C++ Reference

Guide for extending the plugin in C++. Full class listings with members live in the API Reference tab.

Module dependency graph

flowchart TB
  subgraph row1[" "]
    direction LR
    Game["Your game module"] --> OSS["OperatingSystemSimulator"] --> GM["GlobalMessenger"] --> VW["ViewportWorlds"]
  end
  subgraph row2[" "]
    direction LR
    GC["GlobalCore"] --- DW["DraggableWindowUMG"]
  end
  OSS --> GC
  OSS --> DW
  VW --> OSS

Plugin modules

Module	Responsibility
OperatingSystemSimulator	Core OS, programs, filesystem, hardware
GlobalCore	Shared foundations (required — build project after enabling plugin)
GlobalMessenger	UGlobalMessageSubsystem
ViewportWorlds	Secondary worlds in OS viewports
DraggableWindowUMG	Program window dragging/resizing

Build.cs dependencies

Minimal game module extending OS features:

PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine" });

PrivateDependencyModuleNames.AddRange(new string[]
{
    "OperatingSystemSimulator",
    "GlobalMessenger",
    "GameplayTags",
    "UMG",
    "Slate",
    "SlateCore",
    "DraggableWindowUMG"
});

Add ViewportWorlds only when using Viewport World.

Common includes

Header	Types
Core/OperatingSystem.h	UOperatingSystem
Devices/OperatingSystemBaseDevice.h	UOperatingSystemBaseDevice
Programs/OperatingSystemBaseProgram.h	UOperatingSystemBaseProgram
Programs/Terminal/OperatingSystemTerminalCommand.h	UOperatingSystemTerminalCommand
Files/OperatingSystemFile.h	UOperatingSystemFile
Global/OperatingSystemStatics.h	UOperatingSystemStatics
Devices/OperatingSystemDeviceMessenger.h	Device messenger
GlobalMessageSubsystem.h	Global messenger (GlobalMessenger module)

Extension points

Type	Subclass	Override / implement
Program	UOperatingSystemBaseProgram	OnValidate, OnProgramStarted, OnProgramClosed
Terminal command	UOperatingSystemTerminalCommand	OnProcessCommand, OnProcessCommandAsRoot, OnContinueExecution
File	UOperatingSystemFile	OnOpen, validation
Program widget	UOperatingSystemProgramWidget	NativeConstruct, UI logic
OS widget	UOperatingSystemWidget	Notification / login implementable events
Setting module	UOperatingSystemSettingModule	Custom settings panels

Do not subclass UOperatingSystem directly — use UOperatingSystemUnix or UOperatingSystemNonUnix.

Error handling

Plugin code uses FGenericError and the MAKE_ERROR macro:

OutError = MAKE_ERROR("ERROR_CODE", TEXT("Human-readable message."));

Use in OnValidate, terminal ProcessCommand, and filesystem helpers.

Subsystems

Subsystem	Access
UOperatingSystemGameSubsystem	UGameInstance scope
UOperatingSystemWorldSubsystem	Per-world device registry, user manager
UGlobalMessageSubsystem	UGlobalMessageSubsystem::Get(*World)

Device state machine

EOperatingSystemDeviceState on UOperatingSystemBaseDevice:

stateDiagram-v2
  [*] --> None
  None --> Starting
  Starting --> BIOS
  BIOS --> Running
  Running --> Restarting
  Running --> ShuttingDown
  Running --> BSOD
  Restarting --> Starting
  ShuttingDown --> None
  BSOD --> ShuttingDown

Hook device events on AOperatingSystemDeviceActor in your game code when you need cinematic boot sequences or input lock during BIOS.

Tutorials with C++ samples

Topic	Tutorial
All extension types (add / extend)	C++ Extension Examples
All patterns (cookbook)	Examples & Patterns
Native program	C++ program from scratch
Terminal command	Custom terminal command
Global Messenger	Using Global Messenger
Device Messenger	Using Device Messenger
Program validation	New Program

Source location

Plugin source (private repo): OperatingSystemSimulator/Source/. Regenerate API docs with the monorepo build-api-docs.mjs script when headers change.