don't support sub-second timers for redisplay-preemption-period.
If this variable is @code{nil}, Emacs does not check for input during
redisplay, and redisplay cannot be preempted by input.
-This variable is only obeyed on graphical terminals, and is only
-available if Emacs is built with support for sub-second timers. For
-other platforms, see @ref{Terminal Output}.
+This variable is only obeyed on graphical terminals. For
+text terminals, see @ref{Terminal Output}.
@end defvar
@defvar redisplay-dont-pause