remove swing.Seq alias; use immutable.Seq where appropriate

- we leave scala.collection.Seq where the API would use
  Java Arrays, so we do not get sub-par performance in 2.13
- we use the more strict type immutable.Seq where its effortless
  and actually ensures correct behaviour. Since we are in a
  binary incompatible new scala-swing version, in the worst case
  user code that used Array in Scala <2.13 would have to enforce
  toList, toVector or similar

Author: Sciss

examples/src/main/scala/scala/swing/examples/tutorials/components/ListDemo.scala

@@ -76,7 +76,7 @@ class ListDemo extends BorderPanel {
   val nameSelected: String = listModel(initiallySelected)
 
   //Create a panel that uses BoxLayout.
-  val buttonPane = new BoxPanel(Orientation.Horizontal) {
+  val buttonPane: BoxPanel = new BoxPanel(Orientation.Horizontal) {
     border = Swing.EmptyBorder(5, 5, 5, 5)
     contents += fireButton
     contents += Swing.HStrut(5)
@@ -157,7 +157,7 @@ class ListDemo extends BorderPanel {
 }
 
 object ListDemo extends SimpleSwingApplication {
-  lazy val top = new MainFrame() {
+  lazy val top: Frame = new MainFrame() {
     title = "ListDemo"
     //Create and set up the content pane.
     contents = new ListDemo()

src/main/scala-2.13.0-M5/scala/swing/BufferWrapper.scala

@@ -44,7 +44,7 @@ abstract class BufferWrapper[A] extends mutable.Buffer[A] {
     }
   }
 
-  override def patchInPlace(from: Int, patch: Seq[A], replaced: Int): this.type = {
+  override def patchInPlace(from: Int, patch: scala.collection.Seq[A], replaced: Int): this.type = {
     if (replaced > 0) {
       remove(from, replaced)
     }

src/main/scala/scala/swing/ComboBox.scala

@@ -121,7 +121,7 @@ object ComboBox {
   implicit def floatEditor  (c: ComboBox[Float  ]): Editor[Float  ] = new BuiltInEditor(c)(s => s.toFloat , s => s.toString)
   implicit def doubleEditor (c: ComboBox[Double ]): Editor[Double ] = new BuiltInEditor(c)(s => s.toDouble, s => s.toString)
 
-  def newConstantModel[A](items: Seq[A]): ComboBoxModel[A] = {
+  def newConstantModel[A](items: scala.collection.Seq[A]): ComboBoxModel[A] = {
     new AbstractListModel[A] with ComboBoxModel[A] {
       private var selected: A = if (items.isEmpty) null.asInstanceOf[A] else items(0)
       def getSelectedItem: AnyRef = selected.asInstanceOf[AnyRef]
@@ -137,7 +137,7 @@ object ComboBox {
     }
   }
 
-  /*def newMutableModel[A, Self](items: Seq[A] with scala.collection.mutable.Publisher[scala.collection.mutable.Message[A], Self]): ComboBoxModel = {
+  /*def newMutableModel[A, Self](items: scala.collection.Seq[A] with scala.collection.mutable.Publisher[scala.collection.mutable.Message[A], Self]): ComboBoxModel = {
     new AbstractListModel with ComboBoxModel {
       private var selected = items(0)
       def getSelectedItem: AnyRef = selected.asInstanceOf[AnyRef]
@@ -147,8 +147,8 @@ object ComboBox {
     }
   }
 
-  def newConstantModel[A](items: Seq[A]): ComboBoxModel = items match {
-    case items: Seq[A] with scala.collection.mutable.Publisher[scala.collection.mutable.Message[A], Self] => newMutableModel
+  def newConstantModel[A](items: scala.collection.Seq[A]): ComboBoxModel = items match {
+    case items: scala.collection.Seq[A] with scala.collection.mutable.Publisher[scala.collection.mutable.Message[A], Self] => newMutableModel
     case _ => newConstantModel(items)
   }*/
 }
@@ -159,7 +159,7 @@ object ComboBox {
  *
  * @see javax.swing.JComboBox
  */
-class ComboBox[A](items: Seq[A]) extends Component with Publisher {
+class ComboBox[A](items: scala.collection.Seq[A]) extends Component with Publisher {
   override lazy val peer: JComboBox[A] = new JComboBox(ComboBox.newConstantModel(items)) with SuperMixin
 
   object selection extends Publisher {

src/main/scala/scala/swing/Container.scala

@@ -19,7 +19,7 @@ object Container {
     override def peer: javax.swing.JComponent
 
     protected val _contents = new Content
-    def contents: Seq[Component] = _contents
+    def contents: scala.collection.Seq[Component] = _contents
 
     protected class Content extends BufferWrapper[Component] {
       override def clear(): Unit = peer.removeAll()
@@ -61,5 +61,5 @@ trait Container extends UIElement {
   /**
    * The child components of this container.
    */
-  def contents: Seq[Component]
+  def contents: scala.collection.Seq[Component]
 }

src/main/scala/scala/swing/FileChooser.scala

@@ -13,6 +13,8 @@ import java.io.File
 import javax.swing.filechooser.FileFilter
 import javax.swing.{Icon, JFileChooser}
 
