From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: BillyGalbreath 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 652d87fc5d566dba8018c81676329f0e0bca471b..c56e7fb18f9a56c8025eb70a524f028b5942da37 100644 --- a/src/main/java/com/destroystokyo/paper/PaperConfig.java +++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java @@ -474,4 +474,9 @@ public class PaperConfig { private static void trackPluginScoreboards() { trackPluginScoreboards = getBoolean("settings.track-plugin-scoreboards", false); } + + public static boolean fixEntityPositionDesync = true; + private static void fixEntityPositionDesync() { + fixEntityPositionDesync = getBoolean("settings.fix-entity-position-desync", fixEntityPositionDesync); + } } diff --git a/src/main/java/net/minecraft/server/EntityItem.java b/src/main/java/net/minecraft/server/EntityItem.java index ba73d14437cfdf07ef0f1f6266131c113c2741fd..f41aaa7623c052b9f4044898d1bdee898c03057a 100644 --- a/src/main/java/net/minecraft/server/EntityItem.java +++ b/src/main/java/net/minecraft/server/EntityItem.java @@ -523,4 +523,16 @@ public class EntityItem extends Entity { public Packet P() { return new PacketPlayOutSpawnEntity(this); } + + // Paper start - fix MC-4 + public void setPositionRaw(double x, double y, double z) { + if (com.destroystokyo.paper.PaperConfig.fixEntityPositionDesync) { + // encode/decode from PacketPlayOutEntity + x = MathHelper.floorLong(x * 4096.0D) * (1 / 4096.0D); + y = MathHelper.floorLong(y * 4096.0D) * (1 / 4096.0D); + z = MathHelper.floorLong(z * 4096.0D) * (1 / 4096.0D); + } + super.setPositionRaw(x, y, z); + } + // Paper end - fix MC-4 } diff --git a/src/main/java/net/minecraft/server/MathHelper.java b/src/main/java/net/minecraft/server/MathHelper.java index 1731a1bca5ad02fd8cd8701f49c10cb74ee6f503..2e7721a650c5a351b3584665bd236f92ef577761 100644 --- a/src/main/java/net/minecraft/server/MathHelper.java +++ b/src/main/java/net/minecraft/server/MathHelper.java @@ -7,7 +7,7 @@ import java.util.function.IntPredicate; public class MathHelper { public static final float a = c(2.0F); - private static final float[] b = (float[]) SystemUtils.a((Object) (new float[65536]), (afloat) -> { + private static final float[] b = (float[]) SystemUtils.a((new float[65536]), (afloat) -> { // Paper - decompile error for (int i = 0; i < afloat.length; ++i) { afloat[i] = (float) Math.sin((double) i * 3.141592653589793D * 2.0D / 65536.0D); } @@ -47,6 +47,7 @@ public class MathHelper { return d0 < (double) i ? i - 1 : i; } + public static long floorLong(double d0) { return d(d0); } // Paper - OBFHELPER public static long d(double d0) { long i = (long) d0; diff --git a/src/main/java/net/minecraft/server/PacketPlayOutEntity.java b/src/main/java/net/minecraft/server/PacketPlayOutEntity.java index e5da2b19c1177ba7f88f0aaad9d810bb313ce67b..8e48407fd405ac4c3eece7762b8155c5d0f00fa0 100644 --- a/src/main/java/net/minecraft/server/PacketPlayOutEntity.java +++ b/src/main/java/net/minecraft/server/PacketPlayOutEntity.java @@ -15,11 +15,11 @@ public class PacketPlayOutEntity implements Packet { protected boolean i; public static long a(double d0) { - return MathHelper.d(d0 * 4096.0D); + return MathHelper.d(d0 * 4096.0D); // Paper - check EntityItem#setPositionRaw on update } public static Vec3D a(long i, long j, long k) { - return (new Vec3D((double) i, (double) j, (double) k)).a(2.44140625E-4D); + return (new Vec3D((double) i, (double) j, (double) k)).a(2.44140625E-4D); // Paper - check EntityItem#setPositionRaw on update } public PacketPlayOutEntity() {}