This method is called before a snip in the pasteboard is selected or deselected, after can-select? is called to verify that the selection is allowed. The after-select method is guaranteed to be called after the selection has completed. This method is not called when a selected snip is to be deleted (and thus de-selected indirectly); see also on-delete .
The editor is internally locked for writing when this method is called (see also Locks). Use after-select to modify the editor, if necessary.
If on? is #t, then snip will be selected, otherwise snip will be deselected.