Unify Android Webview and Chrome's fling

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

 // Copyright 2012 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.chromium.android_webview;
 
 import android.annotation.SuppressLint;
 import android.app.Activity;
 import android.content.ComponentCallbacks2;
 import android.content.Context;
 import android.content.res.Configuration;
 import android.graphics.Bitmap;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
 import android.graphics.Picture;
 import android.graphics.Rect;
 import android.net.Uri;
 import android.net.http.SslCertificate;
 import android.os.AsyncTask;
 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;
 import android.view.MotionEvent;
 import android.view.View;
 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;
 import android.webkit.JavascriptInterface;
 import android.webkit.ValueCallback;
 import android.widget.OverScroller;
 
 import org.chromium.android_webview.permission.AwPermissionRequest;
 import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
@@ skipping 521 matching lines @@
         public void onPinchEnded() {
             mLayoutSizer.unfreezeLayoutRequests();
         }
 
         @Override
         public void onFlingCancelGesture() {
             mScrollOffsetManager.onFlingCancelGesture();
         }
 
         @Override
-        public void onUnhandledFlingStartEvent(int velocityX, int velocityY) {
-            mScrollOffsetManager.onUnhandledFlingStartEvent(velocityX, velocityY);
-        }
-
-        @Override
         public void onScrollUpdateGestureConsumed() {
             mScrollAccessibilityHelper.postViewScrolledAccessibilityEventCallback();
         }
     }
 
     //--------------------------------------------------------------------------------------------
     private class AwComponentCallbacks implements ComponentCallbacks2 {
         @Override
         public void onTrimMemory(final int level) {
             if (isDestroyed()) return;
@@ skipping 1282 matching lines @@
      */
     public float getScale() {
         return (float) (mPageScaleFactor * mDIPScale);
     }
 
     /**
      * @see android.webkit.WebView#flingScroll(int, int)
      */
     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);

[hush (inactive), 2015/05/27 23:11:38]

Regarding the possibility of scrolling a scrollable sublayer instead of
scrolling just the root layer:

How about replacing 0, 0 with a magic number like -100, -100 so that the hit
test will always fall onto the root layer?
I tried -100, -100 with the test page you provided and flingScroll() correctly
scrolls the root layer.

[jdduke (slow), 2015/05/28 15:18:08]

That's a thought, though it might just be that it happens to work with that test
page. If you scrolled the page down/right by 100, in theory the hit test might
go back to the sublayer.

Another thought would be to make it explicit, so we add a bit to the
GestureScrollBegin (here
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...)
which says "targetRoot" or "targetViewport" or something like that. Then we just
set that bit for flings, and perhaps rename CVC.fling() to CVC.flingRoot()?

[hush (inactive), 2015/05/28 23:49:51]

Yeah... using -100, -100 was too brittle and too much of a hack. I agree with
adding a bit to WebInputEvent, scrollBegin

[bokan, 2015/05/29 19:32:49]

Sorry for late reply, "targetViewport" sgtm. "targetRoot" is ok but maybe a bit
misleading since the viewport may not actually be the root layer. (There's two
viewport scroll layers so they can't both be root, also, above even the top one
is the elastic overscroll layer...) 

     }
 
     /**
      * @see android.webkit.WebView#pageUp(boolean)
      */
     public boolean pageUp(boolean top) {
         if (TRACE) Log.d(TAG, "pageUp");
         return mScrollOffsetManager.pageUp(top);
     }
 
@@ skipping 590 matching lines @@
         // This change notification comes from the renderer thread, not from the cc/ impl thread.
         mLayoutSizer.onContentSizeChanged(widthCss, heightCss);
     }
 
     @CalledByNative
     private void scrollContainerViewTo(int x, int y) {
         mScrollOffsetManager.scrollContainerViewTo(x, y);
     }
 
     @CalledByNative
-    public boolean isFlingActive() {
-        return mScrollOffsetManager.isFlingActive();
+    public boolean isSmoothScrollingActive() {
+        return mScrollOffsetManager.isSmoothScrollingActive();
     }
 
