SceneViewExtensionContext.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "SceneInterface.h"
#include "UnrealClient.h"
#include "ViewportClient.h"
#include "Engine/Engine.h"
#include "SceneViewExtensionContext.generated.h"
 
class FViewport;
class ISceneViewExtension;
class FViewport;
 
struct FSceneViewExtensionContext
{
private:
    // A quick and dirty way to determine which Context (sub)class this is. Every subclass should implement it.
    virtual FName GetRTTI() const { return TEXT("FSceneViewExtensionContext"); }
 
public:
    // The scene view extension can be defined with either a Viewport or a Scene
 
    FViewport* Viewport = nullptr;
    FSceneInterface* Scene = nullptr;
    bool bStereoEnabled = false;
 
    FSceneViewExtensionContext() : Viewport(nullptr), Scene(nullptr) {}
    explicit FSceneViewExtensionContext(FViewport* InViewport) : Viewport(InViewport) {}
    explicit FSceneViewExtensionContext(FSceneInterface* InScene) : Scene(InScene) {}
 
    virtual ~FSceneViewExtensionContext() {}
    
    // Returns true if the given object is of the same type.
    bool IsA(const FSceneViewExtensionContext& Other) const
    { 
        return GetRTTI() == Other.GetRTTI(); 
    }
 
    // Returns true if the given object is of the same type.
    bool IsA(const FSceneViewExtensionContext&& Other) const
    {
        return IsA(static_cast<const FSceneViewExtensionContext&>(Other));
    }
 
    UWorld* GetWorld() const
    {
        if (Viewport != nullptr)
        {
            if (const FViewportClient* ViewportClient = Viewport->GetClient())
            {
                return ViewportClient->GetWorld();
            }
        }
        
        if (Scene != nullptr)
        {
            return Scene->GetWorld();
        }
 
        return nullptr;
    }
 
    bool IsStereoSupported() const
    {
        return bStereoEnabled && GEngine && GEngine->IsStereoscopic3D(Viewport);
    }
 
    // Return true, if HMD supported
    virtual bool IsHMDSupported() const
    {
        return true;
    }
};
 
 
using TSceneViewExtensionIsActiveFunction = TFunction<TOptional<bool>(const ISceneViewExtension* SceneViewExtension, const FSceneViewExtensionContext& Context)>;
 
USTRUCT(BlueprintType)
struct FSceneViewExtensionIsActiveFunctor
{
    GENERATED_BODY()
 
private:
 
    // The Guid is a way to identify the lambda in case it you want to later find it and remove it.
    FGuid Guid;
 
public:
 
    // Constructor
    FSceneViewExtensionIsActiveFunctor()
        : Guid(FGuid::NewGuid())
    {}
 
    // Returns the Guid of this Functor.
    FGuid GetGuid() const
    {
        return Guid;
    }
 
    // This is the lambda function used to determine if the Scene View Extension should be active or not.
    TSceneViewExtensionIsActiveFunction IsActiveFunction;
 
    // Make this a functor so that it behaves like the lambda it carries.
    TOptional<bool> operator () (const ISceneViewExtension* SceneViewExtension, const FSceneViewExtensionContext& Context) const
    {
        // If there is no lambda assigned, simply return an unset optional.
        if (!IsActiveFunction)
        {
            return TOptional<bool>();
        }
 
        // Evaluate the lambda function with the given arguments
        return IsActiveFunction(SceneViewExtension, Context);
    }
};