Add class to Bootstrap login form button

Question

I want to add a class to a button in my login form. I have searched through all the template files and I cannot find where to do this. I found the following code that best matches the form in modules/user/user.module

function user_login_block($form) {
$form['#action'] = url(current_path(), array('query' => drupal_get_destination(), 'external' => FALSE));
$form['#id'] = 'user-login-form';
$form['#validate'] = user_login_default_validators();
$form['#submit'][] = 'user_login_submit';

The HTML for the button is below. My aim is to change btn-default to btn-primary

<button class="btn btn-default form-submit" id="edit-submit" name="op" value="Log in" type="submit">Log in</button>

Please help!

Answer 1

You should refrain from hacking core.

Rather add this code to your sub theme's template.php file:

function MYTHEME_button(&$variables) {
  dpm($variables);
  $element = $variables['element'];
  $label = $element['#value'];
  element_set_attributes($element, array('id', 'name', 'value', 'type'));

  // If a button type class isn't present then add in default.
  $button_classes = array(
    'btn-default',
    'btn-primary',
    'btn-success',
    'btn-info',
    'btn-warning',
    'btn-danger',
    'btn-link',
  );
  $class_intersection = array_intersect($button_classes, $element['#attributes']['class']);
  if ($variables['element']['#type'] == 'submit' && $variables['element']['#value'] == 'Log in') {
    $element['#attributes']['class'][] = 'btn-primary';
  }
  else if (empty($class_intersection)) {
    $element['#attributes']['class'][] = 'btn-default';
  }

  // Add in the button type class.
  $element['#attributes']['class'][] = 'form-' . $element['#button_type'];

  // This line break adds inherent margin between multiple buttons.
  // dpm($variables);
  return '<button' . drupal_attributes($element['#attributes']) . '>' . $label . "</button>\n";
}

Bootstrap theme overrides the theme_button, and this is where I copied this code (minus the alteration of adding the class). We then override Bootstrap's implementation with our own.

The code that adds the class is this part:

if ($variables['element']['#type'] == 'submit' && $variables['element']['#value'] == 'Log in') {
    $element['#attributes']['class'][] = 'btn-primary';
}

It's perhaps no the best way to detect that specific button (going on type and text), but it works.

Answer 2

Checkout hook_form_alter. You can add and change (I would suggest only adding unless you are sure it will only affect the forms you want it to) classes with #attributes