internal void ProcessMouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == System.Windows.Forms.MouseButtons.Left)
            {
                if (m_zoomTool.Enabled)
                {
                    m_zoomTool.Begin(new Point(e.X, e.Y));
                }
                else if (m_panTool.Enabled)
                {
                    m_panTool.Begin(new Point(e.X, e.Y));
                }

                /*      else if ((Control.ModifierKeys & Keys.Control) != Keys.None) {
                 *        SetZoom(m_magnification / 1.5f, true);
                 *    }
                 *    else if ((Control.ModifierKeys & Keys.Shift) != Keys.None) {
                 *        SetZoom(m_magnification * 1.5f, true);
                 *    }*/
                else
                {
                    m_session.GuiInput_MouseDown(sender, e);
                }
            }
        }