The move DND support on OS-X is completely broken. How to reproduce:
* Run the attached application
* Start dragging on the red rect
* Hold the the CMD-Key
* Drag over the blue rect
* End the dragging over the blue rect
Notice that following:
* the output of the console prints null
* the drop-handler is not called

I tracked that back to View#notifyDragOver() where one gets 0 from the
native side. So am I missing something in my code?

I also tried with
https://docs.oracle.com/javafx/2/drag_drop/jfxpub-drag_drop.htm and it
does not work either.