sethome: Do not write empty homes file

[oweals/minetest_game.git] / game_api.txt

Minetest Game API
=================
GitHub Repo: https://github.com/minetest/minetest_game


Introduction
------------

The Minetest Game game offers multiple new possibilities in addition to the Minetest engine's built-in API,
allowing you to add new plants to farming mod, buckets for new liquids, new stairs and custom panes.
For information on the Minetest API, visit https://github.com/minetest/minetest/blob/master/doc/lua_api.txt
Please note:

 * [XYZ] refers to a section the Minetest API
 * [#ABC] refers to a section in this document
 * [pos] refers to a position table `{x = -5, y = 0, z = 200}`


Bucket API
----------

The bucket API allows registering new types of buckets for non-default liquids.

        bucket.register_liquid(
                "default:lava_source",   -- name of the source node
                "default:lava_flowing",  -- name of the flowing node
                "bucket:bucket_lava",    -- name of the new bucket item (or nil if liquid is not takeable)
                "bucket_lava.png",       -- texture of the new bucket item (ignored if itemname == nil)
                "Lava Bucket",           -- text description of the bucket item
                {lava_bucket = 1},       -- groups of the bucket item, OPTIONAL
                false                    -- force-renew, OPTIONAL. Force the liquid source to renew if it has
                                         -- a source neighbour, even if defined as 'liquid_renewable = false'.
                                         -- Needed to avoid creating holes in sloping rivers.
        )

The filled bucket item is returned to the player that uses an empty bucket pointing to the given liquid source.
When punching with an empty bucket pointing to an entity or a non-liquid node, the on_punch of the entity or node will be triggered.


Beds API
--------

        beds.register_bed(
                "beds:bed",    -- Bed name
                def            -- See [#Bed definition]
        )

 * `beds.can_dig(bed_pos)` Returns a boolean whether the bed at `bed_pos` may be dug
 * `beds.read_spawns() `   Returns a table containing players respawn positions
 * `beds.kick_players()`  Forces all players to leave bed
 * `beds.skip_night()`   Sets world time to morning and saves respawn position of all players currently sleeping

### Bed definition

        {
                description = "Simple Bed",
                inventory_image = "beds_bed.png",
                wield_image = "beds_bed.png",
                tiles = {
                        bottom = {'Tile definition'}, -- the tiles of the bottom part of the bed.
                        top = {Tile definition} -- the tiles of the bottom part of the bed.
                },
                nodebox = {
                        bottom = 'regular nodebox',     -- bottom part of bed (see [Node boxes])
                        top = 'regular nodebox',        -- top part of bed (see [Node boxes])
                },
                selectionbox = 'regular nodebox',  -- for both nodeboxes (see [Node boxes])
                recipe = {                                         -- Craft recipe
                        {"group:wool", "group:wool", "group:wool"},
                        {"group:wood", "group:wood", "group:wood"}
                }
        }


Bones API
---------

An ordered list of listnames (default: "main", "craft") of the player inventory,
that will be placed into bones or dropped on player death can be looked up or changed
in `bones.player_inventory_lists`.

e.g. `table.insert(bones.player_inventory_lists, "backpack")`


Creative API
------------

Use `creative.register_tab(name, title, items)` to add a tab with filtered items.
For example,

        creative.register_tab("tools", "Tools", minetest.registered_tools)

is used to show all tools. Name is used in the sfinv page name, title is the
human readable title.

Creative provides `creative.is_enabled_for(name)`, which is identical in
functionality to the engine's `minetest.creative_is_enabled(name)`.
Its use is deprecated and it should also not be overriden.

The contents of `creative.formspec_add` is appended to every creative inventory
page. Mods can use it to add additional formspec elements onto the default
creative inventory formspec to be drawn after each update.

Group overrides can be used for any registered item, node or tool. Use one of
the groups stated below to pick which category it will appear in.

        node = 1      -- Appears in the Nodes category
        tool = 1      -- Appears in the Tools category
        craftitem = 1 -- Appears in the Items category


Chests API
----------

The chests API allows the creation of chests, which have their own inventories for holding items.

