Localization and theming
Translation sources and merge order; theme dictionaries and runtime switching.
Localization
Translations are namespaced key-value JSON, merged from multiple sources at load time.
LocalizationService (Mnemo.Infrastructure/Services/LocalizationService.cs) aggregates ITranslationSource implementations. The built-in source reads embedded files from Mnemo.Infrastructure/Languages/{culture}.json; modules contribute their own strings through EmbeddedJsonTranslationSource pointing at a Translations/ folder inside the module (Notes, Mindmap, Flashcards, and the Overview widgets do this). Sources merge in registration order, later sources overriding earlier ones, which lets a module override a built-in string if it must.
The JSON shape is { "Namespace": { "Key": "Value" } }. Lookup is T(key, namespace); with a namespace, a missing key returns the key itself, which is how untranslated strings become visible in the UI.
Shipped languages are hard-coded in GetAvailableLanguagesAsync: English, Spanish, German, Norwegian Bokmål, and Japanese. If a culture loads empty, the service falls back to English. The chosen language persists as the App.Language setting and is loaded during bootstrap. LanguageChanged notifies live UI such as the sidebar and settings page.
Adding a language means adding the embedded JSON files (core plus each module that has translations) and the entry in the hard-coded list. Note that spellcheck dictionaries are a separate system with a different language set; see the block editor page.
Theming
Themes are Avalonia resource dictionaries under Mnemo.UI/Themes/Core/{Name}/, each with a theme.axaml that merges Colors.axaml, Typography.axaml, and Controls.axaml. Three ship: Dawn (light, default), Noon (warm light), and Dusk (dark).
ThemeService (Mnemo.UI/Services/ThemeService.cs) switches themes at runtime by replacing the StyleInclude whose source path contains /Themes/Core/ in Application.Styles, then persists Appearance.Theme. The saved theme is applied during startup in App.axaml.cs before the window shows.
Feature views should consume theme resources dynamically ({DynamicResource ...}) rather than hard-coding brushes; every color a feature needs should exist as a key in each theme’s Colors.axaml. The sketch renderer’s theme(...) color tokens resolve against these same resources.
Not implemented: user-defined themes and accent colors. ThemeService.ImportAsync always returns false, and the export and file-watching members are stubs. Treat theme import/export as dead surface until someone builds it.
Where the code lives
| Concern | Path |
|---|---|
| Localization service | Mnemo.Infrastructure/Services/LocalizationService.cs |
| Built-in strings | Mnemo.Infrastructure/Languages/ |
| Module strings | Mnemo.UI/Modules/{Feature}/Translations/ |
| Theme service | Mnemo.UI/Services/ThemeService.cs |
| Theme dictionaries | Mnemo.UI/Themes/Core/{Dawn,Noon,Dusk}/ |