C++ Program from Scratch

Use C++ when you need performance, source control–friendly logic, or shared code across multiple OS skins. Programs still use UMG widgets — implement the widget in Blueprint or C++ and assign it on the program class defaults.

Base class: UOperatingSystemBaseProgram.

flowchart TB
  subgraph row1[" "]
    direction LR
    Build["Build.cs modules"] --> Header["UMyNativeProgram.h"] --> CPP["UMyNativeProgram.cpp"]
  end
  subgraph row2[" "]
    direction LR
    BPChild["Blueprint child for widgets"] --> Collection["UOperatingSystemProgramsCollection"] --> OS["UOperatingSystem"]
  end
  CPP --> BPChild

Module setup

In your game module Build.cs:

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

#pragma once

#include "Programs/OperatingSystemBaseProgram.h"
#include "MyNativeProgram.generated.h"

UCLASS(Blueprintable)
class UMyNativeProgram : public UOperatingSystemBaseProgram
{
    GENERATED_BODY()

public:
    UMyNativeProgram();

protected:
    virtual void OnValidate(FGenericError& OutError) const override;
    virtual void OnProgramStarted() override;
};

Source

#include "MyNativeProgram.h"

UMyNativeProgram::UMyNativeProgram()
{
    Name = FText::FromString(TEXT("Native Tool"));
    Identifier = FName("com.mygame.nativetool");
    Version.Major = 1;
    // WidgetClass = LoadClass<UOperatingSystemProgramWidget>(...);
}

void UMyNativeProgram::OnValidate(FGenericError& OutError) const
{
    if (WidgetClass.IsNull())
    {
        OutError = MAKE_ERROR("CONFIG", TEXT("Widget Class is required."));
    }
}

void UMyNativeProgram::OnProgramStarted()
{
    Super::OnProgramStarted();
    // Runtime init — spawn sub-widgets, load data, etc.
}

Blueprint child (recommended)

Create a Blueprint child of UMyNativeProgram to assign Widget Class, icons, and Store metadata in the editor without recompiling for every tweak.

Subclass UOperatingSystemProgramWidget:

UCLASS()
class UMyProgramWidget : public UOperatingSystemProgramWidget
{
    GENERATED_BODY()

protected:
    virtual void NativeConstruct() override;
};

Use GetOwningProgram() to cast back to UMyNativeProgram.

Register with the OS

Add your program class to a UOperatingSystemProgramsCollection Data Asset referenced by your OS Blueprint, or set it on Must Have Programs.

Override cheat sheet

Override	When
`OnValidate`	Reject invalid program configs at cook/runtime
`OnProgramStarted`	First frame of program process
`OnProgramClosed`	Cleanup
`OnProcessCommand`	Only for terminal-like programs

Full virtual list: API reference.

Create a custom program — Blueprint-first walkthrough
C++ Reference — headers and modules
New Program — validation with MAKE_ERROR