From b1b3aa6f0d4cd08b022930a60c4607dfd6da1185 Mon Sep 17 00:00:00 2001
From: Martin Panzer <postremus1996@googlemail.com>
Date: Fri, 3 Jun 2016 23:13:39 +0200
Subject: [PATCH] Fix FallingBlocks being stuck on fences

Fallingblocks would previously only check if directly beneath them a block exists. They also
hover on top of the 1.5 block tall hitbox of fences during these check. This
resulted in them always thinking they would be on air.

We now first check, if if we are already on the ground.
if not, we check if the falling block is inside of the hitbox of the block at y - 1.

diff --git a/src/main/java/net/minecraft/server/BlockFalling.java b/src/main/java/net/minecraft/server/BlockFalling.java
index 8f22dab..d3a0d70 100644
--- a/src/main/java/net/minecraft/server/BlockFalling.java
+++ b/src/main/java/net/minecraft/server/BlockFalling.java
@@ -71,5 +71,11 @@ public class BlockFalling extends Block {
         return block == Blocks.FIRE || material == Material.AIR || material == Material.WATER || material == Material.LAVA;
     }
 
+    // Paper start - OBFHELPER
+    public static boolean canMoveThrough(IBlockData blockdata) {
+        return BlockFalling.i(blockdata);
+    }
+    // Paper end
+
     public void a_(World world, BlockPosition blockposition) {}
 }
diff --git a/src/main/java/net/minecraft/server/EntityFallingBlock.java b/src/main/java/net/minecraft/server/EntityFallingBlock.java
index 491bb11..0d8c438 100644
--- a/src/main/java/net/minecraft/server/EntityFallingBlock.java
+++ b/src/main/java/net/minecraft/server/EntityFallingBlock.java
@@ -2,7 +2,9 @@ package net.minecraft.server;
 
 import com.google.common.collect.Lists;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Iterator;
+import java.util.List;
 import javax.annotation.Nullable;
 
 import org.bukkit.craftbukkit.event.CraftEventFactory; // CraftBukkit
@@ -98,10 +100,9 @@ public class EntityFallingBlock extends Entity {
                 blockposition = new BlockPosition(this);
                 if (this.onGround) {
                     IBlockData iblockdata = this.world.getType(blockposition);
-
-                    if (BlockFalling.i(this.world.getType(new BlockPosition(this.locX, this.locY - 0.009999999776482582D, this.locZ)))) {
+                    if (!isOnGround()) {
                         this.onGround = false;
-                        // return; // CraftBukkit
+                        return; // Paper
                     }
 
                     this.motX *= 0.699999988079071D;
@@ -158,6 +159,30 @@ public class EntityFallingBlock extends Entity {
         }
     }
 
+    // Paper start
+    private boolean isOnGround() {
+        BlockPosition where = new BlockPosition(this.locX, this.locY - 0.009999999776482582D, this.locZ);
+
+        if (!BlockFalling.canMoveThrough(this.world.getType(where))) {
+            return true;
+        }
+
+        IBlockData blockData = this.world.getType(where.down());
+        if (BlockFalling.canMoveThrough(blockData)) {
+            return false;
+        }
+
+        List<AxisAlignedBB> list = new ArrayList<>();
+        addCollisions(blockData, getWorld(), where, this.getBoundingBox(), list, this);
+        return list.size() > 0;
+    }
+
+    // OBFHELPER
+    private void addCollisions(IBlockData blockData, World world, BlockPosition where, AxisAlignedBB collider, List<AxisAlignedBB> list, Entity entity) {
+        blockData.a(world, where, collider, list, entity);
+    }
+    // Paper end
+
     public void e(float f, float f1) {
         Block block = this.block.getBlock();
 
-- 
2.8.3