True if handles are displayed at the topmost level of the tree.

A handle is a small icon that displays adjacent to the node which allows the user to click once to expand or collapse the node. A common interface shows a plus sign (+) for a node which can be expanded and a minus sign (-) for a node which can be collapsed. Handles are always shown for nodes below the topmost level.

If the rootVisible setting specifies that the root node is to be displayed, then that is the only node at the topmost level. If the root node is not displayed, then all of its children are at the topmost level of the tree. Handles are always displayed for nodes other than the topmost.

If the root node isn't visible, it is generally a good to make this value true. Otherwise, the tree looks exactly like a list, and users may not know that the "list entries" are actually tree nodes.