include/androidfw/VelocityTracker.h - platform/frameworks/base - Gitiles

 /*
  * Copyright (C) 2012 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #ifndef _ANDROIDFW_VELOCITY_TRACKER_H
 #define _ANDROIDFW_VELOCITY_TRACKER_H

 #include <androidfw/Input.h>
 #include <utils/Timers.h>
 #include <utils/BitSet.h>

 namespace android {

 class VelocityTrackerStrategy;

 /*
  * Calculates the velocity of pointer movements over time.
  */
 class VelocityTracker {
 public:
     struct Position {
         float x, y;
     };

     struct Estimator {
         static const size_t MAX_DEGREE = 4;

         // Estimator time base.
         nsecs_t time;

         // Polynomial coefficients describing motion in X and Y.
         float xCoeff[MAX_DEGREE + 1], yCoeff[MAX_DEGREE + 1];

         // Polynomial degree (number of coefficients), or zero if no information is
         // available.
         uint32_t degree;

         // Confidence (coefficient of determination), between 0 (no fit) and 1 (perfect fit).
         float confidence;

         inline void clear() {
             time = 0;
             degree = 0;
             confidence = 0;
             for (size_t i = 0; i <= MAX_DEGREE; i++) {
                 xCoeff[i] = 0;
                 yCoeff[i] = 0;
             }
         }
     };

     // Creates a velocity tracker using the specified strategy.
     // If strategy is NULL, uses the default strategy for the platform.
     VelocityTracker(const char* strategy = NULL);

     ~VelocityTracker();

     // Resets the velocity tracker state.
     void clear();

     // Resets the velocity tracker state for specific pointers.
     // Call this method when some pointers have changed and may be reusing
     // an id that was assigned to a different pointer earlier.
     void clearPointers(BitSet32 idBits);

     // Adds movement information for a set of pointers.
     // The idBits bitfield specifies the pointer ids of the pointers whose positions
     // are included in the movement.
     // The positions array contains position information for each pointer in order by
     // increasing id.  Its size should be equal to the number of one bits in idBits.
     void addMovement(nsecs_t eventTime, BitSet32 idBits, const Position* positions);

     // Adds movement information for all pointers in a MotionEvent, including historical samples.
     void addMovement(const MotionEvent* event);

     // Gets the velocity of the specified pointer id in position units per second.
     // Returns false and sets the velocity components to zero if there is
     // insufficient movement information for the pointer.
     bool getVelocity(uint32_t id, float* outVx, float* outVy) const;

     // Gets an estimator for the recent movements of the specified pointer id.
     // Returns false and clears the estimator if there is no information available
     // about the pointer.
     bool getEstimator(uint32_t id, Estimator* outEstimator) const;

     // Gets the active pointer id, or -1 if none.
     inline int32_t getActivePointerId() const { return mActivePointerId; }

     // Gets a bitset containing all pointer ids from the most recent movement.
     inline BitSet32 getCurrentPointerIdBits() const { return mCurrentPointerIdBits; }

 private:
     static const char* DEFAULT_STRATEGY;

     nsecs_t mLastEventTime;
     BitSet32 mCurrentPointerIdBits;
     int32_t mActivePointerId;
     VelocityTrackerStrategy* mStrategy;

     bool configureStrategy(const char* strategy);

     static VelocityTrackerStrategy* createStrategy(const char* strategy);
 };


 /*
  * Implements a particular velocity tracker algorithm.
  */
 class VelocityTrackerStrategy {
 protected:
     VelocityTrackerStrategy() { }

 public:
     virtual ~VelocityTrackerStrategy() { }

     virtual void clear() = 0;
     virtual void clearPointers(BitSet32 idBits) = 0;
     virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
             const VelocityTracker::Position* positions) = 0;
     virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const = 0;
 };


 /*
  * Velocity tracker algorithm based on least-squares linear regression.
  */
 class LeastSquaresVelocityTrackerStrategy : public VelocityTrackerStrategy {
 public:
     enum Weighting {
         // No weights applied.  All data points are equally reliable.
         WEIGHTING_NONE,

         // Weight by time delta.  Data points clustered together are weighted less.
         WEIGHTING_DELTA,

         // Weight such that points within a certain horizon are weighed more than those
         // outside of that horizon.
         WEIGHTING_CENTRAL,

         // Weight such that points older than a certain amount are weighed less.
         WEIGHTING_RECENT,
     };

     // Degree must be no greater than Estimator::MAX_DEGREE.
     LeastSquaresVelocityTrackerStrategy(uint32_t degree, Weighting weighting = WEIGHTING_NONE);
     virtual ~LeastSquaresVelocityTrackerStrategy();

     virtual void clear();
     virtual void clearPointers(BitSet32 idBits);
     virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
             const VelocityTracker::Position* positions);
     virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const;

 private:
     // Sample horizon.
     // We don't use too much history by default since we want to react to quick
     // changes in direction.
     static const nsecs_t HORIZON = 100 * 1000000; // 100 ms

