM *form); /* form to be queried */
1905 The function data_ahead() returns TRUE if (a) the current field is
1906 one-line and has undisplayed data off to the right, (b) the current
1907 field is multi-line and there is data off-screen below it.
1909 The function data_behind() returns TRUE if the first (upper left hand)
1910 character position is off-screen (not being displayed).
1912 Finally, there is a function to restore the form window's cursor to
1913 the value expected by the forms driver:
1915 int pos_form_cursor(FORM *) /* form to be queried */
1917 If your application changes the form window cursor, call this function
1918 before handing control back to the forms driver in order to
1921 Input Processing in the Forms Driver
1923 The function form_driver() handles virtualized input requests for form
1924 navigation, editing, and validation requests, just as menu_driver does
1925 for menus (see the section on menu input handling).
1927 int form_driver(FORM *form, /* form to pass input to */
1928 int request); /* form request code */
1930 Your input virtualization function needs to take input and then
1931 convert it to either an alphanumeric character (which is treated as
1932 data to be entered in the currently-selected field), or a forms
1935 The forms driver provides hooks (through input-validation and
1936 field-termination functions) with which your application code can
1937 check that the input taken by the driver matched what was expected.
1939 Page Navigation Requests
1941 These requests cause page-level moves through the form, triggering
1942 display of a new form screen.
1945 Move to the next form page.
1948 Move to the previous form page.
1951 Move to the first form page.
1954 Move to the last form page.
1956 These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from
1957 the last page goes to the first, and REQ_PREV_PAGE from the first page
1960 Inter-Field Navigation Requests
1962 These requests handle navigation between fields on the same page.
1968 Move to previous field.
1971 Move to the first field.
1974 Move to the last field.
1977 Move to sorted next field.
1980 Move to sorted previous field.
1983 Move to the sorted first field.
1986 Move to the sorted last field.
1992 Move right to field.
2000 These requests treat the list of fields on a page as cyclic; that is,
2001 REQ_NEXT_FIELD from the last field goes to the first, and
2002 REQ_PREV_FIELD from the first field goes to the last. The order of the
2003 fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests)
2004 is simply the order of the field pointers in the form array (as set up
2005 by new_form() or set_form_fields()
2007 It is also possible to traverse the fields as if they had been sorted
2008 in screen-position order, so the sequence goes left-to-right and
2009 top-to-bottom. To do this, use the second group of four
2010 sorted-movement requests.
2012 Finally, it is possible to move between fields using visual directions
2013 up, down, right, and left. To accomplish this, use the third group of
2014 four requests. Note, however, that the position of a form for purposes
2015 of these requests is its upper-left corner.
2017 For example, suppose you have a multi-line field B, and two
2018 single-line fields A and C on the same line with B, with A to the left
2019 of B and C to the right of B. A REQ_MOVE_RIGHT from A will go to B
2020 only if A, B, and C all share the same first line; otherwise it will
2023 Intra-Field Navigation Requests
2025 These requests drive movement of the edit cursor within the currently
2029 Move to next character.
2032 Move to previous character.
2038 Move to previous line.
2044 Move to previous word.
2047 Move to beginning of field.
2050 Move to end of field.
2053 Move to beginning of line.
2056 Move to end of line.
2062 Move right in field.
2070 Each word is separated from the previous and next characters by
2071 whitespace. The commands to move to beginning and end of line or field
2072 look for the first or last non-pad character in their ranges.
