From 7fdfb8644169a25805afd32f00ced38c1c14cec8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Havl=C3=AD=C4=8Dek?=
 <80639037+havel06@users.noreply.github.com>
Date: Wed, 25 Jan 2023 21:46:34 +0100
Subject: Allow certain blocks to be placed on top of upside-down stairs/slabs
 (#5468)

* Placing certain blocks on top of upside down slabs and stairs

* remove TODO

* fix style errors

* IsAnyStairType helper function

* Block placement on stairs and slabs
---
 src/Blocks/BlockRail.h | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

(limited to 'src/Blocks/BlockRail.h')

diff --git a/src/Blocks/BlockRail.h b/src/Blocks/BlockRail.h
index 6c4367334..4e2e6211f 100644
--- a/src/Blocks/BlockRail.h
+++ b/src/Blocks/BlockRail.h
@@ -1,6 +1,14 @@
-
 #pragma once
 
+#include "BlockHandler.h"
+#include "BlockSlab.h"
+#include "BlockStairs.h"
+#include "BlockType.h"
+#include "Blocks/Mixins.h"
+#include "../BlockInfo.h"
+#include "../Chunk.h"
+#include "ChunkDef.h"
+
 
 
 
@@ -154,9 +162,26 @@ public:
 
 private:
 
+	static bool CanBeSupportedBy(BLOCKTYPE a_BlockType, NIBBLETYPE a_BlockMeta)
+	{
+		if (cBlockSlabHandler::IsAnySlabType(a_BlockType))
+		{
+			return (a_BlockMeta & E_META_WOODEN_SLAB_UPSIDE_DOWN);
+		}
+		else if (cBlockStairsHandler::IsAnyStairType(a_BlockType))
+		{
+			return (a_BlockMeta & E_BLOCK_STAIRS_UPSIDE_DOWN);
+		}
+		return cBlockInfo::FullyOccupiesVoxel(a_BlockType);
+	}
+
 	virtual bool CanBeAt(const cChunk & a_Chunk, const Vector3i a_Position, NIBBLETYPE a_Meta) const override
 	{
-		if ((a_Position.y <= 0) || !cBlockInfo::FullyOccupiesVoxel(a_Chunk.GetBlock(a_Position.addedY(-1))))
+		BLOCKTYPE BelowBlock;
+		NIBBLETYPE BelowBlockMeta;
+		a_Chunk.GetBlockTypeMeta(a_Position.addedY(-1), BelowBlock, BelowBlockMeta);
+
+		if ((a_Position.y <= 0) || !CanBeSupportedBy(BelowBlock, BelowBlockMeta))
 		{
 			return false;
 		}
@@ -187,6 +212,7 @@ private:
 				return cBlockInfo::FullyOccupiesVoxel(BlockType);
 			}
 		}
+
 		return true;
 	}
 
-- 
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