NAME¶
doupdate,
redrawwin,
refresh,
wnoutrefresh,
wredrawln,
wrefresh - refresh
curses windows and lines
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¶
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 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 terminal is left at the location of the
cursor for that window.
The
wnoutrefresh and
doupdate routines allow multiple updates with
more efficiency than
wrefresh alone. In addition 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 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 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 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
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.)
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 routine
redrawwin() touches the entire window.
RETURN VALUE¶
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 implementation
- 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.
NOTES¶
Note that
refresh and
redrawwin may be macros.
PORTABILITY¶
The XSI Curses standard, Issue 4 describes these functions.
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).