[Webkit-unassigned] [Bug 182436] New: animation-play-state: paused causes very high cpu load because of style invalidation loop

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=182436

            Bug ID: 182436
           Summary: animation-play-state: paused causes very high cpu load
                    because of style invalidation loop
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Animations
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: steffen at deusch.me
                CC: dino at apple.com

Hello everyone,
when using animation-play-state: paused on an animated element and using a transition on a parent element, Safari, Safari TP and WebKit Nightly are suddenly recalculating styles all the time, causing a high cpu load. Opening the Web Inspector causes an even higher CPU load (using WebKit Nightly):

https://files.steffend.me/public/webkitbug/webkit-style-invalidation.html
Try to open the page in Safari and hover over the card. Then open the Web Inspector.
The same is happening in MobileSafari on iOS 11.2(.x), causing the battery to drain fast.

Next, try opening:
https://files.steffend.me/public/webkitbug/webkit-style-invalidation-playing.html
There, the issue doesn't happen, as the animation is not paused (also no high cpu usage in the Web Inspector).

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