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.\" Copyright 2018-2023,2024 Thomas E. Dickey                                *
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.\" $Id: curs_scr_dump.3x,v 1.41 2024/03/23 20:41:15 tom Exp $
.TH scr_dump 3NCURSES 2024-03-23 "ncurses 6.4" "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\%scr_dump\fP,
\fB\%scr_restore\fP,
\fB\%scr_init\fP,
\fB\%scr_set\fP \-
read/write a \fIcurses\fR screen from/to a file
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fBint scr_dump(const char *\fIfilename\fP);
\fBint scr_restore(const char *\fIfilename\fP);
\fBint scr_init(const char *\fIfilename\fP);
\fBint scr_set(const char *\fIfilename\fP);
.fi
.SH DESCRIPTION
.I curses
provides applications the ability to write the contents of the screen
to a file and read them back.
To read/write a window
(rather than the whole screen)
from/to a file,
use \fB\%getwin\fP(3NCURSES) and
\fB\%putwin\fP(3NCURSES),
respectively.
.SS scr_dump
\fB\%scr_dump\fP writes to
.I filename
the contents of the virtual screen;
see \fB\%curscr\fP(3NCURSES).
.SS scr_restore
\fB\%scr_restore\fP updates the virtual screen to contain the contents
of
.I filename
(if it was validly written with \fB\%scr_dump\fP).
No refresh is performed;
after performing any further desired updates,
call \fB\%doupdate\fP(3NCURSES) or similar.
.SS scr_init
\fB\%scr_init\fP reads
.IR filename ,
using it to initialize
.I curses
data structures describing the state of the terminal screen.
If these data are valid,
.I curses
bases its next update of the screen on this information rather than
clearing it and starting from scratch.
.PP
The data fail the validity check
.bP
if the terminal employs
.I \%term\%info
capabilities
.B \%exit_ca_mode
.RB ( \%rmcup )
or
.B \%non_rev_rmcup
.RB ( \%nrrmc )
are defined,
or
.bP
if
.I curses
knows that the terminal has been written to since the preceding
\fB\%scr_dump\fP call.
.PP
\fB\%scr_init\fP could be used after \fB\%initscr\fP(3NCURSES) or
\fB\%system\fP(3) to share the screen with another process that has
done a \fBscr_dump\fP after \fB\%endwin\fP(3NCURSES).
.SS scr_set
The \fBscr_set\fP routine is a combination of \fBscr_restore\fP and
\fBscr_init\fP.  It tells the program that the information in \fIfilename\fP is
what is currently on the screen, and also what the program wants on the screen.
This can be thought of as a screen inheritance function.
.SH RETURN VALUE
These functions return \fBOK\fP on success and \fBERR\fP on failure.
.PP
X/Open defines no failure conditions.
In this implementation,
each function fails if it cannot open
.IR filename .
.SH NOTES
\fB\%scr_init\fP,
\fB\%scr_set\fP,
and
\fB\%scr_restore\fP may be macros.
.SH PORTABILITY
X/Open Curses, Issue 4, describes these functions.
.PP
.\" SVID 4, p. 529
SVr4 omitted the
.I \%const
qualifiers.
.PP
SVr4 documentation describes \fB\%scr_init\fP such that the dump data is
also considered invalid \*(``if the time-stamp of the tty is old\*(''
but does not define \*(``old\*(''.
.SH SEE ALSO
\fB\%ncurses\fP(3NCURSES),
\fB\%initscr\fP(3NCURSES),
\fB\%refresh\fP(3NCURSES),
\fB\%util\fP(3NCURSES),
\fB\%system\fP(3),
\fB\%scr_dump\fP(5)