Emulate block and item display entities in 1.19.4->1.19.3

common/src/main/java/com/viaversion/viabackwards/protocol/v1_19_4to1_19_3/Protocol1_19_4To1_19_3.java

@@ -23,11 +23,10 @@ import com.viaversion.viabackwards.api.rewriters.SoundRewriter;
 import com.viaversion.viabackwards.api.rewriters.TranslatableRewriter;
 import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.rewriter.BlockItemPacketRewriter1_19_4;
 import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.rewriter.EntityPacketRewriter1_19_4;
+import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.storage.EntityTracker1_19_4;
 import com.viaversion.viaversion.api.connection.UserConnection;
-import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_19_4;
 import com.viaversion.viaversion.api.protocol.packet.PacketWrapper;
 import com.viaversion.viaversion.api.type.Types;
-import com.viaversion.viaversion.data.entity.EntityTrackerBase;
 import com.viaversion.viaversion.libs.gson.JsonElement;
 import com.viaversion.viaversion.protocols.v1_19_1to1_19_3.packet.ClientboundPackets1_19_3;
 import com.viaversion.viaversion.protocols.v1_19_1to1_19_3.packet.ServerboundPackets1_19_3;
@@ -110,7 +109,7 @@ public final class Protocol1_19_4To1_19_3 extends BackwardsProtocol<ClientboundP
 
     @Override
     public void init(final UserConnection user) {
-        addEntityTracker(user, new EntityTrackerBase(user, EntityTypes1_19_4.PLAYER));
+        addEntityTracker(user, new EntityTracker1_19_4(user));
     }
 
     @Override

common/src/main/java/com/viaversion/viabackwards/protocol/v1_19_4to1_19_3/rewriter/EntityPacketRewriter1_19_4.java

@@ -23,9 +23,14 @@ import com.viaversion.nbt.tag.NumberTag;
 import com.viaversion.viabackwards.api.entities.storage.EntityReplacement;
 import com.viaversion.viabackwards.api.rewriters.EntityRewriter;
 import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.Protocol1_19_4To1_19_3;
+import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.storage.LinkedEntityStorage;
+import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.storage.EntityTracker1_19_4;
 import com.viaversion.viaversion.api.minecraft.entities.EntityType;
+import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_19_3;
 import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_19_4;
 import com.viaversion.viaversion.api.minecraft.entitydata.EntityData;
+import com.viaversion.viaversion.api.minecraft.item.Item;
+import com.viaversion.viaversion.api.protocol.packet.PacketWrapper;
 import com.viaversion.viaversion.api.protocol.remapper.PacketHandlers;
 import com.viaversion.viaversion.api.type.Types;
 import com.viaversion.viaversion.api.type.types.version.Types1_19_3;
@@ -171,8 +176,31 @@ public final class EntityPacketRewriter1_19_4 extends EntityRewriter<Clientbound
             final JsonElement element = data.value();
             protocol.getComponentRewriter().processText(event.user(), element);
         }));
+        filter().type(EntityTypes1_19_4.BLOCK_DISPLAY).index(22).handler((event, data) -> {
+            final int value = data.value();
+
+            final EntityTracker1_19_4 tracker = tracker(event.user());
+            tracker.clearLinkedEntityStorage(event.entityId());
+
+            final int linkedEntity = tracker.spawnEntity(EntityTypes1_19_3.FALLING_BLOCK, value);
+            tracker.entityData(event.entityId()).put(new LinkedEntityStorage(linkedEntity));
+
+            final PacketWrapper wrapper = PacketWrapper.create(ClientboundPackets1_19_3.SET_PASSENGERS, event.user());
+            wrapper.write(Types.VAR_INT, event.entityId()); // Entity id
+            wrapper.write(Types.VAR_INT_ARRAY_PRIMITIVE, new int[] { linkedEntity }); // Passenger entity ids
+            wrapper.send(Protocol1_19_4To1_19_3.class);
+        });
+        filter().type(EntityTypes1_19_4.ITEM_DISPLAY).index(22).handler((event, data) -> {
+            final Item value = data.value();
+
+            final PacketWrapper setEquipment = PacketWrapper.create(ClientboundPackets1_19_3.SET_EQUIPMENT, event.user());
+            setEquipment.write(Types.VAR_INT, event.entityId()); // Entity id
+            setEquipment.write(Types.BYTE, (byte) 5); // Slot - head
+            setEquipment.write(Types.ITEM1_13_2, value);
+
+            setEquipment.send(Protocol1_19_4To1_19_3.class);
+        });
         filter().type(EntityTypes1_19_4.DISPLAY).handler((event, data) -> {
-            // TODO Maybe spawn an extra entity to ride the armor stand for blocks and items
             // Remove a large heap of display entity data
             if (event.index() > 7) {
                 event.cancel();

common/src/main/java/com/viaversion/viabackwards/protocol/v1_19_4to1_19_3/storage/EntityTracker1_19_4.java

