diff --git a/mozilla/gfx/src/motif/nsRegionUnix.cpp b/mozilla/gfx/src/motif/nsRegionUnix.cpp
index 681ebce5cf1..71c96e6f56c 100644
--- a/mozilla/gfx/src/motif/nsRegionUnix.cpp
+++ b/mozilla/gfx/src/motif/nsRegionUnix.cpp
@@ -66,6 +66,10 @@ void nsRegionUnix :: Subtract(const nsIRegion &aRegion)
 {
 }
 
+void nsRegionUnix :: Subtract(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
+{
+}
+
 PRBool nsRegionUnix :: IsEmpty(void)
 {
   return PR_FALSE;
diff --git a/mozilla/gfx/src/nsIRegion.h b/mozilla/gfx/src/nsIRegion.h
index 9e20ece4dd1..3ac5f297291 100644
--- a/mozilla/gfx/src/nsIRegion.h
+++ b/mozilla/gfx/src/nsIRegion.h
@@ -119,6 +119,19 @@ public:
   **/
 
   virtual void Subtract(const nsIRegion &aRegion) = 0;
+
+  /**
+  * destructively subtract a rect from this region
+  *
+  * @param      aX xoffset of rect to subtract with region
+  * @param      aY yoffset of rect to subtract with region
+  * @param      aWidth width of rect to subtract with region
+  * @param      aHeight height of rect to subtract with region
+  * @return     void
+  *
+  **/
+
+  virtual void Subtract(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight) = 0;
   
   /**
   * is this region empty? i.e. does it contain any pixels
diff --git a/mozilla/gfx/src/windows/nsRegionWin.cpp b/mozilla/gfx/src/windows/nsRegionWin.cpp
index 74f9b2cddce..075a892cb98 100644
--- a/mozilla/gfx/src/windows/nsRegionWin.cpp
+++ b/mozilla/gfx/src/windows/nsRegionWin.cpp
@@ -69,7 +69,7 @@ void nsRegionWin :: Intersect(const nsIRegion &aRegion)
 {
   nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
 
-  mRegionType = ::CombineRgn(mRegion, pRegion->mRegion, mRegion, RGN_AND);
+  mRegionType = ::CombineRgn(mRegion, mRegion, pRegion->mRegion, RGN_AND);
 }
 
 void nsRegionWin :: Intersect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
@@ -77,7 +77,7 @@ void nsRegionWin :: Intersect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aH
   HRGN tRegion;
 
   tRegion = ::CreateRectRgn(aX, aY, aX + aWidth, aY + aHeight);
-  mRegionType = ::CombineRgn(mRegion, tRegion, mRegion, RGN_AND);
+  mRegionType = ::CombineRgn(mRegion, mRegion, tRegion, RGN_AND);
 
   ::DeleteObject(tRegion);
 }
@@ -86,7 +86,7 @@ void nsRegionWin :: Union(const nsIRegion &aRegion)
 {
   nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
 
-  mRegionType = ::CombineRgn(mRegion, pRegion->mRegion, mRegion, RGN_OR);
+  mRegionType = ::CombineRgn(mRegion, mRegion, pRegion->mRegion, RGN_OR);
 }
 
 void nsRegionWin :: Union(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
@@ -94,7 +94,7 @@ void nsRegionWin :: Union(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeigh
   HRGN tRegion;
 
   tRegion = ::CreateRectRgn(aX, aY, aX + aWidth, aY + aHeight);
-  mRegionType = ::CombineRgn(mRegion, tRegion, mRegion, RGN_OR);
+  mRegionType = ::CombineRgn(mRegion, mRegion, tRegion, RGN_OR);
 
   ::DeleteObject(tRegion);
 }
@@ -106,6 +106,16 @@ void nsRegionWin :: Subtract(const nsIRegion &aRegion)
   mRegionType = ::CombineRgn(mRegion, mRegion, pRegion->mRegion, RGN_DIFF);
 }
 
