scala.swing.Publisher.scala Maven / Gradle / Ivy
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2007-2011, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.swing
import scala.collection._
import scala.collection.mutable.{Buffer, HashSet, Set}
import event.Event
/**
* Notifies registered reactions when an event is published. Publishers are
* also reactors and listen to themselves per default as a convenience.
*
*
* In order to reduce memory leaks, reactions are weakly referenced by default,
* unless they implement Reactions.StronglyReferenced. That way,
* the lifetime of reactions are more easily bound to the registering object,
* which are reactors in common client code and hold strong references to their
* reactions. As a result, reactors can be garbage collected even though they
* still have reactions registered at some publisher, but not vice versa
* since reactors (strongly) reference publishers they are interested in.
*
*/
trait Publisher extends Reactor {
import Reactions._
protected val listeners = new RefSet[Reaction] {
import scala.ref._
val underlying = new HashSet[Reference[Reaction]]
protected def Ref(a: Reaction) = a match {
case a: StronglyReferenced => new StrongReference[Reaction](a) with super.Ref[Reaction]
case _ => new WeakReference[Reaction](a, referenceQueue) with super.Ref[Reaction]
}
}
private[swing] def subscribe(listener: Reaction) { listeners += listener }
private[swing] def unsubscribe(listener: Reaction) { listeners -= listener }
/**
* Notify all registered reactions.
*/
def publish(e: Event) { for (l <- listeners) l(e) }
listenTo(this)
}
/**
* A publisher that subscribes itself to an underlying event source not before the first
* reaction is installed. Can unsubscribe itself when the last reaction is uninstalled.
*/
private[swing] trait LazyPublisher extends Publisher {
import Reactions._
protected def onFirstSubscribe()
protected def onLastUnsubscribe()
override def subscribe(listener: Reaction) {
if(listeners.size == 1) onFirstSubscribe()
super.subscribe(listener)
}
override def unsubscribe(listener: Reaction) {
super.unsubscribe(listener)
if(listeners.size == 1) onLastUnsubscribe()
}
}
import scala.ref._
private[swing] trait SingleRefCollection[+A <: AnyRef] extends Iterable[A] { self =>
trait Ref[+A <: AnyRef] extends Reference[A] {
override def hashCode() = get match {
case Some(x) => x.##
case _ => 0
}
override def equals(that: Any) = that match {
case that: ReferenceWrapper[_] =>
val v1 = this.get
val v2 = that.get
v1 == v2
case _ => false
}
}
//type Ref <: Reference[A] // TODO: could use higher kinded types, but currently crashes
protected[this] def Ref(a: A): Ref[A]
protected[this] val referenceQueue = new ReferenceQueue[A]
protected val underlying: Iterable[Reference[A]]
def purgeReferences() {
var ref = referenceQueue.poll
while (ref != None) {
removeReference(ref.get.asInstanceOf[Reference[A]])
ref = referenceQueue.poll
}
}
protected[this] def removeReference(ref: Reference[A])
def iterator = new Iterator[A] {
private val elems = self.underlying.iterator
private var hd: A = _
private var ahead: Boolean = false
private def skip(): Unit =
while (!ahead && elems.hasNext) {
// make sure we have a reference to the next element,
// otherwise it might be garbage collected
val next = elems.next.get
ahead = next != None
if (ahead) hd = next.get
}
def hasNext: Boolean = { skip; ahead }
def next(): A =
if (hasNext) { ahead = false; hd }
else throw new NoSuchElementException("next on empty iterator")
}
}
private[swing] class StrongReference[+T <: AnyRef](value: T) extends Reference[T] {
private[this] var ref: Option[T] = Some(value)
def isValid: Boolean = ref != None
def apply(): T = ref.get
def get : Option[T] = ref
override def toString = get.map(_.toString).getOrElse("")
def clear() { ref = None }
def enqueue(): Boolean = false
def isEnqueued(): Boolean = false
}
abstract class RefBuffer[A <: AnyRef] extends Buffer[A] with SingleRefCollection[A] { self =>
protected val underlying: Buffer[Reference[A]]
def +=(el: A): this.type = { purgeReferences(); underlying += Ref(el); this }
def +=:(el: A) = { purgeReferences(); Ref(el) +=: underlying; this }
def remove(el: A) { underlying -= Ref(el); purgeReferences(); }
def remove(n: Int) = { val el = apply(n); remove(el); el }
def insertAll(n: Int, iter: Iterable[A]) {
purgeReferences()
underlying.insertAll(n, iter.view.map(Ref(_)))
}
def update(n: Int, el: A) { purgeReferences(); underlying(n) = Ref(el) }
def apply(n: Int) = {
purgeReferences()
var el = underlying(n).get
while (el == None) {
purgeReferences(); el = underlying(n).get
}
el.get
}
def length = { purgeReferences(); underlying.length }
def clear() { underlying.clear(); purgeReferences() }
protected[this] def removeReference(ref: Reference[A]) { underlying -= ref }
}
private[swing] abstract class RefSet[A <: AnyRef] extends Set[A] with SingleRefCollection[A] { self =>
protected val underlying: Set[Reference[A]]
def -=(el: A): this.type = { underlying -= Ref(el); purgeReferences(); this }
def +=(el: A): this.type = { purgeReferences(); underlying += Ref(el); this }
def contains(el: A): Boolean = { purgeReferences(); underlying.contains(Ref(el)) }
override def size = { purgeReferences(); underlying.size }
protected[this] def removeReference(ref: Reference[A]) { underlying -= ref }
}