Readd mc-4 fix

Author: Owen1212055

patches/removed/1.19/0542-MC-4-Fix-item-position-desync.patch

@@ -0,0 +1,49 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: BillyGalbreath <blake.galbreath@gmail.com>
+Date: Tue, 8 Dec 2020 20:24:52 -0600
+Subject: [PATCH] MC-4: Fix item position desync
+
+This fixes item position desync (MC-4) by running the item coordinates
+through the encode/decode methods of the packet that causes the precision
+loss, which forces the server to lose the same precision as the client
+keeping them in sync.
+
+diff --git a/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java b/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java
+index 3768a71491ef7836b9739bdaec7a077c523dbacd..a57957ace1a72b3308487f180a366c3879eceb21 100644
+--- a/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java
++++ b/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java
+@@ -8,11 +8,11 @@ public class VecDeltaCodec {
+     public Vec3 base = Vec3.ZERO; // Paper
+ 
+     private static long encode(double value) {
+-        return Mth.lfloor(value * 4096.0D);
++        return Mth.lfloor(value * 4096.0D); // Paper - check ItemEntity#setPosRaw on update
+     }
+ 
+     private static double decode(long value) {
+-        return (double)value / 4096.0D;
++        return (double)value / 4096.0D; // Paper - check ItemEntity#setPosRaw on update
+     }
+ 
+     public Vec3 decode(long x, long y, long z) {
+diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
+index 6b49e66f0e45eb7ed525fe4314d2a9615212f7e4..4f9a5837d66c1940385e94f80d865cde1c4cf2a2 100644
+--- a/src/main/java/net/minecraft/world/entity/Entity.java
++++ b/src/main/java/net/minecraft/world/entity/Entity.java
+@@ -3888,6 +3888,16 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource {
+     }
+     public final void setPosRaw(double x, double y, double z, boolean forceBoundingBoxUpdate) {
+         // Paper end
++        // Paper start - fix MC-4
++        if (this instanceof ItemEntity) {
++            if (io.papermc.paper.configuration.GlobalConfiguration.get().misc.fixEntityPositionDesync) {
++                // encode/decode from PacketPlayOutEntity
++                x = Mth.lfloor(x * 4096.0D) * (1 / 4096.0D);
++                y = Mth.lfloor(y * 4096.0D) * (1 / 4096.0D);
++                z = Mth.lfloor(z * 4096.0D) * (1 / 4096.0D);
++            }
++        }
++        // Paper end - fix MC-4
+         if (this.position.x != x || this.position.y != y || this.position.z != z) {
+             this.position = new Vec3(x, y, z);
+             int i = Mth.floor(x);