block.module

<?php


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

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

/**
 * Users cannot control whether or not they see this block.
 */
define('BLOCK_CUSTOM_FIXED', 0);

/**
 * Shows this block by default, but lets individual users hide it.
 */
define('BLOCK_CUSTOM_ENABLED', 1);

/**
 * Hides this block by default but lets individual users show it.
 */
define('BLOCK_CUSTOM_DISABLED', 2);

/**
 * Shows this block on every page except the listed pages.
 */
define('BLOCK_VISIBILITY_NOTLISTED', 0);

/**
 * Shows this block on only the listed pages.
 */
define('BLOCK_VISIBILITY_LISTED', 1);

/**
 * Shows this block if the associated PHP code returns TRUE.
 */
define('BLOCK_VISIBILITY_PHP', 2);

/**
 * Implements hook_help().
 */
function block_help($path, $arg) {
    switch ($path) {
        case 'admin/help#block':
            $output = '';
            $output .= '<h3>' . t('About') . '</h3>';
            $output .= '<p>' . t('The Block module allows you to create boxes of content, which are rendered into an area, or region, of one or more pages of a website. The core Seven administration theme, for example, implements the regions "Content", "Help", "Dashboard main", and "Dashboard sidebar", and a block may appear in any one of these regions. 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. For more information, see the online handbook entry for <a href="@block">Block module</a>.', array(
                '@block' => 'http://drupal.org/documentation/modules/block/',
                '@blocks' => url('admin/structure/block'),
            )) . '</p>';
            $output .= '<h3>' . t('Uses') . '</h3>';
            $output .= '<dl>';
            $output .= '<dt>' . t('Positioning content') . '</dt>';
            $output .= '<dd>' . t('When working with blocks, remember that all themes do <em>not</em> implement the same regions, or display regions in the same way. Blocks are positioned on a per-theme basis. Users with the <em>Administer blocks</em> permission can disable blocks. Disabled blocks are listed on the <a href="@blocks">Blocks administration page</a>, but are not displayed in any region.', array(
                '@block' => 'http://drupal.org/documentation/modules/block/',
                '@blocks' => url('admin/structure/block'),
            )) . '</dd>';
            $output .= '<dt>' . t('Controlling visibility') . '</dt>';
            $output .= '<dd>' . t('Blocks can be configured to be visible only on certain pages, only to users of certain roles, or only on pages displaying certain <a href="@content-type">content types</a>. Administrators can also allow specific blocks to be enabled or disabled by users when they edit their <a href="@user">My account</a> page. Some dynamic blocks, such as those generated by modules, will be displayed only on certain pages.', array(
                '@content-type' => url('admin/structure/types'),
                '@user' => url('user'),
            )) . '</dd>';
            $output .= '<dt>' . t('Creating custom blocks') . '</dt>';
            $output .= '<dd>' . t('Users with the <em>Administer blocks</em> permission can <a href="@block-add">add custom blocks</a>, which are then listed on the <a href="@blocks">Blocks administration page</a>. Once created, custom blocks behave just like default and module-generated blocks.', array(
                '@blocks' => url('admin/structure/block'),
                '@block-add' => url('admin/structure/block/add'),
            )) . '</dd>';
            $output .= '</dl>';
            return $output;
        case 'admin/structure/block/add':
            return '<p>' . t('Use this page to create a new custom block.') . '</p>';
    }
    if ($arg[0] == 'admin' && $arg[1] == 'structure' && $arg['2'] == 'block' && (empty($arg[3]) || $arg[3] == 'list')) {
        $demo_theme = !empty($arg[4]) ? $arg[4] : variable_get('theme_default', 'bartik');
        $themes = list_themes();
        $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. Click the <em>configure</em> link next to each block to configure its specific title and visibility settings.') . '</p>';
        $output .= '<p>' . l(t('Demonstrate block regions (!theme)', array(
            '!theme' => $themes[$demo_theme]->info['name'],
        )), 'admin/structure/block/demo/' . $demo_theme) . '</p>';
        return $output;
    }
}

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

/**
 * Implements hook_permission().
 */
function block_permission() {
    return array(
        'administer blocks' => array(
            'title' => t('Administer blocks'),
        ),
    );
}

