PaperMC/nms-patches/ItemHanging.patch

--- a/net/minecraft/server/ItemHanging.java
+++ b/net/minecraft/server/ItemHanging.java
@@ -1,6 +1,10 @@
 package net.minecraft.server;
 
 import javax.annotation.Nullable;
+// CraftBukkit start
+import org.bukkit.entity.Player;
+import org.bukkit.event.hanging.HangingPlaceEvent;
+// CraftBukkit end
 
 public class ItemHanging extends Item {
 
@@ -20,6 +24,18 @@
 
             if (entityhanging != null && entityhanging.survives()) {
                 if (!world.isClientSide) {
+                    // CraftBukkit start - fire HangingPlaceEvent
+                    Player who = (entityhuman == null) ? null : (Player) entityhuman.getBukkitEntity();
+                    org.bukkit.block.Block blockClicked = world.getWorld().getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ());
+                    org.bukkit.block.BlockFace blockFace = org.bukkit.craftbukkit.block.CraftBlock.notchToBlockFace(enumdirection);
+
+                    HangingPlaceEvent event = new HangingPlaceEvent((org.bukkit.entity.Hanging) entityhanging.getBukkitEntity(), who, blockClicked, blockFace);
+                    world.getServer().getPluginManager().callEvent(event);
+
+                    if (event.isCancelled()) {
+                        return EnumInteractionResult.FAIL;
+                    }
+                    // CraftBukkit end
                     entityhanging.p();
                     world.addEntity(entityhanging);
                 }