Papyrus for Programmers

Notes for Skyrim Scripting episode

How does Scripting work in Skyrim and Creation Kit?

Example Scripts:

• KillerItem (Object Reference)
• Magic
  • SpellSelf (Lesser Power, Fire & Forget, Self) Optional:
  • SpellTarget (Spell, Fire & Forget, Target Actor)
  • AbilitySneak (Ability) [on ReferenceAlias]
• No .esp
  • JustAScript
  • HelloOnActivate *Food*
• Other Examples:
  • Dialogue fragments, Quest stage fragments, etc

extends ActiveMagicEffect, Quest, ReferenceAlias,
        ObjectReference, SKIConfigBase, Dialogue...

Then look at how they are attached in Creation Kit.

Language Syntax

• Comments (including {docstring} comments)
• Casing (insensitivity & idioms)

Data Types (and local variables)

• int, float, bool, string
• Arrays
  • Utility to create and resize
• String manipulation
  • StringUtil
  • How does SKSE add scripts and functions?
• Implicit casting
• Explicit as casting
• Type naming collisions of local variables

Control Flow

There is no switch and no for

• if conditionals
• while loops
  • no break

States

• GotoState and organizing with functions
• GotoState("")
• GetState
• OnBeginState and OnEndState

Functions

• Positional and Keyword Arguments
• Default argument values
• Type naming collisions of argument names
• global
  • Global scripts (with only global functions)
• native

SKSE

• What is SKSE?
• Reverse Engineering, Hooks
• Comes with functions!
• Comes with events!
• Can make your own functions and events in your own SKSE plugins!

Script Variables

• View in .ess Elder Scrolls Save files
• Type naming collisions of variable/field names

Script Properties

• auto
• autoReadonly
  • Not saved
• "Full properties"
  • Readonly
  • Writeonly
  • Read and Write
• conditional (only on auto and on conditional scripts)
• Filling properties
  • Fill via CK
    • Pick in render window (ObjectReference) or from cell (ObjectReference)
    • Name it the same as the EditorID and auto-fill or create using CK
  • Fill via No .esp
  • Game.GetForm() versus properties (leads into the next section...)

Forms and Script Types

• Forms and Form IDs and Mod Indexes (FEzz000 zz000000 FF000000)
• Learn the type functions and properties from CreationKit.com and VS Code and reading source
• Form < ObjectReference < Actor
• Form < Book
• Alias < ReferenceAlias
• ActiveMagicEffect
• Fallout 4 has ScriptObject
• Editor IDs and po3 Tweaks

Scripts as Objects

• Attached to objects in the VM (Bind())
• Constructor (OnInit)
• Casting a Quest to a certain script
  • Casting ReferenceAlias etc to a certain script
  • Cannot upcast a script that wasn't attached as a given type
  • If multiple scripts of the same type are attached, first or random instance returned
    • For these circumstances, can store arrays (and arrays) or attached instances

Events

• OnInit
• OnPlayerLoadGame
• See Events page on CreationKit.com
• Can call just like functions
• Events added by SKSE (and when using reloadscript)
  • Finding DXScanCodes
  • Finding UI targets

Waiting

• RegisterForSingleUpdate
• Utility.Wait[MenuMode]

SKSE Mod Events

• Sending
• Receiving
• Sending and Receiving with custom arguments

Debugging

• Debug.MessageBox
• Debug.Notification
• Debug.Trace
  • .ini settings

Patterns: "Control Script" (or "Maintenance")

• Use a Quest and use GetQuest by editor ID to return the singleton

Using Papyrus libraries, e.g. PapyrusUtil or UIExtensions

• Via Creation Kit and MO2
• Via Visual Studio Code and <Import> includes
• Champollion when necessary to get the .psc to compile against / review
  • Anonymization
  • .pas representation

Useful Console Commands

• https://www.creationkit.com/index.php?title=Console_Commands_(Papyrus)