Returns a Boolean indicating whether a drag operation involving the specified items can begin.
- macOS 10.11+
The collection view making the request.
The index paths of the items about to be dragged.
The mouse-down event that began the drag operation.
YES if the drag operation can begin or
NO if it cannot.
If you do not implement this method and your collection view has only one section, the collection view calls the legacy
collection method. If you do not implement either method, the collection view assumes a return value of