Mercurial > hg > isophonics-drupal-site
view core/lib/Drupal/Core/Render/theme.api.php @ 18:af1871eacc83
Update to Drupal core 8.7.1
author | Chris Cannam |
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date | Thu, 09 May 2019 15:33:08 +0100 |
parents | c2387f117808 |
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<?php /** * @file * Hooks and documentation related to the theme and render system. */ /** * @defgroup themeable Theme system overview * @{ * Functions and templates for the user interface that themes can override. * * Drupal's theme system allows a theme to have nearly complete control over * the appearance of the site, which includes both the markup and the CSS used * to style the markup. For this system to work, modules, instead of writing * HTML markup directly, need to return "render arrays", which are structured * hierarchical arrays that include the data to be rendered into HTML (or XML or * another output format), and options that affect the markup. Render arrays * are ultimately rendered into HTML or other output formats by recursive calls * to drupal_render(), traversing the depth of the render array hierarchy. At * each level, the theme system is invoked to do the actual rendering. See the * documentation of drupal_render() and the * @link theme_render Theme system and Render API topic @endlink for more * information about render arrays and rendering. * * @section sec_twig_theme Twig Templating Engine * Drupal 8 uses the templating engine Twig. Twig offers developers a fast, * secure, and flexible method for building templates for Drupal 8 sites. Twig * also offers substantial usability improvements over PHPTemplate, and does * not require front-end developers to know PHP to build and manipulate Drupal * 8 themes. * * For further information on theming in Drupal 8 see * https://www.drupal.org/docs/8/theming * * For further Twig documentation see * http://twig.sensiolabs.org/doc/templates.html * * @section sec_theme_hooks Theme Hooks * The theme system is invoked in \Drupal\Core\Render\Renderer::doRender() by * calling the \Drupal\Core\Theme\ThemeManagerInterface::render() function, * which operates on the concept of "theme hooks". Theme hooks define how a * particular type of data should be rendered. They are registered by modules by * implementing hook_theme(), which specifies the name of the hook, the input * "variables" used to provide data and options, and other information. Modules * implementing hook_theme() also need to provide a default implementation for * each of their theme hooks, normally in a Twig file, and they may also provide * preprocessing functions. For example, the core Search module defines a theme * hook for a search result item in search_theme(): * @code * return array( * 'search_result' => array( * 'variables' => array( * 'result' => NULL, * 'plugin_id' => NULL, * ), * 'file' => 'search.pages.inc', * ), * ); * @endcode * Given this definition, the template file with the default implementation is * search-result.html.twig, which can be found in the * core/modules/search/templates directory, and the variables for rendering are * the search result and the plugin ID. In addition, there is a function * template_preprocess_search_result(), located in file search.pages.inc, which * preprocesses the information from the input variables so that it can be * rendered by the Twig template; the processed variables that the Twig template * receives are documented in the header of the default Twig template file. * * hook_theme() implementations can also specify that a theme hook * implementation is a theme function, but that is uncommon and not recommended. * Note that while Twig templates will auto-escape variables, theme functions * must explicitly escape any variables by using theme_render_and_autoescape(). * Failure to do so is likely to result in security vulnerabilities. Theme * functions are deprecated in Drupal 8.0.x and will be removed before * Drupal 9.0.x. Use Twig templates instead. * * @section sec_overriding_theme_hooks Overriding Theme Hooks * Themes may register new theme hooks within a hook_theme() implementation, but * it is more common for themes to override default implementations provided by * modules than to register entirely new theme hooks. Themes can override a * default implementation by creating a template file with the same name as the * default implementation; for example, to override the display of search * results, a theme would add a file called search-result.html.twig to its * templates directory. A good starting point for doing this is normally to * copy the default implementation template, and then modifying it as desired. * * In the uncommon case that a theme hook uses a theme function instead of a * template file, a module would provide a default implementation function * called theme_HOOK, where HOOK is the name of the theme hook (for example, * theme_search_result() would be the name of the function for search result * theming). In this case, a theme can override the default implementation by * defining a function called THEME_HOOK() in its THEME.theme file, where THEME * is the machine name of the theme (for example, 'bartik' is the machine name * of the core Bartik theme, and it would define a function called * bartik_search_result() in the bartik.theme file, if the search_result hook * implementation was a function instead of a template). Normally, copying the * default function is again a good starting point for overriding its behavior. * Again, note that theme functions (unlike templates) must explicitly escape * variables using theme_render_and_autoescape() or risk security * vulnerabilities. Theme functions are deprecated in Drupal 8.0.x and will be * removed before Drupal 9.0.x. Use Twig templates instead. * * @section sec_preprocess_templates Preprocessing for Template Files * If the theme implementation is a template file, several functions are called * before the template file is invoked to modify the variables that are passed * to the template. These make up the "preprocessing" phase, and are executed * (if they exist), in the following order (note that in the following list, * HOOK indicates the hook being called or a less specific hook. For example, if * '#theme' => 'node__article' is called, hook is node__article and node. MODULE * indicates a module name, THEME indicates a theme name, and ENGINE indicates a * theme engine name). Modules, themes, and theme engines can provide these * functions to modify how the data is preprocessed, before it is passed to the * theme template: * - template_preprocess(&$variables, $hook): Creates a default set of variables * for all theme hooks with template implementations. Provided by Drupal Core. * - template_preprocess_HOOK(&$variables): Should be implemented by the module * that registers the theme