# [XeTeX] Let's discuss \mathchar again

Malte Rosenau xetex_malte at web.de
Wed Dec 14 10:02:12 CET 2005

```Unicode-based TeX for Mac OS X <xetex at tug.org> schrieb am 13.12.05 11:11:30:
>
> On 13 Dec 2005, at 3:48 am, Will Robertson wrote:
>
> > to get around to doing the same thing with maths, but at this stage
> > I'm not sure at the fundamental level how TeX (and thus XeTeX) puts
> > glyphs where they go in maths mode.
>
> If I may nit-pick, what \mathchar could (potentially) give you access
> to would be Unicode *characters*. There are no such things as
> "Unicode glyphs". Unicode is a character encoding; character codes
> get mapped to glyphs within fonts. And one of the issues is that math
> typesetting may well require variant *glyphs* for a single
> *character* (with resizable delimiters being the obvious example; not
> sure if there are others), but we don't currently have a well-defined
> standard way to handle this.
>
> > As far as I'm aware, only extensible delimiters and things require
> > specific metric information that isn't provided by unicode; but I
> > *believe* that there is no other restriction.
>
> Right, I think.... all the "resizable" delimiters (and radical, etc)
> are implemented via special functions in the lig/kern program, in the
> TFM file. To work with Unicode-based math fonts and without TFMs,
> we'll need some kind of mechanism for specifying these "recipes".

as in: a text file with additional typographic data read by XeTeX
on runtime? I think a lot of people would love to manipulate fonts
(not just math fonts) without tampering with the actual font files.
Is this technically possible/hard to implement?

Happy holidays,

Malte

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