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Re: [css3-fonts] font-feature-settings syntax

From: Martin Hosken <martin_hosken@sil.org>
Date: Fri, 20 Apr 2012 11:09:30 +0700
To: www-style@w3.org
Message-ID: <20120420110930.560f0e58@sil-mh6>
Dear John,

>   The <string> is a case-sensitive OpenType feature tag. For it to
>   match an OpenType feature contained in a font, it must follow the
>   syntax rules for these tags. As specified in the OpenType
>   specification, feature tags contain four ASCII characters. Tag
>   strings longer or shorter than four characters, or containing
>   characters outside the U+20-7E codepoint range must be treated as
>   invalid.  User agents must not use a feature tag created by
>   truncating or padding the string to four characters.

Does this mean that I can do font-feature-settings: "alt " 7; ?

I think that there is no reason to limit the feature tag to only 4 characters if we say up front that tags will be padded with spaces up to 4 chars. This then doesn't limit font designers to come up with exactly 4 character tags. I say this not from the perspective of OpenType (which could well come up with a new < 4 char feature id) but also for Graphite where font designers can define feature ids up to 4 chars. If we limit font-feature-settings ids to 4 chars then this places an external constraint on Graphite font designers that doesn't come from the technology. BTW there is no intention to need support for ids of > 4 chars.

Yours,
Martin
Received on Friday, 20 April 2012 11:03:48 GMT

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