[Webkit-unassigned] [Bug 230091] New: binding to a gesture event makes rendering go wrong on iOS 15

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=230091

            Bug ID: 230091
           Summary: binding to a gesture event makes rendering go wrong on
                    iOS 15
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: iPhone / iPad
                OS: Other
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: UI Events
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: wart.claes at gmail.com

We encountered some issues with the "gesturestart" and "gesturechange" events on iOS 15.

When tapping fast through the items on the page it happens that the box doesn't change color on the actual tap.
That color change will happen when you tap anywhere else on the screen.

It seems like the page doesn't re-render it correctly and by tapping again it triggers a paint to correct it.

If we remove the (empty) listeners of "gesturestart" and "gesturechange" the issue is resolved.

(removing one of them keeps the issue so I guess it's also possible that it happens on "gestureend")


Code example
------------
https://stackblitz.com/edit/js-g3qxtk


Test page
---------
https://js-g3qxtk.stackblitz.io


Steps to reproduce
------------------
1. Click in quick succession on Item 1 and then on Item 2
2. Item 1 will be green, Item 2 will still be red.
3. Click anywhere else and Item 2 will turn green.

This only happens on iOS 15 (beta 8 at the moment) and it did not occur on iOS 14.7.1

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