qt Signal and slots for plainly C++ class objects

[high_flyer]

Of course you can still incorporate non Qt C++ in A Qt project.
The only limitation is that the non Qt code on its self will not play with (Qt( signal and slots (you could use boost signals and slots and mix them with Qt's however).
You can still use it in Qt slots however.
That is, you can have a Qt wrapper to your plain C++ code, the wrapper will provide the signals/slots and call within it the plain C++ code.