Different signup form theme function for different node

This patch allows you to define different signup form theme function on a per-node basis. Just define your theme function ala theme_signup_user_form and implement the hook_signup_form_theme_functions() (I know it's too long a name!). For example:

function theme_custom_user_form() {
  global $user;

  $form['signup_form_data']['#tree'] = TRUE;
  
  $form['signup_form_data']['Designation'] = array(
    '#type' => 'select',
    '#title' => t('Designation'),
    '#options' => drupal_map_assoc(array('Mr.', 'Mrs.', 'Ms.')),
  );
  $form['signup_form_data']['Name'] = array(
    '#type' => 'textfield',
    '#title' => t('Name'),
    '#size' => 40, '#maxlength' => 64,
    '#required' => true,
  );
  $form['signup_form_data']['Address'] = array(
    '#type' => 'textarea',
    '#title' => t('Address'),
    '#rows' => 4,
  );

  // If the user is logged in, fill in their name by default.
  if ($user->uid) {
    $form['signup_form_data']['Name']['#default_value'] = $user->name;
  }

  return $form;
}

/**
 * Implementation of hook_signup_form_theme_functions().
 */
function mymodule_signup_form_theme_functions() {
  return array('custom_user_form');
}

and voila! You can now edit your node and select 'custom_user_form' under the 'Theme function' setting.

Please review; if does not belong in signup core, so be it, at least the patch is here if someone needs such functionality ;)