bug#61667: 29.0.60; Failure to redisplay

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Dmitry Gutov <dgutov@yandex.ru> writes:

> On 02/03/2023 02:34, Po Lu wrote:
>> Dmitry Gutov<dgutov@yandex.ru>  writes:
>> 
>>> But blink-cursor-mode was on, of course. It's -Q: everything's on what
>>> was not turned off.
>>>
>>> And it turns out to be the reason for the difference between this and
>>> my personal config. With blink-cursor-mode off, the delay can reach
>>> multiple seconds like I previously reported.
>>>
>>> Attaching new recordings with b-c-m off, same naming scheme.
>>>
>>> x_set_title:*scratch*  - GNU Emacs at potemkin, 565346760276
>>> show_back_buffer: 565346918720
>>> show_back_buffer: 565347019580
>>> show_back_buffer: 565347025374
>>> show_back_buffer: 565347147607
>>> show_back_buffer: 565347299581
>>> show_back_buffer: 565347345317
>>> x_set_title: xassociations.rb - GNU Emacs at potemkin, 565347345457
>>> show_back_buffer: 565347355456
>>> show_back_buffer: 565353039484
>>>
>>> x_set_title:*scratch*  - GNU Emacs at potemkin, 565390536932
>>> show_back_buffer: 565390678689
>>> show_back_buffer: 565390747051
>>> show_back_buffer: 565390750166
>>> show_back_buffer: 565390875109
>>> show_back_buffer: 565391250430
>>> show_back_buffer: 565391380489
>>> show_back_buffer: 565391396116
>>> x_set_title: xassociations.rb - GNU Emacs at potemkin, 565391396257
>>> show_back_buffer: 565391404687
>>> show_back_buffer: 565397707089
>>>
>>> x_set_title:*scratch*  - GNU Emacs at potemkin, 565404022729
>>> show_back_buffer: 565404182867
>>> show_back_buffer: 565404241162
>>> show_back_buffer: 565404244561
>>> show_back_buffer: 565404369071
>>> show_back_buffer: 565404647259
>>> show_back_buffer: 565404666484
>>> x_set_title: xassociations.rb - GNU Emacs at potemkin, 565404666623
>>> show_back_buffer: 565404674305
>>> show_back_buffer: 565405233868
>> Thanks.  Unfortunately, now we're back to square one: all three logs are
>> identical, and I can't see any problems in Emacs.
>
> So... in both problematic cases is seems like there is a
> show_back_buffer call right after x_set_title, and yet it does not
> reflect on screen. Right?

Yes.

> And the next one (the last one) happens much later. From further
> testing, it seems to correlate to me typing 'C-x C-c', rather than to
> when the frame finally refreshes after the delay (for example, when I
> decide to stop waiting and hover with the mouse over the frame, or
> over the title bar buttons).

Indeed, that's what it seems like to me as well.

> 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.
Have you tried disabling GNOME Shell extensions one by one?  Maybe one
of them is responsible for this.