Bump version to 5.2.0 for release

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/automerge_dependabot.yml

@@ -15,7 +15,7 @@ jobs:
       # Note: this is directly from GitHub's example for using data from a triggering workflow:
       # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#using-data-from-the-triggering-workflow
       - name: 'Download artifact'
-        uses: actions/github-script@v7
+        uses: actions/github-script@v8
         with:
           script: |
             let allArtifacts = await github.rest.actions.listWorkflowRunArtifacts({

.github/workflows/ci.yml

@@ -15,9 +15,9 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
-      - uses: actions/setup-java@v4
+      - uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
           java-version: '21'
@@ -33,7 +33,7 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-buildtools-
 
-      - uses: gradle/actions/setup-gradle@v4
+      - uses: gradle/actions/setup-gradle@v5
 
       - name: Build with Gradle
         run: ./gradlew clean build
@@ -41,7 +41,7 @@ jobs:
       # Upload artifacts
       - name: Upload Distributable Jar
         id: upload-final
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: dist
           path: ./dist/*

.github/workflows/draft_release.yml

@@ -13,21 +13,21 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Download build
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: dist
           path: dist
 
       - name: Create Release
         id: create-release
-        uses: softprops/action-gh-release@v2.3.2
+        uses: softprops/action-gh-release@v2.5.0
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           name: OpenInv ${{ env.VERSIONED_NAME }}
           body: |-
             ## Supported server versions
-            **Paper:** TODO VERSION, 1.21.4, 1.21.3, 1.21.1
+            **Paper:** TODO VERSION, 1.21.8, 1.21.7, 1.21.6, 1.21.5, 1.21.4, 1.21.3, 1.21.1  
             **Spigot:** TODO VERSION
             
             TODO HELLO HUMAN, PRESS THE GENERATE CHANGELOG BUTTON PLEASE.

.github/workflows/external_release.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/pull_request.yml

@@ -16,7 +16,7 @@ jobs:
         run: |
           mkdir -p ./pr
           echo ${{ github.event.number }} > ./pr/pr_number
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v5
         with:
           name: pr_number
           path: pr/

.github/workflows/resource_pack_ci.yml

@@ -13,11 +13,11 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Build resource pack
         id: upload-resource-pack
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: openinv-legibility-pack
           path: ./resource-pack/openinv-legibility-pack/

api/src/main/java/com/lishid/openinv/IOpenInv.java

@@ -138,14 +138,21 @@ public interface IOpenInv {
       boolean online
   ) throws InstantiationException;
 
+  /**
+   * @deprecated Use {@link #openInventory(Player, ISpecialInventory, boolean)}
+   */
+  @Deprecated(forRemoval = true, since = "5.2.0")
+  @Nullable InventoryView openInventory(@NotNull Player player, @NotNull ISpecialInventory inventory);
+
   /**
    * Open an {@link ISpecialInventory} for a {@link Player}.
    *
    * @param player the viewer
    * @param inventory the inventory to open
+   * @param viewOnly whether the inventory should be view-only
    * @return the resulting {@link InventoryView}
    */
-  @Nullable InventoryView openInventory(@NotNull Player player, @NotNull ISpecialInventory inventory);
+  @Nullable InventoryView openInventory(@NotNull Player player, @NotNull ISpecialInventory inventory, boolean viewOnly);
 
   /**
    * Check if a {@link Player} is currently loaded by OpenInv.

common/src/main/java/com/lishid/openinv/util/Permissions.java

@@ -42,6 +42,9 @@ public enum Permissions {
   ACCESS_CROSSWORLD("access.crossworld"),
   ACCESS_OFFLINE("access.offline"),
   ACCESS_ONLINE("access.online"),
+  ACCESS_EQUAL_EDIT("access.equal.edit"),
+  ACCESS_EQUAL_VIEW("access.equal.view"),
+  ACCESS_EQUAL_DENY("access.equal.deny"),
 
   SPECTATE_CLICK("spectate.click"),
 

gradle.properties

@@ -1,6 +1,6 @@
 # Project meta
 group=com.lishid.openinv
-version=5.1.13
+version=5.2.0
 description=A Bukkit plugin for opening normally-inaccessible inventories.
 
 # Gradle configuration

gradle/libs.versions.toml

@@ -2,11 +2,11 @@
 spigotapi = "1.21.5-R0.1-SNAPSHOT"
 specialsource = "1.11.5"
 planarwrappers = "3.3.0"
-annotations = "26.0.2"
+annotations = "26.0.2-1"
 paperweight = "2.0.0-beta.17"
-shadow = "8.3.8"
+shadow = "9.2.2"
 folia-scheduler-wrapper = "v0.0.3"
-errorprone-core = "2.39.0"
+errorprone-core = "2.45.0"
 errorprone-gradle = "4.2.0"
 slf4j = "2.0.17"
 

internal/common/build.gradle.kts

@@ -33,7 +33,7 @@ dependencies {
   implementation(project(":openinvapi"))
   implementation(project(":openinvcommon"))
 
-  paperweight.paperDevBundle("1.21.8-R0.1-SNAPSHOT")
+  paperweight.paperDevBundle("1.21.11-R0.1-SNAPSHOT")
 }
 
 val spigot = tasks.register<ShadowJar>("spigotRelocations") {

internal/common/src/main/java/com/lishid/openinv/internal/common/container/BaseOpenInventory.java

@@ -0,0 +1,335 @@
+package com.lishid.openinv.internal.common.container;
+
+import com.lishid.openinv.internal.ISpecialPlayerInventory;
+import com.lishid.openinv.internal.InternalOwned;
+import com.lishid.openinv.internal.common.container.bukkit.OpenPlayerInventory;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
+import com.lishid.openinv.internal.common.container.menu.OpenInventoryMenu;
+import com.lishid.openinv.internal.common.container.slot.Content;
+import com.lishid.openinv.internal.common.container.slot.ContentCrafting;
+import com.lishid.openinv.internal.common.container.slot.ContentCraftingResult;
+import com.lishid.openinv.internal.common.container.slot.ContentCursor;
+import com.lishid.openinv.internal.common.container.slot.ContentDrop;
+import com.lishid.openinv.internal.common.container.slot.ContentEquipment;
+import com.lishid.openinv.internal.common.container.slot.ContentList;
+import com.lishid.openinv.internal.common.container.slot.ContentOffHand;
+import com.lishid.openinv.internal.common.container.slot.ContentViewOnly;
+import com.lishid.openinv.internal.common.container.slot.SlotViewOnly;
+import com.lishid.openinv.internal.common.container.slot.placeholder.Placeholders;
+import com.lishid.openinv.internal.common.player.PlayerManager;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import net.minecraft.core.NonNullList;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Container;
+import net.minecraft.world.entity.EquipmentSlot;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.entity.CraftHumanEntity;
+import org.bukkit.craftbukkit.inventory.CraftInventory;
+import org.bukkit.entity.HumanEntity;
+import org.bukkit.event.inventory.InventoryType;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+
+public abstract class BaseOpenInventory implements Container, InternalOwned<ServerPlayer>, ISpecialPlayerInventory {
+
+  protected final List<Content> slots;
+  private final int size;
+  protected ServerPlayer owner;
+  private int maxStackSize = 99;
+  protected CraftInventory bukkitEntity;
+  public List<HumanEntity> transaction = new ArrayList<>();
+
+  public BaseOpenInventory(@NotNull org.bukkit.entity.Player bukkitPlayer) {
+    owner = PlayerManager.getHandle(bukkitPlayer);
+
+    // Get total size, rounding up to nearest 9 for client compatibility.
+    int rawSize = owner.getInventory().getContainerSize() + owner.inventoryMenu.getCraftSlots().getContainerSize() + 1;
+    size = ((int) Math.ceil(rawSize / 9.0)) * 9;
+
+    slots = NonNullList.withSize(size, new ContentViewOnly(owner));
+    setupSlots();
+  }
+
+  protected void setupSlots() {
+    // Top of inventory: Regular contents.
+    int nextIndex = addMainInventory();
+
+    // If inventory is expected size, we can arrange slots to be pretty.
+    Inventory ownerInv = owner.getInventory();
+    if (ownerInv.getNonEquipmentItems().size() == 36
+        && owner.inventoryMenu.getCraftSlots().getContainerSize() == 4
+        && (Inventory.EQUIPMENT_SLOT_MAPPING.size() == 5 || Inventory.EQUIPMENT_SLOT_MAPPING.size() == 7)) {
+      // Armor slots: Bottom left.
+      addArmor(36);
+      // Off-hand: Below chestplate.
+      addOffHand(46);
+      // Drop slot: Bottom right.
+      slots.set(53, new ContentDrop(owner));
+      // Cursor slot: Above drop.
+      slots.set(44, new ContentCursor(owner));
+
+      // Crafting is displayed in the bottom right corner.
+      // As we're using the pretty view, this is a 3x2.
+      addCrafting(41, true);
+      return;
+    }
+
+    // Otherwise we'll just add elements linearly.
+    nextIndex = addArmor(nextIndex);
+    nextIndex = addOffHand(nextIndex);
+    nextIndex = addCrafting(nextIndex, false);
+    slots.set(nextIndex, new ContentCursor(owner));
+    // Drop slot last.
+    slots.set(slots.size() - 1, new ContentDrop(owner));
+  }
+
+  private int addMainInventory() {
+    int listSize = owner.getInventory().getNonEquipmentItems().size();
+    // Hotbar slots are 0-8. We want those to appear on the bottom of the inventory like a normal player inventory,
+    // so everything else needs to move up a row.
+    int hotbarDiff = listSize - 9;
+    for (int localIndex = 0; localIndex < listSize; ++localIndex) {
+      InventoryType.SlotType type;
+      int invIndex;
+      if (localIndex < hotbarDiff) {
+        invIndex = localIndex + 9;
+        type = InventoryType.SlotType.CONTAINER;
+      } else {
+        type = InventoryType.SlotType.QUICKBAR;
+        invIndex = localIndex - hotbarDiff;
+      }
+
+      slots.set(
+          localIndex,
+          new ContentList(owner, invIndex, type) {
+            @Override
+            public void setHolder(@NotNull ServerPlayer holder) {
+              items = holder.getInventory().getNonEquipmentItems();
+            }
+          }
+      );
+    }
+    return listSize;
+  }
+
+  private int addArmor(int startIndex) {
+    // Armor slots go bottom to top; boots are first and helmet is last.
+    // Since we have to display horizontally due to space restrictions,
+    // making the left side the "top" is more user-friendly.
+    EquipmentSlot[] sorted = Inventory.EQUIPMENT_SLOT_MAPPING.int2ObjectEntrySet()
+        .stream()
+        .sorted(Comparator.comparingInt(Int2ObjectMap.Entry::getIntKey))
+        .map(Map.Entry::getValue)
+        .toArray(EquipmentSlot[]::new);
+    int localIndex = 0;
+    for (int i = sorted.length - 1; i >= 0; --i) {
+      // Skip off-hand, handled separately. Also skip non-player slots.
+      if (sorted[i].getType() != EquipmentSlot.Type.HUMANOID_ARMOR) {
+        continue;
+      }
+
+      slots.set(startIndex + localIndex, new ContentEquipment(owner, sorted[i]));
+      ++localIndex;
+    }
+
+    return startIndex + localIndex;
+  }
+
+  private int addOffHand(int startIndex) {
+    // No off-hand?
+    if (!Inventory.EQUIPMENT_SLOT_MAPPING.containsValue(EquipmentSlot.OFFHAND)) {
+      return startIndex;
+    }
+
+    slots.set(startIndex, new ContentOffHand(owner));
+    return startIndex + 1;
+  }
+
+  private int addCrafting(int startIndex, boolean pretty) {
+    int listSize = owner.inventoryMenu.getCraftSlots().getContents().size();
+    pretty &= listSize == 4;
+
+    for (int localIndex = 0; localIndex < listSize; ++localIndex) {
+      // Pretty display is a 2x2 rather than linear.
+      // If index is in top row, grid is not 2x2, or pretty is disabled, just use current index.
+      // Otherwise, subtract 2 and add 9 to start in the same position on the next row.
+      int modIndex = startIndex + (localIndex < 2 || !pretty ? localIndex : localIndex + 7);
+
+      slots.set(modIndex, new ContentCrafting(owner, localIndex));
+    }
+
+    if (pretty) {
+      slots.set(startIndex + 2, new ContentViewOnly(owner) {
+            @Override
+            public Slot asSlot(Container container, int slot, int x, int y) {
+              return new SlotViewOnly(container, slot, x, y) {
+                @Override
+                public ItemStack getOrDefault() {
+                  return Placeholders.craftingOutput;
+                }
+              };
+            }
+          }
+      );
+      slots.set(startIndex + 11, getCraftingResult(owner));
+    }
+
+    return startIndex + listSize;
+  }
+
+  protected Content getCraftingResult(@NotNull ServerPlayer serverPlayer) {
+    return new ContentCraftingResult(serverPlayer);
+  }
+
+  public Slot getMenuSlot(int index, int x, int y) {
+    return slots.get(index).asSlot(this, index, x, y);
+  }
+
+  public InventoryType.SlotType getSlotType(int index) {
+    return slots.get(index).getSlotType();
+  }
+
+  public abstract Component getTitle(ServerPlayer player, @Nullable OpenChestMenu<?> menu);
+
+  @Override
+  public ServerPlayer getOwnerHandle() {
+    return owner;
+  }
+
+  @Override
+  public @NotNull org.bukkit.inventory.Inventory getBukkitInventory() {
+    if (bukkitEntity == null) {
+      bukkitEntity = new OpenPlayerInventory(this);
+    }
+    return bukkitEntity;
+  }
+
+  @Override
+  public void setPlayerOnline(@NotNull org.bukkit.entity.Player player) {
+    ServerPlayer newOwner = PlayerManager.getHandle(player);
+    // Only transfer regular inventory - crafting and cursor slots are transient.
+    newOwner.getInventory().replaceWith(owner.getInventory());
+    owner = newOwner;
+    // Update slots to point to new inventory.
+    slots.forEach(slot -> slot.setHolder(newOwner));
+  }
+
+  @Override
+  public boolean isInUse() {
+    return !transaction.isEmpty();
+  }
+
+  @Override
+  public @NotNull org.bukkit.entity.Player getPlayer() {
+    return getOwner();
+  }
+
+  @Override
+  public int getContainerSize() {
+    return size;
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return slots.stream().map(Content::get).allMatch(ItemStack::isEmpty);
+  }
+
+  @Override
+  public @NotNull ItemStack getItem(int index) {
+    return slots.get(index).get();
+  }
+
+  @Override
+  public @NotNull ItemStack removeItem(int index, int amount) {
+    return slots.get(index).removePartial(amount);
+  }
+
+  @Override
+  public @NotNull ItemStack removeItemNoUpdate(int index) {
+    return slots.get(index).remove();
+  }
+
+  @Override
+  public void setItem(int index, @NotNull ItemStack itemStack) {
+    slots.get(index).set(itemStack);
+  }
+
+  @Override
+  public int getMaxStackSize() {
+    return maxStackSize;
+  }
+
+  @Override
+  public void setMaxStackSize(int maxStackSize) {
+    this.maxStackSize = maxStackSize;
+  }
+
+  @Override
+  public void setChanged() {
+  }
+
+  @Override
+  public boolean stillValid(@NotNull Player player) {
+    return true;
+  }
+
+  @Override
+  public @NotNull List<ItemStack> getContents() {
+    NonNullList<ItemStack> contents = NonNullList.withSize(getContainerSize(), ItemStack.EMPTY);
+    for (int i = 0; i < getContainerSize(); ++i) {
+      contents.set(i, getItem(i));
+    }
+    return contents;
+  }
+
+  @Override
+  public void onOpen(@NotNull CraftHumanEntity viewer) {
+    transaction.add(viewer);
+  }
+
+  @Override
+  public void onClose(@NotNull CraftHumanEntity viewer) {
+    transaction.remove(viewer);
+  }
+
+  @Override
+  public @NotNull List<HumanEntity> getViewers() {
+    return transaction;
+  }
+
+  @Override
+  public @NotNull org.bukkit.entity.Player getOwner() {
+    return owner.getBukkitEntity();
+  }
+
+  @Override
+  public Location getLocation() {
+    return owner.getBukkitEntity().getLocation();
+  }
+
+  @Override
+  public void clearContent() {
+    owner.getInventory().clearContent();
+    owner.inventoryMenu.getCraftSlots().clearContent();
+    owner.inventoryMenu.slotsChanged(owner.inventoryMenu.getCraftSlots());
+    owner.containerMenu.setCarried(ItemStack.EMPTY);
+  }
+
+  public @Nullable OpenChestMenu<?> createMenu(Player player, int i, boolean viewOnly) {
+    if (player instanceof ServerPlayer serverPlayer) {
+      return new OpenInventoryMenu(this, serverPlayer, i, viewOnly);
+    }
+    return null;
+  }
+
+}

internal/common/src/main/java/com/lishid/openinv/internal/common/container/OpenEnderChest.java

@@ -2,16 +2,17 @@ package com.lishid.openinv.internal.common.container;
 
 import com.lishid.openinv.internal.ISpecialEnderChest;
 import com.lishid.openinv.internal.InternalOwned;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
 import com.lishid.openinv.internal.common.container.menu.OpenEnderChestMenu;
 import com.lishid.openinv.internal.common.player.PlayerManager;
 import net.minecraft.core.NonNullList;
 import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.MutableComponent;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.Container;
 import net.minecraft.world.ContainerHelper;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.entity.player.StackedItemContents;
-import net.minecraft.world.inventory.AbstractContainerMenu;
 import net.minecraft.world.inventory.StackedContentsCompatible;
 import net.minecraft.world.item.ItemStack;
 import org.bukkit.Location;
@@ -177,13 +178,20 @@ public class OpenEnderChest implements Container, StackedContentsCompatible, Int
     }
   }
 
-  public Component getTitle() {
-    return Component.translatableWithFallback("openinv.container.enderchest.prefix", "", owner.getName())
+  public Component getTitle(@Nullable OpenChestMenu<?> menu) {
+    MutableComponent component;
+    if (menu != null && menu.isViewOnly()) {
+      component = Component.translatableWithFallback("openinv.container.enderchest.viewonly", "[RO] ");
+    } else {
+      component = Component.translatableWithFallback("openinv.container.enderchest.editable", "");
+    }
+    return component
+        .append(Component.translatableWithFallback("openinv.container.enderchest.prefix", "", owner.getName()))
         .append(Component.translatable("container.enderchest"))
         .append(Component.translatableWithFallback("openinv.container.enderchest.suffix", " - %s", owner.getName()));
   }
 
