Make velocity tracker strategy configurable.

This change is very useful for testing purposes because it makes it
easy to compare different implementations to see how they behave.

There is no change to the current default strategy.

Bug: 6413587
Change-Id: I4d8567aa4160571ba9fa397ce419882cd9366749

1 files changed, 14 insertions, 6 deletions

diff --git a/include/androidfw/VelocityTracker.h b/include/androidfw/VelocityTracker.h
index cbb0782..1d44f13 100644
--- a/include/androidfw/VelocityTracker.h
+++ b/include/androidfw/VelocityTracker.h
@@ -35,7 +35,7 @@ public:
     };
 
     struct Estimator {
-        static const size_t MAX_DEGREE = 2;
+        static const size_t MAX_DEGREE = 4;
 
         // Estimator time base.
         nsecs_t time;
@@ -61,7 +61,10 @@ public:
         }
     };
 
-    VelocityTracker();
+    // 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.
@@ -99,10 +102,16 @@ public:
     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);
 };
 
 
@@ -129,7 +138,8 @@ public:
  */
 class LeastSquaresVelocityTrackerStrategy : public VelocityTrackerStrategy {
 public:
-    LeastSquaresVelocityTrackerStrategy();
+    // Degree must be no greater than Estimator::MAX_DEGREE.
+    LeastSquaresVelocityTrackerStrategy(uint32_t degree);
     virtual ~LeastSquaresVelocityTrackerStrategy();
 
     virtual void clear();
@@ -139,9 +149,6 @@ public:
     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.
@@ -160,6 +167,7 @@ private:
         }
     };
 
+    const uint32_t mDegree;
     uint32_t mIndex;
     Movement mMovements[HISTORY_SIZE];
 };