+void nsRegionWin :: Subtract(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
+{
+  HRGN tRegion;
+
+  tRegion = ::CreateRectRgn(aX, aY, aX + aWidth, aY + aHeight);
+  mRegionType = ::CombineRgn(mRegion, mRegion, tRegion, RGN_DIFF);
+
+  ::DeleteObject(tRegion);
+}
+
 PRBool nsRegionWin :: IsEmpty(void)
 {
   return (mRegionType == NULLREGION) ? PR_TRUE : PR_FALSE;
diff --git a/mozilla/gfx/src/windows/nsRegionWin.h b/mozilla/gfx/src/windows/nsRegionWin.h
index ed5d193e917..bba6510f357 100644
--- a/mozilla/gfx/src/windows/nsRegionWin.h
+++ b/mozilla/gfx/src/windows/nsRegionWin.h
@@ -38,6 +38,7 @@ public:
   virtual void Union(const nsIRegion &aRegion);
   virtual void Union(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight);
   virtual void Subtract(const nsIRegion &aRegion);
+  virtual void Subtract(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight);
   virtual PRBool IsEmpty(void);
   virtual PRBool IsEqual(const nsIRegion &aRegion);
   virtual void GetBoundingBox(PRInt32 *aX, PRInt32 *aY, PRInt32 *aWidth, PRInt32 *aHeight);
diff --git a/mozilla/gfx/src/windows/nsRenderingContextWin.cpp b/mozilla/gfx/src/windows/nsRenderingContextWin.cpp
index 7c615c8bbf3..4c64115eae3 100644
--- a/mozilla/gfx/src/windows/nsRenderingContextWin.cpp
+++ b/mozilla/gfx/src/windows/nsRenderingContextWin.cpp
@@ -475,12 +475,33 @@ void nsRenderingContextWin :: SetClipRegion(const nsIRegion& aRegion, nsClipComb
 {
   nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
   HRGN hrgn = pRegion->GetHRGN();
+  int cmode;
+
+  switch (aCombine)
+  {
+    case nsClipCombine_kIntersect:
+      cmode = RGN_AND;
+      break;
+
+    case nsClipCombine_kUnion:
+      cmode = RGN_OR;
+      break;
+
+    case nsClipCombine_kSubtract:
+      cmode = RGN_DIFF;
+      break;
+
+    default:
+    case nsClipCombine_kReplace:
+      cmode = RGN_COPY;
+      break;
+  }
 
   if (NULL != hrgn)
   {
     mStates->mFlags &= ~FLAG_LOCAL_CLIP_VALID;
     PushClipState();
-    ::SelectClipRgn(mDC, hrgn);
+    ::ExtSelectClipRgn(mDC, hrgn, cmode);
   }
 }
 
diff --git a/mozilla/view/public/nsIViewManager.h b/mozilla/view/public/nsIViewManager.h
index f13a25501ce..f8acae822dc 100644
--- a/mozilla/view/public/nsIViewManager.h
+++ b/mozilla/view/public/nsIViewManager.h
@@ -134,8 +134,8 @@ public:
    * @param region nsIRegion to be updated
    * @param aUpdateFlags see bottom of nsIViewManager.h for description
    */
-  virtual void Refresh(nsIRenderingContext *aContext, nsIRegion *region,
-                       PRUint32 aUpdateFlags) = 0;
+  virtual void Refresh(nsIView *aView, nsIRenderingContext *aContext,
+                       nsIRegion *region, PRUint32 aUpdateFlags) = 0;
 
   /**
    * Called to refresh an area of the root window. Often called in
@@ -352,5 +352,7 @@ public:
 #define NS_VMREFRESH_SCREEN_RECT    0x0002
 //update view now?
 #define NS_VMREFRESH_IMMEDIATE      0x0004
+//prevent "sync painting"
+#define NS_VMREFRESH_NO_SYNC        0x0008
 
