I am noticing that on my Windows 7 machine with an Intel integrated GPU, I am seeing rectangles of various sizes and position of the screen (including content and browser chrome) flicker occasionally, sometimes showing black and other times showing invalid content. The rectangles seem to vaguely be related to where the mouse is hovering (so may be invalidation related).

This seems to have only started in 69, and only happens with WebRender enabled. If I force the nvidia GPU on (this is an optimus laptop), it doesn't seem to happen. Disabling picture caching via pref seemed to have no effect on this.

It is possibly related to the flickering other people are reporting in this reddit thread: https://www.reddit.com/r/firefox/comments/czidkf/noticeably_worse_font_rendering_in_tab_titles/

Also worth noticing this is an i7-3720qm, which is Ivy Bridge. It looks like in the fix in https://phabricator.services.mozilla.com/D40354 that only Broadwell or Haswell were covered. If this bug is caused by that issue, then we probably want to just force it for any iGPU <= Broadwell?

It'd be worth checking if enabling that angle workaround fixes your issue - although in the case reported, it only affected picture caching tiles.

I think we've seen another bug report recently where we were seeing some black rectangles on Intel drivers after a recent update, and they were occurring on both WR and non-WR paths. Jeff might know which bug that was and/or what the status is?

We're you thinking of bug 1571340?

(In reply to Glenn Watson [:gw] from comment #2)

It'd be worth checking if enabling that angle workaround fixes your issue - although in the case reported, it only affected picture caching tiles.

I think we've seen another bug report recently where we were seeing some black rectangles on Intel drivers after a recent update, and they were occurring on both WR and non-WR paths. Jeff might know which bug that was and/or what the status is?

Enabling that workaround in angle fixes the issue for me, yes. So we should probably include ivy bridge, and maybe sandy bridge, ids in there?

Sounds reasonable to me - let's check with Jeff since it's an ANGLE change though.

Yeah, sounds great.

https://bugs.chromium.org/p/angleproject/issues/detail?id=3980
https://chromium-review.googlesource.com/c/angle/angle/+/1845664

This is going to be a pain to cherry-pick, because ANGLE's been churning the workaround code pretty hard. :(

https://hg.mozilla.org/mozilla-central/rev/4f11f3a676b2