How to tell if DragAndDrop has been cancelled or completed.

I have an EditorWindow that shows visual feedback while the user is dragging an object. It works fine if the user drops on the window, but I haven't found a way to determine if the user has cancelled the drag or dropped the object on another EditorWindow so I can turn the feedback off.

I thought I could use DragAndDrop.visualMode as a hacky workaround, but it returns DragAndDropVisualMode.None for both the regular cursor and the "can't drop here" cursor.

I'm looking for something like DragAndDrop.isComplete, or a reliable way to figure that out. I've looked at all the DragAndDrop properties while dragging and cancelling and none of them seem to work for this... am I missing something obvious?