Implement event capturing

src/main/scala/ocelot/desktop/inventory/Inventory.scala

@@ -1,7 +1,7 @@
 package ocelot.desktop.inventory
 
 import ocelot.desktop.inventory.Inventory.SlotObserver
-import ocelot.desktop.ui.event.{BrainEvent, Event, EventAware}
+import ocelot.desktop.ui.event.{BrainEvent, Dispatchable, EventAware}
 import ocelot.desktop.util.Disposable
 import totoro.ocelot.brain.event.NodeEvent
 
@@ -78,7 +78,7 @@ trait Inventory extends EventAware with Disposable {
     super.shouldReceiveEventsFor(address) ||
       inventoryIterator.flatMap(_.get).exists(_.shouldReceiveEventsFor(address))
 
-  override def handleEvent(event: Event): Unit = {
+  override def handleEvent(event: Dispatchable): Unit = {
     super.handleEvent(event)
 
     for (slot <- inventoryIterator; item <- slot.get) {

src/main/scala/ocelot/desktop/ui/UiHandler.scala

@@ -6,7 +6,7 @@ import ocelot.desktop.geometry.{Rect2D, Size2D, Vector2D}
 import ocelot.desktop.graphics.Graphics
 import ocelot.desktop.ui.event.handlers.HoverHandler
 import ocelot.desktop.ui.event.sources.{BrainEvents, KeyEvents, MouseEvents, ScrollEvents}
-import ocelot.desktop.ui.event.{Event, MouseEvent}
+import ocelot.desktop.ui.event.{Capturing, CapturingEvent, Dispatchable, MouseEvent}
 import ocelot.desktop.ui.widget.window.Window
 import ocelot.desktop.ui.widget.{RootWidget, Widget}
 import ocelot.desktop.util._
@@ -427,16 +427,18 @@ object UiHandler extends Logging {
     Audio.destroy()
   }
 
-  private def dispatchEvent(iter: => IterableOnce[Widget] = hierarchy.reverseIterator)(event: Event): Unit = {
-    for (widget <- iter) {
-      if (event.consumed) {
-        return
-      }
-
+  private def dispatchEvent(iter: => IterableOnce[Widget] = hierarchy.reverseIterator)(event: Dispatchable): Unit = {
+    for (widget <- iter if !event.consumed) {
       widget.handleEvent(event)
     }
   }
 
+  private def dispatchCapturing(target: Widget)(event: CapturingEvent): Unit = {
+    val ancestors = target.ancestors.toSeq
+    dispatchEvent(ancestors.reverseIterator ++ Some(target))(Capturing(event))
+    dispatchEvent(Some(target))(event)
+  }
+
   private def dispatchBrainEvents(): Unit = {
     import totoro.ocelot.brain
 
@@ -476,7 +478,10 @@ object UiHandler extends Logging {
     }
 
     // TODO: dispatch to the focused widget instead of broadcasting to the entire hierarchy.
-    KeyEvents.events.foreach(dispatchEvent())
+    for (event <- KeyEvents.events) {
+      dispatchEvent(hierarchy)(Capturing(event))
+      dispatchEvent()(event)
+    }
 
     MouseEvents.events
       .foreach(dispatchEvent(hierarchy.reverseIterator.filter(w => w.enabled && w.receiveAllMouseEvents)))
@@ -487,17 +492,22 @@ object UiHandler extends Logging {
     val mouseTarget = hierarchy.reverseIterator
       .find(w => w.enabled && w.receiveMouseEvents && w.clippedBounds.contains(mousePos))
 
-    ScrollEvents.events.foreach(dispatchEvent(scrollTarget))
+    for (scrollTarget <- scrollTarget) {
+      ScrollEvents.events.foreach(dispatchCapturing(scrollTarget))
+    }
 
     for (event <- MouseEvents.events) {
       if (event.state == MouseEvent.State.Pressed) {
-        dispatchEvent(mouseTarget)(event)
+        for (mouseTarget <- mouseTarget) {
+          dispatchCapturing(mouseTarget)(event)
+        }
 
