[luatex] open math constants leaks out?

[Hans Hagen]

On 9/5/2016 2:40 PM, Ulrike Fischer wrote:
> I tried to find out why using Linux Libertine in math leads to wrong
> spacing in the limits of an integral
> (http://tex.stackexchange.com/q/326588/2388)
>
> Imho the reason is that linlibertine_R has a mathconstants table.
> When using the font in math something is leaking out and affects
> legacy math. This plain tex example demonstrates the problem (tested
> in texlive 2016)
>
> \input luaotfload.sty
>
> \font\test={Linux Libertine O}
>
> $$ \int_{a}^{a} $$
>
> \textfont4=\test
>
> $$ \int_{a}^{a} $$
>
> \bye
>
> Is this a bug? And what exactly happens that luatex changes the
> spacing?

many mechanisms have two branches: traditional and opentypemath and the 
mathconstants table determines what branch is entered

math italics and kerning is different for both kind of fonts; so using a 
math table for a type one math fonts or omitting one for opentype math 
gives a mess

(of course fonts can have bad constants and bad character properties and 
math fonts are not always that consistent)

Hans

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