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+# Display Lib API
+This document describes Display Lib API. Display Lib allows to add a dynamic display on a node. Node must be wallmounted and Display Lib limits its rotation to vertical positions. 
+## 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\_lib** callbacks.
+	- a **display\_entities** field in node definition containing a entity name indexed table. For each entity, two fields : **depth** indicates the entity position (-0.5 to 0.5) and **on_display_update** is a callback in charge of setting up entity texture.
+
+### Example
+
+		display_lib.register_display_entity("mymod:entity1")
+		display_lib.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 = "wallmounted",
+			...
+			display_entities = {
+				["mymod:entity1"] = { depth = -0.3, 
+					on_display_update = my_display_update1},
+				["mymod:entity1"] = { depth = -0.2, 
+					on_display_update = my_display_update2},
+			},
+			...
+			on_place = display_lib.on_place,
+			on_construct = display_lib.on_construct,
+			on_destruct = display_lib.on_destruct,
+			on_rotate = display_lib.on_rotate,
+			...
+		})
+
+
+