[TASK] Document Footer menu (#339)

* [TASK] Document Footer menu

Releases: main, 13.4

* Update Documentation/Menu/MetaMenu.rst

Co-authored-by: Stefan Frömken <[email protected]>

* Update Documentation/Menu/MetaMenu.rst

Co-authored-by: Stefan Frömken <[email protected]>

---------

Co-authored-by: Stefan Frömken <[email protected]>

Documentation/Menu/Breadcrumb.rst

@@ -1,4 +1,5 @@
 :navigation-title: Breadcrumb
+
 .. include:: /Includes.rst.txt
 
 ..  _breadcrumb:

Documentation/Menu/Index.rst

@@ -1,5 +1,6 @@
 :navigation-title: Menus
-.. include:: /Includes.rst.txt
+
+..  include:: /Includes.rst.txt
 
 ..  _menu:
 
@@ -156,4 +157,6 @@ to demonstrate different menu types:
 *   A breadcrumb configured in
     :file:`packages/my_site_package/Configuration/Sets/SitePackage/TypoScript/Navigation/breadcrumb.typoscript`
     and rendered in :file:`packages/my_site_package/Resources/Private/PageView/Partials/Navigation/Breadcrumb.html`.
-*   A footer menu (example is still missing).
+*   A footer menu consisting of pages within a selected folder configured in
+    :file:`packages/my_site_package/Configuration/Sets/SitePackage/TypoScript/Navigation/footerMenu.typoscript`
+    and rendered in :file:`packages/my_site_package/Resources/Private/PageView/Partials/Navigation/FooterMenu.html`.

Documentation/Menu/MetaMenu.rst

@@ -0,0 +1,111 @@
+:navigation-title: Breadcrumb
+
+..  include:: /Includes.rst.txt
+
+..  _meta-menu:
+
+================================
+Meta menu / Footer menu in TYPO3
+================================
+
+A meta menu - often but not always displayed in the footer of a website -
+displays only selected pages like "Imprint", "Contact", "Data Privacy", ...
+
+If you use a `Generated site package <https://docs.typo3.org/permalink/t3sitepackage:minimal-design>`_
+it already contains a meta menu in the footer of the page.
+
+To display a breadcrumb the `menu data processor <https://docs.typo3.org/permalink/t3tsref:menuprocessor>`_
+can be used with the special type `List <https://docs.typo3.org/permalink/t3tsref:hmenu-special-list>`_
+or `Directory <https://docs.typo3.org/permalink/t3tsref:hmenu-special-directory>`_.
+
+The special menu type "List" allows you to specify a list of UIDs of pages that
+should be displayed in the meta menu. The special menu type "Directory" allows
+you to specify a folder or page of which all subpages should be displayed in
+the menu. We take the second approach here.
+
+..  _meta-menu-typoscript:
+
+Menu of subpages TypoScript - the data processor
+================================================
+
+..  literalinclude:: /CodeSnippets/my_site_package/Configuration/Sets/SitePackage/TypoScript/Navigation/footerMenu.typoscript
+    :caption: packages/my_site_package/Configuration/Sets/SitePackage/TypoScript/Navigation/footerMenu.typoscript
+    :linenos:
+    :emphasize-lines: 7-8
+
+Line 4: Each data processor must have a unique id. We used 10 for the
+`page-content data processor <https://docs.typo3.org/permalink/t3sitepackage:page-content-data-processor>`_
+and 20 for the :ref:`Main menu <main-menu-creation>` and 30 for the
+`Breadcrumb <https://docs.typo3.org/permalink/t3sitepackage:breadcrumb>`_
+therefore we now use 40.
+
+Line 6: The values processed by the data processor should be stored in variable
+`footerMenu`.
+
+Line 7: We configure the menu to use the special type
+`Directory <https://docs.typo3.org/permalink/t3tsref:hmenu-special-directory>`_.
+
+Line 8: The folder which contains the pages to be displayed in the footer menu
+can be configured via site settings. You can find the definition of this setting
+in file :file:`packages/my_site_package/Configuration/Sets/SitePackage/settings.definitions.yaml`.
+
+..  _meta-menu-fluid:
+
+Menu of subpages - Fluid template
+=================================
+
+The special type `directory` delivers the items of the meta menu as an array.
+Therefore we can use the `For ViewHelper <f:for> <https://docs.typo3.org/permalink/t3viewhelper:typo3fluid-fluid-for>`_
+to loop through these elements:
+
+..  literalinclude:: /CodeSnippets/my_site_package/Resources/Private/PageView/Partials/Navigation/FooterMenu.html
+    :caption: packages/my_site_package/Resources/Private/PageView/Partials/Navigation/FooterMenu.html
+    :linenos:
+
+The menu items can be displayed just as we have done in the
+`Fluid partial of the main menu <https://docs.typo3.org/permalink/t3sitepackage:fluid-implement-main-menu>`_.
+
+As we do not need to highlight active pages in the footer menu we omit those
+conditions.
+
+..  _meta-menu-list:
+
+Switching to the menu type list
+===============================
+
+If it is more feasible for your project to list all pages that should be listed
+in the meta menu, you can switch to using the special menu type "List" by
+changing the TypoScript:
+
+..  code-block:: diff
+    :caption: packages/my_site_package/Configuration/Sets/SitePackage/settings.definitions.yaml (diff)
+
+     40 = menu
+     40 {
+         as = footerMenu
+    -    special = directory
+    +    special = list
+         special.value = {$MySitePackage.footerMenuRoot}
+     }
+
+You can now change the setting to accept a comma separated list of integers
+and then list all pages that should be displayed in the meta menu. For example:
+
+..  code-block:: diff
+    :caption: packages/my_site_package/Configuration/Sets/SitePackage/TypoScript/Navigation/footerMenu.typoscript (diff)
+
+     MySitePackage.footerMenuRoot:
+       label: 'Footer menu root uid'
+    -  description: 'The subpages of this page are displayed in the footer'
+    +  description: 'These pages are displayed in the footer'
+       category: MySitePackage.menus
+    -  type: int
+    +  type: stringlist
+    -  default: 2
+    +  default:
+    +    - 5
+    +    - 4
+    +    - 3
+
+We are using the type :ref:`stringlist <t3coreapi:confval-site-setting-type-stringlist>`
+- as of writing these lines - there is no integer list type in the settings yet.