[Laszlo-dev] final vs. sealed

[P T Withington]

Dylan had this cool concept of a "sealed" class.  It meant the class  
was "final" outside the library, but you could still subclass it in  
the library.

What I want to do:

I want to subclass LzEvent to make a special LzIdleEvent that  
automagically registers itself for the idle kernel callback when it is  
ready.  The only way I can see to do this is really a pain.  I think I  
have to make LzEvent an interface, so it can continue to be used in  
type declarations, then I have to make a private base class that is  
not final that implements LzEvent, then I have to make a public class  
that is a subclass of that but final that is used for all actual  
events visible outside the LFC.  Finally, I can make LzIdleEvent a  
public final subclass of the private base class and add my  
functionality there...  What a pain!

Am I missing something obvious?