input-remapper/keymapper/gui/reader.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
# key-mapper - GUI for device specific keyboard mappings
# Copyright (C) 2021 sezanzeb <proxima@sezanzeb.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/>.


"""Talking to the GUI helper that has root permissions.

see gui.helper.helper
"""


import evdev
from evdev.ecodes import EV_REL

from keymapper.logger import logger
from keymapper.key import Key
from keymapper.getdevices import set_devices
from keymapper.ipc.pipe import Pipe
from keymapper.gui.helper import TERMINATE, GET_DEVICES
from keymapper import utils
from keymapper.state import custom_mapping
from keymapper.getdevices import get_devices, GAMEPAD


DEBOUNCE_TICKS = 3


def will_report_up(ev_type):
    """Check if this event will ever report a key up (wheels)."""
    return ev_type != EV_REL


class Reader:
    """Processes events from the helper for the GUI to use.

    Does not serve any purpose for the injection service.

    When a button was pressed, the newest keycode can be obtained from this
    object. GTK has get_key for keyboard keys, but Reader also
    has knowledge of buttons like the middle-mouse button.
    """
    def __init__(self):
        self.previous_event = None
        self.previous_result = None
        self._unreleased = {}
        self._debounce_remove = {}
        self._devices_updated = False
        self._cleared_at = 0
        self.device_name = None

        self._results = None
        self._commands = None
        self.connect()

    def connect(self):
        """Connect to the helper."""
        self._results = Pipe('/tmp/key-mapper/results')
        self._commands = Pipe('/tmp/key-mapper/commands')

    def are_new_devices_available(self):
        """Check if get_devices contains new devices.

        The ui should then update its list.
        """
        outdated = self._devices_updated
        self._devices_updated = False  # assume the ui will react accordingly
        return outdated

    def _get_event(self, message):
        """Return an InputEvent if the message contains one. None otherwise."""
        message_type = message['type']
        message_body = message['message']

        if message_type == 'devices':
            # result of get_devices in the helper
            if message_body != get_devices():
                logger.debug('Received %d devices', len(message_body))
                set_devices(message_body)
                self._devices_updated = True
            return None

        if message_type == 'event':
            return evdev.InputEvent(*message_body)

        logger.error('Received unknown message "%s"', message)
        return None

    def read(self):
        """Get the newest key/combination as Key object.

        Only reports keys from down-events.

        On key-down events the pipe returns changed combinations. Release
        events won't cause that and the reader will return None as in
        "nothing new to report". So In order to change a combination, one
        of its keys has to be released and then a different one pressed.

        Otherwise making combinations wouldn't be possible. Because at
        some point the keys have to be released, and that shouldn't cause
        the combination to get trimmed.
        """
        # this is in some ways similar to the keycode_mapper and
        # event_producer, but its much simpler because it doesn't
        # have to trigger anything, manage any macros and only
        # reports key-down events. This function is called periodically
        # by the window.

        # remember the previous down-event from the pipe in order to
        # be able to tell if the reader should return the updated combination
        previous_event = self.previous_event
        key_down_received = False

        self._debounce_tick()

        while self._results.poll():
            message = self._results.recv()
            event = self._get_event(message)
            if event is None:
                continue

            gamepad = GAMEPAD in get_devices()[self.device_name]['types']
            if not utils.should_map_as_btn(event, custom_mapping, gamepad):
                continue

            event_tuple = (event.type, event.code, event.value)

            type_code = (event.type, event.code)

            if event.value == 0:
                logger.key_spam(event_tuple, 'release')
                self._release(type_code)
                continue

            if self._unreleased.get(type_code) == event_tuple:
                logger.key_spam(event_tuple, 'duplicate key down')
                self._debounce_start(event_tuple)
                continue

            # to keep track of combinations.
            # "I have got this release event, what was this for?" A release
            # event for a D-Pad axis might be any direction, hence this maps
            # from release to input in order to remember it. Since all release
            # events have value 0, the value is not used in the key.
            key_down_received = True
            logger.key_spam(event_tuple, 'down')
            self._unreleased[type_code] = event_tuple
            self._debounce_start(event_tuple)
            previous_event = event

        if not key_down_received:
            # This prevents writing a subset of the combination into
            # result after keys were released. In order to control the gui,
            # they have to be released.
            return None

        self.previous_event = previous_event

        if len(self._unreleased) > 0:
            result = Key(*self._unreleased.values())
            if result == self.previous_result:
                # don't return the same stuff twice
                return None

            self.previous_result = result
            logger.key_spam(result.keys, 'read result')

            return result

        return None

    def start_reading(self, device_name):
        """Start reading keycodes for a device."""
        logger.debug('Sending start msg to helper for "%s"', device_name)
        self._commands.send(device_name)
        self.device_name = device_name
        self.clear()

    def terminate(self):
        """Stop reading keycodes for good."""
        logger.debug('Sending close msg to helper')
        self._commands.send(TERMINATE)

    def get_devices(self):
        """Ask the helper for new devices."""
        self._commands.send(GET_DEVICES)

    def clear(self):
        """Next time when reading don't return the previous keycode."""
        logger.debug('Clearing reader')
        while self._results.poll():
            # clear the results pipe and handle any non-event messages,
            # otherwise a get_devices message might get lost
            message = self._results.recv()
            self._get_event(message)

        self._unreleased = {}
        self.previous_event = None
        self.previous_result = None

    def get_unreleased_keys(self):
        """Get a Key object of the current keyboard state."""
        unreleased = list(self._unreleased.values())

        if len(unreleased) == 0:
            return None

        return Key(*unreleased)

    def _release(self, type_code):
        """Modify the state to recognize the releasing of the key."""
        if type_code in self._unreleased:
            del self._unreleased[type_code]
        if type_code in self._debounce_remove:
            del self._debounce_remove[type_code]

    def _debounce_start(self, event_tuple):
        """Act like the key was released if no new event arrives in time."""
        if not will_report_up(event_tuple[0]):
            self._debounce_remove[event_tuple[:2]] = DEBOUNCE_TICKS

    def _debounce_tick(self):
        """If the counter reaches 0, the key is not considered held down."""
        for type_code in list(self._debounce_remove.keys()):
            if type_code not in self._unreleased:
                continue

            # clear wheel events from unreleased after some time
            if self._debounce_remove[type_code] == 0:
                logger.key_spam(
                    self._unreleased[type_code],
                    'Considered as released'
                )
                self._release(type_code)
            else:
                self._debounce_remove[type_code] -= 1

    def __del__(self):
        self.terminate()


reader = Reader()