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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.
Copies the named window win to the virtual screen
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.
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.