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.

Spigot-Server-Patches/0119-Prevent-Waterflow-BlockFromToEvent-from-loading-chun.patch

@@ -0,0 +1,52 @@
+From 7c816e1d8b983ebe5f4b22653c75160ea66477da 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 51b80cb..0a3d673 100644
+--- a/src/main/java/net/minecraft/server/BlockFlowing.java
++++ b/src/main/java/net/minecraft/server/BlockFlowing.java
+@@ -105,6 +105,7 @@ public class BlockFlowing extends BlockFluids {
+         IBlockData iblockdata2 = world.getType(blockposition.down());
+ 
+         if (this.h(world, blockposition.down(), iblockdata2)) {
++            if (!canFlowTo(world, source, BlockFace.DOWN)) { return; } // Paper
+             // CraftBukkit start - Send "down" to the server
+             BlockFromToEvent event = new BlockFromToEvent(source, BlockFace.DOWN);
+             if (server != null) {
+@@ -142,6 +143,7 @@ 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));
+                 if (server != null) {
+                     server.getPluginManager().callEvent(event);
+@@ -156,8 +158,14 @@ 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.getBlock() != Blocks.AIR) {
+                 if (this.material == Material.LAVA) {
+                     this.fizz(world, blockposition);
+-- 
+2.7.4
+