The following code is an example of how to draw a graphic on every page of a document. The graphic (a grey rectangle) appears in a different place for each chapter, and the chapter number appears in the rectangle as well. This is often called a thumb index - your thumb can flip the pages of a book while you watch the contents flash past...
<texcode>
% by Hans Hagen, of course :-)
<context source="yes">% these first lines are just for wiki layout and visualisation\unprotected setuppapersize[A8][A5,landscape] \defshowframe\rawsectionnumber#1{setuppaper[nx=4,ny=2]\countervalue{setuparranging[XY]\??se#1}} % will be in kernelusemodule[visual]
\setuppagenumbering [alternative=doublesided]\setupcolors [state=start]\setupbackgrounds [page] [background=thumbs] def\defineoverlaycurrentchapternumber [thumbs] [\setups{thumbs}]\def\NOfChapterssomenamedheadnumber{4chapter} % i need to make this one available\startsetups thumbs \definemeasure[thumbheight][\dimexpr\paperheight/\NOfChapters\relax] \vbox to \paperheight \bgroup \vskip \rawsectionnumber{section-2} \measure{thumbheightcurrent} \vskip -1 \measure{thumbheight} \doifoddpageelse\hfill\donothing \framed [background=color, backgroundcolor=darkgray, frame=off, foregroundcolor=white, height=\measure{thumbheight},width=1cm] {\bfa \rawsectionnumber{section-2}} \doifoddpageelse\donothing\hfill \vss \egroup
\stopsetups\starttext def\chapter{first} \dorecurse{10}{\input tufte }lastchapternumber\chapter {second} \dorecurse{10}somenamedheadnumber{\input davis }\chapter{third} \dorecurse{10}{\input zapf }\chapter{fourth} \dorecurse{10}{\input bryson }\stoptext</texcode><context>% by Hans Hagen, of course :-)\unprotected \def\rawsectionnumber#1{\countervalue{\??se#1last}} % will be in kernel
\setuppagenumbering
[alternative=doublesided]
\setupcolors
[state=start]
\setupbackgrounds
[\setups{thumbs}]
\defnewdimen\NOfChapters{4} % i need to make this one availablethumbheight
An example (MkIV) for using Metapost to create thumb indices for chapters.
<texcodecontext source="yes">% these first lines are just for wiki layout and visualisation\setuppapersize[A8][A4]\showframe\setuppaper[A4nx=4,oversizedny=4]\setuparranging[XY]\usemodule[visual]