makeSingleArrangement :: ZoomMode 
                         -> PageDimension 
                         -> CanvasDimension 
                         -> (Double,Double) 
                         -> PageArrangement SinglePage
makeSingleArrangement zmode pdim cdim@(CanvasDimension (Dim w' h')) (x,y) = 
  let (sinvx,sinvy) = getRatioPageCanvas zmode pdim cdim
      bbox = BBox (x,y) (x+w'/sinvx,y+h'/sinvy)
  in SingleArrangement cdim pdim (ViewPortBBox bbox)
makeSingleArrangement :: ZoomMode 
                         -> PageDimension 
                         -> CanvasDimension 
                         -> (Double,Double) 
                         -> PageArrangement SinglePage
makeSingleArrangement zmode pdim cdim@(CanvasDimension (Dim w' h')) (x,y) = 
  let (sinvx,sinvy) = getRatioPageCanvas zmode pdim cdim
      bbox = BBox (x,y) (x+w'/sinvx,y+h'/sinvy)
  in SingleArrangement cdim pdim (ViewPortBBox bbox)
makeSingleArrangement zmode pdim cdim@(CanvasDimension (Dim w' h')) (x,y) = 
  let (sinvx,sinvy) = getRatioPageCanvas zmode pdim cdim
      bbox = BBox (x,y) (x+w'/sinvx,y+h'/sinvy)
  in SingleArrangement cdim pdim (ViewPortBBox bbox)