[XeTeX] How do mapping files affect hyphenation?

[Khaled Hosny]

On Fri, Feb 24, 2012 at 02:22:15PM +0100, Ulrike Fischer wrote:
> Am Fri, 24 Feb 2012 13:40:53 +0100 schrieb Zdenek Wagner:
> 
> >> From an old discussion on the mailing list
> >> (http://tug.org/mailman/htdig/xetex/2005-November/002842.html) I got
> >> the impression that mappings are "invisible" to the hyphenation
> >> routine and so I would have expected the translittered text to be
> >> hyphenated according the original russian rules but actually it is
> >> not hyphenated at all:
> 
> > Do the Russian hyphenation patterns contain patterns for the Latin
> > script? 
> 
> Well I would say, obviously not. 
> 
> But my question is if "...font mappings (unlike traditional
> TFM-based ligatures) are completely invisible to TeX's line-breaking
> process"

I understand this as that the line-breaking process sees the result of
the mapping with no reference to its origin, so a “b” input by the user
and a “b” resulting from a mapping are both identical.

Regards,
 Khaled