学习windows编程 day5 之 区域裁剪

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
    static int cxClient, cyClient;
    HRGN hRgn[];
    static HRGN hTotRgn;
    double fAngle, fRadius;
    HCURSOR hCursor;

    switch (message)
    {
    case WM_SIZE:
        cxClient = LOWORD(lParam);
        cyClient = HIWORD(lParam);

        hCursor = SetCursor(LoadCursor(NULL, IDC_WAIT));
        ShowCursor(TRUE);

        //创建四个区域
        //先左右两个
        hRgn[]=CreateEllipticRgn(, cyClient / , cxClient / , cyClient *  / );
        hRgn[] = CreateEllipticRgn(cxClient, cyClient / , cxClient / , cyClient *  / );
        //后上下两个
        hRgn[] = CreateEllipticRgn(cxClient / , , cxClient *  / , cyClient / );
        hRgn[] = CreateEllipticRgn(cxClient / , cyClient/, cxClient *  / , cyClient);
        //其余的先设为一个较小的区域（空）
        hRgn[] = CreateEllipticRgn(, , , );
        hRgn[] = CreateEllipticRgn(, , , );
        hTotRgn = CreateEllipticRgn(, , , );
        //调用combinRgn后原来这些区域会被销毁

        //先合并左右
        CombineRgn(hRgn[], hRgn[], hRgn[], RGN_OR);
        CombineRgn(hRgn[], hRgn[], hRgn[], RGN_OR);

        //合并为一个总区域句柄
        CombineRgn(hTotRgn, hRgn[], hRgn[], RGN_XOR);

        for (int i = ; i < ; i++)
            DeleteObject(hRgn[i]);

        SetCursor(hCursor);
        ShowCursor(TRUE);
        break;
    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        GetClientRect(hwnd, &rect);

        SetViewportOrgEx(hdc, cxClient / , cyClient / , NULL);
        //选中剪切区域后，会在这个区域作图
        SelectClipRgn(hdc, hTotRgn);

        FrameRgn(hdc, hTotRgn, (HBRUSH)GetStockObject(BLACK_BRUSH),,);

        //内部画阴影
        fRadius = _hypot(cxClient / , cyClient / );//直角三角形斜边

        for (fAngle = 0.0; fAngle < PI * ;fAngle += PI*/)
        {
            MoveToEx(hdc, , , NULL);
            LineTo(hdc, (int)(fRadius*cos(fAngle) + 0.5), (int)(-fRadius*sin(fAngle) + 0.5));
        }

        EndPaint(hwnd, &ps);
        break;
    case WM_DESTROY:
        DeleteObject(hTotRgn);
        PostQuitMessage();
        return ;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}