Add ItemStack Tooltip event (#302)

fabric-events-lifecycle-v0/build.gradle

@@ -1,5 +1,5 @@
 archivesBaseName = "fabric-events-lifecycle-v0"
-version = getSubprojectVersion(project, "0.1.0")
+version = getSubprojectVersion(project, "0.1.1")
 
 dependencies {
 	compile project(path: ':fabric-api-base', configuration: 'dev')

fabric-events-lifecycle-v0/src/main/java/net/fabricmc/fabric/api/event/client/ItemTooltipCallback.java

@@ -0,0 +1,45 @@
+/*
+ * 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.event.client;
+
+import net.fabricmc.fabric.api.event.Event;
+import net.fabricmc.fabric.api.event.EventFactory;
+import net.minecraft.client.item.TooltipContext;
+import net.minecraft.item.ItemStack;
+import net.minecraft.text.Text;
+
+import java.util.List;
+
+public interface ItemTooltipCallback {
+
+	/** Fired after the game has appended all base tooltip lines to the list */
+	Event<ItemTooltipCallback> EVENT = EventFactory.createArrayBacked(ItemTooltipCallback.class, (listeners) ->
+		(stack, tooltipContext, lines) -> {
+			for(ItemTooltipCallback callback : listeners){
+				callback.getTooltip(stack, tooltipContext, lines);
+			}
+		}
+	);
+
+	/**
+	 * Called when an item stack's tooltip is rendered. Text added to {@code lines} will be
+	 * rendered with the tooltip.
+	 * @param lines the list containing the lines of text displayed on the stack's tooltip
+	 */
+	void getTooltip(ItemStack stack, TooltipContext tooltipContext, List<Text> lines);
+
+}

fabric-events-lifecycle-v0/src/main/java/net/fabricmc/fabric/mixin/eventslifecycle/MixinItemStack.java

@@ -0,0 +1,40 @@
+/*
+ * 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.mixin.eventslifecycle;
+
+import net.fabricmc.fabric.api.event.client.ItemTooltipCallback;
+import net.minecraft.client.item.TooltipContext;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.item.ItemStack;
+import net.minecraft.text.Text;
+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.CallbackInfoReturnable;
+import org.spongepowered.asm.mixin.injection.callback.LocalCapture;
+
+import java.util.List;
+
+@Mixin(ItemStack.class)
+public class MixinItemStack {
+
+	@Inject(method = "getTooltip", at = @At("RETURN"))
+	private void getTooltip(PlayerEntity entity, TooltipContext tooltipContext, CallbackInfoReturnable<List<Text>> info){
+		ItemTooltipCallback.EVENT.invoker().getTooltip((ItemStack) (Object)this, tooltipContext, info.getReturnValue());
+	}
+
+}

fabric-events-lifecycle-v0/src/main/resources/fabric-events-lifecycle-v0.mixins.json

@@ -7,6 +7,7 @@
     "MixinWorld"
   ],
   "client": [
+    "MixinItemStack",
     "MixinMinecraftClient"
   ],
   "injectors": {