Changeset 277587 in webkit

Timestamp:

May 17, 2021, 10:59:47 AM (5 years ago)

Author:

Simon Fraser

Message:

Allow wheel events to be coalesced during scroll deceleration
​https://bugs.webkit.org/show_bug.cgi?id=225834
<rdar://70402512>

Reviewed by Tim Horton.

When scrolling slows down towards the tail end of a momentum scroll, we can reduce our
commit frequency to save power, but we only want to do this on displays whose refresh rate
is higher than the default "update rendering" frequency.

We do this by leveraging the existing WebWheelEventCoalescer, which coalesces events
in the UI process. It tracks time since previous event, and coalesces when the
instantaneous velocity is less than 320 points per second (matching other frameworks
on the system).

WebWheelEventCoalescer needs to know when to enable coalescing, which it computes
on creation, and when the window is moved to a different screen with potentially
a different refresh rate.

• Shared/WebWheelEventCoalescer.cpp:

(WebKit::WebWheelEventCoalescer::isInMomentumPhase):
(WebKit::WebWheelEventCoalescer::shouldDispatchEvent):

• Shared/WebWheelEventCoalescer.h:

(WebKit::WebWheelEventCoalescer::shouldCoalesceEventsDuringDeceleration const):
(WebKit::WebWheelEventCoalescer::setShouldCoalesceEventsDuringDeceleration):

• UIProcess/WebPageProxy.cpp:

(WebKit::WebPageProxy::wheelEventCoalescer):
(WebKit::WebPageProxy::shouldCoalesceWheelEventsDuringDeceleration const):
(WebKit::WebPageProxy::windowScreenDidChange):

• UIProcess/WebPageProxy.h:

Location:

trunk/Source/WebKit

Files:

• ChangeLog (modified) (1 diff)
• Shared/WebWheelEventCoalescer.cpp (modified) (4 diffs)
• Shared/WebWheelEventCoalescer.h (modified) (3 diffs)
• UIProcess/WebPageProxy.cpp (modified) (2 diffs)
• UIProcess/WebPageProxy.h (modified) (1 diff)

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2021-05-14  Simon Fraser  <simon.fraser@apple.com>
+
+        Allow wheel events to be coalesced during scroll deceleration
+        https://bugs.webkit.org/show_bug.cgi?id=225834
+        <rdar://70402512>
+
+        Reviewed by Tim Horton.
+
+        When scrolling slows down towards the tail end of a momentum scroll, we can reduce our
+        commit frequency to save power, but we only want to do this on displays whose refresh rate
+        is higher than the default "update rendering" frequency.
+
+        We do this by leveraging the existing WebWheelEventCoalescer, which coalesces events
+        in the UI process. It tracks time since previous event, and coalesces when the
+        instantaneous velocity is less than 320 points per second (matching other frameworks
+        on the system).
+
+        WebWheelEventCoalescer needs to know when to enable coalescing, which it computes
+        on creation, and when the window is moved to a different screen with potentially
+        a different refresh rate.
+
+        * Shared/WebWheelEventCoalescer.cpp:
+        (WebKit::WebWheelEventCoalescer::isInMomentumPhase):
+        (WebKit::WebWheelEventCoalescer::shouldDispatchEvent):
+        * Shared/WebWheelEventCoalescer.h:
+        (WebKit::WebWheelEventCoalescer::shouldCoalesceEventsDuringDeceleration const):
+        (WebKit::WebWheelEventCoalescer::setShouldCoalesceEventsDuringDeceleration):
+        * UIProcess/WebPageProxy.cpp:
+        (WebKit::WebPageProxy::wheelEventCoalescer):
+        (WebKit::WebPageProxy::shouldCoalesceWheelEventsDuringDeceleration const):
+        (WebKit::WebPageProxy::windowScreenDidChange):
+        * UIProcess/WebPageProxy.h:
+
 2021-05-17  Peng Liu  <peng.liu6@apple.com>
 

trunk/Source/WebKit/Shared/WebWheelEventCoalescer.cpp

@@ -30 +30 @@
 #include "NativeWebWheelEvent.h"
 #include "WebEventConversion.h"
+#include <WebCore/AnimationFrameRate.h>
 #include <wtf/text/TextStream.h>
 
@@ -87 +88 @@
 }
 
+bool WebWheelEventCoalescer::isMomentumPhaseEvent(const WebWheelEvent& event)
+{
+    return event.phase() == WebWheelEvent::Phase::PhaseNone && event.momentumPhase() == WebWheelEvent::Phase::PhaseChanged;
+}
+
 bool WebWheelEventCoalescer::shouldDispatchEventNow(const WebWheelEvent& event) const
 {
@@ -136 +142 @@
 bool WebWheelEventCoalescer::shouldDispatchEvent(const NativeWebWheelEvent& event)
 {
-    LOG_WITH_STREAM(WheelEvents, stream << "WebWheelEventCoalescer::shouldDispatchEvent " << event << " (" << m_wheelEventQueue.size() << " events in the queue, " << m_eventsBeingProcessed.size() << " event sequences being processed)");
+    LOG_WITH_STREAM(WheelEvents, stream << "WebWheelEventCoalescer::shouldDispatchEvent " << event << " (" << m_wheelEventQueue.size() << " events in the queue, " << m_eventsBeingProcessed.size() << " event sequences being processed, coalesce during decleration " << m_shouldCoalesceEventsDuringDeceleration << ")");
 
