drupal/core/modules/block/block.module

<?php

/**
 * @file
 * Controls the visual building blocks a page is constructed with.
 */

use Drupal\Component\Utility\Html;
use Drupal\Core\Installer\InstallerKernel;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Link;
use Drupal\Core\Url;
use Drupal\language\ConfigurableLanguageInterface;
use Drupal\system\Entity\Menu;
use Drupal\block\Entity\Block;

/**
 * Implements hook_help().
 */
function block_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.block':
      $block_content = \Drupal::moduleHandler()->moduleExists('block_content') ? Url::fromRoute('help.page', ['name' => 'block_content'])->toString() : '#';
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Block module allows you to place blocks in regions of your installed themes, and configure block settings. For more information, see the <a href=":blocks-documentation">online documentation for the Block module</a>.', [':blocks-documentation' => 'https://www.drupal.org/documentation/modules/block/']) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Placing and moving blocks') . '</dt>';
      $output .= '<dd>' . t('You can place a new block in a region by selecting <em>Place block</em> on the <a href=":blocks">Block layout page</a>. Once a block is placed, it can be moved to a different region by drag-and-drop or by using the <em>Region</em> drop-down list, and then clicking <em>Save blocks</em>.', [':blocks' => Url::fromRoute('block.admin_display')->toString()]) . '</dd>';
      $output .= '<dt>' . t('Toggling between different themes') . '</dt>';
      $output .= '<dd>' . t('Blocks are placed and configured specifically for each theme. The Block layout page opens with the default theme, but you can toggle to other installed themes.') . '</dd>';
      $output .= '<dt>' . t('Demonstrating block regions for a theme') . '</dt>';
      $output .= '<dd>' . t('You can see where the regions are for the current theme by clicking the <em>Demonstrate block regions</em> link on the <a href=":blocks">Block layout page</a>. Regions are specific to each theme.', [':blocks' => Url::fromRoute('block.admin_display')->toString()]) . '</dd>';
      $output .= '<dt>' . t('Configuring block settings') . '</dt>';
      $output .= '<dd>' . t('To change the settings of an individual block click on the <em>Configure</em> link on the <a href=":blocks">Block layout page</a>. The available options vary depending on the module that provides the block. For all blocks you can change the block title and toggle whether to display it.', [':blocks' => Url::fromRoute('block.admin_display')->toString()]) . '</dd>';
      $output .= '<dt>' . t('Controlling visibility') . '</dt>';
      $output .= '<dd>' . t('You can control the visibility of a block by restricting it to specific pages, content types, and/or roles by setting the appropriate options under <em>Visibility settings</em> of the block configuration.') . '</dd>';
      $output .= '<dt>' . t('Adding custom blocks') . '</dt>';
      $output .= '<dd>' . t('You can add custom blocks, if the <em>Custom Block</em> module is installed. For more information, see the <a href=":blockcontent-help">Custom Block help page</a>.', [':blockcontent-help' => $block_content]) . '</dd>';
      $output .= '</dl>';
      return $output;
  }
  if ($route_name == 'block.admin_display' || $route_name == 'block.admin_display_theme') {
    $demo_theme = $route_match->getParameter('theme') ?: \Drupal::config('system.theme')->get('default');
    $themes = \Drupal::service('theme_handler')->listInfo();
    $output = '<p>' . t('Block placement is specific to each theme on your site. Changes will not be saved until you click <em>Save blocks</em> at the bottom of the page.') . '</p>';
    $output .= '<p>' . Link::fromTextAndUrl(t('Demonstrate block regions (@theme)', ['@theme' => $themes[$demo_theme]->info['name']]), Url::fromRoute('block.admin_demo', ['theme' => $demo_theme]))->toString() . '</p>';
    return $output;
  }
}

/**
 * Implements hook_theme().
 */
function block_theme() {
  return [
    'block' => [
      'render element' => 'elements',
    ],
  ];
}

/**
 * Implements hook_page_top().
 */
function block_page_top(array &$page_top) {
  if (\Drupal::routeMatch()->getRouteName() === 'block.admin_demo') {
    $theme = \Drupal::theme()->getActiveTheme()->getName();
    $page_top['backlink'] = [
      '#type' => 'link',
      '#title' => t('Exit block region demonstration'),
      '#options' => ['attributes' => ['class' => ['block-demo-backlink']]],
      '#weight' => -10,
    ];
    if (\Drupal::config('system.theme')->get('default') == $theme) {
      $page_top['backlink']['#url'] = Url::fromRoute('block.admin_display');
    }
    else {
      $page_top['backlink']['#url'] = Url::fromRoute('block.admin_display_theme', ['theme' => $theme]);
    }
  }
}

