Factor the guts of AsyncScroll into a base helper class. (bug 1139220 part 2, r=kgilbert)

layout/generic/AsyncScrollBase.cpp

@@ -0,0 +1,135 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "AsyncScrollBase.h"
+
+using namespace mozilla;
+
+AsyncScrollBase::AsyncScrollBase(nsPoint aStartPos)
+ : mIsFirstIteration(true)
+ , mStartPos(aStartPos)
+{
+}
+
+void
+AsyncScrollBase::Update(TimeStamp aTime,
+                        nsPoint aDestination,
+                        const nsSize& aCurrentVelocity)
+{
+  TimeDuration duration = ComputeDuration(aTime);
+  nsSize currentVelocity = aCurrentVelocity;
+
+  if (!mIsFirstIteration) {
+    // If an additional event has not changed the destination, then do not let
+    // another minimum duration reset slow things down.  If it would then
+    // instead continue with the existing timing function.
+    if (aDestination == mDestination &&
+        aTime + duration > mStartTime + mDuration)
+    {
+      return;
+    }
+
+    currentVelocity = VelocityAt(aTime);
+    mStartPos = PositionAt(aTime);
+  }
+
+  mStartTime = aTime;
+  mDuration = duration;
+  mDestination = aDestination;
+  InitTimingFunction(mTimingFunctionX, mStartPos.x, currentVelocity.width,
+                     aDestination.x);
+  InitTimingFunction(mTimingFunctionY, mStartPos.y, currentVelocity.height,
+                     aDestination.y);
+  mIsFirstIteration = false;
+}
+
+TimeDuration
+AsyncScrollBase::ComputeDuration(TimeStamp aTime)
+{
+  // Average last 3 delta durations (rounding errors up to 2ms are negligible for us)
+  int32_t eventsDeltaMs = (aTime - mPrevEventTime[2]).ToMilliseconds() / 3;
+  mPrevEventTime[2] = mPrevEventTime[1];
+  mPrevEventTime[1] = mPrevEventTime[0];
+  mPrevEventTime[0] = aTime;
+
+  // Modulate duration according to events rate (quicker events -> shorter durations).
+  // The desired effect is to use longer duration when scrolling slowly, such that
+  // it's easier to follow, but reduce the duration to make it feel more snappy when
+  // scrolling quickly. To reduce fluctuations of the duration, we average event
+  // intervals using the recent 4 timestamps (now + three prev -> 3 intervals).
+  int32_t durationMS = clamped<int32_t>(eventsDeltaMs * mIntervalRatio, mOriginMinMS, mOriginMaxMS);
+
+  return TimeDuration::FromMilliseconds(durationMS);
+}
+
+void
+AsyncScrollBase::InitializeHistory(TimeStamp aTime)
+{
+  // Starting a new scroll (i.e. not when extending an existing scroll animation),
+  // create imaginary prev timestamps with maximum relevant intervals between them.
+
+  // Longest relevant interval (which results in maximum duration)
+  TimeDuration maxDelta = TimeDuration::FromMilliseconds(mOriginMaxMS / mIntervalRatio);
+  mPrevEventTime[0] = aTime              - maxDelta;
+  mPrevEventTime[1] = mPrevEventTime[0]  - maxDelta;
+  mPrevEventTime[2] = mPrevEventTime[1]  - maxDelta;
+}
+
+const double kCurrentVelocityWeighting = 0.25;
+const double kStopDecelerationWeighting = 0.4;
+
+void
+AsyncScrollBase::InitTimingFunction(nsSMILKeySpline& aTimingFunction,
+                                    nscoord aCurrentPos,
+                                    nscoord aCurrentVelocity,
+                                    nscoord aDestination)
+{
+  if (aDestination == aCurrentPos || kCurrentVelocityWeighting == 0) {
+    aTimingFunction.Init(0, 0, 1 - kStopDecelerationWeighting, 1);
+    return;
+  }
+
+  const TimeDuration oneSecond = TimeDuration::FromSeconds(1);
+  double slope = aCurrentVelocity * (mDuration / oneSecond) / (aDestination - aCurrentPos);
+  double normalization = sqrt(1.0 + slope * slope);
+  double dt = 1.0 / normalization * kCurrentVelocityWeighting;
+  double dxy = slope / normalization * kCurrentVelocityWeighting;
+  aTimingFunction.Init(dt, dxy, 1 - kStopDecelerationWeighting, 1);
+}
+
+nsPoint
+AsyncScrollBase::PositionAt(TimeStamp aTime) const
+{
+  double progressX = mTimingFunctionX.GetSplineValue(ProgressAt(aTime));
+  double progressY = mTimingFunctionY.GetSplineValue(ProgressAt(aTime));
+  return nsPoint(NSToCoordRound((1 - progressX) * mStartPos.x + progressX * mDestination.x),
+                 NSToCoordRound((1 - progressY) * mStartPos.y + progressY * mDestination.y));
+}
+
+nsSize
+AsyncScrollBase::VelocityAt(TimeStamp aTime) const
+{
+  double timeProgress = ProgressAt(aTime);
+  return nsSize(VelocityComponent(timeProgress, mTimingFunctionX,
+                                  mStartPos.x, mDestination.x),
+                VelocityComponent(timeProgress, mTimingFunctionY,
+                                  mStartPos.y, mDestination.y));
+}
+
+nscoord
+AsyncScrollBase::VelocityComponent(double aTimeProgress,
+                                   const nsSMILKeySpline& aTimingFunction,
+                                   nscoord aStart,
+                                   nscoord aDestination) const
+{
+  double dt, dxy;
+  aTimingFunction.GetSplineDerivativeValues(aTimeProgress, dt, dxy);
+  if (dt == 0)
+    return dxy >= 0 ? nscoord_MAX : nscoord_MIN;
+
+  const TimeDuration oneSecond = TimeDuration::FromSeconds(1);
+  double slope = dxy / dt;
+  return NSToCoordRound(slope * (aDestination - aStart) / (mDuration / oneSecond));
+}

