Enhancing Linux Touchpad Gestures: Implementing 'Three-Finger Drag'

After switching to Linux, I’ve been missing the smooth three-finger drag experience from macOS. Given that recent Windows laptops have significantly improved touchpad size and responsiveness, I decided it was time to tackle touchpad gestures on Linux.

Research and Selection

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There are basically two approaches to implementation:

1. Parsing libinput debug-events output and using tools like xdotool to send keystrokes or mouse clicks.
2. Calling the libinput API directly, which offers the best performance.

Implementation

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I chose to fork and merge two Rust projects to create a unified solution. One project handles general gestures, and the other focuses on the three-finger drag effect at the API level.

Architecture

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graph TD
    A[Touchpad Event] --> B{libinput}
    B --> C[ferstar/gestures 
Rust Engine]
    C --> D{Display Server}
    D -- X11 --> E[libxdo API]
    D -- Wayland --> F[ydotool daemon]
    E --> G[Smooth Drag / Key Stroke]
    F --> G
    
    style C fill:#f96,stroke:#333,stroke-width:2px
    style G fill:#4ecdc4,stroke:#333,stroke-width:2px

The project is now at v0.8.1, with major improvements including:

• Dual Platform Support: Works on both X11 and Wayland (auto-detection).
• Performance Optimization:
  • Direct libxdo API calls for X11 (minimum latency).
  • Optimized ydotool integration for Wayland with 60 FPS throttling.
  • Thread pooling to prevent PID exhaustion.
  • Regex and config caching for speed.

Performance Metrics

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1. Low CPU Usage

   • Even under intense three-finger dragging, this implementation uses less than 1% CPU.
   • Competing Python or Ruby implementations often exceed 20%.

2. Resource Efficiency

   • Memory usage: < 5MB.
   • Binary size: < 2MB.
   • Zero unnecessary dependencies.

Installation & Usage

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Dependencies

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Ubuntu/Debian:

sudo apt install libudev-dev libinput-dev libxdo-dev xdotool
# For Wayland
sudo apt install ydotool

Arch Linux:

sudo pacman -S libinput xdotool
# Wayland
yay -S ydotool

Install Binary

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Option 1: Pre-compiled Binary (Recommended)

wget https://github.com/ferstar/gestures/releases/latest/download/gestures
chmod +x gestures
sudo mv gestures /usr/local/bin/

Option 2: Install via Cargo

cargo install --git https://github.com/ferstar/gestures.git

Configuration

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The config uses the KDL format. Example:

// Three-finger drag (X11 & Wayland)
gesture "drag" swipe any {
    fingers 3
    acceleration 1.0      // Drag speed
    mouse_up_delay 500    // Delay after lifting fingers (ms)
}

// Four-finger swipe up to switch workspace
gesture "switch-workspace-up" swipe up {
    fingers 4
    exec "xdotool" "key" "super+Page_Up"
}

Running the Program

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Systemd Service

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# Install service file
gestures install-service

# Enable and start
systemctl --user enable --now gestures

Common Issues

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Permission Denied

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You need to add your user to the input group:

sudo usermod -aG input $USER

Links

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• GitHub: https://github.com/ferstar/gestures
• Issues: https://github.com/ferstar/gestures/issues

Enjoy!