#282191 by plach, nedjo, catch, et al: TF #1: Allow different interface language for the same path.

13 files changed, 1363 insertions, 254 deletions

diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index cda1bb8b8..fe9a95471 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -154,27 +154,19 @@ define('DRUPAL_AUTHENTICATED_RID', 2);
 define('DRUPAL_KILOBYTE', 1024);
 
 /**
- * No language negotiation. The default language is used.
+ * The type of language used to define the content language.
  */
-define('LANGUAGE_NEGOTIATION_NONE', 0);
+define('LANGUAGE_TYPE_CONTENT', 'language');
 
 /**
- * Path based negotiation with fallback to default language if no defined path
- * prefix identified.
+ * The type of language used to select the user interface.
  */
-define('LANGUAGE_NEGOTIATION_PATH_DEFAULT', 1);
+define('LANGUAGE_TYPE_INTERFACE', 'language_interface');
 
 /**
- * Path based negotiation with fallback to user preferences and browser
- * language detection if no defined path prefix identified.
+ * The type of language used for URLs.
  */
-define('LANGUAGE_NEGOTIATION_PATH', 2);
-
-/**
- * Domain based negotiation with fallback to default language if no language
- * identified by domain.
- */
-define('LANGUAGE_NEGOTIATION_DOMAIN', 3);
+define('LANGUAGE_TYPE_URL', 'language_url');
 
 /**
  * Language written left to right. Possible value of $language->direction.
@@ -1628,23 +1620,50 @@ function get_t() {
 }
 
 /**
- *  Choose a language for the current page, based on site and user preferences.
+ * Initialize all the defined language types.
  */
 function drupal_language_initialize() {
-  global $language, $user;
+  $types = language_types();
 
   // Ensure the language is correctly returned, even without multilanguage support.
   // Useful for eg. XML/HTML 'lang' attributes.
   if (variable_get('language_count', 1) == 1) {
-    $language = language_default();
+    $default = language_default();
+    foreach ($types as $type) {
+      $GLOBALS[$type] = $default;
+    }
   }
   else {
     include_once DRUPAL_ROOT . '/includes/language.inc';
-    $language = language_initialize();
+    foreach ($types as $type) {
+      $GLOBALS[$type] = language_initialize($type);
+    }
   }
 }
 
 /**
+ * The built-in language types.
+ *
+ * @return
+ *   An array of key-values pairs where the key is the language type and the
+ *   value is its configurability.
+ */
+function drupal_language_types() {
+  return array(
+    LANGUAGE_TYPE_CONTENT => TRUE,
+    LANGUAGE_TYPE_INTERFACE => TRUE,
+    LANGUAGE_TYPE_URL => FALSE,
+  );
+}
+
+/**
+ * Return an array of the available language types.
+ */
+function language_types() {
+  return array_keys(variable_get('language_types', drupal_language_types()));
+}
+
+/**
  * Get a list of languages set up indexed by the specified key
  *
  * @param $field The field to index the list with.
diff --git a/includes/common.inc b/includes/common.inc
index 3f26c4949..d8661100c 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -393,6 +393,26 @@ function drupal_get_query_parameters(array $query = NULL, array $exclude = array
 }
 
 /**
+ * Split an URL-encoded query string into an array.
+ *
+ * @param $query
+ *   The query string to split.
+ *
+ * @return
+ *   An array of url decoded couples $param_name => $value.
+ */
+function drupal_get_query_array($query) {
+  $result = array();
+  if (!empty($query)) {
+    foreach (explode('&', $query) as $param) {
+      $param = explode('=', $param);
+      $result[$param[0]] = isset($param[1]) ? rawurldecode($param[1]) : '';
+    }
+  }
+  return $result;
+}
+
+/**
  * Parse an array into a valid, rawurlencoded query string.
  *
  * This differs from http_build_query() as we need to rawurlencode() (instead of
@@ -1455,12 +1475,12 @@ function fix_gpc_magic() {
  *   The translated string.
  */
 function t($string, array $args = array(), array $options = array()) {
-  global $language;
+  global $language_interface;
   static $custom_strings;
 
   // Merge in default.
   if (empty($options['langcode'])) {
-    $options['langcode'] = isset($language->language) ? $language->language : 'en';
+    $options['langcode'] = isset($language_interface->language) ? $language_interface->language : 'en';
   }
   if (empty($options['context'])) {
     $options['context'] = '';
@@ -2438,7 +2458,8 @@ function url($path = NULL, array $options = array()) {
     $path = '';
   }
   elseif (!empty($path) && !$options['alias']) {
-    $path = drupal_get_path_alias($path, isset($options['language']) ? $options['language']->language : '');
+    $language = isset($options['language']) && isset($options['language']->language) ? $options['language']->language : '';
+    $path = drupal_get_path_alias($path, $language);
   }
 
   if (function_exists('custom_url_rewrite_outbound')) {
@@ -2546,7 +2567,7 @@ function drupal_attributes(array $attributes = array()) {
  *   an HTML string containing a link to the given path.
  */
 function l($text, $path, array $options = array()) {
-  global $language;
+  global $language_url;
 
   // Merge in defaults.
   $options += array(
@@ -2556,7 +2577,7 @@ function l($text, $path, array $options = array()) {
 
   // Append active class.
   if (($path == $_GET['q'] || ($path == '<front>' && drupal_is_front_page())) &&
-      (empty($options['language']) || $options['language']->language == $language->language)) {
+      (empty($options['language']) || $options['language']->language == $language_url->language)) {
     $options['attributes']['class'][] = 'active';
   }
 
diff --git a/includes/language.inc b/includes/language.inc
index 9a990a722..f170cf9a0 100644
--- a/includes/language.inc
+++ b/includes/language.inc
@@ -7,138 +7,392 @@
  */
 
 /**
- *  Choose a language for the page, based on language negotiation settings.
- */
-function language_initialize() {
-  global $user;
-
-  // Configured presentation language mode.
-  $mode = variable_get('language_negotiation', LANGUAGE_NEGOTIATION_NONE);
-  // Get a list of enabled languages.
-  $languages = language_list('enabled');
-  $languages = $languages[1];
-
-  switch ($mode) {
-    case LANGUAGE_NEGOTIATION_NONE:
-      return language_default();
-
-    case LANGUAGE_NEGOTIATION_DOMAIN:
-      foreach ($languages as $language) {
-        $host = parse_url($language->domain, PHP_URL_HOST);
-        if ($host && ($_SERVER['HTTP_HOST'] == $host)) {
-          return $language;
-        }
-      }
-      return language_default();
-
-    case LANGUAGE_NEGOTIATION_PATH_DEFAULT:
-    case LANGUAGE_NEGOTIATION_PATH:
-      // $_GET['q'] might not be available at this time, because
-      // path initialization runs after the language bootstrap phase.
-      $args = isset($_GET['q']) ? explode('/', $_GET['q']) : array();
-      $prefix = array_shift($args);
-      // Search prefix within enabled languages.
-      foreach ($languages as $language) {
-        if (!empty($language->prefix) && $language->prefix == $prefix) {
-          // Rebuild $GET['q'] with the language removed.
-          $_GET['q'] = implode('/', $args);
-          return $language;
-        }
+ * No language negotiation. The default language is used.
+ */
+define('LANGUAGE_NEGOTIATION_DEFAULT', 'language-default');
+
+/**
+ * Return all the defined language types.
+ *
+ * @return
+ *   An array of language type names. The name will be used as the global
+ *   variable name the language value will be stored in.
+ */
+function language_types_info() {
+  $language_types = &drupal_static(__FUNCTION__);
+
+  if (!isset($language_types)) {
+    $language_types = module_invoke_all('language_types_info');
+    // Let other modules alter the list of language types.
+    drupal_alter('language_types_info', $language_types);
+  }
+
+  return $language_types;
+}
+
+/**
+ * Return only the configurable language types.
+ *
+ * A language type maybe configurable or fixed. A fixed language type is a type
+ * whose negotiation values are unchangable and defined while defining the
+ * language type itself.
+ *
+ * @return
+ *   An array of language type names.
+ */
+function language_types_configurable() {
+  $configurable = &drupal_static(__FUNCTION__);
+
+  if (!isset($configurable)) {
+    $types = variable_get('language_types', drupal_language_types());
+    $configurable = array_keys(array_filter($types));
+  }
+
+  return $configurable;
+}
+
+/**
+ * Disable the given language types.
+ *
+ * @param $types
+ *   An array of language types.
+ */
+function language_types_disable($types) {
+  $enabled_types = variable_get('language_types', drupal_language_types());
+
+  foreach ($types as $type) {
+    unset($enabled_types[$type]);
+  }
+
+  variable_set('language_types', $enabled_types);
+}
+
+/**
+ * Check if a language provider is enabled.
+ *
+ * This has two possible behaviors:
+ *  - If $provider_id is given return its ID if enabled, FALSE otherwise.
+ *  - If no ID is passed the first enabled language provider is returned.
+ *
+ * @param $type
+ *   The language negotiation type.
+ * @param $provider_id
+ *   The language provider ID.
+ *
+ * @return
+ *   The provider ID if it is enabled, FALSE otherwise.
+ */
+function language_negotiation_get($type, $provider_id = NULL) {
+  $negotiation = variable_get("language_negotiation_$type", array());
+
+  if (empty($negotiation)) {
+    return empty($provider_id) ? LANGUAGE_NEGOTIATION_DEFAULT : FALSE;
+  }
+
+  if (empty($provider_id)) {
+    return key($negotiation);
+  }
+
+  if (isset($negotiation[$provider_id])) {
+    return $provider_id;
+  }
+
+  return FALSE;
+}
+
+/**
+ * Check if the given language provider is enabled for any configurable language
+ * type.
+ *
+ * @param $provider_id
+ *   The language provider ID.
+ *
+ * @return
+ *   TRUE if there is at least one language type for which the give language
+ *   provider is enabled, FALSE otherwise.
+ */
+function language_negotiation_get_any($provider_id) {
+  foreach (language_types_configurable() as $type) {
+    if (language_negotiation_get($type, $provider_id)) {
+      return TRUE;
+    }
+  }
+
+  return FALSE;
+}
+
+/**
+ * Return the language switch links for the given language.
+ *
+ * @param $type
+ *   The language negotiation type.
+ * @param $path
+ *   The internal path the switch links will be relative to.
+ *
+ * @return
+ *   A keyed array of links ready to be themed.
+ */
+function language_negotiation_get_switch_links($type, $path) {
+  $links = FALSE;
+  $negotiation = variable_get("language_negotiation_$type", array());
+
+  foreach ($negotiation as $id => $provider) {
+    if (isset($provider['callbacks']['switcher'])) {
+      if (isset($provider['file'])) {
+        require_once DRUPAL_ROOT . '/' . $provider['file'];
       }
-      if ($mode == LANGUAGE_NEGOTIATION_PATH_DEFAULT) {
-        // If we did not found the language by prefix, choose the default.
-        return language_default();
+
+      $callback = $provider['callbacks']['switcher'];
+      $result = $callback($type, $path);
+
+      if (!empty($result)) {
+        // Allow modules to provide translations for specific links.
+        drupal_alter('language_switch_links', $result, $type, $path);
+        $links = (object) array('links' => $result, 'provider' => $id);
+        break;
       }
-      break;
+    }
+  }
+
+  return $links;
+}
+
+
+/**
+ * Save a list of language providers.
+ *
+ * @param $type
+ *   The language negotiation type.
+ * @param $language_providers
+ *   An array of language provider ids.
+ */
+function language_negotiation_set($type, $language_providers) {
+  // Save only the necessary fields.
+  $provider_fields = array('callbacks', 'file', 'cache');
+
+  $negotiation = array();
+  $providers_weight = array();
+  $defined_providers = language_negotiation_info();
+  $default_types = language_types_configurable();
+
+  // Initialize the providers weight list.
+  foreach ($language_providers as $id => $provider) {
+    $providers_weight[$id] = language_provider_weight($provider);
   }
 
