From 4dc14b231ee541e0b889343ca91e74213763bb4f Mon Sep 17 00:00:00 2001
From: Adrian Roos <roosa@google.com>
Date: Wed, 17 Aug 2016 13:26:33 -0700
Subject: [PATCH] HIC: Improve AccelerationClassifier

Apply a bunch of improvements to the acceleration classifier:

- When dragging from the edges, we get some delay without
  movement between the DOWN and MOVE, which confounds the
  classifier. Now discounts data segments where the delay
  does not match the expected 16ms.
- The distance ratio did not compensate for differences
  in sampling. If it does it's equivalent to the speed
  ratio however. The distance ratio was removed and the
  impact of the speed ratio score doubled.
- If we cannot calculate the ratio, no longer penalize
  the traces for this.

Bug: 27405075
Change-Id: I067eb4d478593afbb20354e5c85a05353e2b4184
(cherry picked from commit 6b312a09fcea77651680f63a876ccd4ea378393f)
---
 .../classifier/AccelerationClassifier.java    | 26 ++++++++---------
 .../classifier/DistanceRatioEvaluator.java    | 29 -------------------
 .../classifier/SpeedRatioEvaluator.java       |  1 +
 3 files changed, 14 insertions(+), 42 deletions(-)
 delete mode 100644 packages/SystemUI/src/com/android/systemui/classifier/DistanceRatioEvaluator.java

diff --git a/packages/SystemUI/src/com/android/systemui/classifier/AccelerationClassifier.java b/packages/SystemUI/src/com/android/systemui/classifier/AccelerationClassifier.java
index bad739fdc7648..4585fe9fb8687 100644
--- a/packages/SystemUI/src/com/android/systemui/classifier/AccelerationClassifier.java
+++ b/packages/SystemUI/src/com/android/systemui/classifier/AccelerationClassifier.java
@@ -62,36 +62,36 @@ public class AccelerationClassifier extends StrokeClassifier {
     @Override
     public float getFalseTouchEvaluation(int type, Stroke stroke) {
         Data data = mStrokeMap.get(stroke);
-        return SpeedRatioEvaluator.evaluate(data.maxSpeedRatio)
-                + DistanceRatioEvaluator.evaluate(data.maxDistanceRatio);
+        return 2 * SpeedRatioEvaluator.evaluate(data.maxSpeedRatio);
     }
 
     private static class Data {
-        public Point previousPoint;
-        public float previousSpeed;
-        public float previousDistance;
-        public float maxSpeedRatio;
-        public float maxDistanceRatio;
+
+        static final float MILLIS_TO_NANOS = 1e6f;
+
+        Point previousPoint;
+        float previousSpeed = 0;
+        float maxSpeedRatio = 0;
 
         public Data(Point point) {
             previousPoint = point;
-            previousSpeed = previousDistance = 0.0f;
-            maxDistanceRatio = maxSpeedRatio = 0.0f;
         }
 
         public void addPoint(Point point) {
             float distance = previousPoint.dist(point);
             float duration = (float) (point.timeOffsetNano - previousPoint.timeOffsetNano + 1);
             float speed = distance / duration;
-            if (previousDistance != 0.0f) {
-                maxDistanceRatio = Math.max(maxDistanceRatio, distance / previousDistance);
-            }
 
+            if (duration > 20 * MILLIS_TO_NANOS || duration < 5 * MILLIS_TO_NANOS) {
+                // reject this segment and ensure we won't use data about it in the next round.
+                previousSpeed = 0;
+                previousPoint = point;
+                return;
+            }
             if (previousSpeed != 0.0f) {
                 maxSpeedRatio = Math.max(maxSpeedRatio, speed / previousSpeed);
             }
 
-            previousDistance = distance;
             previousSpeed = speed;
             previousPoint = point;
         }
diff --git a/packages/SystemUI/src/com/android/systemui/classifier/DistanceRatioEvaluator.java b/packages/SystemUI/src/com/android/systemui/classifier/DistanceRatioEvaluator.java
deleted file mode 100644
index 8acb009a230fe..0000000000000
--- a/packages/SystemUI/src/com/android/systemui/classifier/DistanceRatioEvaluator.java
+++ /dev/null
@@ -1,29 +0,0 @@
-/*
- * Copyright (C) 2015 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
- */
-
-package com.android.systemui.classifier;
-
-public class DistanceRatioEvaluator {
-    public static float evaluate(float value) {
-        float evaluation = 0.0f;
-        if (value <= 1.0) evaluation++;
-        if (value <= 0.5) evaluation++;
-        if (value > 4.0) evaluation++;
-        if (value > 7.0) evaluation++;
-        if (value > 14.0) evaluation++;
-        return evaluation;
-    }
-}
diff --git a/packages/SystemUI/src/com/android/systemui/classifier/SpeedRatioEvaluator.java b/packages/SystemUI/src/com/android/systemui/classifier/SpeedRatioEvaluator.java
index 4c6cea0367adc..e34f222d3799e 100644
--- a/packages/SystemUI/src/com/android/systemui/classifier/SpeedRatioEvaluator.java
+++ b/packages/SystemUI/src/com/android/systemui/classifier/SpeedRatioEvaluator.java
@@ -19,6 +19,7 @@ package com.android.systemui.classifier;
 public class SpeedRatioEvaluator {
     public static float evaluate(float value) {
         float evaluation = 0.0f;
+        if (value == 0) return 0;
         if (value <= 1.0) evaluation++;
         if (value <= 0.5) evaluation++;
         if (value > 9.0) evaluation++;