API Development - QEventLoop: Cannot be used without QApplication

[wysota]

I started to reply to this early on (would have been the first reply, in fact), then bailed when I could not think of a way in DllMain() (or whatever the equivalent is here) to get the event loop started without hanging on the exec() call. After reading all this, I still can't think of a way.

The proper approach is to implement an event loop integration -- either process events of your other toolkit as part of Qt's event loop or process Qt events as part of the other framework's event loop. Qt already integrates quite well with glib's event loop, there is no reason one wouldn't integrate it with other event loops too.

[d_stranz]

Qt already integrates quite well with glib's event loop

Google is not being my friend tonight. Do you have a link to somewhere that discusses how this (or integration with any external event loop) is done (and not just someone blogging about having done it in less than 600 lines of code without sharing the details)?

[wysota]

First there is docs on QAbstractEventDispatcher which is a direct way to do the integration. Second there is or used to be the Qt-Mfc migration framework which I think integrated the two event loops. This there is Qt source code which has a number of event dispatchers implemented. Fourth a basic integration can be done by simply setting a timer in one of the frameworks and processing events of the other framework in the timeout function. I remember a couple of years ago I was using some CORBA framework with Qt and there was integration available for it that I think used the last approach. If I remember correctly it was a Qt Solution so there is a good chance its code is available somewhere on Qt's gitorious. But I think the glib one which Qt uses by default on Unix platforms if glib is available will give you the most information how to implement such integration.

[erichumenay]

I finally have gotten this working.

I had 2 separate problems both related to QCoreApplication not being present in the dll
1. The dll threads weren't being spawned
2. Signals from the threads back to the main thread were not occurring

Both 1 & 2 were occurring due to lack of an event loop in the main thread.

To fix one #1 followed the instruction here:
​http://stackoverflow.com/questions/2...qt-application

To fix #2 I had to change my signal/slot connections
Original code
connect(commMGR, SIGNAL(collectFin()), this, SLOT(ReportCollectFin()));

New and Working code
connect(commMGR, SIGNAL(collectFin()), this, SLOT(ReportCollectFin()), Qt:irectConnection);
commMGR->moveToThread(QAppPriv:Thread );

where QAppPriv:Thread is the thread I created to solve problem #1.

The elegant thing about my solution is that the newly added code is isolated from the original code so there is no way that the new code could introduce a bug in the original code which would necessitate retesting the entire dll.

Thanks for helping me out

- All