hook, to set up default variables. * - MODULE_preprocess(&$variables, $hook): hook_preprocess() is invoked on all * implementing modules. * - MODULE_preprocess_HOOK(&$variables): hook_preprocess_HOOK() is invoked on * all implementing modules, so that modules that didn't define the theme hook * can alter the variables. * - ENGINE_engine_preprocess(&$variables, $hook): Allows the theme engine to * set necessary variables for all theme hooks with template implementations. * - ENGINE_engine_preprocess_HOOK(&$variables): Allows the theme engine to set * necessary variables for the particular theme hook. * - THEME_preprocess(&$variables, $hook): Allows the theme to set necessary * variables for all theme hooks with template implementations. * - THEME_preprocess_HOOK(&$variables): Allows the theme to set necessary * variables specific to the particular theme hook. * * @section sec_preprocess_functions Preprocessing for Theme Functions * If the theming implementation is a function, only the theme-hook-specific * preprocess functions (the ones ending in _HOOK) are called from the list * above. This is because theme hooks with function implementations need to be * fast, and calling the non-theme-hook-specific preprocess functions for them * would incur a noticeable performance penalty. * * @section sec_suggestions Theme hook suggestions * In some cases, instead of calling the base theme hook implementation (either * the default provided by the module that defined the hook, or the override * provided by the theme), the theme system will instead look for "suggestions" * of other hook names to look for. Suggestions can be specified in several * ways: * - In a render array, the '#theme' property (which gives the name of the hook * to use) can be an array of theme hook names instead of a single hook name. * In this case, the render system will look first for the highest-priority * hook name, and if no implementation is found, look for the second, and so * on. Note that the highest-priority suggestion is at the end of the array. * - In a render array, the '#theme' property can be set to the name of a hook * with a '__SUGGESTION' suffix. For example, in search results theming, the * hook 'item_list__search_results' is given. In this case, the render system * will look for theme templates called item-list--search-results.html.twig, * which would only be used for rendering item lists containing search * results, and if this template is not found, it will fall back to using the * base item-list.html.twig template. This type of suggestion can also be * combined with providing an array of theme hook names as described above. * - A module can implement hook_theme_suggestions_HOOK(). This allows the * module that defines the theme template to dynamically return an array * containing specific theme hook names (presumably with '__' suffixes as * defined above) to use as suggestions. For example, the Search module * does this in search_theme_suggestions_search_result() to suggest * search_result__PLUGIN as the theme hook for search result items, where * PLUGIN is the machine name of the particular search plugin type that was * used for the search (such as node_search or user_search). * * For further information on overriding theme hooks see * https://www.drupal.org/node/2186401 * * @section sec_alternate_suggestions Altering theme hook suggestions * Modules can also alter the theme suggestions provided using the mechanisms * of the previous section. There are two hooks for this: the * theme-hook-specific hook_theme_suggestions_HOOK_alter() and the generic * hook_theme_suggestions_alter(). These hooks get the current list of * suggestions as input, and can change this array (adding suggestions and * removing them). * * @section assets Assets * We can distinguish between three types of assets: * - Unconditional page-level assets (loaded on all pages where the theme is in * use): these are defined in the theme's *.info.yml file. * - Conditional page-level assets (loaded on all pages where the theme is in * use and a certain condition is met): these are attached in * hook_page_attachments_alter(), e.g.: * @code * function THEME_page_attachments_alter(array &$page) { * if ($some_condition) { * $page['#attached']['library'][] = 'mytheme/something'; * } * } * @endcode * - Template-specific assets (loaded on all pages where a specific template is * in use): these can be added by in preprocessing functions, using @code * $variables['#attached'] @endcode, e.g.: * @code * function THEME_preprocess_menu_local_action(array &$variables) { * // We require Modernizr's touch test for button styling. * $variables['#attached']['library'][] = 'core/modernizr'; * } * @endcode * * @see hooks * @see callbacks * @see theme_render * * @} */ /** * @defgroup theme_render Render API overview * @{ * Overview of the Theme system and Render API. * * The main purpose of Drupal's Theme system is to give themes complete control * over the appearance of the site, which includes the markup returned from HTTP * requests and the CSS files used to style that markup. In order to ensure that * a theme can completely customize the markup, module developers should avoid * directly writing HTML markup for pages, blocks, and other user-visible output * in their modules, and instead return structured "render arrays" (see * @ref arrays below). Doing this also increases usability, by ensuring that the * markup used for similar functionality on different areas of the site is the * same, which gives users fewer user interface patterns to learn. * * For further information on the Theme and Render APIs, see: * - https://www.drupal.org/docs/8/theming * - https://www.drupal.org/developing/api/8/render * - @link themeable Theme system overview @endlink. * * @section arrays Render arrays * The core structure of the Render API is the render array, which is a * hierarchical associative array containing data to be rendered and properties * describing how the data should be rendered. A render array that is returned * by a function to specify markup to be sent to the web browser or other * services will eventually be rendered by a call to drupal_render(), which will * recurse through the render array hierarchy if appropriate, making calls into * the theme system to do the actual rendering. If a function or method actually * needs to return rendered output rather than a render array, the best practice * would be to create a render array, render it by calling drupal_render(), and * return that result, rather than writing the markup directly. See the * documentation of drupal_render() for more details of the rendering process. * * Each level in the hierarchy of a render array (including the outermost array) * has one or more array elements. Array elements whose names start with '#' are * known as "properties", and the array