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, 161 insertions, 0 deletions

diff --git a/patches/server/0531-Expand-PlayerGameModeChangeEvent.patch b/patches/server/0531-Expand-PlayerGameModeChangeEvent.patch
new file mode 100644
index 0000000000..08394e448a
--- /dev/null
+++ b/patches/server/0531-Expand-PlayerGameModeChangeEvent.patch
@@ -0,0 +1,161 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake Potrebic <[email protected]>
+Date: Sat, 15 May 2021 10:04:43 -0700
+Subject: [PATCH] Expand PlayerGameModeChangeEvent
+
+
+diff --git a/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java b/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
+index b95a979f8f58f43e0becedcd843ff8bb992eb455..a046a0b1519806ff3d987e6402f152b60a3a6f4c 100644
+--- a/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
++++ b/src/main/java/net/minecraft/server/commands/DefaultGameModeCommands.java
+@@ -28,9 +28,13 @@ public class DefaultGameModeCommands {
+         GameType gameType = minecraftServer.getForcedGameType();
+         if (gameType != null) {
+             for (ServerPlayer serverPlayer : minecraftServer.getPlayerList().getPlayers()) {
+-                if (serverPlayer.setGameMode(gameType)) {
+-                    i++;
++                // Paper start - Expand PlayerGameModeChangeEvent
++                org.bukkit.event.player.PlayerGameModeChangeEvent event = serverPlayer.setGameMode(gameType, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.DEFAULT_GAMEMODE, net.kyori.adventure.text.Component.empty());
++                if (event != null && event.isCancelled()) {
++                    source.sendSuccess(() -> io.papermc.paper.adventure.PaperAdventure.asVanilla(event.cancelMessage()), false);
+                 }
++                // Paper end - Expand PlayerGameModeChangeEvent
++                    i++;
+             }
+         }
+ 
+diff --git a/src/main/java/net/minecraft/server/commands/GameModeCommand.java b/src/main/java/net/minecraft/server/commands/GameModeCommand.java
+index 7f09119bc7d661e08a960dd2bd46006efe752d3e..d1da3600dc07107309b20ebe6e7c0c4da0e8de76 100644
+--- a/src/main/java/net/minecraft/server/commands/GameModeCommand.java
++++ b/src/main/java/net/minecraft/server/commands/GameModeCommand.java
+@@ -60,9 +60,14 @@ public class GameModeCommand {
+         int i = 0;
+ 
+         for (ServerPlayer serverPlayer : targets) {
+-            if (serverPlayer.setGameMode(gameMode)) {
++            // Paper start - Expand PlayerGameModeChangeEvent
++            org.bukkit.event.player.PlayerGameModeChangeEvent event = serverPlayer.setGameMode(gameMode, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.COMMAND, net.kyori.adventure.text.Component.empty());
++            if (event != null && !event.isCancelled()) {
+                 logGamemodeChange(context.getSource(), serverPlayer, gameMode);
+                 i++;
++            } else if (event != null && event.cancelMessage() != null) {
++                context.getSource().sendSuccess(() -> io.papermc.paper.adventure.PaperAdventure.asVanilla(event.cancelMessage()), true);
++                // Paper end - Expand PlayerGameModeChangeEvent
+             }
+         }
+ 
+diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+index 52a5274fb811870481a48bf0505769d7ac5df31f..42df8d45ceb963043cf6467b8fc47272ce0873da 100644
+--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
++++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+@@ -2084,10 +2084,18 @@ public class ServerPlayer extends net.minecraft.world.entity.player.Player {
+     }
+ 
+     public boolean setGameMode(GameType gameMode) {
++        // Paper start - Expand PlayerGameModeChangeEvent
++        org.bukkit.event.player.PlayerGameModeChangeEvent event = this.setGameMode(gameMode, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.UNKNOWN, null);
++        return event == null ? false : event.isCancelled();
++    }
++    @Nullable
++    public org.bukkit.event.player.PlayerGameModeChangeEvent setGameMode(GameType gameMode, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause cause, @Nullable net.kyori.adventure.text.Component message) {
+         boolean flag = this.isSpectator();
+ 
+-        if (!this.gameMode.changeGameModeForPlayer(gameMode)) {
+-            return false;
++        org.bukkit.event.player.PlayerGameModeChangeEvent event = this.gameMode.changeGameModeForPlayer(gameMode, cause, message);
++        if (event == null || event.isCancelled()) {
++            return null;
++            // Paper end - Expand PlayerGameModeChangeEvent
+         } else {
+             this.connection.send(new ClientboundGameEventPacket(ClientboundGameEventPacket.CHANGE_GAME_MODE, (float) gameMode.getId()));
+             if (gameMode == GameType.SPECTATOR) {
+@@ -2103,7 +2111,7 @@ public class ServerPlayer extends net.minecraft.world.entity.player.Player {
+ 
+             this.onUpdateAbilities();
+             this.updateEffectVisibility();
+-            return true;
++            return event; // Paper - Expand PlayerGameModeChangeEvent
+         }
+     }
+ 