         // TODO: this should be done in the event capturing phase in [[Window]] itself.
         for (mouseTarget <- mouseTarget if !mouseTarget.isInstanceOf[Window]) {
           focusParentWindow(mouseTarget.parent)
         }
       } else {
+        dispatchEvent(hierarchy)(Capturing(event))
         dispatchEvent(hierarchy.reverseIterator)(event)
       }
     }

src/main/scala/ocelot/desktop/ui/event/CapturingEvent.scala

@@ -0,0 +1,3 @@
+package ocelot.desktop.ui.event
+
+trait CapturingEvent extends Event

src/main/scala/ocelot/desktop/ui/event/Dispatchable.scala

@@ -0,0 +1,28 @@
+package ocelot.desktop.ui.event
+
+sealed trait Dispatchable {
+  def consume(): Unit
+
+  def consumed: Boolean
+}
+
+trait Event extends Dispatchable {
+  private var _consumed: Boolean = false
+
+  def consume(): Unit = {
+    _consumed = true
+  }
+
+  def consumed: Boolean = _consumed
+}
+
+/**
+  * A wrapper for an event that is dispatched during the capture phase.
+  */
+case class Capturing[A <: CapturingEvent](event: A) extends Dispatchable {
+  override def consume(): Unit = {
+    event.consume()
+  }
+
+  override def consumed: Boolean = event.consumed
+}

src/main/scala/ocelot/desktop/ui/event/Event.scala

@@ -1,11 +0,0 @@
-package ocelot.desktop.ui.event
-
-trait Event extends AnyRef {
-  private var _consumed: Boolean = false
-
-  def consume(): Unit = {
-    _consumed = true
-  }
-
-  def consumed: Boolean = _consumed
-}

src/main/scala/ocelot/desktop/ui/event/EventAware.scala

@@ -7,7 +7,7 @@ trait EventAware {
 
   def shouldReceiveEventsFor(address: String): Boolean = false
 
-  def handleEvent(event: Event): Unit = {
+  def handleEvent(event: Dispatchable): Unit = {
     eventHandlers(event)
   }
 }

src/main/scala/ocelot/desktop/ui/event/KeyEvent.scala

@@ -6,4 +6,4 @@ object KeyEvent {
   }
 }
 
-case class KeyEvent(state: KeyEvent.State.Value, code: Int, char: Char) extends Event
+case class KeyEvent(state: KeyEvent.State.Value, code: Int, char: Char) extends CapturingEvent

src/main/scala/ocelot/desktop/ui/event/MouseEvent.scala

@@ -12,4 +12,4 @@ object MouseEvent {
   }
 }
 
-case class MouseEvent(state: MouseEvent.State.Value, button: MouseEvent.Button.Value) extends Event
+case class MouseEvent(state: MouseEvent.State.Value, button: MouseEvent.Button.Value) extends CapturingEvent

src/main/scala/ocelot/desktop/ui/event/ScrollEvent.scala

@@ -1,3 +1,3 @@
 package ocelot.desktop.ui.event
 
-case class ScrollEvent(offset: Int) extends Event
+case class ScrollEvent(offset: Int) extends CapturingEvent

src/main/scala/ocelot/desktop/ui/widget/EventHandlers.scala

@@ -1,27 +1,27 @@
 package ocelot.desktop.ui.widget
 
-import ocelot.desktop.ui.event.Event
+import ocelot.desktop.ui.event.{Dispatchable, Event}
 
 import scala.collection.mutable.ArrayBuffer
 
-class EventHandlers extends PartialFunction[Event, Unit] {
+class EventHandlers extends PartialFunction[Dispatchable, Unit] {
   private val handlers = ArrayBuffer.empty[EventHandler]
 
   def +=(handler: EventHandler): Unit = handlers += handler
 
   def -=(handler: EventHandler): Unit = handlers -= handler
 
-  override def isDefinedAt(event: Event): Boolean = handlers.exists(_.isDefinedAt(event))
+  override def isDefinedAt(event: Dispatchable): Boolean = handlers.exists(_.isDefinedAt(event))
 
-  override def apply(event: Event): Unit = {
+  override def apply(event: Dispatchable): Unit = {
     for (handler <- handlers) {
       if (event.consumed) {
         return
       }
 
-      handler.applyOrElse(event, (_: Event) => ())
+      handler.applyOrElse(event, (_: Dispatchable) => ())
     }
   }
 
-  type EventHandler = PartialFunction[Event, Unit]
+  type EventHandler = PartialFunction[Dispatchable, Unit]
 }

src/main/scala/ocelot/desktop/ui/widget/Widget.scala

@@ -59,6 +59,10 @@ class Widget extends EventAware with Updatable with Disposable {
 
   final def root: Option[RootWidget] = _root
 
+  final def ancestors: Iterator[Widget] = {
+    Iterator.unfold(this)(_.parent.map(w => (w, w)))
+  }
+
   def enabled: Boolean = true
 
   def minimumSize: Size2D = layout.minimumSize