path: root/modules/block/block.module

<?php
// $Id$

/**
 * @file
 * Controls the boxes that are displayed around the main content.
 */

/**
 * Denotes that a block is not enabled in any region and should not be shown.
 */
define('BLOCK_REGION_NONE', -1);

/**
 * Constants defining cache granularity for blocks.
 *
 * Modules specify the caching patterns for their blocks using binary
 * combinations of these constants in their hook_block_list():
 *   $block[delta]['cache'] = BLOCK_CACHE_PER_ROLE | BLOCK_CACHE_PER_PAGE;
 * BLOCK_CACHE_PER_ROLE is used as a default when no caching pattern is
 * specified.
 *
 * The block cache is cleared in cache_clear_all(), and uses the same clearing
 * policy than page cache (node, comment, user, taxonomy added or updated...).
 * Blocks requiring more fine-grained clearing might consider disabling the
 * built-in block cache (BLOCK_NO_CACHE) and roll their own.
 *
 * Note that user 1 is excluded from block caching.
 */

/**
 * The block should not get cached. This setting should be used:
 * - for simple blocks (notably those that do not perform any db query),
 * where querying the db cache would be more expensive than directly generating
 * the content.
 * - for blocks that change too frequently.
 */
define('BLOCK_NO_CACHE', -1);

/**
 * The block can change depending on the roles the user viewing the page belongs to.
 * This is the default setting, used when the block does not specify anything.
 */
define('BLOCK_CACHE_PER_ROLE', 0x0001);

/**
 * The block can change depending on the user viewing the page.
 * This setting can be resource-consuming for sites with large number of users,
 * and thus should only be used when BLOCK_CACHE_PER_ROLE is not sufficient.
 */
define('BLOCK_CACHE_PER_USER', 0x0002);

/**
 * The block can change depending on the page being viewed.
 */
define('BLOCK_CACHE_PER_PAGE', 0x0004);

/**
 * The block is the same for every user on every page where it is visible.
 */
define('BLOCK_CACHE_GLOBAL', 0x0008);

/**
 * Implement hook_help().
 */
function block_help($path, $arg) {
  switch ($path) {
    case 'admin/help#block':
      $output = '<p>' . t('Blocks are boxes of content rendered into an area, or region, of a web page. The default theme Garland, for example, implements the regions "left sidebar", "right sidebar", "content", "header", and "footer", and a block may appear in any one of these areas. The <a href="@blocks">blocks administration page</a> provides a drag-and-drop interface for assigning a block to a region, and for controlling the order of blocks within regions.', array('@blocks' => url('admin/structure/block'))) . '</p>';
      $output .= '<p>' . t('Although blocks are usually generated automatically by modules (like the <em>User login</em> block, for example), administrators can also define custom blocks. Custom blocks have a title, description, and body. The body of the block can be as long as necessary, and can contain content supported by any available <a href="@text-format">text format</a>.', array('@text-format' => url('admin/settings/filter'))) . '</p>';
      $output .= '<p>' . t('When working with blocks, remember that:') . '</p>';
      $output .= '<ul><li>' . t('since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis.') . '</li>';
      $output .= '<li>' . t('disabled blocks, or blocks not in a region, are never shown.') . '</li>';
      $output .= '<li>' . t('blocks can be configured to be visible only on certain pages.') . '</li>';
      $output .= '<li>' . t('blocks can be configured to be visible only when specific conditions are true.') . '</li>';
      $output .= '<li>' . t('blocks can be configured to be visible only for certain user roles.') . '</li>';
      $output .= '<li>' . t('when allowed by an administrator, specific blocks may be enabled or disabled on a per-user basis using the <em>My account</em> page.') . '</li>';
      $output .= '<li>' . t('some dynamic blocks, such as those generated by modules, will be displayed only on certain pages.') . '</li></ul>';
      $output .= '<p>' . t('For more information, see the online handbook entry for <a href="@block">Block module</a>.', array('@block' => 'http://drupal.org/handbook/modules/block/')) . '</p>';
      return $output;
    case 'admin/structure/block':
      $output = '<p>' . t('This page provides a drag-and-drop interface for assigning a block to a region, and for controlling the order of blocks within regions. Since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis. Remember that your changes will not be saved until you click the <em>Save blocks</em> button at the bottom of the page.') . '</p>';
      $output .= '<p>' . t('Click the <em>configure</em> link next to each block to configure its specific title and visibility settings. Use the <a href="@add-block">add block page</a> to create a custom block.', array('@add-block' => url('admin/structure/block/add'))) . '</p>';
      return $output;
    case 'admin/structure/block/add':
      return '<p>' . t('Use this page to create a new custom block. New blocks are disabled by default, and must be moved to a region on the <a href="@blocks">blocks administration page</a> to be visible.', array('@blocks' => url('admin/structure/block'))) . '</p>';
  }
}

