input-remapper/keymapper/reader.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 reading keycodes in the background for the UI to use."""


import evdev

from keymapper.logger import logger
from keymapper.getdevices import get_devices


class _KeycodeReader:
    """Keeps reading keycodes in the background for the UI to use.

    When a button was pressed, the newest keycode can be obtained from this
    object. GTK has get_keycode for keyboard keys, but KeycodeReader also
    has knowledge of buttons like the middle-mouse button.
    """
    def __init__(self):
        self.virtual_devices = []

    def clear(self):
        """Next time when reading don't return the previous keycode."""
        # read all of them to clear the buffer or whatever
        for virtual_device in self.virtual_devices:
            while virtual_device.read_one():
                pass

    def start_reading(self, device):
        """Tell the evdev lib to start looking for keycodes.

        If read is called without prior start_reading, no keycodes
        will be available.
        """
        paths = get_devices()[device]['paths']

        logger.debug(
            'Starting reading keycodes for %s on %s',
            device,
            ', '.join(paths)
        )

        # Watch over each one of the potentially multiple devices per hardware
        self.virtual_devices = [
            evdev.InputDevice(path)
            for path in paths
        ]

    def read(self):
        """Get the newest keycode or None if none was pressed."""
        newest_keycode = None
        for virtual_device in self.virtual_devices:
            while True:
                event = virtual_device.read_one()
                if event is None:
                    break

                logger.spam(
                    'got code:%s value:%s',
                    event.code + 8, event.value
                )

                if event.type == evdev.ecodes.EV_KEY and event.value == 1:
                    # value: 1 for down, 0 for up, 2 for hold.
                    # this happens to report key codes that are 8 lower
                    # than the ones reported by evtest and used in xkb files
                    newest_keycode = event.code + 8
        return newest_keycode


keycode_reader = _KeycodeReader()