Python Win32 APIでウインドウをつくる

実際のところ、Pythonでこれをやる意味は皆無ですが...
WinMainで始まるWindowsプログラムそのものをPythonでつくってみます。
以下のサンプルプログラムをPythonに直します。

Win32 APIで避けて通れないのは、独特な型と複雑な構造体です。
ウインドウメッセージの構造体MSGは、

winuser.h

typedef struct tagMSG {
    HWND        hwnd;
    UINT        message;
    WPARAM      wParam;
    LPARAM      lParam;
    DWORD       time;
    POINT       pt;
} MSG, *PMSG, NEAR *NPMSG, FAR *LPMSG;

Pythonでは以下のようにして(自分で)定義します。

class MSG(Structure):
    _fields_ = [
        ("hwnd", c_void_p),
        ("message", c_int),
        ("wParam", POINTER(c_int)),
        ("lParam", POINTER(c_int)),
        ("time", c_int),
        ("pt", POINT)]

ハンドル(HWND)はポインタなのでc_void_p、他はとりあえずc_intと考えればよいです。
WPARAM,LPARAMはc_intにするとaccess violationになったので、POINTER(c_int)としました。
POINTはWindowsで定義されている構造体です。
このようにして、必要なすべての構造体と定数を定義しておいて(ctypes_windows.py)

from ctypes_windows import *

def WindowProc(hwnd, uMsg, wParam, lParam):
    if uMsg == WM_DESTROY:
        PostQuitMessage(0)
        return 0
    elif uMsg == WM_PAINT:
        ps = PAINTSTRUCT()
        hdc = BeginPaint(hwnd, pointer(ps))
        FillRect(hdc, pointer(ps.rcPaint), c_void_p(COLOR_WINDOW))
        EndPaint(hwnd, pointer(ps))
        return 0
    return DefWindowProc(hwnd, uMsg, wParam, lParam)

def WinMain():
    hInstance = GetModuleHandle(None)

    CLASS_NAME = create_string_buffer(b"Sample Window Class")

    wc = WNDCLASS()
    wc.lpfnWndProc = WNDPROC(WindowProc)
    wc.hInstance = hInstance
    wc.lpszClassName = CLASS_NAME

    RegisterClass(pointer(wc))

    lpWindowName = create_string_buffer(b"Learn to Program Windows")
    hwnd = CreateWindowEx(0, CLASS_NAME, lpWindowName, WS_OVERLAPPEDWINDOW,
                          CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
                          None, None, hInstance, None)
    if hwnd == None:
        raise Exception

    ShowWindow(hwnd, SW_SHOWNORMAL)

    msg = MSG()
    while (GetMessage(pointer(msg), None, 0, 0)):
        TranslateMessage(pointer(msg))
        DispatchMessage(pointer(msg))

if __name__ == "__main__":
    WinMain()

実行結果

構造体と定数

ctypes_windows.py

from ctypes import *

GetModuleHandle = windll.kernel32.GetModuleHandleA
RegisterClass = windll.user32.RegisterClassA
CreateWindowEx = windll.user32.CreateWindowExA
ShowWindow = windll.user32.ShowWindow
GetMessage = windll.user32.GetMessageA
TranslateMessage = windll.user32.TranslateMessage
DispatchMessage = windll.user32.DispatchMessageA
DefWindowProc = windll.user32.DefWindowProcA
PostQuitMessage = windll.user32.PostQuitMessage
BeginPaint = windll.user32.BeginPaint
FillRect = windll.user32.FillRect
EndPaint = windll.user32.EndPaint

WNDPROC = WINFUNCTYPE(c_int, c_void_p, c_int, POINTER(c_int), POINTER(c_int))

class WNDCLASS(Structure):
    _fields_ = [
        ("style", c_int),
        ("lpfnWndProc", WNDPROC),
        ("cbClsExtra", c_int),
        ("cbWndExtra", c_int),
        ("hInstance", c_void_p),
        ("hIcon", c_void_p),
        ("hCursor", c_void_p),
        ("hbrBackground", c_void_p),
        ("lpszMenuName", POINTER(c_char)),
        ("lpszClassName", POINTER(c_char))]

class POINT(Structure):
    _fields_ = [
        ("x", c_int),
        ("y", c_int)]

class MSG(Structure):
    _fields_ = [
        ("hwnd", c_void_p),
        ("message", c_int),
        ("wParam", c_int),
        ("lParam", c_int),
        ("time", c_int),
        ("pt", POINT)]

class RECT(Structure):
    _fields_ = [
        ("left", c_int),
        ("top", c_int),
        ("right", c_int),
        ("bottom", c_int)]

class PAINTSTRUCT(Structure):
    _fields_ = [
        ("hdc", c_void_p),
        ("fErase", c_int),
        ("rcPaint", RECT),
        ("fRestore", c_int),
        ("fIncUpdate", c_int),
        ("rgbReserved", c_char*32)]

WS_OVERLAPPED       = 0x00000000
WS_POPUP            = 0x80000000
WS_CHILD            = 0x40000000
WS_MINIMIZE         = 0x20000000
WS_VISIBLE          = 0x10000000
WS_DISABLED         = 0x08000000
WS_CLIPSIBLINGS     = 0x04000000
WS_CLIPCHILDREN     = 0x02000000
WS_MAXIMIZE         = 0x01000000
WS_CAPTION          = 0x00C00000
WS_BORDER           = 0x00800000
WS_DLGFRAME         = 0x00400000
WS_VSCROLL          = 0x00200000
WS_HSCROLL          = 0x00100000
WS_SYSMENU          = 0x00080000
WS_THICKFRAME       = 0x00040000
WS_GROUP            = 0x00020000
WS_TABSTOP          = 0x00010000
WS_MINIMIZEBOX      = 0x00020000
WS_MAXIMIZEBOX      = 0x00010000
WS_OVERLAPPEDWINDOW = (WS_CAPTION | WS_SYSMENU | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX)

CW_USEDEFAULT = 0x80000000
SW_SHOWNORMAL = 10

WM_CREATE = 0x0001
WM_DESTROY = 0x0002
WM_COMMAND = 0x0111
WM_PAINT = 0x000f

COLOR_WINDOW = 5