Petal::I18N(3) Attempt at implementing ZPT I18N for Petal

SYNOPSIS

in your Perl code:


use Petal;
use Petal::TranslationService::Gettext;
my $translation_service = new Petal::TranslationService::Gettext (
locale_dir => '/path/to/my/app/locale',
target_lang => gimme_target_lang(),
);
my $template = new Petal (
file => 'example.html',
translation_service => $translation_service
);
# we want to internationalize to the h4x0rz 31337 l4nGu4g3z. w00t!
my $translation_service = Petal::TranslationService::h4x0r->new();
my $template = new Petal (
file => 'silly_example.xhtml',
translation_service => $ts,
);
print $template->process ();

I18N Howto

Preparing your templates:

Say your un-internationalized template looks like this: 

  <html xmlns:tal="http://purl.org/petal/1.0/">
    <body>
      <img src="/images/my_logo.png"
           alt="the logo of our organisation" />
      <p>Hello,
         <span petal:content="user_name">Joe</span>.</p>
      <p>How are you today?</p>
    </body>
  </html>

You need to markup your template according to the ZPT I18N specification, which can be found at http://dev.zope.org/Wikis/DevSite/Projects/ComponentArchitecture/ZPTInternationalizationSupport 

  <html xmlns:tal="http://purl.org/petal/1.0/"
        xmlns:i18n="http://xml.zope.org/namespaces/i18n"
        i18n:domain="my_app">
    <body>
      <img src="/images/my_logo.png"
           alt="the logo of our organisation"
           i18n:attributes="alt" />
      <p i18n:translate="">Hello, <span petal:content="user_name">Joe</span>.</p>
      <p i18n:translate="">How are you today?</p>
    </body>
  </html>

Extracting I18N strings:

Once your templates are marked up properly, you will need to use a tool to extract the I18N strings into .pot (po template) files. To my knowledge you can use i18ndude (standalone python executable), i18nextract.py (part of Zope 3), or I18NFool.

I use i18ndude to find strings which are not marked up properly with i18n:translate attributes and I18NFool for extracting strings and managing .po files.

Assuming you're using i18nfool: 

  mkdir -p /path/to/my/app/locale
  cd /path/to/my/app/locale
  i18nfool-extract /path/to/my/template/example.html
  mkdir en
  mkdir fr
  mkdir es
  i18nfool-update

Then you translate the .po files into their respective target languages. When that's done, you type: 

  cd /path/to/my/app/locale
  i18nfool-build

And it builds all the .mo files.

Making your application use a Gettext translation service:

Previously you might have had: 

  use Petal;
  # lotsa code here
  my $template = Petal->new ('example.html');

This needs to become: 

  use Petal;
  use Petal::TranslationService::Gettext;
  # lotsa code here
  my $template = Petal->new ('example.html');
  $template->{translation_service} = Petal::TranslationService::Gettext->new (
      locale_dir  => '/path/to/my/app/locale',
      target_lang => gimme_language_code(),
  );

Where gimme_language_code() returns a language code depending on LC_LANG, content-negotiation, config-file, or whatever mechanism you are using to decide which language is desired.

And then?

And then that's it! Your application should be easily internationalizable. There are a few traps / gotchas thought, which are described below.

BUGS, TRAPS, GOTCHAS and other niceties

Translation Phase

The translation step takes place ONLY ONCE THE TEMPLATE HAS BEEN PROCESSED.

So if you have: 

  <p i18n:translate="">Hello,
    <span i18n:name="user_login" tal:replace="self/user_login">Joe</span>
  </p>

It most likely will not work because the tal:replace would remove the <span> tag and also the i18n:name in the process.

This means that instead of receiving something such as: 

  Hello, ${user_login}

The translation service would receive: 

  Hello, Fred Flintstone

Or 

  Hello, Joe SixPack

etc.

To fix this issue, use tal:content instead of tal:replace and leave the span and its i18n:name attribute.

Character sets

I haven't worried too much about them (yet) so if you run into trouble join the Petal mailing list and we'll try to fix any issues together.

Limitations

At the moment, Petal::I18N supports the following constructs:
xmlns:i18n="http://xml.zope.org/namespaces/i18n"
i18n:translate
i18n:domain
i18n:name
i18n:attribute

It does *NOT* (well, not yet) support i18n:source, i18n:target or i18n:data.

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