Issue #1156576 by Ryan Weal, jhodgdon, plach: Document language negotiation API
Jennifer Hodgdon
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@ -2,7 +2,9 @@
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/**
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* @file
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* Multiple language handling functionality.
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* Language Negotiation API.
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*
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* @see http://drupal.org/node/1497272
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*/
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/**
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@ -11,10 +13,99 @@
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const LANGUAGE_NEGOTIATION_DEFAULT = 'language-default';
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/**
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* Chooses a language for the given type based on language negotiation settings.
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* @defgroup language_negotiation Language Negotiation API functionality
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* @{
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* Functions to customize the language types and the negotiation process.
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*
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* The language negotiation API is based on two major concepts:
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* - Language types: types of translatable data (the types of data that a user
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* can view or request).
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* - Language negotiation methods: functions for determining which language to
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* use to present a particular piece of data to the user.
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* Both language types and language negotiation methods are customizable.
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*
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* Drupal defines three built-in language types:
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* - Interface language: The page's main language, used to present translated
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* user interface elements such as titles, labels, help text, and messages.
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* - Content language: The language used to present content that is available
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* in more than one language (see
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* @link field_language Field Language API @endlink for details).
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* - URL language: The language associated with URLs. When generating a URL,
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* this value will be used by url() as a default if no explicit preference is
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* provided.
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* Modules can define additional language types through
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* hook_language_types_info(), and alter existing language type definitions
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* through hook_language_types_info_alter().
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*
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* Language types may be configurable or fixed. The language negotiation
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* methods associated with a configurable language type can be explicitly
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* set through the user interface. A fixed language type has predetermined
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* (module-defined) language negotiation settings and, thus, does not appear in
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* the configuration page. Here is a code snippet that makes the content
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* language (which by default inherits the interface language's values)
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* configurable:
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* @code
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* function mymodule_language_types_info_alter(&$language_types) {
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* unset($language_types[LANGUAGE_TYPE_CONTENT]['fixed']);
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* }
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* @endcode
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*
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* Every language type can have a different set of language negotiation methods
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* assigned to it. Different language types often share the same language
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* negotiation settings, but they can have independent settings if needed. If
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* two language types are configured the same way, their language switcher
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* configuration will be functionally identical and the same settings will act
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* on both language types.
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*
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* Drupal defines the following built-in language negotiation methods:
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* - URL: Determine the language from the URL (path prefix or domain).
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* - Session: Determine the language from a request/session parameter.
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* - User: Follow the user's language preference.
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* - Browser: Determine the language from the browser's language settings.
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* - Default language: Use the default site language.
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* Language negotiation methods are simple callback functions that implement a
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* particular logic to return a language code. For instance, the URL method
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* searches for a valid path prefix or domain name in the current request URL.
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* If a language negotiation method does not return a valid language code, the
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* next method associated to the language type (based on method weight) is
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* invoked.
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*
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* Modules can define additional language negotiation methods through
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* hook_language_negotiation_info(), and alter existing methods through
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* hook_language_negotiation_info_alter(). Here is an example snippet that lets
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* path prefixes be ignored for administrative paths:
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* @code
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* function mymodule_language_negotiation_info_alter(&$negotiation_info) {
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* // Replace the core function with our own function.
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* module_load_include('language', 'inc', 'language.negotiation');
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* $negotiation_info[LANGUAGE_NEGOTIATION_URL]['callbacks']['negotiation'] = 'mymodule_from_url';
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* $negotiation_info[LANGUAGE_NEGOTIATION_URL]['file'] = drupal_get_path('module', 'mymodule') . '/mymodule.module';
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* }
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*
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* function mymodule_from_url($languages) {
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* // Use the core URL language negotiation method to get a valid language
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* // code.
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* module_load_include('language', 'inc', 'language.negotiation');
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* $langcode = language_from_url($languages);
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*
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* // If we are on an administrative path, override with the default language.
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* if (isset($_GET['q']) && strtok($_GET['q'], '/') == 'admin') {
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* return language_default()->langcode;
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* }
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* return $langcode;
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* }
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* ?>
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* @endcode
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*
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* For more information, see
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* @link http://drupal.org/node/1497272 Language Negotiation API @endlink
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*/
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/**
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* Chooses a language based on language negotiation method settings.
