diff --git a/libs/input/VelocityTracker.cpp b/libs/input/VelocityTracker.cpp
new file mode 100644
index 0000000..6c70c3c
--- /dev/null
+++ b/libs/input/VelocityTracker.cpp
@@ -0,0 +1,927 @@
+/*
+ * 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.
+ */
+
+#define LOG_TAG "VelocityTracker"
+//#define LOG_NDEBUG 0
+
+// Log debug messages about velocity tracking.
+#define DEBUG_VELOCITY 0
+
+// Log debug messages about the progress of the algorithm itself.
+#define DEBUG_STRATEGY 0
+
+#include <math.h>
+#include <limits.h>
+
+#include <cutils/properties.h>
+#include <input/VelocityTracker.h>
+#include <utils/BitSet.h>
+#include <utils/String8.h>
+#include <utils/Timers.h>
+
+namespace android {
+
+// Nanoseconds per milliseconds.
+static const nsecs_t NANOS_PER_MS = 1000000;
+
+// Threshold for determining that a pointer has stopped moving.
+// Some input devices do not send ACTION_MOVE events in the case where a pointer has
+// stopped.  We need to detect this case so that we can accurately predict the
+// velocity after the pointer starts moving again.
+static const nsecs_t ASSUME_POINTER_STOPPED_TIME = 40 * NANOS_PER_MS;
+
+
+static float vectorDot(const float* a, const float* b, uint32_t m) {
+    float r = 0;
+    while (m--) {
+        r += *(a++) * *(b++);
+    }
+    return r;
+}
+
+static float vectorNorm(const float* a, uint32_t m) {
+    float r = 0;
+    while (m--) {
+        float t = *(a++);
+        r += t * t;
+    }
+    return sqrtf(r);
+}
+
+#if DEBUG_STRATEGY || DEBUG_VELOCITY
+static String8 vectorToString(const float* a, uint32_t m) {
+    String8 str;
+    str.append("[");
+    while (m--) {
+        str.appendFormat(" %f", *(a++));
+        if (m) {
+            str.append(",");
+        }
+    }
+    str.append(" ]");
+    return str;
+}
+
+static String8 matrixToString(const float* a, uint32_t m, uint32_t n, bool rowMajor) {
+    String8 str;
+    str.append("[");
+    for (size_t i = 0; i < m; i++) {
+        if (i) {
+            str.append(",");
+        }
+        str.append(" [");
+        for (size_t j = 0; j < n; j++) {
+            if (j) {
+                str.append(",");
+            }
+            str.appendFormat(" %f", a[rowMajor ? i * n + j : j * m + i]);
+        }
+        str.append(" ]");
+    }
+    str.append(" ]");
+    return str;
+}
+#endif
+
+
+// --- VelocityTracker ---
+
+// The default velocity tracker strategy.
+// Although other strategies are available for testing and comparison purposes,
+// this is the strategy that applications will actually use.  Be very careful
+// when adjusting the default strategy because it can dramatically affect
+// (often in a bad way) the user experience.
+const char* VelocityTracker::DEFAULT_STRATEGY = "lsq2";
+
+VelocityTracker::VelocityTracker(const char* strategy) :
+        mLastEventTime(0), mCurrentPointerIdBits(0), mActivePointerId(-1) {
+    char value[PROPERTY_VALUE_MAX];
+
+    // Allow the default strategy to be overridden using a system property for debugging.
+    if (!strategy) {
+        int length = property_get("debug.velocitytracker.strategy", value, NULL);
+        if (length > 0) {
+            strategy = value;
+        } else {
+            strategy = DEFAULT_STRATEGY;
+        }
+    }
+
+    // Configure the strategy.
+    if (!configureStrategy(strategy)) {
+        ALOGD("Unrecognized velocity tracker strategy name '%s'.", strategy);
+        if (!configureStrategy(DEFAULT_STRATEGY)) {
+            LOG_ALWAYS_FATAL("Could not create the default velocity tracker strategy '%s'!",
+                    strategy);
+        }
+    }
+}
+
+VelocityTracker::~VelocityTracker() {
+    delete mStrategy;
+}
+
+bool VelocityTracker::configureStrategy(const char* strategy) {
+    mStrategy = createStrategy(strategy);
+    return mStrategy != NULL;
+}
+
+VelocityTrackerStrategy* VelocityTracker::createStrategy(const char* strategy) {
+    if (!strcmp("lsq1", strategy)) {
+        // 1st order least squares.  Quality: POOR.
