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diff --git a/doc/plugins/po.mdwn b/doc/plugins/po.mdwn new file mode 100644 index 000000000..ddd0f5870 --- /dev/null +++ b/doc/plugins/po.mdwn @@ -0,0 +1,258 @@ +[[!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`). + +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` + + +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 +-------------- + +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 +--------- + +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`: + + <TMPL_IF NAME="OTHERLANGUAGES"> + <div id="otherlanguages"> + <ul> + <TMPL_LOOP NAME="OTHERLANGUAGES"> + <li> + <a href="<TMPL_VAR NAME="URL">"><TMPL_VAR NAME="LANGUAGE"></a> + <TMPL_UNLESS NAME="MASTER"> + (<TMPL_VAR NAME="PERCENT"> %) + </TMPL_UNLESS> + </li> + </TMPL_LOOP> + </ul> + </div> + </TMPL_IF> + +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: + + <TMPL_IF NAME="ISTRANSLATION"> + <div id="percenttranslated"> + <TMPL_VAR NAME="PERCENTTRANSLATED"> + </div> + </TMPL_IF> + +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 +---------------- + +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. + +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. + +TODO +==== + +Security checks +--------------- + +- Can any sort of directives be put in po files that will + cause mischief (ie, include other files, run commands, crash gettext, + whatever). +- Any security issues on running po4a on untrusted content? + +gettext/po4a rough corners +-------------------------- + +- fix infinite loop when synchronizing two ikiwiki (when checkouts + live in different directories): say bla.fr.po has been updated in + repo2; pulling repo2 from repo1 seems to trigger a PO update, that + changes bla.fr.po in repo1; then pushing repo1 to repo2 triggers + a PO update, that changes bla.fr.po in repo2; etc.; fixed in + `629968fc89bced6727981c0a1138072631751fee`? +- new translations created in the web interface must get proper + charset/encoding gettext metadata, else the next automatic PO update + removes any non-ascii chars; possible solution: put such metadata + into the Pot file, and let it propagate; should be fixed in + `773de05a7a1ee68d2bed173367cf5e716884945a`, time will tell. + +Misc. improvements +------------------ + +### page titles + +Use nice page titles from meta plugin in links, as inline already +does. This is actually a duplicate for +[[bugs/pagetitle_function_does_not_respect_meta_titles]], which might +be fixed by something like [[todo/using_meta_titles_for_parentlinks]]. + +Translation quality assurance +----------------------------- + +Modifying a PO file via the CGI must be forbidden if the new version +is not a valid PO file. As a bonus, check that it provides a more +complete translation than the existing one. + +A new `cansave` type of hook would be needed to implement this. + +Note: committing to the underlying repository is a way to bypass +this check. |