XfwScreen is not instantiable from vala

Apologies for the very basic question here.

Looking at the generated gtk-doc for xfwscreen

Functions
XfwScreen * 	xfw_screen_get_default ()
XfwWorkspaceManager * 	xfw_screen_get_workspace_manager ()
GList * 	xfw_screen_get_windows ()
GList * 	xfw_screen_get_windows_stacked ()
XfwWindow * 	xfw_screen_get_active_window ()
GList * 	xfw_screen_get_monitors ()
XfwMonitor * 	xfw_screen_get_primary_monitor ()
gboolean 	xfw_screen_get_show_desktop ()
void 	xfw_screen_set_show_desktop ()

Since this commit dc2f7283 the xfwscreen class has become an abstract class so cannot be instantiated.

Previously it was possible to directly call Screen.get_default(); to get the object (at least under Vala). ScreenWayland doesn't have a constructor - so how do you access the various screen methods above?