Atempt to fix "unknown object" issue + code rework

init.lua

@@ -24,6 +24,9 @@ display_api = {}
 -- variable as spacing between entity and node
 display_api.entity_spacing = 0.002
 
+-- Maximum entity position relative to the node pos
+local max_entity_pos = 1.5
+
 -- Miscelaneous values depending on wallmounted param2
 local wallmounted_values = {
 	[2]={dx=-1, dz=0,  rx=0,  rz=-1, yaw=-math.pi/2},
@@ -43,7 +46,7 @@ local facedir_values = {
 -- dx/dy = depth vector, rx/ly = right vector, yaw = yaw of entity,
 local function get_values(node)
 	local ndef = minetest.registered_nodes[node.name]
-	
+
 	if ndef then
 		local paramtype2 = ndef.paramtype2
 		if paramtype2 == "wallmounted" or paramtype2 == "colorwallmounted" then
@@ -54,27 +57,18 @@ local function get_values(node)
 	end
 end
 
---- Checks if the object is related to the given position
-local function check_entity_pos(pos, objref)
-	local real_pos = vector.round(objref:get_pos())
-	local pos_hash = objref:get_luaentity().pos
-	if pos_hash == nil then
-		return vector.equals(real_pos, vector.round(pos))
-	else
-		return vector.equals(minetest.get_position_from_hash(pos_hash), pos)
-	end
-end
-
 --- Gets the display entities attached with a node. Removes extra ones
 local function get_entities(pos)
 	local objrefs = {}
 	local ndef = minetest.registered_nodes[minetest.get_node(pos).name]
 	if ndef and ndef.display_entities then
-		for _, objref in ipairs(minetest.get_objects_inside_radius(pos, 1.5)) do
+		for _, objref in
+			ipairs(minetest.get_objects_inside_radius(pos, max_entity_pos)) do
 			local entity = objref:get_luaentity()
-			if entity and ndef.display_entities[entity.name] and check_entity_pos(pos, objref) then
+			if entity and ndef.display_entities[entity.name] and
+			   entity.nodepos and vector.equals(pos, entity.nodepos) then
 				if objrefs[entity.name] then
-					objref:remove()
+					objref:remove() -- Remove duplicates
 				else
 					objrefs[entity.name] = objref
 				end
@@ -86,7 +80,7 @@ end
 
 local function clip_pos_prop(posprop)
 	if posprop then
-		return math.max(-1.5, math.min(1.5, posprop))
+		return math.max(-max_entity_pos, math.min(max_entity_pos, posprop))
 	else
 		return 0
 	end
@@ -98,43 +92,52 @@ local function place_entities(pos)
 	local ndef = minetest.registered_nodes[node.name]
 	local values = get_values(node)
 	local objrefs = get_entities(pos)
-	
+
 	if values and ndef and ndef.display_entities then
-		
 		for entity_name, props in pairs(ndef.display_entities) do
 			local depth = clip_pos_prop(props.depth)
 			local right = clip_pos_prop(props.right)
 			local top = clip_pos_prop(props.top)
 			if not objrefs[entity_name] then
-				objrefs[entity_name] = minetest.add_entity(pos, entity_name)
+				objrefs[entity_name] = minetest.add_entity(pos, entity_name,
+					minetest.serialize({ nodepos = pos }))
 			end
-			
+
 			objrefs[entity_name]:setpos({
 				x = pos.x - values.dx * depth + values.rx * right,
 				y = pos.y - top,
 				z = pos.z - values.dz * depth + values.rz * right})
-			
+
 			objrefs[entity_name]:setyaw(values.yaw)
 		end
 	end
 	return objrefs
 end
 
