Data Persistence - LCK Documentation

Overview

LCK automatically persists user settings between sessions:

Camera mode (Selfie, First Person, Third Person)
Quality profile (SD, HD, 2K, 4K)
Camera settings (FOV, smoothness, distance)
Audio configuration

Platform-Specific Paths

Windows
Android

Windows Save Path

FString SavePath = FPaths::ProjectSavedDir() / TEXT("LCK") / TEXT("settings.json");
// Example: C:/Users/Player/AppData/Local/MyGame/Saved/LCK/settings.json

Android Save Path

FString SavePath = FPaths::GamePersistentDownloadDir() / TEXT("LCK") / TEXT("settings.json");
// Example: /storage/emulated/0/Android/data/com.company.mygame/files/LCK/settings.json

Platform Detection

FString GetLCKSettingsPath()
{
#if PLATFORM_ANDROID
    return FPaths::GamePersistentDownloadDir() / TEXT("LCK") / TEXT("settings.json");
#else
    return FPaths::ProjectSavedDir() / TEXT("LCK") / TEXT("settings.json");
#endif
}

Settings Structure

FLCKSavedSettings

USTRUCT(BlueprintType)
struct FLCKSavedSettings
{
    GENERATED_BODY()

    // Camera mode class
    UPROPERTY()
    TSubclassOf<ULCKBaseCameraMode> CameraModeClass;

    // Quality profile
    UPROPERTY()
    ELCKVideoQuality Quality = ELCKVideoQuality::HD;

    // Orientation
    UPROPERTY()
    ELCKScreenOrientation Orientation = ELCKScreenOrientation::Landscape;

    // Selfie mode settings
    UPROPERTY()
    float SelfieFOV = 80.0f;

    UPROPERTY()
    float SelfieSmoothness = 50.0f;

    UPROPERTY()
    bool bSelfieFollowEnabled = false;

    // First person settings
    UPROPERTY()
    float FirstPersonFOV = 90.0f;

    UPROPERTY()
    float FirstPersonSmoothness = 75.0f;

    // Third person settings
    UPROPERTY()
    float ThirdPersonFOV = 90.0f;

    UPROPERTY()
    float ThirdPersonSmoothness = 100.0f;

    UPROPERTY()
    float ThirdPersonDistance = 2.0f;

    // Audio
    UPROPERTY()
    bool bMicrophoneEnabled = true;

    UPROPERTY()
    bool bGameAudioEnabled = true;
};

Saving Settings

Using FJsonObjectConverter

void ULCKTabletDataModel::SaveSettings()
{
    // Create settings struct
    FLCKSavedSettings Settings;
    Settings.CameraModeClass = CurrentCameraMode;
    Settings.Quality = CurrentQuality;
    Settings.SelfieFOV = SelfieModeSettings.FOV;
    // ... populate other fields

    // Convert to JSON
    FString JsonString;
    if (!FJsonObjectConverter::UStructToJsonObjectString(Settings, JsonString))
    {
        UE_LOG(LogLCK, Error, TEXT("Failed to serialize settings to JSON"));
        return;
    }

    // Ensure directory exists
    FString SavePath = GetLCKSettingsPath();
    FString Directory = FPaths::GetPath(SavePath);
    IPlatformFile& PlatformFile = FPlatformFileManager::Get().GetPlatformFile();

    if (!PlatformFile.DirectoryExists(*Directory))
    {
        PlatformFile.CreateDirectoryTree(*Directory);
    }

    // Write to file
    if (!FFileHelper::SaveStringToFile(JsonString, *SavePath))
    {
        UE_LOG(LogLCK, Error, TEXT("Failed to save settings to: %s"), *SavePath);
    }
}

Save Triggers

Settings are saved automatically when:

Camera mode changes
Quality profile changes
Camera settings (FOV, smoothness) change
Audio configuration changes

void ULCKTabletDataModel::SetCameraMode(UClass* NewModeClass)
{
    if (CurrentCameraModeClass != NewModeClass)
    {
        CurrentCameraModeClass = NewModeClass;
        OnTabletCameraModeChanged.Broadcast(NewModeClass);

        // Auto-save
        SaveSettings();
    }
}

Loading Settings

On Tablet Spawn

void ALCKTablet::BeginPlay()
{
    Super::BeginPlay();

    // Try to load saved settings
    LoadSettings();
}

void ALCKTablet::LoadSettings()
{
    FString SavePath = GetLCKSettingsPath();

    // Check if file exists
    if (!FPaths::FileExists(SavePath))
    {
        UE_LOG(LogLCK, Log, TEXT("No saved settings found, using defaults"));
        return;
    }

    // Read file
    FString JsonString;
    if (!FFileHelper::LoadFileToString(JsonString, *SavePath))
    {
        UE_LOG(LogLCK, Warning, TEXT("Failed to read settings file"));
        return;
    }

    // Parse JSON
    FLCKSavedSettings Settings;
    if (!FJsonObjectConverter::JsonObjectStringToUStruct(JsonString, &Settings))
    {
        UE_LOG(LogLCK, Warning, TEXT("Failed to parse settings JSON"));
        return;
    }

