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c5a10665b8
Spigot still maintains some partial implementation of "tick skipping", a practice in which the MinecraftServer.currentTick field is updated not by an increment of one per actual tick, but instead set to System.currentTimeMillis() / 50. This behaviour means that the tracked tick may "skip" a tick value in case a previous tick took more than the expected 50ms. To compensate for this in important paths, spigot/craftbukkit implements "wall-time". Instead of incrementing/decrementing ticks on block entities/entities by one for each call to their tick() method, they instead increment/decrement important values, like an ItemEntity's age or pickupDelay, by the difference of `currentTick - lastTick`, where `lastTick` is the value of `currentTick` during the last tick() call. These "fixes" however do not play nicely with minecraft's simulation distance as entities/block entities implementing the above behaviour would "catch up" their values when moving from a non-ticking chunk to a ticking one as their `lastTick` value remains stuck on the last tick in a ticking chunk and hence lead to a large "catch up" once ticked again. Paper completely removes the "tick skipping" behaviour (See patch "Further-improve-server-tick-loop"), making the above precautions completely unnecessary, which also rids paper of the previous described incompatibility with non-ticking chunks.
105 lines
6 KiB
Diff
105 lines
6 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Spottedleaf <Spottedleaf@users.noreply.github.com>
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Date: Tue, 20 Feb 2024 18:24:16 -0800
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Subject: [PATCH] Fix entity tracker desync when new players are added to the
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tracker
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The delta position packet instructs the client to update
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the entity position by a position difference. However, this position
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difference is relative to the last position in the entity tracker
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state, not the last position which has been sent to the player. As
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a result, if the last position the player has recorded is different
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than the one stored in the entity tracker (which occurs when a new
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player is added to an existing entity tracker state) then the sent
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position difference will cause a position desync for the client.
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We can resolve this problem by either tracking the last position
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sent per-player, or by simply resetting the last sent position
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in the entity tracker state every time a new player is added.
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Resetting the last sent position every time a new player is
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added to the tracker is just easier to do, so that is what
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this patch does.
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This patch also fixes entities appearing to disappear when
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teleporting to players by changing the initial position
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in the spawn packet to the entities current tracking position.
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When teleporting, the spawn packet will contain the old position
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which is most likely in an unloaded chunk - which means that the
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client will not tick the entity and thus not lerp the entity
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from its old position to its new position.
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diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java
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index 854baa554da2215a656f976ae2973341c3b2d61c..792b9a72a610cc512a8920d61013b6ba02f71e47 100644
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--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java
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+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundAddEntityPacket.java
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@@ -42,9 +42,11 @@ public class ClientboundAddEntityPacket implements Packet<ClientGamePacketListen
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this(
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entity.getId(),
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entity.getUUID(),
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- entityTrackerEntry.getPositionBase().x(),
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- entityTrackerEntry.getPositionBase().y(),
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- entityTrackerEntry.getPositionBase().z(),
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+ // Paper start - fix entity tracker desync
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+ entity.trackingPosition().x(),
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+ entity.trackingPosition().y(),
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+ entity.trackingPosition().z(),
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+ // Paper end - fix entity tracker desync
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entityTrackerEntry.getLastSentXRot(),
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entityTrackerEntry.getLastSentYRot(),
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entity.getType(),
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diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
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index 21370ed6c7d98d3f3546f0365ac50e5c26ba3bde..af8cb316ac169aa8d98a88765b85bb013b9ba961 100644
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--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
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+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
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@@ -1269,6 +1269,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
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this.serverEntity.addPairing(player);
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}
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// Paper end - entity tracking events
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+ this.serverEntity.onPlayerAdd(); // Paper - fix desync when a player is added to the tracker
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}
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} else if (this.seenBy.remove(player.connection)) {
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this.serverEntity.removePairing(player);
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diff --git a/src/main/java/net/minecraft/server/level/ServerEntity.java b/src/main/java/net/minecraft/server/level/ServerEntity.java
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index 12d86f27d04bffed8c3844e36b42fbc2f84dacff..8ea2f24695f5dad55e21f238b69442513e7a90c6 100644
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--- a/src/main/java/net/minecraft/server/level/ServerEntity.java
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+++ b/src/main/java/net/minecraft/server/level/ServerEntity.java
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@@ -96,6 +96,13 @@ public class ServerEntity {
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this.trackedDataValues = entity.getEntityData().getNonDefaultValues();
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}
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+ // Paper start - fix desync when a player is added to the tracker
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+ private boolean forceStateResync;
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+ public void onPlayerAdd() {
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+ this.forceStateResync = true;
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+ }
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+ // Paper end - fix desync when a player is added to the tracker
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+
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public void sendChanges() {
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// Paper start - optimise collisions
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if (((ca.spottedleaf.moonrise.patches.chunk_system.entity.ChunkSystemEntity)this.entity).moonrise$isHardColliding()) {
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@@ -145,7 +152,7 @@ public class ServerEntity {
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}
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}
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- if (this.tickCount % this.updateInterval == 0 || this.entity.hasImpulse || this.entity.getEntityData().isDirty()) {
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+ 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
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int i;
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int j;
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@@ -185,7 +192,7 @@ public class ServerEntity {
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long i1 = this.positionCodec.encodeZ(vec3d);
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boolean flag6 = k < -32768L || k > 32767L || l < -32768L || l > 32767L || i1 < -32768L || i1 > 32767L;
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- if (!flag6 && this.teleportDelay <= 400 && !this.wasRiding && this.wasOnGround == this.entity.onGround()) {
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+ 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
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if ((!flag2 || !flag3) && !(this.entity instanceof AbstractArrow)) {
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if (flag2) {
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packet1 = new ClientboundMoveEntityPacket.Pos(this.entity.getId(), (short) ((int) k), (short) ((int) l), (short) ((int) i1), this.entity.onGround());
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@@ -249,6 +256,7 @@ public class ServerEntity {
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}
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this.entity.hasImpulse = false;
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+ this.forceStateResync = false; // Paper - fix desync when a player is added to the tracker
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}
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++this.tickCount;
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