[webkit-changes] [WebKit/WebKit] 32beea: Optimize Intersection Observer computations for in...

[Simon Fraser]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 32beea64ac2d217858f763d4ac4a877e093b7c13
      https://github.com/WebKit/WebKit/commit/32beea64ac2d217858f763d4ac4a877e093b7c13
  Author: Simon Fraser <simon.fraser at apple.com>
  Date:   2023-08-01 (Tue, 01 Aug 2023)

  Changed paths:
    M Source/WebCore/page/IntersectionObserver.cpp

  Log Message:
  -----------
  Optimize Intersection Observer computations for inlines
https://bugs.webkit.org/show_bug.cgi?id=259717
rdar://113238475

Reviewed by Ryosuke Niwa.

When computing intersections for RenderInlines, the code computed absolute quads for the RenderInline and
its continutations, then mapped those to local coordinates. What a waste!

Instead we can just compute those rectangles in local coordinates directly. This drops the time spent in
Document::updateIntersectionObservations() from 24% of the time to 14% of the time scrolling an amazon.com
search results page.

* Source/WebCore/page/IntersectionObserver.cpp:
(WebCore::IntersectionObserver::computeIntersectionState const):

Canonical link: https://commits.webkit.org/266501@main