+++ /dev/null
-
- Writing Programs with NCURSES
-
- by Eric S. Raymond and Zeyd M. Ben-Halim
- updates since release 1.9.9e by Thomas Dickey
-
- Contents
-
- * Introduction
- + A Brief History of Curses
- + Scope of This Document
- + Terminology
- * The Curses Library
- + An Overview of Curses
- o Compiling Programs using Curses
- o Updating the Screen
- o Standard Windows and Function Naming Conventions
- o Variables
- + Using the Library
- o Starting up
- o Output
- o Input
- o Using Forms Characters
- o Character Attributes and Color
- o Mouse Interfacing
- o Finishing Up
- + Function Descriptions
- o Initialization and Wrapup
- o Causing Output to the Terminal
- o Low-Level Capability Access
- o Debugging
- + Hints, Tips, and Tricks
- o Some Notes of Caution
- o Temporarily Leaving ncurses Mode
- o Using ncurses under xterm
- o Handling Multiple Terminal Screens
- o Testing for Terminal Capabilities
- o Tuning for Speed
- o Special Features of ncurses
- + Compatibility with Older Versions
- o Refresh of Overlapping Windows
- o Background Erase
- + XSI Curses Conformance
- * The Panels Library
- + Compiling With the Panels Library
- + Overview of Panels
- + Panels, Input, and the Standard Screen
- + Hiding Panels
- + Miscellaneous Other Facilities
- * The Menu Library
- + Compiling with the menu Library
- + Overview of Menus
- + Selecting items
- + Menu Display
- + Menu Windows
- + Processing Menu Input
- + Miscellaneous Other Features
- * The Forms Library
- + Compiling with the forms Library
- + Overview of Forms
- + Creating and Freeing Fields and Forms
- + Fetching and Changing Field Attributes
- o Fetching Size and Location Data
- o Changing the Field Location
- o The Justification Attribute
- o Field Display Attributes
- o Field Option Bits
- o Field Status
- o Field User Pointer
- + Variable-Sized Fields
- + Field Validation
- o TYPE_ALPHA
- o TYPE_ALNUM
- o TYPE_ENUM
- o TYPE_INTEGER
- o TYPE_NUMERIC
- o TYPE_REGEXP
- + Direct Field Buffer Manipulation
- + Attributes of Forms
- + Control of Form Display
- + Input Processing in the Forms Driver
- o Page Navigation Requests
- o Inter-Field Navigation Requests
- o Intra-Field Navigation Requests
- o Scrolling Requests
- o Field Editing Requests
- o Order Requests
- o Application Commands
- + Field Change Hooks
- + Field Change Commands
- + Form Options
- + Custom Validation Types
- o Union Types
- o New Field Types
- o Validation Function Arguments
- o Order Functions For Custom Types
- o Avoiding Problems
- _________________________________________________________________
-
- Introduction
-
- This document is an introduction to programming with curses. It is not
- an exhaustive reference for the curses Application Programming
- Interface (API); that role is filled by the curses manual pages.
- Rather, it is intended to help C programmers ease into using the
- package.
-
- This document is aimed at C applications programmers not yet
- specifically familiar with ncurses. If you are already an experienced
- curses programmer, you should nevertheless read the sections on Mouse
- Interfacing, Debugging, Compatibility with Older Versions, and Hints,
- Tips, and Tricks. These will bring you up to speed on the special
- features and quirks of the ncurses implementation. If you are not so
- experienced, keep reading.
-
- The curses package is a subroutine library for terminal-independent
- screen-painting and input-event handling which presents a high level
- screen model to the programmer, hiding differences between terminal
- types and doing automatic optimization of output to change one screen
- full of text into another. Curses uses terminfo, which is a database
- format that can describe the capabilities of thousands of different
- terminals.
-
- The curses API may seem something of an archaism on UNIX desktops
- increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX
- still supports tty lines and X supports xterm(1); the curses API has
- the advantage of (a) back-portability to character-cell terminals, and
- (b) simplicity. For an application that does not require bit-mapped
- graphics and multiple fonts, an interface implementation using curses
- will typically be a great deal simpler and less expensive than one
- using an X toolkit.
-
-A Brief History of Curses
-
- Historically, the first ancestor of curses was the routines written to
- provide screen-handling for the game rogue; these used the
- already-existing termcap database facility for describing terminal
- capabilities. These routines were abstracted into a documented library
- and first released with the early BSD UNIX versions.
-
- System III UNIX from Bell Labs featured a rewritten and much-improved
- curses library. It introduced the terminfo format. Terminfo is based
- on Berkeley's termcap database, but contains a number of improvements
- and extensions. Parameterized capabilities strings were introduced,
- making it possible to describe multiple video attributes, and colors
- and to handle far more unusual terminals than possible with termcap.
- In the later AT&T System V releases, curses evolved to use more
- facilities and offer more capabilities, going far beyond BSD curses in
- power and flexibility.
-
-Scope of This Document
-
- This document describes ncurses, a free implementation of the System V
- curses API with some clearly marked extensions. It includes the
- following System V curses features:
-
- * Support for multiple screen highlights (BSD curses could only
- handle one `standout' highlight, usually reverse-video).
- * Support for line- and box-drawing using forms characters.
- * Recognition of function keys on input.
- * Color support.
- * Support for pads (windows of larger than screen size on which the
- screen or a subwindow defines a viewport).
-
- Also, this package makes use of the insert and delete line and
- character features of terminals so equipped, and determines how to
- optimally use these features with no help from the programmer. It
- allows arbitrary combinations of video attributes to be displayed,
- even on terminals that leave ``magic cookies'' on the screen to mark
- changes in attributes.
-
- The ncurses package can also capture and use event reports from a
- mouse in some environments (notably, xterm under the X window system).
- This document includes tips for using the mouse.
-
- The ncurses package was originated by Pavel Curtis. The original
- maintainer of this package is Zeyd Ben-Halim <zmbenhal@netcom.com>.
- Eric S. Raymond <esr@snark.thyrsus.com> wrote many of the new features
- in versions after 1.8.1 and wrote most of this introduction. Jürgen
- Pfeifer wrote all of the menu and forms code as well as the Ada95
- binding. Ongoing work is being done by Thomas Dickey and Jürgen
- Pfeifer. Florian La Roche acts as the maintainer for the Free Software
- Foundation, which holds the copyright on ncurses. Contact the current
- maintainers at bug-ncurses@gnu.org.
-
- This document also describes the panels extension library, similarly
- modeled on the SVr4 panels facility. This library allows you to
- associate backing store with each of a stack or deck of overlapping
- windows, and provides operations for moving windows around in the
- stack that change their visibility in the natural way (handling window
- overlaps).
-
- Finally, this document describes in detail the menus and forms
- extension libraries, also cloned from System V, which support easy
- construction and sequences of menus and fill-in forms.
-
-Terminology
-
- In this document, the following terminology is used with reasonable
- consistency:
-
- window
- A data structure describing a sub-rectangle of the screen
- (possibly the entire screen). You can write to a window as
- though it were a miniature screen, scrolling independently of
- other windows on the physical screen.
-
- screens
- A subset of windows which are as large as the terminal screen,
- i.e., they start at the upper left hand corner and encompass
- the lower right hand corner. One of these, stdscr, is
- automatically provided for the programmer.
-
- terminal screen
- The package's idea of what the terminal display currently looks
- like, i.e., what the user sees now. This is a special screen.
-
- The Curses Library
-
-An Overview of Curses
-
- Compiling Programs using Curses
-
- In order to use the library, it is necessary to have certain types and
- variables defined. Therefore, the programmer must have a line:
- #include <curses.h>
-
- at the top of the program source. The screen package uses the Standard
- I/O library, so <curses.h> includes <stdio.h>. <curses.h> also
- includes <termios.h>, <termio.h>, or <sgtty.h> depending on your
- system. It is redundant (but harmless) for the programmer to do these
- includes, too. In linking with curses you need to have -lncurses in
- your LDFLAGS or on the command line. There is no need for any other
- libraries.
-
- Updating the Screen
-
- In order to update the screen optimally, it is necessary for the
- routines to know what the screen currently looks like and what the
- programmer wants it to look like next. For this purpose, a data type
- (structure) named WINDOW is defined which describes a window image to
- the routines, including its starting position on the screen (the (y,
- x) coordinates of the upper left hand corner) and its size. One of
- these (called curscr, for current screen) is a screen image of what
- the terminal currently looks like. Another screen (called stdscr, for
- standard screen) is provided by default to make changes on.
-
- A window is a purely internal representation. It is used to build and
- store a potential image of a portion of the terminal. It doesn't bear
- any necessary relation to what is really on the terminal screen; it's
- more like a scratchpad or write buffer.
-
- To make the section of physical screen corresponding to a window
- reflect the contents of the window structure, the routine refresh()
- (or wrefresh() if the window is not stdscr) is called.
-
- A given physical screen section may be within the scope of any number
- of overlapping windows. Also, changes can be made to windows in any
- order, without regard to motion efficiency. Then, at will, the
- programmer can effectively say ``make it look like this,'' and let the
- package implementation determine the most efficient way to repaint the
- screen.
-
- Standard Windows and Function Naming Conventions
-
- As hinted above, the routines can use several windows, but two are
- automatically given: curscr, which knows what the terminal looks like,
- and stdscr, which is what the programmer wants the terminal to look
- like next. The user should never actually access curscr directly.
- Changes should be made to through the API, and then the routine
- refresh() (or wrefresh()) called.
-
- Many functions are defined to use stdscr as a default screen. For
- example, to add a character to stdscr, one calls addch() with the
- desired character as argument. To write to a different window. use the
- routine waddch() (for `w'indow-specific addch()) is provided. This
- convention of prepending function names with a `w' when they are to be
- applied to specific windows is consistent. The only routines which do
- not follow it are those for which a window must always be specified.
-
- In order to move the current (y, x) coordinates from one point to
- another, the routines move() and wmove() are provided. However, it is
- often desirable to first move and then perform some I/O operation. In
- order to avoid clumsiness, most I/O routines can be preceded by the
- prefix 'mv' and the desired (y, x) coordinates prepended to the
- arguments to the function. For example, the calls
- move(y, x);
- addch(ch);
-
- can be replaced by
- mvaddch(y, x, ch);
-
- and
- wmove(win, y, x);
- waddch(win, ch);
-
- can be replaced by
- mvwaddch(win, y, x, ch);
-
- Note that the window description pointer (win) comes before the added
- (y, x) coordinates. If a function requires a window pointer, it is
- always the first parameter passed.
-
- Variables
-
- The curses library sets some variables describing the terminal
- capabilities.
- type name description
- ------------------------------------------------------------------
- int LINES number of lines on the terminal
- int COLS number of columns on the terminal
-
- The curses.h also introduces some #define constants and types of
- general usefulness:
-
- bool
- boolean type, actually a `char' (e.g., bool doneit;)
-
- TRUE
- boolean `true' flag (1).
-
- FALSE
- boolean `false' flag (0).