---- Call on_display_update callback of a node for one of its display entities
-local function call_node_on_display_update(pos, objref)
-	local ndef = minetest.registered_nodes[minetest.get_node(pos).name]
-	local entity = objref:get_luaentity()
-	if ndef and ndef.display_entities and entity and ndef.display_entities[entity.name] then
-		ndef.display_entities[entity.name].on_display_update(pos, objref)
+
+--- Entity update
+function update_entity(entity)
+	if not entity.nodepos then
+		entity.object:remove() -- Remove old/buggy entity
+		return
+	end
+
+	local node = minetest.get_node(entity.nodepos)
+	local ndef = minetest.registered_nodes[node.name]
+	if ndef and ndef.display_entities and
+	   ndef.display_entities[entity.name] and
+	   ndef.display_entities[entity.name].on_display_update
+	then
+		-- Call on_display_update callback of a node for one of its display entities
+		ndef.display_entities[entity.name].on_display_update(entity.nodepos,
+			entity.object)
 	end
 end
 
 --- Force entity update
 function display_api.update_entities(pos)
-	local objrefs = place_entities(pos)
-	for _, objref in pairs(objrefs) do
-		objref:get_luaentity().pos = minetest.hash_node_position(pos)
-		call_node_on_display_update(pos, objref)
+	for _, objref in pairs(place_entities(pos)) do
+		update_entity(objref:get_luaentity())
 	end
 end
 
@@ -145,36 +148,28 @@ function display_api.on_activate(entity, staticdata)
 		if string.sub(staticdata, 1, string.len("return")) == "return" then
 			local data = core.deserialize(staticdata)
 			if data and type(data) == "table" then
-				entity.pos = data.pos
+				entity.nodepos = data.nodepos
 			end
+			entity.object:set_armor_groups({immortal=1})
 		end
-		entity.object:set_armor_groups({immortal=1})
-		local pos
-		if entity.pos then
-			pos = minetest.get_position_from_hash(entity.pos)
-		else
-			pos = entity.object:getpos()
-		end
-		display_api.update_entities(pos)
+		update_entity(entity)
 	end
 end
 
---- On_place callback for display_api items. Does nothing more than preventing item
---- from being placed on ceiling or ground 
+--- On_place callback for display_api items.
+-- Does nothing more than preventing node from being placed on ceiling or ground
 function display_api.on_place(itemstack, placer, pointed_thing, override_param2)
 	local ndef = itemstack:get_definition()
 	local above = pointed_thing.above
 	local under = pointed_thing.under
-	local dir = {x = under.x - above.x,
-	             y = 0,
-	             z = under.z - above.z}
-	
+	local dir = {x = under.x - above.x, y = 0, z = under.z - above.z}
+
 	-- If item is not placed on a wall, use the player's view direction instead
 	if dir.x == 0 and dir.z == 0 then
 		dir = placer:get_look_dir()
 		dir.y = 0
 	end
-	
+
 	local param2 = 0
 	if ndef then
 		local paramtype2 = ndef.paramtype2
@@ -184,19 +179,20 @@ function display_api.on_place(itemstack, placer, pointed_thing, override_param2)
 			param2 = minetest.dir_to_facedir(dir)
 		end
 	end
-	return minetest.item_place(itemstack, placer, pointed_thing, param2 + (override_param2 or 0))
+	return minetest.item_place(itemstack, placer, pointed_thing,
+		param2 + (override_param2 or 0))
 end
 
---- On_construct callback for display_api items. Creates entities and update them.
+--- On_construct callback for display_api items.
+-- Creates entities and update them.
 function display_api.on_construct(pos)
 	display_api.update_entities(pos)
 end
 
---- On_destruct callback for display_api items. Removes entities.
+--- On_destruct callback for display_api items.
+-- Removes entities.
 function display_api.on_destruct(pos)
-	local objrefs = get_entities(pos)
-	
-	for _, objref in pairs(objrefs) do 
+	for _, objref in pairs(get_entities(pos)) do
 		objref:remove()
 	end
 end
@@ -222,9 +218,7 @@ function display_api.register_display_entity(entity_name)
 			textures = {},
 			on_activate = display_api.on_activate,
 			get_staticdata = function(self)
-				return minetest.serialize({
-					pos = self.pos,
-				})
+				return minetest.serialize({ nodepos = self.nodepos })
 			end,
 		})
 	end