DFHack modding guide

What is the difference between a script and a mod?

Well, sometimes there is no difference. A mod is anything you add to the game, which can be graphics overrides, content in the raws, DFHack scripts, or all of the above. There are already resources out there for raws modding, so this guide will focus more on scripts, both standalone and as an extension to raws-based mods.

A DFHack script is a Lua file that can be run as a command in DFHack. Scripts can do pretty much anything, from displaying information to enforcing new game mechanics. If you don’t already know Lua, there’s a great primer at lua.org.

Why not just mod the raws?

It depends on what you want to do. Some mods are better to do in just the raws. You don’t need DFHack to add a new race or modify attributes. However, DFHack scripts can do many things that you just can’t do in the raws, like make a creature that trails smoke or launch a unit into the air when they are hit with a certain type of projectile. Some things could be done in the raws, but a script is better (e.g. easier to maintain, easier to extend, and/or not prone to side-effects). A great example is adding a syndrome when a reaction is performed. If done in the raws, you have to create an exploding boulder as an intermediary to apply the syndrome. DFHack scripts can add the syndrome directly and with much more flexibility. In the end, complex mods will likely require a mix of raw modding and DFHack scripting.

The structure of a mod

In the example below, we’ll use a mod name of example-mod. I’m sure your mods will have more creative names! Mods have a basic structure that looks like this:

info.txt
graphics/...
objects/...
blueprints/...
scripts_modactive/example-mod.lua
scripts_modactive/internal/example-mod/...
scripts_modinstalled/...
README.md (optional)

Let’s go through that line by line.

• The info.txt file contains metadata about your mod that DF will

  display in-game. You can read more about this file in the Official DF Modding Guide. It would be a good idea to give your mod a dfhack tag so players can indentify it as requiring DFHack when they subscribe to it on the DF Steam workshop.

• Modifications to the game raws (potentially with

  custom raw tokens) go in the graphics/ and objects/ folders. You can read more about the files that go in these directories on the Modding wiki page.

• Any quickfort blueprints included with your mod go in the

  blueprints folder. Note that your mod can just be blueprints and the info.txt file if you like. See the next section for an example.

• A control script in scripts_modactive/ directory that handles

  system-level event hooks (e.g. reloading state when a world is loaded), registering overlays, and enabling/disabling your mod. You can put other scripts in this directory as well if you want them to appear as runnable DFHack commands when your mod is active for the current world. Lua modules that your main scripts use, but which don’t need to be directly runnable by the player, should go in a subdirectory under scripts_modactive/internal/ so they don’t show up in the DFHack launcher command autocomplete lists.

• Scripts that you want to be available before a world is loaded (i.e. on the

  DF title screen) or that you want to be runnable in any world, regardless of whether your mod is active, should go in the scripts_modinstalled/ folder. You can also have an internal/ subfolder in here for private modules if you like.

• Finally, a README.md file that has more information about your mod.

  If you develop your mod using version control (recommended!), that README.md file can also serve as your git repository documentation.

These files end up in a subdirectory under mods/ when players copy them in or install them from the Steam Workshop, and in data/installed_mods/ when the mod is selected as “active” for the first time.

DFHack will discover scripts in your mod’s scripts_modinstalled/ directory and other DFHack-relevant data files (like blueprints) regardless of whether the mod has been marked “active” for any player world.

What if I just want to distribute quickfort blueprints?

For this, all you need is info.txt and your blueprints.

Your info.txt could look something like this:

[ID:drooble_blueprints]
[NUMERIC_VERSION:1]
[DISPLAYED_VERSION:1.0.0]
[EARLIEST_COMPATIBLE_NUMERIC_VERSION:1]
[EARLIEST_COMPATIBLE_DISPLAYED_VERSION:1.0.0]
[AUTHOR:Drooble]
[NAME:Drooble's blueprints]
[DESCRIPTION:Useful quickfort blueprints for any occasion.]
[STEAM_TITLE:Drooble's blueprints]
[STEAM_DESCRIPTION:Useful quickfort blueprints for any occasion.]
[STEAM_TAG:dfhack]
[STEAM_TAG:quickfort]
[STEAM_TAG:blueprints]

and your blueprints, which could be .csv or .xlsx files, would go in the blueprints/ subdirectory. If you add blueprint file named blueprints/bedrooms.csv, then it will be shown to players as drooble_blueprints/bedrooms.csv in quickfort and gui/quickfort. The “drooble_blueprints” prefix comes from the mod ID specified in info.txt.

What if I just want to distribute a simple standalone script?

