Add support for scroll and fling gestures to SkyShell.

sky/shell/org/domokit/sky/shell/GestureProvider.java

Index: sky/shell/org/domokit/sky/shell/GestureProvider.java
diff --git a/sky/shell/org/domokit/sky/shell/GestureProvider.java b/sky/shell/org/domokit/sky/shell/GestureProvider.java
new file mode 100644
index 0000000000000000000000000000000000000000..af286e9670af1a8de099d908a18899903ee90d6c
--- /dev/null
+++ b/sky/shell/org/domokit/sky/shell/GestureProvider.java
@@ -0,0 +1,126 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.domokit.sky.shell;
+
+import android.content.Context;
+import android.view.GestureDetector;
+import android.view.MotionEvent;
+
+import org.chromium.mojom.sky.EventType;
+import org.chromium.mojom.sky.GestureData;
+import org.chromium.mojom.sky.InputEvent;
+
+/**
+ * Knows how to drive a GestureDetector to turn MotionEvents into Sky's
+ * InputEvents.  Seems like this should not be needed.  That there must exist
+ * some Android class to do most of this work for us?
+ */
+public class GestureProvider implements GestureDetector.OnGestureListener {
+    private static final String TAG = "GestureProvider";
+
+    /**
+     * Callback interface
+     */
+    public interface OnGestureListener {
+        void onGestureEvent(InputEvent e);
+    }
+
+    private OnGestureListener mListener;
+    private GestureDetector mDetector;
+    private boolean mScrolling;
+    private boolean mFlinging;
+
+    public GestureProvider(Context context, OnGestureListener listener) {
+        mListener = listener;
+        mDetector = new GestureDetector(context, this);
+    }
+
+    private InputEvent createGestureEvent(MotionEvent event) {
+        GestureData gestureData = new GestureData();
+        gestureData.x = event.getX();
+        gestureData.y = event.getY();
+        InputEvent inputEvent = new InputEvent();
+        inputEvent.timeStamp = event.getEventTime();
+        inputEvent.gestureData = gestureData;
+        return inputEvent;
+    }
+
+    public void onTouchEvent(MotionEvent event) {
+        // TODO(eseidel): I am not confident that these stops are correct.
+        int maskedAction = event.getActionMasked();
+        if (mScrolling && maskedAction == MotionEvent.ACTION_UP) {
+            mScrolling = false;
+            InputEvent inputEvent = createGestureEvent(event);
+            inputEvent.type = EventType.GESTURE_SCROLL_END;
+            mListener.onGestureEvent(inputEvent);
+        }
+
+        if (mFlinging && maskedAction == MotionEvent.ACTION_DOWN) {
+            mFlinging = false;
+            InputEvent inputEvent = createGestureEvent(event);
+            inputEvent.type = EventType.GESTURE_FLING_CANCEL;
+            mListener.onGestureEvent(inputEvent);
+        }
+
+        mDetector.onTouchEvent(event);
+    }
+
+    @Override
+    public boolean onDown(MotionEvent event) {
+        return true;
+    }
+
+    @Override
+    public boolean onFling(MotionEvent e1, MotionEvent e2,
+            float velocityX, float velocityY) {
+
+        mFlinging = true;
+
+        // Use the first event as a scroll start (for the target hit-test)
+        InputEvent inputEvent = createGestureEvent(e1);
+        inputEvent.gestureData.velocityX = velocityX;
+        inputEvent.gestureData.velocityY = velocityY;
+        inputEvent.type = EventType.GESTURE_FLING_START;
+
+        mListener.onGestureEvent(inputEvent);
+
+        return true;
+    }
+
+    @Override
+    public void onLongPress(MotionEvent event) {
+    }
+
+    @Override
+    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
+            float distanceY) {
+        // Use the first event as a scroll start (for the target hit-test)
+        InputEvent inputEvent = createGestureEvent(e1);
+        inputEvent.gestureData.dx = distanceX;
+        inputEvent.gestureData.dy = -distanceY;
+
+        // If we haven't started scrolling, send a scroll_begin.
+        if (!mScrolling) {
+            mScrolling = true;
+            inputEvent.type = EventType.GESTURE_SCROLL_BEGIN;
+            mListener.onGestureEvent(inputEvent);
+        }
+
+        inputEvent.type = EventType.GESTURE_SCROLL_UPDATE;
+        mListener.onGestureEvent(inputEvent);
+        return true;
+    }
+
+    @Override
+    public void onShowPress(MotionEvent event) {
+    }
+
+    @Override
+    public boolean onSingleTapUp(MotionEvent event) {
+        return true;
+    }
+
+
+}