Source/WTF/wtf/cf/LanguageCF.cpp

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 *
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#include "config.h"
#include <wtf/Language.h>

#include <CoreFoundation/CoreFoundation.h>
#include <mutex>
#include <unicode/uloc.h>
#include <wtf/Assertions.h>
#include <wtf/Lock.h>
#include <wtf/NeverDestroyed.h>
#include <wtf/RetainPtr.h>
#include <wtf/spi/cf/CFBundleSPI.h>
#include <wtf/text/WTFString.h>

namespace WTF {

static Lock preferredLanguagesMutex;

static Vector<String>& preferredLanguages()
{
    static NeverDestroyed<Vector<String>> languages;
    return languages;
}

static String httpStyleLanguageCode(CFStringRef language)
{
    RetainPtr<CFStringRef> preferredLanguageCode;
    // If we can minimize the language list to reduce fingerprinting, we can afford to be more lossless when canonicalizing the locale list.
    if (canMinimizeLanguages())
        preferredLanguageCode = adoptCF(CFLocaleCreateCanonicalLanguageIdentifierFromString(kCFAllocatorDefault, language));
    else {
        SInt32 languageCode;
        SInt32 regionCode;
        SInt32 scriptCode;
        CFStringEncoding stringEncoding;

        // FIXME: This transformation is very wrong:
        // 1. There is no reason why CFBundle localization names would be at all related to language names as used on the Web.
        // 2. Script Manager codes cannot represent all languages that are now supported by the platform, so the conversion is lossy.
        // 3. This should probably match what is sent by the network layer as Accept-Language, but currently, that's implemented separately.
        CFBundleGetLocalizationInfoForLocalization(language, &languageCode, &regionCode, &scriptCode, &stringEncoding);
        preferredLanguageCode = adoptCF(CFBundleCopyLocalizationForLocalizationInfo(languageCode, regionCode, scriptCode, stringEncoding));
    }

    if (!preferredLanguageCode)
        preferredLanguageCode = language;
    auto mutableLanguageCode = adoptCF(CFStringCreateMutableCopy(kCFAllocatorDefault, 0, preferredLanguageCode.get()));

    // Turn a '_' into a '-' if it appears after a 2-letter language code
    if (CFStringGetLength(mutableLanguageCode.get()) >= 3 && CFStringGetCharacterAtIndex(mutableLanguageCode.get(), 2) == '_')
        CFStringReplace(mutableLanguageCode.get(), CFRangeMake(2, 1), CFSTR("-"));

    CFStringLowercase(mutableLanguageCode.get(), nullptr);
    return mutableLanguageCode.get();

}

#if PLATFORM(MAC)
static void languagePreferencesDidChange(CFNotificationCenterRef, void*, CFStringRef, const void*, CFDictionaryRef)
{
    {
        auto locker = holdLock(preferredLanguagesMutex);
        preferredLanguages().clear();
    }
    
    languageDidChange();
}
#endif

Vector<String> platformUserPreferredLanguages()
{
#if PLATFORM(MAC)
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^ {
        CFNotificationCenterAddObserver(CFNotificationCenterGetDistributedCenter(), nullptr, &languagePreferencesDidChange, CFSTR("AppleLanguagePreferencesChangedNotification"), nullptr, CFNotificationSuspensionBehaviorCoalesce);
    });
#endif

    auto locker = holdLock(preferredLanguagesMutex);
    Vector<String>& userPreferredLanguages = preferredLanguages();

    if (userPreferredLanguages.isEmpty()) {
        RetainPtr<CFArrayRef> languages = adoptCF(CFLocaleCopyPreferredLanguages());
        languages = minimizedLanguagesFromLanguages(languages.get());
        CFIndex languageCount = CFArrayGetCount(languages.get());
        if (!languageCount)
            userPreferredLanguages.append("en");
        else {
            for (CFIndex i = 0; i < languageCount; i++)
                userPreferredLanguages.append(httpStyleLanguageCode(static_cast<CFStringRef>(CFArrayGetValueAtIndex(languages.get(), i))));
        }
    }

    Vector<String> userPreferredLanguagesCopy;
    userPreferredLanguagesCopy.reserveInitialCapacity(userPreferredLanguages.size());

    for (auto& language : userPreferredLanguages)
        userPreferredLanguagesCopy.uncheckedAppend(language.isolatedCopy());

    return userPreferredLanguagesCopy;

    return Vector<String>();
}

} // namespace WTF