Bug#552506: gnome-power-manager: "xset dpms force off" don't keep display off

[Kevin Goodsell]

> When you’re using a power management application, don’t complain if it
> tries to manage power. If you stomp on what it is doing using
> lower-level interfaces, you can’t obtain correct results.
> 
> g-p-m has a D-Bus interface that allows to force a display to be shut
> down, you should use this interface instead.

This is a very sensible reply, however it seems to be incorrect. I may 
be mistaken, but after much hunting I have been unable to find such an 
interface. If it does exist please provide details and ideally a working 
example using dbus-send (that would be great because it would provide a 
drop-in replacement for the xset command).

Unless this interface exists and I simply failed to locate it, it 
appears gnome-power-manager has made the only existing option 
non-functional.