2 files changed, 58 insertions, 48 deletions

diff --git a/source/Blocks/BlockSlab.h b/source/Blocks/BlockSlab.h
index 881a85615..6caa3a27a 100644
--- a/source/Blocks/BlockSlab.h
+++ b/source/Blocks/BlockSlab.h
@@ -18,8 +18,7 @@ public:
 
 	virtual void ConvertToPickups(cItems & a_Pickups, NIBBLETYPE a_BlockMeta) override
 	{
-		char Count = ((m_BlockType == E_BLOCK_STONE_SLAB) || (m_BlockType == E_BLOCK_WOODEN_SLAB)) ? 1 : 1;
-		a_Pickups.push_back(cItem(m_BlockType, Count, a_BlockMeta));
+		a_Pickups.push_back(cItem(m_BlockType, 1, a_BlockMeta));
 	}
 
 
@@ -37,39 +36,54 @@ public:
 		int DoubleType;
 		if (Type == E_BLOCK_STONE_SLAB)
 		{
-			DoubleType = 43; //Make it a double slab (with old type wood)
+			DoubleType = 43; // Make it a double slab (with old type wood)
 		}
 		else
 		{
-			 DoubleType = 125; //Make it a wooden double slab (new type)
+			 DoubleType = 125; // Make it a wooden double slab (new type)
 		}
+		// HandlePlaceBlock wants a cItemHandler pointer thing, so let's give it one
 		cItemHandler * ItemHandler = cItemHandler::GetItemHandler(DoubleType);
 
-		switch (a_BlockFace)
+		// Check if the block at the coordinates is a slab. Eligibility for combining etc. were processed in ClientHandle
+		BLOCKTYPE IsSlab;
+		IsSlab = a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ);
+		if ((IsSlab == E_BLOCK_STONE_SLAB) || (IsSlab == E_BLOCK_WOODEN_SLAB))
 		{
-			case BLOCK_FACE_TOP:
+			// Special handling for non top/bottom clicks
+			if ((a_BlockFace == BLOCK_FACE_TOP) || (a_BlockFace == BLOCK_FACE_BOTTOM))
 			{
-				if ((a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_STONE_SLAB) || (a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_WOODEN_SLAB))
+				// As with previous, call the function in ClientHandle that places a block when the client sends the packet
+				// This effectively simulates a client placing a double slab, so it goes through plugins etc. so the slabbing can be cancelled
+				a_Player->GetClientHandle()->HandlePlaceBlock(a_BlockX, a_BlockY, a_BlockZ, a_BlockFace, a_CursorX, a_CursorY, a_CursorZ, *ItemHandler);
+			}
+			else
+			{
+				// If player cursor is at top half of block
+				if (a_CursorY > 7)
 				{
-					a_Player->GetClientHandle()->HandlePlaceBlock(a_BlockX, a_BlockY, a_BlockZ, a_BlockFace, a_CursorX, a_CursorY, a_CursorZ, *ItemHandler);
-					return false;
+					// Edit the call to use BLOCK_FACE_BOTTOM, otherwise it places incorrectly
+					a_Player->GetClientHandle()->HandlePlaceBlock(a_BlockX, a_BlockY, a_BlockZ, BLOCK_FACE_TOP, a_CursorX, a_CursorY, a_CursorZ, *ItemHandler);
 				}
 				else
 				{
-					a_BlockMeta = Meta & 0x7; break;  //Bottom half if on top of non slab block
+					// Edit the call to use BLOCK_FACE_TOP, otherwise it places incorrectly
+					a_Player->GetClientHandle()->HandlePlaceBlock(a_BlockX, a_BlockY, a_BlockZ, BLOCK_FACE_BOTTOM, a_CursorX, a_CursorY, a_CursorZ, *ItemHandler);
 				}
 			}
+			return false; // Cancel the event because dblslabs were already placed, nothing else needed
+		}
+		
+		switch (a_BlockFace)
+		{
+			// Previous IF condition didn't cancel the event (not a slab at coords), so place slab with correct metas
+			case BLOCK_FACE_TOP:
+			{
+				a_BlockMeta = Meta & 0x7; break;  // Bottom half slab block
+			}
 			case BLOCK_FACE_BOTTOM:
 			{
-				if ((a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_STONE_SLAB) || (a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_WOODEN_SLAB))
-				{
-					a_Player->GetClientHandle()->HandlePlaceBlock(a_BlockX, a_BlockY, a_BlockZ, a_BlockFace, a_CursorX, a_CursorY, a_CursorZ, *ItemHandler);
-					return false;
-				}
-				else
-				{
-					a_BlockMeta = Meta | 0x8; break;  //Bottom half if on top of non slab block
-				}
+				a_BlockMeta = Meta | 0x8; break;  // Top half slab block
 			}
 			case BLOCK_FACE_EAST:
 			case BLOCK_FACE_NORTH:
@@ -78,29 +92,13 @@ public:
 			{
 				if (a_CursorY > 7)
 				{
-					// Cursor at the top half of the face, place a top half of slab
-					if ((a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_STONE_SLAB) || (a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_WOODEN_SLAB))
-					{
-						a_Player->GetClientHandle()->HandlePlaceBlock(a_BlockX, a_BlockY, a_BlockZ, a_BlockFace, a_CursorX, a_CursorY, a_CursorZ, *ItemHandler);
-						return false;
-					}
-					else
-					{
-						a_BlockMeta = Meta | 0x8; break;
-					}
+					// Cursor at top half of block, place top slab
+					a_BlockMeta = Meta | 0x8; break;
 				}
 				else
 				{
-					// Cursor at the bottom half of the face, place a bottom half of slab:
-					if ((a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_STONE_SLAB) || (a_World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_WOODEN_SLAB))
-					{
-						a_Player->GetClientHandle()->HandlePlaceBlock(a_BlockX, a_BlockY, a_BlockZ, a_BlockFace, a_CursorX, a_CursorY, a_CursorZ, *ItemHandler);
-						return false;
-					}
-					else
-					{
-						a_BlockMeta = Meta & 0x7; break;
-					}
+					// Cursor at bottom half of block, place bottom slab
+					a_BlockMeta = Meta & 0x7; break;
 				}
 			}
 		}  // switch (a_BlockFace)
diff --git a/source/ClientHandle.cpp b/source/ClientHandle.cpp
index 8ff93ec1b..199f43014 100644
--- a/source/ClientHandle.cpp
+++ b/source/ClientHandle.cpp
@@ -854,19 +854,29 @@ void cClientHandle::HandlePlaceBlock(int a_BlockX, int a_BlockY, int a_BlockZ, c
 
