title: Show context menu for table header and get column index?
body: <p>Is it possible to show a context menu on the header of table column and get the index of the selected column?</p>
  
  <p>I have been having a problem return the index of the selected column in a table.</p>
  
  <ul>
  <li><code>table.getSelectionIndex()</code> returns <code>-1</code></li>
  <li><code>Point point = new Point(event.x, event.y)</code> returns <strong>point {0, 0}</strong></li>
  </ul>
  
  <p>How can this be done?</p>