QT, C# 量算字符串繪製的大小

            //c#量算字符串需要繪製的大小
            IntPtr hWnd = Process.GetCurrentProcess().MainWindowHandle;
            Graphics g = Graphics.FromHwnd(hWnd);

            string strText = new string(cText);

            FontFamily f = new FontFamily("宋體");
            FontStyle fontStyle = FontStyle.Regular;
            Font ft1 = new Font(f, (float)dNewSize, fontStyle);
            SizeF pSize11 = g.MeasureString(strText, ft1);

    //     QPainter m_Painter; 量算字繪製的大小    
    QFont f ("宋體",10);
    m_Painter.setFont(f);
    m_Painter.setPen(QPen());
    int nFlag |= Qt::AlignBottom;
    nFlag |= Qt::AlignLeft;
    QRect rect = m_Painter.boundingRect(rect,nFlag,QString(strText));