Comment 14 for bug 34233

Yes it might be a seperate bug. And still they are connected.

As I tracked down, due to other bugfixes, g-p-m ignores g-s idle events when lid=closed !
Meaning if lid=closed you will never get a running screensaver nor will it ever dpms. Only if lid=open it will dpms !!!

I get the problem when using external monitor and closing my lid, with open lid everythings fine.

Solution proposed in the gnome-bug