use gennotify instead of lbm for placement

keep the lbm for secondary structures

mods/MAPGEN/mcl_structures/api.lua

@@ -17,42 +17,8 @@ local registered_structures = {}
 }
 ]]--
 
-function mcl_structures.register_structure(name,def,nospawn) --nospawn means it will be placed by another (non-nospawn) structure that contains it's structblock i.e. it will not be placed by mapgen directly
-	local structblock = "mcl_structures:structblock_"..name
-	minetest.register_node(":"..structblock, {drawtype="airlike", walkable = false, pointable = false,groups = {structblock=1,not_in_creative_inventory=1}})
-	local flags = "place_center_x, place_center_z, force_placement"
-	local y_offset = 0
-	if def.flags then flags = def.flags end
-	def.name = name
-	if nospawn == nil then
-		def.deco = minetest.register_decoration({
-			decoration = structblock,
-			deco_type = "simple",
-			place_on = def.place_on,
-			spawn_by = def.spawn_by,
-			num_spawn_by = def.num_spawn_by,
-			sidelen = 80,
-			fill_ratio = def.fill_ratio,
-			noise = def.noise,
-			flags = flags,
-			biomes = def.biomes,
-			y_max = def.y_max,
-			y_min = def.y_min
-		})
-	end
-	registered_structures[name] = def
-end
-
-minetest.register_lbm({
-	name = "mcl_structures:struct_lbm",
-	run_at_every_load = true,
-	nodenames = {"group:structblock"},
-	action = function(pos, node)
-		local name = node.name:gsub("mcl_structures:structblock_","")
-		local pr = PseudoRandom(pos.x+pos.y+pos.z)
-		local def = registered_structures[name]
-		local y_offset = 0
-		minetest.set_node(pos,{name="air"})
+local function place_schem(pos, def, pr)
+	if not def then return end
 	if type(def.y_offset) == "function" then
 		y_offset = def.y_offset(pr)
 	elseif def.y_offset then
@@ -66,4 +32,59 @@ minetest.register_lbm({
 		def.after_place(pos,def)
 	end
 end
+
+function mcl_structures.register_structure(name,def,nospawn) --nospawn means it will be placed by another (non-nospawn) structure that contains it's structblock i.e. it will not be placed by mapgen directly
+	local structblock = "mcl_structures:structblock_"..name
+	local flags = "place_center_x, place_center_z, force_placement"
+	local y_offset = 0
+	local sbgroups = { structblock = 1, not_in_creative_inventory=1 }
+	if def.flags then flags = def.flags end
+	def.name = name
+	if nospawn then
+		sbgroups.structblock = nil
+		sbgroups.structblock_lbm = 1
+	else
+		def.deco = minetest.register_decoration({
+			name = "mcl_structures:deco_"..name,
+			decoration = structblock,
+			deco_type = "simple",
+			place_on = def.place_on,
+			spawn_by = def.spawn_by,
+			num_spawn_by = def.num_spawn_by,
+			sidelen = 80,
+			fill_ratio = def.fill_ratio,
+			noise = def.noise,
+			flags = flags,
+			biomes = def.biomes,
+			y_max = def.y_max,
+			y_min = def.y_min
+		})
+		local deco_id = minetest.get_decoration_id("mcl_structures:deco_"..name)
+		minetest.set_gen_notify({decoration=true}, { deco_id })
+		minetest.register_on_generated(function(minp, maxp, blockseed)
+			local gennotify = minetest.get_mapgen_object("gennotify")
+			local pr = PseudoRandom(blockseed + 42)
+			for _, pos in pairs(gennotify["decoration#"..deco_id] or {}) do
+				local realpos = vector.offset(pos,0,-1,0)
+				minetest.remove_node(realpos)
+				place_schem(realpos,def,pr)
+			end
+		end)
+	end
+	minetest.register_node(":"..structblock, {drawtype="airlike", walkable = false, pointable = false,groups = sbgroups})
+	registered_structures[name] = def
+end
+
+--lbm for secondary structures (structblock included in base structure)
+minetest.register_lbm({
+	name = "mcl_structures:struct_lbm",
+	run_at_every_load = true,
+	nodenames = {"group:structblock_lbm"},
+	action = function(pos, node)
+		local name = node.name:gsub("mcl_structures:structblock_","")
+		local def = registered_structures[name]
+		if not def then return end
+		minetest.remove_node(pos)
+		place_schem(pos)
+	end
 })