Give the Mapgen on each EmergeThread its own Biome/Ore/Deco/SchemManager copy

24 files changed, 87 insertions, 44 deletions

diff --git a/src/mapgen/mapgen.cpp b/src/mapgen/mapgen.cpp
index 0094608ec..f57529082 100644
--- a/src/mapgen/mapgen.cpp
+++ b/src/mapgen/mapgen.cpp
@@ -106,8 +106,8 @@ STATIC_ASSERT(
 //// Mapgen
 ////
 
-Mapgen::Mapgen(int mapgenid, MapgenParams *params, EmergeManager *emerge) :
-	gennotify(emerge->gen_notify_on, &emerge->gen_notify_on_deco_ids)
+Mapgen::Mapgen(int mapgenid, MapgenParams *params, EmergeParams *emerge) :
+	gennotify(emerge->gen_notify_on, emerge->gen_notify_on_deco_ids)
 {
 	id           = mapgenid;
 	water_level  = params->water_level;
@@ -156,7 +156,7 @@ const char *Mapgen::getMapgenName(MapgenType mgtype)
 
 
 Mapgen *Mapgen::createMapgen(MapgenType mgtype, MapgenParams *params,
-	EmergeManager *emerge)
+	EmergeParams *emerge)
 {
 	switch (mgtype) {
 	case MAPGEN_CARPATHIAN:
@@ -585,7 +585,7 @@ void Mapgen::spreadLight(const v3s16 &nmin, const v3s16 &nmax)
 //// MapgenBasic
 ////
 
-MapgenBasic::MapgenBasic(int mapgenid, MapgenParams *params, EmergeManager *emerge)
+MapgenBasic::MapgenBasic(int mapgenid, MapgenParams *params, EmergeParams *emerge)
 	: Mapgen(mapgenid, params, emerge)
 {
 	this->m_emerge = emerge;
@@ -642,6 +642,8 @@ MapgenBasic::~MapgenBasic()
 {
 	delete biomegen;
 	delete []heightmap;
+
+	delete m_emerge; // destroying EmergeParams is our responsibility
 }
 
 
@@ -974,7 +976,7 @@ void MapgenBasic::generateDungeons(s16 max_stone_y)
 ////
 
 GenerateNotifier::GenerateNotifier(u32 notify_on,
-	std::set<u32> *notify_on_deco_ids)
+	const std::set<u32> *notify_on_deco_ids)
 {
 	m_notify_on = notify_on;
 	m_notify_on_deco_ids = notify_on_deco_ids;
@@ -987,7 +989,8 @@ void GenerateNotifier::setNotifyOn(u32 notify_on)
 }
 
 
-void GenerateNotifier::setNotifyOnDecoIds(std::set<u32> *notify_on_deco_ids)
+void GenerateNotifier::setNotifyOnDecoIds(
+	const std::set<u32> *notify_on_deco_ids)
 {
 	m_notify_on_deco_ids = notify_on_deco_ids;
 }
@@ -999,7 +1002,7 @@ bool GenerateNotifier::addEvent(GenNotifyType type, v3s16 pos, u32 id)
 		return false;
 
 	if (type == GENNOTIFY_DECORATION &&
-		m_notify_on_deco_ids->find(id) == m_notify_on_deco_ids->end())
+		m_notify_on_deco_ids->find(id) == m_notify_on_deco_ids->cend())
 		return false;
 
 	GenNotifyEvent gne;
diff --git a/src/mapgen/mapgen.h b/src/mapgen/mapgen.h
index dc325c791..7845c5349 100644
--- a/src/mapgen/mapgen.h
+++ b/src/mapgen/mapgen.h
@@ -51,6 +51,7 @@ class Biome;
 class BiomeGen;
 struct BiomeParams;
 class BiomeManager;
+class EmergeParams;
 class EmergeManager;
 class MapBlock;
 class VoxelManipulator;
@@ -87,10 +88,10 @@ struct GenNotifyEvent {
 class GenerateNotifier {
 public:
 	GenerateNotifier() = default;
-	GenerateNotifier(u32 notify_on, std::set<u32> *notify_on_deco_ids);
+	GenerateNotifier(u32 notify_on, const std::set<u32> *notify_on_deco_ids);
 
 	void setNotifyOn(u32 notify_on);
-	void setNotifyOnDecoIds(std::set<u32> *notify_on_deco_ids);
+	void setNotifyOnDecoIds(const std::set<u32> *notify_on_deco_ids);
 
 	bool addEvent(GenNotifyType type, v3s16 pos, u32 id=0);
 	void getEvents(std::map<std::string, std::vector<v3s16> > &event_map);
@@ -98,7 +99,7 @@ public:
 
 private:
 	u32 m_notify_on = 0;
-	std::set<u32> *m_notify_on_deco_ids;
+	const std::set<u32> *m_notify_on_deco_ids;
 	std::list<GenNotifyEvent> m_notify_events;
 };
 
@@ -176,7 +177,7 @@ public:
 	GenerateNotifier gennotify;
 
 	Mapgen() = default;
-	Mapgen(int mapgenid, MapgenParams *params, EmergeManager *emerge);
+	Mapgen(int mapgenid, MapgenParams *params, EmergeParams *emerge);
 	virtual ~Mapgen() = default;
 	DISABLE_CLASS_COPY(Mapgen);
 
@@ -215,7 +216,7 @@ public:
 	static MapgenType getMapgenType(const std::string &mgname);
 	static const char *getMapgenName(MapgenType mgtype);
 	static Mapgen *createMapgen(MapgenType mgtype, MapgenParams *params,
-		EmergeManager *emerge);
+		EmergeParams *emerge);
 	static MapgenParams *createMapgenParams(MapgenType mgtype);
 	static void getMapgenNames(std::vector<const char *> *mgnames, bool include_hidden);
 	static void setDefaultSettings(Settings *settings);
@@ -243,7 +244,7 @@ private:
 */
 class MapgenBasic : public Mapgen {
 public:
-	MapgenBasic(int mapgenid, MapgenParams *params, EmergeManager *emerge);
+	MapgenBasic(int mapgenid, MapgenParams *params, EmergeParams *emerge);
 	virtual ~MapgenBasic();
 
 	virtual void generateBiomes();
@@ -254,7 +255,7 @@ public:
 	virtual void generateDungeons(s16 max_stone_y);
 
 protected:
-	EmergeManager *m_emerge;
+	EmergeParams *m_emerge;
 	BiomeManager *m_bmgr;
 
 	Noise *noise_filler_depth;
diff --git a/src/mapgen/mapgen_carpathian.cpp b/src/mapgen/mapgen_carpathian.cpp
index bd7ae5e7c..feb9b428c 100644
--- a/src/mapgen/mapgen_carpathian.cpp
+++ b/src/mapgen/mapgen_carpathian.cpp
@@ -49,7 +49,7 @@ FlagDesc flagdesc_mapgen_carpathian[] = {
 ///////////////////////////////////////////////////////////////////////////////
 
 
-MapgenCarpathian::MapgenCarpathian(MapgenCarpathianParams *params, EmergeManager *emerge)
+MapgenCarpathian::MapgenCarpathian(MapgenCarpathianParams *params, EmergeParams *emerge)
 	: MapgenBasic(MAPGEN_CARPATHIAN, params, emerge)
 {
 	base_level       = params->base_level;
diff --git a/src/mapgen/mapgen_carpathian.h b/src/mapgen/mapgen_carpathian.h
index acd379958..31b2b91d8 100644
--- a/src/mapgen/mapgen_carpathian.h
+++ b/src/mapgen/mapgen_carpathian.h
@@ -79,7 +79,7 @@ struct MapgenCarpathianParams : public MapgenParams
 class MapgenCarpathian : public MapgenBasic
 {
 public:
-	MapgenCarpathian(MapgenCarpathianParams *params, EmergeManager *emerge);
+	MapgenCarpathian(MapgenCarpathianParams *params, EmergeParams *emerge);
 	~MapgenCarpathian();
 
 	virtual MapgenType getType() const { return MAPGEN_CARPATHIAN; }
diff --git a/src/mapgen/mapgen_flat.cpp b/src/mapgen/mapgen_flat.cpp
index 272964b51..369777ad2 100644
--- a/src/mapgen/mapgen_flat.cpp
+++ b/src/mapgen/mapgen_flat.cpp
@@ -47,7 +47,7 @@ FlagDesc flagdesc_mapgen_flat[] = {
 ///////////////////////////////////////////////////////////////////////////////////////
 
