input-remapper/keymapper/dev/injector.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
# key-mapper - GUI for device specific keyboard mappings
# Copyright (C) 2020 sezanzeb <proxima@hip70890b.de>
#
# This file is part of key-mapper.
#
# key-mapper is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# key-mapper is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with key-mapper.  If not, see <https://www.gnu.org/licenses/>.


"""Keeps injecting keycodes in the background based on the mapping."""


import re
import asyncio
import time
import subprocess
import multiprocessing

import evdev

from keymapper.logger import logger
from keymapper.getdevices import get_devices
from keymapper.state import system_mapping
from keymapper.dev.macros import parse


DEV_NAME = 'key-mapper'
DEVICE_CREATED = 1
FAILED = 2
DEVICE_SKIPPED = 3

# offset between xkb and linux keycodes. linux keycodes are lower
KEYCODE_OFFSET = 8


def is_numlock_on():
    """Get the current state of the numlock."""
    xset_q = subprocess.check_output(['xset', 'q']).decode()
    num_lock_status = re.search(
        r'Num Lock:\s+(.+?)\s',
        xset_q
    )

    if num_lock_status is not None:
        return num_lock_status[1] == 'on'

    return False


def toggle_numlock():
    """Turn the numlock on or off."""
    try:
        subprocess.check_output(['numlockx', 'toggle'])
    except FileNotFoundError:
        # doesn't seem to be installed everywhere
        logger.debug('numlockx not found, trying to inject a keycode')
        # and this doesn't always work.
        device = evdev.UInput(
            name=f'key-mapper numlock-control',
            phys='key-mapper',
        )
        device.write(evdev.ecodes.EV_KEY, evdev.ecodes.KEY_NUMLOCK, 1)
        device.syn()
        device.write(evdev.ecodes.EV_KEY, evdev.ecodes.KEY_NUMLOCK, 0)
        device.syn()


def ensure_numlock(func):
    """Decorator to reset the numlock to its initial state afterwards."""
    def wrapped(*args, **kwargs):
        # for some reason, grabbing a device can modify the num lock state.
        # remember it and apply back later
        numlock_before = is_numlock_on()
        result = func(*args, **kwargs)
        numlock_after = is_numlock_on()
        if numlock_after != numlock_before:
            logger.debug('Reverting numlock status to %s', numlock_before)
            toggle_numlock()
        return result
    return wrapped


class KeycodeInjector:
    """Keeps injecting keycodes in the background based on the mapping.

    Is a process to make it non-blocking for the rest of the code and to
    make running multiple injector easier. There is one procss per
    hardware-device that is being mapped.
    """
    @ensure_numlock
    def __init__(self, device, mapping):
        """Start injecting keycodes based on custom_mapping.

        Parameters
        ----------
        device : string
            the name of the device as available in get_device
        """
        self.device = device
        self.mapping = mapping
        self._process = None

    def start_injecting(self):
        """Start injecting keycodes."""
        self._process = multiprocessing.Process(target=self._start_injecting)
        self._process.start()

    def _prepare_device(self, path):
        """Try to grab the device, return if not needed/possible."""
        device = evdev.InputDevice(path)

        if device is None:
            return None

        capabilities = device.capabilities(absinfo=False)[evdev.ecodes.EV_KEY]

        needed = False
        for keycode, _ in self.mapping:
            if keycode - KEYCODE_OFFSET in capabilities:
                needed = True
                break

        if not needed:
            # skipping reading and checking on events from those devices
            # may be beneficial for performance.
            logger.debug('No need to grab %s', device.path)
            return None

        attempts = 0
        while True:
            device = evdev.InputDevice(path)
            try:
                # grab to avoid e.g. the disabled keycode of 10 to confuse
                # X, especially when one of the buttons of your mouse also
                # uses 10. This also avoids having to load an empty xkb
                # symbols file to prevent writing any unwanted keys.
                device.grab()
                break
            except IOError:
                attempts += 1
                logger.debug('Failed attemt to grab %s %d', path, attempts)

            if attempts >= 4:
                logger.error('Cannot grab %s, it is possibly in use', path)
                return None

            # it might take a little time until the device is free if
            # it was previously grabbed.
            time.sleep(0.15)

        return device

    def _modify_capabilities(self, input_device):
        """Adds all keycode into a copy of a devices capabilities.

