[luatex] glue fill order

Hans Hagen j.hagen at xs4all.nl
Wed Oct 9 12:52:28 CEST 2019

On 10/9/2019 12:26 PM, David Carlisle wrote:
> On Wed, 9 Oct 2019 at 10:27, luigi scarso <luigi.scarso at gmail.com> wrote:
>> 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:-)

we'll add \eTeXglue[stretch|shrink]order for your purpose which returns 
the -1 so we keep the 1..4 range (nicer in an ifcase) in the normal 
primitives so it's then up to latex folks to decide to alias it in latex 
or not

at the lua end nothing will change; after all, node types are also 
different from the etex ones; if needed, you can always overload 
tex.setglue etc. and the interfaces are kind of frozen anyway

> 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 ?
>> At format level one can patch it, the point is at engine level.
>> --
>> luigi


                                           Hans Hagen | PRAGMA ADE
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