MSAA的全称是Microsoft Active Accessibility。这是类似DCOM技术。技术模型是这样的，UI程序可以暴露出一个Interface，方便另一个程序对其进行控制。 MSAA技术的初衷是为了方便残疾人使用Windows 程序。比如盲人看不到窗口，但是盲人可以通过一个USB读屏器连接到电脑上， 读屏器通过UI程序暴露出来的这个Interface，就可以获取程序信息，通过盲文或者其它形式传递给盲人。
MSAA提供了如此方便的功能， UI自动化测试自然可以借用这项技术。MSAA暴露出来的Interface叫做 IAccessible。Python中获取IAccessible接口的方法如下：
from ctypes import windll, oledll, WinError, byref, POINTER
from ctypes.wintypes import POINT
from comtypes import COMError
from comtypes.automation import VARIANT
from comtypes.client import GetModule
# create wrapper for the oleacc.dll type library
GetModule("oleacc.dll")
# import the interface we need from the wrapper
from comtypes.gen.Accessibility import IAccessible
def AccessibleObjectFromPoint(x, y):
"Return an accessible object and an index. See MSDN for details."
pacc = POINTER(IAccessible)()
var = VARIANT()
oledll.oleacc.AccessibleObjectFromPoint(POINT(x, y), byref(pacc),
byref(var))
return pacc, var
def AccessibleObjectFromWindow(hwnd):
ptr = POINTER(IAccessible)()
res = oledll.oleacc.AccessibleObjectFromWindow(
hwnd,0,
byref(IAccessible._iid_),byref(ptr))
return ptr
from ctypes.wintypes import POINT
from comtypes import COMError
from comtypes.automation import VARIANT
from comtypes.client import GetModule
# create wrapper for the oleacc.dll type library
GetModule("oleacc.dll")
# import the interface we need from the wrapper
from comtypes.gen.Accessibility import IAccessible
def AccessibleObjectFromPoint(x, y):
"Return an accessible object and an index. See MSDN for details."
pacc = POINTER(IAccessible)()
var = VARIANT()
oledll.oleacc.AccessibleObjectFromPoint(POINT(x, y), byref(pacc),
byref(var))
return pacc, var
def AccessibleObjectFromWindow(hwnd):
ptr = POINTER(IAccessible)()
res = oledll.oleacc.AccessibleObjectFromWindow(
hwnd,0,
byref(IAccessible._iid_),byref(ptr))
return ptr