[webkit-changes] [WebKit/WebKit] 2f9700: [UI-side compositing] Webpage going blank when nav...

[Nikos Mouchtaris]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 2f97007c9a1e30bf7b5df766ddd68ed029af4fd4
      https://github.com/WebKit/WebKit/commit/2f97007c9a1e30bf7b5df766ddd68ed029af4fd4
  Author: Nikolaos Mouchtaris <nmouchtaris at apple.com>
  Date:   2023-08-07 (Mon, 07 Aug 2023)

  Changed paths:
    A LayoutTests/fast/scrolling/programmatic-scroll-merge-delta-and-position-expected.html
    A LayoutTests/fast/scrolling/programmatic-scroll-merge-delta-and-position.html
    A LayoutTests/fast/scrolling/programmatic-scroll-merge-delta-expected.html
    A LayoutTests/fast/scrolling/programmatic-scroll-merge-delta.html
    A LayoutTests/fast/scrolling/programmatic-scroll-merge-position-and-delta-expected.html
    A LayoutTests/fast/scrolling/programmatic-scroll-merge-position-and-delta.html
    M Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.cpp

  Log Message:
  -----------
  [UI-side compositing] Webpage going blank when navigating diffs in https://whatpr.org/html/9537/238086f...f400a41/canvas.html#drawing-state
https://bugs.webkit.org/show_bug.cgi?id=259813
rdar://113366817

Reviewed by Simon Fraser and Cameron McCormack.

When getting multiple non-animated scroll requests, the current merging code loses the previous
scroll request if a new delta update comes in. To resolve this, add the two scroll requests together
if either or both are a delta update. Added a couple new tests for this since the tests in
imported/w3c/web-platform-tests/css/cssom-view/scroll-behavior-* do not cover this since they
are testing the web process position.

* Source/WebCore/page/scrolling/ScrollingCoordinatorTypes.cpp:
(WebCore::RequestedScrollData::merge):

Canonical link: https://commits.webkit.org/266646@main