The following was never really answered ... see thread for background.

Is it a true statement that "you can't use Qt meta-object system with interface composition"?

With interface composition, it's necessary (at least with C++) to use multiple inheritance. Defined interfaces (abstract base classes that derive from QObject for introspection) are composed to provide a composite interface (via inheriting from multiple base interface classes).

The Qt documentation implies that multiple inheritance of QObject is not supported. However, for me it is working quite well as long as my base classes have unique slot and signal names ... this ambiguity being a problem with multiple inheritance in general ... not just limited to Qt. Is there some other limitation?

The parallel in Java for what I'm trying to do is "a class that implements multiple interfaces".