-  public @Nullable AbstractContainerMenu createMenu(Player player, int i, boolean viewOnly) {
+  public @Nullable OpenChestMenu<?> createMenu(Player player, int i, boolean viewOnly) {
     if (player instanceof ServerPlayer serverPlayer) {
       return new OpenEnderChestMenu(this, serverPlayer, i, viewOnly);
     }

internal/common/src/main/java/com/lishid/openinv/internal/common/container/OpenInventory.java

@@ -1,223 +1,44 @@
 package com.lishid.openinv.internal.common.container;
 
-import com.lishid.openinv.internal.ISpecialPlayerInventory;
-import com.lishid.openinv.internal.InternalOwned;
-import com.lishid.openinv.internal.common.container.bukkit.OpenPlayerInventory;
-import com.lishid.openinv.internal.common.container.menu.OpenInventoryMenu;
-import com.lishid.openinv.internal.common.container.slot.Content;
-import com.lishid.openinv.internal.common.container.slot.ContentCrafting;
-import com.lishid.openinv.internal.common.container.slot.ContentCraftingResult;
-import com.lishid.openinv.internal.common.container.slot.ContentCursor;
-import com.lishid.openinv.internal.common.container.slot.ContentDrop;
-import com.lishid.openinv.internal.common.container.slot.ContentEquipment;
-import com.lishid.openinv.internal.common.container.slot.ContentList;
-import com.lishid.openinv.internal.common.container.slot.ContentOffHand;
-import com.lishid.openinv.internal.common.container.slot.ContentViewOnly;
-import com.lishid.openinv.internal.common.container.slot.SlotViewOnly;
-import com.lishid.openinv.internal.common.container.slot.placeholder.Placeholders;
-import com.lishid.openinv.internal.common.player.PlayerManager;
-import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
 import net.minecraft.ChatFormatting;
-import net.minecraft.core.NonNullList;
 import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.FontDescription;
 import net.minecraft.network.chat.MutableComponent;
-import net.minecraft.resources.ResourceLocation;
+import net.minecraft.resources.Identifier;
 import net.minecraft.server.level.ServerPlayer;
-import net.minecraft.world.Container;
-import net.minecraft.world.entity.EquipmentSlot;
-import net.minecraft.world.entity.player.Inventory;
-import net.minecraft.world.entity.player.Player;
-import net.minecraft.world.inventory.AbstractContainerMenu;
-import net.minecraft.world.inventory.Slot;
-import net.minecraft.world.item.ItemStack;
-import org.bukkit.Location;
-import org.bukkit.craftbukkit.entity.CraftHumanEntity;
-import org.bukkit.craftbukkit.inventory.CraftInventory;
-import org.bukkit.entity.HumanEntity;
-import org.bukkit.event.inventory.InventoryType;
+import org.bukkit.entity.Player;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.ArrayList;
-import java.util.Comparator;
-import java.util.List;
-import java.util.Map;
+public class OpenInventory extends BaseOpenInventory {
 
-public class OpenInventory implements Container, InternalOwned<ServerPlayer>, ISpecialPlayerInventory {
-
-  protected final List<Content> slots;
-  private final int size;
-  protected ServerPlayer owner;
-  private int maxStackSize = 99;
-  protected CraftInventory bukkitEntity;
-  public List<HumanEntity> transaction = new ArrayList<>();
-
-  public OpenInventory(@NotNull org.bukkit.entity.Player bukkitPlayer) {
-    owner = PlayerManager.getHandle(bukkitPlayer);
-
-    // Get total size, rounding up to nearest 9 for client compatibility.
-    int rawSize = owner.getInventory().getContainerSize() + owner.inventoryMenu.getCraftSlots().getContainerSize() + 1;
-    size = ((int) Math.ceil(rawSize / 9.0)) * 9;
-
-    slots = NonNullList.withSize(size, new ContentViewOnly(owner));
-    setupSlots();
+  public OpenInventory(@NotNull Player bukkitPlayer) {
+    super(bukkitPlayer);
   }
 
-  protected void setupSlots() {
-    // Top of inventory: Regular contents.
-    int nextIndex = addMainInventory();
-
-    // If inventory is expected size, we can arrange slots to be pretty.
-    Inventory ownerInv = owner.getInventory();
-    if (ownerInv.getNonEquipmentItems().size() == 36
-        && owner.inventoryMenu.getCraftSlots().getContainerSize() == 4
-        && (Inventory.EQUIPMENT_SLOT_MAPPING.size() == 5 || Inventory.EQUIPMENT_SLOT_MAPPING.size() == 7)) {
-      // Armor slots: Bottom left.
-      addArmor(36);
-      // Off-hand: Below chestplate.
-      addOffHand(46);
-      // Drop slot: Bottom right.
-      slots.set(53, new ContentDrop(owner));
-      // Cursor slot: Above drop.
-      slots.set(44, new ContentCursor(owner));
-
-      // Crafting is displayed in the bottom right corner.
-      // As we're using the pretty view, this is a 3x2.
-      addCrafting(41, true);
-      return;
-    }
-
-    // Otherwise we'll just add elements linearly.
-    nextIndex = addArmor(nextIndex);
-    nextIndex = addOffHand(nextIndex);
-    nextIndex = addCrafting(nextIndex, false);
-    slots.set(nextIndex, new ContentCursor(owner));
-    // Drop slot last.
-    slots.set(slots.size() - 1, new ContentDrop(owner));
-  }
-
-  private int addMainInventory() {
-    int listSize = owner.getInventory().getNonEquipmentItems().size();
-    // Hotbar slots are 0-8. We want those to appear on the bottom of the inventory like a normal player inventory,
-    // so everything else needs to move up a row.
-    int hotbarDiff = listSize - 9;
-    for (int localIndex = 0; localIndex < listSize; ++localIndex) {
-      InventoryType.SlotType type;
-      int invIndex;
-      if (localIndex < hotbarDiff) {
-        invIndex = localIndex + 9;
-        type = InventoryType.SlotType.CONTAINER;
-      } else {
-        type = InventoryType.SlotType.QUICKBAR;
-        invIndex = localIndex - hotbarDiff;
-      }
-
-      slots.set(
-          localIndex,
-          new ContentList(owner, invIndex, type) {
-            @Override
-            public void setHolder(@NotNull ServerPlayer holder) {
-              items = holder.getInventory().getNonEquipmentItems();
-            }
-          }
-      );
-    }
-    return listSize;
-  }
-
-  private int addArmor(int startIndex) {
-    // Armor slots go bottom to top; boots are first and helmet is last.
-    // Since we have to display horizontally due to space restrictions,
-    // making the left side the "top" is more user-friendly.
-    EquipmentSlot[] sorted = Inventory.EQUIPMENT_SLOT_MAPPING.int2ObjectEntrySet()
-        .stream()
-        .sorted(Comparator.comparingInt(Int2ObjectMap.Entry::getIntKey))
-        .map(Map.Entry::getValue)
-        .toArray(EquipmentSlot[]::new);
-    int localIndex = 0;
-    for (int i = sorted.length - 1; i >= 0; --i) {
-      // Skip off-hand, handled separately. Also skip non-player slots.
-      if (sorted[i].getType() != EquipmentSlot.Type.HUMANOID_ARMOR) {
-        continue;
-      }
-
-      slots.set(startIndex + localIndex, new ContentEquipment(owner, sorted[i]));
-      ++localIndex;
-    }
-
-    return startIndex + localIndex;
-  }
-
-  private int addOffHand(int startIndex) {
-    // No off-hand?
-    if (!Inventory.EQUIPMENT_SLOT_MAPPING.containsValue(EquipmentSlot.OFFHAND)) {
-      return startIndex;
-    }
-
-    slots.set(startIndex, new ContentOffHand(owner));
-    return startIndex + 1;
-  }
-
-  private int addCrafting(int startIndex, boolean pretty) {
-    int listSize = owner.inventoryMenu.getCraftSlots().getContents().size();
-    pretty &= listSize == 4;
-
-    for (int localIndex = 0; localIndex < listSize; ++localIndex) {
-      // Pretty display is a 2x2 rather than linear.
-      // If index is in top row, grid is not 2x2, or pretty is disabled, just use current index.
-      // Otherwise, subtract 2 and add 9 to start in the same position on the next row.
-      int modIndex = startIndex + (localIndex < 2 || !pretty ? localIndex : localIndex + 7);
-
-      slots.set(modIndex, new ContentCrafting(owner, localIndex));
-    }
-
-    if (pretty) {
-      slots.set(startIndex + 2, new ContentViewOnly(owner) {
-            @Override
-            public Slot asSlot(Container container, int slot, int x, int y) {
-              return new SlotViewOnly(container, slot, x, y) {
-                @Override
-                public ItemStack getOrDefault() {
-                  return Placeholders.craftingOutput;
-                }
-              };
-            }
-          }
-      );
-      slots.set(startIndex + 11, getCraftingResult(owner));
-    }
-
-    return startIndex + listSize;
-  }
-
-  protected Content getCraftingResult(@NotNull ServerPlayer serverPlayer) {
-    return new ContentCraftingResult(serverPlayer);
-  }
-
-  public Slot getMenuSlot(int index, int x, int y) {
-    return slots.get(index).asSlot(this, index, x, y);
-  }
-
-  public InventoryType.SlotType getSlotType(int index) {
-    return slots.get(index).getSlotType();
-  }
-
-  public @NotNull Component getTitle(@Nullable ServerPlayer viewer) {
+  @Override
+  public @NotNull Component getTitle(@Nullable ServerPlayer viewer, @Nullable OpenChestMenu<?> menu) {
     MutableComponent component = Component.empty();
     // Prefix for use with custom bitmap image fonts.
     if (owner.equals(viewer)) {
       component.append(
           Component.translatableWithFallback("openinv.container.inventory.self", "")
               .withStyle(style -> style
-                  .withFont(ResourceLocation.parse("openinv:font/inventory"))
+                  .withFont(new FontDescription.Resource(Identifier.parse("openinv:font/inventory")))
                   .withColor(ChatFormatting.WHITE)));
     } else {
       component.append(
           Component.translatableWithFallback("openinv.container.inventory.other", "")
               .withStyle(style -> style
-                  .withFont(ResourceLocation.parse("openinv:font/inventory"))
+                  .withFont(new FontDescription.Resource(Identifier.parse("openinv:font/inventory")))
                   .withColor(ChatFormatting.WHITE)));
     }
+    if (menu != null && menu.isViewOnly()) {
+      component.append(Component.translatableWithFallback("openinv.container.inventory.viewonly", "[RO] "));
+    } else {
+      component.append(Component.translatableWithFallback("openinv.container.inventory.editable", ""));
+    }
     // Normal title: "Inventory - OwnerName"
     component.append(Component.translatableWithFallback("openinv.container.inventory.prefix", "", owner.getName()))
         .append(Component.translatable("container.inventory"))
@@ -225,135 +46,4 @@ public class OpenInventory implements Container, InternalOwned<ServerPlayer>, IS
     return component;
   }
 
-  @Override
-  public ServerPlayer getOwnerHandle() {
-    return owner;
-  }
-
-  @Override
-  public @NotNull org.bukkit.inventory.Inventory getBukkitInventory() {
-    if (bukkitEntity == null) {
-      bukkitEntity = new OpenPlayerInventory(this);
-    }
-    return bukkitEntity;
-  }
-
-  @Override
-  public void setPlayerOnline(@NotNull org.bukkit.entity.Player player) {
-    ServerPlayer newOwner = PlayerManager.getHandle(player);
-    // Only transfer regular inventory - crafting and cursor slots are transient.
-    newOwner.getInventory().replaceWith(owner.getInventory());
-    owner = newOwner;
-    // Update slots to point to new inventory.
-    slots.forEach(slot -> slot.setHolder(newOwner));
-  }
-
-  @Override
-  public boolean isInUse() {
-    return !transaction.isEmpty();
-  }
-
-  @Override
-  public @NotNull org.bukkit.entity.Player getPlayer() {
-    return getOwner();
-  }
-
-  @Override
-  public int getContainerSize() {
-    return size;
-  }
-
-  @Override
-  public boolean isEmpty() {
-    return slots.stream().map(Content::get).allMatch(ItemStack::isEmpty);
-  }
-
-  @Override
-  public @NotNull ItemStack getItem(int index) {
-    return slots.get(index).get();
-  }
-
-  @Override
-  public @NotNull ItemStack removeItem(int index, int amount) {
-    return slots.get(index).removePartial(amount);
-  }
-
-  @Override
-  public @NotNull ItemStack removeItemNoUpdate(int index) {
-    return slots.get(index).remove();
-  }
-
-  @Override
-  public void setItem(int index, @NotNull ItemStack itemStack) {
-    slots.get(index).set(itemStack);
-  }
-
-  @Override
-  public int getMaxStackSize() {
-    return maxStackSize;
-  }
-
-  @Override
-  public void setMaxStackSize(int maxStackSize) {
-    this.maxStackSize = maxStackSize;
-  }
-
-  @Override
-  public void setChanged() {
-  }
-
-  @Override
-  public boolean stillValid(@NotNull Player player) {
-    return true;
-  }
-
-  @Override
-  public @NotNull List<ItemStack> getContents() {
-    NonNullList<ItemStack> contents = NonNullList.withSize(getContainerSize(), ItemStack.EMPTY);
-    for (int i = 0; i < getContainerSize(); ++i) {
-      contents.set(i, getItem(i));
-    }
-    return contents;
-  }
-
-  @Override
-  public void onOpen(@NotNull CraftHumanEntity viewer) {
-    transaction.add(viewer);
-  }
-
-  @Override
-  public void onClose(@NotNull CraftHumanEntity viewer) {
-    transaction.remove(viewer);
-  }
-
-  @Override
-  public @NotNull List<HumanEntity> getViewers() {
-    return transaction;
-  }
-
-  @Override
-  public @NotNull org.bukkit.entity.Player getOwner() {
-    return owner.getBukkitEntity();
-  }
-
-  @Override
-  public Location getLocation() {
-    return owner.getBukkitEntity().getLocation();
-  }
-
-  @Override
-  public void clearContent() {
-    owner.getInventory().clearContent();
-    owner.inventoryMenu.getCraftSlots().clearContent();
-    owner.inventoryMenu.slotsChanged(owner.inventoryMenu.getCraftSlots());
-    owner.containerMenu.setCarried(ItemStack.EMPTY);
-  }
-
-  public @Nullable AbstractContainerMenu createMenu(Player player, int i, boolean viewOnly) {
-    if (player instanceof ServerPlayer serverPlayer) {
-      return new OpenInventoryMenu(this, serverPlayer, i, viewOnly);
-    }
-    return null;
-  }
-
 }

internal/common/src/main/java/com/lishid/openinv/internal/common/container/bukkit/OpenPlayerInventory.java

@@ -1,7 +1,7 @@
 package com.lishid.openinv.internal.common.container.bukkit;
 
 import com.google.common.base.Preconditions;
-import com.lishid.openinv.internal.common.container.OpenInventory;
+import com.lishid.openinv.internal.common.container.BaseOpenInventory;
 import net.minecraft.core.NonNullList;
 import net.minecraft.world.entity.EquipmentSlot;
 import net.minecraft.world.entity.player.Inventory;
@@ -18,13 +18,13 @@ import java.util.List;
 
 public class OpenPlayerInventory extends CraftInventory implements PlayerInventory {
 
-  public OpenPlayerInventory(@NotNull OpenInventory inventory) {
+  public OpenPlayerInventory(@NotNull BaseOpenInventory inventory) {
     super(inventory);
   }
 
   @Override
-  public @NotNull OpenInventory getInventory() {
-    return (OpenInventory) super.getInventory();
+  public @NotNull BaseOpenInventory getInventory() {
+    return (BaseOpenInventory) super.getInventory();
   }
 
   @Override

internal/common/src/main/java/com/lishid/openinv/internal/common/container/bukkit/OpenPlayerInventorySelf.java

@@ -1,6 +1,6 @@
 package com.lishid.openinv.internal.common.container.bukkit;
 
-import com.lishid.openinv.internal.common.container.OpenInventory;
+import com.lishid.openinv.internal.common.container.BaseOpenInventory;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 
@@ -8,7 +8,7 @@ public class OpenPlayerInventorySelf extends OpenPlayerInventory {
 
   private final int offset;
 
-  public OpenPlayerInventorySelf(@NotNull OpenInventory inventory, int offset) {
+  public OpenPlayerInventorySelf(@NotNull BaseOpenInventory inventory, int offset) {
     super(inventory);
     this.offset = offset;
   }

internal/common/src/main/java/com/lishid/openinv/internal/common/container/menu/OpenChestMenu.java

@@ -1,26 +1,16 @@
 package com.lishid.openinv.internal.common.container.menu;
 
-import com.google.common.base.Suppliers;
 import com.lishid.openinv.internal.ISpecialInventory;
 import com.lishid.openinv.internal.InternalOwned;
 import com.lishid.openinv.internal.common.container.bukkit.OpenDummyInventory;
-import com.lishid.openinv.internal.common.container.slot.SlotPlaceholder;
 import com.lishid.openinv.internal.common.container.slot.SlotViewOnly;
-import it.unimi.dsi.fastutil.ints.IntArrayList;
-import it.unimi.dsi.fastutil.ints.IntList;
-import net.minecraft.network.HashedStack;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.Container;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.inventory.AbstractContainerMenu;
 import net.minecraft.world.inventory.ChestMenu;
 import net.minecraft.world.inventory.ClickType;
-import net.minecraft.world.inventory.ContainerData;
-import net.minecraft.world.inventory.ContainerListener;
-import net.minecraft.world.inventory.ContainerSynchronizer;
-import net.minecraft.world.inventory.DataSlot;
 import net.minecraft.world.inventory.MenuType;
-import net.minecraft.world.inventory.RemoteSlot;
 import net.minecraft.world.inventory.Slot;
 import net.minecraft.world.item.ItemStack;
 import org.bukkit.craftbukkit.inventory.CraftInventoryView;
@@ -30,14 +20,9 @@ import org.bukkit.inventory.InventoryView;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.ArrayList;
-import java.util.List;
-import java.util.function.Supplier;
-
 /**
- * An extension of {@link AbstractContainerMenu} that supports {@link SlotPlaceholder placeholders}.
+ * An extension of {@link AbstractContainerMenu} storing and managing data common to all special inventories.
  */
-@SuppressWarnings("HidingField") // Revisit when removing 1.21.4 support
 public abstract class OpenChestMenu<T extends Container & ISpecialInventory & InternalOwned<ServerPlayer>>
     extends AbstractContainerMenu {
 
