Here is a patch for the [[plugins/meta]] plugin. It adds the possibility to define the language 
used for a page, with \[[!meta lang="ja"]]

It doesn't insert the langage information in the xhtml meta elements, but defines a LANG
variable to use in the templates, for example with

    <html xmlns="http://www.w3.org/1999/xhtml"
          lang="<TMPL_IF NAME="LANG"><TMPL_VAR LANG><TMPL_ELSE>fr</TMPL_IF>"
          xml:lang="<TMPL_IF NAME="LANG"><TMPL_VAR LANG><TMPL_ELSE>fr</TMPL_IF>">

This way also allows to define a language for a subset of the final page, with custom
templates and inclusion. 

This may be useful for sites with a few pages in different languages, but no full i18n.

> Looks good, but the need to modify the template and include a default
> language in it is a bit problimatic, I think. --[[Joey]]

>> --lang=XX could be a setup option, with a default value, then the template would be 

                <html xmlns="http://www.w3.org/1999/xhtml" lang="<TMPL_VAR LANG>" xml:lang="<TMPL_VAR LANG>">

>>> Yes, that seems reasonable. I guess there's no problem with defaulting
>>> to en if it can be overridden in the setup. --[[Joey]]

>>>> Yes, english default makes sense. I guess we should use the `$config{lang}`, 
>>>> defined from the setup file or command-line options to define the default language
>>>> (`$config{lang}` defaults to `en` which is fine) if the html pages, and override
>>>> it from the `meta` directive.
>>>> — [[NicolasLimare]]

>>>>> ikiwiki already has a $config{locale}, which is a full locale (ie,
>>>>> "en_US.UTF-8". This just needs to be parsed for the lang. --[[Joey]]

>>>>>> My mistake, I meant $config{locale} --[[NicolasLimare]]

> So the patch below could be changed to parse `$config{locale}` for the
> language, and pass it if no specific lang was set for the page. The only
> problem with that would be that this is all done inside the meta plugin,
> so if that plugin were disabled, the lang would be empty. To avoid that,
> I guess that the template needs to look like:

    <html xmlns="http://www.w3.org/1999/xhtml"
          <TMPL_IF NAME="LANG">lang="<TMPL_VAR LANG>" xml:lang="<TMPL_VAR LANG>"</TMPL_IF>>

> Now it just needs to be finished up.. --[[Joey]]

<pre>
--- meta.orig.pm  2007-07-27 00:19:51.000000000 +0200
+++ meta.pm       2007-08-05 22:37:40.000000000 +0200
@@ -11,6 +11,7 @@
 my %permalink;
 my %author;
 my %authorurl;
+my %lang;
 
 sub import {
        hook(type => "preprocess", id => "meta", call => \&preprocess, scan => 1);
@@ -100,6 +101,11 @@
                $meta{$page}.='<link href="'.encode_entities($value).
                        "\" rel=\"openid.delegate\" />\n";
        }
+       elsif ($key eq 'lang') {
+           if ($value =~ /^[A-Za-z]{2}$/) {
+               $lang{$page}=$value;
+           }
+       }
        else {
                $meta{$page}.=scrub("<meta name=\"".encode_entities($key).
                        "\" content=\"".encode_entities($value)."\" />\n");
@@ -131,6 +137,8 @@
                if exists $author{$page} && $template->query(name => "author");
        $template->param(authorurl => $authorurl{$page})
                if exists $authorurl{$page} && $template->query(name => "authorurl");
+       $template->param(lang => $lang{$page})
+               if exists $lang{$page} && $template->query(name => "lang");
 
 }
</pre>

> Please resolve lang somewhere reusable rather than within meta plugin: It is certainly usable outside
> the scope of the meta plugin as well. --[[JonasSmedegaard]]

>> I don't see any problem with having this in meta? meta is on by default, and
>> other plugins are free to use it or even depend on it (e.g. inline does).
>>
>> My only comments on this patch beyond what Joey said are that the page
>> language could usefully go into `$pagestate{$page}{meta}{lang}` for other
>> plugins to be able to see it (is that what you meant?), and that
>> restricting to 2 characters is too restrictive (HTML 4.01 mentions
>> `en`, `en-US` and `i-navajo` as possible language codes).
>> This slightly complicates parsing the locale to get the default language:
>> it'll need `tr/_/-/` after the optional `.encoding` is removed.
>> --[[smcv]]

>>> Now that po has been merged, this patch should probably also be adapted
>>> so that the po plugin forces the meta::lang of every page to what po
>>> thinks it should be. --[[smcv]]

>>>> Agreed, users of the po plugin would greatly benefit from it.
>>>> Seems doable. --[[intrigeri]]

>>> Perhaps [[the_special_po_pagespecs|ikiwiki/pagespec/po]] should
>>> also work with meta-assigned languages? --[[smcv]]

>>>> Yes. But then, these special pagespecs should be moved outside of
>>>> [[plugins/po]], as they could be useful to anyone using the
>>>> currently discussed patch even when not using the po plugin.
>>>> 
>>>> We could add these pagespecs to the core and make them use
>>>> a simple language-guessing system based on a new hook. Any plugin
>>>> that implements such a hook could decide whether it should
>>>> overrides the language guessed by another one, and optionally use
>>>> the `first`/`last` options (e.g. the po plugin will want to be
>>>> authoritative on the pages of type po, and will then use
>>>> `last`). --[[intrigeri]]

[[!tag wishlist patch plugins/meta translation]]
