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[css3-fonts] language system used when language is unknown

From: John Daggett <jdaggett@mozilla.com>
Date: Tue, 5 Feb 2013 10:33:48 -0800 (PST)
To: www-style list <www-style@w3.org>
Message-ID: <1280987544.502809.1360089228221.JavaMail.root@mozilla.com>

There's currently an issue in the CSS3 Fonts spec related to the
OpenType language system used when rendering text in situations where
the HTML lang tag has not been set.  The HTML5 spec says that if the
lang tag hasn't been set then "it must be interpreted as meaning that
the language of the node is explicitly unknown". [1]

The issue, listed in section 6.2 [2], is whether user agents must use
the default language system or whether they can infer based on a
heuristic the language system in certain contexts.  For example, for
some scripts it might be possible to infer the language system.

I propose allowing UA's the option of using heuristics to infer the
language system in these cases:

  When the language of an element is unknown, user agents
  may either use the default language system or infer one
  based on other heuristics if appropriate.

Note that the language system determines whether language-specific
features are applied.  If an author does specify the language then
none of these heuristics would apply.


John Daggett

[1] http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#the-lang-and-xml:lang-attributes
[2] http://dev.w3.org/csswg/css3-fonts/#language-specific-support
Received on Tuesday, 5 February 2013 18:34:11 UTC

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