2 Writing Programs with NCURSES
4 by Eric S. Raymond and Zeyd M. Ben-Halim
5 updates since release 1.9.9e by Thomas Dickey
10 + A Brief History of Curses
11 + Scope of This Document
14 + An Overview of Curses
15 o Compiling Programs using Curses
17 o Standard Windows and Function Naming Conventions
23 o Using Forms Characters
24 o Character Attributes and Color
27 + Function Descriptions
28 o Initialization and Wrapup
29 o Causing Output to the Terminal
30 o Low-Level Capability Access
32 + Hints, Tips, and Tricks
33 o Some Notes of Caution
34 o Temporarily Leaving ncurses Mode
35 o Using ncurses under xterm
36 o Handling Multiple Terminal Screens
37 o Testing for Terminal Capabilities
39 o Special Features of ncurses
40 + Compatibility with Older Versions
41 o Refresh of Overlapping Windows
43 + XSI Curses Conformance
45 + Compiling With the Panels Library
47 + Panels, Input, and the Standard Screen
49 + Miscellaneous Other Facilities
51 + Compiling with the menu Library
56 + Processing Menu Input
57 + Miscellaneous Other Features
59 + Compiling with the forms Library
61 + Creating and Freeing Fields and Forms
62 + Fetching and Changing Field Attributes
63 o Fetching Size and Location Data
64 o Changing the Field Location
65 o The Justification Attribute
66 o Field Display Attributes
70 + Variable-Sized Fields
78 + Direct Field Buffer Manipulation
80 + Control of Form Display
81 + Input Processing in the Forms Driver
82 o Page Navigation Requests
83 o Inter-Field Navigation Requests
84 o Intra-Field Navigation Requests
86 o Field Editing Requests
88 o Application Commands
90 + Field Change Commands
92 + Custom Validation Types
95 o Validation Function Arguments
96 o Order Functions For Custom Types
98 _________________________________________________________________
102 This document is an introduction to programming with curses. It is not
103 an exhaustive reference for the curses Application Programming
104 Interface (API); that role is filled by the curses manual pages.
105 Rather, it is intended to help C programmers ease into using the
108 This document is aimed at C applications programmers not yet
109 specifically familiar with ncurses. If you are already an experienced
110 curses programmer, you should nevertheless read the sections on Mouse
111 Interfacing, Debugging, Compatibility with Older Versions, and Hints,
112 Tips, and Tricks. These will bring you up to speed on the special
113 features and quirks of the ncurses implementation. If you are not so
114 experienced, keep reading.
116 The curses package is a subroutine library for terminal-independent
117 screen-painting and input-event handling which presents a high level
118 screen model to the programmer, hiding differences between terminal
119 types and doing automatic optimization of output to change one screen
120 full of text into another. Curses uses terminfo, which is a database
121 format that can describe the capabilities of thousands of different
124 The curses API may seem something of an archaism on UNIX desktops
125 increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX
126 still supports tty lines and X supports xterm(1); the curses API has
127 the advantage of (a) back-portability to character-cell terminals, and
128 (b) simplicity. For an application that does not require bit-mapped
129 graphics and multiple fonts, an interface implementation using curses
130 will typically be a great deal simpler and less expensive than one
133 A Brief History of Curses
135 Historically, the first ancestor of curses was the routines written to
136 provide screen-handling for the game rogue; these used the
137 already-existing termcap database facility for describing terminal
138 capabilities. These routines were abstracted into a documented library
139 and first released with the early BSD UNIX versions.
141 System III UNIX from Bell Labs featured a rewritten and much-improved
142 curses library. It introduced the terminfo format. Terminfo is based
143 on Berkeley's termcap database, but contains a number of improvements
144 and extensions. Parameterized capabilities strings were introduced,
145 making it possible to describe multiple video attributes, and colors
146 and to handle far more unusual terminals than possible with termcap.
147 In the later AT&T System V releases, curses evolved to use more
148 facilities and offer more capabilities, going far beyond BSD curses in
149 power and flexibility.
151 Scope of This Document
153 This document describes ncurses, a free implementation of the System V
154 curses API with some clearly marked extensions. It includes the
155 following System V curses features:
156 * Support for multiple screen highlights (BSD curses could only
157 handle one `standout' highlight, usually reverse-video).
158 * Support for line- and box-drawing using forms characters.
159 * Recognition of function keys on input.
161 * Support for pads (windows of larger than screen size on which the
162 screen or a subwindow defines a viewport).
164 Also, this package makes use of the insert and delete line and
165 character features of terminals so equipped, and determines how to
166 optimally use these features with no help from the programmer. It
167 allows arbitrary combinations of video attributes to be displayed,
168 even on terminals that leave ``magic cookies'' on the screen to mark
169 changes in attributes.
171 The ncurses package can also capture and use event reports from a
172 mouse in some environments (notably, xterm under the X window system).
173 This document includes tips for using the mouse.
175 The ncurses package was originated by Pavel Curtis. The original
176 maintainer of this package is Zeyd Ben-Halim <zmbenhal@netcom.com>.
177 Eric S. Raymond <esr@snark.thyrsus.com> wrote many of the new features
178 in versions after 1.8.1 and wrote most of this introduction. Jürgen
179 Pfeifer wrote all of the menu and forms code as well as the Ada95
180 binding. Ongoing work is being done by Thomas Dickey (maintainer).
181 Contact the current maintainers at bug-ncurses@gnu.org.
183 This document also describes the panels extension library, similarly
184 modeled on the SVr4 panels facility. This library allows you to
185 associate backing store with each of a stack or deck of overlapping
186 windows, and provides operations for moving windows around in the
187 stack that change their visibility in the natural way (handling window
190 Finally, this document describes in detail the menus and forms
191 extension libraries, also cloned from System V, which support easy
192 construction and sequences of menus and fill-in forms.
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:
225 at the top of the program source. The screen package uses the Standard
226 I/O library, so <curses.h> includes <stdio.h>. <curses.h> also
227 includes <termios.h>, <termio.h>, or <sgtty.h> depending on your
228 system. It is redundant (but harmless) for the programmer to do these
229 includes, too. In linking with curses you need to have -lncurses in
230 your LDFLAGS or on the command line. There is no need for any other
235 In order to update the screen optimally, it is necessary for the
236 routines to know what the screen currently looks like and what the
237 programmer wants it to look like next. For this purpose, a data type
238 (structure) named WINDOW is defined which describes a window image to
239 the routines, including its starting position on the screen (the (y,
240 x) coordinates of the upper left hand corner) and its size. One of
241 these (called curscr, for current screen) is a screen image of what
242 the terminal currently looks like. Another screen (called stdscr, for
243 standard screen) is provided by default to make changes on.
245 A window is a purely internal representation. It is used to build and
246 store a potential image of a portion of the terminal. It doesn't bear
247 any necessary relation to what is really on the terminal screen; it's
248 more like a scratchpad or write buffer.
250 To make the section of physical screen corresponding to a window
251 reflect the contents of the window structure, the routine refresh()
252 (or wrefresh() if the window is not stdscr) is called.
254 A given physical screen section may be within the scope of any number
255 of overlapping windows. Also, changes can be made to windows in any
256 order, without regard to motion efficiency. Then, at will, the
257 programmer can effectively say ``make it look like this,'' and let the
258 package implementation determine the most efficient way to repaint the
261 Standard Windows and Function Naming Conventions
263 As hinted above, the routines can use several windows, but two are
264 automatically given: curscr, which knows what the terminal looks like,
265 and stdscr, which is what the programmer wants the terminal to look
266 like next. The user should never actually access curscr directly.
267 Changes should be made to through the API, and then the routine
268 refresh() (or wrefresh()) called.
270 Many functions are defined to use stdscr as a default screen. For
271 example, to add a character to stdscr, one calls addch() with the
272 desired character as argument. To write to a different window. use the
273 routine waddch() (for `w'indow-specific addch()) is provided. This
274 convention of prepending function names with a `w' when they are to be
275 applied to specific windows is consistent. The only routines which do
276 not follow it are those for which a window must always be specified.
278 In order to move the current (y, x) coordinates from one point to
279 another, the routines move() and wmove() are provided. However, it is
280 often desirable to first move and then perform some I/O operation. In
281 order to avoid clumsiness, most I/O routines can be preceded by the
282 prefix 'mv' and the desired (y, x) coordinates prepended to the
283 arguments to the function. For example, the calls
295 mvwaddch(win, y, x, ch);
297 Note that the window description pointer (win) comes before the added
298 (y, x) coordinates. If a function requires a window pointer, it is
299 always the first parameter passed.
303 The curses library sets some variables describing the terminal
305 type name description
306 ------------------------------------------------------------------
307 int LINES number of lines on the terminal
308 int COLS number of columns on the terminal
310 The curses.h also introduces some #define constants and types of
314 boolean type, actually a `char' (e.g., bool doneit;)
317 boolean `true' flag (1).
320 boolean `false' flag (0).
323 error flag returned by routines on a failure (-1).
326 error flag returned by routines when things go right.
330 Now we describe how to actually use the screen package. In it, we
331 assume all updating, reading, etc. is applied to stdscr. These
332 instructions will work on any window, providing you change the
333 function names and parameters as mentioned above.
335 Here is a sample program to motivate the discussion:
339 static void finish(int sig);
342 main(int argc, char *argv[])
346 /* initialize your non-curses data structures here */
348 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
350 (void) initscr(); /* initialize the curses library */
351 keypad(stdscr, TRUE); /* enable keyboard mapping */
352 (void) nonl(); /* tell curses not to do NL->CR/NL on output */
353 (void) cbreak(); /* take input chars one at a time, no wait for \n */
354 (void) echo(); /* echo input - in color */
361 * Simple color assignment, often all we need. Color pair 0 cannot
362 * be redefined. This example uses the same value for the color
363 * pair as for the foreground color, though of course that is not
366 init_pair(1, COLOR_RED, COLOR_BLACK);
367 init_pair(2, COLOR_GREEN, COLOR_BLACK);
368 init_pair(3, COLOR_YELLOW, COLOR_BLACK);
369 init_pair(4, COLOR_BLUE, COLOR_BLACK);
370 init_pair(5, COLOR_CYAN, COLOR_BLACK);
371 init_pair(6, COLOR_MAGENTA, COLOR_BLACK);
372 init_pair(7, COLOR_WHITE, COLOR_BLACK);
377 int c = getch(); /* refresh, accept single keystroke of input */
378 attrset(COLOR_PAIR(num % 8));
381 /* process the command keystroke */
384 finish(0); /* we're done */
387 static void finish(int sig)
391 /* do your non-curses wrapup here */
398 In order to use the screen package, the routines must know about
399 terminal characteristics, and the space for curscr and stdscr must be
400 allocated. These function initscr() does both these things. Since it
401 must allocate space for the windows, it can overflow memory when
402 attempting to do so. On the rare occasions this happens, initscr()
403 will terminate the program with an error message. initscr() must
404 always be called before any of the routines which affect windows are
405 used. If it is not, the program will core dump as soon as either
406 curscr or stdscr are referenced. However, it is usually best to wait
407 to call it until after you are sure you will need it, like after
408 checking for startup errors. Terminal status changing routines like
409 nl() and cbreak() should be called after initscr().
