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CodingCode
CodingCode

Reputation: 123

SetWindowsHookExW returns 0 with no error | HID Mouse hook attempt

I'm trying to intercept an HID "Mice/other poninting device" left button clicks, and I'm just losing it. I'm running on 64bits Win 11 if it makes any difference.

SetWindowsHookExW returns 0 & GetLastError also returns 0. WinError() call simply returns "[WinError 126] The specified module could not be found."

Please Please help!! Below is my code.

import ctypes
from ctypes import wintypes

import win32api
import win32con

# Define the callback function type
HOOKPROC = ctypes.WINFUNCTYPE(ctypes.c_int, ctypes.c_int, wintypes.WPARAM, wintypes.LPARAM)


# Define the callback function for the mouse hook
def low_level_mouse_proc(nCode, wParam, lParam):
    if nCode == 0:
        return 1
        # if wParam == win32con.WM_LBUTTONDOWN:  # Intercept left-click down event
        #     print("Left click intercepted, disabling original click")
        #     # Return 1 to block the default left-click
        #     return 1
        #
        # if wParam == win32con.WM_LBUTTONUP:  # Intercept left-click up event
        #     print("Left click release intercepted")
        #     # Return 1 to block the default left-click
        #     return 1

    # Call next hook in chain if we are not blocking
    return ctypes.windll.user32.CallNextHookEx(None, nCode, wParam, lParam)


# Convert the Python function to a C callback function
low_level_mouse_proc_c = HOOKPROC(low_level_mouse_proc)


# Setting the hook
def set_mouse_hook():
    WH_MOUSE_LL = 14
    module = ctypes.WinDLL('kernel32', use_last_error=True)
    print("Hooking")
    mouse_hook = ctypes.windll.user32.SetWindowsHookExW(
        WH_MOUSE_LL,
        low_level_mouse_proc_c,
        module.GetModuleHandleW(None),  # Ensure proper module handle
        0
    )
    if not mouse_hook:
        print(ctypes.WinError())
    return mouse_hook

Upvotes: 0

Views: 68

Answers (1)

CristiFati
CristiFati

Reputation: 41147

In short, your code is full of Undefined Behavior.
The cause is explained in [SO]: C function called from Python via ctypes returns incorrect value (@CristiFati's answer) - that's a common pitfall when working with CTypes (calling functions).

The error you're getting (126) is also triggered by that. Check the @TODO line in my code (below).

I'm posting a corrected variant.

code00.py:

#!/usr/bin/env python

import ctypes as cts
import msvcrt
import sys
from ctypes import wintypes as wts

import win32api as wapi
import win32con as wcon


WH_MOUSE = 7
WH_MOUSE_LL = 14

LRESULT = cts.c_size_t

HOOKProc = cts.WINFUNCTYPE(LRESULT, cts.c_int, wts.WPARAM, wts.LPARAM)
LowLevelMouseProc = HOOKProc
MouseProc = HOOKProc

kernel32 = cts.windll.kernel32
user32 = cts.windll.user32

SetWindowsHookExA = user32.SetWindowsHookExA
SetWindowsHookExA.argtypes = (cts.c_int, HOOKProc, wts.HINSTANCE, wts.DWORD)
SetWindowsHookExA.restype = wts.HHOOK

CallNextHookEx = user32.CallNextHookEx
CallNextHookEx.argtypes = (wts.HHOOK, cts.c_int, wts.WPARAM, wts.LPARAM)
CallNextHookEx.restype = LRESULT

UnhookWindowsHookEx = user32.UnhookWindowsHookEx
UnhookWindowsHookEx.argtypes = (wts.HHOOK,)
UnhookWindowsHookEx = wts.BOOL

GetLastError = kernel32.GetLastError
GetLastError.argtypes = ()
GetLastError.restype = wts.DWORD

GetModuleHandleW = kernel32.GetModuleHandleW
GetModuleHandleW.argtypes = (wts.LPCWSTR,)
GetModuleHandleW.restype = wts.HMODULE  # @TODO - cfati: Decomment to run into your error

GetCurrentThreadId = kernel32.GetCurrentThreadId
GetCurrentThreadId.argtypes = ()
GetCurrentThreadId.restype = wts.DWORD


def handle_mouse_event(code, w_param, l_param):
    #print("kkt")
    if code < 0:
        return CallNextHookEx(code, w_param, l_param)
    else:
        if w_param == wcon.WM_LBUTTONDOWN:
            print("LB down")
        elif w_param == wcon.WM_LBUTTONUP:
            print("LB up")
        return CallNextHookEx(code, w_param, l_param)


low_level_mouse_proc = LowLevelMouseProc(handle_mouse_event)


def main(*argv):
    k = b"\x00"
    while k != b"\x1B":
        print("Press a key (ESC to continue) ...")
        k = msvcrt.getch()
    print("Add hook:")
    hinstance = GetModuleHandleW(None)
    tid = 0 #GetCurrentThreadId()
    print(hinstance, tid)
    hook = SetWindowsHookExA(
        WH_MOUSE_LL,
        low_level_mouse_proc,
        hinstance,
        tid,
    )
    print(f"Hook function: {hook}")
    if not hook:
        print(f"Hook creation failed: {GetLastError()}")
        return -1
    k = b"\x00"
    while k != b"\x1B":
        print("Press a key (ESC to continue) ...")
        k = msvcrt.getch()
    UnhookWindowsHookEx(hook)


if __name__ == "__main__":
    print(
        "Python {:s} {:03d}bit on {:s}\n".format(
            " ".join(elem.strip() for elem in sys.version.split("\n")),
            64 if sys.maxsize > 0x100000000 else 32,
            sys.platform,
        )
    )
    rc = main(*sys.argv[1:])
    print("\nDone.\n")
    sys.exit(rc)

Not posting the output, as there's nothing relevant. Note that after setting the hook:

  • Mouse has a huge lag (it's almost unusable)

  • I don't see any text printed from the callback

Might be related:

Upvotes: 0

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