nixos_flake_config/home/fuji/auto-rotate.sh

#!/usr/bin/env bash
# auto-rotate — rotate a wlroots output from iio-sensor-proxy orientation events.
#
# Unlike rot8 this does not read the accelerometer itself. iio-sensor-proxy owns
# sensor selection (fuji has two accel_3d devices), applies its own hysteresis,
# and reports `undefined` when the device is too flat to have a meaningful
# orientation — so there is no dead zone in which we silently keep a stale state.
#
#   SIGUSR1   toggle rotation lock (current transform is kept)
#   SIGUSR2   re-apply the last known orientation (e.g. after kanshi resets it)

set -uo pipefail

OUTPUT="${AUTOROTATE_OUTPUT:-eDP-1}"
HOOKS=()
VERBOSE=0

usage() {
	cat <<-EOF
		usage: auto-rotate [-o OUTPUT] [-H HOOK]... [-v]

		  -o, --output OUTPUT   output to rotate (default: ${OUTPUT})
		  -H, --hook CMD        run CMD after each rotation; may be repeated.
		                        \$ORIENTATION and \$PREV_ORIENTATION are exported.
		  -v, --verbose         log every sensor event, not just rotations
	EOF
}

while [ $# -gt 0 ]; do
	case "$1" in
	-o | --output)
		OUTPUT="${2:?--output needs a value}"
		shift 2
		;;
	-H | --hook)
		HOOKS+=("${2:?--hook needs a value}")
		shift 2
		;;
	-v | --verbose)
		VERBOSE=1
		shift
		;;
	-h | --help)
		usage
		exit 0
		;;
	*)
		printf 'auto-rotate: unknown argument: %s\n' "$1" >&2
		usage >&2
		exit 1
		;;
	esac
done

for cmd in monitor-sensor wlr-randr; do
	command -v "$cmd" >/dev/null || {
		printf 'auto-rotate: %s not found in PATH\n' "$cmd" >&2
		exit 1
	}
done

log() { printf '[auto-rotate] %s\n' "$*"; }
vlog() { [ "$VERBOSE" = 1 ] && log "$@"; return 0; }

# iio-sensor-proxy orientation -> wlr-randr transform.
#
# NOTE: if the screen ends up 180 degrees off, swap the left-up and right-up
# lines. This mapping is the common convention but it is not something the
# sensor tells us, so it has to be confirmed by hand once.
transform_for() {
	case "$1" in
	normal) printf 'normal' ;;
	left-up) printf '90' ;;
	bottom-up) printf '180' ;;
	right-up) printf '270' ;;
	*) return 1 ;;
	esac
}

current_transform() {
	wlr-randr 2>/dev/null |
		awk -v o="$OUTPUT" '
			$1 == o     { found = 1; next }
			/^[^ \t]/   { found = 0 }
			found && $1 == "Transform:" { print $2; exit }
		'
}

applied="$(current_transform)"
[ -n "$applied" ] || {
	printf 'auto-rotate: output %s not found\n' "$OUTPUT" >&2
	exit 1
}
log "output ${OUTPUT}, current transform ${applied}"

orientation=""      # last non-undefined orientation from the sensor
prev_orientation="" # the one before that, exported to hooks
locked=0

toggle_lock() {
	locked=$((1 - locked))
	[ "$locked" = 1 ] && log "rotation locked at ${applied}" || log "rotation unlocked"
}

apply() {
	local target
	target="$(transform_for "$orientation")" || return 0
	[ "$target" = "$applied" ] && return 0

	if ! wlr-randr --output "$OUTPUT" --transform "$target"; then
		# Do not advance `applied` — a failed rotation must not desync our idea
		# of the output state from reality. This was rot8's other failure mode.
		log "wlr-randr failed, keeping transform as ${applied}"
		return 0
	fi
	log "${applied} -> ${target} (${orientation})"
	applied="$target"

	local hook
	for hook in ${HOOKS+"${HOOKS[@]}"}; do
		ORIENTATION="$orientation" PREV_ORIENTATION="$prev_orientation" \
			bash -c "$hook" || log "hook failed: ${hook}"
	done
}

reapply() {
	applied="$(current_transform)"
	log "re-syncing, output is at ${applied}"
	[ "$locked" = 0 ] && [ -n "$orientation" ] && apply
	return 0
}

trap toggle_lock USR1
trap reapply USR2

exec 3< <(stdbuf -oL monitor-sensor 2>&1)
monitor_pid=$!
trap 'kill "$monitor_pid" 2>/dev/null; exit 0' INT TERM EXIT

while :; do
	# A signal interrupts read; that is not an error, so retry rather than exit.
	IFS= read -r line <&3 || {
		kill -0 "$monitor_pid" 2>/dev/null && continue
		break
	}

	case "$line" in
	*"Accelerometer orientation changed: "*)
		new="${line##*: }"
		;;
	*"Has accelerometer (orientation: "*)
		# The initial state only ever arrives on this banner line; a
		# "changed" line is not emitted until the orientation moves.
		new="${line#*orientation: }"
		new="${new%%,*}"
		;;
	*"iio-sensor-proxy appeared"*)
		# The proxy restarted; our cached transform may be stale.
		reapply
		continue
		;;
	*"Compass heading changed"*)
		# ~1 Hz of noise we have no use for; drop it even when verbose.
		continue
		;;
	*)
		vlog "$line"
		continue
		;;
	esac
	vlog "sensor says ${new}"

	# `undefined` means the device is lying too flat to tell. Hold position.
	[ "$new" = undefined ] && continue
	[ "$new" = "$orientation" ] && continue

	prev_orientation="$orientation"
	orientation="$new"

	[ "$locked" = 1 ] && {
		vlog "locked, ignoring ${orientation}"
		continue
	}
	apply
done

log "monitor-sensor exited"