+import scala.collection.immutable
+
 object FileChooser {
   /**
    * The result of a file dialog. The precise meaning of the `Approve`
@@ -90,7 +92,7 @@ class FileChooser(dir: File) {
 
   def selectedFile: File = peer.getSelectedFile
   def selectedFile_=(file: File): Unit = peer.setSelectedFile(file)
-  def selectedFiles: Seq[File] = peer.getSelectedFiles.toSeq
+  def selectedFiles: immutable.Seq[File] = peer.getSelectedFiles.toIndexedSeq
   def selectedFiles_=(files: File*): Unit = peer.setSelectedFiles(files.toArray)
 
   def multiSelectionEnabled: Boolean = peer.isMultiSelectionEnabled

src/main/scala/scala/swing/ListView.scala

@@ -12,6 +12,8 @@ import event._
 import javax.swing._
 import javax.swing.event._
 
+import scala.collection.immutable
+
 object ListView {
   /**
    * The supported modes of user selections.
@@ -143,19 +145,19 @@ class ListView[A] extends Component {
   import ListView._
   override lazy val peer: JList[A] = new JList[A] with SuperMixin
 
-  def this(items: Seq[A]) = {
+  def this(items: scala.collection.Seq[A]) = {
     this()
     listData = items
   }
 
-  protected class ModelWrapper[B](val items: Seq[B]) extends AbstractListModel[B] {
+  protected class ModelWrapper[B](val items: scala.collection.Seq[B]) extends AbstractListModel[B] {
     def getElementAt(n: Int): B = items(n)
     def getSize: Int = items.size
   }
 
-  def listData: Seq[A] = peer.getModel match {
+  def listData: scala.collection.Seq[A] = peer.getModel match {
     case model: ModelWrapper[a] => model.items
-    case model => new Seq[A] { selfSeq =>
+    case model => new immutable.Seq[A] { selfSeq =>
      def length: Int = model.getSize
      def iterator: Iterator[A] = new Iterator[A] {
        var idx = 0
@@ -166,7 +168,7 @@ class ListView[A] extends Component {
     }
   }
 
-  def listData_=(items: Seq[A]): Unit = {
+  def listData_=(items: scala.collection.Seq[A]): Unit = {
     peer.setModel(new AbstractListModel[A] {
       def getElementAt(n: Int): A = items(n)
       def getSize: Int = items.size
@@ -177,7 +179,7 @@ class ListView[A] extends Component {
    * The current item selection.
    */
   object selection extends Publisher {
-    protected abstract class Indices[B](a: => Seq[B]) extends SetWrapper[B] {
+    protected abstract class Indices[B](a: => scala.collection.Seq[B]) extends SetWrapper[B] {
       def contains(n: B): Boolean = a.contains(n)
 
       override def size: Int = a.length
@@ -201,10 +203,11 @@ class ListView[A] extends Component {
     /**
      * The currently selected items.
      */
-    def items: Seq[A] = {
+    def items: immutable.Seq[A] = {
       // note: we should be using `getSelectedValuesList`, but it would break the Scala 2.11
-      // promise of working with Java 6 (requires Java 7)
-      peer.getSelectedValues.iterator.map(_.asInstanceOf[A]).toSeq
+      // promise of working with Java 6 (requires Java 7).
+      // Note: in Scala <= 2.12, toSeq might produce a Stream.
+      peer.getSelectedValues.iterator.map(_.asInstanceOf[A]).toIndexedSeq
     }
 
     def intervalMode: IntervalMode.Value = IntervalMode(peer.getSelectionModel.getSelectionMode)

src/main/scala/scala/swing/RichWindow.scala

@@ -146,7 +146,7 @@ object Dialog {
                   optionType: Options.Value = Options.YesNo,
                   messageType: Message.Value = Message.Question,
                   icon: Icon = EmptyIcon,
-                  entries: Seq[Any],
+                  entries: scala.collection.Seq[Any],
                   initial: Int): Result.Value = {
     val r = JOptionPane.showOptionDialog(nullPeer(parent), message, title,
       optionType.id, messageType.id, Swing.wrapIcon(icon),
@@ -159,10 +159,10 @@ object Dialog {
                    title: String = uiString("OptionPane.inputDialogTitle"),
                    messageType: Message.Value = Message.Question,
                    icon: Icon = EmptyIcon,
-                   entries: Seq[A] = Nil,
+                   entries: scala.collection.Seq[A] = Nil,
                    initial: A): Option[A] = {
     val e = if (entries.isEmpty) null
-    else (entries map toAnyRef).toArray
+    else entries.iterator.map(toAnyRef).toArray
     val r = JOptionPane.showInputDialog(nullPeer(parent), message, title,
       messageType.id, Swing.wrapIcon(icon),
       e, initial)

