libinput-gestures

#!/usr/bin/env python3
'Read gestures from libinput touchpad and action shell commands.'
# Mark Blakeney, Sep 2015.
import os
import sys
import argparse
import subprocess
import shlex
import re
import getpass
import fcntl
import platform
import math
import gi
import hashlib
import threading
from time import monotonic
from collections import OrderedDict
from pathlib import Path

dbus_imported = True
try:
    import dbus
    from dbus.mainloop.glib import DBusGMainLoop
    from gi.repository import GLib
    gi.require_version('Wnck', '3.0')
    gi.require_version('Gtk', '3.0')
    gi.require_version('Bamf', '3')
    from gi.repository import Bamf, Gio

except ImportError:
    dbus_imported = False

session_locked = False

PROGPATH = Path(sys.argv[0])
PROGNAME = PROGPATH.stem
HOME = Path('~').expanduser()

# Conf file containing gesture commands.
# Search first for user file then system file.
CONFNAME = f'{PROGNAME}.conf'
USERDIR = os.getenv('XDG_CONFIG_HOME', os.path.expanduser('~/.config'))
CONFDIRS = (USERDIR, '/etc')

# Ratio of X/Y (or Y/X) at which we consider an oblique swipe gesture.
# The number is the trigger angle in degrees and set to 360/8/2.
OBLIQUE_RATIO = math.tan(math.radians(22.5))

# Default minimum significant distance to move for swipes, in dots.
# Can be changed using configuration command.
swipe_min_threshold = 0

args = None
abzsquare = None

# Timeout on gesture action from start to end. 0 = no timeout. In secs.
# Can be changed using configuration command.
DEFAULT_TIMEOUT = 1.5
timeoutv = DEFAULT_TIMEOUT

# Rotation threshold in degrees to discriminate pinch rotate from in/out
ROTATE_ANGLE = 15.0

# Appname for grouping actions in .conf via [CATCHALL_APPNAME]
CATCHALL_APPNAME='general'

def open_lock(*args):
    'Create lock/pid files based on given list of arguments'
    # We use exclusive assess to a file for this
    fname = Path('/tmp', '-'.join(args))
    flock = fname.with_suffix('.lock').open('w')
    try:
        fcntl.lockf(flock, fcntl.LOCK_EX | fcntl.LOCK_NB)
    except IOError:
        return None, None

    fpid = fname.with_suffix('.pid').open('w')
    return flock, fpid

def run(cmd, *, check=True, block=True):
    'Run function and return standard output, Popen() handle, or None'
    try:
        if block:
            result = subprocess.check_output(cmd, universal_newlines=True,
                    stderr=(None if check else subprocess.DEVNULL))
        else:
            result = bool(subprocess.Popen(cmd))
    except Exception as e:
        result = None
        if check:
            print(str(e), file=sys.stderr)

    return result

def get_libinput_vers():
    'Return the libinput installed version number string'
    # Try to use newer libinput interface then fall back to old
    # (depreciated) interface.
    res = run(('libinput', '--version'), check=False)
    if res:
        return res.strip(), True

    res = run(('libinput-list-devices', '--version'), check=False)
    return res and res.strip(), False



def get_active_window_title():
    root = subprocess.Popen(['xprop', '-root', '_NET_ACTIVE_WINDOW'], stdout=subprocess.PIPE)
    stdout, stderr = root.communicate()

    m = re.search(b'^_NET_ACTIVE_WINDOW.* ([\w]+)$', stdout)
    if m != None:
        window_id = m.group(1)
        if window_id != '0x0':
            if args.verbose:
                print(f'window id: {window_id} from: {stdout}');
            window = subprocess.Popen(['xprop', '-id', window_id, 'WM_NAME'], stdout=subprocess.PIPE)
            stdout, stderr = window.communicate()
        else:
            window = 'Desktop'
    else:
        return None

    match = re.match(b"WM_NAME\(\w+\) = (?P<name>.+)$", stdout)
    if match != None:
        return match.group("name").strip(b'"')

    return None

def get_devices_list(cmd_list_devices, device_list):
    'Get list of devices and their attributes (as a dict) from libinput'
    if device_list:
        with open(device_list) as fd:
            stdout = fd.read()
    else:
        stdout = run(cmd_list_devices.split())

    if stdout:
        dev = {}
        for line in stdout.splitlines():
            line = line.strip()
            if line and ':' in line:
                key, value = line.split(':', maxsplit=1)
                dev[key.strip().lower()] = value.strip()
            elif dev:
                yield dev
                dev = {}

