From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Phoenix616 <mail@moep.tv>
Date: Sun, 7 Jun 2020 21:43:42 +0100
Subject: [PATCH] Maps shouldn't load chunks

Previously maps would load all chunks in a certain radius depending on
 their scale when trying to update their content. This would result in
 main thread chunk loads when they weren't really necessary, especially
 on low view distances or "slow" async chunk loads after teleports or
 other prioritisation.

 This changes it to only try to render already loaded chunks based on
 the assumption that the chunks around the player will get loaded
 eventually anyways and that maps will get checked for update every
 five ticks that movement occur in anyways.

diff --git a/src/main/java/net/minecraft/server/ItemWorldMap.java b/src/main/java/net/minecraft/server/ItemWorldMap.java
index c6feee870be41188b5bced4bb9a8ae1b4e53c942..63b112b38a51873cf5769ad8506c3fdb9d52d42c 100644
--- a/src/main/java/net/minecraft/server/ItemWorldMap.java
+++ b/src/main/java/net/minecraft/server/ItemWorldMap.java
@@ -96,9 +96,9 @@ public class ItemWorldMap extends ItemWorldMapBase {
                             int k2 = (j / i + k1 - 64) * i;
                             int l2 = (k / i + l1 - 64) * i;
                             Multiset<MaterialMapColor> multiset = LinkedHashMultiset.create();
-                            Chunk chunk = world.getChunkAtWorldCoords(new BlockPosition(k2, 0, l2));
+                            Chunk chunk = world.getChunkIfLoaded(new BlockPosition(k2, 0, l2)); // Paper - Maps shouldn't load chunks
 
-                            if (!chunk.isEmpty()) {
+                            if (chunk != null && !chunk.isEmpty()) { // Paper - Maps shouldn't load chunks
                                 ChunkCoordIntPair chunkcoordintpair = chunk.getPos();
                                 int i3 = k2 & 15;
                                 int j3 = l2 & 15;