Version: 167.0.2

(cherry picked from commit 6211cf2e03)

MSBuild/Robust.Engine.Version.props

@@ -1,4 +1,4 @@
 <Project>
 
-    <!-- This file automatically reset by Tools/version.py -->
+    <!-- This file automatically reset by Tools/version.py -->
 

RELEASE-NOTES.md

@@ -54,6 +54,142 @@ END TEMPLATE-->
 *None yet*
 
 
+## 167.0.2
+
+
+## 167.0.1
+
+
+## 167.0.0
+
+### Breaking changes
+
+* Remove ComponentExtensions.
+* Remove ContainerHelpers.
+* Change some TransformSystem methods to fix clientside lerping.
+
+### Bugfixes
+
+* Fixed PVS bugs from dropped entity states.
+
+### Other
+
+* Add more joint debug asserts.
+
+
+## 166.0.0
+
+### Breaking changes
+
+* EntityUid-NetEntity conversion methods now return null when given a null value, rather than returning an invalid id.
+* ExpandPvsEvent now defaults to using null lists to reduce allocations.
+* Various component lifestage related methods have been moved from the `Component` class to `EntityManager`.
+* Session/client specific PVS overrides are now always recursive, which means that all children of the overriden entity will also get sent.
+
+### New features
+
+* Added a SortedSet yaml serializer.
+
+### Other
+
+* AddComponentUninitialized is now marked as obsolete and will be removed in the future.
+* DebugTools.AssertOwner() now accepts null components.
+
+
+## 165.0.0
+
+### Breaking changes
+
+* The arguments of `SplitContainer`s resize-finished event have changed.
+
+### New features
+
+* The YAML validator now checks the default values of ProtoId<T> and EntProtoId data fields. 
+
+### Bugfixes
+
+* The minimum draggable area of split containers now blocks mouse inputs.
+
+
+## 164.0.0
+
+### Breaking changes
+
+* Make automatic component states infer cloneData.
+* Removed cloneData from AutoNetworkedFieldAttribute. This is now automatically inferred.
+
+### Internal
+
+* Reduce Transform GetComponents in RecursiveDeleteEntity.
+
+
+## 163.0.0
+
+### Breaking changes
+
+* Moved TimedDespawn to engine for a component that deletes the attached entity after a timer has elapsed.
+
+### New features
+
+* Add ExecuteCommand for integration tests.
+* Allow adding / removing widgets of cub-controls.
+* Give maps / grids a default name to help with debugging.
+* Use ToPrettyString in component resolve errors to help with debugging.
+
+### Bugfixes
+
+* Fix console backspace exception.
+* Fix rendering invalid maps spamming exceptions every frame.
+
+### Internal
+
+* Move ClientGameStatemanager local variables to fields to avoid re-allocating every tick.
+
+
+## 162.2.1
+
+
+## 162.2.0
+
+### New features
+
+* Add support for automatically networking entity lists and sets.
+* Add nullable conversion operators for ProtoIds.
+* Add LocId serializer for validation.
+
+### Bugfixes
+
+* Fix deleting a contact inside of collision events throwing.
+* Localize VV.
+
+### Internal
+
+* Use CollectionsMarshal in GameStateManager.
+
+
+## 162.1.1
+
+### Bugfixes
+
+* Fixes "NoSpawn" entities appearing in the spawn menu.
+
+
+## 162.1.0
+
+### New features
+
+* Mark ProtoId as NetSerializable.
+
+### Bugfixes
+
+* Temporarily revert NetForceAckThreshold change as it can lead to client stalling.
+* Fix eye visibility layers not updating on children when a parent changes.
+
+### Internal
+
+* Use CollectionsMarshal in RobustTree and AddComponentInternal.
+
+
 ## 162.0.0
 
 ### New features

Resources/Locale/en-US/view-variables.ftl

@@ -1,5 +1,6 @@
 ## ViewVariablesInstanceEntity
 
+view-variables = View Variables
 view-variable-instance-entity-server-components-add-component-button-placeholder = Add Component
 view-variable-instance-entity-client-variables-tab-title = Client Variables
 view-variable-instance-entity-client-components-tab-title = Client Components
@@ -8,4 +9,4 @@ view-variable-instance-entity-server-components-tab-title = Server Components
 view-variable-instance-entity-client-components-search-bar-placeholder = Search
 view-variable-instance-entity-server-components-search-bar-placeholder = Search
 view-variable-instance-entity-add-window-server-components = Add Component [S]
-view-variable-instance-entity-add-window-client-components = Add Component [C]
+view-variable-instance-entity-add-window-client-components = Add Component [C]

Robust.Client/GameObjects/ClientEntityManager.cs

@@ -43,9 +43,9 @@ namespace Robust.Client.GameObjects
             base.FlushEntities();
         }
 
-        EntityUid IClientEntityManagerInternal.CreateEntity(string? prototypeName)
+        EntityUid IClientEntityManagerInternal.CreateEntity(string? prototypeName, out MetaDataComponent metadata)
         {
-            return base.CreateEntity(prototypeName);
+            return base.CreateEntity(prototypeName, out metadata);
         }
 
         void IClientEntityManagerInternal.InitializeEntity(EntityUid entity, MetaDataComponent? meta)
@@ -93,14 +93,10 @@ namespace Robust.Client.GameObjects
                 base.Dirty(uid, component, meta);
         }
 
-        [return: NotNullIfNotNull("uid")]
-        public override EntityStringRepresentation? ToPrettyString(EntityUid? uid)
+        public override EntityStringRepresentation ToPrettyString(EntityUid uid, MetaDataComponent? metaDataComponent = null)
         {
-            if (uid == null)
-                return null;
-
             if (_playerManager.LocalPlayer?.ControlledEntity == uid)
-                return base.ToPrettyString(uid).Value with { Session = _playerManager.LocalPlayer.Session };
+                return base.ToPrettyString(uid) with { Session = _playerManager.LocalPlayer.Session };
 
             return base.ToPrettyString(uid);
         }

Robust.Client/GameObjects/EntitySystems/AnimationPlayerSystem.cs

@@ -4,7 +4,6 @@ using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Utility;
-using TerraFX.Interop.Windows;
 
 namespace Robust.Client.GameObjects
 {
@@ -117,7 +116,7 @@ namespace Robust.Client.GameObjects
 
                 if (compTrack.ComponentType == null)
                 {
-                    _sawmill.Error($"Attempted to play a component animation without any component specified.");
+                    _sawmill.Error("Attempted to play a component animation without any component specified.");
                     return;
                 }
 
@@ -136,8 +135,14 @@ namespace Robust.Client.GameObjects
                 // In principle there is nothing wrong with this, as long as the property of the component being
                 // animated is not part of the networked state and setting it does not dirty the component. Hence only a
                 // warning in debug mode.
-                if (reg.NetID != null)
-                    _sawmill.Warning($"Playing a component animation on a networked component {reg.Name} belonging to {ToPrettyString(component.Owner)}");
+                if (reg.NetID != null && compTrack.Property != null)
+                {
+                    if (animatedComp.GetType().GetProperty(compTrack.Property) is { } property &&
+                        property.HasCustomAttribute<AutoNetworkedFieldAttribute>())
+                    {
+                        _sawmill.Warning($"Playing a component animation on a networked component {reg.Name} belonging to {ToPrettyString(component.Owner)}");
+                    }
+                }
             }
 #endif
 

Robust.Client/GameObjects/EntitySystems/TransformSystem.Component.cs

@@ -1,51 +1,41 @@
 using System.Numerics;
+using Robust.Client.Player;
 using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
 using Robust.Shared.Maths;
 
 namespace Robust.Client.GameObjects;
 
 public sealed partial class TransformSystem
 {
-    public override void SetLocalPosition(TransformComponent xform, Vector2 value)
+    public override void SetLocalPosition(EntityUid uid, Vector2 value, TransformComponent? xform = null)
     {
-        xform.PrevPosition = xform._localPosition;
+        if (!XformQuery.Resolve(uid, ref xform))
+            return;
+
         xform.NextPosition = value;
-        xform.LerpParent = xform.ParentUid;
-        base.SetLocalPosition(xform, value);
-        ActivateLerp(xform);
+        ActivateLerp(uid, xform);
+        base.SetLocalPosition(uid, value, xform);
     }
 
-    public override void SetLocalPositionNoLerp(TransformComponent xform, Vector2 value)
+    public override void SetLocalRotation(EntityUid uid, Angle value, TransformComponent? xform = null)
     {
-        xform.NextPosition = null;
-        xform.LerpParent = EntityUid.Invalid;
-        base.SetLocalPositionNoLerp(xform, value);
+        if (!XformQuery.Resolve(uid, ref xform))
+            return;
+
+        xform.NextRotation = value;
+        ActivateLerp(uid, xform);
+        base.SetLocalRotation(uid, value, xform);
     }
 
-    public override void SetLocalRotationNoLerp(TransformComponent xform, Angle angle)
+    public override void SetLocalPositionRotation(EntityUid uid, Vector2 pos, Angle rot, TransformComponent? xform = null)
     {
-        xform.NextRotation = null;
-        xform.LerpParent = EntityUid.Invalid;
-        base.SetLocalRotationNoLerp(xform, angle);
-    }
+        if (!XformQuery.Resolve(uid, ref xform))
+            return;
 
-    public override void SetLocalRotation(TransformComponent xform, Angle angle)
-    {
-        xform.PrevRotation = xform._localRotation;
-        xform.NextRotation = angle;
-        xform.LerpParent = xform.ParentUid;
-        base.SetLocalRotation(xform, angle);
-        ActivateLerp(xform);
-    }
-
-    public override void SetLocalPositionRotation(TransformComponent xform, Vector2 pos, Angle rot)
-    {
-        xform.PrevPosition = xform._localPosition;
         xform.NextPosition = pos;
-        xform.PrevRotation = xform._localRotation;
         xform.NextRotation = rot;
-        xform.LerpParent = xform.ParentUid;
-        base.SetLocalPositionRotation(xform, pos, rot);
-        ActivateLerp(xform);
+        ActivateLerp(uid, xform);
+        base.SetLocalPositionRotation(uid, pos, rot, xform);
     }
 }

Robust.Client/GameObjects/EntitySystems/TransformSystem.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using System.Numerics;
 using JetBrains.Annotations;
@@ -25,11 +24,6 @@ namespace Robust.Client.GameObjects
         private const float MinInterpolationDistance = 0.001f;
         private const float MinInterpolationDistanceSquared = MinInterpolationDistance * MinInterpolationDistance;
 
-        private const double MinInterpolationAngle = Math.PI / 720;
-
-        // 45 degrees.
-        private const double MaxInterpolationAngle = Math.PI / 4;
-
         [Dependency] private readonly IGameTiming _gameTiming = default!;
 
         // Only keep track of transforms actively lerping.
@@ -48,21 +42,77 @@ namespace Robust.Client.GameObjects
             _lerpingTransforms.Clear();
         }
 
-        public override void ActivateLerp(TransformComponent xform)
+        public override void ActivateLerp(EntityUid uid, TransformComponent xform)
         {
-            if (xform.ActivelyLerping)
+            // This lerping logic is pretty convoluted and generally assumes that the client does not mispredict.
+            // A more foolproof solution would be to just cache the coordinates at which any given entity was most
+            // recently rendered and using that as the lerp origin. However that'd require enumerating over all entities
+            // every tick which is pretty icky.
+
+            // The general considerations are:
+            // - If the client receives a server state for an entity moving from a->b and predicts nothing else, then it
+            //   should show the entity lerping.
+            // - If the client predicts an entity will move while already lerping due to a state-application, it should
+            //   clear the state's lerp, under the assumption that the client predicted the state and already rendered
+            //   the entity in the final position.
+            // - If the client predicts that an entity moves, then we only lerp if this is the first time that the tick
+            //   was predicted. I.e., we assume the entity was already rendered in it's final of that lerp.
+            // - If the client predicts that an entity should lerp twice in the same tick, then we need to combine them.
+            //   I.e. moving from a->b then b->c, the client should lerp from a->c.
+
+            // If the client predicts an entity moves while already lerping, it should clear the
+            // predict a->b, lerp a->b
+            // predicted a->b, then predict b->c. Lerp b->c
+            // predicted a->b, then predict b->c. Lerp b->c
+            // predicted a->b, predicted b->c, then predict c->d. Lerp c->d
+            // server state a->b, then predicted b->c, lerp b->c
+            // server state a->b, then predicted b->c, then predict d, lerp b->c
+
+            if (_gameTiming.ApplyingState)
+            {
+                if (xform.ActivelyLerping)
+                {
+                    // This should not happen, but can happen if some bad component state application code modifies an entity's coordinates.
+                    Log.Error($"Entity {(ToPrettyString(uid))} tried to lerp twice while applying component states.");
+                    return;
+                }
+
+                _lerpingTransforms.Add(xform);
+                xform.ActivelyLerping = true;
+                xform.PredictedLerp = false;
+                xform.LerpParent = xform.ParentUid;
+                xform.PrevRotation = xform._localRotation;
+                xform.PrevPosition = xform._localPosition;
+                xform.LastLerp = _gameTiming.CurTick;
                 return;
+            }
 
-            xform.ActivelyLerping = true;
-            _lerpingTransforms.Add(xform);
-        }
+            xform.LastLerp = _gameTiming.CurTick;
+            if (!_gameTiming.IsFirstTimePredicted)
+            {
+                xform.ActivelyLerping = false;
+                return;
+            }
 
-        public override void DeactivateLerp(TransformComponent component)
-        {
-            // this should cause the lerp to do nothing
-            component.NextPosition = null;
-            component.NextRotation = null;
-            component.LerpParent = EntityUid.Invalid;
+            if (!xform.ActivelyLerping)
+            {
+                _lerpingTransforms.Add(xform);
+                xform.ActivelyLerping = true;
+                xform.PredictedLerp = true;
+                xform.PrevRotation = xform._localRotation;
+                xform.PrevPosition = xform._localPosition;
+                xform.LerpParent = xform.ParentUid;
+                return;
+            }
+
+            if (!xform.PredictedLerp || xform.LerpParent != xform.ParentUid)
+            {
+                // Existing lerp was not due to prediction, but due to state application. That lerp should already
+                // have been rendered, so we will start a new lerp from the current position.
+                xform.PrevRotation = xform._localRotation;
+                xform.PrevPosition = xform._localPosition;
+                xform.LerpParent = xform.ParentUid;
+            }
         }
 
         public override void FrameUpdate(float frameTime)
@@ -74,11 +124,13 @@ namespace Robust.Client.GameObjects
             for (var i = 0; i < _lerpingTransforms.Count; i++)
             {
                 var transform = _lerpingTransforms[i];
+                var uid = transform.Owner;
                 var found = false;
 
                 // Only lerp if parent didn't change.
                 // E.g. entering lockers would do it.
-                if (transform.LerpParent == transform.ParentUid
+                if (transform.ActivelyLerping
+                    && transform.LerpParent == transform.ParentUid
                     && transform.ParentUid.IsValid()
                     && !transform.Deleted)
                 {
@@ -90,8 +142,7 @@ namespace Robust.Client.GameObjects
 
                         if (distance is > MinInterpolationDistanceSquared and < MaxInterpolationDistanceSquared)
                         {
-                            transform.LocalPosition = Vector2.Lerp(lerpSource, lerpDest, step);
-                            // Setting LocalPosition clears LerpPosition so fix that.
+                            SetLocalPositionNoLerp(uid, Vector2.Lerp(lerpSource, lerpDest, step), transform);
                             transform.NextPosition = lerpDest;
                             found = true;
                         }
@@ -101,15 +152,9 @@ namespace Robust.Client.GameObjects
                     {
                         var lerpDest = transform.NextRotation.Value;
                         var lerpSource = transform.PrevRotation;
-                        var distance = Math.Abs(Angle.ShortestDistance(lerpDest, lerpSource));
-
-                        if (distance is > MinInterpolationAngle and < MaxInterpolationAngle)
-                        {
-                            transform.LocalRotation = Angle.Lerp(lerpSource, lerpDest, step);
-                            // Setting LocalRotation clears LerpAngle so fix that.
-                            transform.NextRotation = lerpDest;
-                            found = true;
-                        }
+                        SetLocalRotationNoLerp(uid, Angle.Lerp(lerpSource, lerpDest, step), transform);
+                        transform.NextRotation = lerpDest;
+                        found = true;
                     }
                 }
 

Robust.Client/GameObjects/IClientEntityManagerInternal.cs

@@ -6,7 +6,7 @@ namespace Robust.Client.GameObjects
     {
         // These methods are used by the Game State Manager.
 
-        EntityUid CreateEntity(string? prototypeName);
+        EntityUid CreateEntity(string? prototypeName, out MetaDataComponent metadata);
 
         void InitializeEntity(EntityUid entity, MetaDataComponent? meta = null);
 

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -4,7 +4,9 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using System.Runtime.InteropServices;
 using JetBrains.Annotations;
+using Microsoft.Extensions.ObjectPool;
 using Robust.Client.GameObjects;
 using Robust.Client.Input;
 using Robust.Client.Physics;
@@ -51,6 +53,14 @@ namespace Robust.Client.GameStates
         private readonly Dictionary<NetEntity, EntityState> _toCreate = new();
         private readonly Dictionary<ushort, (IComponent Component, ComponentState? curState, ComponentState? nextState)> _compStateWork = new();
         private readonly Dictionary<EntityUid, HashSet<Type>> _pendingReapplyNetStates = new();
+        private readonly HashSet<NetEntity> _stateEnts = new();
+        private readonly List<EntityUid> _toDelete = new();
+        private readonly List<Component> _toRemove = new();
+        private readonly Dictionary<NetEntity, Dictionary<ushort, ComponentState>> _outputData = new();
+        private readonly List<(EntityUid, TransformComponent)> _queuedBroadphaseUpdates = new();
+
+        private readonly ObjectPool<Dictionary<ushort, ComponentState>> _compDataPool =
+            new DefaultObjectPool<Dictionary<ushort, ComponentState>>(new DictPolicy<ushort, ComponentState>(), 256);
 
         private uint _metaCompNetId;
 
@@ -101,6 +111,13 @@ namespace Robust.Client.GameStates
 
         public event Action<MsgStateLeavePvs>? PvsLeave;
 
+#if DEBUG
+        /// <summary>
+        /// If true, this will cause received game states to be ignored. Used by integration tests.
+        /// </summary>
+        public bool DropStates;
+#endif
+
         /// <inheritdoc />
         public void Initialize()
         {
@@ -193,6 +210,10 @@ namespace Robust.Client.GameStates
 
         private void HandleStateMessage(MsgState message)
         {
+#if DEBUG
+            if (DropStates)
+                return;
+#endif
             // We ONLY ack states that are definitely going to get applied. Otherwise the sever might assume that we
             // applied a state containing entity-creation information, which it would then no longer send to us when
             // we re-encounter this entity
@@ -267,18 +288,15 @@ namespace Robust.Client.GameStates
                     continue;
                 }
 
-                if (PredictionNeedsResetting)
+                try
                 {
-                    try
-                    {
-                        ResetPredictedEntities();
-                    }
-                    catch (Exception e)
-                    {
-                        // avoid exception spam from repeatedly trying to reset the same entity.
-                        _entitySystemManager.GetEntitySystem<ClientDirtySystem>().Reset();
-                        _runtimeLog.LogException(e, "ResetPredictedEntities");
-                    }
+                    ResetPredictedEntities();
+                }
+                catch (Exception e)
+                {
+                    // avoid exception spam from repeatedly trying to reset the same entity.
+                    _entitySystemManager.GetEntitySystem<ClientDirtySystem>().Reset();
+                    _runtimeLog.LogException(e, "ResetPredictedEntities");
                 }
 
                 // If we were waiting for a new state, we are now applying it.
@@ -467,20 +485,22 @@ namespace Robust.Client.GameStates
 
         public void ResetPredictedEntities()
         {
-            PredictionNeedsResetting = false;
-
             using var _ = _prof.Group("ResetPredictedEntities");
             using var __ = _timing.StartStateApplicationArea();
 
+            // This is terrible, and I hate it. This also needs to run even when prediction is disabled.
+            _entitySystemManager.GetEntitySystem<SharedGridTraversalSystem>().QueuedEvents.Clear();
+            _entitySystemManager.GetEntitySystem<TransformSystem>().Reset();
+
+            if (!PredictionNeedsResetting)
+                return;
+
+            PredictionNeedsResetting = false;
             var countReset = 0;
             var system = _entitySystemManager.GetEntitySystem<ClientDirtySystem>();
             var metaQuery = _entityManager.GetEntityQuery<MetaDataComponent>();
             RemQueue<Component> toRemove = new();
 
-            // This is terrible, and I hate it.
-            _entitySystemManager.GetEntitySystem<SharedGridTraversalSystem>().QueuedEvents.Clear();
-            _entitySystemManager.GetEntitySystem<TransformSystem>().Reset();
-
             foreach (var entity in system.DirtyEntities)
             {
                 DebugTools.Assert(toRemove.Count == 0);
@@ -588,14 +608,13 @@ namespace Robust.Client.GameStates
         /// </remarks>
         private void MergeImplicitData(IEnumerable<NetEntity> createdEntities)
         {
-            var outputData = new Dictionary<NetEntity, Dictionary<ushort, ComponentState>>();
             var bus = _entityManager.EventBus;
 
             foreach (var netEntity in createdEntities)
             {
                 var (createdEntity, meta) = _entityManager.GetEntityData(netEntity);
-                var compData = new Dictionary<ushort, ComponentState>();
-                outputData.Add(netEntity, compData);
+                var compData = _compDataPool.Get();
+                _outputData.Add(netEntity, compData);
 
                 foreach (var (netId, component) in meta.NetComponents)
                 {
@@ -608,7 +627,14 @@ namespace Robust.Client.GameStates
                 }
             }
 
-            _processor.MergeImplicitData(outputData);
+            _processor.MergeImplicitData(_outputData);
+
+            foreach (var data in _outputData.Values)
+            {
+                _compDataPool.Return(data);
+            }
+
+            _outputData.Clear();
         }
 
         private void AckGameState(GameTick sequence)
@@ -686,12 +712,10 @@ namespace Robust.Client.GameStates
                     if (metaState == null)
                         throw new MissingMetadataException(es.NetEntity);
 
-                    var uid = _entities.CreateEntity(metaState.PrototypeId);
+                    var uid = _entities.CreateEntity(metaState.PrototypeId, out var newMeta);
                     _toCreate.Add(es.NetEntity, es);
-                    var newMeta = metas.GetComponent(uid);
                     _toApply.Add(uid, (es.NetEntity, newMeta, false, GameTick.Zero, es, null));
 
-
                     // Client creates a client-side net entity for the newly created entity.
                     // We need to clear this mapping before assigning the real net id.
                     // TODO NetEntity Jank: prevent the client from creating this in the first place.
@@ -721,9 +745,7 @@ namespace Robust.Client.GameStates
                 if (_toCreate.ContainsKey(es.NetEntity))
                     continue;
 
-                var uid = _entityManager.GetEntity(es.NetEntity);
-
-                if (!metas.TryGetComponent(uid, out var meta))
+                if (!_entityManager.TryGetEntityData(es.NetEntity, out var uid, out var meta))
                     continue;
 
                 bool isEnteringPvs = (meta.Flags & MetaDataFlags.Detached) != 0;
@@ -738,7 +760,7 @@ namespace Robust.Client.GameStates
                     continue;
                 }
 
-                _toApply.Add(uid, (es.NetEntity, meta, isEnteringPvs, meta.LastStateApplied, es, null));
+                _toApply.Add(uid.Value, (es.NetEntity, meta, isEnteringPvs, meta.LastStateApplied, es, null));
                 meta.LastStateApplied = curState.ToSequence;
             }
 
@@ -759,28 +781,32 @@ namespace Robust.Client.GameStates
                     if (es.EntityLastModified != nextState.ToSequence)
                         continue;
 
-                    if (_toApply.TryGetValue(uid.Value, out var state))
-                        _toApply[uid.Value] = (es.NetEntity, meta, state.EnteringPvs, state.LastApplied, state.curState, es);
+                    ref var state = ref CollectionsMarshal.GetValueRefOrAddDefault(_toApply, uid.Value, out var exists);
+
+                    if (exists)
+                        state = (es.NetEntity, meta, state.EnteringPvs, state.LastApplied, state.curState, es);
                     else
-                        _toApply[uid.Value] = (es.NetEntity, meta, false, GameTick.Zero, null, es);
+                        state = (es.NetEntity, meta, false, GameTick.Zero, null, es);
                 }
             }
 
             // Check pending states and see if we need to force any entities to re-run component states.
             foreach (var uid in _pendingReapplyNetStates.Keys)
             {
-                // State already being re-applied so don't bulldoze it.
-                if (_toApply.ContainsKey(uid))
-                    continue;
-
                 // Original entity referencing the NetEntity may have been deleted.
                 if (!metas.TryGetComponent(uid, out var meta))
                     continue;
 
-                _toApply[uid] = (meta.NetEntity, meta, false, GameTick.Zero, null, null);
+                // State already being re-applied so don't bulldoze it.
+                ref var state = ref CollectionsMarshal.GetValueRefOrAddDefault(_toApply, uid, out var exists);
+
+                if (exists)
+                    continue;
+
+                state = (meta.NetEntity, meta, false, GameTick.Zero, null, null);
             }
 
-            var queuedBroadphaseUpdates = new List<(EntityUid, TransformComponent)>(enteringPvs);
+            _queuedBroadphaseUpdates.Clear();
 
             // Apply entity states.
             using (_prof.Group("Apply States"))
@@ -800,7 +826,7 @@ namespace Robust.Client.GameStates
                     DebugTools.Assert(xform.Broadphase == BroadphaseData.Invalid);
                     xform.Broadphase = null;
                     if (!_toApply.TryGetValue(xform.ParentUid, out var parent) || !parent.EnteringPvs)
-                        queuedBroadphaseUpdates.Add((entity, xform));
+                        _queuedBroadphaseUpdates.Add((entity, xform));
                 }
 
                 _prof.WriteValue("Count", ProfData.Int32(_toApply.Count));
@@ -811,7 +837,7 @@ namespace Robust.Client.GameStates
             {
                 try
                 {
-                    foreach (var (uid, xform) in queuedBroadphaseUpdates)
+                    foreach (var (uid, xform) in _queuedBroadphaseUpdates)
                     {
                         lookupSys.FindAndAddToEntityTree(uid, true, xform);
                     }
@@ -828,7 +854,7 @@ namespace Robust.Client.GameStates
             {
                 try
                 {
-                    ProcessDeletions(delSpan, xforms, metas, xformSys);
+                    ProcessDeletions(delSpan, xforms, xformSys);
                 }
                 catch (Exception e)
                 {
@@ -865,17 +891,17 @@ namespace Robust.Client.GameStates
             _sawmill.Info($"Resetting all entity states to tick {state.ToSequence}.");
 
             // Construct hashset for set.Contains() checks.
+            _stateEnts.Clear();
             var entityStates = state.EntityStates.Span;
-            var stateEnts = new HashSet<NetEntity>();
             foreach (var entState in entityStates)
             {
-                stateEnts.Add(entState.NetEntity);
+                _stateEnts.Add(entState.NetEntity);
             }
 
             var xforms = _entities.GetEntityQuery<TransformComponent>();
             var xformSys = _entitySystemManager.GetEntitySystem<SharedTransformSystem>();
 
-            var toDelete = new List<EntityUid>(Math.Max(64, _entities.EntityCount - stateEnts.Count));
+            _toDelete.Clear();
 
             // Client side entities won't need the transform, but that should always be a tiny minority of entities
             var metaQuery = _entityManager.AllEntityQueryEnumerator<MetaDataComponent, TransformComponent>();
@@ -886,14 +912,16 @@ namespace Robust.Client.GameStates
                 if (metadata.NetEntity.IsClientSide())
                 {
                     if (deleteClientEntities)
-                        toDelete.Add(ent);
+                        _toDelete.Add(ent);
+
                     continue;
                 }
 
-                if (stateEnts.Contains(netEnt))
+                if (_stateEnts.Contains(netEnt))
                 {
                     if (resetAllEntities || metadata.LastStateApplied > state.ToSequence)
                         metadata.LastStateApplied = GameTick.Zero; // TODO track last-state-applied for individual components? Is it even worth it?
+
                     continue;
                 }
 
