// usage creates any necessary tags for actually using the relation in the SVG.
func (r *serviceRelation) usage(canvas *svg.SVG) {
l := r.shortestRelation()
canvas.Line(
l.p0.X,
l.p0.Y,
l.p1.X,
l.p1.Y,
fmt.Sprintf(`stroke=%q`, relationColor),
fmt.Sprintf(`stroke-width="%dpx"`, relationLineWidth),
fmt.Sprintf(`stroke-dasharray=%q`, strokeDashArray(l)),
)
mid := l.p0.Add(l.p1).Div(2).Sub(point(healthCircleRadius, healthCircleRadius))
canvas.Use(mid.X, mid.Y, "#healthCircle")
}
