1 Writing Programs with NCURSES
3 by Eric S. Raymond and Zeyd M. Ben-Halim
4 updates since release 1.9.9e by Thomas Dickey
9 + A Brief History of Curses
10 + Scope of This Document
13 + An Overview of Curses
14 o Compiling Programs using Curses
16 o Standard Windows and Function Naming Conventions
22 o Using Forms Characters
23 o Character Attributes and Color
26 + Function Descriptions
27 o Initialization and Wrapup
28 o Causing Output to the Terminal
29 o Low-Level Capability Access
31 + Hints, Tips, and Tricks
32 o Some Notes of Caution
33 o Temporarily Leaving ncurses Mode
34 o Using ncurses under xterm
35 o Handling Multiple Terminal Screens
36 o Testing for Terminal Capabilities
38 o Special Features of ncurses
39 + Compatibility with Older Versions
40 o Refresh of Overlapping Windows
42 + XSI Curses Conformance
44 + Compiling With the Panels Library
46 + Panels, Input, and the Standard Screen
48 + Miscellaneous Other Facilities
50 + Compiling with the menu Library
55 + Processing Menu Input
56 + Miscellaneous Other Features
58 + Compiling with the forms Library
60 + Creating and Freeing Fields and Forms
61 + Fetching and Changing Field Attributes
62 o Fetching Size and Location Data
63 o Changing the Field Location
64 o The Justification Attribute
65 o Field Display Attributes
69 + Variable-Sized Fields
77 + Direct Field Buffer Manipulation
79 + Control of Form Display
80 + Input Processing in the Forms Driver
81 o Page Navigation Requests
82 o Inter-Field Navigation Requests
83 o Intra-Field Navigation Requests
85 o Field Editing Requests
87 o Application Commands
89 + Field Change Commands
91 + Custom Validation Types
94 o Validation Function Arguments
95 o Order Functions For Custom Types
97 _________________________________________________________________
101 This document is an introduction to programming with curses. It is not
102 an exhaustive reference for the curses Application Programming
103 Interface (API); that role is filled by the curses manual pages.
104 Rather, it is intended to help C programmers ease into using the
107 This document is aimed at C applications programmers not yet
108 specifically familiar with ncurses. If you are already an experienced
109 curses programmer, you should nevertheless read the sections on Mouse
110 Interfacing, Debugging, Compatibility with Older Versions, and Hints,
111 Tips, and Tricks. These will bring you up to speed on the special
112 features and quirks of the ncurses implementation. If you are not so
113 experienced, keep reading.
115 The curses package is a subroutine library for terminal-independent
116 screen-painting and input-event handling which presents a high level
117 screen model to the programmer, hiding differences between terminal
118 types and doing automatic optimization of output to change one screen
119 full of text into another. Curses uses terminfo, which is a database
120 format that can describe the capabilities of thousands of different
123 The curses API may seem something of an archaism on UNIX desktops
124 increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX
125 still supports tty lines and X supports xterm(1); the curses API has
126 the advantage of (a) back-portability to character-cell terminals, and
127 (b) simplicity. For an application that does not require bit-mapped
128 graphics and multiple fonts, an interface implementation using curses
129 will typically be a great deal simpler and less expensive than one
132 A Brief History of Curses
134 Historically, the first ancestor of curses was the routines written to
135 provide screen-handling for the game rogue; these used the
136 already-existing termcap database facility for describing terminal
137 capabilities. These routines were abstracted into a documented library
138 and first released with the early BSD UNIX versions.
140 System III UNIX from Bell Labs featured a rewritten and much-improved
141 curses library. It introduced the terminfo format. Terminfo is based
142 on Berkeley's termcap database, but contains a number of improvements
143 and extensions. Parameterized capabilities strings were introduced,
144 making it possible to describe multiple video attributes, and colors
145 and to handle far more unusual terminals than possible with termcap.
146 In the later AT&T System V releases, curses evolved to use more
147 facilities and offer more capabilities, going far beyond BSD curses in
148 power and flexibility.
150 Scope of This Document
152 This document describes ncurses, a free implementation of the System V
153 curses API with some clearly marked extensions. It includes the
154 following System V curses features:
155 * Support for multiple screen highlights (BSD curses could only
156 handle one "standout" highlight, usually reverse-video).
157 * Support for line- and box-drawing using forms characters.
158 * Recognition of function keys on input.
160 * Support for pads (windows of larger than screen size on which the
161 screen or a subwindow defines a viewport).
163 Also, this package makes use of the insert and delete line and
164 character features of terminals so equipped, and determines how to
165 optimally use these features with no help from the programmer. It
166 allows arbitrary combinations of video attributes to be displayed,
167 even on terminals that leave "magic cookies" on the screen to mark
168 changes in attributes.
170 The ncurses package can also capture and use event reports from a
171 mouse in some environments (notably, xterm under the X window system).
172 This document includes tips for using the mouse.
174 The ncurses package was originated by Pavel Curtis. The original
175 maintainer of this package is Zeyd Ben-Halim <zmbenhal@netcom.com>.
176 Eric S. Raymond <esr@snark.thyrsus.com> wrote many of the new features
177 in versions after 1.8.1 and wrote most of this introduction. Juergen
178 Pfeifer wrote all of the menu and forms code as well as the Ada95
179 binding. Ongoing work is being done by Thomas Dickey (maintainer).
180 Contact the current maintainers at bug-ncurses@gnu.org.
182 This document also describes the panels extension library, similarly
183 modeled on the SVr4 panels facility. This library allows you to
184 associate backing store with each of a stack or deck of overlapping
185 windows, and provides operations for moving windows around in the
186 stack that change their visibility in the natural way (handling window
189 Finally, this document describes in detail the menus and forms
190 extension libraries, also cloned from System V, which support easy
191 construction and sequences of menus and fill-in forms.
195 In this document, the following terminology is used with reasonable
199 A data structure describing a sub-rectangle of the screen
200 (possibly the entire screen). You can write to a window as
201 though it were a miniature screen, scrolling independently of
202 other windows on the physical screen.
205 A subset of windows which are as large as the terminal screen,
206 i.e., they start at the upper left hand corner and encompass
207 the lower right hand corner. One of these, stdscr, is
208 automatically provided for the programmer.
211 The package's idea of what the terminal display currently looks
212 like, i.e., what the user sees now. This is a special screen.
216 An Overview of Curses
218 Compiling Programs using Curses
220 In order to use the library, it is necessary to have certain types and
221 variables defined. Therefore, the programmer must have a line:
224 at the top of the program source. The screen package uses the Standard
225 I/O library, so <curses.h> includes <stdio.h>. <curses.h> also
226 includes <termios.h>, <termio.h>, or <sgtty.h> depending on your
227 system. It is redundant (but harmless) for the programmer to do these
228 includes, too. In linking with curses you need to have -lncurses in
229 your LDFLAGS or on the command line. There is no need for any other
234 In order to update the screen optimally, it is necessary for the
235 routines to know what the screen currently looks like and what the
236 programmer wants it to look like next. For this purpose, a data type
237 (structure) named WINDOW is defined which describes a window image to
238 the routines, including its starting position on the screen (the (y,
239 x) coordinates of the upper left hand corner) and its size. One of
240 these (called curscr, for current screen) is a screen image of what
241 the terminal currently looks like. Another screen (called stdscr, for
242 standard screen) is provided by default to make changes on.
244 A window is a purely internal representation. It is used to build and
245 store a potential image of a portion of the terminal. It does not bear
246 any necessary relation to what is really on the terminal screen; it is
247 more like a scratchpad or write buffer.
249 To make the section of physical screen corresponding to a window
250 reflect the contents of the window structure, the routine refresh()
251 (or wrefresh() if the window is not stdscr) is called.
253 A given physical screen section may be within the scope of any number
254 of overlapping windows. Also, changes can be made to windows in any
255 order, without regard to motion efficiency. Then, at will, the
256 programmer can effectively say "make it look like this," and let the
257 package implementation determine the most efficient way to repaint the
260 Standard Windows and Function Naming Conventions
262 As hinted above, the routines can use several windows, but two are
263 automatically given: curscr, which knows what the terminal looks like,
264 and stdscr, which is what the programmer wants the terminal to look
265 like next. The user should never actually access curscr directly.
266 Changes should be made to through the API, and then the routine
267 refresh() (or wrefresh()) called.
269 Many functions are defined to use stdscr as a default screen. For
270 example, to add a character to stdscr, one calls addch() with the
271 desired character as argument. To write to a different window. use the
272 routine waddch() (for window-specific addch()) is provided. This
273 convention of prepending function names with a "w" when they are to be
274 applied to specific windows is consistent. The only routines which do
275 not follow it are those for which a window must always be specified.
277 In order to move the current (y, x) coordinates from one point to
278 another, the routines move() and wmove() are provided. However, it is
279 often desirable to first move and then perform some I/O operation. In
280 order to avoid clumsiness, most I/O routines can be preceded by the
281 prefix "mv" and the desired (y, x) coordinates prepended to the
282 arguments to the function. For example, the calls
294 mvwaddch(win, y, x, ch);
296 Note that the window description pointer (win) comes before the added
297 (y, x) coordinates. If a function requires a window pointer, it is
298 always the first parameter passed.
