diff --git a/mozilla/widget/public/nsIWidget.h b/mozilla/widget/public/nsIWidget.h
index 2a7b5b097d0..3186d711b02 100644
--- a/mozilla/widget/public/nsIWidget.h
+++ b/mozilla/widget/public/nsIWidget.h
@@ -416,6 +416,24 @@ class nsIWidget : public nsISupports {
 
     virtual void RemoveTooltips() = 0;
 
+     /**
+     * Convert from this widget coordinates to screen coordinates.
+     *
+     * @param  aOldRect  widget coordinates stored in the x,y members
+     * @param  aNewRect  screen coordinates stored in the x,y members
+     */
+
+    virtual void WidgetToScreen(const nsRect& aOldRect, nsRect& aNewRect) = 0;
+
+    /**
+     * Convert from screen coordinates to this widget's coordinates.
+     *
+     * @param  aOldRect  screen coordinates stored in the x,y members
+     * @param  aNewRect  widget's coordinates stored in the x,y members
+     */
+
+    virtual void ScreenToWidget(const nsRect& aOldRect, nsRect& aNewRect) = 0;
+
 };
 
 #endif // nsIWidget_h__
diff --git a/mozilla/widget/src/windows/nsWindow.cpp b/mozilla/widget/src/windows/nsWindow.cpp
index df1b0f373a5..bf8740f2e7c 100644
--- a/mozilla/widget/src/windows/nsWindow.cpp
+++ b/mozilla/widget/src/windows/nsWindow.cpp
@@ -35,19 +35,21 @@
 BOOL nsWindow::sIsRegistered = FALSE;
 
 nsWindow * mCurrentWindow = NULL;
+// Global variable 
+//     g_hinst - handle of the application instance 
+extern HINSTANCE g_hinst; 
 
 static NS_DEFINE_IID(kIWidgetIID, NS_IWIDGET_IID);
 
 
+
+
 // DoCreateTooltip - creates a tooltip control and adds some tools  
 //     to it. 
 // Returns the handle of the tooltip control if successful or NULL
 //     otherwise. 
 // hwndOwner - handle of the owner window 
 // 
-// Global variable 
-//     g_hinst - handle of the application instance 
-extern HINSTANCE g_hinst; 
 
 void nsWindow::AddTooltip(HWND hwndOwner,nsRect& aRect) 
 { 
@@ -85,6 +87,30 @@ void nsWindow::AddTooltip(HWND hwndOwner,nsRect& aRect)
             (LPARAM) (LPTOOLINFO) &ti)) 
         return; 
 
+}
+
+void nsWindow::WidgetToScreen(const nsRect& aOldRect, nsRect& aNewRect)
+{
+  POINT point;
+  point.x = aOldRect.x;
+  point.y = aOldRect.y;
+  ::ClientToScreen((HWND)GetNativeData(NS_NATIVE_WINDOW), &point);
+  aNewRect.x = point.x;
+  aNewRect.y = point.y;
+  aNewRect.width = aOldRect.width;
+  aNewRect.height = aOldRect.height;
+}
+
+void nsWindow::ScreenToWidget(const nsRect& aOldRect, nsRect& aNewRect)
+{
+  POINT point;
+  point.x = aOldRect.x;
+  point.y = aOldRect.y;
+  ::ScreenToClient((HWND)GetNativeData(NS_NATIVE_WINDOW), &point);
+  aNewRect.x = point.x;
+  aNewRect.y = point.y;
+  aNewRect.width = aOldRect.width;
+  aNewRect.height = aOldRect.height;
 } 
 
 //-------------------------------------------------------------------------
diff --git a/mozilla/widget/src/windows/nsWindow.h b/mozilla/widget/src/windows/nsWindow.h
index 6fdb5c8a950..cacd3080b93 100644
--- a/mozilla/widget/src/windows/nsWindow.h
+++ b/mozilla/widget/src/windows/nsWindow.h
@@ -112,6 +112,8 @@ public:
     virtual void            SetTooltips(PRUint32 aNumberOfTips,const nsRect* aTooltipAreas);
     virtual void            RemoveTooltips();
     virtual void            UpdateTooltips(const nsRect* aNewTips);
+    virtual void            WidgetToScreen(const nsRect& aOldRect, nsRect& aNewRect);
+    virtual void            ScreenToWidget(const nsRect& aOldRect, nsRect& aNewRect);
     virtual void            AddMouseListener(nsIMouseListener * aListener);
     virtual void            AddEventListener(nsIEventListener * aListener);
 
@@ -399,7 +401,15 @@ protected:
     void RemoveTooltips() \
     { \
       nsWindow::RemoveTooltips(); \
-    }
+    } \
+    void WidgetToScreen(const nsRect& aOldRect, nsRect& aNewRect) \
+    { \
+      nsWindow::WidgetToScreen(aOldRect, aNewRect); \
+    } \
+    void ScreenToWidget(const nsRect& aOldRect, nsRect& aNewRect) \
+    { \
+      nsWindow::ScreenToWidget(aOldRect, aNewRect); \
+    } 
 
 
 
diff --git a/mozilla/widget/tests/windows/winmain.cpp b/mozilla/widget/tests/windows/winmain.cpp
index 4181fd38be4..ef8ce25c44e 100644
--- a/mozilla/widget/tests/windows/winmain.cpp
+++ b/mozilla/widget/tests/windows/winmain.cpp
@@ -760,9 +760,16 @@ nsEventStatus PR_CALLBACK HandleEvent(nsGUIEvent *aEvent)
     switch(aEvent->message) {
 
         case NS_SHOW_TOOLTIP:
-          statusText->SetText("Show tooltip");
-          tooltipWindow->Move(aEvent->point.x + 5, aEvent->point.y + 5);
-          tooltipWindow->Show(PR_TRUE);
+          {
+            statusText->SetText("Show tooltip");
+            nsRect oldPos;
+            oldPos.x = aEvent->point.x;
+            oldPos.y = aEvent->point.y;
+            nsRect newPos;
+            window->WidgetToScreen(oldPos, newPos);
+            tooltipWindow->Move(newPos.x + 5, newPos.y + 5);
+            tooltipWindow->Show(PR_TRUE);
+          }
           break;
 
         case NS_HIDE_TOOLTIP: