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Advice on porting a Qt 2 Windows Application to Qt 5 ?

  • Has anyone been using Qt since the Qt 2 days? If so can you provide an overview about how big a job porting a QT 2.3.1 application to Qt 5 would be and maybe outline recommended steps?

    Was Qt 3 a big step change from Qt 2? And from Qt 3 to Qt 4? I have seen mention of porting tools to assist with porting Qt 3 to Qt 4. From Qt 4 to Qt 5 is easy.

    I like Qt 5 and have been using it since Qt 4.7. The Qt 2.3.1 application's code base looks familiar. The application works well enough but needs polishing, upgrading, and new features. The application is basically a 2-D drawing program for planning a simple route from point A to point B for constructing new pipelines. The project contains about 180 cpp files.

    Thanks in advance,


  • Lifetime Qt Champion


    I can't comment for the 2 to 3 port. But 3 to 4 can be a big task depending on what component you used. However you have the "porting guide": here that contains a lot of information about e.g. enum changes, new class vs old class. To help make the transition a bit smoother Qt 4 provided the qt3support class but in your case you should completely ignore it and go for a full port.

    Indeed going from 4 to 5 is pretty easy, especially for widgets. The biggest thing is that they were moved in their own module.

    You should go through the program and gather the list of components that were used as well as the functionality they provided then search through Qt 5's documentation to find the equivalent there. Depending on how it was wrote, maybe extract the business logic so you may also use e.g. QML for the GUI (I'm not pushing you to use it, just proposing as an alternative)

    Hope it helps

  • Thank you for your reply.

    I think it is worth spending a day on it and see how far I get.

    Thanks again,


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