[NTG-context] Position of MetaPost graphics

Tim Steenvoorden tim.steenvoorden at gmail.com
Fri Apr 1 11:39:18 CEST 2011


Dear list,

I'm trying to make some fancy chapter headers. With MetaPost I drew a
wave, which I'd like to place in the margin. I've read details.pdf and
metafun.pdf, but I don't manage to get the positioning right. The wave
should begin where the bottomframe ends and move on to the page
border. Also, the graphic is placed in the page background layer, but
nevertheless the text after the the graphic is shifted down.

\startuniqueMPgraphic{wave}
numeric periods, width;
path wave;
periods := 3 + 1/4;
width   := periods * 2*pi;
wave    := origin for x=0 step 0.1 until width:
             -- (x,x*sin(x))
           endfor;
pickup pencircle scaled 1pt;
draw wave xscaled (OverlayWidth/width) yscaled (OverlayHeight/(2*width));
\stopuniqueMPgraphic

\definelayer[decorations][position=yes,option=test,location=r]
\setupbackgrounds[page][background=decorations]
\defineoverlay[wave][\uniqueMPgraphic{wave}]

\starttext

{\ss\bfc A chapter title}
\blank[small]
\framed[frame=off,bottomframe=on,width=broad,rulethickness=1pt]
 {\ss\bfx \date \hfill Author Name}
\setlayer[decorations]{\framed[background=wave,frame=off,width=\cutspace,height=2\lineheight]{}}

\input knuth

\stoptext

What am I doing wrong? Is it a better idea to draw the bottomframe in
MetaPost too? How do I take care of positioning in that case? Absolute
positioning is not an option, because the length of the chapterheads
can be two lines. It should also work on other paper sizes (A5 in
particular).

Kind regards,
Tim Steenvoorden


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