[XeTeX] letter spacing

[public at heslin.eclipse.co.uk]

Adam Twardoch <list.adam at twardoch.com>
writes:

> For some reason, I always assumed that this would be a trivial thing to 
> do in TeX. I guess it's one of the myths of "excellent typographic 
> control offered by TeX" that actually turns out to be false :/

Sigh.  Adam is correct in saying that the ability to control the
letterspacing of full caps and small caps is absolutely essential in
fine typesetting, but it is not true that TeX cannot or could not do
this.  It is true that TeX cannot easily adjust this on the fly, and for
this reason the soul.sty package tends to be brittle.  But that is
because TeX regards letterspacing as a property of the font, not of the
running text.

Once upon a time before Opentype, when one was installing an expert font
set for use with TeX (a task no one ever claimed was easy), one of the
things you had to do routinely was to set up a few separate virtual
fonts with varied letterspacing values for use with full or small caps.
This was done via fontinst, with a command such as
\resetint{letterspacing}{100} (for full details, see pp. 257--61 of
A. Hoenig, _TeX Unbound_).

Once you had set up your virtual font set, then switching to a
letterspaced font was indeed "trivial".  The problem was that the
process of installing the expert font set was not trivial -- but this
was not TeX's fault, as before Opentype, there was no way to specify the
required information.

Now otftotfm and xetex have made fontinst obsolete (thank heavens!), so
it is fitting that they should also provide a way to specify a way of
letterspacing a font, just as fontinst used to do.  In fact, otftotfm
already has provided this facility via the -L switch.

So, Jonathan, it would be great if Xetex would provide this too.  

Thanks,

Peter

-- 
Peter Heslin (http://www.dur.ac.uk/p.j.heslin)