The checking/unchecking of all currently selected items in a listcb control (list of checkboxes or radios) by hitting the spacebar should be covered by the sclick event.

No dialog event is currently associated with the checking/unchecking of items in a list via spacebar, while other "keyboard actions" are already covered by the sclick event (e.g. moving to another item with arrow keys, selecting multiple items in an extsel list with shift-arrowkeys...).
Furthermore, it would make event mapping more consistent, as the sclick event triggers for spacebar-checking of a "regular" (non-list) checkbox/radio.