@@ -911,13 +939,14 @@ namespace Robust.Client.GameStates
                         && !deleteClientEntities // don't add duplicates
                         && _entities.IsClientSide(child.Value))
                     {
-                        toDelete.Add(child.Value);
+                        _toDelete.Add(child.Value);
                     }
                 }
-                toDelete.Add(ent);
+
+                _toDelete.Add(ent);
             }
 
-            foreach (var ent in toDelete)
+            foreach (var ent in _toDelete)
             {
                 _entities.DeleteEntity(ent);
             }
@@ -926,7 +955,6 @@ namespace Robust.Client.GameStates
         private void ProcessDeletions(
             ReadOnlySpan<NetEntity> delSpan,
             EntityQuery<TransformComponent> xforms,
-            EntityQuery<MetaDataComponent> metas,
             SharedTransformSystem xformSys)
         {
             // Processing deletions is non-trivial, because by default deletions will also delete all child entities.
@@ -997,6 +1025,7 @@ namespace Robust.Client.GameStates
             // things like container insertion and ejection.
 
             using var _ = _prof.Group("Leave PVS");
+            detached.EnsureCapacity(toDetach.Count);
 
             foreach (var (tick, ents) in toDetach)
             {
@@ -1019,9 +1048,7 @@ namespace Robust.Client.GameStates
         {
             foreach (var netEntity in entities)
             {
-                var ent = _entityManager.GetEntity(netEntity);
-
-                if (!metas.TryGetComponent(ent, out var meta))
+                if (!_entityManager.TryGetEntityData(netEntity, out var ent, out var meta))
                     continue;
 
                 if (meta.LastStateApplied > maxTick)
@@ -1037,10 +1064,10 @@ namespace Robust.Client.GameStates
                 if (lastStateApplied.HasValue)
                     meta.LastStateApplied = lastStateApplied.Value;
 
-                var xform = xforms.GetComponent(ent);
+                var xform = xforms.GetComponent(ent.Value);
                 if (xform.ParentUid.IsValid())
                 {
-                    lookupSys.RemoveFromEntityTree(ent, xform);
+                    lookupSys.RemoveFromEntityTree(ent.Value, xform);
                     xform.Broadphase = BroadphaseData.Invalid;
 
                     // In some cursed scenarios an entity inside of a container can leave PVS without the container itself leaving PVS.
@@ -1049,13 +1076,13 @@ namespace Robust.Client.GameStates
                     if ((meta.Flags & MetaDataFlags.InContainer) != 0 &&
                         metas.TryGetComponent(xform.ParentUid, out var containerMeta) &&
                         (containerMeta.Flags & MetaDataFlags.Detached) == 0 &&
-                        containerSys.TryGetContainingContainer(xform.ParentUid, ent, out container, null, true))
+                        containerSys.TryGetContainingContainer(xform.ParentUid, ent.Value, out container, null, true))
                     {
-                        container.Remove(ent, _entities, xform, meta, false, true);
+                        container.Remove(ent.Value, _entities, xform, meta, false, true);
                     }
 
                     meta._flags |= MetaDataFlags.Detached;
-                    xformSys.DetachParentToNull(ent, xform);
+                    xformSys.DetachParentToNull(ent.Value, xform);
                     DebugTools.Assert((meta.Flags & MetaDataFlags.InContainer) == 0);
 
                     if (container != null)
@@ -1135,14 +1162,15 @@ namespace Robust.Client.GameStates
             // First remove any deleted components
             if (curState?.NetComponents != null)
             {
-                RemQueue<Component> toRemove = new();
+                _toRemove.Clear();
+
                 foreach (var (id, comp) in meta.NetComponents)
                 {
                     if (comp.NetSyncEnabled && !curState.NetComponents.Contains(id))
-                        toRemove.Add(comp);
+                        _toRemove.Add(comp);
                 }
 
-                foreach (var comp in toRemove)
+                foreach (var comp in _toRemove)
                 {
                     _entities.RemoveComponent(uid, comp, meta);
                 }
@@ -1198,10 +1226,13 @@ namespace Robust.Client.GameStates
                         continue;
                     }
 
-                    if (_compStateWork.TryGetValue(compState.NetID, out var state))
-                        _compStateWork[compState.NetID] = (comp, state.curState, compState.State);
+                    ref var state =
+                        ref CollectionsMarshal.GetValueRefOrAddDefault(_compStateWork, compState.NetID, out var exists);
+
+                    if (exists)
+                        state = (comp, state.curState, compState.State);
                     else
-                        _compStateWork[compState.NetID] = (comp, null, compState.State);
+                        state = (comp, null, compState.State);
                 }
             }
 
@@ -1218,14 +1249,19 @@ namespace Robust.Client.GameStates
                     if (netId == null)
                         continue;
 
-                    if (_compStateWork.ContainsKey(netId.Value) ||
-                        !meta.NetComponents.TryGetValue(netId.Value, out var comp) ||
+                    if (!meta.NetComponents.TryGetValue(netId.Value, out var comp) ||
                         !lastState.TryGetValue(netId.Value, out var lastCompState))
                     {
                         continue;
                     }
 
-                    _compStateWork[netId.Value] = (comp, lastCompState, null);
+                    ref var compState =
+                        ref CollectionsMarshal.GetValueRefOrAddDefault(_compStateWork, netId.Value, out var exists);
+
+                    if (exists)
+                        continue;
+
+                    compState = (comp, lastCompState, null);
                 }
             }
 
@@ -1402,20 +1438,24 @@ namespace Robust.Client.GameStates
             }
 
             // ensure we don't have any extra components
-            RemQueue<Component> toRemove = new();
+            _toRemove.Clear();
+
             foreach (var (id, comp) in meta.NetComponents)
             {
                 if (comp.NetSyncEnabled && !lastState.ContainsKey(id))
-                    toRemove.Add(comp);
+                    _toRemove.Add(comp);
             }
 
-            foreach (var comp in toRemove)
+            foreach (var comp in _toRemove)
             {
                 _entities.RemoveComponent(uid, comp);
             }
         }
         #endregion
 
+        public bool IsQueuedForDetach(NetEntity entity)
+            => _processor.IsQueuedForDetach(entity);
+
         void IPostInjectInit.PostInject()
         {
             _sawmill = _logMan.GetSawmill(CVars.NetPredict.Name);

Robust.Client/GameStates/GameStateProcessor.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Runtime.InteropServices;
 using Robust.Client.Timing;
 using Robust.Shared.GameObjects;
 using Robust.Shared.GameStates;
@@ -361,9 +362,11 @@ namespace Robust.Client.GameStates
 
                 foreach (var (netId, implicitCompState) in implicitEntState)
                 {
-                    if (!fullRep.TryGetValue(netId, out var serverState))
+                    ref var serverState = ref CollectionsMarshal.GetValueRefOrAddDefault(fullRep, netId, out var exists);
+
+                    if (!exists)
                     {
-                        fullRep.Add(netId, implicitCompState);
+                        serverState = implicitCompState;
                         continue;
                     }
 
@@ -379,7 +382,7 @@ namespace Robust.Client.GameStates
                     }
 
                     serverDelta.ApplyToFullState(implicitCompState);
-                    fullRep[netId] = implicitCompState;
+                    serverState = implicitCompState;
                     DebugTools.Assert(implicitCompState is IComponentDeltaState d && d.FullState);
                 }
             }
@@ -401,6 +404,18 @@ namespace Robust.Client.GameStates
             return _lastStateFullRep.TryGetValue(entity, out dictionary);
         }
 
+        public bool IsQueuedForDetach(NetEntity entity)
+        {
+            // This isn't fast, but its just meant for use in tests & debug asserts.
+            foreach (var msg in _pvsDetachMessages.Values)
+            {
+                if (msg.Contains(entity))
+                    return true;
+            }
+
+            return false;
+        }
+
         public int CalculateBufferSize(GameTick fromTick)
         {
             bool foundState;

Robust.Client/GameStates/NetInterpOverlay.cs

@@ -1,19 +1,19 @@
+using System;
 using Robust.Shared.Enums;
 using Robust.Client.Graphics;
 using Robust.Shared.Console;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Maths;
-using Robust.Shared.Physics;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Containers;
-using Robust.Shared.Physics.Components;
 using Robust.Shared.Timing;
 
 namespace Robust.Client.GameStates
 {
     internal sealed class NetInterpOverlay : Overlay
     {
+        [Dependency] private readonly IGameTiming _timing = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
@@ -24,6 +24,11 @@ namespace Robust.Client.GameStates
         private readonly SharedContainerSystem _container;
         private readonly SharedTransformSystem _xform;
 
+        /// <summary>
+        /// When an entity stops lerping the overlay will continue to draw a box around the entity for this amount of time.
+        /// </summary>
+        public static readonly TimeSpan Delay = TimeSpan.FromSeconds(2f);
+
         public NetInterpOverlay(EntityLookupSystem lookup)
         {
             IoCManager.InjectDependencies(this);
@@ -40,8 +45,8 @@ namespace Robust.Client.GameStates
             var worldHandle = (DrawingHandleWorld) handle;
             var viewport = args.WorldAABB;
 
-            var query = _entityManager.AllEntityQueryEnumerator<PhysicsComponent, TransformComponent>();
-            while (query.MoveNext(out var uid, out var physics, out var transform))
+            var query = _entityManager.AllEntityQueryEnumerator<TransformComponent>();
+            while (query.MoveNext(out var uid, out var transform))
             {
                 // if not on the same map, continue
                 if (transform.MapID != _eyeManager.CurrentMap || _container.IsEntityInContainer(uid))
@@ -50,8 +55,8 @@ namespace Robust.Client.GameStates
                 if (transform.GridUid == uid)
                     continue;
 
-                // This entity isn't lerping, no need to draw debug info for it
-                if(transform.NextPosition == null)
+                var delta = (_timing.CurTick.Value - transform.LastLerp.Value) * _timing.TickPeriod;
+                if(!transform.ActivelyLerping && delta > Delay)
                     continue;
 
                 var aabb = _lookup.GetWorldAABB(uid);
@@ -61,7 +66,9 @@ namespace Robust.Client.GameStates
                     continue;
 
                 var (pos, rot) = _xform.GetWorldPositionRotation(transform, _entityManager.GetEntityQuery<TransformComponent>());
-                var boxOffset = transform.NextPosition.Value - transform.LocalPosition;
+                var boxOffset = transform.NextPosition != null
+                    ? transform.NextPosition.Value - transform.LocalPosition
+                    : default;
                 var worldOffset = (rot - transform.LocalRotation).RotateVec(boxOffset);
 
                 var nextPos = pos + worldOffset;

Robust.Client/Graphics/Clyde/Clyde.LightRendering.cs

@@ -338,10 +338,12 @@ namespace Robust.Client.Graphics.Clyde
             }
 
             var mapId = eye.Position.MapId;
+            if (mapId == MapId.Nullspace)
+                return;
 
             // If this map has lighting disabled, return
             var mapUid = _mapManager.GetMapEntityId(mapId);
-            if (!_entityManager.GetComponent<MapComponent>(mapUid).LightingEnabled)
+            if (!_entityManager.TryGetComponent<MapComponent>(mapUid, out var map) || !map.LightingEnabled)
             {
                 return;
             }

Robust.Client/Physics/PhysicsSystem.cs

@@ -82,11 +82,8 @@ namespace Robust.Client.Physics
                     continue;
                 }
 
-                xform.PrevPosition = position;
-                xform.PrevRotation = rotation;
-                xform.LerpParent = parentUid;
-                xform.NextPosition = xform.LocalPosition;
-                xform.NextRotation = xform.LocalRotation;
+                // Transform system will handle lerping.
+                _transform.SetLocalPositionRotation(uid, xform.LocalPosition, xform.LocalRotation, xform);
             }
 
             component.LerpData.Clear();

Robust.Client/Robust.Client.csproj

@@ -17,7 +17,7 @@
     <PackageReference Include="SQLitePCLRaw.bundle_e_sqlite3" Version="2.1.2" Condition="'$(UseSystemSqlite)' != 'True'" PrivateAssets="compile" />
     <PackageReference Include="SpaceWizards.NFluidsynth" Version="0.1.1" PrivateAssets="compile" />
     <PackageReference Include="NVorbis" Version="0.10.1" PrivateAssets="compile" />
-    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.3" />
+    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.7" />
     <PackageReference Include="OpenToolkit.Graphics" Version="4.0.0-pre9.1" PrivateAssets="compile" />
     <PackageReference Include="OpenTK.OpenAL" Version="4.7.5" PrivateAssets="compile" />
     <PackageReference Include="SpaceWizards.SharpFont" Version="1.0.1" PrivateAssets="compile" />

Robust.Client/Spawners/TimedDespawnSystem.cs

@@ -0,0 +1,12 @@
+using Robust.Shared.GameObjects;
+using Robust.Shared.Spawners;
+
+namespace Robust.Client.Spawners;
+
+public sealed class TimedDespawnSystem : SharedTimedDespawnSystem
+{
+    protected override bool CanDelete(EntityUid uid)
+    {
+        return IsClientSide(uid);
+    }
+}

Robust.Client/UserInterface/Controls/LineEdit.cs

@@ -98,6 +98,11 @@ namespace Robust.Client.UserInterface.Controls
                 OnTextChanged?.Invoke(new LineEditEventArgs(this, _text));
         }
 
+        public void ForceSubmitText()
+        {
+            OnTextEntered?.Invoke(new LineEditEventArgs(this, _text));
+        }
+
         /// <summary>
         ///     The text
         /// </summary>
@@ -607,7 +612,7 @@ namespace Robust.Client.UserInterface.Controls
                 {
                     if (Editable)
                     {
-                        OnTextEntered?.Invoke(new LineEditEventArgs(this, _text));
+                        ForceSubmitText();
                     }
 
                     args.Handle();

Robust.Client/UserInterface/Controls/ScrollContainer.cs

@@ -50,13 +50,13 @@ namespace Robust.Client.UserInterface.Controls
             Action<Range> ev = _scrollValueChanged;
             _hScrollBar = new HScrollBar
             {
-                Visible = false,
+                Visible = _hScrollEnabled,
                 VerticalAlignment = VAlignment.Bottom,
                 HorizontalAlignment = HAlignment.Stretch
             };
             _vScrollBar = new VScrollBar
             {
-                Visible = false,
+                Visible = _vScrollEnabled,
                 VerticalAlignment = VAlignment.Stretch,
                 HorizontalAlignment = HAlignment.Right
             };

Robust.Client/UserInterface/Controls/SplitContainer.cs

@@ -2,6 +2,7 @@ using System;
 using System.Numerics;
 using Robust.Shared.Input;
 using Robust.Shared.Maths;
+using Robust.Shared.Utility;
 using Robust.Shared.ViewVariables;
 
 namespace Robust.Client.UserInterface.Controls
@@ -14,7 +15,17 @@ namespace Robust.Client.UserInterface.Controls
         /// for each enum value to see how the different options work.
         /// </summary>
         [ViewVariables(VVAccess.ReadWrite)]
-        public SplitResizeMode ResizeMode { get; set; }
+        public SplitResizeMode ResizeMode
+        {
+            get => _resizeMode;
+            set
+            {
+                _resizeMode = value;
+                _splitDragArea.Visible = value != SplitResizeMode.NotResizable;
+            }
+        }
+
+        private SplitResizeMode _resizeMode = SplitResizeMode.RespectChildrenMinSize;
 
         /// <summary>
         /// Width of the split in virtual pixels
@@ -30,7 +41,7 @@ namespace Robust.Client.UserInterface.Controls
             }
         }
 
-        private float _splitWidth;
+        private float _splitWidth = 10;
 
         /// <summary>
         ///     This width determines the minimum size of the draggable area around the split. This has no effect if it
@@ -38,11 +49,13 @@ namespace Robust.Client.UserInterface.Controls
         /// </summary>
         public float MinDraggableWidth = 10f;
 
+        public float DraggableWidth => MathF.Max(MinDraggableWidth, _splitWidth);
+
         /// <summary>
         /// Virtual pixel offset from the edge beyond which the split cannot be moved.
         /// </summary>
         [ViewVariables(VVAccess.ReadWrite)]
-        public float SplitEdgeSeparation { get; set; }
+        public float SplitEdgeSeparation { get; set; } = 10;
 
         private float _splitStart;
 
@@ -58,6 +71,7 @@ namespace Robust.Client.UserInterface.Controls
                 _splitStart = value - _splitWidth / 2;
                 ClampSplitCenter();
                 InvalidateMeasure();
+                OnSplitResized?.Invoke();
             }
         }
 
@@ -81,13 +95,51 @@ namespace Robust.Client.UserInterface.Controls
             }
         }
 
-        private SplitState _splitState;
-        private bool _dragging;
+        private SplitState _splitState = SplitState.Auto;
         private SplitOrientation _orientation;
-        private SplitStretchDirection _stretchDirection;
+        private SplitStretchDirection _stretchDirection = SplitStretchDirection.BottomRight;
+        private bool _dragging;
+        private float _dragOffset;
 
         private bool Vertical => Orientation == SplitOrientation.Vertical;
 
+        private readonly SplitDragControl _splitDragArea = new();
+
+        /// <summary>
+        /// The upper/left control in the split container.
+        /// </summary>
+        public Control? First
+        {
+            get
+            {
+                if (ChildCount < 3)
+                    return null;
+
+                DebugTools.AssertNotEqual(GetChild(0), _splitDragArea);
+                return GetChild(0);
+            }
+        }
+
+        /// <summary>
+        /// The lower/right control in the split container.
+        /// </summary>
+        public Control? Second
+        {
+            get
+            {
+                if (ChildCount < 3)
+                    return null;
+
+                DebugTools.AssertNotEqual(GetChild(1), _splitDragArea);
+                return GetChild(1);
+            }
+        }
+
+        public (Control First, Control Second)? Splits => ChildCount < 3 ? null : (GetChild(0), GetChild(1));
+
+        public event Action? OnSplitResizeFinished;
+        public event Action? OnSplitResized;
+
         /// <summary>
         /// Whether the split position should be set manually or automatically.
         /// </summary>
@@ -131,73 +183,53 @@ namespace Robust.Client.UserInterface.Controls
         public SplitContainer()
         {
             MouseFilter = MouseFilterMode.Stop;
-            _splitState = SplitState.Auto;
-            _stretchDirection = SplitStretchDirection.BottomRight;
-            _dragging = false;
-            ResizeMode = SplitResizeMode.RespectChildrenMinSize;
-            SplitWidth = 10;
-            SplitEdgeSeparation = 10;
+            AddChild(_splitDragArea);
+            _splitDragArea.Visible = _resizeMode != SplitResizeMode.NotResizable;
+            _splitDragArea.DefaultCursorShape =  Vertical ? CursorShape.VResize : CursorShape.HResize;
+            _splitDragArea.OnMouseUp += StopDragging;
+            _splitDragArea.OnMouseDown += StartDragging;
+            _splitDragArea.OnMouseMove += OnMove;
         }
 
-        protected internal override void MouseMove(GUIMouseMoveEventArgs args)
+        private void OnMove(GUIMouseMoveEventArgs args)
         {
-            base.MouseMove(args);
+            if (ResizeMode == SplitResizeMode.NotResizable)
+                return;
 
-            if (ResizeMode == SplitResizeMode.NotResizable) return;
+            if (!_dragging)
+                return;
 
-            if (_dragging)
-            {
-                var newOffset = Vertical ? args.RelativePosition.Y : args.RelativePosition.X;
-
-                SplitCenter = newOffset;
-                DefaultCursorShape = Vertical ? CursorShape.VResize : CursorShape.HResize;
-            }
-            else
-            {
-                // on mouseover, check if they are over the split and change the cursor accordingly
-                var cursor = CursorShape.Arrow;
-                if (CanDragAt(args.RelativePosition))
-                {
-                    cursor = Vertical ? CursorShape.VResize : CursorShape.HResize;
-                }
-
-                DefaultCursorShape = cursor;
-            }
+            // Source control might be either the container, or the separator.
+            // So we manually calculate the relative coordinates wrt the container.
+            var relative = args.GlobalPosition - GlobalPosition;
+            SplitCenter = Vertical ? relative.Y - _dragOffset : relative.X + _dragOffset;
         }
 
-
-        protected internal override void KeyBindDown(GUIBoundKeyEventArgs args)
+        protected override void ChildAdded(Control newChild)
         {
-            base.KeyBindDown(args);
-
-            if (ResizeMode == SplitResizeMode.NotResizable) return;
-
-            if (_dragging || args.Function != EngineKeyFunctions.UIClick) return;
-
-            if (CanDragAt(args.RelativePosition))
-            {
-                _dragging = true;
-                _splitState = SplitState.Manual;
-            }
+            base.ChildAdded(newChild);
+            _splitDragArea.SetPositionLast();
         }
 
-        protected internal override void KeyBindUp(GUIBoundKeyEventArgs args)
+        public void StartDragging(GUIBoundKeyEventArgs args)
         {
-            base.KeyBindUp(args);
+            if (ResizeMode == SplitResizeMode.NotResizable || _dragging)
+                return;
 
-            if (args.Function != EngineKeyFunctions.UIClick) return;
+            _dragging = true;
+            _dragOffset = DraggableWidth / 2 - (Vertical ? args.RelativePosition.Y : args.RelativePosition.X);
+            _splitState = SplitState.Manual;
+            DefaultCursorShape = Vertical ? CursorShape.VResize : CursorShape.HResize;
+        }
+
+        private void StopDragging(GUIBoundKeyEventArgs args)
+        {
+            if (!_dragging)
+                return;
 
             _dragging = false;
             DefaultCursorShape = CursorShape.Arrow;
-        }
-
-        private bool CanDragAt(Vector2 relativePosition)
-        {
-            var distance = Vertical
-                ? Math.Abs(relativePosition.Y - SplitCenter)
-                : Math.Abs(relativePosition.X - SplitCenter);
-
-            return distance <= _splitWidth || distance <= MinDraggableWidth;
+            OnSplitResizeFinished?.Invoke();
         }
 
         /// <summary>
@@ -218,7 +250,7 @@ namespace Robust.Client.UserInterface.Controls
                 desiredSplit += Vertical ? desiredSize.Value.Y - Size.Y : desiredSize.Value.X - Size.X;
             _splitStart = MathHelper.Clamp(desiredSplit, SplitEdgeSeparation, splitMax);
 
-            if (ResizeMode == SplitResizeMode.RespectChildrenMinSize && ChildCount == 2)
+            if (ResizeMode == SplitResizeMode.RespectChildrenMinSize && ChildCount == 3)
             {
                 var first = GetChild(0);
                 var second = GetChild(1);
@@ -234,7 +266,7 @@ namespace Robust.Client.UserInterface.Controls
 
         protected override Vector2 ArrangeOverride(Vector2 finalSize)
         {
-            if (ChildCount != 2)
+            if (ChildCount < 3)
             {
                 return finalSize;
             }
@@ -287,15 +319,23 @@ namespace Robust.Client.UserInterface.Controls
                 }
             }
 
+            // location & size of the draggable area may be larger than the split area.
+            var dragCenter = _splitStart + _splitWidth / 2;
+            var dragWidth = DraggableWidth;
+            var dragStart = dragCenter - dragWidth / 2;
+            var dragEnd = dragCenter + dragWidth / 2;
+
             if (Vertical)
             {
                 first.Arrange(new UIBox2(0, 0, finalSize.X, _splitStart));
                 second.Arrange(new UIBox2(0, _splitStart + _splitWidth, finalSize.X, finalSize.Y));
+                _splitDragArea.Arrange(new UIBox2(0, dragStart, finalSize.X, dragEnd));
             }
             else
             {
                 first.Arrange(new UIBox2(0, 0, _splitStart, finalSize.Y));
                 second.Arrange(new UIBox2(_splitStart + _splitWidth, 0, finalSize.X, finalSize.Y));
+                _splitDragArea.Arrange(new UIBox2(dragStart, 0, dragEnd, finalSize.Y));
             }
 
             return finalSize;
@@ -303,7 +343,7 @@ namespace Robust.Client.UserInterface.Controls
 
         protected override Vector2 MeasureOverride(Vector2 availableSize)
         {
-            if (ChildCount != 2)
+            if (ChildCount < 3)
             {
                 return Vector2.Zero;
             }
@@ -420,5 +460,40 @@ namespace Robust.Client.UserInterface.Controls
             /// </summary>
             TopLeft,
         }
+
+        /// <summary>
+        /// Simple control to intercept mous events and redirect them to the parent.
+        /// </summary>
+        private sealed class SplitDragControl : Control
+        {
+            public event Action<GUIBoundKeyEventArgs>? OnMouseDown;
+            public event Action<GUIBoundKeyEventArgs>? OnMouseUp;
+            public event Action<GUIMouseMoveEventArgs>? OnMouseMove;
+
+            public SplitDragControl()
+            {
+                MouseFilter = MouseFilterMode.Stop;
+            }
+
+            protected internal override void MouseMove(GUIMouseMoveEventArgs args)
+            {
+                base.MouseMove(args);
+                OnMouseMove?.Invoke(args);
+            }
+
+            protected internal override void KeyBindDown(GUIBoundKeyEventArgs args)
+            {
+                base.KeyBindDown(args);
+                if (args.Function == EngineKeyFunctions.UIClick)
+                    OnMouseDown?.Invoke(args);
+            }
+
+            protected internal override void KeyBindUp(GUIBoundKeyEventArgs args)
+            {
+                base.KeyBindUp(args);
+                if (args.Function == EngineKeyFunctions.UIClick)
+                    OnMouseUp?.Invoke(args);
+            }
+        }
     }
 }

Robust.Client/UserInterface/UIScreen.cs

@@ -69,12 +69,11 @@ public abstract class UIScreen : LayoutContainer
 
     public void RemoveWidget<T>() where T : UIWidget, new()
     {
-        if (_widgets.TryGetValue(typeof(T), out var widget))
-        {
-            RemoveChild(widget);
-        }
+        if (!_widgets.Remove(typeof(T), out var widget))
+            return;
 
-        _widgets.Remove(typeof(T));
+        widget.Parent?.RemoveChild(widget);
+        RemoveChildren(widget);
     }
 
     internal void OnRemoved()
@@ -103,6 +102,14 @@ public abstract class UIScreen : LayoutContainer
         AddChild(widget);
     }
 
+    public void AddWidgetDirect(UIWidget widget)
+    {
+        if (!_widgets.TryAdd(widget.GetType(), widget))
+            throw new Exception("Tried to add duplicate widget to screen!");
+
+        RegisterChildren(widget);
+    }
+
     public T? GetWidget<T>() where T : UIWidget, new()
     {
         return (T?) _widgets.GetValueOrDefault(typeof(T));

Robust.Client/ViewVariables/ClientViewVariablesManager.cs

@@ -10,6 +10,7 @@ using Robust.Client.ViewVariables.Editors;
 using Robust.Client.ViewVariables.Instances;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
+using Robust.Shared.Localization;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Network;
@@ -232,7 +233,7 @@ namespace Robust.Client.ViewVariables
                 instance = new ViewVariablesInstanceObject(this, _robustSerializer);
             }
 
-            var window = new DefaultWindow {Title = "View Variables"};
+            var window = new DefaultWindow {Title = Loc.GetString("view-variables")};
             instance.Initialize(window, obj);
             window.OnClose += () => _closeInstance(instance, false);
             _windows.Add(instance, window);
@@ -250,7 +251,7 @@ namespace Robust.Client.ViewVariables
         {
             var window = new DefaultWindow
             {
-                Title = "View Variables",
+                Title = Loc.GetString("view-variables"),
                 SetSize = _defaultWindowSize
             };
             var loadingLabel = new Label {Text = "Retrieving remote object data from server..."};

Robust.Client/ViewVariables/Instances/ViewVariablesInstanceEntity.cs

@@ -270,7 +270,7 @@ namespace Robust.Client.ViewVariables.Instances
                 button.OnPressed += _ =>
                 {
                     ViewVariablesManager.OpenVV(
-                        new ViewVariablesComponentSelector(_entityManager.GetNetEntity(_entity), componentType.FullName));
+                        new ViewVariablesComponentSelector(_netEntity, componentType.FullName));
                 };
                 removeButton.OnPressed += _ =>
                 {

Robust.Server/Console/SystemConsoleManager.cs

@@ -196,7 +196,7 @@ namespace Robust.Server.Console
                             break;
 
