16:23:53jackdanielso the problem originates in update-mirror-geometry (which is very hairy)
16:48:16jackdanielit seems that port-set-mirror-transformation doesn't take into account window decorations
18:51:31nyefjackdaniel: If you haven't already dug up a copy of the ICCCM, you may wish to now. You're deep into its territory when you're dealing with an X window manager.