drupal/core/modules/system/system.admin.inc

<?php

/**
 * @file
 * Admin page callbacks for the system module.
 */

use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\ReplaceCommand;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
use Drupal\Core\Datetime\DrupalDateTime;
use Drupal\system\Form\ModulesInstallConfirmForm;
use Drupal\system\Form\ModulesUninstallConfirmForm;

/**
 * Menu callback; Provide the administration overview page.
 */
function system_admin_config_page() {
  // Check for status report errors.
  // @todo Use depedancy injection in http://drupal.org/node/1987810.
  if (Drupal::service('system.manager')->checkRequirements() && user_access('administer site configuration')) {
    drupal_set_message(t('One or more problems were detected with your Drupal installation. Check the <a href="@status">status report</a> for more information.', array('@status' => url('admin/reports/status'))), 'error');
  }
  $blocks = array();
  if ($system_link = entity_load_multiple_by_properties('menu_link', array('link_path' => 'admin/config', 'module' => 'system'))) {
    $system_link = reset($system_link);
    $query = Drupal::entityQuery('menu_link')
      ->condition('link_path', 'admin/help', '<>')
      ->condition('menu_name', $system_link->menu_name)
      ->condition('plid', $system_link->id())
      ->condition('hidden', 0);
    $result = $query->execute();
    if (!empty($result)) {
      $menu_links = menu_link_load_multiple($result);

      foreach ($menu_links as $item) {
        _menu_link_translate($item);
        if (!$item['access']) {
          continue;
        }
        // The link description, either derived from 'description' in hook_menu()
        // or customized via menu module is used as title attribute.
        if (!empty($item['localized_options']['attributes']['title'])) {
          $item['description'] = $item['localized_options']['attributes']['title'];
          unset($item['localized_options']['attributes']['title']);
        }
        $block = $item;
        $block['content'] = '';
        $block['content'] .= theme('admin_block_content', array('content' => system_admin_menu_block($item)));
        if (!empty($block['content'])) {
          $block['show'] = TRUE;
        }

        // Prepare for sorting as in function _menu_tree_check_access().
        // The weight is offset so it is always positive, with a uniform 5-digits.
        $blocks[(50000 + $item['weight']) . ' ' . $item['title'] . ' ' . $item['mlid']] = $block;
      }
    }
  }
  if ($blocks) {
    ksort($blocks);
    return theme('admin_page', array('blocks' => $blocks));
  }
  else {
    return t('You do not have any administrative items.');
  }
}

/**
 * Provide a single block from the administration menu as a page.
 *
 * This function is often a destination for these blocks.
 * For example, 'admin/structure/types' needs to have a destination to be valid
 * in the Drupal menu system, but too much information there might be
 * hidden, so we supply the contents of the block.
 *
 * @return
 *   The output HTML.
 */
function system_admin_menu_block_page() {
  $item = menu_get_item();
  if ($content = system_admin_menu_block($item)) {
    $output = theme('admin_block_content', array('content' => $content));
  }
  else {
    $output = t('You do not have any administrative items.');
  }
  return $output;
}

/**
 * Menu callback; displays a listing of all themes.
 */
function system_themes_page() {
  // Get current list of themes.
  $themes = system_rebuild_theme_data();
  uasort($themes, 'system_sort_modules_by_info_name');

  $theme_default = config('system.theme')->get('default');
  $theme_groups  = array();
  $admin_theme = config('system.theme')->get('admin');

  foreach ($themes as &$theme) {
    if (!empty($theme->info['hidden'])) {
      continue;
    }
    $theme->is_default = ($theme->name == $theme_default);

    // Identify theme screenshot.
    $theme->screenshot = NULL;
    // Create a list which includes the current theme and all its base themes.
    if (isset($themes[$theme->name]->base_themes)) {
      $theme_keys = array_keys($themes[$theme->name]->base_themes);
      $theme_keys[] = $theme->name;
    }
    else {
      $theme_keys = array($theme->name);
    }
    // Look for a screenshot in the current theme or in its closest ancestor.
    foreach (array_reverse($theme_keys) as $theme_key) {
      if (isset($themes[$theme_key]) && file_exists($themes[$theme_key]->info['screenshot'])) {
        $theme->screenshot = array(
          'uri' => $themes[$theme_key]->info['screenshot'],
          'alt' => t('Screenshot for !theme theme', array('!theme' => $theme->info['name'])),
          'title' => t('Screenshot for !theme theme', array('!theme' => $theme->info['name'])),
          'attributes' => array('class' => array('screenshot')),
        );
        break;
      }
    }

    if (empty($theme->status)) {
     // Ensure this theme is compatible with this version of core.
     // Require the 'content' region to make sure the main page
     // content has a common place in all themes.
      $theme->incompatible_core = !isset($theme->info['core']) || ($theme->info['core'] != DRUPAL_CORE_COMPATIBILITY) || (!isset($theme->info['regions']['content']));
      $theme->incompatible_php = version_compare(phpversion(), $theme->info['php']) < 0;
      // Confirmed that the base theme is available.
      $theme->incompatible_base = (isset($theme->info['base theme']) && !isset($themes[$theme->info['base theme']]));
      // Confirm that the theme engine is available.
      $theme->incompatible_engine = (isset($theme->info['engine']) && !isset($theme->owner));
    }
    $query['token'] = drupal_get_token('system-theme-operation-link');
    $theme->operations = array();
    if (!empty($theme->status) || !$theme->incompatible_core && !$theme->incompatible_php && !$theme->incompatible_base && !$theme->incompatible_engine) {
      // Create the operations links.
      $query['theme'] = $theme->name;
      if (drupal_theme_access($theme)) {
        $theme->operations[] = array(
          'title' => t('Settings'),
          'href' => 'admin/appearance/settings/' . $theme->name,
          'attributes' => array('title' => t('Settings for !theme theme', array('!theme' => $theme->info['name']))),
        );
      }
      if (!empty($theme->status)) {
        if (!$theme->is_default) {
          if ($theme->name != $admin_theme) {
            $theme->operations[] = array(
              'title' => t('Disable'),
              'href' => 'admin/appearance/disable',
              'query' => $query,
              'attributes' => array('title' => t('Disable !theme theme', array('!theme' => $theme->info['name']))),
            );
          }
          $theme->operations[] = array(
            'title' => t('Set default'),
            'href' => 'admin/appearance/default',
            'query' => $query,
            'attributes' => array('title' => t('Set !theme as default theme', array('!theme' => $theme->info['name']))),
          );
        }
        $admin_theme_options[$theme->name] = $theme->info['name'];
      }
      else {
        $theme->operations[] = array(
          'title' => t('Enable'),
          'href' => 'admin/appearance/enable',
          'query' => $query,
          'attributes' => array('title' => t('Enable !theme theme', array('!theme' => $theme->info['name']))),
        );
        $theme->operations[] = array(
          'title' => t('Enable and set default'),
          'href' => 'admin/appearance/default',
          'query' => $query,
          'attributes' => array('title' => t('Enable !theme as default theme', array('!theme' => $theme->info['name']))),
        );
      }
    }

    // Add notes to default and administration theme.
    $theme->notes = array();
    $theme->classes = array();
    if ($theme->is_default) {
      $theme->classes[] = 'theme-default';
      $theme->notes[] = t('default theme');
    }
    if ($theme->name == $admin_theme || ($theme->is_default && $admin_theme == '0')) {
      $theme->classes[] = 'theme-admin';
      $theme->notes[] = t('admin theme');
    }

    // Sort enabled and disabled themes into their own groups.
    $theme_groups[$theme->status ? 'enabled' : 'disabled'][] = $theme;
  }

  // There are two possible theme groups.
  $theme_group_titles = array(
    'enabled' => format_plural(count($theme_groups['enabled']), 'Enabled theme', 'Enabled themes'),
  );
  if (!empty($theme_groups['disabled'])) {
    $theme_group_titles['disabled'] = format_plural(count($theme_groups['disabled']), 'Disabled theme', 'Disabled themes');
  }

  uasort($theme_groups['enabled'], 'system_sort_themes');
  drupal_alter('system_themes_page', $theme_groups);

  $admin_form = drupal_get_form('system_themes_admin_form', $admin_theme_options);
  return theme('system_themes_page', array('theme_groups' => $theme_groups, 'theme_group_titles' => $theme_group_titles)) . drupal_render($admin_form);
}

