A special
NodeHandler implementation for tracked nodes.
While basic access to a tracked node works in the same way as for usual
immutable nodes, there are differences for other operations. For instance,
the root node of the hierarchy is always the tracked node itself. Also the
parent mapping requires some special attention: as long as the node is not
detached, the parent mapping of the model to which the node belongs can be
used.
This class inherits the major part of the
NodeHandler implementation
from its base class. In order to implement the parent mapping, an underlying
NodeHandler object has to be passed at construction time which
contains this information; requests for a node's parent are delegated to this
handler. Further, the root node has to be provided explicitly.