Re: LMTX, BIdi, full paragraph, and spurious empty line

[Hans Hagen <j.hagen@xs4all.nl>]

On 6/22/2021 4:52 AM, Rik Kabel wrote:
> Hello all,
> 
> Last October Denis Maier complained about a spurious empty line 
> generated with protrusion and bidi active and a full paragraph. (See 
> https://www.mail-archive.com/ntg-context@ntg.nl/msg95916.html 
> <https://www.mail-archive.com/ntg-context@ntg.nl/msg95916.html> or 
> similar on your favorite mail archive.)
> 
> I have recreated the issue without involving protrusion. When a 
> paragraph is very full and bidi is on, an extra line seems to be 
> generated. Without bidi there is no extra line. This is quite sensitive, 
> of course, to line width. I have probably 30 instances of it occurring 
> in a tightly-set bibliography. I would assume that it may occur in any 
> text, but have not noticed it in the body of my book.
> 
> I have created an example document that shows it. The problem disappears 
> if bidi is turned off (comment out the first non-comment line) but of 
> course then the RTL text is mis-set. In this example, the spurious line 
> appears after the Walt Kelly entry.
> 
> This was tested under ConTeXt  ver: 2021.06.18 23:37 LMTX  fmt: 
> 2021.6.21, but is not a new problem with this version. /The problem does 
> not occur with MKIV from the same installation./
> 
>     %% Demonstration of spurious line insertion on full paragraph with
>     bidi active
> 
>     \setupdirections  [bidi=on,method=unicode]
> 
>     \definepapersize  [Testing]
>                        [width=6.69in]
>     \setuppapersize   [Testing]
> 
>     \setuplayout      [width=fit,
>                         backspace=1.4in,
>                         cutspace=1in,
>                         leftmargin=0.65in,
>                         rightmargin=0.65in]
> 
>     \setupwhitespace  [small]
> 
>     \setupbodyfont    [libertinus,11pt]
> 
>     \define\SetupBib{
>        \spaceskip 0.7\interwordspace plus .5\interwordstretch minus
>     \interwordshrink
>        \definedelimitedtext
>          [Exdent]
>          [leftmargin=1em,
>           indenting={yes,-1em},
>           indentnext=yes]}
> 
>     \starttext
>        \input jojomayer
> 
>        \input klein
> 
>        \blank[2*line]
> 
>        \SetupBib
>        \startExdent
> 
>          Kelly, Cynthia C., ed. 2005. {\em Oppenheimer and the Manhattan
>          Project: Insights into J.~Robert Oppenheimer, ‘Father of the
>          Atomic Bomb’}. Singapore: World Scientific.
> 
>          Kelly, Walt. 1953. {\em The Pogo Papers}. New York, NY: Simon
>          & Schuster.
> 
>          Kuhn, Thomas S. 1962. {\em The Structure of Scientific
>          Revolutions}. Chicago, IL: University of Chicago Press.
> 
>          Weinreich, Max. 1945. “Der YIVO un di problemen fun undzer
>          tsayt (דער ייִוואָ און די פּראָבלעמען פֿון אונדזער צײַט).”
>          {\em YIVO Bleter} 25 (1): 3--18. The title is translated as
>          {\em The YIVO and the problems of our time}, and also as
>          {\em The YIVO faces the post-war world}.
> 
>        \stopExdent
>     \stoptext
> 
> Of course, there could be some other mechanism at work here than bidi, 
> but changing that clears the problem in this instance. (It may be the 
> adjustment to spaceskip that I use to tighten up the text in the 
> bibliography, and if it is, I welcome an alternative way to do that.)
I'll send you a possible fix but it needs a bit of testing. It has to do 
with (probably spurious) spaces which means that the parbuilder then 
considers the dir node to be a reasoable breakpoint (well, kin dof okay 
as one gets what one asks for), but I'll be a bit more agressive in 
dealing with that.

Hans


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