Introduced $wgULSAnonCanChangeLanguage

This allows us to enable web fonts and input methods for all
users by disabling just the interface language selection.

Updated the documentation of the variables to make it clearer
what each does. Summary:
* Enabling: $wgULSEnable and $wgULSEnableAnon
* Workarounds: $wgULSAnonCanChangeLanguage and $wgULSLanguageDetection

Cleaned up hooks, in particular rewritten getLanguage to separate
the logged in vs. logged out steps for easier understanding.

A followup commit is needed to disable language selection UI for
anon if $wgULSAnonCanChangeLanguage is false.

Change-Id: Ia8d21c394ff5efac0ce94664710c97dc3b74ec18

UniversalLanguageSelector.hooks.php

@@ -19,15 +19,17 @@
  */
 
 class UniversalLanguageSelectorHooks {
+	/**
+	 * Whether ULS user toolbar (language selection and settings) is enabled.
+	 * @return bool
+	 */
 	public static function isToolbarEnabled( $user ) {
 		global $wgULSEnable, $wgULSEnableAnon;
 		if ( !$wgULSEnable ) {
 			return false;
 		}
-		if ( !$wgULSEnableAnon ) {
-			if ( $user->isAnon() ) {
-				return false;
-			}
+		if ( !$wgULSEnableAnon && $user->isAnon() ) {
+			return false;
 		}
 		return true;
 	}
@@ -141,7 +143,7 @@ class UniversalLanguageSelectorHooks {
 	 * @return bool
 	 */
 	public static function getLanguage( $user, &$code, $context = null ) {
-		global $wgUser, $wgRequest, $wgULSLanguageDetection;
+		global $wgUser, $wgRequest, $wgULSAnonCanChangeLanguage, $wgULSLanguageDetection;
 		if ( !self::isToolbarEnabled( $user ) ) {
 			return true;
 		}
@@ -167,27 +169,40 @@ class UniversalLanguageSelectorHooks {
 			return true;
 		}
 
-		$languageToUse = null;
-		if ( self::isSupportedLanguage( $languageToSave ) ) {
-			if ( $user->isAnon() ) {
-				$request->response()->setcookie( 'language', $languageToSave );
-			} else {
+		// Registered users - simple
+		if ( !$user->isAnon() ) {
+			// Language change
+			if ( self::isSupportedLanguage( $languageToSave ) ) {
 				$user->setOption( 'language', $languageToSave );
 				$user->saveSettings();
+				// Apply immediately
+				$code = $languageToSave;
 			}
-			$languageToUse = $languageToSave;
+			// Otherwise just use what is stored in preferences
+			return true;
 		}
 
-		// Load from cookie unless overriden
-		if ( $languageToUse === null && $user->isAnon() ) {
-			$languageToUse = $request->getCookie( 'language' );
+		// Logged out users - less simple
+		if ( !$wgULSAnonCanChangeLanguage ) {
+			return true;
 		}
 
-		// Check whether we got valid language from store or
-		// explicit language change.
+		// Language change
+		if ( self::isSupportedLanguage( $languageToSave ) ) {
+			$request->response()->setcookie( 'language', $languageToSave );
+			$code = $languageToSave;
+			return true;
+		}
+
+		// Try cookie
+		$languageToUse = $request->getCookie( 'language' );
 		if ( self::isSupportedLanguage( $languageToUse ) ) {
 			$code = $languageToUse;
-		} elseif ( $user->isAnon() && $wgULSLanguageDetection ) {
+			return true;
+		}
+
+		// As last resort, try Accept-Language headers if allowed
+		if ( $wgULSLanguageDetection ) {
 			$preferred = $request->getAcceptLang();
 			$default = self::getDefaultLanguage( $preferred );
 			if ( $default !== '' ) {
@@ -195,7 +210,7 @@ class UniversalLanguageSelectorHooks {
 			}
 		}
 
-		// Fall back to content language
+		// Fall back to other hooks or content language
 		return true;
 	}
 
@@ -205,10 +220,14 @@ class UniversalLanguageSelectorHooks {
 	 * @return bool
 	 */
 	public static function addConfig( &$vars ) {
-		global $wgULSGeoService, $wgULSIMEEnabled;
-		$vars['wgULSGeoService'] = $wgULSGeoService;
+		global $wgULSGeoService, $wgULSIMEEnabled, $wgULSPosition,
+			$wgULSAnonCanChangeLanguage;
 
+		// Place constant stuff here (not depending on request context)
+		$vars['wgULSGeoService'] = $wgULSGeoService;
 		$vars['wgULSIMEEnabled'] = $wgULSIMEEnabled;
+		$vars['wgULSPosition'] = $wgULSPosition;
+		$vars['wgULSAnonCanChangeLanguage'] = $wgULSAnonCanChangeLanguage;
 
 		// ULS is localized using jquery.i18n library. Unless it knows
 		// the localized locales, it can create 404 response. To avoid that,
@@ -253,12 +272,11 @@ class UniversalLanguageSelectorHooks {
 	 * @return bool
 	 */
 	public static function addVariables( &$vars, OutputPage $out ) {
+		// Place request context dependent stuff here
 		$vars['wgULSLanguages'] = Language::fetchLanguageNames(
 			$out->getLanguage()->getCode(), 'mwfile'
 		);
 		$vars['wgULSAcceptLanguageList'] = array_keys( $out->getRequest()->getAcceptLang() );
-		global $wgULSPosition;
-		$vars['wgULSPosition'] = $wgULSPosition;
 
 		return true;
 	}
@@ -284,6 +302,10 @@ class UniversalLanguageSelectorHooks {
 			return true;
 		}
 
+		if ( !self::isToolbarEnabled( $skin->getUser() ) ) {
+			return true;
+		}
+
 		// A dummy link, just to make sure that the section appears
 		$template->data['language_urls'][] = array(
 			'href' => '#',