Alternative, pass the wheel delta as parameter to the hotkey callback. Then you couldn't use a label if you wanted the wheel delta ofc. Or, just renameusing GetKeyState to retrieve the last wheel delta value is a good idea. v2-alpha removes all other uses of A_EventInfo, so if this is done, A_EventInfo can be removed.
A_WheelDelta. (I prefer the first)
I'd expect an exception, since it should be considered invalid input for the reasons in the quote. Maybe there are other reasons it shouldn't?WheelUp is not a key or button and doesn't have any state, so what are you expecting