1 files changed, 63 insertions, 71 deletions

diff --git a/src/Items/ItemSlab.h b/src/Items/ItemSlab.h
index 944336f7e..467975047 100644
--- a/src/Items/ItemSlab.h
+++ b/src/Items/ItemSlab.h
@@ -14,95 +14,87 @@ class cItemSlabHandler:
 
 public:
 
-	/** Creates a new handler for the specified slab item type.
-	Sets the handler to use the specified doubleslab block type for combining self into doubleslabs. */
-	cItemSlabHandler(int a_ItemType, BLOCKTYPE a_DoubleSlabBlockType):
-		Super(a_ItemType),
-		m_DoubleSlabBlockType(a_DoubleSlabBlockType)
+	using Super::Super;
+
+private:
+
+	virtual bool CommitPlacement(cPlayer & a_Player, const cItem & a_HeldItem, const Vector3i a_PlacePosition, const eBlockFace a_ClickedBlockFace, const Vector3i a_CursorPosition) override
 	{
-	}
+		// Confer BlockSlab.h, which we're in cahoots with to make the below logic work.
+
+		// If clicking a slab, combine it into a double-slab:
+		if (cBlockSlabHandler::IsAnySlabType(a_Player.GetWorld()->GetBlock(a_PlacePosition)))
+		{
+			if (!a_Player.PlaceBlock(a_PlacePosition, GetDoubleSlabType(static_cast<BLOCKTYPE>(a_HeldItem.m_ItemType)), static_cast<NIBBLETYPE>(a_HeldItem.m_ItemDamage)))
+			{
+				return false;
+			}
 
+			a_Player.SendBlocksAround(a_PlacePosition.x, a_PlacePosition.y, a_PlacePosition.z, 2);  // (see below)
+			return true;
+		}
+
+		// Set the correct metadata based on player equipped item:
+		if (!a_Player.PlaceBlock(a_PlacePosition, static_cast<BLOCKTYPE>(a_HeldItem.m_ItemType), FaceToMetaData(static_cast<NIBBLETYPE>(a_HeldItem.m_ItemDamage), a_ClickedBlockFace, a_CursorPosition)))
+		{
+			return false;
+		}
 
+		/* This is a workaround for versions < 1.13, where the client combines a slab in the
+		direction of the clicked block face of a block ignoring build collision, rather than replacing said block.
+		Resend blocks to the client to fix the bug.
+		Ref.: https://forum.cuberite.org/thread-434-post-17388.html#pid17388 */
+		a_Player.SendBlocksAround(a_PlacePosition.x, a_PlacePosition.y, a_PlacePosition.z, 2);
 