-  // User language.
-  if ($user->uid && isset($languages[$user->language])) {
-    return $languages[$user->language];
+  // Order providers list by weight.
+  asort($providers_weight);
+
+  foreach ($providers_weight as $id => $weight) {
+    if (isset($defined_providers[$id])) {
+      $provider = $defined_providers[$id];
+      // If the provider does not express any preference about types, make it
+      // available for any configurable type.
+      $types = array_flip(isset($provider['types']) ? $provider['types'] : $default_types);
+      // Check if the provider is defined and has the right type.
+      if (isset($types[$type])) {
+        $provider_data = array();
+        foreach ($provider_fields as $field) {
+          if (isset($provider[$field])) {
+            $provider_data[$field] = $provider[$field];
+          }
+        }
+        $negotiation[$id] = $provider_data;
+      }
+    }
   }
 
-  // Browser accept-language parsing.
-  if ($language = language_from_browser()) {
-    return $language;
+  variable_set("language_negotiation_$type", $negotiation);
+}
+
+/**
+ * Return all the defined language providers.
+ *
+ * @return
+ *   An array of language providers.
+ */
+function language_negotiation_info() {
+  $language_providers = &drupal_static(__FUNCTION__);
+
+  if (!isset($language_providers)) {
+    // Collect all the module-defined language negotiation providers.
+    $language_providers = module_invoke_all('language_negotiation_info');
+
+    // Add the default language provider.
+    $language_providers[LANGUAGE_NEGOTIATION_DEFAULT] = array(
+      'callbacks' => array('language' => 'language_from_default'),
+      'weight' => 10,
+      'name' => t('Default'),
+      'description' => t('The default site language (@language_name) is used.', array('@language_name' => language_default()->native)),
+    );
+
+    // Let other modules alter the list of language providers.
+    drupal_alter('language_negotiation_info', $language_providers);
   }
 
-  // Fall back on the default if everything else fails.
-  return language_default();
+  return $language_providers;
 }
 
 /**
- * Identify language from the Accept-language HTTP header we got.
+ * Helper function used to cache the language providers results.
+ *
+ * @param $provider_id
+ *   The language provider ID.
+ * @param $provider
+ *   The language provider to be invoked. If not passed it will be explicitly
+ *   loaded through language_negotiation_info().
+ *
+ * @return
+ *   The language provider's return value.
  */
-function language_from_browser() {
-  // Specified by the user via the browser's Accept Language setting
-  // Samples: "hu, en-us;q=0.66, en;q=0.33", "hu,en-us;q=0.5"
-  $browser_langs = array();
+function language_provider_invoke($provider_id, $provider = NULL) {
+  $results = &drupal_static(__FUNCTION__);
 
-  if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
-    $browser_accept = explode(",", $_SERVER['HTTP_ACCEPT_LANGUAGE']);
-    for ($i = 0; $i < count($browser_accept); $i++) {
-      // The language part is either a code or a code with a quality.
-      // We cannot do anything with a * code, so it is skipped.
-      // If the quality is missing, it is assumed to be 1 according to the RFC.
-      if (preg_match("!([a-z-]+)(;q=([0-9\\.]+))?!", trim($browser_accept[$i]), $found)) {
-        $browser_langs[$found[1]] = (isset($found[3]) ? (float) $found[3] : 1.0);
-      }
+  if (!isset($results[$provider_id])) {
+    global $user;
+
+    // Get languages grouped by status and select only the enabled ones.
+    $languages = language_list('enabled');
+    $languages = $languages[1];
+
+    if (!isset($provider)) {
+      $providers = language_negotiation_info();
+      $provider = $providers[$provider_id];
+    }
+
+    if (isset($provider['file'])) {
+      require_once DRUPAL_ROOT . '/' . $provider['file'];
     }
+
+    // If the language provider has no cache preference or this is satisified
+    // we can execute the callback.
+    $cache = !isset($provider['cache']) || $user->uid || $provider['cache'] == variable_get('cache', CACHE_DISABLED);
+    $callback = isset($provider['callbacks']['language']) ? $provider['callbacks']['language'] : FALSE;
+    $langcode = $cache && function_exists($callback) ? $callback($languages) : FALSE;
+    $results[$provider_id] = isset($languages[$langcode]) ? $languages[$langcode] : FALSE;
   }
 
-  // Order the codes by quality
-  arsort($browser_langs);
+  return $results[$provider_id];
+}
+
+/**
+ * Return the passed language provider weight or a default value.
+ *
+ * @param $provider
+ *   A language provider data structure.
+ *
+ * @return
+ *   A numeric weight.
+ */
+function language_provider_weight($provider) {
+  $default = is_numeric($provider) ? $provider : 0;
+  return isset($provider['weight']) && is_numeric($provider['weight']) ? $provider['weight'] : $default;
+}
 
-  // Try to find the first preferred language we have
-  $languages = language_list('enabled');
-  foreach ($browser_langs as $langcode => $q) {
-    if (isset($languages['1'][$langcode])) {
-      return $languages['1'][$langcode];
+/**
+ * Choose a language for the given type based on language negotiation settings.
+ *
+ * @param $type
+ *   The language type.
+ *
+ * @return
+ *   The negotiated language object.
+ */
+function language_initialize($type) {
+  // Execute the language providers in the order they were set up and return the
+  // first valid language found.
+  $negotiation = variable_get("language_negotiation_$type", array());
+
+  foreach ($negotiation as $id => $provider) {
+    $language = language_provider_invoke($id, $provider);
+    if ($language) {
+      return $language;
     }
   }
+
+  // If no other language was found use the default one.
+  return language_default();
 }
 
 /**
- * Rewrite URLs with language based prefix. Parameters are the same
- * as those of the url() function.
+ * Default language provider.
+ *
+ * @return
+ *   The default language code.
  */
-function language_url_rewrite(&$path, &$options) {
-  global $language;
+function language_from_default() {
+  return language_default()->language;
+}
 
+/**
+ * Rewrite URLs allowing modules to hook in.
+ *
+ * @param $path
+ *   The path to rewrite.
+ * @param $options
+ *   An associative array of additional options as in url().
+ */
+function language_url_rewrite(&$path, &$options) {
   // Only modify relative (insite) URLs.
   if (!$options['external']) {
+    static $callbacks;
 
-    // Language can be passed as an option, or we go for current language.
-    if (!isset($options['language'])) {
-      $options['language'] = $language;
-    }
+    if (!isset($callbacks)) {
+      $callbacks = array();
 
-    switch (variable_get('language_negotiation', LANGUAGE_NEGOTIATION_NONE)) {
-      case LANGUAGE_NEGOTIATION_NONE:
-        // No language dependent path allowed in this mode.
-        unset($options['language']);
-        break;
+      foreach (language_types_configurable() as $type) {
+        // Get url rewriter callbacks only from enabled language providers.
+        $negotiation = variable_get("language_negotiation_$type", array());
 
-      case LANGUAGE_NEGOTIATION_DOMAIN:
-        if ($options['language']->domain) {
-          // Ask for an absolute URL with our modified base_url.
-          $options['absolute'] = TRUE;
-          $options['base_url'] = $options['language']->domain;
-        }
-        break;
+        foreach ($negotiation as $id => $provider) {
+          if (isset($provider['file'])) {
+            require_once DRUPAL_ROOT . '/' . $provider['file'];
+          }
 
-      case LANGUAGE_NEGOTIATION_PATH_DEFAULT:
-        $default = language_default();
-        if ($options['language']->language == $default->language) {
-          break;
+          // Avoid duplicate callback entries.
+          if (isset($provider['callbacks']['url_rewrite'])) {
+            $callbacks[$provider['callbacks']['url_rewrite']] = NULL;
+          }
         }
-        // Intentionally no break here.
+      }
 
-      case LANGUAGE_NEGOTIATION_PATH:
-        if (!empty($options['language']->prefix)) {
-          $options['prefix'] = $options['language']->prefix . '/';
-        }
-        break;
+      $callbacks = array_keys($callbacks);
+    }
+
+    foreach ($callbacks as $callback) {
+      $callback($path, $options);
     }
   }
 }
+
+/**
+ * Split the given path into prefix and actual path.
+ *
+ * Parse the given path and return the language object identified by the
+ * prefix and the actual path.
+ *
+ * @param $path
+ *   The path to split.
+ * @param $languages
+ *   An array of valid languages.
+ *
+ * @return
+ *   An array composed of:
+ *    - A language object corresponding to the identified prefix on success,
+ *      FALSE otherwise.
+ *    - The path without the prefix on success, the given path otherwise.
+ */
+function language_url_split_prefix($path, $languages) {
+  $args = empty($path) ? array() : explode('/', $path);
+  $prefix = array_shift($args);
+
+  // Search prefix within enabled languages.
+  foreach ($languages as $language) {
+    if (!empty($language->prefix) && $language->prefix == $prefix) {
+      // Rebuild $path with the language removed.
+      return array($language, implode('/', $args));
+    }
+  }
+
+  return array(FALSE, $path);
+}
diff --git a/includes/locale.inc b/includes/locale.inc
index 85e056ce1..cc95ef7f4 100644
--- a/includes/locale.inc
+++ b/includes/locale.inc
@@ -24,6 +24,18 @@ define('LOCALE_IMPORT_OVERWRITE', 0);
 define('LOCALE_IMPORT_KEEP', 1);
 