-
- ERR
- error flag returned by routines on a failure (-1).
-
- OK
- error flag returned by routines when things go right.
-
-Using the Library
-
- Now we describe how to actually use the screen package. In it, we
- assume all updating, reading, etc. is applied to stdscr. These
- instructions will work on any window, providing you change the
- function names and parameters as mentioned above.
-
- Here is a sample program to motivate the discussion:
-
-#include <curses.h>
-#include <signal.h>
-
-static void finish(int sig);
-
-main(int argc, char *argv[])
-{
- /* initialize your non-curses data structures here */
-
- (void) signal(SIGINT, finish); /* arrange interrupts to terminate */
-
- (void) initscr(); /* initialize the curses library */
- keypad(stdscr, TRUE); /* enable keyboard mapping */
- (void) nonl(); /* tell curses not to do NL->CR/NL on output */
- (void) cbreak(); /* take input chars one at a time, no wait for \n */
- (void) noecho(); /* don't echo input */
-
- if (has_colors())
- {
- start_color();
-
- /*
- * Simple color assignment, often all we need.
- */
- init_pair(COLOR_BLACK, COLOR_BLACK, COLOR_BLACK);
- init_pair(COLOR_GREEN, COLOR_GREEN, COLOR_BLACK);
- init_pair(COLOR_RED, COLOR_RED, COLOR_BLACK);
- init_pair(COLOR_CYAN, COLOR_CYAN, COLOR_BLACK);
- init_pair(COLOR_WHITE, COLOR_WHITE, COLOR_BLACK);
- init_pair(COLOR_MAGENTA, COLOR_MAGENTA, COLOR_BLACK);
- init_pair(COLOR_BLUE, COLOR_BLUE, COLOR_BLACK);
- init_pair(COLOR_YELLOW, COLOR_YELLOW, COLOR_BLACK);
- }
-
- for (;;)
- {
- int c = getch(); /* refresh, accept single keystroke of input */
-
- /* process the command keystroke */
- }
-
- finish(0); /* we're done */
-}
-
-static void finish(int sig)
-{
- endwin();
-
- /* do your non-curses wrapup here */
-
- exit(0);
-}
-
- Starting up
-
- In order to use the screen package, the routines must know about
- terminal characteristics, and the space for curscr and stdscr must be
- allocated. These function initscr() does both these things. Since it
- must allocate space for the windows, it can overflow memory when
- attempting to do so. On the rare occasions this happens, initscr()
- will terminate the program with an error message. initscr() must
- always be called before any of the routines which affect windows are
- used. If it is not, the program will core dump as soon as either
- curscr or stdscr are referenced. However, it is usually best to wait
- to call it until after you are sure you will need it, like after
- checking for startup errors. Terminal status changing routines like
- nl() and cbreak() should be called after initscr().
-
- Once the screen windows have been allocated, you can set them up for
- your program. If you want to, say, allow a screen to scroll, use
- scrollok(). If you want the cursor to be left in place after the last
- change, use leaveok(). If this isn't done, refresh() will move the
- cursor to the window's current (y, x) coordinates after updating it.
-
- You can create new windows of your own using the functions newwin(),
- derwin(), and subwin(). The routine delwin() will allow you to get rid
- of old windows. All the options described above can be applied to any
- window.
-
- Output
-
- Now that we have set things up, we will want to actually update the
- terminal. The basic functions used to change what will go on a window
- are addch() and move(). addch() adds a character at the current (y, x)
- coordinates. move() changes the current (y, x) coordinates to whatever
- you want them to be. It returns ERR if you try to move off the window.
- As mentioned above, you can combine the two into mvaddch() to do both
- things at once.
-
- The other output functions, such as addstr() and printw(), all call
- addch() to add characters to the window.
-
- After you have put on the window what you want there, when you want
- the portion of the terminal covered by the window to be made to look
- like it, you must call refresh(). In order to optimize finding
- changes, refresh() assumes that any part of the window not changed
- since the last refresh() of that window has not been changed on the
- terminal, i.e., that you have not refreshed a portion of the terminal
- with an overlapping window. If this is not the case, the routine
- touchwin() is provided to make it look like the entire window has been
- changed, thus making refresh() check the whole subsection of the
- terminal for changes.
-
- If you call wrefresh() with curscr as its argument, it will make the
- screen look like curscr thinks it looks like. This is useful for
- implementing a command which would redraw the screen in case it get
- messed up.
-
- Input
-
- The complementary function to addch() is getch() which, if echo is
- set, will call addch() to echo the character. Since the screen package
- needs to know what is on the terminal at all times, if characters are
- to be echoed, the tty must be in raw or cbreak mode. Since initially
- the terminal has echoing enabled and is in ordinary ``cooked'' mode,
- one or the other has to changed before calling getch(); otherwise, the
- program's output will be unpredictable.
-
- When you need to accept line-oriented input in a window, the functions
- wgetstr() and friends are available. There is even a wscanw() function
- that can do scanf()(3)-style multi-field parsing on window input.
- These pseudo-line-oriented functions turn on echoing while they
- execute.
-
- The example code above uses the call keypad(stdscr, TRUE) to enable
- support for function-key mapping. With this feature, the getch() code
- watches the input stream for character sequences that correspond to
- arrow and function keys. These sequences are returned as
- pseudo-character values. The #define values returned are listed in the
- curses.h The mapping from sequences to #define values is determined by
- key_ capabilities in the terminal's terminfo entry.
-
- Using Forms Characters
-
- The addch() function (and some others, including box() and border())
- can accept some pseudo-character arguments which are specially defined
- by ncurses. These are #define values set up in the curses.h header;
- see there for a complete list (look for the prefix ACS_).
-
- The most useful of the ACS defines are the forms-drawing characters.
- You can use these to draw boxes and simple graphs on the screen. If
- the terminal does not have such characters, curses.h will map them to
- a recognizable (though ugly) set of ASCII defaults.
-
- Character Attributes and Color
-
- The ncurses package supports screen highlights including standout,
- reverse-video, underline, and blink. It also supports color, which is
- treated as another kind of highlight.
-
- Highlights are encoded, internally, as high bits of the
- pseudo-character type (chtype) that curses.h uses to represent the
- contents of a screen cell. See the curses.h header file for a complete
- list of highlight mask values (look for the prefix A_).
-
- There are two ways to make highlights. One is to logical-or the value
- of the highlights you want into the character argument of an addch()
- call, or any other output call that takes a chtype argument.
-
- The other is to set the current-highlight value. This is logical-or'ed
- with any highlight you specify the first way. You do this with the
- functions attron(), attroff(), and attrset(); see the manual pages for
- details. Color is a special kind of highlight. The package actually
- thinks in terms of color pairs, combinations of foreground and
- background colors. The sample code above sets up eight color pairs,
- all of the guaranteed-available colors on black. Note that each color
- pair is, in effect, given the name of its foreground color. Any other
- range of eight non-conflicting values could have been used as the
- first arguments of the init_pair() values.
-
- Once you've done an init_pair() that creates color-pair N, you can use
- COLOR_PAIR(N) as a highlight that invokes that particular color
- combination. Note that COLOR_PAIR(N), for constant N, is itself a
- compile-time constant and can be used in initializers.
-
- Mouse Interfacing
-
- The ncurses library also provides a mouse interface.
-
- NOTE: this facility is specific to ncurses, it is not part of
- either the XSI Curses standard, nor of System V Release 4, nor BSD
- curses. System V Release 4 curses contains code with similar
- interface definitions, however it is not documented. Other than by
- disassembling the library, we have no way to determine exactly how
- that mouse code works. Thus, we recommend that you wrap
- mouse-related code in an #ifdef using the feature macro
- NCURSES_MOUSE_VERSION so it will not be compiled and linked on
- non-ncurses systems.
-
- Presently, mouse event reporting works in the following environments:
- * xterm and similar programs such as rxvt.
- * Linux console, when configured with gpm(1), Alessandro Rubini's
- mouse server.
- * OS/2 EMX
-
- The mouse interface is very simple. To activate it, you use the
- function mousemask(), passing it as first argument a bit-mask that
- specifies what kinds of events you want your program to be able to
- see. It will return the bit-mask of events that actually become
- visible, which may differ from the argument if the mouse device is not
- capable of reporting some of the event types you specify.
-
- Once the mouse is active, your application's command loop should watch
- for a return value of KEY_MOUSE from wgetch(). When you see this, a
- mouse event report has been queued. To pick it off the queue, use the
- function getmouse() (you must do this before the next wgetch(),
- otherwise another mouse event might come in and make the first one
- inaccessible).
-
- Each call to getmouse() fills a structure (the address of which you'll
- pass it) with mouse event data. The event data includes zero-origin,
- screen-relative character-cell coordinates of the mouse pointer. It
- also includes an event mask. Bits in this mask will be set,
- corresponding to the event type being reported.
-
- The mouse structure contains two additional fields which may be
- significant in the future as ncurses interfaces to new kinds of
- pointing device. In addition to x and y coordinates, there is a slot
- for a z coordinate; this might be useful with touch-screens that can
- return a pressure or duration parameter. There is also a device ID
- field, which could be used to distinguish between multiple pointing
- devices.
-
- The class of visible events may be changed at any time via
- mousemask(). Events that can be reported include presses, releases,
- single-, double- and triple-clicks (you can set the maximum
- button-down time for clicks). If you don't make clicks visible, they
- will be reported as press-release pairs. In some environments, the
- event mask may include bits reporting the state of shift, alt, and
- ctrl keys on the keyboard during the event.
-
- A function to check whether a mouse event fell within a given window
- is also supplied. You can use this to see whether a given window
- should consider a mouse event relevant to it.
-
- Because mouse event reporting will not be available in all
- environments, it would be unwise to build ncurses applications that
- require the use of a mouse. Rather, you should use the mouse as a
- shortcut for point-and-shoot commands your application would normally
- accept from the keyboard. Two of the test games in the ncurses
- distribution (bs and knight) contain code that illustrates how this
- can be done.
-
- See the manual page curs_mouse(3X) for full details of the
- mouse-interface functions.
-
- Finishing Up
-
- In order to clean up after the ncurses routines, the routine endwin()
- is provided. It restores tty modes to what they were when initscr()
- was first called, and moves the cursor down to the lower-left corner.
- Thus, anytime after the call to initscr, endwin() should be called
- before exiting.
-
-Function Descriptions
-
- We describe the detailed behavior of some important curses functions
- here, as a supplement to the manual page descriptions.
-
- Initialization and Wrapup
-
- initscr()
- The first function called should almost always be initscr().
- This will determine the terminal type and initialize curses
- data structures. initscr() also arranges that the first call to
- refresh() will clear the screen. If an error occurs a message
- is written to standard error and the program exits. Otherwise
- it returns a pointer to stdscr. A few functions may be called
- before initscr (slk_init(), filter(), ripofflines(), use_env(),
- and, if you are using multiple terminals, newterm().)
