1704478 - Incorrect clipping on MDN mix-blend-mode example

Status: VERIFIED FIXED

(Core :: Graphics: WebRender, defect, P3)

Description

[Jamie Nicol [:jnicol] out of office until 6th Jan]

Attachment: mix-blend-bug.png

Visit https://developer.mozilla.org/en-US/docs/Web/CSS/mix-blend-mode#effect_of_different_mix-blend-mode_values and make the browser window narrow enough that the example becomes scrollable. Then drag the example's scrollbar downwards. The images move up the page and remain visible even when they should be clipped by the scrollable frame's bounds.

Mozregression shows this is regressed by bug 1684781

Comment 1

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

Set release status flags based on info from the regressing bug 1684781

Comment 2

[Ryan VanderMeulen [:RyanVM]]

Is this more likely to affect Mobile where a narrow viewport is the norm?

Comment 3

[Jamie Nicol [:jnicol] out of office until 6th Jan]

Yes, I initially noticed it browsing the page on my phone

Comment 4

[Ryan VanderMeulen [:RyanVM]]

Jim, are we sure this should be P3/S4 then? I'm wondering if this is used widely enough that it'd be an RC respin driver this week.

Comment 5

[Glenn Watson [:gw]]

Attachment: Bug 1704478 - Ensure clips are applied to root level blend containers.

When a root level blend container matches the criteria to be optimized
from a stacking context to a tile cache, we need to ensure that if
the source stacking context had any valid clips, they are propagated
to the shared clips applied by the tile cache.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7fc9de52af91
Ensure clips are applied to root level blend containers. r=gfx-reviewers,lsalzman

Comment 7

[Ryan VanderMeulen [:RyanVM]]

Please nominate this for release approval when you get a chance. Not sure it's enough to drive an RC respin, but it might still make a good ride-along for a dot release.

Comment 8

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/7fc9de52af91

Comment 9

[Glenn Watson [:gw]]

Comment on attachment 9215683 [details]
Bug 1704478 - Ensure clips are applied to root level blend containers.

Beta/Release Uplift Approval Request

• User impact if declined: Mix-blend containers that exist inside a nested scroll frame but no other stacking context containers (e.g. clips / filters / transforms) may render outside that nested scroll frame in some cases. (ryanvm suggested nominating this as a release approval).
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: Per bug report.
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): It's a small patch, only affects mix-blend containers, so it should be relatively low risk.
• String changes made/needed:

Comment 10

[Ryan VanderMeulen [:RyanVM]]

Comment on attachment 9215683 [details]
Bug 1704478 - Ensure clips are applied to root level blend containers.

Approved for 88.0rc2, thanks.

Comment 11

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-release/rev/a5ee4a4a2cc5

Comment 12

[Rares Doghi, Desktop QA]

This issue is Verified as fixed on Windows 10, Mac Osx and Ubuntu in our latest Firefox 88.0rc2 as well as our latest nightly build 89.0a1 (2021-04-15).

Comment 13

[Andrei Bodea[:andrei]]

Verified as fixed on the Firefox RC 88.1.1 with Google Pixel 4 XL (11), Samsung Galaxy S7 (7).