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Re: [css3-writing-modes] real vs. synthetic width glyphs

From: John Daggett <jdaggett@mozilla.com>
Date: Tue, 2 Jul 2013 21:29:37 -0700 (PDT)
To: www-style@w3.org
Message-ID: <1706945091.974829.1372825777292.JavaMail.zimbra@mozilla.com>

fantasai wrote:

> > Elika proposed something similar [1] but and Koji's response was
> > "nah, undefined is better" [2].  However, I think if scaling to
> > 1em is a requirement then how that occurs must to be defined
> > explicitly. Leaving it undefined would force authors to work
> > around naive implementations that simply scale whatever the
> > content is, even if full-width codepoints are used.  I think the
> > examples above make it plain that's not a good idea.
> 
> I think it would be *great* to put your algorithm here as an example
> of good practice, and to point out the dangers of not converting
> full-width codepoints to half-width variants.
> 
> However, I think I'm convinced by Koji and others that the spec's
> normative requirements should leave the exact implementation of this
> open, in case UAs are able to improve on it.

How is a *browser engineer* going to improve on the quality of a
variant glyph specifically designed by a *type designer* for this
case?!? This isn't "allowing improvement", it's permitting substandard
baseline implementations, let's not kid ourselves here. In effect this
is defining the baseline functionality to be a simple, crude scaling
operation. The examples I put together clearly show the problem with
this, the synthesized versions are very poor substitutes for real,
designed variants [1].  This isn't about promoting better quality in
the future, it's about permitting lower quality implementations.

Given that CSS3 Fonts spec and the use of vertical alternates in
Writing Modes already requires a base level support of OpenType
features, I see no reason to not make this a requirement rather than
simply a best practice.  If you want to state this in abstract,
non-OpenType terms, that would be fine:

  "If width-specific variant glyphs are available
   they must be used otherwise the user agent must
   render the content so that it fits within the line."

This will assure better consistency in the rendered results across
user agents displaying web content.  If some vertical market publishing
app only wants to implement this via scaling, that's their choice.  But
there's no reason for us to specify such behavior in the spec.

Regards,

John

[1] http://lists.w3.org/Archives/Public/www-archive/2013Jul/0000.html
Received on Wednesday, 3 July 2013 04:30:04 UTC

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