# To subscribers of the xforms list from Steve Lamont <spl@ncmir.ucsd.edu> :
> > So, why don't FL_RETURN_CHANGED or FL_RETURN_ALWAYS satisfy your
> > requirement for notification? Am I missing some subtlety here?
>
> Yes! But that's probably because you don't use callbacks on your input
> fields.
Most likely.
> The problem is that the interactive behaviour of an input field is different
> depending on whether the user changes input focus from the input field to
> another input field or to some other type of object.
>
> If you have 2 input fields and a button then:
> a) If you enter data in an input field and click to the other input
> callback will be invoked.
>
> b) If you enter data in an input field and click the button the callback
> will not be invoked.
Because XForms has not way of intuiting what that user's intentions
are. They may wish to come back after clicking the button and make
changes to or complete the input. In fact, I'd go so far as saying
that the first scenario (a) is wrong behavior -- the only way an Input
callback should be invoked is upon explicit pressing of Return or Tab.
> The problem with your scheme where all inputs are read when the button is
> pressed is that the facility provided by xforms of invoking a callback as and
> when the input data is changed is lost. That may not be useful in your
> application but in many it is.
I'm not parsing that first sentence in any useful manner. Want to try
again?
> To emulate the RETURN_END_CHANGED behaviour within the application, even a
> simple one, is non-trivial.
So it would appear -- which is probably why XForms doesn't do it
internally. There are too many ambiguities.
> BTW this raised an eyebrow (from earlier email):
>
> > In all the XForms code I've written I don't think I've ever used or
> > found a need for a callback on an Input object.
>
> No file selectors or other input goodies used in your app then!
Of course I do.
In fact, the File Selector goodie uses *exactly* the mechanism I use
-- it does an fl_get_input() to read the user's input before
returning, as does the Input goodie.
spl
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