                         case ConsoleKey.Backspace:
-                            if (currentBuffer.Length > 0)
+                            if (currentBuffer.Length > 0 && internalCursor > 0)
                             {
                                 currentBuffer = currentBuffer.Remove(internalCursor - 1, 1);
                                 internalCursor--;

Robust.Server/GameObjects/EntitySystems/ServerMetaDataSystem.cs

@@ -75,13 +75,4 @@ public sealed class ServerMetaDataSystem : MetaDataSystem
                 Dirty(uid, comp);
         }
     }
-
-    public override void SetVisibilityMask(EntityUid uid, int value, MetaDataComponent? meta = null)
-    {
-        if (!Resolve(uid, ref meta) || meta.VisibilityMask == value)
-            return;
-
-        base.SetVisibilityMask(uid, value, meta);
-        _pvsSystem.MarkDirty(uid);
-    }
 }

Robust.Server/GameObjects/EntitySystems/VisibilitySystem.cs

@@ -1,4 +1,5 @@
 using System;
+using Robust.Server.GameStates;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 
@@ -6,11 +7,18 @@ namespace Robust.Server.GameObjects
 {
     public sealed class VisibilitySystem : EntitySystem
     {
-        [Dependency] private readonly MetaDataSystem _metaSys = default!;
+        [Dependency] private readonly PvsSystem _pvs = default!;
+
+        private EntityQuery<TransformComponent> _xformQuery;
+        private EntityQuery<MetaDataComponent> _metaQuery;
+        private EntityQuery<VisibilityComponent> _visiblityQuery;
 
         public override void Initialize()
         {
             base.Initialize();
+            _xformQuery = GetEntityQuery<TransformComponent>();
+            _metaQuery = GetEntityQuery<MetaDataComponent>();
+            _visiblityQuery = GetEntityQuery<VisibilityComponent>();
             SubscribeLocalEvent<EntParentChangedMessage>(OnParentChange);
             EntityManager.EntityInitialized += OnEntityInit;
         }
@@ -82,27 +90,58 @@ namespace Robust.Server.GameObjects
             RefreshVisibility(uid);
         }
 
-        public void RefreshVisibility(EntityUid uid, MetaDataComponent? metaDataComponent = null, VisibilityComponent? visibilityComponent = null)
+        public void RefreshVisibility(EntityUid uid,
+            VisibilityComponent? visibilityComponent = null,
+            MetaDataComponent? meta = null)
         {
-            if (Resolve(uid, ref metaDataComponent, false))
-                _metaSys.SetVisibilityMask(uid, GetVisibilityMask(uid, visibilityComponent), metaDataComponent);
+            if (!_metaQuery.Resolve(uid, ref meta, false))
+                return;
+
+            // Iterate up through parents and calculate the cumulative visibility mask.
+            var mask = GetParentVisibilityMask(uid, visibilityComponent);
+
+            // Iterate down through children and propagate mask changes.
+            RecursivelyApplyVisibility(uid, mask, meta);
+        }
+
+        private void RecursivelyApplyVisibility(EntityUid uid, int mask, MetaDataComponent meta)
+        {
+            if (meta.VisibilityMask == mask)
+                return;
+
+            var xform = _xformQuery.GetComponent(uid);
+            meta.VisibilityMask = mask;
+            _pvs.MarkDirty(uid, xform);
+
+            foreach (var child in xform.ChildEntities)
+            {
+                if (!_metaQuery.TryGetComponent(child, out var childMeta))
+                    continue;
+
+                var childMask = mask;
+
+                if (_visiblityQuery.TryGetComponent(child, out VisibilityComponent? hildVis))
+                    childMask |= hildVis.Layer;
+
+                RecursivelyApplyVisibility(child, childMask, childMeta);
+            }
         }
 
         [Obsolete("Use overload that takes an EntityUid instead")]
         public void RefreshVisibility(VisibilityComponent visibilityComponent)
         {
-            RefreshVisibility(visibilityComponent.Owner, null, visibilityComponent);
+            RefreshVisibility(visibilityComponent.Owner, visibilityComponent);
         }
 
-        private int GetVisibilityMask(EntityUid uid, VisibilityComponent? visibilityComponent = null, TransformComponent? xform = null)
+        private int GetParentVisibilityMask(EntityUid uid, VisibilityComponent? visibilityComponent = null)
         {
             int visMask = 1; // apparently some content expects everything to have the first bit/flag set to true.
-            if (Resolve(uid, ref visibilityComponent, false))
+            if (_visiblityQuery.Resolve(uid, ref visibilityComponent, false))
                 visMask |= visibilityComponent.Layer;
 
             // Include parent vis masks
-            if (Resolve(uid, ref xform) && xform.ParentUid.IsValid())
-                visMask |= GetVisibilityMask(xform.ParentUid);
+            if (_xformQuery.TryGetComponent(uid, out var xform) && xform.ParentUid.IsValid())
+                visMask |= GetParentVisibilityMask(xform.ParentUid);
 
             return visMask;
         }

Robust.Server/GameObjects/ServerEntityManager.cs

@@ -42,6 +42,7 @@ namespace Robust.Server.GameObjects
 #endif
 
         private ISawmill _netEntSawmill = default!;
+        private EntityQuery<ActorComponent> _actorQuery;
 
         public override void Initialize()
         {
@@ -53,6 +54,12 @@ namespace Robust.Server.GameObjects
             base.Initialize();
         }
 
+        public override void Startup()
+        {
+            base.Startup();
+            _actorQuery = GetEntityQuery<ActorComponent>();
+        }
+
         EntityUid IServerEntityManagerInternal.AllocEntity(EntityPrototype? prototype)
         {
             return AllocEntity(prototype, out _);
@@ -78,15 +85,15 @@ namespace Robust.Server.GameObjects
             StartEntity(entity);
         }
 
-        private protected override EntityUid CreateEntity(string? prototypeName, IEntityLoadContext? context = null)
+        private protected override EntityUid CreateEntity(string? prototypeName, out MetaDataComponent metadata, IEntityLoadContext? context = null)
         {
             if (prototypeName == null)
-                return base.CreateEntity(prototypeName, context);
+                return base.CreateEntity(prototypeName, out metadata, context);
 
             if (!PrototypeManager.TryIndex<EntityPrototype>(prototypeName, out var prototype))
                 throw new EntityCreationException($"Attempted to spawn an entity with an invalid prototype: {prototypeName}");
 
-            var entity = base.CreateEntity(prototype, context);
+            var entity = base.CreateEntity(prototype, out metadata, context);
 
             // At this point in time, all data configure on the entity *should* be purely from the prototype.
             // As such, we can reset the modified ticks to Zero,
@@ -109,15 +116,10 @@ namespace Robust.Server.GameObjects
             }
         }
 
-        [return: NotNullIfNotNull("uid")]
-        public override EntityStringRepresentation? ToPrettyString(EntityUid? uid)
+        public override EntityStringRepresentation ToPrettyString(EntityUid uid, MetaDataComponent? metadata = null)
         {
-            if (uid == null)
-                return null;
-
-            TryGetComponent(uid, out ActorComponent? actor);
-
-            return base.ToPrettyString(uid).Value with { Session = actor?.PlayerSession };
+            _actorQuery.TryGetComponent(uid, out ActorComponent? actor);
+            return base.ToPrettyString(uid) with { Session = actor?.PlayerSession };
         }
 
         #region IEntityNetworkManager impl

Robust.Server/GameStates/PvsCollection.cs

@@ -95,7 +95,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
     /// <summary>
     /// List of <see cref="TIndex"/> that should always get sent to a certain <see cref="ICommonSession"/>.
     /// </summary>
-    private readonly Dictionary<ICommonSession, HashSet<TIndex>> _localOverrides = new();
+    private readonly Dictionary<ICommonSession, HashSet<TIndex>> _sessionOverrides = new();
 
     /// <summary>
     /// Which <see cref="TIndex"/> where last seen/sent to a certain <see cref="ICommonSession"/>.
@@ -207,7 +207,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
     public bool TryGetChunk(EntityUid gridId, Vector2i chunkIndices, [NotNullWhen(true)] out HashSet<TIndex>? indices) =>
         _gridChunkContents[gridId].TryGetValue(chunkIndices, out indices);
 
-    public HashSet<TIndex>.Enumerator GetElementsForSession(ICommonSession session) => _localOverrides[session].GetEnumerator();
+    public HashSet<TIndex>.Enumerator GetSessionOverrides(ICommonSession session) => _sessionOverrides[session].GetEnumerator();
 
     private void AddIndexInternal(TIndex index, IIndexLocation location, HashSet<IChunkIndexLocation> dirtyChunks)
     {
@@ -226,10 +226,10 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
                 gridLoc.Add(index);
                 dirtyChunks.Add(gridChunkLocation);
                 break;
-            case LocalOverride localOverride:
-                // might be gone due to disconnects
-                if(!_localOverrides.ContainsKey(localOverride.Session)) return;
-                _localOverrides[localOverride.Session].Add(index);
+            case SessionOverride sessionOverride:
+                if (!_sessionOverrides.TryGetValue(sessionOverride.Session, out var set))
+                    return;
+                set.Add(index);
                 break;
             case MapChunkLocation mapChunkLocation:
                 // might be gone due to map-deletions
@@ -253,16 +253,14 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
         switch (location)
         {
             case GlobalOverride global:
-                if (global.Recursive)
-                    _globalRecursiveOverrides.Remove(index);
-                else
-                    _globalOverrides.Remove(index);
+                var set = global.Recursive ? _globalRecursiveOverrides : _globalOverrides;
+                set.Remove(index);
                 break;
             case GridChunkLocation gridChunkLocation:
                 _gridChunkContents[gridChunkLocation.GridId][gridChunkLocation.ChunkIndices].Remove(index);
                 break;
-            case LocalOverride localOverride:
-                _localOverrides[localOverride.Session].Remove(index);
+            case SessionOverride sessionOverride:
+                _sessionOverrides.GetValueOrDefault(sessionOverride.Session)?.Remove(index);
                 break;
             case MapChunkLocation mapChunkLocation:
                 _mapChunkContents[mapChunkLocation.MapId][mapChunkLocation.ChunkIndices].Remove(index);
@@ -276,7 +274,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
     /// <inheritdoc />
     public bool AddPlayer(ICommonSession session)
     {
-        return _localOverrides.TryAdd(session, new()) & _lastSeen.TryAdd(session, new());
+        return _sessionOverrides.TryAdd(session, new()) & _lastSeen.TryAdd(session, new());
     }
 
     /// <inheritdoc />
@@ -292,7 +290,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
     /// <inheritdoc />
     public bool RemovePlayer(ICommonSession session)
     {
-        if (_localOverrides.Remove(session, out var indices))
+        if (_sessionOverrides.Remove(session, out var indices))
         {
             foreach (var index in indices)
             {
@@ -412,7 +410,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
             return;
         }
 
-        if (!removeFromOverride && oldLocation is LocalOverride)
+        if (!removeFromOverride && oldLocation is SessionOverride)
             return;
 
         if (oldLocation is GlobalOverride global &&
@@ -426,28 +424,29 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
 
     /// <summary>
     /// Updates an <see cref="TIndex"/> to be sent to a specific <see cref="ICommonSession"/> at all times.
+    /// This will always also send all children of the given entity.
     /// </summary>
     /// <param name="index">The <see cref="TIndex"/> to update.</param>
     /// <param name="session">The <see cref="ICommonSession"/> receiving the object.</param>
     /// <param name="removeFromOverride">An index at an override position will not be updated unless you set this flag.</param>
-    public void UpdateIndex(TIndex index, ICommonSession session, bool removeFromOverride = false)
+    public void AddSessionOverride(TIndex index, ICommonSession session, bool removeFromOverride)
     {
         if (!TryGetLocation(index, out var oldLocation))
         {
-            RegisterUpdate(index, new LocalOverride(session));
+            RegisterUpdate(index, new SessionOverride(session));
             return;
         }
 
-        if (!removeFromOverride || oldLocation is GlobalOverride)
+        if (!removeFromOverride && oldLocation is GlobalOverride)
             return;
 
-        if (oldLocation is LocalOverride local &&
+        if (oldLocation is SessionOverride local &&
             (!removeFromOverride || local.Session == session))
         {
             return;
         }
 
-        RegisterUpdate(index, new LocalOverride(session));
+        RegisterUpdate(index, new SessionOverride(session));
     }
 
     /// <summary>
@@ -460,7 +459,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
     {
         if (!removeFromOverride
             && TryGetLocation(index, out var oldLocation)
-            && oldLocation is GlobalOverride or LocalOverride)
+            && oldLocation is GlobalOverride or SessionOverride)
         {
             return;
         }
@@ -510,7 +509,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
         _indexLocations.TryGetValue(index, out var oldLocation);
 
         //removeFromOverride is false 99% of the time.
-        if ((bufferedLocation ?? oldLocation) is GlobalOverride or LocalOverride && !removeFromOverride)
+        if ((bufferedLocation ?? oldLocation) is GlobalOverride or SessionOverride && !removeFromOverride)
             return;
 
         if (oldLocation is GridChunkLocation oldGrid &&
@@ -541,7 +540,7 @@ public sealed class PVSCollection<TIndex> : IPVSCollection where TIndex : ICompa
         _indexLocations.TryGetValue(index, out var oldLocation);
 
         //removeFromOverride is false 99% of the time.
-        if ((bufferedLocation ?? oldLocation) is GlobalOverride or LocalOverride && !removeFromOverride)
+        if ((bufferedLocation ?? oldLocation) is GlobalOverride or SessionOverride && !removeFromOverride)
             return;
 
         // Is this entity just returning to its old location?
@@ -641,14 +640,14 @@ public struct GlobalOverride : IIndexLocation
     }
 }
 
-public struct LocalOverride : IIndexLocation
+public struct SessionOverride : IIndexLocation
 {
-    public LocalOverride(ICommonSession session)
+    public SessionOverride(ICommonSession session)
     {
         Session = session;
     }
 
-    public ICommonSession Session { get; init; }
+    public readonly ICommonSession Session;
 }
 
 #endregion

Robust.Server/GameStates/PvsOverrideSystem.cs

@@ -22,13 +22,14 @@ public sealed class PvsOverrideSystem : EntitySystem
     }
 
     /// <summary>
-    ///     Used to ensure that an entity is always sent to a specific client. Overrides any global or pre-existing
-    ///     client-specific overrides.
+    ///     Used to ensure that an entity is always sent to a specific client. By default this overrides any global or pre-existing
+    ///     client-specific overrides. Unlike global overrides, this is always recursive.
     /// </summary>
     /// <param name="removeExistingOverride">Whether or not to supersede existing overrides.</param>
-    public void AddSessionOverride(EntityUid uid, ICommonSession session,bool removeExistingOverride = true)
+    /// <param name="recursive">If true, this will also recursively send any children of the given index.</param>
+    public void AddSessionOverride(EntityUid uid, ICommonSession session, bool removeExistingOverride = true)
     {
-        _pvs.EntityPVSCollection.UpdateIndex(GetNetEntity(uid), session, removeExistingOverride);
+        _pvs.EntityPVSCollection.AddSessionOverride(GetNetEntity(uid), session, removeExistingOverride);
     }
 
     /// <summary>

Robust.Server/GameStates/PvsSystem.Dirty.cs

@@ -92,9 +92,9 @@ namespace Robust.Server.GameStates
         /// <summary>
         ///     Marks an entity's current chunk as dirty.
         /// </summary>
-        internal void MarkDirty(EntityUid uid)
+        internal void MarkDirty(EntityUid uid, TransformComponent xform)
         {
-            var coordinates = _transform.GetMoverCoordinates(uid);
+            var coordinates = _transform.GetMoverCoordinates(uid, xform);
             _entityPvsCollection.MarkDirty(_entityPvsCollection.GetChunkIndex(coordinates));
         }
     }

Robust.Server/GameStates/PvsSystem.cs

@@ -35,16 +35,10 @@ internal sealed partial class PvsSystem : EntitySystem
     public const float ChunkSize = 8;
 
     // TODO make this a cvar. Make it in terms of seconds and tie it to tick rate?
-    // Main issue is that I CBF figuring out the logic for handling it changing mid-game.
     public const int DirtyBufferSize = 20;
     // Note: If a client has ping higher than TickBuffer / TickRate, then the server will treat every entity as if it
     // had entered PVS for the first time. Note that due to the PVS budget, this buffer is easily overwhelmed.
 
-    /// <summary>
-    /// See <see cref="CVars.NetForceAckThreshold"/>.
-    /// </summary>
-    public int ForceAckThreshold { get; private set; }
-
     /// <summary>
     /// Maximum number of pooled objects
     /// </summary>
@@ -145,7 +139,6 @@ internal sealed partial class PvsSystem : EntitySystem
 
         _configManager.OnValueChanged(CVars.NetPVS, SetPvs, true);
         _configManager.OnValueChanged(CVars.NetMaxUpdateRange, OnViewsizeChanged, true);
-        _configManager.OnValueChanged(CVars.NetForceAckThreshold, OnForceAckChanged, true);
 
         _serverGameStateManager.ClientAck += OnClientAck;
         _serverGameStateManager.ClientRequestFull += OnClientRequestFull;
@@ -163,7 +156,6 @@ internal sealed partial class PvsSystem : EntitySystem
 
         _configManager.UnsubValueChanged(CVars.NetPVS, SetPvs);
         _configManager.UnsubValueChanged(CVars.NetMaxUpdateRange, OnViewsizeChanged);
-        _configManager.UnsubValueChanged(CVars.NetForceAckThreshold, OnForceAckChanged);
 
         _serverGameStateManager.ClientAck -= OnClientAck;
         _serverGameStateManager.ClientRequestFull -= OnClientRequestFull;
@@ -196,6 +188,7 @@ internal sealed partial class PvsSystem : EntitySystem
         Log.Warning(sb.ToString());
 
         sessionData.LastSeenAt.Clear();
+        sessionData.LastLeftView.Clear();
 
         if (sessionData.Overflow != null)
         {
@@ -219,11 +212,6 @@ internal sealed partial class PvsSystem : EntitySystem
         _viewSize = obj * 2;
     }
 
-    private void OnForceAckChanged(int value)
-    {
-        ForceAckThreshold = value;
-    }
-
     private void SetPvs(bool value)
     {
         _seenAllEnts.Clear();
@@ -269,6 +257,7 @@ internal sealed partial class PvsSystem : EntitySystem
         foreach (var sessionData in PlayerData.Values)
         {
             sessionData.LastSeenAt.Remove(metadata.NetEntity);
+            sessionData.LastLeftView.Remove(metadata.NetEntity);
             if (sessionData.SentEntities.TryGetValue(previousTick, out var ents))
                 ents.Remove(metadata.NetEntity);
         }
@@ -663,16 +652,16 @@ internal sealed partial class PvsSystem : EntitySystem
         }
     }
 
-    private bool AddToChunkSetRecursively(in EntityUid uid, in NetEntity netEntity, MetaDataComponent mComp,
+    private void AddToChunkSetRecursively(in EntityUid uid, in NetEntity netEntity, MetaDataComponent mComp,
         int visMask, RobustTree<NetEntity> tree, Dictionary<NetEntity, MetaDataComponent> set)
     {
-        if (set.ContainsKey(netEntity))
-            return true;
-
-        // TODO: Don't need to know about parents so no longer need to use bool for this method.
-        // If the eye is missing ANY layer this entity or any of its parents belongs to, it is considered invisible.
+        // If the eye is missing ANY layer that this entity is on, or any layer that any of its parents belongs to, then
+        // it is considered invisible.
         if ((visMask & mComp.VisibilityMask) != mComp.VisibilityMask)
-            return false;
+            return;
+
+        if (!set.TryAdd(netEntity, mComp))
+            return; // already sending
 
         var xform = _xformQuery.GetComponent(uid);
 
@@ -682,8 +671,7 @@ internal sealed partial class PvsSystem : EntitySystem
         {
             DebugTools.Assert(_mapManager.IsGrid(uid) || _mapManager.IsMap(uid));
             tree.Set(netEntity);
-            set.Add(netEntity, mComp);
-            return true;
+            return;
         }
 
         DebugTools.Assert(!_mapManager.IsGrid(uid) && !_mapManager.IsMap(uid));
@@ -692,15 +680,12 @@ internal sealed partial class PvsSystem : EntitySystem
         var parentMeta = _metaQuery.GetComponent(parent);
         var parentNetEntity = parentMeta.NetEntity;
 
-        if (!AddToChunkSetRecursively(in parent, in parentNetEntity, parentMeta, visMask, tree, set)) //did we just fail to add the parent?
-        {
-            return false; //we failed? suppose we dont get added either
-        }
+        // Child should have all o the same flags as the parent.
+        DebugTools.Assert((parentMeta.VisibilityMask & mComp.VisibilityMask) == parentMeta.VisibilityMask);
 
-        //i want it to crash here if it gets added double bc that shouldnt happen and will add alot of unneeded cycles
+        // Add our parent.
+        AddToChunkSetRecursively(in parent, in parentNetEntity, parentMeta, visMask, tree, set);
         tree.Set(netEntity, parentNetEntity);
-        set.Add(netEntity, mComp);
-        return true;
     }
 
     internal (List<EntityState>? updates, List<NetEntity>? deletions, List<NetEntity>? leftPvs, GameTick fromTick)
@@ -720,6 +705,7 @@ internal sealed partial class PvsSystem : EntitySystem
         sessionData.SentEntities.TryGetValue(toTick - 1, out var lastSent);
         var lastAcked = sessionData.LastAcked?.Data;
         var lastSeen = sessionData.LastSeenAt;
+        var lastLeft = sessionData.LastLeftView;
         var visibleEnts = _visSetPool.Get();
 
         if (visibleEnts.Count != 0)
@@ -747,7 +733,7 @@ internal sealed partial class PvsSystem : EntitySystem
 
             foreach (var rootNode in cache.Value.tree.RootNodes)
             {
-                RecursivelyAddTreeNode(in rootNode, cache.Value.tree, lastAcked, lastSent, visibleEnts, lastSeen, cache.Value.metadata, stack, in fromTick,
+                RecursivelyAddTreeNode(in rootNode, cache.Value.tree, lastAcked, lastSent, visibleEnts, lastSeen, lastLeft, cache.Value.metadata, stack, in fromTick,
                         ref newEntityCount, ref enteredEntityCount, ref entStateCount,  in newEntityBudget, in enteredEntityBudget);
             }
         }
@@ -758,7 +744,7 @@ internal sealed partial class PvsSystem : EntitySystem
         {
             var netEntity = globalEnumerator.Current;
             var uid = GetEntity(netEntity);
-            RecursivelyAddOverride(in uid, lastAcked, lastSent, visibleEnts, lastSeen, in fromTick,
+            RecursivelyAddOverride(in uid, lastAcked, lastSent, visibleEnts, lastSeen, lastLeft, in fromTick,
                 ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget);
         }
         globalEnumerator.Dispose();
@@ -768,39 +754,45 @@ internal sealed partial class PvsSystem : EntitySystem
         {
             var netEntity = globalRecursiveEnumerator.Current;
             var uid = GetEntity(netEntity);
-            RecursivelyAddOverride(in uid, lastAcked, lastSent, visibleEnts, lastSeen, in fromTick,
+            RecursivelyAddOverride(in uid, lastAcked, lastSent, visibleEnts, lastSeen, lastLeft, in fromTick,
                 ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget, true);
         }
         globalRecursiveEnumerator.Dispose();
 
-        var localEnumerator = _entityPvsCollection.GetElementsForSession(session);
-        while (localEnumerator.MoveNext())
+        var sessionOverrides = _entityPvsCollection.GetSessionOverrides(session);
+        while (sessionOverrides.MoveNext())
         {
-            var netEntity = localEnumerator.Current;
+            var netEntity = sessionOverrides.Current;
             var uid = GetEntity(netEntity);
-            RecursivelyAddOverride(in uid, lastAcked, lastSent, visibleEnts, lastSeen,in fromTick,
-                ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget);
+            RecursivelyAddOverride(in uid, lastAcked, lastSent, visibleEnts, lastSeen, lastLeft, in fromTick,
+                ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget, true);
         }
-        localEnumerator.Dispose();
+        sessionOverrides.Dispose();
 
         foreach (var viewerEntity in viewers)
         {
-            RecursivelyAddOverride(in viewerEntity, lastAcked, lastSent, visibleEnts, lastSeen, in fromTick,
+            RecursivelyAddOverride(in viewerEntity, lastAcked, lastSent, visibleEnts, lastSeen, lastLeft, in fromTick,
                 ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget);
         }
 
         var expandEvent = new ExpandPvsEvent(session);
         RaiseLocalEvent(ref expandEvent);
-        foreach (var entityUid in expandEvent.Entities)
+        if (expandEvent.Entities != null)
         {
-            RecursivelyAddOverride(in entityUid, lastAcked, lastSent, visibleEnts, lastSeen, in fromTick,
-                ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget);
+            foreach (var entityUid in expandEvent.Entities)
+            {
+                RecursivelyAddOverride(in entityUid, lastAcked, lastSent, visibleEnts, lastSeen, lastLeft, in fromTick,
+                    ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget);
+            }
         }
 
-        foreach (var entityUid in expandEvent.RecursiveEntities)
+        if (expandEvent.RecursiveEntities != null)
         {
-            RecursivelyAddOverride(in entityUid, lastAcked, lastSent, visibleEnts, lastSeen,in fromTick,
-                ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget, true);
+            foreach (var entityUid in expandEvent.RecursiveEntities)
+            {
+                RecursivelyAddOverride(in entityUid, lastAcked, lastSent, visibleEnts, lastSeen, lastLeft, in fromTick,
+                    ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget, true);
+            }
         }
 
         var entityStates = new List<EntityState>(entStateCount);
@@ -837,7 +829,7 @@ internal sealed partial class PvsSystem : EntitySystem
         }
 
         // tell a client to detach entities that have left their view
-        var leftView = ProcessLeavePVS(visibleEnts, lastSent);
+        var leftView = ProcessLeavePvs(visibleEnts, lastSent, lastLeft);
 
         if (sessionData.SentEntities.Add(toTick, visibleEnts, out var oldEntry))
         {
@@ -874,18 +866,26 @@ internal sealed partial class PvsSystem : EntitySystem
     ///     Figure out what entities are no longer visible to the client. These entities are sent reliably to the client
     ///     in a separate net message.
     /// </summary>
-    private List<NetEntity>? ProcessLeavePVS(
+    private List<NetEntity>? ProcessLeavePvs(
         Dictionary<NetEntity, PvsEntityVisibility> visibleEnts,
-        Dictionary<NetEntity, PvsEntityVisibility>? lastSent)
+        Dictionary<NetEntity, PvsEntityVisibility>? lastSent,
+        Dictionary<NetEntity, GameTick> lastLeft)
     {
         if (lastSent == null)
             return null;
 
-        var leftView = new List<NetEntity>();
+        var tick = _gameTiming.CurTick;
+        var minSize = Math.Max(0, lastSent.Count - lastSent.Count);
+        var leftView = new List<NetEntity>(minSize);
+
         foreach (var netEntity in lastSent.Keys)
         {
             if (!visibleEnts.ContainsKey(netEntity))
+            {
                 leftView.Add(netEntity);
+                lastLeft[netEntity] = tick;
+            }
+
         }
 
         return leftView.Count > 0 ? leftView : null;
@@ -897,6 +897,7 @@ internal sealed partial class PvsSystem : EntitySystem
         Dictionary<NetEntity, PvsEntityVisibility>? lastSent,
         Dictionary<NetEntity, PvsEntityVisibility> toSend,
         Dictionary<NetEntity, GameTick> lastSeen,
+        Dictionary<NetEntity, GameTick> lastLeft,
         Dictionary<NetEntity, MetaDataComponent> metaDataCache,
         Stack<NetEntity> stack,
         in GameTick fromTick,
@@ -919,7 +920,7 @@ internal sealed partial class PvsSystem : EntitySystem
             ref var value = ref CollectionsMarshal.GetValueRefOrAddDefault(toSend, currentNodeIndex, out var exists);
             if (!exists)
             {
-                var (entered, shouldAdd) = ProcessEntry(in currentNodeIndex, lastAcked, lastSent, lastSeen,
+                var (entered, shouldAdd) = ProcessEntry(in currentNodeIndex, lastAcked, lastSent, lastSeen, lastLeft, fromTick,
                     ref newEntityCount, ref enteredEntityCount, newEntityBudget, enteredEntityBudget);
 
                 if (!shouldAdd)
@@ -949,6 +950,7 @@ internal sealed partial class PvsSystem : EntitySystem
         Dictionary<NetEntity, PvsEntityVisibility>? lastSent,
         Dictionary<NetEntity, PvsEntityVisibility> toSend,
         Dictionary<NetEntity, GameTick> lastSeen,
+        Dictionary<NetEntity, GameTick> lastLeft,
         in GameTick fromTick,
         ref int newEntityCount,
         ref int enteredEntityCount,
@@ -964,7 +966,7 @@ internal sealed partial class PvsSystem : EntitySystem
 
         var xform = _xformQuery.GetComponent(uid);
         var parent = xform.ParentUid;
-        if (parent.IsValid() && !RecursivelyAddOverride(in parent, lastAcked, lastSent, toSend, lastSeen, in fromTick,
+        if (parent.IsValid() && !RecursivelyAddOverride(in parent, lastAcked, lastSent, toSend, lastSeen, lastLeft, in fromTick,
                 ref newEntityCount, ref enteredEntityCount, ref entStateCount, in newEntityBudget,
                 in enteredEntityBudget))
         {
@@ -974,7 +976,6 @@ internal sealed partial class PvsSystem : EntitySystem
         var metadata = _metaQuery.GetComponent(uid);
         var netEntity = metadata.NetEntity;
 
