bug#61667: 29.0.60; Failure to redisplay

[Gregory Heytings]

> I redid the screencast using ffmpeg and x11grab, and it captures the 
> problem fine. See the last two attempts (out of 6) in this video:
>
> https://a.uguu.se/PThfScNL.webm
>
> Note I also added (insert "!") and (redisplay) so that it's easy to see 
> the exact moment "a" was pressed.

Thanks!  After seeing this, I'm now convinced that the problem is not a 
GNOME one, for two reasons:

1.  The effect of (insert "!") (redisplay) is immediately visible on 
screen.  Why would GNOME treat the effect of changing the buffer from 
*scratch* to xassociations.rb differently?

2. The delay is different with emacs -Q (13 frames in that video, which at 
25 FPS means 520 ms) and with your config.  Why would GNOME treat the same 
app differently depending on how it is configured?