Minetest mod library: poschangelib

• version 0.5
• Licence LGPLv2 or, at your discretion, any later version.

This lib adds utilities to watch player movements and trigger things when they are spotted moving.

It does nothing by itself but aim to ease event based upon players or item moving.

All positions are rounded to node position (integer coordinates).

Summary

• General warning
• Watch players' movements
• Watch players walking on particular nodes
• Add _on_walk on nodes
• Set stomping on nodes
• Add footprints
• Configuration/Performances tweaking
• Debugging

General warning

This mod may be resources consuming. The mods relying upon this lib should use small functions not to decrease the server performances too much.

The more functions are provided, the more the server can lag (but probably a little less than running every of them without the lib).

Watch player's movements

Use poschangelib.add_player_pos_listener(name, my_callback)

Name is the identifier the listener, to use in remove_player_pos_listener. You should follow the naming convention like for node names. See http://dev.minetest.net/Intro

The my_callback is a function that takes 4 arguments: the player, last known position, new position and some metadata.

On first call (once a player joins) the last known position will be nil. If your listener does something in that case, it will be called shortly after the player reconnects. It may so be triggered twice from the same position, before leaving and after joining.

Be aware that the new position may not always be a neighbour of the old one. When on teleporting, programatic moves with setpos or moving fast it may be far away.

Quick code sample:

local function my_callback(player, old_pos, new_pos, meta) if old_pos == nil then minetest.chat_send_player(player:get_player_name(), 'Welcome to the world!') else minetest.chat_send_player(player:get_player_name(), "You are now at x:" .. new_pos.x .. ", y:" .. new_pos.y .. "z:" .. new_pos.z) end end poschangelib.add_player_pos_listener("sample:pos_listener", my_callback)

Watch player walking on particular nodes, the rough way

Use poschangelib.add_player_walk_listener(name, my_callback, nodenames)

The name is used in the same way as for player position listeners. It aims at reducing the number of time the stepped node is fetched to share it accross all listeners.

The callback is a function that takes 4 arguments: the player, the position, the node stepped on and that node description. See http://dev.minetest.net/minetest.register_node for node description.

You can register the listener for a list of node name or groups, in the same way you do it to register an ABM. See http://dev.minetest.net/register_abm

For example: local function flop(player, pos, node, desc) minetest.chat_send_player(player:get_player_name(), 'Flop flop') end poschangelib.add_player_walk_listener('sample:flop', flop, {'default:dirt_with_grass'})

local function toptop(player, pos, node, desc) minetest.chat_send_player(player:get_player_name(), 'Top top top') end poschangelib.add_player_walk_listener('sample:top', toptop, {'group:choppy'})

Watch player walking on particular nodes, the fine way

When dealing with non-filled blocks like slab and snow, the trigger may give some false positives and be triggered twice for the same movement. This is because you can hook to a nearby full block and stand above snow without touching it, which messes with the walk detection of regular blocks (which checks for walkable nodes).

Moreover it can't be enough. With the example of slabs, lower slabs can be triggered by hanging to a nearby full block and should not be triggered that way, but higher slabs must be considered like full blocks, because the player is walking on the above node.

If you don't require an accurate checking, just ignore the call when trigger_meta.redo is true like in the example below:

local function toptop(player, pos, node, desc, trigger_meta) if trigger_meta.redo then return end ... do your regular stuff end

If you want to make fine position checking, you can use the 5th argument which holds the trigger metadata. See "More on metadata" below.

Add _on_walk_over to nodes

This behaviour is ported from the walkover mod only for compatibility. https://forum.minetest.net/viewtopic.php?f=9&t=15991

A new node property can be added in node definitions: _on_walk_over =

This function takes the position, the node and the player as argument.

For compatibility with walkover, you can use on_walk_over (without the underscore prefix) but it is discouraged as stated in the forum post. This support may be dropped at any time when most mods have updated the name.

_on_walk is affected by the same issue about non-filled nodes. You can use the 4th argument to check the trigger metadata to adjust your callback.

More on metadata

The metadata are a table that can contain the following elements:

interpolated Is true when the position was assumed and not observed. Most of the time because the player moved too fast to check all nodes in real time.

teleported Is true when the player was moving too fast. The interpolation is then not computed.

player_pos Is set for walk listeners, it contains the player's position. Not set when interpolated.

source Contains the name of the node or group that triggered the walk listener. This is one of thoses passed on registration.

source_level Contains the level of the group when source is a node group.

redo Is true when it was detected that the listener was previously called on that position.

covered Is true when a non-walkable non-air node is present above this node (like grass). Covered is accurate only with full nodes. For half-filled node, you'll have to check by hand.

Set stomping on nodes

Stomping is a dedicated subset of walk listeners that allows to replace a node by an other when a player walks on it.

It is required to be able to declare multiple outputs without messing with one another. And just for ease of use.

Stomping are registered with poschangelib.register_stomp. It takes 3 parameters:

poschangelib.register_stomp:

• source_node_name: the name of the node that can be stomped. It can be a table with multiple node names to declare the same stomping behaviour to multiple nodes at once.
• stomp_node_name: the name of the replacement node, or a function.
• stomp_desc: stomping parameters.

The stomp description is a table that can contains the following set of keys:

stomp_desc:

• chance: inverted chance that the stomp occurs (default 1)
• duration: time in second after which the stomp reverts. When not set, the stomp is forever. If set it will override duration_min and duration_max.
• duration_min: same as duration but to add some randomness for each node.
• duration_max: same as duration but to add some randomness for each node.
• priority: the priority rank. The lower, the more important it is (default 100)
• name: name that is used as walk listener name. Default is to and is rather indigest but probably unique. It has no default when using a function in stomp_node_name and must be set.
• source_node: set it if you want the stomp to revert to an other node than the original.

When multiple stompings are registered for the same node, only the first triggered is applied. This is when priority comes into play. When a player walks on a node that can be stomped, a roll is made for each stomp in order of priority (the lowest priority first). If the roll succeeds, the node is replaced and the next stomps are not run.

When using a function instead of a stomp node name, this function is a regular player walk listener. It must return a node or nil (i.e. {name = , param = etc}). If it returns nil, the stomp is not done and the priority check is not stopped (see just below). When using only a node name, all other node values are kept.

Add footprints

Use poschangelib.register_footprint to quickly register footprinted nodes and the stomping associated to it. The function takes 2 parameters:

register_footprint:

• node_name: the name of the node to extend, or a table to register multiple footprints with the same stomp_desc
• stomp_desc: see above.

The stomp description can have dedicated keys and values:

• footprint_texture: set it to use an other texture than the one embedded.

A new node will be registered with most of it's description copied from the original node. It's top texture will have the footprint layer on it and the stomping behaviour will be automatically created.

poschangelib.register_footprint returns the footprinted node name(s). If you pass nested tables in node_name, the same nesting is returned.

Configuration/Performances tweaking

The lib checks for position at a given interval. Default is every 0.3 seconds.

This can be changed by setting poschangelib.check_interval in minetest.conf or in advanced settings.

Setting a lower value will make the lib more accurate but will be more demanding on resources (down to 0.05 which is a every server tick).

If the server is lagging, try increasing the interval. If the server can afford more precise checks you can decrease the value.

Debugging

With the server privileges, you can list available stompings for the node you are currently on. Use /stomp.

If there is only one stomping available, it is triggered. If there are multiple stomps, it prints the list of stomping names. Use /stomp X to trigger the Xth stomp.