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diff --git a/widget/gonk/libui/VelocityTracker.h b/widget/gonk/libui/VelocityTracker.h
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+++ b/widget/gonk/libui/VelocityTracker.h
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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 "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