Fix drag-drop stripping (#3001)

* Fix drag-drop stripping

* More robust

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Client/GameObjects/EntitySystems/DragDropSystem.cs

@@ -302,6 +302,8 @@ namespace Content.Client.GameObjects.EntitySystems
 
             foreach (var entity in entities)
             {
+                if (entity == _dragDropHelper.Dragged) continue;
+
                 // check if it's able to be dropped on by current dragged entity
                 var dropArgs = new DragDropEventArgs(_dragger, args.Coordinates, _dragDropHelper.Dragged, entity);
                 var valid = true;
@@ -381,10 +383,9 @@ namespace Content.Client.GameObjects.EntitySystems
             var pvsEntities = EntityManager.GetEntitiesIntersecting(_eyeManager.CurrentMap, bounds, true);
             foreach (var pvsEntity in pvsEntities)
             {
-                if (!pvsEntity.TryGetComponent(out ISpriteComponent? inRangeSprite)) continue;
-
-                // can't highlight if there's no sprite or it's not visible
-                if (inRangeSprite.Visible == false) continue;
+                if (!pvsEntity.TryGetComponent(out ISpriteComponent? inRangeSprite) ||
+                    !inRangeSprite.Visible ||
+                    pvsEntity == _dragDropHelper.Dragged) continue;
 
                 var valid = (bool?) null;
                 // check if it's able to be dropped on by current dragged entity

Content.Shared/GameObjects/Components/GUI/SharedStrippingComponent.cs

@@ -0,0 +1,27 @@
+#nullable enable
+using Content.Shared.Interfaces.GameObjects.Components;
+using Robust.Shared.GameObjects;
+
+namespace Content.Shared.GameObjects.Components.GUI
+{
+    /// <summary>
+    ///     Give to an entity to say they can strip another entity.
+    /// </summary>
+    [RegisterComponent]
+    public class SharedStrippingComponent : Component, IDragDropOn
+    {
+        public override string Name => "Stripping";
+
+        public bool CanDragDropOn(DragDropEventArgs eventArgs)
+        {
+            if (!eventArgs.Dragged.TryGetComponent(out SharedStrippableComponent? strippable)) return false;
+            return strippable.CanBeStripped(Owner);
+        }
+
+        public bool DragDropOn(DragDropEventArgs eventArgs)
+        {
+            // Handled by StrippableComponent
+            return true;
+        }
+    }
+}

Resources/Prototypes/Entities/Mobs/Species/human.yml

@@ -196,6 +196,7 @@
   - type: Pullable
   - type: DoAfter
   - type: CreamPied
+  - type: Stripping
   - type: Strippable
   - type: UserInterface
     interfaces: