[XeTeX] \XeTeXuseglyphmetrics (was Re: Re: [OS X TeX] gtamacfonts ligatures: PDF searchability)

[Bruno Voisin]

Le 17 mai 06 à 20:25, Jonathan Kew a écrit :

> A question: should \XeTeXuseglyphmetrics=1 be set in xetex.fmt and
> xelatex.fmt as a default, do you think?

I don't know what the consequences would be for languages which don't  
use Roman scripts, or are typeset vertically. Thus, speaking only for  
Roman-based languages, I would say that \XeTeXuseglyphmetrics=1 is  
mandatory when typesetting math formulae, as exhibited by the  
screenshots I provided earlier. Otherwise, math formulae would look  
just like what one would get with GUI equation editors such as  
shipped with MS Word, or as Expressionist I was using in the past;  
which would mean, for maths, giving up on the quality of output TeX  
had learnt us to expect.

An issue also is backwards compatibility with what TeX normally  
provides (though the fonts with which the effect of  
\XeTeXuseglyphmetrics is noticeable are not those normally used by  
TeX). A possibility would be to compare the output, for the same  
fonts, of text typeset either with pdfLaTeX and the gtamacfonts  
package, or XeLaTeX and the fontspec package, and assess the  
influence of \XeTeXuseglyphmetrics in the second case.

Here is, as an illustration, the same text as in the earlier  
screenshots, first with XeLaTeX, fontspec and \XeTeXuseglyphmetrics=0:

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then with XeLaTeX, fontspec and \XeTeXuseglyphmetrics=1:

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and finally with pdfLaTeX and gtamachoefler:

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I'm still missing the tightier and more regular spacing from the  
third case, which seems essentially caused by the different placement  
of the superscript "1/2" (a bit further on the right, and further  
down, in pdfLaTeX). I've not managed to understand how the metrics  
were created for the Hoefler Text font in the gtamacfonts collection  
of packages; hence I've no idea on what could be done in XeTeX about  
this, if anything can indeed be done.

In any case, count me in for \XeTeXuseglyphmetrics=1 as the default.

Bruno Voisin