38.2 Forcing Redisplay

Emacs redisplay normally stops if input arrives, and does not happen at all if input is available before it starts. Most of the time, this is exactly what you want. However, you can prevent preemption by binding redisplay-dont-pause to a non-nil value.

Variable: redisplay-dont-pause

If this variable is non-nil, pending input does not prevent or halt redisplay; redisplay occurs, and finishes, regardless of whether input is available. This feature is available as of Emacs 21.

You can request a display update, but only if no input is pending, with (sit-for 0). To force a display update even when input is pending, do this:

(let ((redisplay-dont-pause t)) (sit-for 0))