302 The curses library sets some variables describing the terminal
304 type name description
305 ------------------------------------------------------------------
306 int LINES number of lines on the terminal
307 int COLS number of columns on the terminal
309 The curses.h also introduces some #define constants and types of
313 boolean type, actually a "char" (e.g., bool doneit;)
316 boolean "true" flag (1).
319 boolean "false" flag (0).
322 error flag returned by routines on a failure (-1).
325 error flag returned by routines when things go right.
329 Now we describe how to actually use the screen package. In it, we
330 assume all updating, reading, etc. is applied to stdscr. These
331 instructions will work on any window, providing you change the
332 function names and parameters as mentioned above.
334 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 are 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 is not 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, one
458 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-ORed
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 have done an init_pair() that creates color-pair N, you can
514 use 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
554 will pass it) with mouse event data. The event data includes
555 zero-origin, screen-relative character-cell coordinates of the mouse
556 pointer. It also includes an event mask. Bits in this mask will be
557 set, 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 do not 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(), ripoffline(), 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 stdscr.
655 Unless leaveok() has been enabled, the physical cursor of the
656 terminal is left at the location of the window's cursor.
658 doupdate() and wnoutrefresh(win)
659 These two functions allow multiple updates with more efficiency
660 than wrefresh. To use them, it is important to understand how
661 curses works. In addition to all the window structures, curses
662 keeps two data structures representing the terminal screen: a
663 physical screen, describing what is actually on the screen, and
664 a virtual screen, describing what the programmer wants to have
665 on the screen. wrefresh works by first copying the named window
666 to the virtual screen (wnoutrefresh()), and then calling the
667 routine to update the screen (doupdate()). If the programmer
668 wishes to output several windows at once, a series of calls to
669 wrefresh will result in alternating calls to wnoutrefresh() and
670 doupdate(), causing several bursts of output to the screen. By
671 calling wnoutrefresh() for each window, it is then possible to
672 call doupdate() once, resulting in only one burst of output,
673 with fewer total characters transmitted (this also avoids a
674 visually annoying flicker at each update).
676 Low-Level Capability Access
678 setupterm(term, filenum, errret)
679 This routine is called to initialize a terminal's description,
680 without setting up the curses screen structures or changing the
681 tty-driver mode bits. term is the character string representing
682 the name of the terminal being used. filenum is the UNIX file
683 descriptor of the terminal to be used for output. errret is a
684 pointer to an integer, in which a success or failure indication
685 is returned. The values returned can be 1 (all is well), 0 (no
686 such terminal), or -1 (some problem locating the terminfo
689 The value of term can be given as NULL, which will cause the
690 value of TERM in the environment to be used. The errret pointer
691 can also be given as NULL, meaning no error code is wanted. If
692 errret is defaulted, and something goes wrong, setupterm() will
693 print an appropriate error message and exit, rather than
694 returning. Thus, a simple program can call setupterm(0, 1, 0)
695 and not worry about initialization errors.
697 After the call to setupterm(), the global variable cur_term is
698 set to point to the current structure of terminal capabilities.
699 By calling setupterm() for each terminal, and saving and
700 restoring cur_term, it is possible for a program to use two or
701 more terminals at once. Setupterm() also stores the names
702 section of the terminal description in the global character
703 array ttytype[]. Subsequent calls to setupterm() will overwrite
704 this array, so you will have to save it yourself if need be.
708 NOTE: These functions are not part of the standard curses API!
711 This function can be used to explicitly set a trace level. If
712 the trace level is nonzero, execution of your program will
713 generate a file called "trace" in the current working directory
714 containing a report on the library's actions. Higher trace
715 levels enable more detailed (and verbose) reporting -- see
716 comments attached to TRACE_ defines in the curses.h file for
717 details. (It is also possible to set a trace level by assigning
718 a trace level value to the environment variable NCURSES_TRACE).
721 This function can be used to output your own debugging
722 information. It is only available only if you link with
723 -lncurses_g. It can be used the same way as printf(), only it
724 outputs a newline after the end of arguments. The output goes
725 to a file called trace in the current directory.
727 Trace logs can be difficult to interpret due to the sheer volume of
728 data dumped in them. There is a script called tracemunch included with
729 the ncurses distribution that can alleviate this problem somewhat; it
730 compacts long sequences of similar operations into more succinct
731 single-line pseudo-operations. These pseudo-ops can be distinguished
732 by the fact that they are named in capital letters.
734 Hints, Tips, and Tricks
736 The ncurses manual pages are a complete reference for this library. In
737 the remainder of this document, we discuss various useful methods that
738 may not be obvious from the manual page descriptions.
740 Some Notes of Caution
742 If you find yourself thinking you need to use noraw() or nocbreak(),
743 think again and move carefully. It is probably better design to use
744 getstr() or one of its relatives to simulate cooked mode. The noraw()
745 and nocbreak() functions try to restore cooked mode, but they may end
746 up clobbering some control bits set before you started your
747 application. Also, they have always been poorly documented, and are
748 likely to hurt your application's usability with other curses
751 Bear in mind that refresh() is a synonym for wrefresh(stdscr). Do not
752 try to mix use of stdscr with use of windows declared by newwin(); a
753 refresh() call will blow them off the screen. The right way to handle
754 this is to use subwin(), or not touch stdscr at all and tile your
755 screen with declared windows which you then wnoutrefresh() somewhere
756 in your program event loop, with a single doupdate() call to trigger
759 You are much less likely to run into problems if you design your
760 screen layouts to use tiled rather than overlapping windows.
761 Historically, curses support for overlapping windows has been weak,
762 fragile, and poorly documented. The ncurses library is not yet an
763 exception to this rule.
765 There is a panels library included in the ncurses distribution that
766 does a pretty good job of strengthening the overlapping-windows
769 Try to avoid using the global variables LINES and COLS. Use getmaxyx()
770 on the stdscr context instead. Reason: your code may be ported to run
771 in an environment with window resizes, in which case several screens
772 could be open with different sizes.
774 Temporarily Leaving NCURSES Mode
776 Sometimes you will want to write a program that spends most of its
777 time in screen mode, but occasionally returns to ordinary "cooked"
778 mode. A common reason for this is to support shell-out. This behavior
779 is simple to arrange in ncurses.
781 To leave ncurses mode, call endwin() as you would if you were
782 intending to terminate the program. This will take the screen back to
783 cooked mode; you can do your shell-out. When you want to return to
784 ncurses mode, simply call refresh() or doupdate(). This will repaint
787 There is a boolean function, isendwin(), which code can use to test
788 whether ncurses screen mode is active. It returns TRUE in the interval
789 between an endwin() call and the following refresh(), FALSE otherwise.
791 Here is some sample code for shellout:
792 addstr("Shelling out...");
793 def_prog_mode(); /* save current tty modes */
794 endwin(); /* restore original tty modes */
795 system("sh"); /* run shell */
796 addstr("returned.\n"); /* prepare return message */
797 refresh(); /* restore save modes, repaint screen */
799 Using NCURSES under XTERM
801 A resize operation in X sends SIGWINCH to the application running
802 under xterm. The easiest way to handle SIGWINCH is to do an endwin,
803 followed by an refresh and a screen repaint you code yourself. The
804 refresh will pick up the new screen size from the xterm's environment.
806 That is the standard way, of course (it even works with some vendor's
807 curses implementations). Its drawback is that it clears the screen to
808 reinitialize the display, and does not resize subwindows which must be
809 shrunk. Ncurses provides an extension which works better, the
810 resizeterm function. That function ensures that all windows are
811 limited to the new screen dimensions, and pads stdscr with blanks if
812 the screen is larger.
814 The ncurses library provides a SIGWINCH signal handler, which pushes a
815 KEY_RESIZE via the wgetch() calls. When ncurses returns that code, it
816 calls resizeterm to update the size of the standard screen's window,
817 repainting that (filling with blanks or truncating as needed). It also
818 resizes other windows, but its effect may be less satisfactory because
819 it cannot know how you want the screen re-painted. You will usually
820 have to write special-purpose code to handle KEY_RESIZE yourself.
822 Handling Multiple Terminal Screens
824 The initscr() function actually calls a function named newterm() to do
825 most of its work. If you are writing a program that opens multiple
826 terminals, use newterm() directly.
828 For each call, you will have to specify a terminal type and a pair of
829 file pointers; each call will return a screen reference, and stdscr
830 will be set to the last one allocated. You will switch between screens
831 with the set_term call. Note that you will also have to call
832 def_shell_mode and def_prog_mode on each tty yourself.
834 Testing for Terminal Capabilities
836 Sometimes you may want to write programs that test for the presence of
837 various capabilities before deciding whether to go into ncurses mode.
838 An easy way to do this is to call setupterm(), then use the functions
839 tigetflag(), tigetnum(), and tigetstr() to do your testing.
841 A particularly useful case of this often comes up when you want to
842 test whether a given terminal type should be treated as "smart"
843 (cursor-addressable) or "stupid". The right way to test this is to see
844 if the return value of tigetstr("cup") is non-NULL. Alternatively, you
845 can include the term.h file and test the value of the macro
850 Use the addchstr() family of functions for fast screen-painting of
851 text when you know the text does not contain any control characters.
