[luatex] glue fill order

[David Carlisle]

On Wed, 9 Oct 2019 at 10:27, luigi scarso <luigi.scarso at gmail.com> wrote:
>
>
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> On Sat, Oct 5, 2019 at 10:42 PM David Carlisle <d.p.carlisle at gmail.com> wrote:
>>
>> Is there any chance that luatex could change here to be compatible
>> with other systems?
>>
>
> we are  discussing it, but there is not an easy solution.

thanks, yes  I'm not sure my "-1" suggestion is an improvement
actually, it was just a suggestion to
think of a possible change.

> As is now in luatex, \gluestretchorder is consistent (integer always greater than zero and ordered ),
> something else  breaks consistency and backward compatibility (this is a quite old macro).
>

Yes my suggestion aligns 0,1,2,3 with pdftex so a test of
\gluestretchorder=1 works the same way but
tests of \gluestretchorder>0 to mean "stretchy" then break.  It may be
that the best can be done is just document it in the manual.
It's a bit weird but it's not the only place where luatex and pdftex
differ (and as far as I can tell it's always been this way in luatex
without
anyone noticing or complaining before:-)

David

>>
>> If it is not possible to change the default behaviour would it be
>> possible to have a flag settable in the format so that  fi fil fill
>> fill were (say) -1,1,2,3 not 1,2,3,4?
>> both for \gluestretchorder and tex.setglue ?
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> At format level one can patch it, the point is at engine level.
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> --
> luigi