-- | 
getTotalBBox :: (GetBBoxable a) => [a] -> Maybe BBox 
getTotalBBox = foldl f Nothing 
  where f acc = merge acc . Just . getBBox
getTotalBBox :: (GetBBoxable a) => [a] -> Maybe BBox
getTotalBBox = foldl f Nothing 
  where f acc = merge acc . Just . getBBox
getTotalBBox = foldl f Nothing 
  where f acc = merge acc . Just . getBBox