diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..a28a34b
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "display_api"]
+	path = display_api
+	url = https://github.com/pyrollo/display_api.git
diff --git a/display_api b/display_api
new file mode 160000
index 0000000..246b7f9
--- /dev/null
+++ b/display_api
@@ -0,0 +1 @@
+Subproject commit 246b7f958863e7f6b7f604b09361696226928a7b
diff --git a/display_api/API.md b/display_api/API.md
deleted file mode 100644
index 0d52e29..0000000
--- a/display_api/API.md
+++ /dev/null
@@ -1,94 +0,0 @@
-# Display Lib API
-This document describes Display Lib API. Display Lib allows to add a dynamic display on a node. Display Lib limits node rotations. For wallmounted, only vertical positionning is available, and for facedir, only first four position are availabel (those with default axis).
-
-## Provided methods
-### update\_entities
-**display\_lib.update\_entities(pos)**
-
-This method triggers entities update for the display node at pos. Actual entity update is made by `on_display_update` callback associated to the entity.
-
-`pos`: Position of the node
-### register\_display\_entity
-**display\_lib.register\_display\_entity(entity_name)**
-
-This is a helper to register entities used for display. 
-
-`entity_name`: Name of the entity to register.
-## Provided callback implementations
-### on_place
-**display\_lib.on\_place(itemstack, placer, pointed\_thing)**
-
-`on_place` node callback implementation. Display nodes should have this callback (avoid placement of horizontal display node).
-### on_construct
-**display\_lib.on\_construct(pos)**
-
-`on_construct` node callback implementation. Display nodes should have this callback (creates, places and updates display entities on node construction).
-### on_destruct
-**display\_lib.on_destruct(pos)**
-
-`on_destruct` node callback implementation. Display nodes should have this callback (removes display entities on node destruction). 
-### on_rotate
-**display\_lib.on\_rotate(pos, node, user, mode, new_param2)**
-
-`on_rotate` node callback implementation. Display nodes should have this callback (restricts rotations and rotates display entities associated with node).
-### on_activate
-**display\_lib.on_activate(entity, staticdata)**
-
-`On_activate` entity callback implementation for display entities. No need of this method if display entities have been registered using `register_display_entity` (callback is already set). 
-
-## Howto register a display node
-* Register display entities with `register_display_entity`
-
-* Register node with :
-  - `on_place`, `on_construct`, `on_destruct` and `on_rotate` callbacks using display_api callbacks.
-  
-  - `display_modpack_node` group. This will make this node have their entities updated as soon as the mapblock is loaded (Useful after /clearobjects).
-  
-  - a `display_entities` field in node definition containing a entity name indexed table. See below for description of each display_entities fields.
-
-### Display_entities fields
-`on_display_update` is a callback in charge of setting up entity texture. If not set, entity will have no texture and will be displayed as unknown item.
-
-`depth`, `right` and `height` : Entity position regarding to node facedir/wallmounted main axis.
-Values for these fields can be any number between -1.5 and 1.5 (default value is 0).
-Position 0,0,0 is the center of the node.
-`depth` goes from front (-0.5) to rear (0.5), `height` goes from bottom (-0.5) to top (0.5) and `right` goes from left (-0.5) to right (0.5).
-
-In order to avoid flickering text, it's better to have text a little behind node surface. A good spacing value is given by `display_api.entity_spacing` variable.
-
-### Example
-
-	display_api.register_display_entity("mymod:entity1")
-	display_api.register_display_entity("mymod:entity2")
-
-	function my_display_update1(pos, objref) 
-		objref:set_properties({ textures= {"mytexture1.png"},
-		                        visual_size = {x=1, y=1} })
-	end
-
-	function my_display_update2(pos, objref) 
-		objref:set_properties({ textures= {"mytexture2.png"},
-		                        visual_size = {x=1, y=1} })
-	end
-
-	minetest.register_node("mymod:test_display_node", {
-		...
-		paramtype2 = "facedir",
-		...
-		groups = { display_modpack_node = 1, ... },
-		...
-		display_entities = {
-			["mymod:entity1"] = { 
-				depth = 0.3,
-				on_display_update = my_display_update1 },
-			["mymod:entity1"] = { 
-				depth = 0.2, height = 0.1,
-				on_display_update = my_display_update2 },
-			},
-		...
-		on_place = display_api.on_place,
-		on_construct = display_api.on_construct,
-		on_destruct = display_api.on_destruct,
-		on_rotate = display_api.on_rotate,
-		...
