Add AnvilUpdateEvent which is fired when a user places a item in both input slots of a Anvil and allows modders to control the output. Closes #838

src/main/java/net/minecraftforge/common/ForgeHooks.java

@@ -3,7 +3,6 @@ package net.minecraftforge.common;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
-
 import cpw.mods.fml.common.eventhandler.Event;
 import cpw.mods.fml.relauncher.ReflectionHelper;
 import net.minecraft.block.Block;
@@ -14,6 +13,8 @@ import net.minecraft.entity.player.EntityPlayerMP;
 import net.minecraft.init.Blocks;
 import net.minecraft.init.Items;
 import net.minecraft.inventory.Container;
+import net.minecraft.inventory.ContainerRepair;
+import net.minecraft.inventory.IInventory;
 import net.minecraft.item.ItemArmor;
 import net.minecraft.item.ItemAxe;
 import net.minecraft.item.ItemPickaxe;
@@ -33,6 +34,7 @@ import net.minecraft.util.MovingObjectPosition.MovingObjectType;
 import net.minecraft.util.WeightedRandom;
 import net.minecraft.world.World;
 import net.minecraft.world.WorldSettings.GameType;
+import net.minecraftforge.event.AnvilUpdateEvent;
 import net.minecraftforge.event.ServerChatEvent;
 import net.minecraftforge.event.entity.item.ItemTossEvent;
 import net.minecraftforge.event.entity.living.LivingAttackEvent;
@@ -423,4 +425,15 @@ public class ForgeHooks
         }
         return event;
     }
+
+    public static boolean onAnvilChange(ContainerRepair container, ItemStack left, ItemStack right, IInventory outputSlot, String name, int baseCost)
+    {
+        AnvilUpdateEvent e = new AnvilUpdateEvent(left, right, name, baseCost);
+        if (MinecraftForge.EVENT_BUS.post(e)) return false;
+        if (e.output == null) return true;
+
+        outputSlot.setInventorySlotContents(0, e.output);
+        container.maximumCost = e.cost;
+        return false;
+    }
 }

src/main/java/net/minecraftforge/event/AnvilUpdateEvent.java

@@ -0,0 +1,30 @@
+package net.minecraftforge.event;
+
+import cpw.mods.fml.common.eventhandler.Cancelable;
+import cpw.mods.fml.common.eventhandler.Event;
+import net.minecraft.item.ItemStack;
+
+/**
+ * 
+ * AnvilUpdateEvent is fired when a player places items in both the left and right slots of a anvil.
+ * If the event is canceled, vanilla behavior will not run, and the output will be set to null.
+ * If the event is not canceled, but the output is not null, it will set the output and not run vanilla behavior.
+ * if the output is null, and the event is not canceled, vanilla behavior will execute.
+ */
+@Cancelable
+public class AnvilUpdateEvent extends Event
+{
+    public final ItemStack left;  // The left side of the input
+    public final ItemStack right; // The right side of the input
+    public final String name;     // The name to set the item, if the user specified one.
+    public ItemStack output;      // Set this to set the output stack
+    public int cost;              // The base cost, set this to change it if output != null
+
+    public AnvilUpdateEvent(ItemStack left, ItemStack right, String name, int cost)
+    {
+        this.left = left;
+        this.right = right;
+        this.name = name;
+        this.cost = cost;
+    }
+}