drupal/core/modules/system/theme.api.php

320 lines
12 KiB
PHP

<?php
/**
* @defgroup themeable Default theme implementations
* @{
* Functions and templates for the user interface to be implemented by themes.
*
* Drupal's presentation layer is a pluggable system known as the theme
* layer. Each theme can take control over most of Drupal's output, and
* has complete control over the CSS.
*
* Inside Drupal, the theme layer is utilized by the use of the _theme()
* function, which is passed the name of a component (the theme hook)
* and an array of variables. For example,
* _theme('table', array('header' => $header, 'rows' => $rows));
* Additionally, the _theme() function can take an array of theme
* hooks, which can be used to provide 'fallback' implementations to
* allow for more specific control of output. For example, the function:
* _theme(array('table__foo', 'table'), $variables) would look to see if
* 'table__foo' is registered anywhere; if it is not, it would 'fall back'
* to the generic 'table' implementation. This can be used to attach specific
* theme functions to named objects, allowing the themer more control over
* specific types of output.
*
* Calling the _theme() function directly is highly discouraged. Building a
* renderable array is preferred. For example, rather than calling
* _theme('table', array()) in-place, one can assemble a renderable array as
* follows:
*
* @code
* $table = array(
* '#type' => 'table',
* '#header' => '',
* '#rows' => array(),
* );
* @endcode
*
* Note that a table is defined as a type as well as a theme function. Building
* it as a type is preferred. The $table array can simply be passed along as
* a renderable array in a page build process. If necessary, the array may be
* rendered to a string by calling drupal_render().
*
* @code
* $output = drupal_render($table);
* @endcode
*
* As of Drupal 6, every theme hook is required to be registered by the
* module that owns it, so that Drupal can tell what to do with it and
* to make it simple for themes to identify and override the behavior
* for these calls.
*
* The theme hooks are registered via hook_theme(), which returns an
* array of arrays with information about the hook. It describes the
* arguments the function or template will need, and provides
* defaults for the template in case they are not filled in. If the default
* implementation is a function, by convention it is named theme_HOOK().
*
* Each module should provide a default implementation for theme_hooks that
* it registers. This implementation may be either a function or a template;
* if it is a function it must be specified via hook_theme(). By convention,
* default implementations of theme hooks are named theme_HOOK. Default
* template implementations are stored in the module directory.
*
* Drupal's default template renderer is Twig. Drupal's theme engines can
* provide alternate template engines, such as XTemplate, Smarty and PHPTal.
*
* In order to create theme-specific implementations of these hooks, themes can
* implement their own version of theme hooks, either as functions or templates.
* These implementations will be used instead of the default implementation. If
* using a pure .theme without an engine, the .theme is required to implement
* its own version of hook_theme() to tell Drupal what it is implementing;
* themes utilizing an engine will have their well-named theming functions
* automatically registered for them. While this can vary based upon the theme
* engine, the standard is that theme functions should be named THEMENAME_HOOK.
* For example, for Drupal's default theme (Bartik) to implement the 'table'
* hook, the theme function should be called bartik_table().
*
* The theme system is described and defined in theme.inc.
*
* @see _theme()
* @see hook_theme()
* @see hooks
* @see callbacks
* @see system_element_info()
*
* @} End of "defgroup themeable".
*/
/**
* 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 $form_state
* A keyed array containing the current state of the form.
*/
function hook_form_system_theme_settings_alter(&$form, &$form_state) {
// Add a checkbox to toggle the breadcrumb trail.
$form['toggle_breadcrumb'] = array(
'#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 _theme().
*
* @param $variables
* The variables array (modify in place).
* @param $hook
* The name of the theme hook.
*/
function hook_preprocess(&$variables, $hook) {
static $hooks;
// Add contextual links to the variables, if the user has permission.
if (!user_access('access contextual links')) {
return;
}
if (!isset($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 _theme().
*
* @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'] = array('foaf:Image');
}
/**
* Provides alternate named suggestions for a specific theme hook.
*
* This hook allows the module implementing hook_theme() for a theme hook to
* provide alternative theme function or template name suggestions. This hook is
* only invoked for the first module implementing hook_theme() for a theme 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'].
*
* @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 = array();
$suggestions[] = 'node__' . $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()->id;
}
/**
* Alters named suggestions for a specific theme hook.
*
* This hook allows any module or theme to provide altenative 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'].
*
* @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 enabled.
*
* @param array $theme_list
* Array containing the names of the themes being enabled.
*
* @see theme_enable()
*/
function hook_themes_enabled($theme_list) {
foreach ($theme_list as $theme) {
block_theme_initialize($theme);
}
}
/**
* Respond to themes being disabled.
*
* @param array $theme_list
* Array containing the names of the themes being disabled.
*
* @see theme_disable()
*/
function hook_themes_disabled($theme_list) {
// Clear all update module caches.
update_storage_clear();
}