Auto-connect to system output

[crsaracco]

Hi, bit of a Jack development noob here.

Initially I thought this crate was just not working, since I ran sine.rs and heard no output. However, I was messing around with qjackctl and found the "Connections" page, and found that if I manually connected the client's output port to the system:playback_1 and system:playback_2 ports, I could hear the output!

It seems like it doesn't do this by default when I launch the sine example, so I figured I'd try to connect it programmatically at the start of the program. I'm having trouble doing this, though. Here's what I've tried:

let spec = jack::AudioOut::default();
let mut out_port = client.register_port("sine_out_1", spec).unwrap();
let system_out_1 = client.port_by_name("system:playback_1").unwrap();
let connect_result = client.connect_ports(&out_port, &system_out_1);
println!("{:?}", connect_result);

The println just gives me:

Err(PortConnectionError("rust_jack_sine:sine_out_1", "system:playback_1"))

and obviously the program crashes when I try to unwrap it.

Did I do something wrong in setting up the connections? Or is something wrong with my setup somehow, since I assume the sine example just works for most other people?

Bitwig on my system can automatically connect to the jack server and output sound when I start it up, so I think my jack server settings are at least workable.

Not sure what system settings would be useful to debug this... I'm running Arch linux, if it matters. I can provide more details if needed.

[crsaracco]

So I looked into the C examples of Jack, and found something that worked for me.

In their example, you have to connect to the system playback ports after you activate the client, so that's what I did in my program:

// Connect the ports to the system output.
// You can't do this before the client is activated,
// because we can't make connections to clients that aren't running.
let client_out_1 = active_client.as_client().port_by_name("rust_jack_sine:sine_out_1").unwrap();
let system_out_1 = active_client.as_client().port_by_name("system:playback_1").unwrap();
let system_out_2 = active_client.as_client().port_by_name("system:playback_2").unwrap();
active_client.as_client().connect_ports(&client_out_1, &system_out_1);
active_client.as_client().connect_ports(&client_out_1, &system_out_2);

(There's probably a more robust way to do that, but I just wanted to get something working for now)

I'd suggest making a note in the documentation somewhere (or is it already there somewhere?) -- or maybe it's obvious to those that have used Jack before?

Either way, you can close this issue if you want :)

[wmedrano]

You want active_client.as_client().connect_ports_by_name("rust_jack_sine:sine_out_1", "system:playback_1");
I may remove .connect_ports since it doesn't add much value and obfuscates that inactive ports can't be connected and in programs that create ports, it often requires creating an unowned clone or getting a port_by_name since ownership of the port is somewhere else.

Will keep it open as a sign to look into:

• Autoconnecting, to reduce boilerplate that will be written by most programs.
• Improve debugabilty of connect_ports

[crsaracco]

Oh, yep that's probably what I want. Missed that somehow.

One last thing: is there a more robust way to get the system's playback channels other than just assuming it's going to be "system:playback_1" and "system:playback_2"? (or is it always that in Jack?)

From what I could gather, I might be able to do it with:

let system_out_ports = active_client.as_client().ports(None, None, jack::PortFlags::IS_INPUT | jack::PortFlags::IS_PHYSICAL);

but I just wanted to double-check.

Thanks!