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.\" $OpenBSD: curs_refresh.3,v 1.8 2023/10/17 09:52:08 nicm Exp $
.\"
.\"***************************************************************************
.\" Copyright 2018-2022,2023 Thomas E. Dickey *
.\" Copyright 1998-2010,2016 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" "Software"), to deal in the Software without restriction, including *
.\" without limitation the rights to use, copy, modify, merge, publish, *
.\" distribute, distribute with modifications, sublicense, and/or sell *
.\" copies of the Software, and to permit persons to whom the Software is *
.\" furnished to do so, subject to the following conditions: *
.\" *
.\" The above copyright notice and this permission notice shall be included *
.\" in all copies or substantial portions of the Software. *
.\" *
.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
.\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
.\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
.\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
.\" THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
.\" *
.\" Except as contained in this notice, the name(s) of the above copyright *
.\" holders shall not be used in advertising or otherwise to promote the *
.\" sale, use or other dealings in this Software without prior written *
.\" authorization. *
.\"***************************************************************************
.\"
.\" $Id: curs_refresh.3,v 1.8 2023/10/17 09:52:08 nicm Exp $
.TH curs_refresh 3 2023-08-19 "ncurses 6.4" "Library calls"
.ie \n(.g .ds `` \(lq
.el .ds `` ``
.ie \n(.g .ds '' \(rq
.el .ds '' ''
.de bP
.ie n .IP \(bu 4
.el .IP \(bu 2
..
.na
.hy 0
.SH NAME
\fBdoupdate\fP,
\fBredrawwin\fP,
\fBrefresh\fP,
\fBwnoutrefresh\fP,
\fBwredrawln\fP,
\fBwrefresh\fP \- refresh \fBcurses\fP windows and lines
.ad
.hy
.SH SYNOPSIS
\fB#include <curses.h>\fP
.sp
\fBint refresh(void);\fP
.br
\fBint wrefresh(WINDOW *\fIwin\fB);\fR
.br
\fBint wnoutrefresh(WINDOW *\fIwin\fB);\fR
.br
\fBint doupdate(void);\fP
.sp
\fBint redrawwin(WINDOW *\fIwin\fB);\fR
.br
\fBint wredrawln(WINDOW *\fIwin\fB, int \fIbeg_line\fB, int \fInum_lines\fB);\fR
.SH DESCRIPTION
.SS refresh/wrefresh
The \fBrefresh\fP and \fBwrefresh\fP routines (or \fBwnoutrefresh\fP and
\fBdoupdate\fP) must be called to get actual output to the terminal,
as other routines merely manipulate data structures.
The routine \fBwrefresh\fP copies
the named window to the \fIphysical screen\fP,
taking into account what is already there to do optimizations.
The \fBrefresh\fP routine is the
same, using \fBstdscr\fP as the default window.
Unless \fBleaveok\fP(3) has been
enabled, the physical cursor of the terminal is left at the location of the
cursor for that window.
.SS wnoutrefresh/doupdate
The \fBwnoutrefresh\fP and \fBdoupdate\fP routines allow multiple updates with
more efficiency than \fBwrefresh\fP alone.
In addition to all the window
structures, \fBcurses\fP keeps two data structures representing the terminal
screen:
.bP
a \fIphysical screen\fP,
describing what is actually on the screen, and
.bP
a \fIvirtual screen\fP,
describing what the programmer wants to have on the screen.
.PP
The routine \fBwrefresh\fP works by
.bP
first calling \fBwnoutrefresh\fP,
which copies the named window to the \fIvirtual screen\fP, and
.bP
then calling \fBdoupdate\fP, which compares
the \fIvirtual screen\fP to the \fIphysical screen\fP
and does the actual update.
.PP
If the programmer wishes to output several windows at once, a series
of calls to \fBwrefresh\fP results in alternating calls to \fBwnoutrefresh\fP
and \fBdoupdate\fP, causing several bursts of output to the screen.
By first
calling \fBwnoutrefresh\fP for each window, it is then possible to call
\fBdoupdate\fP once, resulting in only one burst of output, with fewer total
characters transmitted and less CPU time used.
.PP
If the \fIwin\fP argument to
\fBwrefresh\fP is the \fIphysical screen\fP
(i.e., the global variable \fBcurscr\fP),
the screen is immediately cleared and repainted from scratch.
.PP
The phrase \*(``copies the named window
to the virtual screen\*('' above is ambiguous.
What actually happens is that all \fItouched\fP (changed) lines in the window
are copied to the virtual screen.
This affects programs that use overlapping
windows; it means that if two windows overlap, you can refresh them in either
order and the overlap region will be modified only when it is explicitly
changed.
(But see the section on \fBPORTABILITY\fP below for a warning about
exploiting this behavior.)
.SS wredrawln/redrawwin
The \fBwredrawln\fP routine indicates to \fBcurses\fP that some screen lines
are corrupted and should be thrown away before anything is written over them.
It touches the indicated lines (marking them changed).
The routine \fBredrawwin\fP touches the entire window.
.SH RETURN VALUE
Routines that return an integer return \fBERR\fP upon failure, and \fBOK\fP
(SVr4 only specifies "an integer value other than \fBERR\fP") upon successful
completion.
.PP
X/Open does not define any error conditions.
In this implementation
.RS 3
.TP 5
\fBwnoutrefresh\fP
returns an error
if the window pointer is null, or
if the window is really a pad.
.TP 5
\fBwredrawln\fP
returns an error
if the associated call to \fBtouchln\fP returns an error.
.RE
.SH NOTES
Note that \fBrefresh\fP and \fBredrawwin\fP may be macros.
.SH PORTABILITY
The XSI Curses standard, Issue 4 describes these functions.
.PP
Whether \fBwnoutrefresh\fP copies to the virtual screen the entire contents
of a window or just its changed portions has never been well-documented in
historic curses versions (including SVr4).
It might be unwise to rely on
either behavior in programs that might have to be linked with other curses
implementations.
Instead, you can do an explicit \fBtouchwin\fP before the
\fBwnoutrefresh\fP call to guarantee an entire-contents copy anywhere.
.SH SEE ALSO
\fBcurses\fP(3),
\fBcurs_outopts\fP(3)
\fBcurs_variables\fP(3).
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