+        // Frequently underfits the touch data especially when the finger accelerates
+        // or changes direction.  Often underestimates velocity.  The direction
+        // is overly influenced by historical touch points.
+        return new LeastSquaresVelocityTrackerStrategy(1);
+    }
+    if (!strcmp("lsq2", strategy)) {
+        // 2nd order least squares.  Quality: VERY GOOD.
+        // Pretty much ideal, but can be confused by certain kinds of touch data,
+        // particularly if the panel has a tendency to generate delayed,
+        // duplicate or jittery touch coordinates when the finger is released.
+        return new LeastSquaresVelocityTrackerStrategy(2);
+    }
+    if (!strcmp("lsq3", strategy)) {
+        // 3rd order least squares.  Quality: UNUSABLE.
+        // Frequently overfits the touch data yielding wildly divergent estimates
+        // of the velocity when the finger is released.
+        return new LeastSquaresVelocityTrackerStrategy(3);
+    }
+    if (!strcmp("wlsq2-delta", strategy)) {
+        // 2nd order weighted least squares, delta weighting.  Quality: EXPERIMENTAL
+        return new LeastSquaresVelocityTrackerStrategy(2,
+                LeastSquaresVelocityTrackerStrategy::WEIGHTING_DELTA);
+    }
+    if (!strcmp("wlsq2-central", strategy)) {
+        // 2nd order weighted least squares, central weighting.  Quality: EXPERIMENTAL
+        return new LeastSquaresVelocityTrackerStrategy(2,
+                LeastSquaresVelocityTrackerStrategy::WEIGHTING_CENTRAL);
+    }
+    if (!strcmp("wlsq2-recent", strategy)) {
+        // 2nd order weighted least squares, recent weighting.  Quality: EXPERIMENTAL
+        return new LeastSquaresVelocityTrackerStrategy(2,
+                LeastSquaresVelocityTrackerStrategy::WEIGHTING_RECENT);
+    }
+    if (!strcmp("int1", strategy)) {
+        // 1st order integrating filter.  Quality: GOOD.
+        // Not as good as 'lsq2' because it cannot estimate acceleration but it is
+        // 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(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);
+    }
+    if (!strcmp("legacy", strategy)) {
+        // Legacy velocity tracker algorithm.  Quality: POOR.
+        // For comparison purposes only.  This algorithm is strongly influenced by
+        // old data points, consistently underestimates velocity and takes a very long
+        // time to adjust to changes in direction.
+        return new LegacyVelocityTrackerStrategy();
+    }
+    return NULL;
+}
+
+void VelocityTracker::clear() {
+    mCurrentPointerIdBits.clear();
+    mActivePointerId = -1;
+
+    mStrategy->clear();
+}
+
+void VelocityTracker::clearPointers(BitSet32 idBits) {
+    BitSet32 remainingIdBits(mCurrentPointerIdBits.value & ~idBits.value);
+    mCurrentPointerIdBits = remainingIdBits;
+
+    if (mActivePointerId >= 0 && idBits.hasBit(mActivePointerId)) {
+        mActivePointerId = !remainingIdBits.isEmpty() ? remainingIdBits.firstMarkedBit() : -1;
+    }
+
+    mStrategy->clearPointers(idBits);
+}
+
+void VelocityTracker::addMovement(nsecs_t eventTime, BitSet32 idBits, const Position* positions) {
+    while (idBits.count() > MAX_POINTERS) {
+        idBits.clearLastMarkedBit();
+    }
+
+    if ((mCurrentPointerIdBits.value & idBits.value)
+            && eventTime >= mLastEventTime + ASSUME_POINTER_STOPPED_TIME) {
+#if DEBUG_VELOCITY
+        ALOGD("VelocityTracker: stopped for %0.3f ms, clearing state.",
+                (eventTime - mLastEventTime) * 0.000001f);
+#endif
+        // We have not received any movements for too long.  Assume that all pointers
+        // have stopped.
