[Webkit-unassigned] [Bug 176458] New: Trackpad keeps causing spurious scroll to top

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=176458

            Bug ID: 176458
           Summary: Trackpad keeps causing spurious scroll to top
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Macintosh
                OS: macOS 10.13
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ashley at scirra.com
                CC: bfulgham at webkit.org, simon.fraser at apple.com,
                    zalan at apple.com

We are developing Construct 3, a game development IDE in the browser. We have found that in one case scrolling with the trackpad in Safari keeps causing a spurious scroll event to Y = 0 (so it jumps back to the top). Trackpad scrolling happens normally until the momentum scrolling comes to a rest, and then the spurious scroll happens.

To reproduce:
1) Visit https://editor.construct.net/?skip-support-check
2) Click "New project"
3) Click "Create"
4) The main view is probably all grey because it's scrolled to the top. Try scrolling down. You should see a white area come in to view.
5) Stop scrolling and let the momentum scroll come to a rest.

Expected result: view remains where it is
Observed result: view scrolls back to top

This does not reproduce in Chrome or Firefox. I've tried to find a way to work around it, but it happens so much that ignoring scroll events to Y=0 completely blocks the ability to scroll.

This bug will block us from supporting Safari with our PWA.

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