[XeTeX] OpenType Math kerning (cut-ins)

[Adam Twardoch (List)]

Dear list members,

I'm forwarding the reply from Ross Mills, one of the principal designers
of Cambria Math. The attachment indicates that the kerning of the said
pair is correct in Word 2007.

Best,
Adam

-------- Original Message --------
Subject: Re: [Fwd: [XeTeX] OpenType Math kerning (cut-ins)]
Date: Fri, 30 Oct 2009 02:01:22 -0700
From: Ross Mills <ross at tiro.ca>

Adam Twardoch wrote:
> -------- Original Message --------
> Subject: [XeTeX] OpenType Math kerning (cut-ins)
> Date: Wed, 28 Oct 2009 11:43:39 -0400
> From: Joel C. Salomon <joelcsalomon at gmail.com>
> Reply-To: Unicode-based TeX for Mac OS X and other platforms <xetex at tug.org>
> To: X�TeX <xetex at tug.org>
>
> Consider the attached files (requires a recent version of
> unicode-math).  There does not seem to be any kerning of f_k, even in
> Cambria Math where it's most obviously needed.
>
> I recall from Rhatigan's TUG 2008 presentation "Three typefaces for
> mathematics" (based on his thesis; see
> <http://ultrasparky.org/school/pdf/DanielRhatigan_Dissertation.pdf>,
> pp. 36�37) that OpenType Math fonts have somewhat complicated kerning
> (cut-ins) for super-/sub-scripts.  Is support for these implemented in
> X�TeX?
>
> �Joel Salomon
>   
Apparently not. The subscript positioning may also be off, judging by
this example. This would tend to indicate lack of support or incorrect
interpretation of Math table values and constants (cut-ins/kerning and
subscript positioning, respectively) within XeTex. I don't know how
complicated the kerning can be categorized as, but the values are stored
in the Math table, and its just a matter of implementing those
correctly, but yes, it is more sophisticated then 'normal' kerning. This
may also account for the bad spacing in the quad integral example you
sent before, but the kerning for integrals is handled in a different
manner, and is likely to cause confusion for implementations.
Positioning of scripts off of the integral are indicated by italic
correction values, rather then by cut-ins. Don't ask me why. Sergey
Malkin may have a better memory then I on that issue.

-Ross


-- 

Adam Twardoch
| Language Typography Unicode Fonts OpenType
| twardoch.com | silesian.com | fontlab.net

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