Fixed invisible monsters

They occur when a freshly spawned monster starts a walk before it has been added to be observed by the player object.
In this case, ObserverToWorldViewAdapter.LocateableRemovedAsync leaves early, because the NewBucket is not null and the player is observing this bucket already.
Therefore, we can only start to walk, when the monster was safely added to the observing players before.

src/GameLogic/MapInitializer.cs

@@ -138,6 +138,7 @@ private void RegisterForConfigChanges(GameMap createdMap, MonsterSpawnArea spawn
                 await createdMap.RemoveAsync(o).ConfigureAwait(false);
                 o.Initialize();
                 await createdMap.AddAsync(o).ConfigureAwait(false);
+                o.OnSpawn();
 
                 if (this._spawnedMonsters.TryGetValue(area, out var previousSpawnCount))
                 {
@@ -275,6 +276,7 @@ public async ValueTask InitializeNpcsOnWaveStartAsync(GameMap createdMap, IEvent
             npc.SpawnIndex = spawnIndex;
             npc.Initialize();
             await createdMap.AddAsync(npc).ConfigureAwait(false);
+            npc.OnSpawn();
             if (spawnArea.SpawnTrigger is SpawnTrigger.Automatic or SpawnTrigger.Wandering)
             {
                 this.RegisterForConfigChanges(createdMap, spawnArea, npc);

src/GameLogic/NPC/AttackableNpcBase.cs

@@ -237,6 +237,7 @@ private async ValueTask RespawnAsync()
 
             this.Initialize();
             await this.CurrentMap.RespawnAsync(this).ConfigureAwait(false);
+            this.OnSpawn();
         }
         catch (Exception ex)
         {

src/GameLogic/NPC/Monster.cs

@@ -41,6 +41,8 @@ public sealed class Monster : AttackableNpcBase, IAttackable, IAttacker, ISuppor
 
     private bool _isCalculatingPath;
 
+    private bool _isReadyToWalk;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="Monster" /> class.
     /// </summary>
@@ -77,7 +79,6 @@ public Monster(MonsterSpawnArea spawnInfo, MonsterDefinition stats, GameMap map,
     /// </summary>
     public Player? SummonedBy => (this._intelligence as SummonedMonsterIntelligence)?.Owner;
 
-    /// <inheritdoc/>
     public Point WalkTarget => this._walker.CurrentTarget;
 
     /// <inheritdoc/>
@@ -104,13 +105,20 @@ public async ValueTask AttackAsync(IAttackable target)
         }
     }
 
+    /// <inheritdoc />
+    public override void OnSpawn()
+    {
+        base.OnSpawn();
+        this._isReadyToWalk = true;
+    }
+
     /// <summary>
     /// Walks to the target coordinates.
     /// </summary>
     /// <param name="target">The target object.</param>
     public async ValueTask<bool> WalkToAsync(Point target)
     {
-        if (this._isCalculatingPath || this.IsWalking)
+        if (this._isCalculatingPath || this.IsWalking || !this._isReadyToWalk)
         {
             return false;
         }
@@ -215,6 +223,11 @@ public ValueTask MoveAsync(Point target)
     /// </summary>
     internal async ValueTask RandomMoveAsync()
     {
+        if (!this._isReadyToWalk)
+        {
+            return;
+        }
+
         byte randx = (byte)GameLogic.Rand.NextInt(Math.Max(0, this.Position.X - 1), Math.Min(0xFF, this.Position.X + 2));
         byte randy = (byte)GameLogic.Rand.NextInt(Math.Max(0, this.Position.Y - 1), Math.Min(0xFF, this.Position.Y + 2));
         if (this.CurrentMap.Terrain.AIgrid[randx, randy] == 1)

src/GameLogic/NPC/NonPlayerCharacter.cs

@@ -96,6 +96,14 @@ public virtual void Initialize()
         this.Rotation = GetSpawnDirection(this.SpawnArea.Direction);
     }
 
+    /// <summary>
+    /// Called when this instance spawned on the map.
+    /// </summary>
+    public virtual void OnSpawn()
+    {
+        // can be overwritten
+    }
+
     /// <inheritdoc/>
     public async ValueTask AddObserverAsync(IWorldObserver observer)
     {

src/GameLogic/Player.cs

@@ -901,6 +901,7 @@ public async ValueTask ClientReadyAfterMapChangeAsync()
         if (this.Summon?.Item1 is { IsAlive: true } summon)
         {
             await this.CurrentMap.AddAsync(summon).ConfigureAwait(false);
+            summon.OnSpawn();
         }
     }
 
@@ -1321,6 +1322,7 @@ public async ValueTask CreateSummonedMonsterAsync(MonsterDefinition definition)
         this.Summon = (monster, intelligence);
         monster.Initialize();
         await gameMap.AddAsync(monster).ConfigureAwait(false);
+        monster.OnSpawn();
     }
 
     /// <summary>