Map first float of 1.21.4 custom model data as int for 1.21.3 clients

common/src/main/java/com/viaversion/viabackwards/ViaBackwardsConfig.java

@@ -37,6 +37,7 @@ public class ViaBackwardsConfig extends Config implements com.viaversion.viaback
     private boolean bedrockAtY0;
     private boolean sculkShriekersToCryingObsidian;
     private boolean mapDarknessEffect;
+    private boolean mapCustomModelData;
     private boolean suppressEmulationWarnings;
 
     public ViaBackwardsConfig(File configFile, Logger logger) {
@@ -59,6 +60,7 @@ private void loadFields() {
         bedrockAtY0 = getBoolean("bedrock-at-y-0", false);
         sculkShriekersToCryingObsidian = getBoolean("sculk-shriekers-to-crying-obsidian", false);
         mapDarknessEffect = getBoolean("map-darkness-effect", true);
+        mapCustomModelData = getBoolean("map-custom-model-data", true);
         suppressEmulationWarnings = getBoolean("suppress-emulation-warnings", false);
     }
 
@@ -107,6 +109,11 @@ public boolean mapDarknessEffect() {
         return mapDarknessEffect;
     }
 
+    @Override
+    public boolean mapCustomModelData() {
+        return mapCustomModelData;
+    }
+
     @Override
     public boolean suppressEmulationWarnings() {
         return suppressEmulationWarnings;

common/src/main/java/com/viaversion/viabackwards/api/ViaBackwardsConfig.java

@@ -85,6 +85,13 @@ public interface ViaBackwardsConfig extends Config {
      */
     boolean mapDarknessEffect();
 
+    /**
+     * If enabled, 1.21.3 clients will receive the first float of 1.21.4+ custom model data as int. Disable if you handle this change yourself.
+     *
+     * @return true if enabled
+     */
+    boolean mapCustomModelData();
+
     /**
      * Suppresses warnings of missing emulations for certain features that are not supported (e.g. world height in 1.17+).
      *

common/src/main/java/com/viaversion/viabackwards/protocol/v1_21_4to1_21_2/rewriter/BlockItemPacketRewriter1_21_4.java

@@ -22,6 +22,7 @@
 import com.viaversion.nbt.tag.IntArrayTag;
 import com.viaversion.nbt.tag.ListTag;
 import com.viaversion.nbt.tag.StringTag;
+import com.viaversion.viabackwards.ViaBackwards;
 import com.viaversion.viabackwards.api.rewriters.BackwardsStructuredItemRewriter;
 import com.viaversion.viabackwards.protocol.v1_21_4to1_21_2.Protocol1_21_4To1_21_2;
 import com.viaversion.viaversion.api.connection.UserConnection;
@@ -95,6 +96,11 @@ public Item handleItemToClient(final UserConnection connection, final Item item)
         final CustomModelData1_21_4 modelData = dataContainer.get(StructuredDataKey.CUSTOM_MODEL_DATA1_21_4);
         if (modelData != null) {
             saveTag(createCustomTag(item), customModelDataToTag(modelData), "custom_model_data");
+            if (ViaBackwards.getConfig().mapCustomModelData() && modelData.floats().length > 0) {
+                // Put first float as old custom model data as this is the most common replacement
+                final int data = (int) modelData.floats()[0];
+                dataContainer.set(StructuredDataKey.CUSTOM_MODEL_DATA1_20_5, data);
+            }
         }
 
         downgradeItemData(item);

common/src/main/resources/assets/viabackwards/config.yml

@@ -31,5 +31,8 @@ sculk-shriekers-to-crying-obsidian: true
 # Maps the darkness effect to blindness for 1.18.2 clients on 1.19+ servers.
 map-darkness-effect: true
 #
+# If enabled, 1.21.3 clients will receive the first float of 1.21.4+ custom model data as int. Disable if you handle this change yourself.
+map-custom-model-data: true
+#
 # Suppresses warnings of missing emulations for certain features that are not supported (e.g. world height in 1.17+).
 suppress-emulation-warnings: false