internal void ProcessMouseMove(object sender, MouseEventArgs e)
        {
            //if left button is down

            if (m_zoomTool.Enabled && !Control.ModifierKeys.HasFlag(Keys.Shift))
            {
                m_zoomTool.Enabled = false;
            }

            if (m_panTool.Enabled && !Control.ModifierKeys.HasFlag(Keys.Alt))
            {
                m_panTool.Enabled = false;
            }

            if ((Control.MouseButtons & System.Windows.Forms.MouseButtons.Left) != System.Windows.Forms.MouseButtons.None)
            {
                if (m_zoomTool.Enabled)
                {
                    m_zoomTool.Move(new Point(e.X, e.Y));
                }
                else if (m_panTool.Enabled)
                {
                    m_panTool.Move(new Point(e.X, e.Y));
                }
                else
                {
                    m_session.GuiInput_MouseMove(sender, e);
                }
            }
        }