Ely Office: six offline-first desktop apps in Rust and GPUI

ElyDoc, ElyTable, ElyShow (LibreOfficeKit), ElyPDF (MuPDF), ElyTree (Git),
ElyMark (Milkdown and CodeMirror in CEF). ElyMail and ElyAgent follow.

crates/ely-platform/src/locale.rs

@@ -0,0 +1,116 @@
+use crate::env;
+
+/// The locale tag: `ELY_LOCALE`, else the OS one.
+pub fn system() -> String {
+    if let Some(tag) = env::value("ELY_LOCALE") {
+        return tag;
+    }
+    platform()
+}
+
+#[cfg(target_os = "macos")]
+fn platform() -> String {
+    use objc2_foundation::NSLocale;
+    if let Some(tag) = NSLocale::preferredLanguages()
+        .firstObject()
+        .map(|tag| tag.to_string())
+        && !tag.is_empty()
+    {
+        return tag;
+    }
+    NSLocale::currentLocale()
+        .localeIdentifier()
+        .to_string()
+        .replace('_', "-")
+}
+
+#[cfg(target_os = "linux")]
+fn platform() -> String {
+    resolve_env(|key| env::value(key))
+}
+
+#[cfg(target_os = "windows")]
+fn platform() -> String {
+    use windows_sys::Win32::Globalization::GetUserDefaultLocaleName;
+    let mut buffer = [0u16; 85];
+    let length = unsafe { GetUserDefaultLocaleName(buffer.as_mut_ptr(), buffer.len() as i32) };
+    if length == 0 {
+        log::warn!("locale: GetUserDefaultLocaleName failed");
+        return "en".into();
+    }
+    String::from_utf16_lossy(&buffer[..length as usize - 1])
+}
+
+/// First non-empty variable wins; C/POSIX ends as en.
+#[cfg(any(target_os = "linux", test))]
+fn resolve_env(get: impl Fn(&str) -> Option<String>) -> String {
+    for key in ["LC_ALL", "LC_MESSAGES", "LANG"] {
+        let Some(value) = get(key) else { continue };
+        if value.is_empty() {
+            continue;
+        }
+        let tag = value
+            .split(['.', '@'])
+            .next()
+            .unwrap_or(&value)
+            .replace('_', "-");
+        return match tag.as_str() {
+            "C" | "POSIX" => "en".into(),
+            _ => tag,
+        };
+    }
+    "en".into()
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashMap;
+
+    use super::resolve_env;
+
+    fn env(pairs: &[(&str, &str)]) -> impl Fn(&str) -> Option<String> {
+        let map: HashMap<String, String> = pairs
+            .iter()
+            .map(|(key, value)| (key.to_string(), value.to_string()))
+            .collect();
+        move |key| map.get(key).cloned()
+    }
+
+    #[test]
+    fn the_first_non_empty_variable_wins() {
+        assert_eq!(resolve_env(env(&[("LANG", "zh_CN.UTF-8")])), "zh-CN");
+        assert_eq!(
+            resolve_env(env(&[
+                ("LC_MESSAGES", "fr_FR.UTF-8"),
+                ("LANG", "zh_CN.UTF-8")
+            ])),
+            "fr-FR"
+        );
+        assert_eq!(
+            resolve_env(env(&[("LC_ALL", ""), ("LANG", "ja_JP.UTF-8")])),
+            "ja-JP"
+        );
+    }
+
+    #[test]
+    fn c_and_posix_resolve_to_en_and_stop() {
+        assert_eq!(
+            resolve_env(env(&[("LC_ALL", "C.UTF-8"), ("LANG", "zh_CN.UTF-8")])),
+            "en"
+        );
+        assert_eq!(
+            resolve_env(env(&[("LC_MESSAGES", "POSIX"), ("LANG", "zh_CN.UTF-8")])),
+            "en"
+        );
+        assert_eq!(
+            resolve_env(env(&[("LC_ALL", "C"), ("LC_MESSAGES", "zh_CN.UTF-8")])),
+            "en"
+        );
+    }
+
+    #[test]
+    fn nothing_set_resolves_to_en() {
+        assert_eq!(resolve_env(env(&[])), "en");
+        assert_eq!(resolve_env(env(&[("LANG", "")])), "en");
+    }
+}