AncestorProcessor processes up the ancestry tree through parents firing events in DescentOf mode.
ContainerEvent
DescendantProcessor processes down the descendant tree through children firing events in Ancestors mode.
Ancestors mode is utilized to listen on a descendant (lower child) of a Listenable and still receive that event.
Descendants mode is utilized to listen on an ancestor (higher parent) of a Listenable and still receive that event.