1 files changed, 59 insertions, 0 deletions
diff --git a/layout/generic/ScrollAnimationMSDPhysics.h b/layout/generic/ScrollAnimationMSDPhysics.h
new file mode 100644
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+++ b/layout/generic/ScrollAnimationMSDPhysics.h
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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_ScrollAnimationMSDPhysics_h_
+#define mozilla_layout_ScrollAnimationMSDPhysics_h_
+
+#include "ScrollAnimationPhysics.h"
+#include "mozilla/layers/AxisPhysicsMSDModel.h"
+
+namespace mozilla {
+
+// This class implements a cubic MSD timing function and automatically
+// adapts the animation duration based on the scrolling rate.
+class ScrollAnimationMSDPhysics final : public ScrollAnimationPhysics {
+ public:
+  typedef mozilla::layers::AxisPhysicsMSDModel AxisPhysicsMSDModel;
+
+  explicit ScrollAnimationMSDPhysics(const nsPoint& aStartPos);
+
+  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 {
+    SimulateUntil(aTime);
+    return mModelX.IsFinished(1) && mModelY.IsFinished(1);
+  }
+
+ protected:
+  double ComputeSpringConstant(const TimeStamp& aTime);
+  void SimulateUntil(const TimeStamp& aTime);
+
+  TimeStamp mPreviousEventTime;
+  TimeDuration mPreviousDelta;
+
+  TimeStamp mStartTime;
+
+  nsPoint mStartPos;
+  nsPoint mDestination;
+  TimeStamp mLastSimulatedTime;
+  AxisPhysicsMSDModel mModelX;
+  AxisPhysicsMSDModel mModelY;
+  bool mIsFirstIteration;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_layout_ScrollAnimationMSDPhysics_h_