refresh(3ncurses)

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 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.

   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 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

   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) curses_variables(3NCURSES).

                                                         refresh(3NCURSES)

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