Example of Gtk.Popover with vala

ExemplePopover.vala

public class Application : Gtk.Window {

    public GLib.Menu menu_model { get; set; }

	public Application () {
		this.set_default_size (700, 600);

		var header_bar = new Gtk.HeaderBar ();
		header_bar.set_title ("teste");
        header_bar.show_close_button = true;
		
        var button = new Gtk.Button();
        button.set_image (new Gtk.Image.from_icon_name ("open-menu-symbolic", Gtk.IconSize.LARGE_TOOLBAR));

    	var menu = new GLib.Menu ();
        var item1 = new GLib.MenuItem ("item 1", null);
        var item2 = new GLib.MenuItem ("item 2", null);
        menu.append_item (item1);
        menu.append_item (item2);
        	
		var menu_popover = new Gtk.Popover(button);
        menu_popover.position = Gtk.PositionType.BOTTOM;
		menu_popover.set_size_request (256, -1);
		menu_popover.modal = false;
        menu_popover.bind_model (menu, null);
       
        button.clicked.connect (() => {
            menu_popover.set_visible (true);
        });

        header_bar.pack_end (button);
        this.set_titlebar (header_bar);
	}

	public static int main (string[] args) {
		Gtk.init (ref args);

		Application app = new Application ();
		app.show_all ();
		Gtk.main ();
		return 0;
	}
}