 #endif  // nsIViewManager_h___
diff --git a/mozilla/view/src/nsView.cpp b/mozilla/view/src/nsView.cpp
index 941ce229e0e..151ea104ba8 100644
--- a/mozilla/view/src/nsView.cpp
+++ b/mozilla/view/src/nsView.cpp
@@ -86,10 +86,7 @@ nsEventStatus PR_CALLBACK HandleEvent(nsGUIEvent *aEvent)
         nsRect            vrect, trect = *((nsPaintEvent*)aEvent)->rect;
         nsIDeviceContext  *dx = px->GetDeviceContext();
 
-        trect.x = NS_TO_INT_ROUND(trect.x * convert);
-        trect.y = NS_TO_INT_ROUND(trect.y * convert);
-        trect.width = NS_TO_INT_ROUND(trect.width * convert);
-        trect.height = NS_TO_INT_ROUND(trect.height * convert);
+        trect *= convert;
 
         //see if the paint region is greater than .75 the area of our root view.
         //if so, enable double buffered painting.
diff --git a/mozilla/view/src/nsViewManager.cpp b/mozilla/view/src/nsViewManager.cpp
index 005107b8db2..2e63ebdfb17 100644
--- a/mozilla/view/src/nsViewManager.cpp
+++ b/mozilla/view/src/nsViewManager.cpp
@@ -24,11 +24,14 @@
 #include "nsIDeviceContext.h"
 #include "nsGfxCIID.h"
 #include "nsIScrollableView.h"
+#include "nsIRegion.h"
 
 static const PRBool gsDebug = PR_FALSE;
 
 #define UPDATE_QUANTUM  1000 / 40
 
+//#define USE_DIRTY_RECT
+
 static void vm_timer_callback(nsITimer *aTimer, void *aClosure)
 {
   nsViewManager *vm = (nsViewManager *)aClosure;
@@ -58,6 +61,7 @@ nsViewManager :: ~nsViewManager()
 
   NS_IF_RELEASE(mRootWindow);
   NS_IF_RELEASE(mRootView);
+  NS_IF_RELEASE(mDirtyRegion);
 
   if (nsnull != mDrawingSurface)
   {
@@ -272,8 +276,69 @@ void nsViewManager :: ResetScrolling(void)
   }
 }
 
-void nsViewManager :: Refresh(nsIRenderingContext *aContext, nsIRegion *region, PRUint32 aUpdateFlags)
+void nsViewManager :: Refresh(nsIView *aView, nsIRenderingContext *aContext, nsIRegion *region, PRUint32 aUpdateFlags)
 {
+  nsRect              wrect;
+  nsIRenderingContext *localcx = nsnull;
+  nscoord             xoff, yoff;
+  float               scale;
+
+  if (nsnull == aContext)
+  {
+    localcx = CreateRenderingContext(*aView);
+
+    //couldn't get rendering context. ack.
+
+    if (nsnull == localcx)
+    {
+      NS_ASSERTION(PR_FALSE, "unable to create rendering context.");
+      return;
+    }
+  }
+  else
+    localcx = aContext;
+
+  if (aUpdateFlags & NS_VMREFRESH_DOUBLE_BUFFER)
+  {
+    mRootWindow->GetBounds(wrect);
+    nsDrawingSurface  ds = GetDrawingSurface(*localcx, wrect);
+    localcx->SelectOffScreenDrawingSurface(ds);
+  }
+
+  scale = mContext->GetTwipsToPixels();
+
+  GetWindowOffsets(&xoff, &yoff);
+
+  region->Offset(NS_TO_INT_ROUND(-xoff * scale), NS_TO_INT_ROUND(-yoff * scale));
+//  localcx->SetClipRegion(*region, nsClipCombine_kIntersect);
+  localcx->SetClipRegion(*region, nsClipCombine_kReplace);
+  region->Offset(NS_TO_INT_ROUND(xoff * scale), NS_TO_INT_ROUND(yoff * scale));
+
+  localcx->Translate(-xoff, -yoff);
+
+  nsRect trect;
+
+  region->GetBoundingBox(&trect.x, &trect.y, &trect.width, &trect.height);
+  trect *= mContext->GetPixelsToTwips();
+
+  localcx->PushState();
+  aView->Paint(*localcx, trect, 0);
+  localcx->PopState();
+
+  if (aUpdateFlags & NS_VMREFRESH_DOUBLE_BUFFER)
+    localcx->CopyOffScreenBits(wrect);
+
+  if (localcx != aContext)
+    NS_RELEASE(localcx);
+
+  //is the dirty region the same as the region we just painted?
+
+  if ((region == mDirtyRegion) || region->IsEqual(*mDirtyRegion))
+    ClearDirtyRegion();
+  else
+    mDirtyRegion->Subtract(*region);
+
+  mLastRefresh = PR_Now();
 }
 