`default.chest.get_chest_formspec(pos)`

 * Returns a formspec for a specific chest.
 * `pos` Location of the chest node, e.g `{x = 1, y = 1, z = 1}`

`default.chest.chest_lid_obstructed(pos)`

 * Returns a boolean depending on whether or not a chest has its top obstructed by a solid node.
 * `pos` Location of the chest node, e.g `{x = 1, y = 1, z = 1}`

`default.chest.chest_lid_close(pn)`

 * Closes the chest that a player is currently looking in.
 * `pn` The name of the player whose chest is going to be closed

`default.chest.open_chests`

 * A table indexed by player name to keep track of who opened what chest.
 * Key: The name of the player.
 * Value: A table containing information about the chest the player is looking at.
   e.g `{ pos = {1, 1, 1}, sound = null, swap = "default:chest" }`

`default.chest.register_chest(name, def)`

 * Registers new chest
 * `name` Name for chest e.g. "default:chest"
 * `def`  See [#Chest Definition]

### Chest Definition

        description = "Chest",
        tiles = {
                "default_chest_top.png",
                "default_chest_top.png",
                "default_chest_side.png",
                "default_chest_side.png",
                "default_chest_front.png",
                "default_chest_inside.png"
        }, -- Textures which are applied to the chest model.
        sounds = default.node_sound_wood_defaults(),
        sound_open = "default_chest_open",
        sound_close = "default_chest_close",
        groups = {choppy = 2, oddly_breakable_by_hand = 2},
        protected = false, -- If true, only placer can modify chest.


Doors API
---------

The doors mod allows modders to register custom doors and trapdoors.

`doors.registered_doors[name] = Door definition` 
 * Table of registered doors, indexed by door name 

`doors.registered_trapdoors[name] = Trapdoor definition` 
 * Table of registered trap doors, indexed by trap door name 

`doors.register_door(name, def)`

 * Registers new door
 * `name` Name for door
 * `def`  See [#Door definition]

`doors.register_trapdoor(name, def)`

 * Registers new trapdoor
 * `name` Name for trapdoor
 * `def`  See [#Trapdoor definition]

`doors.register_fencegate(name, def)`

 * Registers new fence gate
 * `name` Name for fence gate
 * `def`  See [#Fence gate definition]

`doors.get(pos)`

 * `pos` A position as a table, e.g `{x = 1, y = 1, z = 1}`
 * Returns an ObjectRef to a door, or nil if the position does not contain a door

    ### Methods

        :open(player)   -- Open the door object, returns if door was opened
        :close(player)  -- Close the door object, returns if door was closed
        :toggle(player) -- Toggle the door state, returns if state was toggled
        :state()        -- returns the door state, true = open, false = closed

    the "player" parameter can be omitted in all methods. If passed then
    the usual permission checks will be performed to make sure the player
    has the permissions needed to open this door. If omitted then no
    permission checks are performed.

`doors.door_toggle(pos, node, clicker)`

 * Toggle door open or shut
 * `pos` Position of the door
 * `node` Node definition
 * `clicker` Player definition for the player that clicked on the door
 
### Door definition

        description = "Door description",
        inventory_image = "mod_door_inv.png",
        groups = {choppy = 2},
        tiles = {"mod_door.png"}, -- UV map.
        -- The front and back of the door must be identical in appearence as they swap on
        -- open/close.
        recipe = craftrecipe,
        sounds = default.node_sound_wood_defaults(), -- optional
        sound_open = sound play for open door, -- optional
        sound_close = sound play for close door, -- optional
        protected = false, -- If true, only placer can open the door (locked for others)
        on_rightclick = function(pos, node, clicker, itemstack, pointed_thing) 
        -- optional function containing the on_rightclick callback, defaults to a doors.door_toggle-wrapper

### Trapdoor definition

        description = "Trapdoor description",
        inventory_image = "mod_trapdoor_inv.png",
        groups = {choppy = 2},
        tile_front = "doors_trapdoor.png", -- the texture for the front and back of the trapdoor
        tile_side = "doors_trapdoor_side.png",
        -- The texture for the four sides of the trapdoor.
        -- The texture should have the trapdoor side drawn twice, in the lowest and highest
        -- 1/8ths of the texture, both upright. The area between is not used.
        -- The lower 1/8th will be used for the closed trapdoor, the higher 1/8th will be used
        -- for the open trapdoor.
        sounds = default.node_sound_wood_defaults(), -- optional
        sound_open = sound play for open door, -- optional
        sound_close = sound play for close door, -- optional
        protected = false, -- If true, only placer can open the door (locked for others)
        on_rightclick = function(pos, node, clicker, itemstack, pointed_thing) 
        -- function containing the on_rightclick callback
        on_rightclick = function(pos, node, clicker, itemstack, pointed_thing) 
        -- function containing the on_rightclick callback

### Fence gate definition

        description = "Wooden Fence Gate",
        texture = "default_wood.png", -- `backface_culling` will automatically be
                                      -- set to `true` if not specified.
        material = "default:wood",
        groups = {choppy = 2, oddly_breakable_by_hand = 2, flammable = 2},
        sounds = default.node_sound_wood_defaults(), -- optional
        on_rightclick = function(pos, node, clicker, itemstack, pointed_thing) 
        -- function containing the on_rightclick callback


Dungeon Loot API
----------------

The mod that places chests with loot in dungeons provides an API to register additional loot.

