Display location of item frame in item frame map

mods/ITEMS/mcl_itemframes/init.lua

@@ -63,11 +63,50 @@ minetest.register_entity("mcl_itemframes:map", {
 		textures = {"blank.png"},
 	},
 	on_activate = function(self, staticdata)
-		self.id = staticdata
-		self.object:set_properties({textures = {mcl_maps.load_map(self.id)}})
+		local data = minetest.deserialize(staticdata)
+		-- originally this function only got the id
+		if nil == data then
+			self.id = data
+			self._pos = { x = 0/0, y = 0/0, z = 0/0 }
+			self._minp = { x = 0/0, y = 0/0, z = 0/0 }
+			self._maxp = { x = 0/0, y = 0/0, z = 0/0 }
+		else
+			self.id = data.id
+			self._pos = data._pos
+			self._minp = data._minp
+			self._maxp = data._maxp
+		end
+		local marker = ""
+		if (
+			self._pos.x > self._minp.x and
+			self._pos.x < self._maxp.x and
+			self._pos.z > self._minp.z and
+			self._pos.z < self._maxp.z
+		) then
+			-- marker is 8×8, points downwards
+			local x = self._pos.x - self._minp.x - 3
+			local z = self._maxp.z - self._pos.z - 6
+			-- hack to avoid clipping
+			if x < 0 then x = 0 end
+			if z < 0 then z = 0 end
+			if x > 120 then x = 120 end
+			if z > 120 then z = 120 end
+			marker = "^[combine:8x8:" .. x .. "," .. z .. "=mcl_maps_itemframe_location_marker.png"
+		end
+		self.object:set_properties(
+		   {
+		      textures = { mcl_maps.load_map(self.id) .. marker }
+		   }
+		)
 	end,
 	get_staticdata = function(self)
-		return self.id
+		local data = {
+			id = self.id,
+			_pos = self._pos,
+			_minp = self._minp,
+			_maxp = self._maxp,
+		}
+		return minetest.serialize(data)
 	end,
 })
 
@@ -105,7 +144,8 @@ local update_item_entity = function(pos, node, param2)
 			pos.z = pos.z + posad.z*6.5/16
 		end
 		local yaw = math.pi*2 - param2 * math.pi/2
-		local map_id = item:get_meta():get_string("mcl_maps:id")
+		local meta = item:get_meta()
+		local map_id = meta:get_string("mcl_maps:id")
 		if map_id == "" then
 			local e = minetest.add_entity(pos, "mcl_itemframes:item")
 			local lua = e:get_luaentity()
@@ -124,7 +164,13 @@ local update_item_entity = function(pos, node, param2)
 				e:set_yaw(yaw)
 			end
 		else
-			local e = minetest.add_entity(pos, "mcl_itemframes:map", map_id)
+			local staticdata = {
+				id = map_id,
+				_pos = pos,
+				_minp = minetest.string_to_pos(meta:get_string("mcl_maps:minp")),
+				_maxp = minetest.string_to_pos(meta:get_string("mcl_maps:maxp")),
+			}
+			local e = minetest.add_entity(pos, "mcl_itemframes:map", minetest.serialize(staticdata))
 			e:set_yaw(yaw)
 		end
 	end