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/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java index 7413cbbcf0ab572483adc0ab915978593b8ea658..a0a3cec47c8f9e379a5bc1d43eeda5eb9d81f814 100644 --- a/src/main/java/com/destroystokyo/paper/PaperConfig.java +++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java @@ -101,6 +101,11 @@ public class PaperConfig { trackPluginScoreboards = getBoolean("settings.track-plugin-scoreboards", false); } + public static boolean fixEntityPositionDesync = true; + private static void fixEntityPositionDesync() { + fixEntityPositionDesync = getBoolean("settings.fix-entity-position-desync", fixEntityPositionDesync); + } + public static void registerCommands() { for (Map.Entry<String, Command> entry : commands.entrySet()) { MinecraftServer.getServer().server.getCommandMap().register(entry.getKey(), "Paper", entry.getValue()); diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java index b30c08bfb8c55161543a4ef09f2e462e0a1fe4ae..ec93f5300cc7d423ec0d292f0f8443f900d72dab 100644 --- a/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java +++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundMoveEntityPacket.java @@ -21,11 +21,11 @@ public abstract class ClientboundMoveEntityPacket implements Packet<ClientGamePa protected final boolean hasPos; public static long entityToPacket(double coord) { - return Mth.lfloor(coord * 4096.0D); + return Mth.lfloor(coord * 4096.0D); // Paper - check ItemEntity#setPosRaw on update } public static double packetToEntity(long coord) { - return (double)coord / 4096.0D; + return (double)coord / 4096.0D; // Paper - check ItemEntity#setPosRaw on update } public Vec3 updateEntityPosition(Vec3 orig) { diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java index 1e3436849760430b0db303e716f50555046d6f3e..86a9cbc0768575138c09217cd300c2d9d08540fc 100644 --- a/src/main/java/net/minecraft/world/entity/Entity.java +++ b/src/main/java/net/minecraft/world/entity/Entity.java @@ -3828,6 +3828,16 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, i } public final void setPosRaw(double x, double y, double z, boolean forceBoundingBoxUpdate) { // Paper end + // Paper start - fix MC-4 + if (this instanceof ItemEntity) { + if (com.destroystokyo.paper.PaperConfig.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);