If your mod is just a script with no raws modifications, all you need is:

info.txt
scripts_modinstalled/yourscript.lua
README.md (optional)

Adding your script to the scripts_modinstalled/ folder will allow DFHack to find it and add your mod to the Script paths. Your script will be runnable from the title screen and in any loaded world, regardless of whether your mod is explicitly “active”.

A mod-maker’s development environment

Create a folder for development somewhere outside your Dwarf Fortress installation directory (e.g. /path/to/mymods/). If you work on multiple mods, you might want to make a subdirectory for each mod.

If you have changes to the raws, you’ll still have to copy them into DF’s data/installed_mods/ folder to have them take effect, but you can set things up so that scripts are run directly from your dev directory. You can edit your scripts in your dev directory and have the changes available in the game immediately: no copying, no restarting.

How does this magic work? Just add a line like this to your dfhack-config/script-paths.txt file:

+/path/to/mymods/example-mod/scripts_modinstalled

Then that directory will be searched when you run DFHack commands from inside the game. The + at the front of the path means to search that directory first, before any other script directory (like hack/scripts or other versions of your mod in the DF mod folders).

The structure of the game

“The game”, that is, all the Dwarf Fortress state, is in the global variable df. Most of the information relevant to a script is found in df.global.world, which contains data like the lists of active items and units, whether to reindex pathfinding, et cetera. Also relevant to us are the various data types found in the game, e.g. df.pronoun_type which we will be using in this guide. We’ll explore more of the game structures below.

Your first script

So! It’s time to write your first script. This section will walk you through how to make a script that will get the pronoun type of the currently selected unit. If you’re not familiar with Lua script syntax, maybe skim through some topics in the manual first.

First line, we get a reference to an in-game unit:

local unit = dfhack.gui.getSelectedUnit()

If no unit is selected by the player in the DF UI, unit will be nil and an error message will be printed.

If unit is nil, we don’t want the script to run anymore:

if not unit then
    return
end

Now, the field unit.sex is an integer, but each integer corresponds to a string value (“it”, “she”, or “he”). We get this value by indexing the bidirectional map df.pronoun_type. Indexing the other way, with one of the strings, will yield its corresponding number. So:

local pronounTypeString = df.pronoun_type[unit.sex]
print(pronounTypeString)

Simple. The entire script altogether looks like this:

local unit = dfhack.gui.getSelectedUnit()
if not unit then
    return
end
local pronounTypeString = df.pronoun_type[unit.sex]
print(pronounTypeString)

Save the text as a .lua file in your own scripts directory and run it from gui/launcher when a unit is selected in the Dwarf Fortress UI.

DFHack provides a vast library of functionality that make it easier to interact with the game state. When you start asking yourself “How do I get/do X”, search through the DFHack Lua API Reference for relevant functions and look through existing scripts for examples.

Exploring DF state

So how could you have known about the field and type we just used? Well, there are two main tools for discovering the various fields in the game’s data structures. The first is the df-structures repository that contains XML files describing the layouts of the game’s structures. These are complete, but difficult to read (for a human). The second option is the gui/gm-editor interface, an interactive data explorer. You can run the script while objects like units are selected to view the data within them. Press ? while the script is active to view help.

Familiarising yourself with the many structs of the game will help with ideas immensely, and you can always ask for help in the right places.

Reading and writing files and other persistent state

There are several locations and APIs that a mod might need to read or store data:

Global state that is not world-specific should be stored in the directory returned by the scriptmanager.getModStatePath() function. JSON is a convenient format for this kind of stored state, and DFHack provides facilities for reading and writing JSON data. For example:

local json = require('json')
local scriptmanager = require('script-manager')
local path = scriptmanager.getModStatePath('mymodname')
config = config or json.open(path .. 'settings.json')

-- modify state in the config.data table and persist it when it changes with
-- config:write()

State that should be saved with a world or a specific fort within that world should use Persistent configuration storage API. You can attach a state change hook for new world loaded where you can load the state, which often includes whether the mod itself is enabled (if the mod can be dynamically enabled/disabled – see the Enabling and disabling scripts for more details). For example:

--@ enable=true
--@ module=true

local utils = require('utils')

local GLOBAL_KEY = 'mymodname'

local function get_default_state()
    return {
        enabled=false,
        somevar=0,
        somesubtable={
            someothervar=0,
        },
    }
end
state = state or get_default_state()

-- implement the enabled API so DFHack can read this script's status
function isEnabled()
    return state.enabled
end

local function persist_state()
    dfhack.persistent.saveSiteData(GLOBAL_KEY, state)
end

local function do_enable()
    -- initialization tasks, such as hooking events
end

local function do_disable()
    -- cleanup tasks, such as removing event hooks
end

dfhack.onStateChange[GLOBAL_KEY] = function(sc)
    if sc == SC_MAP_UNLOADED then
        do_disable()

