F20: HDMI + Win+P == GDM black screen

[Pedro Francisco]

So, I've used HDMI for the first time this weekend.

I have pressed Win+P a few times which resulted in a black screen
(turned off, I guess).
Suspending and resuming would turn on the internal monitor again (I
had the session running so it was easy).

But now, after a warm reboot, my GDM is a black screen. Inputting the
password appears to login on the session.

Since this is a GDM issue, I need to find out where GDM stores it's
monitor settings -- gconftool-2 recursive-unset on the user-side
didn't work.

So, questions:
a) where does GDM store its monitor settings?
b) what is going on here:
b1) is there a bug report?
b2) any tips on what words to use on the bug report and on what
component to assign?

Hardware:
8086:0416 (Intel HD Graphics 4600 -- HDMI should be connected to this
one, since NVIDIA is always off on Linux)
10DE:0FE4 (NVIDIA GeForce GT 750M -- always disabled on boot via
manual call on rc.local to bbswitch )

Software:
up-to-date Fedora 20.

Thanks in Advance,
-- 
Pedro