[NTG-context] About graphictext macro (Metafun)

Hi, I try to understand how this macro by testing a simple example. Why pdf file is empty ? This question follows my question Cover page (Metafun) http://www.ntg.nl/pipermail/ntg-context/2015/083078.html Thank you. \setuppagenumbering[location=] \setupcolors [state=start] \setMPtext{text}{MATHEMATIQUES} \starttext \startuseMPgraphic{test} picture pic ; pic := image(graphictext \MPstring{text} withdrawcolor red withpen pencircle scaled 1pt ; ) ; addto currentpicture also pic ; \stopuseMPgraphic \stoptext