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.\" $Id$
.TH curs_overlay 3X ""
.na
.hy 0
.SH NAME
\fBoverlay\fR,
\fBoverwrite\fR,
\fBcopywin\fR - overlay and manipulate overlapped \fBcurses\fR windows
.ad
.hy
.SH SYNOPSIS
\fB#include <curses.h>\fR

\fBint overlay(const WINDOW *srcwin, WINDOW *dstwin);\fR
.br
\fBint overwrite(const WINDOW *srcwin, WINDOW *dstwin);\fR
.br
\fBint copywin(const WINDOW *srcwin, WINDOW *dstwin, int sminrow,\fR
      \fBint smincol, int dminrow, int dmincol, int dmaxrow,\fR
      \fBint dmaxcol, int overlay);\fR
.SH DESCRIPTION
The \fBoverlay\fR and \fBoverwrite\fR routines overlay \fIsrcwin\fR on
top of \fIdstwin\fR.  \fIscrwin\fR and \fIdstwin\fR are not required
to be the same size; only text where the two windows overlap is
copied.  The difference is that \fBoverlay\fR is non-destructive
(blanks are not copied) whereas \fBoverwrite\fR is destructive.

The \fBcopywin\fR routine provides a finer granularity of control over the
\fBoverlay\fR and \fBoverwrite\fR routines.  Like in the \fBprefresh\fR
routine, a rectangle is specified in the destination window, (\fIdminrow\fR,
\fIdmincol\fR) and (\fIdmaxrow\fR, \fIdmaxcol\fR), and the upper-left-corner
coordinates of the source window, (\fIsminrow\fR, \fIsmincol\fR).  If the
argument \fIoverlay\fR is \fBtrue\fR, then copying is non-destructive, as in
\fBoverlay\fR.
.SH RETURN VALUE
Routines that return an integer return \fBERR\fR upon failure, and \fBOK\fR
(SVr4 only specifies "an integer value other than \fBERR\fR") 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\fR and \fBoverwrite\fR may be macros.
.SH PORTABILITY
The XSI Curses standard, Issue 4 describes these functions (adding the const
qualifiers).  It further specifies their behavior in the presence of characters
with multibyte renditions (not yet supported in this implementation).
.SH SEE ALSO
\fBcurses\fR(3X), \fBcurs_pad\fR(3X), \fBcurs_refresh\fR(3X)
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