When setting up a notification on this attribute, RapaGUI will run your
event callback whenever the user cancels an editing operation on an item,
for example by pressing the escape key or clicking outside the item edit
widget.
Note that you have to set Listviewcolumn.Editable to True before
you can use this attribute.
Your event handler will be called with the following extra arguments:
Row:-
Row index of the item which the user was editing when he cancelled the operation.
Column:-
Column index of the item which the user was editing when he cancelled the operation.
See Notifications for details.