Improve VelocityTracker numerical stability.

Replaced VelocityTracker with a faster and more accurate
native implementation.  This avoids the duplicate maintenance
overhead of having two implementations.

The new algorithm requires that the sample duration be at least
10ms in order to contribute to the velocity calculation.  This
ensures that the velocity is not severely overestimated when
samples arrive in bursts.

The new algorithm computes the exponentially weighted moving
average using weights based on the relative duration of successive
sample periods.

The new algorithm is also more careful about how it handles
individual pointers going down or up and their effects on the
collected movement traces.  The intent is to preserve the last
known velocity of pointers as they go up while also ensuring
that other motion samples do not count twice in that case.

Bug: 4086785
Change-Id: I2632321232c64d6b8faacdb929e33f60e64dcdd3

1 files changed, 1 insertions, 1 deletions

diff --git a/core/jni/android_view_InputQueue.cpp b/core/jni/android_view_InputQueue.cpp
index b5a5d2e..80c4871 100644
--- a/core/jni/android_view_InputQueue.cpp
+++ b/core/jni/android_view_InputQueue.cpp
@@ -380,7 +380,7 @@ int NativeInputQueue::handleReceiveCallback(int receiveFd, int events, void* dat
 #if DEBUG_DISPATCH_CYCLE
         LOGD("channel '%s' ~ Received motion event.", connection->getInputChannelName());
 #endif
-        inputEventObj = android_view_MotionEvent_fromNative(env,
+        inputEventObj = android_view_MotionEvent_obtainAsCopy(env,
                 static_cast<MotionEvent*>(inputEvent));
         dispatchMethodId = gInputQueueClassInfo.dispatchMotionEvent;
         break;