Unify Windows message handling APIs in messageloop.py. (#932)

* refactor: Eliminates the alias `LRESULT = LPLONG` by directly importing `LPLONG` as `LRESULT` from `ctypes.wintypes`.

* refactor: Streamline `test_eventinterface.py` imports by using `ctypes.wintypes.MSG`

- Removes redundant `POINT` and `MSG` structure definitions.
- Directly imports `MSG` from `ctypes.wintypes`, simplifying the import statements.
- Reduces boilerplate code and improves consistency by leveraging standard
  `wintypes` definitions.

* refactor: Explicitly define WinAPI function signatures in `messageloop.py`.

- Adds `argtypes` and `restype` for `GetMessage`, `TranslateMessage`, and
  `DispatchMessage`.

* refactor: Use `POINTER(MSG)` for message function `argtypes` in `messageloop.py`

* refactor: Use `HWND` for window handle in `GetMessage` argtypes in `messageloop.py`

* refactor: Centralize `PeekMessage` in `messageloop.py` and reuse in tests.

- Define `PeekMessage` with `argtypes` and `restype` in `messageloop.py`.
- Update `test_eventinterface.py` and `test_git.py` to use `PeekMessage` and
  others from `messageloop`, removing redundant WinAPI definitions.

* refactor: Centralize `PeekMessage` constants in `messageloop.py`.

- Add `PM_NOREMOVE`, `PM_REMOVE`, and `PM_NOYIELD` constants to
  `messageloop.py`.
- Update `test_eventinterface.py` and `test_git.py` to import `PM_REMOVE`
  from `messageloop`, removing redundant local definitions.

Author: junkmd

comtypes/messageloop.py

@@ -1,6 +1,7 @@
 import ctypes
-from ctypes import WinDLL, WinError, byref
-from ctypes.wintypes import MSG
+from ctypes import POINTER, WinDLL, WinError, byref
+from ctypes.wintypes import BOOL, HWND, MSG
+from ctypes.wintypes import LPLONG as LRESULT
 from typing import TYPE_CHECKING, SupportsIndex
 
 if TYPE_CHECKING:
@@ -10,12 +11,29 @@
 
     _FilterCallable = Callable[["_CArgObject"], Iterable[Any]]  # type: ignore
 
+# PeekMessage options
+PM_NOREMOVE = 0x0000
+PM_REMOVE = 0x0001
+PM_NOYIELD = 0x0002
+
 _user32 = WinDLL("user32")
 
 GetMessage = _user32.GetMessageA
-GetMessage.argtypes = [ctypes.c_void_p, ctypes.c_void_p, ctypes.c_uint, ctypes.c_uint]
+GetMessage.argtypes = [POINTER(MSG), HWND, ctypes.c_uint, ctypes.c_uint]
+GetMessage.restype = BOOL
+
 TranslateMessage = _user32.TranslateMessage
+TranslateMessage.argtypes = [POINTER(MSG)]
+TranslateMessage.restype = BOOL
+
 DispatchMessage = _user32.DispatchMessageA
+DispatchMessage.argtypes = [POINTER(MSG)]
+DispatchMessage.restype = LRESULT
+
+# https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-peekmessagea
+PeekMessage = _user32.PeekMessageA
+PeekMessage.argtypes = [POINTER(MSG), HWND, ctypes.c_uint, ctypes.c_uint, ctypes.c_uint]
+PeekMessage.restype = BOOL
 
 
 class _MessageLoop:

comtypes/test/test_eventinterface.py

@@ -1,8 +1,14 @@
 import unittest as ut
-from ctypes import POINTER, Structure, WinDLL, byref, c_long, c_uint, c_ulong
-from ctypes.wintypes import BOOL, HWND, LPLONG, UINT
+from ctypes import byref
+from ctypes.wintypes import MSG
 
 from comtypes.client import CreateObject, GetEvents
+from comtypes.messageloop import (
+    PM_REMOVE,
+    DispatchMessage,
+    PeekMessage,
+    TranslateMessage,
+)
 
 # FIXME: External test dependencies like this seem bad.  Find a different
 # built-in win32 API to use.
@@ -42,42 +48,11 @@ def DocumentComplete(self, this, *args):
         self._events.append("DocumentComplete")
 
 
-class POINT(Structure):
-    _fields_ = [("x", c_long), ("y", c_long)]
-
-
-class MSG(Structure):
-    _fields_ = [
-        ("hWnd", c_ulong),
-        ("message", c_uint),
-        ("wParam", c_ulong),
-        ("lParam", c_ulong),
-        ("time", c_ulong),
-        ("pt", POINT),
-    ]
-
-
 def PumpWaitingMessages():
-    _user32 = WinDLL("user32")
-
-    _PeekMessageA = _user32.PeekMessageA
-    _PeekMessageA.argtypes = [POINTER(MSG), HWND, UINT, UINT, UINT]
-    _PeekMessageA.restype = BOOL
-
-    _TranslateMessage = _user32.TranslateMessage
-    _TranslateMessage.argtypes = [POINTER(MSG)]
-    _TranslateMessage.restype = BOOL
-
-    LRESULT = LPLONG
-    _DispatchMessageA = _user32.DispatchMessageA
-    _DispatchMessageA.argtypes = [POINTER(MSG)]
-    _DispatchMessageA.restype = LRESULT
-
     msg = MSG()
-    PM_REMOVE = 0x0001
-    while _PeekMessageA(byref(msg), 0, 0, 0, PM_REMOVE):
-        _TranslateMessage(byref(msg))
-        _DispatchMessageA(byref(msg))
+    while PeekMessage(byref(msg), 0, 0, 0, PM_REMOVE):
+        TranslateMessage(byref(msg))
+        DispatchMessage(byref(msg))
 
 
 class Test(ut.TestCase):

comtypes/test/test_git.py

@@ -7,7 +7,7 @@
 from _ctypes import COMError
 from collections.abc import Iterator
 from ctypes import HRESULT, POINTER, OleDLL, WinDLL, byref
-from ctypes.wintypes import BOOL, DWORD, HANDLE, HWND, MSG, UINT
+from ctypes.wintypes import BOOL, DWORD, HANDLE, MSG
 from pathlib import Path
 from queue import Queue
 
@@ -18,16 +18,16 @@
     RegisterInterfaceInGlobal,
     RevokeInterfaceFromGlobal,
 )
-from comtypes.messageloop import DispatchMessage, TranslateMessage
+from comtypes.messageloop import (
+    PM_REMOVE,
+    DispatchMessage,
+    PeekMessage,
+    TranslateMessage,
+)
 from comtypes.persist import STGM_READ, IPersistFile
 
 _user32 = WinDLL("user32")
 
-# https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-peekmessagea
-PeekMessage = _user32.PeekMessageA
-PeekMessage.argtypes = [POINTER(MSG), HWND, UINT, UINT, UINT]
-PeekMessage.restype = BOOL
-
 # https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-msgwaitformultipleobjects
 MsgWaitForMultipleObjects = _user32.MsgWaitForMultipleObjects
 MsgWaitForMultipleObjects.restype = DWORD
@@ -49,8 +49,6 @@
 
 QS_ALLINPUT = 0x04FF  # All message types including SendMessage
 
-PM_REMOVE = 0x0001  # Remove message from queue after Peek
-
 APTTYPE_MAINSTA = 3
 
 RPC_E_WRONG_THREAD = -2147417842  # 0x8001010E