Paper/patches/server/0853-Fix-Entity-Position-Desync.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Owen1212055 <23108066+Owen1212055@users.noreply.github.com>
Date: Thu, 23 Dec 2021 23:59:12 -0500
Subject: [PATCH] Fix Entity Position Desync

If entities were teleported in the first tick it would not be send to the client.

This excludes hanging entities, as this fix caused problematic behavior due to them having their own
position field.

This also fixes desync caused be relatively teleporting paintings. (https://bugs.mojang.com/browse/MC-249169)
This is caused by the fact that setPacketCoordinates isn't called on paintings when they are spawned (unlike every other entity, like XP orbs)
on the client for some reason. This causes it to be relatively teleported to the world origin (0,0,0).

diff --git a/src/main/java/net/minecraft/server/level/ServerEntity.java b/src/main/java/net/minecraft/server/level/ServerEntity.java
index a482cc1c4d7eab531cd3f5cf42f7d3a43470ef6b..3eb947e16684965b861a07591f18db838e7c874b 100644
--- a/src/main/java/net/minecraft/server/level/ServerEntity.java
+++ b/src/main/java/net/minecraft/server/level/ServerEntity.java
@@ -152,11 +152,12 @@ public class ServerEntity {
                 boolean flag2 = flag1 || this.tickCount % 60 == 0;
                 boolean flag3 = Math.abs(i - this.yRotp) >= 1 || Math.abs(j - this.xRotp) >= 1;
 
-                if (this.tickCount > 0 || this.entity instanceof AbstractArrow) {
+                if (!(this.entity instanceof net.minecraft.world.entity.decoration.HangingEntity) || this.tickCount > 0 || this.entity instanceof AbstractArrow) { // Paper - Always update position
                     long k = this.positionCodec.encodeX(vec3d);
                     long l = this.positionCodec.encodeY(vec3d);
                     long i1 = this.positionCodec.encodeZ(vec3d);
                     boolean flag4 = k < -32768L || k > 32767L || l < -32768L || l > 32767L || i1 < -32768L || i1 > 32767L;
+                    if (this.entity instanceof net.minecraft.world.entity.decoration.Painting) {flag4 = true;} // Paper - Always send exact position for paintings
 
                     if (!flag4 && this.teleportDelay <= 400 && !this.wasRiding && this.wasOnGround == this.entity.isOnGround() && !(com.destroystokyo.paper.PaperConfig.sendFullPosForHardCollidingEntities && this.entity.hardCollides())) { // Paper - send full pos for hard colliding entities to prevent collision problems due to desync
                         if ((!flag2 || !flag3) && !(this.entity instanceof AbstractArrow)) {