CSS Animations: Adjust auto z-index when animating perspective

CSS Animations: Adjust z-index when animating perspective

Styles generated by animations and transitions are currently applied
following adjustment (to avoid triggering transitions on adjustment).

Special handling existed for mirroring the adjustment behavior of
auto z-index when animating transform, however this failed to account
for animations of perspective. This has been broken as far back as
I am able to bisect and remains broken in WebKit for the same reason.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170498

[dstockwell, 2014-03-31 06:07:55]

Need to look into breaking adjustment into phases or moving the transition
impacting parts (eg. intrinsic margins) to the UA stylesheet to prevent more
issues like this.

[rune, 2014-03-31 09:00:06]

lgtm

I take this is a subset of what's done in StyleAdjuster::adjustRenderStyle?
Aren't there more cases from that method which need to be catered for?

You can have step transitions on visibility, display, float etc? Will they work
correctly?

[esprehn, 2014-03-31 09:16:37]

I don't think this is the right approach, we really need to run the style
adjuster after animations. I suspect there's a bunch of security bugs
hiding in there too since you allow the animation engine to make styles
appear in places we don't expect them.

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[dstockwell, 2014-03-31 09:40:09]

On 2014/03/31 09:00:06, rune - CET wrote:
> lgtm
> 
> I take this is a subset of what's done in StyleAdjuster::adjustRenderStyle?
> Aren't there more cases from that method which need to be catered for?
> 
> You can have step transitions on visibility, display, float etc? Will they
work
> correctly?

display and float are not animatable from CSS. The Web Animations implementation
doesn't enable any new properties yet.


On 2014/03/31 09:16:37, esprehn wrote:
> I don't think this is the right approach, we really need to run the style
> adjuster after animations. I suspect there's a bunch of security bugs
> hiding in there too since you allow the animation engine to make styles
> appear in places we don't expect them.

Agreed. I'd like for adjustment to happen after animations. I noted a couple of
possible alternatives in the message above. Are you OK with landing this to fix
the issue in the short term?

This wart has been around since 2008: http://trac.webkit.org/changeset/35207

[dstockwell, 2014-03-31 23:21:03]

The CQ bit was checked by dstockwell@chromium.org

[commit-bot: I haz the power, 2014-03-31 23:21:07]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dstockwell@chromium.org/219013002/1

[commit-bot: I haz the power, 2014-04-01 00:18:03]

Change committed as 170498