Adding Column Rules in ConTeXt's columnsets / pagecolumns

Question

This is my first time playing with ConText and, while I'd like to think I have some decent programming experience, TeX code is something I've never worked with before (and am sufficiently intimidated by).

Long story short, I'm trying to get a three-column layout with vertical rules separating each column, like the journal Science:

I've played a bit around with columnsets and pagecolumns (as suggested on the wiki), but I'm struggling to get the rules how I'd like them. The wiki suggests using some METAFUN code for drawing rules, but unfortunately it's not quite what I'm looking for:

1. There is an unneeded rule on the right side of the page – for N number of columns, I'll always want N - 1 rules separating them
2. The rules continue past the end of the text, even drawing when there is no text in a column at all!

Here is where I'm at:

% Margins
\setuplayout[
  backspace=13mm, width=middle,
  topspace=13mm, height=middle,
  header=0mm, footer=0mm]
% Page Columns
\startuseMPgraphic{verticalrule}
  if CurrentColumn < 3 :
    draw rightboundary OverlayBox shifted (4mm,0);
    setbounds currentpicture to OverlayBox enlarged 2.5mm;
  fi
\stopuseMPgraphic
\defineoverlay
  [verticalrule]
  [\useMPgraphic{verticalrule}]
\startpagecolumns[n=3,background=verticalrule]

Gives me: And on the second page, showing off the second issue:

I'm honestly struggling with getting the height of the actual text (not the whole text area, but the non-blank space) and can't quite figure out a way to get around the extra rule during my playing around with METAFUN. Maybe I need this all to be a page background and not a column overlay? How would that help with my issue #2 though?

I'd greatly appreciate any help you could offer!

Thanks in advance!

Brooks

EDIT:

Here is some code for a minimal working example! The text is a bit bigger and has some ragged bottom edges (what's that all about?) after I removed the custom font:

% Common Imports
\usemodule[ipsum]
% Basic Document Setup
\mainlanguage[en]
\setuppapersize[A4]
% Margins
\setuplayout[
  backspace=13mm, width=middle,
  topspace=13mm, height=middle,
  header=0mm, footer=0mm]
% Page Columns
\startuseMPgraphic{verticalrule}
  if CurrentColumn < 3 :
    draw rightboundary OverlayBox shifted (4mm,0);
    setbounds currentpicture to OverlayBox enlarged 2.5mm;
  fi
\stopuseMPgraphic
\defineoverlay
  [verticalrule]
  [\useMPgraphic{verticalrule}]
\startpagecolumns[n=3,background=verticalrule]
% Dummy Text
\starttext
\setupalign[tolerant,stretch,hanging,hz]
\ipsum
\ipsum
\ipsum
\ipsum
\ipsum
\ipsum
\ipsum
\ipsum
\stoptext

DOUBLE EDIT: Here is my output for context -version:

mtx-context     | ConTeXt Process Management 1.04
mtx-context     |
mtx-context     | main context file: /usr/share/texmf-dist/tex/context/base/mkiv/context.mkiv
mtx-context     | current version: 2021.03.05 19:11
mtx-context     | main context file: /usr/share/texmf-dist/tex/context/base/mkxl/context.mkxl
mtx-context     | current version: 2021.03.05 19:11

And when I run Wolfgang's suggested code with context Article.tex:

resolvers       | formats | executing runner 'run luatex format': /usr/bin/luatex --jobname="Article" --fmt=/home/tll/.texlive/texmf-var/luatex-cache/context/0399a8df3aef8d154781d0a9c2b8e28d/formats/luatex/cont-en.fmt --lua=/home/tll/.texlive/texmf-var/luatex-cache/context/0399a8df3aef8d154781d0a9c2b8e28d/formats/luatex/cont-en.lui cont-yes.mkiv --c:currentrun=1 --c:fulljobname="./Article.tex" --c:input="./Article.tex" --c:kindofrun=1 --c:maxnofruns=9 --c:texmfbinpath="/usr/bin"
This is LuaTeX, Version 1.15.0 (TeX Live 2022/Arch Linux) 
 system commands enabled.
open source     > level 1, order 1, name '/usr/share/texmf-dist/tex/context/base/mkiv/cont-yes.mkiv'
system          > 
system          > ConTeXt  ver: 2021.03.05 19:11 MKIV  fmt: 2022.5.17  int: english/english
system          > 
system          > 'cont-new.mkiv' loaded
open source     > level 2, order 2, name '/usr/share/texmf-dist/tex/context/base/mkiv/cont-new.mkiv'
system          > beware: some patches loaded from cont-new.mkiv
close source    > level 2, order 2, name '/usr/share/texmf-dist/tex/context/base/mkiv/cont-new.mkiv'
system          > files > jobname 'Article', input './Article', result 'Article'
fonts           > latin modern fonts are not preloaded
languages       > language 'en' is active
open source     > level 2, order 3, name '/home/spinning/tll/Documents/University/Y4S2/Literature Review/ConTeXt (RIP)/Article.tex'
fonts           > preloading latin modern fonts (second stage)
fonts           > 'fallback modern-designsize rm 12pt' is loaded
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
Underfull \hbox (badness 1342) in paragraph at lines 1--36
<1: lmroman12-regular @ 12.0pt> sem-per quis fringilla ut, viverra
metapost        > initializing instance 'metafun:1' using format 'metafun' and method 'default'
metapost        > loading 'metafun' as '/usr/share/texmf-dist/metapost/context/base/mpiv/metafun.mpiv' using method 'default'
metapost        > initializing number mode 'scaled'
backend         > xmp > using file '/usr/share/texmf-dist/tex/context/base/mkiv/lpdf-pdx.xml'
pages           > flushing realpage 1, userpage 1, subpage 1
pages           > flushing realpage 2, userpage 2, subpage 2
close source    > level 2, order 3, name '/home/spinning/tll/Documents/University/Y4S2/Literature Review/ConTeXt (RIP)/Article.tex'
close source    > level 1, order 3, name '/usr/share/texmf-dist/tex/context/base/mkiv/cont-yes.mkiv'
mkiv lua stats  > used config file: selfautodir:/share/texmf-dist/web2c/texmfcnf.lua
mkiv lua stats  > used cache path: readable+writable: '/home/tll/.texlive/texmf-var/luatex-cache/context/0399a8df3aef8d154781d0a9c2b8e28d'
mkiv lua stats  > resource resolver: loadtime 0.055 seconds, 0 scans with scantime 0.000 seconds, 0 shared scans, 31 found files, scanned paths: <none>
mkiv lua stats  > stored bytecode data: 454 modules (0.176 sec), 96 tables (0.008 sec), 550 chunks (0.183 sec)
mkiv lua stats  > traced context: maxstack: 1422, freed: 2, unreachable: 1420
mkiv lua stats  > cleaned up reserved nodes: 57 nodes, 9 lists of 442
mkiv lua stats  > node memory usage: 17 attribute, 6 attribute_list, 3 glue, 51 glue_spec, 3 kern, 4 penalty, 2 temp, 2 user_defined
mkiv lua stats  > node list callback tasks: 8 unique task lists, 7 instances (re)created, 374 calls
mkiv lua stats  > driver time: 0.050 seconds 
mkiv lua stats  > used backend: pdf (backend for directly generating pdf output)
mkiv lua stats  > jobdata time: 0.001 seconds saving, 0.000 seconds loading
mkiv lua stats  > callbacks: internal: 842, file: 229, direct: 2, late: 18, function 627, total: 1718 (859 per page)
mkiv lua stats  > randomizer: resumed with value 0.47691170172766
mkiv lua stats  > positions: 3 collected, 3 regular, 0 special
mkiv lua stats  > result saved in file: Article.pdf, compresslevel 3, objectcompresslevel 1
mkiv lua stats  > loaded patterns: en::1, load time: 0.000
mkiv lua stats  > loaded fonts: 2 files: latinmodern-math.otf, lmroman12-regular.otf
mkiv lua stats  > font engine: otf 3.113, afm 1.513, tfm 1.000, 7 instances, 3 shared in backend, 3 common vectors, 0 common hashes, load time 0.106 seconds 
mkiv lua stats  > metapost: 0.001 seconds, loading: 0.010, execution: 0.001, n: 8, average: 0.001, instances: 1, luacalls: 56, memory: 2.851 M
mkiv lua stats  > used platform: linux-64, type: unix, binary subtree: usr
mkiv lua stats  > used engine: luatex version: 1.15, functionality level: 7509, banner: this is luatex, version 1.15.0 (tex live 2022/arch linux)
mkiv lua stats  > used hash slots: 46520 of 65536 + 200000
mkiv lua stats  > lua properties: engine: lua 5.3, used memory: 147 MB, ctx: 147 MB, max: unknown MB, hash chars: min(64,40), symbol mask: utf (τεχ)
mkiv lua stats  > runtime: 0.396 seconds, 2 processed pages, 2 shipped pages, 5.051 pages/second
system          | total runtime: 0.572 seconds