layout/generic/AsyncScrollBase.h

@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layout_AsyncScrollBase_h_
+#define mozilla_layout_AsyncScrollBase_h_
+
+#include "mozilla/TimeStamp.h"
+#include "nsPoint.h"
+#include "nsSMILKeySpline.h"
+
+namespace mozilla {
+
+// This is the base class for driving scroll wheel animation on both the
+// compositor and main thread.
+class AsyncScrollBase
+{
+public:
+  typedef mozilla::TimeStamp TimeStamp;
+  typedef mozilla::TimeDuration TimeDuration;
+
+  AsyncScrollBase(nsPoint aStartPos);
+
+  void Update(TimeStamp aTime,
+              nsPoint aDestination,
+              const nsSize& aCurrentVelocity);
+
+  // Get the velocity at a point in time in nscoords/sec.
+  nsSize VelocityAt(TimeStamp aTime) const;
+
+  // Returns the expected scroll position at a given point in time, in app
+  // units, relative to the scroll frame.
+  nsPoint PositionAt(TimeStamp aTime) const;
+
+protected:
+  double ProgressAt(TimeStamp aTime) const {
+    return clamped((aTime - mStartTime) / mDuration, 0.0, 1.0);
+  }
+
+  nscoord VelocityComponent(double aTimeProgress,
+                            const nsSMILKeySpline& aTimingFunction,
+                            nscoord aStart, nscoord aDestination) const;
+
+  // Calculate duration, possibly dynamically according to events rate and
+  // event origin. (also maintain previous timestamps - which are only used
+  // here).
+  TimeDuration ComputeDuration(TimeStamp aTime);
+
+  // Initialize event history.
+  void InitializeHistory(TimeStamp aTime);
+
+  // Initializes the timing function in such a way that the current velocity is
+  // preserved.
+  void InitTimingFunction(nsSMILKeySpline& aTimingFunction,
+                          nscoord aCurrentPos, nscoord aCurrentVelocity,
+                          nscoord aDestination);
+
+  // mPrevEventTime holds previous 3 timestamps for intervals averaging (to
+  // reduce duration fluctuations). When AsyncScroll is constructed and no
+  // previous timestamps are available (indicated with mIsFirstIteration),
+  // initialize mPrevEventTime using imaginary previous timestamps with maximum
+  // relevant intervals between them.
+  TimeStamp mPrevEventTime[3];
+  bool mIsFirstIteration;
+
+  TimeStamp mStartTime;
+
+  // Cached Preferences value.
+  //
+  // These values are minimum and maximum animation duration per event origin,
+  // and a global ratio which defines how longer is the animation's duration
+  // compared to the average recent events intervals (such that for a relatively
+  // consistent events rate, the next event arrives before current animation ends)
+  int32_t mOriginMinMS;
+  int32_t mOriginMaxMS;
+  double mIntervalRatio;
+
+  nsPoint mStartPos;
+  TimeDuration mDuration;
+  nsPoint mDestination;
+  nsSMILKeySpline mTimingFunctionX;
+  nsSMILKeySpline mTimingFunctionY;
+};
+
+}
+
+#endif // mozilla_layout_AsyncScrollBase_h_

