[FEATURE REQUEST] Add toggle to disable system sounds

[BrodieRobertson]

I and many others don't like random functions on our system making sound, such as the volume slider. It would be nice if there was a toggle to disable all of the sounds.

[cgevans]

The problem here is not directly solvable in cosmic-settings at the moment: notification sounds seem to be played by spawning pw-play directly. That call will, by default, categorize the sounds as the Music media role. While the external call probably isn't intended as a long-term approach, a quick fix for the problem is to add --media-role Notification to the command. That will set the media role so that the sounds will be controlled by settings trying to control notification sounds: for example, it will make the System Sounds control in pavucontrol (which controls the "event" media role in pulseaudio, which seems to be equivalent to "Notification" in pipewire) control the sounds.

With that properly set in the locations where notification sounds are being generated, it should be possible to add a volume control for system sounds here. I've opened pop-os/cosmic-settings-daemon#120 and pop-os/cosmic-osd#163 to do so in the places where I've found calls, though there might be others.

[cgevans]

With the PRs merged, it should now be possible to implement a volume slider here. Unfortunately I'm not very familiar with the pipewire crate, or how to interface with pipewire outside of command line tools in general. Pavucontrol uses pulseaudio's interface, which makes it a bit harder to follow the same approach. However, pavucontrol seems to result, in pipewire, in a 'route-settings' metadata on id 0 with pw-metadata -n route-settings like

> pw-metadata -n route-settings
Found "route-settings" metadata 45
update: id:0 key:'restore.stream.Output/Audio.media.role:Notification' value:'{ "mute": false, "volumes": [ 2.711257 ], "channels": [ "MONO" ] }' type:'Spa:String:JSON'

[mmstick]

Pipewire metadata updates are received here:

cosmic-settings/crates/cosmic-pipewire/src/lib.rs

Lines 328 to 395 in 7251c8c

	ObjectType::Metadata => {
	let Ok(metadata) = registry.bind::<pipewire::metadata::Metadata, _>(obj) else {
	return;
	};
	let id = metadata.upcast_ref().id();
	let listener = metadata
	.add_listener_local()
	.property({
	let state = Rc::downgrade(&state);
	move |_subject, key, _type, value| {
	let Some((key, value)) = key.zip(value) else {
	return 0;
	};
	match key {
	"default.audio.sink" => {
	if let Ok(value) =
	serde_json::de::from_str::<DefaultAudio>(value)
	{
	if let Some(state) = state.upgrade() {
	state
	.borrow_mut()
	.default_sink(value.name.to_owned())
	}
	}
	}
	"default.audio.source" => {
	if let Ok(value) =
	serde_json::de::from_str::<DefaultAudio>(value)
	{
	if let Some(state) = state.upgrade() {
	state
	.borrow_mut()
	.default_source(value.name.to_owned())
	}
	}
	}
	_ => (),
	}
	0
	}
	})
	.register();
	let remove_listener = metadata
	.upcast_ref()
	.add_listener_local()
	.removed({
	let state = Rc::downgrade(&state);
	move || {
	if let Some(state) = state.upgrade() {
	state.borrow_mut().remove_metadata(id);
	}
	}
	})
	.register();
	state
	.borrow_mut()
	.proxies
	.metadata
	.insert(id, (metadata, listener, remove_listener));
	}

.

Metadata objects are stored here:

cosmic-settings/crates/cosmic-pipewire/src/lib.rs

Line 394 in 7251c8c

.insert(id, (metadata, listener, remove_listener));

The object's type has a set_property method: https://pipewire.pages.freedesktop.org/pipewire-rs/pipewire/metadata/struct.Metadata.html#method.set_property.