 /**
+ * URL language negotiation: use the path prefix as URL language
+ * indicator.
+ */
+define('LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX', 0);
+
+/**
+ * URL language negotiation: use the domain as URL language
+ * indicator.
+ */
+define('LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN', 1);
+
+/**
  * @defgroup locale-language-overview Language overview functionality
  * @{
  */
@@ -473,7 +485,7 @@ function locale_languages_delete_form_submit($form, &$form_state) {
  */
 
 /**
- * @defgroup locale-languages-negotiation Language negotiation options screen
+ * @defgroup locale-languages-negotiation Language negotiation options
  * @{
  */
 
@@ -481,33 +493,507 @@ function locale_languages_delete_form_submit($form, &$form_state) {
  * Setting for language negotiation options
  */
 function locale_languages_configure_form() {
-  $form['language_negotiation'] = array(
-    '#title' => t('Language negotiation'),
-    '#type' => 'radios',
-    '#options' => array(
-      LANGUAGE_NEGOTIATION_NONE => t('None.'),
-      LANGUAGE_NEGOTIATION_PATH_DEFAULT => t('Path prefix only.'),
-      LANGUAGE_NEGOTIATION_PATH => t('Path prefix with language fallback.'),
-      LANGUAGE_NEGOTIATION_DOMAIN => t('Domain name only.')),
-    '#default_value' => variable_get('language_negotiation', LANGUAGE_NEGOTIATION_NONE),
-    '#description' => t("Select the mechanism used to determine your site's presentation language. <strong>Modifying this setting may break all incoming URLs and should be used with caution in a production environment.</strong>")
+  include_once DRUPAL_ROOT . '/includes/language.inc';
+
+  $form = array(
+    '#submit' => array('locale_languages_configure_form_submit'),
+    '#theme' => 'locale_languages_configure_form',
+    '#language_types' => language_types_configurable(),
+    '#language_types_info' => language_types_info(),
+    '#language_providers' => language_negotiation_info(),
   );
+
+  foreach ($form['#language_types'] as $type) {
+    _locale_languages_configure_form_language_table($form, $type);
+  }
+
   $form['submit'] = array(
     '#type' => 'submit',
-    '#value' => t('Save settings')
+    '#value' => t('Save settings'),
   );
+
   return $form;
 }
 
