Whether at least one row holding the item passes the other columns' or fields' filters.
Whether the column's filter selects the item, or the field shows it.
The item's identity: the text the column shows for it, or the pivot item's caption; '' for
the blank item. What ISlicer.selectItems takes.
The text shown on the button.
The value of the first cell showing the item, or the pivot item's; null for the blank item.
One button of a slicer.