             }
             if (!isNaN(hspDelta))
             {
-                viewport.horizontalScrollPosition += hspDelta;
+                vp.horizontalScrollPosition += hspDelta;
                 event.stopPropagation();
             }
         }

        if (instance == verticalScrollBar)
        {
        	verticalScrollBar.addEventListener("valueCommit", vsb_valueCommitHandler);
        }
        
        if (instance == horizontalScrollBar)

     */
    override protected function keyDownHandler(event:KeyboardEvent):void
    {
        var vp:IViewport = viewport;
    	if (!vp)
    	    return;
    	    
        // TBD: is special handling for textfields needed here, as in mx.core.Container?
    
        if (verticalScrollBar && verticalScrollBar.visible)
        {
        	var vspDelta:Number = NaN;
