As I was working on the upgrade of the sms framework to D7 I struggled to understand why, after implementing the field, I still couldn't see it in the fields list. Redoing the examples and then removing excess code(such as the formatter) I finally realised that there are some functions that need to be implemented for the module to work. Unfortunately this wasn't obvious at all.
Can anyone tell me why I need a widget hook if I was using the 'text_textfield" which is already implemented?
Why aren't minimum implementation requirements in the API documentation?