Progressively encouraging page/column breaks at \blank with penalties

* Progressively encouraging page/column breaks at \blank with penalties
@ 2021-08-15  5:00 Joey McCollum via ntg-context
  2021-08-15  5:52 ` Aditya Mahajan via ntg-context
  0 siblings, 1 reply; 3+ messages in thread
From: Joey McCollum via ntg-context @ 2021-08-15  5:00 UTC (permalink / raw)
  To: mailing list for ConTeXt users; +Cc: Joey McCollum

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Hi,

I'm trying to implement a section break marker in a grid layout. At a
section break, two lines of space should separate the subsequent segments
of text (just plain paragraphs, in this case), and a symbol (in the example
below, "X") should be set in the middle of these two lines. For my
purposes, the section break symbol should never occur at the top of a page
or column, and it is more desirable to have a page or column end with the
section break symbol than to have a single orphaned line follow the symbol
at the end of the page or column. Based on these constraints, I thought
that using the "samepage" and "preference" options for the first and second
line breaks would work nicely:

```
\define\SectionBreak{%
    \blank[halfline, samepage]% non-breaking to ensure that no column
begins with the section break symbol
    \startalignment[middle]%
        {X}% section break symbol
    \stopalignment%
    \blank[halfline, preference]% this can (and, if possible, should) be
broken across a column
```

This does successfully prevent the placement of the symbol at the top of a
page/column, but it doesn't encourage the placement of the symbol at the
end of a page/column as often as I would like. I tried replacing the
"preference" option with options with better negative penalties, like
"penalty:-1000", "penalty:-2000", and even "penalty:-5000", but these
didn't make any difference. The option "penalty:-10000" trivially works,
but it forces a page/column break at every section break marker, which is
far too extreme.

Is this normal behavior? I would have thought that progressively more
negative penalties would gradually encourage page/column breaks, but this
doesn't seem to happen. In the following MWE, the "preference" and
"penalty" options (apart from "penalty:-10000") for the second line break
don't change the total page count or appearance of the final page at all
(which would be expected in a document of this size):

```

\setuplayout[

grid=yes %enable baseline grid

]

\setupinterlinespace[18bp] % text line spacing

%Define macro for section break:

\define\SectionBreak{%

\blank[halfline, samepage]%non-breaking to ensure that no column begins
with the section break symbol

\startalignment[middle]%

{X}% section break symbol

\stopalignment%

\blank[halfline]% a column break here is neither encouraged nor discouraged

% \blank[halfline, preference]% this should encourage a column break here,
but it doesn't seem to make a difference

% \blank[halfline, penalty:-1000]% still no difference

% \blank[halfline, penalty:-2000]% still no difference

% \blank[halfline, penalty:-5000]% still no difference

% \blank[halfline, penalty:-10000]% this works, but it is too extreme!

}

%Set things up for fakewords:

\usemodule[visual]

\setupsystem[random=10]

\starttext

\dorecurse{400}{\fakewords{20}{100}\SectionBreak}

\stoptext
```

As always, any help is appreciated!

Joey

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