title: Why doesn't my Qt Creator know QPolygon?
body: <p>I have the following simple code. I just start writing my application and get stuck on this problem: Qt Creator tells me, that QPolygon file or directory doesn't exists. I checked it with QT Documentation and it says, ther is.</p>
  
  <pre><code>#include &lt;QPolygon&gt;
  
  class IHledani
  {
  public:
      virtual IHledani();
      virtual ~IHledani();
  
      virtual QPolygon najdiKonturu(IObraz image, int startx, int starty);
  };
  </code></pre>
  
  <p>Thank you</p>