refresh, wrefresh, wnoutrefresh, doupdate, redrawwin, wre-
       drawln - refresh curses windows and lines


       #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);


       The refresh and wrefresh  routines  (or  wnoutrefresh  and
       doupdate)  must be called to get actual output to the ter-
       minal, as other routines  merely  manipulate  data  struc-
       tures.   The  routine  wrefresh copies the named window to
       the physical terminal screen, taking into account what  is
       already  there  in order 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 physi-
       cal 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 overlap-
       ping windows; it means that if two  windows  overlap,  you
       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 any-
       thing is written over them it touches the indicated  lines
       (marking  them changed) then does a refresh of the window.
       The routine redrawwin() touches the entire window and then
       refreshes it.


       Routines  that  return an integer return ERR upon failure,
       and OK (SVr4 only specifies "an integer value  other  than
       ERR") upon successful completion.


       Note that refresh and redrawwin may be macros.


       The  XSI  Curses  standard,  Issue 4 describes these func-

       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.


       curses(3X), curs_outopts(3X)