/**
 * Initializes blocks for installed themes.
 *
 * @param $theme_list
 *   An array of theme names.
 *
 * @see block_modules_installed()
 */
function block_themes_installed($theme_list) {
  // Disable this functionality prior to install profile installation because
  // block configuration is often optional or provided by the install profile
  // itself. block_theme_initialize() will be called when the install profile is
  // installed.
  if (InstallerKernel::installationAttempted() && \Drupal::config('core.extension')->get('module.' . \Drupal::installProfile()) === NULL) {
    return;
  }

  foreach ($theme_list as $theme) {
    // Don't initialize themes that are not displayed in the UI.
    if (\Drupal::service('theme_handler')->hasUi($theme)) {
      block_theme_initialize($theme);
    }
  }
}

/**
 * Assigns an initial, default set of blocks for a theme.
 *
 * This function is called the first time a new theme is installed. The new
 * theme gets a copy of the default theme's blocks, with the difference that if
 * a particular region isn't available in the new theme, the block is assigned
 * to the new theme's default region.
 *
 * @param $theme
 *   The name of a theme.
 */
function block_theme_initialize($theme) {
  // Initialize theme's blocks if none already registered.
  $has_blocks = \Drupal::entityTypeManager()->getStorage('block')->loadByProperties(['theme' => $theme]);
  if (!$has_blocks) {
    $default_theme = \Drupal::config('system.theme')->get('default');
    // Apply only to new theme's visible regions.
    $regions = system_region_list($theme, REGIONS_VISIBLE);
    $default_theme_blocks = \Drupal::entityTypeManager()->getStorage('block')->loadByProperties(['theme' => $default_theme]);
    foreach ($default_theme_blocks as $default_theme_block_id => $default_theme_block) {
      if (str_starts_with($default_theme_block_id, $default_theme . '_')) {
        $id = str_replace($default_theme, $theme, $default_theme_block_id);
      }
      else {
        $id = $theme . '_' . $default_theme_block_id;
      }
      $block = $default_theme_block->createDuplicateBlock($id, $theme);
      // If the region isn't supported by the theme, assign the block to the
      // theme's default region.
      if (!isset($regions[$block->getRegion()])) {
        $block->setRegion(system_default_region($theme));
      }
      $block->save();
    }
  }
}

/**
 * Implements hook_modules_installed().
 *
 * @see block_themes_installed()
 */
function block_modules_installed($modules) {
  // block_themes_installed() does not call block_theme_initialize() during site
  // installation because block configuration can be optional or provided by the
  // profile. Now, when the profile is installed, this configuration exists,
  // call block_theme_initialize() for all installed themes.
  $profile = \Drupal::installProfile();
  if (in_array($profile, $modules, TRUE)) {
    foreach (\Drupal::service('theme_handler')->listInfo() as $theme => $data) {
      block_theme_initialize($theme);
    }
  }
}

/**
 * Implements hook_rebuild().
 */
function block_rebuild() {
  foreach (\Drupal::service('theme_handler')->listInfo() as $theme => $data) {
    if ($data->status) {
      $regions = system_region_list($theme);
      /** @var \Drupal\block\BlockInterface[] $blocks */
      $blocks = \Drupal::entityTypeManager()->getStorage('block')->loadByProperties(['theme' => $theme]);
      foreach ($blocks as $block_id => $block) {
        // Disable blocks in invalid regions.
        if (!isset($regions[$block->getRegion()])) {
          if ($block->status()) {
            \Drupal::messenger()
              ->addWarning(t('The block %info was assigned to the invalid region %region and has been disabled.', [
                '%info' => $block_id,
                '%region' => $block->getRegion(),
              ]));
          }
          $block
            ->setRegion(system_default_region($theme))
            ->disable()
            ->save();
        }
      }
    }
  }
}

/**
 * Implements hook_theme_suggestions_HOOK().
 */
function block_theme_suggestions_block(array $variables) {
  $suggestions = [];

  $suggestions[] = 'block__' . $variables['elements']['#configuration']['provider'];
  // Hyphens (-) and underscores (_) play a special role in theme suggestions.
  // Theme suggestions should only contain underscores, because within
  // drupal_find_theme_templates(), underscores are converted to hyphens to
  // match template file names, and then converted back to underscores to match
  // pre-processing and other function names. So if your theme suggestion
  // contains a hyphen, it will end up as an underscore after this conversion,
  // and your function names won't be recognized. So, we need to convert
  // hyphens to underscores in block deltas for the theme suggestions.

