Re: RFC: flicker-free double-buffered Emacs under X11

[Eli Zaretskii]

> Cc: address@hidden, address@hidden
> From: Daniel Colascione <address@hidden>
> Date: Thu, 27 Oct 2016 12:56:41 -0700
> 
> why would we ever _want_ to allow redisplay to return 
> without having redrawn all garbaged frames? The design of redisplay 
> suggests that a postcondition on redisplay_internal should be that 
> there's nothing left to draw, at least in the case that we weren't 
> interrupted by input.

Not at that point in the code, which is before update_frame was
called.  In particular, the place that detects whether input is
available is inside update_frame.

IOW, redisplay is not going to return there, it is going to call
update_frame, which is the last stage of the redisplay cycle: it
delivers stuff to the glass as needed.