fix: Re-implement head_model with the new model format

src/main/resources/firmament.accesswidener

@@ -26,3 +26,5 @@ accessible method net/minecraft/client/render/RenderPhase$Texture getId ()Ljava/
 accessible field net/minecraft/client/render/RenderLayer$MultiPhase phases Lnet/minecraft/client/render/RenderLayer$MultiPhaseParameters;
 accessible field net/minecraft/client/render/RenderLayer$MultiPhaseParameters texture Lnet/minecraft/client/render/RenderPhase$TextureBase;
 accessible field net/minecraft/client/network/ClientPlayerInteractionManager currentBreakingPos Lnet/minecraft/util/math/BlockPos;
+
+mutable field net/minecraft/client/render/entity/state/LivingEntityRenderState headItemRenderState Lnet/minecraft/client/render/item/ItemRenderState;

src/texturePacks/java/moe/nea/firmament/features/texturepack/CustomModelOverrideParser.kt

@@ -110,6 +110,10 @@ object CustomModelOverrideParser {
 			Firmament.identifier("predicates/legacy"),
 			PredicateModel.Unbaked.CODEC
 		)
+		ItemModelTypes.ID_MAPPER.put(
+			Firmament.identifier("head_model"),
+			HeadModelChooser.Unbaked.CODEC
+		)
 	}
 
 }

src/texturePacks/java/moe/nea/firmament/features/texturepack/HeadModelChooser.kt

@@ -0,0 +1,90 @@
+package moe.nea.firmament.features.texturepack
+
+import com.google.gson.JsonObject
+import com.mojang.serialization.MapCodec
+import com.mojang.serialization.codecs.RecordCodecBuilder
+import net.minecraft.client.item.ItemModelManager
+import net.minecraft.client.render.item.ItemRenderState
+import net.minecraft.client.render.item.model.BasicItemModel
+import net.minecraft.client.render.item.model.ItemModel
+import net.minecraft.client.render.item.model.ItemModelTypes
+import net.minecraft.client.render.model.ResolvableModel
+import net.minecraft.client.world.ClientWorld
+import net.minecraft.entity.LivingEntity
+import net.minecraft.item.ItemStack
+import net.minecraft.item.ModelTransformationMode
+import net.minecraft.util.Identifier
+
+object HeadModelChooser {
+	val IS_CHOOSING_HEAD_MODEL = ThreadLocal.withInitial { false }
+
+	interface HasExplicitHeadModelMarker {
+		fun markExplicitHead_Firmament()
+		fun isExplicitHeadModel_Firmament(): Boolean
+		companion object{
+			@JvmStatic
+			fun cast(state: ItemRenderState) = state as HasExplicitHeadModelMarker
+		}
+	}
+
+	data class Baked(val head: ItemModel, val regular: ItemModel) : ItemModel {
+		override fun update(
+			state: ItemRenderState,
+			stack: ItemStack?,
+			resolver: ItemModelManager?,
+			transformationMode: ModelTransformationMode?,
+			world: ClientWorld?,
+			user: LivingEntity?,
+			seed: Int
+		) {
+			val instance =
+				if (IS_CHOOSING_HEAD_MODEL.get()) {
+					HasExplicitHeadModelMarker.cast(state).markExplicitHead_Firmament()
+					head
+				} else {
+					regular
+				}
+			instance.update(state, stack, resolver, transformationMode, world, user, seed)
+		}
+	}
+
+	data class Unbaked(
+		val head: ItemModel.Unbaked,
+		val regular: ItemModel.Unbaked,
+	) : ItemModel.Unbaked {
+		override fun getCodec(): MapCodec<out ItemModel.Unbaked> {
+			return CODEC
+		}
+
+		override fun bake(context: ItemModel.BakeContext): ItemModel {
+			return Baked(
+				head.bake(context),
+				regular.bake(context)
+			)
+		}
+
+		override fun resolve(resolver: ResolvableModel.Resolver) {
+			head.resolve(resolver)
+			regular.resolve(resolver)
+		}
+
+		companion object {
+			@JvmStatic
+			fun fromLegacyJson(jsonObject: JsonObject, unbakedModel: ItemModel.Unbaked): ItemModel.Unbaked {
+				val model = jsonObject["firmament:head_model"] ?: return unbakedModel
+				val modelUrl = model.asJsonPrimitive.asString
+				val headModel = BasicItemModel.Unbaked(Identifier.of(modelUrl), listOf())
+				return Unbaked(headModel, unbakedModel)
+			}
+
+			val CODEC = RecordCodecBuilder.mapCodec {
+				it.group(
+					ItemModelTypes.CODEC.fieldOf("head")
+						.forGetter(Unbaked::head),
+					ItemModelTypes.CODEC.fieldOf("regular")
+						.forGetter(Unbaked::regular),
+				).apply(it, ::Unbaked)
+			}
+		}
+	}
+}

src/texturePacks/java/moe/nea/firmament/mixins/custommodels/ItemRenderStateExtraInfo.java

