title: Checkboxgroup change columns -> re-render
body: <p>I have a checkbox group with predefined</p>
  
  <pre><code>columns : 6,
  </code></pre>
  
  <p>and a resize event</p>
  
  <pre><code>listeners: {
      resize:function( mee, width, height, e, eOpts ) {
          console.log(me.columns);
          console.log(mee.columns);
          mee.columns = Math.floor(width/200);
          // mee.doAutoRender();
          console.log(me.columns);
          console.log(mee.columns);
          console.log('resize');
      }
  </code></pre>
  
  <p>The console logging shows that both me.columns and mee.columns are 6 before and 9 after first resize (full-hd screen -> floor(1920/200)=9)</p>
  
  <p>But I don't know how to enforce a re-rendering. The columns are not changing as I would like them to.</p>