Environment attribute API for adding custom attribute layers

fabric-environment-attributes-v1/build.gradle

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+version = getSubprojectVersion(project)
+
+moduleDependencies(project, [
+	'fabric-api-base',
+	'fabric-lifecycle-events-v1'
+])
+
+testDependencies(project, [
+	':fabric-resource-loader-v1',
+	':fabric-client-gametest-api-v1'
+])

fabric-environment-attributes-v1/src/main/java/net/fabricmc/fabric/api/environment/attribute/v1/AttributeLayerProvider.java

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+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.api.environment.attribute.v1;
+
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.attribute.EnvironmentAttributeLayer;
+import net.minecraft.world.attribute.EnvironmentAttributeSystem;
+import net.minecraft.world.level.Level;
+
+/**
+ * Provides {@link EnvironmentAttributeLayer}s to an {@link EnvironmentAttributeSystem}. You may register custom
+ * {@link AttributeLayerProvider} implementations using {@link AttributeLayerRegistry#registerLayerProvider}.
+ *
+ * <p>
+ * Attribute layers can be ordered relative to vanilla's layers or other modded layers using
+ * {@link AttributeLayerRegistry#addLayerOrdering}. The order defines which layers override which other layers: layers
+ * that come first in the ordering are overriden by layers that come later in the ordering. For example, in vanilla,
+ * biome layers come after dimension layers, since biome-local attributes override dimension-global attributes.
+ * </p>
+ *
+ * <p>
+ * Minecraft adds layers in four phases: dimension-global attributes, then biome-local attributes, then
+ * timeline-interpolated attributes, and finally some hardcoded weather attributes. Each of these phases, as well modded
+ * layer providers, are associated with an identifier that can be sorted against.
+ * </p>
+ */
+public interface AttributeLayerProvider {
+	/**
+	 * Identifier associated to vanilla's dimension attribute layers.
+	 */
+	Identifier DIMENSION = Identifier.withDefaultNamespace("dimensions");
+
+	/**
+	 * Identifier associated to vanilla's biome attribute layers.
+	 */
+	Identifier BIOMES = Identifier.withDefaultNamespace("biomes");
+
+	/**
+	 * Identifier associated to vanilla's timeline attribute layers.
+	 */
+	Identifier TIMELINES = Identifier.withDefaultNamespace("timelines");
+
+	/**
+	 * Identifier associated to vanilla's weather attribute layers.
+	 */
+	Identifier WEATHER = Identifier.withDefaultNamespace("weather");
+
+	/**
+	 * The identifier associated to the first vanilla phase. Currently, that is {@link #DIMENSION}.
+	 * This constant exists purely for compatibility: if Minecraft ever adds another layer before its dimension phase,
+	 * then this constant is updated.
+	 */
+	Identifier FIRST_VANILLA_PHASE = DIMENSION;
+
+	/**
+	 * The identifier associated to the last vanilla phase. Currently, that is {@link #WEATHER}.
+	 * This constant exists purely for compatibility: if Minecraft ever adds another layer after its weather phase,
+	 * then this constant is updated.
+	 */
+	Identifier LAST_VANILLA_PHASE = WEATHER;
+
+	/**
+	 * Called to add attribute layers to an {@link EnvironmentAttributeSystem.Builder} for the given {@link Level}.
+	 * This is called both on the client and on the server for every {@link Level} that is created.
+	 *
+	 * @param systemBuilder The {@link EnvironmentAttributeSystem.Builder} to add layers to.
+	 * @param level         The {@link Level} that the environment attribute system is being created for.
+	 */
+	void addAttributeLayers(EnvironmentAttributeSystem.Builder systemBuilder, Level level);
+}

fabric-environment-attributes-v1/src/main/java/net/fabricmc/fabric/api/environment/attribute/v1/AttributeLayerRegistry.java

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+/*
+ * Copyright (c) 2016, 2017, 2018, 2019 FabricMC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.fabricmc.fabric.api.environment.attribute.v1;
+
+import org.jspecify.annotations.NullMarked;
+
+import net.minecraft.resources.Identifier;
+
+import net.fabricmc.fabric.impl.environment.attribute.AttributeLayerRegistryImpl;
+
+@NullMarked
+public class AttributeLayerRegistry {
+	/**
+	 * Register a {@link AttributeLayerProvider}. If a layer with the given identifier already exists, an exception
+	 * is thrown.
+	 *
+	 * @param id    The identifier of the layer provider. This can be ordered against by other layer providers.
+	 * @param layer The layer provider to register.
+	 */
+	public static void registerLayerProvider(Identifier id, AttributeLayerProvider layer) {
+		AttributeLayerRegistryImpl.registerLayerProvider(id, layer);
+	}
+
+	/**
+	 * Declares that the layer provider with the first identifier should activate before the layer provider with the
+	 * second identifier. Unless this causes a cyclic dependency, the two layer providers are guaranteed to activate in
+	 * said order. You may use this to order your layer provider against vanilla phases using any of the constants in
+	 * {@link AttributeLayerProvider}. If both layer identifiers are the same, then an exception is thrown.
+	 *
+	 * @param firstLayer  The ID of the layer that should activate earlier.
+	 * @param secondLayer The ID of the layer that should activate later.
+	 */
+	public static void addLayerOrdering(Identifier firstLayer, Identifier secondLayer) {
+		AttributeLayerRegistryImpl.addLayerOrdering(firstLayer, secondLayer);
+	}
+}