/**
 * Implements hook_menu().
 */
function block_menu() {
    $default_theme = variable_get('theme_default', 'bartik');
    $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',
        'page arguments' => array(
            $default_theme,
        ),
        'access arguments' => array(
            'administer blocks',
        ),
        'file' => 'block.admin.inc',
    );
    $items['admin/structure/block/manage/%/%'] = array(
        'title' => 'Configure block',
        'page callback' => 'drupal_get_form',
        'page arguments' => array(
            'block_admin_configure',
            4,
            5,
        ),
        'access arguments' => array(
            'administer blocks',
        ),
        'file' => 'block.admin.inc',
    );
    $items['admin/structure/block/manage/%/%/configure'] = array(
        'title' => 'Configure block',
        'type' => MENU_DEFAULT_LOCAL_TASK,
        'context' => MENU_CONTEXT_INLINE,
    );
    $items['admin/structure/block/manage/%/%/delete'] = array(
        'title' => 'Delete block',
        'page callback' => 'drupal_get_form',
        'page arguments' => array(
            'block_custom_block_delete',
            4,
            5,
        ),
        'access arguments' => array(
            'administer blocks',
        ),
        'type' => MENU_LOCAL_TASK,
        'context' => MENU_CONTEXT_NONE,
        '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',
    );
    foreach (list_themes() as $key => $theme) {
        $items['admin/structure/block/list/' . $key] = array(
            'title' => $theme->info['name'],
            'page arguments' => array(
                $key,
            ),
            'type' => $key == $default_theme ? MENU_DEFAULT_LOCAL_TASK : MENU_LOCAL_TASK,
            'weight' => $key == $default_theme ? -10 : 0,
            'access callback' => '_block_themes_access',
            'access arguments' => array(
                $theme,
            ),
            'file' => 'block.admin.inc',
        );
        if ($key != $default_theme) {
            $items['admin/structure/block/list/' . $key . '/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',
            );
        }
        $items['admin/structure/block/demo/' . $key] = array(
            'title' => $theme->info['name'],
            'page callback' => 'block_admin_demo',
            'page arguments' => array(
                $key,
            ),
            'type' => MENU_CALLBACK,
            'access callback' => '_block_themes_access',
            'access arguments' => array(
                $theme,
            ),
            'theme callback' => '_block_custom_theme',
            'theme arguments' => array(
                $key,
            ),
            'file' => 'block.admin.inc',
        );
    }
    return $items;
}

/**
 * Menu item access callback - only admin or enabled themes can be accessed.
 */
function _block_themes_access($theme) {
    return user_access('administer blocks') && drupal_theme_access($theme);
}

/**
 * Theme callback for the block configuration pages.
 *
 * @param $theme
 *   The theme whose blocks are being configured. If not set, the default theme
 *   is assumed.
 *
 * @return
 *   The theme that should be used for the block configuration page, or NULL
 *   to indicate that the default theme should be used.
 */
function _block_custom_theme($theme = NULL) {
    // We return exactly what was passed in, to guarantee that the page will
    // always be displayed using the theme whose blocks are being configured.
    return $theme;
}

/**
 * Implements hook_block_info().
 */
function block_block_info() {
    $blocks = array();
    $result = db_query('SELECT bid, info FROM {block_custom} ORDER BY info');
    foreach ($result as $block) {
        $blocks[$block->bid]['info'] = $block->info;
        // Not worth caching.
        $blocks[$block->bid]['cache'] = DRUPAL_NO_CACHE;
    }
    return $blocks;
}

/**
 * Implements hook_block_configure().
 */
function block_block_configure($delta = 0) {
    if ($delta) {
        $custom_block = block_custom_block_get($delta);
    }
    else {
        $custom_block = array();
    }
    return block_custom_block_form($custom_block);
}