And end up with the same issue of rules after the last column:

Answer 1

The pagecolumns has support for rules to separate the columns but the code for the rules itself is commented and can't be used.

If the code where enabled you could just enable the separator with separator=rule but this is not an option at the moment.

\setuplayout [tight]
\starttext
\startpagecolumns [n=3,align={verytolerant,stretch},separator=rule]
\dorecurse{10}{\samplefile{lorem}}
\stoppagecolumns
\stoptext

What you can do is to create your own background for each column and use the two register \nofcolumns and \mofcolumns to check of the current column is also the last column.

Both register are available in MetaFun with their own name which can be used in a if-condition.

% \startuseMPgraphic {ColumnSeparator}
%     \ifnum\mofcolumns<\nofcolumns
%         draw rightboundary (OverlayBox rightenlarged \measure{ColumnOffset});
%         setbounds currentpicture to OverlayBox;
%     \fi
% \stopuseMPgraphic
\startuseMPgraphic {ColumnSeparator}
    if CurrentColumn < NOfColumns:
        draw rightboundary (OverlayBox rightenlarged \measure{ColumnOffset});
        setbounds currentpicture to OverlayBox;
    fi
\stopuseMPgraphic
\defineoverlay [ColumnSeparator] [\useMPgraphic{ColumnSeparator}]
\setuplayout [tight]
\definemeasure [ColumnDistance] [1em]
\definemeasure [ColumnOffset]   [\measure{ColumnDistance}/2]
\starttext
\startpagecolumns [n=3,align={verytolerant,stretch},background=ColumnSeparator,distance=\measure{ColumnDistance}]
\dorecurse{10}{\samplefile{lorem}}
\stoppagecolumns
\stoptext

Answer 2

An extension of Wolfgang's answer that uses Lua callbacks to measure the column heights.

(Edited to fix a small bug)

\doifnot{\contextmark}{LMTX}{
    \errmessage{"LMTX/MkXL is required to compile this file."}
}
\startluacode
    local saved_data = job.passes.define("column_height")
    local previous_data = job.passes.getcollected("column_height")
    local bigpoint = tex.sp("1bp")
-- Run this code every time we output a column:
callback.register("pre_output_filter", function(head)
    -- Measure the height of the column (head.next to avoid the topskip)
    local column_height = node.vpack(head.next).height
    local pagenumber = tex.count.realpageno
    -- Get the natural width of the baselineskip
    local baselineskip = tex.skip.baselineskip.width

    -- Save the column height in the .tuc file
    saved_data[pagenumber] = saved_data[pagenumber] or {}
    table.insert(
        saved_data[pagenumber],
        -- Clamp the height to multiples of baselineskip
        math.ceil(column_height / baselineskip) * baselineskip
    )

    return head
end)

function column_height(col)
    local pagedata = previous_data[tex.count.realpageno]
    if not pagedata then
        mp.numeric(0)
        texio.write_nl("Please rerun!")
        return
    end
    -- Get the minimum height of the column on either side of the line
    local minimum = math.max(pagedata[col], pagedata[col + 1])
    mp.numeric(-minimum / bigpoint)
end

