// 派生自CButton类，主要过滤WM_LBUTTONDOWN 、WM_LBUTTONUP和WM_MOUSEMOVE消息。

BOOL m_bFlag = FALSE; // 成员变量，用来标示鼠标是否按下， 初始化为FALSE
CPoint m_pt; // 成员变量，用来保存当前坐标值

BOOL CXXButton::PreTranslateMessage(MSG* pMsg) 
{
	// TODO: Add your specialized code here and/or call the base class
	switch(pMsg->message)
	{
	case WM_LBUTTONDOWN:
		{
			m_pt = pMsg->pt;
			m_bFlag = TRUE;
		}
		break;

	case WM_LBUTTONUP:
		{
			m_bFlag = FALSE;
		}
		break;

	case WM_MOUSEMOVE:
		{
			if(m_bFlag)
			{
				int cx = pMsg->pt.x - m_pt.x;
				int cy = pMsg->pt.y - m_pt.y;

				CRect rc;
				GetWindowRect(&rc);
				GetParent()->ScreenToClient(&rc);
				int nWidth = rc.Width();
				int nHeight = rc.Height();

				rc.left += cx;
				rc.top += cy;
				rc.right = rc.left + nWidth;
				rc.bottom = rc.top + nHeight;

				MoveWindow(rc);

				m_pt = pMsg->pt;
			}
		}
		break;

	default:
		break;
	}
	return CButton::PreTranslateMessage(pMsg);
}