852 Try to make attribute changes infrequent on your screens. Do not use
853 the immedok() option!
855 Special Features of NCURSES
857 The wresize() function allows you to resize a window in place. The
858 associated resizeterm() function simplifies the construction of
859 SIGWINCH handlers, for resizing all windows.
861 The define_key() function allows you to define at runtime function-key
862 control sequences which are not in the terminal description. The
863 keyok() function allows you to temporarily enable or disable
864 interpretation of any function-key control sequence.
866 The use_default_colors() function allows you to construct applications
867 which can use the terminal's default foreground and background colors
868 as an additional "default" color. Several terminal emulators support
869 this feature, which is based on ISO 6429.
871 Ncurses supports up 16 colors, unlike SVr4 curses which defines only
872 8. While most terminals which provide color allow only 8 colors, about
873 a quarter (including XFree86 xterm) support 16 colors.
875 Compatibility with Older Versions
877 Despite our best efforts, there are some differences between ncurses
878 and the (undocumented!) behavior of older curses implementations.
879 These arise from ambiguities or omissions in the documentation of the
882 Refresh of Overlapping Windows
884 If you define two windows A and B that overlap, and then alternately
885 scribble on and refresh them, the changes made to the overlapping
886 region under historic curses versions were often not documented
889 To understand why this is a problem, remember that screen updates are
890 calculated between two representations of the entire display. The
891 documentation says that when you refresh a window, it is first copied
892 to the virtual screen, and then changes are calculated to update the
893 physical screen (and applied to the terminal). But "copied to" is not
894 very specific, and subtle differences in how copying works can produce
895 different behaviors in the case where two overlapping windows are each
896 being refreshed at unpredictable intervals.
898 What happens to the overlapping region depends on what wnoutrefresh()
899 does with its argument -- what portions of the argument window it
900 copies to the virtual screen. Some implementations do "change copy",
901 copying down only locations in the window that have changed (or been
902 marked changed with wtouchln() and friends). Some implementations do
903 "entire copy", copying all window locations to the virtual screen
904 whether or not they have changed.
906 The ncurses library itself has not always been consistent on this
907 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy.
908 Versions 1.8.6 and older, and versions 1.9.9 and newer, do change
911 For most commercial curses implementations, it is not documented and
912 not known for sure (at least not to the ncurses maintainers) whether
913 they do change copy or entire copy. We know that System V release 3
914 curses has logic in it that looks like an attempt to do change copy,
915 but the surrounding logic and data representations are sufficiently
916 complex, and our knowledge sufficiently indirect, that it is hard to
917 know whether this is reliable. It is not clear what the SVr4
918 documentation and XSI standard intend. The XSI Curses standard barely
919 mentions wnoutrefresh(); the SVr4 documents seem to be describing
920 entire-copy, but it is possible with some effort and straining to read
923 It might therefore be unwise to rely on either behavior in programs
924 that might have to be linked with other curses implementations.
925 Instead, you can do an explicit touchwin() before the wnoutrefresh()
926 call to guarantee an entire-contents copy anywhere.
928 The really clean way to handle this is to use the panels library. If,
929 when you want a screen update, you do update_panels(), it will do all
930 the necessary wnoutrefresh() calls for whatever panel stacking order
931 you have defined. Then you can do one doupdate() and there will be a
932 single burst of physical I/O that will do all your updates.
936 If you have been using a very old versions of ncurses (1.8.7 or older)
937 you may be surprised by the behavior of the erase functions. In older
938 versions, erased areas of a window were filled with a blank modified
939 by the window's current attribute (as set by wattrset(), wattron(),
940 wattroff() and friends).
942 In newer versions, this is not so. Instead, the attribute of erased
943 blanks is normal unless and until it is modified by the functions
944 bkgdset() or wbkgdset().
946 This change in behavior conforms ncurses to System V Release 4 and the
949 XSI Curses Conformance
951 The ncurses library is intended to be base-level conformant with the
952 XSI Curses standard from X/Open. Many extended-level features (in
953 fact, almost all features not directly concerned with wide characters
954 and internationalization) are also supported.
956 One effect of XSI conformance is the change in behavior described
957 under "Background Erase -- Compatibility with Old Versions".
959 Also, ncurses meets the XSI requirement that every macro entry point
960 have a corresponding function which may be linked (and will be
961 prototype-checked) if the macro definition is disabled with #undef.
965 The ncurses library by itself provides good support for screen
966 displays in which the windows are tiled (non-overlapping). In the more
967 general case that windows may overlap, you have to use a series of
968 wnoutrefresh() calls followed by a doupdate(), and be careful about
969 the order you do the window refreshes in. It has to be bottom-upwards,
970 otherwise parts of windows that should be obscured will show through.
972 When your interface design is such that windows may dive deeper into
973 the visibility stack or pop to the top at runtime, the resulting
974 book-keeping can be tedious and difficult to get right. Hence the
977 The panel library first appeared in AT&T System V. The version
978 documented here is the panel code distributed with ncurses.
980 Compiling With the Panels Library
982 Your panels-using modules must import the panels library declarations
986 and must be linked explicitly with the panels library using an -lpanel
987 argument. Note that they must also link the ncurses library with
988 -lncurses. Many linkers are two-pass and will accept either order, but
989 it is still good practice to put -lpanel first and -lncurses second.
993 A panel object is a window that is implicitly treated as part of a
994 deck including all other panel objects. The deck has an implicit
995 bottom-to-top visibility order. The panels library includes an update
996 function (analogous to refresh()) that displays all panels in the deck
997 in the proper order to resolve overlaps. The standard window, stdscr,
998 is considered below all panels.
1000 Details on the panels functions are available in the man pages. We
1001 will just hit the highlights here.
1003 You create a panel from a window by calling new_panel() on a window
1004 pointer. It then becomes the top of the deck. The panel's window is
1005 available as the value of panel_window() called with the panel pointer
1008 You can delete a panel (removing it from the deck) with del_panel.
1009 This will not deallocate the associated window; you have to do that
1010 yourself. You can replace a panel's window with a different window by
1011 calling replace_window. The new window may be of different size; the
1012 panel code will re-compute all overlaps. This operation does not
1013 change the panel's position in the deck.
1015 To move a panel's window, use move_panel(). The mvwin() function on
1016 the panel's window is not sufficient because it does not update the
1017 panels library's representation of where the windows are. This
1018 operation leaves the panel's depth, contents, and size unchanged.
1020 Two functions (top_panel(), bottom_panel()) are provided for
1021 rearranging the deck. The first pops its argument window to the top of
1022 the deck; the second sends it to the bottom. Either operation leaves
1023 the panel's screen location, contents, and size unchanged.
1025 The function update_panels() does all the wnoutrefresh() calls needed
1026 to prepare for doupdate() (which you must call yourself, afterwards).
1028 Typically, you will want to call update_panels() and doupdate() just
1029 before accepting command input, once in each cycle of interaction with
1030 the user. If you call update_panels() after each and every panel
1031 write, you will generate a lot of unnecessary refresh activity and
1034 Panels, Input, and the Standard Screen
1036 You should not mix wnoutrefresh() or wrefresh() operations with panels
1037 code; this will work only if the argument window is either in the top
1038 panel or unobscured by any other panels.
1040 The stsdcr window is a special case. It is considered below all
1041 panels. Because changes to panels may obscure parts of stdscr, though,
1042 you should call update_panels() before doupdate() even when you only
1045 Note that wgetch automatically calls wrefresh. Therefore, before
1046 requesting input from a panel window, you need to be sure that the
1047 panel is totally unobscured.
1049 There is presently no way to display changes to one obscured panel
1050 without repainting all panels.
1054 It is possible to remove a panel from the deck temporarily; use
1055 hide_panel for this. Use show_panel() to render it visible again. The
1056 predicate function panel_hidden tests whether or not a panel is
1059 The panel_update code ignores hidden panels. You cannot do top_panel()
1060 or bottom_panel on a hidden panel(). Other panels operations are
1063 Miscellaneous Other Facilities
1065 It is possible to navigate the deck using the functions panel_above()
1066 and panel_below. Handed a panel pointer, they return the panel above
1067 or below that panel. Handed NULL, they return the bottom-most or
1070 Every panel has an associated user pointer, not used by the panel
1071 code, to which you can attach application data. See the man page
1072 documentation of set_panel_userptr() and panel_userptr for details.
1076 A menu is a screen display that assists the user to choose some subset
1077 of a given set of items. The menu library is a curses extension that
1078 supports easy programming of menu hierarchies with a uniform but
1081 The menu library first appeared in AT&T System V. The version
1082 documented here is the menu code distributed with ncurses.
1084 Compiling With the menu Library
1086 Your menu-using modules must import the menu library declarations with
1089 and must be linked explicitly with the menus library using an -lmenu
1090 argument. Note that they must also link the ncurses library with
1091 -lncurses. Many linkers are two-pass and will accept either order, but
1092 it is still good practice to put -lmenu first and -lncurses second.