        # Ensure we include last device
        if dev:
            yield dev

def get_device_info(name, cmd_list_devices, device_list):
    'Determine libinput touchpad device and return device info'
    devices = list(get_devices_list(cmd_list_devices, device_list))

    if not devices:
        print('Can not see any devices, did you add yourself to the '
                'input group and reboot?', file=sys.stderr)
        return None

    # If a specific device name was asked for then return that device
    # This is the "Device" name from libinput list-devices command.
    if name:
        kdev = str(Path(name).resolve()) if name[0] == '/' else None
        for d in devices:
            # If the device name starts with a '/' then it is instead
            # considered as the explicit device path although since
            # device paths can change through reboots this is best to be
            # a symlink. E.g. users should use the corresponding full
            # path link under /dev/input/by-path/ or /dev/input/by-id/.
            if kdev:
                if d.get('kernel') == kdev:
                    return d
            elif d.get('device') == name:
                return d
        return None

    # Otherwise look for 1st device with touchpad capabilities
    for d in devices:
        if 'size' in d and 'pointer' in d.get('capabilities'):
            return d
    # Otherwise look for 1st device with touchpad in it's name
    # or, failing that, 1st device with trackpad in it's name
    for txt in ('touch ?pad', 'track ?pad'):
        for d in devices:
            if re.search(txt, d.get('device', ''), re.I):
                return d

    # Give up
    return None

def get_device(name, cmd_list_devices, device_list):
    'Determine libinput touchpad device and add fixed path info'
    dev = get_device_info(name, cmd_list_devices, device_list)
    if dev:
        devname = dev.get('kernel')
        evname = ''
        if devname:
            devpath = Path(devname)

            # Also determine and prefer a non-volatile path merely
            # because it is more identifying for users.
            for dirstr in ('/dev/input/by-path', '/dev/input/by-id'):
                dirpath = Path(dirstr)
                if dirpath.exists():
                    for path in dirpath.iterdir():
                        if path.resolve() == devpath:
                            devname = str(path)
                            evname = f'({devpath.name})'
                            break
                    if evname:
                        break

        dev['_path'] = devname
        dev['_diag'] = f"{devname}{evname}: {dev.get('device', '?')}"
    return dev

class COMMAND:
    'Generic command handler'
    def __init__(self, args):
        self.reprstr = ' '.join(args)

        # Expand '~' and env vars in executable command name
        args[0] = os.path.expandvars(os.path.expanduser(args[0]))
        self.argslist = args

    def run(self):
        'Run this command + arguments'
        run(self.argslist, block=False)

    def __str__(self):
        'Return string representation'
        return self.reprstr

# Table of internal commands
internal_commands = OrderedDict()

def add_internal_command(cls):
    'Add configuration command to command lookup table based on name'
    internal_commands[re.sub('^COMMAND', '', cls.__name__)] = cls

class ArgumentParser(argparse.ArgumentParser):
    'Custom ArgumentParser to return error text'
    def error(self, msg):
        raise Exception(msg)

@add_internal_command
class COMMAND_internal(COMMAND):
    'Internal command handler.'
    # Commands currently supported follow. Each is configured with the
    # (X,Y) translation to be applied to the desktop grid.
    commands = (
        ('ws_up',         ( 0,  1)),  # noqa: E241,E201
        ('ws_down',       ( 0, -1)),  # noqa: E241,E201
        ('ws_left',       ( 1,  0)),  # noqa: E241,E201
        ('ws_right',      (-1,  0)),  # noqa: E241,E201
        ('ws_left_up',    ( 1,  1)),  # noqa: E241,E201
        ('ws_left_down',  ( 1, -1)),  # noqa: E241,E201
        ('ws_right_up',   (-1,  1)),  # noqa: E241,E201
        ('ws_right_down', (-1, -1)),  # noqa: E241,E201
    )

    commands_list = [c[0] for c in commands]

