[webkit-reviews] review denied: [Bug 101303] Fixed position elements that are out of view still end up forcing non-threaded scrolling : [Attachment 172642] Patch

[bugzilla-daemon at webkit.org]

Simon Fraser (smfr) <simon.fraser at apple.com> has denied Beth Dakin
<bdakin at apple.com>'s request for review:
Bug 101303: Fixed position elements that are out of view still end up forcing
non-threaded scrolling
https://bugs.webkit.org/show_bug.cgi?id=101303

Attachment 172642: Patch
https://bugs.webkit.org/attachment.cgi?id=172642&action=review

------- Additional Comments from Simon Fraser (smfr) <simon.fraser at apple.com>
View in context: https://bugs.webkit.org/attachment.cgi?id=172642&action=review


> Source/WebCore/page/scrolling/ScrollingCoordinator.cpp:279
> +	   bool layerIsInsideViewport =
layer->absoluteBoundingBox().intersects(IntRect(IntPoint(frameView->scrollOffse
tForFixedPosition()), frameView->layoutSize()));

Checking absoluteBoundingBox() isn't sufficient: you can have a 0x0 fixedpos
with an abspos child.

Is hasNonLayerFixedObjects() called after every layout, so it can update at the
right time?

I also think this should share some code with
RenderLayerCompositor::requiresCompositingForPosition(), since if that's
correct, we should never have a visible fixedpos element that is visible.