-        //did we already get added?
         // Note that we check this AFTER adding parents. This is because while this entity may already have been added
         // to the toSend set, it doesn't guarantee that its parents have been. E.g., if a player ghost just teleported
         // to follow a far away entity, the player's own entity is still being sent, but we need to ensure that we also
@@ -982,17 +983,13 @@ internal sealed partial class PvsSystem : EntitySystem
         ref var value = ref CollectionsMarshal.GetValueRefOrAddDefault(toSend, netEntity, out var exists);
         if (!exists)
         {
-            // TODO PERFORMANCE.
-            // ProcessEntry() unnecessarily checks lastSent.ContainsKey() and maybe lastSeen.Contains(). Given that at this
-            // point the budgets are just ignored, this should just bypass those checks. But then again 99% of the time this
-            // is just the player's own entity + maybe a singularity. So currently not all that performance intensive.
-            var (entered, _) = ProcessEntry(in netEntity, lastAcked, lastSent, lastSeen, ref newEntityCount, ref enteredEntityCount, newEntityBudget, enteredEntityBudget);
+            var (entered, _) = ProcessEntry(in netEntity, lastAcked, lastSent, lastSeen, lastLeft, fromTick, ref newEntityCount, ref enteredEntityCount, newEntityBudget, enteredEntityBudget);
             AddToSendSet(in netEntity, metadata, ref value, toSend, fromTick, in entered, ref entStateCount);
         }
 
         if (addChildren)
         {
-            RecursivelyAddChildren(xform, lastAcked, lastSent, toSend, lastSeen, fromTick, ref newEntityCount,
+            RecursivelyAddChildren(xform, lastAcked, lastSent, toSend, lastSeen, lastLeft, fromTick, ref newEntityCount,
                 ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget);
         }
 
@@ -1004,6 +1001,7 @@ internal sealed partial class PvsSystem : EntitySystem
         Dictionary<NetEntity, PvsEntityVisibility>? lastSent,
         Dictionary<NetEntity, PvsEntityVisibility> toSend,
         Dictionary<NetEntity, GameTick> lastSeen,
+        Dictionary<NetEntity, GameTick> lastLeft,
         in GameTick fromTick,
         ref int newEntityCount,
         ref int enteredEntityCount,
@@ -1022,22 +1020,23 @@ internal sealed partial class PvsSystem : EntitySystem
             ref var value = ref CollectionsMarshal.GetValueRefOrAddDefault(toSend, childNetEntity, out var exists);
             if (!exists)
             {
-                var (entered, _) = ProcessEntry(in childNetEntity, lastAcked, lastSent, lastSeen, ref newEntityCount,
+                var (entered, _) = ProcessEntry(in childNetEntity, lastAcked, lastSent, lastSeen, lastLeft, fromTick, ref newEntityCount,
                     ref enteredEntityCount, newEntityBudget, enteredEntityBudget);
 
                 AddToSendSet(in childNetEntity, metadata, ref value, toSend, fromTick, in entered, ref entStateCount);
             }
 
-            RecursivelyAddChildren(childXform, lastAcked, lastSent, toSend, lastSeen, fromTick, ref newEntityCount,
+            RecursivelyAddChildren(childXform, lastAcked, lastSent, toSend, lastSeen, lastLeft, fromTick, ref newEntityCount,
                 ref enteredEntityCount, ref entStateCount, in newEntityBudget, in enteredEntityBudget);
         }
     }
 
-    private (bool Entered, bool ShouldAdd) ProcessEntry(
-        in NetEntity netEntity,
+    private (bool Entered, bool ShouldAdd) ProcessEntry(in NetEntity netEntity,
         Dictionary<NetEntity, PvsEntityVisibility>? lastAcked,
         Dictionary<NetEntity, PvsEntityVisibility>? lastSent,
         Dictionary<NetEntity, GameTick> lastSeen,
+        Dictionary<NetEntity, GameTick> lastLeft,
+        GameTick fromTick,
         ref int newEntityCount,
         ref int enteredEntityCount,
         in int newEntityBudget,
@@ -1045,16 +1044,15 @@ internal sealed partial class PvsSystem : EntitySystem
     {
         var enteredSinceLastSent = lastSent == null || !lastSent.ContainsKey(netEntity);
 
-        var entered = enteredSinceLastSent || // OR, entered since last ack:
-                        lastAcked == null || !lastAcked.ContainsKey(netEntity);
+        var entered = enteredSinceLastSent
+                      || lastAcked == null
+                      || !lastAcked.ContainsKey(netEntity) // entered since last acked
+                      || lastLeft.GetValueOrDefault(netEntity) >= fromTick; // Just in case a packet was lost. I love dictionary lookups
 
         // If the entity is entering, but we already sent this entering entity in the last message, we won't add it to
         // the budget. Chances are the packet will arrive in a nice and orderly fashion, and the client will stick to
         // their requested budget. However this can cause issues if a packet gets dropped, because a player may create
         // 2x or more times the normal entity creation budget.
-        //
-        // The fix for that would be to just also give the PVS budget a client-side aspect that controls entity creation
-        // rate.
         if (enteredSinceLastSent)
         {
             if (newEntityCount >= newEntityBudget || enteredEntityCount >= enteredEntityBudget)
@@ -1385,6 +1383,11 @@ Transform last modified: {Transform(uid).LastModifiedTick}");
         /// </summary>
         public readonly Dictionary<NetEntity, GameTick> LastSeenAt = new();
 
+        /// <summary>
+        ///     Tick at which an entity last left a player's PVS view.
+        /// </summary>
+        public readonly Dictionary<NetEntity, GameTick> LastLeftView = new();
+
         /// <summary>
         ///     <see cref="SentEntities"/> overflow in case a player's last ack is more than <see cref="DirtyBufferSize"/> ticks behind the current tick.
         /// </summary>
@@ -1407,20 +1410,20 @@ Transform last modified: {Transform(uid).LastModifiedTick}");
 }
 
 [ByRefEvent]
-public readonly struct ExpandPvsEvent
+public struct ExpandPvsEvent
 {
     public readonly IPlayerSession Session;
 
     /// <summary>
     /// List of entities that will get added to this session's PVS set.
     /// </summary>
-    public readonly List<EntityUid> Entities = new();
+    public List<EntityUid>? Entities;
 
     /// <summary>
     /// List of entities that will get added to this session's PVS set. Unlike <see cref="Entities"/> this will also
     /// recursively add all children of the given entity.
     /// </summary>
-    public readonly List<EntityUid> RecursiveEntities = new();
+    public List<EntityUid>? RecursiveEntities;
 
     public ExpandPvsEvent(IPlayerSession session)
     {

Robust.Server/GameStates/RobustTree.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
+using System.Runtime.InteropServices;
 using Microsoft.Extensions.ObjectPool;
 using Robust.Shared.Utility;
 
@@ -89,56 +89,76 @@ public sealed class RobustTree<T> where T : notnull
         throw new InvalidOperationException("Node neither had a parent nor was a RootNode.");
     }
 
-    public TreeNode Set(T rootNode)
+    public void Set(T rootNode)
     {
-        //root node, for now
-        if (_nodeIndex.TryGetValue(rootNode, out var node))
+        ref var node = ref CollectionsMarshal.GetValueRefOrAddDefault(_nodeIndex, rootNode, out var exists);
+
+        if (exists)
         {
             if(!RootNodes.Contains(rootNode))
                 throw new InvalidOperationException("Node already exists as non-root node.");
-            return node;
+            return;
         }
 
         node = new TreeNode(rootNode);
-        _nodeIndex.Add(rootNode, node);
-        RootNodes.Add(rootNode);
-        return node;
+        if(!RootNodes.Add(rootNode))
+            throw new InvalidOperationException("Non-existent node was already a root node?");
     }
 
-    public TreeNode Set(T child, T parent)
+    public void Set(T child, T parent)
     {
-        if (!_nodeIndex.TryGetValue(parent, out var parentNode))
-            parentNode = Set(parent);
-
-        if (parentNode.Children == null)
+        // Code block for where parentNode is a valid ref
         {
-            _nodeIndex[parent] = parentNode = parentNode.WithChildren(_pool.Get());
-        }
+            ref var parentNode = ref CollectionsMarshal.GetValueRefOrAddDefault(_nodeIndex, parent, out var parentExists);
 
-        if (_nodeIndex.TryGetValue(child, out var existingNode))
-        {
-            if (RootNodes.Contains(child))
+            // If parent does not exist we make it a new root node.
+            if (!parentExists)
             {
-                parentNode.Children!.Add(existingNode.Value);
-                RootNodes.Remove(child);
-                _parents.Add(child, parent);
-                return existingNode;
+                parentNode = new TreeNode(parent);
+                if (!RootNodes.Add(parent))
+                {
+                    _nodeIndex.Remove(parent);
+                    throw new InvalidOperationException("Non-existent node was already a root node?");
+                }
             }
 
-            if (!_parents.TryGetValue(child, out var previousParent) || _nodeIndex.TryGetValue(previousParent, out var previousParentNode))
-                throw new InvalidOperationException("Could not find old parent for non-root node.");
-
-            previousParentNode.Children?.Remove(existingNode.Value);
-            parentNode.Children!.Add(existingNode.Value);
-            _parents[child] = parent;
-            return existingNode;
+            var children = parentNode.Children;
+            if (children == null)
+            {
+                children = _pool.Get();
+                parentNode = parentNode.WithChildren(children);
+                DebugTools.AssertNotNull(_nodeIndex[parent].Children);
+            }
+            children.Add(child);
         }
 
-        existingNode = new TreeNode(child);
-        _nodeIndex.Add(child, existingNode);
-        parentNode.Children!.Add(existingNode.Value);
-        _parents.Add(child, parent);
-        return existingNode;
+        // No longer safe to access parentNode ref after this.
+
+        ref var node = ref CollectionsMarshal.GetValueRefOrAddDefault(_nodeIndex, child, out var childExists);
+        if (!childExists)
+        {
+            // This is the path that PVS should take 99% of the time.
+            node = new TreeNode(child);
+            _parents.Add(child, parent);
+            return;
+        }
+
+        if (RootNodes.Remove(child))
+        {
+            DebugTools.Assert(!_parents.ContainsKey(child));
+            _parents.Add(child, parent);
+            return;
+        }
+
+        ref var parentEntry = ref CollectionsMarshal.GetValueRefOrAddDefault(_parents, child, out var previousParentExists);
+        if (!previousParentExists || !_nodeIndex.TryGetValue(parentEntry!, out var previousParentNode))
+        {
+            parentEntry = parent;
+            throw new InvalidOperationException("Could not find old parent for non-root node.");
+        }
+
+        previousParentNode.Children?.Remove(child);
+        parentEntry = parent;
     }
 
     public readonly struct TreeNode : IEquatable<TreeNode>

Robust.Server/GameStates/ServerGameStateManager.cs

@@ -373,21 +373,6 @@ Oldest acked clients: {string.Join(", ", players)}
             // If the state is too big we let Lidgren send it reliably. This is to avoid a situation where a state is so
             // large that it (or part of it) consistently gets dropped. When we send reliably, we immediately update the
             // ack so that the next state will not also be huge.
-            //
-            // We also do this if the client's last ack is too old. This helps prevent things like the entity deletion
-            // history from becoming too bloated if a bad client fails to send acks for whatever reason.
-
-            if (_gameTiming.CurTick.Value > lastAck.Value + _pvs.ForceAckThreshold)
-            {
-                stateUpdateMessage.ForceSendReliably = true;
-
-                // Aside from the time shortly after connecting, this shouldn't be common. If it is happening,
-                // something is probably wrong. If it is more frequent than I think, this can be downgraded to a warning.
-                var connectedTime = (DateTime.UtcNow - session.ConnectedTime).TotalMinutes;
-                if (lastAck > GameTick.Zero && connectedTime > 1)
-                    _logger.Error($"Client {session} exceeded ack-tick threshold. Last ack: {lastAck}. Cur tick: {_gameTiming.CurTick}. Connect time: {connectedTime} minutes");
-            }
-
             if (stateUpdateMessage.ShouldSendReliably())
             {
                 sessionData.LastReceivedAck = _gameTiming.CurTick;

Robust.Server/Spawners/TimedDespawnSystem.cs

@@ -0,0 +1,12 @@
+using Robust.Shared.GameObjects;
+using Robust.Shared.Spawners;
+
+namespace Robust.Server.Spawners;
+
+public sealed class TimedDespawnSystem : SharedTimedDespawnSystem
+{
+    protected override bool CanDelete(EntityUid uid)
+    {
+        return true;
+    }
+}

Robust.Server/ViewVariables/ViewVariablesTrait.cs

@@ -94,7 +94,7 @@ namespace Robust.Server.ViewVariables
             }
 
             if (value is EntityUid uid)
-                return IoCManager.Resolve<IEntityManager>().GetNetEntity(uid);
+                return IoCManager.Resolve<IEntityManager>().GetComponentOrNull<MetaDataComponent>(uid)?.NetEntity ?? NetEntity.Invalid;
 
             var valType = value.GetType();
             if (!valType.IsValueType)

Robust.Shared.CompNetworkGenerator/ComponentNetworkGenerator.cs

@@ -6,6 +6,7 @@ using System.Text;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Text;
+using static Microsoft.CodeAnalysis.SymbolDisplayFormat;
 
 namespace Robust.Shared.CompNetworkGenerator
 {
@@ -14,20 +15,31 @@ namespace Robust.Shared.CompNetworkGenerator
     {
         private const string ClassAttributeName = "Robust.Shared.Analyzers.AutoGenerateComponentStateAttribute";
         private const string MemberAttributeName = "Robust.Shared.Analyzers.AutoNetworkedFieldAttribute";
+
         private const string GlobalEntityUidName = "global::Robust.Shared.GameObjects.EntityUid";
         private const string GlobalNullableEntityUidName = "global::Robust.Shared.GameObjects.EntityUid?";
-        private const string GlobalEntityCoordinatesName = "global::Robust.Shared.Map.EntityCoordinates?";
-        private const string GlobalNullableEntityCoordinatesName = "global::Robust.Shared.Map.EntityCoordinates";
+
+        private const string GlobalEntityCoordinatesName = "global::Robust.Shared.Map.EntityCoordinates";
+        private const string GlobalNullableEntityCoordinatesName = "global::Robust.Shared.Map.EntityCoordinates?";
+
+        private const string GlobalEntityUidSetName = "global::System.Collections.Generic.HashSet<global::Robust.Shared.GameObjects.EntityUid>";
+        private const string GlobalNetEntityUidSetName = "global::System.Collections.Generic.HashSet<global::Robust.Shared.GameObjects.NetEntity>";
+
+        private const string GlobalEntityUidListName = "global::System.Collections.Generic.List<global::Robust.Shared.GameObjects.EntityUid>";
+        private const string GlobalNetEntityUidListName = "global::System.Collections.Generic.List<global::Robust.Shared.GameObjects.NetEntity>";
+
+        private const string GlobalDictionaryName = "global::System.Collections.Generic.Dictionary<TKey, TValue>";
+        private const string GlobalHashSetName = "global::System.Collections.Generic.HashSet<T>";
+        private const string GlobalListName = "global::System.Collections.Generic.List<T>";
 
         private static string GenerateSource(in GeneratorExecutionContext context, INamedTypeSymbol classSymbol, CSharpCompilation comp, bool raiseAfterAutoHandle)
         {
-            // Debugger.Launch();
             var nameSpace = classSymbol.ContainingNamespace.ToDisplayString();
             var componentName = classSymbol.Name;
             var stateName = $"{componentName}_AutoState";
 
             var members = classSymbol.GetMembers();
-            var fields = new List<(ITypeSymbol Type, string FieldName, AttributeData Attribute)>();
+            var fields = new List<(ITypeSymbol Type, string FieldName)>();
             var fieldAttr = comp.GetTypeByMetadataName(MemberAttributeName);
 
             foreach (var mem in members)
@@ -44,7 +56,7 @@ namespace Robust.Shared.CompNetworkGenerator
                 switch (mem)
                 {
                     case IFieldSymbol field:
-                        fields.Add((field.Type, field.Name, attribute));
+                        fields.Add((field.Type, field.Name));
                         break;
                     case IPropertySymbol prop:
                     {
@@ -80,7 +92,7 @@ namespace Robust.Shared.CompNetworkGenerator
                             continue;
                         }
 
-                        fields.Add((prop.Type, prop.Name, attribute));
+                        fields.Add((prop.Type, prop.Name));
                         break;
                     }
                 }
@@ -118,9 +130,9 @@ namespace Robust.Shared.CompNetworkGenerator
             //            component.Count = state.Count;
             var handleStateSetters = new StringBuilder();
 
-            foreach (var (type, name, attribute) in fields)
+            foreach (var (type, name) in fields)
             {
-                var typeDisplayStr = type.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
+                var typeDisplayStr = type.ToDisplayString(FullyQualifiedFormat);
                 var nullable = type.NullableAnnotation == NullableAnnotation.Annotated;
                 var nullableAnnotation = nullable ? "?" : string.Empty;
 
@@ -147,12 +159,32 @@ namespace Robust.Shared.CompNetworkGenerator
                         handleStateSetters.Append($@"
             component.{name} = EnsureCoordinates<{componentName}>(state.{name}, uid);");
 
+                        break;
+                    case GlobalEntityUidSetName:
+                        stateFields.Append($@"
+        public {GlobalNetEntityUidSetName} {name} = default!;");
+
+                        getStateInit.Append($@"
+                {name} = GetNetEntitySet(component.{name}),");
+                        handleStateSetters.Append($@"
+            component.{name} = EnsureEntitySet<{componentName}>(state.{name}, uid);");
+
+                        break;
+                    case GlobalEntityUidListName:
+                        stateFields.Append($@"
+        public {GlobalNetEntityUidListName} {name} = default!;");
+
+                        getStateInit.Append($@"
+                {name} = GetNetEntityList(component.{name}),");
+                        handleStateSetters.Append($@"
+            component.{name} = EnsureEntityList<{componentName}>(state.{name}, uid);");
+
                         break;
                     default:
                         stateFields.Append($@"
         public {typeDisplayStr} {name} = default!;");
 
-                        if (attribute.ConstructorArguments[0].Value is bool val && val)
+                        if (IsCloneType(type))
                         {
                             // get first ctor arg of the field attribute, which determines whether the field should be cloned
                             // (like if its a dict or list)
@@ -160,7 +192,9 @@ namespace Robust.Shared.CompNetworkGenerator
                 {name} = component.{name},");
 
                             handleStateSetters.Append($@"
-            if (state.{name} != null)
+            if (state.{name} == null)
+                component.{name} = null;
+            else
                 component.{name} = new(state.{name});");
                         }
                         else
@@ -330,5 +364,20 @@ public partial class {componentName}
             }
             context.RegisterForSyntaxNotifications(() => new NameReferenceSyntaxReceiver());
         }
+
+        private static bool IsCloneType(ITypeSymbol type)
+        {
+            if (type is not INamedTypeSymbol named || !named.IsGenericType)
+            {
+                return false;
+            }
+
+            var constructed = named.ConstructedFrom.ToDisplayString(FullyQualifiedFormat);
+            return constructed switch
+            {
+                GlobalDictionaryName or GlobalHashSetName or GlobalListName => true,
+                _ => false
+            };
+        }
     }
 }

Robust.Shared.CompNetworkGenerator/Robust.Shared.CompNetworkGenerator.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <LangVersion>9</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

Robust.Shared/Analyzers/ComponentNetworkGeneratorAuxiliary.cs

@@ -32,20 +32,6 @@ public sealed class AutoGenerateComponentStateAttribute : Attribute
 [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
 public sealed class AutoNetworkedFieldAttribute : Attribute
 {
-    /// <summary>
-    ///     Determines whether the data should be wrapped in a new() when setting in get/handlestate
-    ///     e.g. for cloning collections like dictionaries or hashsets which is sometimes necessary.
-    /// </summary>
-    /// <remarks>
-    ///     This should only be true if the type actually has a constructor that takes in itself.
-    /// </remarks>
-    [UsedImplicitly]
-    public bool CloneData;
-
-    public AutoNetworkedFieldAttribute(bool cloneData=false)
-    {
-        CloneData = cloneData;
-    }
 }
 
 /// <summary>

Robust.Shared/CVars.cs

@@ -172,13 +172,6 @@ namespace Robust.Shared
         public static readonly CVarDef<float> NetMaxUpdateRange =
             CVarDef.Create("net.maxupdaterange", 12.5f, CVar.ARCHIVE | CVar.REPLICATED | CVar.SERVER);
 
-        /// <summary>
-        /// Maximum allowed delay between the current tick and a client's last acknowledged tick before we send the
-        /// next game state reliably and simply force update the acked tick,
-        /// </summary>
-        public static readonly CVarDef<int> NetForceAckThreshold =
-            CVarDef.Create("net.force_ack_threshold", 40, CVar.ARCHIVE | CVar.SERVERONLY);
-
         /// <summary>
         /// This limits the number of new entities that can be sent to a client in a single game state. This exists to
         /// avoid stuttering on the client when it has to spawn a bunch of entities in a single tick. If ever entity

Robust.Shared/Containers/ContainerHelpers.cs

@@ -1,191 +0,0 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using JetBrains.Annotations;
-using Robust.Shared.GameObjects;
-using Robust.Shared.IoC;
-using Robust.Shared.Map;
-using Robust.Shared.Utility;
-
-namespace Robust.Shared.Containers
-{
-    /// <summary>
-    /// Helper functions for the container system.
-    /// </summary>
-    [PublicAPI]
-    public static class ContainerHelpers
-    {
-        /// <summary>
-        /// Am I inside a container? Only checks the direct parent. To see if the entity, or any parent entity, is
-        /// inside a container, use <see cref="ContainerSystem.IsEntityOrParentInContainer"/>
-        /// </summary>
-        /// <param name="entity">Entity that might be inside a container.</param>
-        /// <returns>If the entity is inside of a container.</returns>
-        [Obsolete("Use ContainerSystem.IsEntityInContainer() instead")]
-        public static bool IsInContainer(this EntityUid entity,
-            IEntityManager? entMan = null)
-        {
-            IoCManager.Resolve(ref entMan);
-            return (entMan.GetComponent<MetaDataComponent>(entity).Flags & MetaDataFlags.InContainer) == MetaDataFlags.InContainer;
-        }
-
-        /// <summary>
-        /// Tries to find the container manager that this entity is inside (if any).
-        /// </summary>
-        /// <param name="entity">Entity that might be inside a container.</param>
-        /// <param name="manager">The container manager that this entity is inside of.</param>
-        /// <returns>If a container manager was found.</returns>
-        public static bool TryGetContainerMan(this EntityUid entity, [NotNullWhen(true)] out ContainerManagerComponent? manager, IEntityManager? entMan = null)
-        {
-            IoCManager.Resolve(ref entMan);
-            DebugTools.Assert(entMan.EntityExists(entity));
-
-            var parent = entMan.GetComponent<TransformComponent>(entity).ParentUid;
-            if (parent.IsValid() && TryGetManagerComp(parent, out manager, entMan) && manager.ContainsEntity(entity))
-                return true;
-
-            manager = default;
-            return false;
-        }
-
-        /// <summary>
-        /// Tries to find the container that this entity is inside (if any).
-        /// </summary>
-        /// <param name="entity">Entity that might be inside a container.</param>
-        /// <param name="container">The container that this entity is inside of.</param>
-        /// <returns>If a container was found.</returns>
-        [Obsolete("Use ContainerSystem.TryGetContainingContainer() instead")]
-        public static bool TryGetContainer(this EntityUid entity, [NotNullWhen(true)] out BaseContainer? container, IEntityManager? entMan = null)
-        {
-            IoCManager.Resolve(ref entMan);
-            DebugTools.Assert(entMan.EntityExists(entity));
-
-            if (TryGetContainerMan(entity, out var manager, entMan))
-                return manager.TryGetContainer(entity, out container);
-
-            container = default;
-            return false;
-        }
-
-        /// <summary>
-        /// Attempts to remove an entity from its container, if any.
-        /// <see cref="SharedContainerSystem.TryRemoveFromContainer"/>
-        /// </summary>
-        /// <param name="entity">Entity that might be inside a container.</param>
-        /// <param name="force">Whether to forcibly remove the entity from the container.</param>
-        /// <param name="wasInContainer">Whether the entity was actually inside a container or not.</param>
-        /// <returns>If the entity could be removed. Also returns false if it wasn't inside a container.</returns>
-        [Obsolete("Use SharedContainerSystem.TryRemoveFromContainer() instead")]
-        public static bool TryRemoveFromContainer(this EntityUid entity, bool force, out bool wasInContainer, IEntityManager? entMan = null)
-        {
-            return IoCManager.Resolve<IEntitySystemManager>().GetEntitySystem<SharedContainerSystem>()
-                .TryRemoveFromContainer(entity, force, out wasInContainer);
-        }
-
-        /// <summary>
-        /// Attempts to remove an entity from its container, if any.
-        /// <see cref="SharedContainerSystem.TryRemoveFromContainer"/>
-        /// </summary>
-        /// <param name="entity">Entity that might be inside a container.</param>
-        /// <param name="force">Whether to forcibly remove the entity from the container.</param>
-        /// <returns>If the entity could be removed. Also returns false if it wasn't inside a container.</returns>
-        [Obsolete("Use SharedContainerSystem.TryRemoveFromContainer() instead")]
-        public static bool TryRemoveFromContainer(this EntityUid entity, bool force = false, IEntityManager? entMan = null)
-        {
-            return IoCManager.Resolve<IEntitySystemManager>().GetEntitySystem<SharedContainerSystem>()
-                .TryRemoveFromContainer(entity, force);
-        }
-
-        /// <summary>
-        /// Attempts to remove all entities in a container.
-        /// <see cref="SharedContainerSystem.EmptyContainer"/>
-        /// </summary>
-        [Obsolete("Use SharedContainerSystem.EmptyContainer() instead")]
-        public static void EmptyContainer(this BaseContainer container, bool force = false, EntityCoordinates? moveTo = null,
-            bool attachToGridOrMap = false, IEntityManager? entMan = null)
-        {
-            IoCManager.Resolve<IEntitySystemManager>().GetEntitySystem<SharedContainerSystem>()
-                .EmptyContainer(container, force, moveTo, attachToGridOrMap);
-        }
-
-        /// <summary>
-        /// Attempts to remove and delete all entities in a container.
-        /// <see cref="SharedContainerSystem.CleanContainer"/>
-        /// </summary>
-        [Obsolete("Use SharedContainerSystem.CleanContainer() instead")]
-        public static void CleanContainer(this BaseContainer container, IEntityManager? entMan = null)
-        {
-            IoCManager.Resolve<IEntitySystemManager>().GetEntitySystem<SharedContainerSystem>()
-                .CleanContainer(container);
-        }
-
-        /// <summary>
-        /// <see cref="SharedContainerSystem.AttachParentToContainerOrGrid"/>
-        /// </summary>
-        [Obsolete("Use SharedContainerSystem.AttachParentToContainerOrGrid() instead")]
-        public static void AttachParentToContainerOrGrid(this TransformComponent transform, IEntityManager? entMan = null)
-        {
-            IoCManager.Resolve<IEntitySystemManager>().GetEntitySystem<SharedContainerSystem>()
-                .AttachParentToContainerOrGrid(transform);
-        }
-
-        /// <summary>
-        /// <see cref="SharedContainerSystem.TryGetManagerComp"/>
-        /// </summary>
-        [Obsolete("Use SharedContainerSystem.TryGetManagerComp() instead")]
-        private static bool TryGetManagerComp(this EntityUid entity, [NotNullWhen(true)] out ContainerManagerComponent? manager, IEntityManager? entMan = null)
-        {
-            IoCManager.Resolve(ref entMan);
-            return entMan.System<SharedContainerSystem>()
-                .TryGetManagerComp(entity, out manager);
-        }
-
-        /// <summary>
-        /// Shortcut method to make creation of containers easier.
-        /// Creates a new container on the entity and gives it back to you.
-        /// </summary>
-        /// <param name="entity">The entity to create the container for.</param>
-        /// <param name="containerId"></param>
-        /// <returns>The new container.</returns>
-        /// <exception cref="ArgumentException">Thrown if there already is a container with the specified ID.</exception>
-        /// <seealso cref="BaseContainerManager.MakeContainer{T}(string)" />
-        [Obsolete("Use ContainerSystem.MakeContainer() instead")]
-        public static T CreateContainer<T>(this EntityUid entity, string containerId, IEntityManager? entMan = null)
-            where T : BaseContainer
-        {
-            IoCManager.Resolve(ref entMan);
-            var containermanager = entMan.EnsureComponent<ContainerManagerComponent>(entity);
-            return containermanager.MakeContainer<T>(containerId);
-        }
-
-        [Obsolete("Use ContainerSystem.EnsureContainer() instead")]
-        public static T EnsureContainer<T>(this EntityUid entity, string containerId, IEntityManager? entMan = null)
-            where T : BaseContainer
-        {
-            IoCManager.Resolve(ref entMan);
-            return EnsureContainer<T>(entity, containerId, out _, entMan);
-        }
-
-        [Obsolete("Use ContainerSystem.EnsureContainer() instead")]
-        public static T EnsureContainer<T>(this EntityUid entity, string containerId, out bool alreadyExisted, IEntityManager? entMan = null)
-            where T : BaseContainer
-        {
-            IoCManager.Resolve(ref entMan);
-            var containerManager = entMan.EnsureComponent<ContainerManagerComponent>(entity);
-
-            if (!containerManager.TryGetContainer(containerId, out var existing))
-            {
-                alreadyExisted = false;
-                return containerManager.MakeContainer<T>(containerId);
-            }
-
-            if (!(existing is T container))
-            {
-                throw new InvalidOperationException(
-                    $"The container exists but is of a different type: {existing.GetType()}");
-            }
-
-            alreadyExisted = true;
-            return container;
-        }
-    }
-}