`dungeon_loot.register(def)`

 * Registers one or more loot items
 * `def` Can be a single [#Loot definition] or a list of them

`dungeon_loot.registered_loot`

 * Table of all registered loot, not to be modified manually

### Loot definition

        name = "item:name",
        chance = 0.5,
        -- ^ chance value from 0.0 to 1.0 that the item will appear in the chest when chosen
        --   Due to an extra step in the selection process, 0.5 does not(!) mean that
        --   on average every second chest will have this item
        count = {1, 4},
        -- ^ table with minimum and maximum amounts of this item
        --   optional, defaults to always single item
        y = {-32768, -512},
        -- ^ table with minimum and maximum heights this item can be found at
        --   optional, defaults to no height restrictions
        types = {"desert"},
        -- ^ table with types of dungeons this item can be found in
        --   supported types: "normal" (the cobble/mossycobble one), "sandstone"
        --   "desert" and "ice"
        --   optional, defaults to no type restrictions


Fence API
---------

Allows creation of new fences with "fencelike" drawtype.

`default.register_fence(name, item definition)`

 Registers a new fence. Custom fields texture and material are required, as
 are name and description. The rest is optional. You can pass most normal
 nodedef fields here except drawtype. The fence group will always be added
 for this node.

### fence definition

        name = "default:fence_wood",
        description = "Wooden Fence",
        texture = "default_wood.png",
        material = "default:wood",
        groups = {choppy = 2, oddly_breakable_by_hand = 2, flammable = 2},
        sounds = default.node_sound_wood_defaults(),


Walls API
---------

The walls API allows easy addition of stone auto-connecting wall nodes.

walls.register(name, desc, texture, mat, sounds)
^ name = "walls:stone_wall". Node name.
^ desc = "A Stone wall"
^ texture = "default_stone.png"
^ mat = "default:stone". Used to auto-generate crafting recipe.
^ sounds = sounds: see [#Default sounds]


Farming API
-----------

The farming API allows you to easily register plants and hoes.

`farming.register_hoe(name, hoe definition)`
 * Register a new hoe, see [#hoe definition]

`farming.register_plant(name, Plant definition)`
 * Register a new growing plant, see [#Plant definition]

`farming.registered_plants[name] = definition`
 * Table of registered plants, indexed by plant name

### Hoe Definition


        {
                description = "",                      -- Description for tooltip
                inventory_image = "unknown_item.png",  -- Image to be used as wield- and inventory image
                max_uses = 30,                         -- Uses until destroyed
                material = "",                         -- Material for recipes
                recipe = {                             -- Craft recipe, if material isn't used
                        {"air", "air", "air"},
                        {"", "group:stick"},
                        {"", "group:stick"},
                }
        }

### Plant definition

        {
                description = "",                      -- Description of seed item
                harvest_description = "",              -- Description of harvest item
                                                       -- (optional, derived automatically if not provided)
                inventory_image = "unknown_item.png",  -- Image to be used as seed's wield- and inventory image
                steps = 8,                             -- How many steps the plant has to grow, until it can be harvested
                -- ^ Always provide a plant texture for each step, format: modname_plantname_i.png (i = stepnumber)
                minlight = 13,                         -- Minimum light to grow
                maxlight = default.LIGHT_MAX           -- Maximum light to grow
        }


Fire API
--------

Add group flammable when registering a node to make fire seek for it.
Add it to an item to make it burn up when dropped in lava or fire.
New node def property:

`on_burn(pos)`

 * Called when fire attempts to remove a burning node.
 * `pos` Position of the burning node.

 `on_ignite(pos, igniter)`

  * Called when Flint and steel (or a mod defined ignitor) is used on a node.
    Defining it may prevent the default action (spawning flames) from triggering.
  * `pos` Position of the ignited node.
  * `igniter` Player that used the tool, when available.


