Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 98bcca039303cd9c62caf7e7d4543e6c2e6794e0
https://github.com/WebKit/WebKit/commit/98bcca039303cd9c62caf7e7d4543e6c2e6794e0
Author: Ben Nham <[email protected]>
Date: 2026-10-14 (Wed, 14 Oct 2026)
Changed paths:
M Source/WebCore/page/EventHandler.cpp
M Source/WebCore/page/EventHandler.h
M Source/WebCore/page/scrolling/ScrollLatchingController.cpp
M Source/WebCore/page/scrolling/ScrollLatchingController.h
M
Tools/TestWebKitAPI/Tests/WebKit/WKWebView/mac/ScrollingCoordinatorTests.mm
Log Message:
-----------
Avoid hit testing wheel events that continue a latched gesture
https://bugs.webkit.org/show_bug.cgi?id=327046
rdar://problem/189656485
Reviewed by Simon Fraser.
EventHandler::handleWheelEventInternal hit tests every wheel event. For events
that continue a
latched gesture (e.g. a Changed or Ended event, which is most of the events
during a scroll),
ScrollLatchingController replaces the hit test's results with the latched
state. So for most of the
events in a scroll gesture, the hit test is wasted work. The hit test also
forces a layout, which is
also extra work if the page changes layout again before the next rendering
update.
Optimize this by using the latched state without a hit test when it's safe,
i.e. when the event
continues a latched gesture with a latched scroller and doesn't scroll on the
main thread
(as scrolling on the main thread requires up-to-date layout).
On the macOS power benchmark, this reduces WebContent CPU usage by ~3%.
Test:
Tools/TestWebKitAPI/Tests/WebKit/WKWebView/mac/ScrollingCoordinatorTests.mm
* Source/WebCore/page/EventHandler.cpp:
(WebCore::EventHandler::fetchLatchedWheelEventTarget):
(WebCore::EventHandler::handleWheelEventInternal):
* Source/WebCore/page/EventHandler.h:
* Source/WebCore/page/scrolling/ScrollLatchingController.cpp:
(WebCore::ScrollLatchingController::fetchLatchedStateIfIndependentOfHitTest
const):
* Source/WebCore/page/scrolling/ScrollLatchingController.h:
* Tools/TestWebKitAPI/Tests/WebKit/WKWebView/mac/ScrollingCoordinatorTests.mm:
(TestWebKitAPI::waitForCondition):
(TestWebKitAPI::TEST(ScrollingCoordinatorTests,
LatchedWheelGestureIgnoresElementCoveringPointer)):
Canonical link: https://commits.webkit.org/323728@main
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