Gtk.MenuButton.prototype.set_popup

function set_popup(popup:Gtk.Widget):void {
    // Gjs wrapper for gtk_menu_button_set_popup()
}

Sets the Gtk.Menu that will be popped up when the button is clicked, or null to disable the button. If Gtk.menu-model is set, it will be set to null.

Since 3.6

popup

a Gtk.Menu