GnomeCanvas and inverting Y cooordinates

[kschumacher uswest net]

Is there a simple way to invert the behavior of
Y coordinates in GnomeCanvas.

In postscript I would use a transform matrix something
like [1 0 0 -1 0 -height] (might be wrong - I haven't
written postscript this decade).  Is this what an
affine is?  If I apply that affine to the root group
will that do what I want?  (And of course, how do I
apply an affine to a root group, it that's the thing
to do).  Grin?

Thanks,
Kent

(My seven year old son, just told me my signature should say
Go Putz!  Is he referring to me?)