d.sorted = edges
	} else {
		oldSorted := d.sorted
		newSorted := make([]edge, len(oldSorted)+len(edges))
		i, j := 0, 0
		for o := range newSorted {
			if i >= len(oldSorted) {
				copy(newSorted[o:], edges[j:])
				break
			} else if j >= len(edges) {
				copy(newSorted[o:], oldSorted[i:])
				break
			} else if oldSorted[i].x < edges[j].x {
				newSorted[o] = oldSorted[i]
				i++
			} else {