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.\" $Id: curs_overlay.3x,v 1.43 2024/04/20 21:20:07 tom Exp $
.TH overlay 3NCURSES 2024-04-20 "ncurses 6.5" "Library calls"
.ie \n(.g \{\
.ds `` \(lq
.ds '' \(rq
.\}
.el \{\
.ie t .ds `` ``
.el   .ds `` ""
.ie t .ds '' ''
.el   .ds '' ""
.\}
.
.SH NAME
\fB\%overlay\fP,
\fB\%overwrite\fP,
\fB\%copywin\fP \-
overlay \fIcurses\fR windows and manipulate them
.SH SYNOPSIS
.nf
\fB#include <ncursesw/curses.h>
.PP
\fBint overlay(const WINDOW *\fIsrcwin\fP, WINDOW *\fIdstwin\fP);
\fBint overwrite(const WINDOW *\fIsrcwin\fP, WINDOW *\fIdstwin\fP);
\fBint copywin(const WINDOW *\fIsrcwin\fP, WINDOW *\fIdstwin\fP, int \fIsminrow\fP,
      \fBint \fIsmincol\fB, int \fIdminrow\fB, int \fIdmincol\fB, int \fIdmaxrow\fB,\fR
      \fBint \fIdmaxcol\fB, int \fIoverlay\fB);\fR
.fi
.SH DESCRIPTION
.SS "overlay, overwrite"
The \fBoverlay\fP and \fBoverwrite\fP routines overlay \fIsrcwin\fP on
top of \fIdstwin\fP.
\fIscrwin\fP and \fIdstwin\fP are not required
to be the same size; only text where the two windows overlap is copied.
The difference is that \fBoverlay\fP is non-destructive
(blanks are not copied) whereas \fBoverwrite\fP is destructive.
.SS copywin
The \fBcopywin\fP routine provides a finer granularity of control over the
\fBoverlay\fP and \fBoverwrite\fP routines.
As in the \fBprefresh\fP routine,
a rectangle is specified in the destination window, (\fIdminrow\fP,
\fIdmincol\fP) and (\fIdmaxrow\fP, \fIdmaxcol\fP), and the upper-left-corner
coordinates of the source window, (\fIsminrow\fP, \fIsmincol\fP).
If the argument \fIoverlay\fP is \fBtrue\fP,
then copying is non-destructive,
as in \fBoverlay\fP.
.SH RETURN VALUE
These routines return the integer \fBERR\fP upon failure and an \fBOK\fP
(SVr4 specifies only
\*(``an integer value other than \fBERR\fP\*('')
upon successful completion.
.PP
X/Open defines no error conditions.
In this implementation,
\fBcopywin\fP,
\fBoverlay\fP and \fBoverwrite\fP return an error
if either of the window pointers are null, or
if some part of the window would be placed off-screen.
.SH NOTES
Note that \fBoverlay\fP and \fBoverwrite\fP may be macros.
.SH PORTABILITY
These functions are described in X/Open Curses, Issue 4,
which adds \fI\%const\fP qualifiers to the arguments.
It further specifies their behavior in the presence of characters
with multibyte renditions (not yet supported in this implementation).
.SH SEE ALSO
\fB\%ncurses\fP(3NCURSES),
\fB\%pad\fP(3NCURSES),
\fB\%refresh\fP(3NCURSES)