        Prameters
        ---------
        input_device : evdev.InputDevice
        """
        # copy the capabilities because the keymapper_device is going
        # to act like the device.
        capabilities = input_device.capabilities(absinfo=False)
        # However, make sure that it supports all keycodes, not just some
        # random ones, because the mapping could contain anything.
        # That's why I avoid from_device for this
        capabilities[evdev.ecodes.EV_KEY] = list(evdev.ecodes.keys.keys())

        # just like what python-evdev does in from_device
        if evdev.ecodes.EV_SYN in capabilities:
            del capabilities[evdev.ecodes.EV_SYN]
        if evdev.ecodes.EV_FF in capabilities:
            del capabilities[evdev.ecodes.EV_FF]

        return capabilities

    def _start_injecting(self):
        """The injection worker that keeps injecting until terminated.

        Stuff is non-blocking by using asyncio in order to do multiple things
        somewhat concurrently.
        """
        loop = asyncio.get_event_loop()
        coroutines = []

        paths = get_devices()[self.device]['paths']

        logger.info('Starting injecting the mapping for %s', self.device)

        # Watch over each one of the potentially multiple devices per hardware
        for path in paths:
            input_device = self._prepare_device(path)
            if input_device is None:
                continue

            uinput = evdev.UInput(
                name=f'key-mapper {input_device.name}',
                phys='key-mapper',
                events=self._modify_capabilities(input_device)
            )
            coroutine = self._injection_loop(input_device, uinput)
            coroutines.append(coroutine)

        if len(coroutines) == 0:
            raise OSError('Could not grab any device')

        loop.run_until_complete(asyncio.gather(*coroutines))

    def _write(self, device, keycode, value):
        """Actually inject."""
        device.write(evdev.ecodes.EV_KEY, keycode - KEYCODE_OFFSET, value)
        device.syn()

    async def _injection_loop(self, device, keymapper_device):
        """Inject keycodes for one of the virtual devices.

        Parameters
        ----------
        device : evdev.InputDevice
            where to read keycodes from
        keymapper_device : evdev.UInput
            where to write keycodes to
        """
        # Parse all macros beforehand
        logger.debug('Parsing macros')
        macros = {}
        for keycode, output in self.mapping:
            if '(' in output and ')' in output and len(output) > 4:
                # probably a macro
                macros[keycode] = parse(
                    output,
                    lambda char, value: (
                        self._write(
                            keymapper_device,
                            system_mapping.get_keycode(char),
                            value
                        )
                    )
                )

        logger.debug(
            'Started injecting into %s, fd %s',
            keymapper_device.device.path, keymapper_device.fd
        )

        async for event in device.async_read_loop():
            if event.type != evdev.ecodes.EV_KEY:
                keymapper_device.write(event.type, event.code, event.value)
                # this already includes SYN events, so need to syn here again
                continue

            if event.value == 2:
                # linux does them itself, no need to trigger them
                continue

            input_keycode = event.code + KEYCODE_OFFSET

            character = self.mapping.get_character(input_keycode)

            if character is None:
                # unknown keycode, forward it
                target_keycode = input_keycode
            elif '(' in character:
                # must be a macro
                if event.value == 0:
                    continue

                logger.spam(
                    'got code:%s value:%s, maps to macro %s',
                    event.code + KEYCODE_OFFSET,
                    event.value,
                    character
                )
                macro = macros.get(input_keycode)
                # TODO test if m(SHIFT_L, k(a)) prints A in injector tests
                if macro is not None:
                    asyncio.ensure_future(macro.run())
                continue
            else:
                target_keycode = system_mapping.get_keycode(character)
                if target_keycode is None:
                    logger.error(
                        'Cannot find character %s in the internal mapping',
                        character
                    )
                    continue

            logger.spam(
                'got code:%s value:%s, maps to code:%s char:%s',
                event.code + KEYCODE_OFFSET,
                event.value,
                target_keycode,
                character
            )

            self._write(keymapper_device, target_keycode, event.value)

        # this should only ever happen in tests to avoid blocking them
        # forever, as soon as all events are consumed. In normal operation
        # there is no end to the events.
        logger.error(
            'The injector for "%s" stopped early',
            keymapper_device.device.path
        )

    @ensure_numlock
    def stop_injecting(self):
        """Stop injecting keycodes."""
        logger.info('Stopping injecting keycodes for device %s', self.device)
        if self._process is not None and self._process.is_alive():
            self._process.terminate()