MusicMixer

A PipeWire audio mixer with a native desktop GUI built in Rust using GPUI.

Features

• Per-app volume control — independently adjust volume and mute for each playing application
• Output routing — route any app to any output device (speakers, headphones, HDMI) with per-port switching
• Live PipeWire graph — monitors nodes, ports, and links in real time via the PipeWire registry
• Clean restore on exit — disconnects custom links and resets all stream volumes/mutes back to defaults
• Custom window chrome — client-side decorations with drag-to-move titlebar and resize handles

Requirements

• Linux with PipeWire running
• pactl (PulseAudio utilities, works with PipeWire's PulseAudio layer)
• pw-link (from pipewire-utils or similar)
• Rust toolchain (stable)

Build & Run

cargo run --release

Architecture

src/
├── main.rs                  # App entry, window setup
├── models.rs                # Data types: AudioNode, MixerState, AppGroup, EngineEvent/Command
├── state.rs                 # GPUI global (shared state + channel ends)
├── audio/
│   └── pipewire_engine.rs   # PipeWire monitor thread + pactl/pw-link command thread
└── ui/
    ├── mixer.rs             # Main window render tree, event polling, drag sliders
    └── icons.rs             # SVG icon helpers

Data Flow

PipeWire registry
    │ (pipewire crate callbacks)
    ▼
monitor thread ──EngineEvent──► poll_events() in render loop
                                      │
                                 MixerState mutation → re-render

User interaction (click / drag)
    │
    ▼
EngineCommand ──channel──► command thread ──► pactl / pw-link

Key Types

Type	Purpose
AudioNode	A PipeWire node (app stream, sink, source, virtual bus)
NodeType	App, AppInput, OutputDevice, InputDevice, VirtualBus
AppGroup	Merges playback + capture streams of the same app into one card
OutputTarget	A routing destination — whole sink or a specific port (e.g. Speakers vs Headphones)
EngineEvent	Node/port/link add/remove, volume/mute changes sent from audio thread to UI
EngineCommand	SetVolume, SetMute, CreateLink, RemoveLink, SetSinkPort sent from UI to audio thread

How Routing Works

1. The UI sends EngineCommand::CreateLink { from_name, to_name } when the user picks an output.
2. The command thread calls pw-link to enumerate real port names for both nodes, then pairs them by channel suffix (FL↔FL, FR↔FR).
3. To switch between ports on the same sink (e.g. Speakers → Headphones), a SetSinkPort command runs pactl set-sink-port before creating the new link.
4. When a new output device appears (e.g. plugging in headphones), existing app→device links are automatically restored via EngineCommand::RestoreLinks.

License

MIT