@@ -49,13 +34,6 @@ public abstract class OpenChestMenu<T extends Container & ISpecialInventory & In
   protected final boolean ownContainer;
   protected final int topSize;
   private CraftInventoryView<OpenChestMenu<T>, Inventory> bukkitEntity;
-  // Syncher fields
-  protected @Nullable ContainerSynchronizer synchronizer;
-  protected final List<DataSlot> dataSlots = new ArrayList<>();
-  protected final IntList remoteDataSlots = new IntArrayList();
-  protected final List<ContainerListener> containerListeners = new ArrayList<>();
-  private RemoteSlot remoteCarried = RemoteSlot.PLACEHOLDER;
-  protected boolean suppressRemoteUpdates;
 
   protected OpenChestMenu(
       @NotNull MenuType<ChestMenu> type,
@@ -125,6 +103,7 @@ public abstract class OpenChestMenu<T extends Container & ISpecialInventory & In
     };
   }
 
+
   protected void preSlotSetup() {
   }
 
@@ -136,6 +115,9 @@ public abstract class OpenChestMenu<T extends Container & ISpecialInventory & In
     return slot;
   }
 
+  public boolean isViewOnly() {
+    return viewOnly;
+  }
 
   @Override
   public final @NotNull CraftInventoryView<OpenChestMenu<T>, Inventory> getBukkitView() {
@@ -303,188 +285,4 @@ public abstract class OpenChestMenu<T extends Container & ISpecialInventory & In
     return true;
   }
 
-  // Overrides from here on are purely to modify the sync process to send placeholder items.
-  @Override
-  protected @NotNull Slot addSlot(@NotNull Slot slot) {
-    slot.index = this.slots.size();
-    this.slots.add(slot);
-    this.lastSlots.add(ItemStack.EMPTY);
-    this.remoteSlots.add(this.synchronizer != null ? this.synchronizer.createSlot() : RemoteSlot.PLACEHOLDER);
-    return slot;
-  }
-
-  @Override
-  protected @NotNull DataSlot addDataSlot(@NotNull DataSlot dataSlot) {
-    this.dataSlots.add(dataSlot);
-    this.remoteDataSlots.add(0);
-    return dataSlot;
-  }
-
-  @Override
-  protected void addDataSlots(ContainerData containerData) {
-    for (int i = 0; i < containerData.getCount(); i++) {
-      this.addDataSlot(DataSlot.forContainer(containerData, i));
-    }
-  }
-
-  @Override
-  public void addSlotListener(@NotNull ContainerListener containerListener) {
-    if (!this.containerListeners.contains(containerListener)) {
-      this.containerListeners.add(containerListener);
-      this.broadcastChanges();
-    }
-  }
-
-  @Override
-  public void setSynchronizer(@NotNull ContainerSynchronizer containerSynchronizer) {
-    this.synchronizer = containerSynchronizer;
-    this.remoteCarried = synchronizer.createSlot();
-    this.remoteSlots.replaceAll(slot -> synchronizer.createSlot());
-    this.sendAllDataToRemote();
-  }
-
-  @Override
-  public void sendAllDataToRemote() {
-    List<ItemStack> contentsCopy = new ArrayList<>();
-    for (int index = 0; index < slots.size(); ++index) {
-      Slot slot = slots.get(index);
-      ItemStack itemStack = slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem();
-      contentsCopy.add(itemStack);
-      this.remoteSlots.get(index).force(itemStack);
-    }
-
-    remoteCarried.force(getCarried());
-
-    for (int index = 0; index < this.dataSlots.size(); ++index) {
-      this.remoteDataSlots.set(index, this.dataSlots.get(index).get());
-    }
-
-    if (this.synchronizer != null) {
-      this.synchronizer.sendInitialData(this, contentsCopy, this.getCarried().copy(), this.remoteDataSlots.toIntArray());
-    }
-  }
-
-  @Override
-  public void broadcastCarriedItem() {
-    ItemStack carried = this.getCarried();
-    this.remoteCarried.force(carried);
-    if (this.synchronizer != null) {
-      this.synchronizer.sendCarriedChange(this, carried.copy());
-    }
-  }
-
-  @Override
-  public void removeSlotListener(@NotNull ContainerListener containerListener) {
-    this.containerListeners.remove(containerListener);
-  }
-
-  @Override
-  public void broadcastChanges() {
-    for (int index = 0; index < this.slots.size(); ++index) {
-      Slot slot = this.slots.get(index);
-      ItemStack itemstack = slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem();
-      Supplier<ItemStack> supplier = Suppliers.memoize(itemstack::copy);
-      this.triggerSlotListeners(index, itemstack, supplier);
-      this.synchronizeSlotToRemote(index, itemstack, supplier);
-    }
-
-    this.synchronizeCarriedToRemote();
-
-    for (int index = 0; index < this.dataSlots.size(); ++index) {
-      DataSlot dataSlot = this.dataSlots.get(index);
-      int j = dataSlot.get();
-      if (dataSlot.checkAndClearUpdateFlag()) {
-        this.updateDataSlotListeners(index, j);
-      }
-
-      this.synchronizeDataSlotToRemote(index, j);
-    }
-  }
-
-  @Override
-  public void broadcastFullState() {
-    for (int index = 0; index < this.slots.size(); ++index) {
-      ItemStack itemstack = this.slots.get(index).getItem();
-      this.triggerSlotListeners(index, itemstack, itemstack::copy);
-    }
-
-    for (int index = 0; index < this.dataSlots.size(); ++index) {
-      DataSlot containerproperty = this.dataSlots.get(index);
-      if (containerproperty.checkAndClearUpdateFlag()) {
-        this.updateDataSlotListeners(index, containerproperty.get());
-      }
-    }
-
-    this.sendAllDataToRemote();
-  }
-
-  private void updateDataSlotListeners(int i, int j) {
-    for (ContainerListener containerListener : this.containerListeners) {
-      containerListener.dataChanged(this, i, j);
-    }
-  }
-
-  private void triggerSlotListeners(int index, ItemStack itemStack, Supplier<ItemStack> supplier) {
-    ItemStack itemStack1 = this.lastSlots.get(index);
-    if (!ItemStack.matches(itemStack1, itemStack)) {
-      ItemStack itemStack2 = supplier.get();
-      this.lastSlots.set(index, itemStack2);
-
-      for (ContainerListener containerListener : this.containerListeners) {
-        containerListener.slotChanged(this, index, itemStack2);
-      }
-    }
-  }
-
-  private void synchronizeSlotToRemote(int i, ItemStack itemStack, Supplier<ItemStack> supplier) {
-    if (!this.suppressRemoteUpdates) {
-      RemoteSlot slot = this.remoteSlots.get(i);
-      if (!slot.matches(itemStack)) {
-        slot.force(itemStack);
-        if (this.synchronizer != null) {
-          this.synchronizer.sendSlotChange(this, i, supplier.get());
-        }
-      }
-    }
-  }
-
-  private void synchronizeDataSlotToRemote(int index, int value) {
-    if (!this.suppressRemoteUpdates) {
-      int existing = this.remoteDataSlots.getInt(index);
-      if (existing != value) {
-        this.remoteDataSlots.set(index, value);
-        if (this.synchronizer != null) {
-          this.synchronizer.sendDataChange(this, index, value);
-        }
-      }
-    }
-  }
-
-  private void synchronizeCarriedToRemote() {
-    if (!this.suppressRemoteUpdates) {
-      ItemStack carried = this.getCarried();
-      if (!this.remoteCarried.matches(carried)) {
-        this.remoteCarried.force(carried);
-        if (this.synchronizer != null) {
-          this.synchronizer.sendCarriedChange(this, carried.copy());
-        }
-      }
-    }
-  }
-
-  @Override
-  public void setRemoteCarried(@NotNull HashedStack stack) {
-    this.remoteCarried.receive(stack);
-  }
-
-  @Override
-  public void suppressRemoteUpdates() {
-    this.suppressRemoteUpdates = true;
-  }
-
-  @Override
-  public void resumeRemoteUpdates() {
-    this.suppressRemoteUpdates = false;
-  }
-
 }

internal/common/src/main/java/com/lishid/openinv/internal/common/container/menu/OpenEnderChestMenu.java

@@ -7,7 +7,7 @@ import net.minecraft.world.inventory.Slot;
 import net.minecraft.world.item.ItemStack;
 import org.jetbrains.annotations.NotNull;
 
-public class OpenEnderChestMenu extends OpenChestMenu<OpenEnderChest> {
+public class OpenEnderChestMenu extends OpenSyncMenu<OpenEnderChest> {
 
   public OpenEnderChestMenu(
       @NotNull OpenEnderChest enderChest,

internal/common/src/main/java/com/lishid/openinv/internal/common/container/menu/OpenInventoryMenu.java

@@ -1,7 +1,7 @@
 package com.lishid.openinv.internal.common.container.menu;
 
 import com.google.common.base.Preconditions;
-import com.lishid.openinv.internal.common.container.OpenInventory;
+import com.lishid.openinv.internal.common.container.BaseOpenInventory;
 import com.lishid.openinv.internal.common.container.bukkit.OpenDummyPlayerInventory;
 import com.lishid.openinv.internal.common.container.bukkit.OpenPlayerInventorySelf;
 import com.lishid.openinv.internal.common.container.slot.ContentDrop;
@@ -23,15 +23,15 @@ import org.bukkit.inventory.InventoryView;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-public class OpenInventoryMenu extends OpenChestMenu<OpenInventory> {
+public class OpenInventoryMenu extends OpenSyncMenu<BaseOpenInventory> {
 
   private int offset;
 
-  public OpenInventoryMenu(OpenInventory inventory, ServerPlayer viewer, int i, boolean viewOnly) {
+  public OpenInventoryMenu(BaseOpenInventory inventory, ServerPlayer viewer, int i, boolean viewOnly) {
     super(getMenuType(inventory, viewer), i, inventory, viewer, viewOnly);
   }
 
-  private static MenuType<ChestMenu> getMenuType(OpenInventory inventory, ServerPlayer viewer) {
+  private static MenuType<ChestMenu> getMenuType(BaseOpenInventory inventory, ServerPlayer viewer) {
     int size = inventory.getContainerSize();
     // Disallow duplicate access to own main inventory contents.
     if (inventory.getOwnerHandle().equals(viewer)) {
@@ -99,7 +99,7 @@ public class OpenInventoryMenu extends OpenChestMenu<OpenInventory> {
   }
 
   @Override
-  protected @NotNull CraftInventoryView<OpenChestMenu<OpenInventory>, Inventory> createBukkitEntity() {
+  protected @NotNull CraftInventoryView<OpenChestMenu<BaseOpenInventory>, Inventory> createBukkitEntity() {
     org.bukkit.inventory.Inventory bukkitInventory;
     if (viewOnly) {
       bukkitInventory = new OpenDummyPlayerInventory(container);

internal/common/src/main/java/com/lishid/openinv/internal/common/container/menu/OpenSyncMenu.java

@@ -0,0 +1,251 @@
+package com.lishid.openinv.internal.common.container.menu;
+
+import com.google.common.base.Suppliers;
+import com.lishid.openinv.internal.ISpecialInventory;
+import com.lishid.openinv.internal.InternalOwned;
+import com.lishid.openinv.internal.common.container.slot.SlotPlaceholder;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntList;
+import net.minecraft.network.HashedStack;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Container;
+import net.minecraft.world.inventory.ChestMenu;
+import net.minecraft.world.inventory.ContainerData;
+import net.minecraft.world.inventory.ContainerListener;
+import net.minecraft.world.inventory.ContainerSynchronizer;
+import net.minecraft.world.inventory.DataSlot;
+import net.minecraft.world.inventory.MenuType;
+import net.minecraft.world.inventory.RemoteSlot;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Supplier;
+
+/**
+ * An extension of {@link OpenChestMenu} that supports {@link SlotPlaceholder placeholders}.
+ */
+@SuppressWarnings("HidingField") // Revisit when removing 1.21.4 support
+public abstract class OpenSyncMenu<T extends Container & ISpecialInventory & InternalOwned<ServerPlayer>>
+    extends OpenChestMenu<T> {
+
+  // Syncher fields
+  protected @Nullable ContainerSynchronizer synchronizer;
+  protected final List<DataSlot> dataSlots = new ArrayList<>();
+  protected final IntList remoteDataSlots = new IntArrayList();
+  protected final List<ContainerListener> containerListeners = new ArrayList<>();
+  private RemoteSlot remoteCarried = RemoteSlot.PLACEHOLDER;
+  protected boolean suppressRemoteUpdates;
+
+  protected OpenSyncMenu(
+      @NotNull MenuType<ChestMenu> type,
+      int containerCounter,
+      @NotNull T container,
+      @NotNull ServerPlayer viewer,
+      boolean viewOnly
+  ) {
+    super(type, containerCounter, container, viewer, viewOnly);
+  }
+
+  // Overrides from here on are purely to modify the sync process to send placeholder items.
+  @Override
+  protected @NotNull Slot addSlot(@NotNull Slot slot) {
+    slot.index = this.slots.size();
+    this.slots.add(slot);
+    this.lastSlots.add(ItemStack.EMPTY);
+    this.remoteSlots.add(this.synchronizer != null ? this.synchronizer.createSlot() : RemoteSlot.PLACEHOLDER);
+    return slot;
+  }
+
+  @Override
+  protected @NotNull DataSlot addDataSlot(@NotNull DataSlot dataSlot) {
+    this.dataSlots.add(dataSlot);
+    this.remoteDataSlots.add(0);
+    return dataSlot;
+  }
+
+  @Override
+  protected void addDataSlots(ContainerData containerData) {
+    for (int i = 0; i < containerData.getCount(); i++) {
+      this.addDataSlot(DataSlot.forContainer(containerData, i));
+    }
+  }
+
+  @Override
+  public void addSlotListener(@NotNull ContainerListener containerListener) {
+    if (!this.containerListeners.contains(containerListener)) {
+      this.containerListeners.add(containerListener);
+      this.broadcastChanges();
+    }
+  }
+
+  @Override
+  public void setSynchronizer(@NotNull ContainerSynchronizer containerSynchronizer) {
+    this.synchronizer = containerSynchronizer;
+    this.remoteCarried = synchronizer.createSlot();
+    this.remoteSlots.replaceAll(slot -> synchronizer.createSlot());
+    this.sendAllDataToRemote();
+  }
+
+  @Override
+  public void sendAllDataToRemote() {
+    List<ItemStack> contentsCopy = new ArrayList<>();
+    for (int index = 0; index < slots.size(); ++index) {
+      Slot slot = slots.get(index);
+      ItemStack itemStack = slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem();
+      contentsCopy.add(itemStack);
+      this.remoteSlots.get(index).force(itemStack);
+    }
+
+    remoteCarried.force(getCarried());
+
+    for (int index = 0; index < this.dataSlots.size(); ++index) {
+      this.remoteDataSlots.set(index, this.dataSlots.get(index).get());
+    }
+
+    if (this.synchronizer != null) {
+      this.synchronizer.sendInitialData(this, contentsCopy, this.getCarried().copy(), this.remoteDataSlots.toIntArray());
+    }
+  }
+
+  @Override
+  public void forceSlot(@NotNull Container container, int slot) {
+    int slotsIndex = this.findSlot(container, slot).orElse(-1);
+    if (slotsIndex != -1) {
+      ItemStack item = this.slots.get(slotsIndex).getItem();
+      this.remoteSlots.get(slotsIndex).force(item);
+      if (this.synchronizer != null) {
+        this.synchronizer.sendSlotChange(this, slotsIndex, item.copy());
+      }
+    }
+  }
+
+  @Override
+  public void broadcastCarriedItem() {
+    ItemStack carried = this.getCarried();
+    this.remoteCarried.force(carried);
+    if (this.synchronizer != null) {
+      this.synchronizer.sendCarriedChange(this, carried.copy());
+    }
+  }
+
+  @Override
+  public void removeSlotListener(@NotNull ContainerListener containerListener) {
+    this.containerListeners.remove(containerListener);
+  }
+
+  @Override
+  public void broadcastChanges() {
+    for (int index = 0; index < this.slots.size(); ++index) {
+      Slot slot = this.slots.get(index);
+      ItemStack itemstack = slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem();
+      Supplier<ItemStack> supplier = Suppliers.memoize(itemstack::copy);
+      this.triggerSlotListeners(index, itemstack, supplier);
+      this.synchronizeSlotToRemote(index, itemstack, supplier);
+    }
+
+    this.synchronizeCarriedToRemote();
+
+    for (int index = 0; index < this.dataSlots.size(); ++index) {
+      DataSlot dataSlot = this.dataSlots.get(index);
+      int j = dataSlot.get();
+      if (dataSlot.checkAndClearUpdateFlag()) {
+        this.updateDataSlotListeners(index, j);
+      }
+
+      this.synchronizeDataSlotToRemote(index, j);
+    }
+  }
+
+  @Override
+  public void broadcastFullState() {
+    for (int index = 0; index < this.slots.size(); ++index) {
+      ItemStack itemstack = this.slots.get(index).getItem();
+      this.triggerSlotListeners(index, itemstack, itemstack::copy);
+    }
+
+    for (int index = 0; index < this.dataSlots.size(); ++index) {
+      DataSlot containerproperty = this.dataSlots.get(index);
+      if (containerproperty.checkAndClearUpdateFlag()) {
+        this.updateDataSlotListeners(index, containerproperty.get());
+      }
+    }
+
+    this.sendAllDataToRemote();
+  }
+
+  private void updateDataSlotListeners(int i, int j) {
+    for (ContainerListener containerListener : this.containerListeners) {
+      containerListener.dataChanged(this, i, j);
+    }
+  }
+
+  @Override
+  public void triggerSlotListeners(int index, @NotNull ItemStack itemStack, @NotNull Supplier<ItemStack> supplier) {
+    ItemStack itemStack1 = this.lastSlots.get(index);
+    if (!ItemStack.matches(itemStack1, itemStack)) {
+      ItemStack itemStack2 = supplier.get();
+      this.lastSlots.set(index, itemStack2);
+
+      for (ContainerListener containerListener : this.containerListeners) {
+        containerListener.slotChanged(this, index, itemStack2);
+      }
+    }
+  }
+
+  @Override
+  public void synchronizeSlotToRemote(int i, @NotNull ItemStack itemStack, @NotNull Supplier<ItemStack> supplier) {
+    if (!this.suppressRemoteUpdates) {
+      RemoteSlot slot = this.remoteSlots.get(i);
+      if (!slot.matches(itemStack)) {
+        slot.force(itemStack);
+        if (this.synchronizer != null) {
+          this.synchronizer.sendSlotChange(this, i, supplier.get());
+        }
+      }
+    }
+  }
+
+  private void synchronizeDataSlotToRemote(int index, int value) {
+    if (!this.suppressRemoteUpdates) {
+      int existing = this.remoteDataSlots.getInt(index);
+      if (existing != value) {
+        this.remoteDataSlots.set(index, value);
+        if (this.synchronizer != null) {
+          this.synchronizer.sendDataChange(this, index, value);
+        }
+      }
+    }
+  }
+
+  private void synchronizeCarriedToRemote() {
+    if (!this.suppressRemoteUpdates) {
+      ItemStack carried = this.getCarried();
+      if (!this.remoteCarried.matches(carried)) {
+        this.remoteCarried.force(carried);
+        if (this.synchronizer != null) {
+          this.synchronizer.sendCarriedChange(this, carried.copy());
+        }
+      }
+    }
+  }
+
+  @Override
+  public void setRemoteCarried(@NotNull HashedStack stack) {
+    this.remoteCarried.receive(stack);
+  }
+
+  @Override
+  public void suppressRemoteUpdates() {
+    this.suppressRemoteUpdates = true;
+  }
+
+  @Override
+  public void resumeRemoteUpdates() {
+    this.suppressRemoteUpdates = false;
+  }
+
+}

internal/common/src/main/java/com/lishid/openinv/internal/common/player/BaseOpenPlayer.java

