The accordion widget is a vertically stacked list of items represented via buttons. By clicking on a button, the item can be "expanded" or "stretched" to reveal the content associated with that item. Within each accordion widget there is always exactly one item "active". When a new item is stretched, the previously active item shrinks back to only show its button.
The accordion widget is similar in purpose to a notebook widget. The accordion widget is useful when dealing with long item descriptions because in that case you quickly run out of horizontal space on a notebook widget.
JOB - 2016-07-29 14:00:22
See as well for an approach to convert the code to a TclOO megawidget: accordion - yet another TclOO implementation.