new: add config for poi unloading

Author: ishland

c2me-rewrites-chunk-system/src/main/java/com/ishland/c2me/rewrites/chunksystem/common/Config.java

@@ -20,6 +20,20 @@ public class Config {
                      """)
             .getBoolean(false, false);
 
+    public static final boolean allowPOIUnloading = new ConfigSystem.ConfigAccessor()
+            .key("chunkSystem.allowPOIUnloading")
+            .comment("""
+                    Whether to allow POIs (Point of Interest) to be unloaded
+                    Unloaded POIs are reloaded on-demand or when the corresponding chunks are loaded again,
+                    which should not cause any behavior change
+                    \s
+                    Note:
+                    Vanilla never unloads POIs when chunks unload, causing small memory leaks
+                    These leaks adds up and eventually cause issues after generating millions of chunks
+                    in a single world instance
+                    """)
+            .getBoolean(true, false);
+
     public static void init() {
         // intentionally empty
     }

c2me-rewrites-chunk-system/src/main/java/com/ishland/c2me/rewrites/chunksystem/mixin/MixinSerializingRegionBasedStorage.java

@@ -1,5 +1,6 @@
 package com.ishland.c2me.rewrites.chunksystem.mixin;
 
+import com.ishland.c2me.rewrites.chunksystem.common.Config;
 import com.ishland.c2me.rewrites.chunksystem.common.ducks.IPOIUnloading;
 import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
 import net.minecraft.util.math.ChunkPos;
@@ -23,6 +24,8 @@ public abstract class MixinSerializingRegionBasedStorage<R> implements IPOIUnloa
 
     @Override
     public void c2me$unloadPoi(ChunkPos pos) {
+        if (!Config.allowPOIUnloading) return;
+
         if (!this.c2me$shouldUnloadPoi(pos)) {
             return;
         }