'\" t
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.\" $Id: curs_inch.3x,v 1.54 2024/05/18 20:07:52 tom Exp $
.TH curs_inch 3X 2024-05-18 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
.ie \n(.g \{\
.ds `` \(lq
.ds '' \(rq
.\}
.el \{\
.ie t .ds `` ``
.el   .ds `` ""
.ie t .ds '' ''
.el   .ds '' ""
.\}
.
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.SH NAME
\fB\%inch\fP,
\fB\%winch\fP,
\fB\%mvinch\fP,
\fB\%mvwinch\fP \-
get a \fIcurses\fR character from a window
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fBchtype inch(void);
\fBchtype winch(WINDOW * \fIwin\fP);
\fBchtype mvinch(int \fIy\fP, int \fIx\fP);
\fBchtype mvwinch(WINDOW * \fIwin\fP, int \fIy\fP, int \fIx\fP);
.fi
.SH DESCRIPTION
.B \%winch
returns the
.I curses
character,
including its attributes and color pair identifier,
at the cursor position in the window
.IR win "."
Subsection \*(``Video Attributes\*('' of \fB\%attron\fP(3X) explains
how to extract these data from a
.IR chtype "."
\fB\%ncurses\fP(3X) describes the variants of this function.
.SH RETURN VALUE
These functions return
.B OK
on success and
.B ERR
on failure.
.PP
In
.IR \%ncurses ","
.B \%winch
returns
.B ERR
if
.I win
is
.BR NULL "."
.PP
Functions prefixed with \*(``mv\*('' first perform cursor movement and
fail if the position
.RI ( y ,
.IR x )
is outside the window boundaries.
.SH NOTES
.BR \%inch ,
.BR \%mvinch ,
and
.B \%mvwinch
may be implemented as macros.
.PP
These functions do not return an error if the window contains cells of
.I curses
complex characters;
that is,
if they contain characters with codes wider than eight bits
(or greater than 255 as an unsigned decimal integer).
They instead extract only the low-order eight bits of the character code
from the cell.
.SH PORTABILITY
X/Open Curses,
Issue 4 describes these functions.
It specifies no error conditions for them.
.SH HISTORY
The original
.I curses
in 4BSD (1980) defined
.I \%winch
as a macro accessing the
.I \%WINDOW
structure member representing character cell data,
at that time a
.IR char ","
containing only a 7-bit ASCII character code
and a \*(``standout\*(`` attribute bit,
the only one the library supported.
.PP
SVr2
.I curses
(1984)
extended this approach,
widening the character code to eight bits
and permitting several attributes to be combined with it
by storing them together in a
.IR \%chtype ","
an alias of
.IR "unsigned short" "."
.\" ...indirectly through a preprocessor macro named CHTYPE, encouraging
.\" builders to change the typedef to `char` or `long` as desired.  More
.\" innocent times with respect to ABI compatibility concerns... --GBR
Because a macro was used,
its value was not type-checked
as a function return value could have been.
Goodheart documented SVr3 (1987)
.I \%winch
as returning an
.IR int "."
.\" ...but the implementation remained unchanged.
SVr3.1's (1987)
.I \%chtype
became an alias of
.IR "unsigned long" ","
using 16 bits for the character code and
widening the type in practical terms to 32 bits,
as 64-bit Unix systems were not yet in wide use,
and fixed-width integral types would not be standard until ISO C99.
.\" Cray's UNICOS was 1985 (how many shops had Crays?).  DEC OSF/1 for
.\" the Alpha arrived in 1993.  --GBR
SVr3.2 (1988)
added a 6-bit color pair identifier alongside the attributes.
.PP
X/Open Curses does not specify the sizes of the character code or
color pair identifier,
nor the quantity of attribute bits,
in
.IR chtype ";"
these are implementation-dependent.
.I \%ncurses
uses eight bits for the character code.
An application requiring a wider character type,
for instance to represent Unicode,
should use the wide-character counterparts of these functions.
.SH SEE ALSO
\fB\%curs_in_wch\fP(3X) describes comparable functions of the
.I \%ncurses
library in its wide-character configuration
.RI ( \%ncursesw ).
.PP
\fB\%curses\fP(3X),
\fB\%curs_instr\fP(3X)