'\" t
.\" $OpenBSD: curs_inopts.3,v 1.9 2023/10/17 09:52:08 nicm Exp $
.\"
.\"***************************************************************************
.\" Copyright 2018-2022,2023 Thomas E. Dickey                                *
.\" Copyright 1998-2016,2017 Free Software Foundation, Inc.                  *
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.\" $Id: curs_inopts.3,v 1.9 2023/10/17 09:52:08 nicm Exp $
.TH curs_inopts 3 2023-08-19 "ncurses 6.4" "Library calls"
.ie \n(.g .ds `` \(lq
.el       .ds `` ``
.ie \n(.g .ds '' \(rq
.el       .ds '' ''
.na
.hy 0
.SH NAME
\fBcbreak\fP,
\fBecho\fP,
\fBhalfdelay\fP,
\fBintrflush\fP,
\fBis_cbreak\fP,
\fBis_echo\fP,
\fBis_nl\fP,
\fBis_raw\fP,
\fBkeypad\fP,
\fBmeta\fP,
\fBnl\fP,
\fBnocbreak\fP,
\fBnodelay\fP,
\fBnoecho\fP,
\fBnonl\fP,
\fBnoqiflush\fP,
\fBnoraw\fP,
\fBnotimeout\fP,
\fBqiflush\fP,
\fBraw\fP,
\fBtimeout\fP,
\fBwtimeout\fP,
\fBtypeahead\fP \- \fBcurses\fP input options
.ad
.hy
.SH SYNOPSIS
\fB#include <curses.h>\fP
.PP
\fBint cbreak(void);\fP
.br
\fBint nocbreak(void);\fP
.sp
\fBint echo(void);\fP
.br
\fBint noecho(void);\fP
.sp
\fBint intrflush(WINDOW *\fIwin\fB, bool \fIbf\fB);\fR
.br
\fBint keypad(WINDOW *\fIwin\fB, bool \fIbf\fB);\fR
.br
\fBint meta(WINDOW *\fIwin\fB, bool \fIbf\fB);\fR
.br
\fBint nodelay(WINDOW *\fIwin\fB, bool \fIbf\fB);\fR
.br
\fBint notimeout(WINDOW *\fIwin\fB, bool \fIbf\fB);\fR
.sp
\fBint nl(void);\fP
.br
\fBint nonl(void);\fP
.sp
\fBint raw(void);\fP
.br
\fBint noraw(void);\fP
.sp
\fBvoid qiflush(void);\fP
.br
\fBvoid noqiflush(void);\fP
.sp
\fBint halfdelay(int \fItenths\fB);\fR
.br
\fBvoid timeout(int \fIdelay\fB);\fR
.br
\fBvoid wtimeout(WINDOW *\fIwin\fB, int \fIdelay\fB);\fR
.sp
\fBint typeahead(int \fIfd\fB);\fR
.sp
/* extensions */
.br
\fBint is_cbreak(void);\fP
.br
\fBint is_echo(void);\fP
.br
\fBint is_nl(void);\fP
.br
\fBint is_raw(void);\fP
.br
.SH DESCRIPTION
The \fBncurses\fP 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.
.\"
.SS cbreak/nocbreak
Normally, the tty driver buffers typed characters until a newline or carriage
return is typed.
The \fBcbreak\fP 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 \fBnocbreak\fP routine returns the terminal to normal (cooked)
mode.
.PP
Initially the terminal may or may not be in \fBcbreak\fP mode, as the mode is
inherited; therefore, a program should call \fBcbreak\fP or \fBnocbreak\fP
explicitly.
Most interactive programs using \fBcurses\fP set the \fBcbreak\fP
mode.
Note that \fBcbreak\fP overrides \fBraw\fP.
[See \fBcurs_getch\fP(3) for a
discussion of how these routines interact with \fBecho\fP and \fBnoecho\fP.]
.\"
.SS echo/noecho
The \fBecho\fP and \fBnoecho\fP routines control whether characters typed by
the user are echoed by \fBgetch\fP(3) as they are typed.
Echoing by the tty
driver is always disabled, but initially \fBgetch\fP 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 \fBnoecho\fP.
