NAME
cbreak, nocbreak, echo, noecho, halfdelay, intrflush, keypad, meta, nodelay, notimeout, raw, noraw, noqiflush, qiflush, timeout, wtimeout, typeahead - curses input options
SYNOPSIS
#include <curses.h>
int
cbreak(void);
int nocbreak(void);
int echo(void);
int noecho(void);
int halfdelay(int tenths);
int intrflush(WINDOW *win, bool bf);
int keypad(WINDOW *win, bool bf);
int meta(WINDOW *win, bool bf);
int nodelay(WINDOW *win, bool bf);
int raw(void);
int noraw(void);
void noqiflush(void);
void qiflush(void);
int notimeout(WINDOW *win, bool bf);
void timeout(int delay);
void wtimeout(WINDOW *win, int delay);
int typeahead(int fd);
DESCRIPTION
The ncurses library provides several functions which let an application change the way input from the terminal is handled. Some are global, applying to all windows. Others apply only to a specific window. Window-specific settings are not automatically applied to new or derived windows. An application must apply these to each window, if the same behavior is needed.
cbreak
Normally, the tty driver buffers typed characters until a
newline or carriage return is typed. The cbreak
routine disables line buffering and erase/kill
character-processing (interrupt and flow control characters
are unaffected), making characters typed by the user
immediately available to the program. The nocbreak
routine returns the terminal to normal (cooked) mode.
Initially the terminal may or may not be in cbreak mode, as the mode is inherited; therefore, a program should call cbreak or nocbreak explicitly. Most interactive programs using curses set the cbreak mode. Note that cbreak overrides raw. [See getch(3NCURSES) for a discussion of how these routines interact with echo and noecho.]
echo/noecho
The echo and noecho routines control whether
characters typed by the user are echoed by getch(3X)
as they are typed. Echoing by the tty driver is always
disabled, but initially getch is in echo mode, so
characters typed are echoed. Authors of most interactive
programs prefer to do their own echoing in a controlled area
of the screen, or not to echo at all, so they disable
echoing by calling noecho. [See
getch(3NCURSES) for a discussion of how these
routines interact with cbreak and
nocbreak.]
halfdelay
The halfdelay routine is used for half-delay mode,
which is similar to cbreak mode in that characters
typed by the user are immediately available to the program.
However, after blocking for tenths tenths of seconds,
ERR is returned if nothing has been typed. The value
of tenths must be a number between 1 and 255. Use
nocbreak to leave half-delay mode.
intrflush
If the intrflush option is enabled (bf is
TRUE), and an interrupt key is pressed on the
keyboard (interrupt, break, quit), all output in the tty
driver queue will be flushed, giving the effect of faster
response to the interrupt, but causing curses to have
the wrong idea of what is on the screen. Disabling the
option (bf is FALSE) prevents the flush. The
default for the option is inherited from the tty driver
settings. The window argument is ignored.
keypad
The keypad option enables the keypad of the
user’s terminal. If enabled (bf is
TRUE), the user can press a function key (such as an
arrow key) and wgetch(3X) returns a single value
representing the function key, as in KEY_LEFT. If
disabled (bf is FALSE), curses does not
treat function keys specially and the program has to
interpret the escape sequences itself. If the keypad in the
terminal can be turned on (made to transmit) and off (made
to work locally), turning on this option causes the terminal
keypad to be turned on when wgetch(3X) is called. The
default value for keypad is FALSE.
meta
Initially, whether the terminal returns 7 or 8 significant
bits on input depends on the control mode of the tty driver
[see termios(3)]. To force 8 bits to be returned,
invoke meta(win, TRUE); this is
equivalent, under POSIX, to setting the CS8 flag on the
terminal. To force 7 bits to be returned, invoke
meta(win, FALSE); this is equivalent,
under POSIX, to setting the CS7 flag on the terminal. The
window argument, win, is always ignored. If the
terminfo capabilities smm (meta_on) and rmm
(meta_off) are defined for the terminal, smm is sent
to the terminal when meta(win, TRUE) is
called and rmm is sent when meta(win,
FALSE) is called.
nodelay
The nodelay option causes getch to be a
non-blocking call. If no input is ready, getch
returns ERR. If disabled (bf is FALSE),
getch waits until a key is pressed.
