From 8f1c94b59a31df7b030beaa7f51f933139f5723d Mon Sep 17 00:00:00 2001
From: VladiStep <vlad2001.21@mail.ru>
Date: Sun, 2 Apr 2023 15:20:27 +0300
Subject: [PATCH] Fixed #1265.

---
 UndertaleModLib/Models/UndertaleRoom.cs       | 20 +++++++++++++++++++
 .../Editors/UndertaleRoomEditor.xaml.cs       |  8 ++++++++
 2 files changed, 28 insertions(+)

diff --git a/UndertaleModLib/Models/UndertaleRoom.cs b/UndertaleModLib/Models/UndertaleRoom.cs
index af20722da..18dc8ab68 100644
--- a/UndertaleModLib/Models/UndertaleRoom.cs
+++ b/UndertaleModLib/Models/UndertaleRoom.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
+using System.Diagnostics;
 using System.Drawing;
 using System.Linq;
 using System.Runtime.CompilerServices;
@@ -422,6 +423,20 @@ public void Unserialize(UndertaleReader reader)
                 if (layer.InstancesData != null)
                 {
                     layer.InstancesData.Instances.Clear();
+                    if (GameObjects.Count > 0 && layer.InstancesData.InstanceIds.Length > 0
+                        && layer.InstancesData.InstanceIds[0] > GameObjects[^1].InstanceID)
+                    {
+                        // Make sure it's not a false positive
+                        uint firstLayerInstID = layer.InstancesData.InstanceIds.OrderBy(x => x).First();
+                        uint lastInstID = GameObjects.OrderBy(x => x.InstanceID).Last().InstanceID;
+                        if (firstLayerInstID > lastInstID)
+                        {
+                            Debug.WriteLine($"The first instance ID ({firstLayerInstID}) " +
+                                            $"of layer (ID {layer.LayerId}) is greater than the last game object ID ({lastInstID}) ?");
+                            continue;
+                        }
+                    }
+
                     foreach (var id in layer.InstancesData.InstanceIds)
                     {
                         GameObject gameObj = GameObjects.ByInstanceID(id);
@@ -1563,6 +1578,11 @@ public class LayerInstancesData : LayerData
             internal uint[] InstanceIds { get; private set; } // 100000, 100001, 100002, 100003 - instance ids from GameObjects list in the room
             public ObservableCollection<GameObject> Instances { get; private set; } = new();
 
+            public bool AreInstancesUnresolved()
+            {
+                return InstanceIds.Length > 0 && Instances.Count == 0;
+            }
+
             /// <inheritdoc />
             public void Serialize(UndertaleWriter writer)
             {
diff --git a/UndertaleModTool/Editors/UndertaleRoomEditor.xaml.cs b/UndertaleModTool/Editors/UndertaleRoomEditor.xaml.cs
index c592608fb..f4dcdbecf 100644
--- a/UndertaleModTool/Editors/UndertaleRoomEditor.xaml.cs
+++ b/UndertaleModTool/Editors/UndertaleRoomEditor.xaml.cs
@@ -187,6 +187,14 @@ private void UndertaleRoomEditor_DataContextChanged(object sender, DependencyPro
                         }
                         else if (layer.LayerType == LayerType.Instances)
                         {
+                            if (layer.InstancesData.AreInstancesUnresolved())
+                            {
+                                _ = mainWindow.Dispatcher.InvokeAsync(() =>
+                                {
+                                    mainWindow.ShowWarning($"The instances list of layer \"{layer.LayerName.Content}\" is empty, but the layer has the instances ID.");
+                                }, DispatcherPriority.ContextIdle);
+                            }
+
                             foreach (GameObject obj in layer.InstancesData.Instances)
                                 roomObjDict.TryAdd(obj.InstanceID, layer);
                         }