ue-ui-umg-slate

UE UI: UMG, Slate, and Common UI

You are an expert in Unreal Engine's UI systems (UMG, Slate, and Common UI).

Context Check

Read .agents/ue-project-context.md to determine: which UI plugins are enabled (CommonUI, MVVM), target platforms (affects input method), whether this is multiplayer (widget ownership per player), and existing UI base class conventions.

Information Gathering

Before writing UI code, confirm: UI type (HUD, full-screen menu, modal, in-world WidgetComponent), input requirements (mouse, gamepad, keyboard), target platforms, and widget lifecycle (persistent, transient, or pooled).

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1. UUserWidget in C++

// MyWidget.h
UCLASS()
class MYGAME_API UMyWidget : public UUserWidget
{
    GENERATED_BODY()
protected:
    virtual void NativeConstruct() override; // Bind delegates here — BindWidget refs valid
    virtual void NativeDestruct() override;
    virtual void NativeTick(const FGeometry& MyGeometry, float InDeltaTime) override;
};

// MyWidget.cpp
void UMyWidget::NativeConstruct()
{
    Super::NativeConstruct();
    if (PlayButton)
        PlayButton->OnClicked.AddDynamic(this, &UMyWidget::HandlePlayClicked);
}

Lifecycle and GC

// Creation — always pass the owning PlayerController for player-UI
UMyWidget* Widget = CreateWidget<UMyWidget>(GetOwningPlayer(), MyWidgetClass);
Widget->AddToViewport(0);          // ZOrder: higher = on top. Roots the widget (won't GC).
Widget->AddToPlayerScreen(0);      // Split-screen: ties to a specific player's viewport region
Widget->RemoveFromParent();        // Un-roots — may be GC'd if no UPROPERTY holds it.

UPROPERTY() TObjectPtr<UMyWidget> CachedWidget; // Strong ref keeps alive after RemoveFromParent

// Visibility
Widget->SetVisibility(ESlateVisibility::Collapsed); // Not drawn, takes no space
Widget->SetVisibility(ESlateVisibility::Hidden);    // Not drawn, takes space
Widget->SetVisibility(ESlateVisibility::Visible);   // Drawn, receives input
// HitTestInvisible: drawn, passes input through; SelfHitTestInvisible: children receive input