[NTG-context] Why must I move frame to center it?

[Aditya Mahajan]

On Mon, 27 Nov 2006, John R. Culleton wrote:

> On Sunday 26 November 2006 11:27, Hans Hagen wrote:
>> setbounds currentpicture to Page ;
>
> Unfortunately the recommended line had no effect.  Did I put it in the right
> place?
> So here is the file that works (so far!)

Here is an alternate approach: Use an overlay as the page background 
for one page. Another approach is to let MetaPost do all the page 
building (see the source of texmfstart manual mtexmfstart.tex)

\definepapersize  [bok]   [width=6.0in,height=9.0in]
\setuppapersize   [bok]   [letter]
\setuplayout 
[marking=on,margin=.5in,textwidth=4.5in,width=middle,location=middle]
\setupcolors      [state=start]


\noheaderandfooterlines

\startuseMPgraphic{bg}
     boolean debug ; debug := false ;
     path Page ; Page = (fullsquare xyscaled (\overlaywidth, 
\overlayheight)) ;
     path p ; p := Page enlarged  -10mm ;
     path q ; q := Page enlarged  -15mm ;
     if debug :
       draw Page  withcolor green;
       draw p withcolor red ;
       draw q withcolor blue ;
     fi ;
     drawoptions(withcolor .85white) ;
     fill reverse topboundary    q -- topboundary    p -- cycle ;
     fill reverse bottomboundary q -- bottomboundary p -- cycle ;
     drawoptions(withcolor .65white) ;
     fill reverse leftboundary   q -- leftboundary   p -- cycle ;
     fill reverse rightboundary  q -- rightboundary  p -- cycle ;
     setbounds currentpicture to Page ;
\stopuseMPgraphic

\defineoverlay[coverpage][\useMPgraphic{bg}]

\starttext
\setupbackgrounds[page]
                  [background=coverpage]

\centerline{Part I}
\vskip .4in
\centerline{Prerequisite for Success:}
\vskip .2in
\centerline{A Thorough Understanding}
\vfil
\tfa

\page[yes]
\setupbackgrounds[page]
                  [background=]

\input knuth

\stoptext


Aditya