diff --git a/view/src/nsScrollPortView.cpp b/view/src/nsScrollPortView.cpp
index c99e4ccaf730..cbe2672f3ed0 100644
--- a/view/src/nsScrollPortView.cpp
+++ b/view/src/nsScrollPortView.cpp
@@ -59,6 +59,13 @@ nsScrollPortView::~nsScrollPortView()
     NS_RELEASE(mListeners);
   }
 
+  if (nsnull != mViewManager) {
+     nsIScrollableView* scrollingView;
+     mViewManager->GetRootScrollableView(&scrollingView);
+     if ((nsnull != scrollingView) && (this == scrollingView)) {
+       mViewManager->SetRootScrollableView(nsnull);
+     }
+  }
 }
 
 nsresult nsScrollPortView::QueryInterface(const nsIID& aIID, void** aInstancePtr)
diff --git a/view/src/nsScrollingView.cpp b/view/src/nsScrollingView.cpp
index d1d49ae41d3e..f6a6877908c1 100644
--- a/view/src/nsScrollingView.cpp
+++ b/view/src/nsScrollingView.cpp
@@ -404,6 +404,14 @@ nsScrollingView::~nsScrollingView()
     mListeners->Clear();
     NS_RELEASE(mListeners);
   }
+
+  if (nsnull != mViewManager) {
+    nsIScrollableView* scrollingView;
+    mViewManager->GetRootScrollableView(&scrollingView);
+    if ((nsnull != scrollingView) && (this == scrollingView)) {
+      mViewManager->SetRootScrollableView(nsnull);
+    }
+  }
 }
 
 nsresult nsScrollingView::QueryInterface(const nsIID& aIID, void** aInstancePtr)
diff --git a/view/src/nsViewManager.cpp b/view/src/nsViewManager.cpp
index 35eabb9681ac..bc14e0f7ccc8 100644
--- a/view/src/nsViewManager.cpp
+++ b/view/src/nsViewManager.cpp
@@ -1445,6 +1445,15 @@ NS_IMETHODIMP nsViewManager::UpdateView(nsIView *aView, PRUint32 aUpdateFlags)
 NS_IMETHODIMP nsViewManager::UpdateView(nsIView *aView, const nsRect &aRect, PRUint32 aUpdateFlags)
 {
 	NS_PRECONDITION(nsnull != aView, "null view");
+
+   // If the rectangle is not visible then abort
+   // without invalidating. This is a performance 
+   // enhancement since invalidating a native widget
+   // can be expensive.
+  if (! IsRectVisible(aView, aRect)) {
+    return NS_OK;
+  }
+
 	if (!mRefreshEnabled) {
 		// accumulate this rectangle in the view's dirty region, so we can process it later.
 		if (aRect.width != 0 && aRect.height != 0) {
@@ -2827,3 +2836,96 @@ void nsViewManager::ViewToWidget(nsIView *aView, nsIView* aWidgetView, nsRect &a
 	aRect.ScaleRoundOut(t2p);
 }
 
+
+nsresult nsViewManager::GetVisibleRect(nsRect& aVisibleRect)
+{
+  nsresult rv = NS_OK;
+
+  // Get the viewport scroller
+  nsIScrollableView* scrollingView;
+  GetRootScrollableView(&scrollingView);
+
+  if (scrollingView) {     
+    // Determine the visible rect in the scrolled view's coordinate space.
+    // The size of the visible area is the clip view size
+    const nsIView*  clipView;
+    nsRect          visibleRect;
+
+    scrollingView->GetScrollPosition(aVisibleRect.x, aVisibleRect.y);
+    scrollingView->GetClipView(&clipView);
+    clipView->GetDimensions(&aVisibleRect.width, &aVisibleRect.height);
+  } else {
+    rv = NS_ERROR_FAILURE;
+  }
+
+  return rv;
+}
+
+nsresult nsViewManager::GetAbsoluteRect(nsIView *aView, const nsRect &aRect, 
+                                         nsRect& aAbsRect)
+{
+  nsIScrollableView* scrollingView = nsnull;
+  nsIView* scrolledView = nsnull;
+  GetRootScrollableView(&scrollingView);
+  if (nsnull == scrollingView) { 
+    return NS_ERROR_FAILURE;
+  }
+
+  scrollingView->GetScrolledView(scrolledView);
+
+   // Calculate the absolute coordinates of the aRect passed in.
+   // aRects values are relative to aView
+  aAbsRect = aRect;
+  nsIView *parentView = aView;
+  while ((parentView != nsnull) && (parentView != scrolledView)) {
+    nscoord x, y;
+    parentView->GetPosition(&x, &y);
+    aAbsRect.MoveBy(x, y);
+    parentView->GetParent(parentView);
+  }
+
+  if (parentView != scrolledView) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+
+PRBool nsViewManager::IsRectVisible(nsIView *aView, const nsRect &aRect)
+{
+   // Calculate the absolute coordinates for the visible rectangle   
+  nsRect visibleRect;
+  if (GetVisibleRect(visibleRect) == NS_ERROR_FAILURE) {
+    return PR_TRUE;
+  }
+
+   // Calculate the absolute coordinates of the aRect passed in.
+   // aRects values are relative to aView
+  nsRect absRect;
+  if ((GetAbsoluteRect(aView, aRect, absRect)) == NS_ERROR_FAILURE) {
+    return PR_TRUE;
+  }
+ 
+    // Compare the visible rect against the rect passed in.
+  PRBool overlaps = absRect.IntersectRect(absRect, visibleRect);
+
+#if 0
+  // Debugging code
+  static int toggle = 0;
+  for (int i = 0; i < toggle; i++) {
+    printf(" ");
+  }
+  if (toggle == 10) {
+    toggle = 0;
+  } else {
+   toggle++;
+  }
+  printf("***overlaps %d\n", overlaps);
+#endif
+
+  return overlaps;
+}
+
+
+
diff --git a/view/src/nsViewManager.h b/view/src/nsViewManager.h
index 66064514a3b0..115a20c24c74 100644
--- a/view/src/nsViewManager.h
+++ b/view/src/nsViewManager.h
@@ -180,6 +180,35 @@ private:
 	void ViewToWidget(nsIView *aView, nsIView* aWidgetView, nsRect &aRect) const;
 	// void WidgetToView(nsIView* aView, nsRect &aWidgetRect);
 