/**
 * Implement hook_theme().
 */
function block_theme() {
  return array(
    'block' => array(
      'arguments' => array('elements' => NULL),
      'template' => 'block',
    ),
    'block_admin_display_form' => array(
      'template' => 'block-admin-display-form',
      'file' => 'block.admin.inc',
      'arguments' => array('form' => NULL),
    ),
  );
}

/**
 * Implement hook_permission().
 */
function block_permission() {
  return array(
    'administer blocks' => array(
      'title' => t('Administer blocks'),
      'description' => t('Select which blocks are displayed, and arrange them on the page.'),
    ),
  );
}

/**
 * Implement hook_menu().
 */
function block_menu() {
  $items['admin/structure/block'] = array(
    'title' => 'Blocks',
    'description' => 'Configure what block content appears in your site\'s sidebars and other regions.',
    'page callback' => 'block_admin_display',
    'access arguments' => array('administer blocks'),
    'file' => 'block.admin.inc',
  );
  $items['admin/structure/block/list'] = array(
    'title' => 'List',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10,
  );
  $items['admin/structure/block/list/js'] = array(
    'title' => 'JavaScript List Form',
    'page callback' => 'block_admin_display_js',
    'access arguments' => array('administer blocks'),
    'type' => MENU_CALLBACK,
    'file' => 'block.admin.inc',
  );
  $items['admin/structure/block/configure'] = array(
    'title' => 'Configure block',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('block_admin_configure'),
    'access arguments' => array('administer blocks'),
    'type' => MENU_CALLBACK,
    'file' => 'block.admin.inc',
  );
  $items['admin/structure/block/delete'] = array(
    'title' => 'Delete block',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('block_box_delete'),
    'access arguments' => array('administer blocks'),
    'type' => MENU_CALLBACK,
    'file' => 'block.admin.inc',
  );
  $items['admin/structure/block/add'] = array(
    'title' => 'Add block',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('block_add_block_form'),
    'access arguments' => array('administer blocks'),
    'type' => MENU_LOCAL_ACTION,
    'file' => 'block.admin.inc',
  );
  $default = variable_get('theme_default', 'garland');
  foreach (list_themes() as $key => $theme) {
    $items['admin/structure/block/list/' . $key] = array(
      'title' => check_plain($theme->info['name']),
      'page arguments' => array($key),
      'type' => $key == $default ? MENU_DEFAULT_LOCAL_TASK : MENU_LOCAL_TASK,
      'weight' => $key == $default ? -10 : 0,
      'access callback' => '_block_themes_access',
      'access arguments' => array($theme),
      'file' => 'block.admin.inc',
    );
  }
  return $items;
}

/**
 * Menu item access callback - only admin or enabled themes can be accessed.
 */
function _block_themes_access($theme) {
  $admin_theme = variable_get('admin_theme');
  return user_access('administer blocks') && ($theme->status || ($admin_theme && ($theme->name == $admin_theme)));
}

/**
 * Implement hook_block_list().
 */
function block_block_list() {
  $blocks = array();

  $result = db_query('SELECT bid, info FROM {box} ORDER BY info');
  foreach ($result as $block) {
    $blocks[$block->bid]['info'] = $block->info;
    // Not worth caching.
    $blocks[$block->bid]['cache'] = BLOCK_NO_CACHE;
  }
  return $blocks;
}

/**
 * Implement hook_block_configure().
 */
function block_block_configure($delta = 0) {
  $box = array('format' => FILTER_FORMAT_DEFAULT);
  if ($delta) {
    $box = block_box_get($delta);
  }
  return block_box_form($box);
}

