python - 如何在 python 中使用 ctypes 获取 Windows 窗口名称

Question

我尝试通过具有长对象的句柄获取 Windows 窗口标题名称和 pids。我的代码有效，但有问题。当我应该得到 10 个或更多时，我只得到 4 个窗口标题。任何人都可以帮助并告诉我如何修复此代码吗？我认为问题在于我如何转换长对象(我不太了解它们，以及一般的 ctypes)。

from __future__ import print_function
from ctypes import *

psapi = windll.psapi
titles = []


# get window title from pid
def gwtfp():
    max_array = c_ulong * 4096
    pProcessIds = max_array()
    pBytesReturned = c_ulong()

    psapi.EnumProcesses(byref(pProcessIds),
                        sizeof(pProcessIds),
                        byref(pBytesReturned))

    # get the number of returned processes
    nReturned = pBytesReturned.value/sizeof(c_ulong())
    pidProcessArray = [i for i in pProcessIds][:nReturned]
    print(pidProcessArray)
    #
    EnumWindows = windll.user32.EnumWindows
    EnumWindowsProc = WINFUNCTYPE(c_bool, POINTER(c_int), POINTER(c_int))
    GetWindowText = windll.user32.GetWindowTextW
    GetWindowTextLength = windll.user32.GetWindowTextLengthW
    IsWindowVisible = windll.user32.IsWindowVisible


    for process in pidProcessArray:
        #print("Process PID %d" % process)
        if IsWindowVisible(process):
            length = GetWindowTextLength(process)
            buff = create_unicode_buffer(length + 1)
            GetWindowText(process, buff, length + 1)
            titles.append(buff.value)


gwtfp()
print(titles)

Answer 1

您正在将进程 ID 传递给采用窗口句柄的函数。您要做的是枚举顶级窗口的句柄，然后将每个窗口映射到进程 ID。

首先让我们定义 ctypes 函数原型(prototype)，以便对函数参数进行正确的类型检查。此外，使用 use_last_error=True 通过 ctypes.get_last_error 获得最安全的错误处理。许多 Windows 函数返回 0 表示错误，因此在这种情况下使用单个 errcheck 函数会很方便，例如 check_zero。

from __future__ import print_function

import ctypes
from ctypes import wintypes
from collections import namedtuple

user32 = ctypes.WinDLL('user32', use_last_error=True)

def check_zero(result, func, args):    
    if not result:
        err = ctypes.get_last_error()
        if err:
            raise ctypes.WinError(err)
    return args

if not hasattr(wintypes, 'LPDWORD'): # PY2
    wintypes.LPDWORD = ctypes.POINTER(wintypes.DWORD)

WindowInfo = namedtuple('WindowInfo', 'pid title')

WNDENUMPROC = ctypes.WINFUNCTYPE(
    wintypes.BOOL,
    wintypes.HWND,    # _In_ hWnd
    wintypes.LPARAM,) # _In_ lParam

user32.EnumWindows.errcheck = check_zero
user32.EnumWindows.argtypes = (
   WNDENUMPROC,      # _In_ lpEnumFunc
   wintypes.LPARAM,) # _In_ lParam

user32.IsWindowVisible.argtypes = (
    wintypes.HWND,) # _In_ hWnd

user32.GetWindowThreadProcessId.restype = wintypes.DWORD
user32.GetWindowThreadProcessId.argtypes = (
  wintypes.HWND,     # _In_      hWnd
  wintypes.LPDWORD,) # _Out_opt_ lpdwProcessId

user32.GetWindowTextLengthW.errcheck = check_zero
user32.GetWindowTextLengthW.argtypes = (
   wintypes.HWND,) # _In_ hWnd

user32.GetWindowTextW.errcheck = check_zero
user32.GetWindowTextW.argtypes = (
    wintypes.HWND,   # _In_  hWnd
    wintypes.LPWSTR, # _Out_ lpString
    ctypes.c_int,)   # _In_  nMaxCount

这是一个列出可见窗口的函数。它使用一个回调，该回调是 result 的闭包，而不是使用可选的 lParam 参数。后者需要提出论点。使用闭包更简单。

def list_windows():
    '''Return a sorted list of visible windows.'''
    result = []
    @WNDENUMPROC
    def enum_proc(hWnd, lParam):
        if user32.IsWindowVisible(hWnd):
            pid = wintypes.DWORD()
            tid = user32.GetWindowThreadProcessId(
                        hWnd, ctypes.byref(pid))
            length = user32.GetWindowTextLengthW(hWnd) + 1
            title = ctypes.create_unicode_buffer(length)
            user32.GetWindowTextW(hWnd, title, length)
            result.append(WindowInfo(pid.value, title.value))
        return True
    user32.EnumWindows(enum_proc, 0)
    return sorted(result)

为了完整起见，这里有一个列出所有进程 ID 的函数。这包括属于其他 Windows session 的进程(例如 session 0 中的服务)。

psapi = ctypes.WinDLL('psapi', use_last_error=True)

psapi.EnumProcesses.errcheck = check_zero
psapi.EnumProcesses.argtypes = (
   wintypes.LPDWORD,  # _Out_ pProcessIds
   wintypes.DWORD,    # _In_  cb
   wintypes.LPDWORD,) # _Out_ pBytesReturned

def list_pids():
    '''Return sorted list of process IDs.'''
    length = 4096
    PID_SIZE = ctypes.sizeof(wintypes.DWORD)
    while True:
        pids = (wintypes.DWORD * length)()
        cb = ctypes.sizeof(pids)
        cbret = wintypes.DWORD()
        psapi.EnumProcesses(pids, cb, ctypes.byref(cbret))
        if cbret.value < cb:
            length = cbret.value // PID_SIZE
            return sorted(pids[:length])
        length *= 2

例如:

if __name__ == '__main__':
    print('Process IDs:')
    print(*list_pids(), sep='\n')
    print('\nWindows:')
    print(*list_windows(), sep='\n')

MSDN 链接:

• EnumWindows
• IsWindowVisible
• GetWindowThreadProcessId
• GetWindowTextLength
• GetWindowText
• EnumProcesses