        -- ensure our mod doesn't run when a different
        -- world is loaded where we are *not* active
        dfhack.onStateChange[GLOBAL_KEY] = nil

        return
    end

    if sc ~= SC_MAP_LOADED or not dfhack.world.isFortressMode() then
        return
    end

    -- retrieve state saved in game. merge with default state so config
    -- saved from previous versions can pick up newer defaults.
    state = get_default_state()
    utils.assign(state, dfhack.persistent.getSiteData(GLOBAL_KEY, state))
    if state.enabled then
        do_enable()
    end
end

Finally, you may have distributed data files with your mod that you need to read at runtime. Your mod directory should be treated as read-only since data there is not backed up. Use the script-manager API to get the path to your mod data and the json (or any other file I/O) API as needed. For example:

local scriptmanager = require('script-manager')

local GLOBAL_KEY = 'mymodname'

local function read_bulk_data_db()
    local mod_source_path = scriptmanager.getModSourcePath(GLOBAL_KEY)
    -- read data from files in the mod directory
    return ...
end

bulk_data_db = bulk_data_db or read_bulk_data_db()

If you want to store state in the savegame so that it is associated with the current world/fort/adventure, use the Persistent configuration storage API. or in the fuller example later in this guide.

Reacting to events

The common method for injecting new behaviour into the game is to define a callback function and get it called when something interesting happens. DFHack provides two libraries for this, repeat-util and eventful. repeat-util is used to run a function once per a configurable number of frames (paused or unpaused), ticks (unpaused), in-game days, months, or years. If you need to be aware the instant something happens, you’ll need to run a check once a tick. Be careful not to do this gratuitously, though, since running callbacks too often can significantly slow down the game!

eventful, on the other hand, is much more performance-friendly since it will only call your callback when a relevant event happens, like a reaction occuring, a job being completed, or a projectile moving to a new tile.

To get something to run once every 1000 ticks, we can call repeat-util.scheduleEvery(). First, we load the module:

local repeatUtil = require('repeat-util')

Both repeat-util and eventful require keys for registered callbacks. You should use something unique, like your mod id:

local GLOBAL_KEY = 'mymodname'

Then, we pass the key, amount of time units between function calls, what the time units are, and finally the callback function itself:

repeatUtil.scheduleEvery(GLOBAL_KEY, 1000, 'ticks', function()
    -- Do something like iterating over all active units and
    -- check for something interesting
    for _, unit in ipairs(df.global.world.units.active) do
        ...
    end
end)

eventful is slightly more involved. First get the module:

local eventful = require('plugins.eventful')

eventful contains a table for each event which you populate with functions. Each function in the table is then called with the appropriate arguments when the event occurs. So, for example, to print the position of a moving (item) projectile:

eventful.onProjItemCheckMovement[GLOBAL_KEY] = function(projectile)
    print(projectile.cur_pos.x, projectile.cur_pos.y,
          projectile.cur_pos.z)
end

Check out the full list of supported events to see what else you can react to with eventful.

Now, you may have noticed that you won’t be able to register multiple callbacks with a single key named after your mod. You can, of course, call all the functions you want from a single registered callback. Alternately, you can create multiple callbacks using different keys, using your mod ID as a key name prefix. If you do register multiple callbacks, though, there are no guarantees about the call order.

Custom raw tokens

In this section, we are going to use custom raw tokens applied to a reaction to transfer the material of a reagent to a product as a handle improvement (like on artifact buckets). As a second example, we are going to make boots that make units go faster when worn.

First, let’s define raws for a custom crossbow with its own custom reaction. The crossbow:

[ITEM_WEAPON:ITEM_WEAPON_CROSSBOW_SIEGE]
    [NAME:crossbow:crossbows]
    [SIZE:600]
    [SKILL:HAMMER]
    [RANGED:CROSSBOW:BOLT]
    [SHOOT_FORCE:4000]
    [SHOOT_MAXVEL:800]
    [TWO_HANDED:0]
    [MINIMUM_SIZE:17500]
    [MATERIAL_SIZE:4]
    [ATTACK:BLUNT:10000:4000:bash:bashes:NO_SUB:1250]
        [ATTACK_PREPARE_AND_RECOVER:3:3]
    [SIEGE_CROSSBOW_MOD_FIRE_RATE_MULTIPLIER:2] custom token (you'll see)

The reaction to make it (you would add the reaction and not the weapon to an entity raw):

