[NTG-context] Let chapter start on odd page and make the even page before show an image

[Henning Hraban Ramm]

In a similar setup I wanted to start every chapter with image and short vita the author and came up with the following (of course not without help from our wizards):


\definefont[ChapterFont][Sans*default at 30pt]

\startsetups normalheader
  % default numbers of my bodyfont are oldstyle
  \setupheadertexts[chapter][{\addff{normnum}\pagenumber}][{\addff{normnum}\pagenumber}][]
\stopsetups

\startsetups noheader
  \setupheadertexts[][][][]
\stopsetups


\startsetups bigchapter
  \setupalign[flushleft,hz,hanging,verytolerant,nothyphenated]
  \doifelse{\structureuservariable{image}}{}{% if image empty
  }{%
    \directsetup{noheader}
    \vbox{%
      {\ChapterFont\structurevariable{title}\par}%
      \blank[big]
      \externalfigure[img/\structureuservariable{image}][width=0.8\textwidth]\par
    }
    \doifnot{\structureuservariable{vita}}{}{% if vita
      \vfill
      \vbox{%
        {\tf\ss\structureuservariable{vita}}
      }%
    }%
    \page[right]
    \vbox{%
      \doifnot{\structureuservariable{subtitle}}{}{% if subtitle
        {\definedfont[SerifItalic*eka at 30pt]\structureuservariable{subtitle}}
      }%
    }%
  }%
  \blank[3*big]
  \directsetup{normalheader}
  \setupalign[width,hz,hanging,hyphenated]% reset alignment
\stopsetups


\setuphead[chapter][
  page=left,
  number=no,
  command=\gobbletwoarguments,
  before=,
  after={\directsetup{bigchapter}},
  style={\ChapterFont},
]


This is the result:
https://www.dreiviertelhaus.de/editionka/lauf-los-buch/
(see preview images linked at the bottom)


Best, Hraban