Provided by: ncurses-doc_5.9-4_all bug


       doupdate, redrawwin, refresh, wnoutrefresh, wredrawln, wrefresh - 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 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.


       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

                   returns  an  error if the window pointer is null, or if the window is really a

                   returns an error if the associated call to touchln returns an error.


       Note that refresh and redrawwin may be macros.


       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.


       ncurses(3NCURSES), outopts(3NCURSES) curses_variables(3NCURSES).