Rewrite interactions as invisible slimes

common/src/main/java/com/viaversion/viabackwards/api/entities/storage/WrappedEntityData.java

@@ -28,6 +28,10 @@ public boolean has(EntityData data) {
         return this.entityDataList.contains(data);
     }
 
+    public boolean has(int index) {
+        return entityDataList.stream().anyMatch(data -> data.id() == index);
+    }
+
     public void remove(EntityData data) {
         this.entityDataList.remove(data);
     }

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

@@ -26,6 +26,7 @@
 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.EntityTracker1_19_4;
+import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.storage.InteractionData;
 import com.viaversion.viabackwards.protocol.v1_19_4to1_19_3.storage.LinkedEntityStorage;
 import com.viaversion.viaversion.api.connection.UserConnection;
 import com.viaversion.viaversion.api.data.entity.TrackedEntity;
@@ -494,9 +495,33 @@ public void registerRewrites() {
             }
         });
 
-        filter().type(EntityTypes1_19_4.INTERACTION).cancel(8); // Width
-        filter().type(EntityTypes1_19_4.INTERACTION).cancel(9); // Height
-        filter().type(EntityTypes1_19_4.INTERACTION).cancel(10); // Response
+        filter().type(EntityTypes1_19_4.INTERACTION).handler(((event, data) -> {
+            if (event.index() == 8 || event.index() == 9) {
+                // Width/Height, use slime of appropriate size
+                InteractionData interactionData = event.trackedEntity().get(InteractionData.class);
+                if (interactionData == null) {
+                    interactionData = new InteractionData();
+                    event.trackedEntity().put(interactionData);
+                }
+                final int slimeSize = interactionData.update(data.value(), event.index() == 8);
+                // let's only send one size data even if we get both width and height
+                final EntityData otherDimData = event.dataAtIndex(16);
+                if (otherDimData != null) {
+                    otherDimData.setTypeAndValue(Types1_19_3.ENTITY_DATA_TYPES.varIntType, slimeSize);
+                    event.cancel();
+                    return;
+                }
+                event.setIndex(16);
+                data.setTypeAndValue(Types1_19_3.ENTITY_DATA_TYPES.varIntType, slimeSize);
+            } else if (event.index() == 10) {
+                // Response
+                event.cancel();
+            } else if (event.index() == 0) {
+                // Keep invisibility
+                final byte flags = data.value();
+                data.setValue((byte) (flags | 0x20));
+            }
+        }));
 
         filter().type(EntityTypes1_19_4.SNIFFER).cancel(17); // State
         filter().type(EntityTypes1_19_4.SNIFFER).cancel(18); // Drop seed at tick
@@ -644,7 +669,13 @@ public void onMappingDataLoaded() {
         mapEntityTypeWithData(EntityTypes1_19_4.ITEM_DISPLAY, EntityTypes1_19_4.ARMOR_STAND).spawnEntityData(displayDataCreator);
         mapEntityTypeWithData(EntityTypes1_19_4.BLOCK_DISPLAY, EntityTypes1_19_4.ARMOR_STAND).spawnEntityData(displayDataCreator);
 
-        mapEntityTypeWithData(EntityTypes1_19_4.INTERACTION, EntityTypes1_19_4.ARMOR_STAND).spawnEntityData(displayDataCreator); // Not much we can do about this one
+        mapEntityTypeWithData(EntityTypes1_19_4.INTERACTION, EntityTypes1_19_4.SLIME).spawnEntityData(storage -> {
+            storage.add(new EntityData(0, Types1_19_3.ENTITY_DATA_TYPES.byteType, (byte) 0x20)); // Invisible
+            storage.add(new EntityData(4, Types1_19_3.ENTITY_DATA_TYPES.booleanType, true)); // Silent
+            if (!storage.has(16)) {
+                storage.add(new EntityData(16, Types1_19_3.ENTITY_DATA_TYPES.varIntType, 2)); // Size
+            }
+        });
 
         mapEntityTypeWithData(EntityTypes1_19_4.SNIFFER, EntityTypes1_19_4.RAVAGER).jsonName();
     }

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

@@ -0,0 +1,50 @@
+/*
+ * This file is part of ViaBackwards - https://github.com/ViaVersion/ViaBackwards
+ * Copyright (C) 2016-2026 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.viaversion.api.connection.StorableObject;
+import com.viaversion.viaversion.util.MathUtil;
+
+public class InteractionData implements StorableObject {
+  private static final double SLIME_DIMENSIONS = 0.52;
+
+  private float width;
+  private float height;
+
+  private int slimeSize;
+
+  public InteractionData() {
+    this.width = 1.0F;
+    this.height = 1.0F;
+    calculateSize();
+  }
+
+  public int update(final float dimension, final boolean isWidth) {
+    if (isWidth) {
+      this.width = dimension;
+    } else {
+      this.height = dimension;
+    }
+    calculateSize();
+    return slimeSize;
+  }
+
+  private void calculateSize() {
+    slimeSize = MathUtil.clamp((int) Math.round(Math.min(width, height) / SLIME_DIMENSIONS), 1, 127);
+  }
+}