elements with other names are "children" * (constituting the next level of the hierarchy); the names of children are * flexible, while property names are specific to the Render API and the * particular type of data being rendered. A special case of render arrays is a * form array, which specifies the form elements for an HTML form; see the * @link form_api Form generation topic @endlink for more information on forms. * * Render arrays (at any level of the hierarchy) will usually have one of the * following properties defined: * - #type: Specifies that the array contains data and options for a particular * type of "render element" (for example, 'form', for an HTML form; * 'textfield', 'submit', for HTML form element types; 'table', for a table * with rows, columns, and headers). See @ref elements below for more on * render element types. * - #theme: Specifies that the array contains data to be themed by a particular * theme hook. Modules define theme hooks by implementing hook_theme(), which * specifies the input "variables" used to provide data and options; if a * hook_theme() implementation specifies variable 'foo', then in a render * array, you would provide this data using property '#foo'. Modules * implementing hook_theme() also need to provide a default implementation for * each of their theme hooks, normally in a Twig file. For more information * and to discover available theme hooks, see the documentation of * hook_theme() and the * @link themeable Default theme implementations topic. @endlink * - #markup: Specifies that the array provides HTML markup directly. Unless * the markup is very simple, such as an explanation in a paragraph tag, it * is normally preferable to use #theme or #type instead, so that the theme * can customize the markup. Note that the value is passed through * \Drupal\Component\Utility\Xss::filterAdmin(), which strips known XSS * vectors while allowing a permissive list of HTML tags that are not XSS * vectors. (For example, <script> and <style> are not allowed.) See * \Drupal\Component\Utility\Xss::$adminTags for the list of allowed tags. If * your markup needs any of the tags not in this whitelist, then you can * implement a theme hook and/or an asset library. Alternatively, you can use * the key #allowed_tags to alter which tags are filtered. * - #plain_text: Specifies that the array provides text that needs to be * escaped. This value takes precedence over #markup. * - #allowed_tags: If #markup is supplied, this can be used to change which * tags are allowed in the markup. The value is an array of tags that * Xss::filter() would accept. If #plain_text is set, this value is ignored. * * Usage example: * @code * $output['admin_filtered_string'] = [ * '#markup' => '<em>This is filtered using the admin tag list</em>', * ]; * $output['filtered_string'] = [ * '#markup' => '<video><source src="v.webm" type="video/webm"></video>', * '#allowed_tags' => ['video', 'source'], * ]; * $output['escaped_string'] = [ * '#plain_text' => '<em>This is escaped</em>', * ]; * @endcode * * @see core.libraries.yml * @see hook_theme() * * JavaScript and CSS assets are specified in the render array using the * #attached property (see @ref sec_attached). * * @section elements Render elements * Render elements are defined by Drupal core and modules. The primary way to * define a render element is to create a render element plugin. There are * two types of render element plugins: * - Generic elements: Generic render element plugins implement * \Drupal\Core\Render\Element\ElementInterface, are annotated with * \Drupal\Core\Render\Annotation\RenderElement annotation, go in plugin * namespace Element, and generally extend the * \Drupal\Core\Render\Element\RenderElement base class. * - Form input elements: Render elements representing form input elements * implement \Drupal\Core\Render\Element\FormElementInterface, are annotated * with \Drupal\Core\Render\Annotation\FormElement annotation, go in plugin * namespace Element, and generally extend the * \Drupal\Core\Render\Element\FormElement base class. * See the @link plugin_api Plugin API topic @endlink for general information * on plugins. You can search for classes with the RenderElement or FormElement * annotation to discover what render elements are available. API reference * sites (such as https://api.drupal.org) generate lists of all existing * elements from these classes. Look for the Elements link in the API Navigation * block. * * Modules can define render elements by defining an element plugin. * * @section sec_caching Caching * The Drupal rendering process has the ability to cache rendered output at any * level in a render array hierarchy. This allows expensive calculations to be * done infrequently, and speeds up page loading. See the * @link cache Cache API topic @endlink for general information about the cache * system. * * In order to make caching possible, the following information needs to be * present: * - Cache keys: Identifiers for cacheable portions of render arrays. These * should be created and added for portions of a render array that * involve expensive calculations in the rendering process. * - Cache contexts: Contexts that may affect rendering, such as user role and * language. When no context is specified, it means that the render array * does not vary by any context. * - Cache tags: Tags for data that rendering depends on, such as for * individual nodes or user accounts, so that when these change the cache * can be automatically invalidated. If the data consists of entities, you * can use \Drupal\Core\Entity\EntityInterface::getCacheTags() to generate * appropriate tags; configuration objects have a similar method. * - Cache max-age: The maximum duration for which a render array may be cached. * Defaults to \Drupal\Core\Cache\Cache::PERMANENT (permanently cacheable). * * Cache information is provided in the #cache property in a render array. In * this property, always supply the cache contexts, tags, and max-age if a * render array varies by context, depends on some modifiable data, or depends * on information that's only valid for a limited time, respectively. Cache keys * should only be set on the portions of a render array that should be cached. * Contexts are automatically replaced with the value for the current request * (e.g. the current language) and combined with the keys to form a cache ID. * The cache contexts, tags, and max-age will be propagated up the render array * hierarchy to determine cacheability for containing render array sections. * * Here's an example of what a #cache property might contain: * @code * '#cache' => [ * 'keys' => ['entity_view', 'node', $node->id()], * 'contexts' => ['languages'], * 'tags' => $node->getCacheTags(), * 'max-age' => Cache::PERMANENT, * ], * @endcode * * At the response level, you'll see X-Drupal-Cache-Contexts