 /**
- * Submit function for language negotiation settings.
+ * Helper function to build a language provider table.
+ */
+function _locale_languages_configure_form_language_table(&$form, $type) {
+  $info = $form['#language_types_info'][$type];
+
+  $table_form = array(
+    '#title' => t('@type language', array('@type' => $info['name'])),
+    '#tree' => TRUE,
+    '#description' => $info['description'],
+    '#language_providers' => array(),
+    '#show_operations' => FALSE,
+    'weight' => array('#tree' => TRUE),
+    'enabled' => array('#tree' => TRUE),
+  );
+
+  $language_providers = $form['#language_providers'];
+  $enabled_providers = variable_get("locale_language_providers_enabled_$type", array());
+  $providers_weight = variable_get("locale_language_providers_weight_$type", array());
+
+  // Add missing data to the providers lists.
+  foreach ($language_providers as $id => $provider) {
+    if (!isset($providers_weight[$id])) {
+      $providers_weight[$id] = language_provider_weight($provider);
+    }
+    if (!isset($enabled_providers[$id])) {
+      $enabled_providers[$id] = FALSE;
+    }
+  }
+
+  // Order providers list by weight.
+  asort($providers_weight);
+
+  foreach ($providers_weight as $id => $weight) {
+    $enabled = $enabled_providers[$id];
+    $provider = $language_providers[$id];
+
+    // List the provider only if the current type is defined in its 'types' key.
+    // If it is not defined default to all the configurabe language types.
+    $types = array_flip(isset($provider['types']) ? $provider['types'] : $form['#language_types']);
+
+    if (isset($types[$type])) {
+      $table_form['#language_providers'][$id] = $provider;
+
+      $table_form['weight'][$id] = array(
+        '#type' => 'weight',
+        '#default_value' => $weight,
+        '#attributes' => array('class' => array("language-provider-weight-$type")),
+      );
+
+      $table_form['title'][$id] = array('#markup' => check_plain($provider['name']));
+
+      $table_form['enabled'][$id] = array('#type' => 'checkbox', '#default_value' => $enabled);
+      if ($id === LANGUAGE_NEGOTIATION_DEFAULT) {
+        $table_form['enabled'][$id]['#default_value'] = TRUE;
+        $table_form['enabled'][$id]['#attributes'] = array('disabled' => 'disabled');
+      }
+
+      $table_form['description'][$id] = array('#markup' => filter_xss_admin($provider['description']));
+
+      $config_op = '';
+      if (isset($provider['config'])) {
+        $config_op = l(t('Configure'), $provider['config']);
+        // If there is at least one operation enabled show the operation column.
+        $table_form['#show_operations'] = TRUE;
+      }
+      $table_form['operation'][$id] = array('#markup' => $config_op);
+    }
+  }
+
+  $form[$type] = $table_form;
+}
+
+/**
+ * Theme the language configure form.
+ *
+ * @ingroup themeable
+ */
+function theme_locale_languages_configure_form($variables) {
+  $form = $variables['form'];
+  $output = '';
+
+  foreach ($form['#language_types'] as $type) {
+    $rows = array();
+    $info = $form['#language_types_info'][$type];
+    $title = '<label>' . $form[$type]['#title'] . '</label>';
+    $description = '<div class="description">' . $form[$type]['#description'] . '</div>';
+
+    foreach ($form[$type]['title'] as $id => $element) {
+      // Do not take form control structures.
+      if (is_array($element) && element_child($id)) {
+        $row = array(
+          'data' => array(
+            '<strong>' . drupal_render($form[$type]['title'][$id]) . '</strong>',
+            drupal_render($form[$type]['description'][$id]),
+            drupal_render($form[$type]['enabled'][$id]),
+            drupal_render($form[$type]['weight'][$id]),
+          ),
+          'class' => array('draggable'),
+        );
+        if ($form[$type]['#show_operations']) {
+          $row['data'][] = drupal_render($form[$type]['operation'][$id]);
+        }
+        $rows[] = $row;
+      }
+    }
+
+    $header = array(
+      array('data' => t('Detection method')),
+      array('data' => t('Description')),
+      array('data' => t('Enabled')),
+      array('data' => t('Weight')),
+    );
+
+    // If there is at least one operation enabled show the operation column.
+    if ($form[$type]['#show_operations']) {
+      $header[] = array('data' => t('Operations'));
+    }
+
+    $variables = array(
+      'header' => $header,
+      'rows' => $rows,
+      'attributes' => array('id' => "language-negotiation-providers-$type"),
+    );
+    $table  = theme('table', $variables);
+    $table .= drupal_render_children($form[$type]);
+
+    drupal_add_tabledrag("language-negotiation-providers-$type", 'order', 'sibling', "language-provider-weight-$type");
+
+    $output .= '<div class="form-item">' . $title . $description . $table . '</div>';
+  }
+
+  $output .= drupal_render_children($form);
+  return $output;
+}
+
+/**
+ * Submit handler for language negotiation settings.
  */
 function locale_languages_configure_form_submit($form, &$form_state) {
-  variable_set('language_negotiation', $form_state['values']['language_negotiation']);
-  drupal_set_message(t('Language negotiation configuration saved.'));
+  $language_types = array();
+  $configurable_types = $form['#language_types'];
+
+  foreach ($configurable_types as $type) {
+    $negotiation = array();
+    $enabled_providers = $form_state['values'][$type]['enabled'];
+    $enabled_providers[LANGUAGE_NEGOTIATION_DEFAULT] = TRUE;
+    $providers_weight = $form_state['values'][$type]['weight'];
+    $language_types[$type] = TRUE;
+
+    foreach ($providers_weight as $id => $weight) {
+      if ($enabled_providers[$id]) {
+        $provider = $form[$type]['#language_providers'][$id];
+        $provider['weight'] = $weight;
+        $negotiation[$id] = $provider;
+      }
+    }
+
+    language_negotiation_set($type, $negotiation);
+    variable_set("locale_language_providers_enabled_$type", $enabled_providers);
+    variable_set("locale_language_providers_weight_$type", $providers_weight);
+  }
+
+  // Save non-configurable language types negotiation.
+  $language_types_info = language_types_info();
+  $defined_providers = $form['#language_providers'];
+  foreach ($language_types_info as $type => $info) {
+    if (isset($info['fixed'])) {
+      $language_types[$type] = FALSE;
+      $negotiation = array();
+      foreach ($info['fixed'] as $id) {
+        if (isset($defined_providers[$id])) {
+          $negotiation[$id] = $defined_providers[$id];
+        }
+      }
+      language_negotiation_set($type, $negotiation);
+    }
+  }
+
+  // Save language types.
+  variable_set('language_types', $language_types);
+
   $form_state['redirect'] = 'admin/config/regional/language';
-  return;
+  drupal_set_message(t('Language negotiation configuration saved.'));
+}
+
+/**
+ * The URL language provider configuration form.
+ */
+function locale_language_providers_url_form() {
+  $form = array();
+
+  $form['locale_language_negotiation_url_part'] = array(
+    '#title' => t('URL language indicator'),
+    '#type' => 'radios',
+    '#options' => array(
+      LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX => t('Path prefix'),
+      LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN => t('Domain'),
+    ),
+    '#default_value' => variable_get('locale_language_negotiation_url_part', LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX),
+    '#description' => t('Select which part of the URL will determine the language.'),
+  );
+
+  $form['#redirect'] = 'admin/config/regional/language/configure';
+
+  return system_settings_form($form);
+}
+
+/**
+ * The URL language provider configuration form.
+ */
+function locale_language_providers_session_form() {
+  $form = array();
+
+  $form['locale_language_negotiation_session_param'] = array(
+    '#title' => t('Request/session parameter'),
+    '#type' => 'textfield',
+    '#default_value' => variable_get('locale_language_negotiation_session_param', 'language'),
+    '#description' => t('This value will be the name of the request/session parameter which will be used to determine the desired language.'),
+  );
+
+  $form['#redirect'] = 'admin/config/regional/language/configure';
+
+  return system_settings_form($form);
+}
+
+/**
+ * Identify the language from the current content language.
+ *
+ * @return
+ *   The current content language code.
+ */
+function locale_language_from_content() {
+  global $language;
+  return isset($language->language) ? $language->language : FALSE;
+}
+
+/**
+ * Identify language from the Accept-language HTTP header we got.
+ *
+ * We perform browser accept-language parsing only if page cache is disabled,
+ * otherwise we would cache a user-specific preference.
+ *
+ * @param $languages
+ *   An array of valid language objects.
+ *
+ * @return
+ *   A valid language code on success, FALSE otherwise.
+ */
+function locale_language_from_browser($languages) {
+  // Specified by the user via the browser's Accept Language setting
+  // Samples: "hu, en-us;q=0.66, en;q=0.33", "hu,en-us;q=0.5"
+  $browser_langs = array();
+
+  if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
+    $browser_accept = explode(",", $_SERVER['HTTP_ACCEPT_LANGUAGE']);
+    foreach ($browser_accept as $langpart) {
+      // The language part is either a code or a code with a quality.
+      // We cannot do anything with a * code, so it is skipped.
+      // If the quality is missing, it is assumed to be 1 according to the RFC.
+      if (preg_match("!([a-z-]+)(;q=([0-9\\.]+))?!", trim($langpart), $found)) {
+        $browser_langs[$found[1]] = (isset($found[3]) ? (float) $found[3] : 1.0);
+      }
+    }
+  }
+
+  // Order the codes by quality
+  arsort($browser_langs);
+
+  // Try to find the first preferred language we have
+  foreach ($browser_langs as $langcode => $q) {
+    if (isset($languages[$langcode])) {
+      return $langcode;
+    }
+  }
+
+  return FALSE;
+}
+
+/**
+ * Identify language from the user preferences.
+ *
+ * @param $languages
+ *   An array of valid language objects.
+ *
+ * @return
+ *   A valid language code on succes, FALSE otherwise.
+ */
+function locale_language_from_user($languages) {
+  // User preference (only for logged users).
+  global $user;
+
+  if ($user->uid) {
+    return $user->language;
+  }
+
+  // No language preference from the user.
+  return FALSE;
+}
+
+/**
+ * Identify language from a request/session parameter.
+ *
+ * @param $languages
+ *   An array of valid language objects.
+ *
+ * @return
+ *   A valid language code on succes, FALSE otherwise.
+ */
+function locale_language_from_session($languages) {
+  $param = variable_get('locale_language_negotiation_session_param', 'language');
+
+  // Request parameter.
+  if (isset($_GET[$param]) && isset($languages[$langcode = $_GET[$param]])) {
+    return $_SESSION[$param] = $langcode;
+  }
+
+  // Session parameter.
+  if (isset($_SESSION[$param])) {
+    return $_SESSION[$param];
+  }
+
+  return FALSE;
 }
+
+/**
+ * Identify language via URL prefix or domain.
+ *
+ * @param $languages
+ *   An array of valid language objects.
+ *
+ * @return
+ *   A valid language code on succes, FALSE otherwise.
+ */
+function locale_language_from_url($languages) {
+  $language_url = FALSE;
+
+  switch (variable_get('locale_language_negotiation_url_part', LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX)) {
+    case LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX:
+      // $_GET['q'] might not be available at this time, because
+      // path initialization runs after the language bootstrap phase.
+      list($language, $_GET['q']) = language_url_split_prefix(isset($_GET['q']) ? $_GET['q'] : NULL, $languages);
+      if ($language !== FALSE) {
+        $language_url = $language->language;
+      }
+      break;
+
+    case LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN:
+      foreach ($languages as $language) {
+        $host = parse_url($language->domain, PHP_URL_HOST);
+        if ($host && ($_SERVER['HTTP_HOST'] == $host)) {
+          $language_url = $language->language;
+          break;
+        }
+      }
+      break;
+  }
+
+  return $language_url;
+}
+
+/**
+ * Return the URL language switcher block. Translation links may be provided by
+ * other modules.
+ */
+function locale_language_switcher_url($type, $path) {
+  $languages = language_list('enabled');
+  $links = array();
+
+  foreach ($languages[1] as $language) {
+    $links[$language->language] = array(
+      'href'       => $path,
+      'title'      => $language->native,
+      'language'   => $language,
+      'attributes' => array('class' => array('language-link')),
+    );
+  }
+
+  return $links;
+}
+
+/**
+ * Return the session language switcher block.
+ */
+function locale_language_switcher_session($type, $path) {
+  drupal_add_css(drupal_get_path('module', 'locale') . '/locale.css');
+
+  $param = variable_get('locale_language_negotiation_session_param', 'language');
+  $language_query = isset($_SESSION[$param]) ? $_SESSION[$param] : $GLOBALS[$type]->language;
+
+  $languages = language_list('enabled');
+  $links = array();
+
+  $query = $_GET;
+  unset($query['q']);
+
+  foreach ($languages[1] as $language) {
+    $langcode = $language->language;
+    $links[$langcode] = array(
+      'href'       => $path,
+      'title'      => $language->native,
+      'attributes' => array('class' => array('language-link')),
+      'query'      => $query,
+    );
+    if ($language_query != $langcode) {
+      $links[$langcode]['query'][$param] = $langcode;
+    }
+    else {
+      $links[$langcode]['attributes']['class'][] = ' session-active';
+    }
+  }
+
+  return $links;
+}
+
+/**
+ * Rewrite URLs for the URL language provider.
+ */
+function locale_language_url_rewrite_url(&$path, &$options) {
+  // Language can be passed as an option, or we go for current URL language.
+  if (!isset($options['language'])) {
+    global $language_url;
+    $options['language'] = $language_url;
+  }
+
+  if (isset($options['language'])) {
+    switch (variable_get('locale_language_negotiation_url_part', LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX)) {
+      case LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN:
+        if ($options['language']->domain) {
+          // Ask for an absolute URL with our modified base_url.
+          $options['absolute'] = TRUE;
+          $options['base_url'] = $options['language']->domain;
+        }
+        break;
+
+      case LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX:
+        if (!empty($options['language']->prefix)) {
+          $options['prefix'] = $options['language']->prefix . '/';
+        }
+        break;
+    }
+  }
+}
+
+/**
+ * Rewrite URLs for the Session language provider.
+ */
+function locale_language_url_rewrite_session(&$path, &$options) {
+  static $query_rewrite, $query_param, $query_value;
+
+  // The following values are not supposed to change during a single page
+  // request processing.
+  if (!isset($query_rewrite)) {
+    global $user;
+    if (!$user->uid) {
+      $languages = language_list('enabled');
+      $languages = $languages[1];
+      $query_param = check_plain(variable_get('locale_language_negotiation_session_param', 'language'));
+      $query_value = isset($_GET[$query_param]) ? check_plain($_GET[$query_param]) : NULL;
+      $query_rewrite = isset($languages[$query_value]) && language_negotiation_get_any(LOCALE_LANGUAGE_NEGOTIATION_SESSION);
+    }
+    else {
+      $query_rewrite = FALSE;
+    }
+  }
+
+  // If the user is anonymous, the user language provider is enabled, and the
+  // corresponding option has been set, we must preserve any explicit user
+  // language preference even with cookies disabled.
+  if ($query_rewrite) {
+    if (is_string($options['query'])) {
+      $options['query'] = drupal_get_query_array($options['query']);
+    }
+    if (!isset($options['query'][$query_param])) {
+      $options['query'][$query_param] = $query_value;
+    }
+  }
+}
+
 /**
  * @} End of "locale-languages-negotiation"
  */
diff --git a/includes/theme.inc b/includes/theme.inc
index b06f62c32..f17f10155 100644
--- a/includes/theme.inc
+++ b/includes/theme.inc
@@ -1397,7 +1397,7 @@ function theme_links($variables) {
   $links = $variables['links'];
   $attributes = $variables['attributes'];
   $heading = $variables['heading'];
-  global $language;
+  global $language_url;
   $output = '';
 
   if (count($links) > 0) {
@@ -1438,7 +1438,7 @@ function theme_links($variables) {
         $class[] = 'last';
       }
       if (isset($link['href']) && ($link['href'] == $_GET['q'] || ($link['href'] == '<front>' && drupal_is_front_page()))
-          && (empty($link['language']) || $link['language']->language == $language->language)) {
+          && (empty($link['language']) || $link['language']->language == $language_url->language)) {
         $class[] = 'active';
       }
       $output .= '<li' . drupal_attributes(array('class' => $class)) . '>';
diff --git a/modules/locale/locale.api.php b/modules/locale/locale.api.php
index 5d0852b51..b1805e2e0 100644
--- a/modules/locale/locale.api.php
+++ b/modules/locale/locale.api.php
@@ -25,20 +25,23 @@ function hook_locale($op = 'groups') {
 }
 
 /**
- * Perform alterations on translation links.
+ * Perform alterations on language switcher links.
  *
- * A translation link may need to point to a different path or use a translated
- * link text before going through l(), which will just handle the path aliases.
+ * A language switcher link may need to point to a different path or use a
+ * translated link text before going through l(), which will just handle the
+ * path aliases.
  *
  * @param $links
  *   Nested array of links keyed by language code.
+ * @param $type
+ *   The language type the links will switch.
  * @param $path
  *   The current path.
  */
-function hook_translation_link_alter(array &$links, $path) {
+function hook_language_switch_link_alter(array &$links, $type, $path) {
   global $language;
 
-  if (isset($links[$language])) {
+  if ($type == LANGUAGE_TYPE_CONTENT && isset($links[$language])) {
     foreach ($links[$language] as $link) {
       $link['attributes']['class'][] = 'active-language';
     }
@@ -46,5 +49,93 @@ function hook_translation_link_alter(array &$links, $path) {
 }
 