     @CalledByNative
     private void updateScrollState(int maxContainerViewScrollOffsetX,
             int maxContainerViewScrollOffsetY, int contentWidthDip, int contentHeightDip,
             float pageScaleFactor, float minPageScaleFactor, float maxPageScaleFactor) {
         mContentWidthDip = contentWidthDip;
         mContentHeightDip = contentHeightDip;
         mScrollOffsetManager.setMaxScrollOffset(maxContainerViewScrollOffsetX,
                 maxContainerViewScrollOffsetY);
         setPageScaleFactorAndLimits(pageScaleFactor, minPageScaleFactor, maxPageScaleFactor);
     }
 
     @CalledByNative
     private void setAwAutofillClient(AwAutofillClient client) {
         mAwAutofillClient = client;
         client.init(mContentViewCore);
     }
 
+    @SuppressLint("NewApi")
     @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) {
         mScrollOffsetManager.overScrollBy(deltaX, deltaY);
 
-        if (mOverScrollGlow != null && mOverScrollGlow.isAnimating()) {
+        if (mOverScrollGlow == null) return;
+
+        mOverScrollGlow.setOverScrollDeltas(deltaX, deltaY);
+        final int oldX = mContainerView.getScrollX();
+        final int oldY = mContainerView.getScrollY();
+        final int x = oldX + deltaX;
+        final int y = oldY + 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();
         }
     }
 
     // -------------------------------------------------------------------------------------------
     // Helper methods
     // -------------------------------------------------------------------------------------------
 
     private void setPageScaleFactorAndLimits(
             float pageScaleFactor, float minPageScaleFactor, float maxPageScaleFactor) {
@@ skipping 383 matching lines @@
             return mScrollOffsetManager.computeVerticalScrollOffset();
         }
 
         @Override
         public int computeVerticalScrollExtent() {
             return mScrollOffsetManager.computeVerticalScrollExtent();
         }
 
         @Override
         public void computeScroll() {
-            mScrollOffsetManager.computeScrollAndAbsorbGlow(mOverScrollGlow);
+            if (mScrollOffsetManager.willComputeScroll()) {
+                mScrollOffsetManager.computeScrollAndAbsorbGlow(mOverScrollGlow);
+            } else {
+                if (isDestroyed()) return;
+                nativeOnComputeScroll(
+                        mNativeAwContents, AnimationUtils.currentAnimationTimeMillis());
+            }
         }
     }
 
     // Return true if the GeolocationPermissionAPI should be used.
     @CalledByNative
     private boolean useLegacyGeolocationPermissionAPI() {
         // Always return true since we are not ready to swap the geolocation yet.
         // TODO: If we decide not to migrate the geolocation, there are some unreachable
         // code need to remove. http://crbug.com/396184.
         return true;
@@ skipping 16 matching lines @@
             AwContentsClientBridge contentsClientBridge,
             AwContentsIoThreadClient ioThreadClient,
             InterceptNavigationDelegate navigationInterceptionDelegate);
     private native WebContents nativeGetWebContents(long nativeAwContents);
 
     private native void nativeDocumentHasImages(long nativeAwContents, Message message);
     private native void nativeGenerateMHTML(
             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);
     private native void nativeFindAllAsync(long nativeAwContents, String searchString);
     private native void nativeFindNext(long nativeAwContents, boolean forward);
     private native void nativeClearMatches(long nativeAwContents);
     private native void nativeClearCache(long nativeAwContents, boolean includeDiskFiles);
     private native byte[] nativeGetCertificate(long nativeAwContents);
 
     // Coordinates in desity independent pixels.
@@ skipping 39 matching lines @@
     private native void nativeCreatePdfExporter(long nativeAwContents, AwPdfExporter awPdfExporter);
 
     private native void nativePreauthorizePermission(long nativeAwContents, String origin,
             long resources);
 
     private native void nativePostMessageToFrame(long nativeAwContents, String frameId,
             String message, String targetOrigin, int[] msgPorts);
 
     private native void nativeCreateMessageChannel(long nativeAwContents, AwMessagePort[] ports);
 }