diff --git a/gfx/src/nsIRegion.h b/gfx/src/nsIRegion.h
index 37ade6caec17..9e20ece4dd1a 100644
--- a/gfx/src/nsIRegion.h
+++ b/gfx/src/nsIRegion.h
@@ -54,12 +54,15 @@ public:
   /**
   * copy operator equivalent that takes a rect
   *
-  * @param      rect to copy
+  * @param      aX xoffset of rect to set region to
+  * @param      aY yoffset of rect to set region to
+  * @param      aWidth width of rect to set region to
+  * @param      aHeight height of rect to set region to
   * @return     void
   *
   **/
 
-  virtual void SetTo(const nsRect &aRect) = 0;
+  virtual void SetTo(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight) = 0;
 
   /**
   * destructively intersect another region with this one
@@ -74,12 +77,15 @@ public:
   /**
   * destructively intersect a rect with this region
   *
-  * @param      rect to intersect
+  * @param      aX xoffset of rect to intersect with region
+  * @param      aY yoffset of rect to intersect with region
+  * @param      aWidth width of rect to intersect with region
+  * @param      aHeight height of rect to intersect with region
   * @return     void
   *
   **/
 
-  virtual void Intersect(const nsRect &aRect) = 0;
+  virtual void Intersect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight) = 0;
 
   /**
   * destructively union another region with this one
@@ -94,12 +100,15 @@ public:
   /**
   * destructively union a rect with this region
   *
-  * @param      rect to union
+  * @param      aX xoffset of rect to union with region
+  * @param      aY yoffset of rect to union with region
+  * @param      aWidth width of rect to union with region
+  * @param      aHeight height of rect to union with region
   * @return     void
   *
   **/
 
-  virtual void Union(const nsRect &aRect) = 0;
+  virtual void Union(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight) = 0;
 
   /**
   * destructively subtract another region with this one
@@ -136,11 +145,14 @@ public:
   * returns the bounding box of the region i.e. the smallest
   * rectangle that completely contains the region.        
   *
-  * @param      rect to set to the bounding box
+  * @param      aX out parameter for xoffset of bounding rect for region
+  * @param      aY out parameter for yoffset of bounding rect for region
+  * @param      aWidth out parameter for width of bounding rect for region
+  * @param      aHeight out parameter for height of bounding rect for region
   * @return     void
   *
   **/
-  virtual void GetBoundingBox(nsRect &aRect) = 0;
+  virtual void GetBoundingBox(PRInt32 *aX, PRInt32 *aY, PRInt32 *aWidth, PRInt32 *aHeight) = 0;
 
   /**
   * offsets the region in x and y
@@ -150,7 +162,7 @@ public:
   * @return          void
   *
   **/
-  virtual void Offset(nscoord aXOffset, nscoord aYOffset) = 0;
+  virtual void Offset(PRInt32 aXOffset, PRInt32 aYOffset) = 0;
 
   /**
   * does the region completely contain the rectangle?
@@ -160,7 +172,7 @@ public:
   *
   **/
 
-  virtual PRBool ContainsRect(const nsRect &aRect) = 0;
+  virtual PRBool ContainsRect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight) = 0;
   
   /**
   * invoke a function for each rectangle in the region
diff --git a/gfx/src/windows/nsRegionWin.cpp b/gfx/src/windows/nsRegionWin.cpp
index 8a81b1e6e62b..74f9b2cddcef 100644
--- a/gfx/src/windows/nsRegionWin.cpp
+++ b/gfx/src/windows/nsRegionWin.cpp
@@ -25,6 +25,7 @@ nsRegionWin :: nsRegionWin()
   NS_INIT_REFCNT();
 
   mRegion = NULL;
+  mRegionType = NULLREGION;
 }
 
 nsRegionWin :: ~nsRegionWin()
@@ -38,58 +39,117 @@ NS_IMPL_RELEASE(nsRegionWin)
 
 nsresult nsRegionWin :: Init(void)
 {
+  mRegion = ::CreateRectRgn(0, 0, 0, 0);
+  mRegionType = NULLREGION;
+
   return NS_OK;
 }
 
 void nsRegionWin :: SetTo(const nsIRegion &aRegion)
 {
+  nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
+
+  mRegionType = ::CombineRgn(mRegion, pRegion->mRegion, NULL, RGN_COPY);
 }
 
-void nsRegionWin :: SetTo(const nsRect &aRect)
+void nsRegionWin :: SetTo(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
 {
+  if (NULL != mRegion)
+    ::DeleteObject(mRegion);
+
+  mRegion = ::CreateRectRgn(aX, aY, aX + aWidth, aY + aHeight);
+
+  if ((aWidth == 0) || (aHeight == 0))
+    mRegionType = NULLREGION;
+  else
+    mRegionType = SIMPLEREGION;
 }
 
 void nsRegionWin :: Intersect(const nsIRegion &aRegion)
 {
+  nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
+
+  mRegionType = ::CombineRgn(mRegion, pRegion->mRegion, mRegion, RGN_AND);
 }
 
