code: def boundingRect( self ):
          
          rect = super(XNode, self).boundingRect()
          
          pad = self.highlightPadding()
          x = rect.x() - pad / 2.0
          y = rect.y() - pad / 2.0
          w = rect.width() + pad
          h = rect.height() + pad
          
          return QRectF( x, y, w, h )
docs: Determines the bounding rectangle for this node.
          
          :return     <QRectF>