One approach might be to alias PluggableButtonView as
    Switchview. This allows you to file things in and even test out
    how compatible the interfaces between the two are. And then when
    you're done, by either changing the way you interface with the
    SwitchView/PluggableButtonView or extending it's interface to be
    compatible with what Draw80 wants, it's easy to drop the alias.

Another approach is to create SwitchView as a subclass of
PluggableButtonView, but don't add any methods or variables.

When there is something that SwitchView does not understand, add it to
that class implemented in terms of its super class.

If they end up too incompatible then you can move SwitchView elsewhere
in the hierarchy.

-- 
Patrick Logan                 mailto:patrickl at gemstone.com
Voice 503-533-3365            Fax   503-629-8556
Gemstone Systems, Inc         http://www.gemstone.com