Is there a built-in way to get windows ordered by visibility or if window under mouse is visible?

[BreyerW]

Something like z-order but i dont care how or in what data shape i get this information. It doesnt have to be ZIndex (doesnt work on windows anyway). It can be a bool or method that checks if window/control is truly visible for a given point or a method that will give me control/window under given point with respect to visibility for that point (so GetVisualAt will NOT work for me since it disregards visibility for given point).

The only limit is i want to avoid interop code.

And i cant rely on enter/leave events because i will need this info while already dragging something.

If there is nothing like that then i guess i will use something like Stack then remove and put back window on focus gained but thats unpleasant i think since i will need ALL windows to subscribe to this event even those created dynamically and since im working on library that will be error prone for consumers unless there is some sort of global point of subscribtion.

Thanks in advance.