localization

This guide covers setting up and configuring Unity Localization, including locales, String and Asset Tables, Addressables integration, and CJK font support via Asset Tables.

0. Package Installation Check

Before doing anything else, verify that the Localization packages is installed. Many APIs in this skill will fail silently or throw confusing errors if the package isn't present.

1. Check: Use UnityEditor.PackageManager.Client.List(true) to check for com.unity.localization.
2. Install: If missing, use Client.Add("com.unity.localization").
3. Wait: Do not proceed until Client.List confirms installation.

1. Localization Settings & Locales

If LocalizationEditorSettings.ActiveLocalizationSettings is null, you must find or create it:

1. Find: Use AssetDatabase.FindAssets("t:LocalizationSettings"). If found, load the first one and assign it to LocalizationEditorSettings.ActiveLocalizationSettings.
2. Create: If not found, create a new instance and save it to Assets/Localization/LocalizationSettings.asset. Use ScriptableObject.CreateInstance<LocalizationSettings>() followed by AssetDatabase.CreateAsset().
3. Activate: Set LocalizationEditorSettings.ActiveLocalizationSettings = settings.
4. Locales: Ensure locales (en, fr, de, etc.) exist. Create them if missing and add them to settings using LocalizationEditorSettings.AddLocale(locale).

2. Modifying Localization Tables

Programmatic changes to String or Asset tables require notification to the Editor.
Always create the required asset tables, unless there is already an existing one in the project.

Safe Population Pattern

When populating tables from a dataset, match by Locale.Identifier.Code explicitly. The order of GetLocales() is not guaranteed to match your input data array — assuming it does will cause silent data mismatches that are very hard to debug.
For Asset Tables, use the GUID of the asset: table.GetEntry(sharedId) ?? table.AddEntry(sharedId, guid);.

Refresh & Notification

After any modification (adding keys, updating values), notify the Editor so it can refresh its internal state. Skipping this will leave the Editor showing stale data until the next reimport.

1. Call EditorUtility.SetDirty(collection), EditorUtility.SetDirty(collection.SharedData), on each modified Table.
2. Unity 6+ Notification: LocalizationEditorSettings.EditorEvents.RaiseCollectionModified(sender, collection);
3. Always call AssetDatabase.SaveAssets() at the end.

3. UI Localization and Layout

Namespacing & Conflicts

• Always qualify names: Use UnityEngine.UI.Image, UnityEngine.UI.VerticalLayoutGroup, UnityEngine.UI.ScrollRect, UnityEngine.UI.Mask, UnityEngine.UI.CanvasScaler, UnityEngine.UI.GraphicRaycaster, UnityEngine.UI.ContentSizeFitter, UnityEngine.UI.LayoutRebuilder, etc.
• UnityEngine.UI is both a namespace and a class container, so unqualified names produce CS0118 (namespace used like a type). Full qualification avoids this entirely.
• Single Instance: Always check GameObject.Find("YourCanvasName") and destroy the old one before creating a new one.
• No Debug Dropdown: NEVER create a manual UI dropdown or debug menu to change the locale. The Localization package has a built-in way to do this properly (e.g., via the "Localization Scene Controls" window for previews).

Localized String Events (Robust Binding)

• Check Component Type: Identify if the target is TextMeshPro or legacy UnityEngine.UI.Text.

• Bind Correctly: add the public UnityEngine.Localization.Components.LocalizeStringEvent
  component and wire it yourself — set StringReference to the table entry, then add an
  OnUpdateString listener that assigns the value to the text component (TMP_Text.text for
  TextMeshPro, UnityEngine.UI.Text.text for legacy Text).

  Do not reflect into UnityEditor.Localization.Plugins.TMPro.LocalizeComponent_TMPro or its
  UGUI counterpart. Those are internal (measured on Localization 1.5.12), so reaching them means
  routing around access control to reach an API Unity makes no stability commitment about — it can
  change or disappear in any package release. LocalizeStringEvent is public and does the same job
  with the wiring made explicit.

• Layout Rebuild: After setting localized text or populating a list, call UnityEngine.UI.LayoutRebuilder.ForceRebuildLayoutImmediate(parentTransform) to ensure dimensions update.

4. Asian Language Font Support (CJK)

Avoid TMP Fallback Fonts for CJK locales. Use Asset Table Font Swapping for each specific locale instead — fallbacks are unreliable and hard to debug when glyphs are missing.

1. Use locale-specific fonts: Western fonts like Arial or Liberation Sans don't contain CJK glyphs, which results in "tofu" (square blocks). Always use a font designed for the target language:
   • For Simplified Chinese (zh-Hans): Use msyh.ttc (Microsoft YaHei) or equivalent.
   • For Japanese (ja): Use msgothic.ttc (MS Gothic) or equivalent.
   • For Korean (ko): Use malgun.ttf (Malgun Gothic) or equivalent.
   • If system font copying fails, stop and report it. Do not substitute with a Western font.
2. Robust Font Creation: Create dynamic TMP_FontAsset from imported fonts.
3. Multi-Atlas & Dynamic: CJK character sets are too large for static atlases; a single atlas will run out of space immediately.
   • fontAsset.atlasPopulationMode = AtlasPopulationMode.Dynamic;
   • fontAsset.isMultiAtlasTexturesEnabled = true;
4. Sub-Assets: Save atlas and material as sub-assets, or they'll be lost on reimport: AssetDatabase.AddObjectToAsset(fontAsset.atlasTexture, fontAsset);.
   • Explicitly link the material's texture: fontAsset.material.mainTexture = fontAsset.atlasTexture; and set both as dirty before saving.
5. Addressables: Every asset referenced in an Asset Table must be marked as Addressable.
   • Do not reference assets inside a Resources/ folder in an Asset Table. This causes OperationException: Failed to load sub-asset errors. If an asset is in Resources/, copy it to Assets/Fonts/ or similar before making it Addressable.
   • If a font asset is deleted and recreated, the new GUID must be manually updated in the Asset Table and re-added to Addressables.
6. Specialized Types: For TextMesh Pro font swapping, prefer LocalizedTmpFont over LocalizedAsset<TMP_FontAsset> to avoid implicit conversion errors.
7. Build Requirement: After updating Asset Tables or Addressable groups, trigger a build: AddressableAssetSettings.BuildPlayerContent();.

