# Internationalization

### Support for multiple languages

Doxygen has built-in support for multiple languages. This means that the text fragments, generated by doxygen, can be produced in languages other than English (the default). The output language is chosen through the configuration file (with default name and known as Doxyfile).

Currently (version 1.4.1), 30 languages are supported (sorted alphabetically): Afrikaans, Brazilian Portuguese, Catalan, Chinese, Chinese Traditional, Croatian, Czech, Danish, Dutch, English, Finnish, French, German, Greek, Hungarian, Italian, Japanese (+En), Korean (+En), Lithuanian, Norwegian, Polish, Portuguese, Romanian, Russian, Serbian, Slovak, Slovene, Spanish, Swedish, and Ukrainian..

The table of information related to the supported languages follows. It is sorted by language alphabetically. The Status column was generated from sources and shows approximately the last version when the translator was updated.

Language | Maintainer | Contact address (replace the at and dot) | Status
Afrikaans | Johan Prinsloo | johan at zippysnoek dot com | 1.3.9
Brazilian Portuguese | Fabio "FJTC" Jun Takada Chino | jun-chino at uol dot com dot br | up-to-date
Catalan | Albert Mora | amora at iua dot upf dot es | 1.2.17
Chinese | Li Daobing Wei Liu | lidaobing at gmail dot com liuwei at asiainfo dot com | up-to-date
Chinese Traditional | Daniel YC Lin Gary Lee | daniel at twpda dot com garylee at ecosine dot com dot tw | 1.3.8
Croatian | Boris Bralo | boris.bralo at zg dot htnet dot hr | up-to-date
Czech | Petr Přikryl | prikrylp at skil dot cz | up-to-date
Danish | Erik Søe Sørensen | eriksoe+doxygen at daimi dot au dot dk | 1.3.9
Dutch | Dimitri van Heesch | dimitri at stack dot nl | up-to-date
English | Dimitri van Heesch | dimitri at stack dot nl | up-to-date
Finnish | Olli Korhonen | olli.korhonen lost at cyberspace | obsolete
French | Xavier Outhier | xouthier at yahoo dot fr | up-to-date
German | Jens Seidel | jensseidel at users dot sf dot net | up-to-date
Greek | Harry Kalogirou | harkal at rainbow dot cs dot unipi dot gr | 1.2.11
Hungarian | Földvári György Ákos Kiss | foldvari lost at cyberspace akiss at users dot sourceforge dot net | up-to-date
Italian | Alessandro Falappa Ahmed Aldo Faisal | alessandro at falappa dot net aaf23 at cam dot ac dot uk | up-to-date
Japanese | Ryunosuke Satoh Kenji Nagamatsu Iwasa Kazmi | sun594 at hotmail dot com naga at joyful dot club dot ne dot jp iwasa at cosmo-system dot jp | 1.3.9
JapaneseEn | see the Japanese language |  | English based
Korean | SooYoung Jung Richard Kim | jung5000 at gmail dot com ryk at dspwiz dot com | up-to-date
KoreanEn | see the Korean language |  | English based
Lithuanian | Tomas Simonaitis Mindaugas Radzius Aidas Berukstis | haden at homelan dot lt mindaugasradzius at takas dot lt aidasber at takas dot lt | 1.3.8
Norwegian | Lars Erik Jordet | lejordet at gmail dot com | 1.3.9
Polish | Piotr Kaminski Grzegorz Kowal | Piotr.Kaminski at ctm dot gdynia dot pl g_kowal at poczta dot onet dot pl | up-to-date
Portuguese | Rui Godinho Lopes | ruiglopes at yahoo dot com | 1.3.3
Romanian | Alexandru Iosup | aiosup at yahoo dot com | 1.2.16
Russian | Alexandr Chelpanov | cav at cryptopro dot ru | up-to-date
Serbian | Dejan Milosavljevic | dmilos at email dot com | up-to-date
Slovak | Stanislav Kudláč | skudlac at pobox dot sk | 1.2.18
Slovene | Matjaž Ostroveršnik | matjaz.ostroversnik at ztm dot si | 1.2.16
Spanish | Francisco Oltra Thennet | foltra at puc dot cl | 1.3.8
Swedish | Mikael Hallin | mikaelhallin at yahoo dot se | up-to-date
Ukrainian | Olexij Tkatchenko | olexij.tkatchenko at parcs dot de | 1.2.11

Most people on the list have indicated that they were also busy doing other things, so if you want to help to speed things up please let them (or me) know.

If you want to add support for a language that is not yet listed please read the next section.

### Adding a new language to doxygen

This short HOWTO explains how to add support for the new language to Doxygen:

Just follow these steps:

1. Tell me for which language you want to add support. If no one else is already working on support for that language, you will be assigned as the maintainer for the language.
2. Create a copy of translator_en.h and name it translator_<your_2_letter_country_code>.h I'll use xx in the rest of this document.
3. Add definition of the symbol for your language into lang_cfg.h:

       #define LANG_xx

   Use capital letters for your `xx` (to be consistent). The `lang_cfg.h` defines which language translators will be compiled into doxygen executable. It is a kind of configuration file. If you are sure that you do not need some of the languages, you can remove (comment out) definitions of symbols for the languages, or you can say `#undef` instead of `#define` for them.
4. Edit language.cpp: Add a

       #ifdef LANG_xx
       #include<translator_xx.h>
       #endif

   Remember to use the same symbol LANG_xx that you added to `lang_cfg.h`. I.e., the `xx` should be capital letters that identify your language. On the other hand, the `xx` inside your `translator_xx.h` should use lower case.

