Type: Top-to-Top Leading follow-ups (review of #385)

- The em box top that Top-to-Top Leading asks of every glyph's line metrics parsed the font's
  cmap and vertical metrics per glyph on every layout: each face now reads it once.
- The Paragraph panel menu shows Top-to-Top / Bottom-to-Bottom Leading with the East Asian
  options (Preferences › Type), as the Mojikumi Set does, and Reset Panel goes back to
  Bottom-to-Bottom Leading, the default.
- Saved as `leading_model`, like the other paragraph attributes in files.
- Simplified Chinese (landed since) translates the two menu items.

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

crates/doc/src/text.rs

@@ -327,7 +327,7 @@ struct ParaStyleFile {
     mojikumi: Mojikumi,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     direction: Option<ParaDirection>,
-    #[serde(default, rename = "leadingModel", skip_serializing_if = "crate::skip::is_default")]
+    #[serde(default, skip_serializing_if = "crate::skip::is_default")]
     leading_model: LeadingModel,
 }
 

crates/engine/src/cmd/typecmd.rs

@@ -428,9 +428,9 @@ mod area_tests {
         let t = text(&s);
         assert_eq!(t.para.leading_model, LeadingModel::EmBoxTop);
         assert_ne!(t.cached_bounds, before, "the first line moves up to the frame's top");
-        assert_eq!(serde_json::to_value(&t.para).unwrap()["leadingModel"], "emBoxTop");
+        assert_eq!(serde_json::to_value(&t.para).unwrap()["leading_model"], "emBoxTop");
         s.execute("edit.undo", &json!({})).unwrap();
-        assert!(serde_json::to_value(&text(&s).para).unwrap().get("leadingModel").is_none());
+        assert!(serde_json::to_value(&text(&s).para).unwrap().get("leading_model").is_none());
     }
 
     #[test]

crates/text/src/fontdb.rs

@@ -77,6 +77,8 @@ pub struct FontFace {
     location: Location,
     /// [`Self::variations`] for the shaper (advances, kerning, feature variations).
     pub(crate) instance: Option<harfrust::ShaperInstance>,
+    /// [`Self::ideographic_centre`], read once: layout asks for it per glyph.
+    ideographic_centre: std::sync::OnceLock<f64>,
 }
 
 impl std::fmt::Debug for FontFace {
@@ -170,8 +172,10 @@ impl FontFace {
     /// vertical metrics (an ideograph's cell), else the usual 0.38 (the box running from 0.12 em
     /// below the baseline to 0.88 em above it).
     pub fn ideographic_centre(&self) -> f64 {
-        let gid = ['国', 'あ', '一'].into_iter().map(|c| self.glyph_for(c)).find(|g| *g != 0);
-        gid.and_then(|g| self.vertical_glyph(g)).map_or(0.38, |(advance, origin)| (origin - advance * 0.5) / self.upem)
+        *self.ideographic_centre.get_or_init(|| {
+            let gid = ['国', 'あ', '一'].into_iter().map(|c| self.glyph_for(c)).find(|g| *g != 0);
+            gid.and_then(|g| self.vertical_glyph(g)).map_or(0.38, |(advance, origin)| (origin - advance * 0.5) / self.upem)
+        })
     }
     /// Glyph id for `c` (0 = .notdef).
     pub fn glyph_for(&self, c: char) -> u32 {
@@ -813,6 +817,7 @@ fn make_face(bytes: FontBytes, index: u32, spec: FaceStyle, path: Option<std::pa
         bytes,
         index,
         path,
+        ideographic_centre: std::sync::OnceLock::new(),
     })
 }
 

crates/ui-egui/src/i18n/es.tsv

@@ -2953,3 +2953,7 @@
 	  — {n} characters from another font	  — {n} caracteres de otra fuente
 	[Normal Character Style]	[Estilo de carácter normal]
 	[Normal Paragraph Style]	[Estilo de párrafo normal]
+
+# Leading model (Paragraph panel menu, East Asian options).
+	Top-to-Top Leading	Interlineado de superior a superior
+	Bottom-to-Bottom Leading	Interlineado de inferior a inferior

crates/ui-egui/src/i18n/zh-hans.tsv

@@ -243,6 +243,7 @@
 	Blur	模糊
 	Bottom	下
 	Bottom in Front	下方置前
+	Bottom-to-Bottom Leading	基线至基线行距
 	Bottom:	下：
 	Bounds	边界
 	Bounds (Fill Proportionally)	边界 (按比例填满)
@@ -2567,6 +2568,7 @@
 	Tools	工具
 	Top	上
 	Top in Front	上方在前
+	Top-to-Top Leading	上缘至上缘行距
 	Top:	上：
 	Total Width:	总宽度：
 	Touch Type Tool	修饰文字工具

crates/ui-egui/src/panels/paragraph.rs

@@ -150,14 +150,17 @@ pub fn menu(app: &mut VectorcraftApp, ui: &mut Ui) {
     for l in [tl!("Roman Hanging Punctuation"), tl!("Justification…"), tl!("Hyphenation…")] {
         menu_item(ui, l, false, false);
     }
-    ui.separator();
-    // How leading is measured (Japanese layout measures it from em box top to em box top).
-    let top_to_top = style.as_ref().is_some_and(|(_, p)| p.leading_model == vectorcraft_doc::LeadingModel::EmBoxTop);
-    if menu_item(ui, tl!("Top-to-Top Leading"), has, top_to_top) {
-        format(app, json!({"leadingModel": "emBoxTop"}));
-    }
-    if menu_item(ui, tl!("Bottom-to-Bottom Leading"), has, has && !top_to_top) {
-        format(app, json!({"leadingModel": "romanBaseline"}));
+    // How leading is measured (Japanese layout measures it from em box top to em box top), with
+    // the East Asian options.
+    if app.session.prefs.show_east_asian_options {
+        ui.separator();
+        let top_to_top = style.as_ref().is_some_and(|(_, p)| p.leading_model == vectorcraft_doc::LeadingModel::EmBoxTop);
+        if menu_item(ui, tl!("Top-to-Top Leading"), has, top_to_top) {
+            format(app, json!({"leadingModel": "emBoxTop"}));
+        }
+        if menu_item(ui, tl!("Bottom-to-Bottom Leading"), has, has && !top_to_top) {
+            format(app, json!({"leadingModel": "romanBaseline"}));
+        }
     }
     ui.separator();
     menu_item(ui, tl!("Single-line Composer"), false, false);
@@ -167,7 +170,7 @@ pub fn menu(app: &mut VectorcraftApp, ui: &mut Ui) {
         para_cmd(app, "text.setStyle", json!({"justify": "auto"}));
         format(
             app,
-            json!({"leftIndent": 0, "rightIndent": 0, "firstLineIndent": 0, "spaceBefore": 0, "spaceAfter": 0, "hyphenate": false, "direction": "auto"}),
+            json!({"leftIndent": 0, "rightIndent": 0, "firstLineIndent": 0, "spaceBefore": 0, "spaceAfter": 0, "hyphenate": false, "direction": "auto", "leadingModel": "romanBaseline"}),
         );
     }
 }