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..32393063d50735ddf2862ff730dbb4952e5590e8 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;
@@ -574,11 +577,6 @@ public class AwContents implements SmartClipProvider,
         }
 
         @Override
-        public void onUnhandledFlingStartEvent(int velocityX, int velocityY) {
-            mScrollOffsetManager.onUnhandledFlingStartEvent(velocityX, velocityY);
-        }
-
-        @Override
         public void onScrollUpdateGestureConsumed() {
             mScrollAccessibilityHelper.postViewScrolledAccessibilityEventCallback();
         }
@@ -1879,7 +1877,7 @@ 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);
     }
 
     /**
@@ -2490,8 +2488,8 @@ public class AwContents implements SmartClipProvider,
     }
 
     @CalledByNative
-    public boolean isFlingActive() {
-        return mScrollOffsetManager.isFlingActive();
+    public boolean isSmoothScrollingActive() {
+        return mScrollOffsetManager.isSmoothScrollingActive();
     }
 
     @CalledByNative
@@ -2512,14 +2510,27 @@ public class AwContents implements SmartClipProvider,
     }
 
     @CalledByNative
-    private void didOverscroll(int deltaX, int deltaY) {
-        if (mOverScrollGlow != null) {
-            mOverScrollGlow.setOverScrollDeltas(deltaX, deltaY);
+    private void didOverscroll(int deltaX, int deltaY, float velocityX, float velocityY,
+            boolean firstOverscrollX, boolean firstOverscrollY) {
+        if (mOverScrollGlow == null) return;
+
+        mOverScrollGlow.setOverScrollDeltas(deltaX, deltaY);
+
+        // TODO(jdduke): Skip this for components with non-zero velocity?

[jdduke (slow), 2015/05/12 20:46:06]

It's quite possible we don't even need these checks for
|firstOverscrollX|/|firstOverscrollY|. It looks like OverscrollGlow.java may
already have the necessary data to make the call on whether to process the glow,
so maybe try removing this guard and see if it works OK?

If so, we can probably get rid of the |firstOverscrollX|/|firstOverscrollY|
computation altogether. I think I may have introduced that b/c we have to do
something with Chrome's version of the overscroll glow, but again, looking at
OverscrollGlow.java I think it may already have the data it needs to know when
an overscroll actually starts.

[hush (inactive), 2015/05/13 23:26:20]

OverScrollGlow class has all the information it needs. I will remove
firstOverScrollX/Y.

+        if ((velocityX != 0 && firstOverscrollX) || (velocityY != 0 && firstOverscrollY)) {

[aelias_OOO_until_Jul13, 2015/05/09 03:32:04]

Could you explain why the first overscroll needs to be special?

[hush (inactive), 2015/05/12 19:08:45]

I guess the original idea to absorb the glow if it is the first overscroll.
However, I just found WebView's overScroll glow is not working properly,
including version m39:
The overscroll glow does not *always* show when you fling the webview towards
the corners. You have to be very close to the corner when you start the fling
for the overscroll glow to appear. This is different from Chrome on Android,
where you always have the edge glow effects when the velocity is non-zero at the
corner.


I am thinking of fixing this by removing WebView's own "OverScrollGlow" if
possible and just Chrome's overscroll glow edge effect. Like what Marcin said in

https://code.google.com/p/chromium/issues/detail?id=378984#c2

[jdduke (slow), 2015/05/12 19:34:11]

I would love for this to be the case, but Chrome's effect uses the browser
compositor so it won't be as simple as a drop-in replacement for what WebView
has.

In theory we could abstract the rendering so that it uses the same logic as
Chrome, but does its rendering differently (similar to selection handles,
CompositedTouchHandleDrawable vs PopupTouchHandleDrawable), but that's probably
best carved out as a separate project (if at all).

[hush (inactive), 2015/05/13 23:26:20]

Okay.. I will just continue using WebView's custom overscroll glow class.

+            final int oldX = mContainerView.getScrollX();
+            final int oldY = mContainerView.getScrollY();
+            final int x = oldX + deltaX;
+            final int y = oldX + deltaY;

[hush (inactive), 2015/05/13 23:26:20]

It should have been oldY + deltaY.

+            final int scrollRangeX = mScrollOffsetManager.computeMaximumHorizontalScrollOffset();
+            final int scrollRangeY = mScrollOffsetManager.computeMaximumVerticalScrollOffset();
+            mOverScrollGlow.absorbGlow(x, y, oldX, oldY, scrollRangeX, scrollRangeY,
+                    FloatMath.hypot(velocityX, velocityY));
+        } else {
+            mScrollOffsetManager.overScrollBy(deltaX, deltaY);
         }
 
-        mScrollOffsetManager.overScrollBy(deltaX, deltaY);
-
-        if (mOverScrollGlow != null && mOverScrollGlow.isAnimating()) {
+        if (mOverScrollGlow.isAnimating()) {
             postInvalidateOnAnimation();
         }
     }
@@ -2923,7 +2934,13 @@ 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 +2977,8 @@ 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);