Robust.Shared/Containers/ContainerManagerComponent.cs

@@ -39,7 +39,7 @@ namespace Robust.Shared.Containers
         }
 
         /// <inheritdoc />
-        protected override void OnRemove()
+        protected internal override void OnRemove()
         {
             base.OnRemove();
 

Robust.Shared/GameObjects/Component.cs

@@ -2,11 +2,8 @@ using System;
 using Robust.Shared.GameStates;
 using Robust.Shared.IoC;
 using Robust.Shared.Reflection;
-using Robust.Shared.Serialization;
-using Robust.Shared.Serialization.Manager;
 using Robust.Shared.Serialization.Manager.Attributes;
 using Robust.Shared.Timing;
-using Robust.Shared.Utility;
 using Robust.Shared.ViewVariables;
 
 namespace Robust.Shared.GameObjects
@@ -36,7 +33,7 @@ namespace Robust.Shared.GameObjects
 
         /// <inheritdoc />
         [ViewVariables]
-        public ComponentLifeStage LifeStage { get; private set; } = ComponentLifeStage.PreAdd;
+        public ComponentLifeStage LifeStage { get; internal set; } = ComponentLifeStage.PreAdd;
 
         /// <summary>
         ///     If true, and if this is a networked component, then component data will only be sent to players if their
@@ -51,93 +48,6 @@ namespace Robust.Shared.GameObjects
         /// </summary>
         public virtual bool SessionSpecific => false;
 
-        /// <summary>
-        /// Increases the life stage from <see cref="ComponentLifeStage.PreAdd" /> to <see cref="ComponentLifeStage.Added" />,
-        /// after raising a <see cref="ComponentAdd"/> event.
-        /// </summary>
-        internal void LifeAddToEntity(IEntityManager entManager, CompIdx type)
-        {
-            DebugTools.Assert(LifeStage == ComponentLifeStage.PreAdd);
-
-            LifeStage = ComponentLifeStage.Adding;
-            CreationTick = entManager.CurrentTick;
-            // networked components are assumed to be dirty when added to entities. See also: ClearTicks()
-            LastModifiedTick = entManager.CurrentTick;
-            entManager.EventBus.RaiseComponentEvent(this, type, CompAddInstance);
-            LifeStage = ComponentLifeStage.Added;
-        }
-
-        /// <summary>
-        /// Increases the life stage from <see cref="ComponentLifeStage.Added" /> to <see cref="ComponentLifeStage.Initialized" />,
-        /// calling <see cref="Initialize" />.
-        /// </summary>
-        internal void LifeInitialize(IEntityManager entManager, CompIdx type)
-        {
-            DebugTools.Assert(LifeStage == ComponentLifeStage.Added);
-
-            LifeStage = ComponentLifeStage.Initializing;
-            entManager.EventBus.RaiseComponentEvent(this, type, CompInitInstance);
-            LifeStage = ComponentLifeStage.Initialized;
-        }
-
-        /// <summary>
-        /// Increases the life stage from <see cref="ComponentLifeStage.Initialized" /> to
-        /// <see cref="ComponentLifeStage.Running" />, calling <see cref="Startup" />.
-        /// </summary>
-        internal void LifeStartup(IEntityManager entManager)
-        {
-            DebugTools.Assert(LifeStage == ComponentLifeStage.Initialized);
-
-            LifeStage = ComponentLifeStage.Starting;
-            entManager.EventBus.RaiseComponentEvent(this, CompStartupInstance);
-            LifeStage = ComponentLifeStage.Running;
-        }
-
-        /// <summary>
-        /// Increases the life stage from <see cref="ComponentLifeStage.Running" /> to <see cref="ComponentLifeStage.Stopped" />,
-        /// calling <see cref="Shutdown" />.
-        /// </summary>
-        /// <remarks>
-        /// Components are allowed to remove themselves in their own Startup function.
-        /// </remarks>
-        internal void LifeShutdown(IEntityManager entManager)
-        {
-            DebugTools.Assert(LifeStage is >= ComponentLifeStage.Initializing and < ComponentLifeStage.Stopping);
-
-            if (LifeStage <= ComponentLifeStage.Initialized)
-            {
-                // Component was never started, no shutdown logic necessary. Simply mark it as stopped.
-                LifeStage = ComponentLifeStage.Stopped;
-                return;
-            }
-
-            LifeStage = ComponentLifeStage.Stopping;
-            entManager.EventBus.RaiseComponentEvent(this, CompShutdownInstance);
-            LifeStage = ComponentLifeStage.Stopped;
-        }
-
-        /// <summary>
-        /// Increases the life stage from <see cref="ComponentLifeStage.Stopped" /> to <see cref="ComponentLifeStage.Deleted" />,
-        /// calling <see cref="OnRemove" />.
-        /// </summary>
-        internal void LifeRemoveFromEntity(IEntityManager entManager)
-        {
-            // can be called at any time after PreAdd, including inside other life stage events.
-            DebugTools.Assert(LifeStage != ComponentLifeStage.PreAdd);
-
-            LifeStage = ComponentLifeStage.Removing;
-            entManager.EventBus.RaiseComponentEvent(this, CompRemoveInstance);
-
-            OnRemove();
-
-#if DEBUG
-            if (LifeStage != ComponentLifeStage.Deleted)
-            {
-                DebugTools.Assert($"Component {this.GetType().Name} did not call base {nameof(OnRemove)} in derived method.");
-            }
-#endif
-        }
-
         /// <inheritdoc />
         [ViewVariables]
         public bool Initialized => LifeStage >= ComponentLifeStage.Initializing;
@@ -152,24 +62,18 @@ namespace Robust.Shared.GameObjects
 
         /// <inheritdoc />
         [ViewVariables]
-        public GameTick CreationTick { get; private set; }
+        public GameTick CreationTick { get; internal set; }
 
         /// <inheritdoc />
         [ViewVariables]
         public GameTick LastModifiedTick { get; internal set; }
 
-        private static readonly ComponentAdd CompAddInstance = new();
-        private static readonly ComponentInit CompInitInstance = new();
-        private static readonly ComponentStartup CompStartupInstance = new();
-        private static readonly ComponentShutdown CompShutdownInstance = new();
-        private static readonly ComponentRemove CompRemoveInstance = new();
-
         /// <summary>
         /// Called when the component is removed from an entity.
         /// Shuts down the component.
         /// The component has already been marked as deleted in the component manager.
         /// </summary>
-        protected virtual void OnRemove()
+        protected internal virtual void OnRemove()
         {
             LifeStage = ComponentLifeStage.Deleted;
         }

Robust.Shared/GameObjects/ComponentExt.cs

@@ -1,75 +0,0 @@
-using System;
-using System.Collections.Generic;
-using JetBrains.Annotations;
-using Robust.Shared.IoC;
-using Robust.Shared.Log;
-
-namespace Robust.Shared.GameObjects
-{
-    [PublicAPI]
-    public static class ComponentExt
-    {
-        /// <summary>
-        ///     Convenience wrapper to implement "create component if it does not already exist".
-        ///     Always gives you back a component, and creates it if it does not exist yet.
-        /// </summary>
-        /// <param name="entity">The entity to fetch or create the component on.</param>
-        /// <typeparam name="T">The type of the component to fetch or create.</typeparam>
-        /// <returns>The existing component, or the new component if none existed yet.</returns>
-        [Obsolete]
-        public static T EnsureComponent<T>(this EntityUid entity) where T : Component, new()
-        {
-            var entMan = IoCManager.Resolve<IEntityManager>();
-            if (entMan.TryGetComponent(entity, out T? component))
-            {
-                return component;
-            }
-
-            return entMan.AddComponent<T>(entity);
-        }
-
-        /// <summary>
-        ///     Convenience wrapper to implement "create component if it does not already exist".
-        ///     Always gives you back a component, and creates it if it does not exist yet.
-        /// </summary>
-        /// <param name="entity">The entity to fetch or create the component on.</param>
-        /// <typeparam name="T">The type of the component to fetch or create.</typeparam>
-        /// <param name="warning">
-        ///     The custom warning message to log if the component did not exist already.
-        ///     Defaults to a predetermined warning if null.
-        /// </param>
-        /// <returns>The existing component, or the new component if none existed yet.</returns>
-        [Obsolete]
-        public static T EnsureComponentWarn<T>(this EntityUid entity, string? warning = null) where T : Component, new()
-        {
-            var entMan = IoCManager.Resolve<IEntityManager>();
-            if (entMan.TryGetComponent(entity, out T? component))
-            {
-                return component;
-            }
-
-            warning ??= $"Entity {entity} at {entMan.GetComponent<TransformComponent>(entity).MapPosition} did not have a {typeof(T)}";
-
-            Logger.Warning(warning);
-
-            return entMan.AddComponent<T>(entity);
-        }
-
-        [Obsolete]
-        public static IComponent SetAndDirtyIfChanged<TValue>(
-            this IComponent comp,
-            ref TValue backingField,
-            TValue value)
-        {
-            if (EqualityComparer<TValue>.Default.Equals(backingField, value))
-            {
-                return comp;
-            }
-
-            backingField = value;
-            comp.Dirty();
-
-            return comp;
-        }
-    }
-}

Robust.Shared/GameObjects/Components/MetaDataComponent.cs

@@ -189,15 +189,8 @@ namespace Robust.Shared.GameObjects
         /// <remarks>
         ///     Every entity will always have the first bit set to true.
         /// </remarks>
-        [Access(typeof(MetaDataSystem))]
-        public int VisibilityMask = 1;
-
-        [UsedImplicitly, ViewVariables(VVAccess.ReadWrite)]
-        private int VVVisibilityMask
-        {
-            get => VisibilityMask;
-            set => IoCManager.Resolve<IEntitySystemManager>().GetEntitySystem<MetaDataSystem>().SetVisibilityMask(Owner, value, this);
-        }
+        [ViewVariables] // TODO ACCESS RRestrict writing to server-side visibility system
+        public int VisibilityMask { get; internal set; }= 1;
 
         [ViewVariables]
         public bool EntityPaused => PauseTime != null;

Robust.Shared/GameObjects/Components/Transform/TransformComponent.cs

@@ -85,8 +85,9 @@ namespace Robust.Shared.GameObjects
         [ViewVariables]
         public Angle PrevRotation { get; internal set; }
 
-        [ViewVariables(VVAccess.ReadWrite)]
-        internal bool ActivelyLerping { get; set; }
+        [ViewVariables] public bool ActivelyLerping;
+
+        [ViewVariables] public GameTick LastLerp = GameTick.Zero;
 
         [ViewVariables] internal readonly HashSet<EntityUid> _children = new();
 
@@ -397,7 +398,8 @@ namespace Robust.Shared.GameObjects
 
         [ViewVariables] public int ChildCount => _children.Count;
 
-        [ViewVariables] internal EntityUid LerpParent { get; set; }
+        [ViewVariables] public EntityUid LerpParent;
+        public bool PredictedLerp;
 
         /// <summary>
         /// Detaches this entity from its parent.

Robust.Shared/GameObjects/EntityManager.Components.cs

@@ -4,6 +4,7 @@ using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using JetBrains.Annotations;
 using Robust.Shared.GameStates;
 using Robust.Shared.Log;
@@ -121,7 +122,7 @@ namespace Robust.Shared.GameObjects
             foreach (var comp in comps)
             {
                 if (comp is { LifeStage:  ComponentLifeStage.Added })
-                    comp.LifeInitialize(this, CompIdx.Index(comp.GetType()));
+                    LifeInitialize(comp, CompIdx.Index(comp.GetType()));
             }
 
 #if DEBUG
@@ -154,20 +155,20 @@ namespace Robust.Shared.GameObjects
             // Init transform first, we always have it.
             var transform = GetComponent<TransformComponent>(uid);
             if (transform.LifeStage == ComponentLifeStage.Initialized)
-                transform.LifeStartup(this);
+                LifeStartup(transform);
 
             // Init physics second if it exists.
             if (TryGetComponent<PhysicsComponent>(uid, out var phys)
                 && phys.LifeStage == ComponentLifeStage.Initialized)
             {
-                phys.LifeStartup(this);
+                LifeStartup(phys);
             }
 
             // Do rest of components.
             foreach (var comp in comps)
             {
                 if (comp is { LifeStage: ComponentLifeStage.Initialized })
-                    comp.LifeStartup(this);
+                    LifeStartup(comp);
             }
         }
 
@@ -215,10 +216,10 @@ namespace Robust.Shared.GameObjects
                     return;
 
                 if (!Comp.Initialized)
-                    Comp.LifeInitialize(_entMan, CompType);
+                    ((EntityManager) _entMan).LifeInitialize(Comp, CompType);
 
                 if (metadata.EntityInitialized && !Comp.Running)
-                    Comp.LifeStartup(_entMan);
+                    ((EntityManager) _entMan).LifeStartup(Comp);
             }
 
             public static implicit operator T(CompInitializeHandle<T> handle)
@@ -228,6 +229,7 @@ namespace Robust.Shared.GameObjects
         }
 
         /// <inheritdoc />
+        [Obsolete]
         public CompInitializeHandle<T> AddComponentUninitialized<T>(EntityUid uid) where T : Component, new()
         {
             var reg = _componentFactory.GetRegistration<T>();
@@ -285,17 +287,29 @@ namespace Robust.Shared.GameObjects
             var dict = _entTraitArray[type.Value];
             DebugTools.Assert(dict != null);
 
-            if (dict.TryGetValue(uid, out var duplicate))
+            // Code block to restrict access to ref comp.
             {
-                if (!overwrite && !duplicate.Deleted)
-                    throw new InvalidOperationException(
-                        $"Component reference type {component.GetType().Name} already occupied by {duplicate}");
+                ref var comp = ref CollectionsMarshal.GetValueRefOrAddDefault(dict, uid, out var exists);
+                if (exists)
+                {
+                    if (!overwrite && !comp!.Deleted)
+                    {
+                        throw new InvalidOperationException(
+                            $"Component reference type {reg.Name} already occupied by {comp}");
+                    }
 
-                RemoveComponentImmediate(duplicate, uid, false, metadata);
+                    // This will invalidate the comp ref as it removes the key from the dictionary.
+                    // This is inefficient, but component overriding rarely ever happens.
+                    RemoveComponentImmediate(comp!, uid, false, metadata);
+                    dict.Add(uid, component);
+                }
+                else
+                {
+                    comp = component;
+                }
             }
 
             // actually ADD the component
-            dict.Add(uid, component);
             _entCompIndex.Add(uid, component);
 
             // add the component to the netId grid
@@ -315,7 +329,7 @@ namespace Robust.Shared.GameObjects
             ComponentAdded?.Invoke(eventArgs);
             _eventBus.OnComponentAdded(eventArgs);
 
-            component.LifeAddToEntity(this, reg.Idx);
+            LifeAddToEntity(component, reg.Idx);
 
             if (skipInit)
                 return;
@@ -328,10 +342,10 @@ namespace Robust.Shared.GameObjects
             if (component.Networked)
                 DirtyEntity(uid, metadata);
 
-            component.LifeInitialize(this, reg.Idx);
+            LifeInitialize(component, reg.Idx);
 
             if (metadata.EntityInitialized)
-                component.LifeStartup(this);
+                LifeStartup(component);
 
             if (metadata.EntityLifeStage >= EntityLifeStage.MapInitialized)
                 EventBus.RaiseComponentEvent(component, MapInitEventInstance);
@@ -502,7 +516,7 @@ namespace Robust.Shared.GameObjects
             }
 
             if (component.LifeStage >= ComponentLifeStage.Initialized && component.LifeStage <= ComponentLifeStage.Running)
-                component.LifeShutdown(this);
+                LifeShutdown(component);
 #if EXCEPTION_TOLERANCE
             }
             catch (Exception e)
@@ -534,10 +548,10 @@ namespace Robust.Shared.GameObjects
             }
 
             if (component.Running)
-                component.LifeShutdown(this);
+                LifeShutdown(component);
 
             if (component.LifeStage != ComponentLifeStage.PreAdd)
-                component.LifeRemoveFromEntity(this); // Sets delete
+                LifeRemoveFromEntity(component); // Sets delete
 
 #if EXCEPTION_TOLERANCE
             }
@@ -568,11 +582,11 @@ namespace Robust.Shared.GameObjects
                 {
                     // TODO add options to cancel deferred deletion?
                     _sawmill.Warning($"Found a running component while culling deferred deletions, owner={ToPrettyString(uid)}, type={component.GetType()}");
-                    component.LifeShutdown(this);
+                    LifeShutdown(component);
                 }
 
                 if (component.LifeStage != ComponentLifeStage.PreAdd)
-                    component.LifeRemoveFromEntity(this);
+                    LifeRemoveFromEntity(component);
 
 #if EXCEPTION_TOLERANCE
             }

Robust.Shared/GameObjects/EntityManager.LifeCycle.cs

@@ -0,0 +1,99 @@
+using Robust.Shared.Utility;
+
+namespace Robust.Shared.GameObjects;
+
+public partial class EntityManager
+{
+    private static readonly ComponentAdd CompAddInstance = new();
+    private static readonly ComponentInit CompInitInstance = new();
+    private static readonly ComponentStartup CompStartupInstance = new();
+    private static readonly ComponentShutdown CompShutdownInstance = new();
+    private static readonly ComponentRemove CompRemoveInstance = new();
+
+    /// <summary>
+    /// Increases the life stage from <see cref="ComponentLifeStage.PreAdd" /> to <see cref="ComponentLifeStage.Added" />,
+    /// after raising a <see cref="ComponentAdd"/> event.
+    /// </summary>
+    internal void LifeAddToEntity(Component component, CompIdx type)
+    {
+        DebugTools.Assert(component.LifeStage == ComponentLifeStage.PreAdd);
+
+        component.LifeStage = ComponentLifeStage.Adding;
+        component.CreationTick = CurrentTick;
+        // networked components are assumed to be dirty when added to entities. See also: ClearTicks()
+        component.LastModifiedTick = CurrentTick;
+        EventBus.RaiseComponentEvent(component, type, CompAddInstance);
+        component.LifeStage = ComponentLifeStage.Added;
+    }
+
+    /// <summary>
+    /// Increases the life stage from <see cref="ComponentLifeStage.Added" /> to <see cref="ComponentLifeStage.Initialized" />,
+    /// calling <see cref="Initialize" />.
+    /// </summary>
+    internal void LifeInitialize(Component component, CompIdx type)
+    {
+        DebugTools.Assert(component.LifeStage == ComponentLifeStage.Added);
+
+        component.LifeStage = ComponentLifeStage.Initializing;
+        EventBus.RaiseComponentEvent(component, type, CompInitInstance);
+        component.LifeStage = ComponentLifeStage.Initialized;
+    }
+
+    /// <summary>
+    /// Increases the life stage from <see cref="ComponentLifeStage.Initialized" /> to
+    /// <see cref="ComponentLifeStage.Running" />, calling <see cref="Startup" />.
+    /// </summary>
+    internal void LifeStartup(Component component)
+    {
+        DebugTools.Assert(component.LifeStage == ComponentLifeStage.Initialized);
+
+        component.LifeStage = ComponentLifeStage.Starting;
+        EventBus.RaiseComponentEvent(component, CompStartupInstance);
+        component.LifeStage = ComponentLifeStage.Running;
+    }
+
+    /// <summary>
+    /// Increases the life stage from <see cref="ComponentLifeStage.Running" /> to <see cref="ComponentLifeStage.Stopped" />,
+    /// calling <see cref="Shutdown" />.
+    /// </summary>
+    /// <remarks>
+    /// Components are allowed to remove themselves in their own Startup function.
+    /// </remarks>
+    internal void LifeShutdown(Component component)
+    {
+        DebugTools.Assert(component.LifeStage is >= ComponentLifeStage.Initializing and < ComponentLifeStage.Stopping);
+
+        if (component.LifeStage <= ComponentLifeStage.Initialized)
+        {
+            // Component was never started, no shutdown logic necessary. Simply mark it as stopped.
+            component.LifeStage = ComponentLifeStage.Stopped;
+            return;
+        }
+
+        component.LifeStage = ComponentLifeStage.Stopping;
+        EventBus.RaiseComponentEvent(component, CompShutdownInstance);
+        component.LifeStage = ComponentLifeStage.Stopped;
+    }
+
+    /// <summary>
+    /// Increases the life stage from <see cref="ComponentLifeStage.Stopped" /> to <see cref="ComponentLifeStage.Deleted" />,
+    /// calling <see cref="Component.OnRemove" />.
+    /// </summary>
+    internal void LifeRemoveFromEntity(Component component)
+    {
+        // can be called at any time after PreAdd, including inside other life stage events.
+        DebugTools.Assert(component.LifeStage != ComponentLifeStage.PreAdd);
+
+        component.LifeStage = ComponentLifeStage.Removing;
+        EventBus.RaiseComponentEvent(component, CompRemoveInstance);
+
+        component.OnRemove();
+
+#if DEBUG
+        if (component.LifeStage != ComponentLifeStage.Deleted)
+        {
+            DebugTools.Assert($"Component {component.GetType().Name} did not call base {nameof(component.OnRemove)} in derived method.");
+        }
+#endif
+    }
+}

Robust.Shared/GameObjects/EntityManager.Network.cs

@@ -68,7 +68,7 @@ public partial class EntityManager
             return true;
         }
 
-        entity = EntityUid.Invalid;
+        entity = null;
         return false;
     }
 
@@ -92,7 +92,7 @@ public partial class EntityManager
     {
         if (nEntity == null)
         {
-            entity = EntityUid.Invalid;
+            entity = null;
             return false;
         }
 
@@ -104,7 +104,7 @@ public partial class EntityManager
     {
         if (uid == EntityUid.Invalid)
         {
-            netEntity = NetEntity.Invalid;
+            netEntity = null;
             return false;
         }
 
@@ -125,7 +125,7 @@ public partial class EntityManager
     {
         if (uid == null)
         {
-            netEntity = NetEntity.Invalid;
+            netEntity = null;
             return false;
         }
 

Robust.Shared/GameObjects/EntityManager.cs

@@ -311,19 +311,19 @@ namespace Robust.Shared.GameObjects
 
         public EntityUid CreateEntityUninitialized(string? prototypeName, EntityUid euid, ComponentRegistry? overrides = null)
         {
-            return CreateEntity(prototypeName, overrides);
+            return CreateEntity(prototypeName, out _, overrides);
         }
 
         /// <inheritdoc />
         public virtual EntityUid CreateEntityUninitialized(string? prototypeName, ComponentRegistry? overrides = null)
         {
-            return CreateEntity(prototypeName, overrides);
+            return CreateEntity(prototypeName, out _, overrides);
         }
 
         /// <inheritdoc />
         public virtual EntityUid CreateEntityUninitialized(string? prototypeName, EntityCoordinates coordinates, ComponentRegistry? overrides = null)
         {
-            var newEntity = CreateEntity(prototypeName, overrides);
+            var newEntity = CreateEntity(prototypeName, out _, overrides);
             _xforms.SetCoordinates(newEntity, TransformQuery.GetComponent(newEntity), coordinates, unanchor: false);
             return newEntity;
         }
@@ -331,7 +331,7 @@ namespace Robust.Shared.GameObjects
         /// <inheritdoc />
         public virtual EntityUid CreateEntityUninitialized(string? prototypeName, MapCoordinates coordinates, ComponentRegistry? overrides = null)
         {
-            var newEntity = CreateEntity(prototypeName, overrides);
+            var newEntity = CreateEntity(prototypeName, out _, overrides);
             var transform = TransformQuery.GetComponent(newEntity);
 
             if (coordinates.MapId == MapId.Nullspace)
@@ -398,6 +398,7 @@ namespace Robust.Shared.GameObjects
             if (component.LifeStage >= ComponentLifeStage.Removing || !component.NetSyncEnabled)
                 return;
 
+            DebugTools.AssertOwner(uid, component);
             DirtyEntity(uid, meta);
             component.LastModifiedTick = CurrentTick;
         }
@@ -435,8 +436,13 @@ namespace Robust.Shared.GameObjects
             // Notify all entities they are being terminated prior to detaching & deleting
             RecursiveFlagEntityTermination(e, meta);
 
+            var xform = TransformQuery.GetComponent(e);
+            TransformComponent? parentXform = null;
+            if (xform.ParentUid.IsValid())
+                TransformQuery.Resolve(xform.ParentUid, ref parentXform);
+
             // Then actually delete them
-            RecursiveDeleteEntity(e, meta);
+            RecursiveDeleteEntity(e, meta, xform, parentXform);
         }
 
         private void RecursiveFlagEntityTermination(
@@ -471,11 +477,14 @@ namespace Robust.Shared.GameObjects
 
         private void RecursiveDeleteEntity(
             EntityUid uid,
-            MetaDataComponent metadata)
+            MetaDataComponent metadata,
+            TransformComponent transform,
+            TransformComponent? parentXform)
         {
+            DebugTools.Assert(transform.ParentUid.IsValid() == (parentXform != null));
+            DebugTools.Assert(parentXform == null || parentXform.ChildEntities.Contains(uid));
+
             // Note about this method: #if EXCEPTION_TOLERANCE is not used here because we're gonna it in the future...
-            var netEntity = GetNetEntity(uid, metadata);
-            var transform = TransformQuery.GetComponent(uid);
 
