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, 42 insertions, 0 deletions

diff --git a/patches/server/0873-Implement-OfflinePlayer-isConnected.patch b/patches/server/0873-Implement-OfflinePlayer-isConnected.patch
new file mode 100644
index 0000000000..199101506f
--- /dev/null
+++ b/patches/server/0873-Implement-OfflinePlayer-isConnected.patch
@@ -0,0 +1,42 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aeltumn <[email protected]>
+Date: Thu, 24 Aug 2023 13:05:30 +0200
+Subject: [PATCH] Implement OfflinePlayer#isConnected
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/CraftOfflinePlayer.java b/src/main/java/org/bukkit/craftbukkit/CraftOfflinePlayer.java
+index 2c2c4db31a746b4eb853dc04c6b3e5631bbfa034..4f4e3ee18d586f61706504218cddc06a38ca5580 100644
+--- a/src/main/java/org/bukkit/craftbukkit/CraftOfflinePlayer.java
++++ b/src/main/java/org/bukkit/craftbukkit/CraftOfflinePlayer.java
+@@ -54,6 +54,13 @@ public class CraftOfflinePlayer implements OfflinePlayer, ConfigurationSerializa
+         return this.getPlayer() != null;
+     }
+ 
++    // Paper start
++    @Override
++    public boolean isConnected() {
++        return false;
++    }
++    // Paper end
++
+     @Override
+     public String getName() {
+         Player player = this.getPlayer();
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+index a3912d4de96a6bb2b9b3977705fa3facb891f73d..a1b870fb3d1fd5d209474c47bf523d0d5d58ce39 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+@@ -256,6 +256,13 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
+         return this.server.getPlayer(this.getUniqueId()) != null;
+     }
+ 
++    // Paper start
++    @Override
++    public boolean isConnected() {
++        return !this.getHandle().hasDisconnected();
++    }
++    // Paper end
++
+     @Override
+     public InetSocketAddress getAddress() {
+         if (this.getHandle().connection.protocol() == null) return null;