\stopluacode
% Draw the separator rules:
\startuseMPgraphic {ColumnSeparator}
    if CurrentColumn < NOfColumns:
        draw urcorner OverlayBox shifted (\measure{ColumnOffset}, 0pt) --
             urcorner OverlayBox shifted
                 (\measure{ColumnOffset}, lua.column_height(CurrentColumn));
        setbounds currentpicture to OverlayBox;
    fi
\stopuseMPgraphic
\defineoverlay [ColumnSeparator] [\useMPgraphic{ColumnSeparator}]
\setuplayout [tight]
\definemeasure [ColumnDistance] [1em]
\definemeasure [ColumnOffset]   [\measure{ColumnDistance}/2]
\starttext
\startpagecolumns [n=3,align={verytolerant,stretch},background=ColumnSeparator,distance=\measure{ColumnDistance}]
\dorecurse{10}{\samplefile{lorem}}
\stoppagecolumns
\stoptext

Above, the separator rule is the length of the shortest of the two columns. If you replace math.min with math.max, the rule will be the length of the longest of the two.

This also works with columns of different heights:

% Insert everything before `\starttext` from the code above,
% EXCEPT with `math.min` replaced with `math.max`
\setuppapersize[legal, landscape]
\starttext
\startpagecolumns [n=5,align={verytolerant,stretch},background=ColumnSeparator,distance=\measure{ColumnDistance}]
\dorecurse{2}{\samplefile{zapf}\par}
\column
\dorecurse{1}{\samplefile{lorem}\par}
\column
\dorecurse{2}{\samplefile{bryson}\par}
\column
\dorecurse{3}{\samplefile{knuth}\par}
\stoppagecolumns
\stoptext

Answer 3

After a discussion with Hans (and with useful input from Wolfgang), the solution below came out. It works well if columns are not balanced. I did not do the main work, so I prefer not to take the credit for it, and mark it as CW.

\setupbodyfont[dejavu,9pt]
\setuphead[subject][
    style=bold,
    before={\blank[line]},
    after={\blank[none]},
]
\setuplayout[
    backspace=13mm,
    width=middle,
    topspace=13mm,
    height=middle,
    header=0mm,
    footer=0mm,
    grid=yes,
]
\startuseMPgraphic{verticalrule}
save a, b, c, p, q, r ;
path b ; b := positioncolumnbox(CurrentColumn) ;
draw image (
    path p ; p := rightboundary b shifted (\frameddimension{distance}/2,0) ;
    numeric c ; c := positioncolumn(positionregion("allendshere")) ;
    if (positionpage("allendshere") = RealPageNumber):
        if (CurrentColumn < c) :
            draw p withcolor black withpen pencircle scaled 1 ;
        elseif (CurrentColumn > c) :
            % nothing
        else :
            if CurrentColumn < NOfColumns :
                pair a ; a := positionxy ("allendshere") ;
                path q ; q := (0,ypart a) -- (PaperWidth,ypart a) ;
                path r ; r := p cutbeforefirst q ;
                draw r withcolor black withpen pencircle scaled 1 ;
            fi ;
        fi ;
    else :
        if CurrentColumn < NOfColumns :
            draw p withcolor black withpen pencircle scaled 1 ;
        fi ;
    fi ;
) shifted -llcorner b ;
setbounds currentpicture to OverlayBox ;
\stopuseMPgraphic
\defineoverlay[verticalrule][\useMPgraphic{verticalrule}]
\setupalign[verytolerant,stretch]
\starttext
\startpagecolumns[n=3,background=verticalrule]
    \dorecurse{10}{%
        \subject[title={Foo \recurselevel}]
        \samplefile{lorem}
    }
    \hpos{allendshere}{}
\stoppagecolumns
\stoptext