Bug 944047 - Store the last FrameMetrics for sub-frames in TabChild. r=botond

As well as the root frame, make sure to store the last received FrameMetrics
for sub-frames in TabChild. This prevents us sending scroll events triggered
by the APZC back to the APZC.

dom/ipc/TabChild.cpp

@@ -322,21 +322,25 @@ TabChild::HandleEvent(nsIDOMEvent* aEvent)
 
     CSSIntPoint scrollOffset = scrollFrame->GetScrollPositionCSSPixels();
 
-    if (viewId == mLastMetrics.mScrollId) {
-      // For the root frame, we store the last metrics, including the last
-      // scroll offset, sent by APZC. (This is updated in ProcessUpdateFrame()).
+    if (viewId == mLastRootMetrics.mScrollId) {
+      // We store the last metrics that was sent via the TabParent (This is
+      // updated in ProcessUpdateFrame and RecvUpdateFrame).
       // We use this here to avoid sending APZC back a scroll event that
       // originally came from APZC (besides being unnecessary, the event might
       // be slightly out of date by the time it reaches APZC).
-      // We should probably do this for subframes, too.
-      if (RoundedToInt(mLastMetrics.mScrollOffset) == scrollOffset) {
+      if (RoundedToInt(mLastRootMetrics.mScrollOffset) == scrollOffset) {
         return NS_OK;
       }
 
       // Update the last scroll offset now, otherwise RecvUpdateDimensions()
       // might trigger a scroll to the old offset before RecvUpdateFrame()
       // gets a chance to update it.
-      mLastMetrics.mScrollOffset = scrollOffset;
+      mLastRootMetrics.mScrollOffset = scrollOffset;
+    } else if (viewId == mLastSubFrameMetrics.mScrollId) {
+      if (RoundedToInt(mLastSubFrameMetrics.mScrollOffset) == scrollOffset) {
+        return NS_OK;
+      }
+      mLastSubFrameMetrics.mScrollOffset = scrollOffset;
     }
 
     SendUpdateScrollOffset(presShellId, viewId, scrollOffset);
@@ -384,21 +388,21 @@ TabChild::Observe(nsISupports *aSubject,
         // Calculate a really simple resolution that we probably won't
         // be keeping, as well as putting the scroll offset back to
         // the top-left of the page.
-        mLastMetrics.mViewport = CSSRect(CSSPoint(), kDefaultViewportSize);
-        mLastMetrics.mCompositionBounds = ScreenIntRect(ScreenIntPoint(), mInnerSize);
-        mLastMetrics.mZoom = mLastMetrics.CalculateIntrinsicScale();
-        mLastMetrics.mDevPixelsPerCSSPixel = mWidget->GetDefaultScale();
+        mLastRootMetrics.mViewport = CSSRect(CSSPoint(), kDefaultViewportSize);
+        mLastRootMetrics.mCompositionBounds = ScreenIntRect(ScreenIntPoint(), mInnerSize);
+        mLastRootMetrics.mZoom = mLastRootMetrics.CalculateIntrinsicScale();
+        mLastRootMetrics.mDevPixelsPerCSSPixel = mWidget->GetDefaultScale();
         // We use ScreenToLayerScale(1) below in order to turn the
         // async zoom amount into the gecko zoom amount.
-        mLastMetrics.mCumulativeResolution =
-          mLastMetrics.mZoom / mLastMetrics.mDevPixelsPerCSSPixel * ScreenToLayerScale(1);
+        mLastRootMetrics.mCumulativeResolution =
+          mLastRootMetrics.mZoom / mLastRootMetrics.mDevPixelsPerCSSPixel * ScreenToLayerScale(1);
         // This is the root layer, so the cumulative resolution is the same
         // as the resolution.
-        mLastMetrics.mResolution = mLastMetrics.mCumulativeResolution / LayoutDeviceToParentLayerScale(1);
-        mLastMetrics.mScrollOffset = CSSPoint(0, 0);
+        mLastRootMetrics.mResolution = mLastRootMetrics.mCumulativeResolution / LayoutDeviceToParentLayerScale(1);
+        mLastRootMetrics.mScrollOffset = CSSPoint(0, 0);
 
-        utils->SetResolution(mLastMetrics.mResolution.scale,
-                             mLastMetrics.mResolution.scale);
+        utils->SetResolution(mLastRootMetrics.mResolution.scale,
+                             mLastRootMetrics.mResolution.scale);
 
         HandlePossibleViewportChange();
       }
@@ -554,7 +558,7 @@ TabChild::HandlePossibleViewportChange()
   }
 
   float oldBrowserWidth = mOldViewportWidth;
-  mLastMetrics.mViewport.SizeTo(viewport);
+  mLastRootMetrics.mViewport.SizeTo(viewport);
   if (!oldBrowserWidth) {
     oldBrowserWidth = kDefaultViewportSize.width;
   }
@@ -600,12 +604,12 @@ TabChild::HandlePossibleViewportChange()
     return;
   }
 
-  float oldScreenWidth = mLastMetrics.mCompositionBounds.width;
+  float oldScreenWidth = mLastRootMetrics.mCompositionBounds.width;
   if (!oldScreenWidth) {
     oldScreenWidth = mInnerSize.width;
   }
 
-  FrameMetrics metrics(mLastMetrics);
+  FrameMetrics metrics(mLastRootMetrics);
   metrics.mViewport = CSSRect(CSSPoint(), viewport);
   metrics.mScrollableRect = CSSRect(CSSPoint(), pageSize);
   metrics.mCompositionBounds = ScreenIntRect(ScreenIntPoint(), mInnerSize);
@@ -1532,6 +1536,7 @@ TabChild::RecvUpdateFrame(const FrameMetrics& aFrameMetrics)
     if (content) {
       FrameMetrics newSubFrameMetrics(aFrameMetrics);
       APZCCallbackHelper::UpdateSubFrame(content, newSubFrameMetrics);
+      mLastSubFrameMetrics = newSubFrameMetrics;
       return true;
     }
   }
@@ -1539,7 +1544,7 @@ TabChild::RecvUpdateFrame(const FrameMetrics& aFrameMetrics)
   // We've recieved a message that is out of date and we want to ignore.
   // However we can't reply without painting so we reply by painting the
   // exact same thing as we did before.
-  return ProcessUpdateFrame(mLastMetrics);
+  return ProcessUpdateFrame(mLastRootMetrics);
 }
 
 bool
@@ -1603,7 +1608,7 @@ TabChild::ProcessUpdateFrame(const FrameMetrics& aFrameMetrics)
 
     DispatchMessageManagerMessage(NS_LITERAL_STRING("Viewport:Change"), data);
 
-    mLastMetrics = newMetrics;
+    mLastRootMetrics = newMetrics;
 
     return true;
 }

dom/ipc/TabChild.h

@@ -463,7 +463,8 @@ private:
     nsCOMPtr<nsIWebNavigation> mWebNav;
     nsCOMPtr<nsIWidget> mWidget;
     nsCOMPtr<nsIURI> mLastURI;
-    FrameMetrics mLastMetrics;
+    FrameMetrics mLastRootMetrics;
+    FrameMetrics mLastSubFrameMetrics;
     RenderFrameChild* mRemoteFrame;
     nsRefPtr<ContentChild> mManager;
     nsRefPtr<TabChildGlobal> mTabChildGlobal;