    CMDTEST = 'wmctrl -m'.split()
    CMDLIST = 'wmctrl -d'.split()
    CMDSET = 'wmctrl -s'.split()

    def __init__(self, args):
        'Action internal swipe commands'
        super().__init__(args)

        # Set up command line arguments
        opt = ArgumentParser(prog=self.argslist[0], description=self.__doc__)
        opt.add_argument('-w', '--wrap', action='store_true',
                help='wrap workspaces when switching to/from start/end')
        opt.add_argument('-c', '--cols', type=int,
                help='number of columns in virtual desktop grid, default=1')
        opt.add_argument('--row', type=int, default=0, help=argparse.SUPPRESS)
        opt.add_argument('--col', type=int, default=0, help=argparse.SUPPRESS)
        opt.add_argument('action', choices=self.commands_list,
                help='Internal command to action')
        args = opt.parse_args(self.argslist[1:])
        self.nowrap = not args.wrap
        self.rows = 0
        self.cols = 0
        cmdi = self.commands_list.index(args.action)

        if self.CMDTEST[0] and not run(self.CMDTEST, check=False):
            print(f'Warning: must install {self.CMDTEST[0]} '
                    'to use _internal command.', file=sys.stderr)

        # Only do above check once
        self.CMDTEST[0] = ''

        if cmdi >= 2:
            if args.row or args.col:
                opt.error('Legacy "--row" and "--col" not supported')
            if args.cols is None:
                if cmdi < 4:
                    self.cols = 1
                    cmdi -= 2
                else:
                    opt.error('"--cols" must be specified')
            elif args.cols < 1:
                opt.error('"--cols" must be >= 1')
            else:
                self.cols = args.cols
        else:
            # Convert old legacy/depreciated arguments to new arguments
            if args.cols is not None:
                if args.cols < 1:
                    opt.error('"--cols" must be >= 1')
                self.cols = args.cols
            elif args.row:
                cmdi += 2
                self.cols = args.row
            elif args.col:
                self.rows = args.col
            else:
                self.cols = 1

        # Save the translations appropriate to this command
        self.xmove, self.ymove = self.commands[cmdi][1]

    def run(self, block=False):
        'Get list of current workspaces and select next one'
        stdout = run(self.CMDLIST, check=False)
        if not stdout:
            # This command can fail on GNOME when you have only a single
            # dynamic workspace (probably a GNOME bug) so let's just
            # fudge that default case.
            stdout = '0 *\n1 -'

        # Parse the output of above command
        lines = [ln.split(maxsplit=2)[1] for ln in stdout.strip().splitlines()]
        start = index = lines.index('*')
        num = len(lines)
        cols = self.cols or num // self.rows
        numv = ((num - 1) // cols + 1) * cols

        # Calculate new workspace X direction index
        count = self.xmove
        if count < 0:
            if index % cols == 0:
                if self.nowrap:
                    return
                index += cols - 1
                if index >= num:
                    if self.ymove == 0:
                        if self.nowrap:
                            return
                        index = num - 1
            else:
                index += count
        elif count > 0:
            index += count
            if index % cols == 0:
                if self.nowrap:
                    return
                index -= cols
            elif index >= num:
                if self.ymove == 0:
                    if self.nowrap:
                        return
                    index -= numv - index

        # Calculate new workspace Y direction index
        count = self.ymove * cols
        if count < 0:
            if index < cols and self.nowrap:
                return
            index = (index + count) % numv
            if index >= num:
                index += count
        elif count > 0:
            index += count
            if index >= numv:
                if self.nowrap:
                    return
                index = index % numv
            elif index >= num:
                if self.nowrap:
                    return
                index = (index + count) % numv