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

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

/**
 * Implements hook_page_build().
 *
 * Renders blocks into their regions.
 */
function block_page_build(&$page) {
    global $theme;
    // The theme system might not yet be initialized. We need $theme.
    drupal_theme_initialize();
    // Fetch a list of regions for the current theme.
    $all_regions = system_region_list($theme);
    $item = menu_get_item();
    if ($item === FALSE || $item['path'] != 'admin/structure/block/demo/' . $theme) {
        // Load all region content assigned via blocks.
        foreach (array_keys($all_regions) as $region) {
            // Assign blocks to region.
            if ($blocks = block_get_blocks_by_region($region)) {
                $page[$region] = $blocks;
            }
        }
        // Once we've finished attaching all blocks to the page, clear the static
        // cache to allow modules to alter the block list differently in different
        // contexts. For example, any code that triggers hook_page_build() more
        // than once in the same page request may need to alter the block list
        // differently each time, so that only certain parts of the page are
        // actually built. We do not clear the cache any earlier than this, though,
        // because it is used each time block_get_blocks_by_region() gets called
        // above.
        drupal_static_reset('block_list');
    }
    else {
        // Append region description if we are rendering the regions demo page.
        if ($item['path'] == 'admin/structure/block/demo/' . $theme) {
            foreach (system_region_list($theme, REGIONS_VISIBLE, FALSE) as $region) {
                $description = '<div class="block-region">' . $all_regions[$region] . '</div>';
                $page[$region]['block_description'] = array(
                    '#markup' => $description,
                    '#weight' => 15,
                );
            }
            $page['page_top']['backlink'] = array(
                '#type' => 'link',
                '#title' => t('Exit block region demonstration'),
                '#href' => 'admin/structure/block' . (variable_get('theme_default', 'bartik') == $theme ? '' : '/list/' . $theme),
                // Add the "overlay-restore" class to indicate this link should restore
                // the context in which the region demonstration page was opened.
'#options' => array(
                    'attributes' => array(
                        'class' => array(
                            'block-demo-backlink',
                            'overlay-restore',
                        ),
                    ),
                ),
                '#weight' => -10,
            );
        }
    }
}

/**
 * Gets a renderable array of a region containing all enabled blocks.
 *
 * @param $region
 *   The requested region.
 *
 * @return
 *   A renderable array of a region containing all enabled blocks.
 */
function block_get_blocks_by_region($region) {
    $build = array();
    if ($list = block_list($region)) {
        $build = _block_get_renderable_array($list);
    }
    return $build;
}

/**
 * Gets an array of blocks suitable for drupal_render().
 *
 * @param $list
 *   A list of blocks such as that returned by block_list().
 *
 * @return
 *   A renderable array.
 */
function _block_get_renderable_array($list = array()) {
    $weight = 0;
    $build = array();
    foreach ($list as $key => $block) {
        $build[$key] = $block->content;
        unset($block->content);
        // Add contextual links for this block; skip the main content block, since
        // contextual links are basically output as tabs/local tasks already. Also
        // skip the help block, since we assume that most users do not need or want
        // to perform contextual actions on the help block, and the links needlessly
        // draw attention on it.
        if ($key != 'system_main' && $key != 'system_help') {
            $build[$key]['#contextual_links']['block'] = array(
                'admin/structure/block/manage',
                array(
                    $block->module,
                    $block->delta,
                ),
            );
        }
        $build[$key] += array(
            '#block' => $block,
            '#weight' => ++$weight,
        );
        $build[$key]['#theme_wrappers'][] = 'block';
    }
    $build['#sorted'] = TRUE;
    return $build;
}

