ConTeXt offers the possibility to have mirrored headers (for odd and even pages); content can be in two parts, at the inner and outer margin of each page. But how do you get a header that will have one part of its content centered and one part in the outer margin? (This is a common setup for books: chapter title centered, page number in outer margin.) Hans posted this solution to the list:

```\setuppagenumbering[alternative=doublesided]

\startsetups[text a]
\rlap{\pagenumber}
\hfill
\getmarking[chapter]
\hfill
\llap{whatever}
\stopsetups

\startsetups[text b]
\rlap{whatever}
\hfill
\getmarking[section]
\hfill
\llap{\pagenumber}
\stopsetups

```

The use of the TeX primitive rlap and llap allows centering of content.