The delegate callback to execute when invoking the command.
This widget to aid method chaining.
These are the fields within the callback's CommandArgs parameter which are populated by this method when the callback is executed.
$(PARAM_TABLE $(PARAM_ROW CommandArgs.element, The tree column.) $(PARAM_ROW CommandArgs.uniqueData, The internal id of the tree view (An implementation detail that's not very useful).) $(PARAM_ROW CommandArgs.callback, The callback which was executed.) )
Convenience method to set the tree column command to be executed when clicking on the heading.