[NTG-context] Newbie questions

[Thomas Moore]

Dear ConTeXt gurus:

OK, I have gotten some off-list help from Mojca, who has answered  
most of my questions and helped me polish the two page version of my  
code (thanks, Mojca!). I have included what he helped me work out  
below. There is one remaining problem. The first page is correct, but  
very subsequent page has a correct-looking header and another  
superimposed. The second superimposed header is not wide enough and  
has the wrong page number (the number of the previous page), though  
the page number is on the correct side. It is as if the page output  
command from TeX is issuing the \setups command *twice*, once before  
fully updating variables like \rightmarginwidth and the page number,  
and once after setups have been done correctly. Is this a bug, or am  
I doing something stupid?

Thanks for any insight, Tom

Code follows:

\usemodule[amsl]
\usemodule[newmat]

\setuppapersize[letter]
\setuppagenumbering
	[alternative=doublesided]
\setuplayout
	[backspace=1.0in,
	topspace=0.5in,
	width=4.5in,
	height=9.5in,
	rightmargin=2.35in,
	rightmargindistance=0.15in,
	leftmargin=0in,
	leftmargindistance=0in,
	header=0.5 in,
	footer=0in]

\definelayer
[leftpage]
[hoffset=\the\dimexpr\cutspace-\leftmarginwidth-\leftmargindistance 
\relax,  % for left pages
   voffset=\topspace,
   width=\paperwidth,
   height=\paperheight]

\definelayer
[rightpage]
[hoffset=\the\dimexpr\backspace\relax,  % for right pages
   voffset=\topspace,
   width=\paperwidth,
   height=\paperheight]

\setupbackgrounds
[leftpage]
[background=leftpage]
\setupbackgrounds
[rightpage]
[background=rightpage]

\startsetups page:setup

\setlayerframed
[leftpage]
[preset=lefttop]
[width=\dimexpr\textwidth+\leftmarginwidth+\leftmargindistance 
\relax,  % for left pages
   rulethickness=1pt,
   frame=off,
   bottomframe=on]
{\pagenumber\hfill\getmarking[chapter][first]}  % for left pages

\setlayerframed
[rightpage]
[preset=lefttop]
[width=\dimexpr\textwidth+\rightmarginwidth+\rightmargindistance 
\relax, % for right pages
   rulethickness=1pt,
   frame=off,
   bottomframe=on]
   {\getmarking[chapter][first]\hfill\pagenumber}  % for right pages

\stopsetups

\setupheadertexts
   [\setups{page:setup}]
	
\starttext
\chapter{Test}
This is a test of some math stuff. $0 = g_{\mu\nu}dx^\nu dx^\nu$.
\dorecurse{10}{\input knuth}

\showlayout
\stoptext