script to fetch the current screen layout from sway and convert to kanshi profile

sway-to-kanshi.sh

#!/usr/bin/env bash
#
# sway-to-kanshi.sh
#
# Fetches the current monitor arrangement from the running sway instance
# (via `swaymsg -t get_outputs`) and prints it in kanshi config format.
#
# kanshi profile syntax reference:
#   https://github.com/emersion/kanshi  (man 5 kanshi)
#
#   profile [<name>] {
#       output <criteria> [enable|disable] [mode <width>x<height>[@<rate>Hz]] \
#           [position <x>,<y>] [scale <factor>] [transform <transform>] \
#           [adaptive_sync on|off]
#       ...
#   }
#
# Usage:
#   ./sway-to-kanshi.sh                 # print profile to stdout
#   ./sway-to-kanshi.sh -n docked       # name the profile "docked"
#   ./sway-to-kanshi.sh -o ~/.config/kanshi/config   # write/append to a file
#   ./sway-to-kanshi.sh --by-name       # match outputs by name instead of make/model/serial

set -euo pipefail

PROFILE_NAME=""
OUTFILE=""
MATCH="identifier"   # identifier = "make model serial"; name = output name (e.g. DP-1)

usage() {
    cat >&2 <<EOF
Usage: ${0##*/} [-n NAME] [-o FILE] [--by-name]

  -n, --name NAME   Set the kanshi profile name (default: unnamed).
  -o, --output FILE Append the generated profile to FILE (default: stdout).
      --by-name     Match outputs by connector name (DP-1, HDMI-A-1, ...)
                    instead of the more portable "make model serial".
  -h, --help        Show this help.
EOF
    exit "${1:-0}"
}

while [[ $# -gt 0 ]]; do
    case "$1" in
        -n|--name)   PROFILE_NAME="$2"; shift 2 ;;
        -o|--output) OUTFILE="$2";      shift 2 ;;
        --by-name)   MATCH="name";      shift   ;;
        -h|--help)   usage 0 ;;
        *) echo "Unknown argument: $1" >&2; usage 1 ;;
    esac
done

command -v swaymsg >/dev/null || { echo "swaymsg not found" >&2; exit 1; }
command -v jq      >/dev/null || { echo "jq not found"      >&2; exit 1; }

if [[ -z "${SWAYSOCK:-}" && -z "${WAYLAND_DISPLAY:-}" ]]; then
    echo "Warning: no SWAYSOCK/WAYLAND_DISPLAY set; is sway running in this session?" >&2
fi

outputs_json="$(swaymsg -t get_outputs)"

# Build the kanshi profile. jq emits one 'output ...' line per connected output.
profile_body="$(
    jq -r --arg match "$MATCH" '
      # kanshi transform names differ slightly from sway; sway uses the same set,
      # so pass through. sway "normal"/"90"/"180"/"270"/"flipped*" are valid in kanshi.
      def crit:
        if $match == "name" then .name
        else ((.make // "Unknown") + " " + (.model // "Unknown") + " " + (.serial // "Unknown"))
        end;

      .[] |
      if (.active | not) then
        "\toutput \"" + crit + "\" disable"
      else
        "\toutput \"" + crit + "\""
        + " enable"
        + " mode " + (.current_mode.width|tostring) + "x" + (.current_mode.height|tostring)
            + "@" + ((.current_mode.refresh/1000)|(.*1000|round/1000)|tostring) + "Hz"
        + " position " + (.rect.x|tostring) + "," + (.rect.y|tostring)
        + " scale " + (.scale|tostring)
        + (if (.transform // "normal") != "normal" then " transform " + .transform else "" end)
        + (if (.adaptive_sync_status // "disabled") == "enabled" then " adaptive_sync on" else "" end)
      end
    ' <<<"$outputs_json"
)"

if [[ -n "$PROFILE_NAME" ]]; then
    profile="profile $PROFILE_NAME {"$'\n'"$profile_body"$'\n'"}"
else
    profile="profile {"$'\n'"$profile_body"$'\n'"}"
fi

if [[ -n "$OUTFILE" ]]; then
    mkdir -p "$(dirname "$OUTFILE")"
    { [[ -s "$OUTFILE" ]] && printf '\n'; printf '%s\n' "$profile"; } >>"$OUTFILE"
    echo "Wrote profile to $OUTFILE" >&2
else
    printf '%s\n' "$profile"
fi