Hoa, we've already spent time building this showcase, and you've just spent time undoing it.

We're building a more or less general-purpose library of widgets, and not all of the functionality we're implementing gets actually used in Spark. For example, we're not using horizontal splitters or vertical splitters with resizing target on the right -- are you suggesting we remove that functionality too?

In addition, there are widgets/example/ which we use for quick testing of the widgets, and with this change you've broken the one for spark-splitter.