root to open it, revealing it's children.
Use the Close button to close it, or again double-click.
Open subnodes, explore the tree, isn't it fascinating?!?
The first row of buttons demonstrate the open/close, hide/show
and enable/disable on nodes that have been selected.
You can also type in a name and carry out the operations on the node
associated with that name.
The only buttons that should be enabled are the ones that `make sense'.
Another demo shows how display of items can be customized, and items can have different sensitive areas.