Add an event to control nether portal formation (#4735)

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

@@ -24,6 +24,7 @@ import java.util.EnumSet;
 import java.util.List;
 import java.util.Random;
 
+import net.minecraft.block.BlockPortal;
 import net.minecraft.block.state.IBlockState;
 import net.minecraft.client.util.ITooltipFlag;
 import net.minecraft.entity.Entity;
@@ -740,6 +741,11 @@ public class ForgeEventFactory
         return result == Result.DEFAULT ? def : result == Result.ALLOW;
     }
 
+    public static boolean onTrySpawnPortal(World world, BlockPos pos, BlockPortal.Size size)
+    {
+        return MinecraftForge.EVENT_BUS.post(new BlockEvent.PortalSpawnEvent(world, pos, world.getBlockState(pos), size));
+    }
+
     public static int onEnchantmentLevelSet(World world, BlockPos pos, int enchantRow, int power, ItemStack itemStack, int level)
     {
         net.minecraftforge.event.enchanting.EnchantmentLevelSetEvent e = new net.minecraftforge.event.enchanting.EnchantmentLevelSetEvent(world, pos, enchantRow, power, itemStack, level);

src/main/java/net/minecraftforge/event/world/BlockEvent.java

@@ -22,6 +22,7 @@ package net.minecraftforge.event.world;
 import java.util.EnumSet;
 import java.util.List;
 
+import net.minecraft.block.BlockPortal;
 import net.minecraft.block.state.IBlockState;
 import net.minecraft.enchantment.EnchantmentHelper;
 import net.minecraft.entity.player.EntityPlayer;
@@ -338,4 +339,27 @@ public class BlockEvent extends Event
             }
         }
     }
+
+    /**
+     * Fired when an attempt is made to spawn a nether portal from
+     * {@link net.minecraft.block.BlockPortal#trySpawnPortal(World, BlockPos)}.
+     *
+     * If cancelled, the portal will not be spawned.
+     */
+    @Cancelable
+    public static class PortalSpawnEvent extends BlockEvent
+    {
+        private final BlockPortal.Size size;
+
+        public PortalSpawnEvent(World world, BlockPos pos, IBlockState state, BlockPortal.Size size)
+        {
+            super(world, pos, state);
+            this.size = size;
+        }
+
+        public BlockPortal.Size getPortalSize()
+        {
+            return size;
+        }
+    }
 }