-	})
diff --git a/display_api/LICENSE.txt b/display_api/LICENSE.txt
deleted file mode 100644
index 341c30b..0000000
--- a/display_api/LICENSE.txt
+++ /dev/null
@@ -1,166 +0,0 @@
-                   GNU LESSER GENERAL PUBLIC LICENSE
-                       Version 3, 29 June 2007
-
- Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
- Everyone is permitted to copy and distribute verbatim copies
- of this license document, but changing it is not allowed.
-
-
-  This version of the GNU Lesser General Public License incorporates
-the terms and conditions of version 3 of the GNU General Public
-License, supplemented by the additional permissions listed below.
-
-  0. Additional Definitions.
-
-  As used herein, "this License" refers to version 3 of the GNU Lesser
-General Public License, and the "GNU GPL" refers to version 3 of the GNU
-General Public License.
-
-  "The Library" refers to a covered work governed by this License,
-other than an Application or a Combined Work as defined below.
-
-  An "Application" is any work that makes use of an interface provided
-by the Library, but which is not otherwise based on the Library.
-Defining a subclass of a class defined by the Library is deemed a mode
-of using an interface provided by the Library.
-
-  A "Combined Work" is a work produced by combining or linking an
-Application with the Library.  The particular version of the Library
-with which the Combined Work was made is also called the "Linked
-Version".
-
-  The "Minimal Corresponding Source" for a Combined Work means the
-Corresponding Source for the Combined Work, excluding any source code
-for portions of the Combined Work that, considered in isolation, are
-based on the Application, and not on the Linked Version.
-
-  The "Corresponding Application Code" for a Combined Work means the
-object code and/or source code for the Application, including any data
-and utility programs needed for reproducing the Combined Work from the
-Application, but excluding the System Libraries of the Combined Work.
-
-  1. Exception to Section 3 of the GNU GPL.
-
-  You may convey a covered work under sections 3 and 4 of this License
-without being bound by section 3 of the GNU GPL.
-
-  2. Conveying Modified Versions.
-
-  If you modify a copy of the Library, and, in your modifications, a
-facility refers to a function or data to be supplied by an Application
-that uses the facility (other than as an argument passed when the
-facility is invoked), then you may convey a copy of the modified
-version:
-
-   a) under this License, provided that you make a good faith effort to
-   ensure that, in the event an Application does not supply the
-   function or data, the facility still operates, and performs
-   whatever part of its purpose remains meaningful, or
-
-   b) under the GNU GPL, with none of the additional permissions of
-   this License applicable to that copy.
-
-  3. Object Code Incorporating Material from Library Header Files.
-
-  The object code form of an Application may incorporate material from
-a header file that is part of the Library.  You may convey such object
-code under terms of your choice, provided that, if the incorporated
-material is not limited to numerical parameters, data structure
-layouts and accessors, or small macros, inline functions and templates
-(ten or fewer lines in length), you do both of the following:
-
-   a) Give prominent notice with each copy of the object code that the
-   Library is used in it and that the Library and its use are
-   covered by this License.
-
-   b) Accompany the object code with a copy of the GNU GPL and this license
-   document.
-
-  4. Combined Works.
-
-  You may convey a Combined Work under terms of your choice that,
-taken together, effectively do not restrict modification of the
-portions of the Library contained in the Combined Work and reverse
-engineering for debugging such modifications, if you also do each of
-the following:
-
-   a) Give prominent notice with each copy of the Combined Work that
-   the Library is used in it and that the Library and its use are
-   covered by this License.
-
-   b) Accompany the Combined Work with a copy of the GNU GPL and this license
-   document.
-
-   c) For a Combined Work that displays copyright notices during
-   execution, include the copyright notice for the Library among
-   these notices, as well as a reference directing the user to the
-   copies of the GNU GPL and this license document.
-
-   d) Do one of the following:
-
-       0) Convey the Minimal Corresponding Source under the terms of this
-       License, and the Corresponding Application Code in a form
-       suitable for, and under terms that permit, the user to
-       recombine or relink the Application with a modified version of
-       the Linked Version to produce a modified Combined Work, in the
-       manner specified by section 6 of the GNU GPL for conveying
-       Corresponding Source.
-
-       1) Use a suitable shared library mechanism for linking with the
-       Library.  A suitable mechanism is one that (a) uses at run time
-       a copy of the Library already present on the user's computer
-       system, and (b) will operate properly with a modified version
-       of the Library that is interface-compatible with the Linked
-       Version.