 /**
+ * Allow modules to define their own language types.
+ *
+ * @return
+ *   An array of language type definitions. Each language type has an identifier
+ *   key. The language type definition is an associative array that may contain
+ *   the following key-value pairs:
+ *   - "name": The human-readable language type identifier.
+ *   - "description": A description of the language type.
+ */
+function hook_language_types_info() {
+  return array(
+    'custom_language_type' => array(
+      'name' => t('Custom language'),
+      'description' => t('A custom language type.'),
+    ),
+  );
+}
+
+/**
+ * Perform alterations on language types.
+ *
+ * @param $language_types
+ *   Array of language type definitions.
+ */
+function hook_language_types_info_alter(array &$language_types) {
+  if (isset($language_types['custom_language_type'])) {
+    $language_types['custom_language_type_custom']['description'] = t('A far better description.');
+  }
+}
+
+/**
+ * Allow modules to define their own language providers.
+ *
+ * @return
+ *   An array of language provider definitions. Each language provider has an
+ *   identifier key. The language provider definition is an associative array
+ *   that may contain the following key-value pairs:
+ *   - "types": An array of allowed language types. If a language provider does
+ *     not specify which language types it should be used with, it will be
+ *     available for all the configurable language types.
+ *   - "callbacks": An array of functions that will be called to perform various
+ *     tasks. Possible key-value pairs are:
+ *     - "language": Required. The callback that will determine the language
+ *       value.
+ *     - "switcher": The callback that will determine the language switch links
+ *       associated to the current language provider.
+ *     - "url_rewrite": The callback that will provide URL rewriting.
+ *   - "file": A file that will be included before the callback is invoked; this
+ *     allows callback functions to be in separate files.
+ *   - "weight": The default weight the language provider has.
+ *   - "name": A human-readable identifier.
+ *   - "description": A description of the language provider.
+ *   - "config": An internal path pointing to the language provider
+ *     configuration page.
+ *   - "cache": The value Drupal's page cache should be set to for the current
+ *     language provider to be invoked.
+ */
+function hook_language_negotiation_info() {
+  return array(
+    'custom_language_provider' => array(
+      'callbacks' => array(
+        'language' => 'custom_language_provider_callback',
+        'switcher' => 'custom_language_switcher_callback',
+        'url_rewrite' => 'custom_language_url_rewrite_callback',
+      ),
+      'file' => drupal_get_path('module', 'custom') . '/custom.module',
+      'weight' => -4,
+      'types' => array('custom_language_type'),
+      'name' => t('Custom language provider'),
+      'description' => t('This is a custom language provider.'),
+      'cache' => CACHE_DISABLED,
+    ),
+  );
+}
+
+/**
+ * Perform alterations on language providers.
+ *
+ * @param $language_providers
+ *   Array of language provider definitions.
+ */
+function hook_language_negotiation_info_alter(array &$language_providers) {
+  if (isset($language_providers['custom_language_provider'])) {
+    $language_providers['custom_language_provider']['config'] = 'admin/config/regional/language/configure/custom-language-provider';
+  }
+}
+
+/**
  * @} End of "addtogroup hooks".
  */
diff --git a/modules/locale/locale.css b/modules/locale/locale.css
index 3923f9ef3..b571a20d1 100644
--- a/modules/locale/locale.css
+++ b/modules/locale/locale.css
@@ -19,3 +19,11 @@
 #locale-translation-filter-form .form-item select.form-select {
   width: 100%;
 }
+
+.language-switcher-locale-session .active a.active {
+  color: #0062A0;
+}
+
+.language-switcher-locale-session .active a.session-active {
+  color: #000000;
+}
diff --git a/modules/locale/locale.install b/modules/locale/locale.install
index 73d8814e1..7800cc0f8 100644
--- a/modules/locale/locale.install
+++ b/modules/locale/locale.install
@@ -41,6 +41,47 @@ function locale_update_7000() {
 }
 
 /**
+ * Upgrade language negotiation settings.
+ */
+function locale_update_7001() {
+  require_once DRUPAL_ROOT . '/includes/language.inc';
+
+  switch (variable_get('language_negotiation', 0)) {
+    // LANGUAGE_NEGOTIATION_NONE.
+    case 0:
+      $negotiation = array();
+      break;
+
+    // LANGUAGE_NEGOTIATION_PATH_DEFAULT.
+    case 1:
+      $negotiation = array(LOCALE_LANGUAGE_NEGOTIATION_URL);
+      break;
+
+    // LANGUAGE_NEGOTIATION_PATH.
+    case 2:
+      $negotiation = array(LOCALE_LANGUAGE_NEGOTIATION_URL, LOCALE_LANGUAGE_NEGOTIATION_USER, LOCALE_LANGUAGE_NEGOTIATION_BROWSER);
+      break;
+
+    // LANGUAGE_NEGOTIATION_DOMAIN.
+    case 3:
+      variable_set('locale_language_negotiation_url_part', LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN);
+      $negotiation = array(LOCALE_LANGUAGE_NEGOTIATION_URL);
+      break;
+  }
+
+  // Save new language negotiation options: UI language is tied to content
+  // language as this was Drupal 6 behavior.
+  language_negotiation_set(LANGUAGE_TYPE_CONTENT, array_flip($negotiation));
+  language_negotiation_set(LANGUAGE_TYPE_INTERFACE, array(LOCALE_LANGUAGE_NEGOTIATION_CONTENT => 0));
+  language_negotiation_set(LANGUAGE_TYPE_URL, array(LOCALE_LANGUAGE_NEGOTIATION_URL => 0));
+
+  // Unset the old language negotiation system variable.
+  variable_del('language_negotiation');
+
+  return array();
+}
+
+/**
  * @} End of "defgroup updates-6.x-to-7.x"
  */
 
@@ -62,15 +103,23 @@ function locale_uninstall() {
   // Clear variables.
   variable_del('language_default');
   variable_del('language_count');
-  variable_del('language_negotiation');
-  variable_del('javascript_parsed');
+  variable_del('language_types');
+  variable_del('locale_language_negotiation_url_part');
+  variable_del('locale_language_negotiation_session_param');
   variable_del('language_content_type_default');
   variable_del('language_content_type_negotiation');
   variable_del('locale_cache_strings');
   variable_del('locale_js_directory');
+  variable_del('javascript_parsed');
+
+  foreach (language_types() as $type) {
+    variable_del("language_negotiation_$type");
+    variable_del("locale_language_providers_enabled_$type");
+    variable_del("locale_language_providers_weight_$type");
+  }
 
   foreach (node_type_get_types() as $type => $content_type) {
-    $setting = variable_del('language_content_type_' . $type);
+    $setting = variable_del("language_content_type_$type");
   }
 
   // Switch back to English: with a $language->language value different from 'en'
diff --git a/modules/locale/locale.module b/modules/locale/locale.module
index f6968c093..e73eaf87b 100644
--- a/modules/locale/locale.module
+++ b/modules/locale/locale.module
@@ -12,6 +12,32 @@
  *   Gettext portable object files are supported.
  */
 
+/**
+ * The language is determined using a URL language indicator:
+ * path prefix or domain according to the configuration.
+ */
+define('LOCALE_LANGUAGE_NEGOTIATION_URL', 'locale-url');
+
+/**
+ * The language is set based on the browser language settings.
+ */
+define('LOCALE_LANGUAGE_NEGOTIATION_BROWSER', 'locale-browser');
+
+/**
+ * The language is determined using the current content language.
+ */
+define('LOCALE_LANGUAGE_NEGOTIATION_CONTENT', 'locale-content');
+
+/**
+ * The language is set based on the user language settings.
+ */
+define('LOCALE_LANGUAGE_NEGOTIATION_USER', 'locale-user');
+
+/**
+ * The language is set based on the request/session parameters.
+ */
+define('LOCALE_LANGUAGE_NEGOTIATION_SESSION', 'locale-session');
+
 // ---------------------------------------------------------------------------------
 // Hook implementations
 
@@ -38,12 +64,10 @@ function locale_help($path, $arg) {
     case 'admin/config/regional/language/add':
       return '<p>' . t('Add all languages to be supported by your site. If your desired language is not available in the <em>Language name</em> drop-down, click <em>Custom language</em> and provide a language code and other details manually. When providing a language code manually, be sure to enter a standardized language code, since this code may be used by browsers to determine an appropriate display language.') . '</p>';
     case 'admin/config/regional/language/configure':
-      $output = '<p>' . t("Language negotiation settings determine the site's presentation language. Available options include:") . '</p>';
-      $output .= '<ul><li>' . t('<strong>None.</strong> The default language is used for site presentation, though users may (optionally) select a preferred language on the <em>My Account</em> page. (User language preferences will be used for site e-mails, if available.)') . '</li>';
-      $output .= '<li>' . t('<strong>Path prefix only.</strong> The presentation language is determined by examining the path for a language code or other custom string that matches the path prefix (if any) specified for each language. If a suitable prefix is not identified, the default language is used. <em>Example: "example.com/de/contact" sets presentation language to German based on the use of "de" within the path.</em>') . '</li>';
-      $output .= '<li>' . t("<strong>Path prefix with language fallback.</strong> The presentation language is determined by examining the path for a language code or other custom string that matches the path prefix (if any) specified for each language. If a suitable prefix is not identified, the display language is determined by the user's language preferences from the <em>My Account</em> page, or by the browser's language settings. If a presentation language cannot be determined, the default language is used.") . '</li>';
-      $output .= '<li>' . t('<strong>Domain name only.</strong> The presentation language is determined by examining the domain used to access the site, and comparing it to the language domain (if any) specified for each language. If a match is not identified, the default language is used. <em>Example: "http://de.example.com/contact" sets presentation language to German based on the use of "http://de.example.com" in the domain.</em>') . '</li></ul>';
-      $output .= '<p>' . t('The path prefix or domain name for a language may be set by editing the <a href="@languages">available languages</a>. In the absence of an appropriate match, the site is displayed in the <a href="@languages">default language</a>.', array('@languages' => url('admin/config/regional/language'))) . '</p>';
+      $output = '<p>' . t("Language negotiation settings determine the site's content and presentation languages. For both <em>language types</em> there is a list of <em>language detection methods</em> which can be used to configure the desired language negotiation logic. Each detection method can be <em>dragged</em> to gain a higher priority, but it must be <em>enabled</em> to affect the language negotiation process. If a language detection method is applied then all the lower ones are <em>ignored</em>, otherwise the following one will be taken into account. Some lanaguage detection methods provide a configuration page to further specify their behavior. The <em>default</em> detection method is always applied, so anything below it is always ignored. <strong>Modifying this setting may break all incoming URLs and should be used with caution in a production environment.</strong>") . '</p>';
+      $output .= '<p>' . t('Available options include:') .'</p>';
+      $output .= '<ul><li>' . t('<strong>URL.</strong> The language is determined by examining the URL for a language code, a custom string, or a domain, that matches the ones (if any) specified for each language. The path prefix or domain name for a language may be set by editing the <a href="@languages">available languages</a>. In the absence of an appropriate match, the site is displayed in the <a href="@languages">default language</a>. A configuration is available to choose whether use the path prefix or the domain. <em>Example: "example.com/de/contact" sets language to German based on the use of "de" within the path. "http://de.example.com/contact" sets presentation language to German based on the use of "http://de.example.com" in the domain.</em>', array('@languages' => url('admin/config/regional/language'))) . '</li>';
+      $output .= '<li>' . t('<strong>Session.</strong> The language is determined from a request/session parameter. A configuration is available to choose the URL parameter name to be used. <em>Example: "example.com?language=de" sets language to German based on the use of "de" within the "language" parameter.</em>') . '</li></ul>';
       return $output;
     case 'admin/config/regional/translate':
       $output = '<p>' . t('This page provides an overview of available translatable strings. Drupal displays translatable strings in text groups; modules may define additional text groups containing other translatable strings. Because text groups provide a method of grouping related strings, they are often used to focus translation efforts on specific areas of the Drupal interface.') . '</p>';
@@ -103,6 +127,22 @@ function locale_menu() {
     'file path' => 'includes',
     'type' => MENU_LOCAL_TASK,
   );
+  $items['admin/config/regional/language/configure/url'] = array(
+    'title' => 'URL language provider configuration',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('locale_language_providers_url_form'),
+    'access arguments' => array('administer languages'),
+    'file' => 'locale.inc',
+    'file path' => 'includes',
+  );
+  $items['admin/config/regional/language/configure/session'] = array(
+    'title' => 'Session language provider configuration',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('locale_language_providers_session_form'),
+    'access arguments' => array('administer languages'),
+    'file' => 'locale.inc',
+    'file path' => 'includes',
+  );
   $items['admin/config/regional/language/edit/%'] = array(
     'title' => 'Edit language',
     'page callback' => 'drupal_get_form',
@@ -249,13 +289,13 @@ function locale_language_selector_form(&$form, &$form_state, $user) {
   );
 
