refresh(3NCURSES) Library calls refresh(3NCURSES)
NAME
doupdate, redrawwin, refresh, wnoutrefresh, wredrawln, wrefresh - re-
fresh curses windows or lines thereupon
SYNOPSIS
#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);
DESCRIPTION
refresh, wrefresh
The refresh and wrefresh routines (or wnoutrefresh and doupdate) must be
called to get actual output to the terminal, as other routines merely
manipulate data structures. The routine wrefresh copies the named win-
dow to the physical 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(3NCURSES) has been enabled, the physical
cursor of the terminal is left at the location of the cursor for that
window.
wnoutrefresh, doupdate
The wnoutrefresh and doupdate routines allow multiple updates with more
efficiency than wrefresh alone. In addition to all the window struc-
tures, 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 series of
calls to wrefresh results in alternating calls to wnoutrefresh and doup-
date, causing several bursts of output to the screen. By first calling
wnoutrefresh for each window, 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 physical screen (i.e., 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 am-
biguous. What actually happens is that all touched (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 PORTABILITY
below for a warning about exploiting this behavior.)
wredrawln, redrawwin
The wredrawln routine indicates to curses 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 rou-
tine redrawwin touches the entire window.
RETURN VALUE
These routines return the integer ERR upon failure and OK
In this implementation
wnoutrefresh
returns ERR if the window pointer is null, or if the window is
really a pad.
wredrawln
return ERR if the associated call to touchln returns ERR.
NOTES
refresh and redrawwin may be implemented as macros.
PORTABILITY
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them.
SVr4 describes a successful return value only as “an integer value other
than ERR”.
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 explicit touchwin before
the wnoutrefresh call to guarantee an entire-contents copy anywhere.
SEE ALSO
ncurses(3NCURSES), outopts(3NCURSES), curses_variables(3NCURSES)
ncurses 6.5 2025-01-18 refresh(3NCURSES)
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