/**
 * Implement hook_block_save().
 */
function block_block_save($delta = 0, $edit = array()) {
  block_box_save($edit, $delta);
}

/**
 * Implement hook_block_view().
 *
 * Generates the administrator-defined blocks for display.
 */
function block_block_view($delta = 0, $edit = array()) {
  $block = db_query('SELECT body, format FROM {box} WHERE bid = :bid', array(':bid' => $delta))->fetchObject();
  $data['content'] = check_markup($block->body, $block->format);
  return $data;
}

/**
 * Implement hook_page_alter().
 *
 * Render blocks into their regions.
 */
function block_page_alter($page) {
  global $theme;

  // The theme system might not yet be initialized. We need $theme.
  drupal_theme_initialize();

  // Populate all block regions
  $all_regions = system_region_list($theme);

  // Load all region content assigned via blocks.
  foreach (array_keys($all_regions) as $region) {
    // Prevent sidebar regions from rendering blocks when 'show_blocks' == FALSE.
    if (!empty($page['#show_blocks']) || (strpos($region, 'sidebar_') !== 0)) {
      // Assign blocks to region.
      if ($blocks = block_get_blocks_by_region($region)) {
        $page[$region] = $blocks;
      }

      // Append region description if we are rendering the block admin page.
      $item = menu_get_item();
      if ($item['path'] == 'admin/structure/block') {
        $visible_regions = system_region_list($theme, REGIONS_VISIBLE);
        if (isset($visible_regions[$region])) {
          $description = '<div class="block-region">' . $all_regions[$region] . '</div>';
          $page[$region]['block_description'] = array(
            '#markup' => $description,
            '#weight' => 15,
          );
        }
      }
    }
  }
}

/**
 * Get a renderable array of a region containing all enabled blocks.
 *
 * @param $region
 *   The requested region.
 */
function block_get_blocks_by_region($region) {
  $weight = 0;
  $build = array();
  if ($list = block_list($region)) {
    foreach ($list as $key => $block) {
      $build[$key] = $block->content;
      unset($block->content);
      $build[$key] += array(
        '#block' => $block,
        '#weight' => ++$weight,
      );
      $build[$key]['#theme_wrappers'][] ='block';
    }
    $build['#sorted'] = TRUE;
  }
  return $build;
}

/**
 * Update the 'block' DB table with the blocks currently exported by modules.
 *
 * @return
 *   Blocks currently exported by modules.
 */
function _block_rehash() {
  global $theme_key;

  drupal_theme_initialize();

  $old_blocks = array();
  $result = db_query("SELECT * FROM {block} WHERE theme = :theme", array(':theme' => $theme_key));
  foreach ($result as $old_block) {
    $old_block = is_object($old_block) ? get_object_vars($old_block) : $old_block;
    $old_blocks[$old_block['module']][$old_block['delta']] = $old_block;
  }

  $blocks = array();
  // Valid region names for the theme.
  $regions = system_region_list($theme_key);

  foreach (module_implements('block_list') as $module) {
    $module_blocks = module_invoke($module, 'block_list');
    if ($module_blocks) {
      foreach ($module_blocks as $delta => $block) {
        if (empty($old_blocks[$module][$delta])) {
          // If it's a new block, add identifiers.
          $block['module'] = $module;
          $block['delta']  = $delta;
          $block['theme']  = $theme_key;
          if (!isset($block['pages'])) {
            // {block}.pages is type 'text', so it cannot have a
            // default value, and not null, so we need to provide
            // value if the module did not.
            $block['pages']  = '';
          }
          // Add defaults and save it into the database.
          drupal_write_record('block', $block);
          // Set region to none if not enabled.
          $block['region'] = $block['status'] ? $block['region'] : BLOCK_REGION_NONE;
          // Add to the list of blocks we return.
          $blocks[] = $block;
        }
        else {
          // If it's an existing block, database settings should overwrite
          // the code. But aside from 'info' everything that's definable in
          // code is stored in the database and we do not store 'info', so we
          // do not need to update the database here.
          // Add 'info' to this block.
          $old_blocks[$module][$delta]['info'] = $block['info'];
          // If the region name does not exist, disable the block and assign it to none.
          if (!empty($old_blocks[$module][$delta]['region']) && !isset($regions[$old_blocks[$module][$delta]['region']])) {
            drupal_set_message(t('The block %info was assigned to the invalid region %region and has been disabled.', array('%info' => $old_blocks[$module][$delta]['info'], '%region' => $old_blocks[$module][$delta]['region'])), 'warning');
            $old_blocks[$module][$delta]['status'] = 0;
            $old_blocks[$module][$delta]['region'] = BLOCK_REGION_NONE;
          }
          else {
            $old_blocks[$module][$delta]['region'] = $old_blocks[$module][$delta]['status'] ? $old_blocks[$module][$delta]['region'] : BLOCK_REGION_NONE;
          }
          // Add this block to the list of blocks we return.
          $blocks[] = $old_blocks[$module][$delta];
          // Remove this block from the list of blocks to be deleted.
          unset($old_blocks[$module][$delta]);
        }
      }
    }
  }