[See \fBcurs_getch\fP(3) for a
discussion of how these routines interact with \fBcbreak\fP and
\fBnocbreak\fP.]
.\"
.SS halfdelay
The \fBhalfdelay\fP routine is used for half-delay mode, which is similar to
\fBcbreak\fP mode in that characters typed by the user are immediately
available to the program.
However, after blocking for \fItenths\fP tenths of
seconds, \fBERR\fP is returned if nothing has been typed.
The value of \fItenths\fP
must be a number between 1 and 255.
Use \fBnocbreak\fP to leave half-delay
mode.
.\"
.SS intrflush
If the \fBintrflush\fP option is enabled (\fIbf\fP is \fBTRUE\fP), 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 \fBcurses\fP to have the wrong idea of what is on
the screen.
Disabling the option (\fIbf\fP is \fBFALSE\fP) prevents the
flush.
The default for the option is inherited from the tty driver settings.
The window argument is ignored.
.\"
.SS keypad
The \fBkeypad\fP option enables the keypad of the user's terminal.
If
enabled (\fIbf\fP is \fBTRUE\fP), the user can press a function key
(such as an arrow key) and \fBwgetch\fP(3) returns a single value
representing the function key, as in \fBKEY_LEFT\fP.
If disabled
(\fIbf\fP is \fBFALSE\fP), \fBcurses\fP 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 \fBwgetch\fP(3) is
called.
The default value for keypad is \fBFALSE\fP.
.\"
.SS meta
Initially, whether the terminal returns 7 or 8 significant bits on
input depends on the control mode of the tty driver [see \fBtermios\fP(3)].
To force 8 bits to be returned, invoke \fBmeta\fP(\fIwin\fP,
\fBTRUE\fP); this is equivalent, under POSIX, to setting the CS8 flag
on the terminal.
To force 7 bits to be returned, invoke
\fBmeta\fP(\fIwin\fP, \fBFALSE\fP); this is equivalent, under POSIX,
to setting the CS7 flag on the terminal.
The window argument,
\fIwin\fP, is always ignored.
If the terminfo capabilities \fBsmm\fP
(meta_on) and \fBrmm\fP (meta_off) are defined for the terminal,
\fBsmm\fP is sent to the terminal when \fBmeta\fP(\fIwin\fP,
\fBTRUE\fP) is called and \fBrmm\fP is sent when \fBmeta\fP(\fIwin\fP,
\fBFALSE\fP) is called.
.\"
.SS nl/nonl
The \fBnl\fP and \fBnonl\fP routines control whether the underlying display
device translates the return key into newline on input.
.\"
.SS nodelay
The \fBnodelay\fP option causes \fBgetch\fP to be a non-blocking call.
If no input is ready, \fBgetch\fP returns \fBERR\fP.
If disabled
(\fIbf\fP is \fBFALSE\fP), \fBgetch\fP waits until a key is pressed.
.SS notimeout
When interpreting an escape sequence, \fBwgetch\fP(3) sets a timer
while waiting for the next character.
If \fBnotimeout(\fIwin\fR,
\fBTRUE\fP) is called, then \fBwgetch\fP 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.
.\"
.SS raw/noraw
The \fBraw\fP and \fBnoraw\fP routines place the terminal into or out of raw
mode.
Raw mode is similar to \fBcbreak\fP 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
\fBcurses\fP.
.\"
.SS qiflush/noqiflush
When the \fBnoqiflush\fP routine is used, normal flush of input and
output queues associated with the \fBINTR\fP, \fBQUIT\fP and
\fBSUSP\fP characters will not be done [see \fBtermios\fP(3)].
When
\fBqiflush\fP is called, the queues will be flushed when these control
characters are read.
You may want to call \fBnoqiflush\fP in a signal
handler if you want output to continue as though the interrupt
had not occurred, after the handler exits.
.\"
.SS timeout/wtimeout
The \fBtimeout\fP and \fBwtimeout\fP routines set blocking or
non-blocking read for a given window.
If \fIdelay\fP is negative,
blocking read is used (i.e., waits indefinitely for
input).
