Add Support for Custom Item Settings

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/api/item/v1/CustomItemSetting.java

@@ -0,0 +1,86 @@
+/*
+ * 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.item.v1;
+
+import java.util.function.Supplier;
+
+import net.minecraft.item.Item;
+
+import net.fabricmc.fabric.impl.item.CustomItemSettingImpl;
+
+/**
+ * A type of setting that can be passed to item constructors.
+ * This feature can be used by mods to add non-standard settings
+ * to items in a way that is compatible with other mods that add
+ * settings to items.
+ *
+ * <p>Values of this setting can be retrieved from an item using {@link CustomItemSetting#get(Item)},
+ * and users that wish to expose a custom setting for use in other mods should do so by exposing
+ * the CustomItemSetting instance.
+ *
+ * <h3>Usage Example</h3>
+ * <pre>{@code
+ * // Create the setting instance. You can think of this as the "setting key".
+ * public static final CustomItemSetting<String> CUSTOM_TOOLTIP = CustomItemSetting.create(() -> null);
+ *
+ * @Override
+ * public void onInitializeClient() {
+ *     ItemTooltipCallback.EVENT.register((stack, context, lines) -> {
+ *         // Gets the setting from the specified item.
+ *         String tooltip = CUSTOM_TOOLTIP.getValue(stack.getItem());
+ *
+ *         if (tooltip != null) {
+ *             lines.add(new LiteralText(tooltip));
+ *         }
+ *     }
+ * }}</pre>
+ *
+ * <p>You should not implement this interface.
+ *
+ * <p>Use {@link CustomItemSetting#create(Supplier)} to retrieve an instance of Fabric API's implementation.
+ *
+ * @param <T> the type of the setting to be attached
+ */
+public interface CustomItemSetting<T> {
+	/**
+	 * Returns the current value of this setting for the given {@link Item}.
+	 *
+	 * @param item the item
+	 * @return the current setting if present, the default setting if not
+	 */
+	T get(Item item);
+
+	/**
+	 * Creates a new CustomItemSetting with the given default value.
+	 *
+	 * @param defaultValue the value all items that do not explicitly set this setting will have.
+	 * @return a new CustomItemSetting
+	 */
+	static <T> CustomItemSetting<T> create(Supplier<T> defaultValue) {
+		return new CustomItemSettingImpl<>(defaultValue);
+	}
+
+	/**
+	 * Creates a new CustomItemSetting with the given default value.
+	 *
+	 * @param defaultValue the value all items that do not explicitly set this setting will have.
+	 * @return a new CustomItemSetting
+	 */
+	static <T> CustomItemSetting<T> create(T defaultValue) {
+		return new CustomItemSettingImpl<>(() -> defaultValue);
+	}
+}

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/api/item/v1/FabricItemSettings.java

@@ -22,7 +22,7 @@
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.Rarity;
 
-import net.fabricmc.fabric.impl.item.FabricItemInternals;
+import net.fabricmc.fabric.impl.item.CustomItemSettingImpl;
 
 /**
  * Fabric's version of Item.Settings. Adds additional methods and hooks
@@ -39,8 +39,7 @@ public class FabricItemSettings extends Item.Settings {
 	 * @return this builder
 	 */
 	public FabricItemSettings equipmentSlot(EquipmentSlotProvider equipmentSlotProvider) {
-		FabricItemInternals.computeExtraData(this).equipmentSlot(equipmentSlotProvider);
-		return this;
+		return this.custom(CustomItemSettingImpl.EQUIPMENT_SLOT_PROVIDER, equipmentSlotProvider);
 	}
 
 	/**
@@ -49,7 +48,22 @@ public FabricItemSettings equipmentSlot(EquipmentSlotProvider equipmentSlotProvi
 	 * @see CustomDamageHandler
 	 */
 	public FabricItemSettings customDamage(CustomDamageHandler handler) {
-		FabricItemInternals.computeExtraData(this).customDamage(handler);
+		return this.custom(CustomItemSettingImpl.CUSTOM_DAMAGE_HANDLER, handler);
+	}
+
+	/**
+	 * Sets a custom setting of the item.
+
+	 * @param setting the unique type for this setting
+	 * @param value the object containing the setting itself
+	 * @return this builder
+	 */
+	public <T> FabricItemSettings custom(CustomItemSetting<T> setting, T value) {
+		if (!(setting instanceof CustomItemSettingImpl)) {
+			throw new UnsupportedOperationException("CustomItemSetting should not be ");
+		}
+
+		((CustomItemSettingImpl<T>) setting).set(this, value);
 		return this;
 	}
 

