Added Held Slot handler

server/player/handler.go

@@ -1,6 +1,8 @@
 package player
 
 import (
+	"net"
+
 	"github.com/df-mc/dragonfly/server/block/cube"
 	"github.com/df-mc/dragonfly/server/cmd"
 	"github.com/df-mc/dragonfly/server/entity"
@@ -11,7 +13,6 @@ import (
 	"github.com/df-mc/dragonfly/server/player/skin"
 	"github.com/df-mc/dragonfly/server/world"
 	"github.com/go-gl/mathgl/mgl64"
-	"net"
 )
 
 // Handler handles events that are called by a player. Implementations of Handler may be used to listen to
@@ -108,6 +109,8 @@ type Handler interface {
 	// HandleItemPickup handles the player picking up an item from the ground. The item stack laying on the
 	// ground is passed. ctx.Cancel() may be called to prevent the player from picking up the item.
 	HandleItemPickup(ctx *event.Context, i item.Stack)
+	// HandleHeldSlotChange handles the player changing the slot they are currently holding. 
+	HandleHeldSlotChange(ctx *event.Context, slot int)
 	// HandleItemDrop handles the player dropping an item on the ground. The dropped item entity is passed.
 	// ctx.Cancel() may be called to prevent the player from dropping the entity.Item passed on the ground.
 	// e.Item() may be called to obtain the item stack dropped.
@@ -134,6 +137,9 @@ var _ Handler = (*NopHandler)(nil)
 // HandleItemDrop ...
 func (NopHandler) HandleItemDrop(*event.Context, *entity.Item) {}
 
+// HandleHeldSlotChange ...
+func (NopHandler) HandleHeldSlotChange(*event.Context, int) {}
+
 // HandleMove ...
 func (NopHandler) HandleMove(*event.Context, mgl64.Vec3, float64, float64) {}
 

server/player/player.go

@@ -2,6 +2,13 @@ package player
 
 import (
 	"fmt"
+	"math"
+	"math/rand"
+	"net"
+	"strings"
+	"sync"
+	"time"
+
 	"github.com/df-mc/dragonfly/server/block"
 	"github.com/df-mc/dragonfly/server/block/cube"
 	"github.com/df-mc/dragonfly/server/cmd"
@@ -28,12 +35,6 @@ import (
 	"github.com/google/uuid"
 	"go.uber.org/atomic"
 	"golang.org/x/text/language"
-	"math"
-	"math/rand"
-	"net"
-	"strings"
-	"sync"
-	"time"
 )
 
 // Player is an implementation of a player entity. It has methods that implement the behaviour that players
@@ -367,6 +368,37 @@ func (p *Player) Transfer(address string) (err error) {
 	return
 }
 
+// SetHeldSlot updates the held slot of the player with the slot passed. It also verifies that the item within the spot
+// is the correct item.
+// This invokes the HandleHeldSlotChange handler.
+func (p *Player) SetHeldSlot(slot int, expected item.Stack) error {
+	if slot > 8 {
+		return fmt.Errorf("new held slot exceeds hotbar range 0-8: slot is %v", slot)
+	}
+
+	if p.heldSlot.Swap(uint32(slot)) == uint32(slot) {
+		return nil
+	}
+
+	p.ReleaseItem()
+
+	clientSideItem := expected
+	actual, _ := p.inv.Item(slot)
+
+	if !clientSideItem.Equal(actual) {
+		return fmt.Errorf("client side item isn't equal to expected slot item")
+	}
+
+	ctx := event.C()
+	p.handler().HandleHeldSlotChange(ctx, slot)
+
+	ctx.Continue(func() {
+		p.session().SetHeldSlot(slot)
+	})
+
+	return nil
+}
+
 // SendCommandOutput sends the output of a command to the player.
 func (p *Player) SendCommandOutput(output *cmd.Output) {
 	p.session().SendCommandOutput(output)

server/session/controllable.go

@@ -23,6 +23,7 @@ type Controllable interface {
 	cmd.Source
 	chat.Subscriber
 	SetHeldItems(right, left item.Stack)
+	SetHeldSlot(slot int, expected item.Stack) error
 
