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Pattern — C++ Program + Blueprint Child

Split program logic between C++ (validation, performance) and a Blueprint child (widget assignment, icons, Store metadata). Recompile only when C++ behavior changes.

flowchart TB
  subgraph cpp["C++ (game module)"]
    Header["UMyNativeProgram.h"]
    Impl["OnValidate, OnProgramStarted"]
  end
  subgraph bp["Blueprint child (Content)"]
    Child["BP_Prog_MyNativeTool"]
    Widget["WBP_MyNativeTool"]
  end
  Header --> Child
  Child -->|"Widget Class, Icon, Store metadata"| Widget
  Child --> Collection["Programs Collection → OS"]

Module setup

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

C++ header pattern

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

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

Screenshot callouts

Blueprint child workflow

sequenceDiagram
  participant Dev as Developer
  participant CPP as UMyNativeProgram
  participant BP as BP_Prog_MyNativeTool
  participant OS as UOperatingSystem
  Dev->>CPP: Implement OnValidate / OnProgramStarted
  Dev->>BP: Create Blueprint child
  BP->>BP: Assign Widget Class, icons, Store fields
  Dev->>OS: Add BP child to Programs Collection
  OS->>CPP: Spawns CDO defaults via Blueprint child