cpal doesn't respect default device chosen through KDE UI

[tesselode]

In KDE, there's this widget which lets me select the default audio device for applications:

This doesn't seem to impact what cpal chooses as the default, though. I have no idea what mechanism KDE uses to set the default device, but can/should cpal read that default?

I'm using Arch with PulseAudio.

[Ralith]

I think it's reasonable to expect this to work. Fixing it will probably require either understanding how (if at all) this default is surfaced to the ALSA API, or for someone to finally review and merge a native pulse backend, which may be a difficult sell now that everything's moving to pipewire anyway.

[dani-corie]

Aren't these settings the default output device for Pulse? From the perspective of cpal, Pulse / Pipewire is just one ALSA device, then the mixing daemon will probably output the stream to wherever you told it to.

[cynthia2006]

@dani-corie No, these are default devices for PipeWire. They modify the session manager's defaults.

[roderickvd]

Because KDE is configuring PipeWire, and cpal is using the pipewire-alsa "proxy", there is nothing we can do about this in the ALSA host. Maybe when a PipeWire host is added via #938 it could support notification of such change events, I don't know.

[cynthia2006]

Just so people know, pipewire-rs repository is no longer maintained; not that it matters, because you could always use the C API, instead of that third-party binding.