layout/generic/moz.build

@@ -61,6 +61,7 @@ with Files('nsVideoFrame.*'):
     BUG_COMPONENT = ('Core', 'Video/Audio')
 
 EXPORTS += [
+    'AsyncScrollBase.h',
     'nsCanvasFrame.h',
     'nsContainerFrame.h',
     'nsDirection.h',
@@ -104,6 +105,7 @@ EXPORTS.mozilla.layout += [
 ]
 
 UNIFIED_SOURCES += [
+    'AsyncScrollBase.cpp',
     'FrameChildList.cpp',
     'MathMLTextRunFactory.cpp',
     'nsAbsoluteContainingBlock.cpp',

layout/generic/nsGfxScrollFrame.cpp

@@ -55,6 +55,7 @@
 #include "nsIFrameInlines.h"
 #include "gfxPlatform.h"
 #include "gfxPrefs.h"
+#include "AsyncScrollBase.h"
 #include <mozilla/layers/AxisPhysicsModel.h>
 #include <mozilla/layers/AxisPhysicsMSDModel.h>
 #include <algorithm>
@@ -1447,9 +1448,6 @@ NS_QUERYFRAME_TAIL_INHERITING(nsBoxFrame)
 
 #define SMOOTH_SCROLL_PREF_NAME "general.smoothScroll"
 
-const double kCurrentVelocityWeighting = 0.25;
-const double kStopDecelerationWeighting = 0.4;
-
 // AsyncSmoothMSDScroll has ref counting.
 class ScrollFrameHelper::AsyncSmoothMSDScroll final : public nsARefreshObserver {
 public:
@@ -1581,14 +1579,16 @@ private:
 };
 
 // AsyncScroll has ref counting.
-class ScrollFrameHelper::AsyncScroll final : public nsARefreshObserver {
+class ScrollFrameHelper::AsyncScroll final
+  : public nsARefreshObserver,
+    public AsyncScrollBase
+{
 public:
   typedef mozilla::TimeStamp TimeStamp;
   typedef mozilla::TimeDuration TimeDuration;
 
   explicit AsyncScroll(nsPoint aStartPos)
-    : mIsFirstIteration(true)
+    : AsyncScrollBase(aStartPos)
-    , mStartPos(aStartPos)
     , mCallee(nullptr)
   {}
 
@@ -1599,9 +1599,6 @@ private:
   }
 
 public:
-  nsPoint PositionAt(TimeStamp aTime);
-  nsSize VelocityAt(TimeStamp aTime); // In nscoords per second
-
   void InitSmoothScroll(TimeStamp aTime, nsPoint aDestination,
                         nsIAtom *aOrigin, const nsRect& aRange,
                         const nsSize& aCurrentVelocity);
@@ -1613,53 +1610,15 @@ public:
     return aTime > mStartTime + mDuration; // XXX or if we've hit the wall
   }
 
-  TimeStamp mStartTime;
+  // Most recent scroll origin.
-
-  // mPrevEventTime holds previous 3 timestamps for intervals averaging (to
-  // reduce duration fluctuations). When AsyncScroll is constructed and no
-  // previous timestamps are available (indicated with mIsFirstIteration),
-  // initialize mPrevEventTime using imaginary previous timestamps with maximum
-  // relevant intervals between them.
-  TimeStamp mPrevEventTime[3];
-  bool mIsFirstIteration;
-
-  // Cached Preferences values to avoid re-reading them when extending an existing
-  // animation for the same event origin (can be as frequent as every 10(!)ms for
-  // a quick roll of the mouse wheel).
-  // These values are minimum and maximum animation duration per event origin,
-  // and a global ratio which defines how longer is the animation's duration
-  // compared to the average recent events intervals (such that for a relatively
-  // consistent events rate, the next event arrives before current animation ends)
   nsCOMPtr<nsIAtom> mOrigin;
-  int32_t mOriginMinMS;
-  int32_t mOriginMaxMS;
-  double  mIntervalRatio;
 