-
- endwin()
- Your program should always call endwin() before exiting or
- shelling out of the program. This function will restore tty
- modes, move the cursor to the lower left corner of the screen,
- reset the terminal into the proper non-visual mode. Calling
- refresh() or doupdate() after a temporary escape from the
- program will restore the ncurses screen from before the escape.
-
- newterm(type, ofp, ifp)
- A program which outputs to more than one terminal should use
- newterm() instead of initscr(). newterm() should be called once
- for each terminal. It returns a variable of type SCREEN * which
- should be saved as a reference to that terminal. The arguments
- are the type of the terminal (a string) and FILE pointers for
- the output and input of the terminal. If type is NULL then the
- environment variable $TERM is used. endwin() should called once
- at wrapup time for each terminal opened using this function.
-
- set_term(new)
- This function is used to switch to a different terminal
- previously opened by newterm(). The screen reference for the
- new terminal is passed as the parameter. The previous terminal
- is returned by the function. All other calls affect only the
- current terminal.
-
- delscreen(sp)
- The inverse of newterm(); deallocates the data structures
- associated with a given SCREEN reference.
-
- Causing Output to the Terminal
-
- refresh() and wrefresh(win)
- These functions must be called to actually get any output on
- the terminal, as other routines merely manipulate data
- structures. wrefresh() copies the named window to the physical
- terminal screen, taking into account what is already there in
- order to do optimizations. refresh() does a refresh of
- stdscr(). Unless leaveok() has been enabled, the physical
- cursor of the terminal is left at the location of the window's
- cursor.
-
- doupdate() and wnoutrefresh(win)
- These two functions allow multiple updates with more efficiency
- than wrefresh. To use them, it is important to understand how
- curses works. In addition to all the window structures, curses
- keeps two data structures representing the terminal screen: a
- physical screen, describing what is actually on the screen, and
- a virtual screen, describing what the programmer wants to have
- on the screen. wrefresh works by first copying the named window
- to the virtual screen (wnoutrefresh()), and then calling the
- routine to update the screen (doupdate()). If the programmer
- wishes to output several windows at once, a series of calls to
- wrefresh will result in alternating calls to wnoutrefresh() and
- doupdate(), causing several bursts of output to the screen. By
- calling wnoutrefresh() for each window, it is then possible to
- call doupdate() once, resulting in only one burst of output,
- with fewer total characters transmitted (this also avoids a
- visually annoying flicker at each update).
-
- Low-Level Capability Access
-
- setupterm(term, filenum, errret)
- This routine is called to initialize a terminal's description,
- without setting up the curses screen structures or changing the
- tty-driver mode bits. term is the character string representing
- the name of the terminal being used. filenum is the UNIX file
- descriptor of the terminal to be used for output. errret is a
- pointer to an integer, in which a success or failure indication
- is returned. The values returned can be 1 (all is well), 0 (no
- such terminal), or -1 (some problem locating the terminfo
- database).
-
- The value of term can be given as NULL, which will cause the
- value of TERM in the environment to be used. The errret pointer
- can also be given as NULL, meaning no error code is wanted. If
- errret is defaulted, and something goes wrong, setupterm() will
- print an appropriate error message and exit, rather than
- returning. Thus, a simple program can call setupterm(0, 1, 0)
- and not worry about initialization errors.
-
- After the call to setupterm(), the global variable cur_term is
- set to point to the current structure of terminal capabilities.
- By calling setupterm() for each terminal, and saving and
- restoring cur_term, it is possible for a program to use two or
- more terminals at once. Setupterm() also stores the names
- section of the terminal description in the global character
- array ttytype[]. Subsequent calls to setupterm() will overwrite
- this array, so you'll have to save it yourself if need be.
-
- Debugging
-
- NOTE: These functions are not part of the standard curses API!
-
- trace()
- This function can be used to explicitly set a trace level. If
- the trace level is nonzero, execution of your program will
- generate a file called `trace' in the current working directory
- containing a report on the library's actions. Higher trace
- levels enable more detailed (and verbose) reporting -- see
- comments attached to TRACE_ defines in the curses.h file for
- details. (It is also possible to set a trace level by assigning
- a trace level value to the environment variable NCURSES_TRACE).
-
- _tracef()
- This function can be used to output your own debugging
- information. It is only available only if you link with
- -lncurses_g. It can be used the same way as printf(), only it
- outputs a newline after the end of arguments. The output goes
- to a file called trace in the current directory.
-
- Trace logs can be difficult to interpret due to the sheer volume of
- data dumped in them. There is a script called tracemunch included with
- the ncurses distribution that can alleviate this problem somewhat; it
- compacts long sequences of similar operations into more succinct
- single-line pseudo-operations. These pseudo-ops can be distinguished
- by the fact that they are named in capital letters.
-
-Hints, Tips, and Tricks
-
- The ncurses manual pages are a complete reference for this library. In
- the remainder of this document, we discuss various useful methods that
- may not be obvious from the manual page descriptions.
-
- Some Notes of Caution
-
- If you find yourself thinking you need to use noraw() or nocbreak(),
- think again and move carefully. It's probably better design to use
- getstr() or one of its relatives to simulate cooked mode. The noraw()
- and nocbreak() functions try to restore cooked mode, but they may end
- up clobbering some control bits set before you started your
- application. Also, they have always been poorly documented, and are
- likely to hurt your application's usability with other curses
- libraries.
-
- Bear in mind that refresh() is a synonym for wrefresh(stdscr). Don't
- try to mix use of stdscr with use of windows declared by newwin(); a
- refresh() call will blow them off the screen. The right way to handle
- this is to use subwin(), or not touch stdscr at all and tile your
- screen with declared windows which you then wnoutrefresh() somewhere
- in your program event loop, with a single doupdate() call to trigger
- actual repainting.
-
- You are much less likely to run into problems if you design your
- screen layouts to use tiled rather than overlapping windows.
- Historically, curses support for overlapping windows has been weak,
- fragile, and poorly documented. The ncurses library is not yet an
- exception to this rule.
-
- There is a panels library included in the ncurses distribution that
- does a pretty good job of strengthening the overlapping-windows
- facilities.
-
- Try to avoid using the global variables LINES and COLS. Use getmaxyx()
- on the stdscr context instead. Reason: your code may be ported to run
- in an environment with window resizes, in which case several screens
- could be open with different sizes.
-
- Temporarily Leaving NCURSES Mode
-
- Sometimes you will want to write a program that spends most of its
- time in screen mode, but occasionally returns to ordinary `cooked'
- mode. A common reason for this is to support shell-out. This behavior
- is simple to arrange in ncurses.
-
- To leave ncurses mode, call endwin() as you would if you were
- intending to terminate the program. This will take the screen back to
- cooked mode; you can do your shell-out. When you want to return to
- ncurses mode, simply call refresh() or doupdate(). This will repaint
- the screen.
-
- There is a boolean function, isendwin(), which code can use to test
- whether ncurses screen mode is active. It returns TRUE in the interval
- between an endwin() call and the following refresh(), FALSE otherwise.
-
- Here is some sample code for shellout:
- addstr("Shelling out...");
- def_prog_mode(); /* save current tty modes */
- endwin(); /* restore original tty modes */
- system("sh"); /* run shell */
- addstr("returned.\n"); /* prepare return message */
- refresh(); /* restore save modes, repaint screen */
-
- Using NCURSES under XTERM
-
- A resize operation in X sends SIGWINCH to the application running
- under xterm. The ncurses library provides an experimental signal
- handler, but in general does not catch this signal, because it cannot
- know how you want the screen re-painted. You will usually have to
- write the SIGWINCH handler yourself. Ncurses can give you some help.
-
- The easiest way to code your SIGWINCH handler is to have it do an
- endwin, followed by an refresh and a screen repaint you code yourself.
- The refresh will pick up the new screen size from the xterm's
- environment.
-
- That is the standard way, of course (it even works with some vendor's
- curses implementations). Its drawback is that it clears the screen to
- reinitialize the display, and does not resize subwindows which must be
- shrunk. Ncurses provides an extension which works better, the
- resizeterm function. That function ensures that all windows are
- limited to the new screen dimensions, and pads stdscr with blanks if
- the screen is larger.
-
- Finally, ncurses can be configured to provide its own SIGWINCH
- handler, based on resizeterm.
-
- Handling Multiple Terminal Screens
-
- The initscr() function actually calls a function named newterm() to do
- most of its work. If you are writing a program that opens multiple
- terminals, use newterm() directly.
-
- For each call, you will have to specify a terminal type and a pair of
- file pointers; each call will return a screen reference, and stdscr
- will be set to the last one allocated. You will switch between screens
- with the set_term call. Note that you will also have to call
- def_shell_mode and def_prog_mode on each tty yourself.
-
- Testing for Terminal Capabilities
-
- Sometimes you may want to write programs that test for the presence of
- various capabilities before deciding whether to go into ncurses mode.
- An easy way to do this is to call setupterm(), then use the functions
- tigetflag(), tigetnum(), and tigetstr() to do your testing.
-
- A particularly useful case of this often comes up when you want to
- test whether a given terminal type should be treated as `smart'
- (cursor-addressable) or `stupid'. The right way to test this is to see
- if the return value of tigetstr("cup") is non-NULL. Alternatively, you
- can include the term.h file and test the value of the macro
- cursor_address.
-
- Tuning for Speed
-
- Use the addchstr() family of functions for fast screen-painting of
- text when you know the text doesn't contain any control characters.
- Try to make attribute changes infrequent on your screens. Don't use
- the immedok() option!
-
- Special Features of NCURSES
-
- The wresize() function allows you to resize a window in place. The
- associated resizeterm() function simplifies the construction of
- SIGWINCH handlers, for resizing all windows.
-
- The define_key() function allows you to define at runtime function-key
- control sequences which are not in the terminal description. The
- keyok() function allows you to temporarily enable or disable
- interpretation of any function-key control sequence.
-
- The use_default_colors() function allows you to construct applications
- which can use the terminal's default foreground and background colors
- as an additional "default" color. Several terminal emulators support
- this feature, which is based on ISO 6429.
-
- Ncurses supports up 16 colors, unlike SVr4 curses which defines only
- 8. While most terminals which provide color allow only 8 colors, about
- a quarter (including XFree86 xterm) support 16 colors.
-
-Compatibility with Older Versions
-
- Despite our best efforts, there are some differences between ncurses
- and the (undocumented!) behavior of older curses implementations.
- These arise from ambiguities or omissions in the documentation of the
- API.
-
- Refresh of Overlapping Windows
-
- If you define two windows A and B that overlap, and then alternately
- scribble on and refresh them, the changes made to the overlapping
- region under historic curses versions were often not documented
- precisely.
-
- To understand why this is a problem, remember that screen updates are
- calculated between two representations of the entire display. The
- documentation says that when you refresh a window, it is first copied
- to to the virtual screen, and then changes are calculated to update
- the physical screen (and applied to the terminal). But "copied to" is
- not very specific, and subtle differences in how copying works can
- produce different behaviors in the case where two overlapping windows
- are each being refreshed at unpredictable intervals.