/**
 * Updates the 'block' DB table with the blocks currently exported by modules.
 *
 * @param $theme
 *   The theme to rehash blocks for. If not provided, defaults to the currently
 *   used theme.
 *
 * @return
 *   Blocks currently exported by modules.
 */
function _block_rehash($theme = NULL) {
    global $theme_key;
    drupal_theme_initialize();
    if (!isset($theme)) {
        // If theme is not specifically set, rehash for the current theme.
        $theme = $theme_key;
    }
    $regions = system_region_list($theme);
    // These are the blocks the function will return.
    $blocks = array();
    // These are the blocks defined by code and modified by the database.
    $current_blocks = array();
    // These are {block}.bid values to be kept.
    $bids = array();
    $or = db_or();
    // Gather the blocks defined by modules.
    foreach (module_implements('block_info') as $module) {
        $module_blocks = module_invoke($module, 'block_info');
        $delta_list = array();
        foreach ($module_blocks as $delta => $block) {
            // Compile a condition to retrieve this block from the database.
            // Add identifiers.
            $delta_list[] = $delta;
            $block['module'] = $module;
            $block['delta'] = $delta;
            $block['theme'] = $theme;
            $current_blocks[$module][$delta] = $block;
        }
        if (!empty($delta_list)) {
            $condition = db_and()->condition('module', $module)
                ->condition('delta', $delta_list);
            $or->condition($condition);
        }
    }
    // Save the blocks defined in code for alter context.
    $code_blocks = $current_blocks;
    $database_blocks = db_select('block', 'b', array(
        'fetch' => PDO::FETCH_ASSOC,
    ))->fields('b')
        ->condition($or)
        ->condition('theme', $theme)
        ->execute();
    $original_database_blocks = array();
    foreach ($database_blocks as $block) {
        $module = $block['module'];
        $delta = $block['delta'];
        $original_database_blocks[$module][$delta] = $block;
        // The cache mode can only by set from hook_block_info(), so that has
        // precedence over the database's value.
        if (isset($current_blocks[$module][$delta]['cache'])) {
            $block['cache'] = $current_blocks[$module][$delta]['cache'];
        }
        // Preserve info which is not in the database.
        $block['info'] = $current_blocks[$module][$delta]['info'];
        // Blocks stored in the database override the blocks defined in code.
        $current_blocks[$module][$delta] = $block;
        // Preserve this block.
        $bids[$block['bid']] = $block['bid'];
    }
    drupal_alter('block_info', $current_blocks, $theme, $code_blocks);
    foreach ($current_blocks as $module => $module_blocks) {
        foreach ($module_blocks as $delta => $block) {
            // Make sure certain attributes are set.
            $block += array(
                'pages' => '',
                'weight' => 0,
                'status' => 0,
            );
            // Check for active blocks in regions that are not available.
            if (!empty($block['region']) && $block['region'] != BLOCK_REGION_NONE && !isset($regions[$block['region']]) && $block['status'] == 1) {
                drupal_set_message(t('The block %info was assigned to the invalid region %region and has been disabled.', array(
                    '%info' => $block['info'],
                    '%region' => $block['region'],
                )), 'warning');
                // Disabled modules are moved into the BLOCK_REGION_NONE later so no
                // need to move the block to another region.
                $block['status'] = 0;
            }
            // Set region to none if not enabled.
            if (empty($block['status'])) {
                $block['status'] = 0;
                $block['region'] = BLOCK_REGION_NONE;
            }
            // There is no point saving disabled blocks. Still, we need to save them
            // because the 'title' attribute is saved to the {blocks} table.
            if (isset($block['bid'])) {
                // If the block has a bid property, it comes from the database and
                // the record needs to be updated, so set the primary key to 'bid'
                // before passing to drupal_write_record().
                $primary_keys = array(
                    'bid',
                );
                // Remove a block from the list of blocks to keep if it became disabled.
                unset($bids[$block['bid']]);
            }
            else {
                $primary_keys = array();
            }
            // If the block is new or differs from the original database block, save
            // it. To determine whether there was a change it is enough to examine
            // the values for the keys in the original database record as that
            // contained every database field.
            if (!$primary_keys || array_diff_assoc($original_database_blocks[$module][$delta], $block)) {
                drupal_write_record('block', $block, $primary_keys);
                // Make it possible to test this.
                $block['saved'] = TRUE;
            }
            // Add to the list of blocks we return.
            $blocks[] = $block;
        }
    }
    if ($bids) {
        // Remove disabled that are no longer defined by the code from the
        // database.
        db_delete('block')->condition('bid', $bids, 'NOT IN')
            ->condition('theme', $theme)
            ->execute();
    }
    return $blocks;
}

/**
 * Returns information from database about a user-created (custom) block.
 *
 * @param $bid
 *   ID of the block to get information for.
 *
 * @return
 *   Associative array of information stored in the database for this block.
 *   Array keys:
 *   - bid: Block ID.
 *   - info: Block description.
 *   - body: Block contents.
 *   - format: Filter ID of the filter format for the body.
 */
function block_custom_block_get($bid) {
    return db_query("SELECT * FROM {block_custom} WHERE bid = :bid", array(
        ':bid' => $bid,
    ))->fetchAssoc();
}