and * X-Drupal-Cache-Tags headers. * * See https://www.drupal.org/developing/api/8/render/arrays/cacheability for * details. * * @section sec_attached Attaching libraries in render arrays * Libraries, JavaScript settings, feeds, HTML <head> tags and HTML <head> links * are attached to elements using the #attached property. The #attached property * is an associative array, where the keys are the attachment types and the * values are the attached data. * * The #attached property can also be used to specify HTTP headers and the * response status code. * * The #attached property allows loading of asset libraries (which may contain * CSS assets, JavaScript assets, and JavaScript setting assets), JavaScript * settings, feeds, HTML <head> tags and HTML <head> links. Specify an array of * type => value pairs, where the type (most often 'library' — for libraries, or * 'drupalSettings' — for JavaScript settings) to attach these response-level * values. Example: * @code * $build['#attached']['library'][] = 'core/jquery'; * $build['#attached']['drupalSettings']['foo'] = 'bar'; * $build['#attached']['feed'][] = [$url, $this->t('Feed title')]; * @endcode * * See \Drupal\Core\Render\AttachmentsResponseProcessorInterface for additional * information. * * See \Drupal\Core\Asset\LibraryDiscoveryParser::parseLibraryInfo() for more * information on how to define libraries. * * @section sec_placeholders Placeholders in render arrays * Render arrays have a placeholder mechanism, which can be used to add data * into the render array late in the rendering process. This works in a similar * manner to \Drupal\Component\Render\FormattableMarkup::placeholderFormat(), * with the text that ends up in the #markup property of the element at the * end of the rendering process getting substitutions from placeholders that * are stored in the 'placeholders' element of the #attached property. * * For example, after the rest of the rendering process was done, if your * render array contained: * @code * $build['my_element'] = [ * '#attached' => ['placeholders' => ['@foo' => 'replacement']], * '#markup' => ['Something about @foo'], * ]; * @endcode * then #markup would end up containing 'Something about replacement'. * * Note that each placeholder value can itself be a render array, which will be * rendered, and any cache tags generated during rendering will be added to the * cache tags for the markup. * * @section render_pipeline The render pipeline * The term "render pipeline" refers to the process Drupal uses to take * information provided by modules and render it into a response. See * https://www.drupal.org/developing/api/8/render for more details on this * process. For background on routing concepts, see * @link routing Routing API. @endlink * * There are in fact multiple render pipelines: * - Drupal always uses the Symfony render pipeline. See * http://symfony.com/doc/2.7/components/http_kernel/introduction.html * - Within the Symfony render pipeline, there is a Drupal render pipeline, * which handles controllers that return render arrays. (Symfony's render * pipeline only knows how to deal with Response objects; this pipeline * converts render arrays into Response objects.) These render arrays are * considered the main content, and can be rendered into multiple formats: * HTML, Ajax, dialog, and modal. Modules can add support for more formats, by * implementing a main content renderer, which is a service tagged with * 'render.main_content_renderer'. * - Finally, within the HTML main content renderer, there is another pipeline, * to allow for rendering the page containing the main content in multiple * ways: no decoration at all (just a page showing the main content) or blocks * (a page with regions, with blocks positioned in regions around the main * content). Modules can provide additional options, by implementing a page * variant, which is a plugin annotated with * \Drupal\Core\Display\Annotation\PageDisplayVariant. * * Routes whose controllers return a \Symfony\Component\HttpFoundation\Response * object are fully handled by the Symfony render pipeline. * * Routes whose controllers return the "main content" as a render array can be * requested in multiple formats (HTML, JSON, etc.) and/or in a "decorated" * manner, as described above. * * @see themeable * @see \Symfony\Component\HttpKernel\KernelEvents::VIEW * @see \Drupal\Core\EventSubscriber\MainContentViewSubscriber * @see \Drupal\Core\Render\MainContent\MainContentRendererInterface * @see \Drupal\Core\Render\MainContent\HtmlRenderer * @see \Drupal\Core\Render\RenderEvents::SELECT_PAGE_DISPLAY_VARIANT * @see \Drupal\Core\Render\Plugin\DisplayVariant\SimplePageVariant * @see \Drupal\block\Plugin\DisplayVariant\BlockPageVariant * @see \Drupal\Core\Render\BareHtmlPageRenderer * * @} */ /** * @defgroup listing_page_element Page header for Elements page * @{ * Introduction to form and render elements * * Render elements are referenced in render arrays. Render arrays contain data * to be rendered, along with meta-data and attributes that specify how to * render the data into markup; see the * @link theme_render Render API topic @endlink for an overview of render * arrays and render elements. Form arrays are a subset of render arrays, * representing HTML forms; form elements are a subset of render elements, * representing HTML elements for forms. See the * @link form_api Form API topic @endlink for an overview of forms, form * processing, and form arrays. * * Each form and render element type corresponds to an element plugin class; * each of them either extends \Drupal\Core\Render\Element\RenderElement * (render elements) or \Drupal\Core\Render\Element\FormElement (form * elements). Usage and properties are documented on the individual classes, * and the two base classes list common properties shared by all render * elements and the form element subset, respectively. * * @see theme_render * @see form_api * @see \Drupal\Core\Render\Element\RenderElement * @see \Drupal\Core\Render\Element\FormElement * * @} */ /** * @addtogroup hooks * @{ */ /** * Allow themes to alter the theme-specific settings form. * * With this hook, themes can alter the theme-specific settings form in any way * allowable by Drupal's Form API, such as adding form elements, changing * default values and removing form elements. See the Form API documentation on * api.drupal.org for detailed information. * * Note that the base theme's form alterations will be run before any sub-theme * alterations. * * @param $form * Nested array of form elements that comprise the form. * @param $form_state * The current state of the form. */ function hook_form_system_theme_settings_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state) { // Add a checkbox to toggle the breadcrumb trail. $form['toggle_breadcrumb'] = [ '#type' => 'checkbox', '#title' => t('Display the breadcrumb'), '#default_value' => theme_get_setting('features.breadcrumb'), '#description' => t('Show a trail of links from the homepage to the current page.'), ]; } /** * Preprocess theme variables for templates. * * This hook allows modules to preprocess theme variables for theme templates. * It is called for all theme hooks implemented as templates, but not for theme * hooks implemented as functions. hook_preprocess_HOOK() can be used to * preprocess variables for a specific theme hook, whether implemented as a * template or function. * * For more detailed information, see the * @link themeable Theme system overview topic @endlink. * * @param $variables * The variables array (modify in place). * @param $hook * The name of the theme hook. */ function hook_preprocess(&$variables, $hook) { static $hooks; // Add contextual links to the variables, if the user has permission. if (!