From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: William Blake Galbreath <blake.galbreath@gmail.com>
Date: Sat, 6 Jul 2019 21:12:58 -0500
Subject: [PATCH] MC-4 Fix - Item position desync


diff --git a/src/main/java/net/minecraft/server/EntityTrackerEntry.java b/src/main/java/net/minecraft/server/EntityTrackerEntry.java
index f322dccd834ff56b99f8796309709b5b6ac01456..5cb6bb896e8e71ee1b6b1ee3fff2fdb40cacfe76 100644
--- a/src/main/java/net/minecraft/server/EntityTrackerEntry.java
+++ b/src/main/java/net/minecraft/server/EntityTrackerEntry.java
@@ -134,6 +134,12 @@ public class EntityTrackerEntry {
                 double vec3d_dz = this.tracker.locZ() - 2.44140625E-4D*(this.zLoc);
                 boolean flag1 = (vec3d_dx * vec3d_dx + vec3d_dy * vec3d_dy + vec3d_dz * vec3d_dz) >= 7.62939453125E-6D;
                 // Paper end - reduce allocation of Vec3D here
+                // Purpur start - fix MC-4
+                if (net.pl3x.purpur.PurpurConfig.fixItemPositionDesync && this.tracker instanceof EntityItem) {
+                    Vec3D loc = PacketPlayOutEntity.decrypt(PacketPlayOutEntity.encrypt(tracker.locX()), PacketPlayOutEntity.encrypt(tracker.locY()), PacketPlayOutEntity.encrypt(tracker.locZ()));
+                    tracker.setPosition(loc.getX(), loc.getY(), loc.getZ());
+                }
+                // Purpur end - fix MC-4
                 Packet<?> packet1 = null;
                 boolean flag2 = flag1 || this.tickCounter % 60 == 0;
                 boolean flag3 = Math.abs(i - this.yRot) >= 1 || Math.abs(j - this.xRot) >= 1;
diff --git a/src/main/java/net/minecraft/server/PacketPlayOutEntity.java b/src/main/java/net/minecraft/server/PacketPlayOutEntity.java
index e5da2b19c1177ba7f88f0aaad9d810bb313ce67b..6d9d52e4fc2cf55b21bfcb6cb1bcc6db9fb56773 100644
--- a/src/main/java/net/minecraft/server/PacketPlayOutEntity.java
+++ b/src/main/java/net/minecraft/server/PacketPlayOutEntity.java
@@ -14,10 +14,12 @@ public class PacketPlayOutEntity implements Packet<PacketListenerPlayOut> {
     protected boolean h;
     protected boolean i;
 
+    public static long encrypt(double d) { return a(d); } // Purpur - OBFHELPER
     public static long a(double d0) {
         return MathHelper.d(d0 * 4096.0D);
     }
 
+    public static Vec3D decrypt(long x, long y, long z) { return a(x, y, z); } // Purpur - OBFHELPER
     public static Vec3D a(long i, long j, long k) {
         return (new Vec3D((double) i, (double) j, (double) k)).a(2.44140625E-4D);
     }
diff --git a/src/main/java/net/pl3x/purpur/PurpurConfig.java b/src/main/java/net/pl3x/purpur/PurpurConfig.java
index 0a14d60703073e6476020c43f8349996f381400a..ef90290d21ecebf6d7c2bfc2f2a63f65a3d429e9 100644
--- a/src/main/java/net/pl3x/purpur/PurpurConfig.java
+++ b/src/main/java/net/pl3x/purpur/PurpurConfig.java
@@ -177,4 +177,9 @@ public class PurpurConfig {
         InventoryType.ENDER_CHEST.setDefaultSize(enderChestSixRows ? 54 : 27);
         enderChestPermissionRows = getBoolean("settings.blocks.ender_chest.use-permissions-for-rows", enderChestPermissionRows);
     }
+
+    public static boolean fixItemPositionDesync = false;
+    private static void fixItemPositionDesync() {
+        fixItemPositionDesync = getBoolean("settings.fix-item-position-desync", fixItemPositionDesync);
+    }
 }