Ok, \starttexdefinition allows blanks, apparently just like setups.

But, it still fails exactly like the version with \def

\setuphead[chapter][

    before={Before: \structureuservariable{author}\blank},

    beforesection={Beforesection: \structureuservariable{author}\blank},

    insidesection={Insidesection: \structureuservariable{author}\blank},

    after={After: \structureuservariable{author}\blank},

    ]

\def\myChapterCommand#1#2{\structureuservariable{author}\space\blank}

\define[2]\myChapterCommand{\structureuservariable{author}\blank #1\space#2}

%\def\myChapterCommand#1#2{\structureuservariable{author}\blank #1\space#2} % does not work

% \starttexdefinition myChapterCommand #1 #2 % doesn't work either, but at least blanks should work

%   \structureuservariable{author}

%   Test

%   \blank

%   #1\space#2

% \stoptexdefinition

\starttext

\myChapterCommand{1}{asdf}

\startchapter[title=First][author=First Author]

\input knuth

\stopchapter

\startchapter[title=Second][author=Second Author]

\input knuth

\stopchapter

\setuphead[chapter]

    [

    before=,after=,beforesection=,insidesection=,

    command=\myChapterCommand,

]

\startchapter[title=Third][author={Third Author}]

\input knuth

\stopchapter

\stoptext

Von: denis.maier@unibe.ch <denis.maier@unibe.ch>
Gesendet: Dienstag, 12. September 2023 17:48
An: ntg-context@ntg.nl
Betreff: [NTG-context] Using structureuservariables before the heading

Hi,

is it possible to access a structureuservariable before the heading’s title ?

Using the «before» key does not seem to work.

As an aside, I’ve tried to use the « command » key to provide my own command, but while \define works here (but ignores \blank), \def gives me an error.

Why is that?

How would you add blanks to a user-defined command?

Best,

Denis

\setuphead[chapter][

    before={Before: \structureuservariable{author}\blank},

    beforesection={Beforesection: \structureuservariable{author}\blank},

    insidesection={Insidesection: \structureuservariable{author}\blank},

    after={After: \structureuservariable{author}\blank},

    ]

\def\myChapterCommand#1#2{\structureuservariable{author}\space\blank}

\define[2]\myChapterCommand{\structureuservariable{author}\blank #1\space#2}

%\def\myChapterCommand#1#2{\structureuservariable{author}\blank #1\space#2} % does not work

\starttext

\macro{1}{2}

\startchapter[title=First][author=First Author]

\input knuth

\stopchapter

\startchapter[title=Second][author=Second Author]

\input knuth

\stopchapter

\setuphead[chapter]

    [

    before=,after=,beforesection=,insidesection=,

    command=\myChapterCommand,

]

\startchapter[title=Third][author=Third Author]

\input knuth

\stopchapter

\stoptext