-  TimeDuration mDuration;
-  nsPoint mStartPos;
-  nsPoint mDestination;
   // Allowed destination positions around mDestination
   nsRect mRange;
-  nsSMILKeySpline mTimingFunctionX;
-  nsSMILKeySpline mTimingFunctionY;
   bool mIsSmoothScroll;
 
-protected:
+private:
-  double ProgressAt(TimeStamp aTime) {
+  void InitPreferences(TimeStamp aTime, nsIAtom *aOrigin);
-    return clamped((aTime - mStartTime) / mDuration, 0.0, 1.0);
-  }
-
-  nscoord VelocityComponent(double aTimeProgress,
-                            nsSMILKeySpline& aTimingFunction,
-                            nscoord aStart, nscoord aDestination);
-
-  // Initializes the timing function in such a way that the current velocity is
-  // preserved.
-  void InitTimingFunction(nsSMILKeySpline& aTimingFunction,
-                          nscoord aCurrentPos, nscoord aCurrentVelocity,
-                          nscoord aDestination);
-
-  TimeDuration CalcDurationForEventTime(TimeStamp aTime, nsIAtom *aOrigin);
 
 // The next section is observer/callback management
 // Bodies of WillRefresh and RefreshDriver contain ScrollFrameHelper specific code.
@@ -1707,36 +1666,22 @@ private:
   }
 };
 
-nsPoint
-ScrollFrameHelper::AsyncScroll::PositionAt(TimeStamp aTime) {
-  double progressX = mTimingFunctionX.GetSplineValue(ProgressAt(aTime));
-  double progressY = mTimingFunctionY.GetSplineValue(ProgressAt(aTime));
-  return nsPoint(NSToCoordRound((1 - progressX) * mStartPos.x + progressX * mDestination.x),
-                 NSToCoordRound((1 - progressY) * mStartPos.y + progressY * mDestination.y));
-}
-
-nsSize
-ScrollFrameHelper::AsyncScroll::VelocityAt(TimeStamp aTime) {
-  double timeProgress = ProgressAt(aTime);
-  return nsSize(VelocityComponent(timeProgress, mTimingFunctionX,
-                                  mStartPos.x, mDestination.x),
-                VelocityComponent(timeProgress, mTimingFunctionY,
-                                  mStartPos.y, mDestination.y));
-}
-
 /*
  * Calculate duration, possibly dynamically according to events rate and event origin.
  * (also maintain previous timestamps - which are only used here).
  */
-TimeDuration
+void
-ScrollFrameHelper::
+ScrollFrameHelper::AsyncScroll::InitPreferences(TimeStamp aTime, nsIAtom *aOrigin)
-AsyncScroll::CalcDurationForEventTime(TimeStamp aTime, nsIAtom *aOrigin) {
+{
   if (!aOrigin){
     aOrigin = nsGkAtoms::other;
   }
 
   // Read preferences only on first iteration or for a different event origin.
-  if (mIsFirstIteration || aOrigin != mOrigin) {
+  if (!mIsFirstIteration && aOrigin == mOrigin) {
+    return;
+  }
+
   mOrigin = aOrigin;
   mOriginMinMS = mOriginMaxMS = 0;
   bool isOriginSmoothnessEnabled = false;
@@ -1772,97 +1717,21 @@ AsyncScroll::CalcDurationForEventTime(TimeStamp aTime, nsIAtom *aOrigin) {
   mIntervalRatio = std::max(1.0, mIntervalRatio);
 
   if (mIsFirstIteration) {
-      // Starting a new scroll (i.e. not when extending an existing scroll animation),
+    InitializeHistory(aTime);
-      //   create imaginary prev timestamps with maximum relevant intervals between them.
-
-      // Longest relevant interval (which results in maximum duration)
-      TimeDuration maxDelta = TimeDuration::FromMilliseconds(mOriginMaxMS / mIntervalRatio);
-      mPrevEventTime[0] = aTime              - maxDelta;
-      mPrevEventTime[1] = mPrevEventTime[0]  - maxDelta;
-      mPrevEventTime[2] = mPrevEventTime[1]  - maxDelta;
   }
 }
 
