      *  @playerversion AIR 1.5
      *  @productversion Flex 4
      */
-    public function getVerticalScrollPositionDelta(scrollUnit:uint):Number
+    public function getVerticalScrollPositionDelta(navigationUnit:uint):Number
     {
         var scrollR:Rectangle = scrollRect;
         if (!scrollR)

        var em:Number = getStyle("fontSize");
            
        // ToDo: what if blockDirection!=TB and direction!=LTR?                   
        switch (scrollUnit)
        {
            case ScrollUnit.LEFT:
                return (scrollR.left <= 0) ? 0 : Math.max(minDelta, -em);
                
            case ScrollUnit.RIGHT:
                return (scrollR.right >= contentWidth) ? 0 : Math.min(maxDelta, em);
                
            case ScrollUnit.PAGE_LEFT:
                return Math.max(minDelta, -scrollR.width);
                
            case ScrollUnit.PAGE_RIGHT:
                return Math.min(maxDelta, scrollR.width);
                
            case ScrollUnit.HOME: 
                return minDelta;
                
            case ScrollUnit.END: 
                return maxDelta;
                
            default:

        var minDelta:Number = -scrollR.top;
                
        // ToDo: what if blockDirection!=TB and direction!=LTR?                   
        switch (navigationUnit)
        {
            case NavigationUnit.UP:
                return _textContainerManager.getScrollDelta(-1);
                
            case NavigationUnit.DOWN:
                return _textContainerManager.getScrollDelta(1);
                
            case NavigationUnit.PAGE_UP:
                return Math.max(minDelta, -scrollR.height);
                
            case NavigationUnit.PAGE_DOWN:
                return Math.min(maxDelta, scrollR.height);
                
            case NavigationUnit.HOME:
                return minDelta;
                
            case NavigationUnit.END:
                return maxDelta;
                
            default:
