Fix backface culling when connecting to new servers.

Introduce a new contentfeatures version (8). When clients
connect using v27 protocol version, they can assume that
the tiledef.backface_culling is trustable, but if clients
connect to servers providing contentfeatures version 7,
then the v27 clients know that backface culling settings
provided by the server in tiledefs are bogus for mesh,
plantlike, firelike or liquid drawtype nodes.

thanks to hmmmm, est31, nerzhul.

Tested on new client - new server, new client - old server
old client - new server.

Author: sofar

src/nodedef.cpp

@@ -139,7 +139,7 @@ void TileDef::serialize(std::ostream &os, u16 protocol_version) const
 	}
 }
 
-void TileDef::deSerialize(std::istream &is, bool culling_ignore)
+void TileDef::deSerialize(std::istream &is, const u8 contenfeatures_version, const NodeDrawType drawtype)
 {
 	int version = readU8(is);
 	name = deSerializeString(is);
@@ -153,10 +153,12 @@ void TileDef::deSerialize(std::istream &is, bool culling_ignore)
 		tileable_horizontal = readU8(is);
 		tileable_vertical = readU8(is);
 	}
-	// when connecting to old servers - do not use
-	// provided values here since culling needs to be
-	// disabled by default for these drawtypes
-	if (culling_ignore)
+
+	if ((contenfeatures_version < 8) &&
+		((drawtype == NDT_MESH) ||
+		 (drawtype == NDT_FIRELIKE) ||
+		 (drawtype == NDT_LIQUID) ||
+		 (drawtype == NDT_PLANTLIKE)))
 		backface_culling = false;
 }
 
@@ -268,7 +270,8 @@ void ContentFeatures::serialize(std::ostream &os, u16 protocol_version) const
 		return;
 	}
 
-	writeU8(os, 7); // version
+	writeU8(os, protocol_version < 27 ? 7 : 8);
+
 	os<<serializeString(name);
 	writeU16(os, groups.size());
 	for(ItemGroupList::const_iterator
@@ -330,9 +333,11 @@ void ContentFeatures::serialize(std::ostream &os, u16 protocol_version) const
 void ContentFeatures::deSerialize(std::istream &is)
 {
 	int version = readU8(is);
-	if(version != 7){
+	if (version < 7) {
 		deSerializeOld(is, version);
 		return;
+	} else if (version > 8) {
+		throw SerializationError("unsupported ContentFeatures version");
 	}
 
 	name = deSerializeString(is);
@@ -345,21 +350,15 @@ void ContentFeatures::deSerialize(std::istream &is)
 	}
 	drawtype = (enum NodeDrawType)readU8(is);
 
-	bool ignore_culling = ((version <= 26) &&
-			((drawtype == NDT_MESH) ||
-			 (drawtype == NDT_PLANTLIKE) ||
-			 (drawtype == NDT_FIRELIKE) ||
-			 (drawtype == NDT_LIQUID)));
-
 	visual_scale = readF1000(is);
 	if(readU8(is) != 6)
 		throw SerializationError("unsupported tile count");
 	for(u32 i = 0; i < 6; i++)
-		tiledef[i].deSerialize(is, ignore_culling);
+		tiledef[i].deSerialize(is, version, drawtype);
 	if(readU8(is) != CF_SPECIAL_COUNT)
 		throw SerializationError("unsupported CF_SPECIAL_COUNT");
 	for(u32 i = 0; i < CF_SPECIAL_COUNT; i++)
-		tiledef_special[i].deSerialize(is, ignore_culling);
+		tiledef_special[i].deSerialize(is, version, drawtype);
 	alpha = readU8(is);
 	post_effect_color.setAlpha(readU8(is));
 	post_effect_color.setRed(readU8(is));
@@ -1284,21 +1283,15 @@ void ContentFeatures::deSerializeOld(std::istream &is, int version)
 		}
 		drawtype = (enum NodeDrawType)readU8(is);
 