411 Once the screen windows have been allocated, you can set them up for
412 your program. If you want to, say, allow a screen to scroll, use
413 scrollok(). If you want the cursor to be left in place after the last
414 change, use leaveok(). If this isn't done, refresh() will move the
415 cursor to the window's current (y, x) coordinates after updating it.
417 You can create new windows of your own using the functions newwin(),
418 derwin(), and subwin(). The routine delwin() will allow you to get rid
419 of old windows. All the options described above can be applied to any
424 Now that we have set things up, we will want to actually update the
425 terminal. The basic functions used to change what will go on a window
426 are addch() and move(). addch() adds a character at the current (y, x)
427 coordinates. move() changes the current (y, x) coordinates to whatever
428 you want them to be. It returns ERR if you try to move off the window.
429 As mentioned above, you can combine the two into mvaddch() to do both
432 The other output functions, such as addstr() and printw(), all call
433 addch() to add characters to the window.
435 After you have put on the window what you want there, when you want
436 the portion of the terminal covered by the window to be made to look
437 like it, you must call refresh(). In order to optimize finding
438 changes, refresh() assumes that any part of the window not changed
439 since the last refresh() of that window has not been changed on the
440 terminal, i.e., that you have not refreshed a portion of the terminal
441 with an overlapping window. If this is not the case, the routine
442 touchwin() is provided to make it look like the entire window has been
443 changed, thus making refresh() check the whole subsection of the
444 terminal for changes.
446 If you call wrefresh() with curscr as its argument, it will make the
447 screen look like curscr thinks it looks like. This is useful for
448 implementing a command which would redraw the screen in case it get
453 The complementary function to addch() is getch() which, if echo is
454 set, will call addch() to echo the character. Since the screen package
455 needs to know what is on the terminal at all times, if characters are
456 to be echoed, the tty must be in raw or cbreak mode. Since initially
457 the terminal has echoing enabled and is in ordinary ``cooked'' mode,
458 one or the other has to changed before calling getch(); otherwise, the
459 program's output will be unpredictable.
461 When you need to accept line-oriented input in a window, the functions
462 wgetstr() and friends are available. There is even a wscanw() function
463 that can do scanf()(3)-style multi-field parsing on window input.
464 These pseudo-line-oriented functions turn on echoing while they
467 The example code above uses the call keypad(stdscr, TRUE) to enable
468 support for function-key mapping. With this feature, the getch() code
469 watches the input stream for character sequences that correspond to
470 arrow and function keys. These sequences are returned as
471 pseudo-character values. The #define values returned are listed in the
472 curses.h The mapping from sequences to #define values is determined by
473 key_ capabilities in the terminal's terminfo entry.
475 Using Forms Characters
477 The addch() function (and some others, including box() and border())
478 can accept some pseudo-character arguments which are specially defined
479 by ncurses. These are #define values set up in the curses.h header;
480 see there for a complete list (look for the prefix ACS_).
482 The most useful of the ACS defines are the forms-drawing characters.
483 You can use these to draw boxes and simple graphs on the screen. If
484 the terminal does not have such characters, curses.h will map them to
485 a recognizable (though ugly) set of ASCII defaults.
487 Character Attributes and Color
489 The ncurses package supports screen highlights including standout,
490 reverse-video, underline, and blink. It also supports color, which is
491 treated as another kind of highlight.
493 Highlights are encoded, internally, as high bits of the
494 pseudo-character type (chtype) that curses.h uses to represent the
495 contents of a screen cell. See the curses.h header file for a complete
496 list of highlight mask values (look for the prefix A_).
498 There are two ways to make highlights. One is to logical-or the value
499 of the highlights you want into the character argument of an addch()
500 call, or any other output call that takes a chtype argument.
502 The other is to set the current-highlight value. This is logical-or'ed
503 with any highlight you specify the first way. You do this with the
504 functions attron(), attroff(), and attrset(); see the manual pages for
505 details. Color is a special kind of highlight. The package actually
506 thinks in terms of color pairs, combinations of foreground and
507 background colors. The sample code above sets up eight color pairs,
508 all of the guaranteed-available colors on black. Note that each color
509 pair is, in effect, given the name of its foreground color. Any other
510 range of eight non-conflicting values could have been used as the
511 first arguments of the init_pair() values.
513 Once you've done an init_pair() that creates color-pair N, you can use
514 COLOR_PAIR(N) as a highlight that invokes that particular color
515 combination. Note that COLOR_PAIR(N), for constant N, is itself a
516 compile-time constant and can be used in initializers.
520 The ncurses library also provides a mouse interface.
522 NOTE: this facility is specific to ncurses, it is not part of
523 either the XSI Curses standard, nor of System V Release 4, nor BSD
524 curses. System V Release 4 curses contains code with similar
525 interface definitions, however it is not documented. Other than by
526 disassembling the library, we have no way to determine exactly how
527 that mouse code works. Thus, we recommend that you wrap
528 mouse-related code in an #ifdef using the feature macro
529 NCURSES_MOUSE_VERSION so it will not be compiled and linked on
532 Presently, mouse event reporting works in the following environments:
533 * xterm and similar programs such as rxvt.
534 * Linux console, when configured with gpm(1), Alessandro Rubini's
536 * FreeBSD sysmouse (console)
539 The mouse interface is very simple. To activate it, you use the
540 function mousemask(), passing it as first argument a bit-mask that
541 specifies what kinds of events you want your program to be able to
542 see. It will return the bit-mask of events that actually become
543 visible, which may differ from the argument if the mouse device is not
544 capable of reporting some of the event types you specify.
546 Once the mouse is active, your application's command loop should watch
547 for a return value of KEY_MOUSE from wgetch(). When you see this, a
548 mouse event report has been queued. To pick it off the queue, use the
549 function getmouse() (you must do this before the next wgetch(),
550 otherwise another mouse event might come in and make the first one
553 Each call to getmouse() fills a structure (the address of which you'll
554 pass it) with mouse event data. The event data includes zero-origin,
555 screen-relative character-cell coordinates of the mouse pointer. It
556 also includes an event mask. Bits in this mask will be set,
557 corresponding to the event type being reported.
559 The mouse structure contains two additional fields which may be
560 significant in the future as ncurses interfaces to new kinds of
561 pointing device. In addition to x and y coordinates, there is a slot
562 for a z coordinate; this might be useful with touch-screens that can
563 return a pressure or duration parameter. There is also a device ID
564 field, which could be used to distinguish between multiple pointing
567 The class of visible events may be changed at any time via
568 mousemask(). Events that can be reported include presses, releases,
569 single-, double- and triple-clicks (you can set the maximum
570 button-down time for clicks). If you don't make clicks visible, they
571 will be reported as press-release pairs. In some environments, the
572 event mask may include bits reporting the state of shift, alt, and
573 ctrl keys on the keyboard during the event.
575 A function to check whether a mouse event fell within a given window
576 is also supplied. You can use this to see whether a given window
577 should consider a mouse event relevant to it.
579 Because mouse event reporting will not be available in all
580 environments, it would be unwise to build ncurses applications that
581 require the use of a mouse. Rather, you should use the mouse as a
582 shortcut for point-and-shoot commands your application would normally
583 accept from the keyboard. Two of the test games in the ncurses
584 distribution (bs and knight) contain code that illustrates how this
587 See the manual page curs_mouse(3X) for full details of the
588 mouse-interface functions.
592 In order to clean up after the ncurses routines, the routine endwin()
593 is provided. It restores tty modes to what they were when initscr()
594 was first called, and moves the cursor down to the lower-left corner.
595 Thus, anytime after the call to initscr, endwin() should be called
598 Function Descriptions
600 We describe the detailed behavior of some important curses functions
601 here, as a supplement to the manual page descriptions.
603 Initialization and Wrapup
606 The first function called should almost always be initscr().
607 This will determine the terminal type and initialize curses
608 data structures. initscr() also arranges that the first call to
609 refresh() will clear the screen. If an error occurs a message
610 is written to standard error and the program exits. Otherwise
611 it returns a pointer to stdscr. A few functions may be called
612 before initscr (slk_init(), filter(), ripofflines(), use_env(),
613 and, if you are using multiple terminals, newterm().)
616 Your program should always call endwin() before exiting or
617 shelling out of the program. This function will restore tty
618 modes, move the cursor to the lower left corner of the screen,
619 reset the terminal into the proper non-visual mode. Calling
620 refresh() or doupdate() after a temporary escape from the
621 program will restore the ncurses screen from before the escape.
623 newterm(type, ofp, ifp)
624 A program which outputs to more than one terminal should use
625 newterm() instead of initscr(). newterm() should be called once
626 for each terminal. It returns a variable of type SCREEN * which
627 should be saved as a reference to that terminal. (NOTE: a
628 SCREEN variable is not a screen in the sense we are describing
629 in this introduction, but a collection of parameters used to
630 assist in optimizing the display.) The arguments are the type
631 of the terminal (a string) and FILE pointers for the output and
632 input of the terminal. If type is NULL then the environment
633 variable $TERM is used. endwin() should called once at wrapup
634 time for each terminal opened using this function.
637 This function is used to switch to a different terminal
638 previously opened by newterm(). The screen reference for the
639 new terminal is passed as the parameter. The previous terminal
640 is returned by the function. All other calls affect only the
644 The inverse of newterm(); deallocates the data structures
645 associated with a given SCREEN reference.