 	World->GetBlockTypeMeta(a_BlockX, a_BlockY, a_BlockZ, ClickedBlock, ClickedBlockMeta);
 
-	//Special slab handler coding
+	// Special slab handler coding
 	if (
+		// If clicked face top: is slab there in the "bottom" position?
+		// If clicked face bottom: is the slab there in the "top" position?
+		// This prevents a dblslab forming below if you click the top face of a "top" slab.
 		(((a_BlockFace == BLOCK_FACE_TOP) && (ClickedBlockMeta == (EquippedBlockDamage & 0x07))) || ((a_BlockFace == BLOCK_FACE_BOTTOM) && (ClickedBlockMeta == (EquippedBlockDamage | 0x08)))) &&
-		((ClickedBlock == E_BLOCK_STONE_SLAB) || (ClickedBlock == E_BLOCK_WOODEN_SLAB)) && //Is clicked a slab?
-		((EquippedBlock == E_BLOCK_STONE_SLAB) || (EquippedBlock == E_BLOCK_WOODEN_SLAB)) && //Is equipped a slab?		
-		((ClickedBlockMeta & 0x07) == (EquippedBlockDamage & 0x07)) //Is clicked same type of slab as item in hand?
+		
+		// Is clicked a slab? This is a SLAB handler, not stone or something!
+		((ClickedBlock == E_BLOCK_STONE_SLAB) || (ClickedBlock == E_BLOCK_WOODEN_SLAB)) &&
+		
+		// Is equipped a some type of slab?
+		// This prevents a bug where, well, you get a dblslab by placing TNT or something not a slab.
+		((EquippedBlock == E_BLOCK_STONE_SLAB) || (EquippedBlock == E_BLOCK_WOODEN_SLAB)) &&
+		
+		// Is equipped slab type same as the slab in the world? After all, we can't combine different slabs!
+		((ClickedBlockMeta & 0x07) == (EquippedBlockDamage & 0x07))
 		)
 	{
-		//Don't move the coordinates
+		// Coordinates at CLICKED block, don't move them anywhere
 	}
 	else
 	{
-		//Check if the block ignores build collision (water, grass etc.):
+		// Check if the block ignores build collision (water, grass etc.):
 		cBlockHandler * Handler = cBlockHandler::GetBlockHandler(ClickedBlock);
 		if (Handler->DoesIgnoreBuildCollision())
 		{
@@ -876,8 +886,9 @@ void cClientHandle::HandlePlaceBlock(int a_BlockX, int a_BlockY, int a_BlockZ, c
 		else
 		{
 			AddFaceDirection(a_BlockX, a_BlockY, a_BlockZ, a_BlockFace);
-			//On side of block, make sure that placement won't be cancelled if there is a slab there
-			//No need to combinability checks, client will do that
+			
+			// Clicked on side of block, make sure that placement won't be cancelled if there is a slab able to be double slabbed.
+			// No need to do combinability (dblslab) checks, client will do that here.
 			if ((World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_STONE_SLAB) || (World->GetBlock(a_BlockX, a_BlockY, a_BlockZ) == E_BLOCK_WOODEN_SLAB))
 			{
 				//Is a slab, don't do checks and proceed to double-slabbing
@@ -904,7 +915,8 @@ void cClientHandle::HandlePlaceBlock(int a_BlockX, int a_BlockY, int a_BlockZ, c
 			}
 		}
 	}
-
+	// Special slab handler coding end
+	
 	BLOCKTYPE BlockType;
 	NIBBLETYPE BlockMeta;
 	if (!a_ItemHandler.GetPlacementBlockTypeMeta(World, m_Player, a_BlockX, a_BlockY, a_BlockZ, a_BlockFace, a_CursorX, a_CursorY, a_CursorZ, BlockType, BlockMeta))