[luatex] luatex/luaotf bug: kerns are missing in discretionary nodes

Petr Olsak petr at olsak.net
Thu Dec 12 14:35:35 CET 2013

Dear All,

it seems there is a serious bug in kerning algorithm. When OpenType font 
is loaded then all kernings are missing in discretionary nodes. You can 
try the following example:


\ifx\directlua\undefined \else \input luafonts \fi % otfload code
% you can use \input luaotfload.sty instead \input luafonts.

\font\f=[lmroman10-regular] \f


\tracingonline=1 \showboxbreadth=25 \nonstopmode \showbox0




You can try to run the command ``luatex test.tex'' (kernings are lost)
or ``xetex text.tex'' (kernings are OK).
It is irrelevant what OpenType font is used.

If the \font\f line is commented out, the original 7bit font is used and 
kernings are OK. The nodes refer: ``\discretionary replacing \kern''.

If the \hyphenation line is commented out but OpenType font is used then 
kernings are OK. It means that only discretionary nodes remove kerning 
information from OpenType fonts.

The used luaTeX version:

This is LuaTeX, Version beta-0.76.0-2013061708 (rev 4627)

Best regards

Petr Olsak

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