   // Get language negotiation settings.
-  $mode = variable_get('language_negotiation', LANGUAGE_NEGOTIATION_NONE);
+  $mode = language_negotiation_get(LANGUAGE_TYPE_INTERFACE) != LANGUAGE_NEGOTIATION_DEFAULT;
   $form['locale']['language'] = array(
     '#type' => (count($names) <= 5 ? 'radios' : 'select'),
     '#title' => t('Language'),
     '#default_value' => $user_preferred_language->language,
     '#options' => $names,
-    '#description' => ($mode == LANGUAGE_NEGOTIATION_PATH) ? t("This account's default language for e-mails, and preferred language for site presentation.") : t("This account's default language for e-mails."),
+    '#description' => $mode ? t("This account's default language for e-mails, and preferred language for site presentation.") : t("This account's default language for e-mails."),
   );
 }
 
@@ -330,12 +370,97 @@ function locale_theme() {
     'locale_languages_overview_form' => array(
       'arguments' => array('form' => array()),
     ),
+    'locale_languages_configure_form' => array(
+      'arguments' => array('form' => array()),
+    ),
     'locale_translation_filters' => array(
       'arguments' => array('form' => array()),
     ),
   );
 }
 
+/**
+ * Implement hook_language_types_info().
+ */
+function locale_language_types_info() {
+  return array(
+    LANGUAGE_TYPE_CONTENT => array(
+      'name' => t('Content'),
+      'description' => t('If a piece of content is available in multiple languages, the one matching the <em>content</em> language will be used.'),
+    ),
+    LANGUAGE_TYPE_INTERFACE => array(
+      'name' => t('Interface'),
+      'description' => t('The interface labels will be displayed in the <em>interface</em> language.'),
+    ),
+    LANGUAGE_TYPE_URL => array(
+      'fixed' => array(LOCALE_LANGUAGE_NEGOTIATION_URL),
+    ),
+  );
+}
+
+/**
+ * Implement hook_language_negotiation_info().
+ */
+function locale_language_negotiation_info() {
+  $file = 'includes/locale.inc';
+  $providers = array();
+
+  $providers[LOCALE_LANGUAGE_NEGOTIATION_URL] = array(
+    'types' => array(LANGUAGE_TYPE_CONTENT, LANGUAGE_TYPE_INTERFACE, LANGUAGE_TYPE_URL),
+    'callbacks' => array(
+      'language' => 'locale_language_from_url',
+      'switcher' => 'locale_language_switcher_url',
+      'url_rewrite' => 'locale_language_url_rewrite_url',
+    ),
+    'file' => $file,
+    'weight' => -8,
+    'name' => t('URL'),
+    'description' => t('The language is determined from the URL (Path prefix or domain).'),
+    'config' => 'admin/config/regional/language/configure/url',
+  );
+
+  $providers[LOCALE_LANGUAGE_NEGOTIATION_SESSION] = array(
+    'callbacks' => array(
+      'language' => 'locale_language_from_session',
+      'switcher' => 'locale_language_switcher_session',
+      'url_rewrite' => 'locale_language_url_rewrite_session',
+    ),
+    'file' => $file,
+    'weight' => -6,
+    'name' => t('Session'),
+    'description' => t('The language is determined from a request/session parameter.'),
+    'config' => 'admin/config/regional/language/configure/session',
+  );
+
+  $providers[LOCALE_LANGUAGE_NEGOTIATION_USER] = array(
+    'callbacks' => array('language' => 'locale_language_from_user'),
+    'file' => $file,
+    'weight' => -4,
+    'name' => t('User'),
+    'description' => t('The language is determined from the language preference set in the user account.'),
+  );
+
+  $providers[LOCALE_LANGUAGE_NEGOTIATION_BROWSER] = array(
+    'callbacks' => array('language' => 'locale_language_from_browser'),
+    'name' => $file,
+    'weight' => -2,
+    'cache' => CACHE_DISABLED,
+    'name' => t('Browser'),
+    'description' => t('The language is determined from the browser\'s language settings.'),
+  );
+
+  $providers[LOCALE_LANGUAGE_NEGOTIATION_CONTENT] = array(
+    'types' => array(LANGUAGE_TYPE_INTERFACE),
+    'callbacks' => array('language' => 'locale_language_from_content'),
+    'file' => $file,
+    'weight' => 8,
+    'name' => t('Content'),
+    'description' => t('The interface language is the same as the negotiated content language.'),
+  );
+
+  return $providers;
+}
+
 // ---------------------------------------------------------------------------------
 // Locale core functionality
 
@@ -625,39 +750,36 @@ function locale_css_alter(&$css) {
  * Implement hook_block_info().
  */
 function locale_block_info() {
-  $block['language-switcher']['info'] = t('Language switcher');
-  // Not worth caching.
-  $block['language-switcher']['cache'] = DRUPAL_NO_CACHE;
+  include_once DRUPAL_ROOT . '/includes/language.inc';
+  $block = array();
+  $info = language_types_info();
+  foreach (language_types_configurable() as $type) {
+    $block[$type] = array(
+      'info' => t('Language switcher (@type)', array('@type' => $info[$type]['name'])),
+      // Not worth caching.
+      'cache' => DRUPAL_NO_CACHE,
+    );
+  }
   return $block;
 }
 
 /**
  * Implement hook_block_view().
  *
- * Displays a language switcher. Translation links may be provided by other modules.
- * Only show if we have at least two languages and language dependent
- * web addresses, so we can actually link to other language versions.
+ * Displays a language switcher. Only show if we have at least two languages.
  */
-function locale_block_view($delta = '') {
-  if (variable_get('language_count', 1) > 1 && variable_get('language_negotiation', LANGUAGE_NEGOTIATION_NONE) != LANGUAGE_NEGOTIATION_NONE) {
+function locale_block_view($type) {
+  if (variable_get('language_count', 1) > 1) {
     $path = drupal_is_front_page() ? '<front>' : $_GET['q'];
-    $languages = language_list('enabled');
-    $links = array();
-    foreach ($languages[1] as $language) {
-      $links[$language->language] = array(
-        'href'       => $path,
-        'title'      => $language->native,
-        'language'   => $language,
-        'attributes' => array('class' => array('language-link')),
-      );
+    $links = language_negotiation_get_switch_links($type, $path);
+
+    if (isset($links->links) && count($links->links > 1)) {
+      $class = "language-switcher-{$links->provider}";
+      $variables = array('links' => $links->links, 'attributes' => array('class' => array($class)));
+      $block['content'] = theme('links', $variables);
+      $block['subject'] = t('Languages');
+      return $block;
     }
-
-    // Allow modules to provide translations for specific links.
-    drupal_alter('translation_link', $links, $path);
-
-    $block['subject'] = t('Languages');
-    $block['content'] = theme('links', array('links' => $links, 'attributes' => array()));
-    return $block;
   }
 }
 
diff --git a/modules/locale/locale.test b/modules/locale/locale.test
index 0078b2eb3..fc598e296 100644
--- a/modules/locale/locale.test
+++ b/modules/locale/locale.test
@@ -910,11 +910,11 @@ class LocaleUninstallFunctionalTest extends DrupalWebTestCase {
   /**
    * The default language set for the UI before uninstall.
    */
-  protected $ui_language;
+  protected $language_interface;
 
   function setUp() {
     parent::setUp('locale');
-    $this->ui_language = 'en';
+    $this->language_interface = 'en';
   }
 
   /**
@@ -925,15 +925,12 @@ class LocaleUninstallFunctionalTest extends DrupalWebTestCase {
 
     // Add a new language and optionally set it as default.
     require_once DRUPAL_ROOT . '/includes/locale.inc';
-    locale_add_language('fr', 'French', 'Français', LANGUAGE_LTR, '', '', TRUE, $this->ui_language == 'fr');
+    locale_add_language('fr', 'French', 'Français', LANGUAGE_LTR, '', '', TRUE, $this->language_interface == 'fr');
 
     // Check the UI language.
     drupal_language_initialize();
-    global $language;
-    $this->assertEqual($language->language, $this->ui_language, t('Current language: %lang', array('%lang' => $language->language)));
-
-    // Change language negotiation options.
-    variable_set('language_negotiation', LANGUAGE_NEGOTIATION_PATH_DEFAULT);
+    global $language_interface;
+    $this->assertEqual($language_interface->language, $this->language_interface, t('Current language: %lang', array('%lang' => $language_interface->language)));
 