-  // Average last 3 delta durations (rounding errors up to 2ms are negligible for us)
-  int32_t eventsDeltaMs = (aTime - mPrevEventTime[2]).ToMilliseconds() / 3;
-  mPrevEventTime[2] = mPrevEventTime[1];
-  mPrevEventTime[1] = mPrevEventTime[0];
-  mPrevEventTime[0] = aTime;
-
-  // Modulate duration according to events rate (quicker events -> shorter durations).
-  // The desired effect is to use longer duration when scrolling slowly, such that
-  // it's easier to follow, but reduce the duration to make it feel more snappy when
-  // scrolling quickly. To reduce fluctuations of the duration, we average event
-  // intervals using the recent 4 timestamps (now + three prev -> 3 intervals).
-  int32_t durationMS = clamped<int32_t>(eventsDeltaMs * mIntervalRatio, mOriginMinMS, mOriginMaxMS);
-
-  return TimeDuration::FromMilliseconds(durationMS);
-}
-
 void
 ScrollFrameHelper::AsyncScroll::InitSmoothScroll(TimeStamp aTime,
                                                  nsPoint aDestination,
                                                  nsIAtom *aOrigin,
                                                  const nsRect& aRange,
-                                                     const nsSize& aCurrentVelocity) {
+                                                 const nsSize& aCurrentVelocity)
+{
+  InitPreferences(aTime, aOrigin);
   mRange = aRange;
-  TimeDuration duration = CalcDurationForEventTime(aTime, aOrigin);
-  nsSize currentVelocity = aCurrentVelocity;
-  if (!mIsFirstIteration) {
-    // If an additional event has not changed the destination, then do not let
-    // another minimum duration reset slow things down.  If it would then
-    // instead continue with the existing timing function.
-    if (aDestination == mDestination &&
-        aTime + duration > mStartTime + mDuration)
-      return;
 
-    currentVelocity = VelocityAt(aTime);
+  Update(aTime, aDestination, aCurrentVelocity);
-    mStartPos = PositionAt(aTime);
-  }
-  mStartTime = aTime;
-  mDuration = duration;
-  mDestination = aDestination;
-  InitTimingFunction(mTimingFunctionX, mStartPos.x, currentVelocity.width,
-                     aDestination.x);
-  InitTimingFunction(mTimingFunctionY, mStartPos.y, currentVelocity.height,
-                     aDestination.y);
-  mIsFirstIteration = false;
-}
-
-
-nscoord
-ScrollFrameHelper::AsyncScroll::VelocityComponent(double aTimeProgress,
-                                                      nsSMILKeySpline& aTimingFunction,
-                                                      nscoord aStart,
-                                                      nscoord aDestination)
-{
-  double dt, dxy;
-  aTimingFunction.GetSplineDerivativeValues(aTimeProgress, dt, dxy);
-  if (dt == 0)
-    return dxy >= 0 ? nscoord_MAX : nscoord_MIN;
-
-  const TimeDuration oneSecond = TimeDuration::FromSeconds(1);
-  double slope = dxy / dt;
-  return NSToCoordRound(slope * (aDestination - aStart) / (mDuration / oneSecond));
-}
-
-void
-ScrollFrameHelper::AsyncScroll::InitTimingFunction(nsSMILKeySpline& aTimingFunction,
-                                                       nscoord aCurrentPos,
-                                                       nscoord aCurrentVelocity,
-                                                       nscoord aDestination)
-{
-  if (aDestination == aCurrentPos || kCurrentVelocityWeighting == 0) {
-    aTimingFunction.Init(0, 0, 1 - kStopDecelerationWeighting, 1);
-    return;
-  }
-
-  const TimeDuration oneSecond = TimeDuration::FromSeconds(1);
-  double slope = aCurrentVelocity * (mDuration / oneSecond) / (aDestination - aCurrentPos);
-  double normalization = sqrt(1.0 + slope * slope);
-  double dt = 1.0 / normalization * kCurrentVelocityWeighting;
-  double dxy = slope / normalization * kCurrentVelocityWeighting;
-  aTimingFunction.Init(dt, dxy, 1 - kStopDecelerationWeighting, 1);
 }
 
 bool