Using default implementation, intefaces and Qt plugins (not designer plugins)

[high_flyer]

Thanks, but :

implement default logic in the application

Your suggestion is very similar to what I wrote in post #5.
And as I wrote later, I see it as bad design, to mix UI and logic, and in general to spread the logic over several modules.

It is much cleaner when each modules logic is self contained.

But thanks never the less!