UserLoginForm::buildForm

public UserLoginForm::buildForm(array $form, FormStateInterface $form_state)

public function buildForm(array $form, FormStateInterface $form_state) {
  $config = $this->config('system.site');

  // Display login form:
  $form['name'] = array(
    '#type' => 'textfield',
    '#title' => $this->t('Username'),
    '#size' => 60,
    '#maxlength' => USERNAME_MAX_LENGTH,
    '#description' => $this->t('Enter your @s username.', array('@s' => $config->get('name'))),
    '#required' => TRUE,
    '#attributes' => array(
      'autocorrect' => 'none',
      'autocapitalize' => 'none',
      'spellcheck' => 'false',
      'autofocus' => 'autofocus',
    ),
  );

  $form['pass'] = array(
    '#type' => 'password',
    '#title' => $this->t('Password'),
    '#size' => 60,
    '#description' => $this->t('Enter the password that accompanies your username.'),
    '#required' => TRUE,
  );

  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array('#type' => 'submit', '#value' => $this->t('Log in'));

  $form['#validate'][] = '::validateName';
  $form['#validate'][] = '::validateAuthentication';
  $form['#validate'][] = '::validateFinal';

  $this->renderer->addCacheableDependency($form, $config);

  return $form;
}