1096 The menus created by this library consist of collections of items
1097 including a name string part and a description string part. To make
1098 menus, you create groups of these items and connect them with menu
1101 The menu can then by posted, that is written to an associated window.
1102 Actually, each menu has two associated windows; a containing window in
1103 which the programmer can scribble titles or borders, and a subwindow
1104 in which the menu items proper are displayed. If this subwindow is too
1105 small to display all the items, it will be a scrollable viewport on
1106 the collection of items.
1108 A menu may also be unposted (that is, undisplayed), and finally freed
1109 to make the storage associated with it and its items available for
1112 The general flow of control of a menu program looks like this:
1113 1. Initialize curses.
1114 2. Create the menu items, using new_item().
1115 3. Create the menu using new_menu().
1116 4. Post the menu using post_menu().
1117 5. Refresh the screen.
1118 6. Process user requests via an input loop.
1119 7. Unpost the menu using unpost_menu().
1120 8. Free the menu, using free_menu().
1121 9. Free the items using free_item().
1122 10. Terminate curses.
1126 Menus may be multi-valued or (the default) single-valued (see the
1127 manual page menu_opts(3x) to see how to change the default). Both
1128 types always have a current item.
1130 From a single-valued menu you can read the selected value simply by
1131 looking at the current item. From a multi-valued menu, you get the
1132 selected set by looping through the items applying the item_value()
1133 predicate function. Your menu-processing code can use the function
1134 set_item_value() to flag the items in the select set.
1136 Menu items can be made unselectable using set_item_opts() or
1137 item_opts_off() with the O_SELECTABLE argument. This is the only
1138 option so far defined for menus, but it is good practice to code as
1139 though other option bits might be on.
1143 The menu library calculates a minimum display size for your window,
1144 based on the following variables:
1145 * The number and maximum length of the menu items
1146 * Whether the O_ROWMAJOR option is enabled
1147 * Whether display of descriptions is enabled
1148 * Whatever menu format may have been set by the programmer
1149 * The length of the menu mark string used for highlighting selected
1152 The function set_menu_format() allows you to set the maximum size of
1153 the viewport or menu page that will be used to display menu items. You
1154 can retrieve any format associated with a menu with menu_format(). The
1155 default format is rows=16, columns=1.
1157 The actual menu page may be smaller than the format size. This depends
1158 on the item number and size and whether O_ROWMAJOR is on. This option
1159 (on by default) causes menu items to be displayed in a "raster-scan"
1160 pattern, so that if more than one item will fit horizontally the first
1161 couple of items are side-by-side in the top row. The alternative is
1162 column-major display, which tries to put the first several items in
1165 As mentioned above, a menu format not large enough to allow all items
1166 to fit on-screen will result in a menu display that is vertically
1169 You can scroll it with requests to the menu driver, which will be
1170 described in the section on menu input handling.
1172 Each menu has a mark string used to visually tag selected items; see
1173 the menu_mark(3x) manual page for details. The mark string length also
1174 influences the menu page size.
1176 The function scale_menu() returns the minimum display size that the
1177 menu code computes from all these factors. There are other menu
1178 display attributes including a select attribute, an attribute for
1179 selectable items, an attribute for unselectable items, and a pad
1180 character used to separate item name text from description text. These
1181 have reasonable defaults which the library allows you to change (see
1182 the menu_attribs(3x) manual page.
1186 Each menu has, as mentioned previously, a pair of associated windows.
1187 Both these windows are painted when the menu is posted and erased when
1188 the menu is unposted.
1190 The outer or frame window is not otherwise touched by the menu
1191 routines. It exists so the programmer can associate a title, a border,
1192 or perhaps help text with the menu and have it properly refreshed or
1193 erased at post/unpost time. The inner window or subwindow is where the
1194 current menu page is displayed.
1196 By default, both windows are stdscr. You can set them with the
1197 functions in menu_win(3x).
1199 When you call post_menu(), you write the menu to its subwindow. When
1200 you call unpost_menu(), you erase the subwindow, However, neither of
1201 these actually modifies the screen. To do that, call wrefresh() or
1204 Processing Menu Input
1206 The main loop of your menu-processing code should call menu_driver()
1207 repeatedly. The first argument of this routine is a menu pointer; the
1208 second is a menu command code. You should write an input-fetching
1209 routine that maps input characters to menu command codes, and pass its
1210 output to menu_driver(). The menu command codes are fully documented
1213 The simplest group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM,
1214 REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_UP_ITEM, REQ_DOWN_ITEM,
1215 REQ_LEFT_ITEM, REQ_RIGHT_ITEM. These change the currently selected
1216 item. These requests may cause scrolling of the menu page if it only
1217 partially displayed.
1219 There are explicit requests for scrolling which also change the
1220 current item (because the select location does not change, but the
1221 item there does). These are REQ_SCR_DLINE, REQ_SCR_ULINE,
1222 REQ_SCR_DPAGE, and REQ_SCR_UPAGE.
1224 The REQ_TOGGLE_ITEM selects or deselects the current item. It is for
1225 use in multi-valued menus; if you use it with O_ONEVALUE on, you will
1226 get an error return (E_REQUEST_DENIED).
1228 Each menu has an associated pattern buffer. The menu_driver() logic
1229 tries to accumulate printable ASCII characters passed in in that
1230 buffer; when it matches a prefix of an item name, that item (or the
1231 next matching item) is selected. If appending a character yields no
1232 new match, that character is deleted from the pattern buffer, and
1233 menu_driver() returns E_NO_MATCH.
1235 Some requests change the pattern buffer directly: REQ_CLEAR_PATTERN,
1236 REQ_BACK_PATTERN, REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter two are
1237 useful when pattern buffer input matches more than one item in a
1240 Each successful scroll or item navigation request clears the pattern
1241 buffer. It is also possible to set the pattern buffer explicitly with
1244 Finally, menu driver requests above the constant MAX_COMMAND are
1245 considered application-specific commands. The menu_driver() code
1246 ignores them and returns E_UNKNOWN_COMMAND.
1248 Miscellaneous Other Features
1250 Various menu options can affect the processing and visual appearance
1251 and input processing of menus. See menu_opts(3x) for details.
1253 It is possible to change the current item from application code; this
1254 is useful if you want to write your own navigation requests. It is
1255 also possible to explicitly set the top row of the menu display. See
1256 mitem_current(3x). If your application needs to change the menu
1257 subwindow cursor for any reason, pos_menu_cursor() will restore it to
1258 the correct location for continuing menu driver processing.
1260 It is possible to set hooks to be called at menu initialization and
1261 wrapup time, and whenever the selected item changes. See
1264 Each item, and each menu, has an associated user pointer on which you
1265 can hang application data. See mitem_userptr(3x) and menu_userptr(3x).
1269 The form library is a curses extension that supports easy programming
1270 of on-screen forms for data entry and program control.
1272 The form library first appeared in AT&T System V. The version
1273 documented here is the form code distributed with ncurses.
1275 Compiling With the form Library
1277 Your form-using modules must import the form library declarations with
1280 and must be linked explicitly with the forms library using an -lform
1281 argument. Note that they must also link the ncurses library with
1282 -lncurses. Many linkers are two-pass and will accept either order, but
1283 it is still good practice to put -lform first and -lncurses second.
1287 A form is a collection of fields; each field may be either a label
1288 (explanatory text) or a data-entry location. Long forms may be
1289 segmented into pages; each entry to a new page clears the screen.
1291 To make forms, you create groups of fields and connect them with form
1292 frame objects; the form library makes this relatively simple.
1294 Once defined, a form can be posted, that is written to an associated
1295 window. Actually, each form has two associated windows; a containing
1296 window in which the programmer can scribble titles or borders, and a
1297 subwindow in which the form fields proper are displayed.
1299 As the form user fills out the posted form, navigation and editing
1300 keys support movement between fields, editing keys support modifying
1301 field, and plain text adds to or changes data in a current field. The
1302 form library allows you (the forms designer) to bind each navigation
1303 and editing key to any keystroke accepted by curses Fields may have
1304 validation conditions on them, so that they check input data for type
1305 and value. The form library supplies a rich set of pre-defined field
1306 types, and makes it relatively easy to define new ones.
1308 Once its transaction is completed (or aborted), a form may be unposted
1309 (that is, undisplayed), and finally freed to make the storage
1310 associated with it and its items available for re-use.
1312 The general flow of control of a form program looks like this:
1313 1. Initialize curses.
1314 2. Create the form fields, using new_field().
1315 3. Create the form using new_form().
1316 4. Post the form using post_form().
1317 5. Refresh the screen.
1318 6. Process user requests via an input loop.
1319 7. Unpost the form using unpost_form().
1320 8. Free the form, using free_form().
1321 9. Free the fields using free_field().
1322 10. Terminate curses.
