Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 80a7823219fb525f15d436935a4ae307db098e68
https://github.com/WebKit/WebKit/commit/80a7823219fb525f15d436935a4ae307db098e68
Author: Ahmad Saleem <[email protected]>
Date: 2026-05-11 (Mon, 11 May 2026)
Changed paths:
M LayoutTests/TestExpectations
M Source/WebCore/style/values/will-change/StyleWillChange.cpp
Log Message:
-----------
[CSS will-change] -webkit-perspective should establish a containing block for
fixed positioned descendants
https://bugs.webkit.org/show_bug.cgi?id=314509
rdar://176729670
Reviewed by Antti Koivisto.
This patch aligns WebKit with Gecko / Firefox and Blink / Chromium.
Per https://drafts.csswg.org/css-will-change/#will-change, if any non-initial
value of a
property would cause the element to generate a containing block for
fixed-position
descendants, specifying that property in `will-change` must do the same.
`-webkit-perspective` is a legacy alias of `perspective`, and a non-initial
value of
`perspective` establishes a containing block for fixed positioned descendants.
Therefore
`will-change: -webkit-perspective` must as well.
`Style::WillChangeAnimatableFeatures::Data::createsContainingBlockForOutOfFlowPositioned`
already accounts for `CSSPropertyPerspective` but was missing the `-webkit-`
alias. The
neighbouring `propertyCreatesStackingContext()` already handles both aliases,
so this
fixes the parallel gap on the containing-block side.
* LayoutTests/TestExpectations: Progression
* Source/WebCore/style/values/will-change/StyleWillChange.cpp:
(WebCore::Style::WillChangeAnimatableFeatures::Data::createsContainingBlockForOutOfFlowPositioned
const):
Canonical link: https://commits.webkit.org/313020@main
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