session/handler_inventory_transaction.go: resend slots from pk.LegacySetItemSlots

server/session/handler_inventory_transaction.go

@@ -15,36 +15,60 @@ import (
 type InventoryTransactionHandler struct{}
 
 // Handle ...
-func (h *InventoryTransactionHandler) Handle(p packet.Packet, s *Session, tx *world.Tx, c Controllable) error {
+func (h *InventoryTransactionHandler) Handle(p packet.Packet, s *Session, tx *world.Tx, c Controllable) (err error) {
 	pk := p.(*packet.InventoryTransaction)
 
+	if len(pk.LegacySetItemSlots) > 2 {
+		return fmt.Errorf("too many slot sync requests in inventory transaction")
+	}
+
+	defer func() {
+		// The client has requested the server to resend the specified slots even if they haven't changed server-side.
+		// Handling these requests is necessary to ensure the client's inventory remains in sync with the server.
+		for _, slot := range pk.LegacySetItemSlots {
+			if len(slot.Slots) > 2 {
+				err = fmt.Errorf("too many slots in slot sync request")
+				return
+			}
+			switch slot.ContainerID {
+			case protocol.ContainerOffhand:
+				s.sendInv(s.offHand, protocol.WindowIDOffHand)
+			case protocol.ContainerInventory:
+				for _, slot := range slot.Slots {
+					if i, err := s.inv.Item(int(slot)); err == nil {
+						s.sendItem(i, int(slot), protocol.WindowIDInventory)
+					}
+				}
+			}
+		}
+	}()
+
 	switch data := pk.TransactionData.(type) {
 	case *protocol.NormalTransactionData:
 		h.resendInventories(s)
 		// Always resend inventories with normal transactions. Most of the time we do not use these
 		// transactions, so we're best off making sure the client and server stay in sync.
 		if err := h.handleNormalTransaction(pk, s, c); err != nil {
 			s.conf.Log.Debug("process packet: InventoryTransaction: verify Normal transaction actions: " + err.Error())
-			return nil
 		}
-		return nil
+		return
 	case *protocol.MismatchTransactionData:
 		// Just resend the inventory and don't do anything.
 		h.resendInventories(s)
-		return nil
+		return
 	case *protocol.UseItemOnEntityTransactionData:
-		if err := s.VerifyAndSetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack), c); err != nil {
-			return err
+		if err = s.VerifyAndSetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack), c); err != nil {
+			return
 		}
 		return h.handleUseItemOnEntityTransaction(data, s, tx, c)
 	case *protocol.UseItemTransactionData:
-		if err := s.VerifyAndSetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack), c); err != nil {
-			return err
+		if err = s.VerifyAndSetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack), c); err != nil {
+			return
 		}
 		return h.handleUseItemTransaction(data, s, c)
 	case *protocol.ReleaseItemTransactionData:
-		if err := s.VerifyAndSetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack), c); err != nil {
-			return err
+		if err = s.VerifyAndSetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack), c); err != nil {
+			return
 		}
 		return h.handleReleaseItemTransaction(c)
 	}