title: How to bind QMessageBox button to action
body: <p>I created a <code>QMessageBox</code> with Save, Discard and Cancel button:</p>
  
  <pre><code>QMessageBox msgBox;
  msgBox.setText("The document has been modified.");
  msgBox.setInformativeText("Do you want to save your changes?");
  msgBox.setStandardButtons(QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel);
  msgBox.setDefaultButton(QMessageBox::Save);
  msgBox.setIcon(QMessageBox::Question);
  </code></pre>
  
  <p>Now, how can I bind each of these buttons to a specific command?</p>