If \fIdelay\fP is zero, then non-blocking read is used
(i.e., read returns \fBERR\fP if no input is waiting).
If
\fIdelay\fP is positive, then read blocks for \fIdelay\fP
milliseconds, and returns \fBERR\fP if there is still no input.
Hence, these routines provide the same functionality as \fBnodelay\fP,
plus the additional capability of being able to block for only
\fIdelay\fP milliseconds (where \fIdelay\fP is positive).
.\"
.SS typeahead
The \fBcurses\fP 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
\fBrefresh\fP(3) or \fBdoupdate\fP is called again.
This allows faster response to commands typed in advance.
Normally, the input FILE
pointer passed to \fBnewterm\fP, or \fBstdin\fP in the case that
\fBinitscr\fP was used, will be used to do this typeahead checking.
The \fBtypeahead\fP routine specifies that the file descriptor
\fIfd\fP is to be used to check for typeahead instead.
If \fIfd\fP is
\-1, then no typeahead checking is done.
.\"
.SH RETURN VALUE
All routines that return an integer return \fBERR\fP upon failure and \fBOK\fP
(SVr4 specifies only \*(``an integer value other than \fBERR\fP\*('')
upon successful completion,
unless otherwise noted in the preceding routine descriptions.
.PP
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,
.RS 3
.TP 5
\fBhalfdelay\fP
returns an error
if its parameter is outside the range 1..255.
.RE
.SH EXTENSIONS
This implementation provides four functions which may be used to detect
if the corresponding flags were set or reset:
.PP
.TS
l l l.
\fBQuery\fP	\fBSet\fP	\fBReset\fP
_
is_cbreak	cbreak	nocbreak
is_echo	echo	noecho
is_nl	nl	nonl
is_raw	raw	noraw
.TE
.PP
In each case, the function returns
.TP 5
1
if the flag is set,
.TP 5
0
if the flag is reset, or
.TP 5
-1
if the curses library was not initialized.
.PP
These routines are specific to ncurses.
They were not supported on Version 7, BSD or System V implementations.
It is recommended that any code depending on ncurses extensions
be conditioned using NCURSES_VERSION.
.SH PORTABILITY
Except as noted in the section on extensions,
these functions are described in the XSI Curses standard, Issue 4.
.PP
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 \fBraw\fP call turned it
off as a side-effect.
For best portability, set \fBecho \fPor \fBnoecho\fP explicitly
just after initialization, even if your program remains in cooked mode.
.PP
The XSI Curses standard is ambiguous on the question of whether \fBraw\fP
should disable the CRLF translations controlled by \fBnl\fP and \fBnonl\fP.
BSD curses did turn off these translations; AT&T curses (at least as late as
SVr1) did not.
We chose to do so, on the theory that a programmer requesting
raw input wants a clean (ideally 8-bit clean) connection that the operating
system will not alter.
.PP
When \fBkeypad\fP 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 \fB\-x\fP option of \fBtic\fP,
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 \fBkeyname\fP 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 \fBdefine_key\fP 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 \fBtigetstr\fP,
and reassign the keycode to match its own needs.
.PP
Low-level applications can use \fBtigetstr\fP to obtain the definition
of any particular string capability.
Higher-level applications which use the curses \fBwgetch\fP
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 \fBwgetch\fP 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.
.SH NOTES
Note that
\fBecho\fP,
\fBnoecho\fP,
\fBhalfdelay\fP,
\fBintrflush\fP,
\fBmeta\fP,
\fBnl\fP,
\fBnonl\fP,
\fBnodelay\fP,
\fBnotimeout\fP,
\fBnoqiflush\fP,
\fBqiflush\fP,
\fBtimeout\fP, and
\fBwtimeout\fP may be macros.
.PP
The \fBnoraw\fP and \fBnocbreak\fP 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.
.SH SEE ALSO
\fBcurses\fP(3),
\fBcurs_getch\fP(3),
\fBcurs_initscr\fP(3),
\fBcurs_util\fP(3),
\fBdefine_key\fP(3),
\fBtermios\fP(3)