Add multi-layer in-hand and clothing support (#6740)

Content.Shared/Clothing/ClothingEvents.cs

@@ -0,0 +1,60 @@
+using System.Collections.Generic;
+using Robust.Shared.GameObjects;
+using static Robust.Shared.GameObjects.SharedSpriteComponent;
+
+namespace Content.Shared.Clothing;
+
+/// <summary>
+///     Raised directed at a piece of clothing to get the set of layers to show on the wearer's sprite
+/// </summary>
+public class GetEquipmentVisualsEvent : EntityEventArgs
+{
+    /// <summary>
+    ///     Entity that is wearing the item.
+    /// </summary>
+    public readonly EntityUid Equipee;
+
+    public readonly string Slot;
+
+    /// <summary>
+    ///     The layers that will be added to the entity that is wearing 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 GetEquipmentVisualsEvent(EntityUid equipee, string slot)
+    {
+        Equipee = equipee;
+        Slot = slot;
+    }
+}
+
+/// <summary>
+///     Raised directed at a piece of clothing 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 EquipmentVisualsUpdatedEvent : EntityEventArgs
+{
+    /// <summary>
+    ///     Entity that is wearing the item.
+    /// </summary>
+    public readonly EntityUid Equipee;
+
+    public readonly string Slot;
+
+    /// <summary>
+    ///     The layers that this item is now revealing.
+    /// </summary>
+    public HashSet<string> RevealedLayers;
+
+    public EquipmentVisualsUpdatedEvent(EntityUid equipee, string slot, HashSet<string> revealedLayers)
+    {
+        Equipee = equipee;
+        Slot = slot;
+        RevealedLayers = revealedLayers;
+    }
+}