 	Move(deltaPos mgl64.Vec3, deltaYaw, deltaPitch float64)
 	Speed() float64

server/session/handler_inventory_transaction.go

@@ -2,6 +2,7 @@ package session
 
 import (
 	"fmt"
+
 	"github.com/df-mc/dragonfly/server/block/cube"
 	"github.com/df-mc/dragonfly/server/event"
 	"github.com/sandertv/gophertunnel/minecraft/protocol"
@@ -30,17 +31,17 @@ func (h *InventoryTransactionHandler) Handle(p packet.Packet, s *Session) error
 		h.resendInventories(s)
 		return nil
 	case *protocol.UseItemOnEntityTransactionData:
-		if err := s.UpdateHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack)); err != nil {
+		if err := s.c.SetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack)); err != nil {
 			return err
 		}
 		return h.handleUseItemOnEntityTransaction(data, s)
 	case *protocol.UseItemTransactionData:
-		if err := s.UpdateHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack)); err != nil {
+		if err := s.c.SetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack)); err != nil {
 			return err
 		}
 		return h.handleUseItemTransaction(data, s)
 	case *protocol.ReleaseItemTransactionData:
-		if err := s.UpdateHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack)); err != nil {
+		if err := s.c.SetHeldSlot(int(data.HotBarSlot), stackToItem(data.HeldItem.Stack)); err != nil {
 			return err
 		}
 		return h.handleReleaseItemTransaction(s)

server/session/handler_mob_equipment.go

@@ -2,6 +2,7 @@ package session
 
 import (
 	"fmt"
+
 	"github.com/sandertv/gophertunnel/minecraft/protocol"
 	"github.com/sandertv/gophertunnel/minecraft/protocol/packet"
 )
@@ -21,7 +22,7 @@ func (*MobEquipmentHandler) Handle(p packet.Packet, s *Session) error {
 		// This window ID is expected, but we don't handle it.
 		return nil
 	case protocol.WindowIDInventory:
-		return s.UpdateHeldSlot(int(pk.InventorySlot), stackToItem(pk.NewItem.Stack))
+		return s.c.SetHeldSlot(int(pk.InventorySlot), stackToItem(pk.NewItem.Stack))
 	default:
 		return fmt.Errorf("only main inventory should be involved in slot chnage, got window ID %v", pk.WindowID)
 	}

server/session/player.go

@@ -3,6 +3,11 @@ package session
 import (
 	"encoding/json"
 	"fmt"
+	"math"
+	"net"
+	"time"
+	_ "unsafe" // Imported for compiler directives.
+
 	"github.com/df-mc/dragonfly/server/block"
 	"github.com/df-mc/dragonfly/server/block/cube"
 	"github.com/df-mc/dragonfly/server/entity"
@@ -18,10 +23,6 @@ import (
 	"github.com/sandertv/gophertunnel/minecraft/protocol"
 	"github.com/sandertv/gophertunnel/minecraft/protocol/packet"
 	"go.uber.org/atomic"
-	"math"
-	"net"
-	"time"
-	_ "unsafe" // Imported for compiler directives.
 )
 
 // StopShowingEntity stops showing a world.Entity to the Session. It will be completely invisible until a call to
@@ -491,36 +492,6 @@ func (s *Session) SetHeldSlot(slot int) error {
 	return nil
 }
 
-// UpdateHeldSlot updates the held slot of the Session to the slot passed. It also verifies that the item in that slot
-// matches an expected item stack.
-func (s *Session) UpdateHeldSlot(slot int, expected item.Stack) error {
-	// The slot that the player might have selected must be within the hotbar: The held item cannot be in a
-	// different place in the inventory.
-	if slot > 8 {
-		return fmt.Errorf("new held slot exceeds hotbar range 0-8: slot is %v", slot)
-	}
-	if s.heldSlot.Swap(uint32(slot)) == uint32(slot) {
-		// Old slot was the same as new slot, so don't do anything.
-		return nil
-	}
-	// The user swapped changed held slots so stop using item right away.
-	s.c.ReleaseItem()
-
-	clientSideItem := expected
-	actual, _ := s.inv.Item(slot)
-
-	// The item the client claims to have must be identical to the one we have registered server-side.
-	if !clientSideItem.Equal(actual) {
-		// Only ever debug these as they are frequent and expected to happen whenever client and server get
-		// out of sync.
-		s.log.Debugf("failed processing packet from %v (%v): failed changing held slot: client-side item must be identical to server-side item, but got differences: client: %v vs server: %v", s.conn.RemoteAddr(), s.c.Name(), clientSideItem, actual)
-	}
-	for _, viewer := range s.c.World().Viewers(s.c.Position()) {
-		viewer.ViewEntityItems(s.c)
-	}
-	return nil
-}
-
 // stackFromItem converts an item.Stack to its network ItemStack representation.
 func stackFromItem(it item.Stack) protocol.ItemStack {
 	if it.Empty() {