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+<?php
+
+/**
+ * @file
+ * Hooks related to the Menu system.
+ */
+
+/**
+ * @defgroup menu Menu and routing system
+ * @{
+ * Define the navigation menus, and route page requests to code based on URLs.
+ *
+ * @section sec_overview Overview and terminology
+ * The Drupal routing system defines how Drupal responds to URL requests that
+ * the web server passes on to Drupal. The routing system is based on the
+ * @link http://symfony.com Symfony framework. @endlink The central idea is
+ * that Drupal subsystems and modules can register routes (basically, URL
+ * paths and context); they can also register to respond dynamically to
+ * routes, for more flexibility. When Drupal receives a URL request, it will
+ * attempt to match the request to a registered route, and query dynamic
+ * responders. If a match is made, Drupal will then instantiate the required
+ * classes, gather the data, format it, and send it back to the web browser.
+ * Otherwise, Drupal will return a 404 or 403 response.
+ *
+ * The menu system uses routes; it is used for navigation menus, local tasks,
+ * local actions, and contextual links:
+ * - Navigation menus are hierarchies of menu links; links point to routes or
+ *   URLs.
+ * - Menu links and their hierarchies can be defined by Drupal subsystems
+ *   and modules, or created in the user interface using the Menu UI module.
+ * - Local tasks are groups of related routes. Local tasks are usually rendered
+ *   as a group of tabs.
+ * - Local actions are used for operations such as adding a new item on a page
+ *   that lists items of some type. Local actions are usually rendered as
+ *   buttons.
+ * - Contextual links are actions that are related to sections of rendered
+ *   output, and are usually rendered as a pop-up list of links. The
+ *   Contextual Links module handles the gathering and rendering of contextual
+ *   links.
+ *
+ * The following sections of this topic provide an overview of the routing and
+ * menu APIs. For more detailed information, see
+ * https://www.drupal.org/developing/api/8/routing and
+ * https://www.drupal.org/developing/api/8/menu
+ *
+ * @section sec_register Registering simple routes
+ * To register a route, add lines similar to this to a module_name.routing.yml
+ * file in your top-level module directory:
+ * @code
+ * dblog.overview:
+ *   path: '/admin/reports/dblog'
+ *   defaults:
+ *     _controller: '\Drupal\dblog\Controller\DbLogController::overview'
+ *     _title: 'Recent log messages'
+ *   requirements:
+ *     _permission: 'access site reports'
+ * @endcode
+ * Some notes:
+ * - The first line is the machine name of the route. Typically, it is prefixed
+ *   by the machine name of the module that defines the route, or the name of
+ *   a subsystem.
+ * - The 'path' line gives the URL path of the route (relative to the site's
+ *   base URL).
+ * - The 'defaults' section tells how to build the main content of the route,
+ *   and can also give other information, such as the page title and additional
+ *   arguments for the route controller method. There are several possibilities
+ *   for how to build the main content, including:
+ *   - _controller: A callable, usually a method on a page controller class
+ *     (see @ref sec_controller below for details).
+ *   - _form: A form controller class. See the
+ *     @link form_api Form API topic @endlink for more information about
+ *     form controllers.
+ *   - _entity_form: A form for editing an entity. See the
+ *     @link entity_api Entity API topic @endlink for more information.
+ * - The 'requirements' section is used in Drupal to give access permission
+ *   instructions (it has other uses in the Symfony framework). Most
+ *   routes have a simple permission-based access scheme, as shown in this
+ *   example. See the @link user_api Permission system topic @endlink for
+ *   more information about permissions.
+ *
+ * See https://www.drupal.org/node/2092643 for more details about *.routing.yml
+ * files, and https://www.drupal.org/node/2122201 for information on how to
+ * set up dynamic routes. The @link events Events topic @endlink is also
+ * relevant to dynamic routes.
+ *
+ * @section sec_placeholders Defining routes with placeholders
+ * Some routes have placeholders in them, and these can also be defined in a
+ * module_name.routing.yml file, as in this example from the Block module:
+ * @code
+ * entity.block.edit_form:
+ *   path: '/admin/structure/block/manage/{block}'
+ *   defaults:
+ *     _entity_form: 'block.default'
+ *     _title: 'Configure block'
+ *   requirements:
+ *     _entity_access: 'block.update'
+ * @endcode
+ * In the path, '{block}' is a placeholder - it will be replaced by the
+ * ID of the block that is being configured by the entity system. See the
+ * @link entity_api Entity API topic @endlink for more information.