1324 Note that this looks much like a menu program; the form library
1325 handles tasks which are in many ways similar, and its interface was
1326 obviously designed to resemble that of the menu library wherever
1329 In forms programs, however, the "process user requests" is somewhat
1330 more complicated than for menus. Besides menu-like navigation
1331 operations, the menu driver loop has to support field editing and data
1334 Creating and Freeing Fields and Forms
1336 The basic function for creating fields is new_field():
1337 FIELD *new_field(int height, int width, /* new field size */
1338 int top, int left, /* upper left corner */
1339 int offscreen, /* number of offscreen rows */
1340 int nbuf); /* number of working buffers */
1342 Menu items always occupy a single row, but forms fields may have
1343 multiple rows. So new_field() requires you to specify a width and
1344 height (the first two arguments, which mist both be greater than
1347 You must also specify the location of the field's upper left corner on
1348 the screen (the third and fourth arguments, which must be zero or
1349 greater). Note that these coordinates are relative to the form
1350 subwindow, which will coincide with stdscr by default but need not be
1351 stdscr if you have done an explicit set_form_win() call.
1353 The fifth argument allows you to specify a number of off-screen rows.
1354 If this is zero, the entire field will always be displayed. If it is
1355 nonzero, the form will be scrollable, with only one screen-full
1356 (initially the top part) displayed at any given time. If you make a
1357 field dynamic and grow it so it will no longer fit on the screen, the
1358 form will become scrollable even if the offscreen argument was
1361 The forms library allocates one working buffer per field; the size of
1362 each buffer is ((height + offscreen)*width + 1, one character for each
1363 position in the field plus a NUL terminator. The sixth argument is the
1364 number of additional data buffers to allocate for the field; your
1365 application can use them for its own purposes.
1366 FIELD *dup_field(FIELD *field, /* field to copy */
1367 int top, int left); /* location of new copy */
1369 The function dup_field() duplicates an existing field at a new
1370 location. Size and buffering information are copied; some attribute
1371 flags and status bits are not (see the form_field_new(3X) for
1373 FIELD *link_field(FIELD *field, /* field to copy */
1374 int top, int left); /* location of new copy */
1376 The function link_field() also duplicates an existing field at a new
1377 location. The difference from dup_field() is that it arranges for the
1378 new field's buffer to be shared with the old one.
1380 Besides the obvious use in making a field editable from two different
1381 form pages, linked fields give you a way to hack in dynamic labels. If
1382 you declare several fields linked to an original, and then make them
1383 inactive, changes from the original will still be propagated to the
1386 As with duplicated fields, linked fields have attribute bits separate
1389 As you might guess, all these field-allocations return NULL if the
1390 field allocation is not possible due to an out-of-memory error or
1391 out-of-bounds arguments.
1393 To connect fields to a form, use
1394 FORM *new_form(FIELD **fields);
1396 This function expects to see a NULL-terminated array of field
1397 pointers. Said fields are connected to a newly-allocated form object;
1398 its address is returned (or else NULL if the allocation fails).
1400 Note that new_field() does not copy the pointer array into private
1401 storage; if you modify the contents of the pointer array during forms
1402 processing, all manner of bizarre things might happen. Also note that
1403 any given field may only be connected to one form.
1405 The functions free_field() and free_form are available to free field
1406 and form objects. It is an error to attempt to free a field connected
1407 to a form, but not vice-versa; thus, you will generally free your form
1410 Fetching and Changing Field Attributes
1412 Each form field has a number of location and size attributes
1413 associated with it. There are other field attributes used to control
1414 display and editing of the field. Some (for example, the O_STATIC bit)
1415 involve sufficient complications to be covered in sections of their
1416 own later on. We cover the functions used to get and set several basic
1419 When a field is created, the attributes not specified by the new_field
1420 function are copied from an invisible system default field. In
1421 attribute-setting and -fetching functions, the argument NULL is taken
1422 to mean this field. Changes to it persist as defaults until your forms
1423 application terminates.
1425 Fetching Size and Location Data
1427 You can retrieve field sizes and locations through:
1428 int field_info(FIELD *field, /* field from which to fetch */
1429 int *height, *int width, /* field size */
1430 int *top, int *left, /* upper left corner */
1431 int *offscreen, /* number of offscreen rows */
1432 int *nbuf); /* number of working buffers */
1434 This function is a sort of inverse of new_field(); instead of setting
1435 size and location attributes of a new field, it fetches them from an
1438 Changing the Field Location
1440 It is possible to move a field's location on the screen:
1441 int move_field(FIELD *field, /* field to alter */
1442 int top, int left); /* new upper-left corner */
1444 You can, of course. query the current location through field_info().
1446 The Justification Attribute
1448 One-line fields may be unjustified, justified right, justified left,
1449 or centered. Here is how you manipulate this attribute:
1450 int set_field_just(FIELD *field, /* field to alter */
1451 int justmode); /* mode to set */
1453 int field_just(FIELD *field); /* fetch mode of field */
1455 The mode values accepted and returned by this functions are
1456 preprocessor macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or
1459 Field Display Attributes
1461 For each field, you can set a foreground attribute for entered
1462 characters, a background attribute for the entire field, and a pad
1463 character for the unfilled portion of the field. You can also control
1464 pagination of the form.
1466 This group of four field attributes controls the visual appearance of
1467 the field on the screen, without affecting in any way the data in the
1469 int set_field_fore(FIELD *field, /* field to alter */
1470 chtype attr); /* attribute to set */
1472 chtype field_fore(FIELD *field); /* field to query */
1474 int set_field_back(FIELD *field, /* field to alter */
1475 chtype attr); /* attribute to set */
1477 chtype field_back(FIELD *field); /* field to query */
1479 int set_field_pad(FIELD *field, /* field to alter */
1480 int pad); /* pad character to set */
1482 chtype field_pad(FIELD *field);
1484 int set_new_page(FIELD *field, /* field to alter */
1485 int flag); /* TRUE to force new page */
1487 chtype new_page(FIELD *field); /* field to query */
1489 The attributes set and returned by the first four functions are normal
1490 curses(3x) display attribute values (A_STANDOUT, A_BOLD, A_REVERSE
1491 etc). The page bit of a field controls whether it is displayed at the
1492 start of a new form screen.
1496 There is also a large collection of field option bits you can set to
1497 control various aspects of forms processing. You can manipulate them
1498 with these functions:
1499 int set_field_opts(FIELD *field, /* field to alter */
1500 int attr); /* attribute to set */
1502 int field_opts_on(FIELD *field, /* field to alter */
1503 int attr); /* attributes to turn on */
1505 int field_opts_off(FIELD *field, /* field to alter */
1506 int attr); /* attributes to turn off */
1508 int field_opts(FIELD *field); /* field to query */
1510 By default, all options are on. Here are the available option bits:
1513 Controls whether the field is visible on the screen. Can be
1514 used during form processing to hide or pop up fields depending
1515 on the value of parent fields.
1518 Controls whether the field is active during forms processing
1519 (i.e. visited by form navigation keys). Can be used to make
1520 labels or derived fields with buffer values alterable by the
1521 forms application, not the user.
1524 Controls whether data is displayed during field entry. If this
1525 option is turned off on a field, the library will accept and
1526 edit data in that field, but it will not be displayed and the
1527 visible field cursor will not move. You can turn off the
1528 O_PUBLIC bit to define password fields.
1531 Controls whether the field's data can be modified. When this
1532 option is off, all editing requests except REQ_PREV_CHOICE and
1533 REQ_NEXT_CHOICE will fail. Such read-only fields may be useful
1537 Controls word-wrapping in multi-line fields. Normally, when any
1538 character of a (blank-separated) word reaches the end of the
1539 current line, the entire word is wrapped to the next line
1540 (assuming there is one). When this option is off, the word will
1541 be split across the line break.
1544 Controls field blanking. When this option is on, entering a
1545 character at the first field position erases the entire field
1546 (except for the just-entered character).
1549 Controls automatic skip to next field when this one fills.
1550 Normally, when the forms user tries to type more data into a
1551 field than will fit, the editing location jumps to next field.
1552 When this option is off, the user's cursor will hang at the end
1553 of the field. This option is ignored in dynamic fields that
1554 have not reached their size limit.
1557 Controls whether validation is applied to blank fields.
1558 Normally, it is not; the user can leave a field blank without
1559 invoking the usual validation check on exit. If this option is
1560 off on a field, exit from it will invoke a validation check.
1563 Controls whether validation occurs on every exit, or only after
1564 the field is modified. Normally the latter is true. Setting
1565 O_PASSOK may be useful if your field's validation function may
1566 change during forms processing.
1569 Controls whether the field is fixed to its initial dimensions.
1570 If you turn this off, the field becomes dynamic and will
1571 stretch to fit entered data.
1573 A field's options cannot be changed while the field is currently
1574 selected. However, options may be changed on posted fields that are
1577 The option values are bit-masks and can be composed with logical-or in
1582 Every field has a status flag, which is set to FALSE when the field is
1583 created and TRUE when the value in field buffer 0 changes. This flag
1584 can be queried and set directly:
1585 int set_field_status(FIELD *field, /* field to alter */
1586 int status); /* mode to set */
1588 int field_status(FIELD *field); /* fetch mode of field */
1590 Setting this flag under program control can be useful if you use the
1591 same form repeatedly, looking for modified fields each time.
