Subject: bug#61667: 29.0.60; Failure to redisplay

From: Gregory Heytings <[email-masked]>
Date: Sun, 26 Feb 2023 15:54:03 +0000

>>> To avoid this measurement affecting the delay itself, as we saw with 
>>> printfs and trace-redisplay, the timings should be sent via pipe to a 
>>> file, not to the screen.
>> 
>> If they indeed don't affect the measurement when they are sent to a 
>> file, it is probably possible to sent them to the screen without 
>> affecting the measurement, by calling 'tail -f' on the file in which 
>> they are recorded in another terminal.
>
> Yes, I suppose this can work, if the new terminal is positioned far away 
> from Emacs's window.
>
> None of the new proposed tests depend on me being able to monitor the 
> output in real time, though.
>

If you want to measure the latency between the moment an XFlush is issued 
by Emacs and the moment you actually see the buffer contents of the buffer 
on screen, I think you could screencast your repro and use the recorded 
video to make that measurement (unless screencasting eliminates the 
problem, too...).