Changeset 286999 in webkit

Timestamp:

Dec 13, 2021, 5:50:21 PM (5 years ago)

Author:

timothy_horton@apple.com

Message:

Momentum Event Dispatcher: Excessive "kick" at the beginning of scrolling (especially on 60fps displays)
​https://bugs.webkit.org/show_bug.cgi?id=234279
<rdar://problem/86425321>

Reviewed by Simon Fraser.

• WebProcess/WebPage/MomentumEventDispatcher.cpp:

(WebKit::MomentumEventDispatcher::handleWheelEvent):
(WebKit::MomentumEventDispatcher::didStartMomentumPhase):
Instead of back-dating the animation to try to acquire a momentum-start
delta, pass the one we got from the event through, and start the animation
curve at momentum-start time. Also, critically, inset ourselves along
the curve by the amount of that initial delta (since the time starts now).

Tested at both 60fps and 120fps, this significantly smooths out the
transition from fingers-down phase to the generated momentum phase,
avoiding the overly large initial delta.

• WebProcess/WebPage/MomentumEventDispatcher.h:

Location:

trunk/Source/WebKit

Files:

• ChangeLog (modified) (1 diff)
• WebProcess/WebPage/MomentumEventDispatcher.cpp (modified) (3 diffs)
• WebProcess/WebPage/MomentumEventDispatcher.h (modified) (1 diff)

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2021-12-13  Tim Horton  <timothy_horton@apple.com>
+
+        Momentum Event Dispatcher: Excessive "kick" at the beginning of scrolling (especially on 60fps displays)
+        https://bugs.webkit.org/show_bug.cgi?id=234279
+        <rdar://problem/86425321>
+
+        Reviewed by Simon Fraser.
+
+        * WebProcess/WebPage/MomentumEventDispatcher.cpp:
+        (WebKit::MomentumEventDispatcher::handleWheelEvent):
+        (WebKit::MomentumEventDispatcher::didStartMomentumPhase):
+        Instead of back-dating the animation to try to acquire a momentum-start
+        delta, pass the one we got from the event through, and start the animation
+        curve at momentum-start time. Also, critically, inset ourselves along
+        the curve by the amount of that initial delta (since the time starts now).
+
+        Tested at both 60fps and 120fps, this significantly smooths out the
+        transition from fingers-down phase to the generated momentum phase,
+        avoiding the overly large initial delta.
+
+        * WebProcess/WebPage/MomentumEventDispatcher.h:
+
 2021-12-13  J Pascoe  <j_pascoe@apple.com>
 

trunk/Source/WebKit/WebProcess/WebPage/MomentumEventDispatcher.cpp

@@ -101 +101 @@
     }
 
-    if (event.phase() == WebWheelEvent::PhaseEnded)
-        m_lastEndedEventTimestamp = event.ioHIDEventTimestamp();
-
     if (eventShouldStartSyntheticMomentumPhase(pageIdentifier, event))
         didStartMomentumPhase(pageIdentifier, event);
@@ -191 +188 @@
     tracePoint(SyntheticMomentumStart);
 
-    auto momentumStartInterval = event.ioHIDEventTimestamp() - m_lastEndedEventTimestamp;
-
     m_currentGesture.active = true;
     m_currentGesture.pageIdentifier = pageIdentifier;
     m_currentGesture.initiatingEvent = event;
     m_currentGesture.currentOffset = { };
-    m_currentGesture.startTime = MonotonicTime::now() - momentumStartInterval;
+    m_currentGesture.startTime = MonotonicTime::now();
     m_currentGesture.displayNominalFrameRate = displayProperties->nominalFrameRate;
     m_currentGesture.accelerationCurve = [&] () -> std::optional<ScrollingAccelerationCurve> {
@@ -214 +209 @@
     buildOffsetTableWithInitialDelta(*event.rawPlatformDelta() * idealCurveMultiplier);
 
-    dispatchSyntheticMomentumEvent(WebWheelEvent::PhaseBegan, consumeDeltaForCurrentTime());
+    WebCore::FloatSize consumedDelta = event.delta();
+    if (m_currentGesture.initiatingEvent->directionInvertedFromDevice())
+        consumedDelta.scale(-1);
+    m_currentGesture.currentOffset += consumedDelta;
+    
+    dispatchSyntheticMomentumEvent(WebWheelEvent::PhaseBegan, event.delta());
 }
 

trunk/Source/WebKit/WebProcess/WebPage/MomentumEventDispatcher.h

@@ -124 +124 @@
 
     std::optional<WallTime> m_lastScrollTimestamp;
-    WallTime m_lastEndedEventTimestamp;
     std::optional<WebWheelEvent> m_lastIncomingEvent;
     WebCore::RectEdges<bool> m_lastRubberBandableEdges;