RustAudio
ALSA or JACK
Should i use ALSA or JACK ? Looking at the documentation, ALSA doesn't have a dedicated thread. JACK is not mentioned. And ALSA is the default backend.
Note: Creating and running a stream will not block the thread. On modern platforms, the given callback is called by a dedicated, high-priority thread responsible for delivering audio data to the system’s audio device in a timely manner. On older platforms that only provide a blocking API (e.g. ALSA), CPAL will create a thread in order to consistently provide non-blocking behaviour (currently this is a thread per stream, but this may change to use a single thread for all streams).
If you only need to target systems with pipewire or Linux users who care about audio latency, I would go with the JACK backend. Pipewire being the default sound system in some linux distros is pretty new, while ALSA will work almost anywhere. (There may be other benefits of ALSA that I'm not aware of.)
An implicit jack feature is inserted because the jack dependency is optional. This should probably be documented somewhere.
can we disable alsa if we don't want to use it at all? that way it saves having to download the dev dependencies...
No, ALSA isn't an optional dependency on Linux, but you could use rust-jack directly on Linux, it's very little extra code: https://github.com/RustAudio/rust-jack/blob/main/examples/sine.rs