[Webkit-unassigned] [Bug 195378] Layer with no backing store should still hit-test over a scroller

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=195378

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

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--- Comment #5 from Simon Fraser (smfr) <simon.fraser at apple.com> ---
Comment on attachment 365028
  --> https://bugs.webkit.org/attachment.cgi?id=365028
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=365028&action=review

r- to fix the pointer-events toggle issue (if it happens to work, please add a test). Don't forget you can use immediateScrollElementAtContentPointToOffset now).

> Source/WebCore/rendering/RenderLayerBacking.cpp:768
> +        updateEventRegion();

Here you're assuming that a layer configuration update will always happen when something changes that affects where renderers are relative to their enclosing compositing layer. This assumption relies on the fact that RenderLayerBacking::setContentsNeedDisplay() calls setNeedsCompositingConfigurationUpdate(), but if future optimizations allow us to update layer configuration in fewer cases, that might break.

In fact, this might break now with something like:

  <div class="composited"><div id="child"></div>

and dynamic toggle of "pointer-events" style on child. That won't issue a repaint (hopefully) and won't update event regions.

You should also add a testcase that just moves elements around and tests event regions, so we can detect regressions caused by future compositing optimizations.

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