  // Remove blocks that are no longer defined by the code from the database.
  foreach ($old_blocks as $module => $old_module_blocks) {
    foreach ($old_module_blocks as $delta => $block) {
      db_delete('block')
        ->condition('module', $module)
        ->condition('delta', $delta)
        ->condition('theme', $theme_key)
        ->execute();
    }
  }
  return $blocks;
}

function block_box_get($bid) {
  return db_query("SELECT * FROM {box} WHERE bid = :bid", array(':bid' => $bid))->fetchAssoc();
}

/**
 * Define the custom block form.
 */
function block_box_form($edit = array()) {
  $edit += array(
    'info' => '',
    'body' => '',
  );
  $form['info'] = array(
    '#type' => 'textfield',
    '#title' => t('Block description'),
    '#default_value' => $edit['info'],
    '#maxlength' => 64,
    '#description' => t('A brief description of your block. Used on the <a href="@overview">blocks administration page</a>.', array('@overview' => url('admin/structure/block'))),
    '#required' => TRUE,
    '#weight' => -19,
  );
  $form['body_field']['#weight'] = -17;
  $form['body_field']['body'] = array(
    '#type' => 'textarea',
    '#title' => t('Block body'),
    '#default_value' => $edit['body'],
    '#text_format' => isset($edit['format']) ? $edit['format'] : FILTER_FORMAT_DEFAULT,
    '#rows' => 15,
    '#description' => t('The content of the block as shown to the user.'),
    '#required' => TRUE,
    '#weight' => -17,
    '#access' => filter_access($edit['format']),
  );

  return $form;
}

function block_box_save($edit, $delta) {
  db_update('box')
    ->fields(array(
      'body' => $edit['body'],
      'info' => $edit['info'],
      'format' => $edit['body_format'],
    ))
    ->condition('bid', $delta)
    ->execute();
  return TRUE;
}

/**
 * Implement hook_user_form().
 */
function block_user_form(&$edit, $account, $category) {
  if ($category == 'account') {
    $rids = array_keys($account->roles);
    $result = db_query("SELECT DISTINCT b.* FROM {block} b LEFT JOIN {block_role} r ON b.module = r.module AND b.delta = r.delta WHERE b.status = 1 AND b.custom <> 0 AND (r.rid IN (:rids) OR r.rid IS NULL) ORDER BY b.weight, b.module", array(':rids' => $rids));
    $form['block'] = array(
      '#type' => 'fieldset',
      '#title' => t('Personalize blocks'),
      '#description' => t('Blocks consist of content or information that complements the main content of the page. Enable or disable optional blocks using the checkboxes below.'),
      '#weight' => 3,
      '#collapsible' => TRUE,
      '#tree' => TRUE
    );
    foreach ($result as $block) {
      $data = module_invoke($block->module, 'block_list');
      if ($data[$block->delta]['info']) {
        $return = TRUE;
        $form['block'][$block->module][$block->delta] = array(
          '#type' => 'checkbox',
          '#title' => check_plain($data[$block->delta]['info']),
          '#default_value' => isset($account->block[$block->module][$block->delta]) ? $account->block[$block->module][$block->delta] : ($block->custom == 1),
        );
      }
    }

    if (!empty($return)) {
      return $form;
    }
  }
}

/**
 * Implement hook_user_validate().
 */
function block_user_validate(&$edit, $account, $category) {
  if (empty($edit['block'])) {
    $edit['block'] = array();
  }
  return $edit;
}