@@ -1,10 +1,13 @@
 package com.lishid.openinv.internal.common.player;
 
+import com.lishid.openinv.event.OpenEvents;
 import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
 import net.minecraft.nbt.NumericTag;
 import net.minecraft.nbt.Tag;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.server.network.ServerGamePacketListenerImpl;
+import net.minecraft.world.level.storage.PlayerDataStorage;
 import net.minecraft.world.level.storage.ValueOutput;
 import org.bukkit.craftbukkit.CraftServer;
 import org.bukkit.craftbukkit.entity.CraftPlayer;
@@ -13,14 +16,18 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.Unmodifiable;
 
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.Set;
 
 public abstract class BaseOpenPlayer extends CraftPlayer {
 
   /**
-   * List of tags to always reset when saving.
+   * List of tags to always reset when saving. These are items that do not get written
+   * if unset or empty, resulting in older values not being clobbered appropriately.
    *
-   * @see net.minecraft.world.entity.Entity#saveWithoutId(ValueOutput)
+   * @see net.minecraft.world.entity.Entity#saveWithoutId(ValueOutput, boolean, boolean, boolean)
    * @see net.minecraft.server.level.ServerPlayer#addAdditionalSaveData(ValueOutput)
    * @see net.minecraft.world.entity.player.Player#addAdditionalSaveData(ValueOutput)
    * @see net.minecraft.world.entity.LivingEntity#addAdditionalSaveData(ValueOutput)
@@ -36,11 +43,12 @@ public abstract class BaseOpenPlayer extends CraftPlayer {
       "TicksFrozen",
       "HasVisualFire",
       "Tags",
+      "data",
       "Passengers",
       // ServerPlayer#addAdditionalSaveData(CompoundTag)
       // Intentional omissions to prevent mount loss: Attach, Entity, and RootVehicle
-      "warden_spawn_tracker",
-      "entered_nether_pos", // Replaces enteredNetherPosition
+      "warden_spawn_tracker", // No longer needed as of 1.21.11
+      "entered_nether_pos", // Replaces enteredNetherPosition as of 1.21.6
       "enteredNetherPosition",
       "respawn", // Replaces SpawnXyz fields as of 1.21.6
       "SpawnX",
@@ -51,9 +59,9 @@ public abstract class BaseOpenPlayer extends CraftPlayer {
       "SpawnDimension",
       "raid_omen_position",
       "ender_pearls",
-      // Player#addAdditionalSaveData(CompoundTag)
       "ShoulderEntityLeft",
       "ShoulderEntityRight",
+      // Player#addAdditionalSaveData(CompoundTag)
       "LastDeathLocation",
       "current_explosion_impact_pos",
       // LivingEntity#addAdditionalSaveData(CompoundTag)
@@ -84,7 +92,40 @@ public abstract class BaseOpenPlayer extends CraftPlayer {
   }
 
   @Override
-  public abstract void saveData();
+  public void saveData() {
+    if (OpenEvents.saveCancelled(this)) {
+      return;
+    }
+
+    trySave(this.getHandle());
+  }
+
+  protected abstract void trySave(ServerPlayer player);
+
+  protected void saveSafe(
+      @NotNull ServerPlayer player,
+      @Nullable CompoundTag oldData,
+      @NotNull CompoundTag playerData,
+      @NotNull PlayerDataStorage worldNbtStorage
+  ) throws IOException {
+    // Revert certain special data values when offline.
+    revertSpecialValues(playerData, oldData);
+
+    Path playerDataDir = worldNbtStorage.getPlayerDir().toPath();
+    Path tempFile = Files.createTempFile(playerDataDir, player.getStringUUID() + "-", ".dat");
+    NbtIo.writeCompressed(playerData, tempFile);
+    Path dataFile = playerDataDir.resolve(player.getStringUUID() + ".dat");
+    Path backupFile = playerDataDir.resolve(player.getStringUUID() + ".dat_old");
+    safeReplaceFile(dataFile, tempFile, backupFile);
+  }
+
+  protected void safeReplaceFile(
+      @NotNull Path dataFile,
+      @NotNull Path tempFile,
+      @NotNull Path backupFile
+  ) {
+    net.minecraft.util.Util.safeReplaceFile(dataFile, tempFile, backupFile);
+  }
 
   @Contract("null -> new")
   protected @NotNull CompoundTag getWritableTag(@Nullable CompoundTag oldData) {
@@ -105,7 +146,11 @@ public abstract class BaseOpenPlayer extends CraftPlayer {
     return oldData;
   }
 
-  protected void revertSpecialValues(@NotNull CompoundTag newData, @NotNull CompoundTag oldData) {
+  protected void revertSpecialValues(@NotNull CompoundTag newData, @Nullable CompoundTag oldData) {
+    if (oldData == null) {
+      return;
+    }
+
     // Revert automatic updates to play timestamps.
     copyValue(oldData, newData, "bukkit", "lastPlayed", NumericTag.class);
     copyValue(oldData, newData, "Paper", "LastSeen", NumericTag.class);
@@ -152,12 +197,14 @@ public abstract class BaseOpenPlayer extends CraftPlayer {
       @Nullable T data
   ) {
     if (data == null) {
-      container.remove(key);
+      remove(container, key);
     } else {
       container.put(key, data);
     }
   }
 
+  protected abstract void remove(@NotNull CompoundTag tag, @NotNull String key);
+
   public static boolean isConnected(@Nullable ServerGamePacketListenerImpl connection) {
     return connection != null && !connection.isDisconnected();
   }

internal/common/src/main/java/com/lishid/openinv/internal/common/player/OpenPlayer.java

@@ -1,21 +1,16 @@
 package com.lishid.openinv.internal.common.player;
 
-import com.lishid.openinv.event.OpenEvents;
 import com.mojang.logging.LogUtils;
-import net.minecraft.Util;
 import net.minecraft.nbt.CompoundTag;
-import net.minecraft.nbt.NbtIo;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.util.ProblemReporter;
 import net.minecraft.world.level.storage.PlayerDataStorage;
 import net.minecraft.world.level.storage.TagValueOutput;
 import net.minecraft.world.level.storage.ValueOutput;
 import org.bukkit.craftbukkit.CraftServer;
+import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 
-import java.nio.file.Files;
-import java.nio.file.Path;
-
 public class OpenPlayer extends BaseOpenPlayer {
 
   protected OpenPlayer(
@@ -27,39 +22,29 @@ public class OpenPlayer extends BaseOpenPlayer {
   }
 
   @Override
-  public void saveData() {
-    if (OpenEvents.saveCancelled(this)) {
-      return;
-    }
-
-    ServerPlayer player = this.getHandle();
+  protected void trySave(ServerPlayer player) {
     Logger logger = LogUtils.getLogger();
     // See net.minecraft.world.level.storage.PlayerDataStorage#save(EntityHuman)
     try (ProblemReporter.ScopedCollector scopedCollector = new ProblemReporter.ScopedCollector(player.problemPath(), logger)) {
-      PlayerDataStorage worldNBTStorage = server.getServer().getPlayerList().playerIo;
+      PlayerDataStorage worldNbtStorage = server.getServer().getPlayerList().playerIo;
 
       CompoundTag oldData = isOnline()
           ? null
-          : worldNBTStorage.load(player.getName().getString(), player.getStringUUID(), scopedCollector).orElse(null);
+          : worldNbtStorage.load(player.nameAndId()).orElse(null);
       CompoundTag playerData = getWritableTag(oldData);
 
       ValueOutput valueOutput = TagValueOutput.createWrappingWithContext(scopedCollector, player.registryAccess(), playerData);
       player.saveWithoutId(valueOutput);
 
-      if (oldData != null) {
-        // Revert certain special data values when offline.
-        revertSpecialValues(playerData, oldData);
-      }
-
-      Path playerDataDir = worldNBTStorage.getPlayerDir().toPath();
-      Path tempFile = Files.createTempFile(playerDataDir, player.getStringUUID() + "-", ".dat");
-      NbtIo.writeCompressed(playerData, tempFile);
-      Path dataFile = playerDataDir.resolve(player.getStringUUID() + ".dat");
-      Path backupFile = playerDataDir.resolve(player.getStringUUID() + ".dat_old");
-      Util.safeReplaceFile(dataFile, tempFile, backupFile);
+      saveSafe(player, oldData, playerData, worldNbtStorage);
     } catch (Exception e) {
       LogUtils.getLogger().warn("Failed to save player data for {}: {}", player.getScoreboardName(), e);
     }
   }
 
+  @Override
+  protected void remove(@NotNull CompoundTag tag, @NotNull String key) {
+    tag.remove(key);
+  }
+
 }

internal/common/src/main/java/com/lishid/openinv/internal/common/player/PlayerManager.java

@@ -1,11 +1,13 @@
 package com.lishid.openinv.internal.common.player;
 
 import com.lishid.openinv.internal.ISpecialInventory;
+import com.lishid.openinv.internal.common.container.BaseOpenInventory;
 import com.lishid.openinv.internal.common.container.OpenEnderChest;
-import com.lishid.openinv.internal.common.container.OpenInventory;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
 import com.lishid.openinv.util.JulLoggerAdapter;
 import com.mojang.authlib.GameProfile;
 import io.papermc.paper.adventure.PaperAdventure;
+import net.minecraft.nbt.CompoundTag;
 import net.minecraft.network.chat.Component;
 import net.minecraft.network.protocol.game.ClientboundOpenScreenPacket;
 import net.minecraft.server.MinecraftServer;
@@ -18,6 +20,8 @@ import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.player.ChatVisiblity;
 import net.minecraft.world.inventory.AbstractContainerMenu;
 import net.minecraft.world.level.Level;
+import net.minecraft.world.level.storage.LevelData;
+import net.minecraft.world.level.storage.TagValueInput;
 import net.minecraft.world.level.storage.ValueInput;
 import org.bukkit.Bukkit;
 import org.bukkit.OfflinePlayer;
@@ -143,26 +147,30 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
     // See CraftPlayer#loadData
 
     try (ProblemReporter.ScopedCollector scopedCollector = new ProblemReporter.ScopedCollector(player.problemPath(), new JulLoggerAdapter(logger))) {
-      ValueInput loadedData = server.getPlayerList().playerIo.load(player, scopedCollector).orElse(null);
+      CompoundTag loadedData = server.getPlayerList().playerIo.load(player.nameAndId()).orElse(null);
 
       if (loadedData == null) {
         // Exceptions with loading are logged.
         return false;
       }
 
+      ValueInput valueInput = TagValueInput.create(scopedCollector, player.registryAccess(), loadedData);
+
       // Read basic data into the player.
-      player.load(loadedData);
-      // Game type settings are loaded separately.
-      player.loadGameTypes(loadedData);
+      player.load(valueInput);
 
       // World is not loaded by ServerPlayer#load(CompoundTag) on Paper.
-      parseWorld(server, player, loadedData);
+      parseWorld(server, player, valueInput);
     }
 
     return true;
   }
 
-  private void parseWorld(@NotNull MinecraftServer server, @NotNull ServerPlayer player, @NotNull ValueInput loadedData) {
+  protected void parseWorld(
+      @NotNull MinecraftServer server,
+      @NotNull ServerPlayer player,
+      @NotNull ValueInput loadedData
+  ) {
     // See PlayerList#placeNewPlayer
     World bukkitWorld;
     Optional<Long> msbs = loadedData.getLong("WorldUUIDMost");
@@ -184,7 +192,8 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
     ServerLevel level = server.getLevel(Level.OVERWORLD);
     if (level != null) {
       // Adjust player to default spawn (in keeping with Paper handling) when world not found.
-      player.snapTo(player.adjustSpawnLocation(level, level.getSharedSpawnPos()).getBottomCenter(), level.getSharedSpawnAngle(), 0.0F);
+      LevelData.RespawnData respawnData = level.levelData.getRespawnData();
+      player.snapTo(player.adjustSpawnLocation(level, respawnData.pos()).getBottomCenter(), respawnData.yaw(), 0.0F);
       player.spawnIn(level);
     } else {
       logger.warning("Tried to load player with invalid world when no fallback was available!");
@@ -208,16 +217,7 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
       if (nmsPlayer.getBukkitEntity() instanceof BaseOpenPlayer openPlayer) {
         return openPlayer;
       }
-      MinecraftServer server = nmsPlayer.getServer();
-      if (server == null) {
-        if (!(Bukkit.getServer() instanceof CraftServer craftServer)) {
-          logger.warning(() ->
-              "Unable to inject ServerPlayer, certain player data may be lost when saving! Server is not a CraftServer: "
-                  + Bukkit.getServer().getClass().getName());
-          return player;
-        }
-        server = craftServer.getServer();
-      }
+      MinecraftServer server = nmsPlayer.level().getServer();
       injectPlayer(server, nmsPlayer);
       return nmsPlayer.getBukkitEntity();
     } catch (IllegalAccessException e) {
@@ -242,14 +242,14 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
     }
 
     // See net.minecraft.server.level.ServerPlayer#openMenu(MenuProvider)
-    AbstractContainerMenu menu;
+    OpenChestMenu<?> menu;
     Component title;
-    if (inventory instanceof OpenInventory playerInv) {
+    if (inventory instanceof BaseOpenInventory playerInv) {
       menu = playerInv.createMenu(player, player.nextContainerCounter(), viewOnly);
-      title = playerInv.getTitle(player);
+      title = playerInv.getTitle(player, menu);
     } else if (inventory instanceof OpenEnderChest enderChest) {
       menu = enderChest.createMenu(player, player.nextContainerCounter(), viewOnly);
-      title = enderChest.getTitle();
+      title = enderChest.getTitle(menu);
     } else {
       return null;
     }
@@ -265,10 +265,10 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
     menu.setTitle(title);
 
     var pair = CraftEventFactory.callInventoryOpenEventWithTitle(player, menu);
-    menu = pair.getSecond();
+    AbstractContainerMenu opened = pair.getSecond();
 
     // Menu is null if event is cancelled.
-    if (menu == null) {
+    if (opened == null) {
       return null;
     }
 
@@ -277,11 +277,11 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
       title = PaperAdventure.asVanilla(newTitle);
     }
 
-    player.containerMenu = menu;
-    player.connection.send(new ClientboundOpenScreenPacket(menu.containerId, menu.getType(), title));
-    player.initMenu(menu);
+    player.containerMenu = opened;
+    player.connection.send(new ClientboundOpenScreenPacket(opened.containerId, opened.getType(), title));
+    player.initMenu(opened);
 
-    return menu.getBukkitView();
+    return opened.getBukkitView();
   }
 
 }

internal/paper1_21_1/build.gradle.kts

@@ -21,6 +21,7 @@ dependencies {
   implementation(project(":openinvapi"))
   implementation(project(":openinvcommon"))
   implementation(project(":openinvadaptercommon"))
+  implementation(project(":openinvadapterpaper1_21_8"))
   implementation(project(":openinvadapterpaper1_21_5"))
   implementation(project(":openinvadapterpaper1_21_4"))
   implementation(project(":openinvadapterpaper1_21_3"))

internal/paper1_21_10/build.gradle.kts

@@ -0,0 +1,26 @@
+plugins {
+  `openinv-base`
+  alias(libs.plugins.paperweight)
+}
+
+configurations.all {
+  resolutionStrategy.capabilitiesResolution.withCapability("org.spigotmc:spigot-api") {
+    val paper = candidates.firstOrNull {
+      it.id.let { id ->
+        id is ModuleComponentIdentifier && id.module == "paper-api"
+      }
+    }
+    if (paper != null) {
+      select(paper)
+    }
+    because("module is written for Paper servers")
+  }
+}
+
+dependencies {
+  implementation(project(":openinvapi"))
+  implementation(project(":openinvcommon"))
+  implementation(project(":openinvadaptercommon"))
+
+  paperweight.paperDevBundle("1.21.10-R0.1-SNAPSHOT")
+}

internal/paper1_21_10/src/main/java/com/lishid/openinv/internal/paper1_21_10/InternalAccessor.java

@@ -0,0 +1,31 @@
+package com.lishid.openinv.internal.paper1_21_10;
+
+import com.lishid.openinv.internal.ISpecialPlayerInventory;
+import com.lishid.openinv.internal.paper1_21_10.container.OpenInventory;
+import com.lishid.openinv.internal.paper1_21_10.player.PlayerManager;
+import com.lishid.openinv.util.lang.LanguageManager;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.logging.Logger;
+
+public class InternalAccessor extends com.lishid.openinv.internal.common.InternalAccessor {
+
+  private final @NotNull PlayerManager manager;
+
+  public InternalAccessor(@NotNull Logger logger, @NotNull LanguageManager lang) {
+    super(logger, lang);
+    manager = new PlayerManager(logger);
+  }
+
+  @Override
+  public @NotNull PlayerManager getPlayerManager() {
+    return manager;
+  }
+
+  @Override
+  public @NotNull ISpecialPlayerInventory createPlayerInventory(@NotNull Player player) {
+    return new OpenInventory(player);
+  }
+
+}

internal/paper1_21_10/src/main/java/com/lishid/openinv/internal/paper1_21_10/container/OpenInventory.java

