[Fontconfig] FontConfig iso15924 tag for autoinstallation via PackageKit

Behdad Esfahbod behdad at behdad.org
Thu May 8 14:34:25 PDT 2014

On 14-04-30 03:45 AM, Frédéric WANG wrote:
> Dear FontConfig & PackageKit developers,
> I've recently worked on automatic font installation in Gecko-based
> applications using PackageKit [1]. The current patch to add notifications for
> missing glyphs in Gecko relies on script tags as defined in iso15924 [2] [3].

The problem with choosing fonts based on script tags is that it doesn't work.

Really.  Find me a font that supports script=Arab.  I don't think you can find
any font right now that supports **all** Unicode characters for Arabic
scripts.  If you did, it probably would be a junk font like GNU Unifont or
some other "quantity-over-quality" font that should be buried.

Fonts can only be meaningfully chosen per language tag, not script tag.

Fix your design.  You should resolve to a language tag given the script and
any hinted languages (HTML tags, etc).  Pango has code for that, and it's easy
to replicate.  I'd be happy to elaborate if you care.


> So it would help if fontconfig & PackageKit would be able to handle some
> metadata for these script tags, for example :script=Khmr (at the moment I
> think only the :lang tag is supported). Also, I'm interested in automatic
> installation of math fonts, so it would be important to support the code
> "Zmth=Mathematical notation" too. This script does not correspond to any
> Unicode script, but you can find some relevant ranges in
> http://www.w3.org/TR/xml-entity-names/#blocks (especially the Mathematical
> Alphanumeric Symbols are important and are required for [4])
> Thanks,
> [1] https://bugzilla.mozilla.org/show_bug.cgi?id=467729
> [2] http://www.unicode.org/iso15924/iso15924-codes.html
> [3] https://bugzilla.mozilla.org/show_bug.cgi?id=619521
> [4] https://bugzilla.mozilla.org/show_bug.cgi?id=930504


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