Merge PR #2872: fix(ui): Korean (Hangul) file names and tab titles draw as boxes

contributors/people.toml

@@ -20,6 +20,11 @@
 [people.YouseifUS]
 sync_github_name = true
 
+[people.brian-moon]
+real_name = "Il Min Brian Moon"
+display_name = "Il Min Brian Moon"
+sync_github_name = false
+
 [people.echelon]
 real_name = "Brandon Thomas"
 display_name = "Brandon Thomas"

crates/ui-egui/src/system_fonts.rs

@@ -3,8 +3,9 @@
 //! The embedded faces (Inter, egui's defaults, craft-fonts) come first in every family; this one
 //! only draws characters none of them has, such as an Arabic file name in a build without
 //! craft-fonts, or the Simplified Chinese interface in a build without a `Hans` face (#826). A
-//! few more installed faces, [`devanagari_fallback`], [`telugu_fallback`], [`sinhala_fallback`]
-//! and [`tamil_fallback`], draw Hindi, Telugu, Sinhala and Tamil when one is installed. It is
+//! few more installed faces, [`devanagari_fallback`], [`telugu_fallback`], [`sinhala_fallback`],
+//! [`tamil_fallback`] and [`hangul_fallback`], draw Hindi, Telugu, Sinhala, Tamil and Korean when
+//! one is installed. It is
 //! read at runtime and never embedded or shipped (AGENTS.md §1.4), and `PDFCRAFT_SYSTEM_FONTS=0`
 //! turns it off (published screenshots do).
 
@@ -32,6 +33,9 @@ const TELUGU_PROBE: char = '\u{0C15}';
 const SINHALA_PROBE: char = '\u{0D9A}';
 /// Tamil letter ka (க): the face must have it to cover Tamil.
 const TAMIL_PROBE: char = '\u{0B95}';
+/// Hangul syllable hih (힣, U+D7A3), the last of the 11,172 modern syllables: a face with it has
+/// the whole block. Droid Sans Fallback, for one, has 가 but few other syllables.
+const HANGUL_PROBE: char = '\u{D7A3}';
 /// 欢 (U+6B22): Simplified only, absent from the Japanese craft-fonts faces.
 const HANS_PROBE: char = '\u{6B22}';
 /// 說 (U+8AAA): Traditional only, absent from the Japanese craft-fonts faces.
@@ -103,6 +107,13 @@ pub fn tamil_fallback() -> Option<Arc<FontData>> {
     CACHE.get_or_init(|| script_fallback(&tamil_candidates(), TAMIL_PROBE)).clone()
 }
 
+/// The installed fallback face for Hangul (Korean), read once. `None` when it is turned off or no
+/// candidate is installed; the interface then draws what the embedded faces can.
+pub fn hangul_fallback() -> Option<Arc<FontData>> {
+    static CACHE: OnceLock<Option<Arc<FontData>>> = OnceLock::new();
+    CACHE.get_or_init(|| script_fallback(&hangul_candidates(), HANGUL_PROBE)).clone()
+}
+
 fn script_fallback(candidates: &[PathBuf], probe: char) -> Option<Arc<FontData>> {
     if std::env::var_os("PDFCRAFT_SYSTEM_FONTS").is_some_and(|v| v == "0") {
         return None;
@@ -288,6 +299,30 @@ fn han_candidates(traditional: bool) -> Vec<PathBuf> {
     }
 }
 
+/// Well-known locations of Korean faces, best first. Noto CJK and Source Han are left out, as for
+/// Chinese (AGENTS.md §1.1).
+fn hangul_candidates() -> Vec<PathBuf> {
+    if cfg!(windows) {
+        ["malgun.ttf", "gulim.ttc", "batang.ttc"].iter().map(|f| windows_fonts().join(f)).collect()
+    } else if cfg!(target_os = "macos") {
+        ["/System/Library/Fonts/AppleSDGothicNeo.ttc", "/System/Library/Fonts/Supplemental/AppleGothic.ttf", "/Library/Fonts/Arial Unicode.ttf"]
+            .iter()
+            .map(PathBuf::from)
+            .collect()
+    } else {
+        unix_fonts(&[
+            "truetype/nanum/NanumGothic.ttf",
+            "nanum/NanumGothic.ttf",
+            "naver-nanum/NanumGothic.ttf",
+            "nhn-nanum/NanumGothic.ttf",
+            "truetype/unfonts-core/UnDotum.ttf",
+            "un-core/UnDotum.ttf",
+            "truetype/baekmuk/dotum.ttf",
+            "baekmuk-ttf-dotum-fonts/dotum.ttf",
+        ])
+    }
+}
+
 fn windows_fonts() -> PathBuf {
     let dir = std::env::var_os("WINDIR").or_else(|| std::env::var_os("SystemRoot")).map_or_else(|| PathBuf::from(r"C:\Windows"), PathBuf::from);
     dir.join("Fonts")
@@ -411,7 +446,7 @@ mod tests {
 
