More VelocityTracker refactoring.

Bug: 6413587
Change-Id: Ida1152e7a34d5fe5caab5e6b5e1bc79f6c7a25e6

5 files changed, 155 insertions, 85 deletions

diff --git a/core/java/android/view/VelocityTracker.java b/core/java/android/view/VelocityTracker.java
index f703e34..f5870e1 100644
--- a/core/java/android/view/VelocityTracker.java
+++ b/core/java/android/view/VelocityTracker.java
@@ -60,8 +60,7 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
     private static native void nativeComputeCurrentVelocity(int ptr, int units, float maxVelocity);
     private static native float nativeGetXVelocity(int ptr, int id);
     private static native float nativeGetYVelocity(int ptr, int id);
-    private static native boolean nativeGetEstimator(int ptr, int id,
-            int degree, int horizonMillis, Estimator outEstimator);
+    private static native boolean nativeGetEstimator(int ptr, int id, Estimator outEstimator);
 
     /**
      * Retrieve a new VelocityTracker object to watch the velocity of a
@@ -227,21 +226,17 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
      * this method.
      *
      * @param id Which pointer's velocity to return.
-     * @param degree The desired polynomial degree.  The actual estimator may have
-     * a lower degree than what is requested here.  If -1, uses the default degree.
-     * @param horizonMillis The maximum age of the oldest sample to consider, in milliseconds.
-     * If -1, uses the default horizon.
      * @param outEstimator The estimator to populate.
      * @return True if an estimator was obtained, false if there is no information
      * available about the pointer.
      *
      * @hide For internal use only.  Not a final API.
      */
-    public boolean getEstimator(int id, int degree, int horizonMillis, Estimator outEstimator) {
+    public boolean getEstimator(int id, Estimator outEstimator) {
         if (outEstimator == null) {
             throw new IllegalArgumentException("outEstimator must not be null");
         }
-        return nativeGetEstimator(mPtr, id, degree, horizonMillis, outEstimator);
+        return nativeGetEstimator(mPtr, id, outEstimator);
     }
 
     /**
diff --git a/core/java/com/android/internal/widget/PointerLocationView.java b/core/java/com/android/internal/widget/PointerLocationView.java
index 1d6af90..85e6c16 100644
--- a/core/java/com/android/internal/widget/PointerLocationView.java
+++ b/core/java/com/android/internal/widget/PointerLocationView.java
@@ -527,7 +527,7 @@ public class PointerLocationView extends View implements InputDeviceListener {
                 ps.addTrace(coords.x, coords.y);
                 ps.mXVelocity = mVelocity.getXVelocity(id);
                 ps.mYVelocity = mVelocity.getYVelocity(id);
-                mVelocity.getEstimator(id, -1, -1, ps.mEstimator);
+                mVelocity.getEstimator(id, ps.mEstimator);
                 ps.mToolType = event.getToolType(i);
             }
         }
diff --git a/core/jni/android_view_VelocityTracker.cpp b/core/jni/android_view_VelocityTracker.cpp
index 04d1056..0180e0a 100644
--- a/core/jni/android_view_VelocityTracker.cpp
+++ b/core/jni/android_view_VelocityTracker.cpp
@@ -48,8 +48,7 @@ public:
     void addMovement(const MotionEvent* event);
     void computeCurrentVelocity(int32_t units, float maxVelocity);
     void getVelocity(int32_t id, float* outVx, float* outVy);
-    bool getEstimator(int32_t id, uint32_t degree, nsecs_t horizon,
-            VelocityTracker::Estimator* outEstimator);
+    bool getEstimator(int32_t id, VelocityTracker::Estimator* outEstimator);
 
 private:
     struct Velocity {
@@ -129,9 +128,8 @@ void VelocityTrackerState::getVelocity(int32_t id, float* outVx, float* outVy) {
     }
 }
 
-bool VelocityTrackerState::getEstimator(int32_t id, uint32_t degree, nsecs_t horizon,
-        VelocityTracker::Estimator* outEstimator) {
-    return mVelocityTracker.getEstimator(id, degree, horizon, outEstimator);
+bool VelocityTrackerState::getEstimator(int32_t id, VelocityTracker::Estimator* outEstimator) {
+    return mVelocityTracker.getEstimator(id, outEstimator);
 }
 
