From c802b1ee3ad985d70fe4036ef7d83fc705611159 Mon Sep 17 00:00:00 2001
From: bloodshot <jdroque@gmail.com>
Date: Mon, 6 Jan 2014 18:02:01 -0500
Subject: [PATCH] Update Client's Hand when BlockPlaceEvent Cancelled

Send a Packet103SetSlot to client when a BlockPlaceEvent is cancelled.

Fixes BUKKIT-5284

Currently, whenever a player places a block in a protected area the
equipped itemstack size on client is never updated properly since the
client thinks the block was placed. The reason this happens is because
ItemStack.matches returns true since the server does not decrement stack
size if a BlockPlaceEvent is cancelled. This causes
PlayerConnection.a(handlePlace) not to send the appropriate packet to
client which causes the bug.

diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
index 248d48e..28bf9d4 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -638,7 +638,9 @@ public class PlayerConnection implements PacketPlayInListener {
                 return;
             }
 
-            this.player.playerInteractManager.interact(this.player, worldserver, itemstack, i, j, k, l, packetplayinblockplace.h(), packetplayinblockplace.i(), packetplayinblockplace.j());
+            if (!this.player.playerInteractManager.interact(this.player, worldserver, itemstack, i, j, k, l, packetplayinblockplace.h(), packetplayinblockplace.i(), packetplayinblockplace.j())) {
+                always = true; // force Packet103SetSlot to be sent to client to update ItemStack count
+            }
             // CraftBukkit end
 
             flag = true;
-- 
1.8.5.2.msysgit.0