/**
 * Form constructor for the custom block form.
 *
 * @param $edit
 *   (optional) An associative array of information retrieved by
 *   block_custom_get_block() if an existing block is being edited, or an empty
 *   array otherwise. Defaults to array().
 *
 * @ingroup forms
 */
function block_custom_block_form($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' => -18,
    );
    $form['body_field']['#weight'] = -17;
    $form['body_field']['body'] = array(
        '#type' => 'text_format',
        '#title' => t('Block body'),
        '#default_value' => $edit['body'],
        '#format' => isset($edit['format']) ? $edit['format'] : NULL,
        '#rows' => 15,
        '#description' => t('The content of the block as shown to the user.'),
        '#required' => TRUE,
        '#weight' => -17,
    );
    return $form;
}

/**
 * Saves a user-created block in the database.
 *
 * @param $edit
 *   Associative array of fields to save. Array keys:
 *   - info: Block description.
 *   - body: Associative array of body value and format.  Array keys:
 *     - value: Block contents.
 *     - format: Filter ID of the filter format for the body.
 * @param $delta
 *   Block ID of the block to save.
 *
 * @return
 *   Always returns TRUE.
 */
function block_custom_block_save($edit, $delta) {
    db_update('block_custom')->fields(array(
        'body' => $edit['body']['value'],
        'info' => $edit['info'],
        'format' => $edit['body']['format'],
    ))
        ->condition('bid', $delta)
        ->execute();
    return TRUE;
}

/**
 * Implements hook_form_FORM_ID_alter() for user_profile_form().
 */
function block_form_user_profile_form_alter(&$form, &$form_state) {
    if ($form['#user_category'] == 'account') {
        $account = $form['#user'];
        $rids = array_keys($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,
        ));
        $blocks = array();
        foreach ($result as $block) {
            $data = module_invoke($block->module, 'block_info');
            if ($data[$block->delta]['info']) {
                $blocks[$block->module][$block->delta] = array(
                    '#type' => 'checkbox',
                    '#title' => check_plain($data[$block->delta]['info']),
                    '#default_value' => isset($account->data['block'][$block->module][$block->delta]) ? $account->data['block'][$block->module][$block->delta] : $block->custom == 1,
                );
            }
        }
        // Only display the fieldset if there are any personalizable blocks.
        if ($blocks) {
            $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,
            );
            $form['block'] += $blocks;
        }
    }
}

/**
 * Implements hook_user_presave().
 */
function block_user_presave(&$edit, $account, $category) {
    if (isset($edit['block'])) {
        $edit['data']['block'] = $edit['block'];
    }
}

/**
 * Initializes blocks for enabled themes.
 *
 * @param $theme_list
 *   An array of theme names.
 */
function block_themes_enabled($theme_list) {
    foreach ($theme_list as $theme) {
        block_theme_initialize($theme);
    }
}

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

/**
 * Returns all blocks in the specified region for the current user.
 *
 * @param $region
 *   The name of a region.
 *
 * @return
 *   An array of block objects, indexed with the module name and block delta
 *   concatenated with an underscore, thus: MODULE_DELTA. If you are displaying
 *   your blocks in one or two sidebars, you may check whether this array is
 *   empty to see how many columns are going to be displayed.
 *
 * @todo
 *   Now that the block table has a primary key, we should use that as the
 *   array key instead of MODULE_DELTA.
 */
function block_list($region) {
    $blocks =& drupal_static(__FUNCTION__);
    if (!isset($blocks)) {
        $blocks = _block_load_blocks();
    }
    // Create an empty array if there are no entries.
    if (!isset($blocks[$region])) {
        $blocks[$region] = array();
    }
    else {
        $blocks[$region] = _block_render_blocks($blocks[$region]);
    }
    return $blocks[$region];
}

/**
 * Loads a block object from the database.
 *
 * This function returns the first block matching the module and delta
 * parameters, so it should not be used for theme-specific functionality.
 *
 * @param $module
 *   Name of the module that implements the block to load.
 * @param $delta
 *   Unique ID of the block within the context of $module. Pass NULL to return
 *   an empty block object for $module.
 *
 * @return
 *   A block object.
 */
function block_load($module, $delta) {
    if (isset($delta)) {
        $block = db_query('SELECT * FROM {block} WHERE module = :module AND delta = :delta', array(
            ':module' => $module,
            ':delta' => $delta,
        ))->fetchObject();
    }
    // If the block does not exist in the database yet return a stub block
    // object.
    if (empty($block)) {
        $block = new stdClass();
        $block->module = $module;
        $block->delta = $delta;
    }
    return $block;
}

