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* @Id: curs_refresh.3x,v 1.10 2001/11/03 18:57:12 tom Exp @
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<H1>curs_refresh 3x</H1>
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<PRE>
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</PRE>
<H2>NAME</H2><PRE>
<STRONG>doupdate</STRONG>, <STRONG>redrawwin</STRONG>, <STRONG>refresh</STRONG>, <STRONG>wnoutrefresh</STRONG>, <STRONG>wredrawln</STRONG>,
<STRONG>wrefresh</STRONG> - refresh <STRONG>curses</STRONG> windows and lines
</PRE>
<H2>SYNOPSIS</H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>int</STRONG> <STRONG>refresh(void);</STRONG>
<STRONG>int</STRONG> <STRONG>wrefresh(WINDOW</STRONG> <STRONG>*win);</STRONG>
<STRONG>int</STRONG> <STRONG>wnoutrefresh(WINDOW</STRONG> <STRONG>*win);</STRONG>
<STRONG>int</STRONG> <STRONG>doupdate(void);</STRONG>
<STRONG>int</STRONG> <STRONG>redrawwin(WINDOW</STRONG> <STRONG>*win);</STRONG>
<STRONG>int</STRONG> <STRONG>wredrawln(WINDOW</STRONG> <STRONG>*win,</STRONG> <STRONG>int</STRONG> <STRONG>beg_line,</STRONG> <STRONG>int</STRONG> <STRONG>num_lines);</STRONG>
</PRE>
<H2>DESCRIPTION</H2><PRE>
The <STRONG>refresh</STRONG> and <STRONG>wrefresh</STRONG> routines (or <STRONG>wnoutrefresh</STRONG> and
<STRONG>doupdate</STRONG>) must be called to get actual output to the ter-
minal, as other routines merely manipulate data struc-
tures. The routine <STRONG>wrefresh</STRONG> copies the named window to
the physical terminal screen, taking into account what is
already there to do optimizations. The <STRONG>refresh</STRONG> routine is
the same, using <STRONG>stdscr</STRONG> as the default window. Unless
<STRONG>leaveok</STRONG> has been enabled, the physical cursor of the ter-
minal is left at the location of the cursor for that win-
dow.
The <STRONG>wnoutrefresh</STRONG> and <STRONG>doupdate</STRONG> routines allow multiple
updates with more efficiency than <STRONG>wrefresh</STRONG> alone. In
addition to all the window structures, <STRONG>curses</STRONG> keeps two
data structures representing the terminal screen: a physi-
cal screen, describing what is actually on the screen, and
a virtual screen, describing what the programmer wants to
have on the screen.
The routine <STRONG>wrefresh</STRONG> works by first calling <STRONG>wnoutrefresh</STRONG>,
which copies the named window to the virtual screen, and
then calling <STRONG>doupdate</STRONG>, which compares the virtual screen
to the physical screen and does the actual update. If the
programmer wishes to output several windows at once, a
series of calls to <STRONG>wrefresh</STRONG> results in alternating calls
to <STRONG>wnoutrefresh</STRONG> and <STRONG>doupdate</STRONG>, causing several bursts of
output to the screen. By first calling <STRONG>wnoutrefresh</STRONG> for
each window, it is then possible to call <STRONG>doupdate</STRONG> once,
resulting in only one burst of output, with fewer total
characters transmitted and less CPU time used. If the <EM>win</EM>
argument to <STRONG>wrefresh</STRONG> is the global variable <STRONG>curscr</STRONG>, the
screen is immediately cleared and repainted from scratch.
The phrase "copies the named window to the virtual screen"
above is ambiguous. What actually happens is that all
<EM>touched</EM> (changed) lines in the window are copied to the
virtual screen. This affects programs that use overlap-
ping 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 <STRONG>PORTABILITY</STRONG> below for a warning about
exploiting this behavior.)
The <STRONG>wredrawln</STRONG> routine indicates to <STRONG>curses</STRONG> that some screen
lines are corrupted and should be thrown away before any-
thing is written over them. It touches the indicated
lines (marking them changed). The routine <STRONG>redrawwin</STRONG>()
touches the entire window.
</PRE>
<H2>RETURN VALUE</H2><PRE>
Routines that return an integer return <STRONG>ERR</STRONG> upon failure,
and <STRONG>OK</STRONG> (SVr4 only specifies "an integer value other than
<STRONG>ERR</STRONG>") upon successful completion.
</PRE>
<H2>NOTES</H2><PRE>
Note that <STRONG>refresh</STRONG> and <STRONG>redrawwin</STRONG> may be macros.
</PRE>
<H2>PORTABILITY</H2><PRE>
The XSI Curses standard, Issue 4 describes these func-
tions.
Whether <STRONG>wnoutrefresh()</STRONG> 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 <STRONG>touchwin()</STRONG> before the <STRONG>wnoutrefresh()</STRONG> call to
guarantee an entire-contents copy anywhere.
</PRE>
<H2>SEE ALSO</H2><PRE>
<STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_outopts.3x.html">curs_outopts(3x)</A></STRONG>
</PRE>
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