647 Causing Output to the Terminal
649 refresh() and wrefresh(win)
650 These functions must be called to actually get any output on
651 the terminal, as other routines merely manipulate data
652 structures. wrefresh() copies the named window to the physical
653 terminal screen, taking into account what is already there in
654 order to do optimizations. refresh() does a refresh of
655 stdscr(). Unless leaveok() has been enabled, the physical
656 cursor of the terminal is left at the location of the window's
659 doupdate() and wnoutrefresh(win)
660 These two functions allow multiple updates with more efficiency
661 than wrefresh. To use them, it is important to understand how
662 curses works. In addition to all the window structures, curses
663 keeps two data structures representing the terminal screen: a
664 physical screen, describing what is actually on the screen, and
665 a virtual screen, describing what the programmer wants to have
666 on the screen. wrefresh works by first copying the named window
667 to the virtual screen (wnoutrefresh()), and then calling the
668 routine to update the screen (doupdate()). If the programmer
669 wishes to output several windows at once, a series of calls to
670 wrefresh will result in alternating calls to wnoutrefresh() and
671 doupdate(), causing several bursts of output to the screen. By
672 calling wnoutrefresh() for each window, it is then possible to
673 call doupdate() once, resulting in only one burst of output,
674 with fewer total characters transmitted (this also avoids a
675 visually annoying flicker at each update).
677 Low-Level Capability Access
679 setupterm(term, filenum, errret)
680 This routine is called to initialize a terminal's description,
681 without setting up the curses screen structures or changing the
682 tty-driver mode bits. term is the character string representing
683 the name of the terminal being used. filenum is the UNIX file
684 descriptor of the terminal to be used for output. errret is a
685 pointer to an integer, in which a success or failure indication
686 is returned. The values returned can be 1 (all is well), 0 (no
687 such terminal), or -1 (some problem locating the terminfo
690 The value of term can be given as NULL, which will cause the
691 value of TERM in the environment to be used. The errret pointer
692 can also be given as NULL, meaning no error code is wanted. If
693 errret is defaulted, and something goes wrong, setupterm() will
694 print an appropriate error message and exit, rather than
695 returning. Thus, a simple program can call setupterm(0, 1, 0)
696 and not worry about initialization errors.
698 After the call to setupterm(), the global variable cur_term is
699 set to point to the current structure of terminal capabilities.
700 By calling setupterm() for each terminal, and saving and
701 restoring cur_term, it is possible for a program to use two or
702 more terminals at once. Setupterm() also stores the names
703 section of the terminal description in the global character
704 array ttytype[]. Subsequent calls to setupterm() will overwrite
705 this array, so you'll have to save it yourself if need be.
709 NOTE: These functions are not part of the standard curses API!
712 This function can be used to explicitly set a trace level. If
713 the trace level is nonzero, execution of your program will
714 generate a file called `trace' in the current working directory
715 containing a report on the library's actions. Higher trace
716 levels enable more detailed (and verbose) reporting -- see
717 comments attached to TRACE_ defines in the curses.h file for
718 details. (It is also possible to set a trace level by assigning
719 a trace level value to the environment variable NCURSES_TRACE).
722 This function can be used to output your own debugging
723 information. It is only available only if you link with
724 -lncurses_g. It can be used the same way as printf(), only it
725 outputs a newline after the end of arguments. The output goes
726 to a file called trace in the current directory.
728 Trace logs can be difficult to interpret due to the sheer volume of
729 data dumped in them. There is a script called tracemunch included with
730 the ncurses distribution that can alleviate this problem somewhat; it
731 compacts long sequences of similar operations into more succinct
732 single-line pseudo-operations. These pseudo-ops can be distinguished
733 by the fact that they are named in capital letters.
735 Hints, Tips, and Tricks
737 The ncurses manual pages are a complete reference for this library. In
738 the remainder of this document, we discuss various useful methods that
739 may not be obvious from the manual page descriptions.
741 Some Notes of Caution
743 If you find yourself thinking you need to use noraw() or nocbreak(),
744 think again and move carefully. It's probably better design to use
745 getstr() or one of its relatives to simulate cooked mode. The noraw()
746 and nocbreak() functions try to restore cooked mode, but they may end
747 up clobbering some control bits set before you started your
748 application. Also, they have always been poorly documented, and are
749 likely to hurt your application's usability with other curses
752 Bear in mind that refresh() is a synonym for wrefresh(stdscr). Don't
753 try to mix use of stdscr with use of windows declared by newwin(); a
754 refresh() call will blow them off the screen. The right way to handle
755 this is to use subwin(), or not touch stdscr at all and tile your
756 screen with declared windows which you then wnoutrefresh() somewhere
757 in your program event loop, with a single doupdate() call to trigger
760 You are much less likely to run into problems if you design your
761 screen layouts to use tiled rather than overlapping windows.
762 Historically, curses support for overlapping windows has been weak,
763 fragile, and poorly documented. The ncurses library is not yet an
764 exception to this rule.
766 There is a panels library included in the ncurses distribution that
767 does a pretty good job of strengthening the overlapping-windows
770 Try to avoid using the global variables LINES and COLS. Use getmaxyx()
771 on the stdscr context instead. Reason: your code may be ported to run
772 in an environment with window resizes, in which case several screens
773 could be open with different sizes.
775 Temporarily Leaving NCURSES Mode
777 Sometimes you will want to write a program that spends most of its
778 time in screen mode, but occasionally returns to ordinary `cooked'
779 mode. A common reason for this is to support shell-out. This behavior
780 is simple to arrange in ncurses.
782 To leave ncurses mode, call endwin() as you would if you were
783 intending to terminate the program. This will take the screen back to
784 cooked mode; you can do your shell-out. When you want to return to
785 ncurses mode, simply call refresh() or doupdate(). This will repaint
788 There is a boolean function, isendwin(), which code can use to test
789 whether ncurses screen mode is active. It returns TRUE in the interval
790 between an endwin() call and the following refresh(), FALSE otherwise.
792 Here is some sample code for shellout:
793 addstr("Shelling out...");
794 def_prog_mode(); /* save current tty modes */
795 endwin(); /* restore original tty modes */
796 system("sh"); /* run shell */
797 addstr("returned.\n"); /* prepare return message */
798 refresh(); /* restore save modes, repaint screen */
800 Using NCURSES under XTERM
802 A resize operation in X sends SIGWINCH to the application running
803 under xterm. The ncurses library provides an experimental signal
804 handler, but in general does not catch this signal, because it cannot
805 know how you want the screen re-painted. You will usually have to
806 write the SIGWINCH handler yourself. Ncurses can give you some help.
808 The easiest way to code your SIGWINCH handler is to have it do an
809 endwin, followed by an refresh and a screen repaint you code yourself.
810 The refresh will pick up the new screen size from the xterm's
813 That is the standard way, of course (it even works with some vendor's
814 curses implementations). Its drawback is that it clears the screen to
815 reinitialize the display, and does not resize subwindows which must be
816 shrunk. Ncurses provides an extension which works better, the
817 resizeterm function. That function ensures that all windows are
818 limited to the new screen dimensions, and pads stdscr with blanks if
819 the screen is larger.
821 Finally, ncurses can be configured to provide its own SIGWINCH
822 handler, based on resizeterm.
824 Handling Multiple Terminal Screens
826 The initscr() function actually calls a function named newterm() to do
827 most of its work. If you are writing a program that opens multiple
828 terminals, use newterm() directly.
830 For each call, you will have to specify a terminal type and a pair of
831 file pointers; each call will return a screen reference, and stdscr
832 will be set to the last one allocated. You will switch between screens
833 with the set_term call. Note that you will also have to call
834 def_shell_mode and def_prog_mode on each tty yourself.
836 Testing for Terminal Capabilities
838 Sometimes you may want to write programs that test for the presence of
839 various capabilities before deciding whether to go into ncurses mode.
840 An easy way to do this is to call setupterm(), then use the functions
841 tigetflag(), tigetnum(), and tigetstr() to do your testing.
843 A particularly useful case of this often comes up when you want to
844 test whether a given terminal type should be treated as `smart'
845 (cursor-addressable) or `stupid'. The right way to test this is to see
846 if the return value of tigetstr("cup") is non-NULL. Alternatively, you
847 can include the term.h file and test the value of the macro
852 Use the addchstr() family of functions for fast screen-painting of
853 text when you know the text doesn't contain any control characters.
854 Try to make attribute changes infrequent on your screens. Don't use
855 the immedok() option!
857 Special Features of NCURSES
859 The wresize() function allows you to resize a window in place. The
860 associated resizeterm() function simplifies the construction of
861 SIGWINCH handlers, for resizing all windows.
863 The define_key() function allows you to define at runtime function-key
864 control sequences which are not in the terminal description. The
865 keyok() function allows you to temporarily enable or disable
866 interpretation of any function-key control sequence.
868 The use_default_colors() function allows you to construct applications
869 which can use the terminal's default foreground and background colors
870 as an additional "default" color. Several terminal emulators support
871 this feature, which is based on ISO 6429.
873 Ncurses supports up 16 colors, unlike SVr4 curses which defines only
874 8. While most terminals which provide color allow only 8 colors, about
875 a quarter (including XFree86 xterm) support 16 colors.
877 Compatibility with Older Versions
879 Despite our best efforts, there are some differences between ncurses
880 and the (undocumented!) behavior of older curses implementations.
881 These arise from ambiguities or omissions in the documentation of the
884 Refresh of Overlapping Windows
886 If you define two windows A and B that overlap, and then alternately
887 scribble on and refresh them, the changes made to the overlapping
888 region under historic curses versions were often not documented
891 To understand why this is a problem, remember that screen updates are
892 calculated between two representations of the entire display. The
893 documentation says that when you refresh a window, it is first copied
894 to to the virtual screen, and then changes are calculated to update
895 the physical screen (and applied to the terminal). But "copied to" is
896 not very specific, and subtle differences in how copying works can
897 produce different behaviors in the case where two overlapping windows
898 are each being refreshed at unpredictable intervals.
900 What happens to the overlapping region depends on what wnoutrefresh()
901 does with its argument -- what portions of the argument window it
902 copies to the virtual screen. Some implementations do "change copy",
903 copying down only locations in the window that have changed (or been
904 marked changed with wtouchln() and friends). Some implementations do
905 "entire copy", copying all window locations to the virtual screen
906 whether or not they have changed.
908 The ncurses library itself has not always been consistent on this
909 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy.