2076 Fields that are dynamic and have grown and fields explicitly created
2077 with offscreen rows are scrollable. One-line fields scroll
2078 horizontally; multi-line fields scroll vertically. Most scrolling is
2079 triggered by editing and intra-field movement (the library scrolls the
2080 field to keep the cursor visible). It is possible to explicitly
2081 request scrolling with the following requests:
2084 Scroll vertically forward a line.
2087 Scroll vertically backward a line.
2090 Scroll vertically forward a page.
2093 Scroll vertically backward a page.
2096 Scroll vertically forward half a page.
2099 Scroll vertically backward half a page.
2102 Scroll horizontally forward a character.
2105 Scroll horizontally backward a character.
2108 Scroll horizontally one field width forward.
2111 Scroll horizontally one field width backward.
2114 Scroll horizontally one half field width forward.
2117 Scroll horizontally one half field width backward.
2119 For scrolling purposes, a page of a field is the height of its visible
2124 When you pass the forms driver an ASCII character, it is treated as a
2125 request to add the character to the field's data buffer. Whether this
2126 is an insertion or a replacement depends on the field's edit mode
2127 (insertion is the default.
2129 The following requests support editing the field and changing the edit
2139 New line request (see below for explanation).
2142 Insert space at character location.
2145 Insert blank line at character location.
2148 Delete character at cursor.
2151 Delete previous word at cursor.
2154 Delete line at cursor.
2157 Delete word at cursor.
2160 Clear to end of line.
2163 Clear to end of field.
2168 The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is
2169 complicated and partly controlled by a pair of forms options. The
2170 special cases are triggered when the cursor is at the beginning of a
2171 field, or on the last line of the field.
2173 First, we consider REQ_NEW_LINE:
2175 The normal behavior of REQ_NEW_LINE in insert mode is to break the
2176 current line at the position of the edit cursor, inserting the portion
2177 of the current line after the cursor as a new line following the
2178 current and moving the cursor to the beginning of that new line (you
2179 may think of this as inserting a newline in the field buffer).
2181 The normal behavior of REQ_NEW_LINE in overlay mode is to clear the
2182 current line from the position of the edit cursor to end of line. The
2183 cursor is then moved to the beginning of the next line.
2185 However, REQ_NEW_LINE at the beginning of a field, or on the last line
2186 of a field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is
2187 off, this special action is disabled.
2189 Now, let us consider REQ_DEL_PREV:
2191 The normal behavior of REQ_DEL_PREV is to delete the previous
2192 character. If insert mode is on, and the cursor is at the start of a
2193 line, and the text on that line will fit on the previous one, it
2194 instead appends the contents of the current line to the previous one
2195 and deletes the current line (you may think of this as deleting a
2196 newline from the field buffer).
2198 However, REQ_DEL_PREV at the beginning of a field is instead treated
2199 as a REQ_PREV_FIELD.
2201 If the O_BS_OVERLOAD option is off, this special action is disabled
2202 and the forms driver just returns E_REQUEST_DENIED.
2204 See Form Options for discussion of how to set and clear the overload
2209 If the type of your field is ordered, and has associated functions for
2210 getting the next and previous values of the type from a given value,
2211 there are requests that can fetch that value into the field buffer:
2214 Place the successor value of the current value in the buffer.
2217 Place the predecessor value of the current value in the buffer.
2219 Of the built-in field types, only TYPE_ENUM has built-in successor and
2220 predecessor functions. When you define a field type of your own (see
2221 Custom Validation Types), you can associate our own ordering
2224 Application Commands
2226 Form requests are represented as integers above the curses value
2227 greater than KEY_MAX and less than or equal to the constant
2228 MAX_COMMAND. If your input-virtualization routine returns a value
2229 above MAX_COMMAND, the forms driver will ignore it.
2233 It is possible to set function hooks to be executed whenever the
2234 current field or form changes. Here are the functions that support
2237 typedef void (*HOOK)(); /* pointer to function returning void */
2239 int set_form_init(FORM *form, /* form to alter */
2240 HOOK hook); /* initialization hook */
2242 HOOK form_init(FORM *form); /* form to query */
2244 int set_form_term(FORM *form, /* form to alter */
2245 HOOK hook); /* termination hook */
2247 HOOK form_term(FORM *form); /* form to query */
2249 int set_field_init(FORM *form, /* form to alter */
2250 HOOK hook); /* initialization hook */
2252 HOOK field_init(FORM *form); /* form to query */
2254 int set_field_term(FORM *form, /* form to alter */
2255 HOOK hook); /* termination hook */
2257 HOOK field_term(FORM *form); /* form to query */
2259 These functions allow you to either set or query four different hooks.
2260 In each of the set functions, the second argument should be the
2261 address of a hook function. These functions differ only in the timing
2265 This hook is called when the form is posted; also, just after
2266 each page change operation.
