-- |                      
apply :: (BBox -> BBox) -> ViewPortBBox -> ViewPortBBox 
apply f (ViewPortBBox bbox1) = ViewPortBBox (f bbox1)
apply :: (BBox -> BBox) -> ViewPortBBox -> ViewPortBBox
apply f (ViewPortBBox bbox1) = ViewPortBBox (f bbox1)
apply f (ViewPortBBox bbox1) = ViewPortBBox (f bbox1)