git clone https://github.com/aydiler/kb-layout-daemon
cd...

kb-layout-daemon

A lightweight daemon that automatically switches keyboard layout based on which physical keyboard you’re typing on.

Perfect for users with multiple keyboards who want different layouts for each (e.g., English on one keyboard, German on another).

Features

• Monitors multiple keyboards simultaneously
• Switches layout on first keypress (~50-100ms latency)
• Native D-Bus integration with KDE Plasma
• Minimal resource usage (~2MB RAM, <1% CPU)
• Single static binary, no runtime dependencies
• Configurable via TOML file
• Systemd user service included

Requirements

• Linux with evdev support
• KDE Plasma (Wayland or X11)
• User must be in the input group

Installation

From source

git clone https://github.com/aydiler/kb-layout-daemon
cd kb-layout-daemon
cargo build --release
sudo cp target/release/kb-layout-daemon /usr/local/bin/

Arch Linux (AUR)

yay -S kb-layout-daemon

From crates.io

cargo install kb-layout-daemon

Setup

Add yourself to the input group:

sudo usermod -aG input $USER

Then log out and back in. 1.

Create config file at ~/.config/kb-layout-daemon/config.toml:

[[keyboards]]
name = "Lofree"
layout_index = 1
layout_name = "English (US)"

[[keyboards]]
name = "CHERRY"
layout_index = 0
layout_name = "German"

The layout_index corresponds to the order in KDE’s keyboard layout settings (0-based). 1.

Install the systemd service:

mkdir -p ~/.config/systemd/user
cp kb-layout-daemon.service ~/.config/systemd/user/
systemctl --user enable --now kb-layout-daemon

Configuration

The config file uses TOML format. Each [[keyboards]] section defines a keyboard to monitor:

Field	Description
name	Substring to match in the device name (case-insensitive)
layout_index	KDE layout index (0-based, matches order in System Settings)
layout_name	Human-readable name for logging

To find your keyboard names:

cat /proc/bus/input/devices | grep -A 4 "Name="

How It Works

1. On startup, scans /dev/input/event* for keyboards matching configured names
2. Uses async I/O (tokio + evdev) to monitor all keyboards concurrently
3. On keypress, checks if layout switch is needed
4. Switches layout via D-Bus call to org.kde.keyboard

Troubleshooting

"No keyboards found"

• Ensure you’re in the input group: groups | grep input
• Log out and back in after adding yourself to the group

Layout not switching

• Check KDE has multiple layouts configured
• Verify layout_index matches your KDE layout order
• Check logs: journalctl --user -u kb-layout-daemon -f

License

MIT