posA: line insertion in the slice
posB: line break position
posC: label position
posAis straightforward thanks to the
centroidfunction of d3. It is used to label pie chart as well.
posB,another arc generator called
outerArcis created. It is not used to draw arcs, but only to compute centroid.
posChas the same Y coordinates than
posB. However its x coordinate is at the extreme part of the svg area.