MaterialExpressionAggregate.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "UObject/ObjectMacros.h"
#include "MaterialExpressionIO.h"
#include "Materials/MaterialExpression.h"
#include "Materials/MaterialAggregate.h"
#include "MaterialExpressionAggregate.generated.h"
 
UENUM()
enum class EMaterialExpressionMakeAggregateKind
{
    MaterialAttributes,
    UserDefined
};
 
USTRUCT(MinimalAPI)
struct FMaterialExpressionAggregateEntry
{
    GENERATED_BODY()
 
    UPROPERTY()
    int32 AttributeIndex{};
 
    UPROPERTY()
    FExpressionInput Input;
};
 
UCLASS(MinimalAPI, meta=(NewMaterialTranslator))
class UMaterialExpressionAggregate : public UMaterialExpression
{
    GENERATED_BODY()
 
public:
    UPROPERTY(EditAnywhere, Category=MaterialAggregate)
    EMaterialExpressionMakeAggregateKind Kind = EMaterialExpressionMakeAggregateKind::MaterialAttributes;
 
    UPROPERTY(EditAnywhere, Category=MaterialAggregate, Meta=(EditCondition="Kind == EMaterialExpressionMakeAggregateKind::UserDefined"))
    TObjectPtr<UMaterialAggregate> UserAggregate;
 
    UPROPERTY(EditAnywhere, Category=MaterialAggregate, Meta=(DisplayName="Attributes", GetOptions="GetPossibleAttributeNames"))
    TArray<FName> AttributeNames;
    
    UPROPERTY()
    FExpressionInput PrototypeInput;
 
    UPROPERTY()
    TArray<FMaterialExpressionAggregateEntry> Entries;
 
    UMaterialExpressionAggregate(const FObjectInitializer& ObjectInitializer);
 
#if WITH_EDITOR
    // Returns the aggregate currently bound to this expression.
    const UMaterialAggregate* GetAggregate() const;
 
    // Returns the attribute with given index of the aggregate currently bound to this expression.
    const FMaterialAggregateAttribute* GetAggregateAttribute(int32 Index) const;
    
    // Utility function to list the attribute names in the attribute selection combobox.
    UFUNCTION()
    TArray<FString> GetPossibleAttributeNames() const;
 
    //~ Begin UMaterialExpression Interface
    virtual void                GetCaption(TArray<FString>& OutCaptions) const override;
    virtual FExpressionInput*   GetInput(int32 InputIndex) override;
    virtual FName               GetInputName(int32 InputIndex) const override;
    virtual EMaterialValueType  GetInputValueType(int32 InputIndex) override;
    virtual EMaterialValueType  GetOutputValueType(int32 OutputIndex) override;
    virtual bool                IsResultMaterialAttributes(int32 OutputIndex) override;
    virtual void                PreEditChange(FProperty* PropertyAboutToChange) override;
    virtual void                PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent) override;
    virtual void                Build(MIR::FEmitter& Emitter) override;
    //~ End UMaterialExpression Interface
#endif // WITH_EDITOR
 
private:
#if WITH_EDITOR
    // Used to store the state of the expression before a change was made.
    struct FPrevEditData
    {
        const UMaterialAggregate* Aggregate{};
        TArray<FName> AttributeNames{};
        TArray<FMaterialExpressionAggregateEntry> Entries{};
    };
 
    FPrevEditData PreEditData;
#endif // WITH_EDITOR
};