Setting Up gtk2 Plugins (Calf, etc...)

How to set up the Calf or other gtk2 plugins to run with Rosegarden.

I've tested this with Ubuntu 24.04. Other distros will have different package names.

$ apt install calf-plugins

For Ubuntu I also needed to install the qt5-style-plugins:

$ apt install qt5-style-plugins

If your distro provides Rosegarden version 26.06 or later, you might be able to get away with using that. However, it is possible that your distro has not built Rosegarden properly and you will need to build it yourself.

If you are building Rosegarden on your own, make sure the following are installed:

• gtk2 dev headers and libs (libgtk2.0-dev)
• lilv (liblilv-dev)
• lv2 (lv2-dev)

You should then be able to build rosegarden as usual and it will find everything it needs. See the README.md that comes with the source for many example cmake commands.

Make sure JACK is up and running or comes up when you launch rg. Without JACK running, most of the audio features are disabled and you will get nowhere.

Launch Rosegarden and adjust the following preferences as needed:

• LV2 Plugin Support: checked
• Setup LV2 Environment: checked

If you needed to make any changes, restart rg.

Confirm audio is ok by checking the bottom right corner of the Rosegarden window and looking for the green audio wave icon. Hover over it and it should say “audio OK”.

Test the Calf plugins: Select an audio track, click on a <no plugin> button, select the Calf Compressor, press on the Editor button.

You might see a warning dialog mentioning how using gtk2 plugins is fraught with peril. You can dismiss.

You might see another warning dialog: “The rosegarden gtk2 library (librosegardenGtk2.so) has not been found.”

To fix this, you'll need to tell rosegarden where to find it by setting LD_LIBRARY_PATH. E.g. if you are running your own build from the build directory, this should fix the problem:

$ LD_LIBRARY_PATH=./ ./rosegarden

And that should do it.

Fixing problems related to gtk2 plugins oftentimes boils down to an exercise in adjusting environment variables.

The preference “Setup LV2 Environment” defines the following:

• QT_QPA_PLATFORMTHEME=gtk2
• XDG_SESSION_TYPE=x11 (but only if it was wayland)

XDG_CURRENT_DESKTOP is another variable that can help at times. See [this post on the bug tracker](https://sourceforge.net/p/rosegarden/bugs/1749/#190b).

• [Bug #1737](https://sourceforge.net/p/rosegarden/bugs/1737/) - Discussion of QT_QPA_PLATFORMTHEME and XDG_SESSION_TYPE.
• [Bug #1738](https://sourceforge.net/p/rosegarden/bugs/1738/) - Some discussion of XDG_SESSION_TYPE.
• [Bug #1749](https://sourceforge.net/p/rosegarden/bugs/1749/#190b) - Discussion of XDG_CURRENT_DESKTOP.

The lv2-gtk-ui-bridge from FalkTX is a special LV2 bundle that allows you to use legacy LV2 Gtk2/3 UIs as LV2 X11 UIs. I've not tried it.