        # Switch to desired workspace
        return run(self.CMDSET + [str(index)], block=block) \
                if index != start else None

# Table of gesture handlers
handlers = OrderedDict()

# cache for application id to name 
appname_cache = {};

def add_gesture_handler(cls):
    'Create gesture handler instance and add to lookup table based on name'
    handlers[cls.__name__] = cls()

class GESTURE:
    'Abstract base class for handling for gestures'
    def __init__(self):
        'Initialise this gesture at program start'
        self.name = type(self).__name__
        self.motions = OrderedDict()
        self.has_extended = False

    def add(self, motion, fingers, command, appname):
        'Add a configured motion command for this gesture'
        if motion not in self.SUPPORTED_MOTIONS:
            opts = '" or "'.join(self.SUPPORTED_MOTIONS)
            return f'Gesture {self.name.lower()} does not support '\
                    f'motion "{motion}".\nMust be "{opts}"'
        if not command:
            return 'No command configured'

        # If any extended gestures configured then set flag to enable
        # their discrimination
        if self.extended_text and self.extended_text in motion:
            self.has_extended = True

        key = (appname, motion, fingers) if fingers else (appname, motion)

        try:
            cmds = shlex.split(command)
        except Exception as e:
            return str(e)

        cls = internal_commands.get(cmds[0], COMMAND)

        try:
            self.motions[key] = cls(cmds)
        except Exception as e:
            return str(e)

        return None

    def begin(self, fingers):
        'Initialise this gesture at the start of motion'
        self.fingers = fingers
        self.data = [0.0, 0.0]
        self.starttime = monotonic()

    def action(self, motion):

	# determine application name of the current active window
        appname = get_active_window_title();
        appl = Bamf.Matcher.get_default().get_active_application()
        if not appl in appname_cache:
                if appl:
                     if appl.get_desktop_file():
                            appname = Gio.DesktopAppInfo.new_from_filename( appl.get_desktop_file() ).get_name()

                     if appname == '':
                            appname =  appl.get_name()

                     appname = appname.lower()
                     appname_cache[appl] = appname;
        else:
                appname = appname_cache[appl];

        if args.debug:
                print(f'current active window [{appname}]')

        'Action a motion command for this gesture'
        command = self.motions.get((appname, motion, self.fingers)) or \
                self.motions.get((appname, motion)) or \
        	self.motions.get((CATCHALL_APPNAME, motion, self.fingers)) or \
                self.motions.get((CATCHALL_APPNAME, motion))


        if args.verbose:
            print(f'{PROGNAME}: [{appname}] {self.name} {motion} '
                    f'{self.fingers} {self.data}')
            if command:
                print('  ', command)
            else:
                print('   ', 'no command')

        if timeoutv > 0 and (self.starttime + timeoutv) < monotonic():
            if args.verbose:
                print('  ', 'timeout - no action')
            return

        if timeoutv > 0 and (self.starttime + timeoutv) < monotonic():
            if args.verbose:
                print('  ', 'timeout - no action')
            return

        if command and not args.debug:
            command.run()

@add_gesture_handler
class SWIPE(GESTURE):
    'Class to handle this type of gesture'
    SUPPORTED_MOTIONS = ('left', 'right', 'up', 'down',
            'left_up', 'right_up', 'left_down', 'right_down')
    extended_text = '_'

    def update(self, coords):
        'Update this gesture for a motion'
        # Ignore this update if we can not parse the numbers we expect
        try:
            x = float(coords[2])
            y = float(coords[3])
        except (ValueError, IndexError):
            return False

        self.data[0] += x
        self.data[1] += y
        return True

    def end(self):
        'Action this gesture at the end of a motion sequence'
        x, y = self.data
        abx = abs(x)
        aby = abs(y)

        # Require absolute distance movement beyond a small thresh-hold.
        if abx**2 + aby**2 < abzsquare:
            return

