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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.
50 lines
2.5 KiB
Diff
50 lines
2.5 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: BillyGalbreath <blake.galbreath@gmail.com>
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Date: Tue, 8 Dec 2020 20:24:52 -0600
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Subject: [PATCH] MC-4: Fix item position desync
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This fixes item position desync (MC-4) by running the item coordinates
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through the encode/decode methods of the packet that causes the precision
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loss, which forces the server to lose the same precision as the client
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keeping them in sync.
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diff --git a/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java b/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java
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index 488ebd443903af812913437f1ade3002093f2470..a043ac10834562d357ef0b5aded2e916e2a0d056 100644
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--- a/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java
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+++ b/src/main/java/net/minecraft/network/protocol/game/VecDeltaCodec.java
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@@ -9,12 +9,12 @@ public class VecDeltaCodec {
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@VisibleForTesting
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static long encode(double value) {
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- return Math.round(value * 4096.0);
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+ return Math.round(value * 4096.0); // Paper - Fix MC-4; diff on change
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}
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@VisibleForTesting
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static double decode(long value) {
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- return (double)value / 4096.0;
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+ return value / 4096.0; // Paper - Fix MC-4; diff on change
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}
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public Vec3 decode(long x, long y, long z) {
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diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
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index dae7643897b47dba304cbea56112445df2736cff..bed376337035545e7ec677f2f7fe3372a3c9ea25 100644
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--- a/src/main/java/net/minecraft/world/entity/Entity.java
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+++ b/src/main/java/net/minecraft/world/entity/Entity.java
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@@ -4260,6 +4260,16 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
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return;
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}
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// Paper end - Block invalid positions and bounding box
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+ // Paper start - Fix MC-4
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+ if (this instanceof ItemEntity) {
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+ if (io.papermc.paper.configuration.GlobalConfiguration.get().misc.fixEntityPositionDesync) {
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+ // encode/decode from ClientboundMoveEntityPacket
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+ x = Mth.lfloor(x * 4096.0) * (1 / 4096.0);
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+ y = Mth.lfloor(y * 4096.0) * (1 / 4096.0);
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+ z = Mth.lfloor(z * 4096.0) * (1 / 4096.0);
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+ }
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+ }
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+ // Paper end - Fix MC-4
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if (this.position.x != x || this.position.y != y || this.position.z != z) {
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this.position = new Vec3(x, y, z);
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int i = Mth.floor(x);
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