public void add_window (Window window)
Adds a window to this.
This call can only happen after the this has started; typically, you should add new application windows in response to the emission of the activate signal.
This call is equivalent to setting the application property of
window to this.
Normally, the connection between the application and the window will remain until the window is destroyed, but you can explicitly remove it with remove_window.
GTK+ will keep the this running as long as it has any windows.