@mandruk1331 QDialog already provides all the signals (accepted() and rejected()) and slots (accept() and reject()) you'd need. You only need to call accept() when you've checked that the login is successful (meaning in the button slot). See my example in post #1 how to connect them! As to the login dialog implementation, something like this:
class MLogIn : public QDialog
explicit MLogIn(QWidget *parent = 0);
//< Try logging the user in
QMessageBox::warning("No such user/password");
It looks like there might be an easier mechanism to do this kind of thing with in the future.
Rather than writing my own MenuBar from scratch, the Qt team have implemented styling support for most of their components. Whilst i haven't tried this yet (I'm stuck on a different part of my project at the moment), MenuBar Style should be perfect for what I was originally trying to acheive, by writing custom delegates, with the appropriate behaviours attached to their properties.
"Have rebuilt the same code with a different version of Qt?" - yes, I did it
"Running both versions of the application on the same machine shows you different results??" - yes
I guess something has changed in Qt sources since version 5.3 or 5.4.
I hope this thing (to show menu shortcuts) is tweakable via Qt API.