pdfcraft/docs/localization.md

Interface language

Choose Edit > Preferences > Interface language and select Auto, English or 日本語. The change applies immediately and persists between launches. Command ids, document contents and file names are unchanged.

Auto (the default) follows the system language: LC_ALL, LC_MESSAGES or LANG, then the preferred-languages list on macOS. A system language without a catalog, such as French, shows English. Windows has no system-language detection yet, so Auto shows English there unless LANG is set.

The control channel exposes the setting through ui.set:

{"method":"ui.set","params":{"key":"language","value":"ja"}}

The value is auto or a language code (en, ja), in any case. ui.state reports language as written in the preferences (auto, en or ja). Unknown values return an error without changing the current setting. Preferences saved before this setting existed follow the system language.

This first translation pass covers the main menu and core registered menu commands. Untranslated labels use English. Vertical Japanese PDF rendering is an existing viewer feature; this change does not add vertical text editing.

Japanese interface text uses BIZ UDPGothic from craft-fonts, an optional build input that every release includes (CRAFT_FONTS_DIR; see the README). A build made without it has no Japanese face, so Japanese labels show replacement boxes.

How translations work

PdfCraft uses the same system as PhotoCraft (crates/ui-egui/src/i18n/):

• Strings in the code stay in English and serve as lookup keys. At draw time, tl!("Save") returns the text in the current language, and falls back to English when there is no entry.
• Each language has a catalog, crates/ui-egui/src/i18n/<code>.tsv, with one entry per line: context<TAB>English<TAB>translation. An empty context marks a plain string. @id keys an entry by command id (for example file.saveAs), so one menu item can read differently from another with the same English label. @plural holds plural forms. Any other context disambiguates an English word with several meanings (tr_ctx). The header of ja.tsv documents the format and escapes.
• Placeholders ({name}) must appear in both columns. A trailing … must be kept. i18n::fmt fills placeholders in one pass, so a value such as a file name containing {n} is inserted as written.
• Catalogs are validated strictly: unknown escapes, unknown @ contexts, placeholder or ellipsis mismatches, wrong plural form counts and duplicates are errors. The tests require the bundled catalogs to have none; at run time a bad line is skipped (and logged) and that string shows in English.
• Catalogs are assets: each .tsv has an ATTRIBUTION.toml entry with kind = "translation" and its SHA-256, checked by cargo xtask assets.
• Translations are clean-room: write them from the meaning of the English text, never from another product's string tables.

Adding a language

1. Copy the header of ja.tsv into xx.tsv and translate entries.
2. Add one row to LANGUAGES in crates/ui-egui/src/i18n/mod.rs: code, native name, catalog and plural rule.
3. Add an ATTRIBUTION.toml entry for the catalog (kind = "translation"), then run cargo xtask assets --write and cargo xtask assets.

The Preferences dropdown, the system-language match and the catalog tests (format, duplicates, placeholders, plural forms, command ids) then pick it up.