Can someone explain to me the basic idea of Qt signals&slots mechanism IMPLEMENTATION? I want to know what all those Q_OBJECT macros do "in plain C++". This question is NOT about signals&slots usage.

added: I know that Qt uses moc compiler to transform Qt-C++ in plain C++. But what does moc do? I tried to read "moc_filename.cpp" files but I have no idea what can something like this mean

void *Widget::qt_metacast(const char *_clname)
{
if (!_clname) return 0;
if (!strcmp(_clname, qt_meta_stringdata_Widget))
    return static_cast<void*>(const_cast< Widget*>(this));
return QDialog::qt_metacast(_clname);
}

Thanks in Advance, anton