[XeTeX] Required feature not applied
Ralf Stubner
ralf.stubner at physik.uni-erlangen.de
Fri Sep 29 21:58:28 CEST 2006
Hi,
when trying to debug some problems with the Junicode font I found that
it looks as if under certain circumstances XeTeX does not apply the
'required feature' specified in a lookup. In particular the [Tt]horn in
the following example is not replaced by its 'nordic' variant even
though this is a required feature for latn{ISL} in that font:
%%%%%%%%%%%%%%%%%%%%%%
\font\a="Junicode-Regular"\a
þ Þ fi
\font\b="Junicode-Regular:language=ISL " \b
þ Þ fi
\bye
%%%%%%%%%%%%%%%%%%%%%%
One can see that latn{ISL} is applied though, as the 'fi'-ligature is
lost, since the required feature is actually the only feature in that
lookup:
,----[ ttx output ]
| <LangSysRecord index="0">
| <LangSysTag value="ISL "/>
| <LangSys>
| <ReqFeatureIndex value="0"/>
| <!-- FeatureCount=0 -->
| </LangSys>
| </LangSysRecord>
`----
That the latn{dflt} features are not replicated in latn{ISL} is a bug in
the font, but still, the required feature should be applied by XeTeX.
Interestingly if I add some other feature to this lookup, XeTeX does
apply the required feature.
What's wrong here?
cheerio
ralf
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