Create a Custom Program

Programs are apps inside the simulated OS — Explorer, Terminal, Store, or your own tools. Each program is a class derived from UOperatingSystemBaseProgram with optional widget, settings, and data classes.

Detailed property tables: New Program.

flowchart TB
  subgraph row1[" "]
    direction LR
    BP["UOperatingSystemBaseProgram"] --> Widget["UOperatingSystemProgramWidget"]
    BP --> Icon["UOperatingSystemProgramIconWidget"]
    BP --> Settings["UOperatingSystemProgramSettings"]
  end
  subgraph row2[" "]
    direction LR
    OS["UOperatingSystem"] -->|"Install program"| BP
    Widget --> UI["UMG program window"]
  end

Step 1 — Create the program Blueprint

1. Content Browser → Blueprint Class
2. Search Operating System Base Program
3. Name it BP_Prog_MyApp
4. Re-open the asset to enter data-only view

Step 2 — Required properties

Property	Guidance
Name	Display name in Store and title bar
Identifier	Unique FName — never duplicate across programs
Version	FOperatingSystemVersion
Widget Class	Main UMG UI — subclass UOperatingSystemProgramWidget
Icon Widget Class	Desktop/taskbar icon — UOperatingSystemProgramIconWidget

Step 3 — Widget Blueprint

1. Create Widget Blueprint parented to Operating System Program Widget (duplicate WBP_Program from plugin as a starting point).
2. Assign to Widget Class on the program.
3. In the widget Graph, use Get Owning Program to reach program settings and data.

Widget graph flow

flowchart LR
  NC["Native Construct"] --> GOP["Get Owning Program"]
  GOP --> GPS["Get Program Settings<br/><i>cast to your settings class</i>"]
  GOP --> GPD["Get Program Data<br/><i>if Data Class set</i>"]
  GOP --> GOS["Get Operating System"]
  GOS --> FS["Filesystem / notifications / install"]

Bundled reference: open WBP_Mail or WBP_Calculator under OperatingSystemContent/Shared/Blueprints/Widgets/Programs/ after duplicating into your project.

Step 4 — Install the program

Add your program class to one of:

• Must Have Programs on your OS Blueprint (pre-installed)
• Post Install Startup Programs (optional install set)
• Store collection Data Asset for in-game installation

Collections live under OperatingSystemContent/.../Programs/ — duplicate into your project.

Step 5 — Validate (optional)

Override On Validate to block broken configs:

Return Create Generic Error when validation fails — same pattern as C++ OnValidate in New Program.

Program lifecycle

stateDiagram-v2
  [*] --> Installed: OS boot / Store install
  Installed --> Validated: On Validate
  Validated --> Running: Player double-clicks icon
  Running --> Running: On Program Started
  Running --> Idle: Player closes window
  Idle --> Running: Launch again
  Idle --> [*]: OS shutdown (SaveOnExit)

Step 6 — Run

Boot the device. Your program should appear in the Start menu / desktop after install. Launch it and confirm window drag, taskbar button, and focus states (EOperatingSystemProgramViewState).

Window behavior

Property	Effect
Allow Dragging / Allow Resizing	Draggable window chrome via Draggable Window integration
Override Window Class	Per-program window frame
Single Instance Only	One process at a time
Start Window State	Normal, maximized, minimized

Next steps

Goal	Tutorial
Native C++ program	C++ program from scratch
Custom file extension	Custom file type
Persist settings	Save and load