Le guide complet de la localisation Unreal Engine

// FText is UE's localization-aware string type.
// ALWAYS use FText for user-facing text, never FString.

// LOCTEXT: localize a literal string (most common)
FText Title = LOCTEXT("MainMenuTitle", "Start Game");

// NSLOCTEXT: specify namespace explicitly
FText Msg = NSLOCTEXT("UI", "WelcomeMessage", "Welcome, adventurer!");

// INVTEXT: invariant text (never translated — debug/logging only)
FText Debug = INVTEXT("Debug overlay active");

// FText::Format: safe variable interpolation
FText Greeting = FText::Format(
    LOCTEXT("PlayerGreeting", "Hello, {PlayerName}!"),
    FText::FromString(PlayerName)
);

// In a UMG Widget (C++)
void UMainMenuWidget::NativeConstruct()
{
    Super::NativeConstruct();

    // Bind localized text to UI elements
    if (TitleLabel)
    {
        TitleLabel->SetText(LOCTEXT("GameTitle", "My Epic Game"));
    }

    if (PlayButton)
    {
        PlayButton->SetText(LOCTEXT("PlayButtonLabel", "Play Now"));
    }
}

// IMPORTANT: Always use LOCTEXT for UMG widget text.
// Setting text via FString bypasses the localization pipeline.

# 1. Open the Localization Dashboard:
#    Window > Localization Dashboard

# 2. Add a localization target (e.g., "Game")

# 3. Add cultures:
#    Click "Add New Culture" > select languages (de, ja, fr, es, ko, zh-Hans...)

# 4. Gather text:
#    Click "Gather Text" — UE scans all LOCTEXT/NSLOCTEXT macros

# 5. Export translations:
#    Click "Export" to generate .po files for each culture

# 6. Import translations:
#    After translating .po files, click "Import"

# 7. Compile translations:
#    Click "Compile" to generate .locres binary files

# 8. Preview:
#    Editor Preferences > Region & Language > Preview Game Language

// Define a namespace at the top of each .cpp file
// All LOCTEXT calls in this file use this namespace
#define LOCTEXT_NAMESPACE "MyGame.MainMenu"

#include "MainMenuWidget.h"

void UMainMenuWidget::NativeConstruct()
{
    Super::NativeConstruct();

    // These use the "MyGame.MainMenu" namespace automatically
    TitleText->SetText(LOCTEXT("Title", "Main Menu"));
    PlayText->SetText(LOCTEXT("PlayButton", "Play"));
    SettingsText->SetText(LOCTEXT("SettingsButton", "Settings"));
    QuitText->SetText(LOCTEXT("QuitButton", "Quit"));
}

// CRITICAL: Always undefine at the end of the file
#undef LOCTEXT_NAMESPACE

// FText::Format — the safe way to build localized strings
// NEVER use FString::Printf or string concatenation for user-facing text.

// Named arguments (recommended)
FText ItemPickup = FText::Format(
    LOCTEXT("ItemPickup", "You picked up {ItemName} x{Count}"),
    FText::FromString(ItemName),
    FText::AsNumber(Count)
);

// FText::AsNumber respects locale formatting:
//   English: 1,234,567
//   German:  1.234.567
//   French:  1 234 567

// FText::AsCurrency for prices:
FText Price = FText::AsCurrency(
    9.99,
    TEXT("USD"),
    &FInternationalization::Get().GetCurrentCulture().Get()
);

// FText::AsDate and FText::AsTime for dates:
FText DateStr = FText::AsDate(FDateTime::Now());

// Blueprint Localization Basics:
//
// 1. All Text properties in Blueprints are FText by default
//    (already localization-ready)
//
// 2. Set the Text property in the Details panel
//    Expand the dropdown to set:
//    - Key: unique identifier for translation
//    - Namespace: grouping for organization
//    - Source String: the text to display/translate
//
// 3. For dynamic text, use the "Format Text" node:
//    Format: "Hello, {PlayerName}!"
//    Connect a "Find" pin named "PlayerName" to your variable
//
// 4. For plurals, use "Text Format with Arguments":
//    Pattern: "{Count}|plural(one=item,other=items)"
//
// 5. Culture switching at runtime:
//    Use "Set Current Culture" node
//    Input: culture code string (e.g., "de", "ja", "fr")

// UE uses ICU message format for plurals.
// Define plural rules in your .po or String Table:

// English source:
// "{Count}|plural(one=You have # item,other=You have # items)"

// German translation:
// "{Count}|plural(one=Du hast # Gegenstand,other=Du hast # Gegenstaende)"

// Arabic translation (6 forms):
// "{Count}|plural(zero=لا عناصر,one=عنصر واحد,two=عنصران,few=# عناصر,many=# عنصرًا,other=# عنصر)"

// Japanese (1 form):
// "{Count}|plural(other=アイテム#個)"

// In C++:
FText ItemCount = FText::Format(
    LOCTEXT("ItemCount",
        "{Count}|plural(one=You have {Count} item,other=You have {Count} items)"),
    ItemCount
);

// Gender-dependent text:
// "{Gender}|gender(masculine=Il est,feminine=Elle est) prêt{Gender}|gender(masculine=,feminine=e)"

# Compile and test localization before packaging:

# 1. Editor Preferences > Region & Language > Preview Game Language
#    Set to each target language and verify all text renders correctly.

# 2. Command-line culture override for testing:
MyGame.exe -culture=ja

# 3. Packaging settings:
#    Project Settings > Packaging > Localizations to Package
#    Select all cultures you want to include in the build.

# 4. Verify .locres files exist after packaging:
MyGame/Content/Localization/Game/
├── en/
│   └── Game.locres
├── de/
│   └── Game.locres
├── ja/
│   └── Game.locres
├── fr/
│   └── Game.locres
└── ko/
    └── Game.locres

# 5. Runtime culture switching:
#    FInternationalization::Get().SetCurrentCulture(TEXT("ja"));
#    This reloads all FText strings from the new culture's .locres files.

MyUnrealProject/
├── Config/
│   └── Localization/
│       └── Game.ini                  # Localization target config
├── Content/
│   └── Localization/
│       ├── Game/
│       │   ├── Game.manifest         # Gather manifest
│       │   ├── en/
│       │   │   ├── Game.po           # Source strings (.po)
│       │   │   └── Game.locres       # Compiled binary
│       │   ├── de/
│       │   │   ├── Game.po
│       │   │   └── Game.locres
│       │   ├── ja/
│       │   │   ├── Game.po
│       │   │   └── Game.locres
│       │   └── fr/
│       │       ├── Game.po
│       │       └── Game.locres
│       └── StringTables/
│           ├── ST_MainMenu.uasset    # String Table asset
│           └── ST_HUD.uasset
├── Plugins/
│   └── LocaleChain/                  # locale-chain-ue plugin
│       ├── LocaleChain.uplugin
│       └── Source/
│           └── LocaleChain/
├── Source/
│   └── MyGame/
│       ├── UI/
│       │   ├── MainMenuWidget.h
│       │   └── MainMenuWidget.cpp    # LOCTEXT macros here
│       └── MyGameInstance.cpp        # ULocaleChain::Configure()
└── MyUnrealProject.uproject