curs_refresh(3X) curs_refresh(3X)
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 op-timizations. optimizations.
timizations. 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 virtu-al virtual
al 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 im-mediately immediately
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 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 val-ue value
ue 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 guar-antee guarantee
antee an entire-contents copy anywhere.
SEE ALSO
curses(3X), curs_outopts(3X)
curs_refresh(3X)
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