1757443 - Screen flickering on some D2L websites

Status: VERIFIED FIXED

(Core :: Layout, defect)

Description

[u673061]

See the attched screenshot
It happens on websites such as Brightspace
Console shows nothing useful other than
"[Elastic APM] Dropped events due to throttling!"

Comment 1

[u673061]

• screen recording https://ppp.woelkli.com/s/eGY4FDPZpgQptbJ
  (because the file is too big for bugzilla)

Comment 2

[u673061]

share password: ScreenFlicker1

Comment 3

[u673061]

Update: Still happening in Firefox 100, also reproduces on Android
Both with WebGPU on or off, Fission on or off or WebRender on or off
Even reproduces with a fresh desktop profile (macOS)

Don't know where is the right component to submit in......

Comment 4

[u673061]

It only happens in Firefox and I have tried Chrome and Safari and the screen does not flicker

Comment 5

[Jeff Muizelaar [:jrmuizel]]

I was able to reproduce on a trial instance: https://try.d2l.com

Comment 6

[Jeff Muizelaar [:jrmuizel]]

It looks like the flickering is being caused by a ResizeObserver

Comment 7

[Jeff Muizelaar [:jrmuizel]]

But the flickering/jiggling still happens even when script is paused...

Comment 8

[Emilio Cobos Álvarez (:emilio)]

[Tracking Requested - why for this release]: Pretty annoying, recent regression.

Mozregression says this was caused by bug 1733042, but that means it shouldn't be reproducible in current release / 98. Reporter says this happens in release so there's something weird going on. David, can you reproduce this in current release?

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1733042

Comment 10

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1757443 - Correctly account for padding in ResizeObserver content-box size for scrollable frames. r=boris,#layout-reviewers

See test.

Comment 11

[Emilio Cobos Álvarez (:emilio)]

Comment on attachment 9268311 [details]
Bug 1757443 - Correctly account for padding in ResizeObserver content-box size for scrollable frames. r=boris,#layout-reviewers

Beta/Release Uplift Approval Request

• User impact if declined: Comment 0
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: comment 0
• List of other uplifts needed: none
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Simple tweak to the logic introduced in the regressor bug, plus test.
• String changes made/needed: none

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ac3ac0c98d2f
Correctly account for padding in ResizeObserver content-box size for scrollable frames. r=boris,layout-reviewers

Comment 13

[Marian-Vasile Laza]

https://hg.mozilla.org/mozilla-central/rev/ac3ac0c98d2f

Comment 14

[Donal Meehan [:dmeehan]]

Comment on attachment 9268311 [details]
Bug 1757443 - Correctly account for padding in ResizeObserver content-box size for scrollable frames. r=boris,#layout-reviewers

Approved for 99.0b6. Thanks.

Comment 15

[Donal Meehan [:dmeehan]]

https://hg.mozilla.org/releases/mozilla-beta/rev/8356082f7623

Comment 16

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/33261 for changes under testing/web-platform/tests

Comment 17

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot

Comment 18

[Peter Magyari (Desktop QA)]

I have verified the fix on Win10, MacOS 11 and Ubuntu 20.04 using Firefox Nightly 100.0a1 (20220320213921) and Firefox Beta 99.0b6 (20220320185956)