Separated the ability of a user widget to intercept all input into its own thing

Source/StevesUEHelpers/Private/StevesUI/MenuStack.cpp

@@ -12,13 +12,6 @@ void UMenuStack::NativeConstruct()
 {
     Super::NativeConstruct();
 
-    if (!InputPreprocessor.IsValid())
-    {
-        InputPreprocessor = MakeShareable(new FUiInputPreprocessor());
-        InputPreprocessor->OnUiKeyDown.BindUObject(this, &UMenuStack::HandleKeyDownEvent);
-    }
-    FSlateApplication::Get().RegisterInputPreProcessor(InputPreprocessor);
-
     // We could technically do input change detection in our own input processor, but since this already does it nicely...
     auto GS = GetStevesGameSubsystem(GetWorld());
     if (GS)
@@ -35,7 +28,6 @@ void UMenuStack::NativeConstruct()
 void UMenuStack::NativeDestruct()
 {
     Super::NativeDestruct();
-    FSlateApplication::Get().UnregisterInputPreProcessor(InputPreprocessor);
 
     auto GS = GetStevesGameSubsystem(GetWorld());
     if (GS)
@@ -96,6 +88,8 @@ void UMenuStack::ApplyGamePauseChange(EGamePauseChange Change) const
 
 bool UMenuStack::HandleKeyDownEvent(const FKeyEvent& InKeyEvent)
 {
+    Super::HandleKeyDownEvent(InKeyEvent);
+    
     // Hardcoding the Back / Exit menu navigation inputs because input mappings can't be trusted in UMG
     // This is probably OK though, no-one redefines menu controls, right?
     FKey Key = InKeyEvent.GetKey();

Source/StevesUEHelpers/Public/StevesUI/FocusableInputInterceptorUserWidget.cpp

@@ -0,0 +1,29 @@
+#include "FocusableInputInterceptorUserWidget.h"
+
+
+void UFocusableInputInterceptorUserWidget::NativeConstruct()
+{
+    Super::NativeConstruct();
+
+    if (!InputPreprocessor.IsValid())
+    {
+        InputPreprocessor = MakeShareable(new FUiInputPreprocessor());
+        InputPreprocessor->OnUiKeyDown.BindUObject(this, &UFocusableInputInterceptorUserWidget::HandleKeyDownEvent);
+    }
+    FSlateApplication::Get().RegisterInputPreProcessor(InputPreprocessor);
+
+}
+
+void UFocusableInputInterceptorUserWidget::NativeDestruct()
+{
+    Super::NativeDestruct();
+    
+    FSlateApplication::Get().UnregisterInputPreProcessor(InputPreprocessor);
+}
+
+
+bool UFocusableInputInterceptorUserWidget::HandleKeyDownEvent(const FKeyEvent& InKeyEvent)
+{
+    // Do nothing by default
+    return false;
+}

Source/StevesUEHelpers/Public/StevesUI/FocusableInputInterceptorUserWidget.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "CoreMinimal.h"
+
+#include "FocusableUserWidget.h"
+#include "Framework/Application/IInputProcessor.h"
+
+#include "FocusableInputInterceptorUserWidget.generated.h"
+
+UCLASS(Blueprintable, BlueprintType)
+class STEVESUEHELPERS_API UFocusableInputInterceptorUserWidget : public UFocusableUserWidget
+{
+    GENERATED_BODY()
+
+    // Nested class which we'll use to poke into input events before anything else eats them
+    // Without this it seems impossible to pick up e.g. Gamepad "B" button with UMG up
+    // It means we hardcode the controls for menus but that's OK in practice
+    class FUiInputPreprocessor : public IInputProcessor, public TSharedFromThis<FUiInputPreprocessor>
+    {
+    public:
+        DECLARE_DELEGATE_RetVal_OneParam(bool, FOnUiKeyDown, const FKeyEvent&);
+        FOnUiKeyDown OnUiKeyDown;
+        
+        virtual bool HandleKeyDownEvent(FSlateApplication& SlateApp, const FKeyEvent& InKeyEvent) override
+        {
+            return OnUiKeyDown.Execute(InKeyEvent);
+        }
+        // Required by IInputProcessor but we don't need
+        virtual void Tick(const float DeltaTime, FSlateApplication& SlateApp, TSharedRef<ICursor> Crs) override{}
+    };
+
+protected:
+    TSharedPtr<FUiInputPreprocessor> InputPreprocessor;
+    
+public:
+
+    virtual void NativeConstruct() override;
+    virtual void NativeDestruct();
+
+    UFUNCTION()
+    virtual bool HandleKeyDownEvent(const FKeyEvent& InKeyEvent);
+
+};

Source/StevesUEHelpers/Public/StevesUI/MenuStack.h

@@ -2,7 +2,8 @@
 
 #include "CoreMinimal.h"
 
-#include "FocusableUserWidget.h"
+
+#include "FocusableInputInterceptorUserWidget.h"
 #include "Framework/Application/IInputProcessor.h"
 #include "StevesHelperCommon.h"
 
@@ -20,34 +21,15 @@ DECLARE_DYNAMIC_MULTICAST_DELEGATE_TwoParams(FOnMenuStackClosed, class UMenuStac
 /// Create a Blueprint subclass of this and make sure you include a UContentWidget with the name
 /// "MenuContainer" somewhere in the tree, which is where the menu contents will be placed. 
 UCLASS(Abstract, BlueprintType)
-class STEVESUEHELPERS_API UMenuStack : public UFocusableUserWidget
+class STEVESUEHELPERS_API UMenuStack : public UFocusableInputInterceptorUserWidget
 {
     GENERATED_BODY()
 
-    // Nested class which we'll use to poke into input events before anything else eats them
-    // Without this it seems impossible to pick up e.g. Gamepad "B" button with UMG up
-    // It means we hardcode the controls for menus but that's OK in practice
-    class FUiInputPreprocessor : public IInputProcessor, public TSharedFromThis<FUiInputPreprocessor>
-    {
-    public:
-        DECLARE_DELEGATE_RetVal_OneParam(bool, FOnUiKeyDown, const FKeyEvent&);
-        FOnUiKeyDown OnUiKeyDown;
-        
-        virtual bool HandleKeyDownEvent(FSlateApplication& SlateApp, const FKeyEvent& InKeyEvent) override
-        {
-            return OnUiKeyDown.Execute(InKeyEvent);
-        }
-        // Required by IInputProcessor but we don't need
-        virtual void Tick(const float DeltaTime, FSlateApplication& SlateApp, TSharedRef<ICursor> Crs) override{}
-    };
-
 protected:
     EInputMode LastInputMode;
     
     TArray<UMenuBase*> Menus;
 
-    TSharedPtr<FUiInputPreprocessor> InputPreprocessor;
-
     virtual void LastMenuClosed(bool bWasCancel);
 
     virtual void NativeConstruct() override;
@@ -57,8 +39,7 @@ protected:
     virtual void ApplyMousePointerVisibility(EMousePointerVisibilityChange Change) const;
     virtual void ApplyGamePauseChange(EGamePauseChange Change) const;
 
-    UFUNCTION()
+    virtual bool HandleKeyDownEvent(const FKeyEvent& InKeyEvent) override;
-    bool HandleKeyDownEvent(const FKeyEvent& InKeyEvent);
     UFUNCTION()
     void InputModeChanged(int PlayerIndex, EInputMode NewMode);