             // Detach the base entity to null before iterating over children
             // This also ensures that the entity-lookup updates don't have to be re-run for every child (which recurses up the transform hierarchy).
@@ -483,7 +492,7 @@ namespace Robust.Shared.GameObjects
             {
                 try
                 {
-                    _xforms.DetachParentToNull(uid, transform);
+                    _xforms.DetachParentToNull(uid, transform, parentXform);
                 }
                 catch (Exception e)
                 {
@@ -495,7 +504,10 @@ namespace Robust.Shared.GameObjects
             {
                 try
                 {
-                    RecursiveDeleteEntity(child, MetaQuery.GetComponent(child));
+                    var childMeta = MetaQuery.GetComponent(child);
+                    var childXform = TransformQuery.GetComponent(child);
+                    DebugTools.AssertEqual(childXform.ParentUid, uid);
+                    RecursiveDeleteEntity(child, childMeta, childXform, transform);
                 }
                 catch(Exception e)
                 {
@@ -513,7 +525,7 @@ namespace Robust.Shared.GameObjects
                 {
                     try
                     {
-                        component.LifeShutdown(this);
+                        LifeShutdown(component);
                     }
                     catch (Exception e)
                     {
@@ -538,7 +550,7 @@ namespace Robust.Shared.GameObjects
             _eventBus.OnEntityDeleted(uid);
             Entities.Remove(uid);
             // Need to get the ID above before MetadataComponent shutdown but only remove it after everything else is done.
-            NetEntityLookup.Remove(netEntity);
+            NetEntityLookup.Remove(metadata.NetEntity);
         }
 
         public virtual void QueueDeleteEntity(EntityUid? uid)
@@ -656,23 +668,23 @@ namespace Robust.Shared.GameObjects
         /// <summary>
         ///     Allocates an entity and loads components but does not do initialization.
         /// </summary>
-        private protected virtual EntityUid CreateEntity(string? prototypeName, IEntityLoadContext? context = null)
+        private protected virtual EntityUid CreateEntity(string? prototypeName, out MetaDataComponent metadata, IEntityLoadContext? context = null)
         {
             if (prototypeName == null)
-                return AllocEntity(out _);
+                return AllocEntity(out metadata);
 
             if (!PrototypeManager.TryIndex<EntityPrototype>(prototypeName, out var prototype))
                 throw new EntityCreationException($"Attempted to spawn an entity with an invalid prototype: {prototypeName}");
 
-            return CreateEntity(prototype, context);
+            return CreateEntity(prototype, out metadata, context);
         }
 
         /// <summary>
         ///     Allocates an entity and loads components but does not do initialization.
         /// </summary>
-        private protected EntityUid CreateEntity(EntityPrototype prototype, IEntityLoadContext? context = null)
+        private protected EntityUid CreateEntity(EntityPrototype prototype, out MetaDataComponent metadata, IEntityLoadContext? context = null)
         {
-            var entity = AllocEntity(prototype, out var metadata);
+            var entity = AllocEntity(prototype, out metadata);
             try
             {
                 EntityPrototype.LoadEntity(metadata.EntityPrototype, entity, ComponentFactory, this, _serManager, context);
@@ -740,36 +752,34 @@ namespace Robust.Shared.GameObjects
 
         /// <inheritdoc />
         [return: NotNullIfNotNull("uid")]
-        public virtual EntityStringRepresentation? ToPrettyString(EntityUid? uid)
+        public EntityStringRepresentation? ToPrettyString(EntityUid? uid, MetaDataComponent? metadata = null)
         {
-            // We want to retrieve the MetaData component even if it is deleted.
-            if (uid == null)
-                return null;
+            return uid == null ? null : ToPrettyString(uid.Value, metadata);
+        }
 
-            if (!_entTraitArray[CompIdx.ArrayIndex<MetaDataComponent>()].TryGetValue(uid.Value, out var component))
-                return new EntityStringRepresentation(uid.Value, true);
+        /// <inheritdoc />
+        public virtual EntityStringRepresentation ToPrettyString(EntityUid uid, MetaDataComponent? metadata = null)
+        {
+            if (!MetaQuery.Resolve(uid, ref metadata, false))
+                return new EntityStringRepresentation(uid, true);
 
-            var metadata = (MetaDataComponent) component;
-
-            return ToPrettyString(uid.Value, metadata);
+            return new EntityStringRepresentation(uid, metadata.EntityDeleted, metadata.EntityName, metadata.EntityPrototype?.ID);
         }
 
         /// <inheritdoc />
         [return: NotNullIfNotNull("netEntity")]
         public EntityStringRepresentation? ToPrettyString(NetEntity? netEntity)
         {
-            return ToPrettyString(GetEntity(netEntity));
+            return netEntity == null ? null : ToPrettyString(netEntity.Value);
         }
 
-        public EntityStringRepresentation ToPrettyString(EntityUid uid)
-            => ToPrettyString((EntityUid?) uid).Value;
-
+        /// <inheritdoc />
         public EntityStringRepresentation ToPrettyString(NetEntity netEntity)
-            => ToPrettyString((NetEntity?) netEntity).Value;
-
-        private EntityStringRepresentation ToPrettyString(EntityUid uid, MetaDataComponent metadata)
         {
-            return new EntityStringRepresentation(uid, metadata.EntityDeleted, metadata.EntityName, metadata.EntityPrototype?.ID);
+            if (!TryGetEntityData(netEntity, out var uid, out var meta))
+                return new EntityStringRepresentation(EntityUid.Invalid, true);
+
+            return ToPrettyString(uid.Value, meta);
         }
 
         #endregion Entity Management

Robust.Shared/GameObjects/EntitySystem.Proxy.cs

@@ -399,9 +399,9 @@ public partial class EntitySystem
     /// <inheritdoc cref="IEntityManager.ToPrettyString"/>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     [return: NotNullIfNotNull("uid")]
-    protected EntityStringRepresentation? ToPrettyString(EntityUid? uid)
+    protected EntityStringRepresentation? ToPrettyString(EntityUid? uid, MetaDataComponent? metadata = null)
     {
-        return EntityManager.ToPrettyString(uid);
+        return EntityManager.ToPrettyString(uid, metadata);
     }
 
     /// <inheritdoc cref="IEntityManager.ToPrettyString"/>
@@ -412,15 +412,20 @@ public partial class EntitySystem
         return EntityManager.ToPrettyString(netEntity);
     }
 
+    /// <inheritdoc cref="IEntityManager.ToPrettyString"/>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected EntityStringRepresentation ToPrettyString(EntityUid uid, MetaDataComponent? metadata)
+        => EntityManager.ToPrettyString(uid, metadata);
+
     /// <inheritdoc cref="IEntityManager.ToPrettyString"/>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     protected EntityStringRepresentation ToPrettyString(EntityUid uid)
-        => ToPrettyString((EntityUid?) uid).Value;
+        => EntityManager.ToPrettyString(uid);
 
     /// <inheritdoc cref="IEntityManager.ToPrettyString"/>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     protected EntityStringRepresentation ToPrettyString(NetEntity netEntity)
-        => ToPrettyString((NetEntity?) netEntity).Value;
+        => EntityManager.ToPrettyString(netEntity);
 
     #endregion
 

Robust.Shared/GameObjects/EntitySystem.Resolve.cs

@@ -27,7 +27,7 @@ namespace Robust.Shared.GameObjects
             var found = EntityManager.TryGetComponent(uid, out component);
 
             if(logMissing && !found)
-                Log.Error($"Can't resolve \"{typeof(TComp)}\" on entity {uid}!\n{new StackTrace(1, true)}");
+                Log.Error($"Can't resolve \"{typeof(TComp)}\" on entity {ToPrettyString(uid)}!\n{new StackTrace(1, true)}");
 
             return found;
         }

Robust.Shared/GameObjects/IEntityManager.Components.cs

@@ -61,6 +61,7 @@ namespace Robust.Shared.GameObjects
         /// <typeparam name="T">Concrete component type to add.</typeparam>
         /// <param name="uid">Entity being modified.</param>
         /// <returns>Component initialization handle. When you are done setting up the component, make sure to dispose this.</returns>
+        [Obsolete]
         EntityManager.CompInitializeHandle<T> AddComponentUninitialized<T>(EntityUid uid) where T : Component, new();
 
         /// <summary>
@@ -221,7 +222,7 @@ namespace Robust.Shared.GameObjects
         /// <param name="uid">Entity to modify.</param>
         /// <param name="component">The output component after being ensured.</param>
         /// <typeparam name="T">Component to add.</typeparam>
-        /// <returns>The component in question</returns>
+        /// <returns>True if the component already existed</returns>
         bool EnsureComponent<T>(EntityUid uid, out T component) where T : Component, new();
 
         /// <summary>

Robust.Shared/GameObjects/IEntityManager.cs

@@ -127,7 +127,7 @@ namespace Robust.Shared.GameObjects
         /// <summary>
         /// Returns a string representation of an entity with various information regarding it.
         /// </summary>
-        EntityStringRepresentation ToPrettyString(EntityUid uid);
+        EntityStringRepresentation ToPrettyString(EntityUid uid, MetaDataComponent? metadata = null);
 
         /// <summary>
         /// Returns a string representation of an entity with various information regarding it.
@@ -138,7 +138,7 @@ namespace Robust.Shared.GameObjects
         /// Returns a string representation of an entity with various information regarding it.
         /// </summary>
         [return: NotNullIfNotNull("uid")]
-        EntityStringRepresentation? ToPrettyString(EntityUid? uid);
+        EntityStringRepresentation? ToPrettyString(EntityUid? uid, MetaDataComponent? metadata = null);
 
         /// <summary>
         /// Returns a string representation of an entity with various information regarding it.

Robust.Shared/GameObjects/Systems/MetaDataSystem.cs

@@ -148,12 +148,6 @@ public abstract class MetaDataSystem : EntitySystem
 
         component.Flags &= ~ev.ToRemove;
     }
-
-    public virtual void SetVisibilityMask(EntityUid uid, int value, MetaDataComponent? meta = null)
-    {
-        if (Resolve(uid, ref meta))
-            meta.VisibilityMask = value;
-    }
 }
 
 /// <summary>

Robust.Shared/GameObjects/Systems/SharedTransformSystem.Component.cs

@@ -149,7 +149,7 @@ public abstract partial class SharedTransformSystem
     /// </summary>
     public bool ContainsEntity(TransformComponent xform, EntityUid entity)
     {
-        return ContainsEntity(xform, entity, _xformQuery);
+        return ContainsEntity(xform, entity, XformQuery);
     }
 
     /// <inheritdoc cref="ContainsEntity(Robust.Shared.GameObjects.TransformComponent,Robust.Shared.GameObjects.EntityUid)"/>
@@ -161,7 +161,7 @@ public abstract partial class SharedTransformSystem
     /// <inheritdoc cref="ContainsEntity(Robust.Shared.GameObjects.TransformComponent,Robust.Shared.GameObjects.EntityUid)"/>
     public bool ContainsEntity(TransformComponent xform, TransformComponent entityTransform)
     {
-        return ContainsEntity(xform, entityTransform, _xformQuery);
+        return ContainsEntity(xform, entityTransform, XformQuery);
     }
 
     /// <inheritdoc cref="ContainsEntity(Robust.Shared.GameObjects.TransformComponent,Robust.Shared.GameObjects.EntityUid)"/>
@@ -222,7 +222,7 @@ public abstract partial class SharedTransformSystem
 
         if (!component._mapIdInitialized)
         {
-            FindMapIdAndSet(uid, component, EntityManager, _xformQuery, _mapManager);
+            FindMapIdAndSet(uid, component, EntityManager, XformQuery, _mapManager);
             component._mapIdInitialized = true;
         }
 
@@ -232,7 +232,7 @@ public abstract partial class SharedTransformSystem
             // Note that _children is a HashSet<EntityUid>,
             // so duplicate additions (which will happen) don't matter.
 
-            var parentXform = _xformQuery.GetComponent(component.ParentUid);
+            var parentXform = XformQuery.GetComponent(component.ParentUid);
             if (parentXform.LifeStage > ComponentLifeStage.Running || LifeStage(component.ParentUid) > EntityLifeStage.MapInitialized)
             {
                 var msg = $"Attempted to re-parent to a terminating object. Entity: {ToPrettyString(component.ParentUid)}, new parent: {ToPrettyString(uid)}";
@@ -298,7 +298,7 @@ public abstract partial class SharedTransformSystem
         if (!xform._parent.IsValid())
             return;
 
-        var parentXform = _xformQuery.GetComponent(xform._parent);
+        var parentXform = XformQuery.GetComponent(xform._parent);
         InitializeGridUid(xform._parent, parentXform);
         xform._gridUid = parentXform._gridUid;
     }
@@ -356,7 +356,7 @@ public abstract partial class SharedTransformSystem
         DebugTools.Assert(!HasComp<MapGridComponent>(uid));
         DebugTools.Assert(gridId == null || HasComp<MapGridComponent>(gridId));
 
-        xformQuery ??= _xformQuery;
+        xformQuery ??= XformQuery;
         SetGridIdRecursive(uid, xform, gridId, xformQuery.Value);
     }
 
@@ -379,27 +379,26 @@ public abstract partial class SharedTransformSystem
 
     #region Local Position
 
-    public void SetLocalPosition(EntityUid uid, Vector2 value, TransformComponent? xform = null)
+    [Obsolete("use override with EntityUid")]
+    public void SetLocalPosition(TransformComponent xform, Vector2 value)
     {
-        if (!Resolve(uid, ref xform)) return;
-        SetLocalPosition(xform, value);
+        SetLocalPosition(xform.Owner, value, xform);
     }
 
-    public virtual void SetLocalPosition(TransformComponent xform, Vector2 value)
-    {
-#pragma warning disable CS0618
-        xform.LocalPosition = value;
-#pragma warning restore CS0618
-    }
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public virtual void SetLocalPosition(EntityUid uid, Vector2 value, TransformComponent? xform = null)
+        => SetLocalPositionNoLerp(uid, value, xform);
+
+
+    [Obsolete("use override with EntityUid")]
+    public void SetLocalPositionNoLerp(TransformComponent xform, Vector2 value)
+        => SetLocalPositionNoLerp(xform.Owner, value, xform);
 
     public void SetLocalPositionNoLerp(EntityUid uid, Vector2 value, TransformComponent? xform = null)
     {
-        if (!Resolve(uid, ref xform)) return;
-        SetLocalPositionNoLerp(xform, value);
-    }
+        if (!XformQuery.Resolve(uid, ref xform))
+            return;
 
-    public virtual void SetLocalPositionNoLerp(TransformComponent xform, Vector2 value)
-    {
 #pragma warning disable CS0618
         xform.LocalPosition = value;
 #pragma warning restore CS0618
@@ -409,27 +408,24 @@ public abstract partial class SharedTransformSystem
 
     #region Local Rotation
 
-    public void SetLocalRotationNoLerp(EntityUid uid, Angle angle)
+    public void SetLocalRotationNoLerp(EntityUid uid, Angle value, TransformComponent? xform = null)
     {
-        SetLocalRotationNoLerp(_xformQuery.GetComponent(uid), angle);
-    }
+        if (!XformQuery.Resolve(uid, ref xform))
+            return;
 
-    public virtual void SetLocalRotationNoLerp(TransformComponent xform, Angle angle)
-    {
-        xform.LocalRotation = angle;
-    }
-
-    public void SetLocalRotation(EntityUid uid, Angle value, TransformComponent? xform = null)
-    {
-        if (!Resolve(uid, ref xform)) return;
-        SetLocalRotation(xform, value);
-    }
-
-    public virtual void SetLocalRotation(TransformComponent xform, Angle value)
-    {
         xform.LocalRotation = value;
     }
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public virtual void SetLocalRotation(EntityUid uid, Angle value, TransformComponent? xform = null)
+        => SetLocalRotationNoLerp(uid, value, xform);
+
+    [Obsolete("use override with EntityUid")]
+    public void SetLocalRotation(TransformComponent xform, Angle value)
+    {
+        SetLocalRotation(xform.Owner, value, xform);
+    }
+
     #endregion
 
     #region Coordinates
@@ -487,7 +483,7 @@ public abstract partial class SharedTransformSystem
 
             if (value.EntityId.IsValid())
             {
-                if (!_xformQuery.Resolve(value.EntityId, ref newParent, false))
+                if (!XformQuery.Resolve(value.EntityId, ref newParent, false))
                 {
                     DetachParentToNull(uid, xform);
                     if (_netMan.IsServer || IsClientSide(uid))
@@ -525,13 +521,13 @@ public abstract partial class SharedTransformSystem
                         }
 
                         recursiveUid = recursiveXform.ParentUid;
-                        recursiveXform = _xformQuery.GetComponent(recursiveUid);
+                        recursiveXform = XformQuery.GetComponent(recursiveUid);
                     }
                 }
             }
 
             if (xform._parent.IsValid())
-                _xformQuery.Resolve(xform._parent, ref oldParent);
+                XformQuery.Resolve(xform._parent, ref oldParent);
 
             oldParent?._children.Remove(uid);
             newParent?._children.Add(uid);
@@ -541,7 +537,7 @@ public abstract partial class SharedTransformSystem
 
             if (newParent != null)
             {
-                xform.ChangeMapId(newParent.MapID, _xformQuery);
+                xform.ChangeMapId(newParent.MapID, XformQuery);
 
                 if (!xform._gridInitialized)
                     InitializeGridUid(uid, xform);
@@ -554,11 +550,11 @@ public abstract partial class SharedTransformSystem
             }
             else
             {
-                xform.ChangeMapId(MapId.Nullspace, _xformQuery);
+                xform.ChangeMapId(MapId.Nullspace, XformQuery);
                 if (!xform._gridInitialized)
                     InitializeGridUid(uid, xform);
                 else
-                    SetGridId(uid, xform, null, _xformQuery);
+                    SetGridId(uid, xform, null, XformQuery);
             }
 
             if (xform.Initialized)
@@ -593,7 +589,7 @@ public abstract partial class SharedTransformSystem
 
     public void ReparentChildren(EntityUid oldUid, EntityUid uid)
     {
-        ReparentChildren(oldUid, uid, _xformQuery);
+        ReparentChildren(oldUid, uid, XformQuery);
     }
 
     /// <summary>
@@ -620,29 +616,29 @@ public abstract partial class SharedTransformSystem
 
     public TransformComponent? GetParent(EntityUid uid)
     {
-        return GetParent(_xformQuery.GetComponent(uid));
+        return GetParent(XformQuery.GetComponent(uid));
     }
 
     public TransformComponent? GetParent(TransformComponent xform)
     {
         if (!xform.ParentUid.IsValid())
             return null;
-        return _xformQuery.GetComponent(xform.ParentUid);
+        return XformQuery.GetComponent(xform.ParentUid);
     }
 
     public EntityUid GetParentUid(EntityUid uid)
     {
-        return _xformQuery.GetComponent(uid).ParentUid;
+        return XformQuery.GetComponent(uid).ParentUid;
     }
 
     public void SetParent(EntityUid uid, EntityUid parent)
     {
-        SetParent(uid, _xformQuery.GetComponent(uid), parent, _xformQuery);
+        SetParent(uid, XformQuery.GetComponent(uid), parent, XformQuery);
     }
 
     public void SetParent(EntityUid uid, TransformComponent xform, EntityUid parent, TransformComponent? parentXform = null)
     {
-        SetParent(uid, xform, parent, _xformQuery, parentXform);
+        SetParent(uid, xform, parent, XformQuery, parentXform);
     }
 
     public void SetParent(EntityUid uid, TransformComponent xform, EntityUid parent, EntityQuery<TransformComponent> xformQuery, TransformComponent? parentXform = null)
@@ -671,9 +667,7 @@ public abstract partial class SharedTransformSystem
     #endregion
 
     #region States
-    public virtual void ActivateLerp(TransformComponent xform) { }
-
-    public virtual void DeactivateLerp(TransformComponent xform) { }
+    public virtual void ActivateLerp(EntityUid uid, TransformComponent xform) { }
 
     internal void OnGetState(EntityUid uid, TransformComponent component, ref ComponentGetState args)
     {
@@ -745,24 +739,18 @@ public abstract partial class SharedTransformSystem
                 RaiseLocalEvent(uid, ref ev, true);
             }
 
-            xform.PrevPosition = newState.LocalPosition;
-            xform.PrevRotation = newState.Rotation;
             xform._noLocalRotation = newState.NoLocalRotation;
 
             DebugTools.Assert(xform.ParentUid == parent, "Transform state failed to set parent");
             DebugTools.Assert(xform.Anchored == newState.Anchored, "Transform state failed to set anchored");
         }
 
-        if (args.Next is TransformComponentState nextTransform)
+        if (args.Next is TransformComponentState nextTransform
+            && nextTransform.ParentID == GetNetEntity(xform.ParentUid))
         {
             xform.NextPosition = nextTransform.LocalPosition;
             xform.NextRotation = nextTransform.Rotation;
-            xform.LerpParent = GetEntity(nextTransform.ParentID);
-            ActivateLerp(xform);
-        }
-        else
-        {
-            DeactivateLerp(xform);
+            ActivateLerp(uid, xform);
         }
     }
 
@@ -773,7 +761,7 @@ public abstract partial class SharedTransformSystem
     [Pure]
     public Matrix3 GetWorldMatrix(EntityUid uid)
     {
-        return GetWorldMatrix(_xformQuery.GetComponent(uid), _xformQuery);
+        return GetWorldMatrix(XformQuery.GetComponent(uid), XformQuery);
     }
 
     // Temporary until it's moved here
@@ -781,7 +769,7 @@ public abstract partial class SharedTransformSystem
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public Matrix3 GetWorldMatrix(TransformComponent component)
     {
-        return GetWorldMatrix(component, _xformQuery);
+        return GetWorldMatrix(component, XformQuery);
     }
 
     [Pure]
@@ -807,7 +795,7 @@ public abstract partial class SharedTransformSystem
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public Vector2 GetWorldPosition(EntityUid uid)
     {
-        return GetWorldPosition(_xformQuery.GetComponent(uid));
+        return GetWorldPosition(XformQuery.GetComponent(uid));
     }
 
     // Temporary until it's moved here
@@ -819,7 +807,7 @@ public abstract partial class SharedTransformSystem
 
         while (component.ParentUid != component.MapUid && component.ParentUid.IsValid())
         {
-            component = _xformQuery.GetComponent(component.ParentUid);
+            component = XformQuery.GetComponent(component.ParentUid);
             pos = component._localRotation.RotateVec(pos) + component._localPosition;
         }
 
@@ -842,7 +830,7 @@ public abstract partial class SharedTransformSystem
     [Pure]
     public (Vector2 WorldPosition, Angle WorldRotation) GetWorldPositionRotation(EntityUid uid)
     {
-        return GetWorldPositionRotation(_xformQuery.GetComponent(uid));
+        return GetWorldPositionRotation(XformQuery.GetComponent(uid));
     }
 
     [Pure]
@@ -853,7 +841,7 @@ public abstract partial class SharedTransformSystem
 
         while (component.ParentUid != component.MapUid && component.ParentUid.IsValid())
         {
-            component = _xformQuery.GetComponent(component.ParentUid);
+            component = XformQuery.GetComponent(component.ParentUid);
             pos = component._localRotation.RotateVec(pos) + component._localPosition;
             angle += component._localRotation;
         }
@@ -947,7 +935,7 @@ public abstract partial class SharedTransformSystem
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public void SetWorldPosition(TransformComponent component, Vector2 worldPos)
     {
-        SetWorldPosition(component, worldPos, _xformQuery);
+        SetWorldPosition(component, worldPos, XformQuery);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -973,7 +961,7 @@ public abstract partial class SharedTransformSystem
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public Angle GetWorldRotation(EntityUid uid)
     {
-        return GetWorldRotation(_xformQuery.GetComponent(uid), _xformQuery);
+        return GetWorldRotation(XformQuery.GetComponent(uid), XformQuery);
     }
 
     // Temporary until it's moved here
@@ -981,7 +969,7 @@ public abstract partial class SharedTransformSystem
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public Angle GetWorldRotation(TransformComponent component)
     {
-        return GetWorldRotation(component, _xformQuery);
+        return GetWorldRotation(component, XformQuery);
     }
 
     [Pure]
@@ -1040,43 +1028,47 @@ public abstract partial class SharedTransformSystem
     #region Set Position+Rotation
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public void SetWorldPositionRotation(EntityUid uid, Vector2 worldPos, Angle worldRot, EntityQuery<TransformComponent> xformQuery)
-    {
-        var component = xformQuery.GetComponent(uid);
-        SetWorldPositionRotation(component, worldPos, worldRot, xformQuery);
-    }
-
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    [Obsolete("Use override with EntityUid")]
     public void SetWorldPositionRotation(TransformComponent component, Vector2 worldPos, Angle worldRot)
     {
-        SetWorldPositionRotation(component, worldPos, worldRot, _xformQuery);
+        SetWorldPositionRotation(component.Owner, worldPos, worldRot, component);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public void SetWorldPositionRotation(TransformComponent component, Vector2 worldPos, Angle worldRot, EntityQuery<TransformComponent> xformQuery)
+    public void SetWorldPositionRotation(EntityUid uid, Vector2 worldPos, Angle worldRot, TransformComponent? component = null)
     {
+        if (!XformQuery.Resolve(uid, ref component))
+            return;
+
         if (!component._parent.IsValid())
         {
             DebugTools.Assert("Parent is invalid while attempting to set WorldPosition - did you try to move root node?");
             return;
         }
 
-        var (curWorldPos, curWorldRot) = GetWorldPositionRotation(component, xformQuery);
+        var (curWorldPos, curWorldRot) = GetWorldPositionRotation(component);
 
         var negativeParentWorldRot = component.LocalRotation - curWorldRot;
 
         var newLocalPos = component.LocalPosition + negativeParentWorldRot.RotateVec(worldPos - curWorldPos);
         var newLocalRot = component.LocalRotation + worldRot - curWorldRot;
 
-        SetLocalPositionRotation(component, newLocalPos, newLocalRot);
+        SetLocalPositionRotation(uid, newLocalPos, newLocalRot, component);
     }
 
+    [Obsolete("Use override with EntityUid")]
+    public void SetLocalPositionRotation(TransformComponent xform, Vector2 pos, Angle rot)
+        => SetLocalPositionRotation(xform.Owner, pos, rot, xform);
+
     /// <summary>
     ///     Simultaneously set the position and rotation. This is better than setting individually, as it reduces the number of move events and matrix rebuilding operations.
     /// </summary>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public virtual void SetLocalPositionRotation(TransformComponent xform, Vector2 pos, Angle rot)
+    public virtual void SetLocalPositionRotation(EntityUid uid, Vector2 pos, Angle rot, TransformComponent? xform = null)
     {
+        if (!XformQuery.Resolve(uid, ref xform))
+            return;
+
         if (!xform._parent.IsValid())
         {
             DebugTools.Assert("Parent is invalid while attempting to set WorldPosition - did you try to move root node?");
@@ -1097,14 +1089,14 @@ public abstract partial class SharedTransformSystem
 
         DebugTools.Assert(!xform.NoLocalRotation || xform.LocalRotation == 0);
 
-        Dirty(xform.Owner, xform);
+        Dirty(uid, xform);
         xform.MatricesDirty = true;
 
         if (!xform.Initialized)
             return;
 
-        var moveEvent = new MoveEvent(xform.Owner, oldPosition, xform.Coordinates, oldRotation, rot, xform, _gameTiming.ApplyingState);
-        RaiseLocalEvent(xform.Owner, ref moveEvent, true);
+        var moveEvent = new MoveEvent(uid, oldPosition, xform.Coordinates, oldRotation, rot, xform, _gameTiming.ApplyingState);
+        RaiseLocalEvent(uid, ref moveEvent, true);
     }
 
     #endregion
@@ -1114,14 +1106,14 @@ public abstract partial class SharedTransformSystem
     [Pure]
     public Matrix3 GetInvWorldMatrix(EntityUid uid)
     {
-        return GetInvWorldMatrix(_xformQuery.GetComponent(uid), _xformQuery);
+        return GetInvWorldMatrix(XformQuery.GetComponent(uid), XformQuery);
     }
 
     [Pure]
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public Matrix3 GetInvWorldMatrix(TransformComponent component)
     {
-        return GetInvWorldMatrix(component, _xformQuery);
+        return GetInvWorldMatrix(component, XformQuery);
     }
 
