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.\" $Id: curs_touch.3x,v 1.42 2023/11/25 14:08:05 tom Exp $
.TH touch 3NCURSES 2023-11-25 "ncurses 6.4" "Library calls"
.SH NAME
\fB\%touchwin\fP,
\fB\%touchline\fP,
\fB\%untouchwin\fP,
\fB\%wtouchln\fP,
\fB\%is_linetouched\fP,
\fB\%is_wintouched\fP \-
control terminal output refresh in a \fIcurses\fR window
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fBint touchline(WINDOW *\fIwin\fP, int \fIstart\fP, int \fIcount\fP);
.PP
\fBint touchwin(WINDOW *\fIwin\fP);
\fBint wtouchln(WINDOW *\fIwin\fP, int \fIy\fP, int \fIn\fP, int \fIchanged\fP);
.PP
\fBint untouchwin(WINDOW *\fIwin\fP);
.PP
\fBbool is_linetouched(WINDOW *\fIwin\fP, int \fIline\fP);
\fBbool is_wintouched(WINDOW *\fIwin\fP);
.fi
.SH DESCRIPTION
The \fB\%touchwin\fP and \fB\%touchline\fP routines throw away all
optimization information about which parts of the window have been
touched, by pretending that the entire window has been drawn on.
This
is sometimes necessary when using overlapping windows, since a change
to one window affects the other window, but the records of which lines
have been changed in the other window do not reflect the change.
The
routine \fB\%touchline\fP only pretends that \fIcount\fP lines have been
changed, beginning with line \fIstart\fP.
.PP
The \fB\%untouchwin\fP routine marks all lines in the window as unchanged since
the last call to \fB\%wrefresh\fP.
.PP
The \fB\%wtouchln\fP routine makes \fIn\fP lines in the window, starting
at line \fIy\fR, look as if they have (\fIchanged\fB=1\fR) or have
not (\fIchanged\fB=0\fR) been changed since the last call to
\fB\%wrefresh\fP.
.PP
The \fB\%is_linetouched\fP and \fB\%is_wintouched\fP routines return
\fBTRUE\fP if the specified line/window was modified since the last
call to \fB\%wrefresh\fP; otherwise they return \fBFALSE\fP.  In
addition, \fB\%is_linetouched\fP returns \fBERR\fP if \fIline\fP is not
valid for the given window.
.SH RETURN VALUE
All routines return the integer \fBERR\fP upon failure and 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
.RS 3
.TP 5
\fBis_linetouched\fP
returns an error
if the window pointer is null, or
if the line number is outside the window.
.IP
The constant \fBERR\fP is distinct from \fBTRUE\fP and \fBFALSE\fP,
which are the normal return values of this function.
Because the function returns a \fBbool\fP,
returning \fBERR\fP (which is neither \fBTRUE\fP nor \fBFALSE\fP)
may not be supported by the compiler.
.IP
To provide error-checking and also match the X/Open function prototype,
the \fBERR\fP is provided by a macro named \fB\%is_linetouched\fP.
The actual function returns \fBFALSE\fP when it detects an error.
.TP 5
\fBwtouchln\fP
returns an error
if the window pointer is null, or
if the line number is outside the window.
.RE
.SH NOTES
All of these routines except \fB\%wtouchln\fP may be macros.
.SH PORTABILITY
These functions were introduced by SVr4.
The Solaris \fIcurses\fP header file,
for instance, defines both an actual function and macro for each.
The macros give the same result as the actual functions.
SVr4 \fIcurses\fP does not check the window parameter \fIwin\fP to ensure
that it is not \fBNULL\fP;
otherwise this implementation behaves the same as SVr4.
.PP
The XSI Curses standard, Issue 4 describes these functions,
but defines no error conditions.
.SH SEE ALSO
\fB\%ncurses\fP(3NCURSES),
\fB\%refresh\fP(3NCURSES),
\fB\%curses_variables\fP(3NCURSES)