+		return true;
+	}
 
 
-	// cItemHandler overrides:
-	virtual bool OnPlayerPlace(
-		cWorld & a_World,
-		cPlayer & a_Player,
-		const cItem & a_EquippedItem,
-		const Vector3i a_ClickedBlockPos,
-		eBlockFace a_ClickedBlockFace,
-		const Vector3i a_CursorPos
-	) override
+	static NIBBLETYPE FaceToMetaData(const NIBBLETYPE a_BaseMeta, const eBlockFace a_ClickedBlockFace, const Vector3i a_CursorPosition)
 	{
-		// If clicking a slab, try combining it into a double-slab:
-		BLOCKTYPE ClickedBlockType;
-		NIBBLETYPE ClickedBlockMeta;
-		a_World.GetBlockTypeMeta(a_ClickedBlockPos, ClickedBlockType, ClickedBlockMeta);
-		if (
-			(ClickedBlockType == m_ItemType) &&                         // Placing the same slab material
-			((ClickedBlockMeta & 0x07) == a_EquippedItem.m_ItemDamage)  // Placing the same slab sub-kind (and existing slab is single)
-		)
+		switch (a_ClickedBlockFace)
 		{
-			if (
-				((a_ClickedBlockFace == BLOCK_FACE_TOP) && ((ClickedBlockMeta & 0x08) == 0)) ||  // Top side of a bottom-half-slab
-				((a_ClickedBlockFace == BLOCK_FACE_BOTTOM) && ((ClickedBlockMeta & 0x08) != 0))  // Bottom side of a top-half-slab
-			)
+			case BLOCK_FACE_TOP:
 			{
-				if (!a_Player.PlaceBlock(a_ClickedBlockPos.x, a_ClickedBlockPos.y, a_ClickedBlockPos.z, m_DoubleSlabBlockType, ClickedBlockMeta & 0x07))
-				{
-					return false;
-				}
-				if (a_Player.IsGameModeSurvival())
-				{
-					a_Player.GetInventory().RemoveOneEquippedItem();
-				}
-				return true;
+				// Bottom half slab block:
+				return a_BaseMeta & 0x07;
 			}
-		}
-
-		// If there's already a slab in the destination, combine it into a double-slab:
-		auto PlacePos = AddFaceDirection(a_ClickedBlockPos, a_ClickedBlockFace);
-		BLOCKTYPE PlaceBlockType;
-		NIBBLETYPE PlaceBlockMeta;
-		a_World.GetBlockTypeMeta(PlacePos, PlaceBlockType, PlaceBlockMeta);
-		if (
-			(PlaceBlockType == m_ItemType) &&                         // Placing the same slab material
-			((PlaceBlockMeta & 0x07) == a_EquippedItem.m_ItemDamage)  // Placing the same slab sub-kind (and existing slab is single)
-		)
-		{
-			if (!a_Player.PlaceBlock(PlacePos.x, PlacePos.y, PlacePos.z, m_DoubleSlabBlockType, PlaceBlockMeta & 0x07))
+			case BLOCK_FACE_BOTTOM:
 			{
-				return false;
+				// Top half slab block:
+				return a_BaseMeta | 0x08;
 			}
-			if (a_Player.IsGameModeSurvival())
+			case BLOCK_FACE_EAST:
+			case BLOCK_FACE_NORTH:
+			case BLOCK_FACE_SOUTH:
+			case BLOCK_FACE_WEST:
 			{
-				a_Player.GetInventory().RemoveOneEquippedItem();
+				if (a_CursorPosition.y > 7)
+				{
+					// Cursor at top half of block, place top slab:
+					return a_BaseMeta | 0x08;
+				}
+				else
+				{
+					// Cursor at bottom half of block, place bottom slab:
+					return a_BaseMeta & 0x07;
+				}
 			}
-			return true;
+			default: UNREACHABLE("Unhandled block face");
 		}
+	}
 
-		// The slabs didn't combine, use the default handler to place the slab:
-		bool res = Super::OnPlayerPlace(a_World, a_Player, a_EquippedItem, a_ClickedBlockPos, a_ClickedBlockFace, a_CursorPos);
 
-		/*
-		The client has a bug when a slab replaces snow and there's a slab above it.
-		The client then combines the slab above, rather than replacing the snow.
-		We send the block above the currently placed block back to the client to fix the bug.
-		Ref.: https://forum.cuberite.org/thread-434-post-17388.html#pid17388
-		*/
-		if ((a_ClickedBlockFace == BLOCK_FACE_TOP) && (a_ClickedBlockPos.y < cChunkDef::Height - 1))
+	/** Converts the single-slab blocktype to its equivalent double-slab blocktype. */
+	static BLOCKTYPE GetDoubleSlabType(BLOCKTYPE a_SingleSlabBlockType)
+	{
+		switch (a_SingleSlabBlockType)
 		{
-			auto AbovePos = a_ClickedBlockPos.addedY(1);
-			a_Player.SendBlocksAround(AbovePos.x, AbovePos.y, AbovePos.z, 1);
+			case E_BLOCK_STONE_SLAB: return E_BLOCK_DOUBLE_STONE_SLAB;
+			case E_BLOCK_WOODEN_SLAB: return E_BLOCK_DOUBLE_WOODEN_SLAB;
+			case E_BLOCK_RED_SANDSTONE_SLAB: return E_BLOCK_DOUBLE_RED_SANDSTONE_SLAB;
+			case E_BLOCK_PURPUR_SLAB: return E_BLOCK_PURPUR_DOUBLE_SLAB;
 		}
-		return res;
+		UNREACHABLE("Unhandled slab type");
 	}
-
-
-protected:
-
-	/** The block type to use when the slab combines into a doubleslab block. */
-	BLOCKTYPE m_DoubleSlabBlockType;
 };