/**
 * Form to select the administration theme.
 *
 * @ingroup forms
 * @see system_themes_admin_form_submit()
 */
function system_themes_admin_form($form, &$form_state, $theme_options) {
  // Administration theme settings.
  $form['admin_theme'] = array(
    '#type' => 'details',
    '#title' => t('Administration theme'),
  );
  $form['admin_theme']['admin_theme'] = array(
    '#type' => 'select',
    '#options' => array(0 => t('Default theme')) + $theme_options,
    '#title' => t('Administration theme'),
    '#description' => t('Choose "Default theme" to always use the same theme as the rest of the site.'),
    '#default_value' => config('system.theme')->get('admin'),
  );
  $form['admin_theme']['actions'] = array('#type' => 'actions');
  $form['admin_theme']['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Save configuration'),
  );
  return $form;
}

/**
 * Process system_themes_admin_form form submissions.
 */
function system_themes_admin_form_submit($form, &$form_state) {
  drupal_set_message(t('The configuration options have been saved.'));
  config('system.theme')->set('admin', $form_state['values']['admin_theme'])->save();
}

/**
 * Menu callback; Set the default theme.
 */
function system_theme_default() {
  if (isset($_REQUEST['theme']) && isset($_REQUEST['token']) && drupal_valid_token($_REQUEST['token'], 'system-theme-operation-link')) {
    $theme = $_REQUEST['theme'];
    // Get current list of themes.
    $themes = list_themes();

    // Check if the specified theme is one recognized by the system.
    if (!empty($themes[$theme])) {
      // Enable the theme if it is currently disabled.
      if (empty($themes[$theme]->status)) {
       theme_enable(array($theme));
      }
      // Set the default theme.
      config('system.theme')
        ->set('default', $theme)
        ->save();

      // Rebuild the menu. This duplicates the menu_router_rebuild() in
      // theme_enable(). However, modules must know the current default theme in
      // order to use this information in hook_menu() or hook_menu_alter()
      // implementations, and doing the variable_set() before the theme_enable()
      // could result in a race condition where the theme is default but not
      // enabled.
      menu_router_rebuild();

      // The status message depends on whether an admin theme is currently in use:
      // a value of 0 means the admin theme is set to be the default theme.
      $admin_theme = config('system.theme')->get('admin');
      if ($admin_theme != 0 && $admin_theme != $theme) {
        drupal_set_message(t('Please note that the administration theme is still set to the %admin_theme theme; consequently, the theme on this page remains unchanged. All non-administrative sections of the site, however, will show the selected %selected_theme theme by default.', array(
          '%admin_theme' => $themes[$admin_theme]->info['name'],
          '%selected_theme' => $themes[$theme]->info['name'],
        )));
      }
      else {
        drupal_set_message(t('%theme is now the default theme.', array('%theme' => $themes[$theme]->info['name'])));
      }
    }
    else {
      drupal_set_message(t('The %theme theme was not found.', array('%theme' => $theme)), 'error');
    }
    drupal_goto('admin/appearance');
  }
  throw new AccessDeniedHttpException();
}

/**
 * Form builder; display theme configuration for entire site and individual themes.
 *
 * @param $key
 *   A theme name.
 * @return
 *   The form structure.
 * @ingroup forms
 * @see system_theme_settings_validate()
 * @see system_theme_settings_submit()
 */
function system_theme_settings($form, &$form_state, $key = '') {
  // Default settings are defined in theme_get_setting() in includes/theme.inc
  if ($key) {
    $var = 'theme_' . $key . '_settings';
    $config_key = $key . '.settings';
    $themes = list_themes();
    $features = $themes[$key]->info['features'];
  }
  else {
    $var = 'theme_settings';
    $config_key = 'system.theme.global';
  }

  $form['var'] = array('#type' => 'hidden', '#value' => $var);
  $form['config_key'] = array('#type' => 'hidden', '#value' => $config_key);

  // Toggle settings
  $toggles = array(
    'logo'                      => t('Logo'),
    'name'                      => t('Site name'),
    'slogan'                    => t('Site slogan'),
    'node_user_picture'         => t('User pictures in posts'),
    'comment_user_picture'      => t('User pictures in comments'),
    'comment_user_verification' => t('User verification status in comments'),
    'favicon'                   => t('Shortcut icon'),
    'main_menu'                 => t('Main menu'),
    'secondary_menu'            => t('Secondary menu'),
  );

  // Some features are not always available
  $disabled = array();
  if (!user_picture_enabled()) {
    $disabled['toggle_node_user_picture'] = TRUE;
    $disabled['toggle_comment_user_picture'] = TRUE;
  }
  if (!module_exists('comment')) {
    $disabled['toggle_comment_user_picture'] = TRUE;
    $disabled['toggle_comment_user_verification'] = TRUE;
  }

  $form['theme_settings'] = array(
    '#type' => 'details',
    '#title' => t('Toggle display'),
    '#description' => t('Enable or disable the display of certain page elements.'),
  );
  foreach ($toggles as $name => $title) {
    if ((!$key) || in_array($name, $features)) {
      $form['theme_settings']['toggle_' . $name] = array('#type' => 'checkbox', '#title' => $title, '#default_value' => theme_get_setting('features.' . $name, $key));
      // Disable checkboxes for features not supported in the current configuration.
      if (isset($disabled['toggle_' . $name])) {
        $form['theme_settings']['toggle_' . $name]['#disabled'] = TRUE;
      }
    }
  }

  if (!element_children($form['theme_settings'])) {
    // If there is no element in the theme settings details then do not show
    // it -- but keep it in the form if another module wants to alter.
    $form['theme_settings']['#access'] = FALSE;
  }

  // Logo settings, only available when file.module is enabled.
  if ((!$key) || in_array('logo', $features) && module_exists('file')) {
    $form['logo'] = array(
      '#type' => 'details',
      '#title' => t('Logo image settings'),
      '#attributes' => array('class' => array('theme-settings-bottom')),
      '#states' => array(
        // Hide the logo image settings fieldset when logo display is disabled.
        'invisible' => array(
          'input[name="toggle_logo"]' => array('checked' => FALSE),
        ),
      ),
    );
    $form['logo']['default_logo'] = array(
      '#type' => 'checkbox',
      '#title' => t('Use the default logo supplied by the theme'),
      '#default_value' => theme_get_setting('logo.use_default', $key),
      '#tree' => FALSE,
    );
    $form['logo']['settings'] = array(
      '#type' => 'container',
      '#states' => array(
        // Hide the logo settings when using the default logo.
        'invisible' => array(
          'input[name="default_logo"]' => array('checked' => TRUE),
        ),
      ),
    );
    $form['logo']['settings']['logo_path'] = array(
      '#type' => 'textfield',
      '#title' => t('Path to custom logo'),
      '#default_value' => theme_get_setting('logo.path', $key),
    );
    $form['logo']['settings']['logo_upload'] = array(
      '#type' => 'file',
      '#title' => t('Upload logo image'),
      '#maxlength' => 40,
      '#description' => t("If you don't have direct file access to the server, use this field to upload your logo.")
    );
  }

  if ((!$key) || in_array('favicon', $features) && module_exists('file')) {
    $form['favicon'] = array(
      '#type' => 'details',
      '#title' => t('Shortcut icon settings'),
      '#description' => t("Your shortcut icon, or 'favicon', is displayed in the address bar and bookmarks of most browsers."),
      '#states' => array(
        // Hide the shortcut icon settings fieldset when shortcut icon display
        // is disabled.
        'invisible' => array(
          'input[name="toggle_favicon"]' => array('checked' => FALSE),
        ),
      ),
    );
    $form['favicon']['default_favicon'] = array(
      '#type' => 'checkbox',
      '#title' => t('Use the default shortcut icon supplied by the theme'),
      '#default_value' => theme_get_setting('favicon.use_default', $key),
    );
    $form['favicon']['settings'] = array(
      '#type' => 'container',
      '#states' => array(
        // Hide the favicon settings when using the default favicon.
        'invisible' => array(
          'input[name="default_favicon"]' => array('checked' => TRUE),
        ),
      ),
    );
    $form['favicon']['settings']['favicon_path'] = array(
      '#type' => 'textfield',
      '#title' => t('Path to custom icon'),
      '#default_value' => theme_get_setting('favicon.path', $key),
    );
    $form['favicon']['settings']['favicon_upload'] = array(
      '#type' => 'file',
      '#title' => t('Upload icon image'),
      '#description' => t("If you don't have direct file access to the server, use this field to upload your shortcut icon.")
    );
  }