Give Initial Stuff API
----------------------

`give_initial_stuff.give(player)`

^ Give initial stuff to "player"

`give_initial_stuff.add(stack)`

^ Add item to the initial stuff
^ Stack can be an ItemStack or a item name eg: "default:dirt 99"
^ Can be called after the game has loaded

`give_initial_stuff.clear()`

^ Removes all items from the initial stuff
^ Can be called after the game has loaded

`give_initial_stuff.get_list()`

^ returns list of item stacks

`give_initial_stuff.set_list(list)`

^ List of initial items with numeric indices.

`give_initial_stuff.add_from_csv(str)`

^ str is a comma separated list of initial stuff
^ Adds items to the list of items to be given


Players API
-----------

The player API can register player models and update the player's appearance.

* `player_api.register_model(name, def)`
        * Register a new model to be used by players
        * name: model filename such as "character.x", "foo.b3d", etc.
        * def: See [#Model definition]
    * saved to player_api.registered_models

* `player_api.registered_player_models[name]`
         * Get a model's definition
         * see [#Model definition]

* `player_api.set_model(player, model_name)`
        * Change a player's model
        * `player`: PlayerRef
        * `model_name`: model registered with player_api.register_model()

* `player_api.set_animation(player, anim_name [, speed])`
        * Applies an animation to a player
        * anim_name: name of the animation.
        * speed: frames per second. If nil, default from the model is used

* `player_api.set_textures(player, textures)`
        * Sets player textures
        * `player`: PlayerRef
        * `textures`: array of textures, If `textures` is nil the default
          textures from the model def are used

* `player_api.get_animation(player)`
        * Returns a table containing fields `model`, `textures` and `animation`.
        * Any of the fields of the returned table may be nil.
        * player: PlayerRef

* `player_api.player_attached`
        * A table that maps a player name to a boolean.
        * If the value for a given player is set to true, the default player
        animations (walking, digging, ...) will no longer be updated.
        Knockback from damage is also prevented for that player.

### Model Definition

        {
                animation_speed = 30,            -- Default animation speed, in FPS.
                textures = {"character.png", },  -- Default array of textures.
                visual_size = {x = 1, y = 1},    -- Used to scale the model.
                animations = {
                        -- <anim_name> = {x = <start_frame>, y = <end_frame>},
                        foo = {x = 0, y = 19},
                        bar = {x = 20, y = 39},
                        -- ...
                },
                collisionbox = {-0.3, 0.0, -0.3, 0.3, 1.7, 0.3}, -- In nodes from feet position
                stepheight = 0.6, -- In nodes
                eye_height = 1.47, -- In nodes above feet position
        }


TNT API
-------

`tnt.register_tnt(definition)`

^ Register a new type of tnt.

 * `name` The name of the node. If no prefix is given `tnt` is used.
 * `description` A description for your TNT.
 * `radius` The radius within which the TNT can destroy nodes. The default is 3.
 * `damage_radius` The radius within which the TNT can damage players and mobs. By default it is twice the `radius`.
 * `sound` The sound played when explosion occurs. By default it is `tnt_explode`.
 * `disable_drops` Disable drops. By default it is set to false.
 * `ignore_protection` Don't check `minetest.is_protected` before removing a node.
 * `ignore_on_blast` Don't call `on_blast` even if a node has one.
 * `tiles` Textures for node
  * `side`  Side tiles. By default the name of the tnt with a suffix of `_side.png`.
  * `top`  Top tile. By default the name of the tnt with a suffix of `_top.png`.
  * `bottom` Bottom tile. By default the name of the tnt with a suffix of `_bottom.png`.
  * `burning` Top tile when lit. By default the name of the tnt with a suffix of `_top_burning_animated.png".

`tnt.boom(position[, definition])`

^ Create an explosion.

* `position` The center of explosion.
* `definition` The TNT definion as passed to `tnt.register` with the following addition:
 * `explode_center` false by default which removes TNT node on blast, when true will explode center node.

`tnt.burn(position, [nodename])`

^ Ignite node at position, triggering its `on_ignite` callback (see fire mod).
If no such callback exists, fallback to turn tnt group nodes to their
"_burning" variant.
  nodename isn't required unless already known.

To make dropping items from node inventories easier, you can use the
following helper function from 'default':

default.get_inventory_drops(pos, inventory, drops)

^ Return drops from node inventory "inventory" in drops.

* `pos` - the node position
* `inventory` - the name of the inventory (string)
* `drops` - an initialized list

The function returns no values. The drops are returned in the `drops`
parameter, and drops is not reinitialized so you can call it several
times in a row to add more inventory items to it.


