畫個紅叉否定Windows

這個是看別人的代碼得到的，不是我寫的。

void CHhDlg::OnOK()
{
  //先得到螢幕的長寬：
  int ScreenWidth = ::GetSystemMetrics(SM_CXSCREEN);
  int ScreenHeight = ::GetSystemMetrics(SM_CYSCREEN);
  HDC hDC = ::GetDC(0);
  //得到“畫布(Canvas)”
  CDC* ScreenCanvas = new CDC();
  ScreenCanvas->m_hDC = hDC;
  //設定畫布的畫筆(Pen)
  CPen pen(1, 10, RGB(255,0,0));
  CPen* oldpen;
  oldpen=ScreenCanvas->SelectObject(&pen);
  //ScreenCanvas->Pen->Color = clRed;  //畫筆的顏色為紅色(Red)
  //ScreenCanvas->Pen->Width = 10;     //畫筆的粗細
  //開始畫叉啦，需要畫兩筆,這是第一筆：左上到右下
  ScreenCanvas->MoveTo(0,0);        //把畫筆移到(Move to)座標0，0處，即螢幕最左上方
  ScreenCanvas->LineTo(ScreenWidth,ScreenHeight);  //從當前位置畫一條線(Line to)到螢幕的右下角。

  //第二筆：右上到左下：
  ScreenCanvas->MoveTo(ScreenWidth,0);
  ScreenCanvas->LineTo(0,ScreenHeight);

  ScreenCanvas->SelectObject(oldpen);
  //釋放“畫布”:
 
  ScreenCanvas->m_hDC = 0;
 
  delete ScreenCanvas;
  ::ReleaseDC(0,hDC);

  //CDialog::OnOK();
}

點擊這裡看圖