Drupal 7 Module Development

Creating New Fields
}
'behaviors' => array(
'multiple values' => FIELD_BEHAVIOR_DEFAULT,
'default value' => FIELD_BEHAVIOR_DEFAULT,
),
),
);
In the preceding snippet, we are defining two widgets rather than just one. The first
is a simple widget, consisting of simple text fields, one for each dimension. In the
second, we offer only a single text field into which the user will enter all two or
three dimensions in H×W×D format.
Both widgets explicitly specify the field types that they will work on. Although
we are defining these widgets in the same module as the field type, that doesn't
necessarily imply a relationship between them. In fact, any module may define
widgets that work with any field type. The widget just needs to know how that field
type wants its data. The second widget also includes a settings array, which allows
us to configure the widget per-instance.
Also note the behaviors property. By default, widgets will handle only a single
field value and Drupal itself will offer a dynamic way to add additional values
from within the form. However, we can also tell Drupal to let our widget handle
multi-value fields in case, for example, we want to offer a clickable map for
multi-value coordinates we discussed earlier.
Simple widget forms
Let's look at the simple widget first, and then come back and look at the more
complex one. The only callback we must define for a widget is its form callback,
which defines the form fields that make up the widget. Let's look at an example:
function dimfield_field_widget_form(&$form, &$form_state, $field,
$instance, $langcode, $items,
$delta, $element) {
$base = $element;
if ($instance['widget']['type'] == 'dimfield_simple') {
$element['height'] = array(
'#type' => 'textfield',
'#title' => t('Height'),
'#default_value' => isset($items[$delta]['height']) ?
$items[$delta]['height'] : NULL,
) + $base;
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