Interface Language dialog: list the languages alphabetically by their own name (#1787)

* Interface Language dialog: 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

* Options dialog lists interface languages in the same order as the picker

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/dialogs.rs

@@ -414,7 +414,7 @@ fn insert_block(app: &mut CadApp, name: &str) {
 fn language(app: &mut CadApp, ctx: &egui::Context, open: &mut bool) {
     egui::Window::new(crate::tl!("Interface Language")).id(egui::Id::new("interface_language")).open(open).resizable(false).show(ctx, |ui| {
         egui::ComboBox::from_id_salt("interface_language_choice").selected_text(app.ui.interface_language.name()).show_ui(ui, |ui| {
-            for preference in crate::i18n::Preference::ALL {
+            for preference in crate::i18n::Preference::for_picker() {
                 if ui.selectable_label(app.ui.interface_language == preference, preference.name()).clicked() {
                     let _ = app.run("ui.language", serde_json::json!({"lang": preference.code()}));
                     ui.ctx().request_repaint();

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

@@ -68,6 +68,23 @@ impl Preference {
         Self::Turkish,
     ];
 
+    /// Every preference in the order the Interface Language dialog lists them: Auto, then English
+    /// (the source language), then the rest by the language's own name with accents folded, so
+    /// Čeština sits under C and Magyar under M. Names in other scripts follow the Latin ones in
+    /// code point order: Greek, Cyrillic, Arabic, then the CJK languages. The order follows the
+    /// registry's native name even where the dialog shows an English label instead (Korean
+    /// without a Hangul face), so the list does not reorder when a font appears.
+    pub fn for_picker() -> Vec<Self> {
+        let mut rest: Vec<Self> = Self::ALL.into_iter().filter(|p| !matches!(p, Self::Auto | Self::English)).collect();
+        rest.sort_by_cached_key(|p| name_sort_key(p.native_name()));
+        [Self::Auto, Self::English].into_iter().chain(rest).collect()
+    }
+
+    /// The language's own name from the registry, whatever the dialog currently shows for it.
+    fn native_name(self) -> &'static str {
+        LANGUAGES.iter().find(|l| l.code.eq_ignore_ascii_case(self.code())).map_or_else(|| self.name(), |l| l.name)
+    }
+
     /// The codes a preference can be given as, for messages ("auto, en or uk").
     pub fn codes() -> String {
         let codes: Vec<&str> = Self::ALL.iter().map(|p| p.code()).collect();
@@ -377,3 +394,43 @@ macro_rules! tf {
 
 #[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_auto_and_english_first_then_names_alphabetically() {
+        let order = Preference::for_picker();
+        assert_eq!(&order[..2], &[Preference::Auto, Preference::English]);
+        assert_eq!(order.len(), Preference::ALL.len());
+        let keys: Vec<String> = order[2..].iter().map(|p| name_sort_key(p.native_name())).collect();
+        assert!(keys.windows(2).all(|w| w[0] <= w[1]), "{keys:?}");
+        let pos = |p: Preference| order.iter().position(|q| *q == p).unwrap_or(usize::MAX);
+        assert!(pos(Preference::Czech) < pos(Preference::German), "Čeština sorts under C");
+        assert!(pos(Preference::Italian) < pos(Preference::Hungarian), "Magyar sorts under M");
+        assert!(pos(Preference::Turkish) < pos(Preference::Greek), "Latin names come before Greek");
+        assert_eq!(name_sort_key("Türkçe"), "turkce");
+    }
+}

crates/ui-egui/src/options/dialog.rs

@@ -467,7 +467,7 @@ fn preferences(app: &CadApp, ui: &mut egui::Ui, changes: &mut Map<String, Value>
         ui.label(crate::tl!("Interface language"));
         let mut lang = app.ui.interface_language;
         egui::ComboBox::from_id_salt("options_language").selected_text(lang.name()).show_ui(ui, |ui| {
-            for p in crate::i18n::Preference::ALL {
+            for p in crate::i18n::Preference::for_picker() {
                 ui.selectable_value(&mut lang, p, p.name());
             }
         });