@@ -0,0 +1,28 @@
+package moe.nea.firmament.mixins.custommodels;
+
+import moe.nea.firmament.features.texturepack.HeadModelChooser;
+import net.minecraft.client.render.item.ItemRenderState;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(ItemRenderState.class)
+public class ItemRenderStateExtraInfo implements HeadModelChooser.HasExplicitHeadModelMarker {
+	boolean hasExplicitHead_firmament = false;
+
+	@Inject(method = "clear", at = @At("HEAD"))
+	private void clear(CallbackInfo ci) {
+		hasExplicitHead_firmament = false;
+	}
+
+	@Override
+	public void markExplicitHead_Firmament() {
+		hasExplicitHead_firmament = true;
+	}
+
+	@Override
+	public boolean isExplicitHeadModel_Firmament() {
+		return hasExplicitHead_firmament;
+	}
+}

src/texturePacks/java/moe/nea/firmament/mixins/custommodels/ReplaceHeadModel.java

@@ -0,0 +1,51 @@
+package moe.nea.firmament.mixins.custommodels;
+
+import moe.nea.firmament.features.texturepack.HeadModelChooser;
+import net.minecraft.client.item.ItemModelManager;
+import net.minecraft.client.render.entity.LivingEntityRenderer;
+import net.minecraft.client.render.entity.model.EntityModel;
+import net.minecraft.client.render.entity.state.LivingEntityRenderState;
+import net.minecraft.client.render.item.ItemRenderState;
+import net.minecraft.entity.EquipmentSlot;
+import net.minecraft.entity.LivingEntity;
+import net.minecraft.item.ModelTransformationMode;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(LivingEntityRenderer.class)
+public class ReplaceHeadModel<T extends LivingEntity, S extends LivingEntityRenderState, M extends EntityModel<? super S>> {
+	@Shadow
+	@Final
+	protected ItemModelManager itemModelResolver;
+
+	@Unique
+	private ItemRenderState tempRenderState = new ItemRenderState();
+
+	@Inject(
+		method = "updateRenderState(Lnet/minecraft/entity/LivingEntity;Lnet/minecraft/client/render/entity/state/LivingEntityRenderState;F)V",
+		at = @At("TAIL")
+	)
+	private void replaceHeadModel(
+		T livingEntity, S livingEntityRenderState, float f, CallbackInfo ci
+	) {
+		var headItemStack = livingEntity.getEquippedStack(EquipmentSlot.HEAD);
+
+		HeadModelChooser.INSTANCE.getIS_CHOOSING_HEAD_MODEL().set(true);
+		tempRenderState.clear();
+		this.itemModelResolver.updateForLivingEntity(tempRenderState, headItemStack, ModelTransformationMode.HEAD, false, livingEntity);
+		HeadModelChooser.INSTANCE.getIS_CHOOSING_HEAD_MODEL().set(false);
+
+		if (HeadModelChooser.HasExplicitHeadModelMarker.cast(tempRenderState)
+			.isExplicitHeadModel_Firmament()) {
+			livingEntityRenderState.wearingSkullType = null;
+			var temp = livingEntityRenderState.headItemRenderState;
+			livingEntityRenderState.headItemRenderState = tempRenderState;
+			tempRenderState = temp;
+		}
+	}
+}

src/texturePacks/java/moe/nea/firmament/mixins/custommodels/SupplyFakeModelPatch.java

@@ -5,6 +5,7 @@ import com.llamalad7.mixinextras.injector.ModifyReturnValue;
 import com.llamalad7.mixinextras.sugar.Local;
 import moe.nea.firmament.Firmament;
 import moe.nea.firmament.features.texturepack.CustomSkyBlockTextures;
+import moe.nea.firmament.features.texturepack.HeadModelChooser;
 import moe.nea.firmament.features.texturepack.PredicateModel;
 import moe.nea.firmament.util.ErrorUtil;
 import net.minecraft.client.item.ItemAsset;
@@ -61,6 +62,7 @@ public class SupplyFakeModelPatch {
 			try (var is = resource.getInputStream()) {
 				var jsonObject = Firmament.INSTANCE.getGson().fromJson(new InputStreamReader(is), JsonObject.class);
 				unbakedModel = PredicateModel.Unbaked.fromLegacyJson(jsonObject, unbakedModel);
+				unbakedModel = HeadModelChooser.Unbaked.fromLegacyJson(jsonObject, unbakedModel);
 			} catch (Exception e) {
 				ErrorUtil.INSTANCE.softError("Could not create resource for fake model supplication: " + model.getKey(), e);
 			}