MFC双缓冲

//在缓冲区作图，最后将缓冲区数据一次全部拷贝至目标DC
void CDoubleBufferView::DrawEx(CDC* pDC)
{
    CRect rect;
    GetClientRect(rect);

    //创建兼容当前DC的缓冲DC
    CDC cacheDC;
    cacheDC.CreateCompatibleDC(pDC);

    //创建兼容当前DC的位图
    CBitmap bitmap;
    bitmap.CreateCompatibleBitmap(pDC, rect.Width(), rect.Height());

    //将位图选入到缓冲DC
    CBitmap* pOldBitmap = cacheDC.SelectObject(&bitmap);

    //填充缓冲DC的背景(默认是黑色)
    cacheDC.FillSolidRect(0, 0, rect.Width(), rect.Height(), RGB(255, 255, 255));

    //在缓冲DC中画图
    int x = 0;
    int y = 0;
    int step = 2;
    int idx = 0;

    while (idx++ < 10000)
    {
        cacheDC.MoveTo(x, y);
        cacheDC.LineTo(rect.Width() - x, y);
        cacheDC.LineTo(rect.Width() - x, rect.Height() - y);
        x += step;
        cacheDC.LineTo(x, rect.Height() - y);
        y += step;
    }

    //将缓冲DC输出到当前DC
    pDC->BitBlt(0, 0, rect.Width(), rect.Height(), &cacheDC, 0, 0, SRCCOPY);

    //选回旧的bitmap
    cacheDC.SelectObject(pOldBitmap);

    //释放资源
    bitmap.DeleteObject();
    cacheDC.DeleteDC();
}

//直接在DC上作图
void CDoubleBufferView::Draw(CDC* pDC)
{
    CRect rect;
    GetClientRect(rect);

    //在缓冲DC中画图
    int x = 0;
    int y = 0;
    int step = 2;
    int idx = 0;
    while (idx++ < 10000)
    {
        pDC->MoveTo(x, y);
        pDC->LineTo(rect.Width() - x, y);
        pDC->LineTo(rect.Width() - x, rect.Height() - y);
        x += step;
        pDC->LineTo(x, rect.Height() - y);
        y += step;
    }
}