title: How to display text in main window?
body: <p>I'm new to Qt and I'm having a hard time finding a simple example illustrating how to display some text on the main window. For example, I just want to save some text in a string and display the contents on the main window. I thought to do something like this in the <code>mainwindow.cpp</code> but to no avail. </p>
  
  <pre><code>this-&gt;setText("Hello, world!\n");
  </code></pre>