-
- What happens to the overlapping region depends on what wnoutrefresh()
- does with its argument -- what portions of the argument window it
- copies to the virtual screen. Some implementations do "change copy",
- copying down only locations in the window that have changed (or been
- marked changed with wtouchln() and friends). Some implementations do
- "entire copy", copying all window locations to the virtual screen
- whether or not they have changed.
-
- The ncurses library itself has not always been consistent on this
- score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy.
- Versions 1.8.6 and older, and versions 1.9.9 and newer, do change
- copy.
-
- For most commercial curses implementations, it is not documented and
- not known for sure (at least not to the ncurses maintainers) whether
- they do change copy or entire copy. We know that System V release 3
- curses has logic in it that looks like an attempt to do change copy,
- but the surrounding logic and data representations are sufficiently
- complex, and our knowledge sufficiently indirect, that it's hard to
- know whether this is reliable. It is not clear what the SVr4
- documentation and XSI standard intend. The XSI Curses standard barely
- mentions wnoutrefresh(); the SVr4 documents seem to be describing
- entire-copy, but it is possible with some effort and straining to read
- them the other way.
-
- It might therefore be unwise to rely on either behavior in programs
- that might have to be linked with other curses implementations.
- Instead, you can do an explicit touchwin() before the wnoutrefresh()
- call to guarantee an entire-contents copy anywhere.
-
- The really clean way to handle this is to use the panels library. If,
- when you want a screen update, you do update_panels(), it will do all
- the necessary wnoutrfresh() calls for whatever panel stacking order
- you have defined. Then you can do one doupdate() and there will be a
- single burst of physical I/O that will do all your updates.
-
- Background Erase
-
- If you have been using a very old versions of ncurses (1.8.7 or older)
- you may be surprised by the behavior of the erase functions. In older
- versions, erased areas of a window were filled with a blank modified
- by the window's current attribute (as set by wattrset(), wattron(),
- wattroff() and friends).
-
- In newer versions, this is not so. Instead, the attribute of erased
- blanks is normal unless and until it is modified by the functions
- bkgdset() or wbkgdset().
-
- This change in behavior conforms ncurses to System V Release 4 and the
- XSI Curses standard.
-
-XSI Curses Conformance
-
- The ncurses library is intended to be base-level conformant with the
- XSI Curses standard from X/Open. Many extended-level features (in
- fact, almost all features not directly concerned with wide characters
- and internationalization) are also supported.
-
- One effect of XSI conformance is the change in behavior described
- under "Background Erase -- Compatibility with Old Versions".
-
- Also, ncurses meets the XSI requirement that every macro entry point
- have a corresponding function which may be linked (and will be
- prototype-checked) if the macro definition is disabled with #undef.
-
- The Panels Library
-
- The ncurses library by itself provides good support for screen
- displays in which the windows are tiled (non-overlapping). In the more
- general case that windows may overlap, you have to use a series of
- wnoutrefresh() calls followed by a doupdate(), and be careful about
- the order you do the window refreshes in. It has to be bottom-upwards,
- otherwise parts of windows that should be obscured will show through.
-
- When your interface design is such that windows may dive deeper into
- the visibility stack or pop to the top at runtime, the resulting
- book-keeping can be tedious and difficult to get right. Hence the
- panels library.
-
- The panel library first appeared in AT&T System V. The version
- documented here is the panel code distributed with ncurses.
-
-Compiling With the Panels Library
-
- Your panels-using modules must import the panels library declarations
- with
- #include <panel.h>
-
- and must be linked explicitly with the panels library using an -lpanel
- argument. Note that they must also link the ncurses library with
- -lncurses. Many linkers are two-pass and will accept either order, but
- it is still good practice to put -lpanel first and -lncurses second.
-
-Overview of Panels
-
- A panel object is a window that is implicitly treated as part of a
- deck including all other panel objects. The deck has an implicit
- bottom-to-top visibility order. The panels library includes an update
- function (analogous to refresh()) that displays all panels in the deck
- in the proper order to resolve overlaps. The standard window, stdscr,
- is considered below all panels.
-
- Details on the panels functions are available in the man pages. We'll
- just hit the highlights here.
-
- You create a panel from a window by calling new_panel() on a window
- pointer. It then becomes the top of the deck. The panel's window is
- available as the value of panel_window() called with the panel pointer
- as argument.
-
- You can delete a panel (removing it from the deck) with del_panel.
- This will not deallocate the associated window; you have to do that
- yourself. You can replace a panel's window with a different window by
- calling replace_window. The new window may be of different size; the
- panel code will re-compute all overlaps. This operation doesn't change
- the panel's position in the deck.
-
- To move a panel's window, use move_panel(). The mvwin() function on
- the panel's window isn't sufficient because it doesn't update the
- panels library's representation of where the windows are. This
- operation leaves the panel's depth, contents, and size unchanged.
-
- Two functions (top_panel(), bottom_panel()) are provided for
- rearranging the deck. The first pops its argument window to the top of
- the deck; the second sends it to the bottom. Either operation leaves
- the panel's screen location, contents, and size unchanged.
-
- The function update_panels() does all the wnoutrefresh() calls needed
- to prepare for doupdate() (which you must call yourself, afterwards).
-
- Typically, you will want to call update_panels() and doupdate() just
- before accepting command input, once in each cycle of interaction with
- the user. If you call update_panels() after each and every panel
- write, you'll generate a lot of unnecessary refresh activity and
- screen flicker.
-
-Panels, Input, and the Standard Screen
-
- You shouldn't mix wnoutrefresh() or wrefresh() operations with panels
- code; this will work only if the argument window is either in the top
- panel or unobscured by any other panels.
-
- The stsdcr window is a special case. It is considered below all
- panels. Because changes to panels may obscure parts of stdscr, though,
- you should call update_panels() before doupdate() even when you only
- change stdscr.
-
- Note that wgetch automatically calls wrefresh. Therefore, before
- requesting input from a panel window, you need to be sure that the
- panel is totally unobscured.
-
- There is presently no way to display changes to one obscured panel
- without repainting all panels.
-
-Hiding Panels
-
- It's possible to remove a panel from the deck temporarily; use
- hide_panel for this. Use show_panel() to render it visible again. The
- predicate function panel_hidden tests whether or not a panel is
- hidden.
-
- The panel_update code ignores hidden panels. You cannot do top_panel()
- or bottom_panel on a hidden panel(). Other panels operations are
- applicable.
-
-Miscellaneous Other Facilities
-
- It's possible to navigate the deck using the functions panel_above()
- and panel_below. Handed a panel pointer, they return the panel above
- or below that panel. Handed NULL, they return the bottom-most or
- top-most panel.
-
- Every panel has an associated user pointer, not used by the panel
- code, to which you can attach application data. See the man page
- documentation of set_panel_userptr() and panel_userptr for details.
-
- The Menu Library
-
- A menu is a screen display that assists the user to choose some subset
- of a given set of items. The menu library is a curses extension that
- supports easy programming of menu hierarchies with a uniform but
- flexible interface.
-
- The menu library first appeared in AT&T System V. The version
- documented here is the menu code distributed with ncurses.
-
-Compiling With the menu Library
-
- Your menu-using modules must import the menu library declarations with
- #include <menu.h>
-
- and must be linked explicitly with the menus library using an -lmenu
- argument. Note that they must also link the ncurses library with
- -lncurses. Many linkers are two-pass and will accept either order, but
- it is still good practice to put -lmenu first and -lncurses second.
-
-Overview of Menus
-
- The menus created by this library consist of collections of items
- including a name string part and a description string part. To make
- menus, you create groups of these items and connect them with menu
- frame objects.
-
- The menu can then by posted, that is written to an associated window.
- Actually, each menu has two associated windows; a containing window in
- which the programmer can scribble titles or borders, and a subwindow
- in which the menu items proper are displayed. If this subwindow is too
- small to display all the items, it will be a scrollable viewport on
- the collection of items.
-
- A menu may also be unposted (that is, undisplayed), and finally freed
- to make the storage associated with it and its items available for
- re-use.
-
- The general flow of control of a menu program looks like this:
- 1. Initialize curses.
- 2. Create the menu items, using new_item().
- 3. Create the menu using new_menu().
- 4. Post the menu using menu_post().
- 5. Refresh the screen.
- 6. Process user requests via an input loop.
- 7. Unpost the menu using menu_unpost().
- 8. Free the menu, using free_menu().
- 9. Free the items using free_item().
- 10. Terminate curses.
-
-Selecting items
-
- Menus may be multi-valued or (the default) single-valued (see the
- manual page menu_opts(3x) to see how to change the default). Both
- types always have a current item.
-
- From a single-valued menu you can read the selected value simply by
- looking at the current item. From a multi-valued menu, you get the
- selected set by looping through the items applying the item_value()
- predicate function. Your menu-processing code can use the function
- set_item_value() to flag the items in the select set.
-
- Menu items can be made unselectable using set_item_opts() or
- item_opts_off() with the O_SELECTABLE argument. This is the only
- option so far defined for menus, but it is good practice to code as
- though other option bits might be on.
-
-Menu Display
-
- The menu library calculates a minimum display size for your window,
- based on the following variables:
-
- * The number and maximum length of the menu items
- * Whether the O_ROWMAJOR option is enabled
- * Whether display of descriptions is enabled
- * Whatever menu format may have been set by the programmer
- * The length of the menu mark string used for highlighting selected
- items
-
- The function set_menu_format() allows you to set the maximum size of
- the viewport or menu page that will be used to display menu items. You
- can retrieve any format associated with a menu with menu_format(). The
- default format is rows=16, columns=1.
-
- The actual menu page may be smaller than the format size. This depends
- on the item number and size and whether O_ROWMAJOR is on. This option
- (on by default) causes menu items to be displayed in a `raster-scan'
- pattern, so that if more than one item will fit horizontally the first
- couple of items are side-by-side in the top row. The alternative is
- column-major display, which tries to put the first several items in
- the first column.
-
- As mentioned above, a menu format not large enough to allow all items
- to fit on-screen will result in a menu display that is vertically
- scrollable.
-
- You can scroll it with requests to the menu driver, which will be
- described in the section on menu input handling.
-
- Each menu has a mark string used to visually tag selected items; see
- the menu_mark(3x) manual page for details. The mark string length also
- influences the menu page size.
-
- The function scale_menu() returns the minimum display size that the
- menu code computes from all these factors. There are other menu
- display attributes including a select attribute, an attribute for
- selectable items, an attribute for unselectable items, and a pad
- character used to separate item name text from description text. These
- have reasonable defaults which the library allows you to change (see
- the menu_attribs(3x) manual page.
-
-Menu Windows
-
- Each menu has, as mentioned previously, a pair of associated windows.
- Both these windows are painted when the menu is posted and erased when
- the menu is unposted.
