curs_refresh(3x) curs_refresh(3x)
doupdate, redrawwin, refresh, wnoutrefresh, wredrawln,
wrefresh - refresh curses windows and lines
#include <curses.h>
int refresh(void);
int wrefresh(WINDOW *win);
int wnoutrefresh(WINDOW *win);
int doupdate(void);
int redrawwin(WINDOW *win);
int wredrawln(WINDOW *win, int beg_line, int num_lines);
The refresh and wrefresh routines (or wnoutrefresh and
doupdate) must be called to get actual output to the ter-
minal, as other routines merely manipulate data struc-
tures. The routine wrefresh copies the named window to
the physical terminal screen, taking into account what is
already there to do optimizations. The refresh routine is
the same, using stdscr as the default window. Unless
leaveok has been enabled, the physical cursor of the ter-
minal is left at the location of the cursor for that win-
dow.
The wnoutrefresh and doupdate routines allow multiple up-
dates with more efficiency than wrefresh alone. In addi-
tion to all the window structures, curses keeps two data
structures representing the terminal screen: a physical
screen, describing what is actually on the screen, and a
virtual screen, describing what the programmer wants to
have on the screen.
The routine wrefresh works by first calling wnoutrefresh,
which copies the named window to the virtual screen, and
then calling doupdate, 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 se-
ries of calls to wrefresh results in alternating calls to
wnoutrefresh and doupdate, causing several bursts of out-
put to the screen. By first calling wnoutrefresh for each
window, it is then possible to call doupdate once, result-
ing in only one burst of output, with fewer total charac-
ters transmitted and less CPU time used. If the win argu-
ment to wrefresh is the global variable curscr, 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
touched (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 PORTABILITY below for a warning about
exploiting this behavior.)
The wredrawln routine indicates to curses 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 redrawwin()
touches the entire window.
Routines that return an integer return ERR upon failure,
and OK (SVr4 only specifies "an integer value other than
ERR") upon successful completion.
X/Open does not define any error conditions. In this im-
plementation
wnoutrefresh
returns an error if the window pointer is
null, or if the window is really a pad.
wredrawln
returns an error if the associated call to
touchln returns an error.
Note that refresh and redrawwin may be macros.
The XSI Curses standard, Issue 4 describes these func-
tions.
Whether wnoutrefresh() 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 ex-
plicit touchwin() before the wnoutrefresh() call to guar-
antee an entire-contents copy anywhere.
curses(3x), curs_outopts(3x) curs_variables(3x).
curs_refresh(3x)