Smoothy

Smoothy is a Rust + Tauri desktop app for Linux that adds smooth, inertial mouse-wheel scrolling (Mac-like feel) with runtime tuning.

It captures wheel input from real devices, processes it with a smoothing/acceleration engine, and re-emits optimized wheel events through a virtual uinput device.

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Features

• Smooth wheel animation with easing (easeOutCubic / linear)
• Exponential acceleration ramp for rapid scrolling
• Backlog handling and sub-step precision output
• Vertical + optional horizontal wheel support
• Runtime controls from GUI (no restart required)
• Profile-based tuning (custom, normal, aggressive, precision)
• Diagnostics panel (permissions, device visibility, velocity graph)
• Exit behavior control: ask, exit, or minimize

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How It Works

Smoothy uses a split pipeline inside one app:

1. Input Reader (evdev)

   • Reads wheel events from /dev/input/event*
   • Supports both standard and hi-res wheel axes

2. Physics Engine (Rust)

   • Converts wheel steps to virtual distance (step_size_px, pulse_scale)
   • Applies acceleration combo scaling for burst input
   • Releases queued impulses over time with easing
   • Converts virtual distance to hi-res + discrete wheel events

3. Virtual Emitter (uinput)

   • Emits smoothed wheel events through /dev/uinput

4. Tauri GUI (React + TypeScript)

   • Updates physics config at runtime through commands
   • Displays service state, permissions, and velocity diagnostics

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Installation and Setup

1) Prerequisites

• Linux desktop environment
• Node.js + npm
• Rust toolchain (cargo, rustc)
• Tauri Linux build dependencies (WebKit/GTK packages for your distro)

If Linux GUI dependencies are missing, cargo check / Tauri build steps will fail.

2) Clone and install dependencies

git clone <your-repo-url>
cd smoothy
npm install

3) Configure Linux input permissions (required)

Smoothy needs read access to /dev/input/event* and write access to /dev/uinput.

Run:

sudo bash resources/install-linux-permissions.sh

Then log out and log back in so your input group membership is applied.

Included resources:

• resources/99-smoothy.rules
• resources/install-linux-permissions.sh
• resources/smoothy.service

4) Run in development mode

npm run tauri dev

5) Build production app

npm run tauri:build

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Usage

1. Open the app and go to Home.
2. Start the service from the app menu.
3. Tune behavior via profile or numeric parameters.
4. Use Settings to:
   • inspect diagnostics
   • view velocity graph
   • configure close-button behavior (ask / exit / minimize)

If the service cannot start, check Settings > Diagnostic first (input readability + uinput availability).

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Run as a User Daemon (Optional)

You can run Smoothy in daemon mode with --daemon.

Use the provided systemd user template:

1. Copy resources/smoothy.service to ~/.config/systemd/user/smoothy.service
2. Update ExecStart= to your installed Smoothy binary path
3. Enable and start:

systemctl --user daemon-reload
systemctl --user enable --now smoothy.service

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Linux Packaging

Build .deb and .AppImage bundles:

npm run package:linux

Alternative direct command:

npm run tauri:bundle:linux

Notes:

• AppImage flow uses NO_STRIP=1 to avoid linuxdeploy strip issues on some RELR-enabled systems.
• Output directory: src-tauri/target/release/bundle/

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Roadmap

Near-term

• Better onboarding for Linux permissions and startup checks
• Per-device profile assignment and automatic device mapping
• Safer profile import/export and sharing

Mid-term

• System tray controls and richer background behavior
• Improved diagnostics (event counters, latency indicators, error hints)
• More preset calibration for different wheel hardware

Long-term

• Optional advanced tuning assistant (guided recommendations)
• Better desktop integration across distros/compositors
• Stability/performance hardening for broader hardware coverage

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Tech Stack

• Backend: Rust, Tokio, evdev, uinput
• Desktop shell: Tauri v2
• Frontend: React + TypeScript + Tailwind + Radix UI primitives

Support / Donation

If Smoothy helps your workflow, you can support development here:

• https://paypal.me/kaotd

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