Show if items can be placed in a slot when hovering (#1480)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers@gmail.com>

Content.Client/UserInterface/ItemSlotButton.cs

@@ -17,6 +17,10 @@ namespace Content.Client.UserInterface
 
         public Action<GUIBoundKeyEventArgs> OnPressed { get; set; }
         public Action<GUIBoundKeyEventArgs> OnStoragePressed { get; set; }
+        public Action<GUIMouseHoverEventArgs> OnHover { get; set; }
+
+        public bool EntityHover { get; set; } = false;
+        public bool MouseIsHovering = false;
 
         public ItemSlotButton(Texture texture, Texture storageTexture)
         {
@@ -56,6 +60,24 @@ namespace Content.Client.UserInterface
 
             StorageButton.OnPressed += OnStorageButtonPressed;
 
+            Button.OnMouseEntered += _ =>
+            {
+                MouseIsHovering = true;
+            };
+            Button.OnMouseEntered += OnButtonHover;
+
+            Button.OnMouseExited += _ =>
+            {
+                MouseIsHovering = false;
+                if (EntityHover)
+                {
+                    SpriteView.Sprite?.Owner.Delete();
+                    EntityHover = false;
+                    SpriteView.Sprite = null;
+                    StorageButton.Visible = false;
+                }
+            };
+
             AddChild(CooldownDisplay = new CooldownGraphic
             {
                 SizeFlagsHorizontal = SizeFlags.Fill,
@@ -80,5 +102,10 @@ namespace Content.Client.UserInterface
                 OnPressed?.Invoke(args.Event);
             }
         }
+
+        private void OnButtonHover(GUIMouseHoverEventArgs args)
+        {
+            OnHover?.Invoke(args);
+        }
     }
 }