drupal_routes/sites/all/themes/bootstrap/templates/system/button.func.php

<?php
/**
 * @file
 * Stub file for bootstrap_button().
 */

/**
 * Returns HTML for a button form element.
 *
 * @param array $variables
 *   An associative array containing:
 *   - element: An associative array containing the properties of the element.
 *     Properties used: #attributes, #button_type, #name, #value.
 *
 * @return string
 *   The constructed HTML.
 *
 * @see theme_button()
 *
 * @ingroup theme_functions
 */
function bootstrap_button($variables) {
  $element = $variables['element'];

  // Allow button text to be appear hidden.
  // @see https://www.drupal.org/node/2327437
  $text = !empty($element['#hide_text']) ? '<span class="element-invisible">' . $element['#value'] . '</span>' : $element['#value'];

  // Add icons before or after the value.
  // @see https://www.drupal.org/node/2219965
  if (!empty($element['#icon'])) {
    if ($element['#icon_position'] === 'before') {
      $text = $element['#icon'] . ' ' . $text;
    }
    elseif ($element['#icon_position'] === 'after') {
      $text .= ' ' . $element['#icon'];
    }
  }

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