A little pie chart

Richard Suchenwirth 2007-04-26 - As a little evening fun project, here's a tiny pie chart code - which together with the screenshot and example should speak for itself:

 proc piechart {w x y width height data} {
    set coords [list $x $y [expr {$x+$width}] [expr {$y+$height}]]
    set xm  [expr {$x+$width/2.}]
    set ym  [expr {$y+$height/2.}]
    set rad [expr {$width/2.+20}]
    set sum 0
    foreach item $data {set sum [expr {$sum + [lindex $item 1]}]}
    set start 270
    foreach item $data {
        foreach {name n color} $item break
        set extent [expr {$n*360./$sum}]
        $w create arc $coords -start $start -extent $extent -fill $color
        set angle [expr {($start-90+$extent/2)/180.*acos(-1)}]
        set tx [expr $xm-$rad*sin($angle)]
        set ty [expr $ym-$rad*cos($angle)]
        $w create text $tx $ty -text $name:$n  -tag txt
        set start [expr $start+$extent]
    }
    $w raise txt
 }
#-- Testing:
 pack [canvas .c -bg white]
 piechart .c 50 50 150 150 {
    {SPD  199 red}
    {CDU  178 gray}
    {CSU   23 blue}
    {FDP   60 yellow}
    {Grüne 58 green}
    {Linke 55 purple}
 }