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 (SVr4 specifies only “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)