# Re: [NTG-context] [luatex-plain] disappearing math-on node

On 4/5/2014 3:12 PM, Philipp Gesang wrote:

···<date: 2014-04-03, Thursday>···<from: Hans Hagen>···


On 4/3/2014 6:29 PM, Dohyun Kim wrote:

This is a bug report based on the issue discussed at

\font\tenrm{file:lmroman10-regular.otf:mode=node;script=latn}\tenrm
\setbox0\vbox{%
x\penalty-10000
$a$x$a$
}
\unvbox0
\setbox0\lastbox
\unhbox0
\end

The plain tex code shown above fails with a lua error:
luatex-fonts-merged.lua:9616: attempt to index local 'current' (a nil value)

My guess is: as math-on (math-off too) is a "discardable" item after a
linebreak, the first math-on node has gone away. So the
math-on/math-off pair has become broken, by which the behavior of
"node.end_of_math" is confused.


mtxrun --script plain test.tex

runs ok here so i need an example that fails with context or luatex-plain


It fails with the luatex-plain format from the minimals as of
yesterday and Luatex 4972:

error: .../context/tex/texmf-context/tex/context/base/font-ota.lua:144:
attempt to index local 'current' (a nil value)
.
\bye ^^@-\par
\vfill \supereject \end
l.17 \bye

Though the issue arises only in node mode.


normally the font callback is called on a hlist and there are always
paired math nodes

(what is line 9616 in the current beta?)


Line 9626 with yesterday’s code. Attached are patches for
font-ota.lua and luatex-fonts-otn.lua that guard all invocations
of end_of_math() with checks for the subtype.



I think that the removed math node is a bad thing so that will change in a next luatex release (i tested a patch but it will not go in the tl release). (Just like the math node at the end of a line it will have zero surround in order to make the backend happy.)


In order to avoid the 'current' issue I'll use an overload of end_of_math in the generic code.


The real solution is to make the built-in end_of_math more strict (trivial patch ready and tested so that can end up in the next luatex).


In the context code i won't intercept it because end_of_math will do that at some point.

Hans

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