/**
 * Implement hook_form_FORM_ID_alter().
 */
function block_form_system_themes_form_alter(&$form, &$form_state) {
  // This function needs to fire before the theme changes are recorded in the
  // database, otherwise it will populate the default list of blocks from the
  // new theme, which is empty.
  array_unshift($form['#submit'], 'block_system_themes_form_submit');
}

/**
 * Initialize blocks for enabled themes.
 */
function block_system_themes_form_submit(&$form, &$form_state) {
  if ($form_state['values']['op'] == t('Save configuration')) {
    if (is_array($form_state['values']['status'])) {
      foreach ($form_state['values']['status'] as $key => $choice) {
        if ($choice || $form_state['values']['theme_default'] == $key) {
          block_theme_initialize($key);
        }
      }
    }
    if ($form_state['values']['admin_theme'] && $form_state['values']['admin_theme'] !== variable_get('admin_theme', 0)) {
      // If we're changing themes, make sure the theme has its blocks initialized.
      $has_blocks = (bool) db_query_range('SELECT 1 FROM {block} WHERE theme = :theme', array(':theme' => $form_state['values']['admin_theme']), 0, 1)->fetchField();
      if (!$has_blocks) {
        block_theme_initialize($form_state['values']['admin_theme']);
      }
    }
  }
}

/**
 * Assign an initial, default set of blocks for a theme.
 *
 * This function is called the first time a new theme is enabled. 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 = (bool) db_query_range('SELECT 1 FROM {block} WHERE theme = :theme', array(':theme' => $theme), 0, 1)->fetchField();
  if (!$has_blocks) {
    $default_theme = variable_get('theme_default', 'garland');
    $regions = system_region_list($theme);
    $result = db_query("SELECT * FROM {block} WHERE theme = :theme", array(':theme' => $default_theme), array('fetch' => PDO::FETCH_ASSOC));
    foreach ($result as $block) {
      // If the region isn't supported by the theme, assign the block to the theme's default region.
      if (!array_key_exists($block['region'], $regions)) {
        $block['region'] = system_default_region($theme);
      }
      $block['theme'] = $theme;
      unset($block['bid']);
      drupal_write_record('block', $block);
    }
  }
}

/**
 * Return all blocks in the specified region for the current user.
 *
 * @param $region
 *   The name of a region.
 *
 * @return
 *   An array of block objects, indexed with <i>module</i>_<i>delta</i>.
 *   If you are displaying your blocks in one or two sidebars, you may check
 *   whether this array is empty to see how many columns are going to be
 *   displayed.
 *
 * @todo
 *   Now that the blocks table has a primary key, we should use that as the
 *   array key instead of <i>module</i>_<i>delta</i>.
 */
function block_list($region) {
  $blocks = &drupal_static(__FUNCTION__, array());

  if (empty($blocks)) {
    $blocks = _block_load_blocks();
  }

  // Create an empty array if there were no entries.
  if (!isset($blocks[$region])) {
    $blocks[$region] = array();
  }

  $blocks[$region] = _block_render_blocks($blocks[$region]);

  return $blocks[$region];
}

/**
 * Load blocks information from the database.
 */
function _block_load_blocks() {
  global $theme_key;

  $query = db_select('block', 'b');
  $result = $query
    ->fields('b')
    ->condition('b.theme', $theme_key)
    ->condition('b.status', 1)
    ->orderBy('b.region')
    ->orderBy('b.weight')
    ->orderBy('b.module')
    ->addTag('block_load')
    ->execute();

  $block_list = $result->fetchAllAssoc('bid');
  // Allow modules to modify the block list.
  drupal_alter('block_list', $block_list);

  $blocks = array();
  foreach ($block_list as $block) {
    $blocks[$block->region]["{$block->module}_{$block->delta}"] = $block;
  }
  return $blocks;
}

/**
 * Implement hook_block_list_alter().
 *
 * Check the page, user role, content type and user specific visibilty settings.
 * Remove the block if the visibility conditions are not met.
 */
function block_block_list_alter(&$blocks) {
  global $user, $theme_key;

  // Build an array of roles for each block.
  $block_roles = array();
  $result = db_query('SELECT module, delta, rid FROM {block_role}');
  foreach ($result as $record) {
    $block_roles[$record->module][$record->delta][] = $record->rid;
  }

