[webkit-changes] [WebKit/WebKit] 373d24: REGRESSION (263946 at main): Scroll momentum broken

[Simon Fraser]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 373d24af71c6ad6f1c03e521fa42de23dc98490a
      https://github.com/WebKit/WebKit/commit/373d24af71c6ad6f1c03e521fa42de23dc98490a
  Author: Simon Fraser <simon.fraser at apple.com>
  Date:   2023-05-13 (Sat, 13 May 2023)

  Changed paths:
    M Source/WebCore/PAL/pal/HysteresisActivity.h
    M Tools/TestWebKitAPI/TestWebKitAPI.xcodeproj/project.pbxproj
    A Tools/TestWebKitAPI/Tests/WebCore/HysteresisActivityTests.cpp

  Log Message:
  -----------
  REGRESSION (263946 at main): Scroll momentum broken
https://bugs.webkit.org/show_bug.cgi?id=256748
rdar://109274749

Reviewed by Chris Dumez.

After 263946 at main, reading HysteresisActivity::state() inside of the `started` callback, triggered
from a call to HysteresisActivity::impulse() returned HysteresisState::Stopped when it should have
returned HysteresisState::Started. This is because we no longer toggled m_active to true, and the
time wasn't started yet.

Fix by toggling m_active to true around the callback. I tried just swapping ordering with the timer
start, but that also caused in behavior changes, as indicated by the new API tests.

Add a set of API tests for HysteresisActivity so we don't mess up again in future.

* Source/WebCore/PAL/pal/HysteresisActivity.h:
(PAL::HysteresisActivity::impulse):
* Tools/TestWebKitAPI/TestWebKitAPI.xcodeproj/project.pbxproj:
* Tools/TestWebKitAPI/Tests/WebCore/HysteresisActivityTests.cpp: Added.
(TestWebKitAPI::TEST):

Canonical link: https://commits.webkit.org/264049@main