3 files changed, 95 insertions, 9 deletions

diff --git a/MCServer/Plugins/APIDump/APIDesc.lua b/MCServer/Plugins/APIDump/APIDesc.lua
index a3695fe17..4f6a499df 100644
--- a/MCServer/Plugins/APIDump/APIDesc.lua
+++ b/MCServer/Plugins/APIDump/APIDesc.lua
@@ -197,13 +197,14 @@ g_APIDesc =
 				baMetas = { Notes = "Operations should work on block metas" },
 				baLight = { Notes = "Operations should work on block (emissive) light" },
 				baSkyLight = { Notes = "Operations should work on skylight" },
-				msDifference = { Notes = "Block becomes air if Src and Dst are the same. Otherwise it becomes the source block." },
-				msOverwrite = { Notes = "Src overwrites anything in Dst" },
-				msFillAir = { Notes = "Dst is overwritten by Src only where Src has air blocks" },
-				msImprint = { Notes = "Src overwrites Dst anywhere where Dst has non-air blocks" },
+				msDifference = { Notes = "Block becomes air if 'self' and src are the same. Otherwise it becomes the src block." },
+				msFillAir = { Notes = "'self' is overwritten by Src only where 'self' has air blocks" },
+				msImprint = { Notes = "Src overwrites 'self' anywhere where 'self' has non-air blocks" },
 				msLake = { Notes = "Special mode for merging lake images" },
+				msMask = { Notes = "The blocks that are exactly the same are kept in 'self', all differing blocks are replaced by air"},
+				msOverwrite = { Notes = "Src overwrites anything in 'self'" },
+				msSimpleCompare = { Notes = "The blocks that are exactly the same are replaced with air, all differing blocks are replaced by stone"},
 				msSpongePrint = { Notes = "Similar to msImprint, sponge block doesn't overwrite anything, all other blocks overwrite everything"},
-				msMask = { Notes = "The blocks that are exactly the same are kept in Dst, all differing blocks are replaced by air"},
 			},
 			ConstantGroups =
 			{
@@ -287,7 +288,7 @@ g_APIDesc =
 						<table><tbody><tr>
 						<th colspan="2"> area block </th><th> </th><th> Notes </th>
 						</tr><tr>
-						<th> this </th><th> Src </th><th> result </th><th> </th>
+						<th> self </th><th> Src </th><th> result </th><th> </th>
 						</tr><tr>
 						<td> A </td><td> sponge </td><td> A </td><td> Sponge is the NOP block </td>
 						</tr><tr>
@@ -321,7 +322,7 @@ g_APIDesc =
 						<table><tbody><tr>
 						<th colspan="2"> area block </th><th> </th><th> Notes </th>
 						</tr><tr>
-						<th> this </th><th> Src </th><th> result </th><th> </th>
+						<th> self </th><th> Src </th><th> result </th><th> </th>
 						</tr><tr>
 						<td> A </td><td> sponge </td><td> A </td><td> Sponge is the NOP block </td>
 						</tr><tr>
@@ -337,13 +338,45 @@ g_APIDesc =
 						<table><tbody><tr>
 						<th colspan="2"> area block </th><th> </th><th> Notes </th>
 						</tr><tr>
-						<th> this </th><th> Src </th><th> result </th><th> </th>
+						<th> self </th><th> Src </th><th> result </th><th> </th>
 						</tr><tr>
 						<td> A </td><td> A </td><td> A </td><td> Same blocks are kept </td>
 						</tr><tr>
 						<td> A </td><td> non-A </td><td> air </td><td> Differing blocks are replaced with air </td>
 						</tr>
 						</tbody></table>
+
+						<p>
+						<strong>msDifference</strong> - the blocks that are the same in both areas are replaced with air, all the
+						differing blocks are kept from the first area. Meta is used in the comparison, too, two blocks of the
+						same type but different meta are considered different.
+						</p>
+						<table><tbody><tr>
+						<th colspan="2"> area block </th><th> </th><th> Notes </th>
+						</tr><tr>
+						<th> self </th><th> Src </th><th> result </th><th> </th>
+						</tr><tr>
+						<td> A </td><td> A </td><td> air </td><td> Same blocks are replaced with air </td>
+						</tr><tr>
+						<td> A </td><td> non-A </td><td> A </td><td> Differing blocks are kept from 'self' </td>
+						</tr>
+						</tbody></table>
+						
+						<p>
+						<strong>msSimpleCompare</strong> - the blocks that are the same in both areas are replaced with air, all the
+						differing blocks are replaced with stone. Meta is used in the comparison, too, two blocks of the
+						same type but different meta are considered different.
+						</p>
+						<table><tbody><tr>
+						<th colspan="2"> area block </th><th> </th><th> Notes </th>
+						</tr><tr>
+						<th> self </th><th> Src </th><th> result </th><th> </th>
+						</tr><tr>
+						<td> A </td><td> A </td><td> air </td><td> Same blocks are replaced with air </td>
+						</tr><tr>
+						<td> A </td><td> non-A </td><td> stone </td><td> Differing blocks are replaced with stone </td>
+						</tr>
+						</tbody></table>
 ]],
 				},  -- Merge strategies
 			},  -- AdditionalInfo
diff --git a/src/BlockArea.cpp b/src/BlockArea.cpp
index 7526e1c32..600940d96 100644
--- a/src/BlockArea.cpp
+++ b/src/BlockArea.cpp
@@ -245,6 +245,26 @@ void MergeCombinatorDifference(BLOCKTYPE & a_DstType, BLOCKTYPE a_SrcType, NIBBL
 