+ *
+ * @section sec_controller Route controllers for simple routes
+ * For simple routes, after you have defined the route in a *.routing.yml file
+ * (see @ref sec_register above), the next step is to define a page controller
+ * class and method. Page controller classes do not necessarily need to
+ * implement any particular interface or extend any particular base class. The
+ * only requirement is that the method specified in your *.routing.yml file
+ * returns:
+ * - A render array (see the
+ *   @link theme_render Theme and render topic @endlink for more information).
+ *   This render array is then rendered in the requested format (HTML, dialog,
+ *   modal, AJAX are supported by default). In the case of HTML, it will be
+ *   surrounded by blocks by default: the Block module is enabled by default,
+ *   and hence its Page Display Variant that surrounds the main content with
+ *   blocks is also used by default.
+ * - A \Symfony\Component\HttpFoundation\Response object.
+ * As a note, if your module registers multiple simple routes, it is usual
+ * (and usually easiest) to put all of their methods on one controller class.
+ *
+ * If the route has placeholders (see @ref sec_placeholders above) the
+ * placeholders will be passed to the method (using reflection) by name.
+ * For example, the placeholder '{myvar}' in a route will become the $myvar
+ * parameter to the method.
+ *
+ * Most controllers will need to display some information stored in the Drupal
+ * database, which will involve using one or more Drupal services (see the
+ * @link container Services and container topic @endlink). In order to properly
+ * inject services, a controller should implement
+ * \Drupal\Core\DependencyInjection\ContainerInjectionInterface; simple
+ * controllers can do this by extending the
+ * \Drupal\Core\Controller\ControllerBase class. See
+ * \Drupal\dblog\Controller\DbLogController for a straightforward example of
+ * a controller class.
+ *
+ * @section sec_links Defining menu links for the administrative menu
+ * Routes for administrative tasks can be added to the main Drupal
+ * administrative menu hierarchy. To do this, add lines like the following to a
+ * module_name.links.menu.yml file (in the top-level directory for your module):
+ * @code
+ * dblog.overview:
+ *   title: 'Recent log messages'
+ *   parent: system.admin_reports
+ *   description: 'View events that have recently been logged.'
+ *   route_name: dblog.overview
+ *   weight: -1
+ * @endcode
+ * Some notes:
+ * - The first line is the machine name for your menu link, which usually
+ *   matches the machine name of the route (given in the 'route_name' line).
+ * - parent: The machine name of the menu link that is the parent in the
+ *   administrative hierarchy. See system.links.menu.yml to find the main
+ *   skeleton of the hierarchy.
+ * - weight: Lower (negative) numbers come before higher (positive) numbers,
+ *   for menu items with the same parent.
+ *
+ * Discovered menu links from other modules can be altered using
+ * hook_menu_links_discovered_alter().
+ *
+ * @todo Derivatives will probably be defined for these; when they are, add
+ *   documentation here.
+ *
+ * @section sec_tasks Defining groups of local tasks (tabs)
+ * Local tasks appear as tabs on a page when there are at least two defined for
+ * a route, including the base route as the main tab, and additional routes as
+ * other tabs. Static local tasks can be defined by adding lines like the
+ * following to a module_name.links.task.yml file (in the top-level directory
+ * for your module):
+ * @code
+ * book.admin:
+ *   route_name: book.admin
+ *   title: 'List'
+ *   base_route: book.admin
+ * book.settings:
+ *   route_name: book.settings
+ *   title: 'Settings'
+ *   base_route: book.admin
+ *   weight: 100
+ * @endcode
+ * Some notes:
+ * - The first line is the machine name for your local task, which usually
+ *   matches the machine name of the route (given in the 'route_name' line).
+ * - base_route: The machine name of the main task (tab) for the set of local
+ *   tasks.
+ * - weight: Lower (negative) numbers come before higher (positive) numbers,
+ *   for tasks on the same base route. If there is a tab whose route
+ *   matches the base route, that will be the default/first tab shown.
+ *
+ * Local tasks from other modules can be altered using
+ * hook_menu_local_tasks_alter().
+ *
+ * @todo Derivatives are in flux for these; when they are more stable, add
+ *   documentation here.
+ *
+ * @section sec_actions Defining local actions for routes
+ * Local actions can be defined for operations related to a given route. For
+ * instance, adding content is a common operation for the content management
+ * page, so it should be a local action. Static local actions can be
+ * defined by adding lines like the following to a
+ * module_name.links.action.yml file (in the top-level directory for your
+ * module):
+ * @code
+ * node.add_page:
+ *   route_name: node.add_page
+ *   title: 'Add content'
+ *   appears_on:
+ *     - system.admin_content
+ * @endcode
+ * Some notes:
+ * - The first line is the machine name for your local action, which usually
+ *   matches the machine name of the route (given in the 'route_name' line).
