[XeTeX] Should xelatex have its own kernel? (was: "Conflict between xunicode and fontspec?")

[Ross Moore]

Hi Joel, and others.

On 08/02/2008, at 5:24 AM, Joel C. Salomon wrote:

> On Feb 7, 2008 3:28 AM, François Charette <firmicus at ankabut.net>  
> wrote:
>> U+2007 -> ? "figure space"
>
> A space the size of a numeral (if using lining figures; if the font
> only has proportional figures I'd guess '8').
>
> Although... mightn't the font include the width of these various
> spaces?  I'd suggest using the values from the font, if such exist.

That is a good point.
For many of those special spaces (e.g. the math-spacing ones)
TeX will have rules that handle those situations.

However, this begs the question...

   ... what to do if they appear within document source?

For example, if a piece of LaTeX source has been constructed
by copy/paste from an existing PDF or other file, then these
characters may well be included.

Should XeTeX treat them as a normal space tokens, then let
the typesetting context determine what to do ?

Or should the meaning of these space tokens be adapted to
the current font, using TeX's  \fontdimen  parameters
for the font(s) specified for typesetting mathematics?


Indeed, should XeTeX be smart enough to *insert* these
spacing characters into the output that it creates?
This is particularly relevant to the typesetting of
mathematics, and it would indeed be a departure from
the way TeX currently works.

Against this is the question of how do "smart" math fonts
handle the spacing? (e.g. the STIX fonts).
Aren't they supposed to know the correct amount of space
to put around operator and relation symbols?
So adding these characters explicitly would be either
redundant or just plain wrong.

More questions.
Interesting thread.

>
> --Joel

Cheers,

	Ross

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Ross Moore                                         ross at maths.mq.edu.au
Mathematics Department                             office: E7A-419
Macquarie University                               tel: +61 +2 9850 8955
Sydney, Australia  2109                            fax: +61 +2 9850 8114
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