One other thing, it may be related to tab-bar mode. It seems to be
connected to when I switch tabs — one tab has a vterm buffer scrolling
output and the other just has a grep output, for example. If I don't get
the flicker in the grep output, I can switch back and forth between the two
tabs a couple times and I'll start to get it.


Aaron


On Sat, Mar 15, 2025 at 11:03 PM, Aaron Jensen <aaronjensen@gmail.com>
wrote:

> On Sat, Mar 15, 2025 at 9:43 PM, Gerd Möllmann <gerd.moellmann@gmail.com>
> wrote:
>
> Aaron Jensen <aaronjensen@gmail.com> writes:
>
> Adding Gerd Möllmann.
>
> The flicker appears to have been introduced by the work done in
> 414de92a562
>
> Initial child frames based on master (Mon Oct 21 18:32:04 2024 +0200, 5
> months ago) <Gerd Möllmann>
>
> It's a fairly large change set, so I don't know yet what might be causing
> it. I can reproduce it fairly consistently using my own setup, but I don't
> know how to narrow it down to something from Emacs -Q because it appears to
> be related to CPU utilization and/or rapid updating of buffers that are not
> currently visible.
>
> Aaron
>
> On Sat, Mar 15, 2025 at 9:49 AM, Aaron Jensen <aaronjensen@gmail.com>
> wrote:
>
> Here's a video clip: https://share.cleanshot.com/x8zWLgYf
>
> It seems to happen more often when there is significant load. In this
> case, I was running an 8 worker web server in a vterm in Emacs and a set of
> 8 parallel UI tests against it. The server was printing log messages at a
> rapid rate, but that vterm buffer was not visible.
>
> Aaron
>
> I'm afraid I have not the slightest idea.
>
> 414de92a562 concerns only ttys, AFAICT. I've looked through the commit
> again right now. The changes to NS code directly are only trivial ones
> (1 -> true, 0 -> false etc.). So it would have to be something in
> redisplay_internal or something similar, in code not specific to NS that is
> used on all window systems, and I don't see a change there that could cause
> something with the symptoms you describe.
>
> Adding Alan Third in CC. Maybe he has an idea.
>
>
> I'll try and eliminate aspects of the patch as best as I can. If this is,
> in fact, a macOS only issue, then it may be that the particular method of
> drawing the windows in macOS is susceptible to some change that was made
> here. No idea what it could be, either. I do see that the NS-specific
> changes appear to be innocuous.
>