[REACTION:MAKE_SIEGE_CROSSBOW]
    [NAME:make siege crossbow]
    [BUILDING:BOWYER:NONE]
    [SKILL:BOWYER]
    [REAGENT:mechanism 1:2:TRAPPARTS:NONE:NONE:NONE]
    [REAGENT:bar:150:BAR:NONE:NONE:NONE]
        [METAL_ITEM_MATERIAL]
    [REAGENT:handle 1:1:BLOCKS:NONE:NONE:NONE] wooden handles
        [ANY_PLANT_MATERIAL]
    [REAGENT:handle 2:1:BLOCKS:NONE:NONE:NONE]
        [ANY_PLANT_MATERIAL]
    [SIEGE_CROSSBOW_MOD_TRANSFER_HANDLE_MATERIAL_TO_PRODUCT_IMPROVEMENT:1]
        another custom token
    [PRODUCT:100:1:WEAPON:ITEM_WEAPON_CROSSBOW_SIEGE:GET_MATERIAL_FROM_REAGENT:bar:NONE]

So, we are going to use the eventful module to react when this crossbow is crafted, allowing us to inject the logic that will add the handle improvement.

First, require the modules we are going to use:

local eventful = require('plugins.eventful')
local customRawTokens = require('custom-raw-tokens')

and attach a callback to the event:

local GLOBAL_KEY = 'mymodname'

local function reaction_handler(reaction, reactionProduct, unit,
        inputItems, inputReagents, outputItems)
    -- we'll be defining the body of this function below
end

eventful.onReactionComplete[GLOBAL_KEY] = reaction_handler

Now let’s look at the reaction_handler function and give it some logic. First, we check to see if it the reaction that just happened is relevant to this callback:

if not customRawTokens.getToken(reaction,
    'SIEGE_CROSSBOW_MOD_TRANSFER_HANDLE_MATERIAL_TO_PRODUCT_IMPROVEMENT')
then
    return
end

Then, we check the reagents for names that start with “handle”. For those reagents, we get the corresponding item and add a handle improvement:

for i, reagent in ipairs(inputReagents) do
    if reagent.code:startswith('handle') then
        -- Found handle reagent
        local item = inputItems[i]
        local improv = df.itemimprovement_itemspecificst:new()
        improv.mat_type, improv.mat_index = item.mat_type, item.mat_index
        improv.type = df.itemimprovement_specific_type.HANDLE
        outputItems[1].improvements:insert('#', improv)
    end
end

Let’s also modify the fire rate of our siege crossbow according to the custom token we added to the item definition in the raws:

eventful.onProjItemCheckMovement[GLOBAL_KEY] = function(projectile)
    if projectile.distance_flown > 0 then
        -- don't make this adjustment more than once
        return
    end

    local firer = projectile.firer
    if not firer then
        return
    end

    local weapon = df.item.find(projectile.bow_id)
    if not weapon then
        return
    end

    local multiplier = tonumber(customRawTokens.getToken(
            weapon.subtype,
            'SIEGE_CROSSBOW_MOD_FIRE_RATE_MULTIPLIER')) or 1
    firer.counters.think_counter = math.floor(
            firer.counters.think_counter * multiplier)
end

Now, let’s see how we could make some “pegasus boots”. First, let’s define the item in the raws:

[ITEM_SHOES:ITEM_SHOES_BOOTS_PEGASUS]
    [NAME:pegasus boot:pegasus boots]
    [ARMORLEVEL:1]
    [UPSTEP:1]
    [METAL_ARMOR_LEVELS]
    [LAYER:OVER]
    [COVERAGE:100]
    [LAYER_SIZE:25]
    [LAYER_PERMIT:15]
    [MATERIAL_SIZE:2]
    [METAL]
    [LEATHER]
    [HARD]
    [PEGASUS_BOOTS_MOD_FOOT_MOVEMENT_TIMER_REDUCTION_PER_TICK:2] custom raw token
        (you don't have to comment the custom token every time,
        but it does clarify what it is)

Then, let’s define a function that will implement the logic associated with the boots:

local function do_pegasus()
    for _,unit in ipairs(df.global.world.units.active) do
        local amount = 0
        for _,inv_entry in ipairs(unit.inventory) do
            if inv_entry.mode == df.unit_inventory_item.T_mode.Worn then
                local reduction = customRawTokens.getToken(
                        inv_entry.item,
                        'PEGASUS_BOOTS_MOD_FOOT_MOVEMENT_TIMER_REDUCTION_PER_TICK')
                amount = amount + (tonumber(reduction) or 0)
            end
        end
        -- Subtract amount from on-foot movement timers if not on ground
        if not unit.flags1.on_ground then
            dfhack.units.subtractActionTimers(unit, amount,
                    df.unit_action_type_group.MovementFeet)
        end
    end
end

Finally, we can schedule the callback to be run once a tick using the repeat-util module:

repeatUtil.scheduleEvery(GLOBAL_KEY, 1, 'ticks', do_pegasus)

Note that the do_pegasus function as written here is extremely inefficient. In a real mod, you would likely want to cache which units are equipping pegasus boots so you don’t have to scan every inventory item of every active unit on every tick.

