Improve plugin compatibility

internal/v1_21_R1/src/main/java/com/lishid/openinv/internal/v1_21_R1/container/OpenInventoryMenu.java

@@ -13,23 +13,27 @@
 import org.bukkit.craftbukkit.v1_21_R1.inventory.CraftInventoryView;
 import org.bukkit.craftbukkit.v1_21_R1.inventory.CraftItemStack;
 import org.bukkit.event.inventory.InventoryType;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.InventoryView;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 public class OpenInventoryMenu extends OpenContainerMenu {
 
   private final OpenInventory inventory;
   private final ServerPlayer viewer;
   private final int topSize;
   private final int offset;
+  private final boolean ownInv;
   private CraftInventoryView bukkitEntity;
 
   protected OpenInventoryMenu(OpenInventory inventory, ServerPlayer viewer, int i) {
     super(getMenuType(inventory, viewer), i);
     this.inventory = inventory;
     this.viewer = viewer;
+    ownInv = inventory.getOwnerHandle().equals(viewer);
 
     int upperRows;
-    boolean ownInv = inventory.getOwnerHandle().equals(viewer);
     if (ownInv) {
       // Disallow duplicate access to own main inventory contents.
       offset = viewer.getInventory().items.size();
@@ -144,7 +148,14 @@ private static MenuType<?> getMenuType(OpenInventory inventory, ServerPlayer vie
   @Override
   public CraftInventoryView getBukkitView() {
     if (bukkitEntity == null) {
-      bukkitEntity = new CraftInventoryView(viewer.getBukkitEntity(), inventory.getBukkitInventory(), this) {
+      org.bukkit.inventory.Inventory bukkitInventory;
+      if (ownInv) {
+        bukkitInventory = new OpenPlayerInventorySelf(inventory, offset);
+      } else {
+        bukkitInventory = inventory.getBukkitInventory();
+      }
+
+      bukkitEntity = new CraftInventoryView(viewer.getBukkitEntity(), bukkitInventory, this) {
         @Override
         public org.bukkit.inventory.ItemStack getItem(int index) {
           if (index < 0) {
@@ -160,6 +171,36 @@ public boolean isInTop(int rawSlot) {
           return rawSlot < topSize;
         }
 
+        @Override
+        public @Nullable Inventory getInventory(int rawSlot) {
+          if (rawSlot < 0) {
+            return super.getInventory(rawSlot);
+          }
+          if (rawSlot > topSize) {
+            return super.getInventory(offset + rawSlot);
+          }
+          Slot slot = slots.get(rawSlot);
+          if (slot.isFake()) {
+            return null;
+          }
+          return getTopInventory();
+        }
+
+        @Override
+        public int convertSlot(int rawSlot) {
+          if (rawSlot < 0) {
+            return rawSlot;
+          }
+          if (rawSlot < topSize) {
+            Slot slot = slots.get(rawSlot);
+            if (slot.isFake()) {
+              return InventoryView.OUTSIDE;
+            }
+            return rawSlot;
+          }
+          return super.convertSlot(offset + rawSlot);
+        }
+
         @Override
         public @NotNull InventoryType.SlotType getSlotType(int slot) {
           if (slot < 0) {
@@ -170,6 +211,11 @@ public boolean isInTop(int rawSlot) {
           }
           return inventory.getSlotType(offset + slot);
         }
+
+        @Override
+        public int countSlots() {
+          return topSize + getBottomInventory().getSize();
+        }
       };
     }
     return bukkitEntity;

internal/v1_21_R1/src/main/java/com/lishid/openinv/internal/v1_21_R1/container/OpenPlayerInventorySelf.java

@@ -0,0 +1,25 @@
+package com.lishid.openinv.internal.v1_21_R1.container;
+
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
+
+public class OpenPlayerInventorySelf extends OpenPlayerInventory {
+
+  private final int offset;
+
+  public OpenPlayerInventorySelf(@NotNull OpenInventory inventory, int offset) {
+    super(inventory);
+    this.offset = offset;
+  }
+
+  @Override
+  public ItemStack getItem(int index) {
+    return super.getItem(offset + index);
+  }
+
+  @Override
+  public void setItem(int index, ItemStack item) {
+    super.setItem(offset + index, item);
+  }
+
+}