-		bool ignore_culling = ((version <= 26) &&
-				((drawtype == NDT_MESH) ||
-				(drawtype == NDT_PLANTLIKE) ||
-				(drawtype == NDT_FIRELIKE) ||
-				(drawtype == NDT_LIQUID)));
-
 		visual_scale = readF1000(is);
 		if (readU8(is) != 6)
 			throw SerializationError("unsupported tile count");
 		for (u32 i = 0; i < 6; i++)
-			tiledef[i].deSerialize(is, ignore_culling);
+			tiledef[i].deSerialize(is, version, drawtype);
 		if (readU8(is) != CF_SPECIAL_COUNT)
 			throw SerializationError("unsupported CF_SPECIAL_COUNT");
 		for (u32 i = 0; i < CF_SPECIAL_COUNT; i++)
-			tiledef_special[i].deSerialize(is, ignore_culling);
+			tiledef_special[i].deSerialize(is, version, drawtype);
 		alpha = readU8(is);
 		post_effect_color.setAlpha(readU8(is));
 		post_effect_color.setRed(readU8(is));
@@ -1342,12 +1335,12 @@ void ContentFeatures::deSerializeOld(std::istream &is, int version)
 		if (readU8(is) != 6)
 			throw SerializationError("unsupported tile count");
 		for (u32 i = 0; i < 6; i++)
-			tiledef[i].deSerialize(is, drawtype);
+			tiledef[i].deSerialize(is, version, drawtype);
 		// CF_SPECIAL_COUNT in version 6 = 2
 		if (readU8(is) != 2)
 			throw SerializationError("unsupported CF_SPECIAL_COUNT");
 		for (u32 i = 0; i < 2; i++)
-			tiledef_special[i].deSerialize(is, drawtype);
+			tiledef_special[i].deSerialize(is, version, drawtype);
 		alpha = readU8(is);
 		post_effect_color.setAlpha(readU8(is));
 		post_effect_color.setRed(readU8(is));

src/nodedef.h

@@ -104,6 +104,30 @@ struct NodeBox
 struct MapNode;
 class NodeMetadata;
 
+enum NodeDrawType
+{
+	NDT_NORMAL, // A basic solid block
+	NDT_AIRLIKE, // Nothing is drawn
+	NDT_LIQUID, // Do not draw face towards same kind of flowing/source liquid
+	NDT_FLOWINGLIQUID, // A very special kind of thing
+	NDT_GLASSLIKE, // Glass-like, don't draw faces towards other glass
+	NDT_ALLFACES, // Leaves-like, draw all faces no matter what
+	NDT_ALLFACES_OPTIONAL, // Fancy -> allfaces, fast -> normal
+	NDT_TORCHLIKE,
+	NDT_SIGNLIKE,
+	NDT_PLANTLIKE,
+	NDT_FENCELIKE,
+	NDT_RAILLIKE,
+	NDT_NODEBOX,
+	NDT_GLASSLIKE_FRAMED, // Glass-like, draw connected frames and all all
+	                      // visible faces
+						  // uses 2 textures, one for frames, second for faces
+	NDT_FIRELIKE, // Draw faces slightly rotated and only on connecting nodes,
+	NDT_GLASSLIKE_FRAMED_OPTIONAL,	// enabled -> connected, disabled -> Glass-like
+									// uses 2 textures, one for frames, second for faces
+	NDT_MESH, // Uses static meshes
+};
+
 /*
 	Stand-alone definition of a TileSpec (basically a server-side TileSpec)
 */
@@ -137,31 +161,7 @@ struct TileDef
 	}
 
 	void serialize(std::ostream &os, u16 protocol_version) const;
-	void deSerialize(std::istream &is, bool culling_ignore);
-};
-
-enum NodeDrawType
-{
-	NDT_NORMAL, // A basic solid block
-	NDT_AIRLIKE, // Nothing is drawn
-	NDT_LIQUID, // Do not draw face towards same kind of flowing/source liquid
-	NDT_FLOWINGLIQUID, // A very special kind of thing
-	NDT_GLASSLIKE, // Glass-like, don't draw faces towards other glass
-	NDT_ALLFACES, // Leaves-like, draw all faces no matter what
-	NDT_ALLFACES_OPTIONAL, // Fancy -> allfaces, fast -> normal
-	NDT_TORCHLIKE,
-	NDT_SIGNLIKE,
-	NDT_PLANTLIKE,
-	NDT_FENCELIKE,
-	NDT_RAILLIKE,
-	NDT_NODEBOX,
-	NDT_GLASSLIKE_FRAMED, // Glass-like, draw connected frames and all all
-	                      // visible faces
-						  // uses 2 textures, one for frames, second for faces
-	NDT_FIRELIKE, // Draw faces slightly rotated and only on connecting nodes,
-	NDT_GLASSLIKE_FRAMED_OPTIONAL,	// enabled -> connected, disabled -> Glass-like
-									// uses 2 textures, one for frames, second for faces
-	NDT_MESH, // Uses static meshes
+	void deSerialize(std::istream &is, const u8 contentfeatures_version, const NodeDrawType drawtype);
 };
 
 #define CF_SPECIAL_COUNT 6