title: QCompleter and Tab key
body: <p>I'm trying to make a Completion when pressing tab, you get the first completion of all possibilities.</p>
  
  <p>But, in a <code>QWidget</code>-based main window, pressing tab will make that <code>QLineEdit</code> lost focus, and completion popup hides after that.</p>
  
  <p>Is there a way to fix it ? </p>