 
-MapgenFlat::MapgenFlat(MapgenFlatParams *params, EmergeManager *emerge)
+MapgenFlat::MapgenFlat(MapgenFlatParams *params, EmergeParams *emerge)
 	: MapgenBasic(MAPGEN_FLAT, params, emerge)
 {
 	spflags            = params->spflags;
diff --git a/src/mapgen/mapgen_flat.h b/src/mapgen/mapgen_flat.h
index c314c7605..4902a802c 100644
--- a/src/mapgen/mapgen_flat.h
+++ b/src/mapgen/mapgen_flat.h
@@ -64,7 +64,7 @@ struct MapgenFlatParams : public MapgenParams
 class MapgenFlat : public MapgenBasic
 {
 public:
-	MapgenFlat(MapgenFlatParams *params, EmergeManager *emerge);
+	MapgenFlat(MapgenFlatParams *params, EmergeParams *emerge);
 	~MapgenFlat();
 
 	virtual MapgenType getType() const { return MAPGEN_FLAT; }
diff --git a/src/mapgen/mapgen_fractal.cpp b/src/mapgen/mapgen_fractal.cpp
index 97f77d947..cb55bc288 100644
--- a/src/mapgen/mapgen_fractal.cpp
+++ b/src/mapgen/mapgen_fractal.cpp
@@ -47,7 +47,7 @@ FlagDesc flagdesc_mapgen_fractal[] = {
 ///////////////////////////////////////////////////////////////////////////////////////
 
 
-MapgenFractal::MapgenFractal(MapgenFractalParams *params, EmergeManager *emerge)
+MapgenFractal::MapgenFractal(MapgenFractalParams *params, EmergeParams *emerge)
 	: MapgenBasic(MAPGEN_FRACTAL, params, emerge)
 {
 	spflags            = params->spflags;
diff --git a/src/mapgen/mapgen_fractal.h b/src/mapgen/mapgen_fractal.h
index 971dfd822..23af925bc 100644
--- a/src/mapgen/mapgen_fractal.h
+++ b/src/mapgen/mapgen_fractal.h
@@ -72,7 +72,7 @@ struct MapgenFractalParams : public MapgenParams
 class MapgenFractal : public MapgenBasic
 {
 public:
-	MapgenFractal(MapgenFractalParams *params, EmergeManager *emerge);
+	MapgenFractal(MapgenFractalParams *params, EmergeParams *emerge);
 	~MapgenFractal();
 
 	virtual MapgenType getType() const { return MAPGEN_FRACTAL; }
diff --git a/src/mapgen/mapgen_singlenode.cpp b/src/mapgen/mapgen_singlenode.cpp
index b64524e1c..cade9e7a8 100644
--- a/src/mapgen/mapgen_singlenode.cpp
+++ b/src/mapgen/mapgen_singlenode.cpp
@@ -29,7 +29,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "emerge.h"
 
 
-MapgenSinglenode::MapgenSinglenode(MapgenParams *params, EmergeManager *emerge)
+MapgenSinglenode::MapgenSinglenode(MapgenParams *params, EmergeParams *emerge)
 	: Mapgen(MAPGEN_SINGLENODE, params, emerge)
 {
 	const NodeDefManager *ndef = emerge->ndef;
diff --git a/src/mapgen/mapgen_singlenode.h b/src/mapgen/mapgen_singlenode.h
index c21089eda..e056d9ab1 100644
--- a/src/mapgen/mapgen_singlenode.h
+++ b/src/mapgen/mapgen_singlenode.h
@@ -38,7 +38,7 @@ public:
 	content_t c_node;
 	u8 set_light;
 
-	MapgenSinglenode(MapgenParams *params, EmergeManager *emerge);
+	MapgenSinglenode(MapgenParams *params, EmergeParams *emerge);
 	~MapgenSinglenode() = default;
 
 	virtual MapgenType getType() const { return MAPGEN_SINGLENODE; }
diff --git a/src/mapgen/mapgen_v5.cpp b/src/mapgen/mapgen_v5.cpp
index 3bd7615c4..124667e5d 100644
--- a/src/mapgen/mapgen_v5.cpp
+++ b/src/mapgen/mapgen_v5.cpp
@@ -44,7 +44,7 @@ FlagDesc flagdesc_mapgen_v5[] = {
 };
 
