Direction of the focus change. This corresponds to the FocusChangeDirection used by the focus ring.
The IFocusRing implementation determines what focus events are generated as a consequence of other input events. Focus events generally occur after any of the following situations:
The direction of the focus change contains information about the cause of the Focus event.
It can be null if the focus change didn't happen as a consequence of another event.
Additional resources: VisualElementFocusChangeDirection, IFocusRing