Fix SetSlotPacket

src/main/java/net/minestom/server/inventory/Inventory.java

@@ -304,11 +304,13 @@ public class Inventory implements InventoryModifier, InventoryClickHandler, View
         if (!isViewer(player))
             return;
 
-        SetSlotPacket setSlotPacket = new SetSlotPacket();
+        final ItemStack currentCursorItem = cursorPlayersItem.get(player);
-        setSlotPacket.windowId = -1;
+        final boolean similar = currentCursorItem != null && currentCursorItem.isSimilar(cursorItem);
-        setSlotPacket.slot = -1;
+
-        setSlotPacket.itemStack = cursorItem;
+        if (!similar) {
-        player.getPlayerConnection().sendPacket(setSlotPacket);
+            final SetSlotPacket setSlotPacket = SetSlotPacket.createCursorPacket(cursorItem);
+            player.getPlayerConnection().sendPacket(setSlotPacket);
+        }
 
         this.cursorPlayersItem.put(player, cursorItem);
     }

src/main/java/net/minestom/server/inventory/PlayerInventory.java

@@ -221,7 +221,8 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
      * @param slot the slot to refresh
      */
     public void refreshSlot(short slot) {
-        sendSlotRefresh((short) convertToPacketSlot(slot), getItemStack(slot));
+        final int packetSlot = convertToPacketSlot(slot);
+        sendSlotRefresh((short) packetSlot, getItemStack(slot));
     }
 
     /**
@@ -240,12 +241,13 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
      * @param cursorItem the new cursor item
      */
     public void setCursorItem(@NotNull ItemStack cursorItem) {
+        final boolean similar = this.cursorItem.isSimilar(cursorItem);
         this.cursorItem = cursorItem;
-        SetSlotPacket setSlotPacket = new SetSlotPacket();
+
-        setSlotPacket.windowId = -1;
+        if (!similar) {
-        setSlotPacket.slot = -1;
+            final SetSlotPacket setSlotPacket = SetSlotPacket.createCursorPacket(cursorItem);
-        setSlotPacket.itemStack = cursorItem;
+            player.getPlayerConnection().sendPacket(setSlotPacket);
-        player.getPlayerConnection().sendPacket(setSlotPacket);
+        }
     }
 
     /**
@@ -340,7 +342,7 @@ public class PlayerInventory implements InventoryModifier, InventoryClickHandler
      */
     protected void sendSlotRefresh(short slot, ItemStack itemStack) {
         SetSlotPacket setSlotPacket = new SetSlotPacket();
-        setSlotPacket.windowId = (byte) (MathUtils.isBetween(slot, 35, INVENTORY_SIZE) ? 0 : -2);
+        setSlotPacket.windowId = 0;
         setSlotPacket.slot = slot;
         setSlotPacket.itemStack = itemStack;
         player.getPlayerConnection().sendPacket(setSlotPacket);

src/main/java/net/minestom/server/listener/WindowListener.java

@@ -4,12 +4,9 @@ import net.minestom.server.entity.Player;
 import net.minestom.server.event.inventory.InventoryCloseEvent;
 import net.minestom.server.inventory.Inventory;
 import net.minestom.server.inventory.InventoryClickHandler;
-import net.minestom.server.inventory.PlayerInventory;
-import net.minestom.server.item.ItemStack;
 import net.minestom.server.network.packet.client.play.ClientClickWindowPacket;
 import net.minestom.server.network.packet.client.play.ClientCloseWindow;
 import net.minestom.server.network.packet.client.play.ClientWindowConfirmationPacket;
-import net.minestom.server.network.packet.server.play.SetSlotPacket;
 import net.minestom.server.network.packet.server.play.WindowConfirmationPacket;
 
 public class WindowListener {
@@ -80,8 +77,6 @@ public class WindowListener {
                 break;
         }
 
-        refreshCursorItem(player, inventory);
-
         WindowConfirmationPacket windowConfirmationPacket = new WindowConfirmationPacket();
         windowConfirmationPacket.windowId = windowId;
         windowConfirmationPacket.actionNumber = actionNumber;
@@ -90,33 +85,6 @@ public class WindowListener {
         player.getPlayerConnection().sendPacket(windowConfirmationPacket);
     }
 
-    /**
-     * @param player    the player to refresh the cursor item
-     * @param inventory the player open inventory, null if not any (could be player inventory)
-     */
-    private static void refreshCursorItem(Player player, Inventory inventory) {
-        PlayerInventory playerInventory = player.getInventory();
-
-        ItemStack cursorItem;
-        if (inventory != null) {
-            cursorItem = inventory.getCursorItem(player);
-        } else {
-            cursorItem = playerInventory.getCursorItem();
-        }
-
-        // Error occurred while retrieving the cursor item, stop here
-        if (cursorItem == null) {
-            return;
-        }
-
-        SetSlotPacket setSlotPacket = new SetSlotPacket();
-        setSlotPacket.windowId = -1;
-        setSlotPacket.slot = -1;
-        setSlotPacket.itemStack = cursorItem;
-
-        player.getPlayerConnection().sendPacket(setSlotPacket);
-    }
-
     public static void closeWindowListener(ClientCloseWindow packet, Player player) {
         // if windowId == 0 then it is player's inventory, meaning that they hadn't been any open inventory packet
         InventoryCloseEvent inventoryCloseEvent = new InventoryCloseEvent(player, player.getOpenInventory());

src/main/java/net/minestom/server/network/packet/server/play/SetSlotPacket.java

@@ -23,4 +23,19 @@ public class SetSlotPacket implements ServerPacket {
     public int getId() {
         return ServerPacketIdentifier.SET_SLOT;
     }
+
+    /**
+     * Returns a {@link SetSlotPacket} used to change a player cursor item.
+     *
+     * @param cursorItem the cursor item
+     * @return a set slot packet to change a player cursor item
+     */
+    @NotNull
+    public static SetSlotPacket createCursorPacket(@NotNull ItemStack cursorItem) {
+        SetSlotPacket setSlotPacket = new SetSlotPacket();
+        setSlotPacket.windowId = -1;
+        setSlotPacket.slot = -1;
+        setSlotPacket.itemStack = cursorItem;
+        return setSlotPacket;
+    }
 }