ThemeInstaller::uninstall

public ThemeInstaller::uninstall(array $theme_list)

public function uninstall(array $theme_list) {
  $extension_config = $this->configFactory->getEditable('core.extension');
  $theme_config = $this->configFactory->getEditable('system.theme');
  $list = $this->themeHandler->listInfo();
  foreach ($theme_list as $key) {
    if (!isset($list[$key])) {
      throw new \InvalidArgumentException("Unknown theme: $key.");
    }
    if ($key === $theme_config->get('default')) {
      throw new \InvalidArgumentException("The current default theme $key cannot be uninstalled.");
    }
    if ($key === $theme_config->get('admin')) {
      throw new \InvalidArgumentException("The current administration theme $key cannot be uninstalled.");
    }
    // Base themes cannot be uninstalled if sub themes are installed, and if
    // they are not uninstalled at the same time.
    // @todo https://www.drupal.org/node/474684 and
    //   https://www.drupal.org/node/1297856 themes should leverage the module
    //   dependency system.
    if (!empty($list[$key]->sub_themes)) {
      foreach ($list[$key]->sub_themes as $sub_key => $sub_label) {
        if (isset($list[$sub_key]) && !in_array($sub_key, $theme_list, TRUE)) {
          throw new \InvalidArgumentException("The base theme $key cannot be uninstalled, because theme $sub_key depends on it.");
        }
      }
    }
  }

  $this->cssCollectionOptimizer->deleteAll();
  $current_theme_data = $this->state->get('system.theme.data', array());
  foreach ($theme_list as $key) {
    // The value is not used; the weight is ignored for themes currently.
    $extension_config->clear("theme.$key");

    // Update the current theme data accordingly.
    unset($current_theme_data[$key]);

    // Reset theme settings.
    $theme_settings = &drupal_static('theme_get_setting');
    unset($theme_settings[$key]);

    // Remove all configuration belonging to the theme.
    $this->configManager->uninstall('theme', $key);

  }
  // Don't check schema when uninstalling a theme since we are only clearing
  // keys.
  $extension_config->save(TRUE);
  $this->state->set('system.theme.data', $current_theme_data);


  // @todo Remove system_list().
  $this->themeHandler->refreshInfo();
  $this->resetSystem();

  $this->moduleHandler->invokeAll('themes_uninstalled', [$theme_list]);
}