     // Enable multilingual workflow option for articles.
     variable_set('language_content_type_article', 1);
@@ -959,6 +956,17 @@ class LocaleUninstallFunctionalTest extends DrupalWebTestCase {
     // Disable string caching.
     variable_set('locale_cache_strings', 0);
 
+    // Change language negotiation options.
+    drupal_load('module', 'locale');
+    variable_set('language_types', drupal_language_types() + array('language_custom' => TRUE));
+    variable_set('language_negotiation_' . LANGUAGE_TYPE_INTERFACE, locale_language_negotiation_info());
+    variable_set('language_negotiation_' . LANGUAGE_TYPE_CONTENT, locale_language_negotiation_info());
+    variable_set('language_negotiation_' . LANGUAGE_TYPE_URL, locale_language_negotiation_info());
+
+    // Change language providers settings.
+    variable_set('locale_language_negotiation_url_part', LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX);
+    variable_set('locale_language_negotiation_session_param', TRUE);
+
     // Uninstall Locale.
     module_disable($locale_module);
     drupal_uninstall_modules($locale_module);
@@ -968,7 +976,7 @@ class LocaleUninstallFunctionalTest extends DrupalWebTestCase {
 
     // Check the init language logic.
     drupal_language_initialize();
-    $this->assertEqual($language->language, 'en', t('Language after uninstall: %lang', array('%lang' => $language->language)));
+    $this->assertEqual($language_interface->language, 'en', t('Language after uninstall: %lang', array('%lang' => $language_interface->language)));
 
     // Check JavaScript files deletion.
     $this->assertTrue($result = !file_exists($js_file), t('JavaScript file deleted: %file', array('%file' => $result ? $js_file : t('found'))));
@@ -978,8 +986,17 @@ class LocaleUninstallFunctionalTest extends DrupalWebTestCase {
     $this->assertEqual($language_count, 1, t('Language count: %count', array('%count' => $language_count)));
 
     // Check language negotiation.
-    $language_negotiation = variable_get('language_negotiation', LANGUAGE_NEGOTIATION_NONE) == LANGUAGE_NEGOTIATION_NONE;
-    $this->assertTrue($language_negotiation, t('Language negotiation: %setting', array('%setting' => t($language_negotiation ? 'none' : 'set'))));
+    $this->assertTrue(count(language_types()) == count(drupal_language_types()), t('Language types reset'));
+    $language_negotiation = language_negotiation_get(LANGUAGE_TYPE_INTERFACE) == LANGUAGE_NEGOTIATION_DEFAULT;
+    $this->assertTrue($language_negotiation, t('Interface language negotiation: %setting', array('%setting' => t($language_negotiation ? 'none' : 'set'))));
+    $language_negotiation = language_negotiation_get(LANGUAGE_TYPE_CONTENT) == LANGUAGE_NEGOTIATION_DEFAULT;
+    $this->assertTrue($language_negotiation, t('Content language negotiation: %setting', array('%setting' => t($language_negotiation ? 'none' : 'set'))));
+    $language_negotiation = language_negotiation_get(LANGUAGE_TYPE_URL) == LANGUAGE_NEGOTIATION_DEFAULT;
+    $this->assertTrue($language_negotiation, t('URL language negotiation: %setting', array('%setting' => t($language_negotiation ? 'none' : 'set'))));
+
+    // Check language providers settings.
+    $this->assertFalse(variable_get('locale_language_negotiation_url_part', FALSE), t('URL language provider indicator settings cleared.'));
+    $this->assertFalse(variable_get('locale_language_negotiation_session_param', FALSE), t('Visit language provider settings cleared.'));
 
     // Check JavaScript parsed.
     $javascript_parsed_count = count(variable_get('javascript_parsed', array()));
@@ -1011,14 +1028,14 @@ class LocaleUninstallFrenchFunctionalTest extends LocaleUninstallFunctionalTest
   public static function getInfo() {
     return array(
       'name' => 'Locale uninstall (FR)',
-      'description' => 'Tests the uninstall process using French as UI language.',
+      'description' => 'Tests the uninstall process using French as interface language.',
       'group' => 'Locale',
     );
   }
 
   function setUp() {
     parent::setUp();
-    $this->ui_language = 'fr';
+    $this->language_interface = 'fr';
   }
 }
 
@@ -1050,7 +1067,7 @@ class LanguageSwitchingFunctionalTest extends DrupalWebTestCase {
   function testLanguageBlock() {
     // Enable the language switching block.
     $edit = array(
-      'locale_language-switcher[region]' => 'sidebar_first',
+      'locale_language[region]' => 'sidebar_first',
     );
     $this->drupalPost('admin/structure/block', $edit, t('Save blocks'));
 
@@ -1061,18 +1078,16 @@ class LanguageSwitchingFunctionalTest extends DrupalWebTestCase {
     $this->drupalPost('admin/config/regional/language/add', $edit, t('Add language'));
 
     // Set language negotiation.
-    $edit = array(
-      'language_negotiation' => LANGUAGE_NEGOTIATION_PATH_DEFAULT,
-    );
-    $this->drupalPost('admin/config/regional/language/configure', $edit, t('Save settings'));
-    $this->assertEqual($this->getUrl(), url('admin/config/regional/language', array('absolute' => TRUE)), t('Correct page redirection.'));
+    drupal_load('module', 'locale');
+    include_once DRUPAL_ROOT . '/includes/language.inc';
+    language_negotiation_set(LANGUAGE_TYPE_CONTENT, locale_language_negotiation_info());
 
     // Assert that the language switching block is displayed on the frontpage.
     $this->drupalGet('');
     $this->assertText(t('Languages'), t('Language switcher block found.'));
 
     // Assert that only the current language is marked as active.
-    list($language_switcher) = $this->xpath('//div[@id="block-locale-language-switcher"]');
+    list($language_switcher) = $this->xpath('//div[@id="block-locale-language"]');
     $links = array(
       'active' => array(),
       'inactive' => array(),
@@ -1243,10 +1258,8 @@ class LocalePathFunctionalTest extends DrupalWebTestCase {
     $this->drupalPost('admin/config/regional/language/add', $edit, t('Add custom language'));
 
     // Set language negotiation.
-    $edit = array(
-      'language_negotiation' => LANGUAGE_NEGOTIATION_PATH_DEFAULT,
-    );
-    $this->drupalPost('admin/config/regional/language/configure', $edit, t('Save settings'));
+    drupal_load('module', 'locale');
+    variable_set('language_negotiation_' . LANGUAGE_TYPE_CONTENT, locale_language_negotiation_info());
 
     // Create a node.
     $node = $this->drupalCreateNode(array('type' => 'page'));
@@ -1352,12 +1365,6 @@ class LocaleContentFunctionalTest extends DrupalWebTestCase {
     );
     $this->drupalPost($path, $edit, t('Save configuration'));
 
-    // Set language negotiation.
-    $edit = array(
-      'language_negotiation' => LANGUAGE_NEGOTIATION_PATH_DEFAULT,
-    );
-    $this->drupalPost('admin/config/regional/language/configure', $edit, t('Save settings'));
-
     // Set page content type to use multilingual support.
     $this->drupalGet('admin/structure/types/manage/page');
     $this->assertText(t('Multilingual support'), t('Multilingual support fieldset present on content type configuration form.'));
@@ -1412,7 +1419,7 @@ class LocaleContentFunctionalTest extends DrupalWebTestCase {
 
 /**
  * Test UI language negotiation
- * 1. LANGUAGE_NEGOTIATION_PATH_DEFAULT
+ * 1. URL (PATH) > DEFAULT
  *    UI Language base on URL prefix, browser language preference has no
  *    influence:
  *      admin/config
@@ -1421,7 +1428,7 @@ class LocaleContentFunctionalTest extends DrupalWebTestCase {
  *        UI in Chinese
  *      blah-blah/admin/config
  *        404
- * 2. LANGUAGE_NEGOTIATION_PATH
+ * 2. URL (PATH) > BROWSER > DEFAULT
  *        admin/config
  *          UI in user's browser language preference if the site has that
  *          language enabled, if not, the default language
@@ -1429,7 +1436,7 @@ class LocaleContentFunctionalTest extends DrupalWebTestCase {
  *          UI in Chinese
  *        blah-blah/admin/config
  *          404
- * 3. LANGUAGE_NEGOTIATION_DOMAIN
+ * 3. URL (DOMAIN) > DEFAULT
  *        http://example.com/admin/config
  *          UI language in site default
  *        http://example.cn/admin/config
@@ -1446,6 +1453,8 @@ class UILanguageNegotiationTest extends DrupalWebTestCase {
 
   function setUp() {
     parent::setUp('locale', 'locale_test');
+    require_once DRUPAL_ROOT . '/includes/language.inc';
+    drupal_load('module', 'locale');
   }
 
   /**
@@ -1505,46 +1514,49 @@ class UILanguageNegotiationTest extends DrupalWebTestCase {
     );
     $this->drupalPost(NULL, $edit, t('Save translations'));
 
