[Webkit-unassigned] [Bug 235576] New: REGRESSION: Element with position: sticky goes past the sticky point before sticking

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=235576

            Bug ID: 235576
           Summary: REGRESSION: Element with position: sticky goes past
                    the sticky point before sticking
           Product: WebKit
           Version: Safari 15
          Hardware: iPhone / iPad
                OS: iOS 15
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Scrolling
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: augus.dupin at gmail.com
                CC: simon.fraser at apple.com

Created attachment 449918

  --> https://bugs.webkit.org/attachment.cgi?id=449918&action=review

Testcase

Since iOS 15, elements with `position: sticky` inside a scroll container other than the page can go past the sticky point "in a flash" (probably just one frame), when scrolling quickly in that direction, then go back to the sticky point.

The expected behaviour would be that the element sticks to the point defined by the `top`/`bottom`/`left`/`right` property value, and not go past that point.

See the attached testcase and video.

The yellow sticky element should not go past the green line (positioned at 100px from the top), but we can see that it crosses it when scrolling (we can see frames with yellow above the green line, and can see that the "Hello" text flashes when the element is supposed to stick).

Steps to reproduce:
- open the testcase
- scroll down to the yellow element
- scroll quickly up and down so that the element touches the green line without lifting your finger
You should see the yellow element cross the green line.

Might be related to:
https://bugs.webkit.org/show_bug.cgi?id=231953
https://bugs.webkit.org/show_bug.cgi?id=234500

-- 
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/20220125/850e07cc/attachment.htm>