plucky (3) doupdate.3ncurses.gz

NAME

       doupdate,  redrawwin,  refresh,  wnoutrefresh,  wredrawln,  wrefresh  -  refresh  curses windows or lines
       thereupon

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(3NCURSES) 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

       These routines return the integer ERR upon failure and OK

       In this implementation

          wnoutrefresh
               returns ERR if the window pointer is null, or if the window is really a pad.

          wredrawln
               return ERR if the associated call to touchln returns ERR.

NOTES

       refresh and redrawwin may be implemented as macros.

PORTABILITY

       X/Open Curses Issue 4 describes these functions.  It specifies no error conditions for them.

       SVr4 describes a successful return value only as “an integer value other than ERR”.

       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), curses_variables(3NCURSES)