Check for falling `float` nodes in liquid transform (#12862)

src/map.cpp

@@ -533,6 +533,8 @@ void ServerMap::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks,
 
 	std::vector<std::pair<v3s16, MapNode> > changed_nodes;
 
+	std::vector<v3s16> check_for_falling;
+
 	u32 liquid_loop_max = g_settings->getS32("liquid_loop_max");
 	u32 loop_max = liquid_loop_max;
 
@@ -595,6 +597,7 @@ void ServerMap::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks,
 		int num_neutrals = 0;
 		bool flowing_down = false;
 		bool ignored_sources = false;
+		bool floating_node_above = false;
 		for (u16 i = 0; i < 6; i++) {
 			NeighborType nt = NEIGHBOR_SAME_LEVEL;
 			switch (i) {
@@ -610,7 +613,9 @@ void ServerMap::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks,
 			v3s16 npos = p0 + liquid_6dirs[i];
 			NodeNeighbor nb(getNode(npos), nt, npos);
 			const ContentFeatures &cfnb = m_nodedef->get(nb.n);
-			switch (m_nodedef->get(nb.n.getContent()).liquid_type) {
+			if (nt == NEIGHBOR_UPPER && cfnb.floats)
+				floating_node_above = true;
+			switch (cfnb.liquid_type) {
 				case LIQUID_NONE:
 					if (cfnb.floodable) {
 						airs[num_airs++] = nb;
@@ -752,6 +757,11 @@ void ServerMap::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks,
 				== flowing_down)))
 			continue;
 
+		/*
+			check if there is a floating node above that needs to be updated.
+		 */
+		if (floating_node_above && new_node_content == CONTENT_AIR)
+			check_for_falling.push_back(p0);
 
 		/*
 			update the current node
@@ -836,6 +846,11 @@ void ServerMap::transformLiquids(std::map<v3s16, MapBlock*> &modified_blocks,
 		m_transforming_liquid.push_back(iter);
 
 	voxalgo::update_lighting_nodes(this, changed_nodes, modified_blocks);
+
+	for (const v3s16 &p : check_for_falling) {
+		env->getScriptIface()->check_for_falling(p);
+	}
+
 	env->getScriptIface()->on_liquid_transformed(changed_nodes);
 
 	/* ----------------------------------------------------------------------

src/nodedef.cpp

@@ -1393,6 +1393,7 @@ content_t NodeDefManager::set(const std::string &name, const ContentFeatures &de
 		eraseIdFromGroups(id);
 
 	m_content_features[id] = def;
+	m_content_features[id].floats = itemgroup_get(def.groups, "float") != 0;
 	m_content_lighting_flag_cache[id] = def.getLightingFlags();
 	verbosestream << "NodeDefManager: registering content id \"" << id
 		<< "\": name=\"" << def.name << "\""<<std::endl;
@@ -1606,6 +1607,7 @@ void NodeDefManager::deSerialize(std::istream &is, u16 protocol_version)
 		if (i >= m_content_features.size())
 			m_content_features.resize((u32)(i) + 1);
 		m_content_features[i] = f;
+		m_content_features[i].floats = itemgroup_get(f.groups, "float") != 0;
 		m_content_lighting_flag_cache[i] = f.getLightingFlags();
 		addNameIdMapping(i, f.name);
 		TRACESTREAM(<< "NodeDef: deserialized " << f.name << std::endl);

src/nodedef.h

@@ -322,6 +322,9 @@ struct ContentFeatures
 	bool has_on_destruct;
 	bool has_after_destruct;
 
+	// "float" group
+	bool floats;
+
 	/*
 		Actual data
 	 */

src/script/cpp_api/s_env.cpp

@@ -257,6 +257,18 @@ void ScriptApiEnv::on_emerge_area_completion(
 	}
 }
 
+void ScriptApiEnv::check_for_falling(v3s16 p)
+{
+	SCRIPTAPI_PRECHECKHEADER
+
+	int error_handler = PUSH_ERROR_HANDLER(L);
+	lua_getglobal(L, "core");
+	lua_getfield(L, -1, "check_for_falling");
+	luaL_checktype(L, -1, LUA_TFUNCTION);
+	push_v3s16(L, p);
+	PCALL_RES(lua_pcall(L, 1, 0, error_handler));
+}
+
 void ScriptApiEnv::on_liquid_transformed(
 	const std::vector<std::pair<v3s16, MapNode>> &list)
 {

src/script/cpp_api/s_env.h

@@ -43,6 +43,8 @@ public:
 	void on_emerge_area_completion(v3s16 blockpos, int action,
 		ScriptCallbackState *state);
 
+	void check_for_falling(v3s16 p);
+
 	// Called after liquid transform changes
 	void on_liquid_transformed(const std::vector<std::pair<v3s16, MapNode>> &list);