title: QT QMainWindow fullscreen without borders
body: <p>How to do a fullscreen without borders using QMainWindow ? I got a fullscreen including window borders all around the screen. I would like to have a "real" fullscreen like video games. Not a windowed fullscreen.</p>
  
  <p>I tried:</p>
  
  <pre><code>MainWindow mainWindow;
  mainWindow.setWindowState(Qt::WindowFullScreen);
  mainWindow.showFullScreen();
  </code></pre>
  
  <p>MainWindow extend of QMainWindow.</p>