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curs_refresh


Section: Miscellaneous Library Functions (3X)
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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

curses(3X), curs_outopts(3X)



 

Index



NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

NOTES

PORTABILITY

SEE ALSO



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