Add support for multi-layer in-hand and clothing sprites (#6252)

Content.Shared/Hands/HandEvents.cs

@@ -1,13 +1,67 @@
 using System;
+using System.Collections.Generic;
 using Content.Shared.Hands.Components;
 using JetBrains.Annotations;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Serialization;
+using static Robust.Shared.GameObjects.SharedSpriteComponent;
 
 namespace Content.Shared.Hands
 {
+    /// <summary>
+    ///     Raised directed at an item that needs to update its in-hand sprites/layers.
+    /// </summary>
+    public class GetInhandVisualsEvent : EntityEventArgs
+    {
+        /// <summary>
+        ///     Entity that owns the hand holding the item.
+        /// </summary>
+        public readonly EntityUid User;
+
+        public readonly HandLocation Location;
+
+        /// <summary>
+        ///     The layers that will be added to the entity that is holding this item.
+        /// </summary>
+        /// <remarks>
+        ///     Note that the actual ordering of the layers depends on the order in which they are added to this list;
+        /// </remarks>
+        public List<(string, PrototypeLayerData)> Layers = new();
+
+        public GetInhandVisualsEvent(EntityUid user, HandLocation location)
+        {
+            User = user;
+            Location = location;
+        }
+    }
+
+    /// <summary>
+    ///     Raised directed at an item after its visuals have been updated.
+    /// </summary>
+    /// <remarks>
+    ///     Useful for systems/components that modify the visual layers that an item adds to a player. (e.g. RGB memes)
+    /// </remarks>
+    public class HeldVisualsUpdatedEvent : EntityEventArgs
+    {
+        /// <summary>
+        ///     Entity that is holding the item.
+        /// </summary>
+        public readonly EntityUid User;
+
+        /// <summary>
+        ///     The layers that this item is now revealing.
+        /// </summary>
+        public HashSet<string> RevealedLayers;
+
+        public HeldVisualsUpdatedEvent(EntityUid user, HashSet<string> revealedLayers)
+        {
+            User = user;
+            RevealedLayers = revealedLayers;
+        }
+    }
+
     /// <summary>
     ///     Raised when an entity item in a hand is deselected.
     /// </summary>