-
-   e) Provide Installation Information, but only if you would otherwise
-   be required to provide such information under section 6 of the
-   GNU GPL, and only to the extent that such information is
-   necessary to install and execute a modified version of the
-   Combined Work produced by recombining or relinking the
-   Application with a modified version of the Linked Version. (If
-   you use option 4d0, the Installation Information must accompany
-   the Minimal Corresponding Source and Corresponding Application
-   Code. If you use option 4d1, you must provide the Installation
-   Information in the manner specified by section 6 of the GNU GPL
-   for conveying Corresponding Source.)
-
-  5. Combined Libraries.
-
-  You may place library facilities that are a work based on the
-Library side by side in a single library together with other library
-facilities that are not Applications and are not covered by this
-License, and convey such a combined library under terms of your
-choice, if you do both of the following:
-
-   a) Accompany the combined library with a copy of the same work based
-   on the Library, uncombined with any other library facilities,
-   conveyed under the terms of this License.
-
-   b) Give prominent notice with the combined library that part of it
-   is a work based on the Library, and explaining where to find the
-   accompanying uncombined form of the same work.
-
-  6. Revised Versions of the GNU Lesser General Public License.
-
-  The Free Software Foundation may publish revised and/or new versions
-of the GNU Lesser General Public License from time to time. Such new
-versions will be similar in spirit to the present version, but may
-differ in detail to address new problems or concerns.
-
-  Each version is given a distinguishing version number. If the
-Library as you received it specifies that a certain numbered version
-of the GNU Lesser General Public License "or any later version"
-applies to it, you have the option of following the terms and
-conditions either of that published version or of any later version
-published by the Free Software Foundation. If the Library as you
-received it does not specify a version number of the GNU Lesser
-General Public License, you may choose any version of the GNU Lesser
-General Public License ever published by the Free Software Foundation.
-
-  If the Library as you received it specifies that a proxy can decide
-whether future versions of the GNU Lesser General Public License shall
-apply, that proxy's public statement of acceptance of any version is
-permanent authorization for you to choose that version for the
-Library.
-
diff --git a/display_api/README.md b/display_api/README.md
deleted file mode 100644
index f51996d..0000000
--- a/display_api/README.md
+++ /dev/null
@@ -1,14 +0,0 @@
-# Display Lib
-
-This library's purpose is to ease creation of nodes with one or more displays on sides. For example, signs and clocks. Display can be dynamic and/or different for each node instance.
-
-**Limitations**: This lib uses entities to draw display. This means display has to be vertical. So display nodes rotation are limitated to "upside up" positions.
-
-**Dependancies**:default
-
-**License**: LPGL
-
-**API**: See [API.md](https://github.com/pyrollo/display_modpack/blob/master/display_api/API.md) document please.
-
-For more information, see the [forum topic](https://forum.minetest.net/viewtopic.php?t=19365) at the Minetest forums.
-
diff --git a/display_api/copyright.txt b/display_api/copyright.txt
deleted file mode 100644
index 02b8467..0000000
--- a/display_api/copyright.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-Code by Pierre-Yves Rollo (pyrollo)
-Contributors:
-(gpcf): Compatibility with signs lib
-(Thomas--S): Fix /clearobjects bug
-(12Me21): on_place improvement and code style fixing
-
diff --git a/display_api/depends.txt b/display_api/depends.txt
deleted file mode 100644
index e69de29..0000000
diff --git a/display_api/init.lua b/display_api/init.lua
deleted file mode 100644
index ca7b779..0000000
--- a/display_api/init.lua
+++ /dev/null
@@ -1,269 +0,0 @@
---[[
-    display_api mod for Minetest - Library to add dynamic display
-    capabilities to nodes
-    (c) Pierre-Yves Rollo
-
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
---]]
-
-display_api = {}
-
--- Prefered gap between node and entity
--- Entity positionment is up to mods but it is a good practice to use this
--- variable as spacing between entity and node
-display_api.entity_spacing = 0.002
-
