[XeTeX] XETEX cannot access OpenType features in PUA?

[mskala at ansuz.sooke.bc.ca]

On Sun, 27 Nov 2011, Aleksandr Andreev wrote:
> I figured out the issue. They work if the entire text is in black, like this:
> {\moo \Huge   }

I've been watching this discussion with interest, having had similar
problems.  I thought the colour thing might be an issue - very likely
XeTeX is putting the contents of the color command in a separate "box" and
thus breaking up the stream of glyphs going to the OpenType substitution -
but when I tried (with your earlier font) eliminating the colour change,
the problem remained, so I didn't post to the list about it.

Something to be aware of is that FontForge's handling of OpenType
substitutions seems to be buggy, especially if Adobe-format "feature
files" are involved in the workflow.  Your problem seemed to be one where
FontForge was rendering the substitution correctly and XeTeX wasn't; but
I've also seen cases where XeTeX does it right and FontForge doesn't, and
where a feature file, loaded into FontForge, seems to produce correct
results, but then when I save the feature file from FontForge, the result
is garbage.  Anything that combines GSUB substitutions with GPOS
positioning seems to be hard to get right.  All in all, I don't think
FontForge can be used as a good reference point for debugging other
software's handling of substitutions.
-- 
Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before principles.
http://ansuz.sooke.bc.ca/