Bug 279516 – [css-transitions] `transition-behavior: allow-discrete` may not start a transition for a custom property

• Component: Animations
• Status: RESOLVED FIXED

[Antoine Quint]

Created attachment 472524 [details]
Test

Consider the attached test case which does the following:

    const target = document.body;
    target.style.setProperty("--foo", "10");
    getComputedStyle(target).getPropertyValue("--foo");
    target.style.transition = "--foo 1s allow-discrete";
    target.style.setProperty("--foo", "20");

This does not yield a transition. I believe this is because we enter the `transitionPropertiesContainAll` code path under `Styleable::updateCSSTransitions()` which fails to account for custom properties, or at least non-registered properties.

[Antoine Quint]

Created attachment 472525 [details]
Test with `transition-property: all`

Another failing test case, likely failing for the same reason.

[Antoine Quint]

"Test" only works in Firefox Nightly. The other test fails in Chrome, Firefox and Safari.

[Radar WebKit Bug Importer]

<rdar://problem/135805387>

[Antoine Quint]

Pull request: https://github.com/WebKit/WebKit/pull/33470

[EWS]

Committed 283498@main (ca687c87a080): <https://commits.webkit.org/283498@main>

Reviewed commits have been landed. Closing PR #33470 and removing active labels.

[Antoine Quint]

Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/48115

[EWS]

Committed 283286.73@safari-7620-branch (2d811327a267): <https://commits.webkit.org/283286.73@safari-7620-branch>

Reviewed commits have been landed. Closing PR #1822 and removing active labels.