On 8/13/2018 10:28, Rik Kabel wrote:
On 8/13/2018 03:01, Hans Hagen wrote:
On 8/13/2018 5:18 AM, Rik Kabel wrote:

  \startparagraph

%     \dontleavehmode\llap{\Mark}\inlinebuffer[TestBuffer]
%     \ (first: \First, arg: \Arg)

    \margintext{\Mark}

    \setupparagraphintro[first][(first: \First, arg: \Arg)]
   %\setupparagraphintro[next][(first: \First, arg: \Arg)]

    \getbuffer[TestBuffer]

  \stopparagraph

Hans,

That works for the over-simplified case here, but fails in practice. For a \startnarrower[left] paragraph, the mark is still in the main margin, not the 'margin' of the narrowed paragraph. Also, the placement of the text in the margin is wrong and not easily controlled as with \llap and \rlap. The code started out more like:

\define\Mark{\color[middlegray]{\hskip.6cm\itb¿\ }}
\setwidthof{\Mark}\to\MarkWidth
...
\starttexdefinition stopBufTest
  \startluacode
      buffers.prepend("TestBuffer","\\dontleavehmode\\llap{\\Mark}")
  \stopluacode
  \setupnarrower[left=\MarkWidth]
  \startnarrower[left,right]
  \startparagraph
    \inlinebuffer[TestBuffer]
  \stopparagraph
  \stopnarrower
  \egroup
\stoptexdefinition

So I am still looking for a way to do this. Meanwhile I am trying to understand Aditya's examples.

Turns out another answer was hidden in Hans's reply. The following seems to meet my needs, but it may complicate other use of \setupparagraphintro (which I don't recall seeing before), so it may not be a generic solution.

An empty string works fine instead of the llaped marking shown here.

This is a less dangerous hack than redefining \par, but still may fail in more complex documents when \setupparagraphintro is used elsewhere.

\starttexdefinition stopBufTest
  \startnarrower[left,right]
  \startparagraph
    \setupparagraphintro[first][\llap{\Mark}]
    \inlinebuffer[TestBuffer] \ (first: \First, arg: \Arg)
  \stopparagraph
  \stopnarrower
  \egroup
\stoptexdefinition

Thank you, Hans.

(For a non-hack generic solution that does not interfere with other use of \setupparagraphintro, surely there must be an easy way to apply string.strip to the buffer.)

--
Rik