客户区也能移动整个窗口实现

void CMainFrame::OnLButtonDown(UINT nFlags, CPoint point)
{
    if (!IsZoomed() && !IsIconic())
    {
        SendMessage(WM_NCLBUTTONDOWN, HTCAPTION, MAKELPARAM(point.x, point.y));
    }
   
    CUIWnd::OnLButtonDown(nFlags, point);
}