Handle root layer fling Java-side in android_webview.

The android_webview implementation needs to handle root layer fling
Java-side. This is required for proper integration with the android
view system which requires the fling scroll offset update to be
performed as a result of the computeScroll method.

BUG=None
TEST=AndroidWebViewTest

Review URL: https://chromiumcodereview.appspot.com/20990009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@215339 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 130 insertions, 10 deletions

diff --git a/android_webview/java/src/org/chromium/android_webview/AwContents.java b/android_webview/java/src/org/chromium/android_webview/AwContents.java
index 22be0d4..2d498da 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -31,6 +31,7 @@ import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
 import android.webkit.GeolocationPermissions;
 import android.webkit.ValueCallback;
+import android.widget.OverScroller;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -372,10 +373,15 @@ public class AwContents {
         public int getContainerViewScrollY() {
             return mContainerView.getScrollY();
         }
+
+        @Override
+        public void invalidate() {
+            mContainerView.invalidate();
+        }
     }
 
     //--------------------------------------------------------------------------------------------
-    private class AwPinchGestureStateListener implements ContentViewCore.PinchGestureStateListener {
+    private class AwGestureStateListener implements ContentViewCore.GestureStateListener {
         @Override
         public void onPinchGestureStart() {
             // While it's possible to re-layout the view during a pinch gesture, the effect is very
@@ -387,9 +393,26 @@ public class AwContents {
             mLayoutSizer.freezeLayoutRequests();
         }
 
+        @Override
         public void onPinchGestureEnd() {
             mLayoutSizer.unfreezeLayoutRequests();
         }
+
+        @Override
+        public void onFlingStartGesture(int velocityX, int velocityY) {
+            mScrollOffsetManager.onFlingStartGesture(velocityX, velocityY);
+        }
+
+
+        @Override
+        public void onFlingCancelGesture() {
+            mScrollOffsetManager.onFlingCancelGesture();
+        }
+
+        @Override
+        public void onUnhandledFlingStartEvent() {
+            mScrollOffsetManager.onUnhandledFlingStartEvent();
+        }
     }
 
     //--------------------------------------------------------------------------------------------
@@ -424,7 +447,7 @@ public class AwContents {
 
     private static ContentViewCore createAndInitializeContentViewCore(ViewGroup containerView,
             InternalAccessDelegate internalDispatcher, int nativeWebContents,
-            ContentViewCore.PinchGestureStateListener pinchGestureStateListener,
+            ContentViewCore.GestureStateListener pinchGestureStateListener,
             ContentViewClient contentViewClient,
             ContentViewCore.ZoomControlsDelegate zoomControlsDelegate) {
       ContentViewCore contentViewCore = new ContentViewCore(containerView.getContext());
@@ -432,7 +455,7 @@ public class AwContents {
       // compositor, not because input events are delivered immediately.
       contentViewCore.initialize(containerView, internalDispatcher, nativeWebContents, null,
                 ContentViewCore.INPUT_EVENTS_DELIVERED_IMMEDIATELY);
-      contentViewCore.setPinchGestureStateListener(pinchGestureStateListener);
+      contentViewCore.setGestureStateListener(pinchGestureStateListener);
       contentViewCore.setContentViewClient(contentViewClient);
       contentViewCore.setZoomControlsDelegate(zoomControlsDelegate);
       return contentViewCore;
@@ -479,7 +502,8 @@ public class AwContents {
         mSettings.setDefaultVideoPosterURL(
                 mDefaultVideoPosterRequestHandler.getDefaultVideoPosterURL());
         mContentsClient.setDIPScale(mDIPScale);
-        mScrollOffsetManager = new AwScrollOffsetManager(new AwScrollOffsetManagerDelegate());
+        mScrollOffsetManager = new AwScrollOffsetManager(new AwScrollOffsetManagerDelegate(),
+                new OverScroller(mContainerView.getContext()));
 
         setOverScrollMode(mContainerView.getOverScrollMode());
 
