title: Take action after the main form is shown in a Qt desktop application
body: <p>In Delphi I often made an <code>OnAfterShow</code> event for the main form.  The standard <code>OnShow()</code> for the form would have little but a <code>postmessage()</code> which would cause the <code>OnafterShow</code> method to be executed.</p>
  
  <p>I did this so that sometimes lengthy data loading or initializations would not stop the normal loading and showing of the main form.</p>
  
  <p>I'd like to do something similar in a Qt application that will run on a desktop computer either Linux or Windows.</p>
  
  <p>What ways are available to me to do this?</p>