    // Apply settings
    ApplySettings(Settings);
}

void ALCKTablet::ApplySettings(const FLCKSavedSettings& Settings)
{
    DataModel->SetCameraMode(Settings.CameraModeClass);
    DataModel->SetQuality(Settings.Quality);
    DataModel->SetScreenOrientation(Settings.Orientation);

    // Apply camera-specific settings
    DataModel->SetSelfieFOV(Settings.SelfieFOV);
    DataModel->SetSelfieSmoothness(Settings.SelfieSmoothness);
    // ... etc
}

Error Handling

Robust Loading Pattern

bool ULCKSettingsManager::TryLoadSettings(FLCKSavedSettings& OutSettings)
{
    FString SavePath = GetLCKSettingsPath();

    // File existence check
    if (!FPaths::FileExists(SavePath))
    {
        return false;
    }

    // Read with error handling
    FString JsonString;
    if (!FFileHelper::LoadFileToString(JsonString, *SavePath))
    {
        UE_LOG(LogLCK, Warning, TEXT("Could not read settings file"));
        return false;
    }

    // Validate JSON is not empty
    if (JsonString.IsEmpty())
    {
        UE_LOG(LogLCK, Warning, TEXT("Settings file is empty"));
        DeleteCorruptedSettings();
        return false;
    }

    // Parse with validation
    if (!FJsonObjectConverter::JsonObjectStringToUStruct(JsonString, &OutSettings))
    {
        UE_LOG(LogLCK, Warning, TEXT("Settings JSON is invalid, resetting"));
        DeleteCorruptedSettings();
        return false;
    }

    // Validate loaded values
    if (!ValidateSettings(OutSettings))
    {
        UE_LOG(LogLCK, Warning, TEXT("Settings values out of range, resetting"));
        OutSettings = FLCKSavedSettings();  // Reset to defaults
        SaveSettings();
    }

    return true;
}

bool ULCKSettingsManager::ValidateSettings(const FLCKSavedSettings& Settings)
{
    // Validate FOV ranges
    if (Settings.SelfieFOV < 20.0f || Settings.SelfieFOV > 120.0f)
        return false;

    // Validate smoothness
    if (Settings.SelfieSmoothness < 0.0f || Settings.SelfieSmoothness > 100.0f)
        return false;

    // Validate distance
    if (Settings.ThirdPersonDistance < 0.5f || Settings.ThirdPersonDistance > 10.0f)
        return false;

    return true;
}

Async Operations

For better performance, especially on Android:

void ULCKSettingsManager::SaveSettingsAsync()
{
    // Capture settings copy
    FLCKSavedSettings SettingsCopy = CurrentSettings;

    Async(EAsyncExecution::ThreadPool, [SettingsCopy]()
    {
        FString JsonString;
        FJsonObjectConverter::UStructToJsonObjectString(SettingsCopy, JsonString);

        FString SavePath = GetLCKSettingsPath();
        FFileHelper::SaveStringToFile(JsonString, *SavePath);
    });
}

void ULCKSettingsManager::LoadSettingsAsync(TFunction<void(FLCKSavedSettings)> Callback)
{
    Async(EAsyncExecution::ThreadPool, [Callback]()
    {
        FLCKSavedSettings Settings;
        bool bLoaded = TryLoadSettings(Settings);

        // Return to game thread
        AsyncTask(ENamedThreads::GameThread, [Callback, Settings, bLoaded]()
        {
            if (bLoaded)
            {
                Callback(Settings);
            }
            else
            {
                Callback(FLCKSavedSettings());  // Defaults
            }
        });
    });
}

Recording Paths

Video recordings are saved to platform-specific locations:

Windows
Android

// Videos saved to user's Videos folder
FString VideoPath = FPaths::VideosDir() / TEXT("LCK") / FileName;
// Example: C:/Users/Player/Videos/LCK/Recording_2024-01-15_14-30-00.mp4

// Videos saved to Movies folder (accessible in gallery)
FString VideoPath = FPaths::GamePersistentDownloadDir() /
                   TEXT("Movies") / AlbumName / FileName;
// Example: /storage/emulated/0/Movies/MyGame/Recording_2024-01-15.mp4

On Android 10+, videos are registered with MediaStore for gallery visibility.

Project Settings

Configure default settings

Integration

Tablet lifecycle

​Overview

​Platform-Specific Paths

​Windows Save Path

​Android Save Path

​Platform Detection

​Settings Structure

​FLCKSavedSettings

​Saving Settings

​Using FJsonObjectConverter

​Save Triggers

​Loading Settings

​On Tablet Spawn

​Error Handling

​Robust Loading Pattern

​Async Operations

​Recording Paths

​See Also

Project Settings

Integration

Overview

Platform-Specific Paths

Windows Save Path

Android Save Path

Platform Detection

Settings Structure

FLCKSavedSettings

Saving Settings

Using FJsonObjectConverter

Save Triggers

Loading Settings

On Tablet Spawn

Error Handling

Robust Loading Pattern

Async Operations

Recording Paths

See Also