Thumb index

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...

% these first lines are just for wiki layout and visualisation
\setuppapersize[A8][A5,landscape] \showframe
\setuppaper[nx=4,ny=2]
\setuparranging[XY]
\usemodule[visual]

\def\currentchapternumber
   {\somenamedheadnumber{chapter}{current}}

\def\lastchapternumber
   {\somenamedheadnumber{chapter}{last}}

\setuppagenumbering
   [alternative=doublesided]

\setupbackgrounds
   [page]
   [background=thumbs]

\defineoverlay
   [thumbs]
   [\setups{thumbs}]

\newdimen\thumbheight

\startsetups thumbs
     \ifnum \lastchapternumber > 0
        \thumbheight=\dimexpr\paperheight/\lastchapternumber\relax
     \fi
     \vbox to \paperheight \bgroup
         \vskip \currentchapternumber \thumbheight
         \vskip -1                    \thumbheight
         \doifoddpageelse\hfill\donothing
         \framed
             [background=color,
              backgroundcolor=blue,
              frame=off,
              foregroundcolor=white,
              height=\thumbheight,
              width=5mm]
             {\bfa \currentchapternumber}
         \doifoddpageelse\donothing\hfill
         \vss
     \egroup

\stopsetups

\starttext

\dorecurse{4}
 {\chapter{\fakewords{1}{5}}
  \fakewords{50}{100}}

\stoptext

Another Example

An example (MkIV) for using Metapost to create thumb indices for chapters.

% these first lines are just for wiki layout and visualisation
\setuppapersize[A8][A4] \showframe
\setuppaper[nx=4,ny=4]
\setuparranging[XY]
\usemodule[visual]

\setuplayout
  [width=middle,
   % margin=\dimexpr\backspace-\margindistance\relax
   location=middle]

\definecolor[chap_frame][g=1,t=1,a=12]
\definecolor[sect_frame][b=1,t=1,a=12]
\definecolor[textcolor] [r=1,t=1,a=12]

\startuseMPgraphic{chapter thumb}
  path chap_frame, sect_frame ;  pair pos,a,b ;  picture text ;

  if  \somenamedheadnumber{chapter}{current} > 0 :
     curr_chap := \somenamedheadnumber{chapter}{current} ; 
  else :
     curr_chap := 1 ;
  fi;
  if \somenamedheadnumber{chapter}{last} > 0 :
     last_chap := \somenamedheadnumber{chapter}{last} ;
  else :
     last_chap := 1 ;
  fi;
  if \somenamedheadnumber{section}{current} > 0 : 
     curr_sect := \somenamedheadnumber{section}{current} ; 
  else: 
     curr_sect := 1 ;
  fi;
  if \somenamedheadnumber{section}{last} > 0 :
     last_sect := \somenamedheadnumber{section}{last};
  else:
     last_sect := 1;
  fi;  

  skip   := TextHeight * (curr_chap-1)/last_chap ;
  height := TextHeight/last_chap ;
  sskip  := height*curr_sect/last_sect ;
 
  text   := textext("\ssbfb\textcolor Chapter\enspace\getmarking[chapternumber]");

  StartPage ;
    chap_frame := fullsquare xyscaled(RightMarginWidth,height) ;

    a := ulcorner chap_frame ;
    b := urcorner chap_frame ;

    sect_frame := a--b--(xpart b,ypart b-sskip)--(xpart a,ypart a-sskip)--cycle;

    pos := urcorner Field[Text][RightMarginSeparator] -
           ulcorner chap_frame - (0,skip);

    fill chap_frame shifted pos withcolor \MPcolor{chap_frame};
    unfill sect_frame shifted pos withcolor white ;
    fill sect_frame shifted pos withcolor \MPcolor{sect_frame};
    draw text rotated 90 shifted pos ;
  StopPage ;
\stopuseMPgraphic


\defineoverlay[chapter thumb][\useMPgraphic{chapter thumb}]

\setupbackgrounds[page][background=chapter thumb]


\starttext  \showframe
\dorecurse{3}{\chapter{Test Chapter #1}
  Chapter \someheadnumber[chapter][current] of
  \someheadnumber[chapter][last]
  \dorecurse{9}{\section{Test Section}
    Section \someheadnumber[section][current] of
    \someheadnumber[section][last] \blank
    \fakewords{10}{20} \par
  }
}
\stoptext