Add DifficultyChangeEvent (#3525)

patches/minecraft/net/minecraft/world/storage/WorldInfo.java.patch

@@ -16,7 +16,15 @@
          p_76064_1_.func_74772_a("RandomSeed", this.field_76100_a);
          p_76064_1_.func_74778_a("generatorName", this.field_76098_b.func_77127_a());
          p_76064_1_.func_74768_a("generatorVersion", this.field_76098_b.func_77131_c());
-@@ -807,6 +809,26 @@
+@@ -709,6 +711,7 @@
+ 
+     public void func_176144_a(EnumDifficulty p_176144_1_)
+     {
++        net.minecraftforge.common.ForgeHooks.onDifficultyChange(p_176144_1_, this.field_176158_z);
+         this.field_176158_z = p_176144_1_;
+     }
+ 
+@@ -807,6 +810,26 @@
          });
      }
  

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

@@ -89,12 +89,14 @@ import net.minecraft.util.text.TextFormatting;
 import net.minecraft.util.text.event.ClickEvent;
 import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
+import net.minecraft.world.EnumDifficulty;
 import net.minecraft.world.GameType;
 import net.minecraft.world.storage.loot.LootEntry;
 import net.minecraft.world.storage.loot.LootTable;
 import net.minecraft.world.storage.loot.conditions.LootCondition;
 import net.minecraftforge.common.util.BlockSnapshot;
 import net.minecraftforge.event.AnvilUpdateEvent;
+import net.minecraftforge.event.DifficultyChangeEvent;
 import net.minecraftforge.event.ForgeEventFactory;
 import net.minecraftforge.event.ServerChatEvent;
 import net.minecraftforge.event.entity.EntityTravelToDimensionEvent;
@@ -510,6 +512,11 @@ public class ForgeHooks
         }
         return false;
     }
+    
+    public static void onDifficultyChange(EnumDifficulty difficulty, EnumDifficulty oldDifficulty)
+    {
+        MinecraftForge.EVENT_BUS.post(new DifficultyChangeEvent(difficulty, oldDifficulty));
+    }
 
     //Optifine Helper Functions u.u, these are here specifically for Optifine
     //Note: When using Optifine, these methods are invoked using reflection, which

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

@@ -0,0 +1,62 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.event;
+
+import javax.annotation.Nonnull;
+
+import net.minecraft.world.EnumDifficulty;
+import net.minecraftforge.common.ForgeHooks;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.fml.common.eventhandler.Cancelable;
+import net.minecraftforge.fml.common.eventhandler.Event;
+import net.minecraftforge.fml.common.eventhandler.Event.HasResult;
+
+/**
+ * DifficultyChangeEvent is fired when difficulty is changing. <br>
+ * <br>
+ * This event is fired via the {@link ForgeHooks#onDifficultyChange(EnumDifficulty, EnumDifficulty)}.<br>
+ * <br>
+ * This event is not {@link Cancelable}.<br>
+ * <br>
+ * This event does not have a result. {@link HasResult}<br>
+ * <br>
+ * This event is fired on the {@link MinecraftForge#EVENT_BUS}.
+ **/
+public class DifficultyChangeEvent extends Event
+{
+    private final EnumDifficulty difficulty;
+    private final EnumDifficulty oldDifficulty;
+
+    public DifficultyChangeEvent(EnumDifficulty difficulty, EnumDifficulty oldDifficulty)
+    {
+        this.difficulty = difficulty;
+        this.oldDifficulty = oldDifficulty;
+    }
+
+    public EnumDifficulty getDifficulty()
+    {
+        return difficulty;
+    }
+
+    public EnumDifficulty getOldDifficulty()
+    {
+        return oldDifficulty;
+    }
+}

src/test/java/net/minecraftforge/test/DifficultyChangeEventTest.java

@@ -0,0 +1,28 @@
+package net.minecraftforge.test;
+
+import net.minecraft.world.EnumDifficulty;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.event.DifficultyChangeEvent;
+import net.minecraftforge.fml.common.Mod;
+import net.minecraftforge.fml.common.Mod.EventHandler;
+import net.minecraftforge.fml.common.event.FMLInitializationEvent;
+import net.minecraftforge.fml.common.eventhandler.Event.Result;
+import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
+
+@Mod(modid = "difficultychangeeventtest", name = "DifficultyChangeEventTest", version = "0.0.0")
+public class DifficultyChangeEventTest
+{
+    private static final boolean ENABLE = false;
+
+    @EventHandler
+    public void init(FMLInitializationEvent event)
+    {
+        if (ENABLE) MinecraftForge.EVENT_BUS.register(this);
+    }
+
+    @SubscribeEvent
+    public void onDifficultyChange(DifficultyChangeEvent event)
+    {
+        System.out.println("Difficulty changed from " + event.getOldDifficulty() + " to " + event.getDifficulty());
+    }
+}