`on_blast` callbacks:

Both nodedefs and entitydefs can provide an `on_blast()` callback

`nodedef.on_blast(pos, intensity)`
^ Allow drop and node removal overriding
* `pos` - node position
* `intensity` - TNT explosion measure. larger or equal to 1.0
^ Should return a list of drops (e.g. {"default:stone"})
^ Should perform node removal itself. If callback exists in the nodedef
^ then the TNT code will not destroy this node.

`entitydef.on_blast(luaobj, damage)`
^ Allow TNT effects on entities to be overridden
* `luaobj` - LuaEntityRef of the entity
* `damage` - suggested HP damage value
^ Should return a list of (bool do_damage, bool do_knockback, table drops)
* `do_damage` - if true then TNT mod wil damage the entity
* `do_knockback` - if true then TNT mod will knock the entity away
* `drops` - a list of drops, e.g. {"wool:red"}


Screwdriver API
---------------

The screwdriver API allows you to control a node's behaviour when a screwdriver is used on it.
To use it, add the `on_screwdriver` function to the node definition.

`on_rotate(pos, node, user, mode, new_param2)`

 * `pos` Position of the node that the screwdriver is being used on
 * `node` that node
 * `user` The player who used the screwdriver
 * `mode` screwdriver.ROTATE_FACE or screwdriver.ROTATE_AXIS
 * `new_param2` the new value of param2 that would have been set if on_rotate wasn't there
 * return value: false to disallow rotation, nil to keep default behaviour, true to allow
        it but to indicate that changed have already been made (so the screwdriver will wear out)
 * use `on_rotate = false` to always disallow rotation
 * use `on_rotate = screwdriver.rotate_simple` to allow only face rotation


Sethome API
-----------

The sethome API adds three global functions to allow mods to read a players home position,
set a players home position and teleport a player to home position.

`sethome.get(name)`

 * `name` Player who's home position you wish to get
 * return value: false if no player home coords exist, position table if true

`sethome.set(name, pos)`

 * `name` Player who's home position you wish to set
 * `pos` Position table containing coords of home position
 * return value: false if unable to set and save new home position, otherwise true

`sethome.go(name)`

 * `name` Player you wish to teleport to their home position
 * return value: false if player cannot be sent home, otherwise true


Sfinv API
---------

It is recommended that you read this link for a good introduction to the
sfinv API by its author: https://rubenwardy.com/minetest_modding_book/en/chapters/sfinv.html

### sfinv Methods

**Pages**

* sfinv.set_page(player, pagename) - changes the page
* sfinv.get_page(player) - get the current page name. Will never return nil
* sfinv.get_homepage_name(player) - get the page name of the first page to show to a player
* sfinv.register_page(name, def) - register a page, see section below
* sfinv.override_page(name, def) - overrides fields of an page registered with register_page.
    * Note: Page must already be defined, (opt)depend on the mod defining it.
* sfinv.set_player_inventory_formspec(player) - (re)builds page formspec
             and calls set_inventory_formspec().
* sfinv.get_formspec(player, context) - builds current page's formspec

**Contexts**

* sfinv.get_or_create_context(player) - gets the player's context
* sfinv.set_context(player, context)

**Theming**

* sfinv.make_formspec(player, context, content, show_inv, size) - adds a theme to a formspec
    * show_inv, defaults to false. Whether to show the player's main inventory
    * size, defaults to `size[8,8.6]` if not specified
* sfinv.get_nav_fs(player, context, nav, current_idx) - creates tabheader or ""

### sfinv Members

* pages - table of pages[pagename] = def
* pages_unordered - array table of pages in order of addition (used to build navigation tabs).
* contexts - contexts[playername] = player_context
* enabled - set to false to disable. Good for inventory rehaul mods like unified inventory

### Context

A table with these keys:

* page - current page name
* nav - a list of page names
* nav_titles - a list of page titles
* nav_idx - current nav index (in nav and nav_titles)
* any thing you want to store
    * sfinv will clear the stored data on log out / log in

### sfinv.register_page

sfinv.register_page(name, def)

def is a table containing:

* `title` - human readable page name (required)
* `get(self, player, context)` - returns a formspec string. See formspec variables. (required)
* `is_in_nav(self, player, context)` - return true to show in the navigation (the tab header, by default)
* `on_player_receive_fields(self, player, context, fields)` - on formspec submit.
* `on_enter(self, player, context)` - called when the player changes pages, usually using the tabs.
* `on_leave(self, player, context)` - when leaving this page to go to another, called before other's on_enter

