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+/* -*- 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;
+
+ explicit 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;
+
+ bool IsFinished(TimeStamp aTime) {
+ return aTime > mStartTime + mDuration;
+ }
+
+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;
+};
+
+// Helper for accelerated wheel deltas. This can be called from the main thread
+// or the APZ Controller thread.
+static inline double
+ComputeAcceleratedWheelDelta(double aDelta, int32_t aCounter, int32_t aFactor)
+{
+ if (!aDelta) {
+ return aDelta;
+ }
+ return (aDelta * aCounter * double(aFactor) / 10);
+}
+
+static const uint32_t kScrollSeriesTimeoutMs = 80; // in milliseconds
+
+} // namespace mozilla
+
+#endif // mozilla_layout_AsyncScrollBase_h_