The ValueHandler (formerly known as ValueChecker) product was created because many (including myself) have been waiting for something that can handle invalid input from the user for quite some time now. It's basic at this point, but it's easily extensible (pluggable),that is, and there's definently a lot of different uses for it..

It has now been a bit extended, to include support for composite values. Have a look in base_item.py, html_widgets.py and composite_widgets.py for some hints..

Feedback and ideas are more than welcome.. =)