bbox

$group bbox: returns coords of bounding box

obj method group bbox {{raw no}} {
  set minX Inf
  set minY Inf
  set maxX -Inf
  set maxY -Inf
  foreach bb [$self elements bbox $raw] {
    foreach {x0 y0 x1 y1} $bb {
      set minX [min $minX $x0]
      set minY [min $minY $y0]
      set maxX [max $maxX $x1]
      set maxY [max $maxY $y1]
    }
  }
  list $minX $minY $maxX $maxY
}