2269 This hook is called when the form is posted; also, just after
2273 This hook is called just after field validation; that is, just
2274 before the field is altered. It is also called when the form is
2278 This hook is called when the form is unposted; also, just
2279 before each page change operation.
2281 Calls to these hooks may be triggered
2282 1. When user editing requests are processed by the forms driver
2283 2. When the current page is changed by set_current_field() call
2284 3. When the current field is changed by a set_form_page() call
2286 See Field Change Commands for discussion of the latter two cases.
2288 You can set a default hook for all fields by passing one of the set
2289 functions a NULL first argument.
2291 You can disable any of these hooks by (re)setting them to NULL, the
2294 Field Change Commands
2296 Normally, navigation through the form will be driven by the user's
2297 input requests. But sometimes it is useful to be able to move the
2298 focus for editing and viewing under control of your application, or
2299 ask which field it currently is in. The following functions help you
2302 int set_current_field(FORM *form, /* form to alter */
2303 FIELD *field); /* field to shift to */
2305 FIELD *current_field(FORM *form); /* form to query */
2307 int field_index(FORM *form, /* form to query */
2308 FIELD *field); /* field to get index of */
2310 The function field_index() returns the index of the given field in the
2311 given form's field array (the array passed to new_form() or
2314 The initial current field of a form is the first active field on the
2315 first page. The function set_form_fields() resets this.
2317 It is also possible to move around by pages.
2319 int set_form_page(FORM *form, /* form to alter */
2320 int page); /* page to go to (0-origin) */
2322 int form_page(FORM *form); /* return form's current page */
2324 The initial page of a newly-created form is 0. The function
2325 set_form_fields() resets this.
2329 Like fields, forms may have control option bits. They can be changed
2330 or queried with these functions:
2332 int set_form_opts(FORM *form, /* form to alter */
2333 int attr); /* attribute to set */
2335 int form_opts_on(FORM *form, /* form to alter */
2336 int attr); /* attributes to turn on */
2338 int form_opts_off(FORM *form, /* form to alter */
2339 int attr); /* attributes to turn off */
2341 int form_opts(FORM *form); /* form to query */
2343 By default, all options are on. Here are the available option bits:
2346 Enable overloading of REQ_NEW_LINE as described in Editing
2347 Requests. The value of this option is ignored on dynamic fields
2348 that have not reached their size limit; these have no last
2349 line, so the circumstances for triggering a REQ_NEXT_FIELD
2353 Enable overloading of REQ_DEL_PREV as described in Editing
2356 The option values are bit-masks and can be composed with logical-or in
2359 Custom Validation Types
2361 The form library gives you the capability to define custom validation
2362 types of your own. Further, the optional additional arguments of
2363 set_field_type effectively allow you to parameterize validation types.
2364 Most of the complications in the validation-type interface have to do
2365 with the handling of the additional arguments within custom validation
2370 The simplest way to create a custom data type is to compose it from
2371 two preexisting ones:
2373 FIELD *link_fieldtype(FIELDTYPE *type1,
2376 This function creates a field type that will accept any of the values
2377 legal for either of its argument field types (which may be either
2378 predefined or programmer-defined). If a set_field_type() call later
2379 requires arguments, the new composite type expects all arguments for
2380 the first type, than all arguments for the second. Order functions
2381 (see Order Requests) associated with the component types will work on
2382 the composite; what it does is check the validation function for the
2383 first type, then for the second, to figure what type the buffer
2384 contents should be treated as.
2388 To create a field type from scratch, you need to specify one or both
2389 of the following things:
2391 * A character-validation function, to check each character as it is
2393 * A field-validation function to be applied on exit from the field.
