[luatex] fine grained discretionary's penalty

[Élie Roux]

> Also, for a quite complex project, I need to assign different penalties
> to discretionaries of the same paragraph. I've asked on [3], but it
> doesn't seem possible with PdfTeX. Is there currently a way to do so in
> LuaTeX (by hacking the nodes)? If not, would it be doable, like by
> adding a 'penalty' field to disc nodes, with \hyphenpenalty (or any
> other relevant value) assigned to it be default, but changeable?

Attached is a patch for this feature. It is very small and
non-intrusive: it basically just sets a new "penalty" field to disc
nodes, always set to 0. If the field value is 0 while line breaking, it
is ignored and the penalty associated to the disc is hyphenpenalty or
exhyphenpenalty. But if the field value is non-zero, then line breaking
uses it as the penalty associated to the disc. The value needs to be set
in a pre_linebreak_filter callback.

Attached is also a small Plain TeX example demonstrating the new feature.

It would be a huge help for me as it unlocks totally new possibilities.

What do you think?

Thank you,
-- 
Elie
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