@@ -0,0 +1,50 @@
+package com.lishid.openinv.internal.paper1_21_10.container;
+
+import com.lishid.openinv.internal.common.container.BaseOpenInventory;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
+import net.minecraft.ChatFormatting;
+import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.FontDescription;
+import net.minecraft.network.chat.MutableComponent;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerPlayer;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public class OpenInventory extends BaseOpenInventory {
+
+  public OpenInventory(@NotNull Player bukkitPlayer) {
+    super(bukkitPlayer);
+  }
+
+  @Override
+  public @NotNull Component getTitle(@Nullable ServerPlayer viewer, @Nullable OpenChestMenu<?> menu) {
+    MutableComponent component = Component.empty();
+    // Prefix for use with custom bitmap image fonts.
+    if (owner.equals(viewer)) {
+      component.append(
+          Component.translatableWithFallback("openinv.container.inventory.self", "")
+              .withStyle(style -> style
+                  .withFont(new FontDescription.Resource(ResourceLocation.parse("openinv:font/inventory")))
+                  .withColor(ChatFormatting.WHITE)));
+    } else {
+      component.append(
+          Component.translatableWithFallback("openinv.container.inventory.other", "")
+              .withStyle(style -> style
+                  .withFont(new FontDescription.Resource(ResourceLocation.parse("openinv:font/inventory")))
+                  .withColor(ChatFormatting.WHITE)));
+    }
+    if (menu != null && menu.isViewOnly()) {
+      component.append(Component.translatableWithFallback("openinv.container.inventory.viewonly", "[RO] "));
+    } else {
+      component.append(Component.translatableWithFallback("openinv.container.inventory.editable", ""));
+    }
+    // Normal title: "Inventory - OwnerName"
+    component.append(Component.translatableWithFallback("openinv.container.inventory.prefix", "", owner.getName()))
+        .append(Component.translatable("container.inventory"))
+        .append(Component.translatableWithFallback("openinv.container.inventory.suffix", " - %s", owner.getName()));
+    return component;
+  }
+
+}

internal/paper1_21_10/src/main/java/com/lishid/openinv/internal/paper1_21_10/player/OpenPlayer.java

@@ -0,0 +1,35 @@
+package com.lishid.openinv.internal.paper1_21_10.player;
+
+import com.lishid.openinv.internal.common.player.PlayerManager;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.level.ServerPlayer;
+import org.bukkit.craftbukkit.CraftServer;
+import org.jetbrains.annotations.NotNull;
+
+import java.nio.file.Path;
+
+public class OpenPlayer extends com.lishid.openinv.internal.common.player.OpenPlayer {
+
+  protected OpenPlayer(
+      CraftServer server,
+      ServerPlayer entity,
+      PlayerManager manager
+  ) {
+    super(server, entity, manager);
+  }
+
+  @Override
+  protected void safeReplaceFile(
+      @NotNull Path dataFile,
+      @NotNull Path tempFile,
+      @NotNull Path backupFile
+  ) {
+    net.minecraft.Util.safeReplaceFile(dataFile, tempFile, backupFile);
+  }
+
+  @Override
+  protected void remove(@NotNull CompoundTag tag, @NotNull String key) {
+    tag.remove(key);
+  }
+
+}

internal/paper1_21_10/src/main/java/com/lishid/openinv/internal/paper1_21_10/player/PlayerManager.java

@@ -0,0 +1,26 @@
+package com.lishid.openinv.internal.paper1_21_10.player;
+
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.logging.Logger;
+
+public class PlayerManager extends com.lishid.openinv.internal.common.player.PlayerManager {
+
+  public PlayerManager(@NotNull Logger logger) {
+    super(logger);
+  }
+
+  @Override
+  protected void injectPlayer(@NotNull MinecraftServer server, @NotNull ServerPlayer player) throws IllegalAccessException {
+    if (bukkitEntity == null) {
+      return;
+    }
+
+    bukkitEntity.setAccessible(true);
+
+    bukkitEntity.set(player, new OpenPlayer(server.server, player, this));
+  }
+
+}

internal/paper1_21_3/build.gradle.kts

@@ -21,6 +21,7 @@ dependencies {
   implementation(project(":openinvapi"))
   implementation(project(":openinvcommon"))
   implementation(project(":openinvadaptercommon"))
+  implementation(project(":openinvadapterpaper1_21_8"))
   implementation(project(":openinvadapterpaper1_21_5"))
   implementation(project(":openinvadapterpaper1_21_4"))
 

internal/paper1_21_4/build.gradle.kts

@@ -21,6 +21,7 @@ dependencies {
   implementation(project(":openinvapi"))
   implementation(project(":openinvcommon"))
   implementation(project(":openinvadaptercommon"))
+  implementation(project(":openinvadapterpaper1_21_8"))
   implementation(project(":openinvadapterpaper1_21_5"))
 
   paperweight.paperDevBundle("1.21.4-R0.1-SNAPSHOT")

internal/paper1_21_4/src/main/java/com/lishid/openinv/internal/paper1_21_4/container/OpenEnderChest.java

@@ -14,7 +14,7 @@ public class OpenEnderChest extends com.lishid.openinv.internal.common.container
   }
 
   @Override
-  public @Nullable AbstractContainerMenu createMenu(
+  public @Nullable OpenEnderChestMenu createMenu(
       net.minecraft.world.entity.player.Player player,
       int i,
       boolean viewOnly

internal/paper1_21_4/src/main/java/com/lishid/openinv/internal/paper1_21_4/container/OpenInventory.java

@@ -1,5 +1,6 @@
 package com.lishid.openinv.internal.paper1_21_4.container;
 
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
 import com.lishid.openinv.internal.common.container.slot.ContentCrafting;
 import com.lishid.openinv.internal.common.container.slot.ContentCursor;
 import com.lishid.openinv.internal.common.container.slot.ContentDrop;
@@ -16,14 +17,13 @@ import net.minecraft.world.Container;
 import net.minecraft.world.entity.EquipmentSlot;
 import net.minecraft.world.entity.player.Inventory;
 import net.minecraft.world.entity.player.Player;
-import net.minecraft.world.inventory.AbstractContainerMenu;
 import net.minecraft.world.inventory.Slot;
 import net.minecraft.world.item.ItemStack;
 import org.bukkit.event.inventory.InventoryType;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-public class OpenInventory extends com.lishid.openinv.internal.common.container.OpenInventory {
+public class OpenInventory extends com.lishid.openinv.internal.paper1_21_8.container.OpenInventory {
 
   public OpenInventory(@NotNull org.bukkit.entity.Player bukkitPlayer) {
     super(bukkitPlayer);
@@ -181,7 +181,7 @@ public class OpenInventory extends com.lishid.openinv.internal.common.container.
   }
 
   @Override
-  public @Nullable AbstractContainerMenu createMenu(Player player, int i, boolean viewOnly) {
+  public @Nullable OpenChestMenu<?> createMenu(Player player, int i, boolean viewOnly) {
     if (player instanceof ServerPlayer serverPlayer) {
       return new OpenInventoryMenu(this, serverPlayer, i, viewOnly);
     }

internal/paper1_21_4/src/main/java/com/lishid/openinv/internal/paper1_21_4/container/menu/OpenChestMenu.java

@@ -1,467 +0,0 @@
-package com.lishid.openinv.internal.paper1_21_4.container.menu;
-
-import com.google.common.base.Suppliers;
-import com.lishid.openinv.internal.ISpecialInventory;
-import com.lishid.openinv.internal.InternalOwned;
-import com.lishid.openinv.internal.common.container.bukkit.OpenDummyInventory;
-import com.lishid.openinv.internal.common.container.slot.SlotPlaceholder;
-import com.lishid.openinv.internal.common.container.slot.SlotViewOnly;
-import it.unimi.dsi.fastutil.ints.IntArrayList;
-import it.unimi.dsi.fastutil.ints.IntList;
-import net.minecraft.server.level.ServerPlayer;
-import net.minecraft.world.Container;
-import net.minecraft.world.entity.player.Player;
-import net.minecraft.world.inventory.AbstractContainerMenu;
-import net.minecraft.world.inventory.ChestMenu;
-import net.minecraft.world.inventory.ClickType;
-import net.minecraft.world.inventory.ContainerData;
-import net.minecraft.world.inventory.ContainerListener;
-import net.minecraft.world.inventory.ContainerSynchronizer;
-import net.minecraft.world.inventory.DataSlot;
-import net.minecraft.world.inventory.MenuType;
-import net.minecraft.world.inventory.Slot;
-import net.minecraft.world.item.ItemStack;
-import org.bukkit.craftbukkit.inventory.CraftInventoryView;
-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;
-
-import java.util.ArrayList;
-import java.util.List;
-import java.util.function.Supplier;
-
-/**
- * An extension of {@link AbstractContainerMenu} that supports {@link SlotPlaceholder placeholders}.
- */
-@SuppressWarnings("HidingField")
-public abstract class OpenChestMenu<T extends Container & ISpecialInventory & InternalOwned<ServerPlayer>>
-    extends AbstractContainerMenu {
-
-  protected static final int BOTTOM_INVENTORY_SIZE = 36;
-
-  protected final T container;
-  protected final ServerPlayer viewer;
-  protected final boolean viewOnly;
-  protected final boolean ownContainer;
-  protected final int topSize;
-  private CraftInventoryView<OpenChestMenu<T>, Inventory> bukkitEntity;
-  // Syncher fields
-  private @Nullable ContainerSynchronizer synchronizer;
-  private final List<DataSlot> dataSlots = new ArrayList<>();
-  private final IntList remoteDataSlots = new IntArrayList();
-  private final List<ContainerListener> containerListeners = new ArrayList<>();
-  private ItemStack remoteCarried = ItemStack.EMPTY;
-  private boolean suppressRemoteUpdates;
-
-  protected OpenChestMenu(
-      @NotNull MenuType<ChestMenu> type,
-      int containerCounter,
-      @NotNull T container,
-      @NotNull ServerPlayer viewer,
-      boolean viewOnly
-  ) {
-    super(type, containerCounter);
-    this.container = container;
-    this.viewer = viewer;
-    this.viewOnly = viewOnly;
-    ownContainer = container.getOwnerHandle().equals(viewer);
-    topSize = getTopSize(viewer);
-
-    preSlotSetup();
-
-    int upperRows = topSize / 9;
-    // View's upper inventory - our container
-    for (int row = 0; row < upperRows; ++row) {
-      for (int col = 0; col < 9; ++col) {
-        // x and y for client purposes, but hey, we're thorough here.
-        // Adapted from net.minecraft.world.inventory.ChestMenu
-        int x = 8 + col * 18;
-        int y = 18 + row * 18;
-        int index = row * 9 + col;
-
-        // Guard against weird inventory sizes.
-        if (index >= container.getContainerSize()) {
-          addSlot(new SlotViewOnly(container, index, x, y));
-          continue;
-        }
-
-        Slot slot = getUpperSlot(index, x, y);
-
-        addSlot(slot);
-      }
-    }
-
-    // View's lower inventory - viewer inventory
-    int playerInvPad = (upperRows - 4) * 18;
-    for (int row = 0; row < 3; ++row) {
-      for (int col = 0; col < 9; ++col) {
-        int x = 8 + col * 18;
-        int y = playerInvPad + row * 18 + 103;
-        addSlot(new Slot(viewer.getInventory(), row * 9 + col + 9, x, y));
-      }
-    }
-    // Hotbar
-    for (int col = 0; col < 9; ++col) {
-      int x = 8 + col * 18;
-      int y = playerInvPad + 161;
-      addSlot(new Slot(viewer.getInventory(), col, x, y));
-    }
-  }
-
-  protected void preSlotSetup() {
-  }
-
-  protected @NotNull Slot getUpperSlot(int index, int x, int y) {
-    Slot slot = new Slot(container, index, x, y);
-    if (viewOnly) {
-      return SlotViewOnly.wrap(slot);
-    }
-    return slot;
-  }
-
-
-  @Override
-  public final @NotNull CraftInventoryView<OpenChestMenu<T>, Inventory> getBukkitView() {
-    if (bukkitEntity == null) {
-      bukkitEntity = createBukkitEntity();
-    }
-
-    return bukkitEntity;
-  }
-
-  protected @NotNull CraftInventoryView<OpenChestMenu<T>, Inventory> createBukkitEntity() {
-    Inventory top;
-    if (viewOnly) {
-      top = new OpenDummyInventory(container, container.getBukkitType());
-    } else {
-      top = container.getBukkitInventory();
-    }
-    return new CraftInventoryView<>(viewer.getBukkitEntity(), top, this) {
-      @Override
-      public @Nullable Inventory getInventory(int rawSlot) {
-        if (viewOnly) {
-          return null;
-        }
-        return super.getInventory(rawSlot);
-      }
-
-      @Override
-      public int convertSlot(int rawSlot) {
-        if (viewOnly) {
-          return InventoryView.OUTSIDE;
-        }
-        return super.convertSlot(rawSlot);
-      }
-
-      @Override
-      public @NotNull InventoryType.SlotType getSlotType(int slot) {
-        if (viewOnly) {
-          return InventoryType.SlotType.OUTSIDE;
-        }
-        return super.getSlotType(slot);
-      }
-    };
-  }
-
-  private int getTopSize(ServerPlayer viewer) {
-    MenuType<?> menuType = getType();
-    if (menuType == MenuType.GENERIC_9x1) {
-      return 9;
-    } else if (menuType == MenuType.GENERIC_9x2) {
-      return 18;
-    } else if (menuType == MenuType.GENERIC_9x3) {
-      return 27;
-    } else if (menuType == MenuType.GENERIC_9x4) {
-      return 36;
-    } else if (menuType == MenuType.GENERIC_9x5) {
-      return 45;
-    } else if (menuType == MenuType.GENERIC_9x6) {
-      return 54;
-    }
-    // This is a bit gross, but allows us a safe fallthrough.
-    return menuType.create(-1, viewer.getInventory()).slots.size() - BOTTOM_INVENTORY_SIZE;
-  }
-
-  /**
-   * Reimplementation of {@link AbstractContainerMenu#moveItemStackTo(ItemStack, int, int, boolean)} that ignores fake
-   * slots and respects {@link Slot#hasItem()}.
-   *
-   * @param itemStack the stack to quick-move
-   * @param rangeLow the start of the range of slots that can be moved to, inclusive
-   * @param rangeHigh the end of the range of slots that can be moved to, exclusive
-   * @param topDown whether to start at the top of the range or bottom
-   * @return whether the stack was modified as a result of being quick-moved
-   */
-  @Override
-  protected boolean moveItemStackTo(ItemStack itemStack, int rangeLow, int rangeHigh, boolean topDown) {
-    boolean modified = false;
-    boolean stackable = itemStack.isStackable();
-    Slot firstEmpty = null;
-
-    for (int index = topDown ? rangeHigh - 1 : rangeLow;
-         !itemStack.isEmpty() && (topDown ? index >= rangeLow : index < rangeHigh);
-         index += topDown ? -1 : 1
-    ) {
-      Slot slot = slots.get(index);
-      // If the slot cannot be added to, check the next slot.
-      if (slot.isFake() || !slot.mayPlace(itemStack)) {
-        continue;
-      }
-
-      if (slot.hasItem()) {
-        // If the item isn't stackable, check the next slot.
-        if (!stackable) {
-          continue;
-        }
-        // Otherwise, add as many as we can from our stack to the slot.
-        modified |= addToExistingStack(itemStack, slot);
-      } else {
-        // If this is the first empty slot, keep track of it for later use.
-        if (firstEmpty == null) {
-          firstEmpty = slot;
-        }
-        // If the item isn't stackable, we've located the slot we're adding it to, so we're done.
-        if (!stackable) {
-          break;
-        }
-      }
-    }
-
-    // If the item hasn't been fully added yet, add as many as we can to the first open slot.
-    if (!itemStack.isEmpty() && firstEmpty != null) {
-      firstEmpty.setByPlayer(itemStack.split(Math.min(itemStack.getCount(), firstEmpty.getMaxStackSize(itemStack))));
-      firstEmpty.setChanged();
-      modified = true;
-    }
-
-    return modified;
-  }
-
-  private static boolean addToExistingStack(ItemStack itemStack, Slot slot) {
-    ItemStack existing = slot.getItem();
-
-    // If the items aren't the same, we can't add our item.
-    if (!ItemStack.isSameItemSameComponents(itemStack, existing)) {
-      return false;
-    }
-
-    int max = slot.getMaxStackSize(existing);
-    int existingCount = existing.getCount();
-
-    // If the stack is already full, we can't add more.
-    if (existingCount >= max) {
-      return false;
-    }
-
-    int total = existingCount + itemStack.getCount();
-
-    // If the existing item can accept the entirety of our item, we're done!
-    if (total <= max) {
-      itemStack.setCount(0);
-      existing.setCount(total);
-      slot.setChanged();
-      return true;
-    }
-
-    // Otherwise, add as many as we can.
-    itemStack.shrink(max - existingCount);
-    existing.setCount(max);
-    slot.setChanged();
-    return true;
-  }
-
-  @Override
-  public void clicked(int i, int j, @NotNull ClickType clickType, @NotNull Player player) {
-    if (viewOnly) {
-      if (clickType == ClickType.QUICK_CRAFT) {
-        sendAllDataToRemote();
-      }
-      return;
-    }
-    super.clicked(i, j, clickType, player);
-  }
-
-  @Override
-  public boolean stillValid(@NotNull Player player) {
-    return true;
-  }
-
-  // Overrides from here on are purely to modify the sync process to send placeholder items.
-  @Override
-  protected @NotNull Slot addSlot(@NotNull Slot slot) {
-    slot.index = this.slots.size();
-    this.slots.add(slot);
-    this.lastSlots.add(ItemStack.EMPTY);
-    this.remoteSlots.add(ItemStack.EMPTY);
-    return slot;
-  }
-
-  @Override
-  protected @NotNull DataSlot addDataSlot(@NotNull DataSlot dataSlot) {
-    this.dataSlots.add(dataSlot);
-    this.remoteDataSlots.add(0);
-    return dataSlot;
-  }
-
-  @Override
-  protected void addDataSlots(ContainerData containerData) {
-    for (int i = 0; i < containerData.getCount(); i++) {
-      this.addDataSlot(DataSlot.forContainer(containerData, i));
-    }
-  }
-
-  @Override
-  public void addSlotListener(@NotNull ContainerListener containerListener) {
-    if (!this.containerListeners.contains(containerListener)) {
-      this.containerListeners.add(containerListener);
-      this.broadcastChanges();
-    }
-  }
-
-  @Override
-  public void setSynchronizer(@NotNull ContainerSynchronizer containerSynchronizer) {
-    this.synchronizer = containerSynchronizer;
-    this.sendAllDataToRemote();
-  }
-
-  @Override
-  public void sendAllDataToRemote() {
-    for (int index = 0; index < slots.size(); ++index) {
-      Slot slot = slots.get(index);
-      this.remoteSlots.set(index, (slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem()).copy());
-    }
-
-    remoteCarried = getCarried().copy();
-
-    for (int index = 0; index < this.dataSlots.size(); ++index) {
-      this.remoteDataSlots.set(index, this.dataSlots.get(index).get());
-    }
-
-    if (this.synchronizer != null) {
-      this.synchronizer.sendInitialData(this, this.remoteSlots, this.remoteCarried, this.remoteDataSlots.toIntArray());
-    }
-  }
-
-  @Override
-  public void broadcastCarriedItem() {
-    this.remoteCarried = this.getCarried().copy();
-    if (this.synchronizer != null) {
-      this.synchronizer.sendCarriedChange(this, this.remoteCarried);
-    }
-  }
-
-  @Override
-  public void removeSlotListener(@NotNull ContainerListener containerListener) {
-    this.containerListeners.remove(containerListener);
-  }
-
-  @Override
-  public void broadcastChanges() {
-    for (int index = 0; index < this.slots.size(); ++index) {
-      Slot slot = this.slots.get(index);
-      ItemStack itemstack = slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem();
-      Supplier<ItemStack> supplier = Suppliers.memoize(itemstack::copy);
-      this.triggerSlotListeners(index, itemstack, supplier);
-      this.synchronizeSlotToRemote(index, itemstack, supplier);
-    }
-
-    this.synchronizeCarriedToRemote();
-
-    for (int index = 0; index < this.dataSlots.size(); ++index) {
-      DataSlot dataSlot = this.dataSlots.get(index);
-      int j = dataSlot.get();
-      if (dataSlot.checkAndClearUpdateFlag()) {
-        this.updateDataSlotListeners(index, j);
-      }
-
-      this.synchronizeDataSlotToRemote(index, j);
-    }
-  }
-
-  @Override
-  public void broadcastFullState() {
-    for (int index = 0; index < this.slots.size(); ++index) {
-      ItemStack itemstack = this.slots.get(index).getItem();
-      this.triggerSlotListeners(index, itemstack, itemstack::copy);
-    }
-
-    for (int index = 0; index < this.dataSlots.size(); ++index) {
-      DataSlot containerproperty = this.dataSlots.get(index);
-      if (containerproperty.checkAndClearUpdateFlag()) {
-        this.updateDataSlotListeners(index, containerproperty.get());
-      }
-    }
-
-    this.sendAllDataToRemote();
-  }
-
-  private void updateDataSlotListeners(int i, int j) {
-    for (ContainerListener containerListener : this.containerListeners) {
-      containerListener.dataChanged(this, i, j);
-    }
-  }
-
-  private void triggerSlotListeners(int index, ItemStack itemStack, Supplier<ItemStack> supplier) {
-    ItemStack itemStack1 = this.lastSlots.get(index);
-    if (!ItemStack.matches(itemStack1, itemStack)) {
-      ItemStack itemStack2 = supplier.get();
-      this.lastSlots.set(index, itemStack2);
-
-      for (ContainerListener containerListener : this.containerListeners) {
-        containerListener.slotChanged(this, index, itemStack2);
-      }
-    }
-  }
-
-  private void synchronizeSlotToRemote(int i, ItemStack itemStack, Supplier<ItemStack> supplier) {
-    if (!this.suppressRemoteUpdates) {
-      ItemStack itemStack1 = this.remoteSlots.get(i);
-      if (!ItemStack.matches(itemStack1, itemStack)) {
-        ItemStack itemstack2 = supplier.get();
-        this.remoteSlots.set(i, itemstack2);
-        if (this.synchronizer != null) {
-          this.synchronizer.sendSlotChange(this, i, itemstack2);
-        }
-      }
-    }
-  }
-
-  private void synchronizeDataSlotToRemote(int index, int value) {
-    if (!this.suppressRemoteUpdates) {
-      int existing = this.remoteDataSlots.getInt(index);
-      if (existing != value) {
-        this.remoteDataSlots.set(index, value);
-        if (this.synchronizer != null) {
-          this.synchronizer.sendDataChange(this, index, value);
-        }
-      }
-    }
-  }
-
-  private void synchronizeCarriedToRemote() {
-    if (!this.suppressRemoteUpdates && !ItemStack.matches(this.getCarried(), this.remoteCarried)) {
-      this.remoteCarried = this.getCarried().copy();
-      if (this.synchronizer != null) {
-        this.synchronizer.sendCarriedChange(this, this.remoteCarried);
-      }
-    }
-  }
-
-  @Override
-  public void setRemoteCarried(ItemStack itemstack) {
-    this.remoteCarried = itemstack.copy();
-  }
-
-  @Override
-  public void suppressRemoteUpdates() {
-    this.suppressRemoteUpdates = true;
-  }
-
-  @Override
-  public void resumeRemoteUpdates() {
-    this.suppressRemoteUpdates = false;
-  }
-
-}

