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-rw-r--r--patches/server/1029-Fix-entity-tracker-desync-when-new-players-are-added.patch105
1 files changed, 105 insertions, 0 deletions
diff --git a/patches/server/1029-Fix-entity-tracker-desync-when-new-players-are-added.patch b/patches/server/1029-Fix-entity-tracker-desync-when-new-players-are-added.patch
new file mode 100644
index 0000000000..f767b9ab91
--- /dev/null
+++ b/patches/server/1029-Fix-entity-tracker-desync-when-new-players-are-added.patch
@@ -0,0 +1,105 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Spottedleaf <[email protected]>
+Date: Tue, 20 Feb 2024 18:24:16 -0800
+Subject: [PATCH] Fix entity tracker desync when new players are added to the
+ tracker
+
+The delta position packet instructs the client to update
+the entity position by a position difference. However, this position
+difference is relative to the last position in the entity tracker
+state, not the last position which has been sent to the player. As
+a result, if the last position the player has recorded is different
+than the one stored in the entity tracker (which occurs when a new
+player is added to an existing entity tracker state) then the sent
+position difference will cause a position desync for the client.
+
+We can resolve this problem by either tracking the last position
+sent per-player, or by simply resetting the last sent position
+in the entity tracker state every time a new player is added.
+Resetting the last sent position every time a new player is
+added to the tracker is just easier to do, so that is what
+this patch does.
+
+This patch also fixes entities appearing to disappear when
+teleporting to players by changing the initial position
+in the spawn packet to the entities current tracking position.
+When teleporting, the spawn packet will contain the old position
+which is most likely in an unloaded chunk - which means that the
+client will not tick the entity and thus not lerp the entity
+from its old position to its new position.
+
+diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java
+index 854baa554da2215a656f976ae2973341c3b2d61c..792b9a72a610cc512a8920d61013b6ba02f71e47 100644
+--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java
++++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java
+@@ -42,9 +42,11 @@ public class ClientboundAddEntityPacket implements Packet<ClientGamePacketListen
+ this(
+ entity.getId(),
+ entity.getUUID(),
+- entityTrackerEntry.getPositionBase().x(),
+- entityTrackerEntry.getPositionBase().y(),
+- entityTrackerEntry.getPositionBase().z(),
++ // Paper start - fix entity tracker desync
++ entity.trackingPosition().x(),
++ entity.trackingPosition().y(),
++ entity.trackingPosition().z(),
++ // Paper end - fix entity tracker desync
+ entityTrackerEntry.getLastSentXRot(),
+ entityTrackerEntry.getLastSentYRot(),
+ entity.getType(),
+diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
+index 21370ed6c7d98d3f3546f0365ac50e5c26ba3bde..af8cb316ac169aa8d98a88765b85bb013b9ba961 100644
+--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
++++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
+@@ -1269,6 +1269,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
+ this.serverEntity.addPairing(player);
+ }
+ // Paper end - entity tracking events
++ this.serverEntity.onPlayerAdd(); // Paper - fix desync when a player is added to the tracker
+ }
+ } else if (this.seenBy.remove(player.connection)) {
+ this.serverEntity.removePairing(player);
+diff --git a/src/main/java/net/minecraft/server/level/ServerEntity.java b/src/main/java/net/minecraft/server/level/ServerEntity.java
+index 12d86f27d04bffed8c3844e36b42fbc2f84dacff..8ea2f24695f5dad55e21f238b69442513e7a90c6 100644
+--- a/src/main/java/net/minecraft/server/level/ServerEntity.java
++++ b/src/main/java/net/minecraft/server/level/ServerEntity.java
+@@ -96,6 +96,13 @@ public class ServerEntity {
+ this.trackedDataValues = entity.getEntityData().getNonDefaultValues();
+ }
+
++ // Paper start - fix desync when a player is added to the tracker
++ private boolean forceStateResync;
++ public void onPlayerAdd() {
++ this.forceStateResync = true;
++ }
++ // Paper end - fix desync when a player is added to the tracker
++
+ public void sendChanges() {
+ // Paper start - optimise collisions
+ if (((ca.spottedleaf.moonrise.patches.chunk_system.entity.ChunkSystemEntity)this.entity).moonrise$isHardColliding()) {
+@@ -145,7 +152,7 @@ public class ServerEntity {
+ }
+ }
+
+- if (this.tickCount % this.updateInterval == 0 || this.entity.hasImpulse || this.entity.getEntityData().isDirty()) {
++ if (this.forceStateResync || this.tickCount % this.updateInterval == 0 || this.entity.hasImpulse || this.entity.getEntityData().isDirty()) { // Paper - fix desync when a player is added to the tracker
+ int i;
+ int j;
+
+@@ -185,7 +192,7 @@ public class ServerEntity {
+ long i1 = this.positionCodec.encodeZ(vec3d);
+ boolean flag6 = k < -32768L || k > 32767L || l < -32768L || l > 32767L || i1 < -32768L || i1 > 32767L;
+
+- if (!flag6 && this.teleportDelay <= 400 && !this.wasRiding && this.wasOnGround == this.entity.onGround()) {
++ if (!this.forceStateResync && !flag6 && this.teleportDelay <= 400 && !this.wasRiding && this.wasOnGround == this.entity.onGround()) { // Paper - fix desync when a player is added to the tracker
+ if ((!flag2 || !flag3) && !(this.entity instanceof AbstractArrow)) {
+ if (flag2) {
+ packet1 = new ClientboundMoveEntityPacket.Pos(this.entity.getId(), (short) ((int) k), (short) ((int) l), (short) ((int) i1), this.entity.onGround());
+@@ -249,6 +256,7 @@ public class ServerEntity {
+ }
+
+ this.entity.hasImpulse = false;
++ this.forceStateResync = false; // Paper - fix desync when a player is added to the tracker
+ }
+
+ ++this.tickCount;