Windows Programming, SDK-Style - Bài vẽ hình elipse trong VS2008

#include <windows.h>

LONG WINAPI WndProc (HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpszCmdLine, int nCmdShow)
{
    WNDCLASS wc;
    HWND hwnd;
    MSG msg;

    wc.style = 0;                                   // Class style
    wc.lpfnWndProc = (WNDPROC) WndProc;             // Window procedure address
    wc.cbClsExtra = 0;                              // Class extra bytes
    wc.cbWndExtra = 0;                              // Window extra bytes
    wc.hInstance = hInstance;                       // Instance handle
    wc.hIcon = LoadIcon (NULL, IDI_WINLOGO);        // Icon handle
    wc.hCursor = LoadCursor (NULL, IDC_ARROW);      // Cursor handle
    wc.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1); // Background color
    wc.lpszMenuName = NULL;                         // Menu name
    wc.lpszClassName = "MyWndClass";                // WNDCLASS name

    RegisterClass (&wc);
    

    hwnd = CreateWindow (
        "MyWndClass",               // WNDCLASS name
        "SDK Application",          // Window title
        WS_OVERLAPPEDWINDOW,        // Window style
        CW_USEDEFAULT,              // Horizontal position
        CW_USEDEFAULT,              // Vertical position        
        CW_USEDEFAULT,              // Initial width
        CW_USEDEFAULT,              // Initial height
        HWND_DESKTOP,               // Handle of parent window
        NULL,                       // Menu handle
        hInstance,                  // Application's instance handle
        NULL                        // Window-creation data
    );

    ShowWindow (hwnd, nCmdShow);
    UpdateWindow (hwnd);

    while (GetMessage (&msg, NULL, 0, 0)) {
        TranslateMessage (&msg);
        DispatchMessage (&msg);
    }
    return msg.wParam;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam,
    LPARAM lParam)
{
    PAINTSTRUCT ps;
    HDC hdc;

    switch (message) {
    
    case WM_PAINT:
        hdc = BeginPaint (hwnd, &ps);
        Ellipse (hdc, 0, 0, 200, 100);
        EndPaint (hwnd, &ps);
        return 0;

    case WM_DESTROY:
        PostQuitMessage (0);
        return 0;
    }
    return DefWindowProc (hwnd, message, wParam, lParam);
}