Description

Linux mouse-to-joystick injector for RetroArch that grabs your mouse via evdev and maps it to a virtual gamepad stick via uinput. Works with any game on any core, on Wayland or X11.

Skills / Tools / Stack

• Rust
• Linux evdev / uinput
• Unix signals (SIGUSR1)
• clap CLI framework

Summary

m2joy reads raw mouse input from /dev/input/eventX, creates a virtual gamepad ("m2joy Stick") via /dev/uinput, and converts mouse velocity to analog stick deflection at 1kHz using an exponential moving average.

Control is fully command-based. Run m2joy toggle from another process to grab or ungrab the mouse—designed for Hyprland, sway, or any window manager keybind. Under the hood, toggle sends a SIGUSR1 signal to the running instance. No keyboard device access required.

Mouse buttons are forwarded as gamepad triggers: left click maps to R2 (shoot) and right click maps to L2 (aim). RetroArch autoconfig is installed on first run so the virtual gamepad is recognized automatically.

Features

• 1kHz polling loop with EMA smoothing for stable analog stick output
• Mouse buttons forwarded as gamepad triggers (left click → R2, right click → L2)
• Virtual gamepad via uinput with automatic RetroArch autoconfig installation
• Command-based toggle with m2joy toggle and m2joy quit
• SIGUSR1 signal toggle for window manager keybind integration
• Auto-detection of mouse device from /dev/input/event*
• Configurable sensitivity, Y-axis inversion, and stick output
• Left or right stick output selection
• Evdev grab/ungrab to capture and release the mouse

Roadmap

1. Add per-game config profiles
2. Build acceleration curves for non-linear sensitivity
3. Add support for multiple mice
4. Create a status indicator via desktop notification

Instructions

1. Add yourself to the input group with sudo usermod -aG input $USER and re-login
2. Ensure uinput is loaded with sudo modprobe uinput
3. Build with cargo build --release
4. Run ./target/release/m2joy to start the daemon
5. Toggle grab with m2joy toggle from another terminal or keybind
6. In RetroArch go to Settings > Input > Port 1 Controls > Device Index and select m2joy Stick

Hyprland

bind = SUPER, F9, exec, m2joy toggle

sway / i3

bindsym $mod+F9 exec m2joy toggle

Options

Option	Default	Description
-s, --sensitivity	1.0	Mouse sensitivity multiplier
--invert-y	off	Invert Y axis
-d, --device	auto	Specific evdev path (e.g. /dev/input/event5)
--left-stick	off	Output to left stick instead of right
--debug	off	Print diagnostics every 100ms

License

MIT