WIP Make static collections thread-safe using ThreadStatic and ThreadLocal

Refactored various static and instance collections to use [ThreadStatic], ThreadLocal, or local variables to prevent concurrent modification issues during parallel updates. This affects status effect targets, affliction lists, damage modifiers, and cached data in Character, CharacterHealth, Limb, Explosion, Hull, Submarine, and ToolBox classes. Also replaced Dictionary caches with ConcurrentDictionary where appropriate for thread safety.

Barotrauma/BarotraumaShared/SharedSource/Map/Explosion.cs

@@ -7,6 +7,7 @@ using Microsoft.Xna.Framework;
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 
 namespace Barotrauma
 {
@@ -648,7 +649,11 @@ namespace Barotrauma
             }
         }
 
-        private static readonly Dictionary<Structure, float> damagedStructures = new Dictionary<Structure, float>();
+        // ThreadLocal for thread-safe structure damage tracking
+        private static readonly ThreadLocal<Dictionary<Structure, float>> damagedStructuresLocal = 
+            new ThreadLocal<Dictionary<Structure, float>>(() => new Dictionary<Structure, float>());
+        private static Dictionary<Structure, float> damagedStructures => damagedStructuresLocal.Value;
+        
         /// <summary>
         /// Returns a dictionary where the keys are the structures that took damage and the values are the amount of damage taken
         /// </summary>

Barotrauma/BarotraumaShared/SharedSource/Map/Hull.cs

@@ -6,6 +6,7 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
+using System.Threading;
 using System.Xml.Linq;
 using Barotrauma.MapCreatures.Behavior;
 using Barotrauma.Items.Components;
@@ -1133,13 +1134,18 @@ namespace Barotrauma
         }
 
         /// <summary>
-        /// Used in <see cref="GetApproximateDistance"/>
+        /// Used in <see cref="GetApproximateDistance"/> - ThreadLocal for thread safety
         /// </summary>
-        private static readonly Dictionary<Hull, float> cachedDistances = [];
+        private static readonly ThreadLocal<Dictionary<Hull, float>> cachedDistancesLocal = 
+            new ThreadLocal<Dictionary<Hull, float>>(() => new Dictionary<Hull, float>());
         /// <summary>
-        /// Used in <see cref="GetApproximateDistance"/>
+        /// Used in <see cref="GetApproximateDistance"/> - ThreadLocal for thread safety
         /// </summary>
-        private static readonly PriorityQueue<(Hull hull, Vector2 pos), float> priorityQueue = new PriorityQueue<(Hull hull, Vector2 pos), float>();
+        private static readonly ThreadLocal<PriorityQueue<(Hull hull, Vector2 pos), float>> priorityQueueLocal = 
+            new ThreadLocal<PriorityQueue<(Hull hull, Vector2 pos), float>>(() => new PriorityQueue<(Hull hull, Vector2 pos), float>());
+        
+        private static Dictionary<Hull, float> cachedDistances => cachedDistancesLocal.Value;
+        private static PriorityQueue<(Hull hull, Vector2 pos), float> priorityQueue => priorityQueueLocal.Value;
 
         /// <summary>
         /// Approximate distance from this hull to the target hull, moving through open gaps without passing through walls.

Barotrauma/BarotraumaShared/SharedSource/Map/Submarine.cs

@@ -12,6 +12,7 @@ using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Linq;
+using System.Threading;
 using System.Xml.Linq;
 using Voronoi2;
 
@@ -97,10 +98,11 @@ namespace Barotrauma
             }
         }
 
-        private static Vector2 lastPickedPosition;
-        private static float lastPickedFraction;
-        private static Fixture lastPickedFixture;
-        private static Vector2 lastPickedNormal;
+        // ThreadLocal for thread-safe ray casting results
+        private static readonly ThreadLocal<Vector2> lastPickedPositionLocal = new ThreadLocal<Vector2>();
+        private static readonly ThreadLocal<float> lastPickedFractionLocal = new ThreadLocal<float>();
+        private static readonly ThreadLocal<Fixture> lastPickedFixtureLocal = new ThreadLocal<Fixture>();
+        private static readonly ThreadLocal<Vector2> lastPickedNormalLocal = new ThreadLocal<Vector2>();
 
         private Vector2 prevPosition;
 
