gtk:window-fullscreened (object)

object -- a gtk:window widget
setting -- a boolean whether the window is fullscreen

The accessor for the fullscreened slot gets or sets the fullscreen state of the window. Setting this property is the equivalent of calling the gtk:window-fullscreen or gtk:window-unfullscreen functions. Either operation is asynchronous, which means you will need to connect to the "notify" signal in order to know whether the operation was successful.

If the window is not yet mapped, the value returned will show whether the initial requested state is fullscreen.