A sealed hierarchy that manages layout inflation and Scene transition animations.

These set of classes form a state machine that can manage switching views when a new Scene becomes active.

Invoking methods on this class may cause a state transition: the resulting state is returned. Consumers of this class must call its methods at the appropriate times (uiVisible, uiNotVisible, withScene, withoutScene) and update their reference to the resulting state accordingly.

This class is not thread-safe, and should only be invoked from the main thread.