1593 Calling field_status() on a field not currently selected for input
1594 will return a correct value. Calling field_status() on a field that is
1595 currently selected for input may not necessarily give a correct field
1596 status value, because entered data is not necessarily copied to buffer
1597 zero before the exit validation check. To guarantee that the returned
1598 status value reflects reality, call field_status() either (1) in the
1599 field's exit validation check routine, (2) from the field's or form's
1600 initialization or termination hooks, or (3) just after a
1601 REQ_VALIDATION request has been processed by the forms driver.
1605 Each field structure contains one character pointer slot that is not
1606 used by the forms library. It is intended to be used by applications
1607 to store private per-field data. You can manipulate it with:
1608 int set_field_userptr(FIELD *field, /* field to alter */
1609 char *userptr); /* mode to set */
1611 char *field_userptr(FIELD *field); /* fetch mode of field */
1613 (Properly, this user pointer field ought to have (void *) type. The
1614 (char *) type is retained for System V compatibility.)
1616 It is valid to set the user pointer of the default field (with a
1617 set_field_userptr() call passed a NULL field pointer.) When a new
1618 field is created, the default-field user pointer is copied to
1619 initialize the new field's user pointer.
1621 Variable-Sized Fields
1623 Normally, a field is fixed at the size specified for it at creation
1624 time. If, however, you turn off its O_STATIC bit, it becomes dynamic
1625 and will automatically resize itself to accommodate data as it is
1626 entered. If the field has extra buffers associated with it, they will
1627 grow right along with the main input buffer.
1629 A one-line dynamic field will have a fixed height (1) but variable
1630 width, scrolling horizontally to display data within the field area as
1631 originally dimensioned and located. A multi-line dynamic field will
1632 have a fixed width, but variable height (number of rows), scrolling
1633 vertically to display data within the field area as originally
1634 dimensioned and located.
1636 Normally, a dynamic field is allowed to grow without limit. But it is
1637 possible to set an upper limit on the size of a dynamic field. You do
1638 it with this function:
1639 int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
1640 int max_size); /* upper limit on field size */
1642 If the field is one-line, max_size is taken to be a column size limit;
1643 if it is multi-line, it is taken to be a line size limit. To disable
1644 any limit, use an argument of zero. The growth limit can be changed
1645 whether or not the O_STATIC bit is on, but has no effect until it is.
1647 The following properties of a field change when it becomes dynamic:
1648 * If there is no growth limit, there is no final position of the
1649 field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored.
1650 * Field justification will be ignored (though whatever justification
1651 is set up will be retained internally and can be queried).
1652 * The dup_field() and link_field() calls copy dynamic-buffer sizes.
1653 If the O_STATIC option is set on one of a collection of links,
1654 buffer resizing will occur only when the field is edited through
1656 * The call field_info() will retrieve the original static size of
1657 the field; use dynamic_field_info() to get the actual dynamic
1662 By default, a field will accept any data that will fit in its input
1663 buffer. However, it is possible to attach a validation type to a
1664 field. If you do this, any attempt to leave the field while it
1665 contains data that does not match the validation type will fail. Some
1666 validation types also have a character-validity check for each time a
1667 character is entered in the field.
1669 A field's validation check (if any) is not called when
1670 set_field_buffer() modifies the input buffer, nor when that buffer is
1671 changed through a linked field.
1673 The form library provides a rich set of pre-defined validation types,
1674 and gives you the capability to define custom ones of your own. You
1675 can examine and change field validation attributes with the following
1677 int set_field_type(FIELD *field, /* field to alter */
1678 FIELDTYPE *ftype, /* type to associate */
1679 ...); /* additional arguments*/
1681 FIELDTYPE *field_type(FIELD *field); /* field to query */
1683 The validation type of a field is considered an attribute of the
1684 field. As with other field attributes, Also, doing set_field_type()
1685 with a NULL field default will change the system default for
1686 validation of newly-created fields.
1688 Here are the pre-defined validation types:
1692 This field type accepts alphabetic data; no blanks, no digits, no
1693 special characters (this is checked at character-entry time). It is
1695 int set_field_type(FIELD *field, /* field to alter */
1696 TYPE_ALPHA, /* type to associate */
1697 int width); /* maximum width of field */
1699 The width argument sets a minimum width of data. Typically you will
1700 want to set this to the field width; if it is greater than the field
1701 width, the validation check will always fail. A minimum width of zero
1702 makes field completion optional.
1706 This field type accepts alphabetic data and digits; no blanks, no
1707 special characters (this is checked at character-entry time). It is
1709 int set_field_type(FIELD *field, /* field to alter */
1710 TYPE_ALNUM, /* type to associate */
1711 int width); /* maximum width of field */
1713 The width argument sets a minimum width of data. As with TYPE_ALPHA,
1714 typically you will want to set this to the field width; if it is
1715 greater than the field width, the validation check will always fail. A
1716 minimum width of zero makes field completion optional.
1720 This type allows you to restrict a field's values to be among a
1721 specified set of string values (for example, the two-letter postal
1722 codes for U.S. states). It is set up with:
1723 int set_field_type(FIELD *field, /* field to alter */
1724 TYPE_ENUM, /* type to associate */
1725 char **valuelist; /* list of possible values */
1726 int checkcase; /* case-sensitive? */
1727 int checkunique); /* must specify uniquely? */
1729 The valuelist parameter must point at a NULL-terminated list of valid
1730 strings. The checkcase argument, if true, makes comparison with the
1731 string case-sensitive.
1733 When the user exits a TYPE_ENUM field, the validation procedure tries
1734 to complete the data in the buffer to a valid entry. If a complete
1735 choice string has been entered, it is of course valid. But it is also
1736 possible to enter a prefix of a valid string and have it completed for
1739 By default, if you enter such a prefix and it matches more than one
1740 value in the string list, the prefix will be completed to the first
1741 matching value. But the checkunique argument, if true, requires prefix
1742 matches to be unique in order to be valid.
1744 The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be
1745 particularly useful with these fields.
1749 This field type accepts an integer. It is set up as follows:
1750 int set_field_type(FIELD *field, /* field to alter */
1751 TYPE_INTEGER, /* type to associate */
1752 int padding, /* # places to zero-pad to */
1753 int vmin, int vmax); /* valid range */
1755 Valid characters consist of an optional leading minus and digits. The
1756 range check is performed on exit. If the range maximum is less than or
1757 equal to the minimum, the range is ignored.
1759 If the value passes its range check, it is padded with as many leading
1760 zero digits as necessary to meet the padding argument.
1762 A TYPE_INTEGER value buffer can conveniently be interpreted with the C
1763 library function atoi(3).
1767 This field type accepts a decimal number. It is set up as follows:
1768 int set_field_type(FIELD *field, /* field to alter */
1769 TYPE_NUMERIC, /* type to associate */
1770 int padding, /* # places of precision */
1771 double vmin, double vmax); /* valid range */
1773 Valid characters consist of an optional leading minus and digits.
1774 possibly including a decimal point. If your system supports locale's,
1775 the decimal point character used must be the one defined by your
1776 locale. The range check is performed on exit. If the range maximum is
1777 less than or equal to the minimum, the range is ignored.
1779 If the value passes its range check, it is padded with as many
1780 trailing zero digits as necessary to meet the padding argument.
1782 A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
1783 library function atof(3).
1787 This field type accepts data matching a regular expression. It is set
1789 int set_field_type(FIELD *field, /* field to alter */
1790 TYPE_REGEXP, /* type to associate */
1791 char *regexp); /* expression to match */
1793 The syntax for regular expressions is that of regcomp(3). The check
1794 for regular-expression match is performed on exit.
1796 Direct Field Buffer Manipulation
1798 The chief attribute of a field is its buffer contents. When a form has
1799 been completed, your application usually needs to know the state of
1800 each field buffer. You can find this out with:
1801 char *field_buffer(FIELD *field, /* field to query */
1802 int bufindex); /* number of buffer to query */
1804 Normally, the state of the zero-numbered buffer for each field is set
1805 by the user's editing actions on that field. It is sometimes useful to
1806 be able to set the value of the zero-numbered (or some other) buffer
1807 from your application:
1808 int set_field_buffer(FIELD *field, /* field to alter */
1809 int bufindex, /* number of buffer to alter */
1810 char *value); /* string value to set */
1812 If the field is not large enough and cannot be resized to a
1813 sufficiently large size to contain the specified value, the value will
1814 be truncated to fit.
1816 Calling field_buffer() with a null field pointer will raise an error.
1817 Calling field_buffer() on a field not currently selected for input
1818 will return a correct value. Calling field_buffer() on a field that is
1819 currently selected for input may not necessarily give a correct field
1820 buffer value, because entered data is not necessarily copied to buffer
1821 zero before the exit validation check. To guarantee that the returned
1822 buffer value reflects on-screen reality, call field_buffer() either
1823 (1) in the field's exit validation check routine, (2) from the field's
1824 or form's initialization or termination hooks, or (3) just after a
1825 REQ_VALIDATION request has been processed by the forms driver.
1829 As with field attributes, form attributes inherit a default from a
1830 system default form structure. These defaults can be queried or set by
1831 of these functions using a form-pointer argument of NULL.
