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// Copyright 2018 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_LEAST_SQUARES_PREDICTOR_H_
#define UI_BASE_PREDICTION_LEAST_SQUARES_PREDICTOR_H_
#include <deque>
#include "base/component_export.h"
#include "base/time/time.h"
#include "ui/base/prediction/input_predictor.h"
#include "ui/gfx/geometry/matrix3_f.h"
namespace ui {
// This class use a quadratic least square regression model:
// y = b0 + b1 * x + b2 * x ^ 2.
// See https://en.wikipedia.org/wiki/Linear_least_squares_(mathematics)
class COMPONENT_EXPORT(UI_BASE_PREDICTION) LeastSquaresPredictor
: public InputPredictor {
public:
static constexpr size_t kSize = 3;
explicit LeastSquaresPredictor();
LeastSquaresPredictor(const LeastSquaresPredictor&) = delete;
LeastSquaresPredictor& operator=(const LeastSquaresPredictor&) = delete;
~LeastSquaresPredictor() override;
const char* GetName() const override;
// Reset the predictor to initial state.
void Reset() override;
// Store current input in queue.
void Update(const InputData& cur_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 time_stamp.
// Return false if no prediction available.
std::unique_ptr<InputData> GeneratePrediction(
base::TimeTicks predict_time,
base::TimeDelta frame_interval) override;
// Return the averaged value of time intervals.
base::TimeDelta TimeInterval() const override;
private:
// Generate X matrix from time_ queue.
gfx::Matrix3F GetXMatrix() const;
std::deque<double> x_queue_;
std::deque<double> y_queue_;
std::deque<base::TimeTicks> time_;
};
} // namespace ui
#endif // UI_BASE_PREDICTION_LEAST_SQUARES_PREDICTOR_H_
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