material_admin-8.x-1.0-alpha7/templates/buttons/input--submit--button.html.twig

{#
/**
 * @file
 * Theme override for an 'input' #type form element.
 *
 * Available variables:
 * - attributes: A list of HTML attributes for the input element.
 * - children: Optional additional rendered elements.
 *
 * @see template_preprocess_input()
 */
#}

{%
  set classes = [
  'waves-effect', 
  'waves-light', 
  'btn'
  ]
 %}

<button{{ attributes.addClass(classes) }}><i class="material-icons">{% block icon %}{% endblock %}</i> <span>{{ attributes.value }}</span></button>