lineNo.getStylesheets().add(stylesheet);
// When removed from the scene, stay subscribed to never(), which is
// a fake subscription that consumes no resources, instead of staying
// subscribed to area's paragraphs.
EventStreams.valuesOf(lineNo.sceneProperty())
.flatMap(scene -> scene != null
? nParagraphs.map(n -> format(idx+1, n))
: EventStreams.<String>never())
.feedTo(lineNo.textProperty());
return lineNo;