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)
refresh(3NCURSES)