  // Inject human-friendly values and form element descriptions for logo and
  // favicon.
  foreach (array('logo' => 'logo.png', 'favicon' => 'favicon.ico') as $type => $default) {
    if (isset($form[$type]['settings'][$type . '_path'])) {
      $element = &$form[$type]['settings'][$type . '_path'];

      // If path is a public:// URI, display the path relative to the files
      // directory; stream wrappers are not end-user friendly.
      $original_path = $element['#default_value'];
      $friendly_path = NULL;
      if (file_uri_scheme($original_path) == 'public') {
        $friendly_path = file_uri_target($original_path);
        $element['#default_value'] = $friendly_path;
      }

      // Prepare local file path for description.
      if ($original_path && isset($friendly_path)) {
        $local_file = strtr($original_path, array('public:/' => variable_get('file_public_path', conf_path() . '/files')));
      }
      elseif ($key) {
        $local_file = drupal_get_path('theme', $key) . '/' . $default;
      }
      else {
        $local_file = path_to_theme() . '/' . $default;
      }

      $element['#description'] = t('Examples: <code>@implicit-public-file</code> (for a file in the public filesystem), <code>@explicit-file</code>, or <code>@local-file</code>.', array(
        '@implicit-public-file' => isset($friendly_path) ? $friendly_path : $default,
        '@explicit-file' => file_uri_scheme($original_path) !== FALSE ? $original_path : 'public://' . $default,
        '@local-file' => $local_file,
      ));
    }
  }

  if ($key) {
    // Call engine-specific settings.
    $function = $themes[$key]->prefix . '_engine_settings';
    if (function_exists($function)) {
      $form['engine_specific'] = array(
        '#type' => 'details',
        '#title' => t('Theme-engine-specific settings'),
        '#description' => t('These settings only exist for the themes based on the %engine theme engine.', array('%engine' => $themes[$key]->prefix)),
      );
      $function($form, $form_state);
    }

    // Create a list which includes the current theme and all its base themes.
    if (isset($themes[$key]->base_themes)) {
      $theme_keys = array_keys($themes[$key]->base_themes);
      $theme_keys[] = $key;
    }
    else {
      $theme_keys = array($key);
    }

    // Save the name of the current theme (if any), so that we can temporarily
    // override the current theme and allow theme_get_setting() to work
    // without having to pass the theme name to it.
    $default_theme = !empty($GLOBALS['theme_key']) ? $GLOBALS['theme_key'] : NULL;
    $GLOBALS['theme_key'] = $key;

    // Process the theme and all its base themes.
    foreach ($theme_keys as $theme) {
      // Include the theme-settings.php file.
      $filename = DRUPAL_ROOT . '/' . str_replace("/$theme.info.yml", '', $themes[$theme]->filename) . '/theme-settings.php';
      if (file_exists($filename)) {
        require_once $filename;
      }

      // Call theme-specific settings.
      $function = $theme . '_form_system_theme_settings_alter';
      if (function_exists($function)) {
        $function($form, $form_state);
      }
    }

    // Restore the original current theme.
    if (isset($default_theme)) {
      $GLOBALS['theme_key'] = $default_theme;
    }
    else {
      unset($GLOBALS['theme_key']);
    }
  }

  return system_config_form($form, $form_state);
}

/**
 * Validator for the system_theme_settings() form.
 */
function system_theme_settings_validate($form, &$form_state) {
  if (module_exists('file')) {
    // Handle file uploads.
    $validators = array('file_validate_is_image' => array());

    // Check for a new uploaded logo.
    $file = file_save_upload('logo_upload', $validators, FALSE, 0);
    if (isset($file)) {
      // File upload was attempted.
      if ($file) {
        // Put the temporary file in form_values so we can save it on submit.
        $form_state['values']['logo_upload'] = $file;
      }
      else {
        // File upload failed.
        form_set_error('logo_upload', t('The logo could not be uploaded.'));
      }
    }

    $validators = array('file_validate_extensions' => array('ico png gif jpg jpeg apng svg'));

    // Check for a new uploaded favicon.
    $file = file_save_upload('favicon_upload', $validators, FALSE, 0);
    if (isset($file)) {
      // File upload was attempted.
      if ($file) {
        // Put the temporary file in form_values so we can save it on submit.
        $form_state['values']['favicon_upload'] = $file;
      }
      else {
        // File upload failed.
        form_set_error('favicon_upload', t('The favicon could not be uploaded.'));
      }
    }

    // If the user provided a path for a logo or favicon file, make sure a file
    // exists at that path.
    if ($form_state['values']['logo_path']) {
      $path = _system_theme_settings_validate_path($form_state['values']['logo_path']);
      if (!$path) {
        form_set_error('logo_path', t('The custom logo path is invalid.'));
      }
    }
    if ($form_state['values']['favicon_path']) {
      $path = _system_theme_settings_validate_path($form_state['values']['favicon_path']);
      if (!$path) {
        form_set_error('favicon_path', t('The custom favicon path is invalid.'));
      }
    }
  }
}

/**
 * Helper function for the system_theme_settings form.
 *
 * Attempts to validate normal system paths, paths relative to the public files
 * directory, or stream wrapper URIs. If the given path is any of the above,
 * returns a valid path or URI that the theme system can display.
 *
 * @param $path
 *   A path relative to the Drupal root or to the public files directory, or
 *   a stream wrapper URI.
 * @return mixed
 *   A valid path that can be displayed through the theme system, or FALSE if
 *   the path could not be validated.
 */
function _system_theme_settings_validate_path($path) {
  // Absolute local file paths are invalid.
  if (drupal_realpath($path) == $path) {
    return FALSE;
  }
  // A path relative to the Drupal root or a fully qualified URI is valid.
  if (is_file($path)) {
    return $path;
  }
  // Prepend 'public://' for relative file paths within public filesystem.
  if (file_uri_scheme($path) === FALSE) {
    $path = 'public://' . $path;
  }
  if (is_file($path)) {
    return $path;
  }
  return FALSE;
}

/**
 * Process system_theme_settings form submissions.
 */
function system_theme_settings_submit($form, &$form_state) {
  $config = Drupal::config($form_state['values']['config_key']);

  // Exclude unnecessary elements before saving.
  form_state_values_clean($form_state);
  $key = $form_state['values']['var'];
  unset($form_state['values']['var']);
  unset($form_state['values']['config_key']);

  $values = $form_state['values'];

  // If the user uploaded a new logo or favicon, save it to a permanent location
  // and use it in place of the default theme-provided file.
  if (module_exists('file')) {
    if ($file = $values['logo_upload']) {
      unset($values['logo_upload']);
      $filename = file_unmanaged_copy($file->getFileUri());
      $values['default_logo'] = 0;
      $values['logo_path'] = $filename;
      $values['toggle_logo'] = 1;
    }
    if ($file = $values['favicon_upload']) {
      unset($values['favicon_upload']);
      $filename = file_unmanaged_copy($file->getFileUri());
      $values['default_favicon'] = 0;
      $values['favicon_path'] = $filename;
      $values['toggle_favicon'] = 1;
    }

    // If the user entered a path relative to the system files directory for
    // a logo or favicon, store a public:// URI so the theme system can handle it.
    if (!empty($values['logo_path'])) {
      $values['logo_path'] = _system_theme_settings_validate_path($values['logo_path']);
    }
    if (!empty($values['favicon_path'])) {
      $values['favicon_path'] = _system_theme_settings_validate_path($values['favicon_path']);
    }

    if (empty($values['default_favicon']) && !empty($values['favicon_path'])) {
      $values['favicon_mimetype'] = file_get_mimetype($values['favicon_path']);
    }
  }

  theme_settings_convert_to_config($values, $config)->save();

  cache_invalidate_tags(array('content' => TRUE));
}

/**
 * Recursively check compatibility.
 *
 * @param $incompatible
 *   An associative array which at the end of the check contains all
 *   incompatible files as the keys, their values being TRUE.
 * @param $files
 *   The set of files that will be tested.
 * @param $file
 *   The file at which the check starts.
 * @return
 *   Returns TRUE if an incompatible file is found, NULL (no return value)
 *   otherwise.
 */
function _system_is_incompatible(&$incompatible, $files, $file) {
  if (isset($incompatible[$file->name])) {
    return TRUE;
  }
  // Recursively traverse required modules, looking for incompatible modules.
  foreach ($file->requires as $requires) {
    if (isset($files[$requires]) && _system_is_incompatible($incompatible, $files, $files[$requires])) {
      $incompatible[$file->name] = TRUE;
      return TRUE;
    }
  }
}

