Added chunk unload event listener.

src/net/jitse/npclib/NPCLib.java

@@ -5,6 +5,7 @@
 package net.jitse.npclib;
 
 import net.jitse.npclib.api.NPC;
+import net.jitse.npclib.listeners.ChunkListener;
 import net.jitse.npclib.listeners.PacketListener;
 import net.jitse.npclib.listeners.PlayerLeaveListener;
 import net.jitse.npclib.listeners.PlayerMoveListener;
@@ -47,6 +48,7 @@ public class NPCLib {
 
         pluginManager.registerEvents(new PlayerMoveListener(), plugin);
         pluginManager.registerEvents(new PlayerLeaveListener(), plugin);
+        pluginManager.registerEvents(new ChunkListener(), plugin);
 
         new PacketListener().start(plugin);
     }

src/net/jitse/npclib/listeners/ChunkListener.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) Jitse Boonstra 2018 All rights reserved.
+ */
+
+package net.jitse.npclib.listeners;
+
+import net.jitse.npclib.NPCManager;
+import net.jitse.npclib.api.NPC;
+import org.bukkit.Bukkit;
+import org.bukkit.Chunk;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.world.ChunkUnloadEvent;
+
+import java.util.UUID;
+
+/**
+ * @author Jitse Boonstras
+ */
+public class ChunkListener implements Listener {
+
+    @EventHandler
+    public void onChunkUnload(ChunkUnloadEvent event) {
+        Chunk chunk = event.getChunk();
+
+        for (NPC npc : NPCManager.getAllNPCs()) {
+            Chunk npcChunk = npc.getLocation().getChunk();
+
+            if (chunk.getX() == npcChunk.getX() && chunk.getZ() == npcChunk.getZ()) {
+                // Unloaded chunk with NPC in it. Hiding it from all players currently shown to.
+
+                for (UUID uuid : npc.getShown()) {
+                    // Safety check so it doesn't send packets if the NPC has already
+                    // been automatically despawned by the system.
+                    if (npc.getAutoHidden().contains(uuid)) {
+                        continue;
+                    }
+
+                    npc.hide(Bukkit.getPlayer(uuid), true);
+                }
+            }
+        }
+    }
+}

src/net/jitse/npclib/listeners/PlayerMoveListener.java

@@ -6,6 +6,7 @@ package net.jitse.npclib.listeners;
 
 import net.jitse.npclib.NPCManager;
 import net.jitse.npclib.api.NPC;
+import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.entity.Player;
 import org.bukkit.event.EventHandler;
@@ -41,8 +42,11 @@ public class PlayerMoveListener implements Listener {
                 continue; // NPC was never supposed to be shown to the player.
             }
 
+            // If Bukkit doesn't track the NPC entity anymore, bypass the hiding distance variable.
+            // This will cause issues otherwise (e.g. custom skin disappearing).
             double hideDistance = npc.getAutoHideDistance();
-            boolean inRange = player.getLocation().distanceSquared(npc.getLocation()) <= (hideDistance * hideDistance);
+            double distanceSquared = player.getLocation().distanceSquared(npc.getLocation());
+            boolean inRange = distanceSquared <= (hideDistance * hideDistance) || distanceSquared <= (Bukkit.getViewDistance() << 4);
             if (npc.getAutoHidden().contains(player.getUniqueId())) {
                 // Check if the player and NPC are within the range to sendShowPackets it again.
                 if (inRange) {