### get formspec

Use sfinv.make_formspec to apply a layout:

        return sfinv.make_formspec(player, context, [[
                list[current_player;craft;1.75,0.5;3,3;]
                list[current_player;craftpreview;5.75,1.5;1,1;]
                image[4.75,1.5;1,1;gui_furnace_arrow_bg.png^[transformR270]
                listring[current_player;main]
                listring[current_player;craft]
                image[0,4.25;1,1;gui_hb_bg.png]
                image[1,4.25;1,1;gui_hb_bg.png]
                image[2,4.25;1,1;gui_hb_bg.png]
                image[3,4.25;1,1;gui_hb_bg.png]
                image[4,4.25;1,1;gui_hb_bg.png]
                image[5,4.25;1,1;gui_hb_bg.png]
                image[6,4.25;1,1;gui_hb_bg.png]
                image[7,4.25;1,1;gui_hb_bg.png]
        ]], true)

See above (methods section) for more options.

### Customising themes

Simply override this function to change the navigation:

        function sfinv.get_nav_fs(player, context, nav, current_idx)
                return "navformspec"
        end

And override this function to change the layout:

        function sfinv.make_formspec(player, context, content, show_inv, size)
                local tmp = {
                        size or "size[8,8.6]",
                        theme_main,
                        sfinv.get_nav_fs(player, context, context.nav_titles, context.nav_idx),
                        content
                }
                if show_inv then
                        tmp[4] = theme_inv
                end
                return table.concat(tmp, "")
        end


Stairs API
----------

The stairs API lets you register stairs and slabs and ensures that they are registered the same way as those
delivered with Minetest Game, to keep them compatible with other mods.

`stairs.register_stair(subname, recipeitem, groups, images, description, sounds, worldaligntex)`

 * Registers a stair
 * `subname`: Basically the material name (e.g. cobble) used for the stair name. Nodename pattern: "stairs:stair_subname"
 * `recipeitem`: Item used in the craft recipe, e.g. "default:cobble", may be `nil`
 * `groups`: See [Known damage and digging time defining groups]
 * `images`: See [Tile definition]
 * `description`: Used for the description field in the stair's definition
 * `sounds`: See [#Default sounds]
 * `worldaligntex`: A bool to set all textures world-aligned. Default false. See [Tile definition]

`stairs.register_slab(subname, recipeitem, groups, images, description, sounds, worldaligntex)`

 * Registers a slab
 * `subname`: Basically the material name (e.g. cobble) used for the slab name. Nodename pattern: "stairs:slab_subname"
 * `recipeitem`: Item used in the craft recipe, e.g. "default:cobble"
 * `groups`: See [Known damage and digging time defining groups]
 * `images`: See [Tile definition]
 * `description`: Used for the description field in the slab's definition
 * `sounds`: See [#Default sounds]
 * `worldaligntex`: A bool to set all textures world-aligned. Default false. See [Tile definition]

`stairs.register_stair_inner(subname, recipeitem, groups, images, description, sounds, worldaligntex, full_description)`

 * Registers an inner corner stair
 * `subname`: Basically the material name (e.g. cobble) used for the stair name. Nodename pattern: "stairs:stair_inner_subname"
 * `recipeitem`: Item used in the craft recipe, e.g. "default:cobble", may be `nil`
 * `groups`: See [Known damage and digging time defining groups]
 * `images`: See [Tile definition]
 * `description`: Used for the description field in the stair's definition with "Inner" prepended
 * `sounds`: See [#Default sounds]
 * `worldaligntex`: A bool to set all textures world-aligned. Default false. See [Tile definition]
 * `full_description`: Overrides the description, bypassing string concatenation. This is useful for translation. (optional)

`stairs.register_stair_outer(subname, recipeitem, groups, images, description, sounds, worldaligntex, full_description)`

 * Registers an outer corner stair
 * `subname`: Basically the material name (e.g. cobble) used for the stair name. Nodename pattern: "stairs:stair_outer_subname"
 * `recipeitem`: Item used in the craft recipe, e.g. "default:cobble", may be `nil`
 * `groups`: See [Known damage and digging time defining groups]
 * `images`: See [Tile definition]
 * `description`: Used for the description field in the stair's definition with "Outer" prepended
 * `sounds`: See [#Default sounds]
 * `worldaligntex`: A bool to set all textures world-aligned. Default false. See [Tile definition]
 * `full_description`: Overrides the description, bypassing string concatenation. This is useful for translation. (optional)