\Drupal::currentUser()->hasPermission('access contextual links')) { return; } if (!isset($hooks)) { $hooks = theme_get_registry(); } // Determine the primary theme function argument. if (isset($hooks[$hook]['variables'])) { $keys = array_keys($hooks[$hook]['variables']); $key = $keys[0]; } else { $key = $hooks[$hook]['render element']; } if (isset($variables[$key])) { $element = $variables[$key]; } if (isset($element) && is_array($element) && !empty($element['#contextual_links'])) { $variables['title_suffix']['contextual_links'] = contextual_links_view($element); if (!empty($variables['title_suffix']['contextual_links'])) { $variables['attributes']['class'][] = 'contextual-links-region'; } } } /** * Preprocess theme variables for a specific theme hook. * * This hook allows modules to preprocess theme variables for a specific theme * hook. It should only be used if a module needs to override or add to the * theme preprocessing for a theme hook it didn't define. * * For more detailed information, see the * @link themeable Theme system overview topic @endlink. * * @param $variables * The variables array (modify in place). */ function hook_preprocess_HOOK(&$variables) { // This example is from rdf_preprocess_image(). It adds an RDF attribute // to the image hook's variables. $variables['attributes']['typeof'] = ['foaf:Image']; } /** * Provides alternate named suggestions for a specific theme hook. * * This hook allows modules to provide alternative theme function or template * name suggestions. * * HOOK is the least-specific version of the hook being called. For example, if * '#theme' => 'node__article' is called, then hook_theme_suggestions_node() * will be invoked, not hook_theme_suggestions_node__article(). The specific * hook called (in this case 'node__article') is available in * $variables['theme_hook_original']. * * Implementations of this hook must be placed in *.module or *.theme files, or * must otherwise make sure that the hook implementation is available at * any given time. * * @todo Add @code sample. * * @param array $variables * An array of variables passed to the theme hook. Note that this hook is * invoked before any preprocessing. * * @return array * An array of theme suggestions. * * @see hook_theme_suggestions_HOOK_alter() */ function hook_theme_suggestions_HOOK(array $variables) { $suggestions = []; $suggestions[] = 'hookname__' . $variables['elements']['#langcode']; return $suggestions; } /** * Alters named suggestions for all theme hooks. * * This hook is invoked for all theme hooks, if you are targeting a specific * theme hook it's best to use hook_theme_suggestions_HOOK_alter(). * * The call order is as follows: all existing suggestion alter functions are * called for module A, then all for module B, etc., followed by all for any * base theme(s), and finally for the active theme. The order is * determined by system weight, then by extension (module or theme) name. * * Within each module or theme, suggestion alter hooks are called in the * following order: first, hook_theme_suggestions_alter(); second, * hook_theme_suggestions_HOOK_alter(). So, for each module or theme, the more * general hooks are called first followed by the more specific. * * In the following example, we provide an alternative template suggestion to * node and taxonomy term templates based on the user being logged in. * @code * function MYMODULE_theme_suggestions_alter(array &$suggestions, array $variables, $hook) { * if (\Drupal::currentUser()->isAuthenticated() && in_array($hook, array('node', 'taxonomy_term'))) { * $suggestions[] = $hook . '__' . 'logged_in'; * } * } * * @endcode * * @param array $suggestions * An array of alternate, more specific names for template files or theme * functions. * @param array $variables * An array of variables passed to the theme hook. Note that this hook is * invoked before any variable preprocessing. * @param string $hook * The base hook name. For example, if '#theme' => 'node__article' is called, * then $hook will be 'node', not 'node__article'. The specific hook called * (in this case 'node__article') is available in * $variables['theme_hook_original']. * * @return array * An array of theme suggestions. * * @see hook_theme_suggestions_HOOK_alter() */ function hook_theme_suggestions_alter(array &$suggestions, array $variables, $hook) { // Add an interface-language specific suggestion to all theme hooks. $suggestions[] = $hook . '__' . \Drupal::languageManager()->getCurrentLanguage()->getId(); } /** * Alters named suggestions for a specific theme hook. * * This hook allows any module or theme to provide alternative theme function or * template name suggestions and reorder or remove suggestions provided by * hook_theme_suggestions_HOOK() or by earlier invocations of this hook. * * HOOK is the least-specific version of the hook being called. For example, if * '#theme' => 'node__article' is called, then node_theme_suggestions_node() * will be invoked, not node_theme_suggestions_node__article(). The specific * hook called (in this case 'node__article') is available in * $variables['theme_hook_original']. * * Implementations of this hook must be placed in *.module or *.theme files, or * must otherwise make sure that the hook implementation is available at * any given time. * * @todo Add @code sample. * * @param array $suggestions * An array of theme suggestions. * @param array $variables * An array of variables passed to the theme hook. Note that this hook is * invoked before any preprocessing. * * @see hook_theme_suggestions_alter() * @see hook_theme_suggestions_HOOK() */ function hook_theme_suggestions_HOOK_alter(array &$suggestions, array $variables) { if (empty($variables['header'])) { $suggestions[] = 'hookname__no_header'; } } /** * Respond to themes being installed. * * @param array $theme_list * Array containing the names of the themes being installed. * * @see \Drupal\Core\Extension\ThemeHandler::install() */ function