Leaf/leaf-server/minecraft-patches/features/0273-preload-mob-spawning-position.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: hayanesuru <hayanesuru@outlook.jp>
Date: Wed, 4 Jun 2025 20:54:32 +0900
Subject: [PATCH] preload mob spawning position


diff --git a/net/minecraft/world/level/NaturalSpawner.java b/net/minecraft/world/level/NaturalSpawner.java
index a55abb08093847a8bfec446659f9af5fb1df2824..555983c7fa7b1f2d72ebbc148ca3dcb7cd217c56 100644
--- a/net/minecraft/world/level/NaturalSpawner.java
+++ b/net/minecraft/world/level/NaturalSpawner.java
@@ -243,12 +243,61 @@ public final class NaturalSpawner {
         // Paper end - throttle failed spawn attempts
     ) {
         // Paper end - Optional per player mob spawns
-        BlockPos randomPosWithin = getRandomPosWithin(level, chunk);
-        if (randomPosWithin.getY() >= level.getMinY() + 1) {
-            return spawnCategoryForPosition(category, level, chunk, randomPosWithin, filter, callback, maxSpawns, trackEntity, false); // Paper - Optional per player mob spawns // Paper - throttle failed spawn attempts
-        }
+        // Leaf start - preload mob spawning position
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
 
-        return 0; // Paper - throttle failed spawn attempts
+        if (org.dreeam.leaf.config.modules.opt.PreloadNaturalMobSpawning.enabled) {
+            if (chunk.cacheSpawnPosIndex == 16 || chunk.cacheSpawnPosIndex == -1) {
+                if (chunk.cacheSpawnPos == null) {
+                    chunk.cacheSpawnPos = new long[16];
+                }
+                // cache friendly
+                for (int i = 0; i < 16; i++) {
+                    mutableRandomPosWithin(pos, level, chunk);
+                    if (pos.getY() >= level.getMinY() + 1
+                        && level.getWorldBorder().isWithinBounds(pos)
+                        && !level.isOutsideBuildHeight(pos)) {
+                        LevelChunk chunk1 = chunk.getPos().longKey == ChunkPos.asLong(pos)
+                            ? chunk
+                            : level.chunkSource.getChunkAtIfLoadedImmediately(pos.getX() >> 4, pos.getZ() >> 4);
+                        if (chunk1 != null) {
+                            BlockState bs = chunk1.getBlockStateFinal(pos.getX(), pos.getY(), pos.getZ());
+                            if (bs != null && !bs.isRedstoneConductor(level, pos)) {
+                                chunk.cacheSpawnPos[i] = BlockPos.asLong(pos.getX(), pos.getY(), pos.getZ());
+                                continue;
+                            }
+                        }
+                    }
+                    chunk.cacheSpawnPos[i] = -1;
+                }
+                chunk.cacheSpawnPosIndex = 0;
+            }
+            long cachePos = chunk.cacheSpawnPos[chunk.cacheSpawnPosIndex];
+            chunk.cacheSpawnPosIndex++;
+            if (cachePos == -1) {
+                return 0;
+            }
+            pos.set(cachePos);
+        } else {
+            mutableRandomPosWithin(pos, level, chunk);
+            if (pos.getY() < level.getMinY() + 1
+                || !level.getWorldBorder().isWithinBounds(pos)
+                || level.isOutsideBuildHeight(pos)) {
+                return 0;
+            }
+            LevelChunk chunk1 = chunk.getPos().longKey == ChunkPos.asLong(pos)
+                ? chunk
+                : level.chunkSource.getChunkAtIfLoadedImmediately(pos.getX() >> 4, pos.getZ() >> 4);
+            if (chunk1 == null) {
+                return 0;
+            }
+            BlockState bs = chunk1.getBlockStateFinal(pos.getX(), pos.getY(), pos.getZ());
+            if (bs == null || bs.isRedstoneConductor(level, pos)) {
+                return 0;
+            }
+        }
+        return spawnCategoryForPosition(category, level, chunk, pos, filter, callback, maxSpawns, trackEntity, false); // Paper - Optional per player mob spawns // Paper - throttle failed spawn attempts
+                        // Leaf end - preload mob spawning position
     }
 
     @VisibleForDebug
@@ -270,7 +319,12 @@ public final class NaturalSpawner {
         MobCategory category, ServerLevel level, ChunkAccess chunk, BlockPos pos, NaturalSpawner.SpawnPredicate filter, NaturalSpawner.AfterSpawnCallback callback, final int maxSpawns, final @Nullable Consumer<Entity> trackEntity
         // Paper start - throttle failed spawn attempts
     ) {
-        spawnCategoryForPosition(category, level, chunk, pos, filter, callback, maxSpawns, trackEntity, false);
+        // Leaf start - preload mob spawning position
+        BlockState blockState = level.getBlockStateIfLoadedAndInBounds(pos);
+        if (blockState != null && !blockState.isRedstoneConductor(chunk, pos)) {
+            spawnCategoryForPosition(category, level, chunk, pos, filter, callback, maxSpawns, trackEntity, false);
+        }
+        // Leaf end - preload mob spawning position
     }
     public static int spawnCategoryForPosition(
         MobCategory category, ServerLevel level, ChunkAccess chunk, BlockPos pos, NaturalSpawner.SpawnPredicate filter, NaturalSpawner.AfterSpawnCallback callback, final int maxSpawns, final @Nullable Consumer<Entity> trackEntity, final boolean nothing
@@ -281,8 +335,8 @@ public final class NaturalSpawner {
         ChunkGenerator generator = level.getChunkSource().getGenerator();
         int y = pos.getY();
         int i = 0; // Paper - throttle failed spawn attempts
-        BlockState blockState = level.getBlockStateIfLoadedAndInBounds(pos); // Paper - don't load chunks for mob spawn
-        if (blockState != null && !blockState.isRedstoneConductor(chunk, pos)) { // Paper - don't load chunks for mob spawn
+        //BlockState blockState = level.getBlockStateIfLoadedAndInBounds(pos); // Paper - don't load chunks for mob spawn // Leaf - preload mob spawning position
+        if (true /*blockState != null && !blockState.isRedstoneConductor(chunk, pos)*/) { // Paper - don't load chunks for mob spawn // Leaf - preload mob spawning position
             BlockPos.MutableBlockPos mutableBlockPos = new BlockPos.MutableBlockPos();
             //int i = 0; // Paper - throttle failed spawn attempts - move up
 
diff --git a/net/minecraft/world/level/chunk/LevelChunk.java b/net/minecraft/world/level/chunk/LevelChunk.java
index 31f19dfe16e270b55f3b44754c97ed8d9fa422cf..b79eefb182b0a9e9f22ccb649c4659483228082c 100644
--- a/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/net/minecraft/world/level/chunk/LevelChunk.java
@@ -107,6 +107,8 @@ public class LevelChunk extends ChunkAccess implements ca.spottedleaf.moonrise.p
     // Paper start - rewrite chunk system
     private boolean postProcessingDone;
     private ca.spottedleaf.moonrise.patches.chunk_system.scheduling.NewChunkHolder chunkAndHolder;
+    public long[] cacheSpawnPos = null; // Leaf - preload mob spawning position
+    public int cacheSpawnPosIndex = -1; // Leaf - preload mob spawning position
 
     @Override
     public final boolean moonrise$isPostProcessingDone() {