4 files changed, 59 insertions, 17 deletions

diff --git a/src/mapgen/mapgen.cpp b/src/mapgen/mapgen.cpp
index 0639f149f..ce281e2c1 100644
--- a/src/mapgen/mapgen.cpp
+++ b/src/mapgen/mapgen.cpp
@@ -1063,9 +1063,20 @@ void MapgenParams::writeParams(Settings *settings) const
 }
 
 
-// Calculate exact edges of the outermost mapchunks that are within the
-// set 'mapgen_limit'.
-void MapgenParams::calcMapgenEdges()
+s32 MapgenParams::getSpawnRangeMax()
+{
+	if (!m_mapgen_edges_calculated) {
+		std::pair<s16, s16> edges = get_mapgen_edges(mapgen_limit, chunksize);
+		mapgen_edge_min = edges.first;
+		mapgen_edge_max = edges.second;
+		m_mapgen_edges_calculated = true;
+	}
+
+	return MYMIN(-mapgen_edge_min, mapgen_edge_max);
+}
+
+
+std::pair<s16, s16> get_mapgen_edges(s16 mapgen_limit, s16 chunksize)
 {
 	// Central chunk offset, in blocks
 	s16 ccoff_b = -chunksize / 2;
@@ -1089,17 +1100,5 @@ void MapgenParams::calcMapgenEdges()
 	s16 numcmin = MYMAX((ccfmin - mapgen_limit_min) / csize_n, 0);
 	s16 numcmax = MYMAX((mapgen_limit_max - ccfmax) / csize_n, 0);
 	// Mapgen edges, in nodes
-	mapgen_edge_min = ccmin - numcmin * csize_n;
-	mapgen_edge_max = ccmax + numcmax * csize_n;
-
-	m_mapgen_edges_calculated = true;
-}
-
-
-s32 MapgenParams::getSpawnRangeMax()
-{
-	if (!m_mapgen_edges_calculated)
-		calcMapgenEdges();
-
-	return MYMIN(-mapgen_edge_min, mapgen_edge_max);
+	return std::pair<s16, s16>(ccmin - numcmin * csize_n, ccmax + numcmax * csize_n);
 }
diff --git a/src/mapgen/mapgen.h b/src/mapgen/mapgen.h
index ef5de6029..b61608039 100644
--- a/src/mapgen/mapgen.h
+++ b/src/mapgen/mapgen.h
@@ -25,6 +25,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "nodedef.h"
 #include "util/string.h"
 #include "util/container.h"
+#include <utility>
 
 #define MAPGEN_DEFAULT MAPGEN_V7
 #define MAPGEN_DEFAULT_NAME "v7"
@@ -139,7 +140,6 @@ struct MapgenParams {
 	s32 getSpawnRangeMax();
 
 private:
-	void calcMapgenEdges();
 	bool m_mapgen_edges_calculated = false;
 };
 
@@ -329,3 +329,7 @@ protected:
 	s16 dungeon_ymin;
 	s16 dungeon_ymax;
 };
+
+// Calculate exact edges of the outermost mapchunks that are within the set
+// mapgen_limit. Returns the minimum and maximum edges in nodes in that order.
+std::pair<s16, s16> get_mapgen_edges(s16 mapgen_limit, s16 chunksize);
diff --git a/src/script/lua_api/l_mapgen.cpp b/src/script/lua_api/l_mapgen.cpp
index 1e4197df3..2e17d0d67 100644
--- a/src/script/lua_api/l_mapgen.cpp
+++ b/src/script/lua_api/l_mapgen.cpp
@@ -810,6 +810,41 @@ int ModApiMapgen::l_set_mapgen_params(lua_State *L)
 	return 0;
 }
 
+// get_mapgen_edges([mapgen_limit[, chunksize]])
+int ModApiMapgen::l_get_mapgen_edges(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	MapSettingsManager *settingsmgr = getServer(L)->getEmergeManager()->map_settings_mgr;
+
+	// MapSettingsManager::makeMapgenParams cannot be used here because it would
+	// make mapgen settings immutable from then on. Mapgen settings should stay
+	// mutable until after mod loading ends.
+
+	s16 mapgen_limit;
+	if (lua_isnumber(L, 1)) {
+		 mapgen_limit = lua_tointeger(L, 1);
+	} else {
+		std::string mapgen_limit_str;
+		settingsmgr->getMapSetting("mapgen_limit", &mapgen_limit_str);
+		mapgen_limit = stoi(mapgen_limit_str, 0, MAX_MAP_GENERATION_LIMIT);
+	}
+
+	s16 chunksize;
+	if (lua_isnumber(L, 2)) {
+		chunksize = lua_tointeger(L, 2);
+	} else {
+		std::string chunksize_str;
+		settingsmgr->getMapSetting("chunksize", &chunksize_str);
+		chunksize = stoi(chunksize_str, -32768, 32767);
+	}
+
+	std::pair<s16, s16> edges = get_mapgen_edges(mapgen_limit, chunksize);
+	push_v3s16(L, v3s16(1, 1, 1) * edges.first);
+	push_v3s16(L, v3s16(1, 1, 1) * edges.second);
+	return 2;
+}
+
 // get_mapgen_setting(name)
 int ModApiMapgen::l_get_mapgen_setting(lua_State *L)
 {
@@ -1782,6 +1817,7 @@ void ModApiMapgen::Initialize(lua_State *L, int top)
 
 	API_FCT(get_mapgen_params);
 	API_FCT(set_mapgen_params);
+	API_FCT(get_mapgen_edges);
 	API_FCT(get_mapgen_setting);
 	API_FCT(set_mapgen_setting);
 	API_FCT(get_mapgen_setting_noiseparams);
diff --git a/src/script/lua_api/l_mapgen.h b/src/script/lua_api/l_mapgen.h
index 0bdc56fc5..1428a91c8 100644
--- a/src/script/lua_api/l_mapgen.h
+++ b/src/script/lua_api/l_mapgen.h
@@ -61,6 +61,9 @@ private:
 	// set mapgen parameters
 	static int l_set_mapgen_params(lua_State *L);
 
+	// get_mapgen_edges([mapgen_limit[, chunksize]])
+	static int l_get_mapgen_edges(lua_State *L);
+
 	// get_mapgen_setting(name)
 	static int l_get_mapgen_setting(lua_State *L);