/**
 * Form constructor for the module enable/disable interface.
 *
 * The list of modules gets populated by module.info.yml files, which contain
 * each module's name, description, and information about which modules it
 * requires.
 * See drupal_parse_info_file() for information on module.info.yml descriptors.
 *
 * Dependency checking is performed to ensure that a module:
 * - can not be enabled if there are disabled modules it requires.
 * - can not be disabled if there are enabled modules which depend on it.
 *
 * @see system_menu()
 * @see theme_system_modules()
 * @see system_modules_submit()
 *
 * @ingroup forms
 */
function system_modules($form, $form_state = array()) {
  // Get current list of modules.
  $files = system_rebuild_module_data();

  // Remove hidden modules from display list.
  $visible_files = $files;
  foreach ($visible_files as $filename => $file) {
    if (!empty($file->info['hidden'])) {
      unset($visible_files[$filename]);
    }
  }

  uasort($visible_files, 'system_sort_modules_by_info_name');

  // If the modules form was submitted, then system_modules_submit() runs first
  // and if there are unfilled required modules, then $form_state['storage'] is
  // filled, triggering a rebuild. In this case we need to display a
  // confirmation form.
  if (!empty($form_state['storage'])) {
    // Contents of confirm form is injected here because already in form
    // building function.
    $confirm_form = new ModulesInstallConfirmForm();
    return $confirm_form->buildForm($form, $form_state, $visible_files, $form_state['storage']);
  }

  // JS-only table filters.
  $form['filters'] = array(
    '#type' => 'container',
    '#attributes' => array(
      'class' => array('table-filter', 'js-show'),
    ),
  );
  $form['filters']['text'] = array(
    '#type' => 'search',
    '#title' => t('Search'),
    '#size' => 30,
    '#placeholder' => t('Enter module name…'),
    '#attributes' => array(
      'class' => array('table-filter-text'),
      'data-table' => '#system-modules',
      'autocomplete' => 'off',
      'title' => t('Enter a part of the module name or description to filter by.'),
    ),
  );

  $modules = array();
  $form['modules'] = array('#tree' => TRUE);

  // Used when checking if module implements a help page.
  $help_arg = module_exists('help') ? drupal_help_arg() : FALSE;

  // Used when displaying modules that are required by the installation profile.
  require_once DRUPAL_ROOT . '/core/includes/install.inc';
  $distribution_name = check_plain(drupal_install_profile_distribution_name());

  // Iterate through each of the modules.
  foreach ($visible_files as $filename => $module) {
    $extra = array();
    $extra['enabled'] = (bool) $module->status;
    if (!empty($module->info['required'] )) {
      $extra['disabled'] = TRUE;
      $extra['required_by'][] = $distribution_name . (!empty($module->info['explanation']) ? ' ('. $module->info['explanation'] .')' : '');
    }

    // If this module requires other modules, add them to the array.
    foreach ($module->requires as $requires => $v) {
      if (!isset($files[$requires])) {
        $extra['requires'][$requires] = t('@module (<span class="admin-missing">missing</span>)', array('@module' => drupal_ucfirst($requires)));
        $extra['disabled'] = TRUE;
      }
      // Only display visible modules.
      elseif (isset($visible_files[$requires])) {
        $requires_name = $files[$requires]->info['name'];
        // Disable this module if it is incompatible with the dependency's version.
        if ($incompatible_version = drupal_check_incompatibility($v, str_replace(DRUPAL_CORE_COMPATIBILITY . '-', '', $files[$requires]->info['version']))) {
          $extra['requires'][$requires] = t('@module (<span class="admin-missing">incompatible with</span> version @version)', array(
            '@module' => $requires_name . $incompatible_version,
            '@version' => $files[$requires]->info['version'],
          ));
          $extra['disabled'] = TRUE;
        }
        // Disable this module if the dependency is incompatible with this
        // version of Drupal core.
        elseif ($files[$requires]->info['core'] != DRUPAL_CORE_COMPATIBILITY) {
          $extra['requires'][$requires] = t('@module (<span class="admin-missing">incompatible with</span> this version of Drupal core)', array(
            '@module' => $requires_name,
          ));
          $extra['disabled'] = TRUE;
        }
        elseif ($files[$requires]->status) {
          $extra['requires'][$requires] = t('@module', array('@module' => $requires_name));
        }
        else {
          $extra['requires'][$requires] = t('@module (<span class="admin-disabled">disabled</span>)', array('@module' => $requires_name));
        }
      }
    }
    // Generate link for module's help page, if there is one.
    if ($help_arg && $module->status && in_array($filename, module_implements('help'))) {
      if (module_invoke($filename, 'help', "admin/help#$filename", $help_arg)) {
        $extra['links']['help'] = array(
          '#type' => 'link',
          '#title' => t('Help'),
          '#href' => "admin/help/$filename",
          '#options' => array('attributes' => array('class' =>  array('module-link', 'module-link-help'), 'title' => t('Help'))),
        );
      }
    }
    // Generate link for module's permission, if the user has access to it.
    if ($module->status && user_access('administer permissions') && in_array($filename, module_implements('permission'))) {
      $extra['links']['permissions'] = array(
        '#type' => 'link',
        '#title' => t('Permissions'),
        '#href' => 'admin/people/permissions',
        '#options' => array('fragment' => 'module-' . $filename, 'attributes' => array('class' => array('module-link', 'module-link-permissions'), 'title' => t('Configure permissions'))),
      );
    }
    // Generate link for module's configuration page, if the module provides
    // one.
    if ($module->status && isset($module->info['configure'])) {
      $configure_link = menu_get_item($module->info['configure']);
      if ($configure_link['access']) {
        $extra['links']['configure'] = array(
          '#type' => 'link',
          '#title' => t('Configure'),
          '#href' => $configure_link['href'],
          '#options' => array('attributes' => array('class' => array('module-link', 'module-link-configure'), 'title' => $configure_link['description'])),
        );
      }
    }

    // If this module is required by other modules, list those, and then make it
    // impossible to disable this one.
    foreach ($module->required_by as $required_by => $v) {
      // Hidden modules are unset already.
      if (isset($visible_files[$required_by])) {
        if ($files[$required_by]->status == 1 && $module->status == 1) {
          $extra['required_by'][] = t('@module', array('@module' => $files[$required_by]->info['name']));
          $extra['disabled'] = TRUE;
        }
        else {
          $extra['required_by'][] = t('@module (<span class="admin-disabled">disabled</span>)', array('@module' => $files[$required_by]->info['name']));
        }
      }
    }
    $form['modules'][$module->info['package']][$filename] = _system_modules_build_row($module->info, $extra);
  }

  // Add basic information to the details.
  foreach (element_children($form['modules']) as $package) {
    $form['modules'][$package] += array(
      '#type' => 'details',
      '#title' => t($package),
      '#theme' => 'system_modules_details',
      '#header' => array(
        array('data' => t('<span class="element-invisible">Enabled</span>'), 'class' => array('checkbox')),
        array('data' => t('Name'), 'class' => array('name')),
        array('data' => t('Description'), 'class' => array('description', RESPONSIVE_PRIORITY_LOW)),
      ),
      // Ensure that the "Core" package comes first.
      '#weight' => $package == 'Core' ? -10 : NULL,
    );
  }

  // Lastly, sort all packages by title.
  uasort($form['modules'], 'element_sort_by_title');

  $form['#attached']['library'][] = array('system', 'drupal.system.modules');
  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Save configuration'),
  );
  $form['#action'] = url('admin/modules/list/confirm');

  return $form;
}

/**
 * Array sorting callback; sorts modules or themes by their name.
 */
function system_sort_modules_by_info_name($a, $b) {
  return strcasecmp($a->info['name'], $b->info['name']);
}

