[NTG-context] Pass string into text background graphic

From: Thangalin <thangalin@gmail.com>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: [NTG-context] Pass string into text background graphic
Date: Fri, 11 Aug 2023 12:57:48 -0700	[thread overview]
Message-ID: <CAANrE7rTZ5-PEeF4Zn82=wjAn52Z_Pkzf-3BgCh21wc=Q4rqPA@mail.gmail.com> (raw)

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Hi list,

I'm attempting to make a stylized border around paragraphs that can span
pages. The border runs along the side and the top. (Ideally the top border
wouldn't repeat, but that's a minor issue.) The issue I'm having is that
the title for the text doesn't always appear. Instead, there's a small gap
along the top border where the title should be.

Am I going about this the wrong way?

% SOT
\startbuffer[demo]
<html>
<body>
<div class="concurrent" data-title="Berth 5" data-location="San Diego">
Text Goes Here
</div>
<div class="concurrent" data-title="Road" data-location="Beale AFB">
Different Text Goes Here
</div>
</body>
</html>\stopbuffer
\startxmlsetups xml:xhtml
  \xmlsetsetup{\xmldocument}{*}{-}
  \xmlsetsetup{\xmldocument}{html|body}{xml:*}
  \xmlsetsetup{\xmldocument}{div}{xml:*}\stopxmlsetups
\xmlregistersetup{xml:xhtml}
\startxmlsetups xml:html
  \xmlflush{#1}\stopxmlsetups
\startxmlsetups xml:body
  \xmlflush{#1}\stopxmlsetups
\startxmlsetups xml:div
  \setvariable{div}{\xmlatt{#1}{class}}{#1}
  \start[\xmlatt{#1}{class}]\xmlflush{#1}\stop\stopxmlsetups
\startusableMPgraphic{GraphicConcurrent}
  begingroup;
    string legend;

    picture title;
    picture border;
    picture bg;

    numeric tw;
    numeric th;

    legend := \MPstring{concurrent};

    title := nullpicture;
    border := nullpicture;
    bg := textext( "\strut " & legend );

    tw := xpart lrcorner bg - xpart llcorner bg;
    th := ypart ulcorner bg - ypart llcorner bg;

    addto title also image(
      fill unitsquare
        xysized (tw + 8, th)
        shifted ulcorner multipars[1]
        shifted 28 right
        shifted 8 down
        withcolor white;

      draw
        textext.drt( legend )
        shifted ulcorner multipars[1]
        shifted 32 right
        shifted 3 down;
    );

    addto border also image(
      for i = 1 upto nofmultipars:
        draw
          llcorner multipars[i] --
          ulcorner multipars[i] shifted 8 down ..
          ulcorner multipars[i] shifted 8 right --
          urcorner multipars[i]
          withpen pencircle scaled 0.75 withcolor black;
      endfor;
    );

    draw image(
      draw border;
      draw title;
    );
  endgroup;\stopusableMPgraphic
\definetextbackground[TextConcurrentFrame][
  mp=GraphicConcurrent,
  frame=off,
  topoffset=1em,
  leftoffset=1em,
  location=paragraph,
]
\definestartstop[concurrent][
  before={%
    \blank[big]%
    LEGEND: \xmlatt{\getvariable{div}{concurrent}}{data-title}%
    \blank[big]%
    \setMPtext{concurrent}{\xmlatt{\getvariable{div}{concurrent}}{data-title}}
    \startTextConcurrentFrame},
  after={\stopTextConcurrentFrame\blank[big]},
]
\starttext
  \xmlprocessbuffer{main}{demo}{}\stoptext
% EOT

If I change the following line:

legend := \MPstring{concurrent};

to:

legend := "some string";

Then the title "some string" is repeated. It seems like the value for
\MPstring{concurrent} is being cached in some situations and ignored in
others.

Essentially, I'm trying to visually offset multiple paragraphs using a
left-hand vertical rule along with a top horizontal rule that has a title.
Each new "concurrent" section needs its own header that doesn't repeat.

Is there a ConTeXt-way to accomplish this feat?

Cheers!

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