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*
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* @param $type
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* The language type key.
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* The language type key to find the language for.
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*
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* @return
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* The negotiated language object.
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@ -68,8 +159,8 @@ function language_types_info() {
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* Returns only the configurable language types.
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*
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* A language type maybe configurable or fixed. A fixed language type is a type
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* whose negotiation values are unchangeable and defined while defining the
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* language type itself.
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* whose language negotiation methods are module-defined and not altered through
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* the user interface.
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*
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* @param $stored
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* (optional) By default, retrieves values from the 'language_types' variable
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@ -162,6 +253,10 @@ function language_types_set() {
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*
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* @param $type
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* The language type.
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*
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* @return
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* The identifier of the first language negotiation method for the given
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* language type, or the default method if none exists.
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*/
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function language_negotiation_method_get_first($type) {
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$negotiation = variable_get("language_negotiation_$type", array());
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@ -169,7 +264,7 @@ function language_negotiation_method_get_first($type) {
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}
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/**
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* Checks if a language negotiation method is enabled for a language type.
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* Checks whether a language negotiation method is enabled for a language type.
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*
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* @param $method_id
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* The language negotiation method ID.
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@ -259,7 +354,7 @@ function language_negotiation_purge() {
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* @param $type
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* The language type.
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* @param $method_weights
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* An array of language negotiation method weights keyed by method id.
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* An array of language negotiation method weights keyed by method ID.
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*/
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function language_negotiation_set($type, $method_weights) {
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// Save only the necessary fields.
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@ -278,8 +373,7 @@ function language_negotiation_set($type, $method_weights) {
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// If the language negotiation method does not express any preference
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// about types, make it available for any configurable type.
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$types = array_flip(isset($method['types']) ? $method['types'] : $default_types);
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// Check if the language negotiation method is defined and has the right
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// type.
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// Check whether the method is defined and has the right type.
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if (isset($types[$type])) {
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$method_data = array();
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foreach ($method_fields as $field) {
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@ -328,13 +422,14 @@ function language_negotiation_info() {
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* Invokes a language negotiation method and caches the results.
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*
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* @param $method_id
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* The language negotiation method ID.
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* The language negotiation method's identifier.
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* @param $method
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* (optional) The language negotiation method to be invoked. If not passed it
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* will be explicitly loaded through language_negotiation_info().
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* (optional) An associative array of information about the method to be
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* invoked (see hook_language_negotiation_info() for details). If not passed
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* in, it will be loaded through language_negotiation_info().
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*
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* @return
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* The language negotiation method's return value.
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* A language object representing the language chosen by the method.
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*/
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function language_negotiation_method_invoke($method_id, $method = NULL) {
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$results = &drupal_static(__FUNCTION__);
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@ -361,10 +456,10 @@ function language_negotiation_method_invoke($method_id, $method = NULL) {
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$results[$method_id] = isset($languages[$langcode]) ? $languages[$langcode] : FALSE;
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}
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// Since objects are resources we need to return a clone to prevent the
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// language negotiation method cache to be unintentionally altered. The same
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// language negotiation methods might be used with different language types
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// based on configuration.
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// Since objects are resources, we need to return a clone to prevent the
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// language negotiation method cache from being unintentionally altered. The
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// same methods might be used with different language types based on
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// configuration.
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return !empty($results[$method_id]) ? clone($results[$method_id]) : $results[$method_id];
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}
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@ -381,8 +476,8 @@ function language_from_default() {
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/**
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* Split the given path into prefix and actual path.
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*
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* Parse the given path and return the language object identified by the
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* prefix and the actual path.
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* Parse the given path and return the language object identified by the prefix
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* and the actual path.
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*
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* @param $path
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* The path to split.
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@ -434,3 +529,7 @@ function language_fallback_get_candidates($type = LANGUAGE_TYPE_CONTENT) {
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return $fallback_candidates;
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}
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/**
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* @} End of "language_negotiation"
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*/
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@ -62,22 +62,22 @@ function hook_language_switch_links_alter(array &$links, $type, $path) {
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}
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/**
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* Allow modules to define their own language types.
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* Define language types.
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*
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* @return
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* An associative array of language type definitions.
