title: Add QWidget on top of QOpenGLWindow
body: <p>I want to add QWidget on top of my QOpenGLWindow. For example:</p>
  
  <p>In qmainwindow.cpp:</p>
  
  <pre><code>QWidget *mywidget = new QWidget(this);
  mywidget-&gt;hide();
  
  QOpenGLWindow *glwindow = new QOpenGLWindow();
  QWidget *container = QWidget::createWindowContainer(glwindow, this);
  
  // ...
  
  ui-&gt;tabWidget-&gt;addTab(container, "Container");
  
  // then I want mywidget to be at the top of my tabWidget and container.
  mywidget-&gt;show();
  </code></pre>
  
  <p>But <strong>mywidget</strong> is behind the <strong>container</strong>.</p>
  
  <p>How can I solve this problem?</p>