gboolean gtk_window_is_maximized ( GtkWindow* window )
Retrieves the current maximized state of
Note that since maximization is ultimately handled by the window
manager and happens asynchronously to an application request, you
shouldn’t assume the return value of this function changing
immediately (or at all), as an effect of calling
gtk_window_maximize() or gtk_window_unmaximize().
Available since: 3.12