/**
 * Array sorting callback; sorts modules or themes by their name.
 */
function system_sort_themes($a, $b) {
  if ($a->is_default) {
    return -1;
  }
  if ($b->is_default) {
    return 1;
  }
  return strcasecmp($a->info['name'], $b->info['name']);
}

/**
 * Build a table row for the system modules page.
 */
function _system_modules_build_row($info, $extra) {
  // Add in the defaults.
  $extra += array(
    'requires' => array(),
    'required_by' => array(),
    'disabled' => FALSE,
    'enabled' => FALSE,
    'links' => array(),
  );
  $form = array(
    '#tree' => TRUE,
  );
  // Set the basic properties.
  $form['name'] = array(
    '#markup' => $info['name'],
  );
  $form['description'] = array(
    '#markup' => t($info['description']),
  );
  $form['version'] = array(
    '#markup' => $info['version'],
  );
  $form['#requires'] = $extra['requires'];
  $form['#required_by'] = $extra['required_by'];

  // Check the compatibilities.
  $compatible = TRUE;
  $status_short = '';
  $status_long = '';

  // Check the core compatibility.
  if (!isset($info['core']) || $info['core'] != DRUPAL_CORE_COMPATIBILITY) {
    $compatible = FALSE;
    $status_short .= t('Incompatible with this version of Drupal core.');
    $status_long .= t('This version is not compatible with Drupal !core_version and should be replaced.', array('!core_version' => DRUPAL_CORE_COMPATIBILITY));
  }

  // Ensure this module is compatible with the currently installed version of PHP.
  if (version_compare(phpversion(), $info['php']) < 0) {
    $compatible = FALSE;
    $status_short .= t('Incompatible with this version of PHP');
    $php_required = $info['php'];
    if (substr_count($info['php'], '.') < 2) {
      $php_required .= '.*';
    }
    $status_long .= t('This module requires PHP version @php_required and is incompatible with PHP version !php_version.', array('@php_required' => $php_required, '!php_version' => phpversion()));
  }

  // If this module is compatible, present a checkbox indicating
  // this module may be installed. Otherwise, show a big red X.
  if ($compatible) {
    $form['enable'] = array(
      '#type' => 'checkbox',
      '#title' => t('Enable'),
      '#default_value' => $extra['enabled'],
      '#attributes' => array('role' => 'disabled'),
    );
    if ($extra['disabled']) {
      $form['enable']['#disabled'] = TRUE;
    }
  }
  else {
    $form['enable'] = array(
      '#markup' =>  theme('image', array('uri' => 'core/misc/watchdog-error.png', 'alt' => $status_short, 'title' => $status_short)),
    );
    $form['description']['#markup'] .= theme('system_modules_incompatible', array('message' => $status_long));
  }

  // Build operation links.
  foreach (array('help', 'permissions', 'configure') as $key) {
    $form['links'][$key] = (isset($extra['links'][$key]) ? $extra['links'][$key] : array());
  }

  return $form;
}

/**
 * Submit callback; handles modules form submission.
 */
function system_modules_submit($form, &$form_state) {
  include_once DRUPAL_ROOT . '/core/includes/install.inc';

  // Builds list of modules.
  $modules = array();
  // If we're not coming from the confirmation form, build the list of modules.
  if (empty($form_state['storage'])) {
    // If we're not coming from the confirmation form, build the module list.
    foreach ($form_state['values']['modules'] as $group_name => $group) {
      foreach ($group as $module => $enabled) {
        $modules[$module] = array('group' => $group_name, 'enabled' => $enabled['enable']);
      }
    }
  }
  else {
    // If we are coming from the confirmation form, fetch
    // the modules out of $form_state.
    $modules = $form_state['storage']['modules'];
  }

  // Collect data for all modules to be able to determine dependencies.
  $files = system_rebuild_module_data();

  // Sorts modules by weight.
  $sort = array();
  foreach (array_keys($modules) as $module) {
    $sort[$module] = $files[$module]->sort;
  }
  array_multisort($sort, $modules);

  // Makes sure all required modules are set to be enabled.
  $more_required = array();
  $missing_modules = array();
  foreach ($modules as $name => $module) {
    if ($module['enabled']) {
      // Checks that all dependencies are set to be enabled.  Stores the ones
      // that are not in $dependencies variable so that the user can be alerted
      // in the confirmation form that more modules need to be enabled.
      $dependencies = array();
      foreach (array_keys($files[$name]->requires) as $required) {
        if (empty($modules[$required]['enabled'])) {
          if (isset($files[$required])) {
            $dependencies[] = $files[$required]->info['name'];
            $modules[$required]['enabled'] = TRUE;
          }
          else {
            $missing_modules[$required]['depends'][] = $name;
            $modules[$name]['enabled'] = FALSE;
          }
        }
      }

      // Stores additional modules that need to be enabled in $more_required.
      if (!empty($dependencies)) {
        $more_required[$name] = array(
          'name' => $files[$name]->info['name'],
          'requires' => $dependencies,
        );
      }
    }
  }

  // Redirects to confirmation form if more modules need to be enabled.
  if ((!empty($more_required) || !empty($missing_modules)) && !isset($form_state['values']['confirm'])) {
    $form_state['storage'] = array(
      'more_required' => $more_required,
      'modules' => $modules,
      'missing_modules' => $missing_modules,
    );
    $form_state['rebuild'] = TRUE;
    return;
  }

  // Invokes hook_requirements('install').  If failures are detected, makes sure
  // the dependent modules aren't installed either.
  foreach ($modules as $name => $module) {
    // Only invoke hook_requirements() on modules that are going to be installed.
    if ($module['enabled'] && drupal_get_installed_schema_version($name) == SCHEMA_UNINSTALLED) {
      if (!drupal_check_module($name)) {
        $modules[$name]['enabled'] = FALSE;
        foreach (array_keys($files[$name]->required_by) as $required_by) {
          $modules[$required_by]['enabled'] = FALSE;
        }
      }
    }
  }

  // Initializes array of actions.
  $actions = array(
    'enable' => array(),
    'disable' => array(),
    'install' => array(),
  );

  // Builds arrays of modules that need to be enabled, disabled, and installed.
  foreach ($modules as $name => $module) {
    if ($module['enabled']) {
      if (drupal_get_installed_schema_version($name) == SCHEMA_UNINSTALLED) {
        $actions['install'][] = $name;
        $actions['enable'][] = $name;
      }
      elseif (!module_exists($name)) {
        $actions['enable'][] = $name;
      }
    }
    elseif (module_exists($name)) {
      $actions['disable'][] = $name;
    }
  }

  // Gets list of modules prior to install process, unsets $form_state['storage']
  // so we don't get redirected back to the confirmation form.
  $pre_install_list = Drupal::moduleHandler()->getModuleList();
  unset($form_state['storage']);

  // Reverse the 'enable' list, to order dependencies before dependents.
  krsort($actions['enable']);

  // Installs, enables, and disables modules.
  module_enable($actions['enable'], FALSE);
  module_disable($actions['disable'], FALSE);

  // Gets module list after install process, flushes caches and displays a
  // message if there are changes.
  $post_install_list = Drupal::moduleHandler()->getModuleList();
  if ($pre_install_list != $post_install_list) {
    drupal_flush_all_caches();
    drupal_set_message(t('The configuration options have been saved.'));
  }

  $form_state['redirect'] = 'admin/modules';
}

/**
 * Uninstall functions
 */

/**
 * Form constructor for the uninstalling disabled modules form.
 *
 * @see system_menu()
 * @see system_modules_uninstall_validate()
 * @see system_modules_uninstall_submit()
 *
 * @ingroup forms
 */
function system_modules_uninstall($form, $form_state = NULL) {
  // Make sure the install API is available.
  include_once DRUPAL_ROOT . '/core/includes/install.inc';

  // Display the confirm form if any modules have been submitted.
  if (!empty($form_state['storage']['uninstall']) && $modules = array_filter($form_state['storage']['uninstall'])) {
    // Contents of confirm form is injected here because already in form
    // building function.
    $confirm_form = new ModulesUninstallConfirmForm();
    return $confirm_form->buildForm($form, $form_state, $modules);
  }

  // Get a list of disabled, installed modules.
  $all_modules = system_rebuild_module_data();
  $disabled_modules = array();
  foreach ($all_modules as $name => $module) {
    if (empty($module->status) && drupal_get_installed_schema_version($name) > SCHEMA_UNINSTALLED) {
      $disabled_modules[$name] = $module;
    }
  }

