Implement this method to determine when a dragging session will begin.
- macOS 10.7+
The table view.
The dragging session.
The initial drag location in screen coordinates.
The indexes of the rows to be dragged, excluding rows that were not dragged due to
View: pasteboard Writer For Row:
Implement this method to know when the dragging session is about to begin and to potentially modify the dragging session.
The dragged item order will directly match the pasteboard writer array used to begin the dragging session with the
begin. Hence, the order is deterministic, and can be used in
table when enumerating the
NSDragging pasteboard classes.