Scala Swing is a thin wrapper around Java's Swing GUI framework that aims to simplify it. It uses Scala features like case classes for events, partial functions for event handling, and integrates with Scala collections. This allows building GUI components like panels, buttons, and list views with less verbose code compared to plain Java Swing. Custom painting and mixing in traits also allows flexibility in building component appearances.

1. Scala Swing Ken Scambler

2. Origins of Swing Java’s main desktop programming environment

3. Single Threaded, MVC framework

4. Developed from Abstract Windowing Toolkit (AWT) in the late 90s

5. Sun has focused on the web rather than desktop

6. Has faded from the limelight

7. However still has many users and devotees

8. Swing’s Advantages Cross-platform (mostly!)

9. Extremely powerful

10. Flexible

11. Extensible

12. Uses hardware acceleration

13. Comparable to native performance (nowadays!)

14. Swing’s Disadvantages Huge, complex API

15. Requires very verbose code

16. Events require anonymous inner class gymnastics!

17. Doesn’t integrate with Collection API

18. Models aren’t typesafe

19. Introducing Scala Swing Thin wrapper framework

20. Far less code

21. Dramatically simpler API

22. Full integration with Scala Collections

23. Introducing Scala Swing Scala getter/setter properties

24. Events use pattern-matching and partial functions

25. Performance is just as good

26. Panels & Layouts Layouts are built into the panel

27. Eg. BorderPanel, GridPanel, FlowPanel

28. Add components with 'contents' buffer

29. FlowPanel new FlowPanel { contents += new Button( "A" ) contents += new Button( "B" ) contents += new Button( "C" ) contents += new Button( "D" ) }

30. GridPanel new GridPanel(3,3) { contents ++= 1 to 9 map ( n => new Button(n.toString)) }

31. BorderPanel new BorderPanel { import BorderPanel.Position._ layout( new Button( "West" )) = West layout( new Button( "Center" )) = Center layout( new Button( "North" )) = North }

32. Events No more XXXListeners!

33. Individual events are case classes

34. Event handlers are PartialFunctions which pattern match on events

35. Classes which emit events have the Publisher trait

36. Classes which listen to Publishers have the Reactor trait.

37. Publishers & Reactors trait Reactor { val reactions: Reactions def listenTo(ps: Publisher*): Unit def deafTo(ps: Publisher*): Unit } trait Publisher extends Reactor { def publish(e: Event): Unit listenTo( this ) }

38. ButtonClicked events new FlowPanel { // Panels are Reactors // Buttons are Publishers val button = new Button( "abc" ) listenTo(button) reactions += { case ButtonClicked(b) => println( "Clicked " + b.text) } //... }

39. ButtonClicked events // All publishers are reactors // that listen to themselves new Button( "abc" ) { reactions += { case ButtonClicked(b) => println( "Clicked " + b.text) } }

40. Mouse Events new FlowPanel { val pub = new FlowPanel listenTo( pub .mouse.clicks, pub .mouse.moves, pub .mouse.wheel) reactions += { case me: MouseClicked => case me: MouseDragged => case me: MouseEntered => case me: MouseExited => case me: MouseMoved => case me: MouseWheelMoved => } }

41. Selection Events new FlowPanel { val fruitList = List( "apples", "bananas", "pears" ) val listView = new ListView(fruitList ) listenTo( listView .selection) reactions += { case SelectionChanged(`fruitList`) => } }

42. ListViews class ListView[A] extends Component { def this (items: Seq[A]) = //... //... }

43. ListViews case class City(name: String, country: String, population: Int , capital: Boolean ) val items = List( City( "Lausanne" , "Schweiz" , 129273, false ), City( "Paris" , "France" , 2203817, true ), City( "New York" , "USA" , 8363710 , false ), City( "Berlin" , "Germany" , 3416300, true ), City( "Tokyo" , "Japan" , 12787981, true )) val view = new ListView(items) val cityNames = view.selection.items.map(_.name)

44. Renderers From the last example... val view = new ListView(items) { renderer = ListView.Renderer(_.name) } From the last example...

45. Custom Painting val panel = new Panel { background = Color.blue override protected def paintComponent(g: Graphics2D) { super .paintComponent(g) g setColor Color.red for (x <- 0 until size.width by 10) g.drawLine(x, 0, x, size.height) } }

46. Fun with mixins trait BlueBackground { this : Panel => background = Color.blue} trait BlackBackground { this : Panel => background = Color.black} trait VerticalLines extends Panel { override protected def paintComponent(g: Graphics2D) { super .paintComponent(g) g setColor Color.red for (x <- 0 until size.width by 10) g.drawLine(x, 0, x, size.height) } } trait HorizontalLines extends Panel { override protected def paintComponent(g: Graphics2D) { super .paintComponent(g) g setColor Color.white for (y <- 0 until size.height by 20) g.drawLine(0, y, size.width, y) } } trait Blobs extends Panel { override protected def paintComponent(g: Graphics2D) { super .paintComponent(g) g setColor Color.green for (x <- 0 until size.width by 20; y <- 0 until size.height by 40) g.fillOval(x-4, y-4, 8, 8) } }

47. Fun with mixins val panel = new Panel with BlueBackground with HorizontalLines with VerticalLines with Blobs

48. Fun with mixins val panel = new Panel with BlackBackground with Blobs with VerticalLines with HorizontalLines

49. A basic complete app object SwingTalk extends SimpleSwingApplication { def top = new MainFrame { contents = new GridPanel(1, 4) { val nameLabel = new Label( &quot;Name&quot; ) val nameText = new TextField val helloButton = new Button( &quot;Say Hello&quot; ) val goodbyeButton = new Button( &quot;Say Goodbye&quot; ) listenTo(helloButton, goodbyeButton) contents ++= nameLabel :: nameText :: helloButton :: goodbyeButton :: Nil reactions += { case ButtonClicked(`helloButton`) => Dialog.showMessage(nameLabel, &quot;Hello, &quot; + nameText.text) case ButtonClicked(`goodbyeButton`) => Dialog.showMessage(nameLabel, &quot;Goodbye, &quot; + nameText.text) } } } }

50. What's missing? Work in progress Drag N' Drop

51. Tree views

52. Better actor support for multi-threading EPFL are snowed under!

53. Community contributions will make a big difference

54. Questions