title: Mandatory fields in Wizard
body: <p>I have created a wizard using the GUI and so my pages are all part of the UI.</p>
  
  <p>Now, on one of the pages I want to make the fields mandatory. From looking into the API it appears there is a <code>registerField()</code> function which can also make sure the next button isn't available until the fields are filled in. However, that function is protected to <code>QWizardPage</code> which means I cannot set this up. Is there a way to carry out this behaviour without needing to create a new class?</p>
  
  <p>I know I can create a new class but I am considering if I create even more pages then I would need to create classes for every page I have. I also thought for sucha  simple case it felt a bit like overkill.</p>