+    /**
+	 * Transforms a rectangle from specified view's coordinate system to
+	 * an absolute coordinate rectangle which can be compared against the
+   * rectangle returned by GetVisibleRect to determine visibility.
+   * @param aView view that aRect coordinates are specified relative to
+   * @param aRect rectangle in twips to convert to absolute coordinates
+   * @param aAbsRect rectangle in absolute coorindates.
+   * @returns NS_OK if successful otherwise, NS_ERROR_FAILURE 
+	 */
+
+  nsresult GetAbsoluteRect(nsIView *aView, const nsRect &aRect, 
+                           nsRect& aAbsRect);
+  /**
+	 * Determine the visible rect 
+   * @param aVisibleRect visible rectangle in twips
+   * @returns NS_OK if successful, otherwise NS_ERROR_FAILURE.
+   */
+
+  nsresult GetVisibleRect(nsRect& aVisibleRect);
+
+  /**
+	 * Determine if a rectangle specified in the view's coordinate system 
+	 * is completely, or partially visible.
+   * @param aView view that aRect coordinates are specified relative to
+   * @param aRect rectangle in twips to test for visibility 
+   * @returns PR_TRUE if the rect is visible, PR_FALSE otherwise.
+	 */
+  PRBool IsRectVisible(nsIView *aView, const nsRect &aRect);
+
 private:
   nsIDeviceContext  *mContext;
   nsIViewObserver   *mObserver;
diff --git a/view/src/nsViewManager2.cpp b/view/src/nsViewManager2.cpp
index 41562c7c4477..4fab65ecf63e 100755
--- a/view/src/nsViewManager2.cpp
+++ b/view/src/nsViewManager2.cpp
@@ -853,8 +853,8 @@ nsresult nsViewManager2::CreateBlendingBuffers(nsIRenderingContext &aRC)
 		mBlender->Init(mContext);
 	}
 
-	gBlendWidth = mTranslucentBounds.width * mPixelsToTwips;
-	gBlendHeight = mTranslucentBounds.height * mPixelsToTwips;
+	gBlendWidth = (PRInt32)(mTranslucentBounds.width * mPixelsToTwips);
+	gBlendHeight = (PRInt32)(mTranslucentBounds.height * mPixelsToTwips);
 