hook_themes_installed($theme_list) { foreach ($theme_list as $theme) { block_theme_initialize($theme); } } /** * Respond to themes being uninstalled. * * @param array $themes * Array containing the names of the themes being uninstalled. * * @see \Drupal\Core\Extension\ThemeHandler::uninstall() */ function hook_themes_uninstalled(array $themes) { // Remove some state entries depending on the theme. foreach ($themes as $theme) { \Drupal::state()->delete('example.' . $theme); } } /** * Declare a template file extension to be used with a theme engine. * * This hook is used in a theme engine implementation in the format of * ENGINE_extension(). * * @return string * The file extension the theme engine will recognize. */ function hook_extension() { // Extension for template base names in Twig. return '.html.twig'; } /** * Render a template using the theme engine. * * It is the theme engine's responsibility to escape variables. The only * exception is if a variable implements * \Drupal\Component\Render\MarkupInterface. Drupal is inherently unsafe if * other variables are not escaped. The helper function * theme_render_and_autoescape() may be used for this. * * @param string $template_file * The path (relative to the Drupal root directory) to the template to be * rendered including its extension in the format 'path/to/TEMPLATE_NAME.EXT'. * @param array $variables * A keyed array of variables that are available for composing the output. The * theme engine is responsible for passing all the variables to the template. * Depending on the code in the template, all or just a subset of the * variables might be used in the template. * * @return string * The output generated from the template. In most cases this will be a string * containing HTML markup. */ function hook_render_template($template_file, $variables) { $twig_service = \Drupal::service('twig'); return $twig_service->loadTemplate($template_file)->render($variables); } /** * Alter the element type information returned from modules. * * A module may implement this hook in order to alter the element type defaults * defined by a module. * * @param array $info * An associative array with structure identical to that of the return value * of \Drupal\Core\Render\ElementInfoManagerInterface::getInfo(). * * @see \Drupal\Core\Render\ElementInfoManager * @see \Drupal\Core\Render\Element\ElementInterface */ function hook_element_info_alter(array &$info) { // Decrease the default size of textfields. if (isset($info['textfield']['#size'])) { $info['textfield']['#size'] = 40; } } /** * Perform necessary alterations to the JavaScript before it is presented on * the page. * * @param $javascript * An array of all JavaScript being presented on the page. * @param \Drupal\Core\Asset\AttachedAssetsInterface $assets * The assets attached to the current response. * * @see drupal_js_defaults() * @see \Drupal\Core\Asset\AssetResolver */ function hook_js_alter(&$javascript, \Drupal\Core\Asset\AttachedAssetsInterface $assets) { // Swap out jQuery to use an updated version of the library. $javascript['core/assets/vendor/jquery/jquery.min.js']['data'] = drupal_get_path('module', 'jquery_update') . '/jquery.js'; } /** * Add dynamic library definitions. * * Modules may implement this hook to add dynamic library definitions. Static * libraries, which do not depend on any runtime information, should be declared * in a modulename.libraries.yml file instead. * * @return array[] * An array of library definitions to register, keyed by library ID. The * library ID will be prefixed with the module name automatically. * * @see core.libraries.yml * @see hook_library_info_alter() */ function hook_library_info_build() { $libraries = []; // Add a library whose information changes depending on certain conditions. $libraries['mymodule.zombie'] = [ 'dependencies' => [ 'core/backbone', ], ]; if (Drupal::moduleHandler()->moduleExists('minifyzombies')) { $libraries['mymodule.zombie'] += [ 'js' => [ 'mymodule.zombie.min.js' => [], ], 'css' => [ 'base' => [ 'mymodule.zombie.min.css' => [], ], ], ]; } else { $libraries['mymodule.zombie'] += [ 'js' => [ 'mymodule.zombie.js' => [], ], 'css' => [ 'base' => [ 'mymodule.zombie.css' => [], ], ], ]; } // Add a library only if a certain condition is met. If code wants to // integrate with this library it is safe to (try to) load it unconditionally // without reproducing this check. If the library definition does not exist // the library (of course) not be loaded but no notices or errors will be // triggered. if (Drupal::moduleHandler()->moduleExists('vampirize')) { $libraries['mymodule.vampire'] = [ 'js' => [ 'js/vampire.js' => [], ], 'css' => [ 'base' => [ 'css/vampire.css', ], ], 'dependencies' => [ 'core/jquery', ], ]; } return $libraries; } /** * Modify the JavaScript settings (drupalSettings). * * @param array &$settings * An array of all JavaScript settings (drupalSettings) being presented on the * page. * @param \Drupal\Core\Asset\AttachedAssetsInterface $assets * The assets attached to the current response. * * @see \Drupal\Core\Asset\AssetResolver * * The results of this hook are cached, however modules may use * hook_js_settings_alter() to dynamically alter settings. */ function hook_js_settings_build(array &$settings, \Drupal\Core\Asset\AttachedAssetsInterface $assets) { // Manipulate settings. if (isset($settings['dialog'])) { $settings['dialog']['autoResize'] = FALSE; } } /** * Perform necessary alterations to the JavaScript settings (drupalSettings). * * @param array &$settings * An array of all JavaScript settings (drupalSettings) being presented on the * page. * @param \Drupal\Core\Asset\AttachedAssetsInterface $assets * The assets attached to the current response. * * @see \Drupal\Core\Asset\AssetResolver */ function hook_js_settings_alter(array &$settings, \Drupal\Core\Asset\AttachedAssetsInterface $assets) { // Add settings. $settings['user']['uid'] = \Drupal::currentUser(); // Manipulate settings. if (isset($settings['dialog'])) { $settings['dialog']['autoResize'] = FALSE; } } /** * Alter libraries provided by an extension. * * Allows modules and themes to change libraries' definitions; mostly used to * update a library to a newer version, while ensuring backward compatibility. * In general, such manipulations should only be done to extend the library's * functionality in a backward-compatible way, to avoid breaking other modules * and themes that may be using the library. * * @param array $libraries * An associative array of libraries registered by $extension. Keyed by * internal library name and passed by reference. * @param string $extension * Can either be 'core' or the machine name of the extension that registered * the libraries. * * @see \Drupal\Core\Asset\LibraryDiscoveryParser::parseLibraryInfo() */ function hook_library_info_alter(&$libraries, $extension) { // Update