@@ -513,7 +537,7 @@ public class AwContents {
         int nativeWebContents = nativeGetWebContents(mNativeAwContents);
         mContentViewCore = createAndInitializeContentViewCore(
                 mContainerView, mInternalAccessAdapter, nativeWebContents,
-                new AwPinchGestureStateListener(), mContentsClient.getContentViewClient(),
+                new AwGestureStateListener(), mContentsClient.getContentViewClient(),
                 mZoomControls);
         nativeSetJavaPeers(mNativeAwContents, this, mWebContentsDelegate, mContentsClientBridge,
                 mIoThreadClient, mInterceptNavigationDelegate);
@@ -870,6 +894,13 @@ public class AwContents {
     }
 
     /**
+     * @see View.computeScroll()
+     */
+    public void computeScroll() {
+        mScrollOffsetManager.computeScrollAndAbsorbGlow(mOverScrollGlow);
+    }
+
+    /**
      * @see View#computeHorizontalScrollRange()
      */
     public int computeHorizontalScrollRange() {
@@ -1174,8 +1205,8 @@ public class AwContents {
     /**
      * @see android.webkit.WebView#flingScroll(int, int)
      */
-    public void flingScroll(int vx, int vy) {
-        mContentViewCore.flingScroll(vx, vy);
+    public void flingScroll(int velocityX, int velocityY) {
+        mContentViewCore.flingScroll(velocityX, velocityY);
     }
 
     /**
@@ -1656,7 +1687,7 @@ public class AwContents {
             mOverScrollGlow.setOverScrollDeltas(deltaX, deltaY);
         }
 
-        mScrollOffsetManager.overscrollBy(deltaX, deltaY);
+        mScrollOffsetManager.overScrollBy(deltaX, deltaY);
 
         if (mOverScrollGlow != null && mOverScrollGlow.isAnimating()) {
             mContainerView.invalidate();
diff --git a/android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java b/android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java
index 4564b42..86f693b 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwScrollOffsetManager.java
@@ -4,6 +4,10 @@
 
 package org.chromium.android_webview;
 
+import android.widget.OverScroller;
+
+import com.google.common.annotations.VisibleForTesting;
+
 import org.chromium.base.CalledByNative;
 
 /**
@@ -12,6 +16,7 @@ import org.chromium.base.CalledByNative;
  *
  * Unless otherwise values (sizes, scroll offsets) are in physical pixels.
  */
+@VisibleForTesting
 public class AwScrollOffsetManager {
     // The unit of all the values in this delegate are physical pixels.
     public interface Delegate {
@@ -24,8 +29,11 @@ public class AwScrollOffsetManager {
         // operation, the native side shouldn't synchronously alter the scroll offset from within
         // this call.
         void scrollNativeTo(int x, int y);
+
         int getContainerViewScrollX();
         int getContainerViewScrollY();
+
+        void invalidate();
     }
 
     private final Delegate mDelegate;
@@ -42,14 +50,24 @@ public class AwScrollOffsetManager {
     private int mContainerViewWidth;
     private int mContainerViewHeight;
 
+    // Whether we're in the middle of processing a touch event.
     private boolean mProcessingTouchEvent;
 
+    // Whether (and to what value) to update the native side scroll offset after we've finished
+    // provessing a touch event.
     private boolean mApplyDeferredNativeScroll;
     private int mDeferredNativeScrollX;
     private int mDeferredNativeScrollY;
 
-    public AwScrollOffsetManager(Delegate delegate) {
+    // The velocity of the last recorded fling,
+    private int mLastFlingVelocityX;
+    private int mLastFlingVelocityY;
+
+    private OverScroller mScroller;
+
+    public AwScrollOffsetManager(Delegate delegate, OverScroller overScroller) {
         mDelegate = delegate;
+        mScroller = overScroller;
     }
 
     //----- Scroll range and extent calculation methods -------------------------------------------
@@ -133,12 +151,25 @@ public class AwScrollOffsetManager {
     }
 
