[Zope3-dev] Re: browser widgets: items widgets and label tags

[Fred Drake]

On 11/10/06, yuppie <y.2006_ at wcm-solutions.de> wrote:
> While pointing the label to the div element that contains the input
> fields is not very useful, this seems to be valid HTML::

Sorry for not replying earlier, but I wanted to have time to think
before responding.  ;)

There's valid according to the DTD (the XML definition of validity),
and there's valid according to the specification.  DTDs aren't able to
specify the constraint documented in the specification document; in
this case, that means the DTD can be used to help detect invalid HTML
documents, but not determine whether an HTML document is valid.  More
expressive schema languages could be used to produce a more useful
schema definition.

Given that the specification clearly states that the "for" attribute's
value be an ID for a control, I must conclude that referring to the ID
of a <div> or other non-control element causes the HTML to be invalid.

> Making sure that radio and checkbox widgets have a div tag with the
> required ID is a simple bugfix. No API changes are required and
> zope.formlib still can use the widget name in the 'for' attribute.

Regardless of the HTML specification, this is a semantic change in the
contract of the IWidget API.  So it's a change, just not in the set of
attributes and methods and their signatures.

> So IBrowserWidget's __call__ method *has to* return a snipped that
> contains a tag with the widget's name as ID. All widgets that don't
> follow that rule have to be fixed.
>
> If there are no objections, I'll make the required changes on 3.2
> branch, 3.3 branch and trunk.

I object; this is still a change to the contract.

You were on the right track with your first proposal.  There's a need
for widgets to provide more information to support integration in a
form.  Unfortunately, adding an attribute to the IWidget or other
existing interfaces doesn't work well, since it makes it harder to
write code that supports multiple versions of Zope.

Another way to expose the required information is to create a new
interface and provide adapters for the existing widgets (possibly by
simply implementing the new interface on the existing widgets).  A
form that's aware of the new interface can use the additional
information.

The new interface could look something like this:

    class IWidgetControlInformation(zope.interface.Interface):
        labelControlId = zope.schema.TextLine(
            title=_("Label control id"),
            description=_("Id of the control element that should be"
                          " associated with any <label> element rendered"
                          " for the widget."),
            required=False,
            )

        focusControlId = zope.schema.TextLine(
            title=_("Focus control id"),
            description=_("Id of the control element that should be"
                          " focused when the form is initially rendered."
                          " Since each widget may suggest an element for"
                          " the initial focus, this should only be regarded"
                          " as a hint."),
            required=False,
            )


  -Fred

-- 
Fred L. Drake, Jr.    <fdrake at gmail.com>
"Every sin is the result of a collaboration." --Lucius Annaeus Seneca