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Scalaxy/Fx: JavaFX eye-candy experiment for Scala 2.10

Minimal set of Scala 2.11.x macros, dynamics and implicits for maximal JavaFX eye-candy (BSD-licensed)! (does not depend on the rest of Scalaxy)

Important: this "library" was designed as a DSL with no runtime dependency.

This means that all the methods defined in the scalaxy.fx package are macros that rewrite the code to something pure-JavaFX, with no reference to any additional class. If you want to learn how to write non-trivial macros, have a look at the code!

As a result, you may say think of Scalaxy/Fx as a compiler plugin rather than a library (but technically, it is just a library of macros).


This library is a very limited proof of concept without proper tests (should work mostly well, though).

If you're looking for a complete and supported JavaFX experience in Scala, please use ScalaFX (great mature library written by Stephen Chin and other committers, although it doesn't use macros as of yet and hence has some more exotic syntax for bindings).


import scalaxy.fx._

import javafx._
import javafx.event._

object HelloWorld extends App {
  Application.launch(classOf[HelloWorld], args: _*)

class HelloWorld extends Application {
  override def start(primaryStage: Stage) {
    val slider = new Slider().set(
      min = 0,
      max = 100,
      blockIncrement = 1,
      value = 50
    slider.valueProperty onChange {
      println("Slider changed")
      title = "Hello World!",
      scene = new Scene(
        new StackPane() {
            new BorderPane().set(
              bottom = new Button().set(
                text = "Say 'Hello World'",
                onAction = {
                  println("Hello World!")
              center = slider,
              top = new Label().set(
                text = bind {
                  s"Slider is at ${slider.getValue.toInt}"


To use with sbt 0.13.0+, please have a look at the HelloWorld example and make your build.sbt file look like:

scalaVersion := "2.11.6"

// Add JavaFX Runtime as an unmanaged dependency, hoping to find it in the JRE's library folder.
unmanagedJars in Compile ++= Seq(new File(System.getProperty("java.home")) / "lib" / "jfxrt.jar")

// This is the bulk of Scalaxy/Fx, needed only during compilation (no runtime dependency here).
libraryDependencies += "com.nativelibs4java" %% "scalaxy-fx" % "0.3-SNAPSHOT" % "provided"

// JavaFX doesn't cleanup everything well, need to fork tests / runs.
fork := true

// Scalaxy snapshots are published on the Sonatype repository.
resolvers += Resolver.sonatypeRepo("snapshots")


The syntactic facilities available so far are:

  • JavaFX Script-like syntax for setters (without any runtime penalty or loss of type-safetiness):

      text = "Say 'Hello World'",
      tooltip = new Tooltip("Hover me"),
      minHeight = 300,
      minHidth = 200
  • More natural bindings:

    val moo = newProperty(10)
    val foo = bind { Math.sqrt(moo.get) }
    val button = new Button().set(
      text = bind { s"Foo is ${foo.get}" },
      cancelButton = true

    Instead of:

    val moo = new SimpleIntegerProperty(10)
    val foo = new DoubleBinding() {
      override def computeValue() =
    val button = new Button()
      new StringBinding() {
        override def computeValue() =
          s"Foo is ${foo.get}"
  • Simpler syntax for event handlers, with or without the event parameter:

      text = "Click me!",
      onAction = println("clicked")
      text = "Click me!",
      onAction = (event: ActionEvent) => {
        println(s"clicked: $event")
    button2.maxWidthProperty onChange {
      println("Constraint changed!")

    Instead of:

    button3.setText("Click me!")
    button3.setOnAction(new EventHandler[ActionEvent]() {
      override def handle(event: ActionEvent) {
        println(s"clicked: $event")
    button3.maxWidthProperty.addListener(new ChangeListener[Double]() {
      override def changed(observable: ObservableValue[_ <: Double], oldValue: Double, newValue: Double) {
        println("Constraint changed!")
  • Natural Scala getters / setters for all of the JavaFX API, with IDE completion and still no runtime dependencies! (TODO document this / give examples)


Scalaxy/Fx uses some interesting techniques:

  • Combination of Dynamic and macros for a type-safe setters syntax for Java beans, that uses named parameters. (see Scalaxy/Beans and my blog post on the matter for more details on this technique)

  • CanBuildFrom-style implicits to associate value types T to their Binding[T] or Property[T] subclasses. What's interesting here is that there is no implementation of these evidence objects, which only serve to the typer and are thrown away by the macros.

    As a result, the following property and binding are correctly typed to their concrete implementation:

    import scalaxy.fx._
    val p: SimpleIntegerProperty = newProperty(10)
    val b: IntegerBinding = bind { p.get + 10 }
  • Despite it not being officially supported, creates anonymous handler classes from inside macros. (see EventHandlerMacros.scala)

  • Macros all over, for absolutely no runtime dependency. This means the dependency in sbt / Maven can be marked as provided, and won't be needed when running your program.


If you want to build / test / hack on this project:

  • Make sure to use paulp's sbt script with sbt 0.12.2+

  • Install Oracle's JDK + JavaFX and make sure the java command in the path points to that version

  • Use the following commands to checkout the sources and build the tests continuously:

    git clone git://github.com/ochafik/Scalaxy.git
    cd Scalaxy
    sbt "project scalaxy-fx" "; clean ; ~test"