Creates a new instance of GtkWindow of type type. If no type is passed, the window will be created as a Gtk::WINDOW_TOPLEVEL. This means that the window will have borders and a title bar by default. Windows of type Gtk::WINDOW_POPUP will not have borders or a title bar. Popup windows are used for things such as tooltips and menus. They should not be used to create regular windows without borders. For that you should use a toplevel window and set_decorated() .