-void nsRegionWin :: Intersect(const nsRect &aRect)
+void nsRegionWin :: Intersect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
 {
+  HRGN tRegion;
+
+  tRegion = ::CreateRectRgn(aX, aY, aX + aWidth, aY + aHeight);
+  mRegionType = ::CombineRgn(mRegion, tRegion, mRegion, RGN_AND);
+
+  ::DeleteObject(tRegion);
 }
 
 void nsRegionWin :: Union(const nsIRegion &aRegion)
 {
+  nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
+
+  mRegionType = ::CombineRgn(mRegion, pRegion->mRegion, mRegion, RGN_OR);
 }
 
-void nsRegionWin :: Union(const nsRect &aRect)
+void nsRegionWin :: Union(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
 {
+  HRGN tRegion;
+
+  tRegion = ::CreateRectRgn(aX, aY, aX + aWidth, aY + aHeight);
+  mRegionType = ::CombineRgn(mRegion, tRegion, mRegion, RGN_OR);
+
+  ::DeleteObject(tRegion);
 }
 
 void nsRegionWin :: Subtract(const nsIRegion &aRegion)
 {
+  nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
+
+  mRegionType = ::CombineRgn(mRegion, mRegion, pRegion->mRegion, RGN_DIFF);
 }
 
 PRBool nsRegionWin :: IsEmpty(void)
 {
-  return PR_TRUE;
+  return (mRegionType == NULLREGION) ? PR_TRUE : PR_FALSE;
 }
 
 PRBool nsRegionWin :: IsEqual(const nsIRegion &aRegion)
 {
-  return PR_FALSE;
+  nsRegionWin *pRegion = (nsRegionWin *)&aRegion;
+
+  return ::EqualRgn(mRegion, pRegion->mRegion) ? PR_TRUE : PR_FALSE;
 }
 
-void nsRegionWin :: GetBoundingBox(nsRect &aRect)
+void nsRegionWin :: GetBoundingBox(PRInt32 *aX, PRInt32 *aY, PRInt32 *aWidth, PRInt32 *aHeight)
 {
+  RECT  bounds;
+
+  if (mRegionType != NULLREGION)
+  {
+    ::GetRgnBox(mRegion, &bounds);
+
+    *aX = bounds.left;
+    *aY = bounds.top;
+    *aWidth = bounds.right - bounds.left;
+    *aHeight = bounds.bottom - bounds.top;
+  }
+  else
+    *aX = *aY = *aWidth = *aHeight = 0;
 }
 
-void nsRegionWin :: Offset(nscoord aXOffset, nscoord aYOffset)
+void nsRegionWin :: Offset(PRInt32 aXOffset, PRInt32 aYOffset)
 {
+  ::OffsetRgn(mRegion, aXOffset, aYOffset);
 }
 
-PRBool nsRegionWin :: ContainsRect(const nsRect &aRect)
+PRBool nsRegionWin :: ContainsRect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight)
 {
-  return PR_FALSE;
+  RECT  trect;
+
+  trect.left = aX;
+  trect.top = aY;
+  trect.right = aX + aWidth;
+  trect.bottom = aY + aHeight;
+
+  return ::RectInRegion(mRegion, &trect) ? PR_TRUE : PR_FALSE;
 }
 
 PRBool nsRegionWin :: ForEachRect(nsRectInRegionFunc *func, void *closure)
diff --git a/gfx/src/windows/nsRegionWin.h b/gfx/src/windows/nsRegionWin.h
index bc5d65f2d012..ed5d193e9173 100644
--- a/gfx/src/windows/nsRegionWin.h
+++ b/gfx/src/windows/nsRegionWin.h
@@ -32,17 +32,17 @@ public:
   virtual nsresult Init();
 
   virtual void SetTo(const nsIRegion &aRegion);
-  virtual void SetTo(const nsRect &aRect);
+  virtual void SetTo(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight);
   virtual void Intersect(const nsIRegion &aRegion);
-  virtual void Intersect(const nsRect &aRect);
+  virtual void Intersect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight);
   virtual void Union(const nsIRegion &aRegion);
-  virtual void Union(const nsRect &aRect);
+  virtual void Union(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight);
   virtual void Subtract(const nsIRegion &aRegion);
   virtual PRBool IsEmpty(void);
   virtual PRBool IsEqual(const nsIRegion &aRegion);
-  virtual void GetBoundingBox(nsRect &aRect);
-  virtual void Offset(nscoord aXOffset, nscoord aYOffset);
-  virtual PRBool ContainsRect(const nsRect &aRect);
+  virtual void GetBoundingBox(PRInt32 *aX, PRInt32 *aY, PRInt32 *aWidth, PRInt32 *aHeight);
+  virtual void Offset(PRInt32 aXOffset, PRInt32 aYOffset);
+  virtual PRBool ContainsRect(PRInt32 aX, PRInt32 aY, PRInt32 aWidth, PRInt32 aHeight);
   virtual PRBool ForEachRect(nsRectInRegionFunc *func, void *closure);
 
   //windows specific
@@ -53,6 +53,7 @@ private:
   ~nsRegionWin();
 
   HRGN  mRegion;
+  int   mRegionType;
 };
 
 #endif  // nsRegionWin_h___