From fd37edca846d81afb65cd70f00f7b94d3b61bf39 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 28 Mar 2016 22:03:09 -0400
Subject: [PATCH] Prevent Waterflow BlockFromToEvent from loading chunks

Many protection plugins would unintentionally trigger chunk loads
by calling .getToBlock() on an unloaded chunk, killing performance.

Simply skip the event call. as CraftBukkit blocks changing the block
of unloaded chunks anyways.

This keeps behavior consistent, vs inconsistent flowing based on plugin triggered loads.

diff --git a/src/main/java/net/minecraft/server/BlockFlowing.java b/src/main/java/net/minecraft/server/BlockFlowing.java
index 739b9aac..ff90e08e 100644
--- a/src/main/java/net/minecraft/server/BlockFlowing.java
+++ b/src/main/java/net/minecraft/server/BlockFlowing.java
@@ -96,6 +96,7 @@ public class BlockFlowing extends BlockFluids {
 
         if (this.h(world, blockposition.down(), iblockdata2)) {
             // CraftBukkit start
+            if (!canFlowTo(world, source, BlockFace.DOWN)) { return; } // Paper
             BlockFromToEvent event = new BlockFromToEvent(source, BlockFace.DOWN);
             world.getServer().getPluginManager().callEvent(event);
 
@@ -136,6 +137,7 @@ public class BlockFlowing extends BlockFluids {
                 EnumDirection enumdirection1 = (EnumDirection) iterator1.next();
 
                 // CraftBukkit start
+                if (!canFlowTo(world, source, org.bukkit.craftbukkit.block.CraftBlock.notchToBlockFace(enumdirection1))) { continue; } // Paper
                 BlockFromToEvent event = new BlockFromToEvent(source, org.bukkit.craftbukkit.block.CraftBlock.notchToBlockFace(enumdirection1));
                 world.getServer().getPluginManager().callEvent(event);
 
@@ -148,8 +150,14 @@ public class BlockFlowing extends BlockFluids {
 
     }
 
+    // Paper start
+    private boolean canFlowTo(World world, org.bukkit.block.Block source, BlockFace face) {
+        return source.getWorld().isChunkLoaded((source.getX() + face.getModX()) >> 4, (source.getZ() + face.getModZ()) >> 4);
+    }
+    // Paper end
+
     private void flow(World world, BlockPosition blockposition, IBlockData iblockdata, int i) {
-        if (world.isLoaded(blockposition) && this.h(world, blockposition, iblockdata)) { // CraftBukkit - add isLoaded check
+        if (/*world.isLoaded(blockposition) &&*/ this.h(world, blockposition, iblockdata)) { // CraftBukkit - add isLoaded check // Paper - Already checked before we get here for isLoaded
             if (iblockdata.getMaterial() != Material.AIR) {
                 if (this.material == Material.LAVA) {
                     this.fizz(world, blockposition);
-- 
2.13.1.windows.2