hook_widget.php

/**
 * Implementation of hook_widget().
 */
function etherpad_widget(&$form, &$form_state, $field, $items, $delta = 0) {
  $element['etherpad_url'] = array(
    '#type' => 'value',
    '#value' => (isset($items[$delta]['etherpad_url']) && !empty($form['nid']['#value'])) ? $items[$delta]['etherpad_url'] : $field['etherpad_url'] . etherpad_generate_padid($field['etherpad_url']),
  );
  $element['etherpad_text'] = array(
    '#type' => 'value',
    '#value' => (isset($items[$delta]['etherpad_text']) && !empty($form['nid']['#value'])) ? $items[$delta]['etherpad_text'] : "default value for now until we have a function to generate one",
  );
  $element['attributes'] = array(
    '#type' => 'value',
    '#value' => (isset($items[$delta]['attributes']) && !empty($form['nid']['#value'])) ? $items[$delta]['attributes'] : serialize($field['attributes']),
  );
  // Used so that hook_field('validate') knows where to 
  // flag an error in deeply nested forms.
  if (empty($form['#parents'])) {
    $form['#parents'] = array();
  }
  $element['_error_element'] = array(
    '#type' => 'value',
    '#value' => implode('][', array_merge($form['#parents'], array('value'))),
  );

  return $element;
}