title: How to keep Sencha Ext.Msg from closing on button click
body: <p>So i Have a Message box I built to be able to send a message. It has 2 inputs, and an OK and Cancel buttons. I can access the contents and do the normal logic quite easily how I set it up:</p>
  
  <pre><code>Ext.Msg.show({
          title: 'Send a Message: ',
          cls: 'MessageBox',
          html: '&lt;div class="message-InnerContainer" &gt;' +
              '&lt;input type="text" id="messageBoxSubject" placeholder="Subject" class="messageBox-Input"/&gt;' +
              '&lt;textarea id="messageBoxMessage" placeholder="Message" class="messageBox-TextArea"&gt;&lt;/textarea&gt;' +
              '&lt;div&gt;',
          closable: false,
          buttons: [
              { no: 'Cancel', text:'Cancel', cls:'messageBox-CancelButton'},
              { yes: 'OK', text:'Ok', cls:'messageBox-OkButton'}
          ],
          fn: function (btn) {
              if (btn == 'ok') {
                  //do success logic
              }
              else (){
                  //do failure logic
              }
          }
      });
  </code></pre>
  
  <p>There is only one problem: I can't seem to find a way to keep the box from auto closing when OK is pressed. Ideally I would like to run a quick check to ensure that the two inputs are not empty. I think I might just be able to override buttons by placing custom buttons in the html section, but if there is a way to halt the auto closing it would be more syntactically pleasing and readable. Does anyone know if its possible?</p>