`stairs.register_stair_and_slab(subname, recipeitem, groups, images, desc_stair, desc_slab, sounds, worldaligntex)`

 * A wrapper for stairs.register_stair, stairs.register_slab, stairs.register_stair_inner, stairs.register_stair_outer
 * Uses almost the same arguments as stairs.register_stair
 * `desc_stair`: Description for stair nodes. For corner stairs 'Inner' or 'Outer' will be prefixed
 * `desc_slab`: Description for slab node


Xpanes API
----------

Creates panes that automatically connect to each other

`xpanes.register_pane(subname, def)`

 * `subname`: used for nodename. Result: "xpanes:subname" and "xpanes:subname_{2..15}"
 * `def`: See [#Pane definition]

### Pane definition

        {
                textures = {
                        "texture for front and back",
                        (unused),
                        "texture for the 4 edges"
                }, -- More tiles aren't supported
                groups = {group = rating}, -- Uses the known node groups, see [Known damage and digging time defining groups]
                sounds = SoundSpec,        -- See [#Default sounds]
                recipe = {{"","","","","","","","",""}}, -- Recipe field only
                use_texture_alpha = true, -- Optional boolean (default: `false`) for colored glass panes
        }


Raillike definitions
--------------------

The following nodes use the group `connect_to_raillike` and will only connect to
raillike nodes within this group and the same group value.
Use `minetest.raillike_group(<Name>)` to get the group value.

| Node type             | Raillike group name
|-----------------------|---------------------
| default:rail          | "rail"
| tnt:gunpowder         | "gunpowder"
| tnt:gunpowder_burning | "gunpowder"

Example:
If you want to add a new rail type and want it to connect with default:rail,
add `connect_to_raillike=minetest.raillike_group("rail")` into the `groups` table
of your node.


Default sounds
--------------

Sounds inside the default table can be used within the sounds field of node definitions.

 * `default.node_sound_defaults()`
 * `default.node_sound_stone_defaults()`
 * `default.node_sound_dirt_defaults()`
 * `default.node_sound_sand_defaults()`
 * `default.node_sound_wood_defaults()`
 * `default.node_sound_leaves_defaults()`
 * `default.node_sound_glass_defaults()`
 * `default.node_sound_metal_defaults()`


Default constants
-----------------

`default.LIGHT_MAX`  The maximum light level (see [Node definition] light_source)


GUI and formspecs
-----------------

`default.get_hotbar_bg(x, y)`

 * Get the hotbar background as string, containing the formspec elements
 * x: Horizontal position in the formspec
 * y: Vertical position in the formspec

`default.gui_bg`

 * Deprecated, remove from mods.

`default.gui_bg_img`

 * Deprecated, remove from mods.

`default.gui_slots`

 * Deprecated, remove from mods.

`default.gui_survival_form`

 * Entire formspec for the survival inventory

`default.get_furnace_active_formspec(fuel_percent, item_percent)`

 * Get the active furnace formspec using the defined GUI elements
 * fuel_percent: Percent of how much the fuel is used
 * item_percent: Percent of how much the item is cooked

`default.get_furnace_inactive_formspec()`

 * Get the inactive furnace formspec using the defined GUI elements


Leafdecay
---------

To enable leaf decay for leaves when a tree is cut down by a player,
register the tree with the default.register_leafdecay(leafdecaydef)
function.

If `param2` of any registered node is ~= 0, the node will always be
preserved. Thus, if the player places a node of that kind, you will
want to set `param2 = 1` or so.

The function `default.after_place_leaves` can be set as
`after_place_node of a node` to set param2 to 1 if the player places
the node (should not be used for nodes that use param2 otherwise
(e.g. facedir)).

If the node is in the `leafdecay_drop` group then it will always be
dropped as an item.

`default.register_leafdecay(leafdecaydef)`

`leafdecaydef` is a table, with following members:
        {
                trunks = {"default:tree"}, -- nodes considered trunks
                leaves = {"default:leaves", "default:apple"},
                        -- nodes considered for removal
                radius = 3, -- radius to consider for searching
        }

Note: all the listed nodes in `trunks` have their `on_after_destruct`
callback overridden. All the nodes listed in `leaves` have their
`on_timer` callback overridden.


Dyes
----

Minetest Game dyes are registered with:

    groups = {dye = 1, color_<color> = 1},

To make recipes that will work with dyes from many mods, define them using the
dye group and the color groups.

