isMaximized
Retrieves the current maximized state of @window.
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 method@Gtk.Window.maximize or method@Gtk.Window.unmaximize.
If the window isn't yet mapped, the value returned will whether the initial requested state is maximized.
Return
whether the window has a maximized state.