[webkit-changes] [WebKit/WebKit] c74949: InteractionRegions: refine the overlay heuristic

[Commit Queue]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: c749494c731ac6dde55999f9a65983d053bf8197
      https://github.com/WebKit/WebKit/commit/c749494c731ac6dde55999f9a65983d053bf8197
  Author: Etienne Segonzac <sgz at apple.com>
  Date:   2023-06-08 (Thu, 08 Jun 2023)

  Changed paths:
    M LayoutTests/interaction-region/overlay-expected.txt
    M LayoutTests/interaction-region/overlay.html
    M Source/WebCore/page/InteractionRegion.cpp

  Log Message:
  -----------
  InteractionRegions: refine the overlay heuristic
https://bugs.webkit.org/show_bug.cgi?id=257851
<rdar://109538187>

Reviewed by Tim Horton.

Use `position: fixed` as a signal for InteractionRegion occlusion
layers, as fixed content can easily be overlaid on other regions.
It might come from an ancestor that doesn't paint. To avoid generating
occlusion layers for every element in a `position: fixed` container, we
only look at ancestors with the same absolute content box.

* Source/WebCore/page/InteractionRegion.cpp:
(WebCore::interactionRegionForRenderedRegion):
(WebCore::isOverlay):
Extract the overlay detection in its own function.

* LayoutTests/interaction-region/overlay-expected.txt:
* LayoutTests/interaction-region/overlay.html:
Update test to cover all heuristics.

Canonical link: https://commits.webkit.org/264990@main