 void nsViewManager :: Refresh(nsIView *aView, nsIRenderingContext *aContext, nsRect *rect, PRUint32 aUpdateFlags)
@@ -289,10 +354,10 @@ void nsViewManager :: Refresh(nsIView *aView, nsIRenderingContext *aContext, nsR
     //couldn't get rendering context. ack.
 
     if (nsnull == localcx)
-{
-printf("unable to get rc\n");
+    {
+      NS_ASSERTION(PR_FALSE, "unable to create rendering context.");
       return;
-}
+    }
   }
   else
     localcx = aContext;
@@ -328,6 +393,8 @@ printf("unable to get rc\n");
   if (localcx != aContext)
     NS_RELEASE(localcx);
 
+#ifdef USE_DIRTY_RECT
+
   nsRect  updaterect = *rect;
 
   //does our dirty rect intersect the rect we just painted?
@@ -341,13 +408,36 @@ printf("unable to get rc\n");
       ClearDirtyRegion();
   }
 
+#else
+
+  //subtract the area we just painted from the dirty region
+
+  if ((nsnull != mDirtyRegion) && !mDirtyRegion->IsEmpty())
+  {
+    nsRect pixrect = trect;
+
+    pixrect *= mContext->GetTwipsToPixels();
+    mDirtyRegion->Subtract(pixrect.x, pixrect.y, pixrect.width, pixrect.height);
+  }
+
+#endif
+
   mLastRefresh = PR_Now();
 }
 
 void nsViewManager :: Composite()
 {
-  if ((nsnull != mRootView) && (mDirtyRect.IsEmpty() == PR_FALSE))
+#ifdef USE_DIRTY_RECT
+
+  if ((nsnull != mRootView) && !mDirtyRect.IsEmpty())
     Refresh(mRootView, nsnull, &mDirtyRect, NS_VMREFRESH_DOUBLE_BUFFER);
+
+#else
+
+  if ((nsnull != mRootView) && (nsnull != mDirtyRegion) && !mDirtyRegion->IsEmpty())
+    Refresh(mRootView, nsnull, mDirtyRegion, NS_VMREFRESH_DOUBLE_BUFFER);
+
+#endif
 }
 
 void nsViewManager :: UpdateView(nsIView *aView, nsIRegion *aRegion, PRUint32 aUpdateFlags)
@@ -388,16 +478,28 @@ void nsViewManager :: UpdateView(nsIView *aView, const nsRect &aRect, PRUint32 a
     while (par = par->GetParent());
   }
 
+#ifdef USE_DIRTY_RECT
+
   if (mDirtyRect.IsEmpty())
     mDirtyRect = trect;
   else
     mDirtyRect.UnionRect(mDirtyRect, trect);
 
