W3C home > Mailing lists > Public > www-svg@w3.org > May 2012

Re: should we remove the kerning property in favour of font-kerning?

From: John Daggett <jdaggett@mozilla.com>
Date: Wed, 30 May 2012 23:34:11 -0700 (PDT)
To: Cameron McCormack <cam@mcc.id.au>
Cc: Dirk Schulze <dschulze@adobe.com>, Nikolas Zimmermann <zimmermann@kde.org>, SVG public list <www-svg@w3.org>
Message-ID: <1048033239.23407807.1338446051259.JavaMail.root@mozilla.com>
Cameron McCormack wrote:

> > Not sure what you're kvetching about here.  The CSS 'font-kerning'
> > property enables or disables metrics-based kerning based on kerning
> > data in the font.  It does not take a length value.  So the two
> > properties are not equivalent.
> >
> > The SVG 'kerning' feature seems designed to allow
> > character-by-character tweaking.  One sets the 'letter-spacing' for an
> > entire text span and tweaks individual pairs of letters by wrapping a
> > span around each pair of characters and applying the appropriate relative
> > adjustment via 'kerning'.  My guess is that this was designed to allow
> > PDF-like layout where an app spits out a set of characters with
> > positions.
> >
> > The CSS property is only designed to enable/disable font-based
> > kerning.  It's not designed to support character-by-character tweaking
> > nor do I think it should.
> 
> Do you think it is reasonable to use "letter-spacing: 3px; font-kerning: 
> none" in place of "kerning: 3px" for SVG content?  If we are in the 
> situation where we could drop "kerning" in favour of authors using a 
> combination of font-kerning and letter-spacing, should we do that?  Or 
> is letter-spacing something different enough from kerning adjustment 
> that it should be kept separate?
 
Right, most of the time that's all that would be needed. The only
thing you wouldn't be able to do without the 'kerning' property around
is to be able to use the combined effect of letter-spacing + kerning
with a fixed length. So the question is whether there's content that
relies on that use case.

The SVG kerning property is just an odd thing to me.  Kerning
adjustments are typically made to pairs of letters (e.g. Ta, To, AV,
etc.) and that's what font kerning data has, adjustments based on
glyph combinations.  Generic span-wide adjustments to spacing are
never called "kerning".

I would suggest dropping the 'kerning' property.

John Daggett
Received on Thursday, 31 May 2012 06:34:45 GMT

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