"handles" an event, depending on the type of the event object.
A Lisp object.
The generic function
. What this actually means depends on the type of the object.
There are system defined methods for these classes:
If fbound call it, otherwise do nothing.
You can add methods for your own classes.
is used by all functions that process events, for example wait-processing-events and process-all-events, as well as by internal waiting functions.
LispWorks User Guide and Reference Manual - 21 Dec 2011