Farbtastic to version 2.0. if ($extension == 'core' && isset($libraries['jquery.farbtastic'])) { // Verify existing version is older than the one we are updating to. if (version_compare($libraries['jquery.farbtastic']['version'], '2.0', '<')) { // Update the existing Farbtastic to version 2.0. $libraries['jquery.farbtastic']['version'] = '2.0'; // To accurately replace library files, the order of files and the options // of each file have to be retained; e.g., like this: $old_path = 'assets/vendor/farbtastic'; // Since the replaced library files are no longer located in a directory // relative to the original extension, specify an absolute path (relative // to DRUPAL_ROOT / base_path()) to the new location. $new_path = '/' . drupal_get_path('module', 'farbtastic_update') . '/js'; $new_js = []; $replacements = [ $old_path . '/farbtastic.js' => $new_path . '/farbtastic-2.0.js', ]; foreach ($libraries['jquery.farbtastic']['js'] as $source => $options) { if (isset($replacements[$source])) { $new_js[$replacements[$source]] = $options; } else { $new_js[$source] = $options; } } $libraries['jquery.farbtastic']['js'] = $new_js; } } } /** * Alter CSS files before they are output on the page. * * @param $css * An array of all CSS items (files and inline CSS) being requested on the page. * @param \Drupal\Core\Asset\AttachedAssetsInterface $assets * The assets attached to the current response. * * @see Drupal\Core\Asset\LibraryResolverInterface::getCssAssets() */ function hook_css_alter(&$css, \Drupal\Core\Asset\AttachedAssetsInterface $assets) { // Remove defaults.css file. unset($css[drupal_get_path('module', 'system') . '/defaults.css']); } /** * Add attachments (typically assets) to a page before it is rendered. * * Use this hook when you want to conditionally add attachments to a page. * * If you want to alter the attachments added by other modules or if your module * depends on the elements of other modules, use hook_page_attachments_alter() * instead, which runs after this hook. * * If you try to add anything but #attached and #cache to the array, an * exception is thrown. * * @param array &$attachments * An array that you can add attachments to. * * @see hook_page_attachments_alter() */ function hook_page_attachments(array &$attachments) { // Unconditionally attach an asset to the page. $attachments['#attached']['library'][] = 'core/domready'; // Conditionally attach an asset to the page. if (!\Drupal::currentUser()->hasPermission('may pet kittens')) { $attachments['#attached']['library'][] = 'core/jquery'; } } /** * Alter attachments (typically assets) to a page before it is rendered. * * Use this hook when you want to remove or alter attachments on the page, or * add attachments to the page that depend on another module's attachments (this * hook runs after hook_page_attachments(). * * If you try to add anything but #attached and #cache to the array, an * exception is thrown. * * @param array &$attachments * Array of all attachments provided by hook_page_attachments() implementations. * * @see hook_page_attachments() */ function hook_page_attachments_alter(array &$attachments) { // Conditionally remove an asset. if (in_array('core/jquery', $attachments['#attached']['library'])) { $index = array_search('core/jquery', $attachments['#attached']['library']); unset($attachments['#attached']['library'][$index]); } } /** * Add a renderable array to the top of the page. * * @param array $page_top * A renderable array representing the top of the page. */ function hook_page_top(array &$page_top) { $page_top['mymodule'] = ['#markup' => 'This is the top.']; } /** * Add a renderable array to the bottom of the page. * * @param array $page_bottom * A renderable array representing the bottom of the page. */ function hook_page_bottom(array &$page_bottom) { $page_bottom['mymodule'] = ['#markup' => 'This is the bottom.']; } /** * Register a module or theme's theme implementations. * * The implementations declared by this hook specify how a particular render * array is to be rendered as HTML. * * @param array $existing * An array of existing implementations that may be used for override * purposes. This is primarily useful for themes that may wish to examine * existing implementations to extract data (such as arguments) so that * it may properly register its own, higher priority implementations. * @param $type * Whether a theme, module, etc. is being processed. This is primarily useful * so that themes tell if they are the actual theme being called or a parent * theme. May be one of: * - 'module': A module is being checked for theme implementations. * - 'base_theme_engine': A theme engine is being checked for a theme that is * a parent of the actual theme being used. * - 'theme_engine': A theme engine is being checked for the actual theme * being used. * - 'base_theme': A base theme is being checked for theme implementations. * - 'theme': The actual theme in use is being checked. * @param $theme * The actual name of theme, module, etc. that is being being processed. * @param $path * The directory path of the theme or module, so that it doesn't need to be * looked up. * * @return array * An associative array of information about theme implementations. The keys * on the outer array are known as "theme hooks". For theme suggestions, * instead of the array key being the base theme hook, the key is a theme * suggestion name with the format 'base_hook_name__sub_hook_name'. * For render elements, the key is the machine name of the render element. * The array values are themselves arrays containing information about the * theme hook and its implementation. Each information array must contain * either a 'variables' element (for using a #theme element) or a * 'render element' element (for render elements), but not both. * The following elements may be part of each information array: * - variables: Only used for #theme in render array: an array of variables, * where the array keys are the names of the variables, and the array * values are the default values if they are not given in the render array. * Template implementations receive each array key as a variable in the * template file (so they must be legal PHP/Twig variable names). Function * implementations are passed the variables in a single $variables function * argument. If you are using these variables in a render array, prefix the * variable names defined here with a #. * - render element: Used for render element items only: the name of the * renderable element or element tree to pass to the theme function. This * name is used as the name of the variable that holds the renderable * element or tree in preprocess and process functions. * - file: The file the implementation resides in. This file will be included * prior to the theme being rendered, to make sure that the function or * preprocess function (as needed) is