+@@ -2509,6 +2517,16 @@ public class ServerPlayer extends net.minecraft.world.entity.player.Player {
+     }
+ 
+     public void loadGameTypes(@Nullable CompoundTag nbt) {
++        // Paper start - Expand PlayerGameModeChangeEvent
++        if (this.server.getForcedGameType() != null && this.server.getForcedGameType() != ServerPlayer.readPlayerMode(nbt, "playerGameType")) {
++            if (new org.bukkit.event.player.PlayerGameModeChangeEvent(this.getBukkitEntity(), org.bukkit.GameMode.getByValue(this.server.getDefaultGameType().getId()), org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.DEFAULT_GAMEMODE, null).callEvent()) {
++                this.gameMode.setGameModeForPlayer(this.server.getForcedGameType(), GameType.DEFAULT_MODE);
++            } else {
++                this.gameMode.setGameModeForPlayer(ServerPlayer.readPlayerMode(nbt,"playerGameType"), ServerPlayer.readPlayerMode(nbt, "previousPlayerGameType"));
++            }
++            return;
++        }
++        // Paper end - Expand PlayerGameModeChangeEvent
+         this.gameMode.setGameModeForPlayer(this.calculateGameModeForNewPlayer(ServerPlayer.readPlayerMode(nbt, "playerGameType")), ServerPlayer.readPlayerMode(nbt, "previousPlayerGameType"));
+     }
+ 
+diff --git a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
+index 5de472df78940d1b8320f73d18b2edf3a796227e..073cf184a0e7af41048ae67a9b17b4cdfcc43c35 100644
+--- a/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
++++ b/src/main/java/net/minecraft/server/level/ServerPlayerGameMode.java
+@@ -74,14 +74,21 @@ public class ServerPlayerGameMode {
+     }
+ 
+     public boolean changeGameModeForPlayer(GameType gameMode) {
++        // Paper start - Expand PlayerGameModeChangeEvent
++        PlayerGameModeChangeEvent event = this.changeGameModeForPlayer(gameMode, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.UNKNOWN, null);
++        return event != null && event.isCancelled();
++    }
++    @Nullable
++    public PlayerGameModeChangeEvent changeGameModeForPlayer(GameType gameMode, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause cause, @Nullable net.kyori.adventure.text.Component cancelMessage) {
++        // Paper end - Expand PlayerGameModeChangeEvent
+         if (gameMode == this.gameModeForPlayer) {
+-            return false;
++            return null; // Paper - Expand PlayerGameModeChangeEvent
+         } else {
+             // CraftBukkit start
+-            PlayerGameModeChangeEvent event = new PlayerGameModeChangeEvent(this.player.getBukkitEntity(), GameMode.getByValue(gameMode.getId()));
++            PlayerGameModeChangeEvent event = new PlayerGameModeChangeEvent(this.player.getBukkitEntity(), GameMode.getByValue(gameMode.getId()), cause, cancelMessage); // Paper
+             this.level.getCraftServer().getPluginManager().callEvent(event);
+             if (event.isCancelled()) {
+-                return false;
++                return event; // Paper - Expand PlayerGameModeChangeEvent
+             }
+             // CraftBukkit end
+             this.setGameModeForPlayer(gameMode, this.previousGameModeForPlayer);
+@@ -92,7 +99,7 @@ public class ServerPlayerGameMode {
+                 this.player.resetCurrentImpulseContext();
+             }
+ 
+-            return true;
++            return event; // Paper - Expand PlayerGameModeChangeEvent
+         }
+     }
+ 
+diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+index 276c0b017452a1d7b60a2a8e779f2f3fcf4960cc..9781047aa5e0a6e6bc9f9c43a1eb347b6ecdff66 100644
+--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
++++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+@@ -2730,7 +2730,7 @@ public class ServerGamePacketListenerImpl extends ServerCommonPacketListenerImpl
+ 
+                     this.player = this.server.getPlayerList().respawn(this.player, false, Entity.RemovalReason.KILLED, RespawnReason.DEATH); // CraftBukkit
+                     if (this.server.isHardcore()) {
+-                        this.player.setGameMode(GameType.SPECTATOR);
++                        this.player.setGameMode(GameType.SPECTATOR, org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.HARDCORE_DEATH, null); // Paper - Expand PlayerGameModeChangeEvent
+                         ((GameRules.BooleanValue) this.player.level().getGameRules().getRule(GameRules.RULE_SPECTATORSGENERATECHUNKS)).set(false, this.player.serverLevel()); // CraftBukkit - per-world
+                     }
+                 }
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+index 7de53f6750d478a052bc8ade6edac056565fe068..a85983b947147a1557908846b8773aab29c17fae 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+@@ -1654,7 +1654,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
+         Preconditions.checkArgument(mode != null, "GameMode cannot be null");
+         if (this.getHandle().connection == null) return;
+ 
+-        this.getHandle().setGameMode(GameType.byId(mode.getValue()));
++        this.getHandle().setGameMode(GameType.byId(mode.getValue()), org.bukkit.event.player.PlayerGameModeChangeEvent.Cause.PLUGIN, null); // Paper - Expand PlayerGameModeChangeEvent
+     }
+ 
+     @Override