when xfpm is set to lock the screen on lid close, it just does not do this in multihead mode. Looking at the code, this seems intentionally [0]. I see that some people may want this behaviour. However, if you are not aware of this, when you close the lid and walk away, you will find your computer unlocked, although you expected it locked. This is thus a seacurity breach. And with the interface as it is now, xfpm just does not do what it is claiming to do: it does not lock the screen!

Therefore I propose a new checkbox that activates non-locking in multihead mode that is only shown when locking is set for lid-close that is disabled by default. The disabled state is important, because a user wanting non-locking behaviour will recognize imediately that their computer is not doing what they want it to do and those whose security is impacted might not.

[0] http://git.xfce.org/xfce/xfce4-power-manager/tree/src/xfpm-manager.c?id=1.0.10#n324