     // Called by the native side to over-scroll the container view.
-    public void overscrollBy(int deltaX, int deltaY) {
+    public void overScrollBy(int deltaX, int deltaY) {
+        // TODO(mkosiba): Once http://crbug.com/260663 and http://crbug.com/261239 are fixed it
+        // should be possible to uncomment the following asserts:
+        // if (deltaX < 0) assert mDelegate.getContainerViewScrollX() == 0;
+        // if (deltaX > 0) assert mDelegate.getContainerViewScrollX() ==
+        //          computeMaximumHorizontalScrollOffset();
+        scrollBy(deltaX, deltaY);
+    }
+
+    private void scrollBy(int deltaX, int deltaY) {
+        if (deltaX == 0 && deltaY == 0) return;
+
         final int scrollX = mDelegate.getContainerViewScrollX();
         final int scrollY = mDelegate.getContainerViewScrollY();
         final int scrollRangeX = computeMaximumHorizontalScrollOffset();
         final int scrollRangeY = computeMaximumVerticalScrollOffset();
 
+        // The android.view.View.overScrollBy method is used for both scrolling and over-scrolling
+        // which is why we use it here.
         mDelegate.overScrollContainerViewBy(deltaX, deltaY, scrollX, scrollY,
                 scrollRangeX, scrollRangeY, mProcessingTouchEvent);
     }
@@ -201,4 +232,62 @@ public class AwScrollOffsetManager {
 
         mDelegate.scrollNativeTo(x, y);
     }
+
+    // Called at the beginning of every fling gesture.
+    public void onFlingStartGesture(int velocityX, int velocityY) {
+        mLastFlingVelocityX = velocityX;
+        mLastFlingVelocityY = velocityY;
+    }
+
+    // Called whenever some other touch interaction requires the fling gesture to be canceled.
+    public void onFlingCancelGesture() {
+        // TODO(mkosiba): Support speeding up a fling by flinging again.
+        // http://crbug.com/265841
+        mScroller.forceFinished(true);
+    }
+
+    // Called when a fling gesture is not handled by the renderer.
+    // We explicitly ask the renderer not to handle fling gestures targeted at the root
+    // scroll layer.
+    public void onUnhandledFlingStartEvent() {
+        flingScroll(-mLastFlingVelocityX, -mLastFlingVelocityY);
+    }
+
+    // Starts the fling animation. Called both as a response to a fling gesture and as via the
+    // public WebView#flingScroll(int, int) API.
+    public void flingScroll(int velocityX, int velocityY) {
+        final int scrollX = mDelegate.getContainerViewScrollX();
+        final int scrollY = mDelegate.getContainerViewScrollY();
+        final int rangeX = computeMaximumHorizontalScrollOffset();
+        final int rangeY = computeMaximumVerticalScrollOffset();
+
+        mScroller.fling(scrollX, scrollY, velocityX, velocityY,
+                0, rangeX, 0, rangeY);
+        mDelegate.invalidate();
+    }
+
+    // Called immediately before the draw to update the scroll offset.
+    public void computeScrollAndAbsorbGlow(OverScrollGlow overScrollGlow) {
+        final boolean stillAnimating = mScroller.computeScrollOffset();
+        if (!stillAnimating) return;
+
+        final int oldX = mDelegate.getContainerViewScrollX();
+        final int oldY = mDelegate.getContainerViewScrollY();
+        int x = mScroller.getCurrX();
+        int y = mScroller.getCurrY();
+
+        int rangeX = computeMaximumHorizontalScrollOffset();
+        int rangeY = computeMaximumVerticalScrollOffset();
+
+        if (overScrollGlow != null) {
+            overScrollGlow.absorbGlow(x, y, oldX, oldY, rangeX, rangeY,
+                    mScroller.getCurrVelocity());
+        }
+
+        // The mScroller is configured not to go outside of the scrollable range, so this call
+        // should never result in attempting to scroll outside of the scrollable region.
+        scrollBy(x - oldX, y - oldY);
+
+        mDelegate.invalidate();
+    }
 }