Certain state changes within a Treeview
widget
generate virtual events that you can use to respond to these
changes; see Section 54.8, “Virtual events”.
Whenever there is a change in the selection, either
by items becoming selected or becoming unselected,
the widget generates a “<<TreeviewSelect>>
” event.
Whenever an item is opened,
the widget generates a “<<TreeviewOpen>>
” event.
Whenever an item is closed, the widget generates a
“<<TreeviewClose>>
” event.