Presently there's no clean way for a component that's not defined as
part of an existing look and feel to "track" the current look and feel
and update the look and feel specific defaults as needed. There are two
missing Swing features that make doing this difficult:

- No access to the table of look and feel specific defaults. Applications
and random components can only set "user" defaults, i.e. defaults that
persist when the look and feel changes. A component could reset its "user"
defaults each time the L&F changed however it would be difficult to prevent
developer overrides from being obliterated.

- No way to identify a LookAndFeel other than instanceof. Using instanceof,
e.g. instance com.sun.java.swing.motif.MotifLookAndFeel is unacceptable because
it assumes the L&F class is available and that it's desirable to load it.