The calculator widget is written in QML, a relatively young language, so my experience is rather limited. But playing with QML widgets is very easy: you just need a text editor, change the source, and use the
plasma-windowed command to launch the modified plasmoid. No compilation or installing is needed.
So did I fix the bug? Yes and no. Changing some “if’s”, I was able to fix the bug, but playing with the calculator, I noticed a severe regression: If you typed “3+4+5=6+7=” it would first calculate 12, then 25.
To be honest, I was simply too lazy to investigate further. I reverted the changes, and marked the bug as a Junior Job instead. These are bugs that KDE developers believe to be relatively easy to fix. My intention was evil: Someone else should get his hands dirty! And I got rewarded …
A few days later, Paul added a patch to the bug report, fixing it without nasty regressions. After it went through code review at reviewboard.kde.org, it had been committed to the KDE code repositories, and you can see his work starting with the coming 4.11.2 release of our software compilation.
Why am I telling you all this? First, if you are a looking for a way to contribute to KDE projects, the list of junior jobs might be a good start. If you get stuck and need help, check http://techbase.kde.org/Contribute. It contains many links for ways to contact KDE developers.
Second, as the maintainer of KDE software, you should keep an eye on bug reports. If a bug looks easy, do not fix it immediately, but mark it as a junior job instead. This way, you give new contributors a chance to start contributing. Without a list of junior jobs, you will have a much harder time finding help.
And finally, the number of Plasma widgets written in QML is growing. Even if not marked as a junior job, some Plasma bugs can be solved without much coding experience. See this bug for another example.