Subscribe registry.global_remove so we know when routed stream nodes
vanish; drop them from routed_node_ids and emit LastRoutedStreamGone
on the N→0 transition. Tokio side re-runs `pactl load-module
module-loopback` with the same args as start, restoring the
default-sink monitor mirror so the viewer hears system audio again
instead of going silent when the routed app exits mid-session.
FirstRoutedStream now fires on every 0→N transition (not just the
first), so the pair oscillates cleanly: each app open/close cycle
unloads → re-loads the loopback.
Verified cross-machine 2026-05-22 16:29 EDT — host with Strawberry
picked, laptop viewer over mpv with YouTube playing on host as a
control. Strawberry audible on laptop, YouTube silent (route active).
Quit Strawberry → YouTube became audible (loopback restored).
Reopened Strawberry → routed again, YouTube dropped out (loopback
unloaded). Clean Ctrl+C teardown.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
When opts.app is set, a dedicated OS thread runs a libpipewire
MainLoop, subscribes to the registry, and writes target.object to
the "default" metadata so WirePlumber reroutes matching streams to
our per-PID null-sink. Activation is now opts.app.is_some() OR the
existing PIXELPASS_AUDIO_VIA_NULL_SINK env var (kept for
no-filter dogfooding).
Threading: tokio side spawns a std::thread; the two sides bridge via
pipewire::channel for cmd→thread (Shutdown) and tokio::sync::mpsc
for event→tokio (FirstRoutedStream). Cross-thread quit goes through
the libpipewire channel so MainLoop is only mutated from its own
thread. Shutdown clears target.object on every routed stream before
quitting so WirePlumber doesn't log orphans.
Routing decisions:
- Filter is case-insensitive equality on application.name (predictable;
no surprise matches from substring).
- target.object is written as Spa:Id with the sink's object.serial.
- Default-sink loopback stays loaded until the first stream is
actually routed — avoids viewer silence if the user picks an app
that isn't producing sound yet. On first route, the event task
takes() the loopback module ID and unloads it.
Session 2 picker explainer + (app pick saved: ...) banner softening
both removed; banner is back to plain app-audio=NAME.
Verified end-to-end cross-machine: desktop host with Strawberry
selected, laptop viewer over mpv. Strawberry audible on the laptop;
YouTube playback started on the desktop was NOT audible on the
laptop. Routing isolates the filtered app.
Session 4 still open: recreate loopback when the last filtered stream
disappears (avoid silence), handle app-disappears-mid-session,
multi-instance, --repair coupling for orphan sink cleanup.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
list_playing_apps() shells out to `pactl -f json list sink-inputs`,
parses with serde_json, dedupes by application.name (BTreeMap for
stable ordering), returns Vec<App { name, stream_count }>.
Picker fires in interactive::run after preflight, before host::run.
Bypassed when --app NAME is on the CLI. Shows the apps with a
"per-app routing isn't live yet" explainer so users aren't surprised
that audio still captures system-wide. Empty-list path shows the
default + a "start your app first" hint so the feature stays
discoverable.
Banner softened to `system-audio (app pick saved: <name>)` when
opts.app is set — keeps the choice visible without lying about what
gets captured. Routing activation still gated on the
PIXELPASS_AUDIO_VIA_NULL_SINK env var (session 1's locked decision
#2); --app flips to that activation in session 3 once per-stream
filtering exists.
Verified end-to-end interactively: Strawberry shows up in the picker
during music playback, both default and app-pick paths advance into
the portal handshake, banner matches choice.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Session 1 of the per-app audio routing feature. Adds host/audio.rs
with a Routing struct that owns the lifecycle of two pactl-loaded
modules: a per-PID null-sink (pixelpass_capture_<pid>) and a loopback
mirroring @DEFAULT_SINK@.monitor into it at 20ms latency. Activated
by PIXELPASS_AUDIO_VIA_NULL_SINK=1 — kept hidden behind an env var
because without per-stream filtering (session 3) the user-facing
behavior of --app foo would be identical to no flag, which would
mislead users about what the flag does.
When the env var is set, wayland::start substitutes the gst pulsesrc
device from {DEFAULT_SINK}.monitor to pixelpass_capture_<pid>.monitor;
audio still works end-to-end via the loopback. CaptureHandle owns the
Routing alongside gst and serve; teardown order is gst → audio → serve
so streams unlink from the null-sink before the sink is destroyed.
Lifecycle is via pactl shell-outs rather than pipewire-rs. Null-sink
+ loopback are one-shot graph mutations with no event subscription;
the libpipewire route would mean dragging a MainLoop thread in for no
benefit until session 3 needs stream events.
Known cosmetic: the null-sink appears in Plasma's audio mixer as a
user-facing volume slider. Pactl's sink_properties= quoting is fiddly
enough that the device.hidden=true fix is parked for a follow-up.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
molluskandClaude Opus 4.7