Ubuntu Manpage: doupdate, redrawwin, refresh, wnoutrefresh, wredrawln, wrefresh

Provided by: ncurses-doc_6.3+20220423-2_all

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

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 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:

• 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 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

       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