On Thu, Apr 08 2010, Wolfgang Werners-Lucchini wrote:

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but MyPreLB() is not called. What I am doing wrong here?

Hello Wolfgang, I don't know, but I've played a bit with your example file: \starttext \startluacode local OldPreLB function MyPreLB(head,gc) tex.print("Here I am!") return OldPreLB(head,gc) end local id, error = callback.register('pre_linebreak_filter', MyPreLB) if id == nil then tex.print("Error string:", type(error), "\\par") end \stopluacode Problem: callback.register returns nil, but no error message. \stoptext Cheers, Peter -- Contact information: http://pmrb.free.fr/contact/