So I can create one of these renderers based on parameters I let the user set. Some parameter combinations either create invalid conditions or no conditions at all - missing data, too many breaks or too few, and so on. This obviously unacceptable. I've considered doing what the desktop product does and display the list of breaks and let the user fiddle with the parameters until they do something useful. Has anyone done that? Is there a sample somewhere on how to do that? If not can someone offer advice on either doing that or suggest another way to ensure that a renderer "works?"