 
-MapgenV5::MapgenV5(MapgenV5Params *params, EmergeManager *emerge)
+MapgenV5::MapgenV5(MapgenV5Params *params, EmergeParams *emerge)
 	: MapgenBasic(MAPGEN_V5, params, emerge)
 {
 	spflags            = params->spflags;
diff --git a/src/mapgen/mapgen_v5.h b/src/mapgen/mapgen_v5.h
index 17bc466f0..cf4ee4899 100644
--- a/src/mapgen/mapgen_v5.h
+++ b/src/mapgen/mapgen_v5.h
@@ -64,7 +64,7 @@ struct MapgenV5Params : public MapgenParams
 class MapgenV5 : public MapgenBasic
 {
 public:
-	MapgenV5(MapgenV5Params *params, EmergeManager *emerge);
+	MapgenV5(MapgenV5Params *params, EmergeParams *emerge);
 	~MapgenV5();
 
 	virtual MapgenType getType() const { return MAPGEN_V5; }
diff --git a/src/mapgen/mapgen_v6.cpp b/src/mapgen/mapgen_v6.cpp
index da9ae1428..e9692246c 100644
--- a/src/mapgen/mapgen_v6.cpp
+++ b/src/mapgen/mapgen_v6.cpp
@@ -54,7 +54,7 @@ FlagDesc flagdesc_mapgen_v6[] = {
 /////////////////////////////////////////////////////////////////////////////
 
 
-MapgenV6::MapgenV6(MapgenV6Params *params, EmergeManager *emerge)
+MapgenV6::MapgenV6(MapgenV6Params *params, EmergeParams *emerge)
 	: Mapgen(MAPGEN_V6, params, emerge)
 {
 	m_emerge = emerge;
@@ -160,6 +160,8 @@ MapgenV6::~MapgenV6()
 	delete noise_humidity;
 
 	delete[] heightmap;
+
+	delete m_emerge; // our responsibility
 }
 
 
diff --git a/src/mapgen/mapgen_v6.h b/src/mapgen/mapgen_v6.h
index d8cdcb26f..ff565edec 100644
--- a/src/mapgen/mapgen_v6.h
+++ b/src/mapgen/mapgen_v6.h
@@ -83,7 +83,7 @@ struct MapgenV6Params : public MapgenParams {
 
 class MapgenV6 : public Mapgen {
 public:
-	EmergeManager *m_emerge;
+	EmergeParams *m_emerge;
 
 	int ystride;
 	u32 spflags;
@@ -133,7 +133,7 @@ public:
 	content_t c_stair_cobble;
 	content_t c_stair_desert_stone;
 
-	MapgenV6(MapgenV6Params *params, EmergeManager *emerge);
+	MapgenV6(MapgenV6Params *params, EmergeParams *emerge);
 	~MapgenV6();
 
 	virtual MapgenType getType() const { return MAPGEN_V6; }
diff --git a/src/mapgen/mapgen_v7.cpp b/src/mapgen/mapgen_v7.cpp
index 82556cc4f..43d5d822f 100644
--- a/src/mapgen/mapgen_v7.cpp
+++ b/src/mapgen/mapgen_v7.cpp
@@ -51,7 +51,7 @@ FlagDesc flagdesc_mapgen_v7[] = {
 ////////////////////////////////////////////////////////////////////////////////
 
 
-MapgenV7::MapgenV7(MapgenV7Params *params, EmergeManager *emerge)
+MapgenV7::MapgenV7(MapgenV7Params *params, EmergeParams *emerge)
 	: MapgenBasic(MAPGEN_V7, params, emerge)
 {
 	spflags            = params->spflags;
diff --git a/src/mapgen/mapgen_v7.h b/src/mapgen/mapgen_v7.h
index 0605c5c97..eeae3a956 100644
--- a/src/mapgen/mapgen_v7.h
+++ b/src/mapgen/mapgen_v7.h
@@ -75,7 +75,7 @@ struct MapgenV7Params : public MapgenParams {
 
 class MapgenV7 : public MapgenBasic {
 public:
-	MapgenV7(MapgenV7Params *params, EmergeManager *emerge);
+	MapgenV7(MapgenV7Params *params, EmergeParams *emerge);
 	~MapgenV7();
 
 	virtual MapgenType getType() const { return MAPGEN_V7; }
diff --git a/src/mapgen/mapgen_valleys.cpp b/src/mapgen/mapgen_valleys.cpp
index ff908b7bb..efcc8ee85 100644
--- a/src/mapgen/mapgen_valleys.cpp
+++ b/src/mapgen/mapgen_valleys.cpp
@@ -54,7 +54,7 @@ FlagDesc flagdesc_mapgen_valleys[] = {
 };
 