src/main/scala/scala/swing/RootPanel.scala

@@ -8,6 +8,8 @@
 
 package scala.swing
 
+import scala.collection.immutable
+
 /**
  * The root of a component hierarchy. Contains at most one component.
  *
@@ -19,7 +21,7 @@ trait RootPanel extends Container {
   /**
    * At most one component.
    */
-  def contents: Seq[Component] =
+  def contents: immutable.Seq[Component] =
     if (peer.getContentPane.getComponentCount == 0) Nil
     else {
       val c = peer.getContentPane.getComponent(0).asInstanceOf[javax.swing.JComponent]

src/main/scala/scala/swing/ScrollPane.scala

@@ -10,6 +10,8 @@ package scala.swing
 
 import javax.swing.{JScrollPane, ScrollPaneConstants}
 
+import scala.collection.immutable
+
 object ScrollPane {
   object BarPolicy extends Enumeration {
     import ScrollPaneConstants._
@@ -46,7 +48,7 @@ class ScrollPane extends Component with Container {
     this()
     contents = c
   }
-  def contents: Seq[Component] =
+  def contents: immutable.Seq[Component] =
     List(UIElement.cachedWrapper[Component](peer.getViewport.getView.asInstanceOf[javax.swing.JComponent]))
 
   /**

src/main/scala/scala/swing/SplitPane.scala

@@ -10,6 +10,7 @@ package scala.swing
 
 import javax.swing.JSplitPane
 
+import scala.collection.immutable
 import scala.swing.Swing.nullPeer
 
 /**
@@ -25,7 +26,7 @@ class SplitPane(o: Orientation.Value, left: Component, right: Component) extends
   def this(o: Orientation.Value) = this(o, new Component {}, new Component {})
   def this() = this(Orientation.Horizontal)
 
-  def contents: Seq[Component] = List(leftComponent, rightComponent)
+  def contents: immutable.Seq[Component] = List(leftComponent, rightComponent)
   def contents_=(left: Component, right: Component): Unit = {
     peer.setLeftComponent(nullPeer(left))
     peer.setRightComponent(nullPeer(right))

src/main/scala/scala/swing/Table.scala

@@ -133,7 +133,7 @@ class Table extends Component with Scrollable.Wrapper {
     *                     by calling `toString` on the elements. The size of this sequence
     *                     must correspond with the inner dimension of `rowData`.
     */
-  def this(rowData: Array[Array[Any]], columnNames: Seq[_]) = {
+  def this(rowData: Array[Array[Any]], columnNames: scala.collection.Seq[_]) = {
     this()
     model = new AbstractTableModel {
       override def getColumnName(column: Int): String = columnNames(column).toString
@@ -196,7 +196,7 @@ class Table extends Component with Scrollable.Wrapper {
 
   object selection extends Publisher {
     // TODO: could be a sorted set
-    protected abstract class SelectionSet[A](a: => Seq[A]) extends SetWrapper[A] {
+    protected abstract class SelectionSet[A](a: => scala.collection.Seq[A]) extends SetWrapper[A] {
       // def -=(n: A): this.type
       // def +=(n: A): this.type
 

src/main/scala/scala/swing/package.scala

@@ -22,12 +22,11 @@ package object swing {
   type Image      = java.awt.Image
   type Font       = java.awt.Font
 
-  type Seq[+A]    = scala.collection.Seq[A] // because scala.Seq differs between Scala 2.12 and 2.13
-
   implicit lazy val reflectiveCalls     = scala.language.reflectiveCalls
   implicit lazy val implicitConversions = scala.language.implicitConversions
 
-  private[swing] def ifNull[A](o: Object, a: A): A = if(o eq null) a else o.asInstanceOf[A]
-  private[swing] def toOption[A](o: Object): Option[A] = if(o eq null) None else Some(o.asInstanceOf[A])
+  private[swing] def ifNull   [A](o: Object, a: A): A   = if(o eq null) a     else o.asInstanceOf[A]
+  private[swing] def toOption [A](o: Object): Option[A] = if(o eq null) None  else Some(o.asInstanceOf[A])
+
   private[swing] def toAnyRef(x: Any): AnyRef = x.asInstanceOf[AnyRef]
 }