doupdate, redrawwin, refresh, wnoutrefresh, wredrawln, wrefresh - refresh curses windows and lines
int wrefresh(WINDOW *win);
int wnoutrefresh(WINDOW *win);
int redrawwin(WINDOW *win);
int wredrawln(WINDOW *win, int beg_line, int num_lines);
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 en-
abled, 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.
Routines that return an integer return ERR upon failure, and OK (SVr4 only specifies "an integer value other than ERR") upon successful
X/Open does not define any error conditions. In this implementation
returns an error if the window pointer is null, or if the window is really a pad.
returns an error if the associated call to touchln returns an error.
Note that refresh and redrawwin may be macros.
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-docu-
mented 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 en-
tire-contents copy anywhere.