910 Versions 1.8.6 and older, and versions 1.9.9 and newer, do change
913 For most commercial curses implementations, it is not documented and
914 not known for sure (at least not to the ncurses maintainers) whether
915 they do change copy or entire copy. We know that System V release 3
916 curses has logic in it that looks like an attempt to do change copy,
917 but the surrounding logic and data representations are sufficiently
918 complex, and our knowledge sufficiently indirect, that it's hard to
919 know whether this is reliable. It is not clear what the SVr4
920 documentation and XSI standard intend. The XSI Curses standard barely
921 mentions wnoutrefresh(); the SVr4 documents seem to be describing
922 entire-copy, but it is possible with some effort and straining to read
925 It might therefore be unwise to rely on either behavior in programs
926 that might have to be linked with other curses implementations.
927 Instead, you can do an explicit touchwin() before the wnoutrefresh()
928 call to guarantee an entire-contents copy anywhere.
930 The really clean way to handle this is to use the panels library. If,
931 when you want a screen update, you do update_panels(), it will do all
932 the necessary wnoutrfresh() calls for whatever panel stacking order
933 you have defined. Then you can do one doupdate() and there will be a
934 single burst of physical I/O that will do all your updates.
938 If you have been using a very old versions of ncurses (1.8.7 or older)
939 you may be surprised by the behavior of the erase functions. In older
940 versions, erased areas of a window were filled with a blank modified
941 by the window's current attribute (as set by wattrset(), wattron(),
942 wattroff() and friends).
944 In newer versions, this is not so. Instead, the attribute of erased
945 blanks is normal unless and until it is modified by the functions
946 bkgdset() or wbkgdset().
948 This change in behavior conforms ncurses to System V Release 4 and the
951 XSI Curses Conformance
953 The ncurses library is intended to be base-level conformant with the
954 XSI Curses standard from X/Open. Many extended-level features (in
955 fact, almost all features not directly concerned with wide characters
956 and internationalization) are also supported.
958 One effect of XSI conformance is the change in behavior described
959 under "Background Erase -- Compatibility with Old Versions".
961 Also, ncurses meets the XSI requirement that every macro entry point
962 have a corresponding function which may be linked (and will be
963 prototype-checked) if the macro definition is disabled with #undef.
967 The ncurses library by itself provides good support for screen
968 displays in which the windows are tiled (non-overlapping). In the more
969 general case that windows may overlap, you have to use a series of
970 wnoutrefresh() calls followed by a doupdate(), and be careful about
971 the order you do the window refreshes in. It has to be bottom-upwards,
972 otherwise parts of windows that should be obscured will show through.
974 When your interface design is such that windows may dive deeper into
975 the visibility stack or pop to the top at runtime, the resulting
976 book-keeping can be tedious and difficult to get right. Hence the
979 The panel library first appeared in AT&T System V. The version
980 documented here is the panel code distributed with ncurses.
982 Compiling With the Panels Library
984 Your panels-using modules must import the panels library declarations
988 and must be linked explicitly with the panels library using an -lpanel
989 argument. Note that they must also link the ncurses library with
990 -lncurses. Many linkers are two-pass and will accept either order, but
991 it is still good practice to put -lpanel first and -lncurses second.
995 A panel object is a window that is implicitly treated as part of a
996 deck including all other panel objects. The deck has an implicit
997 bottom-to-top visibility order. The panels library includes an update
998 function (analogous to refresh()) that displays all panels in the deck
999 in the proper order to resolve overlaps. The standard window, stdscr,
1000 is considered below all panels.
1002 Details on the panels functions are available in the man pages. We'll
1003 just hit the highlights here.
1005 You create a panel from a window by calling new_panel() on a window
1006 pointer. It then becomes the top of the deck. The panel's window is
1007 available as the value of panel_window() called with the panel pointer
1010 You can delete a panel (removing it from the deck) with del_panel.
1011 This will not deallocate the associated window; you have to do that
1012 yourself. You can replace a panel's window with a different window by
1013 calling replace_window. The new window may be of different size; the
1014 panel code will re-compute all overlaps. This operation doesn't change
1015 the panel's position in the deck.
1017 To move a panel's window, use move_panel(). The mvwin() function on
1018 the panel's window isn't sufficient because it doesn't update the
1019 panels library's representation of where the windows are. This
1020 operation leaves the panel's depth, contents, and size unchanged.
1022 Two functions (top_panel(), bottom_panel()) are provided for
1023 rearranging the deck. The first pops its argument window to the top of
1024 the deck; the second sends it to the bottom. Either operation leaves
1025 the panel's screen location, contents, and size unchanged.
1027 The function update_panels() does all the wnoutrefresh() calls needed
1028 to prepare for doupdate() (which you must call yourself, afterwards).
1030 Typically, you will want to call update_panels() and doupdate() just
1031 before accepting command input, once in each cycle of interaction with
1032 the user. If you call update_panels() after each and every panel
1033 write, you'll generate a lot of unnecessary refresh activity and
1036 Panels, Input, and the Standard Screen
1038 You shouldn't mix wnoutrefresh() or wrefresh() operations with panels
1039 code; this will work only if the argument window is either in the top
1040 panel or unobscured by any other panels.
1042 The stsdcr window is a special case. It is considered below all
1043 panels. Because changes to panels may obscure parts of stdscr, though,
1044 you should call update_panels() before doupdate() even when you only
1047 Note that wgetch automatically calls wrefresh. Therefore, before
1048 requesting input from a panel window, you need to be sure that the
1049 panel is totally unobscured.
1051 There is presently no way to display changes to one obscured panel
1052 without repainting all panels.
1056 It's possible to remove a panel from the deck temporarily; use
1057 hide_panel for this. Use show_panel() to render it visible again. The
1058 predicate function panel_hidden tests whether or not a panel is
1061 The panel_update code ignores hidden panels. You cannot do top_panel()
1062 or bottom_panel on a hidden panel(). Other panels operations are
1065 Miscellaneous Other Facilities
1067 It's possible to navigate the deck using the functions panel_above()
1068 and panel_below. Handed a panel pointer, they return the panel above
1069 or below that panel. Handed NULL, they return the bottom-most or
1072 Every panel has an associated user pointer, not used by the panel
1073 code, to which you can attach application data. See the man page
1074 documentation of set_panel_userptr() and panel_userptr for details.
1078 A menu is a screen display that assists the user to choose some subset
1079 of a given set of items. The menu library is a curses extension that
1080 supports easy programming of menu hierarchies with a uniform but
1083 The menu library first appeared in AT&T System V. The version
1084 documented here is the menu code distributed with ncurses.
1086 Compiling With the menu Library
1088 Your menu-using modules must import the menu library declarations with
1091 and must be linked explicitly with the menus library using an -lmenu
1092 argument. Note that they must also link the ncurses library with
1093 -lncurses. Many linkers are two-pass and will accept either order, but
1094 it is still good practice to put -lmenu first and -lncurses second.
1098 The menus created by this library consist of collections of items
1099 including a name string part and a description string part. To make
1100 menus, you create groups of these items and connect them with menu
1103 The menu can then by posted, that is written to an associated window.
1104 Actually, each menu has two associated windows; a containing window in
1105 which the programmer can scribble titles or borders, and a subwindow
1106 in which the menu items proper are displayed. If this subwindow is too
1107 small to display all the items, it will be a scrollable viewport on
1108 the collection of items.
1110 A menu may also be unposted (that is, undisplayed), and finally freed
1111 to make the storage associated with it and its items available for
1114 The general flow of control of a menu program looks like this:
1115 1. Initialize curses.
1116 2. Create the menu items, using new_item().
1117 3. Create the menu using new_menu().
1118 4. Post the menu using menu_post().
1119 5. Refresh the screen.
1120 6. Process user requests via an input loop.
1121 7. Unpost the menu using menu_unpost().
1122 8. Free the menu, using free_menu().
1123 9. Free the items using free_item().
1124 10. Terminate curses.
1128 Menus may be multi-valued or (the default) single-valued (see the
1129 manual page menu_opts(3x) to see how to change the default). Both
1130 types always have a current item.
1132 From a single-valued menu you can read the selected value simply by
1133 looking at the current item. From a multi-valued menu, you get the
1134 selected set by looping through the items applying the item_value()
1135 predicate function. Your menu-processing code can use the function
1136 set_item_value() to flag the items in the select set.
1138 Menu items can be made unselectable using set_item_opts() or
1139 item_opts_off() with the O_SELECTABLE argument. This is the only
1140 option so far defined for menus, but it is good practice to code as
1141 though other option bits might be on.
1145 The menu library calculates a minimum display size for your window,
1146 based on the following variables:
1147 * The number and maximum length of the menu items
1148 * Whether the O_ROWMAJOR option is enabled
1149 * Whether display of descriptions is enabled
1150 * Whatever menu format may have been set by the programmer
1151 * The length of the menu mark string used for highlighting selected
1154 The function set_menu_format() allows you to set the maximum size of
1155 the viewport or menu page that will be used to display menu items. You
1156 can retrieve any format associated with a menu with menu_format(). The
1157 default format is rows=16, columns=1.
1159 The actual menu page may be smaller than the format size. This depends
1160 on the item number and size and whether O_ROWMAJOR is on. This option
1161 (on by default) causes menu items to be displayed in a `raster-scan'
1162 pattern, so that if more than one item will fit horizontally the first
1163 couple of items are side-by-side in the top row. The alternative is
1164 column-major display, which tries to put the first several items in
1167 As mentioned above, a menu format not large enough to allow all items
1168 to fit on-screen will result in a menu display that is vertically
1171 You can scroll it with requests to the menu driver, which will be
1172 described in the section on menu input handling.
1174 Each menu has a mark string used to visually tag selected items; see
1175 the menu_mark(3x) manual page for details. The mark string length also
1176 influences the menu page size.
1178 The function scale_menu() returns the minimum display size that the
1179 menu code computes from all these factors. There are other menu
1180 display attributes including a select attribute, an attribute for
1181 selectable items, an attribute for unselectable items, and a pad
1182 character used to separate item name text from description text. These
1183 have reasonable defaults which the library allows you to change (see
1184 the menu_attribs(3x) manual page.
1188 Each menu has, as mentioned previously, a pair of associated windows.
1189 Both these windows are painted when the menu is posted and erased when
1190 the menu is unposted.