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/impl/item/CustomItemSettingImpl.java

@@ -0,0 +1,77 @@
+/*
+ * 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.impl.item;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+import java.util.WeakHashMap;
+import java.util.function.Supplier;
+
+import net.minecraft.item.Item;
+
+import net.fabricmc.fabric.api.item.v1.CustomItemSetting;
+import net.fabricmc.fabric.api.item.v1.CustomDamageHandler;
+import net.fabricmc.fabric.api.item.v1.EquipmentSlotProvider;
+
+public class CustomItemSettingImpl<T> implements CustomItemSetting<T> {
+	public static final CustomItemSetting<EquipmentSlotProvider> EQUIPMENT_SLOT_PROVIDER = CustomItemSetting.create(() -> null);
+	public static final CustomItemSetting<CustomDamageHandler> CUSTOM_DAMAGE_HANDLER = CustomItemSetting.create(() -> null);
+
+	private static final Map<Item.Settings, Collection<CustomItemSettingImpl<?>>> CUSTOM_SETTINGS = new WeakHashMap<>();
+
+	private final Map<Item.Settings, T> customSettings = new WeakHashMap<>();
+	private final Map<Item, T> customItemSettings = new HashMap<>();
+	private final Supplier<T> defaultValue;
+
+	public CustomItemSettingImpl(Supplier<T> defaultValue) {
+		Objects.requireNonNull(defaultValue);
+
+		this.defaultValue = defaultValue;
+	}
+
+	@Override
+	public T get(Item item) {
+		Objects.requireNonNull(item);
+
+		return this.customItemSettings.computeIfAbsent(item, i -> this.defaultValue.get());
+	}
+
+	public void set(Item.Settings settings, T value) {
+		Objects.requireNonNull(settings);
+
+		this.customSettings.put(settings, value);
+		CUSTOM_SETTINGS.computeIfAbsent(settings, s -> new HashSet<>()).add(this);
+	}
+
+	public void apply(Item.Settings settings, Item item) {
+		Objects.requireNonNull(settings);
+
+		this.customItemSettings.put(item, this.customSettings.getOrDefault(settings, this.defaultValue.get()));
+	}
+
+	// Because item settings are reusable, it is possible that the same item settings object will be applied
+	// to multiple items.
+	public static void onBuild(Item.Settings settings, Item item) {
+		for (CustomItemSettingImpl<?> setting : CUSTOM_SETTINGS.getOrDefault(settings, Collections.emptyList())) {
+			setting.apply(settings, item);
+		}
+	}
+}

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/mixin/item/ItemMixin.java

@@ -17,48 +17,18 @@
 package net.fabricmc.fabric.mixin.item;
 
 import org.spongepowered.asm.mixin.Mixin;
-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;
 
 import net.minecraft.item.Item;
 
-import net.fabricmc.fabric.api.item.v1.CustomDamageHandler;
-import net.fabricmc.fabric.api.item.v1.EquipmentSlotProvider;
-import net.fabricmc.fabric.impl.item.FabricItemInternals;
-import net.fabricmc.fabric.impl.item.ItemExtensions;
+import net.fabricmc.fabric.impl.item.CustomItemSettingImpl;
 
 @Mixin(Item.class)
-abstract class ItemMixin implements ItemExtensions {
-	@Unique
-	private EquipmentSlotProvider equipmentSlotProvider;
-
-	@Unique
-	private CustomDamageHandler customDamageHandler;
-
+class ItemMixin {
 	@Inject(method = "<init>", at = @At("RETURN"))
 	private void onConstruct(Item.Settings settings, CallbackInfo info) {
-		FabricItemInternals.onBuild(settings, (Item) (Object) this);
-	}
-
-	@Override
-	public EquipmentSlotProvider fabric_getEquipmentSlotProvider() {
-		return equipmentSlotProvider;
-	}
-
-	@Override
-	public void fabric_setEquipmentSlotProvider(EquipmentSlotProvider equipmentSlotProvider) {
-		this.equipmentSlotProvider = equipmentSlotProvider;
-	}
-
-	@Override
-	public CustomDamageHandler fabric_getCustomDamageHandler() {
-		return customDamageHandler;
-	}
-
-	@Override
-	public void fabric_setCustomDamageHandler(CustomDamageHandler handler) {
-		this.customDamageHandler = handler;
+		CustomItemSettingImpl.onBuild(settings, (Item) (Object) this);
 	}
 }

