[XeTeX] XeTeX, fontspec, OTF, and fontdimens

[Peter Dyballa]

Am 20.02.2011 um 15:50 schrieb mskala at ansuz.sooke.bc.ca:

> With fontspec and not WordSpace,
> the space scales but is stretchable; with fontspec and an appropriate
> WordSpace setting, the space is non-stretchable, but doesn't scale.

I've noticed these effects before, which become clearly visible with  
your

	\noindent
	x x x\\
	xxxxx\\
	x x x\\
	xxxxx

test pattern, that is when the 'x x x' lines are shorter than the  
'xxxxx' lines, and thought they might come from some wrongly coded  
dimension in the font file which XeTeX picks up. This should not  
happen with a mono-spaced font. And the Latin Modern Mono fonts are  
recognised as mono-spaced by Mac OS X, as ftxinstalledfonts from the  
Apple Font Tools suite reports.

Could be it's a fontspec bug. With \XeTeXtracingfonts=1 I see in the  
LOG file:

	Requested font "[lmroman12-regular]:mapping=tex-text" at 14.4pt
	Loaded mapping `tex-text.tec' for font `[lmroman12- 
regular]:mapping=tex-text'.
	 -> /usr/local/texlive/2010/texmf-dist/fonts/opentype/public/lm/ 
lmroman12-regular.otf

although by default it should have been a 10 pt font, when using for  
example the article class without font size option. And *I* never  
wanted any mapping to be used...

Anyway, I can load Latin Modern without fontspec:

	\font\1="Latin Modern Mono"
	\1

Now the LOG file for your test case (at normal size and at \Large  
size) tells me:

	Requested font "Latin Modern Mono" scaled 1000
	 -> /usr/local/texlive/2010/texmf-dist/fonts/opentype/public/lm/ 
lmmono10-regular.otf
	Requested font "cmr12" at 14.4pt
	 -> /usr/local/texlive/2010/texmf-dist/fonts/tfm/public/cm/cmr12.tfm

and the Large test case does not look OK. One would need to  
\renewcommand{\Large} to load the same font for \Large, but LaTeX and  
TeX don't team up here. But this (overloading?) works:

	\font\Large="Latin Modern Mono" at 14.4pt

The LOG file tells:

	Requested font "Latin Modern Mono" scaled 1000
	 -> /usr/local/texlive/2010/texmf-dist/fonts/opentype/public/lm/ 
lmmono10-regular.otf
	Requested font "Latin Modern Mono" at 14.4pt
	 -> /usr/local/texlive/2010/texmf-dist/fonts/opentype/public/lm/ 
lmmono12-regular.otf

and both test cases look OK! (Even Watson could name the culprit now.)

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>
> I wonder if the difference is simply that there are TFM files for
> Postscript Computer Modern and not for OpenType Latin Roman; and in  
> that
> case maybe it could be addressed by creating TFM files for Latin  
> Roman.
> I don't know if XeTeX will look for and load a TFM file in the case  
> of an
> OpenType font, but if it could, maybe that would be a solution. One
> sticking point, of course, would be the 256-character limit of TFM  
> files.


It's possible to check with some trace utility which files xetex or  
xelatex open and read, but with Apple's Font Book I can activate Latin  
Modern from different TeX Live distributions. Always files from the  
active set were logged, so I presume that XeTeX only then uses TFM  
files when it has to use non-OT, non-TT fonts. And it look's, as you  
suspicioned, like another fontspec bug.


pTeX and cjkTeX are (partly) TFM files based. Did you try these  
variants?

--
Greetings

   Pete

A morning without coffee is like something without something else.