we're using custom grid popup editors where he have lots of different lookup controls (well not really controls, but just text with buttons).
E.g. a text-box with a button: one uses that button and it fetches a new sequence number and display that number.
Or a text-box with a customer name and a button: one uses that button and selects a customer from a customer-lookup dialog; the customer name goes into the text-box and the customer's ID goes into a hidden form field.
How to display validation errors w.r.t. *required* constraints for such common scenarios?
Easiest way would be to have text-input elements instead of text-boxes and mark those as required and readonly. But HTML5 defines readonly inputs as being immutable. Which makes me wonder how to provide an input element for validation? Or can this be achieved without input elements?
Essentially the lookup dialogs (maybe together with the selector buttons) are the input elements. Has this been addressed anywhere in the HTML5 spec?
I.e. what about input that does not live on the current form?
What about wizards with complex steps which may lead to a final form with completely broken constraints, but one cannot inform the user of those, because - according to HTML5 - obviously a readonly input cannot be wrong. Doesn't make sense to me.