compose-vst

A VST3/CLAP audio plugin with a Rust backend (nih-plug) and a Compose Multiplatform desktop UI.

Architecture

┌─────────────────┐     TCP/JSON      ┌──────────────────────┐
│  DAW (host)      │    localhost:9847  │  Compose Desktop UI  │
│                  │◄─────────────────►│                      │
│  ┌──────────────┐│                   │  - Cutoff slider     │
│  │ Rust Plugin  ││   state updates   │  - Resonance slider  │
│  │ (nih-plug)   ││ ────────────────► │  - Freq response plot│
│  │              ││   param changes   │                      │
│  │ Biquad LPF   ││ ◄──────────────── │  Material 3 dark UI  │
│  └──────────────┘│                   │                      │
└─────────────────┘                   └──────────────────────┘

Plugin (Rust) — loaded by the DAW as a native .vst3 shared library. Handles real-time audio processing with zero GC pauses.

UI (Compose Desktop) — separate JVM process. Communicates with the plugin over TCP with newline-delimited JSON.

Building

Prerequisites

• Rust (stable) — curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
• JDK 21+ — for Compose Desktop
• Gradle wrapper is included in ui/

Rust Plugin

cd plugin
cargo build --release

The compiled .vst3 bundle will be in target/release/. Copy it to your DAW's VST3 folder.

Compose Desktop UI

cd ui
./gradlew run          # Run directly
./gradlew packageDeb   # Package as .deb

IPC Protocol

Newline-delimited JSON over TCP on localhost:9847.

Plugin → UI (state updates, ~30Hz):

{"type":"state","cutoff":1000.0,"resonance":0.5}

UI → Plugin (parameter changes):

{"type":"set_param","name":"cutoff","value":2000.0}
{"type":"set_param","name":"resonance","value":0.7}

Project Structure

compose-vst/
├── plugin/                    # Rust VST3/CLAP plugin
│   ├── Cargo.toml
│   └── src/
│       ├── lib.rs             # Plugin entry + DSP loop
│       ├── filter.rs          # Biquad low-pass filter
│       └── ipc.rs             # TCP server for UI communication
└── ui/                        # Compose Desktop app
    ├── build.gradle.kts
    ├── settings.gradle.kts
    └── src/main/kotlin/com/composevst/
        ├── Main.kt            # App entry + main Compose UI
        ├── IpcClient.kt       # TCP client with auto-reconnect
        └── components/
            ├── ParamSlider.kt         # Logarithmic/linear slider
            └── FrequencyResponse.kt   # Biquad magnitude response plot

License

MIT