-
- The outer or frame window is not otherwise touched by the menu
- routines. It exists so the programmer can associate a title, a border,
- or perhaps help text with the menu and have it properly refreshed or
- erased at post/unpost time. The inner window or subwindow is where the
- current menu page is displayed.
-
- By default, both windows are stdscr. You can set them with the
- functions in menu_win(3x).
-
- When you call menu_post(), you write the menu to its subwindow. When
- you call menu_unpost(), you erase the subwindow, However, neither of
- these actually modifies the screen. To do that, call wrefresh() or
- some equivalent.
-
-Processing Menu Input
-
- The main loop of your menu-processing code should call menu_driver()
- repeatedly. The first argument of this routine is a menu pointer; the
- second is a menu command code. You should write an input-fetching
- routine that maps input characters to menu command codes, and pass its
- output to menu_driver(). The menu command codes are fully documented
- in menu_driver(3x).
-
- The simplest group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM,
- REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_UP_ITEM, REQ_DOWN_ITEM,
- REQ_LEFT_ITEM, REQ_RIGHT_ITEM. These change the currently selected
- item. These requests may cause scrolling of the menu page if it only
- partially displayed.
-
- There are explicit requests for scrolling which also change the
- current item (because the select location does not change, but the
- item there does). These are REQ_SCR_DLINE, REQ_SCR_ULINE,
- REQ_SCR_DPAGE, and REQ_SCR_UPAGE.
-
- The REQ_TOGGLE_ITEM selects or deselects the current item. It is for
- use in multi-valued menus; if you use it with O_ONEVALUE on, you'll
- get an error return (E_REQUEST_DENIED).
-
- Each menu has an associated pattern buffer. The menu_driver() logic
- tries to accumulate printable ASCII characters passed in in that
- buffer; when it matches a prefix of an item name, that item (or the
- next matching item) is selected. If appending a character yields no
- new match, that character is deleted from the pattern buffer, and
- menu_driver() returns E_NO_MATCH.
-
- Some requests change the pattern buffer directly: REQ_CLEAR_PATTERN,
- REQ_BACK_PATTERN, REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter two are
- useful when pattern buffer input matches more than one item in a
- multi-valued menu.
-
- Each successful scroll or item navigation request clears the pattern
- buffer. It is also possible to set the pattern buffer explicitly with
- set_menu_pattern().
-
- Finally, menu driver requests above the constant MAX_COMMAND are
- considered application-specific commands. The menu_driver() code
- ignores them and returns E_UNKNOWN_COMMAND.
-
-Miscellaneous Other Features
-
- Various menu options can affect the processing and visual appearance
- and input processing of menus. See menu_opts(3x) for details.
-
- It is possible to change the current item from application code; this
- is useful if you want to write your own navigation requests. It is
- also possible to explicitly set the top row of the menu display. See
- mitem_current(3x). If your application needs to change the menu
- subwindow cursor for any reason, pos_menu_cursor() will restore it to
- the correct location for continuing menu driver processing.
-
- It is possible to set hooks to be called at menu initialization and
- wrapup time, and whenever the selected item changes. See
- menu_hook(3x).
-
- Each item, and each menu, has an associated user pointer on which you
- can hang application data. See mitem_userptr(3x) and menu_userptr(3x).
-
- The Forms Library
-
- The form library is a curses extension that supports easy programming
- of on-screen forms for data entry and program control.
-
- The form library first appeared in AT&T System V. The version
- documented here is the form code distributed with ncurses.
-
-Compiling With the form Library
-
- Your form-using modules must import the form library declarations with
- #include <form.h>
-
- and must be linked explicitly with the forms library using an -lform
- argument. Note that they must also link the ncurses library with
- -lncurses. Many linkers are two-pass and will accept either order, but
- it is still good practice to put -lform first and -lncurses second.
-
-Overview of Forms
-
- A form is a collection of fields; each field may be either a label
- (explanatory text) or a data-entry location. Long forms may be
- segmented into pages; each entry to a new page clears the screen.
-
- To make forms, you create groups of fields and connect them with form
- frame objects; the form library makes this relatively simple.
-
- Once defined, a form can be posted, that is written to an associated
- window. Actually, each form has two associated windows; a containing
- window in which the programmer can scribble titles or borders, and a
- subwindow in which the form fields proper are displayed.
-
- As the form user fills out the posted form, navigation and editing
- keys support movement between fields, editing keys support modifying
- field, and plain text adds to or changes data in a current field. The
- form library allows you (the forms designer) to bind each navigation
- and editing key to any keystroke accepted by curses Fields may have
- validation conditions on them, so that they check input data for type
- and value. The form library supplies a rich set of pre-defined field
- types, and makes it relatively easy to define new ones.
-
- Once its transaction is completed (or aborted), a form may be unposted
- (that is, undisplayed), and finally freed to make the storage
- associated with it and its items available for re-use.
-
- The general flow of control of a form program looks like this:
- 1. Initialize curses.
- 2. Create the form fields, using new_field().
- 3. Create the form using new_form().
- 4. Post the form using form_post().
- 5. Refresh the screen.
- 6. Process user requests via an input loop.
- 7. Unpost the form using form_unpost().
- 8. Free the form, using free_form().
- 9. Free the fields using free_field().
- 10. Terminate curses.
-
- Note that this looks much like a menu program; the form library
- handles tasks which are in many ways similar, and its interface was
- obviously designed to resemble that of the menu library wherever
- possible.
-
- In forms programs, however, the `process user requests' is somewhat
- more complicated than for menus. Besides menu-like navigation
- operations, the menu driver loop has to support field editing and data
- validation.
-
-Creating and Freeing Fields and Forms
-
- The basic function for creating fields is new_field():
-
-FIELD *new_field(int height, int width, /* new field size */
- int top, int left, /* upper left corner */
- int offscreen, /* number of offscreen rows */
- int nbuf); /* number of working buffers */
-
- Menu items always occupy a single row, but forms fields may have
- multiple rows. So new_field() requires you to specify a width and
- height (the first two arguments, which mist both be greater than
- zero).
-
- You must also specify the location of the field's upper left corner on
- the screen (the third and fourth arguments, which must be zero or
- greater). Note that these coordinates are relative to the form
- subwindow, which will coincide with stdscr by default but need not be
- stdscr if you've done an explicit set_form_window() call.
-
- The fifth argument allows you to specify a number of off-screen rows.
- If this is zero, the entire field will always be displayed. If it is
- nonzero, the form will be scrollable, with only one screen-full
- (initially the top part) displayed at any given time. If you make a
- field dynamic and grow it so it will no longer fit on the screen, the
- form will become scrollable even if the offscreen argument was
- initially zero.
-
- The forms library allocates one working buffer per field; the size of
- each buffer is ((height + offscreen)*width + 1, one character for each
- position in the field plus a NUL terminator. The sixth argument is the
- number of additional data buffers to allocate for the field; your
- application can use them for its own purposes.
-
-FIELD *dup_field(FIELD *field, /* field to copy */
- int top, int left); /* location of new copy */
-
- The function dup_field() duplicates an existing field at a new
- location. Size and buffering information are copied; some attribute
- flags and status bits are not (see the form_field_new(3X) for
- details).
-
-FIELD *link_field(FIELD *field, /* field to copy */
- int top, int left); /* location of new copy */
-
- The function link_field() also duplicates an existing field at a new
- location. The difference from dup_field() is that it arranges for the
- new field's buffer to be shared with the old one.
-
- Besides the obvious use in making a field editable from two different
- form pages, linked fields give you a way to hack in dynamic labels. If
- you declare several fields linked to an original, and then make them
- inactive, changes from the original will still be propagated to the
- linked fields.
-
- As with duplicated fields, linked fields have attribute bits separate
- from the original.
-
- As you might guess, all these field-allocations return NULL if the
- field allocation is not possible due to an out-of-memory error or
- out-of-bounds arguments.
-
- To connect fields to a form, use
-
-FORM *new_form(FIELD **fields);
-
- This function expects to see a NULL-terminated array of field
- pointers. Said fields are connected to a newly-allocated form object;
- its address is returned (or else NULL if the allocation fails).
-
- Note that new_field() does not copy the pointer array into private
- storage; if you modify the contents of the pointer array during forms
- processing, all manner of bizarre things might happen. Also note that
- any given field may only be connected to one form.
-
- The functions free_field() and free_form are available to free field
- and form objects. It is an error to attempt to free a field connected
- to a form, but not vice-versa; thus, you will generally free your form
- objects first.
-
-Fetching and Changing Field Attributes
-
- Each form field has a number of location and size attributes
- associated with it. There are other field attributes used to control
- display and editing of the field. Some (for example, the O_STATIC bit)
- involve sufficient complications to be covered in sections of their
- own later on. We cover the functions used to get and set several basic
- attributes here.
-
- When a field is created, the attributes not specified by the new_field
- function are copied from an invisible system default field. In
- attribute-setting and -fetching functions, the argument NULL is taken
- to mean this field. Changes to it persist as defaults until your forms
- application terminates.
-
- Fetching Size and Location Data
-
- You can retrieve field sizes and locations through:
-
-int field_info(FIELD *field, /* field from which to fetch */
- int *height, *int width, /* field size */
- int *top, int *left, /* upper left corner */
- int *offscreen, /* number of offscreen rows */
- int *nbuf); /* number of working buffers */
-
- This function is a sort of inverse of new_field(); instead of setting
- size and location attributes of a new field, it fetches them from an
- existing one.
-
- Changing the Field Location
-
- It is possible to move a field's location on the screen:
-
-int move_field(FIELD *field, /* field to alter */
- int top, int left); /* new upper-left corner */
-
- You can, of course. query the current location through field_info().
-
- The Justification Attribute
-
- One-line fields may be unjustified, justified right, justified left,
- or centered. Here is how you manipulate this attribute:
-
-int set_field_just(FIELD *field, /* field to alter */
- int justmode); /* mode to set */
-
-int field_just(FIELD *field); /* fetch mode of field */
-
- The mode values accepted and returned by this functions are
- preprocessor macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or
- JUSTIFY_CENTER.
-
- Field Display Attributes
-
- For each field, you can set a foreground attribute for entered
- characters, a background attribute for the entire field, and a pad
- character for the unfilled portion of the field. You can also control
- pagination of the form.
-
- This group of four field attributes controls the visual appearance of
- the field on the screen, without affecting in any way the data in the
- field buffer.
-
-int set_field_fore(FIELD *field, /* field to alter */
- chtype attr); /* attribute to set */
-
-chtype field_fore(FIELD *field); /* field to query */
-
-int set_field_back(FIELD *field, /* field to alter */
- chtype attr); /* attribute to set */
-
-chtype field_back(FIELD *field); /* field to query */
-
-int set_field_pad(FIELD *field, /* field to alter */
- int pad); /* pad character to set */
-
-chtype field_pad(FIELD *field);
-
-int set_new_page(FIELD *field, /* field to alter */
- int flag); /* TRUE to force new page */
-
-chtype new_page(FIELD *field); /* field to query */
-
- The attributes set and returned by the first four functions are normal
- curses(3x) display attribute values (A_STANDOUT, A_BOLD, A_REVERSE
- etc). The page bit of a field controls whether it is displayed at the
- start of a new form screen.
