Batching MotionEvents and processing them on the UI thread

Change-Id: I2dc972af8360e719db743740074893bac0213ded

1 files changed, 93 insertions, 0 deletions

diff --git a/quickstep/src/com/android/quickstep/MotionEventQueue.java b/quickstep/src/com/android/quickstep/MotionEventQueue.java
new file mode 100644
index 000000000..e3c3a1b89
--- /dev/null
+++ b/quickstep/src/com/android/quickstep/MotionEventQueue.java
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2017 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.quickstep;
+
+import static android.view.MotionEvent.ACTION_CANCEL;
+import static android.view.MotionEvent.ACTION_MOVE;
+
+import android.view.Choreographer;
+import android.view.MotionEvent;
+
+import com.android.systemui.shared.system.ChoreographerCompat;
+
+import java.util.ArrayList;
+import java.util.function.Consumer;
+
+/**
+ * Helper class for batching input events
+ */
+public class MotionEventQueue implements Runnable {
+
+    // We use two arrays and swap the current index when one array is being consumed
+    private final EventArray[] mArrays = new EventArray[] {new EventArray(), new EventArray()};
+    private int mCurrentIndex = 0;
+
+    private final Choreographer mChoreographer;
+    private final Consumer<MotionEvent> mConsumer;
+
+    public MotionEventQueue(Choreographer choreographer, Consumer<MotionEvent> consumer) {
+        mChoreographer = choreographer;
+        mConsumer = consumer;
+    }
+
+    public void queue(MotionEvent event) {
+        synchronized (mArrays) {
+            EventArray array = mArrays[mCurrentIndex];
+            if (array.isEmpty()) {
+                ChoreographerCompat.postInputFrame(mChoreographer, this);
+            }
+
+            int eventAction = event.getAction();
+            if (eventAction == ACTION_MOVE && array.lastEventAction == ACTION_MOVE) {
+                // Replace and recycle the last event
+                array.set(array.size() - 1, event).recycle();
+            } else {
+                array.add(event);
+                array.lastEventAction = eventAction;
+            }
+        }
+    }
+
+    @Override
+    public void run() {
+        EventArray array = swapAndGetCurrentArray();
+        int size = array.size();
+        for (int i = 0; i < size; i++) {
+            MotionEvent event = array.get(i);
+            mConsumer.accept(event);
+            event.recycle();
+        }
+        array.clear();
+        array.lastEventAction = ACTION_CANCEL;
+    }
+
+    private EventArray swapAndGetCurrentArray() {
+        synchronized (mArrays) {
+            EventArray current = mArrays[mCurrentIndex];
+            mCurrentIndex = mCurrentIndex ^ 1;
+            return current;
+        }
+    }
+
+    private static class EventArray extends ArrayList<MotionEvent> {
+
+        public int lastEventAction = ACTION_CANCEL;
+
+        public EventArray() {
+            super(4);
+        }
+    }
+}