set_layout() sets the spacing arrangement of the buttons in accordance with one of the five GtkButtonBoxStyle settings.

The default setting is always the GTK_BUTTONBOX_DEFAULT_STYLE, which is itself pre-set to GTK_BUTTONBOX_EDGE. This can be reset for an entire application by using gtk::hbutton_box_set_layout_default() or gtk::vbutton_box_set_layout_default() .