     [Pure]
@@ -1146,14 +1138,14 @@ public abstract partial class SharedTransformSystem
     public (Vector2 WorldPosition, Angle WorldRotation, Matrix3 WorldMatrix)
         GetWorldPositionRotationMatrix(EntityUid uid)
     {
-        return GetWorldPositionRotationMatrix(_xformQuery.GetComponent(uid), _xformQuery);
+        return GetWorldPositionRotationMatrix(XformQuery.GetComponent(uid), XformQuery);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public (Vector2 WorldPosition, Angle WorldRotation, Matrix3 WorldMatrix)
         GetWorldPositionRotationMatrix(TransformComponent xform)
     {
-        return GetWorldPositionRotationMatrix(xform, _xformQuery);
+        return GetWorldPositionRotationMatrix(xform, XformQuery);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -1177,13 +1169,13 @@ public abstract partial class SharedTransformSystem
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public (Vector2 WorldPosition, Angle WorldRotation, Matrix3 InvWorldMatrix) GetWorldPositionRotationInvMatrix(EntityUid uid)
     {
-        return GetWorldPositionRotationInvMatrix(_xformQuery.GetComponent(uid));
+        return GetWorldPositionRotationInvMatrix(XformQuery.GetComponent(uid));
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public (Vector2 WorldPosition, Angle WorldRotation, Matrix3 InvWorldMatrix) GetWorldPositionRotationInvMatrix(TransformComponent xform)
     {
-        return GetWorldPositionRotationInvMatrix(xform, _xformQuery);
+        return GetWorldPositionRotationInvMatrix(xform, XformQuery);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -1207,14 +1199,14 @@ public abstract partial class SharedTransformSystem
     public (Vector2 WorldPosition, Angle WorldRotation, Matrix3 WorldMatrix, Matrix3 InvWorldMatrix)
         GetWorldPositionRotationMatrixWithInv(EntityUid uid)
     {
-        return GetWorldPositionRotationMatrixWithInv(_xformQuery.GetComponent(uid), _xformQuery);
+        return GetWorldPositionRotationMatrixWithInv(XformQuery.GetComponent(uid), XformQuery);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public (Vector2 WorldPosition, Angle WorldRotation, Matrix3 WorldMatrix, Matrix3 InvWorldMatrix)
         GetWorldPositionRotationMatrixWithInv(TransformComponent xform)
     {
-        return GetWorldPositionRotationMatrixWithInv(xform, _xformQuery);
+        return GetWorldPositionRotationMatrixWithInv(xform, XformQuery);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -1237,8 +1229,8 @@ public abstract partial class SharedTransformSystem
     #region AttachToGridOrMap
     public void AttachToGridOrMap(EntityUid uid, TransformComponent? xform = null)
     {
-        if (_xformQuery.Resolve(uid, ref xform))
-            AttachToGridOrMap(uid, xform, _xformQuery);
+        if (XformQuery.Resolve(uid, ref xform))
+            AttachToGridOrMap(uid, xform, XformQuery);
     }
 
     public void AttachToGridOrMap(EntityUid uid, TransformComponent xform, EntityQuery<TransformComponent> query)
@@ -1278,15 +1270,15 @@ public abstract partial class SharedTransformSystem
     {
         coordinates = null;
 
-        if (!_xformQuery.Resolve(uid, ref xform))
+        if (!XformQuery.Resolve(uid, ref xform))
             return false;
 
         if (!xform.ParentUid.IsValid())
             return false;
 
         EntityUid newParent;
-        var oldPos = GetWorldPosition(xform, _xformQuery);
-        if (_mapManager.TryFindGridAt(xform.MapID, oldPos, _xformQuery, out var gridUid, out _))
+        var oldPos = GetWorldPosition(xform, XformQuery);
+        if (_mapManager.TryFindGridAt(xform.MapID, oldPos, XformQuery, out var gridUid, out _))
         {
             newParent = gridUid;
         }
@@ -1299,7 +1291,7 @@ public abstract partial class SharedTransformSystem
             return false;
         }
 
-        coordinates = new(newParent, GetInvWorldMatrix(newParent, _xformQuery).Transform(oldPos));
+        coordinates = new(newParent, GetInvWorldMatrix(newParent, XformQuery).Transform(oldPos));
         return true;
     }
     #endregion
@@ -1308,7 +1300,7 @@ public abstract partial class SharedTransformSystem
 
     public void DetachParentToNull(EntityUid uid, TransformComponent xform)
     {
-        _xformQuery.TryGetComponent(xform.ParentUid, out var oldXform);
+        XformQuery.TryGetComponent(xform.ParentUid, out var oldXform);
         DetachParentToNull(uid, xform, oldXform);
     }
 
@@ -1369,7 +1361,7 @@ public abstract partial class SharedTransformSystem
     {
         if (LifeStage(uid) > EntityLifeStage.Initialized)
         {
-            SetGridId(uid, component, uid, _xformQuery);
+            SetGridId(uid, component, uid, XformQuery);
             return;
         }
         component._gridInitialized = true;
@@ -1383,10 +1375,10 @@ public abstract partial class SharedTransformSystem
     public void PlaceNextToOrDrop(EntityUid uid, EntityUid target,
         TransformComponent? xform = null, TransformComponent? targetXform = null)
     {
-        if (!_xformQuery.Resolve(target, ref targetXform))
+        if (!XformQuery.Resolve(target, ref targetXform))
             return;
 
-        if (!_xformQuery.Resolve(uid, ref xform))
+        if (!XformQuery.Resolve(uid, ref xform))
             return;
 
         var meta = _metaQuery.GetComponent(target);

Robust.Shared/GameObjects/Systems/SharedTransformSystem.cs

@@ -26,7 +26,7 @@ namespace Robust.Shared.GameObjects
 
         private EntityQuery<MapGridComponent> _gridQuery;
         private EntityQuery<MetaDataComponent> _metaQuery;
-        private EntityQuery<TransformComponent> _xformQuery;
+        protected EntityQuery<TransformComponent> XformQuery;
 
         private readonly Queue<MoveEvent> _gridMoves = new();
         private readonly Queue<MoveEvent> _otherMoves = new();
@@ -39,7 +39,7 @@ namespace Robust.Shared.GameObjects
 
             _gridQuery = GetEntityQuery<MapGridComponent>();
             _metaQuery = GetEntityQuery<MetaDataComponent>();
-            _xformQuery = GetEntityQuery<TransformComponent>();
+            XformQuery = GetEntityQuery<TransformComponent>();
 
             SubscribeLocalEvent<TileChangedEvent>(MapManagerOnTileChanged);
             SubscribeLocalEvent<TransformComponent, ComponentInit>(OnCompInit);
@@ -85,17 +85,17 @@ namespace Robust.Shared.GameObjects
             if (!TryComp(gridId, out BroadphaseComponent? lookup) || !_mapManager.TryGetGrid(gridId, out var grid))
                 return;
 
-            if (!_xformQuery.TryGetComponent(gridId, out var gridXform))
+            if (!XformQuery.TryGetComponent(gridId, out var gridXform))
                 return;
 
-            if (!_xformQuery.TryGetComponent(gridXform.MapUid, out var mapTransform))
+            if (!XformQuery.TryGetComponent(gridXform.MapUid, out var mapTransform))
                 return;
 
             var aabb = _lookup.GetLocalBounds(tileIndices, grid.TileSize);
 
             foreach (var entity in _lookup.GetEntitiesIntersecting(lookup, aabb, LookupFlags.Uncontained | LookupFlags.Approximate))
             {
-                if (!_xformQuery.TryGetComponent(entity, out var xform) || xform.ParentUid != gridId)
+                if (!XformQuery.TryGetComponent(entity, out var xform) || xform.ParentUid != gridId)
                     continue;
 
                 if (!aabb.Contains(xform.LocalPosition))
@@ -148,7 +148,7 @@ namespace Robust.Shared.GameObjects
 
         public EntityCoordinates GetMoverCoordinates(EntityUid uid)
         {
-            return GetMoverCoordinates(uid, _xformQuery.GetComponent(uid));
+            return GetMoverCoordinates(uid, XformQuery.GetComponent(uid));
         }
 
         public EntityCoordinates GetMoverCoordinates(EntityUid uid, TransformComponent xform)
@@ -168,11 +168,11 @@ namespace Robust.Shared.GameObjects
             DebugTools.Assert(!_mapManager.IsGrid(uid) && !_mapManager.IsMap(uid));
 
             // Not parented to grid so convert their pos back to the grid.
-            var worldPos = GetWorldPosition(xform, _xformQuery);
+            var worldPos = GetWorldPosition(xform, XformQuery);
 
             return xform.GridUid == null
                 ? new EntityCoordinates(xform.MapUid ?? xform.ParentUid, worldPos)
-                : new EntityCoordinates(xform.GridUid.Value, _xformQuery.GetComponent(xform.GridUid.Value).InvLocalMatrix.Transform(worldPos));
+                : new EntityCoordinates(xform.GridUid.Value, XformQuery.GetComponent(xform.GridUid.Value).InvLocalMatrix.Transform(worldPos));
         }
 
         public EntityCoordinates GetMoverCoordinates(EntityCoordinates coordinates, EntityQuery<TransformComponent> xformQuery)
@@ -191,7 +191,7 @@ namespace Robust.Shared.GameObjects
             if (!parentUid.IsValid())
                 return coordinates;
 
-            var parentXform = _xformQuery.GetComponent(parentUid);
+            var parentXform = XformQuery.GetComponent(parentUid);
 
             // GriddUid is only set after init.
             if (!parentXform._gridInitialized)
@@ -209,11 +209,11 @@ namespace Robust.Shared.GameObjects
             DebugTools.Assert(!_mapManager.IsGrid(parentUid) && !_mapManager.IsMap(parentUid));
 
             // Not parented to grid so convert their pos back to the grid.
-            var worldPos = GetWorldMatrix(parentXform, _xformQuery).Transform(coordinates.Position);
+            var worldPos = GetWorldMatrix(parentXform, XformQuery).Transform(coordinates.Position);
 
             return parentXform.GridUid == null
                 ? new EntityCoordinates(mapId ?? parentUid, worldPos)
-                : new EntityCoordinates(parentXform.GridUid.Value, _xformQuery.GetComponent(parentXform.GridUid.Value).InvLocalMatrix.Transform(worldPos));
+                : new EntityCoordinates(parentXform.GridUid.Value, XformQuery.GetComponent(parentXform.GridUid.Value).InvLocalMatrix.Transform(worldPos));
         }
 
         /// <summary>
@@ -231,15 +231,15 @@ namespace Robust.Shared.GameObjects
 
             // Is the entity directly parented to the grid?
             if (xform.GridUid == xform.ParentUid)
-                return (xform.Coordinates, GetWorldRotation(xform, _xformQuery));
+                return (xform.Coordinates, GetWorldRotation(xform, XformQuery));
 
             DebugTools.Assert(!_mapManager.IsGrid(uid) && !_mapManager.IsMap(uid));
 
-            var (pos, worldRot) = GetWorldPositionRotation(xform, _xformQuery);
+            var (pos, worldRot) = GetWorldPositionRotation(xform, XformQuery);
 
             var coords = xform.GridUid == null
                 ? new EntityCoordinates(xform.MapUid ?? xform.ParentUid, pos)
-                : new EntityCoordinates(xform.GridUid.Value, _xformQuery.GetComponent(xform.GridUid.Value).InvLocalMatrix.Transform(pos));
+                : new EntityCoordinates(xform.GridUid.Value, XformQuery.GetComponent(xform.GridUid.Value).InvLocalMatrix.Transform(pos));
 
             return (coords, worldRot);
         }

Robust.Shared/Localization/ILocalizationManager.cs

@@ -2,7 +2,6 @@ using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using JetBrains.Annotations;
-using Robust.Shared.ContentPack;
 using Robust.Shared.Serialization;
 
 namespace Robust.Shared.Localization
@@ -23,7 +22,7 @@ namespace Robust.Shared.Localization
     public interface ILocalizationManager
     {
         /// <summary>
-        ///     Gets a language approrpiate string represented by the supplied messageId.
+        ///     Gets a language appropriate string represented by the supplied messageId.
         /// </summary>
         /// <param name="messageId">Unique Identifier for a translated message.</param>
         /// <returns>
@@ -31,6 +30,13 @@ namespace Robust.Shared.Localization
         /// </returns>
         string GetString(string messageId);
 
+        /// <summary>
+        ///     Checks if the specified id has been registered, without checking its arguments.
+        /// </summary>
+        /// <param name="messageId">Unique Identifier for a translated message.</param>
+        /// <returns>true if it exists, even if it requires any parameters to be passed.</returns>
+        bool HasString(string messageId);
+
         /// <summary>
         ///     Try- version of <see cref="GetString(string)"/>
         /// </summary>
@@ -46,7 +52,7 @@ namespace Robust.Shared.Localization
         string GetString(string messageId, params (string, object)[] args);
 
         /// <summary>
-        ///     Try- version of <see cref="GetString(string, ValueTuple{string, object}[])"/>
+        ///     Try- version of <see cref="GetString(string, (string, object)[])"/>
         /// </summary>
         /// <remarks>
         ///     Does not log a warning if the message does not exist.

Robust.Shared/Localization/LocId.cs

@@ -0,0 +1,43 @@
+using System;
+using Robust.Shared.Serialization;
+using Robust.Shared.Serialization.TypeSerializers.Implementations;
+
+namespace Robust.Shared.Localization;
+
+/// <summary>
+///     Wrapper type for a localization string id.
+/// </summary>
+/// <param name="Id">The id of the localization string.</param>
+/// <remarks>
+///     This will be automatically validated by <see cref="LocIdSerializer"/> if used in data fields.</remarks>
+/// <seealso cref="Loc.GetString(string)"/>
+[Serializable, NetSerializable]
+public readonly record struct LocId(string Id) : IEquatable<string>, IComparable<LocId>
+{
+    public static implicit operator string(LocId locId)
+    {
+        return locId.Id;
+    }
+
+    public static implicit operator LocId(string id)
+    {
+        return new LocId(id);
+    }
+
+    public static implicit operator LocId?(string? id)
+    {
+        return id == null ? default(LocId?) : new LocId(id);
+    }
+
+    public bool Equals(string? other)
+    {
+        return Id == other;
+    }
+
+    public int CompareTo(LocId other)
+    {
+        return string.Compare(Id, other.Id, StringComparison.Ordinal);
+    }
+
+    public override string ToString() => Id ?? String.Empty;
+}

Robust.Shared/Localization/LocalizationManager.cs

@@ -4,7 +4,6 @@ using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
 using System.Linq;
-using JetBrains.Annotations;
 using Linguini.Bundle;
 using Linguini.Bundle.Builder;
 using Linguini.Bundle.Errors;
@@ -55,7 +54,6 @@ namespace Robust.Shared.Localization
             return msg;
         }
 
-
         public string GetString(string messageId, params (string, object)[] args0)
         {
             if (_defaultCulture == null)
@@ -70,6 +68,11 @@ namespace Robust.Shared.Localization
             return msg;
         }
 
+        public bool HasString(string messageId)
+        {
+            return HasMessage(messageId, out _);
+        }
+
         public bool TryGetString(string messageId, [NotNullWhen(true)] out string? value)
         {
             return TryGetString(messageId, out value, null);

Robust.Shared/Map/MapManager.GridCollection.cs

@@ -151,7 +151,9 @@ internal partial class MapManager
         var fallbackParentEuid = GetMapEntityIdOrThrow(currentMapId);
         EntityManager.GetComponent<TransformComponent>(gridEnt).AttachParent(fallbackParentEuid);
 
-        EntityManager.InitializeComponents(gridEnt);
+        var meta = EntityManager.GetComponent<MetaDataComponent>(gridEnt);
+        EntityManager.System<MetaDataSystem>().SetEntityName(gridEnt, $"grid", meta);
+        EntityManager.InitializeComponents(gridEnt, meta);
         EntityManager.StartComponents(gridEnt);
         return grid;
     }

Robust.Shared/Map/MapManager.MapCollection.cs

@@ -236,8 +236,10 @@ internal partial class MapManager
 
                 var mapComp = EntityManager.AddComponent<MapComponent>(newEnt);
                 mapComp.MapId = actualId;
-                EntityManager.Dirty(mapComp);
-                EntityManager.InitializeComponents(newEnt);
+                var meta = EntityManager.GetComponent<MetaDataComponent>(newEnt);
+                EntityManager.System<MetaDataSystem>().SetEntityName(newEnt, $"map {actualId}", meta);
+                EntityManager.Dirty(newEnt, mapComp, meta);
+                EntityManager.InitializeComponents(newEnt, meta);
                 EntityManager.StartComponents(newEnt);
                 _sawmill.Debug($"Binding map {actualId} to entity {newEnt}");
             }

Robust.Shared/Network/Messages/MsgState.cs

@@ -95,8 +95,6 @@ namespace Robust.Shared.Network.Messages
             MsgSize = buffer.LengthBytes;
         }
 
-        public bool ForceSendReliably;
-
         /// <summary>
         ///     Whether this state message is large enough to warrant being sent reliably.
         ///     This is only valid after
@@ -105,7 +103,7 @@ namespace Robust.Shared.Network.Messages
         public bool ShouldSendReliably()
         {
             DebugTools.Assert(_hasWritten, "Attempted to determine sending method before determining packet size.");
-            return ForceSendReliably || MsgSize > ReliableThreshold;
+            return MsgSize > ReliableThreshold;
         }
 
         public override NetDeliveryMethod DeliveryMethod

Robust.Shared/Physics/Dynamics/Contacts/Contact.cs

@@ -365,5 +365,7 @@ namespace Robust.Shared.Physics.Dynamics.Contacts
         /// Is this a special contact for grid-grid collisions
         /// </summary>
         Grid = 1 << 2,
+
+        Deleting = 1 << 3,
     }
 }

Robust.Shared/Physics/Systems/FixtureSystem.cs

@@ -189,8 +189,6 @@ namespace Robust.Shared.Physics.Systems
                 _lookup.DestroyProxies(uid, fixtureId, fixture, xform, broadphase, physicsMap);
             }
 
-
-
             if (updates)
             {
                 var resetMass = fixture.Density > 0f;

Robust.Shared/Physics/Systems/SharedJointSystem.Relay.cs

@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using Robust.Shared.GameObjects;
 using Robust.Shared.GameStates;
 using Robust.Shared.Physics.Components;
-using Robust.Shared.Physics.Dynamics.Joints;
 using Robust.Shared.Serialization;
 using Robust.Shared.Utility;
 
@@ -110,5 +109,29 @@ public abstract partial class SharedJointSystem
         }
 
         Dirty(uid, component);
+
+#if DEBUG
+        if (component.Relay == null)
+            return;
+
+        if (TryComp(uid, out JointComponent? jointComp))
+        {
+            foreach (var joint in jointComp.Joints.Values)
+            {
+                DebugTools.AssertNotEqual(joint.BodyAUid, component.Relay);
+                DebugTools.AssertNotEqual(joint.BodyBUid, component.Relay);
+
+            }
+        }
+
+        if (TryComp(component.Relay, out JointComponent? relayJointComp))
+        {
+            foreach (var joint in relayJointComp.Joints.Values)
+            {
+                DebugTools.AssertNotEqual(joint.BodyAUid, uid);
+                DebugTools.AssertNotEqual(joint.BodyBUid, uid);
+            }
+        }
+#endif
     }
 }

Robust.Shared/Physics/Systems/SharedJointSystem.cs

@@ -140,6 +140,8 @@ public abstract partial class SharedJointSystem : EntitySystem
         jointComponentA ??= EnsureComp<JointComponent>(aUid);
         jointComponentB ??= EnsureComp<JointComponent>(bUid);
         DebugTools.Assert(jointComponentA.Owner == aUid && jointComponentB.Owner == bUid);
+        DebugTools.AssertNotEqual(jointComponentA.Relay, bUid);
+        DebugTools.AssertNotEqual(jointComponentB.Relay, aUid);
 
         var jointsA = jointComponentA.Joints;
         var jointsB = jointComponentB.Joints;
@@ -190,10 +192,10 @@ public abstract partial class SharedJointSystem : EntitySystem
 
         _physics.WakeBody(aUid, body: bodyA);
         _physics.WakeBody(bUid, body: bodyB);
-        Dirty(bodyA);
-        Dirty(bodyB);
-        Dirty(jointComponentA);
-        Dirty(jointComponentB);
+        Dirty(aUid, bodyA);
+        Dirty(bUid, bodyB);
+        Dirty(aUid, jointComponentA);
+        Dirty(bUid, jointComponentB);
 
         // Also flag these for checking juusssttt in case.
         _dirtyJoints.Add(jointComponentA);

Robust.Shared/Physics/Systems/SharedPhysicsSystem.Contacts.cs

@@ -312,12 +312,17 @@ public abstract partial class SharedPhysicsSystem
 
     public void DestroyContact(Contact contact)
     {
+        // Don't recursive update or we're in for a bad time.
+        if ((contact.Flags & ContactFlags.Deleting) != 0x0)
+            return;
+
         Fixture fixtureA = contact.FixtureA!;
         Fixture fixtureB = contact.FixtureB!;
         var bodyA = contact.BodyA!;
         var bodyB = contact.BodyB!;
         var aUid = contact.EntityA;
         var bUid = contact.EntityB;
+        contact.Flags |= ContactFlags.Deleting;
 
         if (contact.IsTouching)
         {

Robust.Shared/Physics/Systems/SharedPhysicsSystem.Island.cs

@@ -423,16 +423,19 @@ public abstract partial class SharedPhysicsSystem
 
                             var uidA = joint.BodyAUid;
                             var uidB = joint.BodyBUid;
+                            DebugTools.AssertNotEqual(uidA, uidB);
 
                             if (jointQuery.TryGetComponent(uidA, out var jointCompA) &&
                                 jointCompA.Relay != null)
                             {
+                                DebugTools.AssertNotEqual(uidB, jointCompA.Relay.Value);
                                 uidA = jointCompA.Relay.Value;
                             }
 
                             if (jointQuery.TryGetComponent(uidB, out var jointCompB) &&
                                 jointCompB.Relay != null)
                             {
+                                DebugTools.AssertNotEqual(uidA, jointCompB.Relay.Value);
                                 uidB = jointCompB.Relay.Value;
                             }
 

Robust.Shared/Prototypes/EntProtoId.cs

@@ -13,7 +13,7 @@ namespace Robust.Shared.Prototypes;
 /// </remarks>
 /// <remarks><seealso cref="ProtoId{T}"/> for a wrapper of other prototype kinds.</remarks>
 [Serializable, NetSerializable]
-public readonly record struct EntProtoId(string Id)
+public readonly record struct EntProtoId(string Id) : IEquatable<string>, IComparable<EntProtoId>
 {
     public static implicit operator string(EntProtoId protoId)
     {
@@ -24,4 +24,21 @@ public readonly record struct EntProtoId(string Id)
     {
         return new EntProtoId(id);
     }
+
+    public static implicit operator EntProtoId?(string? id)
+    {
+        return id == null ? default(EntProtoId?) : new EntProtoId(id);
+    }
+
+    public bool Equals(string? other)
+    {
+        return Id == other;
+    }
+
+    public int CompareTo(EntProtoId other)
+    {
+        return string.Compare(Id, other.Id, StringComparison.Ordinal);
+    }
+
+    public override string ToString() => Id ?? string.Empty;
 }

Robust.Shared/Prototypes/EntityPrototype.cs

@@ -102,7 +102,7 @@ namespace Robust.Shared.Prototypes
         [Obsolete("Use the HideSpawnMenu")]
         public bool NoSpawn { get; private set; }
 
-        public bool HideSpawnMenu => Categories.Contains(HideCategory);
+        public bool HideSpawnMenu => Categories.Contains(HideCategory) || NoSpawn;
 
         [DataField("placement")]
         private EntityPlacementProperties PlacementProperties = new();

Robust.Shared/Prototypes/ProtoId.cs

@@ -1,4 +1,5 @@
-using Robust.Shared.Serialization.TypeSerializers.Implementations.Generic;
+using System;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Generic;
 
 namespace Robust.Shared.Prototypes;
 
@@ -11,7 +12,8 @@ namespace Robust.Shared.Prototypes;
 ///     This will be automatically validated by <see cref="ProtoIdSerializer{T}"/> if used in data fields.
 /// </remarks>
 /// <remarks><seealso cref="EntProtoId"/> for an <see cref="EntityPrototype"/> alias.</remarks>
-public readonly record struct ProtoId<T>(string Id) where T : class, IPrototype
+[Serializable]
+public readonly record struct ProtoId<T>(string Id) : IEquatable<string>, IComparable<ProtoId<T>> where T : class, IPrototype
 {
     public static implicit operator string(ProtoId<T> protoId)
     {
@@ -22,4 +24,21 @@ public readonly record struct ProtoId<T>(string Id) where T : class, IPrototype
     {
         return new ProtoId<T>(id);
     }
+
+    public static implicit operator ProtoId<T>?(string? id)
+    {
+        return id == null ? default(ProtoId<T>?) : new ProtoId<T>(id);
+    }
+
+    public bool Equals(string? other)
+    {
+        return Id == other;
+    }
+
+    public int CompareTo(ProtoId<T> other)
+    {
+        return string.Compare(Id, other.Id, StringComparison.Ordinal);
+    }
+
+    public override string ToString() => Id ?? string.Empty;
 }

Robust.Shared/Prototypes/PrototypeManager.ValidateFields.cs

@@ -60,24 +60,18 @@ public partial class PrototypeManager
         if (!TryGetFieldPrototype(field, out var proto, out var canBeNull, out var canBeEmpty))
             return;
 
-        if (field.FieldType != typeof(string))
-        {
-            errors.Add($"Prototype id field failed validation. Field is not a string. Field: {field.Name} in {type.FullName}");
-            return;
-        }
-
         if (!TryGetFieldValue(field, type, ref instance, errors, out var value))
             return;
 
-        if (value == null)
+        var id = value?.ToString();
+
+        if (id == null)
         {
             if (!canBeNull)
-                errors.Add($"Prototype id field failed validation. Const/Static fields should not be null. Field: {field.Name} in {type.FullName}");
+                errors.Add($"Prototype id field failed validation. Fields should not be null. Field: {field.Name} in {type.FullName}");
             return;
         }
 
-        var id = (string) value;
-
         if (string.IsNullOrWhiteSpace(id))
         {
             if (!canBeEmpty)
@@ -141,7 +135,6 @@ public partial class PrototypeManager
         canBeNull = false;
         canBeEmpty = false;
 
-        // Check for a [PrototypeId] attribute.
         var attrib = field.GetCustomAttribute(typeof(ValidatePrototypeIdAttribute<>), false);
         if (attrib != null)
         {
@@ -149,16 +142,39 @@ public partial class PrototypeManager
             return true;
         }
 
-        // Next, check for a data field attribute.
         if (!field.TryGetCustomAttribute(out DataFieldAttribute? dataField))
             return false;
 
+        var fieldType = field.FieldType;
+        canBeEmpty = dataField.Required;
         DebugTools.Assert(!field.IsStatic);
 
+        // Resolve nullable structs
+        if (fieldType.IsGenericType && fieldType.GetGenericTypeDefinition() == typeof(Nullable<>))
+        {
+            fieldType = fieldType.GetGenericArguments().Single();
+            canBeNull = true;
+        }
+
+        if (fieldType == typeof(EntProtoId))
+        {
+            proto = typeof(EntityPrototype);
+            return true;
+        }
+
+        if (fieldType.IsGenericType && field.FieldType.GetGenericTypeDefinition() == typeof(ProtoId<>))
+        {
+            proto = field.FieldType.GetGenericArguments().Single();
+            return true;
+        }
+
+        // As far as I know there is no way to check for the nullability of a string field, so we will assume that null
+        // values imply that the field itself is properly marked as nullable.
+        canBeNull = true;
+
         if (dataField.CustomTypeSerializer == null)
             return false;
 
-        // Check that this is a prototype id serializer
         if (!dataField.CustomTypeSerializer.IsGenericType)
             return false;
 
@@ -166,12 +182,6 @@ public partial class PrototypeManager
             return false;
 
         proto = dataField.CustomTypeSerializer.GetGenericArguments().First();
-        canBeEmpty = dataField.Required;
-
-        // We will assume null values imply that the field itself is marked as nullable.
-        // Unless someone can tell me how to figure out the nullability of a string field.
-        canBeNull = true;
-
         return true;
     }
 }

Robust.Shared/Robust.Shared.csproj

@@ -19,7 +19,7 @@
     <PackageReference Include="Linguini.Bundle" Version="0.1.3" />
     <PackageReference Include="SharpZstd.Interop" Version="1.5.2-beta2" PrivateAssets="compile" />
     <PackageReference Include="SpaceWizards.Sodium" Version="0.2.1" PrivateAssets="compile" />
-    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.3" />
+    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.7" />
     <PackageReference Include="TerraFX.Interop.Windows" Version="10.0.20348-rc2" PrivateAssets="compile" />
   </ItemGroup>
   <ItemGroup>

