title: Change Drag Style On NSOutlineView
body: <p>I try to change the style from the blue horizontal line to Drop On style but found no luck. Does anybody knows why. I searched for a morning and do everything but still not luck replace that horizontal line with the row highlight focus on the row being dropped on.</p>
  
  <pre><code>- (NSDragOperation)outlineView:(NSOutlineView *)outlineView validateDrop:(id &lt; NSDraggingInfo &gt;)info proposedItem:(id)targetItem proposedChildIndex:(NSInteger)index{
  
  BOOL canDrop = index &gt;= 0 &amp;&amp; targetItem;
  
  if (canDrop) {
      [outlineView setDropRow:index dropOperation:NSOutlineViewDropOnItemIndex];
      return NSDragOperationCopy;
  } else {
      return NSDragOperationNone;
  }
  </code></pre>
  
  <p>}</p>