It feels as if our knowledge of drag-and-drop on the Web has come pretty far from our understanding in the earlier chapters. We started off by discussing some of the typical demonstrations of drag-and-drop, which were developed to show off the Web 2.0 functionality. Some of those demonstrations suffered from a lack of real utility, but they were undeniably compelling. We showed how to create a few 'fancy but pointless' effects of our own to get a grasp of the underlying concepts of the Ext.dd package, and then quickly expanded our knowledge to harness the drag-and-drop classes that allow our applications to take advantage of this feature.
The wide range of in-built support that Ext provides is only part of the story, albeit a very important part. The TreePanel, for example, certainly wouldn't be as impressive a component were it not for its ability to rearrange nodes within a hierarchy using simple drag-and-drop. But the other part of our tale is just as interesting...