List panels -- all choices, in fact -- can have selections, and you can set them from within Lisp. This is useful for providing default settings in a choice, or when a user selection has an effect on other settings than just the one they made.
The selection is represented as a vector of offsets into the list of the choice's items, unless it is a single-selection choice, in which case it is just represented as an offset.
The initial selection is controlled with the initarg
:selection
. The accessor
choice-selection
is provided.
CAPI User Guide (Unix version) - 30 Aug 2011