keyboard_hook.py

from logging import getLogger
logger = getLogger('keyboard_hook')

import ctypes
from ctypes import (
	wintypes,
	Structure,
	c_long,
	c_int,
)


HC_ACTION = 0
WH_KEYBOARD_LL = 13
LLKHF_INJECTED = 16
LLKHF_UP = 128
KF_EXTENDED = 0x0100
LLKHF_EXTENDED = KF_EXTENDED >> 8

class KBDLLHOOKSTRUCT(Structure):
	_fields_ = [
		('vkCode', wintypes.DWORD),
		('scanCode', wintypes.DWORD),
		('flags', wintypes.DWORD),
		('time', wintypes.DWORD),
		('dwExtraInfo', wintypes.DWORD),
	]

LRESULT = c_long

LowLevelKeyboardProc = ctypes.WINFUNCTYPE(LRESULT, c_int, wintypes.LPARAM, wintypes.WPARAM)


class KeyboardHook:

	def __init__(self):
		self.callbacks = list()
		self.proc = LowLevelKeyboardProc(self.keyboard_proc)
		self.handle = ctypes.windll.user32.SetWindowsHookExW(WH_KEYBOARD_LL, self.proc, ctypes.windll.kernel32.GetModuleHandleW(None), 0)

	def register_callback(self, callback):
		self.callbacks.append(callback)

	def unregister_callback(self, callback):
		self.callbacks.remove(callback)

	def keyboard_proc(self, code, wParam, lParam):
		if code < 0 or code != HC_ACTION:
			return ctypes.windll.user32.CallNextHookEx(0, code, wParam, lParam)
		event_type = wParam
		kbd = KBDLLHOOKSTRUCT.from_address(lParam)
		vk_code = kbd.vkCode
		scan_code = kbd.scanCode
		extended = bool(kbd.flags&LLKHF_EXTENDED)
		pressed = not bool(kbd.flags&LLKHF_UP)
		should_pass_on = True
		for callback in self.callbacks:
			try:
				should_pass_on = not callback(vk_code=vk_code, scan_code=scan_code, extended=extended, pressed=pressed)
			except Exception as e:
				logger.exception("Error calling callback %r" % callback)
		if not should_pass_on:
			return 1
		return ctypes.windll.user32.CallNextHookEx(0, code, wParam, lParam)

	def free(self):
		if self.handle:
			ctypes.windll.user32.UnhookWindowsHookEx(self.handle)
			self.handle = None