Add an event for when the chunk ticket level is updated (#8909)

src/main/java/net/minecraftforge/event/ForgeEventFactory.java

@@ -16,6 +16,7 @@ import com.mojang.brigadier.CommandDispatcher;
 import net.minecraft.commands.CommandBuildContext;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.ReloadableServerResources;
+import net.minecraft.server.level.ChunkHolder;
 import net.minecraft.server.players.PlayerList;
 import net.minecraft.util.RandomSource;
 import net.minecraft.util.random.WeightedRandomList;
@@ -118,6 +119,7 @@ import net.minecraftforge.event.level.BlockEvent.CreateFluidSourceEvent;
 import net.minecraftforge.event.level.BlockEvent.EntityMultiPlaceEvent;
 import net.minecraftforge.event.level.BlockEvent.EntityPlaceEvent;
 import net.minecraftforge.event.level.BlockEvent.NeighborNotifyEvent;
+import net.minecraftforge.event.level.ChunkTicketLevelUpdatedEvent;
 import net.minecraftforge.event.level.ChunkWatchEvent;
 import net.minecraftforge.event.level.ExplosionEvent;
 import net.minecraftforge.event.level.PistonEvent;
@@ -610,6 +612,12 @@ public class ForgeEventFactory
         return event.getResult() != Result.DENY;
     }
 
+    public static void fireChunkTicketLevelUpdated(ServerLevel level, long chunkPos, int oldTicketLevel, int newTicketLevel, @Nullable ChunkHolder chunkHolder)
+    {
+        if (oldTicketLevel != newTicketLevel)
+            MinecraftForge.EVENT_BUS.post(new ChunkTicketLevelUpdatedEvent(level, chunkPos, oldTicketLevel, newTicketLevel, chunkHolder));
+    }
+
     public static void fireChunkWatch(ServerPlayer entity, LevelChunk chunk, ServerLevel level)
     {
         MinecraftForge.EVENT_BUS.post(new ChunkWatchEvent.Watch(entity, chunk, level));

src/main/java/net/minecraftforge/event/level/ChunkTicketLevelUpdatedEvent.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.event.level;
+
+import net.minecraft.server.level.ChunkHolder;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.eventbus.api.Cancelable;
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.LogicalSide;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * This event is fired whenever a chunk has its ticket level changed via the server's ChunkMap.
+ * <p>
+ * This event does not fire if the new ticket level is the same as the old level, or if both the
+ * new <strong>AND</strong> old ticket levels represent values past the max chunk distance.
+ * <p>
+ * Due to how vanilla processes ticket level changes this event may be fired "twice" in one tick for the same chunk.
+ * The scenario where this happens is when increasing the level from say 31 (ticking) to 32, the way vanilla does it
+ * is by first changing it from 31 to 46, and then queuing the update from 46 to 32. However, when going from 32 to 31,
+ * vanilla is able to go directly.
+ * <p>
+ * This event is not {@linkplain Cancelable cancellable} and does not {@linkplain HasResult have a result}.
+ * <p>
+ * This event is fired on the {@linkplain MinecraftForge#EVENT_BUS main Forge event bus}
+ * only on the {@linkplain LogicalSide#SERVER logical server}.
+ **/
+public class ChunkTicketLevelUpdatedEvent extends Event
+{
+    private final ServerLevel level;
+    private final long chunkPos;
+    private final int oldTicketLevel;
+    private final int newTicketLevel;
+    @Nullable
+    private final ChunkHolder chunkHolder;
+
+    public ChunkTicketLevelUpdatedEvent(ServerLevel level, long chunkPos, int oldTicketLevel, int newTicketLevel, @Nullable ChunkHolder chunkHolder)
+    {
+        this.level = level;
+        this.chunkPos = chunkPos;
+        this.oldTicketLevel = oldTicketLevel;
+        this.newTicketLevel = newTicketLevel;
+        this.chunkHolder = chunkHolder;
+    }
+
+    /**
+     * {@return the server level containing the chunk}
+     */
+    public ServerLevel getLevel()
+    {
+        return this.level;
+    }
+
+    /**
+     * {@return the long representation of the chunk position the ticket level changed for}
+     */
+    public long getChunkPos()
+    {
+        return this.chunkPos;
+    }
+
+    /**
+     * {@return the previous ticket level the chunk had}
+     */
+    public int getOldTicketLevel()
+    {
+        return this.oldTicketLevel;
+    }
+
+    /**
+     * {@return the new ticket level for the chunk}
+     */
+    public int getNewTicketLevel()
+    {
+        return this.newTicketLevel;
+    }
+
+    /**
+     * {@return chunk that had its ticket level updated}
+     */
+    @Nullable
+    public ChunkHolder getChunkHolder()
+    {
+        return this.chunkHolder;
+    }
+}