        # Discriminate left/right or up/down.
        # If significant movement in both planes the consider it a
        # oblique swipe (but only if any are configured)
        if abx > aby:
            motion = 'left' if x < 0 else 'right'
            if self.has_extended and abx > 0 and aby / abx > OBLIQUE_RATIO:
                motion += '_up' if y < 0 else '_down'
        else:
            motion = 'up' if y < 0 else 'down'
            if self.has_extended and aby > 0 and abx / aby > OBLIQUE_RATIO:
                motion = ('left_' if x < 0 else 'right_') + motion

        self.action(motion)

@add_gesture_handler
class PINCH(GESTURE):
    'Class to handle this type of gesture'
    SUPPORTED_MOTIONS = ('in', 'out', 'clockwise', 'anticlockwise')
    extended_text = 'clock'

    def update(self, coords):
        'Update this gesture for a motion'
        # Ignore this update if we can not parse the numbers we expect
        try:
            x = float(coords[4])
            y = float(coords[5])
        except (ValueError, IndexError):
            return False

        self.data[0] += x - 1.0
        self.data[1] += y
        return True

    def end(self):
        'Action this gesture at the end of a motion sequence'
        ratio, angle = self.data

        if self.has_extended and abs(angle) > ROTATE_ANGLE:
            self.action('clockwise' if angle >= 0.0 else 'anticlockwise')
        elif ratio != 0.0:
            self.action('in' if ratio <= 0.0 else 'out')

@add_gesture_handler
class HOLD(GESTURE):
    'Class to handle this type of gesture'
    SUPPORTED_MOTIONS = ('on',)
    extended_text = None

    def update(self, coords):
        return True

    def end(self):
        'Action this gesture at the end of a motion sequence'
        self.action('on')

# Table of configuration commands
conf_commands = OrderedDict()

def add_conf_command(func):
    'Add configuration command to command lookup table based on name'
    conf_commands[re.sub('^conf_', '', func.__name__)] = func

@add_conf_command
def conf_gesture(lineargs, appname):
    'Process a single gesture line in conf file'
    fields = lineargs.split(maxsplit=2)

    # Look for configured gesture. Sanity check the line.
    if len(fields) < 3:
        return 'Invalid gesture line - not enough fields'

    gesture, motion, command = fields
    handler = handlers.get(gesture.upper())

    if not handler:
        opts = '" or "'.join([h.lower() for h in handlers])
        return f'Gesture "{gesture}" is not supported.\nMust be "{opts}"'

    # Gesture command can be configured with optional specific finger
    # count so look for that
    fingers, *fcommand = command.split(maxsplit=1)
    if fingers.isdigit() and len(fingers) == 1:
        command = fcommand[0] if fcommand else ''
    else:
        fingers = None

    # Add the configured gesture
    return handler.add(motion.lower(), fingers, command, appname)

@add_conf_command
def conf_device(lineargs):
    'Process a single device line in conf file'
    # Command line overrides configuration file
    if not args.device:
        args.device = lineargs

    return None if args.device else 'No device specified'

@add_conf_command
def swipe_threshold(lineargs):
    'Change swipe threshold'
    global swipe_min_threshold
    try:
        swipe_min_threshold = int(lineargs)
    except Exception:
        return 'Must be integer value'

    return None if swipe_min_threshold >= 0 else 'Must be >= 0'

@add_conf_command
def timeout(lineargs):
    'Change gesture timeout'
    global timeoutv
    try:
        timeoutv = float(lineargs)
    except Exception:
        return 'Must be float value'

    return None if timeoutv >= 0 else 'Must be >= 0'

def get_conf_line(line, appname):
    'Process a single line in conf file'
    key, *argslist = line.split(maxsplit=1)

    # Old format conf files may have a ":" appended to the key
    key = key.rstrip(':')
    conf_func = conf_commands.get(key)

    if not conf_func:
        opts = '" or "'.join(conf_commands)
        return f'Configuration command "{key}" is not supported.\n' \
                f'Must be "{opts}"'

    return conf_func(argslist[0] if argslist else '', appname)

def get_conf(conffile, confname):
    'Read given configuration file and store internal actions etc'
    with conffile.open() as fp:
        appname = CATCHALL_APPNAME
        for num, line in enumerate(fp, 1):
            line = line.strip()
            if not line or line[0] == '#':
                continue

            if line[0] == '[':
                appname = line[1:-1].strip().lower();
                continue

            errmsg = get_conf_line(line, appname)
            if errmsg:
                sys.exit(f'Error at line {num} in file {confname}:\n'
                        f'>> {line} <<\n{errmsg}.')

