display_modpack/display_lib/API.md

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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,
...
})