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/mixin/item/ItemStackMixin.java

@@ -31,7 +31,7 @@
 import net.minecraft.item.ItemStack;
 
 import net.fabricmc.fabric.api.item.v1.CustomDamageHandler;
-import net.fabricmc.fabric.impl.item.ItemExtensions;
+import net.fabricmc.fabric.impl.item.CustomItemSettingImpl;
 
 @Mixin(ItemStack.class)
 public abstract class ItemStackMixin {
@@ -51,7 +51,7 @@ private void saveDamager(int amount, LivingEntity entity, Consumer<LivingEntity>
 
 	@ModifyArg(method = "damage(ILnet/minecraft/entity/LivingEntity;Ljava/util/function/Consumer;)V", at = @At(value = "INVOKE", target = "Lnet/minecraft/item/ItemStack;damage(ILjava/util/Random;Lnet/minecraft/server/network/ServerPlayerEntity;)Z"), index = 0)
 	private int hookDamage(int amount) {
-		CustomDamageHandler handler = ((ItemExtensions) getItem()).fabric_getCustomDamageHandler();
+		CustomDamageHandler handler = CustomItemSettingImpl.CUSTOM_DAMAGE_HANDLER.get(this.getItem());
 
 		if (handler != null) {
 			return handler.damage((ItemStack) (Object) this, amount, fabric_damagingEntity, fabric_breakCallback);

fabric-item-api-v1/src/main/java/net/fabricmc/fabric/mixin/item/MobEntityMixin.java

@@ -27,14 +27,14 @@
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
 
+import net.fabricmc.fabric.impl.item.CustomItemSettingImpl;
 import net.fabricmc.fabric.api.item.v1.EquipmentSlotProvider;
-import net.fabricmc.fabric.impl.item.ItemExtensions;
 
 @Mixin(MobEntity.class)
 abstract class MobEntityMixin {
 	@Inject(method = "getPreferredEquipmentSlot", at = @At(value = "INVOKE_ASSIGN", target = "Lnet/minecraft/item/ItemStack;getItem()Lnet/minecraft/item/Item;"), cancellable = true, locals = LocalCapture.CAPTURE_FAILHARD)
 	private static void onGetPreferredEquipmentSlot(ItemStack stack, CallbackInfoReturnable<EquipmentSlot> info, Item item) {
-		EquipmentSlotProvider equipmentSlotProvider = ((ItemExtensions) item).fabric_getEquipmentSlotProvider();
+		EquipmentSlotProvider equipmentSlotProvider = CustomItemSettingImpl.EQUIPMENT_SLOT_PROVIDER.get(item);
 
 		if (equipmentSlotProvider != null) {
 			info.setReturnValue(equipmentSlotProvider.getPreferredEquipmentSlot(stack));

fabric-item-api-v1/src/testmod/java/net/fabricmc/fabric/test/item/FabricItemSettingsTests.java

@@ -24,12 +24,18 @@
 
 import net.fabricmc.api.ModInitializer;
 import net.fabricmc.fabric.api.item.v1.FabricItemSettings;
+import net.fabricmc.fabric.api.item.v1.CustomItemSetting;
 
 public class FabricItemSettingsTests implements ModInitializer {
+	public static final CustomItemSetting<String> CUSTOM_DATA_TEST = CustomItemSetting.create(() -> null);
+
 	@Override
 	public void onInitialize() {
 		// Registers an item with a custom equipment slot.
 		Item testItem = new Item(new FabricItemSettings().group(ItemGroup.MISC).equipmentSlot(stack -> EquipmentSlot.CHEST));
 		Registry.register(Registry.ITEM, new Identifier("fabric-item-api-v1-testmod", "test_item"), testItem);
+
+		Item testItem2 = new Item(new FabricItemSettings().group(ItemGroup.MISC).custom(CUSTOM_DATA_TEST, "Look at me! I have a custom setting!"));
+		Registry.register(Registry.ITEM, new Identifier("fabric-item-api-v1-testmod", "test_item2"), testItem2);
 	}
 }