     // Number of samples to keep.
     static const uint32_t HISTORY_SIZE = 20;

     struct Movement {
         nsecs_t eventTime;
         BitSet32 idBits;
         VelocityTracker::Position positions[MAX_POINTERS];

         inline const VelocityTracker::Position& getPosition(uint32_t id) const {
             return positions[idBits.getIndexOfBit(id)];
         }
     };

     float chooseWeight(uint32_t index) const;

     const uint32_t mDegree;
     const Weighting mWeighting;
     uint32_t mIndex;
     Movement mMovements[HISTORY_SIZE];
 };


 /*
  * Velocity tracker algorithm that uses an IIR filter.
  */
 class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {
 public:
     // Degree must be 1 or 2.
     IntegratingVelocityTrackerStrategy(uint32_t degree);
     ~IntegratingVelocityTrackerStrategy();

     virtual void clear();
     virtual void clearPointers(BitSet32 idBits);
     virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
             const VelocityTracker::Position* positions);
     virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const;

 private:
     // Current state estimate for a particular pointer.
     struct State {
         nsecs_t updateTime;
         uint32_t degree;

         float xpos, xvel, xaccel;
         float ypos, yvel, yaccel;
     };

     const uint32_t mDegree;
     BitSet32 mPointerIdBits;
     State mPointerState[MAX_POINTER_ID + 1];

     void initState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
     void updateState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
     void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator) const;
 };


 /*
  * Velocity tracker strategy used prior to ICS.
  */
 class LegacyVelocityTrackerStrategy : public VelocityTrackerStrategy {
 public:
     LegacyVelocityTrackerStrategy();
     virtual ~LegacyVelocityTrackerStrategy();

     virtual void clear();
     virtual void clearPointers(BitSet32 idBits);
     virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
             const VelocityTracker::Position* positions);
     virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const;

 private:
     // Oldest sample to consider when calculating the velocity.
     static const nsecs_t HORIZON = 200 * 1000000; // 100 ms

     // Number of samples to keep.
     static const uint32_t HISTORY_SIZE = 20;

     // The minimum duration between samples when estimating velocity.
     static const nsecs_t MIN_DURATION = 10 * 1000000; // 10 ms

     struct Movement {
         nsecs_t eventTime;
         BitSet32 idBits;
         VelocityTracker::Position positions[MAX_POINTERS];

         inline const VelocityTracker::Position& getPosition(uint32_t id) const {
             return positions[idBits.getIndexOfBit(id)];
         }
     };

     uint32_t mIndex;
     Movement mMovements[HISTORY_SIZE];
 };

 } // namespace android

 #endif // _ANDROIDFW_VELOCITY_TRACKER_H
	/*
	* Copyright (C) 2012 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#ifndef _ANDROIDFW_VELOCITY_TRACKER_H
	#define _ANDROIDFW_VELOCITY_TRACKER_H

	#include <androidfw/Input.h>
	#include <utils/Timers.h>
	#include <utils/BitSet.h>

	namespace android {

	class VelocityTrackerStrategy;

	/*
	* Calculates the velocity of pointer movements over time.
	*/
	class VelocityTracker {
	public:
	struct Position {
	float x, y;
	};

	struct Estimator {
	static const size_t MAX_DEGREE = 4;

	// Estimator time base.
	nsecs_t time;

	// Polynomial coefficients describing motion in X and Y.
	float xCoeff[MAX_DEGREE + 1], yCoeff[MAX_DEGREE + 1];

	// Polynomial degree (number of coefficients), or zero if no information is
	// available.
	uint32_t degree;

	// Confidence (coefficient of determination), between 0 (no fit) and 1 (perfect fit).
	float confidence;

	inline void clear() {
	time = 0;
	degree = 0;
	confidence = 0;
	for (size_t i = 0; i <= MAX_DEGREE; i++) {
	xCoeff[i] = 0;
	yCoeff[i] = 0;
	}
	}
	};

	// Creates a velocity tracker using the specified strategy.
	// If strategy is NULL, uses the default strategy for the platform.
	VelocityTracker(const char* strategy = NULL);

	~VelocityTracker();

	// Resets the velocity tracker state.
	void clear();

	// Resets the velocity tracker state for specific pointers.
	// Call this method when some pointers have changed and may be reusing
	// an id that was assigned to a different pointer earlier.
	void clearPointers(BitSet32 idBits);

	// Adds movement information for a set of pointers.
	// The idBits bitfield specifies the pointer ids of the pointers whose positions
	// are included in the movement.
	// The positions array contains position information for each pointer in order by
	// increasing id. Its size should be equal to the number of one bits in idBits.
	void addMovement(nsecs_t eventTime, BitSet32 idBits, const Position* positions);

	// Adds movement information for all pointers in a MotionEvent, including historical samples.
	void addMovement(const MotionEvent* event);

	// Gets the velocity of the specified pointer id in position units per second.
	// Returns false and sets the velocity components to zero if there is
	// insufficient movement information for the pointer.
	bool getVelocity(uint32_t id, float* outVx, float* outVy) const;

	// Gets an estimator for the recent movements of the specified pointer id.
	// Returns false and clears the estimator if there is no information available
	// about the pointer.
	bool getEstimator(uint32_t id, Estimator* outEstimator) const;