def unexpanduser(cfile):
    'Return absolute path name, with $HOME replaced by ~'
    cfile_abs = cfile.resolve()

    if cfile_abs.parts[:len(HOME.parts)] != HOME.parts:
        return str(cfile_abs)

    return str(Path('~', *cfile_abs.parts[len(HOME.parts):]))

# Search for configuration file. Use file given as command line
# argument, else look for file in search dir order.
def read_conf(conffile, defname):
    if conffile:
        confpath = Path(conffile)
        if not confpath.exists():
            sys.exit(f'Conf file "{conffile}" does not exist.')
    else:
        for confdir in CONFDIRS:
            confpath = Path(confdir, defname)
            if confpath.exists():
                break
        else:
            opts = ' or '.join([unexpanduser(Path(c)) for c in CONFDIRS])
            sys.exit(f'No file {defname} in {opts}.')

    # Hide any personal user dir/names from diag output
    confname = unexpanduser(confpath)

    # Read and process the conf file
    get_conf(confpath, confname)
    return confname

def lockcheck():
    'Listen on DBus to set session_locked state'
    def proc(busname, vals, _):
        global session_locked
        if busname == 'org.freedesktop.login1.Session':
            val = vals.get('LockedHint')
            if val is not None:
                session_locked = bool(val)

    DBusGMainLoop(set_as_default=True)
    dbus.SystemBus().add_signal_receiver(
        proc,
        'PropertiesChanged',
        'org.freedesktop.DBus.Properties',
        'org.freedesktop.login1',
    )

    GLib.MainLoop().run()

def gethash():
    'Return a crude hash identifier for this software version'
    progs = (PROGPATH, PROGPATH.with_name(PROGNAME + '-setup'))
    return hashlib.md5(b''.join(p.read_bytes() for p in progs if
        p.exists())).hexdigest()

def main():
    global args, abzsquare

    # Set up command line arguments
    opt = argparse.ArgumentParser(description=__doc__)
    opt.add_argument('-c', '--conffile',
            help='alternative configuration file')
    opt.add_argument('-v', '--verbose', action='store_true',
            help='output diagnostic messages')
    opt.add_argument('-d', '--debug', action='store_true',
            help='output diagnostic messages only, do not action gestures')
    opt.add_argument('-r', '--raw', action='store_true',
            help='output raw libinput debug-event messages only, '
            'do not action gestures')
    opt.add_argument('-l', '--list', action='store_true',
            help='just list out environment and configuration')
    opt.add_argument('--device',
            help='explicit device name to use (or path if starts with /)')
    # Test/diag hidden option to specify a file containing libinput list
    # device output to parse
    opt.add_argument('--device-list', help=argparse.SUPPRESS)
    args = opt.parse_args()

    if args.debug or args.raw or args.list:
        args.verbose = True

    # Libinput changed the way in which it's utilities are called
    libvers, has_subcmd = get_libinput_vers()
    if not libvers:
        sys.exit('libinput helper tools do not seem to be installed?')

    if has_subcmd:
        cmd_debug_events = 'libinput debug-events'
        cmd_list_devices = 'libinput list-devices'
    else:
        cmd_debug_events = 'libinput-debug-events'
        cmd_list_devices = 'libinput-list-devices'

    if args.verbose:
        # Output various info/version info
        xsession = os.getenv('XDG_SESSION_DESKTOP') or \
                os.getenv('DESKTOP_SESSION') or 'unknown'
        xtype = os.getenv('XDG_SESSION_TYPE') or 'unknown'
        xstr = f'session {xsession}+{xtype}'
        pf = platform.platform()
        pfpy = f'python {platform.python_version()}'
        lstr = f'libinput {libvers}'
        print(f'{PROGNAME}: {xstr} on {pf}, {pfpy}, {lstr}')

