`GtkRoot` is the interface implemented by all widgets that can act as a toplevel widget.
The root widget takes care of providing the connection to the windowing system and manages layout, drawing and event delivery for its widget hierarchy.
The obvious example of a `GtkRoot` is `GtkWindow`.
To get the display to which a `GtkRoot` belongs, use [method@Gtk.Root.get_display].
`GtkRoot` also maintains the location of keyboard focus inside its widget hierarchy, with [method@Gtk.Root.set_focus] and [ method@Gtk.Root.get_focus].