ctypes与Win32 API交互：深度解析输出参数与原始返回值获取

BOOL GetWindowRect(
  [in]  HWND   hWnd,
  [out] LPRECT lpRect
);

from ctypes import POINTER, WINFUNCTYPE, windll
from ctypes.wintypes import BOOL, HWND, RECT
prototype = WINFUNCTYPE(BOOL, HWND, POINTER(RECT))
paramflags = (1, "hwnd"), (2, "lprect")
GetWindowRect = prototype(("GetWindowRect", windll.user32), paramflags)

import ctypes as ct
import ctypes.wintypes as w

# 可重用的基类，用于结构体打印自身
class Repr(ct.Structure):
    def __repr__(self):
        return (f'{self.__class__.__name__}(' +
                ', '.join([f'{n}={getattr(self, n)}'
                           for n, _ in self._fields_]) + ')')

# 自定义可打印的RECT结构体
class RECT(w.RECT, Repr):
    pass

# 针对返回BOOL类型且失败时支持GetLastError()的Win32函数的错误检查
def boolcheck(result, func, args):
    if not result:
        # 如果result为False，则抛出WinError异常，包含GetLastError()信息
        raise ct.WinError(ct.get_last_error())
    # 如果成功，则不返回任何值，表示原始返回值已通过异常处理或不需关心
    return None

# 确保在函数调用后立即捕获最后一个错误代码
user32 = ct.WinDLL('user32', use_last_error=True)

# 定义GetForegroundWindow函数
# 该函数没有参数，返回HWND（窗口句柄）
GetForegroundWindow = user32.GetForegroundWindow
GetForegroundWindow.argtypes = ()
GetForegroundWindow.restype = w.HWND

# 定义GetWindowRect函数
_GetWindowRect = user32.GetWindowRect
# argtypes定义输入参数类型：HWND和指向RECT的指针
_GetWindowRect.argtypes = w.HWND, ct.POINTER(RECT)
# restype定义函数原始返回类型：BOOL
_GetWindowRect.restype = w.BOOL
# errcheck指定自定义的错误检查函数
_GetWindowRect.errcheck = boolcheck

# 封装GetWindowRect，提供更友好的Python接口
def GetWindowRect(hwnd):
    r = RECT() # 创建一个RECT实例用于接收输出
    # 调用_GetWindowRect，并将RECT实例的引用传入
    # 如果API调用失败，_GetWindowRect会通过errcheck抛出异常
    _GetWindowRect(hwnd, ct.byref(r))
    return r # 成功时返回填充好的RECT实例

import ctypes as ct
import ctypes.wintypes as w

# Reusable base class for structures to print themselves.
class Repr(ct.Structure):
    def __repr__(self):
        return (f'{self.__class__.__name__}(' +
                ', '.join([f'{n}={getattr(self, n)}'
                           for n, _ in self._fields_]) + ')')

# My version of RECT that can print itself
class RECT(w.RECT, Repr):
    pass

# Error checking for Win32 functions that return BOOL
# and support GetLastError() on failure.
def boolcheck(result, func, args):
    if not result:
        raise ct.WinError(ct.get_last_error())
    return None

# Ensure capturing the last error code directly after the function call
user32 = ct.WinDLL('user32', use_last_error=True)

GetForegroundWindow = user32.GetForegroundWindow
GetForegroundWindow.argtypes = ()
GetForegroundWindow.restype = w.HWND

_GetWindowRect = user32.GetWindowRect
_GetWindowRect.argtypes = w.HWND, ct.POINTER(RECT)
_GetWindowRect.restype = w.BOOL
_GetWindowRect.errcheck = boolcheck
# My preference instead of using prototype()...more control using a wrapper
def GetWindowRect(hwnd):
    r = RECT()
    _GetWindowRect(hwnd, ct.byref(r))  # will now throw exception on failure
    return r

# 获取当前活动窗口的矩形信息
print(GetWindowRect(GetForegroundWindow()))

# 尝试使用无效句柄，预期会抛出异常
try:
    GetWindowRect(None)
except OSError as e:
    print(f"捕获到错误: {e}")

RECT(left=2561, top=400, right=3461, bottom=1437)
捕获到错误: [WinError 1400] 无效的窗口句柄。