# curs_refresh 3x 2024-01-05 ncurses 6.4 Library calls

    curs_refresh(3x)                 Library calls                curs_refresh(3x)

## 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(3x) 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:

           o   a physical screen, describing what is actually on the screen, and

           o   a virtual screen, describing what the programmer wants to  have  on
               the screen.

           The routine wrefresh works by

           o   first  calling  wnoutrefresh,  which copies the named window to the
               virtual screen, and

           o   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

           curses(3x), curs_outopts(3x) curs_variables(3x)

    ncurses 6.4                       2024-01-05                  curs_refresh(3x)