| // Copyright 2017 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef REMOTING_CLIENT_UI_FLING_TRACKER_H_ |
| #define REMOTING_CLIENT_UI_FLING_TRACKER_H_ |
| |
| #include "base/time/time.h" |
| |
| namespace remoting { |
| |
| // A class for tracking the positions of an object moving through a viscous |
| // liquid. |
| class FlingTracker { |
| public: |
| // time_constant: The larger the number the longer it takes to fling and the |
| // further the object can move. |
| explicit FlingTracker(float time_constant); |
| |
| ~FlingTracker(); |
| |
| // Sets the position of the object and start fling. This will reset the |
| // existing fling. |
| // |velocity_x| and |velocity_y| need to be in pixel per second. |
| void StartFling(float velocity_x, float velocity_y); |
| |
| void StopFling(); |
| |
| bool IsFlingInProgress() const; |
| |
| // time_elapsed: The time elapsed since the animation has started. |
| // Moves forward the object to catch up with |time_elapsed|. The change in |
| // positions will be written to |dx| and |dy|. |
| // Returns true if the fling is still in progress at |time_elapsed|, false |
| // otherwise, in which case |dx| and |dy| will not be touched. |
| bool TrackMovement(base::TimeDelta time_elapsed, float* dx, float* dy); |
| |
| private: |
| float time_constant_; |
| float initial_speed_rate_ = 0.f; |
| float fling_duration_ = 0.f; |
| float velocity_ratio_x_ = 0.f; |
| float velocity_ratio_y_ = 0.f; |
| float previous_position_x_ = 0.f; |
| float previous_position_y_ = 0.f; |
| |
| // FlingTracker is neither copyable nor movable. |
| FlingTracker(const FlingTracker&) = delete; |
| FlingTracker& operator=(const FlingTracker&) = delete; |
| }; |
| |
| } // namespace remoting |
| #endif // REMOTING_CLIENT_UI_FLING_TRACKER_H_ |