[Webkit-unassigned] [Bug 184250] Unable to call event.preventDefault in dynamically added event listener

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=184250

Tadeu Zagallo <tzagallo at apple.com> changed:

           What    |Removed                     |Added
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                 CC|                            |tzagallo at apple.com
           Assignee|webkit-unassigned at lists.web |tzagallo at apple.com
                   |kit.org                     |

--- Comment #10 from Tadeu Zagallo <tzagallo at apple.com> ---
I think I finally understood how the behaviour actually changed. Dynamic touchmove listeners haven't been cancelable since iOS 10, so I couldn't find a minimal repro case at first, which was confusing, since the events *were* cancelable in the example provided here. What I realised was that the only reason the example worked in the first place was that there was already a touchmove listener on the document, added by React. So, before iOS 11.3, a touchmove event was cancelable as long as there was already one touchmove listener in the region of the touch. Since iOS 11.3, touchmove events cannot be prevented by dynamic listeners, regardless of whether there was already another listener. I have not yet identified what cause this regression though, but I'm working on that now that I have reduced the example.

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