   Now, in `setTranslator()` add

       #ifdef LANG_xx
           else if (L_EQUAL("your_language_name"))
           {
             theTranslator = new TranslatorYourLanguage;
           }
       #endif

   after the `if { ... }`. I.e., it must be placed after the code for creating the English translator at the beginning, and before the `else { ... }` part that creates the translator for the default language (English again).
5. Edit libdoxygen.pro.in and add `translator_xx.h` to the `HEADERS` line.
6. Edit `translator_xx.h`:
   - Rename `TRANSLATOR_EN_H` to `TRANSLATOR_XX_H` twice (i.e. in the `#ifndef` and `#define` preprocessor commands at the beginning of the file).
   - Rename TranslatorEnglish to TranslatorYourLanguage
   - In the member `idLanguage()` change "english" into the name of your language (use lower case characters only). Depending on the language you may also wish to change the member functions latexLanguageSupportCommand(), idLanguageCharset() and others (you will recognize them when you start the work).
   - Edit all the strings that are returned by the member functions that start with tr. Try to match punctuation and capitals! To enter special characters (with accents) you can:
     - Enter them directly if your keyboard supports that and you are using a Latin-1 font. Doxygen will translate the characters to proper and leave the HTML and man output for what it is (which is fine, if idLanguageCharset() is set correctly).
     - Use html codes like &auml; for an a with an umlaut (i.e. ä). See the HTML specification for the codes.
7. Run configure and make again from the root of the distribution, in order to regenerated the Makefiles.
8. Now you can use `OUTPUT_LANGUAGE = your_language_name` in the config file to generate output in your language.
9. Send `translator_xx.h` to me so I can add it to doxygen. Send also your name and e-mail address to be included in the `maintainers.txt` list.

### Maintaining a language

New versions of doxygen may use new translated sentences. In such situation, the `Translator` class requires implementation of new methods -- its interface changes. Of course, the English sentences need to be translated to the other languages. At least, new methods have to be implemented by the language-related translator class; otherwise, doxygen wouldn't even compile. Waiting until all language maintainers have translated the new sentences and sent the results would not be very practical. The following text describes the usage of translator adapters to solve the problem.

The role of Translator Adapters. Whenever the `Translator` class interface changes in the new release, the new class `TranslatorAdapter_x_y_z` is added to the `translator_adapter.h` file (here x, y, and z are numbers that correspond to the current official version of doxygen). All translators that previously derived from the `Translator` class now derive from this adapter class.

The `TranslatorAdapter_x_y_z` class implements the new, required methods. If the new method replaces some similar but obsolete method(s) (e.g. if the number of arguments changed and/or the functionality of the older method was changed or enriched), the `TranslatorAdapter_x_y_z` class may use the obsolete method to get the result which is as close as possible to the older result in the target language. If it is not possible, the result (the default translation) is obtained using the English translator, which is (by definition) always up-to-date.

For example, when the new `trFile()` method with parameters (to determine the capitalization of the first letter and the singular/plural form) was introduced to replace the older method `trFiles()` without arguments, the following code appeared in one of the translator adapter classes:

        /*! This is the default implementation of the obsolete method
         * used in the documentation of a group before the list of
         * links to documented files.  This is possibly localized.
         */
        virtual QCString trFiles()
        { return "Files"; }

        /*! This is the localized implementation of newer equivalent
         * using the obsolete method trFiles().
         */
        virtual QCString trFile(bool first_capital, bool singular)
        {
          if (first_capital && !singular)
            return trFiles();  // possibly localized, obsolete method
          else
            return english.trFile(first_capital, singular);
        }

The `trFiles()` is not present in the `TranslatorEnglish` class, because it was removed as obsolete. However, it was used until now and its call was replaced by

        trFile(true, false)

in the doxygen source files. Probably, many language translators implemented the obsolete method, so it perfectly makes sense to use the same language dependent result in those cases. The `TranslatorEnglish` does not implement the old method. It derives from the abstract `Translator` class. On the other hand, the old translator for a different language does not implement the new `trFile()` method. Because of that it is derived from another base class -- `TranslatorAdapter_x_y_z`. The `TranslatorAdapter_x_y_z` class have to implement the new, required `trFile()` method. However, the translator adapter would not be compiled if the `trFiles()` method was not implemented. This is the reason for implementing the old method in the translator adapter class (using the same code, that was removed from the TranslatorEnglish).

The simplest way would be to pass the arguments to the English translator and to return its result. Instead, the adapter uses the old `trFiles()` in one special case -- when the new `trFile(true, false)` is called. This is the mostly used case at the time of introducing the new method -- see above. While this may look too complicated, the technique allows the developers of the core sources to change the Translator interface, while the users may not even notice the change. Of course, when the new `trFile()` is used with different arguments, the English result is returned and it will be noticed by non English users. Here the maintainer of the language translator should implement at least that one particular method.