internal/paper1_21_4/src/main/java/com/lishid/openinv/internal/paper1_21_4/container/menu/OpenEnderChestMenu.java

@@ -1,13 +1,14 @@
 package com.lishid.openinv.internal.paper1_21_4.container.menu;
 
 import com.lishid.openinv.internal.common.container.OpenEnderChest;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.inventory.Slot;
 import net.minecraft.world.item.ItemStack;
 import org.jetbrains.annotations.NotNull;
 
-public class OpenEnderChestMenu extends OpenChestMenu<OpenEnderChest> {
+public class OpenEnderChestMenu extends OpenSyncMenu<OpenEnderChest> {
 
   public OpenEnderChestMenu(
       @NotNull OpenEnderChest enderChest,
@@ -16,7 +17,7 @@ public class OpenEnderChestMenu extends OpenChestMenu<OpenEnderChest> {
       boolean viewOnly
   ) {
     super(
-        com.lishid.openinv.internal.common.container.menu.OpenChestMenu.getChestMenuType(enderChest.getContainerSize()),
+        OpenChestMenu.getChestMenuType(enderChest.getContainerSize()),
         containerId,
         enderChest,
         viewer,

internal/paper1_21_4/src/main/java/com/lishid/openinv/internal/paper1_21_4/container/menu/OpenInventoryMenu.java

@@ -2,6 +2,7 @@ package com.lishid.openinv.internal.paper1_21_4.container.menu;
 
 import com.google.common.base.Preconditions;
 import com.lishid.openinv.internal.common.container.bukkit.OpenDummyPlayerInventory;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
 import com.lishid.openinv.internal.common.container.slot.ContentDrop;
 import com.lishid.openinv.internal.common.container.slot.SlotViewOnly;
 import com.lishid.openinv.internal.paper1_21_4.container.OpenInventory;
@@ -23,7 +24,7 @@ import org.bukkit.inventory.InventoryView;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-public class OpenInventoryMenu extends OpenChestMenu<OpenInventory> {
+public class OpenInventoryMenu extends OpenSyncMenu<OpenInventory> {
 
   private int offset;
 
@@ -39,7 +40,7 @@ public class OpenInventoryMenu extends OpenChestMenu<OpenInventory> {
       size = ((int) Math.ceil(size / 9.0)) * 9;
     }
 
-    return com.lishid.openinv.internal.common.container.menu.OpenChestMenu.getChestMenuType(size);
+    return OpenChestMenu.getChestMenuType(size);
   }
 
   @Override

internal/paper1_21_4/src/main/java/com/lishid/openinv/internal/paper1_21_4/container/menu/OpenSyncMenu.java

@@ -0,0 +1,229 @@
+package com.lishid.openinv.internal.paper1_21_4.container.menu;
+
+import com.google.common.base.Suppliers;
+import com.lishid.openinv.internal.ISpecialInventory;
+import com.lishid.openinv.internal.InternalOwned;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
+import com.lishid.openinv.internal.common.container.slot.SlotPlaceholder;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntList;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Container;
+import net.minecraft.world.inventory.AbstractContainerMenu;
+import net.minecraft.world.inventory.ChestMenu;
+import net.minecraft.world.inventory.ContainerData;
+import net.minecraft.world.inventory.ContainerListener;
+import net.minecraft.world.inventory.ContainerSynchronizer;
+import net.minecraft.world.inventory.DataSlot;
+import net.minecraft.world.inventory.MenuType;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Supplier;
+
+/**
+ * An extension of {@link AbstractContainerMenu} that supports {@link SlotPlaceholder placeholders}.
+ */
+@SuppressWarnings("HidingField")
+public abstract class OpenSyncMenu<T extends Container & ISpecialInventory & InternalOwned<ServerPlayer>>
+    extends OpenChestMenu<T> {
+
+  // Syncher fields
+  private @Nullable ContainerSynchronizer synchronizer;
+  private final List<DataSlot> dataSlots = new ArrayList<>();
+  private final IntList remoteDataSlots = new IntArrayList();
+  private final List<ContainerListener> containerListeners = new ArrayList<>();
+  private ItemStack remoteCarried = ItemStack.EMPTY;
+  private boolean suppressRemoteUpdates;
+
+  protected OpenSyncMenu(
+      @NotNull MenuType<ChestMenu> type,
+      int containerCounter,
+      @NotNull T container,
+      @NotNull ServerPlayer viewer,
+      boolean viewOnly
+  ) {
+    super(type, containerCounter, container, viewer, viewOnly);
+  }
+
+  // Overrides from here on are purely to modify the sync process to send placeholder items.
+  @Override
+  protected @NotNull Slot addSlot(@NotNull Slot slot) {
+    slot.index = this.slots.size();
+    this.slots.add(slot);
+    this.lastSlots.add(ItemStack.EMPTY);
+    this.remoteSlots.add(ItemStack.EMPTY);
+    return slot;
+  }
+
+  @Override
+  protected @NotNull DataSlot addDataSlot(@NotNull DataSlot dataSlot) {
+    this.dataSlots.add(dataSlot);
+    this.remoteDataSlots.add(0);
+    return dataSlot;
+  }
+
+  @Override
+  protected void addDataSlots(ContainerData containerData) {
+    for (int i = 0; i < containerData.getCount(); i++) {
+      this.addDataSlot(DataSlot.forContainer(containerData, i));
+    }
+  }
+
+  @Override
+  public void addSlotListener(@NotNull ContainerListener containerListener) {
+    if (!this.containerListeners.contains(containerListener)) {
+      this.containerListeners.add(containerListener);
+      this.broadcastChanges();
+    }
+  }
+
+  @Override
+  public void setSynchronizer(@NotNull ContainerSynchronizer containerSynchronizer) {
+    this.synchronizer = containerSynchronizer;
+    this.sendAllDataToRemote();
+  }
+
+  @Override
+  public void sendAllDataToRemote() {
+    for (int index = 0; index < slots.size(); ++index) {
+      Slot slot = slots.get(index);
+      this.remoteSlots.set(index, (slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem()).copy());
+    }
+
+    remoteCarried = getCarried().copy();
+
+    for (int index = 0; index < this.dataSlots.size(); ++index) {
+      this.remoteDataSlots.set(index, this.dataSlots.get(index).get());
+    }
+
+    if (this.synchronizer != null) {
+      this.synchronizer.sendInitialData(this, this.remoteSlots, this.remoteCarried, this.remoteDataSlots.toIntArray());
+    }
+  }
+
+  @Override
+  public void broadcastCarriedItem() {
+    this.remoteCarried = this.getCarried().copy();
+    if (this.synchronizer != null) {
+      this.synchronizer.sendCarriedChange(this, this.remoteCarried);
+    }
+  }
+
+  @Override
+  public void removeSlotListener(@NotNull ContainerListener containerListener) {
+    this.containerListeners.remove(containerListener);
+  }
+
+  @Override
+  public void broadcastChanges() {
+    for (int index = 0; index < this.slots.size(); ++index) {
+      Slot slot = this.slots.get(index);
+      ItemStack itemstack = slot instanceof SlotPlaceholder placeholder ? placeholder.getOrDefault() : slot.getItem();
+      Supplier<ItemStack> supplier = Suppliers.memoize(itemstack::copy);
+      this.triggerSlotListeners(index, itemstack, supplier);
+      this.synchronizeSlotToRemote(index, itemstack, supplier);
+    }
+
+    this.synchronizeCarriedToRemote();
+
+    for (int index = 0; index < this.dataSlots.size(); ++index) {
+      DataSlot dataSlot = this.dataSlots.get(index);
+      int j = dataSlot.get();
+      if (dataSlot.checkAndClearUpdateFlag()) {
+        this.updateDataSlotListeners(index, j);
+      }
+
+      this.synchronizeDataSlotToRemote(index, j);
+    }
+  }
+
+  @Override
+  public void broadcastFullState() {
+    for (int index = 0; index < this.slots.size(); ++index) {
+      ItemStack itemstack = this.slots.get(index).getItem();
+      this.triggerSlotListeners(index, itemstack, itemstack::copy);
+    }
+
+    for (int index = 0; index < this.dataSlots.size(); ++index) {
+      DataSlot containerproperty = this.dataSlots.get(index);
+      if (containerproperty.checkAndClearUpdateFlag()) {
+        this.updateDataSlotListeners(index, containerproperty.get());
+      }
+    }
+
+    this.sendAllDataToRemote();
+  }
+
+  private void updateDataSlotListeners(int i, int j) {
+    for (ContainerListener containerListener : this.containerListeners) {
+      containerListener.dataChanged(this, i, j);
+    }
+  }
+
+  private void triggerSlotListeners(int index, ItemStack itemStack, Supplier<ItemStack> supplier) {
+    ItemStack itemStack1 = this.lastSlots.get(index);
+    if (!ItemStack.matches(itemStack1, itemStack)) {
+      ItemStack itemStack2 = supplier.get();
+      this.lastSlots.set(index, itemStack2);
+
+      for (ContainerListener containerListener : this.containerListeners) {
+        containerListener.slotChanged(this, index, itemStack2);
+      }
+    }
+  }
+
+  private void synchronizeSlotToRemote(int i, ItemStack itemStack, Supplier<ItemStack> supplier) {
+    if (!this.suppressRemoteUpdates) {
+      ItemStack itemStack1 = this.remoteSlots.get(i);
+      if (!ItemStack.matches(itemStack1, itemStack)) {
+        ItemStack itemstack2 = supplier.get();
+        this.remoteSlots.set(i, itemstack2);
+        if (this.synchronizer != null) {
+          this.synchronizer.sendSlotChange(this, i, itemstack2);
+        }
+      }
+    }
+  }
+
+  private void synchronizeDataSlotToRemote(int index, int value) {
+    if (!this.suppressRemoteUpdates) {
+      int existing = this.remoteDataSlots.getInt(index);
+      if (existing != value) {
+        this.remoteDataSlots.set(index, value);
+        if (this.synchronizer != null) {
+          this.synchronizer.sendDataChange(this, index, value);
+        }
+      }
+    }
+  }
+
+  private void synchronizeCarriedToRemote() {
+    if (!this.suppressRemoteUpdates && !ItemStack.matches(this.getCarried(), this.remoteCarried)) {
+      this.remoteCarried = this.getCarried().copy();
+      if (this.synchronizer != null) {
+        this.synchronizer.sendCarriedChange(this, this.remoteCarried);
+      }
+    }
+  }
+
+  @Override
+  public void setRemoteCarried(ItemStack itemstack) {
+    this.remoteCarried = itemstack.copy();
+  }
+
+  @Override
+  public void suppressRemoteUpdates() {
+    this.suppressRemoteUpdates = true;
+  }
+
+  @Override
+  public void resumeRemoteUpdates() {
+    this.suppressRemoteUpdates = false;
+  }
+
+}

internal/paper1_21_5/build.gradle.kts

@@ -21,6 +21,7 @@ dependencies {
   implementation(project(":openinvapi"))
   implementation(project(":openinvcommon"))
   implementation(project(":openinvadaptercommon"))
+  implementation(project(":openinvadapterpaper1_21_8"))
 
   paperweight.paperDevBundle("1.21.5-R0.1-SNAPSHOT")
 }

internal/paper1_21_5/src/main/java/com/lishid/openinv/internal/paper1_21_5/InternalAccessor.java

@@ -9,7 +9,7 @@ import org.jetbrains.annotations.NotNull;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
-public class InternalAccessor extends com.lishid.openinv.internal.common.InternalAccessor {
+public class InternalAccessor extends com.lishid.openinv.internal.paper1_21_8.InternalAccessor {
 
   private final @NotNull PlayerManager manager;
 

internal/paper1_21_5/src/main/java/com/lishid/openinv/internal/paper1_21_5/player/OpenPlayer.java

@@ -1,16 +1,13 @@
 package com.lishid.openinv.internal.paper1_21_5.player;
 
-import com.lishid.openinv.event.OpenEvents;
 import com.lishid.openinv.internal.common.player.BaseOpenPlayer;
 import com.mojang.logging.LogUtils;
-import net.minecraft.Util;
 import net.minecraft.nbt.CompoundTag;
-import net.minecraft.nbt.NbtIo;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.level.storage.PlayerDataStorage;
 import org.bukkit.craftbukkit.CraftServer;
+import org.jetbrains.annotations.NotNull;
 
-import java.nio.file.Files;
 import java.nio.file.Path;
 
 public class OpenPlayer extends BaseOpenPlayer {
@@ -20,12 +17,7 @@ public class OpenPlayer extends BaseOpenPlayer {
   }
 
   @Override
-  public void saveData() {
-    if (OpenEvents.saveCancelled(this)) {
-      return;
-    }
-
-    ServerPlayer player = this.getHandle();
+  protected void trySave(ServerPlayer player) {
     // See net.minecraft.world.level.storage.PlayerDataStorage#save(EntityHuman)
     try {
       PlayerDataStorage worldNBTStorage = player.server.getPlayerList().playerIo;
@@ -35,20 +27,20 @@ public class OpenPlayer extends BaseOpenPlayer {
 
       playerData = player.saveWithoutId(playerData);
 
-      if (oldData != null) {
-        // Revert certain special data values when offline.
-        revertSpecialValues(playerData, oldData);
-      }
-
-      Path playerDataDir = worldNBTStorage.getPlayerDir().toPath();
-      Path tempFile = Files.createTempFile(playerDataDir, player.getStringUUID() + "-", ".dat");
-      NbtIo.writeCompressed(playerData, tempFile);
-      Path dataFile = playerDataDir.resolve(player.getStringUUID() + ".dat");
-      Path backupFile = playerDataDir.resolve(player.getStringUUID() + ".dat_old");
-      Util.safeReplaceFile(dataFile, tempFile, backupFile);
+      saveSafe(player, oldData, playerData, worldNBTStorage);
     } catch (Exception e) {
       LogUtils.getLogger().warn("Failed to save player data for {}: {}", player.getScoreboardName(), e);
     }
   }
 
