Find out active graphics device programmatically (registry key)

Hello all.

I am trying to control graphics hardware acceleration programmatically.

My question is: How can I find the GUID of the active display device?

What I already found out:
The registry key for controlling this hardware acceleration is
HKLM\SYSTEM\CurrentControlSet\Control\Video\[GUID of graphics
card]\0000\Acceleration.Level

I thought that another registry key can be used to find out about the
graphics adapter GUID:
HKLM\Hardware\Devicemap\Video\ and there \Device\Video0
However on another computer it is not Video0 but Video7 and Video8

Is there any (official) documentation on this matter?

Thank you in advance
Ulrich