 	return NS_OK;
 }
@@ -946,6 +946,15 @@ NS_IMETHODIMP nsViewManager2::UpdateView(nsIView *aView, PRUint32 aUpdateFlags)
 NS_IMETHODIMP nsViewManager2::UpdateView(nsIView *aView, const nsRect &aRect, PRUint32 aUpdateFlags)
 {
 	NS_PRECONDITION(nsnull != aView, "null view");
+
+   // If the rectangle is not visible then abort
+   // without invalidating. This is a performance 
+   // enhancement since invalidating a native widget
+   // can be expensive.
+  if (! IsRectVisible(aView, aRect)) {
+    return NS_OK;
+  }
+
 	if (!mRefreshEnabled) {
 		// accumulate this rectangle in the view's dirty region, so we can process it later.
 		if (aRect.width != 0 && aRect.height != 0) {
@@ -2368,3 +2377,95 @@ void nsViewManager2::ViewToWidget(nsIView *aView, nsIView* aWidgetView, nsRect &
 	mContext->GetAppUnitsToDevUnits(t2p);
 	aRect.ScaleRoundOut(t2p);
 }
+
+nsresult nsViewManager2::GetVisibleRect(nsRect& aVisibleRect)
+{
+  nsresult rv = NS_OK;
+
+  // Get the viewport scroller
+  nsIScrollableView* scrollingView;
+  GetRootScrollableView(&scrollingView);
+
+  if (scrollingView) {     
+    // Determine the visible rect in the scrolled view's coordinate space.
+    // The size of the visible area is the clip view size
+    const nsIView*  clipView;
+    nsRect          visibleRect;
+
+    scrollingView->GetScrollPosition(aVisibleRect.x, aVisibleRect.y);
+    scrollingView->GetClipView(&clipView);
+    clipView->GetDimensions(&aVisibleRect.width, &aVisibleRect.height);
+  } else {
+    rv = NS_ERROR_FAILURE;
+  }
+
+  return rv;
+}
+
+nsresult nsViewManager2::GetAbsoluteRect(nsIView *aView, const nsRect &aRect, 
+                                         nsRect& aAbsRect)
+{
+  nsIScrollableView* scrollingView = nsnull;
+  nsIView* scrolledView = nsnull;
+  GetRootScrollableView(&scrollingView);
+  if (nsnull == scrollingView) { 
+    return NS_ERROR_FAILURE;
+  }
+
+  scrollingView->GetScrolledView(scrolledView);
+
+   // Calculate the absolute coordinates of the aRect passed in.
+   // aRects values are relative to aView
+  aAbsRect = aRect;
+  nsIView *parentView = aView;
+  while ((parentView != nsnull) && (parentView != scrolledView)) {
+    nscoord x, y;
+    parentView->GetPosition(&x, &y);
+    aAbsRect.MoveBy(x, y);
+    parentView->GetParent(parentView);
+  }
+
+  if (parentView != scrolledView) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+
+PRBool nsViewManager2::IsRectVisible(nsIView *aView, const nsRect &aRect)
+{
+   // Calculate the absolute coordinates for the visible rectangle   
+  nsRect visibleRect;
+  if (GetVisibleRect(visibleRect) == NS_ERROR_FAILURE) {
+    return PR_TRUE;
+  }
+
+   // Calculate the absolute coordinates of the aRect passed in.
+   // aRects values are relative to aView
+  nsRect absRect;
+  if ((GetAbsoluteRect(aView, aRect, absRect)) == NS_ERROR_FAILURE) {
+    return PR_TRUE;
+  }
+ 
+    // Compare the visible rect against the rect passed in.
+  PRBool overlaps = absRect.IntersectRect(absRect, visibleRect);
+
+#if 0
+  // Debugging code
+  static int toggle = 0;
+  for (int i = 0; i < toggle; i++) {
+    printf(" ");
+  }
+  if (toggle == 10) {
+    toggle = 0;
+  } else {
+   toggle++;
+  }
+  printf("***overlaps %d\n", overlaps);
+#endif
+
+  return overlaps;
+}
+
+
diff --git a/view/src/nsViewManager2.h b/view/src/nsViewManager2.h
index 0d3f2e925a66..6d92aa7465aa 100755
--- a/view/src/nsViewManager2.h
+++ b/view/src/nsViewManager2.h
@@ -193,6 +193,35 @@ private:
 	void ViewToWidget(nsIView *aView, nsIView* aWidgetView, nsRect &aRect) const;
 	// void WidgetToView(nsIView* aView, nsRect &aWidgetRect);
 
+  /**
+	 * Transforms a rectangle from specified view's coordinate system to
+	 * an absolute coordinate rectangle which can be compared against the
+   * rectangle returned by GetVisibleRect to determine visibility.
+   * @param aView view that aRect coordinates are specified relative to
+   * @param aRect rectangle in twips to convert to absolute coordinates
+   * @param aAbsRect rectangle in absolute coorindates.
+   * @returns NS_OK if successful otherwise, NS_ERROR_FAILURE 
+	 */
+
+  nsresult GetAbsoluteRect(nsIView *aView, const nsRect &aRect, 
+                           nsRect& aAbsRect);
+  /**
+	 * Determine the visible rect 
+   * @param aVisibleRect visible rectangle in twips
+   * @returns NS_OK if successful, otherwise NS_ERROR_FAILURE.
+   */
+
+  nsresult GetVisibleRect(nsRect& aVisibleRect);
+
+  /**
+	 * Determine if a rectangle specified in the view's coordinate system 
+	 * is completely, or partially visible.
+   * @param aView view that aRect coordinates are specified relative to
+   * @param aRect rectangle in twips to test for visibility 
+   * @returns PR_TRUE if the rect is visible, PR_FALSE otherwise.
+	 */
+  PRBool IsRectVisible(nsIView *aView, const nsRect &aRect);
+
 private:
   nsIDeviceContext  *mContext;
   float				mTwipsToPixels;