+  @Override
+  protected void safeReplaceFile(@NotNull Path dataFile, @NotNull Path tempFile, @NotNull Path backupFile) {
+    net.minecraft.Util.safeReplaceFile(dataFile, tempFile, backupFile);
+  }
+
+  @Override
+  protected void remove(@NotNull CompoundTag tag, @NotNull String key) {
+    tag.remove(key);
+  }
+
 }

internal/paper1_21_5/src/main/java/com/lishid/openinv/internal/paper1_21_5/player/PlayerManager.java

@@ -16,7 +16,7 @@ import java.util.Optional;
 import java.util.UUID;
 import java.util.logging.Logger;
 
-public class PlayerManager extends com.lishid.openinv.internal.common.player.PlayerManager {
+public class PlayerManager extends com.lishid.openinv.internal.paper1_21_8.player.PlayerManager {
 
   public PlayerManager(@NotNull Logger logger) {
     super(logger);

internal/paper1_21_8/build.gradle.kts

@@ -0,0 +1,26 @@
+plugins {
+  `openinv-base`
+  alias(libs.plugins.paperweight)
+}
+
+configurations.all {
+  resolutionStrategy.capabilitiesResolution.withCapability("org.spigotmc:spigot-api") {
+    val paper = candidates.firstOrNull {
+      it.id.let { id ->
+        id is ModuleComponentIdentifier && id.module == "paper-api"
+      }
+    }
+    if (paper != null) {
+      select(paper)
+    }
+    because("module is written for Paper servers")
+  }
+}
+
+dependencies {
+  implementation(project(":openinvapi"))
+  implementation(project(":openinvcommon"))
+  implementation(project(":openinvadaptercommon"))
+
+  paperweight.paperDevBundle("1.21.8-R0.1-SNAPSHOT")
+}

internal/paper1_21_8/src/main/java/com/lishid/openinv/internal/paper1_21_8/InternalAccessor.java

@@ -0,0 +1,31 @@
+package com.lishid.openinv.internal.paper1_21_8;
+
+import com.lishid.openinv.internal.ISpecialPlayerInventory;
+import com.lishid.openinv.internal.paper1_21_8.container.OpenInventory;
+import com.lishid.openinv.internal.paper1_21_8.player.PlayerManager;
+import com.lishid.openinv.util.lang.LanguageManager;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.logging.Logger;
+
+public class InternalAccessor extends com.lishid.openinv.internal.common.InternalAccessor {
+
+  private final @NotNull PlayerManager manager;
+
+  public InternalAccessor(@NotNull Logger logger, @NotNull LanguageManager lang) {
+    super(logger, lang);
+    manager = new PlayerManager(logger);
+  }
+
+  @Override
+  public @NotNull PlayerManager getPlayerManager() {
+    return manager;
+  }
+
+  @Override
+  public @NotNull ISpecialPlayerInventory createPlayerInventory(@NotNull Player player) {
+    return new OpenInventory(player);
+  }
+
+}

internal/paper1_21_8/src/main/java/com/lishid/openinv/internal/paper1_21_8/container/OpenInventory.java

@@ -0,0 +1,49 @@
+package com.lishid.openinv.internal.paper1_21_8.container;
+
+import com.lishid.openinv.internal.common.container.BaseOpenInventory;
+import com.lishid.openinv.internal.common.container.menu.OpenChestMenu;
+import net.minecraft.ChatFormatting;
+import net.minecraft.network.chat.Component;
+import net.minecraft.network.chat.MutableComponent;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerPlayer;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public class OpenInventory extends BaseOpenInventory {
+
+  public OpenInventory(@NotNull Player bukkitPlayer) {
+    super(bukkitPlayer);
+  }
+
+  @Override
+  public @NotNull Component getTitle(@Nullable ServerPlayer viewer, @Nullable OpenChestMenu<?> menu) {
+    MutableComponent component = Component.empty();
+    // Prefix for use with custom bitmap image fonts.
+    if (owner.equals(viewer)) {
+      component.append(
+          Component.translatableWithFallback("openinv.container.inventory.self", "")
+              .withStyle(style -> style
+                  .withFont(ResourceLocation.parse("openinv:font/inventory"))
+                  .withColor(ChatFormatting.WHITE)));
+    } else {
+      component.append(
+          Component.translatableWithFallback("openinv.container.inventory.other", "")
+              .withStyle(style -> style
+                  .withFont(ResourceLocation.parse("openinv:font/inventory"))
+                  .withColor(ChatFormatting.WHITE)));
+    }
+    if (menu != null && menu.isViewOnly()) {
+      component.append(Component.translatableWithFallback("openinv.container.inventory.viewonly", "[RO] "));
+    } else {
+      component.append(Component.translatableWithFallback("openinv.container.inventory.editable", ""));
+    }
+    // Normal title: "Inventory - OwnerName"
+    component.append(Component.translatableWithFallback("openinv.container.inventory.prefix", "", owner.getName()))
+        .append(Component.translatable("container.inventory"))
+        .append(Component.translatableWithFallback("openinv.container.inventory.suffix", " - %s", owner.getName()));
+    return component;
+  }
+
+}

internal/paper1_21_8/src/main/java/com/lishid/openinv/internal/paper1_21_8/player/OpenPlayer.java

@@ -0,0 +1,58 @@
+package com.lishid.openinv.internal.paper1_21_8.player;
+
+import com.lishid.openinv.internal.common.player.BaseOpenPlayer;
+import com.mojang.logging.LogUtils;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.util.ProblemReporter;
+import net.minecraft.world.level.storage.PlayerDataStorage;
+import net.minecraft.world.level.storage.TagValueOutput;
+import net.minecraft.world.level.storage.ValueOutput;
+import org.bukkit.craftbukkit.CraftServer;
+import org.jetbrains.annotations.NotNull;
+import org.slf4j.Logger;
+
+import java.nio.file.Path;
+
+public class OpenPlayer extends BaseOpenPlayer {
+
+  protected OpenPlayer(
+      CraftServer server,
+      ServerPlayer entity,
+      PlayerManager manager
+  ) {
+    super(server, entity, manager);
+  }
+
+  @Override
+  protected void trySave(ServerPlayer player) {
+    Logger logger = LogUtils.getLogger();
+    // See net.minecraft.world.level.storage.PlayerDataStorage#save(EntityHuman)
+    try (ProblemReporter.ScopedCollector scopedCollector = new ProblemReporter.ScopedCollector(player.problemPath(), logger)) {
+      PlayerDataStorage worldNbtStorage = server.getServer().getPlayerList().playerIo;
+
+      CompoundTag oldData = isOnline()
+          ? null
+          : worldNbtStorage.load(player.getName().getString(), player.getStringUUID(), scopedCollector).orElse(null);
+      CompoundTag playerData = getWritableTag(oldData);
+
+      ValueOutput valueOutput = TagValueOutput.createWrappingWithContext(scopedCollector, player.registryAccess(), playerData);
+      player.saveWithoutId(valueOutput);
+
+      saveSafe(player, oldData, playerData, worldNbtStorage);
+    } catch (Exception e) {
+      LogUtils.getLogger().warn("Failed to save player data for {}: {}", player.getScoreboardName(), e);
+    }
+  }
+
+  @Override
+  protected void safeReplaceFile(@NotNull Path dataFile, @NotNull Path tempFile, @NotNull Path backupFile) {
+    net.minecraft.Util.safeReplaceFile(dataFile, tempFile, backupFile);
+  }
+
+  @Override
+  protected void remove(@NotNull CompoundTag tag, @NotNull String key) {
+    tag.remove(key);
+  }
+
+}

internal/paper1_21_8/src/main/java/com/lishid/openinv/internal/paper1_21_8/player/PlayerManager.java

@@ -0,0 +1,100 @@
+package com.lishid.openinv.internal.paper1_21_8.player;
+
+import com.lishid.openinv.internal.common.player.BaseOpenPlayer;
+import com.lishid.openinv.util.JulLoggerAdapter;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.util.ProblemReporter;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.storage.ValueInput;
+import org.bukkit.Bukkit;
+import org.bukkit.craftbukkit.CraftServer;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.logging.Logger;
+
+public class PlayerManager extends com.lishid.openinv.internal.common.player.PlayerManager {
+
+  public PlayerManager(@NotNull Logger logger) {
+    super(logger);
+  }
+
+  @Override
+  protected boolean loadData(@NotNull MinecraftServer server, @NotNull ServerPlayer player) {
+    // See CraftPlayer#loadData
+
+    try (ProblemReporter.ScopedCollector scopedCollector = new ProblemReporter.ScopedCollector(player.problemPath(), new JulLoggerAdapter(logger))) {
+      ValueInput loadedData = server.getPlayerList().playerIo.load(player, scopedCollector).orElse(null);
+
+      if (loadedData == null) {
+        // Exceptions with loading are logged.
+        return false;
+      }
+
+      // Read basic data into the player.
+      player.load(loadedData);
+      // Game type settings are loaded separately.
+      player.loadGameTypes(loadedData);
+
+      // World is not loaded by ServerPlayer#load(CompoundTag) on Paper.
+      parseWorld(server, player, loadedData);
+    }
+
+    return true;
+  }
+
+  @Override
+  protected void spawnInDefaultWorld(@NotNull MinecraftServer server, @NotNull ServerPlayer player) {
+    ServerLevel level = server.getLevel(Level.OVERWORLD);
+    if (level != null) {
+      // Adjust player to default spawn (in keeping with Paper handling) when world not found.
+      player.snapTo(player.adjustSpawnLocation(level, level.getSharedSpawnPos()).getBottomCenter(), level.getSharedSpawnAngle(), 0.0F);
+      player.spawnIn(level);
+    } else {
+      logger.warning("Tried to load player with invalid world when no fallback was available!");
+    }
+  }
+
+  @Override
+  protected void injectPlayer(@NotNull MinecraftServer server, @NotNull ServerPlayer player) throws IllegalAccessException {
+    if (bukkitEntity == null) {
+      return;
+    }
+
+    bukkitEntity.setAccessible(true);
+
+    bukkitEntity.set(player, new OpenPlayer(server.server, player, this));
+  }
+
+  @Override
+  public @NotNull Player inject(@NotNull Player player) {
+    try {
+      ServerPlayer nmsPlayer = getHandle(player);
+      if (nmsPlayer.getBukkitEntity() instanceof BaseOpenPlayer openPlayer) {
+        return openPlayer;
+      }
+      MinecraftServer server = nmsPlayer.getServer();
+      if (server == null) {
+        if (!(Bukkit.getServer() instanceof CraftServer craftServer)) {
+          logger.warning(() ->
+              "Unable to inject ServerPlayer, certain player data may be lost when saving! Server is not a CraftServer: "
+                  + Bukkit.getServer().getClass().getName());
+          return player;
+        }
+        server = craftServer.getServer();
+      }
+      injectPlayer(server, nmsPlayer);
+      return nmsPlayer.getBukkitEntity();
+    } catch (IllegalAccessException e) {
+      logger.log(
+          java.util.logging.Level.WARNING,
+          e,
+          () -> "Unable to inject ServerPlayer, certain player data may be lost when saving!"
+      );
+      return player;
+    }
+  }
+
+}

internal/spigot/build.gradle.kts

@@ -10,9 +10,9 @@ plugins {
 apply<SpigotSetup>()
 apply<SpigotReobf>()
 
-val spigotVer = "1.21.8-R0.1-SNAPSHOT"
+val spigotVer = "1.21.11-R0.1-SNAPSHOT"
 // Used by common adapter to relocate Craftbukkit classes to a versioned package.
-rootProject.extra["craftbukkitPackage"] = "v1_21_R5"
+rootProject.extra["craftbukkitPackage"] = "v1_21_R7"
 
 configurations.all {
   resolutionStrategy.capabilitiesResolution.withCapability("org.spigotmc:spigot-api") {

internal/spigot/src/main/java/com/lishid/openinv/internal/reobf/container/bukkit/OpenPlayerInventory.java

@@ -1,11 +1,11 @@
 package com.lishid.openinv.internal.reobf.container.bukkit;
 
 import com.google.common.base.Preconditions;
-import com.lishid.openinv.internal.reobf.container.OpenInventory;
+import com.lishid.openinv.internal.reobf.container.BaseOpenInventory;
 import net.minecraft.core.NonNullList;
 import net.minecraft.world.entity.player.Inventory;
-import org.bukkit.craftbukkit.v1_21_R5.inventory.CraftInventory;
-import org.bukkit.craftbukkit.v1_21_R5.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.v1_21_R7.inventory.CraftInventory;
+import org.bukkit.craftbukkit.v1_21_R7.inventory.CraftItemStack;
 import org.bukkit.entity.Player;
 import org.bukkit.event.inventory.InventoryType;
 import org.bukkit.inventory.ItemStack;
@@ -15,13 +15,13 @@ import org.jetbrains.annotations.Nullable;
 
 public class OpenPlayerInventory extends CraftInventory implements PlayerInventory {
 
-  public OpenPlayerInventory(@NotNull OpenInventory inventory) {
+  public OpenPlayerInventory(@NotNull BaseOpenInventory inventory) {
     super(inventory);
   }
 
   @Override
-  public @NotNull OpenInventory getInventory() {
-    return (OpenInventory) super.getInventory();
+  public @NotNull BaseOpenInventory getInventory() {
+    return (BaseOpenInventory) super.getInventory();
   }
 
   @Override

internal/spigot/src/main/java/com/lishid/openinv/internal/reobf/container/slot/ContentEquipment.java

@@ -6,8 +6,8 @@ import net.minecraft.world.Container;
 import net.minecraft.world.entity.EquipmentSlot;
 import net.minecraft.world.inventory.Slot;
 import net.minecraft.world.item.ItemStack;
-import org.bukkit.craftbukkit.v1_21_R5.CraftEquipmentSlot;
-import org.bukkit.craftbukkit.v1_21_R5.inventory.CraftItemStack;
+import org.bukkit.craftbukkit.v1_21_R7.CraftEquipmentSlot;
+import org.bukkit.craftbukkit.v1_21_R7.inventory.CraftItemStack;
 import org.bukkit.event.inventory.InventoryType;
 import org.bukkit.inventory.PlayerInventory;
 import org.jetbrains.annotations.NotNull;

internal/spigot/src/main/java/com/lishid/openinv/internal/reobf/player/OpenPlayer.java

@@ -2,7 +2,6 @@ package com.lishid.openinv.internal.reobf.player;
 
 import com.lishid.openinv.event.OpenEvents;
 import com.mojang.logging.LogUtils;
-import net.minecraft.Util;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.nbt.NbtIo;
 import net.minecraft.nbt.NumericTag;
@@ -10,13 +9,12 @@ import net.minecraft.nbt.Tag;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.server.network.ServerGamePacketListenerImpl;
 import net.minecraft.util.ProblemReporter;
+import net.minecraft.util.Util;
 import net.minecraft.world.level.storage.PlayerDataStorage;
-import net.minecraft.world.level.storage.TagValueInput;
 import net.minecraft.world.level.storage.TagValueOutput;
-import net.minecraft.world.level.storage.ValueInput;
 import net.minecraft.world.level.storage.ValueOutput;
-import org.bukkit.craftbukkit.v1_21_R5.CraftServer;
-import org.bukkit.craftbukkit.v1_21_R5.entity.CraftPlayer;
+import org.bukkit.craftbukkit.v1_21_R7.CraftServer;
+import org.bukkit.craftbukkit.v1_21_R7.entity.CraftPlayer;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -108,17 +106,9 @@ public class OpenPlayer extends CraftPlayer {
     try (ProblemReporter.ScopedCollector scopedCollector = new ProblemReporter.ScopedCollector(player.problemPath(), logger)) {
       PlayerDataStorage worldNBTStorage = server.getServer().getPlayerList().playerIo;
 
-      ValueInput oldDataInput = isOnline()
+      CompoundTag oldData = isOnline()
           ? null
-          : worldNBTStorage.load(player.getName().getString(), player.getStringUUID(), scopedCollector, player.registryAccess()).orElse(null);
-      // Grab CompoundTag out of TagValueInput - we can't iterate over the fields via TagValueInput.
-      CompoundTag oldData = null;
-      if (oldDataInput != null) {
-        Field tagValueInputInput = TagValueInput.class.getDeclaredField("input");
-        tagValueInputInput.setAccessible(true);
-        oldData = (CompoundTag) tagValueInputInput.get(oldDataInput);
-      }
-
+          : worldNBTStorage.load(player.nameAndId()).orElse(null);
       CompoundTag playerData = getWritableTag(oldData);
 
       ValueOutput valueOutput = TagValueOutput.createWithContext(scopedCollector, player.registryAccess());

internal/spigot/src/main/java/com/lishid/openinv/internal/reobf/player/PlayerManager.java

@@ -3,8 +3,10 @@ package com.lishid.openinv.internal.reobf.player;
 import com.lishid.openinv.internal.ISpecialInventory;
 import com.lishid.openinv.internal.reobf.container.OpenEnderChest;
 import com.lishid.openinv.internal.reobf.container.OpenInventory;
+import com.lishid.openinv.internal.reobf.container.menu.OpenChestMenu;
 import com.lishid.openinv.util.JulLoggerAdapter;
 import com.mojang.authlib.GameProfile;
+import net.minecraft.nbt.CompoundTag;
 import net.minecraft.network.chat.Component;
 import net.minecraft.network.protocol.game.ClientboundOpenScreenPacket;
 import net.minecraft.server.MinecraftServer;
@@ -17,13 +19,14 @@ import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.player.ChatVisiblity;
 import net.minecraft.world.inventory.AbstractContainerMenu;
 import net.minecraft.world.level.Level;
+import net.minecraft.world.level.storage.TagValueInput;
 import net.minecraft.world.level.storage.ValueInput;
 import org.bukkit.Bukkit;
 import org.bukkit.OfflinePlayer;
 import org.bukkit.Server;
-import org.bukkit.craftbukkit.v1_21_R5.CraftServer;
-import org.bukkit.craftbukkit.v1_21_R5.entity.CraftPlayer;
-import org.bukkit.craftbukkit.v1_21_R5.event.CraftEventFactory;
+import org.bukkit.craftbukkit.v1_21_R7.CraftServer;
+import org.bukkit.craftbukkit.v1_21_R7.entity.CraftPlayer;
+import org.bukkit.craftbukkit.v1_21_R7.event.CraftEventFactory;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.InventoryView;
 import org.jetbrains.annotations.NotNull;
@@ -138,17 +141,17 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
     // See CraftPlayer#loadData
 
     try (ProblemReporter.ScopedCollector scopedCollector = new ProblemReporter.ScopedCollector(player.problemPath(), new JulLoggerAdapter(logger))) {
-      ValueInput loadedData = player.server.getPlayerList().playerIo.load(player, scopedCollector).orElse(null);
+      CompoundTag loadedData = player.server.getPlayerList().playerIo.load(player.nameAndId()).orElse(null);
 
       if (loadedData == null) {
         // Exceptions with loading are logged.
         return false;
       }
 