+    // Configure URL language rewrite.
+    variable_set('locale_language_negotiation_url_type', LANGUAGE_TYPE_INTERFACE);
+
     $tests = array(
       // Default, browser preference should have no influence.
       array(
-        'language_negotiation' => LANGUAGE_NEGOTIATION_PATH_DEFAULT,
+        'language_negotiation' => array(LOCALE_LANGUAGE_NEGOTIATION_URL, LANGUAGE_NEGOTIATION_DEFAULT),
         'path' => 'admin/config',
         'expect' => $default_string,
         'http_header' => $http_header_browser_fallback,
-        'message' => 'LANGUAGE_NEGOTIATION_PATH_DEFAULT: no language prefix, UI language is default and not the browser language preference setting is used.',
+        'message' => 'URL (PATH) > DEFAULT: no language prefix, UI language is default and the browser language preference setting is not used.',
       ),
       // Language prefix.
       array(
-        'language_negotiation' => LANGUAGE_NEGOTIATION_PATH_DEFAULT,
+        'language_negotiation' => array(LOCALE_LANGUAGE_NEGOTIATION_URL, LANGUAGE_NEGOTIATION_DEFAULT),
         'path' => "$language/admin/config",
         'expect' => $language_string,
         'http_header' => $http_header_browser_fallback,
-        'message' => 'LANGUAGE_NEGOTIATION_PATH_DEFAULT: with language prefix, UI language is switched based on path prefix',
+        'message' => 'URL (PATH) > DEFAULT: with language prefix, UI language is switched based on path prefix',
       ),
       // Default, go by browser preference.
       array(
-        'language_negotiation' => LANGUAGE_NEGOTIATION_PATH,
+        'language_negotiation' => array(LOCALE_LANGUAGE_NEGOTIATION_URL, LOCALE_LANGUAGE_NEGOTIATION_BROWSER),
         'path' => 'admin/config',
         'expect' => $language_browser_fallback_string,
         'http_header' => $http_header_browser_fallback,
-        'message' => 'LANGUAGE_NEGOTIATION_PATH: no language prefix, UI language is determined by browser language preference',
+        'message' => 'URL (PATH) > BROWSER: no language prefix, UI language is determined by browser language preference',
       ),
       // Prefix, switch to the language.
       array(
-        'language_negotiation' => LANGUAGE_NEGOTIATION_PATH,
+        'language_negotiation' => array(LOCALE_LANGUAGE_NEGOTIATION_URL, LOCALE_LANGUAGE_NEGOTIATION_BROWSER),
         'path' => "$language/admin/config",
         'expect' => $language_string,
         'http_header' => $http_header_browser_fallback,
-        'message' => 'LANGUAGE_NEGOTIATION_PATH: with langage prefix, UI language is based on path prefix',
+        'message' => 'URL (PATH) > BROWSER: with langage prefix, UI language is based on path prefix',
       ),
       // Default, browser language preference is not one of site's lang.
       array(
-        'language_negotiation' => LANGUAGE_NEGOTIATION_PATH,
+        'language_negotiation' => array(LOCALE_LANGUAGE_NEGOTIATION_URL, LOCALE_LANGUAGE_NEGOTIATION_BROWSER, LANGUAGE_NEGOTIATION_DEFAULT),
         'path' => 'admin/config',
         'expect' => $default_string,
         'http_header' => $http_header_blah,
-        'message' => 'LANGUAGE_NEGOTIATION_PATH: no language prefix and browser language preference set to unknown language should use default language',
+        'message' => 'URL (PATH) > BROWSER > DEFAULT: no language prefix and browser language preference set to unknown language should use default language',
       ),
     );
 
@@ -1553,35 +1565,36 @@ class UILanguageNegotiationTest extends DrupalWebTestCase {
     }
 
     // Unknown language prefix should return 404.
-    foreach(array(LANGUAGE_NEGOTIATION_PATH_DEFAULT, LANGUAGE_NEGOTIATION_PATH) as $negotiation) {
-      variable_set('language_negotiation', $negotiation);
-      $this->drupalGet("$language_unknown/admin/config", array(), $http_header_browser_fallback);
-      $this->assertResponse(404, "Unknown language path prefix should return 404, code = $negotiation");
-    }
+    variable_set('language_negotiation_' . LANGUAGE_TYPE_INTERFACE, locale_language_negotiation_info());
+    $this->drupalGet("$language_unknown/admin/config", array(), $http_header_browser_fallback);
+    $this->assertResponse(404, "Unknown language path prefix should return 404");
 
     // Setup for domain negotiation, first configure the language to have domain
     // URL.
     $edit = array('prefix' => '', 'domain' => "http://$language_domain");
     $this->drupalPost("admin/config/regional/language/edit/$language", $edit, t('Save language'));
     // Set the site to use domain language negotiation.
-    variable_set('language_negotiation', LANGUAGE_NEGOTIATION_DOMAIN);
 
     $tests = array(
       // Default domain, browser preference should have no influence.
       array(
+        'language_negotiation' => array(LOCALE_LANGUAGE_NEGOTIATION_URL, LANGUAGE_NEGOTIATION_DEFAULT),
+        'locale_language_negotiation_url_part' => LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN,
         'path' => 'admin/config',
         'expect' => $default_string,
         'http_header' => $http_header_browser_fallback,
-        'message' => 'LANGUAGE_NEGOTIATION_DOMAIN: default domain should get default language',
+        'message' => 'URL (DOMAIN) > DEFAULT: default domain should get default language',
       ),
       // Language domain specific URL, we set the $_SERVER['HTTP_HOST'] in
       // locale_test.module hook_boot() to simulate this.
       array(
+        'language_negotiation' => array(LOCALE_LANGUAGE_NEGOTIATION_URL, LANGUAGE_NEGOTIATION_DEFAULT),
+        'locale_language_negotiation_url_part' => LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN,
         'locale_test_domain' => $language_domain,
         'path' => 'admin/config',
         'expect' => $language_string,
         'http_header' => $http_header_browser_fallback,
-        'message' => 'LANGUAGE_NEGOTIATION_DOMAIN: domain example.cn should switch to Chinese',
+        'message' => 'URL (DOMAIN) > DEFAULT: domain example.cn should switch to Chinese',
       ),
     );
 
@@ -1592,7 +1605,11 @@ class UILanguageNegotiationTest extends DrupalWebTestCase {
 
   private function runTest($test) {
     if (!empty($test['language_negotiation'])) {
-      variable_set('language_negotiation', $test['language_negotiation']);
+      $negotiation = array_flip($test['language_negotiation']);
+      language_negotiation_set(LANGUAGE_TYPE_INTERFACE, $negotiation);
+    }
+    if (!empty($test['locale_language_negotiation_url_part'])) {
+      variable_set('locale_language_negotiation_url_part', $test['locale_language_negotiation_url_part']);
     }
     if (!empty($test['locale_test_domain'])) {
       variable_set('locale_test_domain', $test['locale_test_domain']);
diff --git a/modules/node/node.module b/modules/node/node.module
index ad30fba0d..2e6a3800c 100644
--- a/modules/node/node.module
+++ b/modules/node/node.module
@@ -1138,6 +1138,52 @@ function node_build_content($node, $build_mode = 'full') {
 }
 
 /**
+ * Implement hook_language_negotiation_info().
+ */
+function node_language_negotiation_info() {
+  $providers = array();
+
+  $providers['node-language'] = array(
+    'types' => array(LANGUAGE_TYPE_CONTENT),
+    'callbacks' => array('language' => 'node_language_provider'),
+    'file' => drupal_get_path('module', 'node') . '/node.module',
+    'name' => t('Node'),
+    'description' => t('The current node language is used.'),
+  );
+
+  return $providers;
+}
+
+/**
+ * Return the language of the current node.
+ *
+ * @param $languages
+ *   An array of valid language objects.
+ *
+ * @return
+ *   A valid language code on succes, FALSE otherwise.
+ */
+function node_language_provider($languages) {
+  require_once DRUPAL_ROOT . '/includes/path.inc';
+
+  $path = isset($_GET['q']) ? $_GET['q'] : '';
+  list($language, $path) = language_url_split_prefix($path, $languages);
+  $language = $language ? $language : language_default();
+  $path = drupal_get_normal_path($path, $language->language);
+
+  // We cannot use args now.
+  $path = explode('/', $path);
+  // Act only if we are in a node page.
+  if ($path[0] == 'node' && $nid = intval($path[1])) {
+    // We cannot perform a node load here.
+    $result = db_query('SELECT n.language FROM {node} n WHERE n.nid = :nid', array(':nid' => $nid))->fetchAssoc();
+    return $result['language'];
+  }
+
+  return FALSE;
+}
+
+/**
  * Generate an array which displays a node detail page.
  *
  * @param $node
diff --git a/modules/path/path.test b/modules/path/path.test
index d0abc0a2c..21cbb5ab9 100644
--- a/modules/path/path.test
+++ b/modules/path/path.test
@@ -183,7 +183,9 @@ class PathLanguageTestCase extends DrupalWebTestCase {
     drupal_static_reset('language_list');
 
     // Set language negotiation to "Path prefix with fallback".
-    variable_set('language_negotiation', LANGUAGE_NEGOTIATION_PATH);
+    include_once DRUPAL_ROOT . '/includes/locale.inc';
+    variable_set('language_negotiation_' . LANGUAGE_TYPE_CONTENT, locale_language_negotiation_info());
+    variable_set('locale_language_negotiation_url_part', LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX);
 
     // Force inclusion of language.inc.
     drupal_language_initialize();
diff --git a/modules/translation/translation.module b/modules/translation/translation.module
index 4684c7f2f..a35dfb86a 100644
--- a/modules/translation/translation.module
+++ b/modules/translation/translation.module
@@ -170,23 +170,17 @@ function translation_form_alter(&$form, &$form_state, $form_id) {
  */
 function translation_node_view($node, $build_mode) {
   if (isset($node->tnid) && $translations = translation_node_get_translations($node->tnid)) {
-    // Do not show link to the same node.
-    unset($translations[$node->language]);
-    $languages = language_list();
-    foreach ($languages as $langcode => $language) {
-      if (isset($translations[$langcode])) {
-        $links["node_translation_$langcode"] = array(
-          'title' => $language->native,
-          'href' => 'node/' . $translations[$langcode]->nid,
-          'language' => $language,
-          'attributes' => array('title' => $translations[$langcode]->title, 'class' => array('translation-link')),
-        );
-        $node->content['links']['translation'] = array(
-          '#theme' => 'links',
-          '#links' => $links,
-          '#attributes' => array('class' => array('links', 'inline')),
-        );
-      }
+    $path = 'node/' . $node->nid;
+    $links = language_negotiation_get_switch_links(LANGUAGE_TYPE_CONTENT, $path);
+    if (is_object($links)) {
+      $links = $links->links;
+      // Do not show link to the same node.
+      unset($links[$node->language]);
+      $node->content['links']['translation'] = array(
+        '#theme' => 'links',
+        '#links' => $links,
+        '#attributes' => array('class' => array('links', 'inline')),
+      );
     }
   }
 }
@@ -407,12 +401,12 @@ function translation_path_get_translations($path) {
 }
 
 /**
- * Implement hook_translation_link_alter().
+ * Implement hook_language_switch_link_alter().
  *
  * Replaces links with pointers to translated versions of the content.
  */
-function translation_translation_link_alter(array &$links, $path) {
-  if ($paths = translation_path_get_translations($path)) {
+function translation_language_switch_links_alter(array &$links, $type, $path) {
+  if ($type == LANGUAGE_TYPE_CONTENT && $paths = translation_path_get_translations($path)) {
     foreach ($links as $langcode => $link) {
       if (isset($paths[$langcode])) {
         // Translation in a different node.