Hey,
I just finished half of "the C++ GUI Programming with Qt 4". I wanted to find some small-scale or medium-scale opensource projects that are built on Qt 4, then I can learn something from the source code.
Could anyone recommend some projects from your experience when you start to learn Qt?
Thanks a lot.
If you are on Linux (but there are ports for win and mac too), you shoul definitely take a look at any KDE application. It uses KDE libraries, but everything is built on top of QT, so it's a good start. Especially because there is a huge number of available apps, ranging from the smallest game to the large mail client ending up with an entire desktop environment. All is open source, freely available, well documented and you can get in touch with lots of people who can help you starting up.
You can try http://www.qt-apps.org/. That's Qt only rather than KDE.
For KDE you can try installing it on your Ubuntu, use it for a while, pick one application that you like and look at it's source code. You can then get that from the KDE SVN repository, compile it yourself, change it, fix bugs, submit patches etc.
But remember that KDE is not Qt. KDE uses kdelibs which are another layer built on top of Qt. Maybe the cross-platform aspect also interests you: Qt works great on Linux, Mac and Windows while KDE works great on Linux and it's in the process of being ported to Mac and Windows. There is progress there (you can get KDE applications on Windows here) but they are by far not as polished as Qt is on Windows.
I guess you can say that if you aim to learn for getting a job using Qt or want strong cross-platform support then focusing on plain Qt is better, while if you aim to develop open-source applications using Qt KDE could be the better choice.
I wouldn't suggest going through qt-apps.org or kde-apps.org. You can find a lot of badly written applications there.
Look at the Arora browser if you want something to learn from. It isn't that large, and the source code is nicely organized.
For small to medium Qt softwares, I recommend the site www.dprog.net That's a community building small and medium softwares with a very high Qt code source quality, perfect for you !
Hope it helps !