[cairo] Coordinate from device to user space without a context

[Donn]

Follow up summary.

So far it seems to me, from my recent experience, that ..

cr.device_to_user(x,y); //where cr is a Cairo.Context

.. actually works, and that there is no equivalent way to do this in 
situations where you have no context.

I have tried the suggested manual formulas, as well as the "invert then 
transform_point" approach. (Thx, btw.) Neither have done what the 
cr.device_to_user does. (And I'm likely the reason for any bugs.)

"How can I take a pair of coordinates in device space into user space 
(by way of a pre-saved matrix) in some handler that has no access to the 
Cairo Context?"

Is my wording of the problem clear? I'm not sure because math. :)

\d