  // Only build the rest of the form if there are any modules available to
  // uninstall.
  if (!empty($disabled_modules)) {
    $profile = drupal_get_profile();
    uasort($disabled_modules, 'system_sort_modules_by_info_name');
    $form['uninstall'] = array('#tree' => TRUE);
    foreach ($disabled_modules as $module) {
      $module_name = $module->info['name'] ? $module->info['name'] : $module->name;
      $form['modules'][$module->name]['#module_name'] = $module_name;
      $form['modules'][$module->name]['name']['#markup'] = $module_name;
      $form['modules'][$module->name]['description']['#markup'] = t($module->info['description']);
      $form['uninstall'][$module->name] = array(
        '#type' => 'checkbox',
        '#title' => t('Uninstall @module module', array('@module' => $module_name)),
        '#title_display' => 'invisible',
      );
      // All modules which depend on this one must be uninstalled first, before
      // we can allow this module to be uninstalled. (The installation profile
      // is excluded from this list.)
      foreach (array_keys($module->required_by) as $dependent) {
        if ($dependent != $profile && drupal_get_installed_schema_version($dependent) != SCHEMA_UNINSTALLED) {
          $dependent_name = isset($all_modules[$dependent]->info['name']) ? $all_modules[$dependent]->info['name'] : $dependent;
          $form['modules'][$module->name]['#required_by'][] = $dependent_name;
          $form['uninstall'][$module->name]['#disabled'] = TRUE;
        }
      }
    }
    $form['actions'] = array('#type' => 'actions');
    $form['actions']['submit'] = array(
      '#type' => 'submit',
      '#value' => t('Uninstall'),
    );
    $form['#action'] = url('admin/modules/uninstall/confirm');
  }
  else {
    $form['modules'] = array();
  }

  return $form;
}

/**
 * Validates the submitted uninstall form.
 */
function system_modules_uninstall_validate($form, &$form_state) {
  // Form submitted, but no modules selected.
  if (!count(array_filter($form_state['values']['uninstall']))) {
    drupal_set_message(t('No modules selected.'), 'error');
    drupal_goto('admin/modules/uninstall');
  }
}

/**
 * Processes the submitted uninstall form.
 */
function system_modules_uninstall_submit($form, &$form_state) {
  // Make sure the install API is available.
  include_once DRUPAL_ROOT . '/core/includes/install.inc';

  if (!empty($form['#confirmed'])) {
    // Call the uninstall routine for each selected module.
    $modules = array_keys($form_state['values']['uninstall']);
    module_uninstall($modules);
    drupal_set_message(t('The selected modules have been uninstalled.'));

    $form_state['redirect'] = 'admin/modules/uninstall';
  }
  else {
    $form_state['storage'] = $form_state['values'];
    $form_state['rebuild'] = TRUE;
  }
}

/**
 * Default page callback for batches.
 */
function system_batch_page() {
  require_once DRUPAL_ROOT . '/core/includes/batch.inc';
  $output = _batch_page();

  if ($output === FALSE) {
    throw new AccessDeniedHttpException();
  }
  elseif ($output instanceof Response) {
    return $output;
  }
  elseif (isset($output)) {
    // Force a page without blocks or messages to
    // display a list of collected messages later.
    drupal_set_page_content($output);
    $page = element_info('page');
    $page['#show_messages'] = FALSE;
    return $page;
  }
}

/**
 * Returns HTML for an administrative block for display.
 *
 * @param $variables
 *   An associative array containing:
 *   - block: An array containing information about the block:
 *     - show: A Boolean whether to output the block. Defaults to FALSE.
 *     - title: The block's title.
 *     - content: (optional) Formatted content for the block.
 *     - description: (optional) Description of the block. Only output if
 *       'content' is not set.
 *
 * @ingroup themeable
 */
function theme_admin_block($variables) {
  $block = $variables['block'];
  $output = '';

  // Don't display the block if it has no content to display.
  if (empty($block['show'])) {
    return $output;
  }

  $output .= '<div class="admin-panel">';
  if (!empty($block['title'])) {
    $output .= '<h3>' . $block['title'] . '</h3>';
  }
  if (!empty($block['content'])) {
    $output .= '<div class="body">' . $block['content'] . '</div>';
  }
  else {
    $output .= '<div class="description">' . $block['description'] . '</div>';
  }
  $output .= '</div>';

  return $output;
}

/**
 * Returns HTML for the content of an administrative block.
 *
 * @param $variables
 *   An associative array containing:
 *   - content: An array containing information about the block. Each element
 *     of the array represents an administrative menu item, and must at least
 *     contain the keys 'title', 'href', and 'localized_options', which are
 *     passed to l(). A 'description' key may also be provided.
 *
 * @ingroup themeable
 */
function theme_admin_block_content($variables) {
  $content = $variables['content'];
  $output = '';

  if (!empty($content)) {
    $class = 'admin-list';
    if ($compact = system_admin_compact_mode()) {
      $class .= ' compact';
    }
    $output .= '<dl class="' . $class . '">';
    foreach ($content as $item) {
      $output .= '<dt>' . l($item['title'], $item['href'], $item['localized_options']) . '</dt>';
      if (!$compact && isset($item['description'])) {
        $output .= '<dd>' . filter_xss_admin($item['description']) . '</dd>';
      }
    }
    $output .= '</dl>';
  }
  return $output;
}

/**
 * Returns HTML for an administrative page.
 *
 * @param $variables
 *   An associative array containing:
 *   - blocks: An array of blocks to display. Each array should include a
 *     'title', a 'description', a formatted 'content' and a 'position' which
 *     will control which container it will be in. This is usually 'left' or
 *     'right'.
 *
 * @ingroup themeable
 */
function theme_admin_page($variables) {
  $blocks = $variables['blocks'];

  $stripe = 0;
  $container = array();

  foreach ($blocks as $block) {
    if ($block_output = theme('admin_block', array('block' => $block))) {
      if (empty($block['position'])) {
        // perform automatic striping.
        $block['position'] = ++$stripe % 2 ? 'left' : 'right';
      }
      if (!isset($container[$block['position']])) {
        $container[$block['position']] = '';
      }
      $container[$block['position']] .= $block_output;
    }
  }

  $output = '<div class="admin clearfix">';
  $output .= theme('system_compact_link');

  foreach ($container as $id => $data) {
    $output .= '<div class="' . $id . ' clearfix">';
    $output .= $data;
    $output .= '</div>';
  }
  $output .= '</div>';
  return $output;
}

/**
 * Returns HTML for the output of the admin index page.
 *
 * @param $variables
 *   An associative array containing:
 *   - menu_items: An array of modules to be displayed.
 *
 * @ingroup themeable
 */
function theme_system_admin_index($variables) {
  $menu_items = $variables['menu_items'];

  $stripe = 0;
  $container = array('left' => '', 'right' => '');
  $flip = array('left' => 'right', 'right' => 'left');
  $position = 'left';

  // Iterate over all modules.
  foreach ($menu_items as $module => $block) {
    list($description, $items) = $block;

    // Output links.
    if (count($items)) {
      $block = array();
      $block['title'] = $module;
      $block['content'] = theme('admin_block_content', array('content' => $items));
      $block['description'] = t($description);
      $block['show'] = TRUE;

      if ($block_output = theme('admin_block', array('block' => $block))) {
        if (!isset($block['position'])) {
          // Perform automatic striping.
          $block['position'] = $position;
          $position = $flip[$position];
        }
        $container[$block['position']] .= $block_output;
      }
    }
  }