 
-MapgenValleys::MapgenValleys(MapgenValleysParams *params, EmergeManager *emerge)
+MapgenValleys::MapgenValleys(MapgenValleysParams *params, EmergeParams *emerge)
 	: MapgenBasic(MAPGEN_VALLEYS, params, emerge)
 {
 	// NOTE: MapgenValleys has a hard dependency on BiomeGenOriginal
diff --git a/src/mapgen/mapgen_valleys.h b/src/mapgen/mapgen_valleys.h
index 1aec68842..34a923dfa 100644
--- a/src/mapgen/mapgen_valleys.h
+++ b/src/mapgen/mapgen_valleys.h
@@ -84,7 +84,7 @@ class MapgenValleys : public MapgenBasic {
 public:
 
 	MapgenValleys(MapgenValleysParams *params,
-		EmergeManager *emerge);
+		EmergeParams *emerge);
 	~MapgenValleys();
 
 	virtual MapgenType getType() const { return MAPGEN_VALLEYS; }
diff --git a/src/mapgen/mg_biome.cpp b/src/mapgen/mg_biome.cpp
index 3a72c43bf..f3bc4e829 100644
--- a/src/mapgen/mg_biome.cpp
+++ b/src/mapgen/mg_biome.cpp
@@ -78,7 +78,7 @@ void BiomeManager::clear()
 	EmergeManager *emerge = m_server->getEmergeManager();
 
 	// Remove all dangling references in Decorations
-	DecorationManager *decomgr = emerge->decomgr;
+	DecorationManager *decomgr = emerge->getWritableDecorationManager();
 	for (size_t i = 0; i != decomgr->getNumObjects(); i++) {
 		Decoration *deco = (Decoration *)decomgr->getRaw(i);
 		deco->biomes.clear();
@@ -104,7 +104,7 @@ BiomeManager *BiomeManager::clone() const
 
 // For BiomeGen type 'BiomeGenOriginal'
 float BiomeManager::getHeatAtPosOriginal(v3s16 pos, NoiseParams &np_heat,
-	NoiseParams &np_heat_blend, u64 seed)
+	NoiseParams &np_heat_blend, u64 seed) const
 {
 	return
 		NoisePerlin2D(&np_heat,       pos.X, pos.Z, seed) +
@@ -114,7 +114,7 @@ float BiomeManager::getHeatAtPosOriginal(v3s16 pos, NoiseParams &np_heat,
 
 // For BiomeGen type 'BiomeGenOriginal'
 float BiomeManager::getHumidityAtPosOriginal(v3s16 pos, NoiseParams &np_humidity,
-	NoiseParams &np_humidity_blend, u64 seed)
+	NoiseParams &np_humidity_blend, u64 seed) const
 {
 	return
 		NoisePerlin2D(&np_humidity,       pos.X, pos.Z, seed) +
@@ -123,7 +123,7 @@ float BiomeManager::getHumidityAtPosOriginal(v3s16 pos, NoiseParams &np_humidity
 
 
 // For BiomeGen type 'BiomeGenOriginal'
-Biome *BiomeManager::getBiomeFromNoiseOriginal(float heat, float humidity, v3s16 pos)
+Biome *BiomeManager::getBiomeFromNoiseOriginal(float heat, float humidity, v3s16 pos) const
 {
 	Biome *biome_closest = nullptr;
 	Biome *biome_closest_blend = nullptr;
diff --git a/src/mapgen/mg_biome.h b/src/mapgen/mg_biome.h
index 6aadc32fa..0a4471cc3 100644
--- a/src/mapgen/mg_biome.h
+++ b/src/mapgen/mg_biome.h
@@ -230,10 +230,10 @@ public:
 
 	// For BiomeGen type 'BiomeGenOriginal'
 	float getHeatAtPosOriginal(v3s16 pos, NoiseParams &np_heat,
-		NoiseParams &np_heat_blend, u64 seed);
+		NoiseParams &np_heat_blend, u64 seed) const;
 	float getHumidityAtPosOriginal(v3s16 pos, NoiseParams &np_humidity,
-		NoiseParams &np_humidity_blend, u64 seed);
-	Biome *getBiomeFromNoiseOriginal(float heat, float humidity, v3s16 pos);
+		NoiseParams &np_humidity_blend, u64 seed) const;
+	Biome *getBiomeFromNoiseOriginal(float heat, float humidity, v3s16 pos) const;
 
 private:
 	BiomeManager() {};
diff --git a/src/mapgen/mg_decoration.cpp b/src/mapgen/mg_decoration.cpp
index db9c696ed..a9b67d239 100644
--- a/src/mapgen/mg_decoration.cpp
+++ b/src/mapgen/mg_decoration.cpp
@@ -391,6 +391,13 @@ size_t DecoSimple::generate(MMVManip *vm, PcgRandom *pr, v3s16 p, bool ceiling)
 ///////////////////////////////////////////////////////////////////////////////
 