  // Build an array of node types for each block.
  $block_node_types = array();
  $result = db_query('SELECT module, delta, type FROM {block_node_type}');
  foreach ($result as $record) {
    $block_node_types[$record->module][$record->delta][] = $record->type;
  }

  foreach ($blocks as $key => $block) {
    if ($block->theme != $theme_key || $block->status != 1) {
      // This block was added by a contrib module, leave it in the list.
      continue;
    }

    // If a block has no roles associated, it is displayed for every role.
    // For blocks with roles associated, if none of the user's roles matches
    // the settings from this block, remove it from the block list.
    if (isset($block_roles[$block->module][$block->delta]) && !array_intersect($block_roles[$block->module][$block->delta], array_keys($user->roles))) {
      // No match.
      unset($blocks[$key]);
      continue;
    }

    // If a block has no node types associated, it is displayed for every type.
    // For blocks with node types associated, if the node type does not match
    // the settings from this block, remove it from the block list.
    if (isset($block_node_types[$block->module][$block->delta])) {
      $node = menu_get_object();
      if (!empty($node)) {
        // This is a node or node edit page.
        if (!in_array($node->type, $block_node_types[$block->module][$block->delta])) {
          // This block should not be displayed for this node type.
          unset($blocks[$key]);
          continue;
        }
      }
      elseif (arg(0) == 'node' && arg(1) == 'add' && in_array(arg(2), array_keys(node_type_get_types()))) {
        // This is a node creation page
        if (!in_array(arg(2), $block_node_types[$block->module][$block->delta])) {
          // This block should not be displayed for this node type.
          unset($blocks[$key]);
          continue;
        }
      }
      else {
        // This is not a node page, remove the block.
        unset($blocks[$key]);
        continue;
      }
    }

    // Use the user's block visibility setting, if necessary.
    if ($block->custom != 0) {
      if ($user->uid && isset($user->block[$block->module][$block->delta])) {
        $enabled = $user->block[$block->module][$block->delta];
      }
      else {
        $enabled = ($block->custom == 1);
      }
    }
    else {
      $enabled = TRUE;
    }
    if (!$enabled) {
      unset($blocks[$key]);
      continue;
    }

    // Match path if necessary.
    if ($block->pages) {
      if ($block->visibility < 2) {
        $path = drupal_get_path_alias($_GET['q']);
        // Compare with the internal and path alias (if any).
        $page_match = drupal_match_path($path, $block->pages);
        if ($path != $_GET['q']) {
          $page_match = $page_match || drupal_match_path($_GET['q'], $block->pages);
        }
        // When $block->visibility has a value of 0, the block is displayed on
        // all pages except those listed in $block->pages. When set to 1, it
        // is displayed only on those pages listed in $block->pages.
        $page_match = !($block->visibility xor $page_match);
      }
      elseif (module_exists('php')) {
        $page_match = php_eval($block->pages);
      }
      else {
        $page_match = FALSE;
      }
    }
    else {
      $page_match = TRUE;
    }
    if (!$page_match) {
      unset($blocks[$key]);
    }
  }
}

/**
 * Render the content and subject for a set of blocks.
 *
 * @param $region_blocks
 *   An array of block objects such as returned for one region by _block_load_blocks().
 *
 * @return
 *   An array of visible blocks with subject and content rendered.
 */
function _block_render_blocks($region_blocks) {
  foreach ($region_blocks as $key => $block) {
    // Render the block content if it has not been created already.
    if (!isset($block->content)) {
      // Erase the block from the static array - we'll put it back if it has
      // content.
      unset($region_blocks[$key]);
      // Try fetching the block from cache. Block caching is not compatible
      // with node_access modules. We also preserve the submission of forms in
      // blocks, by fetching from cache only if the request method is 'GET'
      // (or 'HEAD').
      if (!count(module_implements('node_grants')) && ($_SERVER['REQUEST_METHOD'] == 'GET' || $_SERVER['REQUEST_METHOD'] == 'HEAD') && ($cid = _block_get_cache_id($block)) && ($cache = cache_get($cid, 'cache_block'))) {
        $array = $cache->data;
      }
      else {
        $array = module_invoke($block->module, 'block_view', $block->delta);
        if (isset($cid)) {
          cache_set($cid, $array, 'cache_block', CACHE_TEMPORARY);
        }
      }

