Quote Originally Posted by fullmetalcoder View Post
All the dependencies are NOT in Qt Designer itself but in Qt libs, including QtDesigner and QtDesignerComponents library...
The only dependency is QObject and obviously you need that anyway to create Qt plugins.

It will be OK as long as Blah inherits ONLY from Qt classes, or other external libraries BTW, (thus accessible from the plugin without the need to create an intermediary library) AND does not implement any method of its own (except inline methods and possibly, but might depend on compiler, methods implemented inside the header file).
I don't see how moving those "non-inline" methods to the interface class would help. And besides that's really not a problem - you can create a library with symbols needed by the plugin and you're there. Exactly like Qt and Designer do it.