Question

I tried this:

renderer : function( strValue, oMetaData, oRecord ) {
  var i;
  if( oRecord.data.leaf )
  {
    for( i in this.items )
    {
      this.items[i].disable();
    }
  }
}

But it disabled the actions for the whole column and not just the specific record which was a leaf.

Answer 1

I guess the this reference is the problem, it seems to contains the wrong scope for what you archive. Take a look at renderer arguments, specially the meta Information.