actually loaded. * - path: Override the path of the file to be used. Ordinarily the module or * theme path will be used, but if the file will not be in the default * path, include it here. This path should be relative to the Drupal root * directory. * - template: If specified, the theme implementation is a template file, and * this is the template name. Do not add 'html.twig' on the end of the * template name. The extension will be added automatically by the default * rendering engine (which is Twig.) If 'path' is specified, 'template' * should also be specified. If neither 'template' nor 'function' are * specified, a default template name will be assumed. For example, if a * module registers the 'search_result' theme hook, 'search-result' will be * assigned as its template name. * - function: (deprecated in Drupal 8.0.x, will be removed in Drupal 9.0.x) * If specified, this will be the function name to invoke for this * implementation. If neither 'template' nor 'function' are specified, a * default template name will be assumed. See above for more details. * - base hook: Used for theme suggestions only: the base theme hook name. * Instead of this suggestion's implementation being used directly, the base * hook will be invoked with this implementation as its first suggestion. * The base hook's files will be included and the base hook's preprocess * functions will be called in addition to any suggestion's preprocess * functions. If an implementation of hook_theme_suggestions_HOOK() (where * HOOK is the base hook) changes the suggestion order, a different * suggestion may be used in place of this suggestion. If after * hook_theme_suggestions_HOOK() this suggestion remains the first * suggestion, then this suggestion's function or template will be used to * generate the rendered output. * - pattern: A regular expression pattern to be used to allow this theme * implementation to have a dynamic name. The convention is to use __ to * differentiate the dynamic portion of the theme. For example, to allow * forums to be themed individually, the pattern might be: 'forum__'. Then, * when the forum is rendered, following render array can be used: * @code * $render_array = array( * '#theme' => array('forum__' . $tid, 'forum'), * '#forum' => $forum, * ); * @endcode * - preprocess functions: A list of functions used to preprocess this data. * Ordinarily this won't be used; it's automatically filled in. By default, * for a module this will be filled in as template_preprocess_HOOK. For * a theme this will be filled in as twig_preprocess and * twig_preprocess_HOOK as well as themename_preprocess and * themename_preprocess_HOOK. * - override preprocess functions: Set to TRUE when a theme does NOT want * the standard preprocess functions to run. This can be used to give a * theme FULL control over how variables are set. For example, if a theme * wants total control over how certain variables in the page.html.twig are * set, this can be set to true. Please keep in mind that when this is used * by a theme, that theme becomes responsible for making sure necessary * variables are set. * - type: (automatically derived) Where the theme hook is defined: * 'module', 'theme_engine', or 'theme'. * - theme path: (automatically derived) The directory path of the theme or * module, so that it doesn't need to be looked up. * * @see themeable * @see hook_theme_registry_alter() */ function hook_theme($existing, $type, $theme, $path) { return [ 'forum_display' => [ 'variables' => ['forums' => NULL, 'topics' => NULL, 'parents' => NULL, 'tid' => NULL, 'sortby' => NULL, 'forum_per_page' => NULL], ], 'forum_list' => [ 'variables' => ['forums' => NULL, 'parents' => NULL, 'tid' => NULL], ], 'forum_icon' => [ 'variables' => ['new_posts' => NULL, 'num_posts' => 0, 'comment_mode' => 0, 'sticky' => 0], ], 'status_report' => [ 'render element' => 'requirements', 'file' => 'system.admin.inc', ], ]; } /** * Alter the theme registry information returned from hook_theme(). * * The theme registry stores information about all available theme hooks, * including which callback functions those hooks will call when triggered, * what template files are exposed by these hooks, and so on. * * Note that this hook is only executed as the theme cache is re-built. * Changes here will not be visible until the next cache clear. * * The $theme_registry array is keyed by theme hook name, and contains the * information returned from hook_theme(), as well as additional properties * added by \Drupal\Core\Theme\Registry::processExtension(). * * For example: * @code * $theme_registry['block_content_add_list'] = array ( * 'template' => 'block-content-add-list', * 'path' => 'core/themes/seven/templates', * 'type' => 'theme_engine', * 'theme path' => 'core/themes/seven', * 'includes' => array ( * 0 => 'core/modules/block_content/block_content.pages.inc', * ), * 'variables' => array ( * 'content' => NULL, * ), * 'preprocess functions' => array ( * 0 => 'template_preprocess', * 1 => 'template_preprocess_block_content_add_list', * 2 => 'contextual_preprocess', * 3 => 'seven_preprocess_block_content_add_list', * ), * ); * @endcode * * @param $theme_registry * The entire cache of theme registry information, post-processing. * * @see hook_theme() * @see \Drupal\Core\Theme\Registry::processExtension() */ function hook_theme_registry_alter(&$theme_registry) { // Kill the next/previous forum topic navigation links. foreach ($theme_registry['forum_topic_navigation']['preprocess functions'] as $key => $value) { if ($value == 'template_preprocess_forum_topic_navigation') { unset($theme_registry['forum_topic_navigation']['preprocess functions'][$key]); } } } /** * Alter the default, hook-independent variables for all templates. * * Allows modules to provide additional default template variables or manipulate * existing. This hook is invoked from template_preprocess() after basic default * template variables have been set up and before the next template preprocess * function is invoked. * * Note that the default template variables are statically cached within a * request. When adding a template variable that depends on other context, it is * your responsibility to appropriately reset the static cache in * template_preprocess() when needed: * @code * drupal_static_reset('template_preprocess'); * @endcode * * See user_template_preprocess_default_variables_alter() for an example. * * @param array $variables * An associative array of default template variables, as set up by * _template_preprocess_default_variables(). Passed by reference. * * @see template_preprocess() * @see _template_preprocess_default_variables() */ function hook_template_preprocess_default_variables_alter(&$variables) { $variables['is_admin'] = \Drupal::currentUser()->hasPermission('access administration pages'); } /** * @} End of "addtogroup hooks". */