      if (isset($array) && is_array($array)) {
        foreach ($array as $k => $v) {
          $block->$k = $v;
        }
      }
      if (isset($block->content) && $block->content) {
        // Normalize to the drupal_render() structure.
        if (is_string($block->content)) {
          $block->content = array('#markup' => $block->content);
        }
        // Override default block title if a custom display title is present.
        if ($block->title) {
          // Check plain here to allow module generated titles to keep any
          // markup.
          $block->subject = $block->title == '<none>' ? '' : check_plain($block->title);
        }
        if (!isset($block->subject)) {
          $block->subject = '';
        }
        $region_blocks["{$block->module}_{$block->delta}"] = $block;
      }
    }
  }
  return $region_blocks;
}

/**
 * Assemble the cache_id to use for a given block.
 *
 * The cache_id string reflects the viewing context for the current block
 * instance, obtained by concatenating the relevant context information
 * (user, page, ...) according to the block's cache settings (BLOCK_CACHE_*
 * constants). Two block instances can use the same cached content when
 * they share the same cache_id.
 *
 * Theme and language contexts are automatically differentiated.
 *
 * @param $block
 * @return
 *   The string used as cache_id for the block.
 */
function _block_get_cache_id($block) {
  global $theme, $base_root, $user;

  // User 1 being out of the regular 'roles define permissions' schema,
  // it brings too many chances of having unwanted output get in the cache
  // and later be served to other users. We therefore exclude user 1 from
  // block caching.
  if (variable_get('block_cache', 0) && $block->cache != BLOCK_NO_CACHE && $user->uid != 1) {
    $cid_parts = array();

    // Start with common sub-patterns: block identification, theme, language.
    $cid_parts[] = $block->module;
    $cid_parts[] = $block->delta;
    $cid_parts[] = $theme;
    if (module_exists('locale')) {
      global $language;
      $cid_parts[] = $language->language;
    }

    // 'PER_ROLE' and 'PER_USER' are mutually exclusive. 'PER_USER' can be a
    // resource drag for sites with many users, so when a module is being
    // equivocal, we favor the less expensive 'PER_ROLE' pattern.
    if ($block->cache & BLOCK_CACHE_PER_ROLE) {
      $cid_parts[] = 'r.' . implode(',', array_keys($user->roles));
    }
    elseif ($block->cache & BLOCK_CACHE_PER_USER) {
      $cid_parts[] = "u.$user->uid";
    }

    if ($block->cache & BLOCK_CACHE_PER_PAGE) {
      $cid_parts[] = $base_root . request_uri();
    }

    return implode(':', $cid_parts);
  }
}

/**
 * Implement hook_flush_caches().
 */
function block_flush_caches() {
  return array('cache_block');
}

/**
 * Process variables for block.tpl.php
 *
 * Prepare 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.tpl.php is used.
 *
 * Most themes utilize their own copy of block.tpl.php. The default is located
 * inside "modules/block/block.tpl.php". Look in there for the full list of
 * variables.
 *
 * The $variables array contains the following arguments:
 * - $block
 *
 * @see block.tpl.php
 */
function template_preprocess_block(&$variables) {
  $block_counter = &drupal_static(__FUNCTION__, array());
  $variables['block'] = $variables['elements']['#block'];
  // All blocks get an independent counter for each region.
  if (!isset($block_counter[$variables['block']->region])) {
    $block_counter[$variables['block']->region] = 1;
  }
  // Same with zebra striping.
  $variables['block_zebra'] = ($block_counter[$variables['block']->region] % 2) ? 'odd' : 'even';
  $variables['block_id'] = $block_counter[$variables['block']->region]++;

  // Create the $content variable that templates expect.
  $variables['content'] = $variables['elements']['#children'];

  $variables['classes_array'][] = 'block-' . $variables['block']->module;

  $variables['template_files'][] = 'block-' . $variables['block']->region;
  $variables['template_files'][] = 'block-' . $variables['block']->module;
  $variables['template_files'][] = 'block-' . $variables['block']->module . '-' . $variables['block']->delta;
}