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, 50 insertions, 2 deletions

diff --git a/core/java/com/android/internal/widget/PointerLocationView.java b/core/java/com/android/internal/widget/PointerLocationView.java
index 85e6c16..34cdd93 100644
--- a/core/java/com/android/internal/widget/PointerLocationView.java
+++ b/core/java/com/android/internal/widget/PointerLocationView.java
@@ -23,6 +23,7 @@ import android.graphics.RectF;
 import android.graphics.Paint.FontMetricsInt;
 import android.hardware.input.InputManager;
 import android.hardware.input.InputManager.InputDeviceListener;
+import android.os.SystemProperties;
 import android.util.Log;
 import android.view.InputDevice;
 import android.view.KeyEvent;
@@ -36,7 +37,11 @@ import java.util.ArrayList;
 
 public class PointerLocationView extends View implements InputDeviceListener {
     private static final String TAG = "Pointer";
-    
+
+    // The system property key used to specify an alternate velocity tracker strategy
+    // to plot alongside the default one.  Useful for testing and comparison purposes.
+    private static final String ALT_STRATEGY_PROPERY_KEY = "debug.velocitytracker.alt";
+
     public static class PointerState {
         // Trace of previous points.
         private float[] mTraceX = new float[32];
@@ -53,9 +58,12 @@ public class PointerLocationView extends View implements InputDeviceListener {
         // Most recent velocity.
         private float mXVelocity;
         private float mYVelocity;
+        private float mAltXVelocity;
+        private float mAltYVelocity;
 
         // Position estimator.
         private VelocityTracker.Estimator mEstimator = new VelocityTracker.Estimator();
+        private VelocityTracker.Estimator mAltEstimator = new VelocityTracker.Estimator();
 
         public void clearTrace() {
             mTraceCount = 0;
@@ -103,7 +111,8 @@ public class PointerLocationView extends View implements InputDeviceListener {
     private final PointerCoords mTempCoords = new PointerCoords();
     
     private final VelocityTracker mVelocity;
-    
+    private final VelocityTracker mAltVelocity;
+
     private final FasterStringBuilder mText = new FasterStringBuilder();
     
     private boolean mPrintCoords = true;
@@ -145,6 +154,14 @@ public class PointerLocationView extends View implements InputDeviceListener {
         mActivePointerId = 0;
         
         mVelocity = VelocityTracker.obtain();
+
+        String altStrategy = SystemProperties.get(ALT_STRATEGY_PROPERY_KEY);
+        if (altStrategy.length() != 0) {
+            Log.d(TAG, "Comparing default velocity tracker strategy with " + altStrategy);
+            mAltVelocity = VelocityTracker.obtain(altStrategy);
+        } else {
+            mAltVelocity = null;
+        }
     }
 
     public void setPrintCoords(boolean state) {
@@ -296,6 +313,25 @@ public class PointerLocationView extends View implements InputDeviceListener {
                 float xVel = ps.mXVelocity * (1000 / 60);
                 float yVel = ps.mYVelocity * (1000 / 60);
                 canvas.drawLine(lastX, lastY, lastX + xVel, lastY + yVel, mPaint);
+
+                // Draw alternate estimate.
+                if (mAltVelocity != null) {
+                    mPaint.setARGB(128, 0, 128, 128);
+                    lx = ps.mAltEstimator.estimateX(-ESTIMATE_PAST_POINTS * ESTIMATE_INTERVAL);
+                    ly = ps.mAltEstimator.estimateY(-ESTIMATE_PAST_POINTS * ESTIMATE_INTERVAL);
+                    for (int i = -ESTIMATE_PAST_POINTS + 1; i <= ESTIMATE_FUTURE_POINTS; i++) {
+                        float x = ps.mAltEstimator.estimateX(i * ESTIMATE_INTERVAL);
+                        float y = ps.mAltEstimator.estimateY(i * ESTIMATE_INTERVAL);
+                        canvas.drawLine(lx, ly, x, y, mPaint);
+                        lx = x;
+                        ly = y;
+                    }
+
+                    mPaint.setARGB(255, 64, 255, 128);
+                    xVel = ps.mAltXVelocity * (1000 / 60);
+                    yVel = ps.mAltYVelocity * (1000 / 60);
+                    canvas.drawLine(lastX, lastY, lastX + xVel, lastY + yVel, mPaint);
+                }
             }
 
             if (mCurDown && ps.mCurDown) {
@@ -470,6 +506,9 @@ public class PointerLocationView extends View implements InputDeviceListener {
                 mCurNumPointers = 0;
                 mMaxNumPointers = 0;
                 mVelocity.clear();
+                if (mAltVelocity != null) {
+                    mAltVelocity.clear();
+                }
             }
 
             mCurNumPointers += 1;
@@ -497,6 +536,10 @@ public class PointerLocationView extends View implements InputDeviceListener {
 
         mVelocity.addMovement(event);
         mVelocity.computeCurrentVelocity(1);
+        if (mAltVelocity != null) {
+            mAltVelocity.addMovement(event);
+            mAltVelocity.computeCurrentVelocity(1);
+        }
 
         final int N = event.getHistorySize();
         for (int historyPos = 0; historyPos < N; historyPos++) {
@@ -528,6 +571,11 @@ public class PointerLocationView extends View implements InputDeviceListener {
                 ps.mXVelocity = mVelocity.getXVelocity(id);
                 ps.mYVelocity = mVelocity.getYVelocity(id);
                 mVelocity.getEstimator(id, ps.mEstimator);
+                if (mAltVelocity != null) {
+                    ps.mAltXVelocity = mAltVelocity.getXVelocity(id);
+                    ps.mAltYVelocity = mAltVelocity.getYVelocity(id);
+                    mAltVelocity.getEstimator(id, ps.mAltEstimator);
+                }
                 ps.mToolType = event.getToolType(i);
             }
         }