Question: Accessing CV (Control Voltage) ports in clack host

[KiSetsuFu-PuLiN]

I'm new to rust and experimenting with clack to develop a CLAP host.
Some CLAP plugins (e.g. Cardinal) expose CV input/output ports (see screenshot below), but I couldn’t find an API in clack to handle CV ports.

It’s possible that I’m misunderstanding the API rather than facing an actual limitation of clack, so please forgive me if this is a basic question.

Questions

• Does clack support the CLAP CV port interface?
• If yes, how can a host read/write CV data?
• If not, is there a plan to add support?

Environment

• Host under development in Rust using clack
• Tested with Cardinal CLAP plugins

Screenshot:

[prokopyl]

Hi! I'm not very familiar with Cardinal, so I cannot say for certain.

I'd guess it probably uses the CV draft extension. That extension was never stabilized however, and in fact it was removed in the CLAP 1.2 release. (Which is why there is no first-party CV extension provided by Clack).

However, you can still use Clack to implement this CV extension, as a custom extension with the same ID as the draft CV extension. I'm still working on documenting it properly, but you can find an example in the docs for the clack_plugin::extensions module.

I'll be closing this issue as I do not plan to implement non-standardized extensions in Clack, but I'll convert this thread to a discussion in case you have further questions. 🙂