Bullets: a symbol the text font lacks falls back to a font that has it (#284)

Circled-number lists (circleNumDbPlain) and character bullets whose glyph
isn't in the paragraph's font were drawn as missing-glyph boxes (numbers)
or always from Inter (characters). Both now go through the usual font
fallback, as PowerPoint draws them.

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/text/src/lib.rs

@@ -492,9 +492,7 @@ fn shape_para(ctx: &Ctx, shape: &Shape, body: &TextBody, pi: usize, scale: f64,
                 st.baseline = 0.0;
                 // Symbol fonts (Wingdings) aren't available: map common private-use bullets.
                 let ch = map_symbol_bullet(char, props.bullet_font.as_deref());
-                if !st.face.covers(ch.chars().next().unwrap_or('•')) {
-                    st.face = db.face("Inter", "Regular");
-                }
+                bullet_face(db, &mut st, &ch);
                 Some((ch, st))
             }
             Some(Bullet::AutoNum { scheme, start_at }) => {
@@ -504,8 +502,10 @@ fn shape_para(ctx: &Ctx, shape: &Shape, body: &TextBody, pi: usize, scale: f64,
                 }
                 rp.size = Some(lead.size.unwrap_or(18.0) * props.bullet_size.unwrap_or(1.0));
                 rp.underline = None;
-                let st = make_style(ctx, &rp, scale, opts.prompt_color);
-                Some((autonum(scheme, start_at.saturating_sub(1).saturating_add(number.unwrap_or(1))), st))
+                let mut st = make_style(ctx, &rp, scale, opts.prompt_color);
+                let label = autonum(scheme, start_at.saturating_sub(1).saturating_add(number.unwrap_or(1)));
+                bullet_face(db, &mut st, &label);
+                Some((label, st))
             }
             _ => None,
         }
@@ -513,6 +513,15 @@ fn shape_para(ctx: &Ctx, shape: &Shape, body: &TextBody, pi: usize, scale: f64,
     ParaShaped { cells, styles, faces, props, lead_size, lead_face, bullet, level: para.level, rtl }
 }
 
+/// A face that draws the bullet `label` when the bullet's own can't (circled numbers ①, arrows
+/// and other symbols missing from the text font), by the usual fallback.
+fn bullet_face(db: &FontDb, st: &mut Style, label: &str) {
+    let chars: Vec<char> = label.chars().collect();
+    if !chars.is_empty() && !deckcraft_fonts::covers_cluster(&st.face, &chars) {
+        st.face = db.cascade(&chars, std::slice::from_ref(&st.face), st.style_name);
+    }
+}
+
 /// Shape a logical paragraph into cells: bidi levels, per-grapheme faces, items of one level,
 /// script, face and shaping style, each shaped with the whole paragraph as context.
 /// A run's outer shadow and glow (inner shadows aren't drawn on text), at the layout's `scale`.

crates/text/src/tests.rs

@@ -602,3 +602,25 @@ fn emoji_take_a_colour_face_when_one_is_installed() {
         assert!(l.runs.iter().filter(|r| r.cells.iter().all(|(_, c)| c.is_ascii())).all(|r| !r.face.is_color()), "the letters keep a text face");
     }
 }
+
+#[test]
+fn a_bullet_the_text_font_lacks_falls_back_to_a_face_that_has_it() {
+    // circleNumDbPlain numbers ①②…: the text font usually has no circled digits; PowerPoint draws
+    // them from a fallback font instead of a missing-glyph box. Skipped when no installed or
+    // bundled face has ①.
+    let db = FontDb::global();
+    if !db.cascade(&['①'], &[], "Regular").covers('①') {
+        return;
+    }
+    let (p, mut sh) = setup("One\nTwo", 600.0, 300.0);
+    for para in &mut sh.text.as_mut().unwrap().paragraphs {
+        para.props.bullet = Some(Bullet::AutoNum { scheme: "circleNumDbPlain".into(), start_at: 1 });
+    }
+    let l = lay(&p, &sh, 600.0, 300.0);
+    let bullets: Vec<_> = l.runs.iter().filter(|r| r.cells.is_empty()).collect();
+    assert_eq!(bullets.len(), 2);
+    for b in bullets {
+        assert!(b.face.covers('①'), "drawn with {}, which lacks the circled digit", b.face.family);
+        assert!(b.glyphs.iter().all(|g| g.0 != 0), "no missing-glyph box");
+    }
+}