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.\" $Id: curs_get_wch.3x,v 1.43 2024/06/08 20:25:25 tom Exp $
.TH curs_get_wch 3X 2024-06-08 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
.ie \n(.g \{\
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.SH NAME
\fB\%get_wch\fP,
\fB\%wget_wch\fP,
\fB\%mvget_wch\fP,
\fB\%mvwget_wch\fP,
\fB\%unget_wch\fP \-
get (or push back) a wide character from \fIcurses\fR terminal keyboard
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fBint get_wch(wint_t *\fIwch\fP);
\fBint wget_wch(WINDOW *\fIwin\fP, wint_t *\fIwch\fP);
\fBint mvget_wch(int \fIy\fP, int \fIx\fP, wint_t *\fIwch\fP);
\fBint mvwget_wch(WINDOW *\fIwin\fP, int \fIy\fP, int \fIx\fP, wint_t *\fIwch\fP);
.PP
\fBint unget_wch(const wchar_t \fIwc\fP);
.fi
.SH DESCRIPTION
.SS "Reading Characters"
.B \%wget_wch
gathers a key event from the terminal keyboard associated with a
.I curses
window
.IR win ","
returning
.B OK
if a wide character is read,
.B \%KEY_CODE_YES
if a function key is read,
and
.B ERR
if no key event is available.
\fB\%ncurses\fP(3X) describes the variants of this function.
.PP
When input is pending,
.B \%wget_wch
stores an integer
identifying the key event in
.IR wch ";"
for alphanumeric and punctuation keys,
this value corresponds to the character encoding used by the terminal.
Use of the control key as a modifier,
by holding it down while pressing and releasing another key,
often results in a distinct code.
The behavior of other keys depends on whether
.I win
is in keypad mode;
see subsections \*(``Keypad Mode\*('' and \*(``Predefined Key Codes\*(''
in \fB\%getch\fP(3X).
.PP
If no input is pending,
then if the no-delay flag is set in the window
(see \fB\%nodelay\fP(3X)),
the function returns
.BR ERR ";"
otherwise,
.I curses
waits until the terminal has input.
If \fB\%cbreak\fP(3X)
has been called,
this happens after one character is read.
If \fB\%nocbreak\fP(3X) or \fB\%noraw\fP(3X)
has been called,
it occurs when the next newline is read.
(Because the terminal's normal or \*(``cooked\*('' mode
is line-buffered,
multiple
.B \%wget_wch
calls may then be necessary to empty the input queue.)
If \fB\%halfdelay\fP(3X)
has been called,
.I curses
waits until input is available or the specified delay elapses.
.PP
If \fB\%echo\fP(3X) has been called,
and the window is not a pad,
.I curses
writes the wide character
from the input queue
to the window
(at the cursor position)
per the following rules.
.bP
If the wide character
matches the terminal's erase character
(see \fB\%erasewchar\fP(3X)),
the cursor moves leftward one position
and the new position is erased
as if \fB\%wmove\fP(3X) and then \fB\%wdelch\fP(3X) were called.
When the window's keypad mode is enabled
(see below),
.B \%KEY_LEFT
and
.B \%KEY_BACKSPACE
are handled the same way.
.bP
.I curses
writes any other
wide character
to the window,
as with \fB\%wecho_wchar\fP(3X).
.bP
If the window
.I win
has been moved or modified since the last call to
\fB\%wrefresh\fP(3X),
.I curses
calls
.B \%wrefresh
on it.
.PP
If the wide character
is a carriage return and \fBnl\fP(3X) has been called,
.B \%wgetch
stores the the wide character code for line feed in
.I wch
instead.
.SS "Ungetting Characters"
.B \%unget_wch
places
.I wc
into the input queue to be retrieved by the next call to
.BR \%wget_wch "."
A single input queue serves all windows associated with the terminal.
.SH RETURN VALUE
.B \%wget_wch
returns
.B OK
when it reads a wide character and
.B \%KEY_CODE_YES
when it reads a function key code.
It returns
.B ERR
if
.bP
the
.I \%WINDOW
pointer is
.BR NULL ","
or
.bP
its timeout expires without any data arriving,
or
.bP
execution was interrupted by a signal,
in which case
.B \%errno
is set to
.BR \%EINTR "."
.PP
Functions prefixed with \*(``mv\*('' first perform cursor movement and
fail if the position
.RI ( y ,
.IR x ")"
is outside the window boundaries.
.PP
.B \%unget_wch
returns
.B OK
on success and
.B ERR
if there is no more room in the input queue.
.SH NOTES
See the \*(``NOTES\*('' section of \fB\%wgetch\fP(3X).
.PP
All of these functions except
.B \%wget_wch
and
.B \%unget_wch
may be implemented as macros.
.PP
Unlike \fB\%wgetch\fP(3X),
.B \%wget_wch
and its variants store the value of the input character in an additional
.I wch
parameter instead of the return value.
.PP
Unlike
.BR \%ungetch ","
.B \%unget_wch
cannot distinguish function key codes from conventional character codes.
An application can overcome this limitation by pushing function key
codes with
.B \%ungetch
and subsequently checking the return value of
.B \%wget_wch
for a match with
.BR \%KEY_CODE_YES "."
.SH EXTENSIONS
See the \*(``EXTENSIONS\*('' section of \fB\%wgetch\fP(3X).
.SH PORTABILITY
Applications employing
.I \%ncurses
extensions should condition their use on the visibility of the
.B \%NCURSES_VERSION
preprocessor macro.
.PP
X/Open Curses,
Issue 4 describes these functions.
It specifies no error conditions for them.
.PP
See the \*(``PORTABILITY\*('' section of \fB\%wgetch\fP(3X) regarding
the interaction of
.B \%wget_wch
with signal handlers.
.SH SEE ALSO
\fB\%curs_getch\fP(3X) describes comparable functions of the
.I \%ncurses
library in its non-wide-character configuration.
.PP
\fB\%curses\fP(3X),
\fB\%curs_add_wch\fP(3X),
\fB\%curs_inopts\fP(3X),
\fB\%curs_move\fP(3X),
\fB\%curs_refresh\fP(3X)