+        mStrategy->clear();
+    }
+    mLastEventTime = eventTime;
+
+    mCurrentPointerIdBits = idBits;
+    if (mActivePointerId < 0 || !idBits.hasBit(mActivePointerId)) {
+        mActivePointerId = idBits.isEmpty() ? -1 : idBits.firstMarkedBit();
+    }
+
+    mStrategy->addMovement(eventTime, idBits, positions);
+
+#if DEBUG_VELOCITY
+    ALOGD("VelocityTracker: addMovement eventTime=%lld, idBits=0x%08x, activePointerId=%d",
+            eventTime, idBits.value, mActivePointerId);
+    for (BitSet32 iterBits(idBits); !iterBits.isEmpty(); ) {
+        uint32_t id = iterBits.firstMarkedBit();
+        uint32_t index = idBits.getIndexOfBit(id);
+        iterBits.clearBit(id);
+        Estimator estimator;
+        getEstimator(id, &estimator);
+        ALOGD("  %d: position (%0.3f, %0.3f), "
+                "estimator (degree=%d, xCoeff=%s, yCoeff=%s, confidence=%f)",
+                id, positions[index].x, positions[index].y,
+                int(estimator.degree),
+                vectorToString(estimator.xCoeff, estimator.degree + 1).string(),
+                vectorToString(estimator.yCoeff, estimator.degree + 1).string(),
+                estimator.confidence);
+    }
+#endif
+}
+
+void VelocityTracker::addMovement(const MotionEvent* event) {
+    int32_t actionMasked = event->getActionMasked();
+
+    switch (actionMasked) {
+    case AMOTION_EVENT_ACTION_DOWN:
+    case AMOTION_EVENT_ACTION_HOVER_ENTER:
+        // Clear all pointers on down before adding the new movement.
+        clear();
+        break;
+    case AMOTION_EVENT_ACTION_POINTER_DOWN: {
+        // Start a new movement trace for a pointer that just went down.
+        // We do this on down instead of on up because the client may want to query the
+        // final velocity for a pointer that just went up.
+        BitSet32 downIdBits;
+        downIdBits.markBit(event->getPointerId(event->getActionIndex()));
+        clearPointers(downIdBits);
+        break;
+    }
+    case AMOTION_EVENT_ACTION_MOVE:
+    case AMOTION_EVENT_ACTION_HOVER_MOVE:
+        break;
+    default:
+        // Ignore all other actions because they do not convey any new information about
+        // pointer movement.  We also want to preserve the last known velocity of the pointers.
+        // Note that ACTION_UP and ACTION_POINTER_UP always report the last known position
+        // of the pointers that went up.  ACTION_POINTER_UP does include the new position of
+        // pointers that remained down but we will also receive an ACTION_MOVE with this
+        // information if any of them actually moved.  Since we don't know how many pointers
+        // will be going up at once it makes sense to just wait for the following ACTION_MOVE
+        // before adding the movement.
+        return;
+    }
+
+    size_t pointerCount = event->getPointerCount();
+    if (pointerCount > MAX_POINTERS) {
+        pointerCount = MAX_POINTERS;
+    }
+
+    BitSet32 idBits;
+    for (size_t i = 0; i < pointerCount; i++) {
+        idBits.markBit(event->getPointerId(i));
+    }
+
+    uint32_t pointerIndex[MAX_POINTERS];
+    for (size_t i = 0; i < pointerCount; i++) {
+        pointerIndex[i] = idBits.getIndexOfBit(event->getPointerId(i));
+    }
+
+    nsecs_t eventTime;
+    Position positions[pointerCount];
+
+    size_t historySize = event->getHistorySize();
+    for (size_t h = 0; h < historySize; h++) {
+        eventTime = event->getHistoricalEventTime(h);
+        for (size_t i = 0; i < pointerCount; i++) {
+            uint32_t index = pointerIndex[i];
+            positions[index].x = event->getHistoricalX(i, h);
+            positions[index].y = event->getHistoricalY(i, h);
+        }
+        addMovement(eventTime, idBits, positions);
+    }
+
+    eventTime = event->getEventTime();
+    for (size_t i = 0; i < pointerCount; i++) {
+        uint32_t index = pointerIndex[i];
+        positions[index].x = event->getX(i);
+        positions[index].y = event->getY(i);
+    }
+    addMovement(eventTime, idBits, positions);
+}
+
+bool VelocityTracker::getVelocity(uint32_t id, float* outVx, float* outVy) const {
