viewPortBBox :: Simple Lens (PageArrangement a) ViewPortBBox 
viewPortBBox = lens getter setter 
  where 
    getter :: PageArrangement a -> ViewPortBBox   
    getter (SingleArrangement _ _ vbbox) = vbbox 
    getter (ContinuousArrangement _ _ _ vbbox) = vbbox 
    setter :: PageArrangement a -> ViewPortBBox -> PageArrangement a
    setter (SingleArrangement cdim pdim _) vbbox = SingleArrangement cdim pdim vbbox 
    setter (ContinuousArrangement cdim ddim pfunc _) vbbox = 
      ContinuousArrangement cdim ddim pfunc vbbox

-- | 
viewPortBBox :: Simple Lens (PageArrangement a) ViewPortBBox
viewPortBBox = lens getter setter 
  where 
    getter :: PageArrangement a -> ViewPortBBox   
    getter (SingleArrangement _ _ vbbox) = vbbox 
    getter (ContinuousArrangement _ _ _ vbbox) = vbbox 
    setter :: PageArrangement a -> ViewPortBBox -> PageArrangement a
    setter (SingleArrangement cdim pdim _) vbbox = SingleArrangement cdim pdim vbbox 
    setter (ContinuousArrangement cdim ddim pfunc _) vbbox = 
      ContinuousArrangement cdim ddim pfunc vbbox

-- | 
viewPortBBox = lens getter setter 
  where 
    getter :: PageArrangement a -> ViewPortBBox   
    getter (SingleArrangement _ _ vbbox) = vbbox 
    getter (ContinuousArrangement _ _ _ vbbox) = vbbox 
    setter :: PageArrangement a -> ViewPortBBox -> PageArrangement a
    setter (SingleArrangement cdim pdim _) vbbox = SingleArrangement cdim pdim vbbox 
    setter (ContinuousArrangement cdim ddim pfunc _) vbbox = 
      ContinuousArrangement cdim ddim pfunc vbbox

-- | 