es of mapping the graphics context
    attributes (cap styles, join styles, line widths, colors) to a particular
    backend.  In cairo this is done by wrapping a cairo.Context object and
    forwarding the appropriate calls to it using a dictionary mapping styles
    to gdk constants.  In Postscript, all the work is done by the renderer,
    mapping line styles to postscript calls.

    If it's more appropriate to do the mapping at the renderer level (as in
    the postscript backend), you don't need to override any of the GC methods.
    If it's more appropriate to wrap an instance (as in the cairo backend) and
    do the mapping here, you'll need to override several of the setter
    methods.

    The base GraphicsContext stores colors as an RGB tuple on the unit
    interval, e.g., (0.5, 0.0, 1.0). You may need to map this to colors
    appropriate for your backend.
    NŠ