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SLADE Scripting Documentation

Here is the documentation for the SLADE Lua scripting system. To start with it is probably best to take a look at the examples to get an idea of how things work, since currently there aren't any real tutorials or basic 'how-to' articles (something like that may come later).

Documentation Conventions

Type Properties

Type properties can either be read-only or read+write. Trying to modify a property that is read only will result in a script error.

In this documentation, a symbol is displayed to the left of each property indicating whether the property can be modified:

  • property: Read-only, can not be modified
  • property: Can be modified

Lua Language

Since the SLADE scripting functionality uses Lua as its language, it is recommended to read up on Lua (Programming in Lua).

Below are some general notes about some things that may trip you up if you're used to other languages such as C or ZScript.

Array and List Indices

Lua differs from most other languages in the way array indices work - usually, the first element of an array is index 0, but in Lua the first element will be index 1.

SLADE scripting functions and types use the 'standard' (0-based) convention for things like index parameters. This means you may need to be careful when using an index from a Lua array in a SLADE scripting function.

Also note that functions that return an array will return a Lua array, which means it starts at index 1.

local archive = Archives.OpenFile("c:/games/doom/somewad.wad")

-- The first element in entries is entries[1], because it is a Lua array
-- (entries[0] is invalid)
local entries = archive.entries

-- Will print "0" because entries in SLADE begin at index 0

Type Member Functions

Any function that is a member of a type has self as the first parameter, which is how 'member functions' work in lua.

Lua provides the : shortcut to call member functions with an automatic self parameter:

local object =

-- The following lines are equivalent
object:SomeFunction(param1, param2)
object.SomeFunction(object, param1, param2)
SomeType.SomeFunction(object, param1, param2)

It is generally recommended to use the : format in these cases, as it is shorter and less error-prone.

Multiple Return Values

Lua allows functions to return multiple values, which is something some SLADE scripting functions take advantage of.

An example of this is Colour.AsHSL. The values returned can be retrieved as per the example below:

local red =, 0, 0)
local h, s, l = red:AsHSL()

-- Prints "Red HSL: 0.0, 1.0, 0.5"
App.LogMessage(string.format("Red HSL: %1.1f, %1.1f, %1.1f", h, s, l))


Running Scripts

State is not presereved after running a script - eg. a global variable defined in a script will not be available next time a script is run.