The following classes implement the standard output protocols.
Summary: This class is mixed into any sheet that provides the standard output protocol, such as repainting and graphics.
Summary: This class is mixed into any sheet that provides none of the output protocol.
permanent-medium-sheet-output-mixin
Summary: This class is mixed into any sheet that always has a medium associated with it.
temporary-medium-sheet-output-mixin
Summary: This class is mixed into any sheet that may have a medium associated with it, but does not necessarily have a medium at any given instant.
Common Lisp Interface Manager 2.0 User's Guide - 3 Mar 2015