Fix item position desync

docs/source/configuration.rst

@@ -58,6 +58,14 @@ dont-send-useless-entity-packets
 .. warning::
     The `dont-send-useless-entity-packets` option is highly experimental! Only enable this if you are feeling brave.
 
+fix-item-position-desync
+~~~~~~~~~~~~~~~~~~~~~~~~
+* **default**: false
+* **description**: Update item positions according to the rounding the client does
+
+.. warning::
+    The `fix-item-position-desync` option is highly experimental! Only enable this if you are feeling brave.
+
 large-ender-chests
 ~~~~~~~~~~~~~~
 * **default**: true

patches/server/0043-Fix-item-position-desync.patch

@@ -0,0 +1,46 @@
+From 1ad2c6ff752f602b69eda84ee39a2b65642d4c09 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] Fix item position desync
+
+---
+ src/main/java/net/minecraft/server/EntityTrackerEntry.java | 6 ++++++
+ src/main/java/net/pl3x/purpur/PurpurConfig.java            | 5 +++++
+ 2 files changed, 11 insertions(+)
+
+diff --git a/src/main/java/net/minecraft/server/EntityTrackerEntry.java b/src/main/java/net/minecraft/server/EntityTrackerEntry.java
+index 448602057..8885009ff 100644
+--- a/src/main/java/net/minecraft/server/EntityTrackerEntry.java
++++ b/src/main/java/net/minecraft/server/EntityTrackerEntry.java
+@@ -124,6 +124,12 @@ public class EntityTrackerEntry {
+                 ++this.o;
+                 i = MathHelper.d(this.tracker.yaw * 256.0F / 360.0F);
+                 j = MathHelper.d(this.tracker.pitch * 256.0F / 360.0F);
++                // Purpur start
++                if (net.pl3x.purpur.PurpurConfig.fixItemPositionDesync && this.tracker instanceof EntityItem) {
++                    Vec3D v = PacketPlayOutEntity.a(PacketPlayOutEntity.a(tracker.locX), PacketPlayOutEntity.a(tracker.locY), PacketPlayOutEntity.a(tracker.locZ));
++                    tracker.setPosition(v.x, v.y, v.z);
++                }
++                // Purpur end
+                 Vec3D vec3d = (new Vec3D(this.tracker.locX, this.tracker.locY, this.tracker.locZ)).d(PacketPlayOutEntity.a(this.xLoc, this.yLoc, this.zLoc));
+                 boolean flag1 = vec3d.g() >= 7.62939453125E-6D;
+                 Packet<?> packet1 = null;
+diff --git a/src/main/java/net/pl3x/purpur/PurpurConfig.java b/src/main/java/net/pl3x/purpur/PurpurConfig.java
+index c0ae6accd..c0f02edce 100644
+--- a/src/main/java/net/pl3x/purpur/PurpurConfig.java
++++ b/src/main/java/net/pl3x/purpur/PurpurConfig.java
+@@ -146,6 +146,11 @@ public class PurpurConfig {
+         dontSendUselessEntityPackets = getBoolean("settings.dont-send-useless-entity-packets", dontSendUselessEntityPackets);
+     }
+ 
++    public static boolean fixItemPositionDesync = false;
++    private static void fixItemPositionDesync() {
++        fixItemPositionDesync = getBoolean("settings.fix-item-position-desync", fixItemPositionDesync);
++    }
++
+     public static boolean requireShiftToMount = true;
+     private static void requireShiftToMount() {
+         requireShiftToMount = getBoolean("settings.mobs.require-shift-to-mount", requireShiftToMount);
+-- 
+2.20.1
+