Eclipse Visual Editor extensions - source code?

[Steven J. Sobol]

I found a very useful Swing layout (http://datadosen.se/riverlayout/index.jsp)
that I am now using in some of my GUIs. Since Eclipse's Visual Editor doesn't
support it out-of-the-box, I'd like to create an addon that will allow me to
use it in VE.

Decent documentation exists for creating VE extensions for UI
components you create as Java Beans, but the documentation for adding
layout manager support to VE is sketchy, other than "edit a couple
layout.override files and create a class that extends LayoutPolicy".

Does anyone know of any existing, working Visual Editor addons
that have source code available that I could build on??

Thanks,
SJS