🥁 Opensampler Drummer (osmpdrum)

A lightweight, high-performance desktop drum sampler application. Built with a custom Rust native audio engine and a modern React + TypeScript frontend, packaged together using a lean WebView (wry + winit)

✨ Features

Audio Engine (Rust Backend)

• Low-Latency Playback: Built on cpal for direct, raw access to the system's native audio output.
• Polyphonic Mixing: Supports multiple overlapping drum voices simultaneously.
• Soft Clipping Protection: Built-in audio limiting to prevent harsh digital distortion when stacking multiple loud samples.
• Zero-Latency Caching: Audio files are parsed (hound) and cached in memory upon first load for instant playback.
• Native Waveform Analysis: The backend calculates peak data in background threads and streams it to the frontend.

User Interface (React Frontend)

• 32-Pad Grid System: Interactive drum pads with Mute, Solo, and Active states.
• OS Drag & Drop: Seamlessly drop .wav, .mp3, or .ogg files directly from your file explorer onto any pad.
• Interactive Waveforms: Real-time audio visualization using D3.js with draggable start/end points and a synchronized playhead.
• Hardware-Style Controls: Custom rotary knob components for Envelope (Attack/Decay/Sustain) and Master Volume.
• Keyboard Integration: Play the 32 pads instantly using your computer keyboard (QWERTY layout).
• Unsaved Changes Protection: Native exit confirmation dialog intercepts accidental window closures if work is unsaved.

🛠️ Tech Stack

Backend (Core & Audio)

• Rust - Core logic and audio processing.
• cpal - Cross-platform audio I/O.
• hound - WAV encoding/decoding.
• wry & winit - Minimalist WebView windowing.
• serde - IPC message serialization.

Frontend (UI)

• React 18 + TypeScript
• Tailwind CSS - Utility-first styling with a dark-mode studio theme.
• D3.js - SVG waveform rendering and playhead animation.
• Lucide React - UI Iconography.

🏗️ Architecture & IPC

The application communicates between the Rust host and the WebView frontend using a lightweight JSON protocol:

1. Frontend to Backend: Sends commands via window.ipc.postMessage() (e.g., Play, Stop, Load, SetMasterVolume, ConfirmExit).
2. Backend to Frontend: Dispatches CustomEvents to the window object (e.g., rust-file-drop, rust-waveform-ready).

🎹 Keyboard Mapping

Play the pads using your keyboard's typing keys:

• Row 1 (Pads 1-8): Q W E R T Y U I
• Row 2 (Pads 9-16): A S D F G H J K
• Row 3 (Pads 17-24): Z X C V B N M ,

🚀 Getting Started

Prerequisites

• Rust toolchain (cargo)
• Node.js and npm/yarn (for building the frontend)

Build & Run

1. Build the Frontend Ensure the frontend is built and output to the dist folder, as the Rust backend expects to load dist/index.html.

   bun install
   bun run build

2. Run the Application It is highly recommended to run the app in release mode to ensure the audio thread performs without stuttering.

cargo run --release