[Webkit-unassigned] [Bug 195360] [iOS] Hit test for content overlapping fast-scrollable overflow

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=195360

Simon Fraser (smfr) <simon.fraser at apple.com> changed:

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--- Comment #6 from Simon Fraser (smfr) <simon.fraser at apple.com> ---
Comment on attachment 363739
  --> https://bugs.webkit.org/attachment.cgi?id=363739
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=363739&action=review

I think the first version of this patch needs at least to have a a bit that comes from the web process that says "does this layer contain some content that should participate in hit testing". It should lay the groundwork for the region-based approach (I don't think we can ship without that).

> Source/WebKit/UIProcess/RemoteLayerTree/ios/RemoteLayerTreeViews.mm:52
> +            if (view.layer.contents)
> +                return false;

We can make layer with no contents for empty divs (see isSimpleContainerCompositingLayer()), yet they should still intercept hit testing. In addition, there may be other views in the hierarchy which are there for structural purposes and should not participate in hit testing (e.g. a GraphicsLayer's m_structuralLayer).

I think you need to actually send data from the web process about which layers are hit-testable (and, in future, that data would include a region).

Also, a GraphicsLayer can paint one or more renderers which don't cover its entire area. Trivially, you can do this with box-shadow: 0 0 20px black to add layer padding that should not hit test. It can also happen with nested positioned elements.

Also, elements with pointer-events: none need to be ignored.

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