C++语言 填充选区

void CSelRectDlg::OnPaint() 
{
    if (IsIconic())
    {
        CPaintDC dc(this); // device context for painting

        SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

        // Center icon in client rectangle
        int cxIcon = GetSystemMetrics(SM_CXICON);
        int cyIcon = GetSystemMetrics(SM_CYICON);
        CRect rect;
        GetClientRect(&rect);
        int x = (rect.Width() - cxIcon + 1) / 2;
        int y = (rect.Height() - cyIcon + 1) / 2;

        // Draw the icon
        dc.DrawIcon(x, y, m_hIcon);
    }
    else
    {
        CRgn r1, r2, r3;
        bool combin;
        CPaintDC dc(this);
        combin = true;
        CRect rect1(20, 20, 200, 200);
        CRect rect2(150, 20, 330, 200);
        dc.BeginPath();
        dc.Ellipse(&rect1);
        dc.EndPath();
        r1.CreateFromPath(&dc); //创建一个圆形路径
        dc.Ellipse(&rect1); //画出圆形
        dc.BeginPath();
        dc.Ellipse(&rect2);
        dc.EndPath();
        r2.CreateFromPath(&dc);
        dc.Ellipse(&rect2);
        CString str1;
        if(r1.CombineRgn(&r1, &r2, RGN_AND) == NULLREGION) //合并重叠区
            combin = false;
        if(combin == true)
        {
            CBrush br;
            br.CreateSolidBrush(RGB(128, 128, 128));
            dc.FillRgn(&r1, &br);
        }
        CDialog::OnPaint();
    }
}