Merge PR #1669: macOS: bold interface text draws Cyrillic е open, not like ө

Conflicts:
- crates/ui-egui/src/theme.rs: appended tests from both PRs kept; the mut fd hinting tweak applies to the FontData from_static in try_load

crates/ui-egui/src/theme.rs

@@ -418,7 +418,12 @@ pub fn font_definitions_with(language: crate::i18n::Language, used: &[String]) -
         let paths = candidates(role);
         let refs: Vec<(&str, u32)> = paths.iter().map(|(p, i)| (p.as_str(), *i)).collect();
         let mut chain: Vec<String> = Vec::new();
-        if let Some(fd) = try_load(&refs) {
+        if let Some(mut fd) = try_load(&refs) {
+            // Helvetica Neue Bold's own TrueType hints close Cyrillic е into ө at 13 pt on a Retina
+            // screen (#1184). Core Text never runs them, so this draws it the way macOS does.
+            if cfg!(target_os = "macos") && role == UI_BOLD {
+                fd.tweak.hinting = Some(false);
+            }
             let key = format!("sys-{role}");
             fonts.font_data.insert(key.clone(), Arc::new(fd));
             chain.push(key);
@@ -1045,4 +1050,19 @@ mod tests {
         assert_eq!(*a, epaint_default_fonts::UBUNTU_LIGHT);
         assert!(try_load(&[(p.as_str(), 3)]).is_none(), "a face the kept file doesn't have is still refused");
     }
+
+    #[test]
+    fn macos_bold_interface_face_is_drawn_unhinted() {
+        // #1184: Helvetica Neue Bold's own TrueType hints close Cyrillic е into ө at 13 pt on a
+        // Retina screen. Core Text never runs them, so on macOS the face goes unhinted like every
+        // other app draws it; the regular face and the other platforms keep egui's default.
+        let fonts = font_definitions_for_language(Language::En);
+        let hinting = |key: &str| fonts.font_data.get(key).map(|fd| fd.tweak.hinting);
+        if let Some(bold) = hinting(&format!("sys-{UI_BOLD}")) {
+            assert_eq!(bold, if cfg!(target_os = "macos") { Some(false) } else { None });
+        }
+        if let Some(regular) = hinting(&format!("sys-{UI}")) {
+            assert_eq!(regular, None, "only the bold face is affected");
+        }
+    }
 }