+    Estimator estimator;
+    if (getEstimator(id, &estimator) && estimator.degree >= 1) {
+        *outVx = estimator.xCoeff[1];
+        *outVy = estimator.yCoeff[1];
+        return true;
+    }
+    *outVx = 0;
+    *outVy = 0;
+    return false;
+}
+
+bool VelocityTracker::getEstimator(uint32_t id, Estimator* outEstimator) const {
+    return mStrategy->getEstimator(id, outEstimator);
+}
+
+
+// --- LeastSquaresVelocityTrackerStrategy ---
+
+const nsecs_t LeastSquaresVelocityTrackerStrategy::HORIZON;
+const uint32_t LeastSquaresVelocityTrackerStrategy::HISTORY_SIZE;
+
+LeastSquaresVelocityTrackerStrategy::LeastSquaresVelocityTrackerStrategy(
+        uint32_t degree, Weighting weighting) :
+        mDegree(degree), mWeighting(weighting) {
+    clear();
+}
+
+LeastSquaresVelocityTrackerStrategy::~LeastSquaresVelocityTrackerStrategy() {
+}
+
+void LeastSquaresVelocityTrackerStrategy::clear() {
+    mIndex = 0;
+    mMovements[0].idBits.clear();
+}
+
+void LeastSquaresVelocityTrackerStrategy::clearPointers(BitSet32 idBits) {
+    BitSet32 remainingIdBits(mMovements[mIndex].idBits.value & ~idBits.value);
+    mMovements[mIndex].idBits = remainingIdBits;
+}
+
+void LeastSquaresVelocityTrackerStrategy::addMovement(nsecs_t eventTime, BitSet32 idBits,
+        const VelocityTracker::Position* positions) {
+    if (++mIndex == HISTORY_SIZE) {
+        mIndex = 0;
+    }
+
+    Movement& movement = mMovements[mIndex];
+    movement.eventTime = eventTime;
+    movement.idBits = idBits;
+    uint32_t count = idBits.count();
+    for (uint32_t i = 0; i < count; i++) {
+        movement.positions[i] = positions[i];
+    }
+}
+
+/**
+ * Solves a linear least squares problem to obtain a N degree polynomial that fits
+ * the specified input data as nearly as possible.
+ *
+ * Returns true if a solution is found, false otherwise.
+ *
+ * The input consists of two vectors of data points X and Y with indices 0..m-1
+ * along with a weight vector W of the same size.
+ *
+ * The output is a vector B with indices 0..n that describes a polynomial
+ * that fits the data, such the sum of W[i] * W[i] * abs(Y[i] - (B[0] + B[1] X[i]
+ * + B[2] X[i]^2 ... B[n] X[i]^n)) for all i between 0 and m-1 is minimized.
+ *
+ * Accordingly, the weight vector W should be initialized by the caller with the
+ * reciprocal square root of the variance of the error in each input data point.
+ * In other words, an ideal choice for W would be W[i] = 1 / var(Y[i]) = 1 / stddev(Y[i]).
+ * The weights express the relative importance of each data point.  If the weights are
+ * all 1, then the data points are considered to be of equal importance when fitting
+ * the polynomial.  It is a good idea to choose weights that diminish the importance
+ * of data points that may have higher than usual error margins.
+ *
+ * Errors among data points are assumed to be independent.  W is represented here
+ * as a vector although in the literature it is typically taken to be a diagonal matrix.
+ *
+ * That is to say, the function that generated the input data can be approximated
+ * by y(x) ~= B[0] + B[1] x + B[2] x^2 + ... + B[n] x^n.
+ *
+ * The coefficient of determination (R^2) is also returned to describe the goodness
+ * of fit of the model for the given data.  It is a value between 0 and 1, where 1
+ * indicates perfect correspondence.
+ *
+ * This function first expands the X vector to a m by n matrix A such that
+ * A[i][0] = 1, A[i][1] = X[i], A[i][2] = X[i]^2, ..., A[i][n] = X[i]^n, then
+ * multiplies it by w[i]./
+ *
+ * Then it calculates the QR decomposition of A yielding an m by m orthonormal matrix Q
+ * and an m by n upper triangular matrix R.  Because R is upper triangular (lower
+ * part is all zeroes), we can simplify the decomposition into an m by n matrix
+ * Q1 and a n by n matrix R1 such that A = Q1 R1.
+ *
+ * Finally we solve the system of linear equations given by R1 B = (Qtranspose W Y)
+ * to find B.
+ *
+ * For efficiency, we lay out A and Q column-wise in memory because we frequently
+ * operate on the column vectors.  Conversely, we lay out R row-wise.
