[noahbclarkson]

Foundation for #55: the rgitui_i18n crate and the language setting. #89's Simplified Chinese translations are being ported onto this in a follow-up PR (stacked on this branch), and git operation messages in another after that.

Rebased onto main (0.5.0) and reworked after reviewing it against #89. The original commit is kept as the first of two; the second carries the review fixes.

What works

• Settings → Appearance → Language. Lists Match system language plus every locale found, each written in its own script, with a count of strings it still leaves in English.
• Switching applies immediately, with no restart.
• New installs and existing settings.json files follow the OS language. A missing language key defaults to system.
• Simplified Chinese ships as the first translation. Only the Appearance panel is converted here.

Design

English is Rust, translations are JSON. crates/rgitui_i18n/src/en.rs is the source of truth, one key => message line per entry. Translations live in assets/locales/*.json, embedded at build time. User files in <config>/rgitui/locales/ are layered over a shipped locale with the same id, so a translator can fix a few strings against a release build.

Keys are checked at compile time. t!, tp! and key! take literal keys and expand to const assertions against the English table:

t!("settings.nav.genral")
// error: evaluation panicked: unknown translation key "settings.nav.genral": add it to crates/rgitui_i18n/src/en.rs
t!("settings.language.system_detail", lang = id)
// error: the arguments to t!("settings.language.system_detail") do not match the placeholders in its English message

This keeps #89's main advantage (rustc catches key typos) without putting translations in Rust. Lookup is a binary search. An unsorted or duplicated en.rs fails the build and names the first key out of place. key! checks a key stored as data, for menus and filter lists that are translated later.

set_language(cx, …) refreshes every window and replaces an ActiveLanguage GPUI global. Anything translated in render updates on its own. Views that keep text outside render (input placeholders) observe ActiveLanguage, and only that, instead of every settings change.

Plurals: tp!("key", n) picks .one / .other under the locale's rule and fills {count} itself.

Changes since the original commit

• Traditional Chinese no longer gets Simplified. zh-TW, zh-HK, zh-MO and zh-Hant matched zh-CN on the primary subtag. Matching now requires the same script, stated or implied. POSIX tags (zh_CN.UTF-8) are accepted.
• A complete zh-CN no longer reports "1 string not translated". Plural forms a locale's rule never selects aren't counted.
• No per-render work for the picker. The system language and the missing counts are computed once at init.
• Loader:
  • User files must be regular files under 1 MiB, so a FIFO named *.json can't hang startup.
  • Files are read in path order.
  • Keys English doesn't define are logged.
  • An unknown plural_rule is an error instead of silently becoming one_other.
• Tests:
  • Shipped locales must use exactly the English placeholders (it used to be one-way), and only the plural forms their rule selects.
  • A test reports English keys no code uses.
• CJK fonts. The UI font gains Simplified Chinese fallback families when the UI is Simplified Chinese, and only then, so Japanese or Traditional Chinese text in an English UI keeps the platform's glyph choice.
• Settings view. It reads the selection from rgitui_i18n instead of keeping a second copy. "Detected:" shows the matched language's own name, or says the system language has no translation yet.
• zh-CN. Applied @aiysya's wording fix: {count} 条尚未翻译.
• Housekeeping. Crate version 0.5.0; CHANGELOG entry under [Unreleased].

Verified

• cargo fmt --check: clean.
• cargo clippy --workspace --all-targets -D warnings: clean.
• cargo test -p rgitui_i18n -p rgitui_settings -p rgitui_workspace: 50 + 31 + 771 passed.
• Confirmed by hand that each kind of mistake fails to compile: unknown key, missing arguments, misnamed argument, unknown plural stem, and an unsorted table.

Known gaps

• The settings window doesn't use the workspace's UI font, before or after this PR. Language names in other scripts there rely on the platform's font fallback.
• Relative times ("3d ago") are still built by hand in English. That's covered in the port PR.

🤖 Generated with Claude Code

[aiysya]

@noahbclarkson I'm a native Simplified Chinese speaker — happy to review, done.

The translation is in good shape: terminology is consistent (Appearance = 外观,
Light/Dark = 浅色/深色), the renderings are natural rather than literal
(auto-detect → 自动跟随系统, Color Theme → 配色主题), and the full-width
punctuation is used consistently. I found it very usable as-is.

One suggestion, purely idiomatic polish (not a bug): settings.language.missing.other
"{count} 条文本尚未翻译" — the collocation 条文本 reads a bit stiff. I'd write
"{count} 条尚未翻译" instead.

Two things worth flagging from your own "Known gaps" section, since they hit
Chinese users first:

• The bundled fonts have no CJK glyphs. On Windows this falls back to the system
  font and is usually fine, but it's untested on the other platforms — I'd
  prioritize the per-locale default ui_font follow-up.
• The zh-CN file is other_only, which is correct for Chinese — no action needed
  there, just confirming.

[noahbclarkson]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-19T08:38:34.106983Z	4bc9034	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🎉

Reviewed commit: 4bc90344d4

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