-
- Field Option Bits
-
- There is also a large collection of field option bits you can set to
- control various aspects of forms processing. You can manipulate them
- with these functions:
-int set_field_opts(FIELD *field, /* field to alter */
- int attr); /* attribute to set */
-
-int field_opts_on(FIELD *field, /* field to alter */
- int attr); /* attributes to turn on */
-
-int field_opts_off(FIELD *field, /* field to alter */
- int attr); /* attributes to turn off */
-
-int field_opts(FIELD *field); /* field to query */
-
- By default, all options are on. Here are the available option bits:
-
- O_VISIBLE
- Controls whether the field is visible on the screen. Can be
- used during form processing to hide or pop up fields depending
- on the value of parent fields.
-
- O_ACTIVE
- Controls whether the field is active during forms processing
- (i.e. visited by form navigation keys). Can be used to make
- labels or derived fields with buffer values alterable by the
- forms application, not the user.
-
- O_PUBLIC
- Controls whether data is displayed during field entry. If this
- option is turned off on a field, the library will accept and
- edit data in that field, but it will not be displayed and the
- visible field cursor will not move. You can turn off the
- O_PUBLIC bit to define password fields.
-
- O_EDIT
- Controls whether the field's data can be modified. When this
- option is off, all editing requests except REQ_PREV_CHOICE and
- REQ_NEXT_CHOICE will fail. Such read-only fields may be useful
- for help messages.
-
- O_WRAP
- Controls word-wrapping in multi-line fields. Normally, when any
- character of a (blank-separated) word reaches the end of the
- current line, the entire word is wrapped to the next line
- (assuming there is one). When this option is off, the word will
- be split across the line break.
-
- O_BLANK
- Controls field blanking. When this option is on, entering a
- character at the first field position erases the entire field
- (except for the just-entered character).
-
- O_AUTOSKIP
- Controls automatic skip to next field when this one fills.
- Normally, when the forms user tries to type more data into a
- field than will fit, the editing location jumps to next field.
- When this option is off, the user's cursor will hang at the end
- of the field. This option is ignored in dynamic fields that
- have not reached their size limit.
-
- O_NULLOK
- Controls whether validation is applied to blank fields.
- Normally, it is not; the user can leave a field blank without
- invoking the usual validation check on exit. If this option is
- off on a field, exit from it will invoke a validation check.
-
- O_PASSOK
- Controls whether validation occurs on every exit, or only after
- the field is modified. Normally the latter is true. Setting
- O_PASSOK may be useful if your field's validation function may
- change during forms processing.
-
- O_STATIC
- Controls whether the field is fixed to its initial dimensions.
- If you turn this off, the field becomes dynamic and will
- stretch to fit entered data.
-
- A field's options cannot be changed while the field is currently
- selected. However, options may be changed on posted fields that are
- not current.
-
- The option values are bit-masks and can be composed with logical-or in
- the obvious way.
-
-Field Status
-
- Every field has a status flag, which is set to FALSE when the field is
- created and TRUE when the value in field buffer 0 changes. This flag
- can be queried and set directly:
-
-int set_field_status(FIELD *field, /* field to alter */
- int status); /* mode to set */
-
-int field_status(FIELD *field); /* fetch mode of field */
-
- Setting this flag under program control can be useful if you use the
- same form repeatedly, looking for modified fields each time.
-
- Calling field_status() on a field not currently selected for input
- will return a correct value. Calling field_status() on a field that is
- currently selected for input may not necessarily give a correct field
- status value, because entered data isn't necessarily copied to buffer
- zero before the exit validation check. To guarantee that the returned
- status value reflects reality, call field_status() either (1) in the
- field's exit validation check routine, (2) from the field's or form's
- initialization or termination hooks, or (3) just after a
- REQ_VALIDATION request has been processed by the forms driver.
-
-Field User Pointer
-
- Each field structure contains one character pointer slot that is not
- used by the forms library. It is intended to be used by applications
- to store private per-field data. You can manipulate it with:
-int set_field_userptr(FIELD *field, /* field to alter */
- char *userptr); /* mode to set */
-
-char *field_userptr(FIELD *field); /* fetch mode of field */
-
- (Properly, this user pointer field ought to have (void *) type. The
- (char *) type is retained for System V compatibility.)
-
- It is valid to set the user pointer of the default field (with a
- set_field_userptr() call passed a NULL field pointer.) When a new
- field is created, the default-field user pointer is copied to
- initialize the new field's user pointer.
-
-Variable-Sized Fields
-
- Normally, a field is fixed at the size specified for it at creation
- time. If, however, you turn off its O_STATIC bit, it becomes dynamic
- and will automatically resize itself to accommodate data as it is
- entered. If the field has extra buffers associated with it, they will
- grow right along with the main input buffer.
-
- A one-line dynamic field will have a fixed height (1) but variable
- width, scrolling horizontally to display data within the field area as
- originally dimensioned and located. A multi-line dynamic field will
- have a fixed width, but variable height (number of rows), scrolling
- vertically to display data within the field area as originally
- dimensioned and located.
-
- Normally, a dynamic field is allowed to grow without limit. But it is
- possible to set an upper limit on the size of a dynamic field. You do
- it with this function:
-
-int set_max_field(FIELD *field, /* field to alter (may not be NULL) */
- int max_size); /* upper limit on field size */
-
- If the field is one-line, max_size is taken to be a column size limit;
- if it is multi-line, it is taken to be a line size limit. To disable
- any limit, use an argument of zero. The growth limit can be changed
- whether or not the O_STATIC bit is on, but has no effect until it is.
-
- The following properties of a field change when it becomes dynamic:
- * If there is no growth limit, there is no final position of the
- field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored.
- * Field justification will be ignored (though whatever justification
- is set up will be retained internally and can be queried).
- * The dup_field() and link_field() calls copy dynamic-buffer sizes.
- If the O_STATIC option is set on one of a collection of links,
- buffer resizing will occur only when the field is edited through
- that link.
- * The call field_info() will retrieve the original static size of
- the field; use dynamic_field_info() to get the actual dynamic
- size.
-
-Field Validation
-
- By default, a field will accept any data that will fit in its input
- buffer. However, it is possible to attach a validation type to a
- field. If you do this, any attempt to leave the field while it
- contains data that doesn't match the validation type will fail. Some
- validation types also have a character-validity check for each time a
- character is entered in the field.
-
- A field's validation check (if any) is not called when
- set_field_buffer() modifies the input buffer, nor when that buffer is
- changed through a linked field.
-
- The form library provides a rich set of pre-defined validation types,
- and gives you the capability to define custom ones of your own. You
- can examine and change field validation attributes with the following
- functions:
-
-int set_field_type(FIELD *field, /* field to alter */
- FIELDTYPE *ftype, /* type to associate */
- ...); /* additional arguments*/
-
-FIELDTYPE *field_type(FIELD *field); /* field to query */
-
- The validation type of a field is considered an attribute of the
- field. As with other field attributes, Also, doing set_field_type()
- with a NULL field default will change the system default for
- validation of newly-created fields.
-
- Here are the pre-defined validation types:
-
- TYPE_ALPHA
-
- This field type accepts alphabetic data; no blanks, no digits, no
- special characters (this is checked at character-entry time). It is
- set up with:
-
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_ALPHA, /* type to associate */
- int width); /* maximum width of field */
-
- The width argument sets a minimum width of data. Typically you'll want
- to set this to the field width; if it's greater than the field width,
- the validation check will always fail. A minimum width of zero makes
- field completion optional.
-
- TYPE_ALNUM
-
- This field type accepts alphabetic data and digits; no blanks, no
- special characters (this is checked at character-entry time). It is
- set up with:
-
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_ALNUM, /* type to associate */
- int width); /* maximum width of field */
-
- The width argument sets a minimum width of data. As with TYPE_ALPHA,
- typically you'll want to set this to the field width; if it's greater
- than the field width, the validation check will always fail. A minimum
- width of zero makes field completion optional.
-
- TYPE_ENUM
-
- This type allows you to restrict a field's values to be among a
- specified set of string values (for example, the two-letter postal
- codes for U.S. states). It is set up with:
-
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_ENUM, /* type to associate */
- char **valuelist; /* list of possible values */
- int checkcase; /* case-sensitive? */
- int checkunique); /* must specify uniquely? */
-
- The valuelist parameter must point at a NULL-terminated list of valid
- strings. The checkcase argument, if true, makes comparison with the
- string case-sensitive.
-
- When the user exits a TYPE_ENUM field, the validation procedure tries
- to complete the data in the buffer to a valid entry. If a complete
- choice string has been entered, it is of course valid. But it is also
- possible to enter a prefix of a valid string and have it completed for
- you.
-
- By default, if you enter such a prefix and it matches more than one
- value in the string list, the prefix will be completed to the first
- matching value. But the checkunique argument, if true, requires prefix
- matches to be unique in order to be valid.
-
- The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be
- particularly useful with these fields.
-
- TYPE_INTEGER
-
- This field type accepts an integer. It is set up as follows:
-
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_INTEGER, /* type to associate */
- int padding, /* # places to zero-pad to */
- int vmin, int vmax); /* valid range */
-
- Valid characters consist of an optional leading minus and digits. The
- range check is performed on exit. If the range maximum is less than or
- equal to the minimum, the range is ignored.
-
- If the value passes its range check, it is padded with as many leading
- zero digits as necessary to meet the padding argument.
-
- A TYPE_INTEGER value buffer can conveniently be interpreted with the C
- library function atoi(3).
-
- TYPE_NUMERIC
-
- This field type accepts a decimal number. It is set up as follows:
-
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_NUMERIC, /* type to associate */
- int padding, /* # places of precision */
- double vmin, double vmax); /* valid range */
-
- Valid characters consist of an optional leading minus and digits.
- possibly including a decimal point. If your system supports locale's,
- the decimal point character used must be the one defined by your
- locale. The range check is performed on exit. If the range maximum is
- less than or equal to the minimum, the range is ignored.
-
- If the value passes its range check, it is padded with as many
- trailing zero digits as necessary to meet the padding argument.
-
- A TYPE_NUMERIC value buffer can conveniently be interpreted with the C
- library function atof(3).
-
- TYPE_REGEXP
-
- This field type accepts data matching a regular expression. It is set
- up as follows:
-
-int set_field_type(FIELD *field, /* field to alter */
- TYPE_REGEXP, /* type to associate */
- char *regexp); /* expression to match */
-
- The syntax for regular expressions is that of regcomp(3). The check
- for regular-expression match is performed on exit.
