Qt cross thread call

Question

I have a Qt/C++ application, with the usual GUI thread, and a network thread. The network thread is using an external library, which has its own select() based event loop... so the network thread isn't using Qt's event system.

At the moment, the network thread just emit()s signals when various events occur, such as a successful connection. I think this works okay, as the signals/slots mechanism posts the signals correctly for the GUI thread.

Now, I need for the network thread to be able to call the GUI thread to ask questions. For example, the network thread may require the GUI thread to request put up a dialog, to request a password.

Does anyone know a suitable mechanism for doing this?

My current best idea is to have the network thread wait using a QWaitCondition, after emitting an object (emit passwordRequestedEvent(passwordRequest);. The passwordRequest object would have a handle on the particular QWaitCondition, and so can signal it when a decision has been made..

Is this sort of thing sensible? or is there another option?

Answer 1

Using signals to send messages between threads is fine, if you don't like using the Condition Variable, then you can send signals in both directions in a more-or-less asynchronous manner: this might be a better option if you want to continue processing network stuff while you wait for a reply from the GUI.