RESOLVED DUPLICATE of bug 201048 204805
CSS animation skip frames if a sibling slot and/or assigned element is removed during animation 
https://bugs.webkit.org/show_bug.cgi?id=204805
Summary CSS animation skip frames if a sibling slot and/or assigned element is remove...
Tim Guan-tin Chien [:timdream]
Reported 2019-12-03 11:42:09 PST
Created attachment 384730 [details] slotted-element-animation.html STR: See test case slotted-element-animation.html. Expected result: I should see the same animation as the test case slotted-element-animation-no-sr.html Actual: Frames are skipped for quite some time on the test case. The element no longer animates. Note: Chrome and Firefox works fine. Version: STP Release 96 (Safari 13.1, WebKit 14609.1.9.7) macOS 10.14.6 (18G1012)
Attachments
slotted-element-animation.html (1.51 KB, text/html)
2019-12-03 11:42 PST, Tim Guan-tin Chien [:timdream] 		no flags
Details
slotted-element-animation-no-sr.html (1.08 KB, text/html)
2019-12-03 11:42 PST, Tim Guan-tin Chien [:timdream] 		no flags
Details
test case that reproes the bug without any shadow trees (991 bytes, text/html)
2020-02-03 04:08 PST, Antti Koivisto 		no flags
Details
wip (5.15 KB, patch)
2020-02-03 06:10 PST, Antti Koivisto 		no flags
DetailsFormatted DiffDiff
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Tim Guan-tin Chien [:timdream]
Comment 1 2019-12-03 11:42:25 PST
Created attachment 384731 [details] slotted-element-animation-no-sr.html
Radar WebKit Bug Importer
Comment 2 2019-12-03 11:42:51 PST
<rdar://problem/57597579>
Antoine Quint
Comment 3 2019-12-03 13:34:01 PST
Sounds similar to bug 201048.
Antti Koivisto
Comment 4 2020-02-03 02:04:36 PST
This only happens with pure accelerated animations. Adding a color animation to the test case makes it work.
Antti Koivisto
Comment 5 2020-02-03 02:37:46 PST
The underlying problem seems to be that we tear down and reconstruct the renderer when an animation is in progress but then fail to restart the animation on the new renderer/layer. Slots and shadow trees are incidental, they just trigger the wider-than-usual teardown.
Antti Koivisto
Comment 6 2020-02-03 02:46:32 PST
Though it would also be good to avoid overly wide render tree updates on slot changes.
Antti Koivisto
Comment 7 2020-02-03 04:08:03 PST
Created attachment 389498 [details] test case that reproes the bug without any shadow trees
Antti Koivisto
Comment 8 2020-02-03 04:09:15 PST
This test case sets ::first-letter on body to cause render tree rebuild and break the accelerated animation. Works fine in Firefox and Chrome.
Antti Koivisto
Comment 9 2020-02-03 06:10:50 PST
Created attachment 389502 [details] wip
Antti Koivisto
Comment 10 2020-02-03 06:55:06 PST
The patch also fixes 204805, duping to the older bug. *** This bug has been marked as a duplicate of bug 201048 ***
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