What says the base class of a language translator? If the language translator class inherits from any adapter class the maintenance is needed. In such case, the language translator is not considered up-to-date. On the other hand, if the language translator derives directly from the abstract class `Translator`, the language translator is up-to-date.

The translator adapter classes are chained so that the older translator adapter class uses the one-step-newer translator adapter as the base class. The newer adapter does less adapting work than the older one. The oldest adapter class derives (indirectly) from all of the adapter classes. The name of the adapter class is chosen so that its suffix is derived from the previous official version of doxygen that did not need the adapter. This way, one can say approximately, when the language translator class was last updated -- see details below.

The newest translator adapter derives from the abstract `TranslatorAdapterBase` class that derives directly from the abstract `Translator` class. It adds only the private English-translator member for easy implementation of the default translation inside the adapter classes, and it also enforces implementation of one method for noticing the user that the language translation is not up-to-date (because of that some sentences in the generated files may appear in English).

Once the oldest adapter class is not used by any of the language translators, it can be removed from the doxygen project. The maintainers should try to reach the state with the minimal number of translator adapter classes.

To simplify the maintenance of the language translator classes for the supported languages, the `translator.py` Python script was developed (located in `doxygen/doc` directory). It extracts the important information about obsolete and new methods from the source files for each of the languages. The information is stored in the translator report ASCII file (translator_report.txt). If you compiled this documentation from sources and if you have also doxygen sources available the link `doxygen/doc/translator_report.txt` should be valid.

Looking at the base class of the language translator, the script guesses also the status of the translator -- see the last column of the table with languages above. The `translator.py` is called automatically when the doxygen documentation is generated. You can also run the script manualy whenever you feel that it can help you. Of course, you are not forced to use the results of the script. You can find the same information by looking at the adapter class and its base classes.

How should I update my language translator? Firstly, you should be the language maintainer, or you should let him/her know about the changes. The following text was written for the language maintainers as the primary audience.

There are several approaches to be taken when updating your language. If you are not extremely busy, you should always chose the most radical one. When the update takes much more time than you expected, you can always decide use some suitable translator adapter to finish the changes later and still make your translator working.

The most radical way of updating the language translator is to make your translator class derive directly from the abstract class `Translator` and provide translations for the methods that are required to be implemented -- the compiler will tell you if you forgot to implement some of them. If you are in doubt, have a look at the `TranslatorEnglish` class to recognize the purpose of the implemented method. Looking at the previously used adapter class may help you sometimes, but it can also be misleading because the adapter classes do implement also the obsolete methods (see the previous `trFiles()` example).

In other words, the up-to-date language translators do not need the `TranslatorAdapter_x_y_z` classes at all, and you do not need to implement anything else than the methods required by the Translator class (i.e. the pure virtual methods of the `Translator` -- they end with `=0;`).

If everything compiles fine, try to run `translator.py`, and have a look at the translator report (ASCII file) at the `doxygen/doc` directory. Even if your translator is marked as up-to-date, there still may be some remarks related to your souce code. Namely, the obsolete methods--that are not used at all--may be listed in the section for your language. Simply, remove their code (and run the `translator.py` again). Also, you will be informed when you forgot to change the base class of your translator class to some newer adapter class or directly to the Translator class.

If you do not have time to finish all the updates you should still start with the most radical approach as described above. You can always change the base class to the translator adapter class that implements all of the not-yet-implemented methods.

If you prefer to update your translator gradually, have a look at `TranslatorEnglish` (the `translator_en.h` file). Inside, you will find the comments like `new since 1.2.4` that separate always a number of methods that were implemented in the stated version. Do implement the group of methods that are placed below the comment that uses the same version numbers as your translator adapter class. (For example, your translator class have to use the `TranslatorAdapter_1_2_4`, if it does not implement the methods below the comment `new since 1.2.4`. When you implement them, your class should use newer translator adapter.

Run the `translator.py` script occasionaly and give it your `xx` identification (from `translator_xx.h`) to create the translator report shorter (also produced faster) -- it will contain only the information related to your translator. Once you reach the state when the base class should be changed to some newer adapter, you will see the note in the translator report.

Warning: Don't forget to compile Doxygen to discover, whether it is compilable. The `translator.py` does not check if everything is correct with respect to the compiler. Because of that, it may lie sometimes about the necessary base class.

The most obsolete language translators would lead to implementation of too complicated adapters. Because of that, doxygen developers may decide to derive such translators from the `TranslatorEnglish` class, which is by definition always up-to-date.

When doing so, all the missing methods will be replaced by the English translation. This means that not-implemented methods will always return the English result. Such translators are marked using word `obsolete`. You should read it really obsolete. No guess about the last update can be done.

Often, it is possible to construct better result from the obsolete methods. Because of that, the translator adapter classes should be used if possible. On the other hand, implementation of adapters for really obsolete translators brings too much maintenance and run-time overhead.