curs_refresh
Section: Library calls (3X)
Updated: 202-0-18
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NAME
doupdate,
redrawwin,
refresh,
wnoutrefresh,
wredrawln,
wrefresh -
refresh
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 window 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(3X) 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
structures,
curses keeps two data structures representing the terminal
screen:
.IP * 4
a
physical screen,
describing what is actually on the screen, and
.IP * 4
a
virtual screen,
describing what the programmer wants to have on the screen.
The routine wrefresh works by
.IP * 4
first calling wnoutrefresh,
which copies the named window to the virtual screen, and
.IP * 4
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 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 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.)
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 routine
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 wel-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 entir-contents copy anywhere.
SEE ALSO
curses(3X),
curs_outopts(3X),
curs_variables(3X)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- refresh, wrefresh
-
- wnoutrefresh, doupdate
-
- wredrawln, redrawwin
-
- RETURN VALUE
-
- NOTES
-
- PORTABILITY
-
- SEE ALSO
-
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