curs_refresh(3) UNIX Programmer's Manual curs_refresh(3)
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 doup-
date) must be called to get actual output to the terminal,
as other routines merely manipulate data structures. 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 en-
abled, the physical cursor of the terminal is left at the
location of the cursor for that window.
The wnoutrefresh and doupdate routines allow multiple up-
dates with more efficiency than wrefresh alone. In addition
to all the window structures, curses keeps two data struc-
tures 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 pro-
grammer wishes to output several windows at once, a series
of calls to wrefresh results in alternating calls to
wnoutrefresh and doupdate, causing several bursts of output
to the screen. By first calling wnoutrefresh for each win-
dow, it is then possible to call doupdate once, resulting in
only one burst of output, with fewer total characters
transmitted and less CPU time used. If the win argument to
wrefresh is the global variable curscr, the screen is im-
mediately 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 vir-
tual screen. This affects programs that use overlapping win-
dows; it means that if two windows overlap, you can refresh
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curs_refresh(3) UNIX Programmer's Manual curs_refresh(3)
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 imple-
mentation
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 functions.
Whether wnoutrefresh() copies to the virtual screen the en-
tire contents of a window or just its changed portions has
never been well-documented in historic curses versions (in-
cluding 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 touchwin()
before the wnoutrefresh() call to guarantee an entire-
contents copy anywhere.
curses(3), curs_outopts(3)
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