The ui_listbox widget is a ‘lite’ version of the ui_listbox_ext. It doesn’t use the same resources and overhead of the listbox_ext widget. ui_listbox doesn’t use surfaces for clipping and may be a more appropriate to use if you need just a simple listbox widget without all the overhead. It is a legacy widget so no new features will be added, but it is a very feature rich listbox as it stands. It does support custom draw scripts (however you cannot have variable heights when using this widget).