gobject:object, common-lisp:standard-object, common-lisp:t

gtk:box, gtk:box-layout, gtk:cell-area-box, gtk:cell-renderer-progress, gtk:cell-view, gtk:center-box, gtk:flow-box, gtk:grid, gtk:grid-view, gtk:level-bar, gtk:list-base, gtk:paned, gtk:progress-bar, gtk:range, gtk:scale, gtk:scale-button, gtk:scrollbar, gtk:separator, gtk:shortcuts-group, gtk:shortcuts-section, gtk:spin-button, gtk:stack-switcher, gtk:volume-button

The gtk:orientable interface is implemented by all widgets that can be oriented horizontally or vertically. A gtk:orientable widget is more flexible in that it allows the orientation to be changed at runtime, allowing the widget to "flip". The gtk:widget objects that implement the gtk:orientable interface will automatically acquire the horizontal or vertical CSS class, depending on the value of the orientation property.