gtk-application-add-window (application window)

application -- a gtk-application instance
window -- a gtk-window widget

Adds a window to the application. This call is equivalent to setting the application property of window to application.

Normally, the connection between the application and the window will remain until the window is destroyed, but you can explicitly remove it with the gtk-application-remove-window function.

GTK will keep the application running as long as it has any windows.