title: I want to hide checkboxes on non-leaf nodes in a treegrid (treepanel with columns)
body: <p>In an Ext JS app I have a tree panel with a checkbox column (xtype: 'checkcolumn'). But I only want to display the checkbox on the leaf nodes. In the parent nodes I want to hide the checkboxes (or at least disable them).</p>
  
  <p>How can I achieve this?</p>