1192 The outer or frame window is not otherwise touched by the menu
1193 routines. It exists so the programmer can associate a title, a border,
1194 or perhaps help text with the menu and have it properly refreshed or
1195 erased at post/unpost time. The inner window or subwindow is where the
1196 current menu page is displayed.
1198 By default, both windows are stdscr. You can set them with the
1199 functions in menu_win(3x).
1201 When you call menu_post(), you write the menu to its subwindow. When
1202 you call menu_unpost(), you erase the subwindow, However, neither of
1203 these actually modifies the screen. To do that, call wrefresh() or
1206 Processing Menu Input
1208 The main loop of your menu-processing code should call menu_driver()
1209 repeatedly. The first argument of this routine is a menu pointer; the
1210 second is a menu command code. You should write an input-fetching
1211 routine that maps input characters to menu command codes, and pass its
1212 output to menu_driver(). The menu command codes are fully documented
1215 The simplest group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM,
1216 REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_UP_ITEM, REQ_DOWN_ITEM,
1217 REQ_LEFT_ITEM, REQ_RIGHT_ITEM. These change the currently selected
1218 item. These requests may cause scrolling of the menu page if it only
1219 partially displayed.
1221 There are explicit requests for scrolling which also change the
1222 current item (because the select location does not change, but the
1223 item there does). These are REQ_SCR_DLINE, REQ_SCR_ULINE,
1224 REQ_SCR_DPAGE, and REQ_SCR_UPAGE.
1226 The REQ_TOGGLE_ITEM selects or deselects the current item. It is for
1227 use in multi-valued menus; if you use it with O_ONEVALUE on, you'll
1228 get an error return (E_REQUEST_DENIED).
1230 Each menu has an associated pattern buffer. The menu_driver() logic
1231 tries to accumulate printable ASCII characters passed in in that
1232 buffer; when it matches a prefix of an item name, that item (or the
1233 next matching item) is selected. If appending a character yields no
1234 new match, that character is deleted from the pattern buffer, and
1235 menu_driver() returns E_NO_MATCH.
1237 Some requests change the pattern buffer directly: REQ_CLEAR_PATTERN,
1238 REQ_BACK_PATTERN, REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter two are
1239 useful when pattern buffer input matches more than one item in a
1242 Each successful scroll or item navigation request clears the pattern
1243 buffer. It is also possible to set the pattern buffer explicitly with
1246 Finally, menu driver requests above the constant MAX_COMMAND are
1247 considered application-specific commands. The menu_driver() code
1248 ignores them and returns E_UNKNOWN_COMMAND.
1250 Miscellaneous Other Features
1252 Various menu options can affect the processing and visual appearance
1253 and input processing of menus. See menu_opts(3x) for details.
1255 It is possible to change the current item from application code; this
1256 is useful if you want to write your own navigation requests. It is
1257 also possible to explicitly set the top row of the menu display. See
1258 mitem_current(3x). If your application needs to change the menu
1259 subwindow cursor for any reason, pos_menu_cursor() will restore it to
1260 the correct location for continuing menu driver processing.
1262 It is possible to set hooks to be called at menu initialization and
1263 wrapup time, and whenever the selected item changes. See
1266 Each item, and each menu, has an associated user pointer on which you
1267 can hang application data. See mitem_userptr(3x) and menu_userptr(3x).
1271 The form library is a curses extension that supports easy programming
1272 of on-screen forms for data entry and program control.
1274 The form library first appeared in AT&T System V. The version
1275 documented here is the form code distributed with ncurses.
1277 Compiling With the form Library
1279 Your form-using modules must import the form library declarations with
1282 and must be linked explicitly with the forms library using an -lform
1283 argument. Note that they must also link the ncurses library with
1284 -lncurses. Many linkers are two-pass and will accept either order, but
1285 it is still good practice to put -lform first and -lncurses second.
1289 A form is a collection of fields; each field may be either a label
1290 (explanatory text) or a data-entry location. Long forms may be
1291 segmented into pages; each entry to a new page clears the screen.
1293 To make forms, you create groups of fields and connect them with form
1294 frame objects; the form library makes this relatively simple.
1296 Once defined, a form can be posted, that is written to an associated
1297 window. Actually, each form has two associated windows; a containing
1298 window in which the programmer can scribble titles or borders, and a
1299 subwindow in which the form fields proper are displayed.
1301 As the form user fills out the posted form, navigation and editing
1302 keys support movement between fields, editing keys support modifying
1303 field, and plain text adds to or changes data in a current field. The
1304 form library allows you (the forms designer) to bind each navigation
1305 and editing key to any keystroke accepted by curses Fields may have
1306 validation conditions on them, so that they check input data for type
1307 and value. The form library supplies a rich set of pre-defined field
1308 types, and makes it relatively easy to define new ones.
1310 Once its transaction is completed (or aborted), a form may be unposted
1311 (that is, undisplayed), and finally freed to make the storage
1312 associated with it and its items available for re-use.
1314 The general flow of control of a form program looks like this:
1315 1. Initialize curses.
1316 2. Create the form fields, using new_field().
1317 3. Create the form using new_form().
1318 4. Post the form using form_post().
1319 5. Refresh the screen.
1320 6. Process user requests via an input loop.
1321 7. Unpost the form using form_unpost().
1322 8. Free the form, using free_form().
1323 9. Free the fields using free_field().
1324 10. Terminate curses.
1326 Note that this looks much like a menu program; the form library
1327 handles tasks which are in many ways similar, and its interface was
1328 obviously designed to resemble that of the menu library wherever
1331 In forms programs, however, the `process user requests' is somewhat
1332 more complicated than for menus. Besides menu-like navigation
1333 operations, the menu driver loop has to support field editing and data
1336 Creating and Freeing Fields and Forms
1338 The basic function for creating fields is new_field():
1339 FIELD *new_field(int height, int width, /* new field size */
1340 int top, int left, /* upper left corner */
1341 int offscreen, /* number of offscreen rows */
1342 int nbuf); /* number of working buffers */
1344 Menu items always occupy a single row, but forms fields may have
1345 multiple rows. So new_field() requires you to specify a width and
1346 height (the first two arguments, which mist both be greater than
1349 You must also specify the location of the field's upper left corner on
1350 the screen (the third and fourth arguments, which must be zero or
1351 greater). Note that these coordinates are relative to the form
1352 subwindow, which will coincide with stdscr by default but need not be
1353 stdscr if you've done an explicit set_form_window() call.
1355 The fifth argument allows you to specify a number of off-screen rows.
1356 If this is zero, the entire field will always be displayed. If it is
1357 nonzero, the form will be scrollable, with only one screen-full
1358 (initially the top part) displayed at any given time. If you make a
1359 field dynamic and grow it so it will no longer fit on the screen, the
1360 form will become scrollable even if the offscreen argument was
1363 The forms library allocates one working buffer per field; the size of
1364 each buffer is ((height + offscreen)*width + 1, one character for each
1365 position in the field plus a NUL terminator. The sixth argument is the
1366 number of additional data buffers to allocate for the field; your
1367 application can use them for its own purposes.
1368 FIELD *dup_field(FIELD *field, /* field to copy */
1369 int top, int left); /* location of new copy */
1371 The function dup_field() duplicates an existing field at a new
1372 location. Size and buffering information are copied; some attribute
1373 flags and status bits are not (see the form_field_new(3X) for
1375 FIELD *link_field(FIELD *field, /* field to copy */
1376 int top, int left); /* location of new copy */
1378 The function link_field() also duplicates an existing field at a new
1379 location. The difference from dup_field() is that it arranges for the
1380 new field's buffer to be shared with the old one.
1382 Besides the obvious use in making a field editable from two different
1383 form pages, linked fields give you a way to hack in dynamic labels. If
1384 you declare several fields linked to an original, and then make them
1385 inactive, changes from the original will still be propagated to the
1388 As with duplicated fields, linked fields have attribute bits separate
1391 As you might guess, all these field-allocations return NULL if the
1392 field allocation is not possible due to an out-of-memory error or
1393 out-of-bounds arguments.
1395 To connect fields to a form, use
1396 FORM *new_form(FIELD **fields);
1398 This function expects to see a NULL-terminated array of field
1399 pointers. Said fields are connected to a newly-allocated form object;
1400 its address is returned (or else NULL if the allocation fails).
1402 Note that new_field() does not copy the pointer array into private
1403 storage; if you modify the contents of the pointer array during forms
1404 processing, all manner of bizarre things might happen. Also note that
1405 any given field may only be connected to one form.
1407 The functions free_field() and free_form are available to free field
1408 and form objects. It is an error to attempt to free a field connected
1409 to a form, but not vice-versa; thus, you will generally free your form
1412 Fetching and Changing Field Attributes
1414 Each form field has a number of location and size attributes
1415 associated with it. There are other field attributes used to control
1416 display and editing of the field. Some (for example, the O_STATIC bit)
1417 involve sufficient complications to be covered in sections of their
1418 own later on. We cover the functions used to get and set several basic
1421 When a field is created, the attributes not specified by the new_field
1422 function are copied from an invisible system default field. In
1423 attribute-setting and -fetching functions, the argument NULL is taken
1424 to mean this field. Changes to it persist as defaults until your forms
1425 application terminates.
1427 Fetching Size and Location Data
1429 You can retrieve field sizes and locations through:
1430 int field_info(FIELD *field, /* field from which to fetch */
1431 int *height, *int width, /* field size */
1432 int *top, int *left, /* upper left corner */
1433 int *offscreen, /* number of offscreen rows */
1434 int *nbuf); /* number of working buffers */
1436 This function is a sort of inverse of new_field(); instead of setting
1437 size and location attributes of a new field, it fetches them from an
1440 Changing the Field Location
1442 It is possible to move a field's location on the screen:
1443 int move_field(FIELD *field, /* field to alter */
1444 int top, int left); /* new upper-left corner */
1446 You can, of course. query the current location through field_info().
1448 The Justification Attribute
1450 One-line fields may be unjustified, justified right, justified left,
1451 or centered. Here is how you manipulate this attribute:
1452 int set_field_just(FIELD *field, /* field to alter */
1453 int justmode); /* mode to set */
1455 int field_just(FIELD *field); /* fetch mode of field */
1457 The mode values accepted and returned by this functions are
1458 preprocessor macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or
1461 Field Display Attributes
1463 For each field, you can set a foreground attribute for entered
1464 characters, a background attribute for the entire field, and a pad
1465 character for the unfilled portion of the field. You can also control
1466 pagination of the form.