  $output = '<div class="admin clearfix">';
  $output .= theme('system_compact_link');
  foreach ($container as $id => $data) {
    $output .= '<div class="' . $id . ' clearfix">';
    $output .= $data;
    $output .= '</div>';
  }
  $output .= '</div>';

  return $output;
}

/**
 * Returns HTML for the status report.
 *
 * @param $variables
 *   An associative array containing:
 *   - requirements: An array of requirements.
 *
 * @ingroup themeable
 */
function theme_status_report($variables) {
  $requirements = $variables['requirements'];
  $severities = array(
    REQUIREMENT_INFO => array(
      'title' => t('Info'),
      'class' => 'info',
    ),
    REQUIREMENT_OK => array(
      'title' => t('OK'),
      'class' => 'ok',
    ),
    REQUIREMENT_WARNING => array(
      'title' => t('Warning'),
      'class' => 'warning',
    ),
    REQUIREMENT_ERROR => array(
      'title' => t('Error'),
      'class' => 'error',
    ),
  );
  $output = '<table class="system-status-report"><thead><tr class="element-invisible">';
  $output .= '<th>' . t('Status') . '</th><th>' . t('Component') . '</th><th>' . t('Details') . '</th>';
  $output .= '</tr></thead><tbody>';

  foreach ($requirements as $requirement) {
    if (empty($requirement['#type'])) {
      // Always use the explicit requirement severity, if defined. Otherwise,
      // default to REQUIREMENT_OK in the installer to visually confirm that
      // installation requirements are met. And default to REQUIREMENT_INFO to
      // denote neutral information without special visualization.
      if (isset($requirement['severity'])) {
        $severity = $severities[(int) $requirement['severity']];
      }
      elseif (defined('MAINTENANCE_MODE') && MAINTENANCE_MODE == 'install') {
        $severity = $severities[REQUIREMENT_OK];
      }
      else {
        $severity = $severities[REQUIREMENT_INFO];
      }

      $severity['icon'] = '<div title="' . $severity['title'] . '"><span class="element-invisible">' . $severity['title'] . '</span></div>';

      // Output table rows.
      $output .= '<tr class="' . $severity['class'] . '">';
      $output .= '<td class="status-icon">' . $severity['icon'] . '</td>';
      $output .= '<td class="status-title">' . $requirement['title'] . '</td>';
      $output .= '<td class="status-value">' . $requirement['value'];
      if (!empty($requirement['description'])) {
        $output .= '<div class="description">' . $requirement['description'] . '</div>';
      }
      $output .= '</td></tr>';
    }
  }

  $output .= '</tbody></table>';
  return $output;
}

/**
 * Returns HTML for the modules form.
 *
 * @param $variables
 *   An associative array containing:
 *   - form: A render element representing the form.
 *
 * @ingroup themeable
 */
function theme_system_modules_details($variables) {
  $form = $variables['form'];

  // Individual table headers.
  $rows = array();
  // Iterate through all the modules, which are children of this element.
  foreach (element_children($form) as $key) {
    // Stick the key into $module for easier access.
    $module = $form[$key];
    // Create the row for the table.
    $row = array();
    // Add the checkbox into the first cell.
    unset($module['enable']['#title']);
    $module['#requires'] = array_filter($module['#requires']);
    $module['#required_by'] = array_filter($module['#required_by']);

    $requires = !empty($module['#requires']);
    $required_by = !empty($module['#required_by']);
    $version = !empty($module['version']['#markup']);

    $row[] = array('class' => array('checkbox'), 'data' => drupal_render($module['enable']));

    // Add the module label and expand/collapse functionalty.
    $col2 = '<label id="module-' . $key . '" for="' . $module['enable']['#id'] . '" class="module-name table-filter-text-source">' . drupal_render($module['name']) . '</label>';
    $row[] = array('class' => array('module'), 'data' => $col2);

    // Add the description, along with any modules it requires.
    $description = '<span class="details"><span class="text table-filter-text-source">' . drupal_render($module['description']) . '</span></span>';
    if ($version || $requires || $required_by) {
      $description .= ' <div class="requirements">';
      if ($version) {
        $description .= '<div class="admin-requirements">' . t('Version: !module-version', array('!module-version' => drupal_render($module['version']))) . '</div>';
      }
      if ($requires) {
        $description .= '<div class="admin-requirements">' . t('Requires: !module-list', array('!module-list' => implode(', ', $module['#requires']))) . '</div>';
      }
      if ($required_by) {
        $description .= '<div class="admin-requirements">' . t('Required by: !module-list', array('!module-list' => implode(', ', $module['#required_by']))) . '</div>';
      }
      $description .= '</div>';
    }
    $links = '';
    foreach (array('help', 'permissions', 'configure') as $key) {
      $links .= drupal_render($module['links'][$key]);
    }
    if ($links) {
      $description .= '  <div class="links">';
      $description .= $links;
      $description .= '</div>';
    }
    $col4 = '<div class="inner" tabindex="0" role="button"><span class="module-description-prefix element-invisible">Show description</span> ' . $description . '</div>';
    $row[] = array('class' => array('description', 'expand'), 'data' => $col4);

    $rows[] = $row;
  }

  return theme('table', array('header' => $form['#header'], 'rows' => $rows));
}

/**
 * Returns HTML for a message about incompatible modules.
 *
 * @param $variables
 *   An associative array containing:
 *   - message: The form array representing the currently disabled modules.
 *
 * @ingroup themeable
 */
function theme_system_modules_incompatible($variables) {
  return '<div class="incompatible">' . $variables['message'] . '</div>';
}

/**
 * Returns HTML for a table of currently disabled modules.
 *
 * @param $variables
 *   An associative array containing:
 *   - form: A render element representing the form.
 *
 * @ingroup themeable
 */
function theme_system_modules_uninstall($variables) {
  $form = $variables['form'];

  // No theming for the confirm form.
  if (isset($form['confirm'])) {
    return drupal_render($form);
  }

  // Table headers.
  $header = array(t('Uninstall'),
    t('Name'),
    t('Description'),
  );

  // Display table.
  $rows = array();
  foreach (element_children($form['modules']) as $module) {
    if (!empty($form['modules'][$module]['#required_by'])) {
      $disabled_message = format_plural(count($form['modules'][$module]['#required_by']),
        'To uninstall @module, the following module must be uninstalled first: @required_modules',
        'To uninstall @module, the following modules must be uninstalled first: @required_modules',
        array('@module' => $form['modules'][$module]['#module_name'], '@required_modules' => implode(', ', $form['modules'][$module]['#required_by'])));
      $disabled_message = '<div class="admin-requirements">' . $disabled_message . '</div>';
    }
    else {
      $disabled_message = '';
    }
    $rows[] = array(
      array('data' => drupal_render($form['uninstall'][$module]), 'align' => 'center'),
      '<strong><label for="' . $form['uninstall'][$module]['#id'] . '">' . drupal_render($form['modules'][$module]['name']) . '</label></strong>',
      array('data' => drupal_render($form['modules'][$module]['description']) . $disabled_message, 'class' => array('description')),
    );
  }

  $output  = theme('table', array('header' => $header, 'rows' => $rows, 'empty' => t('No modules are available to uninstall.')));
  $output .= drupal_render_children($form);

  return $output;
}

/**
 * Returns HTML for the Appearance page.
 *
 * @param $variables
 *   An associative array containing:
 *   - theme_groups: An associative array containing groups of themes.
 *
 * @ingroup themeable
 */
function theme_system_themes_page($variables) {
  $theme_groups = $variables['theme_groups'];

  $output = '<div id="system-themes-page">';

  foreach ($variables['theme_group_titles'] as $state => $title) {
    if (!count($theme_groups[$state])) {
      // Skip this group of themes if no theme is there.
      continue;
    }
    // Start new theme group.
    $output .= '<div class="system-themes-list system-themes-list-'. $state .' clearfix"><h2>'. $title .'</h2>';

    foreach ($theme_groups[$state] as $theme) {

      // Theme the screenshot.
      $screenshot = $theme->screenshot ? theme('image', $theme->screenshot) : '<div class="no-screenshot"><div class="no-screenshot__text">' . t('no screenshot') . '</div></div>';

      // Localize the theme description.
      $description = t($theme->info['description']);

      // Style theme info
      $notes = count($theme->notes) ? ' (' . join(', ', $theme->notes) . ')' : '';
      $theme->classes[] = 'theme-selector';
      $theme->classes[] = 'clearfix';
      $output .= '<div class="'. join(' ', $theme->classes) .'">' . $screenshot . '<div class="theme-info"><h3>' . $theme->info['name'] . ' ' . (isset($theme->info['version']) ? $theme->info['version'] : '') . $notes . '</h3><div class="theme-description">' . $description . '</div>';