     m_wheelEventQueue.append(event);
+
+    auto lastEventInterval = event.timestamp() - m_lastEventTime;
+    m_lastEventTime = event.timestamp();
+
+    if (isMomentumPhaseEvent(event) && shouldCoalesceEventsDuringDeceleration() && lastEventInterval) {
+        constexpr double momentumVelocityEventFrequencyReductionThreashold = 320.0; // Points per second.
+        auto instantaneousVelocity = std::max(std::abs(event.delta().width()), std::abs(event.delta().height())) / lastEventInterval.seconds();
+
+        constexpr auto maxCoalescingInterval = WebCore::FullSpeedAnimationInterval;
+        auto lastDispatchedEventInterval = event.timestamp() - m_lastDispatchedEventTime;
+
+        if (instantaneousVelocity < momentumVelocityEventFrequencyReductionThreashold && lastDispatchedEventInterval < maxCoalescingInterval) {
+            LOG_WITH_STREAM(WheelEvents, stream << " coalesced event that came within " << lastDispatchedEventInterval.milliseconds() << " of previous dispatch");
+            return false;
+        }
+    }
 
     if (!m_eventsBeingProcessed.isEmpty()) {
@@ -149 +171 @@
     }
 
+    m_lastDispatchedEventTime = event.timestamp();
     return true;
 }

trunk/Source/WebKit/Shared/WebWheelEventCoalescer.h

@@ -29 +29 @@
 #include <wtf/Deque.h>
 #include <wtf/FastMalloc.h>
+#include <wtf/WallTime.h>
 
 namespace WebKit {
@@ -38 +39 @@
     bool shouldDispatchEvent(const NativeWebWheelEvent&);
     Optional<WebWheelEvent> nextEventToDispatch();
-    
+
     NativeWebWheelEvent takeOldestEventBeingProcessed();
 
     bool hasEventsBeingProcessed() const { return !m_eventsBeingProcessed.isEmpty(); }
     
+    bool shouldCoalesceEventsDuringDeceleration() const { return m_shouldCoalesceEventsDuringDeceleration; }
+    void setShouldCoalesceEventsDuringDeceleration(bool shouldCoalsce) { m_shouldCoalesceEventsDuringDeceleration = shouldCoalsce; }
+
     void clear();
 
@@ -51 +55 @@
     static WebWheelEvent coalesce(const WebWheelEvent&, const WebWheelEvent&);
 
+    static bool isMomentumPhaseEvent(const WebWheelEvent&);
+
     bool shouldDispatchEventNow(const WebWheelEvent&) const;
 
     Deque<NativeWebWheelEvent, 2> m_wheelEventQueue;
     Deque<std::unique_ptr<CoalescedEventSequence>> m_eventsBeingProcessed;
+
+    WallTime m_lastEventTime;
+    WallTime m_lastDispatchedEventTime;
+    bool m_shouldCoalesceEventsDuringDeceleration { false };
 };
 

trunk/Source/WebKit/UIProcess/WebPageProxy.cpp

@@ -2852 +2852 @@
 WebWheelEventCoalescer& WebPageProxy::wheelEventCoalescer()
 {
-    if (!m_wheelEventCoalescer)
+    if (!m_wheelEventCoalescer) {
         m_wheelEventCoalescer = makeUnique<WebWheelEventCoalescer>();
+        m_wheelEventCoalescer->setShouldCoalesceEventsDuringDeceleration(shouldCoalesceWheelEventsDuringDeceleration());
+    }
 
     return *m_wheelEventCoalescer;
+}
+
+bool WebPageProxy::shouldCoalesceWheelEventsDuringDeceleration() const
+{
+#if HAVE(CVDISPLAYLINK)
+    if (!m_displayID)
+        return false;
+
+    auto framesPerSecond = m_process->processPool().nominalFramesPerSecondForDisplay(*m_displayID);
+    return framesPerSecond > WebCore::FullSpeedFramesPerSecond;
+#else
+    return false;
+#endif
 }
 
@@ -3871 +3886 @@
 {
     m_displayID = displayID;
+
+    if (m_wheelEventCoalescer)
+        m_wheelEventCoalescer->setShouldCoalesceEventsDuringDeceleration(shouldCoalesceWheelEventsDuringDeceleration());
 
     if (!hasRunningProcess())

trunk/Source/WebKit/UIProcess/WebPageProxy.h

@@ -2336 +2336 @@
 
     WebWheelEventCoalescer& wheelEventCoalescer();
+    bool shouldCoalesceWheelEventsDuringDeceleration() const;
 
 #if HAVE(CVDISPLAYLINK)