This article describes the Doomsday Script language and its role in Doomsday 2.

Doomsday Script is a scripting language with features such as a class-based object system, and exceptions. It is designed to harmoniously work together with Doomsday9;s native code and objects.

Scripting is used for several things internally, for example managing engine configuration and controlling 3D model asset animation. Doomsday Script is not a compiled language and thus is not intended for high-performance or time-critical tasks. Game plugins, for instance, should be written in native code.

Below is an example of the syntax:

def exampleFunc(a)
    if a
        return "It is true!"
    else
        return "Nay, it is false."
    end
end
print exampleFunc(True)

The syntax is heavily influenced by Python and Ruby, with a few notable differences:

• Unlike Python, the amount of indentation whitespace has no special meaning.
• Compounds are explicitly closed with end.
• A colon (:) always indicates a single-line compound that does not need to be closed:

  def func2(): return 9;World9;

• Objects are weakly typed: they may have one or more superclass objects that provide common members, but otherwise there is no type safety or checking. Objects are called Records and they represent native de::Record instances:

  record myrec
  myrec.newMember = 100

• There are only modifiable arrays. Non-modifiable tuples are not supported:

  array = [1, 2, 3, 4]
  array[1] = 100
  # array is now [1, 100, 3, 4]

• There are a couple of special assignment operators. Global assignment (:=) will assign into variables in parent scopes if no local variable with the given name is found. Weak assignment (?=) will only assign a value if a variable has not yet been created.

The following pages walk though the features of Doomsday Script with brief code snippets:

• Basic expressions
• Operator expressions
• Statements and compounds
• Exceptions
• Records
• Functions
• Scopes
• Miscellaneous

These larger examples may be examined to get a better feel of what Doomsday Script is like in practice. (Spoiler alert: Very much like Python.)

• Game controller presets script
• The "Kitchen Sink" test script

As of 2.3, scripts can be used for the following:

• Animating 3D models:
  • Initializing the animator of a thing (onInit)
  • When receiving damage or when the thing state changes
  • At specific points in time
  • Manipulate shader variables, render passes, and the active material
• Application:
  • Loading fonts
  • Callbacks for game load/unload
• Audio:
  • Start local sounds
• Configuration:
  • Applications run a Config.ds script at startup
  • Client runs bootstrap.ds when initialization is complete (e.g., maintenance during upgrades, SF2 soundfont caching)
• Console:
  • List, get, and set cvars
  • Interactive scripting prompt (toggle in taskbar)
• Definitions:
  • Accessing currently loaded DEDs via the Defs module
• Files:
  • Reading/writing files and folders using File objects
• Game:
  • Show a HUD message
• Input:
  • Binding controls and events (e.g., Input.bindEvent)
  • Game controller presets
• Packages:
  • Modify package metadata and assets (__init.ds__)
  • Adding modules to the import path
  • onLoad/onUnload callbacks
• Players:
  • Query health, armor, and powerups
  • Earthquake effect
• Things:
  • State action function
  • Attack, drop items, start sounds
  • Query and change thing flags
  • Query hit points, type, height, position, and momentum
  • Change momentum
  • "On touch" and "On death" scripts

In older versions: 2.2

• Visual Studio Code: skyjake.doomsdaylang package
• Syntax definitions in TextMate format for compatible editors

See the Language reference for information about the syntax, and built-in functions and modules.