+ *
+ * http://en.wikipedia.org/wiki/Numerical_methods_for_linear_least_squares
+ * http://en.wikipedia.org/wiki/Gram-Schmidt
+ */
+static bool solveLeastSquares(const float* x, const float* y,
+        const float* w, uint32_t m, uint32_t n, float* outB, float* outDet) {
+#if DEBUG_STRATEGY
+    ALOGD("solveLeastSquares: m=%d, n=%d, x=%s, y=%s, w=%s", int(m), int(n),
+            vectorToString(x, m).string(), vectorToString(y, m).string(),
+            vectorToString(w, m).string());
+#endif
+
+    // Expand the X vector to a matrix A, pre-multiplied by the weights.
+    float a[n][m]; // column-major order
+    for (uint32_t h = 0; h < m; h++) {
+        a[0][h] = w[h];
+        for (uint32_t i = 1; i < n; i++) {
+            a[i][h] = a[i - 1][h] * x[h];
+        }
+    }
+#if DEBUG_STRATEGY
+    ALOGD("  - a=%s", matrixToString(&a[0][0], m, n, false /*rowMajor*/).string());
+#endif
+
+    // Apply the Gram-Schmidt process to A to obtain its QR decomposition.
+    float q[n][m]; // orthonormal basis, column-major order
+    float r[n][n]; // upper triangular matrix, row-major order
+    for (uint32_t j = 0; j < n; j++) {
+        for (uint32_t h = 0; h < m; h++) {
+            q[j][h] = a[j][h];
+        }
+        for (uint32_t i = 0; i < j; i++) {
+            float dot = vectorDot(&q[j][0], &q[i][0], m);
+            for (uint32_t h = 0; h < m; h++) {
+                q[j][h] -= dot * q[i][h];
+            }
+        }
+
+        float norm = vectorNorm(&q[j][0], m);
+        if (norm < 0.000001f) {
+            // vectors are linearly dependent or zero so no solution
+#if DEBUG_STRATEGY
+            ALOGD("  - no solution, norm=%f", norm);
+#endif
+            return false;
+        }
+
+        float invNorm = 1.0f / norm;
+        for (uint32_t h = 0; h < m; h++) {
+            q[j][h] *= invNorm;
+        }
+        for (uint32_t i = 0; i < n; i++) {
+            r[j][i] = i < j ? 0 : vectorDot(&q[j][0], &a[i][0], m);
+        }
+    }
+#if DEBUG_STRATEGY
+    ALOGD("  - q=%s", matrixToString(&q[0][0], m, n, false /*rowMajor*/).string());
+    ALOGD("  - r=%s", matrixToString(&r[0][0], n, n, true /*rowMajor*/).string());
+
+    // calculate QR, if we factored A correctly then QR should equal A
+    float qr[n][m];
+    for (uint32_t h = 0; h < m; h++) {
+        for (uint32_t i = 0; i < n; i++) {
+            qr[i][h] = 0;
+            for (uint32_t j = 0; j < n; j++) {
+                qr[i][h] += q[j][h] * r[j][i];
+            }
+        }
+    }
+    ALOGD("  - qr=%s", matrixToString(&qr[0][0], m, n, false /*rowMajor*/).string());
+#endif
+
+    // Solve R B = Qt W Y to find B.  This is easy because R is upper triangular.
+    // We just work from bottom-right to top-left calculating B's coefficients.
+    float wy[m];
+    for (uint32_t h = 0; h < m; h++) {
+        wy[h] = y[h] * w[h];
+    }
+    for (uint32_t i = n; i-- != 0; ) {
+        outB[i] = vectorDot(&q[i][0], wy, m);
+        for (uint32_t j = n - 1; j > i; j--) {
+            outB[i] -= r[i][j] * outB[j];
+        }
+        outB[i] /= r[i][i];
+    }
+#if DEBUG_STRATEGY
+    ALOGD("  - b=%s", vectorToString(outB, n).string());
+#endif
+
+    // Calculate the coefficient of determination as 1 - (SSerr / SStot) where
+    // SSerr is the residual sum of squares (variance of the error),
+    // and SStot is the total sum of squares (variance of the data) where each
+    // has been weighted.
