ClientToScreen 和ScreenToClient

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转载地址：http://blog.csdn.net/sding/article/details/4481786

ClientToScreen( )是把窗口坐标转换为屏幕坐标
ScreenToClient( )是把屏幕坐标转换为窗口坐标
屏幕坐标是相对于屏幕左上角的，而窗口坐标是相对于窗口用户区左上角的
VC下，有些函数使用窗口坐标，有些使用屏幕坐标，使用时要分清。

一个窗体分为两部分：系统区和客户区
象标题和菜单之类的是系统区，由系统来控制，客户区就是你的地盘喽！！！
Width, Height 是指整体的，ClientWidth, ClientHeight是指客户区的，两者相减就是
系统区的啦！！！
ClientToScreen是把坐标从当前窗体转化成全屏幕的！！！
ScreenToClient是把屏幕坐标转化成相对当前窗体的坐标！！！！

bool   m_bIsLButtonDawn  = false ;

void  CDrawDlg::OnMouseMove(UINT nFlags, CPoint point)
{
   //  TODO: Add your message handler code here and/or call default
  CWnd  * pwnd = GetDlgItem(IDC_EDIT1);
     CDC  * pdc = pwnd -> GetDC();
  CRect rect;
   this -> ClientToScreen( & point);
  pwnd -> ScreenToClient( & point);
  pwnd -> GetClientRect( & rect);

//   HCURSOR hcur=::LoadCursorFromFile("pen.cur");
   //   SetClassLong(GetSafeHwnd(),GCL_HCURSOR,(LONG)hcur);

//  CPen pen(PS_INSIDEFRAME,-1,RGB(255,255,255));
//      CPen* olePen=pdc->SelectObject(&pen);
   if (rect.PtInRect(point)  &&   m_bIsLButtonDawn )
   {

   pdc -> DPtoLP( & m_fp);
   pdc -> MoveTo(m_fp);
   pdc -> DPtoLP( & point);
   pdc -> LineTo(point);

  }
   m_fp = point;
//   pdc->SelectObject(olePen);
  ReleaseDC(pdc);
  CDialog::OnMouseMove(nFlags, point);
}

void  CDrawDlg::OnLButtonUp(UINT nFlags, CPoint point)
{
   m_bIsLButtonDawn  = false ;
   //  TODO: Add your message handler code here and/or call default
/*
    CWnd *pwnd=GetDlgItem(IDC_EDIT1);
      CDC *pdc=pwnd->GetDC();
   CRect rect;
   this->ClientToScreen(&point);
   pwnd->ScreenToClient(&point);
   pwnd->GetClientRect(&rect);

   if(rect.PtInRect(point))
   {
    pdc->DPtoLP(&m_fp);
    pdc->MoveTo(m_fp);
    pdc->DPtoLP(&point);
    pdc->LineTo(point);

   }
   ReleaseDC(pdc); */

  CDialog::OnLButtonUp(nFlags, point);
}

void  CDrawDlg::OnLButtonDown(UINT nFlags, CPoint point)
{
   //  TODO: Add your message handler code here and/or call default
  CWnd  * pwnd = GetDlgItem(IDC_EDIT1);
  CDC  * pDC = pwnd -> GetDC();
  CRect rect;
   this -> ClientToScreen( & point);
  pwnd -> ScreenToClient( & point);
  pwnd -> GetClientRect( & rect);
   if (rect.PtInRect(point))
   {
   m_fp.x = point.x;
   m_fp.y = point.y;
  }
  ReleaseDC(pDC);
   m_bIsLButtonDawn  = true ;
  CDialog::OnLButtonDown(nFlags, point);
}

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