void CDocViewView::OnLButtonUp(UINT nFlags, CPoint point) 
{
	// TODO: Add your message handler code here and/or call default
	m_bMouseDown = false;
	ReleaseCapture();
	ClipCursor( NULL );
	CClientDC dc(this);
	dc.SetROP2( R2_NOT );
	dc.MoveTo( m_ptStart );       //д(갴µ)
	dc.LineTo( m_ptOld );          //ϴƶλ֮ʱ   
	dc.SetROP2( R2_COPYPEN );
	dc.MoveTo( m_ptStart );      //д㵽굱ǰλû
	dc.LineTo( point );                //
	SetCursor(m_hArrow);          //״Ϊ׼ͷ
	CView::OnLButtonUp(nFlags, point);
}
