I would like to get the caller's object private data, who call the slot. Any suggestions, please.

The Scenario:
The Package Class Handler -> many classes was called ... -> The Slot Class.

The Package Class Handler has to be attached the private data to some object.

void PackgeHandler::unpack(void)
{
...
    // Somehow to attach the private data to "e" and emit the signal to the slot.
    // How to attach the private data to the object?  Please.
    emit mousePressEvent(e);
...
}

The Slot Class will take it and see the information.

// I have compiled the container_of() and no error reported.
template<class P, class M>
size_t cpp_offsetof(const M P::*member)
{
    return (size_t) &( reinterpret_cast<P*>(0)->*member);
}

template<class P, class M>
P* container_of(M* ptr, const M P::*member)
{
    return (P*)( (char*)ptr - cpp_offsetof(member));
}

void Button::mousePressEvent(QMouseEvent *e)
{
    // What is A & B?
    // Assume the attached private data is represented to QObject or other class-type.
    QObject myObj = container_of(A, B;
    ...
}

The PackgeHandler and Button Classes in living on different DLL file, both of them are plug-in.
Can not create new signal / slot, because the architecture has to be no changes.

Question:
I do not know, how to use container_of()? Does it work in this way?
Or could you suggest me with any method would work for me?

Thank you so much,
Abhisit.