|GTK+ Reference Manual|
Why. Named icons automatically adapt to theme changes, giving your application a much more integrated appearance.
Since GTK+ 2.6, named icons can be used for window icons (see
gtk_window_set_icon_name()) and images (see
In GTK+ 2.8, you can also use named icons for drag-and-drop (see
gtk_drag_source_set_icon_name()) and in treeview cells (see the
property of GtkCellRendererPixbuf).