 
+DecoSchematic::~DecoSchematic()
+{
+	if (was_cloned)
+		delete schematic;
+}
+
+
 ObjDef *DecoSchematic::clone() const
 {
 	auto def = new DecoSchematic();
@@ -398,9 +405,12 @@ ObjDef *DecoSchematic::clone() const
 	NodeResolver::cloneTo(def);
 
 	def->rotation = rotation;
-	/* FIXME: This is not ideal, we only have a pointer to the schematic despite
-	 * not owning it. Optimally this would be a handle. */
-	def->schematic = schematic; // not cloned
+	/* FIXME: We do not own this schematic, yet we only have a pointer to it
+	 * and not a handle. We are left with no option but to clone it ourselves.
+	 * This is a waste of memory and should be replaced with an alternative
+	 * approach sometime. */
+	def->schematic = dynamic_cast<Schematic*>(schematic->clone());
+	def->was_cloned = true;
 
 	return def;
 }
diff --git a/src/mapgen/mg_decoration.h b/src/mapgen/mg_decoration.h
index af8fcd7bf..1f9eb4510 100644
--- a/src/mapgen/mg_decoration.h
+++ b/src/mapgen/mg_decoration.h
@@ -99,11 +99,13 @@ public:
 	ObjDef *clone() const;
 
 	DecoSchematic() = default;
+	virtual ~DecoSchematic();
 
 	virtual size_t generate(MMVManip *vm, PcgRandom *pr, v3s16 p, bool ceiling);
 
 	Rotation rotation;
 	Schematic *schematic = nullptr;
+	bool was_cloned = false; // see FIXME inside DecoSchemtic::clone()
 };
 
 
diff --git a/src/mapgen/mg_schematic.cpp b/src/mapgen/mg_schematic.cpp
index 2e04d30e6..c3bd89f3a 100644
--- a/src/mapgen/mg_schematic.cpp
+++ b/src/mapgen/mg_schematic.cpp
@@ -43,12 +43,21 @@ SchematicManager::SchematicManager(Server *server) :
 }
 
 
+SchematicManager *SchematicManager::clone() const
+{
+	auto mgr = new SchematicManager();
+	assert(mgr);
+	ObjDefManager::cloneTo(mgr);
+	return mgr;
+}
+
+
 void SchematicManager::clear()
 {
 	EmergeManager *emerge = m_server->getEmergeManager();
 
 	// Remove all dangling references in Decorations
-	DecorationManager *decomgr = emerge->decomgr;
+	DecorationManager *decomgr = emerge->getWritableDecorationManager();
 	for (size_t i = 0; i != decomgr->getNumObjects(); i++) {
 		Decoration *deco = (Decoration *)decomgr->getRaw(i);
 
@@ -79,7 +88,21 @@ Schematic::~Schematic()
 
 ObjDef *Schematic::clone() const
 {
-	FATAL_ERROR("not cloneable");
+	auto def = new Schematic();
+	ObjDef::cloneTo(def);
+	NodeResolver::cloneTo(def);
+
+	def->c_nodes = c_nodes;
+	def->flags = flags;
+	def->size = size;
+	FATAL_ERROR_IF(!schemdata, "Schematic can only be cloned after loading");
+	u32 nodecount = size.X * size.Y * size.Z;
+	def->schemdata = new MapNode[nodecount];
+	memcpy(def->schemdata, schemdata, sizeof(MapNode) * nodecount);
+	def->slice_probs = new u8[size.Y];
+	memcpy(def->slice_probs, slice_probs, sizeof(u8) * size.Y);
+
+	return def;
 }
 
 
diff --git a/src/mapgen/mg_schematic.h b/src/mapgen/mg_schematic.h
index 770f74053..3222085e6 100644
--- a/src/mapgen/mg_schematic.h
+++ b/src/mapgen/mg_schematic.h
@@ -130,7 +130,7 @@ public:
 	SchematicManager(Server *server);
 	virtual ~SchematicManager() = default;
 
-	// not cloneable
+	SchematicManager *clone() const;
 
 	virtual void clear();
 
@@ -145,6 +145,8 @@ public:
 	}
 
 private:
+	SchematicManager() {};
+
 	Server *m_server;
 };