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[[!template id=plugin name=po core=0 author="[[intrigeri]]"]] [[!tag type/format]]

This plugin adds support for multi-lingual wikis, translated with gettext, using po4a.

It depends on the Perl Locale::Po4a::Po library (apt-get install po4a). As detailed bellow in the security section, po4a is subject to denial-of-service attacks before version 0.35.

[[!toc levels=2]]

Introduction

A language is chosen as the "master" one, and any other supported language is a "slave" one.

A page written in the "master" language is a "master" page. It can be of any page type supported by ikiwiki, except po. It does not have to be named a special way: migration to this plugin does not imply any page renaming work.

Example: bla/page.mdwn is a "master" Markdown page written in English; if usedirs is enabled, it is rendered as bla/page/index.en.html, else as bla/page.en.html.

Any translation of a "master" page into a "slave" language is called a "slave" page; it is written in the gettext PO format. po is now a page type supported by ikiwiki.

Example: bla/page.fr.po is the PO "message catalog" used to translate bla/page.mdwn into French; if usedirs is enabled, it is rendered as bla/page/index.fr.html, else as bla/page.fr.html

(In)Compatibility

This plugin does not support the indexpages mode. If you don't know what it is, you probably don't care.

Configuration

Supported languages

po_master_language is used to set the "master" language in ikiwiki.setup, such as:

    po_master_language => { 'code' => 'en', 'name' => 'English' }

po_slave_languages is used to set the list of supported "slave" languages, such as:

    po_slave_languages => { 'fr' => 'Français',
                            'es' => 'Español',
                            'de' => 'Deutsch',
    }

Decide which pages are translatable

The po_translatable_pages setting configures what pages are translatable. It is a [[ikiwiki/PageSpec]], so you have lots of control over what kind of pages are translatable.

The .po files are not considered as being translatable, so you don't need to worry about excluding them explicitly from this [[ikiwiki/PageSpec]].

Internal links

Links targets

The po_link_to option in ikiwiki.setup is used to decide how internal links should be generated, depending on web server features and site-specific preferences.

Default linking behavior

If po_link_to is unset, or set to default, ikiwiki's default linking behavior is preserved: \[[destpage]] links to the master language's page.

Link to current language

If po_link_to is set to current, \[[destpage]] links to the destpage's version written in the current page's language, if available, i.e.:

  • foo/destpage/index.LL.html if usedirs is enabled
  • foo/destpage.LL.html if usedirs is disabled

Link to negotiated language

If po_link_to is set to negotiated, \[[page]] links to the negotiated preferred language, i.e. foo/page/.

(In)compatibility notes:

  • if usedirs is disabled, it does not make sense to set po_link_to to negotiated; this option combination is neither implemented nor allowed.
  • if the web server does not support Content Negotiation, setting po_link_to to negotiated will produce a unusable website.

Server support

Apache

Using Apache mod_negotiation makes it really easy to have Apache serve any page in the client's preferred language, if available.

Add 'Options MultiViews' to the wiki directory's configuration in Apache.

When usedirs is enabled, one has to set DirectoryIndex index for the wiki context.

Setting DefaultLanguage LL (replace LL with your default MIME language code) for the wiki context can help to ensure bla/page/index.en.html is served as Content-Language: LL.

For details, see Apache's documentation.

lighttpd

lighttpd unfortunately does not support content negotiation.

FIXME: does mod_magnet provide the functionality needed to emulate this?

Usage

Templates

When po_link_to is not set to negotiated, one should replace some occurrences of BASEURL with HOMEPAGEURL to get correct links to the wiki homepage.

The ISTRANSLATION and ISTRANSLATABLE variables can be used to display things only on translatable or translation pages.

Display page's versions in other languages

The OTHERLANGUAGES loop provides ways to display other languages' versions of the same page, and the translations' status.

An example of its use can be found in the default templates/page.tmpl. In case you want to customize it, the following variables are available inside the loop (for every page in):

  • URL - url to the page
  • CODE - two-letters language code
  • LANGUAGE - language name (as defined in po_slave_languages)
  • MASTER - is true (1) if, and only if the page is a "master" page
  • PERCENT - for "slave" pages, is set to the translation completeness, in percents

Display the current translation status

The PERCENTTRANSLATED variable is set to the translation completeness, expressed in percent, on "slave" pages. It is used by the default templates/page.tmpl.