/**
 * Loads blocks' information from the database.
 *
 * @return
 *   An array of blocks grouped by region.
 */
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')
        ->addTag('translatable')
        ->execute();
    $block_info = $result->fetchAllAssoc('bid');
    // Allow modules to modify the block list.
    drupal_alter('block_list', $block_info);
    $blocks = array();
    foreach ($block_info as $block) {
        $blocks[$block->region]["{$block->module}_{$block->delta}"] = $block;
    }
    return $blocks;
}

/**
 * Implements hook_block_list_alter().
 *
 * Checks the page, user role, and user-specific visibility settings.
 * Removes 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][] = $record->rid;
    }
    foreach ($blocks as $key => $block) {
        if (!isset($block->theme) || !isset($block->status) || $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;
        }
        // Use the user's block visibility setting, if necessary.
        if ($block->custom != BLOCK_CUSTOM_FIXED) {
            if ($user->uid && isset($user->data['block'][$block->module][$block->delta])) {
                $enabled = $user->data['block'][$block->module][$block->delta];
            }
            else {
                $enabled = $block->custom == BLOCK_CUSTOM_ENABLED;
            }
        }
        else {
            $enabled = TRUE;
        }
        // Limited visibility blocks must list at least one page.
        if ($block->visibility == BLOCK_VISIBILITY_LISTED && empty($block->pages)) {
            $enabled = FALSE;
        }
        if (!$enabled) {
            unset($blocks[$key]);
            continue;
        }
        // Match path if necessary.
        if ($block->pages) {
            // Convert path to lowercase. This allows comparison of the same path
            // with different case. Ex: /Page, /page, /PAGE.
            $pages = drupal_strtolower($block->pages);
            if ($block->visibility < BLOCK_VISIBILITY_PHP) {
                // Convert the Drupal path to lowercase.
                $path = drupal_strtolower(drupal_get_path_alias($_GET['q']));
                // Compare the lowercase internal and lowercase path alias (if any).
                $page_match = drupal_match_path($path, $pages);
                if ($path != $_GET['q']) {
                    $page_match = $page_match || drupal_match_path($_GET['q'], $pages);
                }
                // When $block->visibility has a value of 0
                // (BLOCK_VISIBILITY_NOTLISTED), the block is displayed on all pages
                // except those listed in $block->pages. When set to 1
                // (BLOCK_VISIBILITY_LISTED), 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 $region_blocks
 *   An array of block objects such as returned for one region by
 *   _block_load_blocks().
 *
 * @return
 *   An array of visible blocks as expected by drupal_render().
 */
function _block_render_blocks($region_blocks) {
    $cacheable = TRUE;
    // We preserve the submission of forms in blocks, by fetching from cache only
    // if the request method is 'GET' (or 'HEAD').
    if ($_SERVER['REQUEST_METHOD'] != 'GET' && $_SERVER['REQUEST_METHOD'] != 'HEAD') {
        $cacheable = FALSE;
    }
    elseif (!variable_get('block_cache_bypass_node_grants', FALSE) && count(module_implements('node_grants'))) {
        $cacheable = FALSE;
    }
    // Proceed to loop over all blocks in order to compute their respective cache
    // identifiers; this allows us to do one single cache_get_multiple() call
    // instead of doing one cache_get() call per block.
    $cached_blocks = array();
    $cids = array();
    if ($cacheable) {
        foreach ($region_blocks as $key => $block) {
            if (!isset($block->content)) {
                if ($cid = _block_get_cache_id($block)) {
                    $cids[$key] = $cid;
                }
            }
        }
        if ($cids) {
            // We cannot pass $cids in directly because cache_get_multiple() will
            // modify it, and we need to use it later on in this function.
            $cid_values = array_values($cids);
            $cached_blocks = cache_get_multiple($cid_values, 'cache_block');
        }
    }
    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]);
            $cid = empty($cids[$key]) ? NULL : $cids[$key];
            // Try fetching the block from the previously loaded cache entries.
            if (isset($cached_blocks[$cid])) {
                $array = $cached_blocks[$cid]->data;
            }
            else {
                $array = module_invoke($block->module, 'block_view', $block->delta);
                // Valid PHP function names cannot contain hyphens.
                $delta = str_replace('-', '_', $block->delta);
                // Allow modules to modify the block before it is viewed, via either
                // hook_block_view_alter() or hook_block_view_MODULE_DELTA_alter().
                drupal_alter(array(
                    'block_view',
                    "block_view_{$block->module}_{$delta}",
                ), $array, $block);
                if (isset($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 $block
 *   The block to get the cache_id from.
 *
 * @return
 *   The string used as cache_id for the block.
 */
function _block_get_cache_id($block) {
    global $user;
    // User 1 being out of the regular 'roles define permissions' schema,
    // it brings too many chances of having unwanted output get in the cache
    // and later be served to other users. We therefore exclude user 1 from
    // block caching.
    if (variable_get('block_cache', FALSE) && !in_array($block->cache, array(
        DRUPAL_NO_CACHE,
        DRUPAL_CACHE_CUSTOM,
    )) && $user->uid != 1) {
        // Start with common sub-patterns: block identification, theme, language.
        $cid_parts[] = $block->module;
        $cid_parts[] = $block->delta;
        drupal_alter('block_cid_parts', $cid_parts, $block);
        $cid_parts = array_merge($cid_parts, drupal_render_cid_parts($block->cache));
        return implode(':', $cid_parts);
    }
}

