The Exploding Pixels blog has an entry on clean FX code formatting. I didn't really like the options provided so far, so I decided to write a quick blog with my version.
def backgroundImage = Image { url: "{__DIR__}background.png" };
var verticalPositionOfLine:Number;
var s = Stage {
title: "Background Image"
scene: Scene {
width: 200
height: 232
content...