1468 This group of four field attributes controls the visual appearance of
1469 the field on the screen, without affecting in any way the data in the
1471 int set_field_fore(FIELD *field, /* field to alter */
1472 chtype attr); /* attribute to set */
1474 chtype field_fore(FIELD *field); /* field to query */
1476 int set_field_back(FIELD *field, /* field to alter */
1477 chtype attr); /* attribute to set */
1479 chtype field_back(FIELD *field); /* field to query */
1481 int set_field_pad(FIELD *field, /* field to alter */
1482 int pad); /* pad character to set */
1484 chtype field_pad(FIELD *field);
1486 int set_new_page(FIELD *field, /* field to alter */
1487 int flag); /* TRUE to force new page */
1489 chtype new_page(FIELD *field); /* field to query */
1491 The attributes set and returned by the first four functions are normal
1492 curses(3x) display attribute values (A_STANDOUT, A_BOLD, A_REVERSE
1493 etc). The page bit of a field controls whether it is displayed at the
1494 start of a new form screen.
1498 There is also a large collection of field option bits you can set to
1499 control various aspects of forms processing. You can manipulate them
1500 with these functions:
1501 int set_field_opts(FIELD *field, /* field to alter */
1502 int attr); /* attribute to set */
1504 int field_opts_on(FIELD *field, /* field to alter */
1505 int attr); /* attributes to turn on */
1507 int field_opts_off(FIELD *field, /* field to alter */
1508 int attr); /* attributes to turn off */
1510 int field_opts(FIELD *field); /* field to query */
1512 By default, all options are on. Here are the available option bits:
1515 Controls whether the field is visible on the screen. Can be
1516 used during form processing to hide or pop up fields depending
1517 on the value of parent fields.
1520 Controls whether the field is active during forms processing
1521 (i.e. visited by form navigation keys). Can be used to make
1522 labels or derived fields with buffer values alterable by the
1523 forms application, not the user.
1526 Controls whether data is displayed during field entry. If this
1527 option is turned off on a field, the library will accept and
1528 edit data in that field, but it will not be displayed and the
1529 visible field cursor will not move. You can turn off the
1530 O_PUBLIC bit to define password fields.
1533 Controls whether the field's data can be modified. When this
1534 option is off, all editing requests except REQ_PREV_CHOICE and
1535 REQ_NEXT_CHOICE will fail. Such read-only fields may be useful
1539 Controls word-wrapping in multi-line fields. Normally, when any
1540 character of a (blank-separated) word reaches the end of the
1541 current line, the entire word is wrapped to the next line
1542 (assuming there is one). When this option is off, the word will
1543 be split across the line break.
1546 Controls field blanking. When this option is on, entering a
1547 character at the first field position erases the entire field
1548 (except for the just-entered character).
1551 Controls automatic skip to next field when this one fills.
1552 Normally, when the forms user tries to type more data into a
1553 field than will fit, the editing location jumps to next field.
1554 When this option is off, the user's cursor will hang at the end
1555 of the field. This option is ignored in dynamic fields that
1556 have not reached their size limit.
1559 Controls whether validation is applied to blank fields.
1560 Normally, it is not; the user can leave a field blank without
1561 invoking the usual validation check on exit. If this option is
1562 off on a field, exit from it will invoke a validation check.
1565 Controls whether validation occurs on every exit, or only after
1566 the field is modified. Normally the latter is true. Setting
1567 O_PASSOK may be useful if your field's validation function may
1568 change during forms processing.
1571 Controls whether the field is fixed to its initial dimensions.
1572 If you turn this off, the field becomes dynamic and will
1573 stretch to fit entered data.
1575 A field's options cannot be changed while the field is currently
1576 selected. However, options may be changed on posted fields that are
1579 The option values are bit-masks and can be composed with logical-or in
1584 Every field has a status flag, which is set to FALSE when the field is
1585 created and TRUE when the value in field buffer 0 changes. This flag
1586 can be queried and set directly:
1587 int set_field_status(FIELD *field, /* field to alter */
1588 int status); /* mode to set */
1590 int field_status(FIELD *field); /* fetch mode of field */
1592 Setting this flag under program control can be useful if you use the
1593 same form repeatedly, looking for modified fields each time.
1595 Calling field_status() on a field not currently selected for input
1596 will return a correct value. Calling field_status() on a field that is
1597 currently selected for input may not necessarily give a correct field
1598 status value, because entered data isn't necessarily copied to buffer
1599 zero before the exit validation check. To guarantee that the returned
1600 status value reflects reality, call field_status() either (1) in the
1601 field's exit validation check routine, (2) from the field's or form's
1602 initialization or termination hooks, or (3) just after a
1603 REQ_VALIDATION request has been processed by the forms driver.
1607 Each field structure contains one character pointer slot that is not
1608 used by the forms library. It is intended to be used by applications
1609 to store private per-field data. You can manipulate it with:
1610 int set_field_userptr(FIELD *field, /* field to alter */
1611 char *userptr); /* mode to set */
1613 char *field_userptr(FIELD *field); /* fetch mode of field */
1615 (Properly, this user pointer field ought to have (void *) type. The
1616 (char *) type is retained for System V compatibility.)
1618 It is valid to set the user pointer of the default field (with a
1619 set_field_userptr() call passed a NULL field pointer.) When a new
1620 field is created, the default-field user pointer is copied to
1621 initialize the new field's user pointer.
1623 Variable-Sized Fields
1625 Normally, a field is fixed at the size specified for it at creation
1626 time. If, however, you turn off its O_STATIC bit, it becomes dynamic
1627 and will automatically resize itself to accommodate data as it is
1628 entered. If the field has extra buffers associated with it, they will
1629 grow right along with the main input buffer.
1631 A one-line dynamic field will have a fixed height (1) but variable
1632 width, scrolling horizontally to display data within the field area as
1633 originally dimensioned and located. A multi-line dynamic field will
1634 have a fixed width, but variable height (number of rows), scrolling
1635 vertically to display data within the field area as originally
1636 dimensioned and located.
1638 Normally, a dynamic field is allowed to grow without limit. But it is
1639 possible to set an upper limit on the size of a dynamic field. You do
1640 it with this function:
1641 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
1642 int max_size); /* upper limit on field size */
1644 If the field is one-line, max_size is taken to be a column size limit;
1645 if it is multi-line, it is taken to be a line size limit. To disable
1646 any limit, use an argument of zero. The growth limit can be changed
1647 whether or not the O_STATIC bit is on, but has no effect until it is.
1649 The following properties of a field change when it becomes dynamic:
1650 * If there is no growth limit, there is no final position of the
1651 field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored.
1652 * Field justification will be ignored (though whatever justification
1653 is set up will be retained internally and can be queried).
1654 * The dup_field() and link_field() calls copy dynamic-buffer sizes.
1655 If the O_STATIC option is set on one of a collection of links,
1656 buffer resizing will occur only when the field is edited through
1658 * The call field_info() will retrieve the original static size of
1659 the field; use dynamic_field_info() to get the actual dynamic
1664 By default, a field will accept any data that will fit in its input
1665 buffer. However, it is possible to attach a validation type to a
1666 field. If you do this, any attempt to leave the field while it
1667 contains data that doesn't match the validation type will fail. Some
1668 validation types also have a character-validity check for each time a
1669 character is entered in the field.
1671 A field's validation check (if any) is not called when
1672 set_field_buffer() modifies the input buffer, nor when that buffer is
1673 changed through a linked field.
1675 The form library provides a rich set of pre-defined validation types,
1676 and gives you the capability to define custom ones of your own. You
1677 can examine and change field validation attributes with the following
1679 int set_field_type(FIELD *field, /* field to alter */
1680 FIELDTYPE *ftype, /* type to associate */
1681 ...); /* additional arguments*/
1683 FIELDTYPE *field_type(FIELD *field); /* field to query */
1685 The validation type of a field is considered an attribute of the
1686 field. As with other field attributes, Also, doing set_field_type()
1687 with a NULL field default will change the system default for
1688 validation of newly-created fields.
1690 Here are the pre-defined validation types:
1694 This field type accepts alphabetic data; no blanks, no digits, no
1695 special characters (this is checked at character-entry time). It is
1697 int set_field_type(FIELD *field, /* field to alter */
1698 TYPE_ALPHA, /* type to associate */
1699 int width); /* maximum width of field */
1701 The width argument sets a minimum width of data. Typically you'll want
1702 to set this to the field width; if it's greater than the field width,
1703 the validation check will always fail. A minimum width of zero makes
1704 field completion optional.
1708 This field type accepts alphabetic data and digits; no blanks, no
1709 special characters (this is checked at character-entry time). It is
1711 int set_field_type(FIELD *field, /* field to alter */
1712 TYPE_ALNUM, /* type to associate */
1713 int width); /* maximum width of field */
1715 The width argument sets a minimum width of data. As with TYPE_ALPHA,
1716 typically you'll want to set this to the field width; if it's greater
1717 than the field width, the validation check will always fail. A minimum
1718 width of zero makes field completion optional.
1722 This type allows you to restrict a field's values to be among a
1723 specified set of string values (for example, the two-letter postal
1724 codes for U.S. states). It is set up with:
1725 int set_field_type(FIELD *field, /* field to alter */
1726 TYPE_ENUM, /* type to associate */
1727 char **valuelist; /* list of possible values */
1728 int checkcase; /* case-sensitive? */
1729 int checkunique); /* must specify uniquely? */
1731 The valuelist parameter must point at a NULL-terminated list of valid
1732 strings. The checkcase argument, if true, makes comparison with the
1733 string case-sensitive.
1735 When the user exits a TYPE_ENUM field, the validation procedure tries
1736 to complete the data in the buffer to a valid entry. If a complete
1737 choice string has been entered, it is of course valid. But it is also
1738 possible to enter a prefix of a valid string and have it completed for
1741 By default, if you enter such a prefix and it matches more than one
1742 value in the string list, the prefix will be completed to the first
1743 matching value. But the checkunique argument, if true, requires prefix
1744 matches to be unique in order to be valid.
1746 The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be
1747 particularly useful with these fields.