 
@@ -186,14 +184,10 @@ static jfloat android_view_VelocityTracker_nativeGetYVelocity(JNIEnv* env, jclas
 }
 
 static jboolean android_view_VelocityTracker_nativeGetEstimator(JNIEnv* env, jclass clazz,
-        jint ptr, jint id, jint degree, jint horizonMillis, jobject outEstimatorObj) {
+        jint ptr, jint id, jobject outEstimatorObj) {
     VelocityTrackerState* state = reinterpret_cast<VelocityTrackerState*>(ptr);
     VelocityTracker::Estimator estimator;
-    bool result = state->getEstimator(id,
-            degree < 0 ? VelocityTracker::DEFAULT_DEGREE : uint32_t(degree),
-            horizonMillis < 0 ? VelocityTracker::DEFAULT_HORIZON :
-                    nsecs_t(horizonMillis) * 1000000L,
-            &estimator);
+    bool result = state->getEstimator(id, &estimator);
 
     jfloatArray xCoeffObj = jfloatArray(env->GetObjectField(outEstimatorObj,
             gEstimatorClassInfo.xCoeff));
@@ -236,7 +230,7 @@ static JNINativeMethod gVelocityTrackerMethods[] = {
             "(II)F",
             (void*)android_view_VelocityTracker_nativeGetYVelocity },
     { "nativeGetEstimator",
-            "(IIIILandroid/view/VelocityTracker$Estimator;)Z",
+            "(IILandroid/view/VelocityTracker$Estimator;)Z",
             (void*)android_view_VelocityTracker_nativeGetEstimator },
 };
 
diff --git a/include/androidfw/VelocityTracker.h b/include/androidfw/VelocityTracker.h
index 6d17e1f..6964588 100644
--- a/include/androidfw/VelocityTracker.h
+++ b/include/androidfw/VelocityTracker.h
@@ -23,19 +23,13 @@
 
 namespace android {
 
+class VelocityTrackerStrategy;
+
 /*
  * 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;
     };
@@ -64,6 +58,8 @@ public:
     };
 
     VelocityTracker();
+    VelocityTracker(VelocityTrackerStrategy* strategy);
+    ~VelocityTracker();
 
     // Resets the velocity tracker state.
     void clear();
@@ -88,35 +84,80 @@ public:
     // 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.
+    // 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, uint32_t degree, nsecs_t horizon,
-            Estimator* outEstimator) const;
+    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 mMovements[mIndex].idBits; }
+    inline BitSet32 getCurrentPointerIdBits() const { return mCurrentPointerIdBits; }
+
+private:
+    BitSet32 mCurrentPointerIdBits;
+    int32_t mActivePointerId;
+    VelocityTrackerStrategy* mStrategy;
+};
+
+
+/*
+ * 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:
+    LeastSquaresVelocityTrackerStrategy();
+    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:
+    // Polynomial degree.  Must be less than or equal to Estimator::MAX_DEGREE.
+    static const uint32_t DEGREE = 2;
+
+    // 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;
-        Position positions[MAX_POINTERS];
+        VelocityTracker::Position positions[MAX_POINTERS];
 
-        inline const Position& getPosition(uint32_t id) const {
+        inline const VelocityTracker::Position& getPosition(uint32_t id) const {
             return positions[idBits.getIndexOfBit(id)];
         }
     };
 
     uint32_t mIndex;
     Movement mMovements[HISTORY_SIZE];
-    int32_t mActivePointerId;
 };
 
 } // namespace android
diff --git a/libs/androidfw/VelocityTracker.cpp b/libs/androidfw/VelocityTracker.cpp
index 2fb094e..de214f8 100644
--- a/libs/androidfw/VelocityTracker.cpp
+++ b/libs/androidfw/VelocityTracker.cpp
@@ -33,13 +33,7 @@
 
 namespace android {
 
-// --- VelocityTracker ---
-
-const uint32_t VelocityTracker::DEFAULT_DEGREE;
-const nsecs_t VelocityTracker::DEFAULT_HORIZON;
-const uint32_t VelocityTracker::HISTORY_SIZE;
-
-static inline float vectorDot(const float* a, const float* b, uint32_t m) {
+static float vectorDot(const float* a, const float* b, uint32_t m) {
     float r = 0;
     while (m--) {
         r += *(a++) * *(b++);
@@ -47,7 +41,7 @@ static inline float vectorDot(const float* a, const float* b, uint32_t m) {
     return r;
 }
 
