doc/calibration-helper.bash

#!/bin/bash

# Copyright 2018 Collabora, Ltd.
# Copyright 2018 General Electric Company
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# This is an example script working as Weston's calibration helper.
# Its purpose is to permanently store the calibration matrix for the given
# touchscreen input device into a udev property. Since this script naturally
# runs as the user that runs Weston, it presumably cannot write directly into
# /etc. It is left for the administrator to set up appropriate files and
# permissions.

# To use this script, one needs to edit weston.ini, in section [libinput], add:
#   calibration_helper=/path/to/bin/calibration-helper.bash

# exit immediately if any command fails
set -e

# The arguments Weston gives us:
SYSPATH="$1"
MATRIX="$2 $3 $4 $5 $6 $7"

# Pick something to recognize the right touch device with.
# Usually one would use something like a serial.
SERIAL=$(udevadm info "$SYSPATH" --query=property | \
	awk -- 'BEGIN { FS="=" } { if ($1 == "ID_SERIAL") { print $2; exit } }')

# If cannot find a serial, tell the server to not use the new calibration.
[ -z "$SERIAL" ] && exit 1

# You'd have this write a file instead.
echo "ACTION==\"add|change\",SUBSYSTEM==\"input\",ENV{ID_SERIAL}==\"$SERIAL\",ENV{LIBINPUT_CALIBRATION_MATRIX}=\"$MATRIX\""

# Then you'd tell udev to reload the rules:
#udevadm control --reload
# This lets Weston get the new calibration if you unplug and replug the input
# device. Instead of writing a udev rule directly, you could have a udev rule
# with IMPORT{file}="/path/to/calibration", write
# "LIBINPUT_CALIBRATION_MATRIX=\"$MATRIX\"" into /path/to/calibration instead,
# and skip this reload step.

# Make udev process the new rule by triggering a "change" event:
#udevadm trigger "$SYSPATH"
# If you were to restart Weston without rebooting, this lets it pick up the new
# calibration.