ScalaFX PickResult with subclassed nodes

I have a simple scalafx app but I am struggling to get simple mouse interactions working.

I have custom Canvas node class called Square :

case class Square(val index: Int) extends Canvas

I then have a custom GridPane that is filled with squares :

class BoardPane extends GridPane
{
  val squares: Array[Square] = (0 to 63).toArray.map(index => Square(index))
  (0 to 63).foreach(index => add(squares(index), index%8, 7-index/8))
}

When I try to get the pick result from a mouse event :

class PlayableBoardPane extends BoardPane
{
  onMouseDragged = (event => {
    val node: Option[Node] = event.pickResult.intersectedNode
  ...
  })
}

The intersected node is not a Square but a "scalafx.scene.LowerPriorityIncludes$$anon$4" (with implicit conversion)

Is there a way I can map this node back to my squares?

Without that I fail to see how to even use node picking with subclassed nodes at all.

Solution

Keep in mind that ScalaFX helps you build a JavaFX application - the underlaying structures are JavaFX. That is, when you build a scene graph in ScalaFX it is composed of JavaFX objects.

For that reason, ScalaFX application should be build trough composition not inheritance. When you simply inherit from a ScalaFX wrapper, like in your example:

    case class Square(val index: Int) extends Canvas

it is extending a wrapper not the actual JavaFX class. When you build a scene graph and then examine it through picking you will see JavaFX objects not the wrappers you created. You can deal with that is various ways. A simple one is to set userData that is passed to underlying JavaFX object. I complete example from fragments you posed would be like this:

import scalafx.Includes._
import scalafx.application.JFXApp
import scalafx.application.JFXApp.PrimaryStage
import scalafx.scene.Scene
import scalafx.scene.canvas.Canvas
import scalafx.scene.layout.GridPane

object PickResultWithSubclassedNodes extends JFXApp {

  case class Square(index: Int) extends Canvas {
    height = 25
    width = 25
    userData = index.toString
  }

  class BoardPane extends GridPane {
    val squares: Array[Square] = (0 to 63).toArray.map(index => Square(index))
    (0 to 63).foreach(index => add(squares(index), index % 8, 7 - index / 8))
  }

  class PlayableBoardPane extends BoardPane {
    onMouseReleased = (event => {
      val node = event.pickResult.intersectedNode
      node match {
        case Some(n) => println("Picked: " + n.userData)
        case None =>
      }
    })
  }

  stage = new PrimaryStage {
    title = "Blocking"
    scene = new Scene {
      root = new PlayableBoardPane()
    }
  }
}

Clicking on the window will produce output like this:

Picked: 40
Picked: 42
Picked: 17
Picked: 36
Picked: 52
Picked: 38
Picked: 27

No issue with unusual implicit classes.