curs_refresh



curs_refresh(3)           OpenBSD Programmer's Manual          curs_refresh(3)


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(3), curs_outopts(3)

                                                               curs_refresh(3)

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