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
  

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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
  

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