+#else
+
+  AddRectToDirtyRegion(trect);
+
+#endif
+
   if (nsnull != mContext)
   {
     if (aUpdateFlags & NS_VMREFRESH_IMMEDIATE)
+#ifdef USE_DIRTY_RECT
       Refresh(mRootView, nsnull, &mDirtyRect, aUpdateFlags & NS_VMREFRESH_DOUBLE_BUFFER);
-    else if (mFrameRate > 0)
+#else
+      Refresh(mRootView, nsnull, mDirtyRegion, aUpdateFlags & NS_VMREFRESH_DOUBLE_BUFFER);
+#endif
+    else if ((mFrameRate > 0) && !(aUpdateFlags & NS_VMREFRESH_NO_SYNC))
     {
       PRTime now = PR_Now();
       PRTime conversion, ustoms;
@@ -524,7 +626,7 @@ void nsViewManager :: RemoveChild(nsIView *parent, nsIView *child)
 
   if ((nsnull != parent) && (nsnull != child))
   {
-    UpdateView(child, nsnull, 0);
+    UpdateView(child, nsnull, NS_VMREFRESH_NO_SYNC);
     parent->RemoveChild(child);
   }
 }
@@ -678,10 +780,19 @@ nsDrawingSurface nsViewManager :: GetDrawingSurface(nsIRenderingContext &aContex
 
 void nsViewManager :: ClearDirtyRegion()
 {
+#ifdef USE_DIRTY_RECT
+
   mDirtyRect.x = 0;
   mDirtyRect.y = 0;
   mDirtyRect.width = 0;
   mDirtyRect.height = 0;
+
+#else
+
+  if (nsnull != mDirtyRegion)
+    mDirtyRegion->SetTo(0, 0, 0, 0);
+
+#endif
 }
 
 nsIRenderingContext * nsViewManager :: CreateRenderingContext(nsIView &aView)
@@ -727,3 +838,25 @@ nsIRenderingContext * nsViewManager :: CreateRenderingContext(nsIView &aView)
 
   return cx;
 }
+
+void nsViewManager :: AddRectToDirtyRegion(nsRect &aRect)
+{
+  if (nsnull == mDirtyRegion)
+  {
+    static NS_DEFINE_IID(kRegionCID, NS_REGION_CID);
+    static NS_DEFINE_IID(kIRegionIID, NS_IREGION_IID);
+
+    nsresult rv = NSRepository::CreateInstance(kRegionCID, 
+                                       nsnull, 
+                                       kIRegionIID, 
+                                       (void **)&mDirtyRegion);
+
+    if (NS_OK != rv)
+      return;
+  }
+
+  nsRect  trect = aRect;
+
+  trect *= mContext->GetTwipsToPixels();
+  mDirtyRegion->Union(trect.x, trect.y, trect.width, trect.height);
+}
diff --git a/mozilla/view/src/nsViewManager.h b/mozilla/view/src/nsViewManager.h
index 18a12a85fb5..7813b7580b2 100644
--- a/mozilla/view/src/nsViewManager.h
+++ b/mozilla/view/src/nsViewManager.h
@@ -73,8 +73,8 @@ public:
   // the region or rectangle passed in should be in the window's
   // coordinate space. Often called in response to a paint/redraw event
   // from the native windowing system.
-  virtual void Refresh(nsIRenderingContext *aContext, nsIRegion *region,
-                       PRUint32 aUpdateFlags);
+  virtual void Refresh(nsIView *aView, nsIRenderingContext *aContext,
+                       nsIRegion *region, PRUint32 aUpdateFlags);
   virtual void Refresh(nsIView* aView, nsIRenderingContext *aContext,
                        nsRect *rect, PRUint32 aUpdateFlags);
 
@@ -170,12 +170,14 @@ public:
 private:
   ~nsViewManager();
   nsIRenderingContext *CreateRenderingContext(nsIView &aView);
+  void AddRectToDirtyRegion(nsRect &aRect);
 
   nsIPresContext    *mContext;
   nsIWidget         *mRootWindow;
   nsRect            mDSBounds;
   nsDrawingSurface  mDrawingSurface;
   PRTime            mLastRefresh;
+  nsIRegion         *mDirtyRegion;
                             
 public:
   //these are public so that our timer callback can poke them.