Bug 229317

Summary:

Ancestors with opacity should not affect top layer elements

Product:

WebKit

Reporter:

Tim Nguyen (:ntim) <ntim>

Component:

Layout and Rendering

Assignee:

Tim Nguyen (:ntim) <ntim>

Status:

RESOLVED FIXED

Severity:

Normal

CC:

bfulgham, changseok, clopez, esprehn+autocc, ews-watchlist, fred.wang, glenn, koivisto, kondapallykalyan, pdr, simon.fraser, webkit-bug-importer, youennf, zalan

Priority:

Keywords:

InRadar

Version:

WebKit Nightly Build

Hardware:

Unspecified

OS:

Unspecified

Bug Depends on:

229350

Bug Blocks:

84635

Attachments:

Description	Flags
Patch	none

Description Tim Nguyen (:ntim) 2021-08-19 17:56:03 PDT

From: https://fullscreen.spec.whatwg.org/#new-stacking-layer

Ancestor elements with overflow, opacity, masks, etc. cannot affect it.

Comment 1 Tim Nguyen (:ntim) 2021-08-19 18:00:32 PDT

This needs a test too, unfortunately there's no WPT for this.

Comment 2 Radar WebKit Bug Importer 2021-08-19 23:23:53 PDT

<rdar://problem/82158248>

Comment 3 Tim Nguyen (:ntim) 2021-08-19 23:56:31 PDT

https://github.com/web-platform-tests/wpt/pull/30104

Comment 4 Tim Nguyen (:ntim) 2021-08-20 00:00:53 PDT

Created attachment 435945 [details]
Patch

Comment 5 EWS Watchlist 2021-08-20 00:01:55 PDT

This patch modifies the imported WPT tests. Please ensure that any changes on the tests (not coming from a WPT import) are exported to WPT. Please see https://trac.webkit.org/wiki/WPTExportProcess

Comment 6 EWS 2021-08-20 01:04:02 PDT

Committed r281299 (240723@main): <https://commits.webkit.org/240723@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 435945 [details].

Comment 7 Simon Fraser (smfr) 2021-08-20 11:43:49 PDT

Comment on attachment 435945 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=435945&action=review

> Source/WebCore/rendering/RenderLayerBacking.cpp:2435
> +    // Top layer elements should not be affected by parent elements opacity
> +    if (m_owningLayer.establishesTopLayer())
> +        return finalOpacity;

This seems like the wrong way to fix this. Here we're in compositing code, but don't we want to reset opacity in style? If for some reason we end up not using compositing for top layers, we'll get bad rendering.

Comment 8 Tim Nguyen (:ntim) 2021-08-20 13:51:25 PDT

(In reply to Simon Fraser (smfr) from comment #7)
> Comment on attachment 435945 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=435945&action=review
> 
> > Source/WebCore/rendering/RenderLayerBacking.cpp:2435
> > +    // Top layer elements should not be affected by parent elements opacity
> > +    if (m_owningLayer.establishesTopLayer())
> > +        return finalOpacity;
> 
> This seems like the wrong way to fix this. Here we're in compositing code,
> but don't we want to reset opacity in style? If for some reason we end up
> not using compositing for top layers, we'll get bad rendering.

I filed https://bugs.webkit.org/show_bug.cgi?id=229350