        # Output hash version/checksum of this program
        print(f'Hash: {gethash()}')

    # Read and process the conf file
    confname = read_conf(args.conffile, CONFNAME)

    # List out available gestures if that is asked for
    if args.verbose:
        if not args.raw:
            print(f'Gestures configured in {confname}:')
            for h in handlers.values():
                for mpair, cmd in h.motions.items():
                  if len(mpair) == 2:
                     appname, motion = mpair
                     fingers = ''
                  else:
                      appname, motion, fingers = mpair
                  print(f'[{appname}] {h.name.lower()} {motion:10}{fingers:>2} {cmd}')

            if swipe_min_threshold:
                print(f'swipe_threshold {swipe_min_threshold}')
            if timeoutv != DEFAULT_TIMEOUT:
                print(f'timeout {timeoutv}')

        if args.device:
            print(f'device {args.device}')

    # Get touchpad device
    if not args.device or args.device.lower() != "all":
        device = get_device(args.device, cmd_list_devices, args.device_list)
        if not device:
            sys.exit('Could not determine touchpad device.')
    else:
        device = None

    if args.verbose:
        if device:
            print(f"{PROGNAME}: device {device.get('_diag')}")
        else:
            print(f'{PROGNAME}: monitoring all devices')

    # If just called to list out above environment info then exit now
    if args.list:
        status = run((PROGNAME + '-setup', 'status'), check=False)
        if status:
            print(status.strip())
        sys.exit()

    # Make sure only one instance running for current user
    user = getpass.getuser()
    lockfile, pidfile = open_lock(PROGNAME, user)
    if not lockfile:
        sys.exit(f'{PROGNAME} is already running for {user}, terminating ..')

    # Set up square of swipe threshold
    abzsquare = swipe_min_threshold**2

    # Note your must "sudo gpasswd -a $USER input" then reboot for
    # permission to access the device.
    devstr = f" --device {device.get('_path')}" if device else ''
    command = f'stdbuf -oL -- {cmd_debug_events}{devstr}'

    if dbus_imported:
        t = threading.Thread(target=lockcheck)
        t.daemon = True
        t.start()

    cmd = subprocess.Popen(shlex.split(command), stdout=subprocess.PIPE,
            bufsize=1, universal_newlines=True)

    # Store PIDs for potential kill
    pidfile.write(f'{os.getpid()}\n{cmd.pid}\n')
    pidfile.flush()
    os.fsync(pidfile.fileno())

    # Sit in a loop forever reading the libinput messages ..
    handler = None
    for line in cmd.stdout:

        # Ignore gestures if this session is locked
        if session_locked:
            continue

        # Just output raw messages if in that mode
        if args.raw:
            print(line.strip())
            continue

        # Only interested in gestures
        if 'GESTURE_' not in line:
            continue

        # Split received message line into relevant fields
        dev, gevent, time, other = line.strip().split(maxsplit=3)
        try:
            gesture, event = gevent[8:].split('_')
        except Exception:
            continue

        fingers, *argslist = other.split(maxsplit=1)
        params = argslist[0] if argslist else ''

        # Action each type of event
        if event == 'UPDATE':
            if handler:
                # Split parameters into list of clean numbers
                if not handler.update(re.split(r'[^-.\d]+', params)):
                    print('Could not parse {gesture} {event}: {params}',
                            file=sys.stderr)

        elif event == 'BEGIN':
            handler = handlers.get(gesture)
            if handler:
                handler.begin(fingers)
            else:
                print(f'Unknown gesture received: {gesture}.',
                        file=sys.stderr)
        elif event == 'END':
            # Ignore gesture if final action is cancelled
            if handler:
                if params != 'cancelled':
                    handler.end()
                handler = None
        else:
            print(f'Unknown gesture {gesture} + event {event} received.',
                    file=sys.stderr)

if __name__ == '__main__':
    main()