-
-Direct Field Buffer Manipulation
-
- The chief attribute of a field is its buffer contents. When a form has
- been completed, your application usually needs to know the state of
- each field buffer. You can find this out with:
-
-char *field_buffer(FIELD *field, /* field to query */
- int bufindex); /* number of buffer to query */
-
- Normally, the state of the zero-numbered buffer for each field is set
- by the user's editing actions on that field. It's sometimes useful to
- be able to set the value of the zero-numbered (or some other) buffer
- from your application:
-int set_field_buffer(FIELD *field, /* field to alter */
- int bufindex, /* number of buffer to alter */
- char *value); /* string value to set */
-
- If the field is not large enough and cannot be resized to a
- sufficiently large size to contain the specified value, the value will
- be truncated to fit.
-
- Calling field_buffer() with a null field pointer will raise an error.
- Calling field_buffer() on a field not currently selected for input
- will return a correct value. Calling field_buffer() on a field that is
- currently selected for input may not necessarily give a correct field
- buffer value, because entered data isn't necessarily copied to buffer
- zero before the exit validation check. To guarantee that the returned
- buffer value reflects on-screen reality, call field_buffer() either
- (1) in the field's exit validation check routine, (2) from the field's
- or form's initialization or termination hooks, or (3) just after a
- REQ_VALIDATION request has been processed by the forms driver.
-
-Attributes of Forms
-
- As with field attributes, form attributes inherit a default from a
- system default form structure. These defaults can be queried or set by
- of these functions using a form-pointer argument of NULL.
-
- The principal attribute of a form is its field list. You can query and
- change this list with:
-
-int set_form_fields(FORM *form, /* form to alter */
- FIELD **fields); /* fields to connect */
-
-char *form_fields(FORM *form); /* fetch fields of form */
-
-int field_count(FORM *form); /* count connect fields */
-
- The second argument of set_form_fields() may be a NULL-terminated
- field pointer array like the one required by new_form(). In that case,
- the old fields of the form are disconnected but not freed (and
- eligible to be connected to other forms), then the new fields are
- connected.
-
- It may also be null, in which case the old fields are disconnected
- (and not freed) but no new ones are connected.
-
- The field_count() function simply counts the number of fields
- connected to a given from. It returns -1 if the form-pointer argument
- is NULL.
-
-Control of Form Display
-
- In the overview section, you saw that to display a form you normally
- start by defining its size (and fields), posting it, and refreshing
- the screen. There is an hidden step before posting, which is the
- association of the form with a frame window (actually, a pair of
- windows) within which it will be displayed. By default, the forms
- library associates every form with the full-screen window stdscr.
-
- By making this step explicit, you can associate a form with a declared
- frame window on your screen display. This can be useful if you want to
- adapt the form display to different screen sizes, dynamically tile
- forms on the screen, or use a form as part of an interface layout
- managed by panels.
-
- The two windows associated with each form have the same functions as
- their analogues in the menu library. Both these windows are painted
- when the form is posted and erased when the form is unposted.
-
- The outer or frame window is not otherwise touched by the form
- routines. It exists so the programmer can associate a title, a border,
- or perhaps help text with the form and have it properly refreshed or
- erased at post/unpost time. The inner window or subwindow is where the
- current form page is actually displayed.
-
- In order to declare your own frame window for a form, you'll need to
- know the size of the form's bounding rectangle. You can get this
- information with:
-
-int scale_form(FORM *form, /* form to query */
- int *rows, /* form rows */
- int *cols); /* form cols */
-
- The form dimensions are passed back in the locations pointed to by the
- arguments. Once you have this information, you can use it to declare
- of windows, then use one of these functions:
-int set_form_win(FORM *form, /* form to alter */
- WINDOW *win); /* frame window to connect */
-
-WINDOW *form_win(FORM *form); /* fetch frame window of form */
-
-int set_form_sub(FORM *form, /* form to alter */
- WINDOW *win); /* form subwindow to connect */
-
-WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */
-
- Note that curses operations, including refresh(), on the form, should
- be done on the frame window, not the form subwindow.
-
- It is possible to check from your application whether all of a
- scrollable field is actually displayed within the menu subwindow. Use
- these functions:
-
-int data_ahead(FORM *form); /* form to be queried */
-
-int data_behind(FORM *form); /* form to be queried */
-
- The function data_ahead() returns TRUE if (a) the current field is
- one-line and has undisplayed data off to the right, (b) the current
- field is multi-line and there is data off-screen below it.
-
- The function data_behind() returns TRUE if the first (upper left hand)
- character position is off-screen (not being displayed).
-
- Finally, there is a function to restore the form window's cursor to
- the value expected by the forms driver:
-
-int pos_form_cursor(FORM *) /* form to be queried */
-
- If your application changes the form window cursor, call this function
- before handing control back to the forms driver in order to
- re-synchronize it.
-
-Input Processing in the Forms Driver
-
- The function form_driver() handles virtualized input requests for form
- navigation, editing, and validation requests, just as menu_driver does
- for menus (see the section on menu input handling).
-
-int form_driver(FORM *form, /* form to pass input to */
- int request); /* form request code */
-
- Your input virtualization function needs to take input and then
- convert it to either an alphanumeric character (which is treated as
- data to be entered in the currently-selected field), or a forms
- processing request.
-
- The forms driver provides hooks (through input-validation and
- field-termination functions) with which your application code can
- check that the input taken by the driver matched what was expected.
-
- Page Navigation Requests
-
- These requests cause page-level moves through the form, triggering
- display of a new form screen.
-
- REQ_NEXT_PAGE
- Move to the next form page.
-
- REQ_PREV_PAGE
- Move to the previous form page.
-
- REQ_FIRST_PAGE
- Move to the first form page.
-
- REQ_LAST_PAGE
- Move to the last form page.
-
- These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from
- the last page goes to the first, and REQ_PREV_PAGE from the first page
- goes to the last.
-
- Inter-Field Navigation Requests
-
- These requests handle navigation between fields on the same page.
-
- REQ_NEXT_FIELD
- Move to next field.
-
- REQ_PREV_FIELD
- Move to previous field.
-
- REQ_FIRST_FIELD
- Move to the first field.
-
- REQ_LAST_FIELD
- Move to the last field.
-
- REQ_SNEXT_FIELD
- Move to sorted next field.
-
- REQ_SPREV_FIELD
- Move to sorted previous field.
-
- REQ_SFIRST_FIELD
- Move to the sorted first field.
-
- REQ_SLAST_FIELD
- Move to the sorted last field.
-
- REQ_LEFT_FIELD
- Move left to field.
-
- REQ_RIGHT_FIELD
- Move right to field.
-
- REQ_UP_FIELD
- Move up to field.
-
- REQ_DOWN_FIELD
- Move down to field.
-
- These requests treat the list of fields on a page as cyclic; that is,
- REQ_NEXT_FIELD from the last field goes to the first, and
- REQ_PREV_FIELD from the first field goes to the last. The order of the
- fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests)
- is simply the order of the field pointers in the form array (as set up
- by new_form() or set_form_fields()
-
- It is also possible to traverse the fields as if they had been sorted
- in screen-position order, so the sequence goes left-to-right and
- top-to-bottom. To do this, use the second group of four
- sorted-movement requests.
-
- Finally, it is possible to move between fields using visual directions
- up, down, right, and left. To accomplish this, use the third group of
- four requests. Note, however, that the position of a form for purposes
- of these requests is its upper-left corner.
-
- For example, suppose you have a multi-line field B, and two
- single-line fields A and C on the same line with B, with A to the left
- of B and C to the right of B. A REQ_MOVE_RIGHT from A will go to B
- only if A, B, and C all share the same first line; otherwise it will
- skip over B to C.
-
- Intra-Field Navigation Requests
-
- These requests drive movement of the edit cursor within the currently
- selected field.
-
- REQ_NEXT_CHAR
- Move to next character.
-
- REQ_PREV_CHAR
- Move to previous character.
-
- REQ_NEXT_LINE
- Move to next line.
-
- REQ_PREV_LINE
- Move to previous line.
-
- REQ_NEXT_WORD
- Move to next word.
-
- REQ_PREV_WORD
- Move to previous word.
-
- REQ_BEG_FIELD
- Move to beginning of field.
-
- REQ_END_FIELD
- Move to end of field.
-
- REQ_BEG_LINE
- Move to beginning of line.
-
- REQ_END_LINE
- Move to end of line.
-
- REQ_LEFT_CHAR
- Move left in field.
-
- REQ_RIGHT_CHAR
- Move right in field.
-
- REQ_UP_CHAR
- Move up in field.
-
- REQ_DOWN_CHAR
- Move down in field.
-
- Each word is separated from the previous and next characters by
- whitespace. The commands to move to beginning and end of line or field
- look for the first or last non-pad character in their ranges.
-
- Scrolling Requests
-
- Fields that are dynamic and have grown and fields explicitly created
- with offscreen rows are scrollable. One-line fields scroll
- horizontally; multi-line fields scroll vertically. Most scrolling is
- triggered by editing and intra-field movement (the library scrolls the
- field to keep the cursor visible). It is possible to explicitly
- request scrolling with the following requests:
-
- REQ_SCR_FLINE
- Scroll vertically forward a line.
-
- REQ_SCR_BLINE
- Scroll vertically backward a line.
-
- REQ_SCR_FPAGE
- Scroll vertically forward a page.
-
- REQ_SCR_BPAGE
- Scroll vertically backward a page.
-
- REQ_SCR_FHPAGE
- Scroll vertically forward half a page.
-
- REQ_SCR_BHPAGE
- Scroll vertically backward half a page.
-
- REQ_SCR_FCHAR
- Scroll horizontally forward a character.
-
- REQ_SCR_BCHAR
- Scroll horizontally backward a character.
-
- REQ_SCR_HFLINE
- Scroll horizontally one field width forward.
-
- REQ_SCR_HBLINE
- Scroll horizontally one field width backward.
-
- REQ_SCR_HFHALF
- Scroll horizontally one half field width forward.
-
- REQ_SCR_HBHALF
- Scroll horizontally one half field width backward.
-
- For scrolling purposes, a page of a field is the height of its visible
- part.
-
- Editing Requests
-
- When you pass the forms driver an ASCII character, it is treated as a
- request to add the character to the field's data buffer. Whether this
- is an insertion or a replacement depends on the field's edit mode
- (insertion is the default.
-
- The following requests support editing the field and changing the edit
- mode:
-
- REQ_INS_MODE
- Set insertion mode.
-
- REQ_OVL_MODE
- Set overlay mode.
-
- REQ_NEW_LINE
- New line request (see below for explanation).
-
- REQ_INS_CHAR
- Insert space at character location.
-
- REQ_INS_LINE
- Insert blank line at character location.
-
- REQ_DEL_CHAR
- Delete character at cursor.
-
- REQ_DEL_PREV
- Delete previous word at cursor.
-
- REQ_DEL_LINE
- Delete line at cursor.
-
- REQ_DEL_WORD
- Delete word at cursor.
-
- REQ_CLR_EOL
- Clear to end of line.
-
- REQ_CLR_EOF
- Clear to end of field.
-
- REQ_CLEAR_FIELD
- Clear entire field.
