5 files changed, 87 insertions, 3 deletions
diff --git a/src/script/common/c_converter.h b/src/script/common/c_converter.h
index 2af726d16..f1e4e47ec 100644
--- a/src/script/common/c_converter.h
+++ b/src/script/common/c_converter.h
@@ -121,3 +121,12 @@ void                warn_if_field_exists(lua_State *L, int table,
 
 size_t write_array_slice_float(lua_State *L, int table_index, float *data,
 	v3u16 data_size, v3u16 slice_offset, v3u16 slice_size);
+
+// This must match the implementation in builtin/game/misc_s.lua
+// Note that this returns a floating point result as Lua integers are 32-bit
+inline lua_Number hash_node_position(v3s16 pos)
+{
+	return (((s64)pos.Z + 0x8000L) << 32)
+			| (((s64)pos.Y + 0x8000L) << 16)
+			| ((s64)pos.X + 0x8000L);
+}
diff --git a/src/script/cpp_api/s_env.cpp b/src/script/cpp_api/s_env.cpp
index e49113405..3cbb13cd2 100644
--- a/src/script/cpp_api/s_env.cpp
+++ b/src/script/cpp_api/s_env.cpp
@@ -299,3 +299,36 @@ void ScriptApiEnv::on_liquid_transformed(
 
 	runCallbacks(2, RUN_CALLBACKS_MODE_FIRST);
 }
+
+void ScriptApiEnv::on_mapblocks_changed(const std::unordered_set<v3s16> &set)
+{
+	SCRIPTAPI_PRECHECKHEADER
+
+	// Get core.registered_on_mapblocks_changed
+	lua_getglobal(L, "core");
+	lua_getfield(L, -1, "registered_on_mapblocks_changed");
+	luaL_checktype(L, -1, LUA_TTABLE);
+	lua_remove(L, -2);
+
+	// Convert the set to a set of position hashes
+	lua_createtable(L, 0, set.size());
+	for(const v3s16 &p : set) {
+		lua_pushnumber(L, hash_node_position(p));
+		lua_pushboolean(L, true);
+		lua_rawset(L, -3);
+	}
+	lua_pushinteger(L, set.size());
+
+	runCallbacks(2, RUN_CALLBACKS_MODE_FIRST);
+}
+
+bool ScriptApiEnv::has_on_mapblocks_changed()
+{
+	SCRIPTAPI_PRECHECKHEADER
+
+	// Get core.registered_on_mapblocks_changed
+	lua_getglobal(L, "core");
+	lua_getfield(L, -1, "registered_on_mapblocks_changed");
+	luaL_checktype(L, -1, LUA_TTABLE);
+	return lua_objlen(L, -1) > 0;
+}
diff --git a/src/script/cpp_api/s_env.h b/src/script/cpp_api/s_env.h
index 9a50a01cc..bc4c4cd4d 100644
--- a/src/script/cpp_api/s_env.h
+++ b/src/script/cpp_api/s_env.h
@@ -22,6 +22,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "cpp_api/s_base.h"
 #include "irr_v3d.h"
 #include "mapnode.h"
+#include <unordered_set>
 #include <vector>
 
 class ServerEnvironment;
@@ -48,5 +49,11 @@ public:
 	// Called after liquid transform changes
 	void on_liquid_transformed(const std::vector<std::pair<v3s16, MapNode>> &list);
 
+	// Called after mapblock changes
+	void on_mapblocks_changed(const std::unordered_set<v3s16> &set);
+
+	// Determines whether there are any on_mapblocks_changed callbacks
+	bool has_on_mapblocks_changed();
+
 	void initializeEnvironment(ServerEnvironment *env);
 };
diff --git a/src/serverenvironment.cpp b/src/serverenvironment.cpp
index 9dd5ba621..aa6ba2f96 100644
--- a/src/serverenvironment.cpp
+++ b/src/serverenvironment.cpp
@@ -382,6 +382,18 @@ void ActiveBlockList::update(std::vector<PlayerSAO*> &active_players,
 }
 
 /*
+	OnMapblocksChangedReceiver
+*/
+
+void OnMapblocksChangedReceiver::onMapEditEvent(const MapEditEvent &event)
+{
+	assert(receiving);
+	for (const v3s16 &p : event.modified_blocks) {
+		modified_blocks.insert(p);
+	}
+}
+
+/*
 	ServerEnvironment
 */
 
@@ -476,6 +488,11 @@ void ServerEnvironment::init()
 
 	m_player_database = openPlayerDatabase(player_backend_name, m_path_world, conf);
 	m_auth_database = openAuthDatabase(auth_backend_name, m_path_world, conf);
+
+	if (m_map && m_script->has_on_mapblocks_changed()) {
+		m_map->addEventReceiver(&m_on_mapblocks_changed_receiver);
+		m_on_mapblocks_changed_receiver.receiving = true;
+	}
 }
 
 ServerEnvironment::~ServerEnvironment()
@@ -1570,6 +1587,14 @@ void ServerEnvironment::step(float dtime)
 	// Send outdated detached inventories
 	m_server->sendDetachedInventories(PEER_ID_INEXISTENT, true);
 
+	// Notify mods of modified mapblocks
+	if (m_on_mapblocks_changed_receiver.receiving &&
+			!m_on_mapblocks_changed_receiver.modified_blocks.empty()) {
+		std::unordered_set<v3s16> modified_blocks;
+		std::swap(modified_blocks, m_on_mapblocks_changed_receiver.modified_blocks);
+		m_script->on_mapblocks_changed(modified_blocks);
+	}
+
 	const auto end_time = porting::getTimeUs();
 	m_step_time_counter->increment(end_time - start_time);
 }
diff --git a/src/serverenvironment.h b/src/serverenvironment.h
index 5c4b23f40..bb40a33ce 100644
--- a/src/serverenvironment.h
+++ b/src/serverenvironment.h
@@ -21,7 +21,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "activeobject.h"
 #include "environment.h"
-#include "mapnode.h"
+#include "map.h"
 #include "settings.h"
 #include "server/activeobjectmgr.h"
 #include "util/numeric.h"
@@ -30,9 +30,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <random>
 
 class IGameDef;
-class ServerMap;
 struct GameParams;
-class MapBlock;
 class RemotePlayer;
 class PlayerDatabase;
 class AuthDatabase;
@@ -194,6 +192,16 @@ public:
 };
 
 /*
+	ServerEnvironment::m_on_mapblocks_changed_receiver
+*/
+struct OnMapblocksChangedReceiver : public MapEventReceiver {
+	std::unordered_set<v3s16> modified_blocks;
+	bool receiving = false;
+
+	void onMapEditEvent(const MapEditEvent &event) override;
+};
+
+/*
 	Operation mode for ServerEnvironment::clearObjects()
 */
 enum ClearObjectsMode {
@@ -455,6 +463,8 @@ private:
 	Server *m_server;
 	// Active Object Manager
 	server::ActiveObjectMgr m_ao_manager;
+	// on_mapblocks_changed map event receiver
+	OnMapblocksChangedReceiver m_on_mapblocks_changed_receiver;
 	// World path
 	const std::string m_path_world;
 	// Outgoing network message buffer for active objects