Getting the XRROutputInfo for a window xid

[Richard Hughes]

gnome-color-manager currently manages the per-session display
correction. It sets up the gamma ramp and sets an atom called
_ICC_PROFILE on each _output_ as you should have different vcgt
profiles for each physical monitor.  We currently also set the primary
output profile as an atom on the _screen_ for compatibility.

Now, at the moment applications like GIMP check the per-screen
_ICC_PROFILE and use that as the output profile. This doesn't work
very well when there is more than one output, as GIMP could be using
the "wrong" ICC profile for the output it's currently being displayed
on. It can get more pathological, where one window could be spanning
more than one output, although this isn't the common case.

For experimenting with this idea, I would like to be able to get the
xrandr-output from the window xid. I've been told by a few people that
the only way to do this would be to construct the display space (where
the monitors are positioned) and then work out the window co-ordinates
and try to fit one to the other. If there is any better ideas you've
got, or any code to do this, I would be very grateful. Thanks.

Richard.