1833 The principal attribute of a form is its field list. You can query and
1834 change this list with:
1835 int set_form_fields(FORM *form, /* form to alter */
1836 FIELD **fields); /* fields to connect */
1838 char *form_fields(FORM *form); /* fetch fields of form */
1840 int field_count(FORM *form); /* count connect fields */
1842 The second argument of set_form_fields() may be a NULL-terminated
1843 field pointer array like the one required by new_form(). In that case,
1844 the old fields of the form are disconnected but not freed (and
1845 eligible to be connected to other forms), then the new fields are
1848 It may also be null, in which case the old fields are disconnected
1849 (and not freed) but no new ones are connected.
1851 The field_count() function simply counts the number of fields
1852 connected to a given from. It returns -1 if the form-pointer argument
1855 Control of Form Display
1857 In the overview section, you saw that to display a form you normally
1858 start by defining its size (and fields), posting it, and refreshing
1859 the screen. There is an hidden step before posting, which is the
1860 association of the form with a frame window (actually, a pair of
1861 windows) within which it will be displayed. By default, the forms
1862 library associates every form with the full-screen window stdscr.
1864 By making this step explicit, you can associate a form with a declared
1865 frame window on your screen display. This can be useful if you want to
1866 adapt the form display to different screen sizes, dynamically tile
1867 forms on the screen, or use a form as part of an interface layout
1870 The two windows associated with each form have the same functions as
1871 their analogues in the menu library. Both these windows are painted
1872 when the form is posted and erased when the form is unposted.
1874 The outer or frame window is not otherwise touched by the form
1875 routines. It exists so the programmer can associate a title, a border,
1876 or perhaps help text with the form and have it properly refreshed or
1877 erased at post/unpost time. The inner window or subwindow is where the
1878 current form page is actually displayed.
1880 In order to declare your own frame window for a form, you will need to
1881 know the size of the form's bounding rectangle. You can get this
1883 int scale_form(FORM *form, /* form to query */
1884 int *rows, /* form rows */
1885 int *cols); /* form cols */
1887 The form dimensions are passed back in the locations pointed to by the
1888 arguments. Once you have this information, you can use it to declare
1889 of windows, then use one of these functions:
1890 int set_form_win(FORM *form, /* form to alter */
1891 WINDOW *win); /* frame window to connect */
1893 WINDOW *form_win(FORM *form); /* fetch frame window of form */
1895 int set_form_sub(FORM *form, /* form to alter */
1896 WINDOW *win); /* form subwindow to connect */
1898 WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
1900 Note that curses operations, including refresh(), on the form, should
1901 be done on the frame window, not the form subwindow.
1903 It is possible to check from your application whether all of a
1904 scrollable field is actually displayed within the menu subwindow. Use
1906 int data_ahead(FORM *form); /* form to be queried */
1908 int data_behind(FORM *form); /* form to be queried */
1910 The function data_ahead() returns TRUE if (a) the current field is
1911 one-line and has undisplayed data off to the right, (b) the current
1912 field is multi-line and there is data off-screen below it.
1914 The function data_behind() returns TRUE if the first (upper left hand)
1915 character position is off-screen (not being displayed).
1917 Finally, there is a function to restore the form window's cursor to
1918 the value expected by the forms driver:
1919 int pos_form_cursor(FORM *) /* form to be queried */
1921 If your application changes the form window cursor, call this function
1922 before handing control back to the forms driver in order to
1925 Input Processing in the Forms Driver
1927 The function form_driver() handles virtualized input requests for form
1928 navigation, editing, and validation requests, just as menu_driver does
1929 for menus (see the section on menu input handling).
1930 int form_driver(FORM *form, /* form to pass input to */
1931 int request); /* form request code */
1933 Your input virtualization function needs to take input and then
1934 convert it to either an alphanumeric character (which is treated as
1935 data to be entered in the currently-selected field), or a forms
1938 The forms driver provides hooks (through input-validation and
1939 field-termination functions) with which your application code can
1940 check that the input taken by the driver matched what was expected.
1942 Page Navigation Requests
1944 These requests cause page-level moves through the form, triggering
1945 display of a new form screen.
1948 Move to the next form page.
1951 Move to the previous form page.
1954 Move to the first form page.
1957 Move to the last form page.
1959 These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from
1960 the last page goes to the first, and REQ_PREV_PAGE from the first page
1963 Inter-Field Navigation Requests
1965 These requests handle navigation between fields on the same page.
1971 Move to previous field.
1974 Move to the first field.
1977 Move to the last field.
1980 Move to sorted next field.
1983 Move to sorted previous field.
1986 Move to the sorted first field.
1989 Move to the sorted last field.
1995 Move right to field.
2003 These requests treat the list of fields on a page as cyclic; that is,
2004 REQ_NEXT_FIELD from the last field goes to the first, and
2005 REQ_PREV_FIELD from the first field goes to the last. The order of the
2006 fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests)
2007 is simply the order of the field pointers in the form array (as set up
2008 by new_form() or set_form_fields()
2010 It is also possible to traverse the fields as if they had been sorted
2011 in screen-position order, so the sequence goes left-to-right and
2012 top-to-bottom. To do this, use the second group of four
2013 sorted-movement requests.
2015 Finally, it is possible to move between fields using visual directions
2016 up, down, right, and left. To accomplish this, use the third group of
2017 four requests. Note, however, that the position of a form for purposes
2018 of these requests is its upper-left corner.
2020 For example, suppose you have a multi-line field B, and two
2021 single-line fields A and C on the same line with B, with A to the left
2022 of B and C to the right of B. A REQ_MOVE_RIGHT from A will go to B
2023 only if A, B, and C all share the same first line; otherwise it will
2026 Intra-Field Navigation Requests
2028 These requests drive movement of the edit cursor within the currently
2032 Move to next character.
2035 Move to previous character.
2041 Move to previous line.
2047 Move to previous word.
2050 Move to beginning of field.
2053 Move to end of field.
2056 Move to beginning of line.
2059 Move to end of line.
2065 Move right in field.
2073 Each word is separated from the previous and next characters by
2074 whitespace. The commands to move to beginning and end of line or field
2075 look for the first or last non-pad character in their ranges.
2079 Fields that are dynamic and have grown and fields explicitly created
2080 with offscreen rows are scrollable. One-line fields scroll
2081 horizontally; multi-line fields scroll vertically. Most scrolling is
2082 triggered by editing and intra-field movement (the library scrolls the
2083 field to keep the cursor visible). It is possible to explicitly
2084 request scrolling with the following requests:
2087 Scroll vertically forward a line.
2090 Scroll vertically backward a line.
2093 Scroll vertically forward a page.
2096 Scroll vertically backward a page.
2099 Scroll vertically forward half a page.
2102 Scroll vertically backward half a page.
2105 Scroll horizontally forward a character.
2108 Scroll horizontally backward a character.
2111 Scroll horizontally one field width forward.
2114 Scroll horizontally one field width backward.
2117 Scroll horizontally one half field width forward.
2120 Scroll horizontally one half field width backward.
2122 For scrolling purposes, a page of a field is the height of its visible
2127 When you pass the forms driver an ASCII character, it is treated as a
2128 request to add the character to the field's data buffer. Whether this
2129 is an insertion or a replacement depends on the field's edit mode
2130 (insertion is the default.
2132 The following requests support editing the field and changing the edit
2142 New line request (see below for explanation).
2145 Insert space at character location.
2148 Insert blank line at character location.
2151 Delete character at cursor.
2154 Delete previous word at cursor.
2157 Delete line at cursor.
2160 Delete word at cursor.
2163 Clear to end of line.
2166 Clear to end of field.
2171 The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is
2172 complicated and partly controlled by a pair of forms options. The
2173 special cases are triggered when the cursor is at the beginning of a
2174 field, or on the last line of the field.
2176 First, we consider REQ_NEW_LINE:
2178 The normal behavior of REQ_NEW_LINE in insert mode is to break the
2179 current line at the position of the edit cursor, inserting the portion
2180 of the current line after the cursor as a new line following the
2181 current and moving the cursor to the beginning of that new line (you
2182 may think of this as inserting a newline in the field buffer).
2184 The normal behavior of REQ_NEW_LINE in overlay mode is to clear the
2185 current line from the position of the edit cursor to end of line. The
2186 cursor is then moved to the beginning of the next line.
2188 However, REQ_NEW_LINE at the beginning of a field, or on the last line
2189 of a field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is
2190 off, this special action is disabled.
2192 Now, let us consider REQ_DEL_PREV:
2194 The normal behavior of REQ_DEL_PREV is to delete the previous
2195 character. If insert mode is on, and the cursor is at the start of a
2196 line, and the text on that line will fit on the previous one, it
2197 instead appends the contents of the current line to the previous one
2198 and deletes the current line (you may think of this as deleting a
2199 newline from the field buffer).
2201 However, REQ_DEL_PREV at the beginning of a field is instead treated
2202 as a REQ_PREV_FIELD.
2204 If the O_BS_OVERLOAD option is off, this special action is disabled
2205 and the forms driver just returns E_REQUEST_DENIED.