@@ -114,22 +116,22 @@ namespace Barotrauma
 
         public static Vector2 LastPickedPosition
         {
-            get { return lastPickedPosition; }
+            get { return lastPickedPositionLocal.Value; }
         }
 
         public static float LastPickedFraction
         {
-            get { return lastPickedFraction; }
+            get { return lastPickedFractionLocal.Value; }
         }
 
         public static Fixture LastPickedFixture
         {
-            get { return lastPickedFixture; }
+            get { return lastPickedFixtureLocal.Value; }
         }
 
         public static Vector2 LastPickedNormal
         {
-            get { return lastPickedNormal; }
+            get { return lastPickedNormalLocal.Value; }
         }
 
         public bool Loading
@@ -854,10 +856,10 @@ namespace Barotrauma
                 }, ref aabb);
                 if (closestFraction <= 0.0f)
                 {
-                    lastPickedPosition = rayStart;
-                    lastPickedFraction = closestFraction;
-                    lastPickedFixture = closestFixture;
-                    lastPickedNormal = closestNormal;
+                    lastPickedPositionLocal.Value = rayStart;
+                    lastPickedFractionLocal.Value = closestFraction;
+                    lastPickedFixtureLocal.Value = closestFixture;
+                    lastPickedNormalLocal.Value = closestNormal;
                     return closestBody;
                 }
             }
@@ -876,16 +878,22 @@ namespace Barotrauma
                 return fraction;
             }, rayStart, rayEnd, collisionCategory ?? Category.All);
 
-            lastPickedPosition = rayStart + (rayEnd - rayStart) * closestFraction;
-            lastPickedFraction = closestFraction;
-            lastPickedFixture = closestFixture;
-            lastPickedNormal = closestNormal;
+            lastPickedPositionLocal.Value = rayStart + (rayEnd - rayStart) * closestFraction;
+            lastPickedFractionLocal.Value = closestFraction;
+            lastPickedFixtureLocal.Value = closestFixture;
+            lastPickedNormalLocal.Value = closestNormal;
 
             return closestBody;
         }
 
-        private static readonly Dictionary<Body, float> bodyDist = new Dictionary<Body, float>();
-        private static readonly List<Body> bodies = new List<Body>();
+        // ThreadLocal for thread-safe body picking
+        private static readonly ThreadLocal<Dictionary<Body, float>> bodyDistLocal = 
+            new ThreadLocal<Dictionary<Body, float>>(() => new Dictionary<Body, float>());
+        private static readonly ThreadLocal<List<Body>> bodiesLocal = 
+            new ThreadLocal<List<Body>>(() => new List<Body>());
+        
+        private static Dictionary<Body, float> bodyDist => bodyDistLocal.Value;
+        private static List<Body> bodies => bodiesLocal.Value;
 
         public static float LastPickedBodyDist(Body body)
         {
@@ -919,10 +927,10 @@ namespace Barotrauma
                 }
                 if (fraction < closestFraction)
                 {
-                    lastPickedPosition = rayStart + (rayEnd - rayStart) * fraction;
-                    lastPickedFraction = fraction;
-                    lastPickedNormal = normal;
-                    lastPickedFixture = fixture;
+                    lastPickedPositionLocal.Value = rayStart + (rayEnd - rayStart) * fraction;
+                    lastPickedFractionLocal.Value = fraction;
+                    lastPickedNormalLocal.Value = normal;
+                    lastPickedFixtureLocal.Value = fixture;
                 }
                 //continue
                 return -1;
@@ -940,10 +948,10 @@ namespace Barotrauma
                     if (!fixture.Shape.TestPoint(ref transform, ref rayStart)) { return true; }
 
                     closestFraction = 0.0f;
-                    lastPickedPosition = rayStart;
-                    lastPickedFraction = 0.0f;
-                    lastPickedNormal = Vector2.Normalize(rayEnd - rayStart);
-                    lastPickedFixture = fixture;
+                    lastPickedPositionLocal.Value = rayStart;
+                    lastPickedFractionLocal.Value = 0.0f;
+                    lastPickedNormalLocal.Value = Vector2.Normalize(rayEnd - rayStart);
+                    lastPickedFixtureLocal.Value = fixture;
                     bodies.Add(fixture.Body);
                     bodyDist[fixture.Body] = 0.0f;
                     return false;
@@ -1011,7 +1019,7 @@ namespace Barotrauma
 
             if (Vector2.DistanceSquared(rayStart, rayEnd) < 0.01f)
             {
-                lastPickedPosition = rayEnd;
+                lastPickedPositionLocal.Value = rayEnd;
                 return null;
             }
 
@@ -1053,10 +1061,10 @@ namespace Barotrauma
             , rayStart, rayEnd);
 
 
-            lastPickedPosition = rayStart + (rayEnd - rayStart) * closestFraction;
-            lastPickedFraction = closestFraction;
-            lastPickedFixture = closestFixture;
-            lastPickedNormal = closestNormal;
+            lastPickedPositionLocal.Value = rayStart + (rayEnd - rayStart) * closestFraction;
+            lastPickedFractionLocal.Value = closestFraction;
+            lastPickedFixtureLocal.Value = closestFixture;
+            lastPickedNormalLocal.Value = closestNormal;
             return closestBody;
         }