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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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_ScrollAnimationBezierPhysics_h_
+#define mozilla_layout_ScrollAnimationBezierPhysics_h_
+
+#include "ScrollAnimationPhysics.h"
+#include "mozilla/SMILKeySpline.h"
+
+namespace mozilla {
+
+struct ScrollAnimationBezierPhysicsSettings {
+ // These values are minimum and maximum animation duration per event,
+ // 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 mMinMS;
+ int32_t mMaxMS;
+ double mIntervalRatio;
+};
+
+// This class implements a cubic bezier timing function and automatically
+// adapts the animation duration based on the scrolling rate.
+class ScrollAnimationBezierPhysics final : public ScrollAnimationPhysics {
+ public:
+ explicit ScrollAnimationBezierPhysics(
+ const nsPoint& aStartPos,
+ const ScrollAnimationBezierPhysicsSettings& aSettings);
+
+ void Update(const TimeStamp& aTime, const nsPoint& aDestination,
+ const nsSize& aCurrentVelocity) override;
+
+ void ApplyContentShift(const CSSPoint& aShiftDelta) override;
+
+ // Get the velocity at a point in time in nscoords/sec.
+ nsSize VelocityAt(const TimeStamp& aTime) override;
+
+ // Returns the expected scroll position at a given point in time, in app
+ // units, relative to the scroll frame.
+ nsPoint PositionAt(const TimeStamp& aTime) override;
+
+ bool IsFinished(const TimeStamp& aTime) override {
+ return aTime > mStartTime + mDuration;
+ }
+
+ protected:
+ double ProgressAt(const TimeStamp& aTime) const {
+ return clamped((aTime - mStartTime) / mDuration, 0.0, 1.0);
+ }
+
+ nscoord VelocityComponent(double aTimeProgress,
+ const SMILKeySpline& 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(const TimeStamp& aTime);
+
+ // Initializes the timing function in such a way that the current velocity is
+ // preserved.
+ void InitTimingFunction(SMILKeySpline& aTimingFunction, nscoord aCurrentPos,
+ nscoord aCurrentVelocity, nscoord aDestination);
+
+ // Initialize event history.
+ void InitializeHistory(const TimeStamp& aTime);
+
+ // Cached Preferences values.
+ ScrollAnimationBezierPhysicsSettings mSettings;
+
+ // 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];
+
+ TimeStamp mStartTime;
+
+ nsPoint mStartPos;
+ nsPoint mDestination;
+ TimeDuration mDuration;
+ SMILKeySpline mTimingFunctionX;
+ SMILKeySpline mTimingFunctionY;
+ bool mIsFirstIteration;
+};
+
+} // namespace mozilla
+
+#endif // mozilla_layout_ScrollAnimationBezierPhysics_h_