[XeTeX] Microtypography?

[Will Robertson]

On 11/05/2006, at 17:56 , Jonathan Kew wrote:

> On 10 May 2006, at 11:36 pm, Will Robertson wrote:
>
>> Off the top of my head, I'm pretty sure that the AAT font format can
>> support optical protrusion,
>
> Yes, the 'opbd' table is defined for that purpose. And if it were
> present in the font, XeTeX could use it. Try finding a font that has
> one, though....

:)
I suspect it'd be pretty easy to adapt the data from microtype if  
anyone ever wanted an AAT computer modern. Beyond that, I guess the  
designers of AAT were too ahead of their time (and lacking a  
marketing department).

>> and *fairly* sure that OpenType can do it
>> as well.
>
> I don't recall seeing this in the OpenType spec, but I'm less
> familiar with that.

Took me a second to find it: feature 'opbd' "Optical bounds":
   <http://www.microsoft.com/typography/otspec/features_ko.htm#opbd>

>> It's firstly a matter of font support (which is true in
>> pdfTeX as well)
>
> I had the impression that in pdfTeX, this information is provided
> from within the TeX document (or, equivalently, a LaTeX package,
> etc), in the form of values per character/font. (But as mentioned,
> setting protrusion metrics on a per *character* basis is wrong, in
> the XeTeX world; it would have to be per *glyph*.)

Oh, I guess that's what I mean by font support; it's not *automatic*  
was my point.

>> and secondly a matter of XeTeX support, which would
>> be tricky since it uses its own justification algorithm instead of
>> ATSUI/<whatever it is Linux uses>.
>
> Actually, when working with ATSUI on OS X, XeTeX uses a hybrid of TeX
> and ATSUI justification.

Yes, I've seen this and been quite upset with it :(
I don't suppose there's a way to turn it off?

Anyway, I'm surprised that the the combination of XeTeX and ATSUI  
works for beginning-of-line and end-of-line interactions -- I thought  
the contextuals in this area (Hoefler Text Italics' swashes, for  
example) were fairly broken at this stage and assumed that margin  
kerning would be similarly non-functional.

> There's no equivalent support for the OpenType 'JSTF' at this point,
> though. This whole area is not yet very well developed in XeTeX.

Presumably we'll be able to deactivate it if it's an OpenType  
feature! It would be great for new fonts to actually support this.

Will