title: Using QApplication in a non blocking way
body: <p>I want to use 'connect', but if I write </p>
  
  <pre><code>QApplication a(argc, argv);
  connect ....
  a.exec();
  </code></pre>
  
  <p>I get blocked after the last command (<code>a.exec</code>). But if I don't use this command, then the callbacks don't work.</p>
  
  <p>It is important to say that I don't open any window. All I want to work is the 'connect' option. </p>