| // Copyright 2019 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 UI_BASE_PREDICTION_LINEAR_RESAMPLING_H_ |
| #define UI_BASE_PREDICTION_LINEAR_RESAMPLING_H_ |
| |
| #include <deque> |
| |
| #include "base/component_export.h" |
| #include "ui/base/prediction/input_predictor.h" |
| |
| namespace ui { |
| |
| // This class use linear extrapolates / interpolates to resample events to |
| // frame_time - kResampleLatency. This resampling logic is to match the |
| // resampling behavior on Android. It's not designed for pointerevent's |
| // PredictedEvent and should not be used for that purpose. |
| // Resampling on Android see: |
| // https://android.googlesource.com/platform/frameworks/native/+/master/libs/input/InputTransport.cpp |
| class COMPONENT_EXPORT(UI_BASE_PREDICTION) LinearResampling |
| : public InputPredictor { |
| public: |
| explicit LinearResampling(); |
| ~LinearResampling() override; |
| |
| const char* GetName() const override; |
| |
| // Reset the predictor to initial state. |
| void Reset() override; |
| |
| // Store current input in queue. |
| void Update(const InputData& new_input) override; |
| |
| // Return if there is enough data in the queue to generate prediction. |
| bool HasPrediction() const override; |
| |
| // Generate the prediction based on stored points and given frame_time. |
| // Return false if no prediction available. |
| std::unique_ptr<InputData> GeneratePrediction( |
| base::TimeTicks frame_time, |
| base::TimeDelta frame_interval) override; |
| |
| // Return the average time delta in the event queue. |
| base::TimeDelta TimeInterval() const override; |
| |
| private: |
| // Class to cache the Resample Latency to avoid its recalculation each frame. |
| class LatencyCalculator { |
| public: |
| base::TimeDelta GetResampleLatency(base::TimeDelta frame_interval); |
| |
| private: |
| base::TimeDelta CalculateLatency(); |
| base::TimeDelta resample_latency_; |
| base::TimeDelta frame_interval_; |
| }; |
| |
| static constexpr size_t kNumEventsForResampling = 2; |
| |
| // Store the last events received |
| std::deque<InputData> events_queue_; |
| |
| // Store the current delta time between the last 2 events |
| base::TimeDelta events_dt_; |
| |
| LatencyCalculator latency_calculator_; |
| |
| DISALLOW_COPY_AND_ASSIGN(LinearResampling); |
| }; |
| |
| } // namespace ui |
| |
| #endif // UI_BASE_PREDICTION_LINEAR_RESAMPLING_H_ |