Scala Swing reactions in an extended Panel

Question

Well, simple question: I have a singleton object that extends scala.swing.Panel, and I want to have it react on a simple mouse click. But... well, it doesn't work. Since Scala's such a new language, finding infos to specific problems is not so easy. Maybe you can help:

import scala.swing._
import scala.swing.event._
import java.awt.{Graphics2D, Color}

object GamePanel extends Panel {
  val map: TileMap = new TileMap(10, 10)({
    (x, y) =>
      if (x == y) new Wood
      else if (x == 5) new Water
      else new Grass
  })

  reactions += {
    case MouseClicked(src, pt, mod, clicks, pops) => {
      selectedTile = (pt.x / map.tw, pt.y / map.th)
      println("Clicked")
      repaint
    }
  }

  var selectedTile = (0, 0)

  override def paint(g: Graphics2D) = {
    map.draw(g)
    g.setColor(Color.red)
    g.drawRect(selectedTile._1 - 1, selectedTile._2 - 1, 33, 33)
  }
}

Thanks for listening.

Answer 1

Mouse events are not handled by default in Scala Swing for performance reasons. In your case you need to add a

listenTo(mouse.clicks)

to your object but there is also an event publisher mouse.moves you can listen to if you need to track the mouse move events.