Additional PageSpec tests

This plugin enhances the regular [[ikiwiki/PageSpec]] syntax with some additional tests that are documented [[here|ikiwiki/pagespec/po]].

Automatic PO file update

Committing changes to a "master" page:

  1. updates the POT file and the PO files for the "slave" languages; the updated PO files are then put under version control;
  2. triggers a refresh of the corresponding HTML slave pages.

Also, when the plugin has just been enabled, or when a page has just been declared as being translatable, the needed POT and PO files are created, and the PO files are checked into version control.

Discussion pages and other sub-pages

Discussion should happen in the language in which the pages are written for real, i.e. the "master" one. If discussion pages are enabled, "slave" pages therefore link to the "master" page's discussion page.

Likewise, "slave" pages are not supposed to have sub-pages; [[WikiLinks|wikilink]] that appear on a "slave" page therefore link to the master page's sub-pages.

Translating

One can edit the PO files using ikiwiki's CGI (a message-by-message interface could also be implemented at some point).

If [[tips/untrusted_git_push]] is setup, one can edit the PO files in one's preferred $EDITOR, without needing to be online.

Markup languages support

[[Markdown|mdwn]] is well supported. Some other markup languages supported by ikiwiki mostly work, but some pieces of syntax are not rendered correctly on the slave pages:

  • [[reStructuredText|rst]]: anonymous hyperlinks and internal cross-references
  • [[wikitext]]: conversion of newlines to paragraphs
  • [[creole]]: verbatim text is wrapped, tables are broken
  • [[html]] and LaTeX: not supported yet; the dedicated po4a modules could be used to support them, but they would need a security audit
  • other markup languages have not been tested.

Security

[[po/discussion]] contains a detailed security analysis of this plugin and its dependencies.

When using po4a older than 0.35, it is recommended to uninstall Text::WrapI18N (Debian package libtext-wrapi18n-perl), in order to avoid a potential denial of service.

TODO

Better links

Once the fix to [[bugs/pagetitle_function_does_not_respect_meta_titles]] from [[intrigeri]]'s meta branch is merged into ikiwiki upstream, the generated links' text will be optionally based on the page titles set with the [[meta|plugins/meta]] plugin, and will thus be translatable. It will also allow displaying the translation status in links to slave pages. Both were implemented, and reverted in commit ea753782b222bf4ba2fb4683b6363afdd9055b64, which should be reverted once [[intrigeri]]'s meta branch is merged.

An integration branch, called meta-po, merges [[intrigeri]]'s po and meta branches, and thus has this additional features.

Language display order

Jonas pointed out that one might want to control the order that links to other languages are listed, for various reasons. Currently, there is no order, as po_slave_languages is a hash. It would need to be converted to an array to support this. (If twere done, twere best done quickly.) --[[Joey]]

Pagespecs

I was suprised that, when using the map directive, a pagespec of "*" listed all the translated pages as well as regular pages. That can make a big difference to an existing wiki when po is turned on, and seems generally not wanted. (OTOH, you do want to match translated pages by default when locking pages.) --[[Joey]]

Edit links on untranslated pages

If a page is not translated yet, the "translated" version of it displays wikilinks to other, existing (but not yet translated?) pages as edit links, as if those pages do not exist.

That's really confusing, especially as clicking such a link brings up an edit form to create a new, english page.

This is with po_link_to=current or negotiated. With default, it doesn't happen..

Also, this may only happen if the page being linked to is coming from an underlay, and the underlays lack translation to a given language. --[[Joey]]

Double commits of po files

When adding a new english page, the po files are created, committed, and then committed again. The second commit makes this change:

-"Content-Type: text/plain; charset=utf-8\n"
-"Content-Transfer-Encoding: ENCODING"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: ENCODING\n"

Same thing happens when a change to an existing page triggers a po file update. --[[Joey]]

Ugly messages with empty files

If there are empty .mdwn files, the po plugin displays some ugly messages.

Translation of directives

If a translated page contains a directive, it may expand to some english text, or text in whatever single language ikiwiki is configured to "speak".

Maybe there could be a way to switch ikiwiki to speaking another language when building a non-english page? Then the directives would get translated.

(We also will need this in order to use translated templates, when they are available.)

Documentation

Maybe write separate documentation depending on the people it targets: translators, wiki administrators, hackers. This plugin may be complex enough to deserve this.