	// Gets the active pointer id, or -1 if none.
	inline int32_t getActivePointerId() const { return mActivePointerId; }

	// Gets a bitset containing all pointer ids from the most recent movement.
	inline BitSet32 getCurrentPointerIdBits() const { return mCurrentPointerIdBits; }

	private:
	static const char* DEFAULT_STRATEGY;

	nsecs_t mLastEventTime;
	BitSet32 mCurrentPointerIdBits;
	int32_t mActivePointerId;
	VelocityTrackerStrategy* mStrategy;

	bool configureStrategy(const char* strategy);

	static VelocityTrackerStrategy* createStrategy(const char* strategy);
	};


	/*
	* Implements a particular velocity tracker algorithm.
	*/
	class VelocityTrackerStrategy {
	protected:
	VelocityTrackerStrategy() { }

	public:
	virtual ~VelocityTrackerStrategy() { }

	virtual void clear() = 0;
	virtual void clearPointers(BitSet32 idBits) = 0;
	virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
	const VelocityTracker::Position* positions) = 0;
	virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const = 0;
	};


	/*
	* Velocity tracker algorithm based on least-squares linear regression.
	*/
	class LeastSquaresVelocityTrackerStrategy : public VelocityTrackerStrategy {
	public:
	enum Weighting {
	// No weights applied. All data points are equally reliable.
	WEIGHTING_NONE,

	// Weight by time delta. Data points clustered together are weighted less.
	WEIGHTING_DELTA,

	// Weight such that points within a certain horizon are weighed more than those
	// outside of that horizon.
	WEIGHTING_CENTRAL,

	// Weight such that points older than a certain amount are weighed less.
	WEIGHTING_RECENT,
	};

	// Degree must be no greater than Estimator::MAX_DEGREE.
	LeastSquaresVelocityTrackerStrategy(uint32_t degree, Weighting weighting = WEIGHTING_NONE);
	virtual ~LeastSquaresVelocityTrackerStrategy();

	virtual void clear();
	virtual void clearPointers(BitSet32 idBits);
	virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
	const VelocityTracker::Position* positions);
	virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const;

	private:
	// Sample horizon.
	// We don't use too much history by default since we want to react to quick
	// changes in direction.
	static const nsecs_t HORIZON = 100 * 1000000; // 100 ms

	// Number of samples to keep.
	static const uint32_t HISTORY_SIZE = 20;

	struct Movement {
	nsecs_t eventTime;
	BitSet32 idBits;
	VelocityTracker::Position positions[MAX_POINTERS];

	inline const VelocityTracker::Position& getPosition(uint32_t id) const {
	return positions[idBits.getIndexOfBit(id)];
	}
	};

	float chooseWeight(uint32_t index) const;

	const uint32_t mDegree;
	const Weighting mWeighting;
	uint32_t mIndex;
	Movement mMovements[HISTORY_SIZE];
	};


	/*
	* Velocity tracker algorithm that uses an IIR filter.
	*/
	class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {
	public:
	// Degree must be 1 or 2.
	IntegratingVelocityTrackerStrategy(uint32_t degree);
	~IntegratingVelocityTrackerStrategy();

	virtual void clear();
	virtual void clearPointers(BitSet32 idBits);
	virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
	const VelocityTracker::Position* positions);
	virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const;

	private:
	// Current state estimate for a particular pointer.
	struct State {
	nsecs_t updateTime;
	uint32_t degree;

	float xpos, xvel, xaccel;
	float ypos, yvel, yaccel;
	};

	const uint32_t mDegree;
	BitSet32 mPointerIdBits;
	State mPointerState[MAX_POINTER_ID + 1];

	void initState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
	void updateState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
	void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator) const;
	};


	/*
	* Velocity tracker strategy used prior to ICS.
	*/
	class LegacyVelocityTrackerStrategy : public VelocityTrackerStrategy {
	public:
	LegacyVelocityTrackerStrategy();
	virtual ~LegacyVelocityTrackerStrategy();

	virtual void clear();
	virtual void clearPointers(BitSet32 idBits);
	virtual void addMovement(nsecs_t eventTime, BitSet32 idBits,
	const VelocityTracker::Position* positions);
	virtual bool getEstimator(uint32_t id, VelocityTracker::Estimator* outEstimator) const;

	private:
	// Oldest sample to consider when calculating the velocity.
	static const nsecs_t HORIZON = 200 * 1000000; // 100 ms

	// Number of samples to keep.
	static const uint32_t HISTORY_SIZE = 20;

	// The minimum duration between samples when estimating velocity.
	static const nsecs_t MIN_DURATION = 10 * 1000000; // 10 ms

	struct Movement {
	nsecs_t eventTime;
	BitSet32 idBits;
	VelocityTracker::Position positions[MAX_POINTERS];

	inline const VelocityTracker::Position& getPosition(uint32_t id) const {
	return positions[idBits.getIndexOfBit(id)];
	}
	};

	uint32_t mIndex;
	Movement mMovements[HISTORY_SIZE];
	};

	} // namespace android

	#endif // _ANDROIDFW_VELOCITY_TRACKER_H