1751 This field type accepts an integer. It is set up as follows:
1752 int set_field_type(FIELD *field, /* field to alter */
1753 TYPE_INTEGER, /* type to associate */
1754 int padding, /* # places to zero-pad to */
1755 int vmin, int vmax); /* valid range */
1757 Valid characters consist of an optional leading minus and digits. The
1758 range check is performed on exit. If the range maximum is less than or
1759 equal to the minimum, the range is ignored.
1761 If the value passes its range check, it is padded with as many leading
1762 zero digits as necessary to meet the padding argument.
1764 A TYPE_INTEGER value buffer can conveniently be interpreted with the C
1765 library function atoi(3).
1769 This field type accepts a decimal number. It is set up as follows:
1770 int set_field_type(FIELD *field, /* field to alter */
1771 TYPE_NUMERIC, /* type to associate */
1772 int padding, /* # places of precision */
1773 double vmin, double vmax); /* valid range */
1775 Valid characters consist of an optional leading minus and digits.
1776 possibly including a decimal point. If your system supports locale's,
1777 the decimal point character used must be the one defined by your
1778 locale. The range check is performed on exit. If the range maximum is
1779 less than or equal to the minimum, the range is ignored.
1781 If the value passes its range check, it is padded with as many
1782 trailing zero digits as necessary to meet the padding argument.
1784 A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
1785 library function atof(3).
1789 This field type accepts data matching a regular expression. It is set
1791 int set_field_type(FIELD *field, /* field to alter */
1792 TYPE_REGEXP, /* type to associate */
1793 char *regexp); /* expression to match */
1795 The syntax for regular expressions is that of regcomp(3). The check
1796 for regular-expression match is performed on exit.
1798 Direct Field Buffer Manipulation
1800 The chief attribute of a field is its buffer contents. When a form has
1801 been completed, your application usually needs to know the state of
1802 each field buffer. You can find this out with:
1803 char *field_buffer(FIELD *field, /* field to query */
1804 int bufindex); /* number of buffer to query */
1806 Normally, the state of the zero-numbered buffer for each field is set
1807 by the user's editing actions on that field. It's sometimes useful to
1808 be able to set the value of the zero-numbered (or some other) buffer
1809 from your application:
1810 int set_field_buffer(FIELD *field, /* field to alter */
1811 int bufindex, /* number of buffer to alter */
1812 char *value); /* string value to set */
1814 If the field is not large enough and cannot be resized to a
1815 sufficiently large size to contain the specified value, the value will
1816 be truncated to fit.
1818 Calling field_buffer() with a null field pointer will raise an error.
1819 Calling field_buffer() on a field not currently selected for input
1820 will return a correct value. Calling field_buffer() on a field that is
1821 currently selected for input may not necessarily give a correct field
1822 buffer value, because entered data isn't necessarily copied to buffer
1823 zero before the exit validation check. To guarantee that the returned
1824 buffer value reflects on-screen reality, call field_buffer() either
1825 (1) in the field's exit validation check routine, (2) from the field's
1826 or form's initialization or termination hooks, or (3) just after a
1827 REQ_VALIDATION request has been processed by the forms driver.
1831 As with field attributes, form attributes inherit a default from a
1832 system default form structure. These defaults can be queried or set by
1833 of these functions using a form-pointer argument of NULL.
1835 The principal attribute of a form is its field list. You can query and
1836 change this list with:
1837 int set_form_fields(FORM *form, /* form to alter */
1838 FIELD **fields); /* fields to connect */
1840 char *form_fields(FORM *form); /* fetch fields of form */
1842 int field_count(FORM *form); /* count connect fields */
1844 The second argument of set_form_fields() may be a NULL-terminated
1845 field pointer array like the one required by new_form(). In that case,
1846 the old fields of the form are disconnected but not freed (and
1847 eligible to be connected to other forms), then the new fields are
1850 It may also be null, in which case the old fields are disconnected
1851 (and not freed) but no new ones are connected.
1853 The field_count() function simply counts the number of fields
1854 connected to a given from. It returns -1 if the form-pointer argument
1857 Control of Form Display
1859 In the overview section, you saw that to display a form you normally
1860 start by defining its size (and fields), posting it, and refreshing
1861 the screen. There is an hidden step before posting, which is the
1862 association of the form with a frame window (actually, a pair of
1863 windows) within which it will be displayed. By default, the forms
1864 library associates every form with the full-screen window stdscr.
1866 By making this step explicit, you can associate a form with a declared
1867 frame window on your screen display. This can be useful if you want to
1868 adapt the form display to different screen sizes, dynamically tile
1869 forms on the screen, or use a form as part of an interface layout
1872 The two windows associated with each form have the same functions as
1873 their analogues in the menu library. Both these windows are painted
1874 when the form is posted and erased when the form is unposted.
1876 The outer or frame window is not otherwise touched by the form
1877 routines. It exists so the programmer can associate a title, a border,
1878 or perhaps help text with the form and have it properly refreshed or
1879 erased at post/unpost time. The inner window or subwindow is where the
1880 current form page is actually displayed.
1882 In order to declare your own frame window for a form, you'll need to
1883 know the size of the form's bounding rectangle. You can get this
1885 int scale_form(FORM *form, /* form to query */
1886 int *rows, /* form rows */
1887 int *cols); /* form cols */
1889 The form dimensions are passed back in the locations pointed to by the
1890 arguments. Once you have this information, you can use it to declare
1891 of windows, then use one of these functions:
1892 int set_form_win(FORM *form, /* form to alter */
1893 WINDOW *win); /* frame window to connect */
1895 WINDOW *form_win(FORM *form); /* fetch frame window of form */
1897 int set_form_sub(FORM *form, /* form to alter */
1898 WINDOW *win); /* form subwindow to connect */
1900 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
1902 Note that curses operations, including refresh(), on the form, should
1903 be done on the frame window, not the form subwindow.
1905 It is possible to check from your application whether all of a
1906 scrollable field is actually displayed within the menu subwindow. Use
1908 int data_ahead(FORM *form); /* form to be queried */
1910 int data_behind(FORM *form); /* form to be queried */
1912 The function data_ahead() returns TRUE if (a) the current field is
1913 one-line and has undisplayed data off to the right, (b) the current
1914 field is multi-line and there is data off-screen below it.
1916 The function data_behind() returns TRUE if the first (upper left hand)
1917 character position is off-screen (not being displayed).
1919 Finally, there is a function to restore the form window's cursor to
1920 the value expected by the forms driver:
1921 int pos_form_cursor(FORM *) /* form to be queried */
1923 If your application changes the form window cursor, call this function
1924 before handing control back to the forms driver in order to
1927 Input Processing in the Forms Driver
1929 The function form_driver() handles virtualized input requests for form
1930 navigation, editing, and validation requests, just as menu_driver does
1931 for menus (see the section on menu input handling).
1932 int form_driver(FORM *form, /* form to pass input to */
1933 int request); /* form request code */
1935 Your input virtualization function needs to take input and then
1936 convert it to either an alphanumeric character (which is treated as
1937 data to be entered in the currently-selected field), or a forms
1940 The forms driver provides hooks (through input-validation and
1941 field-termination functions) with which your application code can
1942 check that the input taken by the driver matched what was expected.
1944 Page Navigation Requests
1946 These requests cause page-level moves through the form, triggering
1947 display of a new form screen.
1950 Move to the next form page.
1953 Move to the previous form page.
1956 Move to the first form page.
1959 Move to the last form page.
1961 These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from
1962 the last page goes to the first, and REQ_PREV_PAGE from the first page
1965 Inter-Field Navigation Requests
1967 These requests handle navigation between fields on the same page.
1973 Move to previous field.
1976 Move to the first field.
1979 Move to the last field.
1982 Move to sorted next field.
1985 Move to sorted previous field.
1988 Move to the sorted first field.
1991 Move to the sorted last field.
1997 Move right to field.
2005 These requests treat the list of fields on a page as cyclic; that is,
2006 REQ_NEXT_FIELD from the last field goes to the first, and
2007 REQ_PREV_FIELD from the first field goes to the last. The order of the
2008 fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests)
2009 is simply the order of the field pointers in the form array (as set up
2010 by new_form() or set_form_fields()
2012 It is also possible to traverse the fields as if they had been sorted
2013 in screen-position order, so the sequence goes left-to-right and
2014 top-to-bottom. To do this, use the second group of four
2015 sorted-movement requests.
2017 Finally, it is possible to move between fields using visual directions
2018 up, down, right, and left. To accomplish this, use the third group of
2019 four requests. Note, however, that the position of a form for purposes
2020 of these requests is its upper-left corner.
2022 For example, suppose you have a multi-line field B, and two
2023 single-line fields A and C on the same line with B, with A to the left
2024 of B and C to the right of B. A REQ_MOVE_RIGHT from A will go to B
2025 only if A, B, and C all share the same first line; otherwise it will
2028 Intra-Field Navigation Requests
2030 These requests drive movement of the edit cursor within the currently
2034 Move to next character.
2037 Move to previous character.
2043 Move to previous line.
2049 Move to previous word.
2052 Move to beginning of field.
2055 Move to end of field.
2058 Move to beginning of line.
2061 Move to end of line.
2067 Move right in field.
2075 Each word is separated from the previous and next characters by
2076 whitespace. The commands to move to beginning and end of line or field
2077 look for the first or last non-pad character in their ranges.
2081 Fields that are dynamic and have grown and fields explicitly created
2082 with offscreen rows are scrollable. One-line fields scroll
2083 horizontally; multi-line fields scroll vertically. Most scrolling is
2084 triggered by editing and intra-field movement (the library scrolls the
2085 field to keep the cursor visible). It is possible to explicitly
2086 request scrolling with the following requests:
2089 Scroll vertically forward a line.
2092 Scroll vertically backward a line.
2095 Scroll vertically forward a page.
2098 Scroll vertically backward a page.
2101 Scroll vertically forward half a page.
2104 Scroll vertically backward half a page.
2107 Scroll horizontally forward a character.
2110 Scroll horizontally backward a character.
2113 Scroll horizontally one field width forward.
2116 Scroll horizontally one field width backward.
2119 Scroll horizontally one half field width forward.
2122 Scroll horizontally one half field width backward.
2124 For scrolling purposes, a page of a field is the height of its visible
2129 When you pass the forms driver an ASCII character, it is treated as a
2130 request to add the character to the field's data buffer. Whether this
2131 is an insertion or a replacement depends on the field's edit mode
2132 (insertion is the default.
