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198
barcode_server/keyevent_reader.py
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198
barcode_server/keyevent_reader.py
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import logging
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from evdev import KeyEvent, InputDevice, categorize
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LOGGER = logging.getLogger(__name__)
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US_EN_UPPER_DICT = {
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"`": "~",
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"1": "!",
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"2": "@",
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"3": "#",
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"4": "$",
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"5": "%",
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"6": "^",
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"7": "&",
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"8": "*",
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"9": "(",
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"0": ")",
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"-": "_",
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"=": "+",
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",": "<",
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".": ">",
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"/": "?",
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";": ":",
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"'": "\"",
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"\\": "|",
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"[": "{",
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"]": "}"
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}
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class KeyEventReader:
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"""
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Class used to convert a sequence of KeyEvents to text
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"""
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def __init__(self):
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self._shift = False
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self._caps = False
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self._alt = False
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self._unicode_number_input_buffer = ""
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self._line = ""
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def read_line(self, input_device: InputDevice) -> str:
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"""
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Reads a line
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:param input_device: the device to read from
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:return: line
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"""
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self._line = ""
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# While there is a function called async_read_loop, it tends
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# to skip input events, so we use the non-async read-loop here.
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# async for event in input_device.async_read_loop():
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for event in input_device.read_loop():
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try:
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event = categorize(event)
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if hasattr(event, "event"):
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if not hasattr(event, "keystate") and hasattr(event.event, "keystate"):
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event.keystate = event.event.keystate
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if not hasattr(event, "keystate") or not hasattr(event, "keycode"):
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continue
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keycode = event.keycode
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keystate = event.keystate
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if isinstance(event, KeyEvent):
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if self._on_key_event(keycode, keystate):
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return self._line
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elif hasattr(event, "event") and event.event.type == 1:
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if self._on_key_event(keycode, keystate):
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return self._line
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except Exception as ex:
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LOGGER.exception(ex)
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def _on_key_event(self, code: str, state: int) -> bool:
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if code in ["KEY_ENTER", "KEY_KPENTER"]:
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if state == KeyEvent.key_up:
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# line is finished
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self._reset_modifiers()
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return True
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elif code in ["KEY_RIGHTSHIFT", "KEY_LEFTSHIFT"]:
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if state in [KeyEvent.key_down, KeyEvent.key_hold]:
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self._shift = True
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else:
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self._shift = False
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elif code in ["KEY_LEFTALT", "KEY_RIGHTALT"]:
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if state in [KeyEvent.key_down, KeyEvent.key_hold]:
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self._alt = True
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else:
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self._alt = False
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character = self._unicode_numbers_to_character(self._unicode_number_input_buffer)
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self._unicode_number_input_buffer = ""
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if character is not None:
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self._line += character
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elif code == "KEY_BACKSPACE":
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self._line = self._line[:-1]
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elif state == KeyEvent.key_down:
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character = self._code_to_character(code)
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if self._alt:
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self._unicode_number_input_buffer += character
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else:
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if character is not None and not self._alt:
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# append the current character
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self._line += character
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return False
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def _code_to_character(self, code: str) -> chr or None:
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character = None
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if len(code) == 5:
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character = code[-1]
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elif code.startswith("KEY_KP") and len(code) == 7:
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character = code[-1]
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elif code in ["KEY_DOWN"]:
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character = '\n'
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elif code in ["KEY_SPACE"]:
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character = ' '
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elif code in ["KEY_ASTERISK", "KEY_KPASTERISK"]:
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character = '*'
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elif code in ["KEY_MINUS", "KEY_KPMINUS"]:
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character = '-'
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elif code in ["KEY_PLUS", "KEY_KPPLUS"]:
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character = '+'
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elif code in ["KEY_QUESTION"]:
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character = '?'
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elif code in ["KEY_COMMA", "KEY_KPCOMMA"]:
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character = ','
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elif code in ["KEY_DOT", "KEY_KPDOT"]:
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character = '.'
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elif code in ["KEY_EQUAL", "KEY_KPEQUAL"]:
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character = '='
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elif code in ["KEY_LEFTPAREN", "KEY_KPLEFTPAREN"]:
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character = '('
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elif code in ["KEY_PLUSMINUS", "KEY_KPPLUSMINUS"]:
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character = '+-'
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elif code in ["KEY_RIGHTPAREN", "KEY_KPRIGHTPAREN"]:
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character = ')'
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elif code in ["KEY_RIGHTBRACE"]:
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character = ']'
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elif code in ["KEY_LEFTBRACE"]:
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character = '['
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elif code in ["KEY_SLASH", "KEY_KPSLASH"]:
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character = '/'
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elif code in ["KEY_BACKSLASH"]:
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character = '\\'
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elif code in ["KEY_COLON"]:
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character = ';'
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elif code in ["KEY_SEMICOLON"]:
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character = ';'
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elif code in ["KEY_APOSTROPHE"]:
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character = '\''
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elif code in ["KEY_GRAVE"]:
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character = '`'
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if character is None:
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character = code[4:]
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if len(character) > 1:
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LOGGER.warning(f"Unhandled Keycode: {code}")
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if self._shift or self._caps:
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character = character.upper()
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if character in US_EN_UPPER_DICT.keys():
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character = US_EN_UPPER_DICT[character]
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else:
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character = character.lower()
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return character
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@staticmethod
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def _unicode_numbers_to_character(code: str) -> chr or None:
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if code is None or len(code) <= 0:
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return None
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try:
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# convert to hex
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i = int(code)
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h = hex(i)
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s = f"{h}"
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return bytearray.fromhex(s[2:]).decode('utf-8')
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except Exception as ex:
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LOGGER.exception(ex)
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return None
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def _reset_modifiers(self):
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self._alt = False
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self._unicode_number_input_buffer = ""
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self._shift = False
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self._caps = False
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