Unify Android Webview and Chrome's fling

android_webview/java/src/org/chromium/android_webview/AwContents.java

Index: android_webview/java/src/org/chromium/android_webview/AwContents.java
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 4a97cab364ca63bdccb5c33181ec2a7d5728df4f..94226d331fa5df852e78c2f8f14c4c7459adc756 100644
--- a/android_webview/java/src/org/chromium/android_webview/AwContents.java
+++ b/android_webview/java/src/org/chromium/android_webview/AwContents.java
@@ -22,8 +22,10 @@ import android.os.Build;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
+import android.os.SystemClock;
 import android.text.TextUtils;
 import android.util.Base64;
+import android.util.FloatMath;
 import android.util.Log;
 import android.util.Pair;
 import android.view.KeyEvent;
@@ -33,6 +35,7 @@ import android.view.ViewGroup;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityNodeInfo;
 import android.view.accessibility.AccessibilityNodeProvider;
+import android.view.animation.AnimationUtils;
 import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
 import android.webkit.GeolocationPermissions;
@@ -575,7 +578,8 @@ public class AwContents implements SmartClipProvider,
 
         @Override
         public void onUnhandledFlingStartEvent(int velocityX, int velocityY) {

[jdduke (slow), 2015/05/04 22:02:10]

Looks like we can completely eliminate this method from the GestureStateListener
interface.

[hush (inactive), 2015/05/05 21:15:32]

Done.

-            mScrollOffsetManager.onUnhandledFlingStartEvent(velocityX, velocityY);
+            // Nothing. Renderer does not ignore the fling gestures targeted at
+            // the root layer any more.
         }
 
         @Override
@@ -1879,7 +1883,7 @@ public class AwContents implements SmartClipProvider,
      */
     public void flingScroll(int velocityX, int velocityY) {
         if (TRACE) Log.d(TAG, "flingScroll");
-        mScrollOffsetManager.flingScroll(velocityX, velocityY);
+        mContentViewCore.fling(SystemClock.uptimeMillis(), 0, 0, -velocityX, -velocityY);
     }
 
     /**
@@ -2512,14 +2516,29 @@ public class AwContents implements SmartClipProvider,
     }
 
     @CalledByNative
-    private void didOverscroll(int deltaX, int deltaY) {
+    private void didOverscroll(int deltaX, int deltaY, float velocityX, float velocityY,
+            boolean firstOverscrollX, boolean firstOverscrollY) {
         if (mOverScrollGlow != null) {
             mOverScrollGlow.setOverScrollDeltas(deltaX, deltaY);
         }
 
+        // TODO(jdduke): Skip this for components with non-zero velocity?

[jdduke (slow), 2015/05/04 22:11:48]

How important is this todo? Can you verify that the glow works if you can
overscroll both horizontally and vertically from a fling (i.e., start the fling
when both axes are scrollable and overscroll into the corner)?

[hush (inactive), 2015/05/05 21:15:32]

Glow works with the current logic.
I actually just did this TODO and glow works as well (both in flinging near the
corner and scrolling at the corner)

         mScrollOffsetManager.overScrollBy(deltaX, deltaY);
 
-        if (mOverScrollGlow != null && mOverScrollGlow.isAnimating()) {
+        if (mOverScrollGlow == null) return;
+
+        if ((velocityX != 0 && firstOverscrollX) || (velocityY != 0 && firstOverscrollY)) {
+            final int oldX = mContainerView.getScrollX();
+            final int oldY = mContainerView.getScrollY();
+            final int x = oldX + deltaX;
+            final int y = oldX + deltaY;
+            final int scrollRangeX = mScrollOffsetManager.computeMaximumHorizontalScrollOffset();
+            final int scrollRangeY = mScrollOffsetManager.computeMaximumVerticalScrollOffset();
+            mOverScrollGlow.absorbGlow(x, y, oldX, oldY, scrollRangeX, scrollRangeY,
+                    FloatMath.hypot(velocityX, velocityY));
+        }
+
+        if (mOverScrollGlow.isAnimating()) {
             postInvalidateOnAnimation();
         }
     }
@@ -2923,7 +2942,13 @@ public class AwContents implements SmartClipProvider,
 
         @Override
         public void computeScroll() {
-            mScrollOffsetManager.computeScrollAndAbsorbGlow(mOverScrollGlow);
+            if (mScrollOffsetManager.willComputeScroll()) {
+                mScrollOffsetManager.computeScrollAndAbsorbGlow(mOverScrollGlow);
+            } else {
+                if (isDestroyed()) return;
+                nativeOnComputeScroll(
+                        mNativeAwContents, AnimationUtils.currentAnimationTimeMillis());
+            }
         }
     }
 
@@ -2960,6 +2985,8 @@ public class AwContents implements SmartClipProvider,
             long nativeAwContents, String path, ValueCallback<String> callback);
 
     private native void nativeAddVisitedLinks(long nativeAwContents, String[] visitedLinks);
+    private native void nativeOnComputeScroll(
+            long nativeAwContents, long currentAnimationTimeMillis);
     private native boolean nativeOnDraw(long nativeAwContents, Canvas canvas,
             boolean isHardwareAccelerated, int scrollX, int scrollY,
             int visibleLeft, int visibleTop, int visibleRight, int visibleBottom);