Bug 250387

Summary:	Using `rotate: x` and `transform: rotate(x)` yields different behavior with SVG
Product:	WebKit	Reporter:	Cory LaViska <cory>
Component:	Animations	Assignee:	Antoine Quint <graouts>
Status:	RESOLVED FIXED
Severity:	Normal	CC:	ahmad.saleem792, dino, graouts, graouts, karlcow, sabouhallawa, simon.fraser, webkit-bug-importer
Priority:	P2	Keywords:	BrowserCompat, InRadar
Version:	Safari 16
Hardware:	Unspecified
OS:	Unspecified
See Also:	https://github.com/web-platform-tests/wpt/pull/37933
Bug Depends on:
Bug Blocks:	250901

Description Cory LaViska 2023-01-10 07:37:06 PST

This was reported to me in Shoelace (https://github.com/shoelace-style/shoelace/issues/1121) after switching `transform: rotate(x)` to `rotate: x`. The spinner component suddenly started animating strangely, despite the values supposedly being equivalent. I've only been able to reproduce this in Safari.

I reduced the problem down to what seems like an issue with SVG elements, possibly limited to animating `stroke-dasharray`. The following CodePen example draws two SVGs. Both are identical, but the one on the left uses `rotate: x` and the one on the right uses `transform: rotate(x)`. The one on the left animates back and forth, whereas the one on the right animates the full circle.

https://codepen.io/claviska/pen/dyjvebY?editors=1100

I haven't been able to find other reports of this in the bug tracker. It happens in Safari 16 and TP (Release 160).

Comment 1 Ahmad Saleem 2023-01-11 07:34:20 PST

I am able to reproduce this bug in Safari 16.2 and Safari Technology Preview 160 using CodePen from Comment 0, while Chrome Canary 111 & Firefox Nightly 110 match each other and does not exhibit same error as Safari.

Comment 2 Antoine Quint 2023-01-13 03:04:22 PST

This seems to be specific to animation, static use of `rotate` and `transform: rotate()` yield similar results.

Comment 3 Antoine Quint 2023-01-13 04:20:11 PST

We fail to create a CSSAnimation for the "rotate" case while we do for the "transform" case. We must maintain a list somewhere of properties that are eligible for animation on SVG elements.

Comment 4 Antoine Quint 2023-01-13 04:40:30 PST

Actually, this was user error :) The problem is that when we get to LegacyRenderSVGShape::layout(), m_needsTransformUpdate is false. We most likely need to make LegacyRenderSVGModelObject::styleDidChange() aware of individual transform properties.

Comment 5 Antoine Quint 2023-01-13 07:11:12 PST

Pull request: https://github.com/WebKit/WebKit/pull/8620

Comment 6 Antoine Quint 2023-01-13 07:12:37 PST

Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/37933

Comment 7 EWS 2023-01-13 11:58:13 PST

Committed 258882@main (540afd688321): <https://commits.webkit.org/258882@main>

Reviewed commits have been landed. Closing PR #8620 and removing active labels.

Comment 8 Radar WebKit Bug Importer 2023-01-13 11:59:20 PST

<rdar://problem/104234342>