+ * - appears_on: Machine names of one or more routes that this local task
+ *   should appear on.
+ *
+ * Local actions from other modules can be altered using
+ * hook_menu_local_actions_alter().
+ *
+ * @todo Derivatives are in flux for these; when they are more stable, add
+ *   documentation here.
+ *
+ * @section sec_contextual Defining contextual links
+ * Contextual links are displayed by the Contextual Links module for user
+ * interface elements whose render arrays have a '#contextual_links' element
+ * defined. For example, a block render array might look like this, in part:
+ * @code
+ * array(
+ *   '#contextual_links' => array(
+ *     'block' => array(
+ *       'route_parameters' => array('block' => $entity->id()),
+ *     ),
+ *   ),
+ * @endcode
+ * In this array, the outer key 'block' defines a "group" for contextual
+ * links, and the inner array provides values for the route's placeholder
+ * parameters (see @ref sec_placeholders above).
+ *
+ * To declare that a defined route should be a contextual link for a
+ * contextual links group, put lines like the following in a
+ * module_name.links.contextual.yml file (in the top-level directory for your
+ * module):
+ * @code
+ * block_configure:
+ *   title: 'Configure block'
+ *   route_name: 'entity.block.edit_form'
+ *   group: 'block'
+ * @endcode
+ * Some notes:
+ * - The first line is the machine name for your contextual link, which usually
+ *   matches the machine name of the route (given in the 'route_name' line).
+ * - group: This needs to match the link group defined in the render array.
+ *
+ * Contextual links from other modules can be altered using
+ * hook_contextual_links_alter().
+ *
+ * @todo Derivatives are in flux for these; when they are more stable, add
+ *   documentation here.
+ */
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Alters all the menu links discovered by the menu link plugin manager.
+ *
+ * @param array $links
+ *   The link definitions to be altered.
+ *
+ * @return array
+ *   An array of discovered menu links. Each link has a key that is the machine
+ *   name, which must be unique. By default, use the route name as the
+ *   machine name. In cases where multiple links use the same route name, such
+ *   as two links to the same page in different menus, or two links using the
+ *   same route name but different route parameters, the suggested machine name
+ *   patten is the route name followed by a dot and a unique suffix. For
+ *   example, an additional logout link might have a machine name of
+ *   user.logout.navigation, and default links provided to edit the article and
+ *   page content types could use machine names
+ *   entity.node_type.edit_form.article and entity.node_type.edit_form.page.
+ *   Since the machine name may be arbitrary, you should never write code that
+ *   assumes it is identical to the route name.
+ *
+ *   The value corresponding to each machine name key is an associative array
+ *   that may contain the following key-value pairs:
+ *   - title: (required) The untranslated title of the menu link.
+ *   - description: The untranslated description of the link.
+ *   - route_name: (optional) The route name to be used to build the path.
+ *     Either a route_name or a link_path must be provided.
+ *   - route_parameters: (optional) The route parameters to build the path.
+ *   - link_path: (optional) If you have an external link use link_path instead
+ *     of providing a route_name.
+ *   - parent: (optional) The machine name of the link that is this link's menu
+ *     parent.
+ *   - weight: (optional) An integer that determines the relative position of
+ *     items in the menu; higher-weighted items sink. Defaults to 0. Menu items
+ *     with the same weight are ordered alphabetically.
+ *   - menu_name: (optional) The machine name of a menu to put the link in, if
+ *     not the default Tools menu.
+ *   - expanded: (optional) If set to TRUE, and if a menu link is provided for
+ *     this menu item (as a result of other properties), then the menu link is
+ *     always expanded, equivalent to its 'always expanded' checkbox being set
+ *     in the UI.
+ *   - options: (optional) An array of options to be passed to _l() when
+ *     generating a link from this menu item.
+ *
+ * @ingroup menu
+ */
+function hook_menu_links_discovered_alter(&$links) {
+  // Change the weight and title of the user.logout link.
+  $links['user.logout']['weight'] = -10;
+  $links['user.logout']['title'] = 'Logout';
+}
+
+/**
+ * Alter tabs and actions displayed on the page before they are rendered.
+ *
+ * This hook is invoked by menu_local_tasks(). The system-determined tabs and
+ * actions are passed in by reference. Existing tabs or actions may be altered.