Putting it all together

Ok, you’re all set up! Now, let’s take a look at an example scripts_modinstalled/example-mod.lua file:

-- main file for the example-mod mod

-- these lines indicate that the script supports the "enable"
-- API so you can start it by running "enable example-mod" and
-- stop it by running "disable example-mod"
--@ module=true
--@ enable=true

-- this is the help text that will appear in `help` and
-- `gui/launcher`. see possible tags here:
-- https://docs.dfhack.org/en/stable/docs/Tags.html
--[====[
example-mod
===========

Tags: fort | gameplay

Short one-sentence description.

Longer description ...

Usage
-----

    enable example-mod
    disable example-mod
]====]

local eventful = require('plugins.eventful')
local repeatUtil = require('repeat-util')
local utils = require('utils')

-- you can reference global values or functions declared in any of
-- your internal modules
local moduleA = reqscript('internal/example-mod/module-a')
local moduleB = reqscript('internal/example-mod/module-b')

local GLOBAL_KEY = 'example-mod'

local function get_default_state()
    return {
        enabled=false,
        somevar=0,
        somesubtable={
            someothervar=0,
        },
    }
end
state = state or get_default_state()

-- implement the enabled API so DFHack can read this script's status
function isEnabled()
    return state.enabled
end

-- call this whenever the contents of the state table changes
local function persist_state()
    dfhack.persistent.saveSiteData(GLOBAL_KEY, state)
end

local function do_enable()
    -- do any initialization your internal scripts might require
    moduleA.onEnable()
    moduleB.onEnable()

    repeatUtil.scheduleEvery(GLOBAL_KEY, 1000, 'ticks', function()
        moduleA.cycle()
        moduleB.cycle()
    end)

    eventful.onProjItemCheckMovement[GLOBAL_KEY] =
        moduleB.onProjItemCheckMovement
    eventful.onProjUnitCheckImpact[GLOBAL_KEY] =
        moduleB.onProjUnitCheckImpact
end

local function do_disable()
    -- call any shutdown functions your internal scripts might require
    moduleA.onDisable()
    moduleB.onDisable()

    repeatUtil.cancel(GLOBAL_KEY)

    eventful.onProjItemCheckMovement[GLOBAL_KEY] = nil
    eventful.onProjUnitCheckImpact[GLOBAL_KEY] = nil
end

dfhack.onStateChange[GLOBAL_KEY] = function(sc)
    if sc == SC_MAP_UNLOADED then
        do_disable()

        -- ensure our mod doesn't run when a different
        -- world is loaded where we are *not* active
        dfhack.onStateChange[GLOBAL_KEY] = nil

        return
    end

    if sc ~= SC_MAP_LOADED or not dfhack.world.isFortressMode() then
        return
    end

    -- retrieve state saved in game. merge with default state so config
    -- saved from previous versions can pick up newer defaults.
    state = get_default_state()
    utils.assign(state, dfhack.persistent.getSiteData(GLOBAL_KEY, state))
    if state.enabled then
        do_enable()
    end
end

if dfhack_flags.module then
    return
end

if not dfhack_flags.enable then
    print(dfhack.script_help())
    print()
    print(('Example mod is currently '):format(
            enabled and 'enabled' or 'disabled'))
    return
end

if dfhack_flags.enable_state then
    state.enabled = true
    do_enable()
else
    state.enabled = false
    do_disable()
end

persist_state()

The scripts_modinstalled/internal/example-mod/module-a.lua file could look something like this:

--@ module=true

-- global (non-local) variables and functions are exported
function onEnable()
    -- ...
end

function onDisable()
    -- ...
end

-- this is a local function: local functions/variables
-- are not accessible to other scripts.
local function usedByCycle(unit)
    -- ...
end

function cycle() -- exported
    for _,unit in ipairs(df.global.world.units.active) do
        usedByCycle(unit)
    end
end

The reqscript function reloads scripts that have changed, so you can modify your scripts while DF is running and just disable/enable your mod to load the changes into your running game!