Bug 148384 – Wheel events stop propagating when target element is removed from DOM

• Status: RESOLVED
• Resolution: FIXED
• Component: Layout and Rendering

[Brent Fulgham]

When listening to the ‘wheel’ or ‘mousewheel’ event on the document, if the event’s original target element is removed from the DOM the wheel event is no longer dispatched. 

1. Add a listener for ‘wheel’ on the document that removes the target of the event from the DOM. Have this happen after the element moves a specific amount or a certain number of events is received.
2. Scroll on the page (over the relevant element)
3. Keep scrolling

You will observe that the DOM event is no longer dispatched.

[Brent Fulgham]

<rdar://problem/19732211>

[Brent Fulgham]

Created attachment 259762 [details]
Patch

[Tim Horton]

Comment on attachment 259762 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=259762&action=review

> Source/WebCore/page/mac/EventHandlerMac.mm:919
> +        return false;

Frames can be removed...

> Source/WebCore/page/mac/EventHandlerMac.mm:922
> +        return true;

Anonymous nodes can't be scrollable? (probably true)

> Source/WebCore/page/mac/EventHandlerMac.mm:925
> +        return true;

What if a node is moved around in the DOM? (removed and reinserted before we get here) Is that OK?

[Brent Fulgham]

Comment on attachment 259762 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=259762&action=review

>> Source/WebCore/page/mac/EventHandlerMac.mm:925
>> +        return true;
> 
> What if a node is moved around in the DOM? (removed and reinserted before we get here) Is that OK?

It does seem like it would be a problem if we removed a node from one scrolling container, and inserted it into a new location. In that case, even with this code, we would start our event handling with this "migrated" node.

Maybe it would be better to just break the caching state in Element::removedFrom.

[Brent Fulgham]

Created attachment 259786 [details]
Patch

[Brent Fulgham]

Created attachment 259797 [details]
Patch

[Dave Hyatt]

Comment on attachment 259797 [details]
Patch

r=me

[Brent Fulgham]

Committed r188920: <http://trac.webkit.org/changeset/188920>