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Demo how to use localization (translate your game into multiple languages) with Castle Game Engine.

We use CastleLocalizationGetText, based on FPC GetText unit, for this. See CGE manual about text and localization: .

Creating translations

  1. To translate strings used in Pascal code:

    1. Place strings in resourcestring. You can use English text in code, or you can use internal translation identifiers (never to be seen by normal users) -- both approaches are possible.

    2. Create initial game.pot file (that describes the possible strings to translate).

      Note that this step is optional. If you want, you can work without any game.pot file, and just create translations by manually creating files like for each language. The syntax of PO files is trivial, see po_files subdirectory here.

      The game.pot can serve a basis for translations. You can create it using strings from the source code:

      • Compile the game (castle-engine compile).

      • Use rstconv (distributed with FPC) like this: rstconv -i castle-engine-output/compilation/x86_64-linux/game.rsj -o po_files/game.pot

      • Note that FPC will create one xxx.rsj file for each unit. But this should not limit you. It's normal to put all the strings from the complete application into a single xxx.pot file. In general, the format of the .pot and .po` files (they are the same) is trivial, they are simple text files that can be concatenated together etc.

  2. To translate user interface:

    1. Design it using the CGE editor, and write as xxx.castle-user-interface files. (More complex scenarios can also be handled using CastleLocalizationGetText utilities, like TranslateDesign.)

    2. Generate the user_interface.pot file using GenerateGetTextPo. See the trivial utility inside po_files/generator/po_generator.lpr in this example.

  3. Then translate the PO files.

    • For each xxxx.pot, you create a file like xxxx.ll.po inserting the 2-latter character code indicating a language.

      You can create the .po file from .pot just by copying it -- it's the same file format, the .pot (PO Template) extension is just a way to indicate "this is a basis for translation".

      Or you can create the .po by calling msginit --locale=pl --input=game.pot --no-translator This creates, with the initial translated strings having contents from game.pot. This makes sense if game.pot contains English text, and it's a good starting point for a new translation.

    • E.g. you copy game.pot to to translate to Polish the resourcestrings, and you copy user_interface.pot to to translate to Polish the user interface designed using the CGE Editor. pl stands for a Polish translation, de for German, en for English etc.

    • Edit the using a normal text editor. Or use a specialized editor like

  4. Generate .mo file: msgfmt po_files/ --output-file=data/locale/ We have a trivial script here doing that. You need to rerun it after every modification to po_files.

Using translations from Pascal code

Translating resourcestrings

  • Call in Pascal CastleTranslateResourceStrings('castle-data:/locale/'); to use the Polish translation. This simply updates all resourcestring contents to the Polish versions.

  • Call TranslateAllDesigns('castle-data:/locale/'); to translate all user interface to Polish.

  • If needed, you can also translate custom things, using more PO files.

    Load them using LoadGetTextMo and use the Translate method, see FPC docs of TMOFile and the TMOFile.Translate method. Example:

  Language: String;
  Translations: TCastleMOFile;
  Language := 'pl';
  Translations := LoadGetTextMo('castle-data:/locale/game.' + Language + '.mo');
  Writeln('Translated: ', Translations.Translate('message identifier to translate'));


Note that we also adjust font in this application. The default font contains only basic ASCII (English) characters, so we load a font with additional German, Polish, Russian and Ukrainian characters. See about loading fonts in Castle Game Engine.

Lazarus references

While we don't use Lazarus LCL code in CGE, but this mechanism is consistent with how Lazarus application can be localized. So a lot of Lazarus documentation apply also to us:

See also resources about gettext:

All the tools and editors for gettext files should work fine. There are even online services that take a ready PO file for translating.

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