LevelInstanceTypes.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "Misc/Guid.h"
#include "Templates/SubclassOf.h"
#include "WorldPartition/WorldPartitionActorContainerID.h"
#include "LevelInstanceTypes.generated.h"
 
// FLevelInstanceID is a runtime unique id that is computed from the Hash of LevelInstance Actor Guid and all its ancestor LevelInstance Actor Guids.
// Resulting in a different ID for all instances whether they load the same level or not.
struct FLevelInstanceID
{
    FLevelInstanceID() {}
    FLevelInstanceID(class ULevelInstanceSubsystem* LevelInstanceSubsystem, class ILevelInstanceInterface* LevelInstance);
 
    inline friend uint32 GetTypeHash(const FLevelInstanceID& Key)
    {
        return ::GetTypeHash(Key.GetHash());
    }
 
    inline bool operator!=(const FLevelInstanceID& Other) const
    {
        return !(*this == Other);
    }
 
    inline bool operator==(const FLevelInstanceID& Other) const
    {
        return Hash == Other.Hash && ContainerID == Other.ContainerID && ActorName == Other.ActorName && PackageShortName == Other.PackageShortName;
    }
 
    inline bool IsValid() const { return !ContainerID.IsMainContainer(); }
 
    inline uint64 GetHash() const { return Hash; }
 
    inline const FActorContainerID& GetContainerID() const { return ContainerID; }
 
private:
    uint64 Hash = 0;
    FActorContainerID ContainerID;
    
    // Hashed only for Loaded LevelInstances 
    // Spawned LevelInstances have a unique Guid which is enough.
    
    // Name allows distinguishing between LevelInstances with embedded parent LevelInstances because embedded actors have a guaranteed unique name (ContainerID suffix)
    FName ActorName;
    // PackageShortName allows distinguising between instanced LevelInstances of the same source level.
    // - Loading /Game/Path/WorldA.WorldA as /Game/Path/WorldA_LevelInstance1.WorldA & /Game/Path/WorldA_LevelInstance".WorldA
    //   with the source WorldA containing one of many LevelInstance actors. 
    //   Those actors would end up with the same hash. We use PackageShortName (WorldA_LevelInstance1 & WorldA_LevelInstance2) to distinguish them.
    FString PackageShortName;
};
 
UENUM()
enum class ELevelInstanceRuntimeBehavior : uint8
{
    None UMETA(Hidden),
    // Deprecated exists only to avoid breaking Actor Desc serialization
    Embedded_Deprecated UMETA(Hidden),
    // Move level instance actors to the main world partition
    Partitioned UMETA(DisplayName = "Embedded"),
    // Use level streaming to load level instance actors
    LevelStreaming UMETA(DisplayName = "Standalone"),
};
 
UENUM()
enum class ELevelInstanceCreationType : uint8
{
    LevelInstance,
    PackedLevelActor
};
 
UENUM()
enum class ELevelInstancePivotType : uint8
{
    CenterMinZ,
    Center,
    Actor,
    WorldOrigin
};
 
USTRUCT()
struct FNewLevelInstanceParams
{
    GENERATED_USTRUCT_BODY()
            
    UPROPERTY(EditAnywhere, Category = Default, meta = (EditCondition = "!bHideCreationType", EditConditionHides, HideEditConditionToggle))
    ELevelInstanceCreationType Type = ELevelInstanceCreationType::LevelInstance;
 
    UPROPERTY(EditAnywhere, Category = Pivot)
    ELevelInstancePivotType PivotType = ELevelInstancePivotType::CenterMinZ;
 
    UPROPERTY(EditAnywhere, Category = Pivot)
    TObjectPtr<AActor> PivotActor = nullptr;
 
    UPROPERTY()
    bool bAlwaysShowDialog = true;
 
    UPROPERTY()
    TObjectPtr<UWorld> TemplateWorld = nullptr;
        
    UPROPERTY()
    FString LevelPackageName = TEXT("");
 
    UPROPERTY()
    bool bPromptForSave = false;
 
    UPROPERTY()
    TSubclassOf<AActor> LevelInstanceClass;
 
    UPROPERTY()
    bool bEnableStreaming = false;
 
private:
    UPROPERTY(EditAnywhere, Category = Default, meta = (EditCondition = "!bForceExternalActors", EditConditionHides, HideEditConditionToggle))
    bool bExternalActors = true;
    
    UPROPERTY()
    bool bForceExternalActors = false;
 
    UPROPERTY()
    bool bHideCreationType = false;
 
public:
    void HideCreationType() { bHideCreationType = true; }
    void SetForceExternalActors(bool bInForceExternalActors) { bForceExternalActors = bInForceExternalActors; }
    void SetExternalActors(bool bInExternalActors) { bExternalActors = bInExternalActors; }
    bool UseExternalActors() const { return bForceExternalActors || bExternalActors; }
};