title: Alternative of cvGetWindowHandle() in opencv4+
body: <p>I am using Opencv3.4.8 in my MFC application. I am using cvGetWindowHandle() to get the handle of the window as follows;</p>
  
  <pre><code>namedWindow(windowname, WINDOW_AUTOSIZE);
  HWND hWnd = (HWND) cvGetWindowHandle(windowname.c_str());
  HWND hParent = ::GetParent(hWnd);
  ::SetParent(hWnd, GetDlgItem(IDC_PICTURE)-&gt;m_hWnd);
  ::ShowWindow(hParent, SW_HIDE);
  CWnd* pWnd = new CWnd();
  pWnd-&gt;CWnd::Attach(hParent);
  </code></pre>
  
  <p>Now I want to upgrade to Opencv4+ and there is no cvGetWindowHandle() in Opencv4+. I want to know if there is an alternative function in Opencv4+ and if not how can I do the same task in opencv4+.</p>