Building Plasma against Qt6 - Nico's blog

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2023-03-26 17:00:03

As you probably have heard by now the lastest development versions of Plasma and KDE Frameworks require Qt6. This transition has been in the works for a few years by now, but it was only somewhat recently that we took the plunge and started relying on Qt6 exclusively for Plasma. Plasma 5.27 is the last Plasma 5 release and continues in bugfix-only mode.

Before diving into this, a word of warning: Current Plasma master is in no way “ready for production”. There are known-broken things and things may temporarily regress at any time. That said, the only way to get towards a stable thing is to dig in and fix things. So let’s see how to do that.

For this explanation I’m assuming you have build KDE software with kdesrc-build before. If not we have some extensive documentation for that. First you need at least Qt 6.4 installed. The usually best way to get that is from your distribution. If your distribution does not have Qt6 packaged yet please complain^Wtalk to them. CMake should complain about any missing Qt6 modules/development files, but make sure you have the qtpaths tool installed beforehand. It should be named something like qtpaths6 or qtpaths-qt6.

Now we need to teach kdesrc-build to build Plasma with the right configuration (git branches, CMake arguments etc) for building with Qt6. The easiest way to do that is by using a separate kdesrc-buildrc file. kdesrc-build comes with a sample Qt6 configuration file that you should use as a starting point. Replace the line include ~/kde6/usr/share/kdesrc-build/kf6-qt6-build-include with a path to your existing kdesrc-build installation. For me that would be include ~/kde/src/kdesrc-build/kf6-qt6-build-include. You can also apply other customizations that you usually do in your kdesrc-buildrc. Then save the file as e.g. ~/kde6/kdesrc-buildrc. This configuration will download, build, and install everything under ~/kde6. Currently it is very important to keep Qt5-based and Qt6-based builds separate since there will be conflicts between the installed files.