The class of all user interface backends.

A backend is represented by a type. This technique allows the class system to be used to manage different implementations of the same interface. UIBackend declares an interface to basic functionality and is implemented by all user interface backends. Subclasses of UIBackend extend the basic interface. A backend can be an instance of only some of these subclasses when some functionality is not yet implemented or cannot be provided by the backend. Backend types are typically used as phantom parameters. However, in some cases, an explicit value of a backend type is needed as a function argument. Therefore, a backend is usually a single-value type whose only value is named like the type.

All associated types and methods of UIBackend are used internally by Grapefruit and should not be used directly by the user.