ClientToScreen 和ScreenToClient用法

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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