This seems to be more of an issue with your custom theme. I'm not clear on what you mean though, can you share a screenshot?
EDIT: I think I might understand. If it's what I think it is, then it's also a problem on W8 which does away with titlebar transparency. @DarkstaR is already aware of this although I'm not sure if there's a plan to fix it any time soon.
I don't think anyone answered this. It's done via hotkey message so it will work with non-visible supplies.