Verification Step

Before concluding any CJK localization task:

1. The Tofu Check: Switch the editor locale to zh-Hans, ja, and ko. Inspect the UI. If any characters appear as squares (tofu), the font setup has FAILED.
2. Asset Table Check: Verify that the AssetTable for the CJK locale points to the correct CJK TMP_FontAsset, NOT a default Western font.
3. Multi-Atlas Check: Confirm isMultiAtlasTexturesEnabled is true on the CJK font assets.

5. Automatic Layout (UGUI)

• Parent: VerticalLayoutGroup with Child Control Height: True, Child Force Expand Height: False.
• Labels: Each label must have a ContentSizeFitter set to Vertical Fit: Preferred Size.
• TMP: Set Enable Word Wrapping: True and Overflow: Overflow.

Notes when translating an existing project

• Minimal Code Changes: Never modify code unrelated to localization. Use a static helper class (e.g., L10n) to wrap LocalizationSettings.StringDatabase.GetLocalizedString for easy injection into existing scripts.
• Robust Mapping Strategy: When mapping existing UI text to keys, sort keys by string length (descending) and match longest strings first. This prevents short strings (like "NO") from matching parts of longer sentences. Use case-insensitive matching where appropriate.
• Component Event Listeners: When setting up LocalizeStringEvent via script, avoid UnityEventTools.AddPersistentListener as it often fails to set the dynamic mode (Mode 0) correctly.
  Instead, use the SerializedObject Pattern described in Section 3 to explicitly set m_MethodName to set_text and m_Mode to 0. Persistent listeners MUST point to a method on a UnityEngine.Object; lambdas will fail.
• Initialization & Refresh:
  • LocalizationEditorSettings.CreateStringTableCollection expects a directory path (e.g., Assets/Localization), not a full asset path.
  • Always call lEvent.RefreshString() after assigning a LocalizedString reference programmatically to update the UI immediately.
  • Ensure keys are added to all tables in a collection (en, de, ja, etc.) to avoid "No translation found" errors.
• Namespaces & Linq: Always include using System.Linq; when searching collections and using UnityEngine.Localization; when working with locales or tables.
• Verification: After modifying tables or addressables, run AddressableAssetSettings.BuildPlayerContent() and switch the Editor locale to verify changes. Check LocalizationSettings.Instance status after activation.
• Smart Strings: Set up smart strings where needed. Inspect the context of each string by taking the entire UI it is on, and any scripts that affect it, into account. Set the context on the string table to ensure translations make sense.

6. Recommended Translation Strategy

To efficiently translate an existing project, follow this multi-step workflow:

1. Extraction & Component Setup:

   • Find all occurrences: Scan all scenes and prefabs for strings in code and UI components (Legacy UnityEngine.UI.Text, TextMeshPro, buttons, etc.).
   • Shared Table: Create a central String Table (e.g., UIStrings) with the base language and a "Context" column for each key to guide translators.
   • Attach Components: For every UI element found, attach a LocalizeStringEvent (for text) and a LocalizedFont helper (for font swapping).
   • Validation: Ensure these components are set up with persistent listeners (EditorAndRuntime) so they update in the Editor immediately when the locale changes.

2. Context-Aware Translation:

   • Translate: Once the table is populated, provide translations for each locale.
   • Context is King: Always refer to the "Context" column or inspect the UI layout to ensure the translation fits the intended meaning and space.
   • Grammar & Tone: Ensure the tone matches the game's style. For example, use imperative verbs for buttons (e.g., German: "Lauf!" instead of "Laufen") and correct pluralization for labels (e.g., "Punkte" instead of "Punkt").

3. Quality Assurance (QA):

   • Scene Controls: Use Window > Asset Management > Localization Scene Controls or script: LocalizationSettings.SelectedLocale = LocalizationSettings.AvailableLocales.GetLocale("de");.
   • Visual Inspection: Methodically inspect every prefab and scene in the base language and all target languages.
   • Layout Fit: Check for text overflows or "tofu" (missing glyphs). Adjust font sizes or use ContentSizeFitter if strings are too long.

API Reference

For detailed API usage, common namespace conflicts, Addressables patterns, and font repair steps, see references/api-notes.md.

7. Accelerated Localization Workflow

To localize an entire project efficiently, use a batch processing script that handles all scenes in one pass.

Ask before acting: Before running any batch operation, confirm with the user:

"This will open every scene in the project, attach LocalizeStringEvent components, and save all modified scenes. This cannot be undone automatically. Shall I proceed?"

Only proceed once the user has confirmed. The batch processor template is in resources/L10nBatchProcessor.cs.

Technical Tips for Speed

• Table References: Use TableReference names (strings) instead of GUIDs — they are easier to read and maintain.
• Batch Refresh: Use LocalizationSettings.Instance.ForceRefresh() after modifications to force the UI to update in the editor.
• Font Swap Automation: Create the GameAssets table once and use a script to re-assign LocalizeFontEvent to all labels in one pass.
• LocalizedFontAsset component: The template is in resources/LocalizedFontAsset.cs.