Scala+swing

Scala Swing Ken Scambler

Origins of Swing
Java’s main desktop programming environment
Single Threaded, MVC framework
Developed from Abstract Windowing Toolkit (AWT) in the late 90s
Sun has focused on the web rather than desktop
Has faded from the limelight
However still has many users and devotees

Swing’s Advantages
Cross-platform (mostly!)
Extremely powerful
Flexible
Extensible
Uses hardware acceleration
Comparable to native performance (nowadays!)

Swing’s Disadvantages
Huge, complex API
Requires very verbose code
Events require anonymous inner class gymnastics!
Doesn’t integrate with Collection API
Models aren’t typesafe

Introducing Scala Swing
Thin wrapper framework
Far less code
Dramatically simpler API
Full integration with Scala Collections

Introducing Scala Swing
Scala getter/setter properties
Events use pattern-matching and partial functions
Performance is just as good

Panels & Layouts
Layouts are built into the panel
Eg. BorderPanel, GridPanel, FlowPanel
Add components with 'contents' buffer

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

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

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

Events
No more XXXListeners!
Individual events are case classes
Event handlers are PartialFunctions which pattern match on events
Classes which emit events have the Publisher trait
Classes which listen to Publishers have the Reactor trait.

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 ) }

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) } //... }

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

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 => } }

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

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

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)

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

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) } }

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) } }

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

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

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

What's missing?
Work in progress
Drag N' Drop
Tree views
Better actor support for multi-threading
EPFL are snowed under!
Community contributions will make a big difference

Questions

Scala+swing

by perneto on Aug 31, 2010

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Scala+swing — Presentation Transcript

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