Bug 218842 – Force wheel event listeners on the root to be passive

• Component: UI Events
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

Follow Chrome:
   https://www.chromestatus.com/feature/6662647093133312
   https://developers.google.com/web/updates/2019/02/scrolling-intervention

and make wheel/mousewheel event listeners registered on the window/document/body to be passive, as we do for touch listeners.

[Radar WebKit Bug Importer]

<rdar://problem/71312668>

[Simon Fraser (smfr)]

Created attachment 413985 [details]
Patch

[Chris Dumez]

Comment on attachment 413985 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=413985&action=review

r=me with nits

> Source/WebCore/page/Quirks.cpp:818
> +        if (is<DOMWindow>(eventTarget))

I believe can can  simply do:
return downcast<Document>(eventTarget.scriptExecutionContext());

since we know here to EventTarget is a Window or a Node, and thus its script execution context has to be a Document.

> LayoutTests/fast/events/wheel/wheel-event-listeners-on-body-made-passive.html:26
> +                event.preventDefault();

In these tests, I would recommend checking event.defaultPrevented after calling preventDefault(). This is the easiest way to check if we are passive.

[Simon Fraser (smfr)]

Created attachment 413994 [details]
Patch

[Simon Fraser (smfr)]

Created attachment 414001 [details]
Patch

[Simon Fraser (smfr)]

https://trac.webkit.org/changeset/269780/webkit