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The refresh() and wrefresh() routines (or wnoutrefresh() and doupdate()) must be called to get any output on 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 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 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 redrawwin() routine indicates to curses that some screen lines are corrupted and should be thrown away before anything is written over them. These routines
could be used for programs such as editors, which want a command to redraw some part of the screen or the entire screen. The routine redrawln() is preferred over redrawwin()
where a noisy communication line exists and redrawing the entire window could be subject to even more communication noise. Just redrawing several lines offers the possibility that they would show up unblemished.
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