Adds a window to the application.
This call can only happen after the application has started; typically, you should add new application windows in response to the
emission of the [signal@GIO.Application:GtkApplication:activate] signal.
This call is equivalent to setting the [property@Gtk.Window:application] property of the 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 [method@Gtk.Application.remove_window].
GTK will keep the application running as long as it has any windows.
| this |
an application |
| window |
a window |