-
- The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is
- complicated and partly controlled by a pair of forms options. The
- special cases are triggered when the cursor is at the beginning of a
- field, or on the last line of the field.
-
- First, we consider REQ_NEW_LINE:
-
- The normal behavior of REQ_NEW_LINE in insert mode is to break the
- current line at the position of the edit cursor, inserting the portion
- of the current line after the cursor as a new line following the
- current and moving the cursor to the beginning of that new line (you
- may think of this as inserting a newline in the field buffer).
-
- The normal behavior of REQ_NEW_LINE in overlay mode is to clear the
- current line from the position of the edit cursor to end of line. The
- cursor is then moved to the beginning of the next line.
-
- However, REQ_NEW_LINE at the beginning of a field, or on the last line
- of a field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is
- off, this special action is disabled.
-
- Now, let us consider REQ_DEL_PREV:
-
- The normal behavior of REQ_DEL_PREV is to delete the previous
- character. If insert mode is on, and the cursor is at the start of a
- line, and the text on that line will fit on the previous one, it
- instead appends the contents of the current line to the previous one
- and deletes the current line (you may think of this as deleting a
- newline from the field buffer).
-
- However, REQ_DEL_PREV at the beginning of a field is instead treated
- as a REQ_PREV_FIELD.
-
- If the O_BS_OVERLOAD option is off, this special action is disabled
- and the forms driver just returns E_REQUEST_DENIED.
-
- See Form Options for discussion of how to set and clear the overload
- options.
-
- Order Requests
-
- If the type of your field is ordered, and has associated functions for
- getting the next and previous values of the type from a given value,
- there are requests that can fetch that value into the field buffer:
-
- REQ_NEXT_CHOICE
- Place the successor value of the current value in the buffer.
-
- REQ_PREV_CHOICE
- Place the predecessor value of the current value in the buffer.
-
- Of the built-in field types, only TYPE_ENUM has built-in successor and
- predecessor functions. When you define a field type of your own (see
- Custom Validation Types), you can associate our own ordering
- functions.
-
- Application Commands
-
- Form requests are represented as integers above the curses value
- greater than KEY_MAX and less than or equal to the constant
- MAX_COMMAND. If your input-virtualization routine returns a value
- above MAX_COMMAND, the forms driver will ignore it.
-
-Field Change Hooks
-
- It is possible to set function hooks to be executed whenever the
- current field or form changes. Here are the functions that support
- this:
-
-typedef void (*HOOK)(); /* pointer to function returning void */
-
-int set_form_init(FORM *form, /* form to alter */
- HOOK hook); /* initialization hook */
-
-HOOK form_init(FORM *form); /* form to query */
-
-int set_form_term(FORM *form, /* form to alter */
- HOOK hook); /* termination hook */
-
-HOOK form_term(FORM *form); /* form to query */
-
-int set_field_init(FORM *form, /* form to alter */
- HOOK hook); /* initialization hook */
-
-HOOK field_init(FORM *form); /* form to query */
-
-int set_field_term(FORM *form, /* form to alter */
- HOOK hook); /* termination hook */
-
-HOOK field_term(FORM *form); /* form to query */
-
- These functions allow you to either set or query four different hooks.
- In each of the set functions, the second argument should be the
- address of a hook function. These functions differ only in the timing
- of the hook call.
-
- form_init
- This hook is called when the form is posted; also, just after
- each page change operation.
-
- field_init
- This hook is called when the form is posted; also, just after
- each field change
-
- field_term
- This hook is called just after field validation; that is, just
- before the field is altered. It is also called when the form is
- unposted.
-
- form_term
- This hook is called when the form is unposted; also, just
- before each page change operation.
-
- Calls to these hooks may be triggered
- 1. When user editing requests are processed by the forms driver
- 2. When the current page is changed by set_current_field() call
- 3. When the current field is changed by a set_form_page() call
-
- See Field Change Commands for discussion of the latter two cases.
-
- You can set a default hook for all fields by passing one of the set
- functions a NULL first argument.
-
- You can disable any of these hooks by (re)setting them to NULL, the
- default value.
-
-Field Change Commands
-
- Normally, navigation through the form will be driven by the user's
- input requests. But sometimes it is useful to be able to move the
- focus for editing and viewing under control of your application, or
- ask which field it currently is in. The following functions help you
- accomplish this:
-
-int set_current_field(FORM *form, /* form to alter */
- FIELD *field); /* field to shift to */
-
-FIELD *current_field(FORM *form); /* form to query */
-
-int field_index(FORM *form, /* form to query */
- FIELD *field); /* field to get index of */
-
- The function field_index() returns the index of the given field in the
- given form's field array (the array passed to new_form() or
- set_form_fields()).
-
- The initial current field of a form is the first active field on the
- first page. The function set_form_fields() resets this.
-
- It is also possible to move around by pages.
-
-int set_form_page(FORM *form, /* form to alter */
- int page); /* page to go to (0-origin) */
-
-int form_page(FORM *form); /* return form's current page */
-
- The initial page of a newly-created form is 0. The function
- set_form_fields() resets this.
-
-Form Options
-
- Like fields, forms may have control option bits. They can be changed
- or queried with these functions:
-
-int set_form_opts(FORM *form, /* form to alter */
- int attr); /* attribute to set */
-
-int form_opts_on(FORM *form, /* form to alter */
- int attr); /* attributes to turn on */
-
-int form_opts_off(FORM *form, /* form to alter */
- int attr); /* attributes to turn off */
-
-int form_opts(FORM *form); /* form to query */
-
- By default, all options are on. Here are the available option bits:
-
- O_NL_OVERLOAD
- Enable overloading of REQ_NEW_LINE as described in Editing
- Requests. The value of this option is ignored on dynamic fields
- that have not reached their size limit; these have no last
- line, so the circumstances for triggering a REQ_NEXT_FIELD
- never arise.
-
- O_BS_OVERLOAD
- Enable overloading of REQ_DEL_PREV as described in Editing
- Requests.
-
- The option values are bit-masks and can be composed with logical-or in
- the obvious way.
-
-Custom Validation Types
-
- The form library gives you the capability to define custom validation
- types of your own. Further, the optional additional arguments of
- set_field_type effectively allow you to parameterize validation types.
- Most of the complications in the validation-type interface have to do
- with the handling of the additional arguments within custom validation
- functions.
-
- Union Types
-
- The simplest way to create a custom data type is to compose it from
- two preexisting ones:
-
-FIELD *link_fieldtype(FIELDTYPE *type1,
- FIELDTYPE *type2);
-
- This function creates a field type that will accept any of the values
- legal for either of its argument field types (which may be either
- predefined or programmer-defined). If a set_field_type() call later
- requires arguments, the new composite type expects all arguments for
- the first type, than all arguments for the second. Order functions
- (see Order Requests) associated with the component types will work on
- the composite; what it does is check the validation function for the
- first type, then for the second, to figure what type the buffer
- contents should be treated as.
-
- New Field Types
-
- To create a field type from scratch, you need to specify one or both
- of the following things:
-
- * A character-validation function, to check each character as it is
- entered.
- * A field-validation function to be applied on exit from the field.
-
- Here's how you do that:
-
-typedef int (*HOOK)(); /* pointer to function returning int */
-
-FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */
- HOOK c_validate) /* character validator */
-
-
-int free_fieldtype(FIELDTYPE *ftype); /* type to free */
-
- At least one of the arguments of new_fieldtype() must be non-NULL. The
- forms driver will automatically call the new type's validation
- functions at appropriate points in processing a field of the new type.
-
- The function free_fieldtype() deallocates the argument fieldtype,
- freeing all storage associated with it.
-
- Normally, a field validator is called when the user attempts to leave
- the field. Its first argument is a field pointer, from which it can
- get to field buffer 0 and test it. If the function returns TRUE, the
- operation succeeds; if it returns FALSE, the edit cursor stays in the
- field.
-
- A character validator gets the character passed in as a first
- argument. It too should return TRUE if the character is valid, FALSE
- otherwise.
-
- Validation Function Arguments
-
- Your field- and character- validation functions will be passed a
- second argument as well. This second argument is the address of a
- structure (which we'll call a pile) built from any of the
- field-type-specific arguments passed to set_field_type(). If no such
- arguments are defined for the field type, this pile pointer argument
- will be NULL.
-
- In order to arrange for such arguments to be passed to your validation
- functions, you must associate a small set of storage-management
- functions with the type. The forms driver will use these to synthesize
- a pile from the trailing arguments of each set_field_type() argument,
- and a pointer to the pile will be passed to the validation functions.
-
- Here is how you make the association:
-
-typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */
-typedef void (*VOIDHOOK)(); /* pointer to function returning void */
-
-int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
- PTRHOOK make_str, /* make structure from args */
- PTRHOOK copy_str, /* make copy of structure */
- VOIDHOOK free_str); /* free structure storage */
-
- Here is how the storage-management hooks are used:
-
- make_str
- This function is called by set_field_type(). It gets one
- argument, a va_list of the type-specific arguments passed to
- set_field_type(). It is expected to return a pile pointer to a
- data structure that encapsulates those arguments.
-
- copy_str
- This function is called by form library functions that allocate
- new field instances. It is expected to take a pile pointer,
- copy the pile to allocated storage, and return the address of
- the pile copy.
-
- free_str
- This function is called by field- and type-deallocation
- routines in the library. It takes a pile pointer argument, and
- is expected to free the storage of that pile.
-
- The make_str and copy_str functions may return NULL to signal
- allocation failure. The library routines will that call them will
- return error indication when this happens. Thus, your validation
- functions should never see a NULL file pointer and need not check
- specially for it.
-
- Order Functions For Custom Types
-
- Some custom field types are simply ordered in the same well-defined
- way that TYPE_ENUM is. For such types, it is possible to define
- successor and predecessor functions to support the REQ_NEXT_CHOICE and
- REQ_PREV_CHOICE requests. Here's how:
-
-typedef int (*INTHOOK)(); /* pointer to function returning int */
-
-int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */
- INTHOOK succ, /* get successor value */
- INTHOOK pred); /* get predecessor value */
-
- The successor and predecessor arguments will each be passed two
- arguments; a field pointer, and a pile pointer (as for the validation
- functions). They are expected to use the function field_buffer() to
- read the current value, and set_field_buffer() on buffer 0 to set the
- next or previous value. Either hook may return TRUE to indicate
- success (a legal next or previous value was set) or FALSE to indicate
- failure.
-
- Avoiding Problems
-
- The interface for defining custom types is complicated and tricky.
- Rather than attempting to create a custom type entirely from scratch,
- you should start by studying the library source code for whichever of
- the pre-defined types seems to be closest to what you want.
-
- Use that code as a model, and evolve it towards what you really want.
- You will avoid many problems and annoyances that way. The code in the
- ncurses library has been specifically exempted from the package
- copyright to support this.
-
- If your custom type defines order functions, have do something
- intuitive with a blank field. A useful convention is to make the
- successor of a blank field the types minimum value, and its
- predecessor the maximum.
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