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The Tor Browser
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FlingAccelerator.h (1929B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef mozilla_layers_FlingAccelerator_h
      8 #define mozilla_layers_FlingAccelerator_h
      9 
     10 #include "mozilla/layers/SampleTime.h"
     11 #include "Units.h"
     12 
     13 namespace mozilla {
     14 namespace layers {
     15 
     16 struct FlingHandoffState;
     17 
     18 /**
     19 * This class is used to track state that is used when determining whether a
     20 * fling should be accelerated.
     21 */
     22 class FlingAccelerator final {
     23 public:
     24  FlingAccelerator() {}
     25 
     26  // Resets state so that the next fling will not be accelerated.
     27  void Reset();
     28 
     29  // Returns false after a reset or before the first fling.
     30  bool IsTracking() const { return mIsTracking; }
     31 
     32  // Starts a new fling, and returns the (potentially accelerated) velocity that
     33  // should be used for that fling.
     34  ParentLayerPoint GetFlingStartingVelocity(
     35      const SampleTime& aNow, const ParentLayerPoint& aVelocity,
     36      const FlingHandoffState& aHandoffState);
     37 
     38  void ObserveFlingCanceled(const ParentLayerPoint& aVelocity) {
     39    mPreviousFlingCancelVelocity = aVelocity;
     40  }
     41 
     42 protected:
     43  bool ShouldAccelerate(const SampleTime& aNow,
     44                        const ParentLayerPoint& aVelocity,
     45                        const FlingHandoffState& aHandoffState) const;
     46 
     47  // The initial velocity of the most recent fling.
     48  ParentLayerPoint mPreviousFlingStartingVelocity;
     49  // The velocity that the previous fling animation had at the point it was
     50  // interrupted.
     51  ParentLayerPoint mPreviousFlingCancelVelocity;
     52  // Whether the upcoming fling is eligible for acceleration.
     53  bool mIsTracking = false;
     54 };
     55 
     56 }  // namespace layers
     57 }  // namespace mozilla
     58 
     59 #endif  // mozilla_layers_FlingAccelerator_h