+    float ymean = 0;
+    for (uint32_t h = 0; h < m; h++) {
+        ymean += y[h];
+    }
+    ymean /= m;
+
+    float sserr = 0;
+    float sstot = 0;
+    for (uint32_t h = 0; h < m; h++) {
+        float err = y[h] - outB[0];
+        float term = 1;
+        for (uint32_t i = 1; i < n; i++) {
+            term *= x[h];
+            err -= term * outB[i];
+        }
+        sserr += w[h] * w[h] * err * err;
+        float var = y[h] - ymean;
+        sstot += w[h] * w[h] * var * var;
+    }
+    *outDet = sstot > 0.000001f ? 1.0f - (sserr / sstot) : 1;
+#if DEBUG_STRATEGY
+    ALOGD("  - sserr=%f", sserr);
+    ALOGD("  - sstot=%f", sstot);
+    ALOGD("  - det=%f", *outDet);
+#endif
+    return true;
+}
+
+bool LeastSquaresVelocityTrackerStrategy::getEstimator(uint32_t id,
+        VelocityTracker::Estimator* outEstimator) const {
+    outEstimator->clear();
+
+    // Iterate over movement samples in reverse time order and collect samples.
+    float x[HISTORY_SIZE];
+    float y[HISTORY_SIZE];
+    float w[HISTORY_SIZE];
+    float time[HISTORY_SIZE];
+    uint32_t m = 0;
+    uint32_t index = mIndex;
+    const Movement& newestMovement = mMovements[mIndex];
+    do {
+        const Movement& movement = mMovements[index];
+        if (!movement.idBits.hasBit(id)) {
+            break;
+        }
+
+        nsecs_t age = newestMovement.eventTime - movement.eventTime;
+        if (age > HORIZON) {
+            break;
+        }
+
+        const VelocityTracker::Position& position = movement.getPosition(id);
+        x[m] = position.x;
+        y[m] = position.y;
+        w[m] = chooseWeight(index);
+        time[m] = -age * 0.000000001f;
+        index = (index == 0 ? HISTORY_SIZE : index) - 1;
+    } while (++m < HISTORY_SIZE);
+
+    if (m == 0) {
+        return false; // no data
+    }
+
+    // Calculate a least squares polynomial fit.
+    uint32_t degree = mDegree;
+    if (degree > m - 1) {
+        degree = m - 1;
+    }
+    if (degree >= 1) {
+        float xdet, ydet;
+        uint32_t n = degree + 1;
+        if (solveLeastSquares(time, x, w, m, n, outEstimator->xCoeff, &xdet)
+                && solveLeastSquares(time, y, w, m, n, outEstimator->yCoeff, &ydet)) {
+            outEstimator->time = newestMovement.eventTime;
+            outEstimator->degree = degree;
+            outEstimator->confidence = xdet * ydet;
+#if DEBUG_STRATEGY
+            ALOGD("estimate: degree=%d, xCoeff=%s, yCoeff=%s, confidence=%f",
+                    int(outEstimator->degree),
+                    vectorToString(outEstimator->xCoeff, n).string(),
+                    vectorToString(outEstimator->yCoeff, n).string(),
+                    outEstimator->confidence);
+#endif
+            return true;
+        }
+    }
+
+    // No velocity data available for this pointer, but we do have its current position.
+    outEstimator->xCoeff[0] = x[0];
+    outEstimator->yCoeff[0] = y[0];
+    outEstimator->time = newestMovement.eventTime;
+    outEstimator->degree = 0;
+    outEstimator->confidence = 1;
+    return true;
+}
+
+float LeastSquaresVelocityTrackerStrategy::chooseWeight(uint32_t index) const {
+    switch (mWeighting) {
+    case WEIGHTING_DELTA: {
+        // Weight points based on how much time elapsed between them and the next
+        // point so that points that "cover" a shorter time span are weighed less.
+        //   delta  0ms: 0.5
+        //   delta 10ms: 1.0
+        if (index == mIndex) {
+            return 1.0f;
+        }
+        uint32_t nextIndex = (index + 1) % HISTORY_SIZE;
+        float deltaMillis = (mMovements[nextIndex].eventTime- mMovements[index].eventTime)
+                * 0.000001f;
+        if (deltaMillis < 0) {
+            return 0.5f;
+        }
+        if (deltaMillis < 10) {
+            return 0.5f + deltaMillis * 0.05;
+        }
+        return 1.0f;
+    }
+
+    case WEIGHTING_CENTRAL: {
+        // Weight points based on their age, weighing very recent and very old points less.
