Hunsberger, Peter wrote:
why would you ever do validation on a field that the user cannot change?
There is an example. That's exactly how AggregateWidget works. It consists out of several visible widgets and one invisible (or vice versa - depending on direction). Invisible one gets value by aggregated values of visible fields, and then it can run its own validation. And there are scenarios when separate values are visible, but aggregated is not.
Similar things could be employed by application developers - and that's when they might use this invisible widget.
And even if widget is not visible by itself, you can always show it's validation errors.
Vadim
