I've had some strange behavior with F12. I'm not sure if it was new in F12, but it happens in both KDE and XFCE. Pretty sure this is X and not the WM, but I thought I'd mention it.
Docked in "dumb" dock with DVI output
DVI monitor connected
Laptop lid closed
From a cold start, X detects and enables both LVDS1 and DVI1. The problem is, LVDS1 is closed and should not be enabled. A simple xrandr command or tweak in the Display settings fixes this. But I don't understand why it doesn't disable a closed display from the get-go.
Is this a power thing? A quirks thing?
Any help to diagnose is welcome. I know for sure that in the past (F8/F9 timeframe?) X always behaved well and gave me sensible configurations -- even on resume from sleep!