     #[test]
     fn script_candidates_are_absolute_font_files() {
-        for list in [devanagari_candidates(), telugu_candidates(), sinhala_candidates(), tamil_candidates()] {
+        for list in [devanagari_candidates(), telugu_candidates(), sinhala_candidates(), tamil_candidates(), hangul_candidates()] {
             assert!(!list.is_empty());
             assert!(list.iter().all(|p| p.is_absolute() || cfg!(windows)), "{list:?}");
             assert!(list.iter().all(|p| p.extension().is_some_and(|e| e == "ttf" || e == "ttc")), "{list:?}");

crates/ui-egui/src/theme.rs

@@ -224,6 +224,8 @@ pub const SYSTEM_TELUGU_FALLBACK: &str = "system-telugu-fallback";
 pub const SYSTEM_SINHALA_FALLBACK: &str = "system-sinhala-fallback";
 /// The name of the installed Tamil face [`installed_font_definitions`] may add.
 pub const SYSTEM_TAMIL_FALLBACK: &str = "system-tamil-fallback";
+/// The name of the installed Hangul (Korean) face [`installed_font_definitions`] may add.
+pub const SYSTEM_HANGUL_FALLBACK: &str = "system-hangul-fallback";
 
 /// What [`install_fonts_for`] installs: [`font_definitions_for`], then, on desktop, one face
 /// already installed on this machine. It only draws characters no embedded face has.
@@ -236,9 +238,9 @@ pub const SYSTEM_TAMIL_FALLBACK: &str = "system-tamil-fallback";
 /// - Otherwise it is the last fallback of every family (an Arabic file name in a build without
 ///   craft-fonts).
 ///
-/// Installed Devanagari, Telugu, Sinhala and Tamil faces, when there are, end every family just
-/// before that one, so Hindi, Telugu (#1531), Sinhala and Tamil (#1688) text, such as a file
-/// name, draws in a build without such faces.
+/// Installed Devanagari, Telugu, Sinhala, Tamil and Hangul faces, when there are, end every family
+/// just before that one, so Hindi, Telugu (#1531), Sinhala and Tamil (#1688) and Korean text, such
+/// as a file name or a tab title, draws in a build without such faces.
 ///
 /// `PDFCRAFT_SYSTEM_FONTS=0` leaves them out.
 pub fn installed_font_definitions(cjk: CjkPreference) -> FontDefinitions {
@@ -253,6 +255,7 @@ pub fn installed_font_definitions(cjk: CjkPreference) -> FontDefinitions {
             (SYSTEM_TELUGU_FALLBACK, crate::system_fonts::telugu_fallback()),
             (SYSTEM_SINHALA_FALLBACK, crate::system_fonts::sinhala_fallback()),
             (SYSTEM_TAMIL_FALLBACK, crate::system_fonts::tamil_fallback()),
+            (SYSTEM_HANGUL_FALLBACK, crate::system_fonts::hangul_fallback()),
         ] {
             let Some(data) = data else { continue };
             fonts.font_data.insert(name.to_owned(), data);

crates/ui-egui/tests/fonts.rs

@@ -337,3 +337,27 @@ fn primary_ui_fonts_cover_latin_and_cyrillic_catalogs() {
         }
     }
 }
+
+/// On a machine with an installed Korean font, the installed definitions include it and Hangul has
+/// glyphs, so a Korean file name in a tab title is not boxes. macOS always ships Apple SD Gothic
+/// Neo and Windows Malgun Gothic, so there the test never skips.
+#[test]
+fn system_fallback_covers_hangul() {
+    const HANGUL: &str = "성가대 찬양곡 목록";
+    assert!(!theme::font_definitions().font_data.contains_key(theme::SYSTEM_HANGUL_FALLBACK));
+    let defs = theme::installed_font_definitions(theme::CjkPreference::Default);
+    let off = std::env::var_os("PDFCRAFT_SYSTEM_FONTS").is_some_and(|v| v == "0");
+    if !defs.font_data.contains_key(theme::SYSTEM_HANGUL_FALLBACK) && (off || cfg!(all(unix, not(target_os = "macos")))) {
+        eprintln!("skipping system_fallback_covers_hangul: no installed Korean fallback font (or PDFCRAFT_SYSTEM_FONTS=0)");
+        assert!(defs.families.values().all(|stack| !stack.iter().any(|n| n == theme::SYSTEM_HANGUL_FALLBACK)));
+        return;
+    }
+    for (family, stack) in &defs.families {
+        assert_eq!(stack.iter().filter(|n| *n == theme::SYSTEM_HANGUL_FALLBACK).count(), 1, "{family:?}: {stack:?}");
+    }
+    let mut fonts = Fonts::new(TextOptions::default(), defs);
+    for id in families() {
+        assert!(fonts.has_glyphs(&id, HANGUL), "{id:?} lacks {HANGUL}");
+    }
+    assert!(layout_widths(&mut fonts, HANGUL).iter().all(|w| w.is_finite() && *w > 0.0));
+}