2207 See Form Options for discussion of how to set and clear the overload
2212 If the type of your field is ordered, and has associated functions for
2213 getting the next and previous values of the type from a given value,
2214 there are requests that can fetch that value into the field buffer:
2217 Place the successor value of the current value in the buffer.
2220 Place the predecessor value of the current value in the buffer.
2222 Of the built-in field types, only TYPE_ENUM has built-in successor and
2223 predecessor functions. When you define a field type of your own (see
2224 Custom Validation Types), you can associate our own ordering
2227 Application Commands
2229 Form requests are represented as integers above the curses value
2230 greater than KEY_MAX and less than or equal to the constant
2231 MAX_COMMAND. If your input-virtualization routine returns a value
2232 above MAX_COMMAND, the forms driver will ignore it.
2236 It is possible to set function hooks to be executed whenever the
2237 current field or form changes. Here are the functions that support
2239 typedef void (*HOOK)(); /* pointer to function returning void */
2241 int set_form_init(FORM *form, /* form to alter */
2242 HOOK hook); /* initialization hook */
2244 HOOK form_init(FORM *form); /* form to query */
2246 int set_form_term(FORM *form, /* form to alter */
2247 HOOK hook); /* termination hook */
2249 HOOK form_term(FORM *form); /* form to query */
2251 int set_field_init(FORM *form, /* form to alter */
2252 HOOK hook); /* initialization hook */
2254 HOOK field_init(FORM *form); /* form to query */
2256 int set_field_term(FORM *form, /* form to alter */
2257 HOOK hook); /* termination hook */
2259 HOOK field_term(FORM *form); /* form to query */
2261 These functions allow you to either set or query four different hooks.
2262 In each of the set functions, the second argument should be the
2263 address of a hook function. These functions differ only in the timing
2267 This hook is called when the form is posted; also, just after
2268 each page change operation.
2271 This hook is called when the form is posted; also, just after
2275 This hook is called just after field validation; that is, just
2276 before the field is altered. It is also called when the form is
2280 This hook is called when the form is unposted; also, just
2281 before each page change operation.
2283 Calls to these hooks may be triggered
2284 1. When user editing requests are processed by the forms driver
2285 2. When the current page is changed by set_current_field() call
2286 3. When the current field is changed by a set_form_page() call
2288 See Field Change Commands for discussion of the latter two cases.
2290 You can set a default hook for all fields by passing one of the set
2291 functions a NULL first argument.
2293 You can disable any of these hooks by (re)setting them to NULL, the
2296 Field Change Commands
2298 Normally, navigation through the form will be driven by the user's
2299 input requests. But sometimes it is useful to be able to move the
2300 focus for editing and viewing under control of your application, or
2301 ask which field it currently is in. The following functions help you
2303 int set_current_field(FORM *form, /* form to alter */
2304 FIELD *field); /* field to shift to */
2306 FIELD *current_field(FORM *form); /* form to query */
2308 int field_index(FORM *form, /* form to query */
2309 FIELD *field); /* field to get index of */
2311 The function field_index() returns the index of the given field in the
2312 given form's field array (the array passed to new_form() or
2315 The initial current field of a form is the first active field on the
2316 first page. The function set_form_fields() resets this.
2318 It is also possible to move around by pages.
2319 int set_form_page(FORM *form, /* form to alter */
2320 int page); /* page to go to (0-origin) */
2322 int form_page(FORM *form); /* return form's current page */
2324 The initial page of a newly-created form is 0. The function
2325 set_form_fields() resets this.
2329 Like fields, forms may have control option bits. They can be changed
2330 or queried with these functions:
2331 int set_form_opts(FORM *form, /* form to alter */
2332 int attr); /* attribute to set */
2334 int form_opts_on(FORM *form, /* form to alter */
2335 int attr); /* attributes to turn on */
2337 int form_opts_off(FORM *form, /* form to alter */
2338 int attr); /* attributes to turn off */
2340 int form_opts(FORM *form); /* form to query */
2342 By default, all options are on. Here are the available option bits:
2345 Enable overloading of REQ_NEW_LINE as described in Editing
2346 Requests. The value of this option is ignored on dynamic fields
2347 that have not reached their size limit; these have no last
2348 line, so the circumstances for triggering a REQ_NEXT_FIELD
2352 Enable overloading of REQ_DEL_PREV as described in Editing
2355 The option values are bit-masks and can be composed with logical-or in
2358 Custom Validation Types
2360 The form library gives you the capability to define custom validation
2361 types of your own. Further, the optional additional arguments of
2362 set_field_type effectively allow you to parameterize validation types.
2363 Most of the complications in the validation-type interface have to do
2364 with the handling of the additional arguments within custom validation
2369 The simplest way to create a custom data type is to compose it from
2370 two preexisting ones:
2371 FIELD *link_fieldtype(FIELDTYPE *type1,
2374 This function creates a field type that will accept any of the values
2375 legal for either of its argument field types (which may be either
2376 predefined or programmer-defined). If a set_field_type() call later
2377 requires arguments, the new composite type expects all arguments for
2378 the first type, than all arguments for the second. Order functions
2379 (see Order Requests) associated with the component types will work on
2380 the composite; what it does is check the validation function for the
2381 first type, then for the second, to figure what type the buffer
2382 contents should be treated as.
2386 To create a field type from scratch, you need to specify one or both
2387 of the following things:
2388 * A character-validation function, to check each character as it is
2390 * A field-validation function to be applied on exit from the field.
2392 Here is how you do that:
2393 typedef int (*HOOK)(); /* pointer to function returning int */
2395 FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
2396 HOOK c_validate) /* character validator */
2399 int free_fieldtype(FIELDTYPE *ftype); /* type to free */
2401 At least one of the arguments of new_fieldtype() must be non-NULL. The
2402 forms driver will automatically call the new type's validation
2403 functions at appropriate points in processing a field of the new type.
2405 The function free_fieldtype() deallocates the argument fieldtype,
2406 freeing all storage associated with it.
2408 Normally, a field validator is called when the user attempts to leave
2409 the field. Its first argument is a field pointer, from which it can
2410 get to field buffer 0 and test it. If the function returns TRUE, the
2411 operation succeeds; if it returns FALSE, the edit cursor stays in the
2414 A character validator gets the character passed in as a first
2415 argument. It too should return TRUE if the character is valid, FALSE
2418 Validation Function Arguments
2420 Your field- and character- validation functions will be passed a
2421 second argument as well. This second argument is the address of a
2422 structure (which we will call a pile) built from any of the
2423 field-type-specific arguments passed to set_field_type(). If no such
2424 arguments are defined for the field type, this pile pointer argument
2427 In order to arrange for such arguments to be passed to your validation
2428 functions, you must associate a small set of storage-management
2429 functions with the type. The forms driver will use these to synthesize
2430 a pile from the trailing arguments of each set_field_type() argument,
2431 and a pointer to the pile will be passed to the validation functions.
2433 Here is how you make the association:
2434 typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
2435 typedef void (*VOIDHOOK)(); /* pointer to function returning void */
2437 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2438 PTRHOOK make_str, /* make structure from args */
2439 PTRHOOK copy_str, /* make copy of structure */
2440 VOIDHOOK free_str); /* free structure storage */
2442 Here is how the storage-management hooks are used:
2445 This function is called by set_field_type(). It gets one
2446 argument, a va_list of the type-specific arguments passed to
2447 set_field_type(). It is expected to return a pile pointer to a
2448 data structure that encapsulates those arguments.
2451 This function is called by form library functions that allocate
2452 new field instances. It is expected to take a pile pointer,
2453 copy the pile to allocated storage, and return the address of
2457 This function is called by field- and type-deallocation
2458 routines in the library. It takes a pile pointer argument, and
2459 is expected to free the storage of that pile.
2461 The make_str and copy_str functions may return NULL to signal
2462 allocation failure. The library routines will that call them will
2463 return error indication when this happens. Thus, your validation
2464 functions should never see a NULL file pointer and need not check
2467 Order Functions For Custom Types
2469 Some custom field types are simply ordered in the same well-defined
2470 way that TYPE_ENUM is. For such types, it is possible to define
2471 successor and predecessor functions to support the REQ_NEXT_CHOICE and
2472 REQ_PREV_CHOICE requests. Here is how:
2473 typedef int (*INTHOOK)(); /* pointer to function returning int */
2475 int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
2476 INTHOOK succ, /* get successor value */
2477 INTHOOK pred); /* get predecessor value */
2479 The successor and predecessor arguments will each be passed two
2480 arguments; a field pointer, and a pile pointer (as for the validation
2481 functions). They are expected to use the function field_buffer() to
2482 read the current value, and set_field_buffer() on buffer 0 to set the
2483 next or previous value. Either hook may return TRUE to indicate
2484 success (a legal next or previous value was set) or FALSE to indicate
2489 The interface for defining custom types is complicated and tricky.
2490 Rather than attempting to create a custom type entirely from scratch,
2491 you should start by studying the library source code for whichever of
2492 the pre-defined types seems to be closest to what you want.
2494 Use that code as a model, and evolve it towards what you really want.
2495 You will avoid many problems and annoyances that way. The code in the
2496 ncurses library has been specifically exempted from the package
2497 copyright to support this.
2499 If your custom type defines order functions, have do something
2500 intuitive with a blank field. A useful convention is to make the
2501 successor of a blank field the types minimum value, and its
2502 predecessor the maximum.