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5.2.33 Refresh windows and lines

Procedure: refresh win

The refresh routine (or noutrefresh and doupdate) must be called to get actual output to the terminal, as other routines merely manipulate data structures. The routine refresh 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.

Procedure: noutrefresh win

Copies the named window win to the virtual screen

Procedure: doupdate

Compares the virtual screen to the physical screen and updates it where necessary.

The noutrefresh and doupdate routines allow multiple updates with more efficiency than refresh 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 refresh works by first calling noutrefresh, 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 refresh results in alternating calls to noutrefresh and doupdate, causing several bursts of output to the screen. By first calling noutrefresh 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 refresh 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.

Procedure: redrawwin win
Procedure: redrawln win beg-line num-lines

The redrawln 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.

Returns #t on success and #f on failure.

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