The function redraw-frame clears and redisplays the entire
contents of a given frame (see Frames). This is useful if the
screen is corrupted.
This function clears and redisplays frame frame. If frame
is omitted or nil, it redraws the selected frame.
Even more powerful is redraw-display:
This function clears and redisplays all visible frames.
In Emacs, processing user input takes priority over redisplay. If you call these functions when input is available, they don’t redisplay immediately, but the requested redisplay does happen eventually—after all the input has been processed.
On text terminals, suspending and resuming Emacs normally also refreshes the screen. Some terminal emulators record separate contents for display-oriented programs such as Emacs and for ordinary sequential display. If you are using such a terminal, you might want to inhibit the redisplay on resumption.
This variable controls whether Emacs redraws the entire screen after it
has been suspended and resumed. Non-nil means there is no need
to redraw, nil means redrawing is needed. The default is nil.