[webkit-changes] [WebKit/WebKit] 7c2201: REGRESSION (263724 at main): Jumpiness and jitterines...

[Ryosuke Niwa]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 7c2201e62a9afb3da7a0f19e6bcd8bda1f0dd2e2
      https://github.com/WebKit/WebKit/commit/7c2201e62a9afb3da7a0f19e6bcd8bda1f0dd2e2
  Author: Ryosuke Niwa <rniwa at webkit.org>
  Date:   2023-06-07 (Wed, 07 Jun 2023)

  Changed paths:
    A LayoutTests/fast/scrolling/scroll-anchoring-after-page-load-expected.html
    A LayoutTests/fast/scrolling/scroll-anchoring-after-page-load.html
    M Source/WebCore/loader/FrameLoader.cpp
    M Source/WebCore/page/LocalFrameView.cpp
    M Source/WebCore/page/LocalFrameView.h

  Log Message:
  -----------
  REGRESSION (263724 at main): Jumpiness and jitteriness in scrolling on searchfox.org
https://bugs.webkit.org/show_bug.cgi?id=257576
<rdar://problem/110095194>

Reviewed by Simon Fraser.

The bug was caused by WebKit no longer clearing the scroll anchoring element upon page load completion.
This turned out to be not a Web compatible change.

Fix fast/dynamic/anchor-lock.html in another way by remembering to which node scrolling was scheduled
in LocalFrameView instead of relying on m_maintainScrollPositionAnchor to be not cleared upon page load
completion, which is not generally Web compatible.

* LayoutTests/fast/scrolling/scroll-anchoring-after-page-load-expected.html: Added.
* LayoutTests/fast/scrolling/scroll-anchoring-after-page-load.html: Added.
* Source/WebCore/loader/FrameLoader.cpp:
(WebCore::FrameLoader::completed):
* Source/WebCore/page/LocalFrameView.cpp:
(WebCore::LocalFrameView::scheduleScrollToAnchorAndTextFragment):
* Source/WebCore/page/LocalFrameView.h:

Canonical link: https://commits.webkit.org/264940@main