bug#61667: 29.0.60; Failure to redisplay

[Gregory Heytings]

> > Does that mean, then, that the refresh of the frame after the delay 
> > does not correspond to any buffer flushing on Emacs' part?
>
> Yes.  It sure sounds like a bug in the GNOME compositor now.

It doesn't.  The numbers are there, in front of you, and they clearly 
point to a problem in Emacs (the third column is the delta in 
milliseconds):

ERROR 1 | show_back_buffer |                  |  152
ERROR 1 | show_back_buffer |                  |   46
ERROR 1 | x_set_title      | xassociations.rb |    0
ERROR 1 | show_back_buffer |                  |   10
ERROR 1 | show_back_buffer |                  | 5684

ERROR 2 | show_back_buffer |                  |  130
ERROR 2 | show_back_buffer |                  |   16
ERROR 2 | x_set_title      | xassociations.rb |    0
ERROR 2 | show_back_buffer |                  |    8
ERROR 2 | show_back_buffer |                  | 6302

OKAY    | show_back_buffer |                  |  278
OKAY    | show_back_buffer |                  |   19
OKAY    | x_set_title      | xassociations.rb |    0
OKAY    | show_back_buffer |                  |    8
OKAY    | show_back_buffer |                  |  560