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* @Id: curs_refresh.3x,v 1.12 2005/05/15 16:18:49 tom Exp @

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<HTML>

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<TITLE>curs_refresh 3x</TITLE>

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<BODY>

<H1>curs_refresh 3x</H1>

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<HR>

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<PRE>

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<A HREF="curs_refresh.3x.html">curs_refresh(3x)</A> <A HREF="curs_refresh.3x.html">curs_refresh(3x)</A>

</PRE>

doupdate, redrawwin, refresh, wnoutrefresh, wredrawln,

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wrefresh - refresh curses windows and lines

</PRE>

<H2>SYNOPSIS</H2><PRE>

#include <curses.h>

int refresh(void);

int wrefresh(WINDOW *win);

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int wnoutrefresh(WINDOW *win);

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int doupdate(void);

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int redrawwin(WINDOW *win);

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int wredrawln(WINDOW *win, int beg_line, int num_lines);

</PRE>

<H2>DESCRIPTION</H2><PRE>

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The refresh and wrefresh routines (or wnoutrefresh and

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doupdate) must be called to get actual output to the ter-

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minal, as other routines merely manipulate data struc-

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tures. The routine wrefresh copies the named window to

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the physical terminal screen, taking into account what is

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already there to do optimizations. The refresh routine is

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the same, using stdscr as the default window. Unless

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leaveok has been enabled, the physical cursor of the ter-

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minal is left at the location of the cursor for that win-

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dow.

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The wnoutrefresh and doupdate routines allow multiple up-

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dates with more efficiency than wrefresh alone. In addi-

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tion to all the window structures, curses keeps two data

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structures representing the terminal screen: a physical

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screen, describing what is actually on the screen, and a

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virtual screen, describing what the programmer wants to

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have on the screen.

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The routine wrefresh works by first calling wnoutrefresh,

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which copies the named window to the virtual screen, and

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then calling doupdate, which compares the virtual screen

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to the physical screen and does the actual update. If the

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programmer wishes to output several windows at once, a se-

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ries of calls to wrefresh results in alternating calls to

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wnoutrefresh and doupdate, causing several bursts of out-

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put to the screen. By first calling wnoutrefresh for each

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window, it is then possible to call doupdate once, result-

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ing in only one burst of output, with fewer total charac-

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ters transmitted and less CPU time used. If the win argu-

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ment to wrefresh is the global variable curscr, the screen

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is immediately cleared and repainted from scratch.

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The phrase "copies the named window to the virtual screen"

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above is ambiguous. What actually happens is that all

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touched (changed) lines in the window are copied to the

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virtual screen. This affects programs that use overlap-

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ping windows; it means that if two windows overlap, you

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can refresh them in either order and the overlap region

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will be modified only when it is explicitly changed. (But

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see the section on PORTABILITY below for a warning about

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exploiting this behavior.)

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The wredrawln routine indicates to curses that some screen

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lines are corrupted and should be thrown away before any-

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thing is written over them. It touches the indicated

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lines (marking them changed). The routine redrawwin()

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touches the entire window.

</PRE>

<H2>RETURN VALUE</H2><PRE>

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Routines that return an integer return ERR upon failure,

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and OK (SVr4 only specifies "an integer value other than

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ERR") upon successful completion.

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X/Open does not define any error conditions. In this im-

plementation

wnoutrefresh

returns an error if the window pointer is

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null, or if the window is really a pad.

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wredrawln

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returns an error if the associated call to

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touchln returns an error.

</PRE>

<H2>NOTES</H2><PRE>

Note that refresh and redrawwin may be macros.

</PRE>

<H2>PORTABILITY</H2><PRE>

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The XSI Curses standard, Issue 4 describes these func-

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tions.

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Whether wnoutrefresh() copies to the virtual screen the

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entire contents of a window or just its changed portions

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has never been well-documented in historic curses versions

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(including SVr4). It might be unwise to rely on either

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behavior in programs that might have to be linked with

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other curses implementations. Instead, you can do an ex-

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plicit touchwin() before the wnoutrefresh() call to guar-

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antee an entire-contents copy anywhere.

</PRE>

<A HREF="ncurses.3x.html">curses(3x)</A>, <A HREF="curs_outopts.3x.html">curs_outopts(3x)</A>

<A HREF="curs_refresh.3x.html">curs_refresh(3x)</A>

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