[[!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](http://po4a.alioth.debian.org/).
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' => 'Castellano',
'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.
This is the default Debian Apache configuration.
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`.
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.
One typically adds the following code to `templates/page.tmpl`:
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.
One can use it this way:
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 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
========
[[./security]] 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 thise additional features.
Robustness tests
----------------
### Enabling/disabling the plugin
* enabling the plugin with `po_translatable_pages` set to blacklist: **OK**
* enabling the plugin with `po_translatable_pages` set to whitelist: **OK**
* enabling the plugin without `po_translatable_pages` set: **OK**
* disabling the plugin: **OK**
### Changing the plugin config
* adding existing pages to `po_translatable_pages`: **OK**
* removing existing pages from `po_translatable_pages`: **OK**
* adding a language to `po_slave_languages`: **OK**
* removing a language from `po_slave_languages`: **OK**
* changing `po_master_language`: **OK**
* replacing `po_master_language` with a language previously part of
`po_slave_languages`: needs two rebuilds, but **OK** (this is quite
a perverse test actually)
### Creating/deleting/renaming pages
All cases of master/slave page creation/deletion/rename, both via RCS
and via CGI, have been tested.
### Misc
* general test with `usedirs` disabled: **OK**
* general test with `indexpages` enabled: **not OK**
* general test with `po_link_to=default` with `userdirs` enabled: **OK**
* general test with `po_link_to=default` with `userdirs` disabled: **OK**
Misc. bugs
----------
Documentation
-------------
Maybe write separate documentation depending on the people it targets:
translators, wiki administrators, hackers. This plugin may be complex
enough to deserve this.