I'm making an overlay that you can dismiss by clicking away on an empty area. I want only that empty area to be clickable, while the contents of popup/dialog/overlay to be unclickable. Same goes for objects partially obscured by any overlaying object.

I found myself, and many of my presenters, to be clicking on an element (not necessarily a button) that is part of a popup/dialog, just to simulate a clicking behaviour. This causes an underlaying interaction to trigger, and that's undesirable.