      // Make sure to provide feedback on compatibility.
      if (!empty($theme->incompatible_core)) {
        $output .= '<div class="incompatible">' . t('This version is not compatible with Drupal !core_version and should be replaced.', array('!core_version' => DRUPAL_CORE_COMPATIBILITY)) . '</div>';
      }
      elseif (!empty($theme->incompatible_php)) {
        if (substr_count($theme->info['php'], '.') < 2) {
          $theme->info['php'] .= '.*';
        }
        $output .= '<div class="incompatible">' . t('This theme requires PHP version @php_required and is incompatible with PHP version !php_version.', array('@php_required' => $theme->info['php'], '!php_version' => phpversion())) . '</div>';
      }
      elseif (!empty($theme->incompatible_base)) {
        $output .= '<div class="incompatible">' . t('This theme requires the base theme @base_theme to operate correctly.', array('@base_theme' => $theme->info['base theme'])) . '</div>';
      }
      elseif (!empty($theme->incompatible_engine)) {
        $output .= '<div class="incompatible">' . t('This theme requires the theme engine @theme_engine to operate correctly.', array('@theme_engine' => $theme->info['engine'])) . '</div>';
      }
      else {
        $output .= theme('links', array('links' => $theme->operations, 'attributes' => array('class' => array('operations', 'clearfix'))));
      }
      $output .= '</div></div>';
    }
    $output .= '</div>';
  }
  $output .= '</div>';

  return $output;
}

/**
 * Displays the date format strings overview page.
 */
function system_date_time_formats() {
  $header = array(
    array('data' => t('Machine name'), 'field' => 'machine_name'),
    array('data' => t('Name'), 'field' => 'name'),
    array('data' => t('Pattern'), 'field' => 'pattern'),
    array('data' => t('Operations'))
  );
  $rows = array();

  $formats = system_get_date_formats();

  if (!empty($formats)) {
    foreach ($formats as $date_format_id => $format_info) {
      // Do not display date formats that are locked.
      if (empty($format_info['locked'])) {
        $row = array();
        $row[] = array('data' => $date_format_id);
        $row[] = array('data' => $format_info['name']);
        $row[] = array('data' => format_date(REQUEST_TIME, $date_format_id));

        // Prepare Operational links.
        $links = array();
        $links['edit'] = array(
          'title' => t('Edit'),
          'href' => 'admin/config/regional/date-time/formats/' . $date_format_id . '/edit',
        );
        $links['delete'] = array(
          'title' => t('Delete'),
          'href' => 'admin/config/regional/date-time/formats/' . $date_format_id . '/delete',
        );
        $row['operations'] = array('data' => array(
          '#type' => 'operations',
          '#links' => $links,
        ));

        $rows[] = $row;
      }
    }
  }

  $build['date_formats_table'] = array(
    '#theme' => 'table',
    '#header' => $header,
    '#rows' => $rows,
    '#empty' => t('No custom date formats available. <a href="@link">Add date format</a>.', array('@link' => url('admin/config/regional/date-time/formats/add'))),
  );

  return $build;
}

/**
 * Checks if the chosen machine_name exists or not.
 */
function system_date_format_exists($candidate_machine_name) {
  if ($formats = system_get_date_formats()) {
    return array_key_exists($candidate_machine_name, $formats);
  }
  return FALSE;
}

/**
 * Page callback: Displays edit date format links for each language.
 *
 * @see locale_menu()
 */
function system_date_format_language_overview_page() {
  $header = array(t('Language'), t('Operations'));

  $languages = language_list();
  foreach ($languages as $langcode => $language) {
    $row = array();
    $row[] = $language->name;
    $links = array();
    $links['edit'] = array(
      'title' => t('Edit'),
      'href' => "admin/config/regional/date-time/locale/$langcode/edit",
    );
    $links['reset'] = array(
      'title' => t('Reset'),
      'href' => "admin/config/regional/date-time/locale/$langcode/reset",
    );
    $row[] = array(
      'data' => array(
        '#type' => 'operations',
        '#links' => $links,
      ),
    );
    $rows[] = $row;
  }

  return theme('table', array('header' => $header, 'rows' => $rows));
}

/**
 * Form constructor for the date localization configuration form.
 *
 * @param $langcode
 *   The code for the current language.
 *
 * @see locale_menu()
 * @see system_date_format_localize_form_submit()
 * @ingroup forms
 */
function system_date_format_localize_form($form, &$form_state, $langcode) {
  // Display the current language name.
  $form['language'] = array(
    '#type' => 'item',
    '#title' => t('Language'),
    '#markup' => language_load($langcode)->name,
    '#weight' => -10,
  );
  $form['langcode'] = array(
    '#type' => 'value',
    '#value' => $langcode,
  );

  // Get list of available formats.
  $formats = system_get_date_formats();
  $choices = array();
  foreach ($formats as $date_format_id => $format_info) {
    // Ignore values that are localized.
    if (empty($format_info['locales'])) {
      $choices[$date_format_id] = format_date(REQUEST_TIME, $date_format_id);
    }
    else {
      unset($formats[$date_format_id]);
    }
  }

  // Get configured formats for each language.
  $locale_formats = system_date_format_locale($langcode);
  if (!empty($locale_formats)) {
    $formats += $locale_formats;
    foreach ($locale_formats as $date_format_id => $format_info) {
      $choices[$date_format_id] = format_date(REQUEST_TIME, $date_format_id);
    }
  }

  // Display a form field for each format type.
  foreach ($formats as $date_format_id => $format_info) {
    // Show date format select list.
    $form['date_formats']['date_format_' . $date_format_id] = array(
      '#type' => 'select',
      '#title' => check_plain($format_info['name']),
      '#attributes' => array('class' => array('date-format')),
      '#default_value' => isset($choices[$date_format_id]) ? $date_format_id : 'custom',
      '#options' => $choices,
    );
  }

  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Save configuration'),
  );

  return $form;
}

/**
 * Ajax callback; Returns the date for a given format string.
 */
function system_date_time_lookup($form, &$form_state) {
  $format = '';
  if (!empty($form_state['values']['date_format_pattern'])) {
    $format = t('Displayed as %date_format', array('%date_format' => format_date(REQUEST_TIME, 'custom', $form_state['values']['date_format_pattern'])));
  }
  // Return a command instead of a string, since the Ajax framework
  // automatically prepends an additional empty DIV element for a string, which
  // breaks the layout.
  $response = new AjaxResponse();
  $response->addCommand(new ReplaceCommand('#edit-date-format-suffix', '<small id="edit-date-format-suffix">' . $format . '</small>'));
  return $response;
}

/**
 * Form submission handler for system_date_format_localize_form().
 */
function system_date_format_localize_form_submit($form, &$form_state) {
  $langcode = $form_state['values']['langcode'];

  $formats = system_get_date_formats();
  foreach ($formats as $date_format_id => $format_info) {
    if (isset($form_state['values']['date_format_' . $date_format_id])) {
      $format = $form_state['values']['date_format_' . $date_format_id];
      system_date_format_localize_form_save($langcode, $date_format_id, $formats[$format]['pattern']);
    }
  }
  drupal_set_message(t('Configuration saved.'));
  $form_state['redirect'] = 'admin/config/regional/date-time/locale';
}

/**
 * Returns HTML for a locale date format form.
 *
 * @param $variables
 *   An associative array containing:
 *   - form: A render element representing the form.
 *
 * @ingroup themeable
 */
function theme_system_date_format_localize_form($variables) {
  $form = $variables['form'];
  $header = array(
    'machine_name' => t('Machine Name'),
    'pattern' => t('Format'),
  );

  foreach (element_children($form['date_formats']) as $key) {
    $row = array();
    $row[] = $form['date_formats'][$key]['#title'];
    unset($form['date_formats'][$key]['#title']);
    $row[] = array('data' => drupal_render($form['date_formats'][$key]));
    $rows[] = $row;
  }

  $output = drupal_render($form['language']);
  $output .= theme('table', array('header' => $header, 'rows' => $rows));
  $output .= drupal_render_children($form);

  return $output;
}

/**
 * Save locale specific date formats to the database.
 *
 * @param $langcode
 *   Language code, can be 2 characters, e.g. 'en' or 5 characters, e.g.
 *   'en-CA'.
 * @param $date_format_id
 *   Date format id, e.g. 'short', 'medium'.
 * @param $format
 *   The date format string.
 */
function system_date_format_localize_form_save($langcode, $date_format_id, $format) {
  config('locale.config.' . $langcode . '.system.date')
    ->set('formats.' . $date_format_id . '.pattern', $format)
    ->save();
}