为什么不拨打LineTo＆amp; SetPixel画什么？

Question

我编写了一个简单的MFC应用程序来在对话框中绘制多边形，complete code being here。

代码打开一个对话框，默认标准灰色背景，定义

std::vector<CPoint> m_LeftPolygon;

然后执行以下操作：

void DrawPitons(std::vector<CPoint> points, COLORREF rgbColor, HDC hDC)
{
    static unsigned short XDiff[7] = { 5,4,4,3,2,1,0 },
                          YDiff[7] = { 0,1,2,3,4,4,5 };

    for (unsigned pnt = 0; pnt < points.size(); pnt++)
    {
        SetPixel(hDC, points[pnt].x, points[pnt].y, rgbColor);

        for (unsigned short i = 0; i < 7; i++)
        {
            SetPixel(hDC, points[pnt].x + XDiff[i], points[pnt].y + YDiff[i], rgbColor);
            SetPixel(hDC, points[pnt].x + XDiff[i], points[pnt].y - YDiff[i], rgbColor);
            SetPixel(hDC, points[pnt].x - XDiff[i], points[pnt].y + YDiff[i], rgbColor);
            SetPixel(hDC, points[pnt].x - XDiff[i], points[pnt].y - YDiff[i], rgbColor);
        }
    }
}

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

        SendMessage(WM_ICONERASEBKGND, reinterpret_cast<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
    {
        CPaintDC dc(this);          // device context for painting
        HDC hDC = dc.GetSafeHdc();

        HPEN hPen = CreatePen(PS_SOLID, 1, RGB(255, 0, 0)),
             oldPen = (HPEN)SelectObject(hDC, hPen);

        SetROP2(hDC, R2_COPYPEN);

        // Draw the polygon
        if (m_LeftPolygon.size() > 1)
        {
            BOOL stat = MoveToEx(hDC, (int)m_LeftPolygon[0].x, (int)m_LeftPolygon[0].y, NULL);

            for (size_t index = 1; index < m_LeftPolygon.size(); index++)
                stat = LineTo(hDC, (int)m_LeftPolygon[index].x, (int)m_LeftPolygon[index].y);

            stat = LineTo(hDC, (int)m_LeftPolygon[0].x, (int)m_LeftPolygon[0].y);
        }

        // Draw the control points
        DrawPitons(m_LeftPolygon, RGB(255, 0, 0), hDC);

        SelectObject(hDC, oldPen);
        DeleteObject(hPen);
    }
}

void CROIDlg::OnLButtonUp(UINT nFlags, CPoint point)
{
    m_LeftPolygon.push_back(point);

    SendMessage(WM_PAINT);
}

出于某种原因，没有画出任何东西，但我希望在灰色背景上用红色绘制岩钉和连接线。

我错过了什么？