Options: list the languages alphabetically by their own name

- English (and Auto where offered) stays first as the source language and fallback; the rest sort by native name with accents folded, so Čeština is under C and Magyar under M; Cyrillic and CJK names follow the Latin ones
- The list used the registry order, which is the order the languages were added

crates/ui-egui/src/i18n/mod.rs

@@ -256,6 +256,16 @@ impl Lang {
         LANGUAGES.iter().map(Lang)
     }
 
+    /// Every registered language in the order a picker lists them: English first (the source
+    /// language and the fallback), then the rest by their own name with accents folded, so
+    /// Čeština sits under C rather than after Z. Names in other scripts follow the Latin ones in
+    /// code point order: Greek, Cyrillic, Arabic, then the CJK languages.
+    pub fn for_picker() -> Vec<Lang> {
+        let mut rest: Vec<Lang> = Lang::all().filter(|l| l.code() != Lang::EN.code()).collect();
+        rest.sort_by_cached_key(|l| name_sort_key(l.name()));
+        std::iter::once(Lang::EN).chain(rest).collect()
+    }
+
     fn catalog(self) -> &'static Catalog {
         self.0.catalog()
     }
@@ -474,3 +484,40 @@ mod audit;
 pub(crate) mod pseudo;
 #[cfg(test)]
 mod tests;
+
+/// `name` lowercased with the Latin accents that occur in language names folded away, so a
+/// byte-wise sort reads alphabetically. Other scripts are left as they are.
+fn name_sort_key(name: &str) -> String {
+    name.chars()
+        .flat_map(char::to_lowercase)
+        .map(|c| match c {
+            'à'..='å' | 'ā' | 'ă' | 'ą' => 'a',
+            'ç' | 'ć' | 'č' => 'c',
+            'è'..='ë' | 'ē' | 'ě' | 'ę' | 'ế' | 'ệ' => 'e',
+            'ì'..='ï' | 'ī' => 'i',
+            'ñ' | 'ń' | 'ň' => 'n',
+            'ò'..='ö' | 'ø' | 'ő' => 'o',
+            'ś' | 'š' => 's',
+            'ù'..='ü' | 'ū' | 'ů' | 'ű' => 'u',
+            'ý' | 'ÿ' => 'y',
+            'ź' | 'ż' | 'ž' => 'z',
+            c => c,
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod picker_order_tests {
+    use super::*;
+
+    #[test]
+    fn picker_lists_english_first_then_names_alphabetically() {
+        let order = Lang::for_picker();
+        assert_eq!(order.first().map(|l| l.code()), Some(Lang::EN.code()));
+        assert_eq!(order.len(), Lang::all().count());
+        let keys: Vec<String> = order[1..].iter().map(|l| name_sort_key(l.name())).collect();
+        assert!(keys.windows(2).all(|w| w[0] <= w[1]), "{keys:?}");
+        assert_eq!(name_sort_key("Čeština"), "cestina");
+        assert_eq!(name_sort_key("Türkçe"), "turkce");
+    }
+}

crates/ui-egui/src/options.rs

@@ -634,7 +634,7 @@ fn language_picker(app: &mut WordApp, ui: &mut Ui) {
             if ui.selectable_label(app.ui.language == AUTO, auto_label.as_str()).clicked() {
                 let _ = app.run("ui.language", json!({"value": AUTO}));
             }
-            for lang in Lang::all() {
+            for lang in Lang::for_picker() {
                 if ui.selectable_label(app.ui.language == lang.code(), lang.name()).clicked() {
                     let _ = app.run("ui.language", json!({"value": lang.code()}));
                 }