How to use winapi SetWinEventHook in python?

Question

I want to get the handle of every new Dialog which pops up from a specific application.
I understand I should set a hook with SetWinEventHook which is in user32.dll in windows, but I don't know how to do that in python. Would you give me an example ?

Answer 1

Here's a very simple example that prints to the console the window text for each dialog that is opened:

import sys
import time
import ctypes
import ctypes.wintypes

EVENT_SYSTEM_DIALOGSTART = 0x0010
WINEVENT_OUTOFCONTEXT = 0x0000

user32 = ctypes.windll.user32
ole32 = ctypes.windll.ole32

ole32.CoInitialize(0)

WinEventProcType = ctypes.WINFUNCTYPE(
    None, 
    ctypes.wintypes.HANDLE,
    ctypes.wintypes.DWORD,
    ctypes.wintypes.HWND,
    ctypes.wintypes.LONG,
    ctypes.wintypes.LONG,
    ctypes.wintypes.DWORD,
    ctypes.wintypes.DWORD
)

def callback(hWinEventHook, event, hwnd, idObject, idChild, dwEventThread, dwmsEventTime):
    length = user32.GetWindowTextLengthA(hwnd)
    buff = ctypes.create_string_buffer(length + 1)
    user32.GetWindowTextA(hwnd, buff, length + 1)
    print buff.value

WinEventProc = WinEventProcType(callback)

user32.SetWinEventHook.restype = ctypes.wintypes.HANDLE
hook = user32.SetWinEventHook(
    EVENT_SYSTEM_DIALOGSTART,
    EVENT_SYSTEM_DIALOGSTART,
    0,
    WinEventProc,
    0,
    0,
    WINEVENT_OUTOFCONTEXT
)
if hook == 0:
    print 'SetWinEventHook failed'
    sys.exit(1)

msg = ctypes.wintypes.MSG()
while user32.GetMessageW(ctypes.byref(msg), 0, 0, 0) != 0:
    user32.TranslateMessageW(msg)
    user32.DispatchMessageW(msg)

user32.UnhookWinEvent(hook)
ole32.CoUninitialize()