Bug 224910 - REGRESSION (r276377): [ iOS, EWS ] scrollingcoordinator/ios/fixed-inside-sticky-no-stacking-context-2.html is a constant Image Failure
Summary: REGRESSION (r276377): [ iOS, EWS ] scrollingcoordinator/ios/fixed-inside-stic...
Status: RESOLVED FIXED
Alias: None
Product: WebKit
Classification: Unclassified
Component: Scrolling (show other bugs)
Version: WebKit Nightly Build
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Tim Nguyen (:ntim)
URL:
Keywords: InRadar
Depends on:
Blocks:
 
Reported: 2021-04-21 19:15 PDT by Robert Jenner
Modified: 2021-04-28 08:45 PDT (History)
7 users (show)

See Also:


Attachments
Expected, Actual, and Diff images for failing test. (5.54 KB, application/zip)
2021-04-21 19:16 PDT, Robert Jenner
no flags Details
Patch (2.44 KB, patch)
2021-04-28 00:04 PDT, Tim Nguyen (:ntim)
no flags Details | Formatted Diff | Diff
Patch (3.28 KB, patch)
2021-04-28 05:47 PDT, Tim Nguyen (:ntim)
no flags Details | Formatted Diff | Diff

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Description Robert Jenner 2021-04-21 19:15:40 PDT
scrollingcoordinator/ios/fixed-inside-sticky-no-stacking-context-2.html

is a constant Image failure on iOS, and is slowing down EWS queues. 

WEBKIT RESULTS HISTORY:
https://results.webkit.org/?suite=layout-tests&test=scrollingcoordinator%2Fios%2Ffixed-inside-sticky-no-stacking-context-2.html

EWS FAILURE:
https://ews-build.s3-us-west-2.amazonaws.com/iOS-14-Simulator-WK2-Tests-EWS/r426730-11881/results.html

IMAGE DIFF LINK:
https://build.webkit.org/results/Apple-iOS-14-Simulator-Release-WK2-Tests/r276393%20(1090)/scrollingcoordinator/ios/fixed-inside-sticky-no-stacking-context-2-diffs.html

Diff images are also attached to this bug below.
Comment 1 Robert Jenner 2021-04-21 19:16:53 PDT
Created attachment 426764 [details]
Expected, Actual, and Diff images for failing test.

Attaching images to this bug.
Comment 2 Robert Jenner 2021-04-21 19:28:23 PDT
Updated test expectations to Failure here to speed up EWS:
https://trac.webkit.org/changeset/276416/webkit
Comment 3 Robert Jenner 2021-04-21 19:46:06 PDT
Was able to reproduce the failure on iOS14 Simulator Release ToT using the following test:

run-webkit-tests --ios-simulator scrollingcoordinator/ios/fixed-inside-sticky-no-stacking-context-2.html -f

There are a lot of revisions that did not get built, so I'm not able to verify a regression point. However, it appears that changes to Scroll Snap at r276382 is the likely cause of the test's failure:
https://trac.webkit.org/changeset/276382/webkit
Comment 4 Radar WebKit Bug Importer 2021-04-21 19:51:23 PDT
<rdar://problem/76995693>
Comment 5 Martin Robinson 2021-04-22 08:49:45 PDT
I took a look at this and I think the culprit here might be r276377. The test starts passing after reverting that commit, but not after reverting r276382.
Comment 6 Ryan Haddad 2021-04-22 14:13:42 PDT
(In reply to Martin Robinson from comment #5)
> I took a look at this and I think the culprit here might be r276377. The
> test starts passing after reverting that commit, but not after reverting
> r276382.
Thanks for looking! I see the test uses "will-change: transform", so that is likely.
Comment 7 Tim Nguyen (:ntim) 2021-04-28 00:04:47 PDT
Created attachment 427242 [details]
Patch
Comment 8 Tim Nguyen (:ntim) 2021-04-28 05:47:02 PDT
Created attachment 427254 [details]
Patch
Comment 9 EWS 2021-04-28 08:45:07 PDT
Committed r276716 (237120@main): <https://commits.webkit.org/237120@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 427254 [details].