Remove wall-time / unused skip tick protection (#11412)

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.

1 files changed, 22 insertions, 0 deletions

diff --git a/patches/server/0808-Prevent-GameEvents-being-fired-from-unloaded-chunks.patch b/patches/server/0808-Prevent-GameEvents-being-fired-from-unloaded-chunks.patch
new file mode 100644
index 0000000000..3306163498
--- /dev/null
+++ b/patches/server/0808-Prevent-GameEvents-being-fired-from-unloaded-chunks.patch
@@ -0,0 +1,22 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shane Freeder <[email protected]>
+Date: Wed, 5 Apr 2023 20:15:47 +0100
+Subject: [PATCH] Prevent GameEvents being fired from unloaded chunks
+
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
+index 07f7752651095abdd9e9408a419aed7d78173d3a..fd4d1cab675b7b423ac0fdf9a8c9f472ddc68c36 100644
+--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
++++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
+@@ -1372,6 +1372,11 @@ public class ServerLevel extends Level implements WorldGenLevel {
+ 
+     @Override
+     public void gameEvent(Holder<GameEvent> event, Vec3 emitterPos, GameEvent.Context emitter) {
++        // Paper start - Prevent GameEvents being fired from unloaded chunks
++        if (this.getChunkIfLoadedImmediately((Mth.floor(emitterPos.x) >> 4), (Mth.floor(emitterPos.z) >> 4)) == null) {
++            return;
++        }
++        // Paper end - Prevent GameEvents being fired from unloaded chunks
+         this.gameEventDispatcher.post(event, emitterPos, emitter);
+     }
+