[XeTeX] XeTeX, fontspec, OTF, and fontdimens

[mskala at ansuz.sooke.bc.ca]

On Sun, 20 Feb 2011, Peter Dyballa wrote:
> > Loading fontspec causes it to use Latin Modern and we're back where we
> > started.
>
> XeTeX' Computer Modern default is actually Latin Modern. Without fontspec it
> loads the PostScript variants of Computer Modern. Latin Modern is constructed
> as an OpenType font, PostScript based, to act exactly like CM.

There is clearly some meaningful difference between the two scenarios
because without fontspec, the interword space is correct - it scales with
the font but doesn't become stretchable.  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.

Without fontspec, pdffonts reports the font as:

name                                 type              emb sub uni object ID
------------------------------------ ----------------- --- --- --- ---------
JFXQIA+CMTT12                        Type 1C           yes yes no       4  0

With fontspec (no other changes, just loading the package), it looks like:

name                                 type              emb sub uni object ID
------------------------------------ ----------------- --- --- --- ---------
JXESXO+LMMono12-Regular-Identity-H   CID Type 0C       yes yes yes      5  0

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.
-- 
Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before principles.
http://ansuz.sooke.bc.ca/