[XeTeX] Why do I get small caps/random font?

[Ralf Stubner]

Jonathan Kew <jonathan_kew at sil.org> writes:

> The problem is that "Latin Modern Roman" is a family name shared by  
> dozens of LM fonts. If you don't specify anything more precise, xetex  
> is supposed to try and use "the regular face" from that family. But  
> it has a hard time identifying which of all the "Latin Modern Roman"  
> fonts is the one you really want. And things are further confused by  
> the fact that OpenType fonts may have multiple family and style names.

Is this a font issue (the font should provide more/better information
about itself), a fontconfig issue (fontconfig does not get all relevant
information out of the font or does not pass this information on to
xetex) or a xetex issue (xetex should make better use of the information
provided)? I am asking because I have seen this sort of random behaviour
from fontconfig in conjunction with Latin Modern fonts in Type 1 format
as well as with other families with many fonts in them (see
<URL:http://bugs.debian.org/354537>). Already using 'fc-match' on the
commandline gives sometimes very strange results.

> If an OpenType 'size' (optical size) feature gets added to LM, that  
> will help somewhat, as then xetex will be able to choose among the  
> different design sizes. And in that case, perhaps the size can be  
> removed from the OpenType style names. Merging the small caps into  
> the normal font (and accessing the small caps as an OpenType feature)  
> would also help.

Both features are desireable indeed. Would it be possible to use them at
the same time? While LM comes in many design sizes, there are only 10pt
small caps. Would activation of the smcp feature automatically switch to
this design size? Or would one have to add the 10pt small caps to all
design sizes? 

cheerio
ralf