Few fixes for FastModeExtent.

worldedit-bukkit/src/main/java/com/boydti/fawe/bukkit/adapter/v1_13_1/Spigot_v1_13_R2.java

@@ -549,4 +549,10 @@ public final class Spigot_v1_13_R2 extends CachedBukkitAdapter implements Bukkit
 		// TODO Auto-generated method stub
 		
 	}
+
+	@Override
+	public void notifyAndLightBlock(Location position, BlockState previousType) {
+		// TODO Auto-generated method stub
+		
+	}
 }

worldedit-core/src/main/java/com/boydti/fawe/jnbt/anvil/HeightMapMCAGenerator.java

@@ -2280,4 +2280,10 @@ public class HeightMapMCAGenerator extends MCAWriter implements StreamChange, Dr
 		// TODO Auto-generated method stub
 		return false;
 	}
+
+	@Override
+	public boolean notifyAndLightBlock(BlockVector3 position, BlockState previousType) throws WorldEditException {
+		// TODO Auto-generated method stub
+		return false;
+	}
 }

worldedit-core/src/main/java/com/boydti/fawe/jnbt/anvil/MCAWorld.java

@@ -121,4 +121,10 @@ public class MCAWorld implements SimpleWorld {
 		// TODO Auto-generated method stub
 		return false;
 	}
+
+	@Override
+	public boolean notifyAndLightBlock(BlockVector3 position, BlockState previousType) throws WorldEditException {
+		// TODO Auto-generated method stub
+		return false;
+	}
 }

worldedit-core/src/main/java/com/boydti/fawe/object/schematic/visualizer/SchemVis.java

@@ -33,6 +33,7 @@ import com.sk89q.worldedit.session.ClipboardHolder;
 import com.sk89q.worldedit.util.Location;
 import com.sk89q.worldedit.util.TargetBlock;
 import com.sk89q.worldedit.world.biome.BaseBiome;
+import com.sk89q.worldedit.world.block.BlockState;
 import com.sk89q.worldedit.world.block.BlockTypes;
 import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
 import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
@@ -633,4 +634,10 @@ public class SchemVis extends ImmutableVirtualWorld {
 		// TODO Auto-generated method stub
 		return false;
 	}
+
+	@Override
+	public boolean notifyAndLightBlock(BlockVector3 position, BlockState previousType) throws WorldEditException {
+		// TODO Auto-generated method stub
+		return false;
+	}
 }

worldedit-core/src/main/java/com/sk89q/worldedit/extent/world/FastModeExtent.java

@@ -31,10 +31,9 @@ import com.sk89q.worldedit.world.World;
 import com.sk89q.worldedit.world.block.BlockStateHolder;
 import com.sk89q.worldedit.world.block.BlockTypes;
 
-import java.util.ArrayDeque;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
-import java.util.Queue;
 import java.util.Set;
 
 /**
@@ -43,7 +42,7 @@ import java.util.Set;
 public class FastModeExtent extends AbstractDelegateExtent {
 
     private final World world;
-    private final Queue<BlockVector3> positions = new ArrayDeque<>();
+    private final Set<BlockVector3> positions = new HashSet<>();
     private final Set<BlockVector2> dirtyChunks = new HashSet<>();
     private boolean enabled = true;
     private boolean postEditSimulation;
@@ -106,7 +105,7 @@ public class FastModeExtent extends AbstractDelegateExtent {
 
             if (world.setBlock(location, block, false)) {
                 if (postEditSimulation) {
-                    positions.offer(location);
+                    positions.add(location);
                 }
                 return true;
             }
@@ -117,6 +116,10 @@ public class FastModeExtent extends AbstractDelegateExtent {
         }
     }
 
+    public boolean commitRequired() {
+        return !dirtyChunks.isEmpty() || !positions.isEmpty();
+    }
+
     @Override
     protected Operation commitBefore() {
         return new Operation() {
@@ -127,9 +130,11 @@ public class FastModeExtent extends AbstractDelegateExtent {
                 }
 
                 if (postEditSimulation) {
-                    while (run.shouldContinue() && !positions.isEmpty()) {
+                    Iterator<BlockVector3> positionIterator = positions.iterator();
-                        BlockVector3 position = positions.poll(); // Remove from queue
+                    while (run.shouldContinue() && positionIterator.hasNext()) {
+                        BlockVector3 position = positionIterator.next();
                         world.notifyAndLightBlock(position, BlockTypes.AIR.getDefaultState());
+                        positionIterator.remove();
                     }
 
                     return !positions.isEmpty() ? this : null;