2395 Here's how you do that:
2397 typedef int (*HOOK)(); /* pointer to function returning int */
2399 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
2400 HOOK c_validate) /* character validator */
2403 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
2405 At least one of the arguments of new_fieldtype() must be non-NULL. The
2406 forms driver will automatically call the new type's validation
2407 functions at appropriate points in processing a field of the new type.
2409 The function free_fieldtype() deallocates the argument fieldtype,
2410 freeing all storage associated with it.
2412 Normally, a field validator is called when the user attempts to leave
2413 the field. Its first argument is a field pointer, from which it can
2414 get to field buffer 0 and test it. If the function returns TRUE, the
2415 operation succeeds; if it returns FALSE, the edit cursor stays in the
2418 A character validator gets the character passed in as a first
2419 argument. It too should return TRUE if the character is valid, FALSE
2422 Validation Function Arguments
2424 Your field- and character- validation functions will be passed a
2425 second argument as well. This second argument is the address of a
2426 structure (which we'll call a pile) built from any of the
2427 field-type-specific arguments passed to set_field_type(). If no such
2428 arguments are defined for the field type, this pile pointer argument
2431 In order to arrange for such arguments to be passed to your validation
2432 functions, you must associate a small set of storage-management
2433 functions with the type. The forms driver will use these to synthesize
2434 a pile from the trailing arguments of each set_field_type() argument,
2435 and a pointer to the pile will be passed to the validation functions.
2437 Here is how you make the association:
2439 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
2440 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
2442 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2443 PTRHOOK make_str, /* make structure from args */
2444 PTRHOOK copy_str, /* make copy of structure */
2445 VOIDHOOK free_str); /* free structure storage */
2447 Here is how the storage-management hooks are used:
2450 This function is called by set_field_type(). It gets one
2451 argument, a va_list of the type-specific arguments passed to
2452 set_field_type(). It is expected to return a pile pointer to a
2453 data structure that encapsulates those arguments.
2456 This function is called by form library functions that allocate
2457 new field instances. It is expected to take a pile pointer,
2458 copy the pile to allocated storage, and return the address of
2462 This function is called by field- and type-deallocation
2463 routines in the library. It takes a pile pointer argument, and
2464 is expected to free the storage of that pile.
2466 The make_str and copy_str functions may return NULL to signal
2467 allocation failure. The library routines will that call them will
2468 return error indication when this happens. Thus, your validation
2469 functions should never see a NULL file pointer and need not check
2472 Order Functions For Custom Types
2474 Some custom field types are simply ordered in the same well-defined
2475 way that TYPE_ENUM is. For such types, it is possible to define
2476 successor and predecessor functions to support the REQ_NEXT_CHOICE and
2477 REQ_PREV_CHOICE requests. Here's how:
2479 typedef int (*INTHOOK)(); /* pointer to function returning int */
2481 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2482 INTHOOK succ, /* get successor value */
2483 INTHOOK pred); /* get predecessor value */
2485 The successor and predecessor arguments will each be passed two
2486 arguments; a field pointer, and a pile pointer (as for the validation
2487 functions). They are expected to use the function field_buffer() to
2488 read the current value, and set_field_buffer() on buffer 0 to set the
2489 next or previous value. Either hook may return TRUE to indicate
2490 success (a legal next or previous value was set) or FALSE to indicate
2495 The interface for defining custom types is complicated and tricky.
2496 Rather than attempting to create a custom type entirely from scratch,
2497 you should start by studying the library source code for whichever of
2498 the pre-defined types seems to be closest to what you want.
2500 Use that code as a model, and evolve it towards what you really want.
2501 You will avoid many problems and annoyances that way. The code in the
2502 ncurses library has been specifically exempted from the package
2503 copyright to support this.
2505 If your custom type defines order functions, have do something
2506 intuitive with a blank field. A useful convention is to make the
2507 successor of a blank field the types minimum value, and its
2508 predecessor the maximum.