Dye color groups:

 * `color_white`
 * `color_grey`
 * `color_dark_grey`
 * `color_black`
 * `color_red`
 * `color_pink`
 * `color_orange`
 * `color_brown`
 * `color_yellow`
 * `color_green`
 * `color_dark_green`
 * `color_blue`
 * `color_cyan`
 * `color_violet`
 * `color_magenta`

Example of one shapeless recipe using the dye group and a color group:

        minetest.register_craft({
                type = "shapeless",
                output = "<mod>:item_yellow",
                recipe = {"<mod>:item_no_color", "group:dye,color_yellow"},
        })


Trees
-----

 * `default.grow_tree(pos, is_apple_tree)`
  * Grows a mgv6 tree or apple tree at pos

 * `default.grow_jungle_tree(pos)`
  * Grows a mgv6 jungletree at pos

 * `default.grow_pine_tree(pos)`
  * Grows a mgv6 pinetree at pos

 * `default.grow_new_apple_tree(pos)`
  * Grows a new design apple tree at pos

 * `default.grow_new_jungle_tree(pos)`
  * Grows a new design jungle tree at pos

 * `default.grow_new_pine_tree(pos)`
  * Grows a new design pine tree at pos

 * `default.grow_new_snowy_pine_tree(pos)`
  * Grows a new design snowy pine tree at pos

 * `default.grow_new_acacia_tree(pos)`
  * Grows a new design acacia tree at pos

 * `default.grow_new_aspen_tree(pos)`
  * Grows a new design aspen tree at pos

 * `default.grow_bush(pos)`
  * Grows a bush at pos

 * `default.grow_acacia_bush(pos)`
  * Grows an acaia bush at pos

 * `default.grow_pine_bush(pos)`
  * Grows a pine bush at pos

 * `default.grow_blueberry_bush(pos)`
  * Grows a blueberry bush at pos


Carts
-----

        carts.register_rail(
                "mycarts:myrail", -- Rail name
                nodedef,          -- standard nodedef
                railparams        -- rail parameter struct (optional)
        )

        railparams = {
                on_step(obj, dtime), -- Event handler called when
                                     -- cart is on rail
                acceleration, -- integer acceleration factor (negative
                              -- values to brake)
        }

        The event handler is called after all default calculations
        are made, so the custom on_step handler can override things
        like speed, acceleration, player attachment. The handler will
        likely be called many times per second, so the function needs
        to make sure that the event is handled properly.


Key API
-------

The key API allows mods to add key functionality to nodes that have
ownership or specific permissions. Using the API will make it so
that a node owner can use skeleton keys on their nodes to create keys
for that node in that location, and give that key to other players,
allowing them some sort of access that they otherwise would not have
due to node protection.

To make your new nodes work with the key API, you need to register
two callback functions in each nodedef:


`on_key_use(pos, player)`
 * Is called when a player right-clicks (uses) a normal key on your
 * node.
 * `pos` - position of the node
 * `player` - PlayerRef
 * return value: none, ignored

The `on_key_use` callback should validate that the player is wielding
a key item with the right key meta secret. If needed the code should
deny access to the node functionality.

If formspecs are used, the formspec callbacks should duplicate these
checks in the metadata callback functions.


`on_skeleton_key_use(pos, player, newsecret)`

 * Is called when a player right-clicks (uses) a skeleton key on your
 * node.
 * `pos` - position of the node
 * `player` - PlayerRef
 * `newsecret` - a secret value(string)
 * return values:
 * `secret` - `nil` or the secret value that unlocks the door
 * `name` - a string description of the node ("a locked chest")
 * `owner` - name of the node owner

The `on_skeleton_key_use` function should validate that the player has
the right permissions to make a new key for the item. The newsecret
value is useful if the node has no secret value. The function should
store this secret value somewhere so that in the future it may compare
key secrets and match them to allow access. If a node already has a
secret value, the function should return that secret value instead
of the newsecret value. The secret value stored for the node should
not be overwritten, as this would invalidate existing keys.

Aside from the secret value, the function should retun a descriptive
name for the node and the owner name. The return values are all
encoded in the key that will be given to the player in replacement
for the wielded skeleton key.

if `nil` is returned, it is assumed that the wielder did not have
permissions to create a key for this node, and no key is created.

`default.register_craft_metadata_copy(ingredient, result)`
----------------------------------------------------------

This function registers a shapeless recipe that takes `ingredient`
and `result` as input and outputs `result`.

The metadata of the input `result` is copied to the output `result`.