Bug 279514 – [css-transitions] `getKeyframes()` returns the same values for "from" and "to" with a custom property

• Component: Animations
• Status: RESOLVED FIXED

[Antoine Quint]

Created attachment 472522 [details]
Test

See the attached test case and notice how transitioning a custom property will yield a CSSTransition with the same reported value for the custom property for both the "from" and "to" keyframe. This simply can't be right, otherwise no transition would be created. It also appears that the computed style for the targeted element is incorrect, which could be the same underlying issue.

[Antoine Quint]

I think the issue is that we're lacking the equivalent of `ComputedStyleExtractor::valueForPropertyInStyle()` for custom properties and we're wrongly calling `ComputedStyleExtractor::customPropertyValue()` in the `customPropertyValue` lambda under `KeyframeEffect::getKeyframes()`. This means we'll only ever show the current computed value for the target element rather than the keyframe value.

[Radar WebKit Bug Importer]

<rdar://problem/135802510>

[Antoine Quint]

Pull request: https://github.com/WebKit/WebKit/pull/33468

[Antoine Quint]

Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/48103

[EWS]

Committed 283485@main (cd5cb9415972): <https://commits.webkit.org/283485@main>

Reviewed commits have been landed. Closing PR #33468 and removing active labels.

[EWS]

Committed 283286.69@safari-7620-branch (fedfc266a326): <https://commits.webkit.org/283286.69@safari-7620-branch>

Reviewed commits have been landed. Closing PR #1821 and removing active labels.