[Webkit-unassigned] [Bug 215853] New: [iOS 14 Regression] updating easing on accelerated animation results in incorrect playback

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=215853

            Bug ID: 215853
           Summary: [iOS 14 Regression] updating easing on accelerated
                    animation results in incorrect playback
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: All
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Animations
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ldebeasi at gmail.com
                CC: dino at apple.com

Created attachment 407301

  --> https://bugs.webkit.org/attachment.cgi?id=407301&action=review

Code Reproduction

Updating the easing on an accelerated animation causes the animation to abruptly jump to the end.

Steps to Reproduce:

1. Open the attached code reproduction on iOS 14/STP.
2. Click "Play". The blue square should translate from left to right linearly.
3. Click "Play, but switch easing after a timeout". The blue square should translate from left to right, pause after a timeout, updating its easing, and then abruptly jump to the end.

Expected Behavior:
I would expect that after updating the easing the animation would smoothly play to the end.

Actual Behavior:
Upon updating the easing, the animation jumps to the end.

Additional Info:

1. I was only able to reproduce this on iOS 14/STP (iOS 14 beta 6 and STP 112 as of writing).
2. I was only able to reproduce this with accelerated animations. Animating background or margin results in the correct playback.
3. While the code reproduction uses Web Animations, some of our users have also noticed this bug when using CSS Animations.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20200826/23c54b87/attachment.htm>