 
 
+/** Combinator used for cBlockArea::msSimpleCompare merging */
+template <bool MetaValid>
+void MergeCombinatorSimpleCompare(BLOCKTYPE & a_DstType, BLOCKTYPE a_SrcType, NIBBLETYPE & a_DstMeta, NIBBLETYPE a_SrcMeta)
+{
+	if ((a_DstType == a_SrcType) && (!MetaValid || (a_DstMeta == a_SrcMeta)))
+	{
+		// The blocktypes are the same, and the blockmetas are not present or are the same
+		a_DstType = E_BLOCK_AIR;
+	}
+	else
+	{
+		// The blocktypes or blockmetas differ
+		a_DstType = E_BLOCK_STONE;
+	}
+}
+
+
+
+
+
 /** Combinator used for cBlockArea::msMask merging */
 template <bool MetaValid>
 void MergeCombinatorMask(BLOCKTYPE & a_DstType, BLOCKTYPE a_SrcType, NIBBLETYPE & a_DstMeta, NIBBLETYPE a_SrcMeta)
@@ -2188,10 +2208,12 @@ void cBlockArea::RelSetData(
 
 
 
+
+
 template <bool MetasValid>
 void cBlockArea::MergeByStrategy(const cBlockArea & a_Src, int a_RelX, int a_RelY, int a_RelZ, eMergeStrategy a_Strategy, const NIBBLETYPE * SrcMetas, NIBBLETYPE * DstMetas)
 {
-	// Block types are compulsory, block metas are voluntary
+	// Block types are compulsory, block metas are optional
 	if (!HasBlockTypes() || !a_Src.HasBlockTypes())
 	{
 		LOGWARNING("%s: cannot merge because one of the areas doesn't have blocktypes.", __FUNCTION__);
@@ -2297,6 +2319,20 @@ void cBlockArea::MergeByStrategy(const cBlockArea & a_Src, int a_RelX, int a_Rel
 			return;
 		}  // case msDifference
 		
+		case cBlockArea::msSimpleCompare:
+		{
+			InternalMergeBlocks<MetasValid, MergeCombinatorSimpleCompare<MetasValid> >(
+				m_BlockTypes, a_Src.GetBlockTypes(),
+				DstMetas, SrcMetas,
+				SizeX, SizeY, SizeZ,
+				SrcOffX, SrcOffY, SrcOffZ,
+				DstOffX, DstOffY, DstOffZ,
+				a_Src.GetSizeX(), a_Src.GetSizeY(), a_Src.GetSizeZ(),
+				m_Size.x, m_Size.y, m_Size.z
+			);
+			return;
+		}  // case msSimpleCompare
+		
 		case cBlockArea::msMask:
 		{
 			InternalMergeBlocks<MetasValid, MergeCombinatorMask<MetasValid> >(
diff --git a/src/BlockArea.h b/src/BlockArea.h
index 6b8b30443..ce417ceb4 100644
--- a/src/BlockArea.h
+++ b/src/BlockArea.h
@@ -54,6 +54,7 @@ public:
 		msLake,
 		msSpongePrint,
 		msDifference,
+		msSimpleCompare,
 		msMask,
 	} ;
 	
@@ -156,6 +157,22 @@ public:
 	| A        | sponge | A      |  Sponge is the NOP block
 	| *        | B      | B      |  Everything else overwrites anything
 	
+	msDifference:
+	Used to determine the differences between two areas. Only the differring blocks are preserved:
+	|  area block  |        |
+	| this | Src   | result |
+	+------+-------+--------+
+	| A    | A     | air    |  Same blocks are replaced with air
+	| A    | non-A | A      |  Differring blocks are kept from "this"
+
+	msSimpleCompare:
+	Used to determine the differences between two areas. Blocks that differ are replaced with stone, same blocks are replaced with air
+	|  area block  |        |
+	| this | Src   | result |
+	+------+-------+--------+
+	| A    | A     | air    |  Same blocks are replaced with air
+	| A    | non-A | stone  |  Differring blocks are replaced with stone
+
 	msMask:
 	Combines two areas, the blocks that are the same are kept, differing ones are reset to air
 	|  area block  |        |