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| 1 // Copyright 2017 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef REMOTING_CLIENT_FLING_TRACKER_H_ |
| 6 #define REMOTING_CLIENT_FLING_TRACKER_H_ |
| 7 |
| 8 #include "base/time/time.h" |
| 9 |
| 10 namespace remoting { |
| 11 |
| 12 // A class for tracking the positions of an object moving through a viscous |
| 13 // liquid. |
| 14 class FlingTracker { |
| 15 public: |
| 16 // time_constant: The larger the number the longer it takes to fling. |
| 17 explicit FlingTracker(float time_constant); |
| 18 |
| 19 ~FlingTracker(); |
| 20 |
| 21 // Sets the position of the object and start fling. This will reset the |
| 22 // existing fling. |
| 23 void StartFling(float velocity_x, float velocity_y); |
| 24 |
| 25 void StopFling(); |
| 26 |
| 27 bool IsFlingInProgress() const; |
| 28 |
| 29 // time_elapsed: The time elapsed since the animation has started. |
| 30 // Moves forward the object to catch up with |time_elapsed|. The change in |
| 31 // positions will be written to |dx| and |dy|. |
| 32 // Returns true if the fling is still in progress at |time_elapsed|, false |
| 33 // otherwise, in which case |dx| and |dy| will not be touched. |
| 34 bool TrackMovement(base::TimeDelta time_elapsed, float* dx, float* dy); |
| 35 |
| 36 private: |
| 37 float time_constant_; |
| 38 float initial_speed_rate_ = 0.f; |
| 39 float velocity_ratio_x_ = 0.f; |
| 40 float velocity_ratio_y_ = 0.f; |
| 41 float previous_position_x_ = 0.f; |
| 42 float previous_position_y_ = 0.f; |
| 43 |
| 44 base::TimeTicks start_time_; |
| 45 |
| 46 // FlingTracker is neither copyable nor movable. |
| 47 FlingTracker(const FlingTracker&) = delete; |
| 48 FlingTracker& operator=(const FlingTracker&) = delete; |
| 49 }; |
| 50 |
| 51 } // namespace remoting |
| 52 #endif // REMOTING_CLIENT_FLING_TRACKER_H_ |
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