While interpreting an input escape sequence, wgetch(3X) sets a timer while waiting for the next character. If notimeout(win, TRUE) is called, then wgetch does not set a timer. The purpose of the timeout is to differentiate between sequences received from a function key and those typed by a user.
raw/noraw
The raw and noraw routines place the terminal
into or out of raw mode. Raw mode is similar to
cbreak mode, in that characters typed are immediately
passed through to the user program. The differences are that
in raw mode, the interrupt, quit, suspend, and flow control
characters are all passed through uninterpreted, instead of
generating a signal. The behavior of the BREAK key depends
on other bits in the tty driver that are not set by
curses.
noqiflush
When the noqiflush routine is used, normal flush of
input and output queues associated with the INTR,
QUIT and SUSP characters will not be done [see
termios(3)]. When qiflush is called, the
queues will be flushed when these control characters are
read. You may want to call noqiflush in a signal
handler if you want output to continue as though the
interrupt had not occurred, after the handler exits.
timeout/wtimeout
The timeout and wtimeout routines set blocking
or non-blocking read for a given window. If delay is
negative, blocking read is used (i.e., waits indefinitely
for input). If delay is zero, then non-blocking read
is used (i.e., read returns ERR if no input is
waiting). If delay is positive, then read blocks for
delay milliseconds, and returns ERR if there
is still no input. Hence, these routines provide the same
functionality as nodelay, plus the additional
capability of being able to block for only delay
milliseconds (where delay is positive).
typeahead
The curses library does “line-breakout
optimization” by looking for typeahead periodically
while updating the screen. If input is found, and it is
coming from a tty, the current update is postponed until
refresh(3X) or doupdate is called again. This
allows faster response to commands typed in advance.
Normally, the input FILE pointer passed to newterm,
or stdin in the case that initscr was used,
will be used to do this typeahead checking. The
typeahead routine specifies that the file descriptor
fd is to be used to check for typeahead instead. If
fd is -1, then no typeahead checking is done.
RETURN VALUE
All routines that return an integer return ERR upon failure and OK (SVr4 specifies only “an integer value other than ERR”) upon successful completion, unless otherwise noted in the preceding routine descriptions.
X/Open does not define any error conditions. In this implementation, functions with a window parameter will return an error if it is null. Any function will also return an error if the terminal was not initialized. Also,
halfdelay
returns an error if its parameter is outside the range 1..255.
PORTABILITY
These functions are described in the XSI Curses standard, Issue 4.
The ncurses library obeys the XPG4 standard and the historical practice of the AT&T curses implementations, in that the echo bit is cleared when curses initializes the terminal state. BSD curses differed from this slightly; it left the echo bit on at initialization, but the BSD raw call turned it off as a side-effect. For best portability, set echo or noecho explicitly just after initialization, even if your program remains in cooked mode.
When keypad is first enabled, ncurses loads the key-definitions for the current terminal description. If the terminal description includes extended string capabilities, e.g., from using the -x option of tic, then ncurses also defines keys for the capabilities whose names begin with “k”. The corresponding keycodes are generated and (depending on previous loads of terminal descriptions) may differ from one execution of a program to the next. The generated keycodes are recognized by the keyname function (which will then return a name beginning with “k” denoting the terminfo capability name rather than “K”, used for curses key-names). On the other hand, an application can use define_key to establish a specific keycode for a given string. This makes it possible for an application to check for an extended capability’s presence with tigetstr, and reassign the keycode to match its own needs.
Low-level applications can use tigetstr to obtain the definition of any particular string capability. Higher-level applications which use the curses wgetch and similar functions to return keycodes rely upon the order in which the strings are loaded. If more than one key definition has the same string value, then wgetch can return only one keycode. Most curses implementations (including ncurses) load key definitions in the order defined by the array of string capability names. The last key to be loaded determines the keycode which will be returned. In ncurses, you may also have extended capabilities interpreted as key definitions. These are loaded after the predefined keys, and if a capability’s value is the same as a previously-loaded key definition, the later definition is the one used.
NOTES
Note that echo, noecho, halfdelay, intrflush, meta, nodelay, notimeout, noqiflush, qiflush, timeout, and wtimeout may be macros.
The noraw and nocbreak calls follow historical practice in that they attempt to restore to normal (“cooked”) mode from raw and cbreak modes respectively. Mixing raw/noraw and cbreak/nocbreak calls leads to tty driver control states that are hard to predict or understand; it is not recommended.
SEE ALSO
ncurses(3NCURSES), getch(3NCURSES), initscr(3NCURSES), util(3NCURSES), define_key(3NCURSES), termios(3)