2134 The following requests support editing the field and changing the edit
2144 New line request (see below for explanation).
2147 Insert space at character location.
2150 Insert blank line at character location.
2153 Delete character at cursor.
2156 Delete previous word at cursor.
2159 Delete line at cursor.
2162 Delete word at cursor.
2165 Clear to end of line.
2168 Clear to end of field.
2173 The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is
2174 complicated and partly controlled by a pair of forms options. The
2175 special cases are triggered when the cursor is at the beginning of a
2176 field, or on the last line of the field.
2178 First, we consider REQ_NEW_LINE:
2180 The normal behavior of REQ_NEW_LINE in insert mode is to break the
2181 current line at the position of the edit cursor, inserting the portion
2182 of the current line after the cursor as a new line following the
2183 current and moving the cursor to the beginning of that new line (you
2184 may think of this as inserting a newline in the field buffer).
2186 The normal behavior of REQ_NEW_LINE in overlay mode is to clear the
2187 current line from the position of the edit cursor to end of line. The
2188 cursor is then moved to the beginning of the next line.
2190 However, REQ_NEW_LINE at the beginning of a field, or on the last line
2191 of a field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is
2192 off, this special action is disabled.
2194 Now, let us consider REQ_DEL_PREV:
2196 The normal behavior of REQ_DEL_PREV is to delete the previous
2197 character. If insert mode is on, and the cursor is at the start of a
2198 line, and the text on that line will fit on the previous one, it
2199 instead appends the contents of the current line to the previous one
2200 and deletes the current line (you may think of this as deleting a
2201 newline from the field buffer).
2203 However, REQ_DEL_PREV at the beginning of a field is instead treated
2204 as a REQ_PREV_FIELD.
2206 If the O_BS_OVERLOAD option is off, this special action is disabled
2207 and the forms driver just returns E_REQUEST_DENIED.
2209 See Form Options for discussion of how to set and clear the overload
2214 If the type of your field is ordered, and has associated functions for
2215 getting the next and previous values of the type from a given value,
2216 there are requests that can fetch that value into the field buffer:
2219 Place the successor value of the current value in the buffer.
2222 Place the predecessor value of the current value in the buffer.
2224 Of the built-in field types, only TYPE_ENUM has built-in successor and
2225 predecessor functions. When you define a field type of your own (see
2226 Custom Validation Types), you can associate our own ordering
2229 Application Commands
2231 Form requests are represented as integers above the curses value
2232 greater than KEY_MAX and less than or equal to the constant
2233 MAX_COMMAND. If your input-virtualization routine returns a value
2234 above MAX_COMMAND, the forms driver will ignore it.
2238 It is possible to set function hooks to be executed whenever the
2239 current field or form changes. Here are the functions that support
2241 typedef void (*HOOK)(); /* pointer to function returning void */
2243 int set_form_init(FORM *form, /* form to alter */
2244 HOOK hook); /* initialization hook */
2246 HOOK form_init(FORM *form); /* form to query */
2248 int set_form_term(FORM *form, /* form to alter */
2249 HOOK hook); /* termination hook */
2251 HOOK form_term(FORM *form); /* form to query */
2253 int set_field_init(FORM *form, /* form to alter */
2254 HOOK hook); /* initialization hook */
2256 HOOK field_init(FORM *form); /* form to query */
2258 int set_field_term(FORM *form, /* form to alter */
2259 HOOK hook); /* termination hook */
2261 HOOK field_term(FORM *form); /* form to query */
2263 These functions allow you to either set or query four different hooks.
2264 In each of the set functions, the second argument should be the
2265 address of a hook function. These functions differ only in the timing
2269 This hook is called when the form is posted; also, just after
2270 each page change operation.
2273 This hook is called when the form is posted; also, just after
2277 This hook is called just after field validation; that is, just
2278 before the field is altered. It is also called when the form is
2282 This hook is called when the form is unposted; also, just
2283 before each page change operation.
2285 Calls to these hooks may be triggered
2286 1. When user editing requests are processed by the forms driver
2287 2. When the current page is changed by set_current_field() call
2288 3. When the current field is changed by a set_form_page() call
2290 See Field Change Commands for discussion of the latter two cases.
2292 You can set a default hook for all fields by passing one of the set
2293 functions a NULL first argument.
2295 You can disable any of these hooks by (re)setting them to NULL, the
2298 Field Change Commands
2300 Normally, navigation through the form will be driven by the user's
2301 input requests. But sometimes it is useful to be able to move the
2302 focus for editing and viewing under control of your application, or
2303 ask which field it currently is in. The following functions help you
2305 int set_current_field(FORM *form, /* form to alter */
2306 FIELD *field); /* field to shift to */
2308 FIELD *current_field(FORM *form); /* form to query */
2310 int field_index(FORM *form, /* form to query */
2311 FIELD *field); /* field to get index of */
2313 The function field_index() returns the index of the given field in the
2314 given form's field array (the array passed to new_form() or
2317 The initial current field of a form is the first active field on the
2318 first page. The function set_form_fields() resets this.
2320 It is also possible to move around by pages.
2321 int set_form_page(FORM *form, /* form to alter */
2322 int page); /* page to go to (0-origin) */
2324 int form_page(FORM *form); /* return form's current page */
2326 The initial page of a newly-created form is 0. The function
2327 set_form_fields() resets this.
2331 Like fields, forms may have control option bits. They can be changed
2332 or queried with these functions:
2333 int set_form_opts(FORM *form, /* form to alter */
2334 int attr); /* attribute to set */
2336 int form_opts_on(FORM *form, /* form to alter */
2337 int attr); /* attributes to turn on */
2339 int form_opts_off(FORM *form, /* form to alter */
2340 int attr); /* attributes to turn off */
2342 int form_opts(FORM *form); /* form to query */
2344 By default, all options are on. Here are the available option bits:
2347 Enable overloading of REQ_NEW_LINE as described in Editing
2348 Requests. The value of this option is ignored on dynamic
2349 fields that have not reached their size limit; these have no
2350 last line, so the circumstances for triggering a REQ_NEXT_FIELD
2354 Enable overloading of REQ_DEL_PREV as described in Editing
2357 The option values are bit-masks and can be composed with logical-or in
2360 Custom Validation Types
2362 The form library gives you the capability to define custom validation
2363 types of your own. Further, the optional additional arguments of
2364 set_field_type effectively allow you to parameterize validation types.
2365 Most of the complications in the validation-type interface have to do
2366 with the handling of the additional arguments within custom validation
2371 The simplest way to create a custom data type is to compose it from
2372 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:
2390 * A character-validation function, to check each character as it is
2392 * A field-validation function to be applied on exit from the field.
2394 Here's how you do that:
2395 typedef int (*HOOK)(); /* pointer to function returning int */
2397 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
2398 HOOK c_validate) /* character validator */
2401 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
2403 At least one of the arguments of new_fieldtype() must be non-NULL. The
2404 forms driver will automatically call the new type's validation
2405 functions at appropriate points in processing a field of the new type.
2407 The function free_fieldtype() deallocates the argument fieldtype,
2408 freeing all storage associated with it.
2410 Normally, a field validator is called when the user attempts to leave
2411 the field. Its first argument is a field pointer, from which it can
2412 get to field buffer 0 and test it. If the function returns TRUE, the
2413 operation succeeds; if it returns FALSE, the edit cursor stays in the
2416 A character validator gets the character passed in as a first
2417 argument. It too should return TRUE if the character is valid, FALSE
2420 Validation Function Arguments
2422 Your field- and character- validation functions will be passed a
2423 second argument as well. This second argument is the address of a
2424 structure (which we'll call a pile) built from any of the
2425 field-type-specific arguments passed to set_field_type(). If no such
2426 arguments are defined for the field type, this pile pointer argument
2429 In order to arrange for such arguments to be passed to your validation
2430 functions, you must associate a small set of storage-management
2431 functions with the type. The forms driver will use these to synthesize
2432 a pile from the trailing arguments of each set_field_type() argument,
2433 and a pointer to the pile will be passed to the validation functions.
2435 Here is how you make the association:
2436 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
2437 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
2439 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2440 PTRHOOK make_str, /* make structure from args */
2441 PTRHOOK copy_str, /* make copy of structure */
2442 VOIDHOOK free_str); /* free structure storage */
2444 Here is how the storage-management hooks are used:
2447 This function is called by set_field_type(). It gets one
2448 argument, a va_list of the type-specific arguments passed to
2449 set_field_type(). It is expected to return a pile pointer to a
2450 data structure that encapsulates those arguments.
2453 This function is called by form library functions that allocate
2454 new field instances. It is expected to take a pile pointer,
2455 copy the pile to allocated storage, and return the address of
2459 This function is called by field- and type-deallocation
2460 routines in the library. It takes a pile pointer argument, and
2461 is expected to free the storage of that pile.
2463 The make_str and copy_str functions may return NULL to signal
2464 allocation failure. The library routines will that call them will
2465 return error indication when this happens. Thus, your validation
2466 functions should never see a NULL file pointer and need not check
2469 Order Functions For Custom Types
2471 Some custom field types are simply ordered in the same well-defined
2472 way that TYPE_ENUM is. For such types, it is possible to define
2473 successor and predecessor functions to support the REQ_NEXT_CHOICE and
2474 REQ_PREV_CHOICE requests. Here's how:
2475 typedef int (*INTHOOK)(); /* pointer to function returning int */
2477 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2478 INTHOOK succ, /* get successor value */
2479 INTHOOK pred); /* get predecessor value */
2481 The successor and predecessor arguments will each be passed two
2482 arguments; a field pointer, and a pile pointer (as for the validation
2483 functions). They are expected to use the function field_buffer() to
2484 read the current value, and set_field_buffer() on buffer 0 to set the
2485 next or previous value. Either hook may return TRUE to indicate
2486 success (a legal next or previous value was set) or FALSE to indicate
2491 The interface for defining custom types is complicated and tricky.
2492 Rather than attempting to create a custom type entirely from scratch,
2493 you should start by studying the library source code for whichever of
2494 the pre-defined types seems to be closest to what you want.
2496 Use that code as a model, and evolve it towards what you really want.
2497 You will avoid many problems and annoyances that way. The code in the
2498 ncurses library has been specifically exempted from the package
2499 copyright to support this.
2501 If your custom type defines order functions, have do something
2502 intuitive with a blank field. A useful convention is to make the
2503 successor of a blank field the types minimum value, and its
2504 predecessor the maximum.