  // We can safely explode on : because we know the Block plugin type manager
  // enforces that delimiter for all derivatives.
  $parts = explode(':', $variables['elements']['#plugin_id']);
  $suggestion = 'block';
  while ($part = array_shift($parts)) {
    $suggestions[] = $suggestion .= '__' . strtr($part, '-', '_');
  }

  if (!empty($variables['elements']['#id'])) {
    $suggestions[] = 'block__' . $variables['elements']['#id'];
  }

  return $suggestions;
}

/**
 * Prepares variables for block templates.
 *
 * Default template: block.html.twig.
 *
 * Prepares the values passed to the theme_block function to be passed
 * into a pluggable template engine. Uses block properties to generate a
 * series of template file suggestions. If none are found, the default
 * block.html.twig is used.
 *
 * Most themes use their own copy of block.html.twig. The default is located
 * inside "core/modules/block/templates/block.html.twig". Look in there for the
 * full list of available variables.
 *
 * @param array $variables
 *   An associative array containing:
 *   - elements: An associative array containing the properties of the element.
 *     Properties used: #block, #configuration, #children, #plugin_id.
 */
function template_preprocess_block(&$variables) {
  $variables['configuration'] = $variables['elements']['#configuration'];
  $variables['plugin_id'] = $variables['elements']['#plugin_id'];
  $variables['base_plugin_id'] = $variables['elements']['#base_plugin_id'];
  $variables['derivative_plugin_id'] = $variables['elements']['#derivative_plugin_id'];
  $variables['in_preview'] = $variables['elements']['#in_preview'] ?? FALSE;
  $variables['label'] = !empty($variables['configuration']['label_display']) ? $variables['configuration']['label'] : '';
  $variables['content'] = $variables['elements']['content'];
  // A block's label is configuration: it is static. Allow dynamic labels to be
  // set in the render array.
  if (isset($variables['elements']['content']['#title']) && !empty($variables['configuration']['label_display'])) {
    $variables['label'] = $variables['elements']['content']['#title'];
  }

  // Create a valid HTML ID and make sure it is unique.
  if (!empty($variables['elements']['#id'])) {
    $variables['attributes']['id'] = Html::getUniqueId('block-' . $variables['elements']['#id']);
  }

  // Proactively add aria-describedby if possible to improve accessibility.
  if ($variables['label'] && isset($variables['attributes']['role'])) {
    $variables['title_attributes']['id'] = Html::getUniqueId($variables['label']);
    $variables['attributes']['aria-describedby'] = $variables['title_attributes']['id'];
  }

}

/**
 * Implements hook_ENTITY_TYPE_delete() for user_role entities.
 *
 * Removes deleted role from blocks that use it.
 */
function block_user_role_delete($role) {
  foreach (Block::loadMultiple() as $block) {
    /** @var \Drupal\block\BlockInterface $block */
    $visibility = $block->getVisibility();
    if (isset($visibility['user_role']['roles'][$role->id()])) {
      unset($visibility['user_role']['roles'][$role->id()]);
      $block->setVisibilityConfig('user_role', $visibility['user_role']);
      $block->save();
    }
  }
}

/**
 * Implements hook_ENTITY_TYPE_delete() for menu entities.
 */
function block_menu_delete(Menu $menu) {
  if (!$menu->isSyncing()) {
    foreach (Block::loadMultiple() as $block) {
      if ($block->getPluginId() == 'system_menu_block:' . $menu->id()) {
        $block->delete();
      }
    }
  }
}

/**
 * Implements hook_ENTITY_TYPE_delete() for 'configurable_language'.
 *
 * Delete the potential block visibility settings of the deleted language.
 */
function block_configurable_language_delete(ConfigurableLanguageInterface $language) {
  // Remove the block visibility settings for the deleted language.
  foreach (Block::loadMultiple() as $block) {
    /** @var \Drupal\block\BlockInterface $block */
    $visibility = $block->getVisibility();
    if (isset($visibility['language']['langcodes'][$language->id()])) {
      unset($visibility['language']['langcodes'][$language->id()]);
      $block->setVisibilityConfig('language', $visibility['language']);
      $block->save();
    }
  }
}