Process a snapshot of the BrainEvent queue on update

Closes #177.

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

@@ -4,9 +4,9 @@ import buildinfo.BuildInfo
 import ocelot.desktop.audio.{Audio, SoundBuffers, SoundSource}
 import ocelot.desktop.geometry.{Rect2D, Size2D, Vector2D}
 import ocelot.desktop.graphics.Graphics
-import ocelot.desktop.ui.event.{Event, MouseEvent}
 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.widget.window.Window
 import ocelot.desktop.ui.widget.{RootWidget, Widget}
 import ocelot.desktop.util._
@@ -15,7 +15,6 @@ import org.apache.commons.lang3.SystemUtils
 import org.lwjgl.BufferUtils
 import org.lwjgl.input.Mouse
 import org.lwjgl.opengl._
-import totoro.ocelot.brain.event.{InventoryEvent, NodeEvent}
 
 import java.awt.Toolkit
 import java.awt.datatransfer.{DataFlavor, StringSelection, UnsupportedFlavorException}
@@ -437,14 +436,37 @@ object UiHandler extends Logging {
     }
   }
 
+  private def dispatchBrainEvents(): Unit = {
+    val cutoff = BrainEvents.events.peekLast()
+
+    if (cutoff == null) {
+      return
+    }
+
+    // we're effectively taking a snapshot of all events we have received at the point of the call.
+    // new events may still be added to the queue, but we'll defer everything after the cutoff until the next update.
+    val events = LazyList.continually(BrainEvents.events.poll()).takeWhile({
+      var inSnapshot = true
+
+      { event =>
+        val pass = inSnapshot
+        inSnapshot = !(event eq cutoff)
+
+        pass
+      }
+    })
+
+    for (event <- events) {
+      root.workspaceView.dispatchBrainEvent(event)
+    }
+  }
+
   private def update(): Unit = {
     if (shouldUpdateHierarchy) {
       _updateHierarchy()
     }
 
-    for (event <- LazyList.continually(BrainEvents.events.poll()).takeWhile(_ != null)) {
+    dispatchBrainEvents()
-      root.workspaceView.dispatchBrainEvent(event)
-    }
 
     val mousePos = mousePosition
     if (mousePos.x < 0 || mousePos.y < 0 || mousePos.x > root.width || mousePos.y > root.height) {

src/main/scala/ocelot/desktop/ui/event/sources/BrainEvents.scala

@@ -2,10 +2,10 @@ package ocelot.desktop.ui.event.sources
 
 import totoro.ocelot.brain.event.{Event, EventBus}
 
-import java.util.concurrent.ConcurrentLinkedQueue
+import java.util.concurrent.ConcurrentLinkedDeque
 
 object BrainEvents {
-  val events = new ConcurrentLinkedQueue[Event]()
+  val events = new ConcurrentLinkedDeque[Event]()
 
   private val eventSubscription = EventBus.subscribe { event =>
     events.add(event)