+        //   age  0ms: 0.5
+        //   age 10ms: 1.0
+        //   age 50ms: 1.0
+        //   age 60ms: 0.5
+        float ageMillis = (mMovements[mIndex].eventTime - mMovements[index].eventTime)
+                * 0.000001f;
+        if (ageMillis < 0) {
+            return 0.5f;
+        }
+        if (ageMillis < 10) {
+            return 0.5f + ageMillis * 0.05;
+        }
+        if (ageMillis < 50) {
+            return 1.0f;
+        }
+        if (ageMillis < 60) {
+            return 0.5f + (60 - ageMillis) * 0.05;
+        }
+        return 0.5f;
+    }
+
+    case WEIGHTING_RECENT: {
+        // Weight points based on their age, weighing older points less.
+        //   age   0ms: 1.0
+        //   age  50ms: 1.0
+        //   age 100ms: 0.5
+        float ageMillis = (mMovements[mIndex].eventTime - mMovements[index].eventTime)
+                * 0.000001f;
+        if (ageMillis < 50) {
+            return 1.0f;
+        }
+        if (ageMillis < 100) {
+            return 0.5f + (100 - ageMillis) * 0.01f;
+        }
+        return 0.5f;
+    }
+
+    case WEIGHTING_NONE:
+    default:
+        return 1.0f;
+    }
+}
+
+
+// --- IntegratingVelocityTrackerStrategy ---
+
+IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy(uint32_t degree) :
+        mDegree(degree) {
+}
+
+IntegratingVelocityTrackerStrategy::~IntegratingVelocityTrackerStrategy() {
+}
+
+void IntegratingVelocityTrackerStrategy::clear() {
+    mPointerIdBits.clear();
+}
+
+void IntegratingVelocityTrackerStrategy::clearPointers(BitSet32 idBits) {
+    mPointerIdBits.value &= ~idBits.value;
+}
+
+void IntegratingVelocityTrackerStrategy::addMovement(nsecs_t eventTime, BitSet32 idBits,
+        const VelocityTracker::Position* positions) {
+    uint32_t index = 0;
+    for (BitSet32 iterIdBits(idBits); !iterIdBits.isEmpty();) {
+        uint32_t id = iterIdBits.clearFirstMarkedBit();
+        State& state = mPointerState[id];
+        const VelocityTracker::Position& position = positions[index++];
+        if (mPointerIdBits.hasBit(id)) {
+            updateState(state, eventTime, position.x, position.y);
+        } else {
+            initState(state, eventTime, position.x, position.y);
+        }
+    }
+
+    mPointerIdBits = idBits;
+}
+
+bool IntegratingVelocityTrackerStrategy::getEstimator(uint32_t id,
+        VelocityTracker::Estimator* outEstimator) const {
+    outEstimator->clear();
+
+    if (mPointerIdBits.hasBit(id)) {
+        const State& state = mPointerState[id];
+        populateEstimator(state, outEstimator);
+        return true;
+    }
+
+    return false;
+}
+
+void IntegratingVelocityTrackerStrategy::initState(State& state,
+        nsecs_t eventTime, float xpos, float ypos) const {
+    state.updateTime = eventTime;
+    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) const {
+    const nsecs_t MIN_TIME_DELTA = 2 * NANOS_PER_MS;
+    const float FILTER_TIME_CONSTANT = 0.010f; // 10 milliseconds
+
+    if (eventTime <= state.updateTime + MIN_TIME_DELTA) {
+        return;
+    }
+
+    float dt = (eventTime - state.updateTime) * 0.000000001f;
+    state.updateTime = eventTime;
+
+    float xvel = (xpos - state.xpos) / dt;
+    float yvel = (ypos - state.ypos) / dt;
+    if (state.degree == 0) {
+        state.xvel = xvel;
+        state.yvel = yvel;
+        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) const {
+    outEstimator->time = state.updateTime;
+    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;
+}
+
+
+// --- LegacyVelocityTrackerStrategy ---
+
+const nsecs_t LegacyVelocityTrackerStrategy::HORIZON;
+const uint32_t LegacyVelocityTrackerStrategy::HISTORY_SIZE;
+const nsecs_t LegacyVelocityTrackerStrategy::MIN_DURATION;
+
+LegacyVelocityTrackerStrategy::LegacyVelocityTrackerStrategy() {
+    clear();
+}
+
+LegacyVelocityTrackerStrategy::~LegacyVelocityTrackerStrategy() {
+}
+
+void LegacyVelocityTrackerStrategy::clear() {
+    mIndex = 0;
+    mMovements[0].idBits.clear();
+}
+
+void LegacyVelocityTrackerStrategy::clearPointers(BitSet32 idBits) {
+    BitSet32 remainingIdBits(mMovements[mIndex].idBits.value & ~idBits.value);
+    mMovements[mIndex].idBits = remainingIdBits;
+}
+
+void LegacyVelocityTrackerStrategy::addMovement(nsecs_t eventTime, BitSet32 idBits,
+        const VelocityTracker::Position* positions) {
+    if (++mIndex == HISTORY_SIZE) {
+        mIndex = 0;
+    }
+
+    Movement& movement = mMovements[mIndex];
+    movement.eventTime = eventTime;
+    movement.idBits = idBits;
+    uint32_t count = idBits.count();
+    for (uint32_t i = 0; i < count; i++) {
+        movement.positions[i] = positions[i];
+    }
+}
+
+bool LegacyVelocityTrackerStrategy::getEstimator(uint32_t id,
+        VelocityTracker::Estimator* outEstimator) const {
+    outEstimator->clear();
+
+    const Movement& newestMovement = mMovements[mIndex];
+    if (!newestMovement.idBits.hasBit(id)) {
+        return false; // no data
+    }
+
+    // Find the oldest sample that contains the pointer and that is not older than HORIZON.
