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// Copyright 2019 The Chromium Authors
// 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 "base/time/time.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(const LinearResampling&) = delete;
LinearResampling& operator=(const LinearResampling&) = delete;
~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_;
};
} // namespace ui
#endif // UI_BASE_PREDICTION_LINEAR_RESAMPLING_H_
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