Merge branch 'pr/639' into batch1

crates/compose/src/tests.rs

@@ -1959,6 +1959,23 @@ fn cjk_fallback_follows_the_language() {
     assert_eq!(Some(han.family.clone()), db.fallback_for('直', primary.id(), None).map(|f| f.family.clone()));
 }
 
+#[test]
+fn malayalam_falls_back_to_a_font_that_forms_its_conjuncts() {
+    // Run against the installed fonts: on macOS the first file mapping Malayalam is Arial
+    // Unicode MS, which leaves ക്ഷ as three glyphs.
+    let db = designcraft_fonts::FontDb::global();
+    if !["Malayalam Sangam MN", "Malayalam MN", "Nirmala UI", "Noto Sans Malayalam"].iter().any(|f| db.has_family(f)) {
+        return;
+    }
+    let text = "ക്ഷ";
+    let (mut d, sid, _) = doc_with(text, Rect::new(0.0, 0.0, 300.0, 100.0), ParaAttrs::default());
+    d.settings.glyph_fallback = true;
+    let cs = compose_story(&d, sid, &ComposeOptions::default());
+    let glyphs: Vec<_> = all_lines(&cs).iter().flat_map(|l| l.glyphs.iter()).map(|g| (g.face.family.clone(), g.gid)).collect();
+    assert_eq!(glyphs.len(), 1, "one conjunct: {glyphs:?}");
+    assert_ne!(glyphs[0].1, 0);
+}
+
 #[test]
 fn missing_glyphs_are_the_fonts_box_unless_fallback_is_on() {
     use designcraft_fonts::testing::font_with;

crates/fonts/src/fontdb.rs

@@ -435,6 +435,29 @@ const KOREAN_FALLBACKS: &[&str] = &[
     "Source Han Sans K",
 ];
 
+/// Fonts made for Malayalam (macOS, Windows, Noto, Linux). A font that only maps the characters
+/// (Arial Unicode MS, first by path on macOS) sets them without conjuncts or vowel signs.
+const MALAYALAM_FALLBACKS: &[&str] = &[
+    "Malayalam Sangam MN",
+    "Malayalam MN",
+    "Nirmala UI",
+    "Kartika",
+    "Noto Sans Malayalam",
+    "Noto Serif Malayalam",
+    "Manjari",
+    "Rachana",
+    "Meera",
+    "Lohit Malayalam",
+];
+
+/// The fallback chain of a script that only fonts made for it set well, whatever the language.
+fn script_chain(c: char) -> Option<&'static [&'static str]> {
+    match c as u32 {
+        0x0D00..=0x0D7F => Some(MALAYALAM_FALLBACKS),
+        _ => None,
+    }
+}
+
 /// The Japanese fallback chain: the craft-fonts Japanese faces' families in document order
 /// (Mincho first; none without craft-fonts), then [`JAPANESE_FALLBACKS`].
 fn japanese_chain() -> &'static [&'static str] {
@@ -1375,12 +1398,12 @@ impl ScopedFonts<'_> {
     }
 
     /// A face other than `exclude` that covers `c` in `language` (a BCP 47 tag, `None` when
-    /// unknown). CJK characters try their language's chain first (see [`cjk_chain`]); then the
-    /// first face (fallback family first, then load order, the document's fonts last) that covers
-    /// `c`. On native, system fonts are cataloged and loaded lazily the first time no loaded face
-    /// covers a character.
+    /// unknown). CJK characters try their language's chain first (see [`cjk_chain`]), Malayalam
+    /// the fonts made for it (see [`script_chain`]); then the first face (fallback family first,
+    /// then load order, the document's fonts last) that covers `c`. On native, system fonts are
+    /// cataloged and loaded lazily the first time no loaded face covers a character.
     pub fn fallback_for(&self, c: char, exclude: u32, language: Option<&str>) -> Option<Arc<FontFace>> {
-        if let Some(chain) = cjk_chain(c, language)
+        if let Some(chain) = cjk_chain(c, language).or_else(|| script_chain(c))
             && let Some(f) = chain.iter().find_map(|family| self.chain_face(family, c, exclude))
         {
             return Some(f);

crates/fonts/src/tests_fallback.rs

@@ -127,3 +127,33 @@ fn chain_fonts_load_from_the_font_folders_when_first_needed() {
     assert_eq!(family(&db, HAN, Some("ko")).as_deref(), Some(first_loaded("Other CJK")));
     assert!(!db.is_loaded("AppleMyungjo"));
 }
+
+const KA: char = 'ക';
+const VIRAMA: char = '\u{0D4D}';
+const AA: char = '\u{0D3E}';
+
+#[test]
+fn malayalam_takes_a_font_made_for_it() {
+    // Arial Unicode MS maps Malayalam but can't shape it (no conjuncts); loaded first, it won.
+    let db = db_with(&[("Arial Unicode MS", &[KA, VIRAMA, AA]), ("Malayalam Sangam MN", &[KA, VIRAMA, AA])]);
+    for c in [KA, VIRAMA, AA] {
+        for language in [None, Some("en-US"), Some("ml")] {
+            assert_eq!(family(&db, c, language).as_deref(), Some("Malayalam Sangam MN"), "{c:?} {language:?}");
+        }
+    }
+    // Past the Malayalam fonts, the language-blind search as before.
+    let sangam = db.face("Malayalam Sangam MN", "Regular");
+    assert_eq!(db.fallback_for(KA, sangam.id(), None).map(|f| f.family.clone()).as_deref(), Some("Arial Unicode MS"));
+}
+
+#[test]
+fn malayalam_fonts_load_from_the_font_folders_when_first_needed() {
+    let dir = std::env::temp_dir().join(format!("dc-malayalam-fallback-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    std::fs::create_dir_all(&dir).unwrap();
+    std::fs::write(dir.join("noto.ttf"), font_with("Noto Sans Malayalam", &[KA]).unwrap()).unwrap();
+    let db = FontDb::with_font_dirs(vec![dir]);
+    db.add_font(font_with("Arial Unicode MS", &[KA]).unwrap());
+    assert!(!db.is_loaded("Noto Sans Malayalam"));
+    assert_eq!(family(&db, KA, None).as_deref(), Some("Noto Sans Malayalam"));
+}