Robust.Shared/Serialization/Manager/Attributes/CopyByRefAttribute.cs

@@ -1,14 +1,61 @@
 using System;
 
-namespace Robust.Shared.Serialization.Manager.Attributes
+namespace Robust.Shared.Serialization.Manager.Attributes;
+
+/// <summary>
+///     Makes a type always be copied by reference when using it as the generic parameter in
+///     <see cref="ISerializationManager.CopyTo"/> and <see cref="ISerializationManager.CreateCopy"/>.
+///     This means that the source instance is returned directly.
+///     This attribute is not inherited.
+///     <remarks>
+///         Note that when calling any of the generic <see cref="ISerializationManager.CopyTo{T}"/> and
+///         <see cref="ISerializationManager.CreateCopy{T}"/> methods, this attribute will only be respected
+///         if the generic parameter passed to the copying methods has this attribute.
+///         For example, if a copy method is called with a generic parameter T that is not annotated with this attribute,
+///         but the actual type of the source parameter is annotated with this attribute, it will not be copied by ref.
+///         Conversely, if the generic parameter T is annotated with this attribute, but the actual type of the source
+///         is an inheritor which is not annotated with this attribute, it will still be copied by ref.
+///         If the generic parameter T is a type derived from another that is annotated with the attribute,
+///         but it itself is not annotated with this attribute, source will not be copied by ref as this attribute
+///         is not inherited.
+///         <code>
+///             public class A {}
+///
+///             [CopyByRef]
+///             public class B : A {}
+///
+///             public class C : B {}
+///
+///             public class Copier(ISerializationManager manager)
+///             {
+///                 var a = new A();
+///                 var b = new B();
+///                 var c = new C();
+///
+///                 // false, not copied by ref
+///                 manager.CreateCopy(a) == a
+///
+///                 // false, not copied by ref
+///                 manager.CreateCopy&lt;A&gt;(b) == b
+///
+///                 // true, copied by ref
+///                 manager.CreateCopy(b) == b
+///
+///                 // false, not copied by ref
+///                 manager.CreateCopy(c) == c
+///
+///                 // true, copied by ref
+///                 manager.CreateCopy&lt;B&gt;(c) == c
+///             }
+///         </code>
+///     </remarks>
+/// </summary>
+[AttributeUsage(
+    AttributeTargets.Class |
+    AttributeTargets.Struct |
+    AttributeTargets.Enum |
+    AttributeTargets.Interface,
+    Inherited = false)]
+public sealed class CopyByRefAttribute : Attribute
 {
-    [AttributeUsage(
-        AttributeTargets.Class |
-        AttributeTargets.Struct |
-        AttributeTargets.Enum |
-        AttributeTargets.Interface,
-        Inherited = false)]
-    public sealed class CopyByRefAttribute : Attribute
-    {
-    }
 }

Robust.Shared/Serialization/TypeSerializers/Implementations/Generic/SortedSetSerializer.cs

@@ -0,0 +1,76 @@
+using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Robust.Shared.Serialization.Manager;
+using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.Serialization.Markdown;
+using Robust.Shared.Serialization.Markdown.Sequence;
+using Robust.Shared.Serialization.Markdown.Validation;
+using Robust.Shared.Serialization.TypeSerializers.Interfaces;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Robust.Shared.Serialization.TypeSerializers.Implementations.Generic;
+
+[TypeSerializer]
+public sealed class SortedSetSerializer<T> :
+    ITypeSerializer<SortedSet<T>, SequenceDataNode>,
+    ITypeCopyCreator<SortedSet<T>>
+{
+    SortedSet<T> ITypeReader<SortedSet<T>, SequenceDataNode>.Read(ISerializationManager serializationManager,
+        SequenceDataNode node,
+        IDependencyCollection dependencies,
+        SerializationHookContext hookCtx,
+        ISerializationContext? context,
+        ISerializationManager.InstantiationDelegate<SortedSet<T>>? instanceProvider)
+    {
+        var set = instanceProvider != null ? instanceProvider() : new SortedSet<T>();
+
+        foreach (var dataNode in node.Sequence)
+        {
+            set.Add(serializationManager.Read<T>(dataNode, hookCtx, context));
+        }
+
+        return set;
+    }
+
+    ValidationNode ITypeValidator<SortedSet<T>, SequenceDataNode>.Validate(ISerializationManager serializationManager,
+        SequenceDataNode node, IDependencyCollection dependencies, ISerializationContext? context)
+    {
+        var list = new List<ValidationNode>();
+        foreach (var elem in node.Sequence)
+        {
+            list.Add(serializationManager.ValidateNode<T>(elem, context));
+        }
+
+        return new ValidatedSequenceNode(list);
+    }
+
+    public DataNode Write(ISerializationManager serializationManager, SortedSet<T> value,
+        IDependencyCollection dependencies, bool alwaysWrite = false,
+        ISerializationContext? context = null)
+    {
+        var sequence = new SequenceDataNode();
+
+        foreach (var elem in value)
+        {
+            sequence.Add(serializationManager.WriteValue(elem, alwaysWrite, context));
+        }
+
+        return sequence;
+    }
+
+    SortedSet<T> ITypeCopyCreator<SortedSet<T>>.CreateCopy(ISerializationManager serializationManager, SortedSet<T> source,
+        IDependencyCollection dependencies,
+        SerializationHookContext hookCtx,
+        ISerializationContext? context)
+    {
+        var target = new SortedSet<T>();
+
+        foreach (var val in source)
+        {
+            target.Add(serializationManager.CreateCopy(val, hookCtx, context));
+        }
+
+        return target;
+    }
+}

Robust.Shared/Serialization/TypeSerializers/Implementations/LocIdSerializer.cs

@@ -0,0 +1,42 @@
+using Robust.Shared.IoC;
+using Robust.Shared.Localization;
+using Robust.Shared.Serialization.Manager;
+using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.Serialization.Markdown;
+using Robust.Shared.Serialization.Markdown.Validation;
+using Robust.Shared.Serialization.Markdown.Value;
+using Robust.Shared.Serialization.TypeSerializers.Interfaces;
+using static Robust.Shared.Serialization.Manager.ISerializationManager;
+
+namespace Robust.Shared.Serialization.TypeSerializers.Implementations;
+
+/// <summary>
+///     Serializer used automatically for <see cref="LocId"/> types.
+/// </summary>
+[TypeSerializer]
+public sealed class LocIdSerializer : ITypeSerializer<LocId, ValueDataNode>, ITypeCopyCreator<LocId>
+{
+    public ValidationNode Validate(ISerializationManager serializationManager, ValueDataNode node, IDependencyCollection dependencies, ISerializationContext? context = null)
+    {
+        var loc = dependencies.Resolve<ILocalizationManager>();
+        if (loc.HasString(node.Value))
+            return new ValidatedValueNode(node);
+
+        return new ErrorNode(node, $"No localization message found with id {node.Value}");
+    }
+
+    public LocId Read(ISerializationManager serializationManager, ValueDataNode node, IDependencyCollection dependencies, SerializationHookContext hookCtx, ISerializationContext? context = null, InstantiationDelegate<LocId>? instanceProvider = null)
+    {
+        return new LocId(node.Value);
+    }
+
+    public DataNode Write(ISerializationManager serializationManager, LocId value, IDependencyCollection dependencies, bool alwaysWrite = false, ISerializationContext? context = null)
+    {
+        return new ValueDataNode(value);
+    }
+
+    public LocId CreateCopy(ISerializationManager serializationManager, LocId source, IDependencyCollection dependencies, SerializationHookContext hookCtx, ISerializationContext? context = null)
+    {
+        return source;
+    }
+}

Robust.Shared/Spawners/SharedTimedDespawnSystem.cs

@@ -0,0 +1,45 @@
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Timing;
+
+namespace Robust.Shared.Spawners;
+
+public abstract class SharedTimedDespawnSystem : EntitySystem
+{
+    [Dependency] private readonly IGameTiming _timing = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+        UpdatesOutsidePrediction = true;
+    }
+
+    public override void Update(float frameTime)
+    {
+        base.Update(frameTime);
+
+        // AAAAAAAAAAAAAAAAAAAAAAAAAAA
+        // Client both needs to predict this, but also can't properly handle prediction resetting.
+        if (!_timing.IsFirstTimePredicted)
+            return;
+
+        var query = EntityQueryEnumerator<TimedDespawnComponent>();
+
+        while (query.MoveNext(out var uid, out var comp))
+        {
+            comp.Lifetime -= frameTime;
+
+            if (!CanDelete(uid))
+                continue;
+
+            if (comp.Lifetime <= 0)
+            {
+                var ev = new TimedDespawnEvent();
+                RaiseLocalEvent(uid, ref ev);
+                QueueDel(uid);
+            }
+        }
+    }
+
+    protected abstract bool CanDelete(EntityUid uid);
+}

Robust.Shared/Spawners/TimedDespawnComponent.cs

@@ -0,0 +1,20 @@
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization.Manager.Attributes;
+
+namespace Robust.Shared.Spawners;
+
+/// <summary>
+/// Put this component on something you would like to despawn after a certain amount of time
+/// </summary>
+/// <remarks>
+/// NOT networked as we don't want clients predicting networked entity deletions.
+/// </remarks>
+[RegisterComponent]
+public sealed partial class TimedDespawnComponent : Component
+{
+    /// <summary>
+    /// How long the entity will exist before despawning
+    /// </summary>
+    [DataField("lifetime")]
+    public float Lifetime = 5f;
+}

Robust.Shared/Spawners/TimedDespawnEvent.cs

@@ -0,0 +1,9 @@
+using Robust.Shared.GameObjects;
+
+namespace Robust.Shared.Spawners;
+
+/// <summary>
+/// Raised directed on an entity when its timed despawn is over.
+/// </summary>
+[ByRefEvent]
+public readonly record struct TimedDespawnEvent;

Robust.Shared/Utility/DebugTools.cs

@@ -88,13 +88,16 @@ namespace Robust.Shared.Utility
 
         [Conditional("DEBUG")]
         [AssertionMethod]
-        public static void AssertOwner(EntityUid? uid, IComponent component)
+        public static void AssertOwner(EntityUid? uid, IComponent? component)
         {
+            if (component == null)
+                return;
+
             if (uid == null)
                 throw new DebugAssertException($"Null entity uid cannot own a component. Component: {component.GetType().Name}");
 
             // Whenever .owner is removed this will need to be replaced by something.
-            // We need some way to ensure that people don't mix up uids & components when calling methods.
+            // As long as components are just reference types, we could just get the component and check if the references are equal?
             if (component.Owner != uid)
                 throw new DebugAssertException($"Entity {uid} is not the owner of the component. Component: {component.GetType().Name}");
         }

Robust.Shared/Utility/UniqueIndexHkm.cs

@@ -43,14 +43,7 @@ namespace Robust.Shared.Utility
         public bool Add(TKey key, TValue value)
         {
             InitializedCheck();
-
-            if (_index.TryGetValue(key, out var set))
-            {
-                return set.Add(value);
-            }
-
-            _index.Add(key, new HashSet<TValue> {value});
-            return true;
+            return _index.GetOrNew(key).Add(value);
         }
 
         /// <inheritdoc />

Robust.UnitTesting/RobustIntegrationTest.cs

@@ -22,6 +22,7 @@ using Robust.Server.ServerStatus;
 using Robust.Shared;
 using Robust.Shared.Asynchronous;
 using Robust.Shared.Configuration;
+using Robust.Shared.Console;
 using Robust.Shared.ContentPack;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Input;
@@ -269,6 +270,7 @@ namespace Robust.UnitTesting
             public ISharedPlayerManager PlayerMan { get; private set; } = default!;
             public IGameTiming Timing { get; private set; } = default!;
             public IMapManager MapMan { get; private set; } = default!;
+            public IConsoleHost ConsoleHost { get; private set; } = default!;
 
             protected virtual void ResolveIoC(IDependencyCollection deps)
             {
@@ -278,6 +280,7 @@ namespace Robust.UnitTesting
                 PlayerMan = deps.Resolve<ISharedPlayerManager>();
                 Timing = deps.Resolve<IGameTiming>();
                 MapMan = deps.Resolve<IMapManager>();
+                ConsoleHost = deps.Resolve<IConsoleHost>();
             }
 
             public T System<T>() where T : IEntitySystem
@@ -295,6 +298,11 @@ namespace Robust.UnitTesting
                 return EntMan.GetComponent<MetaDataComponent>(uid);
             }
 
+            public async Task ExecuteCommand(string cmd)
+            {
+                await WaitPost(() => ConsoleHost.ExecuteCommand(cmd));
+            }
+
             /// <summary>
             ///     Whether the instance is still alive.
             ///     "Alive" indicates that it is able to receive and process commands.

Robust.UnitTesting/RobustUnitTest.cs

@@ -128,6 +128,7 @@ namespace Robust.UnitTesting
 
             // Required components for the engine to work
             // Why are we still here? Just to suffer? Why can't we just use [RegisterComponent] magic?
+            // TODO End Suffering.
             var compFactory = deps.Resolve<IComponentFactory>();
 
             if (!compFactory.AllRegisteredTypes.Contains(typeof(EyeComponent)))
@@ -225,6 +226,11 @@ namespace Robust.UnitTesting
                 compFactory.RegisterClass<Gravity2DComponent>();
             }
 
+            if (!compFactory.AllRegisteredTypes.Contains(typeof(ActorComponent)))
+            {
+                compFactory.RegisterClass<ActorComponent>();
+            }
+
             // So by default EntityManager does its own EntitySystemManager initialize during Startup.
             // We want to bypass this and load our own systems hence we will manually initialize it here.
             entMan.Initialize();

Robust.UnitTesting/Server/GameObjects/Components/Container_Test.cs

@@ -222,9 +222,9 @@ namespace Robust.UnitTesting.Server.GameObjects.Components
             Assert.That(entManager.GetComponent<TransformComponent>(containerEntity).ChildCount, Is.EqualTo(1));
             Assert.That(entManager.GetComponent<TransformComponent>(containerEntity).ChildEntities.First(), Is.EqualTo(insertEntity));
 
-            result = insertEntity.TryGetContainerMan(out var resultContainerMan);
+            result = containerSys.TryGetContainingContainer(insertEntity, out var resultContainerMan);
             Assert.That(result, Is.True);
-            Assert.That(resultContainerMan, Is.EqualTo(container.Manager));
+            Assert.That(resultContainerMan?.Manager, Is.EqualTo(container.Manager));
         }
 
         [Test]

Robust.UnitTesting/Server/GameStates/PvsReEntryTest.cs

@@ -0,0 +1,214 @@
+using System.Linq;
+using System.Numerics;
+using System.Threading.Tasks;
+using NUnit.Framework;
+using Robust.Client.GameStates;
+using Robust.Client.Timing;
+using Robust.Server.GameObjects;
+using Robust.Server.Player;
+using Robust.Shared;
+using Robust.Shared.Configuration;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Map;
+using Robust.Shared.Network;
+using Robust.Shared.Timing;
+using cIPlayerManager = Robust.Client.Player.IPlayerManager;
+using sIPlayerManager = Robust.Server.Player.IPlayerManager;
+
+namespace Robust.UnitTesting.Server.GameStates;
+
+public sealed class PvsReEntryTest : RobustIntegrationTest
+{
+#if DEBUG
+    /// <summary>
+    /// Checks that there are no issues when an entity enters, leaves, then enters pvs while the client drops packets.
+    /// </summary>
+    [Test]
+    public async Task TestLossyReEntry()
+    {
+        var server = StartServer();
+        var client = StartClient();
+
+        await Task.WhenAll(client.WaitIdleAsync(), server.WaitIdleAsync());
+
+        var mapMan = server.ResolveDependency<IMapManager>();
+        var sEntMan = server.ResolveDependency<IEntityManager>();
+        var confMan = server.ResolveDependency<IConfigurationManager>();
+        var sPlayerMan = server.ResolveDependency<sIPlayerManager>();
+        var xforms = sEntMan.System<SharedTransformSystem>();
+        var stateMan = (ClientGameStateManager) client.ResolveDependency<IClientGameStateManager>();
+
+        var cEntMan = client.ResolveDependency<IEntityManager>();
+        var netMan = client.ResolveDependency<IClientNetManager>();
+        var cPlayerMan = client.ResolveDependency<cIPlayerManager>();
+
+        Assert.DoesNotThrow(() => client.SetConnectTarget(server));
+        client.Post(() => netMan.ClientConnect(null!, 0, null!));
+        server.Post(() => confMan.SetCVar(CVars.NetPVS, true));
+
+        for (int i = 0; i < 10; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        // Ensure client & server ticks are synced.
+        // Client runs 1 tick ahead
+        {
+            var sTick = (int)server.Timing.CurTick.Value;
+            var cTick = (int)client.Timing.CurTick.Value;
+            var delta = cTick - sTick;
+
+            if (delta > 1)
+                await server.WaitRunTicks(delta - 1);
+            else if (delta < 1)
+                await client.WaitRunTicks(1 - delta);
+
+            sTick = (int)server.Timing.CurTick.Value;
+            cTick = (int)client.Timing.CurTick.Value;
+            delta = cTick - sTick;
+            Assert.That(delta, Is.EqualTo(1));
+        }
+
+        // Set up map and spawn player
+        EntityUid map = default;
+        NetEntity player = default;
+        NetEntity entity = default;
+        EntityCoordinates coords = default;
+        await server.WaitPost(() =>
+        {
+            var mapId = mapMan.CreateMap();
+            map = mapMan.GetMapEntityId(mapId);
+            coords = new(map, default);
+
+            var playerUid = sEntMan.SpawnEntity(null, coords);
+            var entUid = sEntMan.SpawnEntity(null, coords);
+            entity = sEntMan.GetNetEntity(entUid);
+            player = sEntMan.GetNetEntity(playerUid);
+
+            // Attach player.
+            var session = (IPlayerSession) sPlayerMan.Sessions.First();
+            sEntMan.System<ActorSystem>().Attach(playerUid, session);
+            session.JoinGame();
+        });
+
+        for (int i = 0; i < 10; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        Assert.That(player, Is.Not.EqualTo(NetEntity.Invalid));
+        Assert.That(entity, Is.Not.EqualTo(NetEntity.Invalid));
+
+        // Check player got properly attached, and has received the other entity.
+        MetaDataComponent? meta = default!;
+        await client.WaitPost(() =>
+        {
+            Assert.That(cEntMan.TryGetEntityData(entity, out _, out meta));
+            Assert.That(cEntMan.TryGetEntity(player, out var cPlayerUid));
+            Assert.That(cPlayerMan.LocalPlayer?.ControlledEntity, Is.EqualTo(cPlayerUid));
+            Assert.That(meta!.Flags & MetaDataFlags.Detached, Is.EqualTo(MetaDataFlags.None));
+            Assert.That(stateMan.IsQueuedForDetach(entity), Is.False);
+        });
+
+        var lastDirty = meta.LastModifiedTick;
+        Assert.That(lastDirty, Is.GreaterThan(GameTick.Zero));
+
+        // Move the player outside of the entity's PVS range
+        // note that we move the PLAYER not the entity, as we don't want to dirty the entity.
+        var farAway = new EntityCoordinates(map, new Vector2(100, 100));
+        await server.WaitPost( () => xforms.SetCoordinates(sEntMan.GetEntity(player), farAway));
+        for (int i = 0; i < 10; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        // Client should have detached the entity to null space.
+        Assert.That(meta!.Flags & MetaDataFlags.Detached, Is.EqualTo(MetaDataFlags.Detached));
+        Assert.That(stateMan.IsQueuedForDetach(entity), Is.False);
+
+        // Move the player back into range
+        await server.WaitPost( () => xforms.SetCoordinates(sEntMan.GetEntity(player), coords));
+        for (int i = 0; i < 10; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        // Entity is back in pvs range
+        Assert.That(meta!.Flags & MetaDataFlags.Detached, Is.EqualTo(MetaDataFlags.None));
+        Assert.That(stateMan.IsQueuedForDetach(entity), Is.False);
+
+        // Oh no, the client is going through a tunnel!
+        stateMan.DropStates = true;
+        var timing = client.ResolveDependency<IClientGameTiming>();
+        var lastRealTick = timing.LastRealTick;
+
+        for (int i = 0; i < 5; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        // Even though the client is receiving no new states, it will still have applied some from the state buffer.
+        Assert.That(timing.LastRealTick, Is.GreaterThan(lastRealTick));
+        lastRealTick = timing.LastRealTick;
+
+        // Move the player outside of pvs range.
+        Assert.That(meta!.Flags & MetaDataFlags.Detached, Is.EqualTo(MetaDataFlags.None));
+        await server.WaitPost(() => xforms.SetCoordinates(sEntMan.GetEntity(player), farAway));
+
+        for (int i = 0; i < 5; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        // Client should have exhausted the buffer -- client has not been applying any states.
+        Assert.That(timing.LastRealTick, Is.EqualTo(lastRealTick));
+        Assert.That(meta!.Flags & MetaDataFlags.Detached, Is.EqualTo(MetaDataFlags.None));
+
+        // However pvs-leave messages are sent separately, and are sent reliably. So they are still being received.
+        // Though in a realistic scenario they should probably be delayed somewhat.
+        Assert.That(stateMan.IsQueuedForDetach(entity), Is.True);
+
+        // Move the entity back into range
+        await server.WaitPost( () => xforms.SetCoordinates(sEntMan.GetEntity(player), coords));
+
+        for (int i = 0; i < 5; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        // Still hasn't been applying states.
+        Assert.That(timing.LastRealTick, Is.EqualTo(lastRealTick));
+        Assert.That(meta!.Flags & MetaDataFlags.Detached, Is.EqualTo(MetaDataFlags.None));
+
+        // The pvs-leave message has not yet been processed, detaching is still queued.
+        Assert.That(stateMan.IsQueuedForDetach(entity), Is.True);
+
+        // Client clears the tunnel, starts receiving states again.
+        stateMan.DropStates = false;
+
+        for (int i = 0; i < 10; i++)
+        {
+            await server.WaitRunTicks(1);
+            await client.WaitRunTicks(1);
+        }
+
+        // Entity should be in PVS range, client should know about it:
+        Assert.That(timing.LastRealTick, Is.GreaterThan(lastRealTick));
+        Assert.That(meta!.Flags & MetaDataFlags.Detached, Is.EqualTo(MetaDataFlags.None));
+        Assert.That(stateMan.IsQueuedForDetach(entity), Is.False);
+
+        // The entity itself should not have been dirtied since creation -- only the player has been moving.
+        // If the test moves the entity instead of the player, then the test doesn't actually work.
+        Assert.That(meta.LastModifiedTick, Is.EqualTo(lastDirty));
+
+    }
+#endif
+}
+

Robust.UnitTesting/Server/Maps/MapLoaderTest.cs

@@ -61,7 +61,6 @@ entities:
             var compFactory = IoCManager.Resolve<IComponentFactory>();
             compFactory.RegisterClass<MapDeserializeTestComponent>();
             compFactory.RegisterClass<VisibilityComponent>();
-            compFactory.RegisterClass<ActorComponent>();
             compFactory.RegisterClass<IgnoreUIRangeComponent>();
             compFactory.GenerateNetIds();
             IoCManager.Resolve<ISerializationManager>().Initialize();

Robust.UnitTesting/Shared/GameState/VisibilityTest.cs

@@ -0,0 +1,131 @@
+using System.Linq;
+using System.Numerics;
+using System.Threading.Tasks;
+using NUnit.Framework;
+using Robust.Server.GameObjects;
+using Robust.Server.Player;
+using Robust.Shared;
+using Robust.Shared.GameObjects;
+using Robust.Shared.GameStates;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+using Robust.Shared.Network;
+
+namespace Robust.UnitTesting.Shared.GameState;
+
+public sealed partial class VisibilityTest : RobustIntegrationTest
+{
+    /// <summary>
+    /// This tests checks that entity visibility masks are recursively applied to children.
+    /// </summary>
+    [Test]
+    public async Task UnknownEntityTest()
+    {
+        var server = StartServer();
+
+        var xforms = server.System<SharedTransformSystem>();
+        var vis = server.System<VisibilitySystem>();
+
+        const int RequiredMask = 1;
+        // All entities need to have this mask set ... which defeat the whole point of that bit?
+
+        // Spawn a stack of entities
+        int N = 6;
+        var ents = new EntityUid[N];
+        var metaComp = new MetaDataComponent[N];
+        var visComp = new VisibilityComponent[N];
+        await server.WaitPost(() =>
+        {
+            for (int i = 0; i < N; i++)
+            {
+                var ent = server.EntMan.Spawn();
+
+                ents[i] = ent;
+                metaComp[i] = server.EntMan.GetComponent<MetaDataComponent>(ent);
+                visComp[i] = server.EntMan.AddComponent<VisibilityComponent>(ent);
+
+                vis.AddLayer(ent, visComp[i], 1 << i);
+                if (i > 0)
+                    xforms.SetParent(ent, ents[i - 1]);
+            }
+        });
+
+        // Each entity's visibility mask should include the parent's mask
+        var mask = RequiredMask;
+        for (int i = 0; i < N; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+
+        // Adding a layer to the root entity's mask will apply it to all children
+        var extraMask = 1 << (N + 1);
+        mask = RequiredMask | extraMask;
+        vis.AddLayer(ents[0], visComp[0], extraMask);
+        for (int i = 0; i < N; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+
+        // Removing the removes it from all children.
+        vis.RemoveLayer(ents[0], visComp[0], extraMask);
+        mask = RequiredMask;
+        for (int i = 0; i < N; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+
+        // Detaching an entity from the stack updates it, and it's children's mask
+        var split = N / 2;
+        await server.WaitPost(() => xforms.SetParent(ents[split], EntityUid.Invalid));
+
+        mask = RequiredMask;
+        for (int i = 0; i < split; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+
+        mask = RequiredMask;
+        for (int i = split; i < N; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+
+        // Re-attaching the entity also updates the masks.
+        await server.WaitPost(() => xforms.SetParent(ents[split], ents[split-1]));
+        mask = RequiredMask;
+        for (int i = 0; i < N; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+
+        // Setting a mask on a child does not propagate upwards, only downwards
+        vis.AddLayer(ents[split], visComp[split], extraMask);
+        mask = RequiredMask;
+        for (int i = 0; i < split; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+
+        mask |= extraMask;
+        for (int i = split; i < N; i++)
+        {
+            mask |= 1 << i;
+            var meta = metaComp[i];
+            Assert.That(meta.VisibilityMask, Is.EqualTo(mask));
+        }
+    }
+}

Robust.UnitTesting/Shared/Serialization/TypeSerializers/SortedSetSerializerTest.cs

@@ -0,0 +1,36 @@
+using System.Collections.Generic;
+using NUnit.Framework;
+using Robust.Shared.Serialization.Manager;
+using Robust.Shared.Serialization.Markdown.Sequence;
+using Robust.Shared.Serialization.Markdown.Value;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Generic;
+
+// ReSharper disable AccessToStaticMemberViaDerivedType
+
+namespace Robust.UnitTesting.Shared.Serialization.TypeSerializers;
+
+[TestFixture]
+[TestOf(typeof(SortedSetSerializer<>))]
+public sealed class SortedSetSerializerTest : SerializationTest
+{
+    [Test]
+    public void SerializationTest()
+    {
+        var list = new SortedSet<string> {"A", "B", "C"};
+        var node = Serialization.WriteValueAs<SequenceDataNode>(list);
+
+        Assert.That(node.Cast<ValueDataNode>(0).Value, Is.EqualTo("A"));
+        Assert.That(node.Cast<ValueDataNode>(1).Value, Is.EqualTo("B"));
+        Assert.That(node.Cast<ValueDataNode>(2).Value, Is.EqualTo("C"));
+    }
+
+    [Test]
+    public void DeserializationTest()
+    {
+        var list = new SortedSet<string> {"A", "B", "C"};
+        var node = new SequenceDataNode("A", "B", "C");
+        var deserializedList = Serialization.Read<SortedSet<string>>(node, notNullableOverride: true);
+
+        Assert.That(deserializedList, Is.EqualTo(list));
+    }
+}

global.json

@@ -0,0 +1,6 @@
+{
+  "sdk": {
+    "version": "7.0.100",
+    "rollForward": "latestFeature"
+  }
+}