Count positions an arc being for bounding box of the path. - An arc is part of a circle/ellipse. - We add positions of 4 corners into the list of points of the path. - The position of 4 corners will be included in the bounding box of the path.

divert([-1])

define([_arg1], [$1])

define([_foreach], [ifelse([$2], [()], [],
[define([$1], _arg1$2)$3[]_foreach([$1], (shift$2), [$3])])])

define([foreach], [pushdef([$1])_foreach($@)popdef([$1])])

divert[]dnl