From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Samsuik <40902469+Samsuik@users.noreply.github.com>
Date: Thu, 30 Nov 2023 15:54:49 +0000
Subject: [PATCH] Reduce entity tracker player updates


diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 34fdb52904a26bc7c4c95eee91882a3924ab037c..e372993dffc7012c6dfadacb99b2a7fc43b2aebd 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1161,6 +1161,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         try {
             for (TrackedEntity tracker : this.entityMap.values()) {
                 // update tracker entry
+                if (!tracker.shouldLookForPlayers()) continue; // Sakura - delay entities looking for nearby players
                 tracker.updatePlayers(tracker.entity.getPlayersInTrackRange());
             }
         } finally {
@@ -1325,14 +1326,34 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         private final int range;
         SectionPos lastSectionPos;
         public final Set<ServerPlayerConnection> seenBy = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>(); // Paper - Perf: optimise map impl
+        private final int playerSearchInterval; // Sakura - reduce entity tracker player updates
+        private Vec3 entityPosition; // Sakura - reduce entity tracker player updates
 
         public TrackedEntity(final Entity entity, final int i, final int j, final boolean flag) {
             this.serverEntity = new ServerEntity(ChunkMap.this.level, entity, j, flag, this::broadcast, this.seenBy); // CraftBukkit
             this.entity = entity;
             this.range = i;
             this.lastSectionPos = SectionPos.of((EntityAccess) entity);
+            // Sakura start - reduce entities looking for nearby players
+            // Use a maximum of 20 ticks because stationary entities use Integer.MAX_VALUE
+            // which causes them to turn invisible after untracking.
+            this.playerSearchInterval = Math.min(j, 20);
+            this.entityPosition = entity.position();
         }
 
+        final boolean shouldLookForPlayers() {
+            // We have to always update players otherwise they can turn invisible on teleports (why?)
+            if (entity instanceof net.minecraft.world.entity.player.Player || entity.tickCount % playerSearchInterval == 0) {
+                return true;
+            }
+
+            Vec3 lastPosition = entityPosition;
+            entityPosition = entity.position();
+
+            return entity.position().distanceToSqr(lastPosition) >= (double) range / 2.0;
+        }
+        // Sakura end - reduce entities looking for nearby players
+
         // Paper start - use distance map to optimise tracker
         com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> lastTrackerCandidates;