+      ValueInput valueInput = TagValueInput.create(scopedCollector, player.registryAccess(), loadedData);
+
       // Read basic data into the player.
-      player.load(loadedData);
-      // Game type settings are loaded separately.
-      player.loadGameTypes(loadedData);
+      player.load(valueInput);
     }
 
     return true;
@@ -195,14 +198,14 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
     }
 
     // See net.minecraft.server.level.ServerPlayer#openMenu(MenuProvider)
-    AbstractContainerMenu menu;
+    OpenChestMenu<?> menu;
     Component title;
     if (inventory instanceof OpenInventory playerInv) {
       menu = playerInv.createMenu(player, player.nextContainerCounter(), viewOnly);
-      title = playerInv.getTitle(player);
+      title = playerInv.getTitle(player, menu);
     } else if (inventory instanceof OpenEnderChest enderChest) {
       menu = enderChest.createMenu(player, player.nextContainerCounter(), viewOnly);
-      title = enderChest.getTitle();
+      title = enderChest.getTitle(menu);
     } else {
       return null;
     }
@@ -217,18 +220,18 @@ public class PlayerManager implements com.lishid.openinv.internal.PlayerManager
     // resulting in a title change but no other state modifications (like cursor position).
     menu.setTitle(title);
 
-    menu = CraftEventFactory.callInventoryOpenEvent(player, menu, false);
+    AbstractContainerMenu opened = CraftEventFactory.callInventoryOpenEvent(player, menu, false);
 
     // Menu is null if event is cancelled.
-    if (menu == null) {
+    if (opened == null) {
       return null;
     }
 
-    player.containerMenu = menu;
-    player.connection.send(new ClientboundOpenScreenPacket(menu.containerId, menu.getType(), menu.getTitle()));
-    player.initMenu(menu);
+    player.containerMenu = opened;
+    player.connection.send(new ClientboundOpenScreenPacket(opened.containerId, opened.getType(), opened.getTitle()));
+    player.initMenu(opened);
 
-    return menu.getBukkitView();
+    return opened.getBukkitView();
   }
 
 }

plugin/build.gradle.kts

@@ -13,6 +13,8 @@ dependencies {
   implementation(project(":openinvapi"))
   implementation(project(":openinvcommon"))
   implementation(project(":openinvadaptercommon"))
+  implementation(project(":openinvadapterpaper1_21_10"))
+  implementation(project(":openinvadapterpaper1_21_8"))
   implementation(project(":openinvadapterpaper1_21_5"))
   implementation(project(":openinvadapterpaper1_21_4"))
   implementation(project(":openinvadapterpaper1_21_3"))

plugin/src/main/java/com/lishid/openinv/OpenInv.java

@@ -244,6 +244,7 @@ public class OpenInv extends FoliaWrappedJavaPlugin implements IOpenInv {
   }
 
   @Override
+  @Deprecated(forRemoval = true)
   public @Nullable InventoryView openInventory(@NotNull Player player, @NotNull ISpecialInventory inventory) {
     Permissions edit = null;
     HumanEntity target = inventory.getPlayer();
@@ -256,10 +257,12 @@ public class OpenInv extends FoliaWrappedJavaPlugin implements IOpenInv {
 
     boolean viewOnly = edit != null && !edit.hasPermission(player);
 
-    if (ownContainer || (viewOnly && config.getAccessEqualMode() != AccessEqualMode.DENY)) {
+    if (ownContainer) {
       return this.accessor.openInventory(player, inventory, viewOnly);
     }
 
+    AccessEqualMode accessMode = AccessEqualMode.getByPerm(player, config);
+
     for (int level = 4; level > 0; --level) {
       String permission = "openinv.access.level." + level;
       // If the target doesn't have this access level...
@@ -273,17 +276,22 @@ public class OpenInv extends FoliaWrappedJavaPlugin implements IOpenInv {
       }
 
       // If the viewer doesn't have an equal access level or equal access is a denial, deny.
-      if (!player.hasPermission(permission) || config.getAccessEqualMode() == AccessEqualMode.DENY) {
+      if (!player.hasPermission(permission) || accessMode == AccessEqualMode.DENY) {
         return null;
       }
 
       // Since this is a tie, setting decides view state.
-      if (config.getAccessEqualMode() == AccessEqualMode.VIEW) {
+      if (accessMode == AccessEqualMode.VIEW) {
         viewOnly = true;
       }
       break;
     }
 
+    return openInventory(player, inventory, viewOnly);
+  }
+
+  @Override
+  public @Nullable InventoryView openInventory(@NotNull Player player, @NotNull ISpecialInventory inventory, boolean viewOnly) {
     return this.accessor.openInventory(player, inventory, viewOnly);
   }
 

plugin/src/main/java/com/lishid/openinv/command/ClearInvCommand.java

@@ -87,10 +87,11 @@ public class ClearInvCommand extends PlayerLookupCommand {
   @Override
   protected void handle(
       @NotNull CommandSender sender,
-      @NotNull Player onlineTarget,
+      @NotNull PlayerAccess playerAccess,
       boolean accessInv,
       @NotNull String @NotNull [] args
   ) {
+    Player onlineTarget = playerAccess.player();
     // Create the inventory
     final ISpecialInventory inv;
     try {

plugin/src/main/java/com/lishid/openinv/command/OpenInvCommand.java

@@ -151,11 +151,12 @@ public class OpenInvCommand extends PlayerLookupCommand {
   @Override
   protected void handle(
       @NotNull CommandSender sender,
-      @NotNull Player target,
+      @NotNull PlayerAccess playerAccess,
       boolean accessInv,
       @NotNull String @NotNull [] args
   ) {
     Player player = (Player) sender;
+    Player target = playerAccess.player();
     if (!config.doesNoArgsOpenSelf()) {
       // Record the target
       (accessInv ? this.openInvHistory : this.openEnderHistory).put(player, target.getUniqueId().toString());
@@ -172,7 +173,7 @@ public class OpenInvCommand extends PlayerLookupCommand {
     }
 
     // Open the inventory
-    plugin.openInventory(player, inv);
+    plugin.openInventory(player, inv, playerAccess.viewOnly());
   }
 
 }

plugin/src/main/java/com/lishid/openinv/command/PlayerLookupCommand.java

@@ -79,7 +79,7 @@ public abstract class PlayerLookupCommand implements TabExecutor {
             }
 
             // Perform access checks and load target if necessary.
-            Player onlineTarget = access(sender, target, accessInv);
+            PlayerAccess onlineTarget = access(sender, target, accessInv);
 
             if (onlineTarget != null) {
               handle(sender, onlineTarget, accessInv, args);
@@ -135,7 +135,11 @@ public abstract class PlayerLookupCommand implements TabExecutor {
    * @param invPerms {@code true} to use inventory permissions, {@code false} for ender chest
    * @return the {@link Player} loaded or {@code null} if target is not accessible
    */
-  protected @Nullable Player access(@NotNull CommandSender sender, @NotNull OfflinePlayer target, boolean invPerms) {
+  protected @Nullable PlayerAccess access(
+      @NotNull CommandSender sender,
+      @NotNull OfflinePlayer target,
+      boolean invPerms
+  ) {
     // Attempt to load online player dependent on permissions and configuration.
     Player onlineTarget = accessAsPlayer(sender, target);
 
@@ -144,11 +148,11 @@ public abstract class PlayerLookupCommand implements TabExecutor {
     }
 
     // Permissions checks.
-    if (deniedCommand(sender, onlineTarget, invPerms) || deniedAccess(sender, onlineTarget)) {
+    if (deniedCommand(sender, onlineTarget, invPerms)) {
       return null;
     }
 
-    return onlineTarget;
+    return accessGeneralized(sender, onlineTarget, invPerms);
   }
 
   /**
@@ -203,30 +207,33 @@ public abstract class PlayerLookupCommand implements TabExecutor {
   );
 
   /**
-   * Check for a lack of generalized permissions for accessing the target.
+   * Check for generalized permissions for accessing the target.
    * By default, this is access levels and cross-world restrictions.
    *
    * @param sender the {@link CommandSender} attempting access
    * @param onlineTarget the {@link Player} being targeted by the command
-   * @return {@code true} if the sender does not have access to the target
+   * @param invPerms {@code true} to use inventory permissions, {@code false} for ender chest
+   * @return a {@link PlayerAccess} containing the accessed player and view mode, or {@code null} if denied
    */
-  protected boolean deniedAccess(@NotNull CommandSender sender, @NotNull Player onlineTarget) {
-    if (sender.equals(onlineTarget)) {
-      return false;
+  protected @Nullable PlayerAccess accessGeneralized(
+      @NotNull CommandSender sender,
+      @NotNull Player onlineTarget,
+      boolean invPerms
+  ) {
+
+    boolean ownContainer = sender.equals(onlineTarget);
+    Permissions edit;
+    if (invPerms) {
+      edit = ownContainer ? Permissions.INVENTORY_EDIT_SELF : Permissions.INVENTORY_EDIT_OTHER;
+    } else {
+      edit = ownContainer ? Permissions.ENDERCHEST_EDIT_SELF : Permissions.ENDERCHEST_EDIT_OTHER;
     }
 
-    // Protected check
-    for (int level = 4; level > 0; --level) {
-      String permission = "openinv.access.level." + level;
-      if (onlineTarget.hasPermission(permission)
-          && (!sender.hasPermission(permission) || config.getAccessEqualMode() == AccessEqualMode.DENY)) {
-        lang.sendMessage(
-            sender,
-            "messages.error.permissionExempt",
-            new Replacement("%target%", onlineTarget.getDisplayName())
-        );
-        return true;
-      }
+    boolean viewOnly = !edit.hasPermission(sender);
+
+    if (ownContainer) {
+      // Skip other access checks for self.
+      return new PlayerAccess(onlineTarget, viewOnly);
     }
 
     // Crossworld check
@@ -238,10 +245,41 @@ public abstract class PlayerLookupCommand implements TabExecutor {
           "messages.error.permissionCrossWorld",
           new Replacement("%target%", onlineTarget.getDisplayName())
       );
-      return true;
+      return null;
     }
 
-    return false;
+    AccessEqualMode accessMode = AccessEqualMode.getByPerm(sender, config);
+
+    for (int level = 4; level > 0; --level) {
+      String permission = "openinv.access.level." + level;
+      // If the target doesn't have this access level...
+      if (!onlineTarget.hasPermission(permission)) {
+        // If the viewer does have the access level, all good.
+        if (sender.hasPermission(permission)) {
+          break;
+        }
+        // Otherwise check next access level.
+        continue;
+      }
+
+      // If the viewer doesn't have an equal access level or equal access is a denial, deny.
+      if (!sender.hasPermission(permission) || accessMode == AccessEqualMode.DENY) {
+        lang.sendMessage(
+            sender,
+            "messages.error.permissionExempt",
+            new Replacement("%target%", onlineTarget.getDisplayName())
+        );
+        return null;
+      }
+
+      // Since this is a tie, setting decides view state.
+      if (accessMode == AccessEqualMode.VIEW) {
+        viewOnly = true;
+      }
+      break;
+    }
+
+    return new PlayerAccess(onlineTarget, viewOnly);
   }
 
   /**
@@ -254,7 +292,7 @@ public abstract class PlayerLookupCommand implements TabExecutor {
    */
   protected abstract void handle(
       @NotNull CommandSender sender,
-      @NotNull Player target,
+      @NotNull PlayerAccess target,
       boolean accessInv,
       @NotNull String @NotNull [] args
   );
@@ -273,4 +311,6 @@ public abstract class PlayerLookupCommand implements TabExecutor {
     return TabCompleter.completeOnlinePlayer(sender, args[0]);
   }
 
+  protected record PlayerAccess(Player player, boolean viewOnly) {}
+
 }

plugin/src/main/java/com/lishid/openinv/util/AccessEqualMode.java

@@ -1,5 +1,7 @@
 package com.lishid.openinv.util;
 
+import com.lishid.openinv.util.config.Config;
+import org.bukkit.permissions.Permissible;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -20,4 +22,17 @@ public enum AccessEqualMode {
     };
   }
 
+  public static @NotNull AccessEqualMode getByPerm(@NotNull Permissible permissible, @NotNull Config config) {
+    if (Permissions.ACCESS_EQUAL_EDIT.hasPermission(permissible)) {
+      return AccessEqualMode.ALLOW;
+    }
+    if (Permissions.ACCESS_EQUAL_VIEW.hasPermission(permissible)) {
+      return AccessEqualMode.VIEW;
+    }
+    if (Permissions.ACCESS_EQUAL_DENY.hasPermission(permissible)) {
+      return AccessEqualMode.DENY;
+    }
+    return config.getAccessEqualMode();
+  }
+
 }

plugin/src/main/java/com/lishid/openinv/util/InternalAccessor.java

@@ -64,7 +64,7 @@ public class InternalAccessor {
   }
 
   private @Nullable Accessor getAccessor(@NotNull Logger logger, @NotNull LanguageManager lang) {
-    Version maxSupported = Version.of(1, 21, 8);
+    Version maxSupported = Version.of(1, 21, 11);
     Version minSupported = Version.of(1, 21, 1);
 
     // Ensure version is in supported range.
@@ -74,7 +74,7 @@ public class InternalAccessor {
 
     // Load Spigot accessor.
     if (!PAPER) {
-      if (BukkitVersions.MINECRAFT.equals(maxSupported) || BukkitVersions.MINECRAFT.equals(Version.of(1, 21, 7))) {
+      if (BukkitVersions.MINECRAFT.equals(maxSupported)) {
         // Current Spigot, remapped internals are available.
         return new com.lishid.openinv.internal.reobf.InternalAccessor(logger, lang);
       } else {
@@ -84,10 +84,17 @@ public class InternalAccessor {
     }
 
     // Paper or a Paper fork, can use Mojang-mapped internals.
-    if (BukkitVersions.MINECRAFT.lessThanOrEqual(maxSupported)
-        && BukkitVersions.MINECRAFT.greaterThanOrEqual(Version.of(1, 21, 6))) { // 1.21.6, 1.21.7, 1.21.8
+    if (BukkitVersions.MINECRAFT.equals(maxSupported)) { // 1.21.11
       return new com.lishid.openinv.internal.common.InternalAccessor(logger, lang);
     }
+    if (BukkitVersions.MINECRAFT.lessThanOrEqual(Version.of(1, 21, 10))
+        && BukkitVersions.MINECRAFT.greaterThanOrEqual(Version.of(1, 21, 9))) { // 1.21.9, 1.21.10
+      return new com.lishid.openinv.internal.paper1_21_10.InternalAccessor(logger, lang);
+    }
+    if (BukkitVersions.MINECRAFT.lessThanOrEqual(Version.of(1, 21, 8))
+        && BukkitVersions.MINECRAFT.greaterThanOrEqual(Version.of(1, 21, 6))) { // 1.21.6, 1.21.7, 1.21.8
+      return new com.lishid.openinv.internal.paper1_21_8.InternalAccessor(logger, lang);
+    }
     if (BukkitVersions.MINECRAFT.equals(Version.of(1, 21, 5))) { // 1.21.5
       return new com.lishid.openinv.internal.paper1_21_5.InternalAccessor(logger, lang);
     }
@@ -176,7 +183,7 @@ public class InternalAccessor {
     if (!PAPER) {
       return getSpigotReleaseLink();
     }
-    // Paper 1.21.1-1.21.7
+    // Paper 1.21.1+
     return "https://github.com/Jikoo/OpenInv/releases";
   }
 
@@ -196,6 +203,15 @@ public class InternalAccessor {
     if (BukkitVersions.MINECRAFT.lessThanOrEqual(Version.of(1, 21, 6))) {
       return "Unsupported; upgrade to 1.21.7: https://github.com/Jikoo/OpenInv/releases";
     }
+    if (BukkitVersions.MINECRAFT.lessThanOrEqual(Version.of(1, 21, 8))) {
+      return "https://github.com/Jikoo/OpenInv/releases/tag/5.1.13";
+    }
+    if (BukkitVersions.MINECRAFT.lessThanOrEqual(Version.of(1, 21, 9))) {
+      return "Unsupported; upgrade to 1.21.10: https://github.com/Jikoo/OpenInv/releases/tag/5.1.15";
+    }
+    if (BukkitVersions.MINECRAFT.lessThanOrEqual(Version.of(1, 21, 10))) {
+      return "https://github.com/Jikoo/OpenInv/releases/tag/5.1.15";
+    }
 
     return "https://github.com/Jikoo/OpenInv/releases";
   }

plugin/src/main/resources/plugin.yml

@@ -66,6 +66,9 @@ permissions:
           openinv.access.level.2: false
           openinv.access.level.3: false
           openinv.access.level.4: false
+          openinv.access.equal.edit: false
+          openinv.access.equal.view: false
+          openinv.access.equal.deny: false
       # Spectate features
       openinv.spectate:
         children:

resource-pack/openinv-legibility-pack/pack.mcmeta

@@ -1,13 +1,17 @@
 {
   "pack": {
     "description": "Improve OpenInv's legibility",
-    "pack_format": 55,
-    "supported_formats": [ 34, 64 ]
+    "min_format": 34,
+    "max_format": [75, 0],
+    "pack_format": 64,
+    "supported_formats": [ 34, 75 ]
   },
   "overlays": {
     "entries": [
       {
-        "formats": [ 44, 64 ],
+        "min_format": 44,
+        "max_format": [75, 0],
+        "formats": [ 44, 75 ],
         "directory": "openinv_44"
       },
       {

settings.gradle.kts

@@ -19,6 +19,8 @@ if (!java.lang.Boolean.getBoolean("jitpack")) {
 
   val internals = listOf(
     "common",
+    "paper1_21_10",
+    "paper1_21_8",
     "paper1_21_5",
     "paper1_21_4",
     "paper1_21_3",