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/*
* 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 {
/*
* Calculates the velocity of pointer movements over time.
*/
class VelocityTracker {
public:
// Default polynomial degree. (used by getVelocity)
static const uint32_t DEFAULT_DEGREE = 2;
// Default sample horizon. (used by getVelocity)
// We don't use too much history by default since we want to react to quick
// changes in direction.
static const nsecs_t DEFAULT_HORIZON = 100 * 1000000; // 100 ms
struct Position {
float x, y;
};
struct Estimator {
static const size_t MAX_DEGREE = 2;
// 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() {
degree = 0;
confidence = 0;
for (size_t i = 0; i <= MAX_DEGREE; i++) {
xCoeff[i] = 0;
yCoeff[i] = 0;
}
}
};
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 a quadratic estimator for the 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, uint32_t degree, nsecs_t horizon,
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 mMovements[mIndex].idBits; }
private:
// Number of samples to keep.
static const uint32_t HISTORY_SIZE = 20;
struct Movement {
nsecs_t eventTime;
BitSet32 idBits;
Position positions[MAX_POINTERS];
inline const Position& getPosition(uint32_t id) const {
return positions[idBits.getIndexOfBit(id)];
}
};
uint32_t mIndex;
Movement mMovements[HISTORY_SIZE];
int32_t mActivePointerId;
};
} // namespace android
#endif // _ANDROIDFW_VELOCITY_TRACKER_H
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