-static inline float vectorNorm(const float* a, uint32_t m) {
+static float vectorNorm(const float* a, uint32_t m) {
     float r = 0;
     while (m--) {
         float t = *(a++);
@@ -91,46 +85,53 @@ static String8 matrixToString(const float* a, uint32_t m, uint32_t n, bool rowMa
 }
 #endif
 
-VelocityTracker::VelocityTracker() {
-    clear();
+
+// --- VelocityTracker ---
+
+VelocityTracker::VelocityTracker() :
+        mCurrentPointerIdBits(0), mActivePointerId(-1),
+        mStrategy(new LeastSquaresVelocityTrackerStrategy()) {
+}
+
+VelocityTracker::VelocityTracker(VelocityTrackerStrategy* strategy) :
+        mCurrentPointerIdBits(0), mActivePointerId(-1),
+        mStrategy(strategy) {
+}
+
+VelocityTracker::~VelocityTracker() {
+    delete mStrategy;
 }
 
 void VelocityTracker::clear() {
-    mIndex = 0;
-    mMovements[0].idBits.clear();
+    mCurrentPointerIdBits.clear();
     mActivePointerId = -1;
+
+    mStrategy->clear();
 }
 
 void VelocityTracker::clearPointers(BitSet32 idBits) {
-    BitSet32 remainingIdBits(mMovements[mIndex].idBits.value & ~idBits.value);
-    mMovements[mIndex].idBits = remainingIdBits;
+    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) {
-    if (++mIndex == HISTORY_SIZE) {
-        mIndex = 0;
-    }
-
     while (idBits.count() > MAX_POINTERS) {
         idBits.clearLastMarkedBit();
     }
 
-    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];
-    }
-
+    mCurrentPointerIdBits = idBits;
     if (mActivePointerId < 0 || !idBits.hasBit(mActivePointerId)) {
-        mActivePointerId = count != 0 ? idBits.firstMarkedBit() : -1;
+        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);
@@ -139,7 +140,7 @@ void VelocityTracker::addMovement(nsecs_t eventTime, BitSet32 idBits, const Posi
         uint32_t index = idBits.getIndexOfBit(id);
         iterBits.clearBit(id);
         Estimator estimator;
-        getEstimator(id, DEFAULT_DEGREE, DEFAULT_HORIZON, &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,
@@ -215,6 +216,61 @@ void VelocityTracker::addMovement(const MotionEvent* event) {
     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 uint32_t LeastSquaresVelocityTrackerStrategy::DEGREE;
+const nsecs_t LeastSquaresVelocityTrackerStrategy::HORIZON;
+const uint32_t LeastSquaresVelocityTrackerStrategy::HISTORY_SIZE;
+
+LeastSquaresVelocityTrackerStrategy::LeastSquaresVelocityTrackerStrategy() {
+    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.
@@ -361,22 +417,8 @@ static bool solveLeastSquares(const float* x, const float* y, uint32_t m, uint32
     return true;
 }
 
-bool VelocityTracker::getVelocity(uint32_t id, float* outVx, float* outVy) const {
-    Estimator estimator;
-    if (getEstimator(id, DEFAULT_DEGREE, DEFAULT_HORIZON, &estimator)) {
-        if (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, uint32_t degree, nsecs_t horizon,
-        Estimator* outEstimator) const {
+bool LeastSquaresVelocityTrackerStrategy::getEstimator(uint32_t id,
+        VelocityTracker::Estimator* outEstimator) const {
     outEstimator->clear();
 
     // Iterate over movement samples in reverse time order and collect samples.
@@ -393,11 +435,11 @@ bool VelocityTracker::getEstimator(uint32_t id, uint32_t degree, nsecs_t horizon
         }
 
         nsecs_t age = newestMovement.eventTime - movement.eventTime;
-        if (age > horizon) {
+        if (age > HORIZON) {
             break;
         }
 
-        const Position& position = movement.getPosition(id);
+        const VelocityTracker::Position& position = movement.getPosition(id);
         x[m] = position.x;
         y[m] = position.y;
         time[m] = -age * 0.000000001f;
@@ -409,9 +451,7 @@ bool VelocityTracker::getEstimator(uint32_t id, uint32_t degree, nsecs_t horizon
     }
 
     // Calculate a least squares polynomial fit.
-    if (degree > Estimator::MAX_DEGREE) {
-        degree = Estimator::MAX_DEGREE;
-    }
+    uint32_t degree = DEGREE;
     if (degree > m - 1) {
         degree = m - 1;
     }