/**
 * Implements hook_flush_caches().
 */
function block_flush_caches() {
    // Rehash blocks for active themes. We don't use list_themes() here,
    // because if MAINTENANCE_MODE is defined it skips reading the database,
    // and we can't tell which themes are active.
    $themes = db_query("SELECT name FROM {system} WHERE type = 'theme' AND status = 1");
    foreach ($themes as $theme) {
        _block_rehash($theme->name);
    }
    return array(
        'cache_block',
    );
}

/**
 * Processes variables for block.tpl.php.
 *
 * 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.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'][] = drupal_html_class('block-' . $variables['block']->module);
    $variables['theme_hook_suggestions'][] = 'block__' . $variables['block']->region;
    $variables['theme_hook_suggestions'][] = 'block__' . $variables['block']->module;
    // 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.
    $variables['theme_hook_suggestions'][] = 'block__' . $variables['block']->module . '__' . strtr($variables['block']->delta, '-', '_');
    // Create a valid HTML ID and make sure it is unique.
    $variables['block_html_id'] = drupal_html_id('block-' . $variables['block']->module . '-' . $variables['block']->delta);
}

/**
 * Implements hook_user_role_delete().
 *
 * Removes deleted role from blocks that use it.
 */
function block_user_role_delete($role) {
    db_delete('block_role')->condition('rid', $role->rid)
        ->execute();
}

/**
 * Implements hook_menu_delete().
 */
function block_menu_delete($menu) {
    db_delete('block')->condition('module', 'menu')
        ->condition('delta', $menu['menu_name'])
        ->execute();
    db_delete('block_role')->condition('module', 'menu')
        ->condition('delta', $menu['menu_name'])
        ->execute();
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function block_form_system_performance_settings_alter(&$form, &$form_state) {
    $disabled = !variable_get('block_cache_bypass_node_grants', FALSE) && count(module_implements('node_grants'));
    $form['caching']['block_cache'] = array(
        '#type' => 'checkbox',
        '#title' => t('Cache blocks'),
        '#default_value' => variable_get('block_cache', FALSE),
        '#disabled' => $disabled,
        '#description' => $disabled ? t('Block caching is inactive because you have enabled modules defining content access restrictions.') : NULL,
        '#weight' => -1,
    );
}

/**
 * Implements hook_admin_paths().
 */
function block_admin_paths() {
    $paths = array(
        // Exclude the block demonstration page from admin (overlay) treatment.
        // This allows us to present this page in its true form, full page.
'admin/structure/block/demo/*' => FALSE,
    );
    return $paths;
}

/**
 * Implements hook_modules_uninstalled().
 *
 * Cleans up {block} and {block_role} tables from modules' blocks.
 */
function block_modules_uninstalled($modules) {
    db_delete('block')->condition('module', $modules, 'IN')
        ->execute();
    db_delete('block_role')->condition('module', $modules, 'IN')
        ->execute();
}