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* An associative array of language type definitions. The keys are the
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* identifiers, which are also used as names for global variables representing
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* the types in the bootstrap phase. The values are associative arrays that
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* may contain the following elements:
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* - name: The human-readable language type identifier.
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* - description: A description of the language type.
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* - fixed: A fixed array of language negotiation method identifiers to use to
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* initialize this language. Defining this key makes the language type
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* non-configurable, so it will always use the specified methods in the
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* given priority order. Omit to make the language type configurable.
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*
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* Each language type has an identifier key which is used as the name for the
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* global variable corresponding to the language type in the bootstrap phase.
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*
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* The language type definition is an associative array that may contain the
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* following key-value pairs:
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* - "name": The human-readable language type identifier.
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* - "description": A description of the language type.
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* - "fixed": A fixed array of language negotiation method identifiers to use
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* to initialize this language. Defining this key makes the language type
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* non-configurable and will always use the specified methods in the given
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* priority order.
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* @see hook_language_types_info_alter()
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* @ingroup language_negotiation
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*/
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function hook_language_types_info() {
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return array(
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@ -94,10 +94,11 @@ function hook_language_types_info() {
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/**
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* Perform alterations on language types.
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*
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* @see hook_language_types_info().
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*
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* @param $language_types
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* Array of language type definitions.
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*
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* @see hook_language_types_info()
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* @ingroup language_negotiation
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*/
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function hook_language_types_info_alter(array &$language_types) {
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if (isset($language_types['custom_language_type'])) {
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@ -106,31 +107,35 @@ function hook_language_types_info_alter(array &$language_types) {
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}
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/**
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* Allow modules to define their own language negotiation methods.
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* Define language negotiation methods.
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*
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* @return
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* An array of language negotiation method definitions. Each method has an
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* identifier key. The language negotiation method definition is an indexed
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* array that may contain the following key-value pairs:
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* - "types": An array of allowed language types. If a language negotiation
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* An associative array of language negotiation method definitions. The keys
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* are method identifiers, and the values are associative arrays definining
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* each method, with the following elements:
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* - types: An array of allowed language types. If a language negotiation
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* method does not specify which language types it should be used with, it
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* will be available for all the configurable language types.
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* - "callbacks": An array of functions that will be called to perform various
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* tasks. Possible key-value pairs are:
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* - "negotiation": Required. The callback that will determine the language
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* value.
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* - "language_switch": The callback that will determine the language
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* switch links associated to the current language method.
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* - "url_rewrite": The callback that will provide URL rewriting.
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* - "file": A file that will be included before the callback is invoked; this
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* allows callback functions to be in separate files.
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* - "weight": The default weight the language negotiation method has.
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* - "name": A human-readable identifier.
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* - "description": A description of the language negotiation method.
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* - "config": An internal path pointing to the language negotiation method
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* configuration page.
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* - "cache": The value Drupal's page cache should be set to for the current
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* language negotiation method to be invoked.
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* - callbacks: An associative array of functions that will be called to
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* perform various tasks. Possible elements are:
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* - negotiation: (required) Name of the callback function that determines
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* the language value.
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* - language_switch: (optional) Name of the callback function that
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* determines links for a language switcher block associated with this
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* method. See language_switcher_url() for an example.
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* - url_rewrite: (optional) Name of the callback function that provides URL
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* rewriting, if needed by this method.
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* - file: The file where callback functions are defined (this file will be
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* included before the callbacks are invoked).
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* - weight: The default weight of the method.
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* - name: The translated human-readable name for the method.
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* - description: A translated longer description of the method.
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* - config: An internal path pointing to the method's configuration page.
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* - cache: The value Drupal's page cache should be set to for the current
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* method to be invoked.
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*
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* @see hook_language_negotiation_info_alter()
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* @ingroup language_negotiation
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*/
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function hook_language_negotiation_info() {
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return array(
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@ -155,6 +160,9 @@ function hook_language_negotiation_info() {
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*
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* @param $negotiation_info
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* Array of language negotiation method definitions.
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*
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* @see hook_language_negotiation_info()
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* @ingroup language_negotiation
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*/
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function hook_language_negotiation_info_alter(array &$negotiation_info) {
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if (isset($negotiation_info['custom_language_method'])) {
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