@@ -0,0 +1,102 @@
+/*
+ * This file is part of ViaBackwards - https://github.com/ViaVersion/ViaBackwards
+ * Copyright (C) 2016-2024 ViaVersion and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.storage;
+
+import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.Protocol1_19_4To1_19_3;
+import com.viaversion.viaversion.api.connection.UserConnection;
+import com.viaversion.viaversion.api.data.entity.TrackedEntity;
+import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_19_3;
+import com.viaversion.viaversion.api.minecraft.entities.EntityTypes1_19_4;
+import com.viaversion.viaversion.api.protocol.packet.PacketWrapper;
+import com.viaversion.viaversion.api.type.Types;
+import com.viaversion.viaversion.data.entity.EntityTrackerBase;
+import com.viaversion.viaversion.libs.fastutil.ints.IntArraySet;
+import com.viaversion.viaversion.libs.fastutil.ints.IntSet;
+import com.viaversion.viaversion.protocols.v1_19_1to1_19_3.packet.ClientboundPackets1_19_3;
+import java.util.UUID;
+import java.util.concurrent.ThreadLocalRandom;
+
+public final class EntityTracker1_19_4 extends EntityTrackerBase {
+
+    private final IntSet generatedEntities = new IntArraySet(); // Track entities spawned to prevent duplicated entity ids
+
+    public EntityTracker1_19_4(final UserConnection connection) {
+        super(connection, EntityTypes1_19_4.PLAYER);
+    }
+
+    public int spawnEntity(final EntityTypes1_19_3 entityType, final int data) {
+        final int entityId = nextEntityId();
+
+        final PacketWrapper addEntity = PacketWrapper.create(ClientboundPackets1_19_3.ADD_ENTITY, user());
+        addEntity.write(Types.VAR_INT, entityId); // Entity id
+        addEntity.write(Types.UUID, UUID.randomUUID()); // Entity UUID
+        addEntity.write(Types.VAR_INT, entityType.getId()); // Entity type
+        addEntity.write(Types.DOUBLE, 0.0); // X
+        addEntity.write(Types.DOUBLE, 0.0); // Y
+        addEntity.write(Types.DOUBLE, 0.0); // Z
+        addEntity.write(Types.BYTE, (byte) 0); // Pitch
+        addEntity.write(Types.BYTE, (byte) 0); // Yaw
+        addEntity.write(Types.BYTE, (byte) 0); // Head yaw
+        addEntity.write(Types.VAR_INT, data); // Data
+        addEntity.write(Types.SHORT, (short) 0); // Velocity X
+        addEntity.write(Types.SHORT, (short) 0); // Velocity Y
+        addEntity.write(Types.SHORT, (short) 0); // Velocity Z
+
+        addEntity.send(Protocol1_19_4To1_19_3.class);
+
+        generatedEntities.add(entityId);
+        return entityId;
+    }
+
+
+    @Override
+    public void clearEntities() {
+        for (final Integer id : entities.keySet()) {
+            clearLinkedEntityStorage(id);
+        }
+        super.clearEntities();
+    }
+
+    @Override
+    public void removeEntity(final int id) {
+        clearLinkedEntityStorage(id);
+        super.removeEntity(id);
+    }
+
+    public void clearLinkedEntityStorage(final int id) {
+        final TrackedEntity entity = entity(id);
+        if (!entity.hasData()) {
+            return;
+        }
+
+        final LinkedEntityStorage storage = entity.data().get(LinkedEntityStorage.class);
+        if (storage != null) {
+            storage.remove(user());
+            generatedEntities.remove(id);
+        }
+    }
+
+    private int nextEntityId() {
+        final int entityId = -ThreadLocalRandom.current().nextInt(10_000);
+        if (generatedEntities.contains(entityId)) {
+            return nextEntityId();
+        }
+        return entityId;
+    }
+
+}

common/src/main/java/com/viaversion/viabackwards/protocol/v1_19_4to1_19_3/storage/LinkedEntityStorage.java

@@ -0,0 +1,36 @@
+/*
+ * This file is part of ViaBackwards - https://github.com/ViaVersion/ViaBackwards
+ * Copyright (C) 2016-2024 ViaVersion and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.storage;
+
+import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.Protocol1_19_4To1_19_3;
+import com.viaversion.viaversion.api.connection.StorableObject;
+import com.viaversion.viaversion.api.connection.UserConnection;
+import com.viaversion.viaversion.api.protocol.packet.PacketWrapper;
+import com.viaversion.viaversion.api.type.Types;
+import com.viaversion.viaversion.protocols.v1_19_1to1_19_3.packet.ClientboundPackets1_19_3;
+
+public record LinkedEntityStorage(int... entities) implements StorableObject {
+
+    public void remove(final UserConnection connection) {
+        final PacketWrapper wrapper = PacketWrapper.create(ClientboundPackets1_19_3.REMOVE_ENTITIES, connection);
+        wrapper.write(Types.VAR_INT_ARRAY_PRIMITIVE, entities);
+
+        wrapper.send(Protocol1_19_4To1_19_3.class);
+    }
+
+}