+    nsecs_t minTime = newestMovement.eventTime - HORIZON;
+    uint32_t oldestIndex = mIndex;
+    uint32_t numTouches = 1;
+    do {
+        uint32_t nextOldestIndex = (oldestIndex == 0 ? HISTORY_SIZE : oldestIndex) - 1;
+        const Movement& nextOldestMovement = mMovements[nextOldestIndex];
+        if (!nextOldestMovement.idBits.hasBit(id)
+                || nextOldestMovement.eventTime < minTime) {
+            break;
+        }
+        oldestIndex = nextOldestIndex;
+    } while (++numTouches < HISTORY_SIZE);
+
+    // Calculate an exponentially weighted moving average of the velocity estimate
+    // at different points in time measured relative to the oldest sample.
+    // This is essentially an IIR filter.  Newer samples are weighted more heavily
+    // than older samples.  Samples at equal time points are weighted more or less
+    // equally.
+    //
+    // One tricky problem is that the sample data may be poorly conditioned.
+    // Sometimes samples arrive very close together in time which can cause us to
+    // overestimate the velocity at that time point.  Most samples might be measured
+    // 16ms apart but some consecutive samples could be only 0.5sm apart because
+    // the hardware or driver reports them irregularly or in bursts.
+    float accumVx = 0;
+    float accumVy = 0;
+    uint32_t index = oldestIndex;
+    uint32_t samplesUsed = 0;
+    const Movement& oldestMovement = mMovements[oldestIndex];
+    const VelocityTracker::Position& oldestPosition = oldestMovement.getPosition(id);
+    nsecs_t lastDuration = 0;
+
+    while (numTouches-- > 1) {
+        if (++index == HISTORY_SIZE) {
+            index = 0;
+        }
+        const Movement& movement = mMovements[index];
+        nsecs_t duration = movement.eventTime - oldestMovement.eventTime;
+
+        // If the duration between samples is small, we may significantly overestimate
+        // the velocity.  Consequently, we impose a minimum duration constraint on the
+        // samples that we include in the calculation.
+        if (duration >= MIN_DURATION) {
+            const VelocityTracker::Position& position = movement.getPosition(id);
+            float scale = 1000000000.0f / duration; // one over time delta in seconds
+            float vx = (position.x - oldestPosition.x) * scale;
+            float vy = (position.y - oldestPosition.y) * scale;
+            accumVx = (accumVx * lastDuration + vx * duration) / (duration + lastDuration);
+            accumVy = (accumVy * lastDuration + vy * duration) / (duration + lastDuration);
+            lastDuration = duration;
+            samplesUsed += 1;
+        }
+    }
+
+    // Report velocity.
+    const VelocityTracker::Position& newestPosition = newestMovement.getPosition(id);
+    outEstimator->time = newestMovement.eventTime;
+    outEstimator->confidence = 1;
+    outEstimator->xCoeff[0] = newestPosition.x;
+    outEstimator->yCoeff[0] = newestPosition.y;
+    if (samplesUsed) {
+        outEstimator->xCoeff[1] = accumVx;
+        outEstimator->yCoeff[1] = accumVy;
+        outEstimator->degree = 1;
+    } else {
+        outEstimator->degree = 0;
+    }
+    return true;
+}
+
+} // namespace android