--- Miscelaneous values depending on wallmounted param2
-local wallmounted_values = {
-	[0]={dx=0,  dz=0,  rx=0,  rz=0,  yaw=0,          rotate=0}, -- Should never be used
-		{dx=0,  dz=0,  rx=0,  rz=0,  yaw=0,          rotate=1}, -- Should never be used
-		{dx=-1, dz=0,  rx=0,  rz=-1, yaw=-math.pi/2, rotate=5},
-		{dx=1,  dz=0,  rx=0,  rz=1,  yaw=math.pi/2,  rotate=4},
-		{dx=0,  dz=-1, rx=1,  rz=0,  yaw=0,          rotate=2},
-		{dx=0,  dz=1,  rx=-1, rz=0,  yaw=math.pi,    rotate=3}
-}
-
--- Miscelaneous values depending on facedir param2
-local facedir_values = {
-	[0]={dx=0,  dz=-1, rx=1,  rz=0,  yaw=0,          rotate=1},
-		{dx=-1, dz=0,  rx=0,  rz=-1, yaw=-math.pi/2, rotate=2},
-		{dx=0,  dz=1,  rx=-1, rz=0,  yaw=math.pi,    rotate=3},
-		{dx=1,  dz=0,  rx=0,  rz=1,  yaw=math.pi/2,  rotate=0},
-		-- Forbiden values :
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-		{dx=0, dz=0, rx=0, rz=0, yaw=0, rotate=0},
-	}
-
--- dx/dy = depth vector, rx/ly = right vector, yaw = yaw of entity,
--- rotate = next facedir/wallmount on rotate
-
-local function get_values(node)
-	local ndef = minetest.registered_nodes[node.name]
-
-	if ndef then
-		if ndef.paramtype2 == "wallmounted" then
-			return wallmounted_values[node.param2]
-		end
-		if ndef.paramtype2 == "facedir" then
-			return facedir_values[node.param2]
-		end
-	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
-			local entity = objref:get_luaentity()
-		    if entity and ndef.display_entities[entity.name] and check_entity_pos(pos, objref) then
-				if objrefs[entity.name] then
-				    objref:remove()
-				else
-					objrefs[entity.name] = objref
-				end
-			end
-		end
-	end
-	return objrefs
-end
-
-local function clip_pos_prop(posprop)
-	if posprop then
-		return math.max(-1.5, math.min(1.5, posprop))
-	else
-		return 0
-	end
-end
-
---- (Create and) place display entities according to the node orientation
-local function place_entities(pos)
-	local node = minetest.get_node(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)
-			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)
-	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)
-	end
-end
-
---- On_activate callback for display_api entities. Calls on_display_update callbacks
---- of corresponding node for each entity.
-function display_api.on_activate(entity, staticdata)
-	if entity then
-		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
-			end
-		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)
-	end
-end
-
---- On_place callback for display_api items. Does nothing more than preventing item
---- from being placed on ceiling or ground 
-function display_api.on_place(itemstack, placer, pointed_thing)
-	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}
-	
-	-- 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
-	if ndef then
-		if ndef.paramtype2 == "wallmounted" then
-			param2 = minetest.dir_to_wallmounted(dir)
-		elseif ndef.paramtype2 == "facedir" then
-			param2 = minetest.dir_to_facedir(dir)
-		end
-	end
-	return minetest.item_place(itemstack, placer, pointed_thing, param2)
-end
-
---- 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.
-function display_api.on_destruct(pos)
-	local objrefs = get_entities(pos)
-	
-	for _, objref in pairs(objrefs) do 
-		objref:remove()
-	end
-end
-
--- On_rotate (screwdriver) callback for display_api items. Prevents axis rotation and reorients entities.
-function display_api.on_rotate(pos, node, user, mode, new_param2)
-	if mode ~= 1 then return false end
-
-	local values = get_values(node)
-
-	if values then
-		minetest.swap_node(pos, {name = node.name, param1 = node.param1, param2 = values.rotate})
-		place_entities(pos)
-		return true
-	else
-		return false
-	end
-end
-
---- Creates display entity with some fields and the on_activate callback
-function display_api.register_display_entity(entity_name)
-	if not minetest.registered_entity then
-		minetest.register_entity(':'..entity_name, {
-			collisionbox = { 0, 0, 0, 0, 0, 0 },
-			visual = "upright_sprite",
-			textures = {},
-			on_activate = display_api.on_activate,
-			get_staticdata = function(self)
-				return minetest.serialize({
-					pos = self.pos,
-				})
-			end,
-		})
-	end
-end
-
-minetest.register_lbm({
-	label = "Update display_api entities",
-	name = "display_api:update_entities",
-	run_at_every_load = true,
-	nodenames = {"group:display_modpack_node", "group:display_lib_node"},
-	action = function(pos, node) display_api.update_entities(pos) end,
-})
-
--- Compatibility
-display_lib = display_api