callback_filter_process $langcode parameter is always "und"

@jhodgdon,
did you test whether your answer makes sense on an actual multilingual site?

I am writing a filter for a multilingual site that needs to do different things depending on the language of the text filtered. In my callback, I check the $langcode variable to discover the language of the text. However. if the node is tagged with "es" (for Spanish), the $langcode passed into the callback is not "es", but "und" for undefined. I know how to use this $langcode in the callback for my filter, provided it has the correct value. This is not why I reported this incomplete documentation.

I reported this documentation as incomplete because it does not tell you how to get the correct value passed into the callback. In your reply, you just repeat what the existing documentation say (set up a multilingual site, and make sure your nodes are tagged with language codes that indicate what language the text is). However, if one acts on this documentation, one discovers that this not how it actually works. Hence, the documentation is wrong or incomplete.

That is why I report this as documentation problem.

Please do not think this is as programming support. The problem is not with programming, but with the documentation not telling you how to set up the use of this callback function on a multilingual site to get sensible values passed into the callback through the $langcode parameter.

I don't think this documentation is "fixed".

Changing the category to "Bug report" since the choice of the category "Support request" clearly caused a misunderstanding. And to avoid further misunderstanding: The "bug" reported here is in the documentation, because the documentation does not explain how a developer of a multilingual site can set up the callback to get a useable value passed into the callback by means of the $langcode parameter.