smhkd

smhkd (Simple MIDI hotkontrol daemon) is a daemon that reacts to MIDI events by executing commands.

It's inspired by sxhkd, but handles ALSA MIDI events rather than X events.

Current Status

smhkd is still in design phase and not yet ready for mainstream usage.

At the moment, and at the moment only, it reads a configuration file in ~/.config/smhkd/smhkdrc.json, which looks like this:

{
    "@nanoKONTROL2": {
        "0": "pactl set-sink-volume @DEFAULT_SINK@ $VALUE%",
        "+32": "pactl set-sink-volume @DEFAULT_SINK@ 100%",
        "+48": "pactl set-sink-volume @DEFAULT_SINK@ 30%",
        "+64": "pactl set-sink-volume @DEFAULT_SINK@ 0%",

        "+41": "playerctl play-pause",
        "+42": "playerctl stop",
        "+43": "playerctl position 15-",
        "+44": "playerctl position 15+",
        "+58": "playerctl previous",
        "+59": "playerctl next",

        "+61": "ddcutil --display 2 setvcp 60 0x11",
        "+62": "ddcutil --display 2 setvcp 60 0x0f",

        "7": "v4l2-ctl -d /dev/video0 --set-ctrl=zoom_absolute=$VALUE"
    },
    "129:0": {
        "1": "pactl set-sink-volume @DEFAULT_SINK@ $VALUE%",
        "+67": "pactl set-sink-volume @DEFAULT_SINK@ 100%",
        "+66": "pactl set-sink-volume @DEFAULT_SINK@ 30%",
        "+64": "pactl set-sink-volume @DEFAULT_SINK@ 0%"
    }
}

and it listens to each pair of client and port (28:0 — where 28 is the client number for nanoKONTROL2 and 0 the first available port for it — 129:0 and so on…) for MIDI events.

Every time it receives an event, it runs the command associated with the controller ID (if any). Occurences of $VALUE in that command are replaced with the value of the event. Buttons are usually associated with value 127 for press and value 0 for release, so to avoid buttons running commands twice, you can prefix the controller ID with either + (to run command on press) or - (to run command on release). In the example above, it:

• sets the volume of a PulseAudio sink (which can actually be a PipeWire);
• controls a music / video player;
• switches the active input source of a DisplayPort / HDMI monitor;
• sets the zoom level of a webcam

but any command could be executed instead.

Keep in mind that this configuration format is only temporary and will ultimately be replaced with something more similar to what sxhkd uses. There is no plan to provide backward compatibility with JSON or even a migration path when than happens.

Usage

Usage: smhkd list
       smhkd run
       smhkd -h | --help
       smhkd --version

Commands:
    list                     List available MIDI controllers.
    run                      Listen to MIDI events and run commands.

Arguments:

Options:
    -h, --help               Show this screen.
    --version                Show version.

Running on startup

Run systemctl --user enable --now smhkd after installing.

Compiling

Run cargo build --release in your working copy.

Contributing and reporting bugs

Contributions are welcome through GitHub pull requests.

Please report bugs and feature requests on GitHub issues.

License

smhkd is copyright (C) 2022-2024 Jérémie Roquet jroquet@arkanosis.net and licensed under the ISC license.