Android WebView: flush input events during onVSync

ui/android/java/src/org/chromium/ui/VSyncMonitor.java

 // Copyright 2014 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.ui;
 
 import android.annotation.SuppressLint;
 import android.content.Context;
 import android.os.Build;
 import android.os.Handler;
 import android.view.Choreographer;
 import android.view.WindowManager;
 
 import org.chromium.base.TraceEvent;
 
 /**
  * Notifies clients of the default displays's vertical sync pulses.
  * On ICS, VSyncMonitor relies on setVSyncPointForICS() being called to set a reasonable
  * approximation of a vertical sync starting point; see also http://crbug.com/156397.
  */
 @SuppressLint("NewApi")
 public class VSyncMonitor {
     private static final long NANOSECONDS_PER_SECOND = 1000000000;
     private static final long NANOSECONDS_PER_MILLISECOND = 1000000;
     private static final long NANOSECONDS_PER_MICROSECOND = 1000;
 
+    private boolean mInsideVSync = false;
+
     /**
      * VSync listener class
      */
     public interface Listener {
         /**
          * Called very soon after the start of the display's vertical sync period.
          * @param monitor The VSyncMonitor that triggered the signal.
          * @param vsyncTimeMicros Absolute frame time in microseconds.
          */
         public void onVSync(VSyncMonitor monitor, long vsyncTimeMicros);
@@ skipping 106 matching lines @@
     }
 
     /**
      * Set the best guess of the point in the past when the vsync has happened.
      * @param goodStartingPointNano Known vsync point in the past.
      */
     public void setVSyncPointForICS(long goodStartingPointNano) {
         mGoodStartingPointNano = goodStartingPointNano;
     }
 
+    /**
+     * @return true if onVSync handler is executing. If onVSync handler
+     * introduces invalidations, View#invalidate() should be called. If
+     * View#postInvalidateOnAnimation is called instead, the corresponding onDraw
+     * will be delayed by one frame. The embedder of VSyncMonitor should check
+     * this value if it wants to post an invalidation.
+     */
+    public boolean isInsideVSync() {
+        return mInsideVSync;
+    }
+
     private long getCurrentNanoTime() {
         return System.nanoTime();
     }
 
     private void onVSyncCallback(long frameTimeNanos, long currentTimeNanos) {
         assert mHaveRequestInFlight;
+        mInsideVSync = true;
         mHaveRequestInFlight = false;
         mLastVSyncCpuTimeNano = currentTimeNanos;
-        if (mListener != null) {
-            mListener.onVSync(this, frameTimeNanos / NANOSECONDS_PER_MICROSECOND);
+        try {
+            if (mListener != null) {
+                mListener.onVSync(this, frameTimeNanos / NANOSECONDS_PER_MICROSECOND);
+            }
+        }
+        finally {

[boliu, 2014/08/20 20:30:00]

nit: move finally one one above

+            mInsideVSync = false;
         }
     }
 
     private void postCallback() {
         if (mHaveRequestInFlight) return;
         mHaveRequestInFlight = true;
         if (postSyntheticVSync()) return;
         if (isVSyncSignalAvailable()) {
             mChoreographer.postFrameCallback(mVSyncFrameCallback);
         } else {
@@ skipping 26 matching lines @@
 
         if (currentTime + delay <= mLastPostedNano + mRefreshPeriodNano / 2) {
             delay += mRefreshPeriodNano;
         }
 
         mLastPostedNano = currentTime + delay;
         if (delay == 0) mHandler.post(mVSyncRunnableCallback);
         else mHandler.postDelayed(mVSyncRunnableCallback, delay / NANOSECONDS_PER_MILLISECOND);
     }
 }