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

From: John Daggett <jdaggett@mozilla.com>
Date: Sun, 22 Apr 2012 19:40:21 -0700 (PDT)
To: Martin Hosken <martin_hosken@sil.org>
Cc: www-style@w3.org
Message-ID: <706543229.5805320.1335148821074.JavaMail.root@zmmbox3.mail.corp.phx1.mozilla.com>
Hi Martin,

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

Yes, "alt " is a four-letter tag using only characters in the U+20-7e
range so it would be considered a valid tag.

> 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.

This is definitely an option, implementations could automatically pad
strings of length 1-3 out to four characters with spaces.  But given
that all registered OpenType features have four characters, in most
cases shorter strings would be a typo.

Are there Graphite fonts that make extensive use of feature tags that
assume spaces in the tag?  And are tags less than four characters
always space-padded (as opposed to null-padded)?  It seems to me if
the font data contains a 4-byte tag value then it's not unreasonable
to require a four character tag to match that explicitly and not leave
things up to automagic rules.  But I'm sort of ambivalent, it's easy
enough to allow either automatic padding.


John Daggett
Received on Monday, 23 April 2012 02:40:50 UTC

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