#462 LV2 plugin support

[Ted Felix]

We really should support LV2 plugins.

For now, one can use an external plugin host like Carla to connect plugins via JACK.

See [bugs:#1433].

[Philip Leishman]

I installed fedora 40 in a virtual machine and I could reproduce the problem.
I think this is the usual qt/gtk2/gtk3 clash.
If I run with the setup described in bug 1674 rosegarden starts !
The fix was:
install the qt5-style-plugins package
export QT_QPA_PLATFORMTHEME=gtk2

So now rosegarden is running (compiled with lilv and gtk2) but I cannot get an lv2 editor window to open. Neither the gtk editors nor the X11 editors start (maybe a wayland problem ?)
I am still looking into this

[Philip Leishman]

So one problem was my audio setup - using pipewire.
After sorting that out I still had some problems with the editor windows - probably related to wayland.
I found a workaround:
export XDG_SESSION_TYPE=x11

[Philip Leishman]

To summarize:
install the qt5-style-plugins package
set the environment variables:
export QT_QPA_PLATFORMTHEME=gtk2
export XDG_SESSION_TYPE=x11

and rosegarden should work with the lv2 plugins and gtk editors

[Philip Leishman]

I have added a check for the existence of the gui library (See the mails from Chuck Elliot on the user list).
Please merge

[Ted Felix]

Pushed as [e9dfb9]. Please test latest git.

[Philip Leishman]

Not directly related to lv2 but I got some compile errors on the latest git.
Please merge

[Ted Felix]

Thanks for keeping me honest on Qt6. 🤣 Merged as [bff3eb]. Please test latest git.

[Philip Leishman]

Looking at the first few comments here - I noticed the one about "direct export / render".
That makes sense if I just have synth plugins and audio tracks.
I have made a try at this - see my feature-462-lv2 branch.
There is a new command in the File->Export menu. This will record the next play to a wav file.
It would be nice to render in non real time but that is more difficult. No idea how to approach that.
Attached is an example - part of the aveverum example rendered with the calf fluidsynth and organ plugins.