Headers with centered content
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] \setupheadertexts[] \setupheadertexts[\setups{text a}][][][\setups{text b}] \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.