+ *
+ * @param array $data
+ *   An associative array containing tabs and actions. See
+ *   hook_menu_local_tasks() for details.
+ * @param string $route_name
+ *   The route name of the page.
+ *
+ * @see hook_menu_local_tasks()
+ *
+ * @ingroup menu
+ */
+function hook_menu_local_tasks_alter(&$data, $route_name) {
+}
+
+/**
+ * Alter local actions plugins.
+ *
+ * @param array $local_actions
+ *   The array of local action plugin definitions, keyed by plugin ID.
+ *
+ * @see \Drupal\Core\Menu\LocalActionInterface
+ * @see \Drupal\Core\Menu\LocalActionManager
+ *
+ * @ingroup menu
+ */
+function hook_menu_local_actions_alter(&$local_actions) {
+}
+
+/**
+ * Alter local tasks plugins.
+ *
+ * @param array $local_tasks
+ *   The array of local tasks plugin definitions, keyed by plugin ID.
+ *
+ * @see \Drupal\Core\Menu\LocalTaskInterface
+ * @see \Drupal\Core\Menu\LocalTaskManager
+ */
+function hook_local_tasks_alter(&$local_tasks) {
+  // Remove a specified local task plugin.
+  unset($local_tasks['example_plugin_id']);
+}
+
+/**
+ * Alter contextual links before they are rendered.
+ *
+ * This hook is invoked by
+ * \Drupal\Core\Menu\ContextualLinkManager::getContextualLinkPluginsByGroup().
+ * The system-determined contextual links are passed in by reference. Additional
+ * links may be added and existing links can be altered.
+ *
+ * Each contextual link contains the following entries:
+ * - title: The localized title of the link.
+ * - route_name: The route name of the link.
+ * - route_parameters: The route parameters of the link.
+ * - localized_options: An array of options to pass to _url().
+ * - (optional) weight: The weight of the link, which is used to sort the links.
+ *
+ *
+ * @param array $links
+ *   An associative array containing contextual links for the given $group,
+ *   as described above. The array keys are used to build CSS class names for
+ *   contextual links and must therefore be unique for each set of contextual
+ *   links.
+ * @param string $group
+ *   The group of contextual links being rendered.
+ * @param array $route_parameters.
+ *   The route parameters passed to each route_name of the contextual links.
+ *   For example:
+ *   @code
+ *   array('node' => $node->id())
+ *   @endcode
+ *
+ * @see \Drupal\Core\Menu\ContextualLinkManager
+ *
+ * @ingroup menu
+ */
+function hook_contextual_links_alter(array &$links, $group, array $route_parameters) {
+  if ($group == 'menu') {
+    // Dynamically use the menu name for the title of the menu_edit contextual
+    // link.
+    $menu = \Drupal::entityManager()->getStorage('menu')->load($route_parameters['menu']);
+    $links['menu_edit']['title'] = t('Edit menu: !label', array('!label' => $menu->label()));
+  }
+}
+
+/**
+ * Alter the plugin definition of contextual links.
+ *
+ * @param array $contextual_links
+ *   An array of contextual_links plugin definitions, keyed by contextual link
+ *   ID. Each entry contains the following keys:
+ *     - title: The displayed title of the link
+ *     - route_name: The route_name of the contextual link to be displayed
+ *     - group: The group under which the contextual links should be added to.
+ *       Possible values are e.g. 'node' or 'menu'.
+ *
+ * @see \Drupal\Core\Menu\ContextualLinkManager
+ */
+function hook_contextual_links_plugins_alter(array &$contextual_links) {
+  $contextual_links['menu_edit']['title'] = 'Edit the menu';
+}
+
+/**
+ * Perform alterations to the breadcrumb built by the BreadcrumbManager.
+ *
+ * @param array $breadcrumb
+ *   An array of breadcrumb link a tags, returned by the breadcrumb manager
+ *   build method, for example
+ *   @code
+ *     array('<a href="/">Home</a>');
+ *   @endcode
+ * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
+ *   The current route match.
+ * @param array $context
+ *   May include the following key:
+ *   - builder: the instance of
+ *     \Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface that constructed this
+ *     breadcrumb, or NULL if no builder acted based on the current attributes.
+ */
+function hook_system_breadcrumb_alter(array &$breadcrumb, \Drupal\Core\Routing\RouteMatchInterface $route_match, array $context) {
+  // Add an item to the end of the breadcrumb.
+  $breadcrumb[] = Drupal::l(t('Text'), 'example_route_name');
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */
+
+/**
+ * @} End of "defgroup menu".
+ */