am a5b06982: Implement a second order integrating VT strategy. (ba582217) · Commits · e / os / android_frameworks_base

include/androidfw/VelocityTracker.h

+9 −7

Original line number	Diff line number	Diff line
		@@ -196,7 +196,8 @@ private:
		*/
		class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {
		public:
		IntegratingVelocityTrackerStrategy();
		// Degree must be 1 or 2.
		IntegratingVelocityTrackerStrategy(uint32_t degree);
		~IntegratingVelocityTrackerStrategy();

		virtual void clear();
		@@ -209,18 +210,19 @@ private:
		// Current state estimate for a particular pointer.
		struct State {
		nsecs_t updateTime;
		bool first;
		uint32_t degree;

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

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

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

		} // namespace android

libs/androidfw/VelocityTracker.cpp

+37 −11

Original line number	Diff line number	Diff line
		@@ -182,7 +182,13 @@ VelocityTrackerStrategy* VelocityTracker::createStrategy(const char* strategy) {
		// more tolerant of errors. Like 'lsq1', this strategy tends to underestimate
		// the velocity of a fling but this strategy tends to respond to changes in
		// direction more quickly and accurately.
		return new IntegratingVelocityTrackerStrategy();
		return new IntegratingVelocityTrackerStrategy(1);
		}
		if (!strcmp("int2", strategy)) {
		// 2nd order integrating filter. Quality: EXPERIMENTAL.
		// For comparison purposes only. Unlike 'int1' this strategy can compensate
		// for acceleration but it typically overestimates the effect.
		return new IntegratingVelocityTrackerStrategy(2);
		}
		return NULL;
		}
		@@ -680,7 +686,8 @@ float LeastSquaresVelocityTrackerStrategy::chooseWeight(uint32_t index) const {

		// --- IntegratingVelocityTrackerStrategy ---

		IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy() {
		IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy(uint32_t degree) :
		mDegree(degree) {
		}

		IntegratingVelocityTrackerStrategy::~IntegratingVelocityTrackerStrategy() {
		@@ -725,18 +732,20 @@ bool IntegratingVelocityTrackerStrategy::getEstimator(uint32_t id,
		}

		void IntegratingVelocityTrackerStrategy::initState(State& state,
		nsecs_t eventTime, float xpos, float ypos) {
		nsecs_t eventTime, float xpos, float ypos) const {
		state.updateTime = eventTime;
		state.first = true;
		state.degree = 0;

		state.xpos = xpos;
		state.xvel = 0;
		state.xaccel = 0;
		state.ypos = ypos;
		state.yvel = 0;
		state.yaccel = 0;
		}

		void IntegratingVelocityTrackerStrategy::updateState(State& state,
		nsecs_t eventTime, float xpos, float ypos) {
		nsecs_t eventTime, float xpos, float ypos) const {
		const nsecs_t MIN_TIME_DELTA = 2 * NANOS_PER_MS;
		const float FILTER_TIME_CONSTANT = 0.010f; // 10 milliseconds

		@@ -749,28 +758,45 @@ void IntegratingVelocityTrackerStrategy::updateState(State& state,

		float xvel = (xpos - state.xpos) / dt;
		float yvel = (ypos - state.ypos) / dt;
		if (state.first) {
		if (state.degree == 0) {
		state.xvel = xvel;
		state.yvel = yvel;
		state.first = false;
		state.degree = 1;
		} else {
		float alpha = dt / (FILTER_TIME_CONSTANT + dt);
		if (mDegree == 1) {
		state.xvel += (xvel - state.xvel) * alpha;
		state.yvel += (yvel - state.yvel) * alpha;
		} else {
		float xaccel = (xvel - state.xvel) / dt;
		float yaccel = (yvel - state.yvel) / dt;
		if (state.degree == 1) {
		state.xaccel = xaccel;
		state.yaccel = yaccel;
		state.degree = 2;
		} else {
		state.xaccel += (xaccel - state.xaccel) * alpha;
		state.yaccel += (yaccel - state.yaccel) * alpha;
		}
		state.xvel += (state.xaccel * dt) * alpha;
		state.yvel += (state.yaccel * dt) * alpha;
		}
		}
		state.xpos = xpos;
		state.ypos = ypos;
		}

		void IntegratingVelocityTrackerStrategy::populateEstimator(const State& state,
		VelocityTracker::Estimator* outEstimator) {
		VelocityTracker::Estimator* outEstimator) const {
		outEstimator->time = state.updateTime;
		outEstimator->degree = 1;
		outEstimator->confidence = 1.0f;
		outEstimator->degree = state.degree;
		outEstimator->xCoeff[0] = state.xpos;
		outEstimator->xCoeff[1] = state.xvel;
		outEstimator->xCoeff[2] = state.xaccel / 2;
		outEstimator->yCoeff[0] = state.ypos;
		outEstimator->yCoeff[1] = state.yvel;
		outEstimator->yCoeff[2] = state.yaccel / 2;
		}

		} // namespace android