trackingArea
The tracking area for the event.
Declaration
var trackingArea: NSTrackingArea? { get }Discussion
If you access this property on an event object that is not a mouse-tracking event — that is, its event type isn’t NSMouseEntered, NSMouseExited, or NSCursorUpdate —AppKit raises an internalInconsistencyException.
If the event corresponds to a tracking rectangle installed with the addTrackingRect(_:owner:userData:assumeInside:) method of NSView, the value of this property is nil. The trackingNumber property contains either an NSTrackingArea object or NSView.TrackingRectTag, depending on how AppKit generated the event.