fixes horizontal furigana

render-wasm/src/render.rs

@@ -1727,6 +1727,11 @@ impl RenderState {
                         }
                     }
                 }
+
+                if !text_content.is_vertical() && self.options.is_text_grid_visible() {
+                    let canvas = self.surfaces.canvas_and_mark_dirty(fills_surface_id);
+                    text::paint_horizontal_grid(canvas, &shape, text_content);
+                }
             }
             _ => {
                 self.surfaces.apply_mut(surface_ids, |s| {

render-wasm/src/render/text.rs

@@ -11,7 +11,9 @@ use crate::{
 use skia_safe::{
     self as skia,
     canvas::SaveLayerRec,
-    textlayout::{ParagraphBuilder, StyleMetrics, TextDecoration, TextStyle},
+    textlayout::{
+        ParagraphBuilder, RectHeightStyle, RectWidthStyle, StyleMetrics, TextDecoration, TextStyle,
+    },
     Canvas, ImageFilter, Paint,
 };
 
@@ -100,6 +102,62 @@ pub fn render_vertical_text(
     Ok(())
 }
 
+/// Paint a viewport-only grid over SkParagraph horizontal text. Blue outlines
+/// show line boxes, green boxes show the per-scalar tight rectangles returned
+/// by SkParagraph, and amber rules show baselines. This mirrors the vertical
+/// text grid while making horizontal annotation anchors inspectable.
+pub fn paint_horizontal_grid(canvas: &Canvas, shape: &Shape, text_content: &TextContent) {
+    let mut builders = text_content.paragraph_builder_group_from_text(None);
+    let layout = calculate_text_layout_data(shape, text_content, &mut builders, true);
+
+    let mut line_paint = Paint::default();
+    line_paint.set_anti_alias(true);
+    line_paint.set_style(skia::PaintStyle::Stroke);
+    line_paint.set_stroke_width(1.0);
+    line_paint.set_color(skia::Color::from_argb(0xAA, 0x2F, 0x80, 0xED));
+
+    let mut glyph_paint = Paint::default();
+    glyph_paint.set_anti_alias(true);
+    glyph_paint.set_style(skia::PaintStyle::Stroke);
+    glyph_paint.set_stroke_width(1.0);
+    glyph_paint.set_color(skia::Color::from_argb(0x99, 0x27, 0xAE, 0x60));
+
+    let mut baseline_paint = Paint::default();
+    baseline_paint.set_anti_alias(true);
+    baseline_paint.set_stroke_width(1.0);
+    baseline_paint.set_color(skia::Color::from_argb(0xCC, 0xEB, 0x57, 0x57));
+
+    for paragraph in &layout.paragraphs {
+        for line in paragraph.paragraph.get_line_metrics() {
+            let baseline = line.baseline as f32;
+            let top = paragraph.y + baseline - line.ascent as f32;
+            let left = paragraph.x + line.left as f32;
+            let width = line.width as f32;
+            canvas.draw_rect(
+                Rect::from_xywh(left, top, width, line.height as f32),
+                &line_paint,
+            );
+            canvas.draw_line(
+                (left, paragraph.y + baseline),
+                (left + width, paragraph.y + baseline),
+                &baseline_paint,
+            );
+
+            for offset in line.start_index..line.end_index {
+                for textbox in paragraph.paragraph.get_rects_for_range(
+                    offset..offset + 1,
+                    RectHeightStyle::Tight,
+                    RectWidthStyle::Tight,
+                ) {
+                    let mut rect = textbox.rect;
+                    rect.offset((paragraph.x, paragraph.y));
+                    canvas.draw_rect(rect, &glyph_paint);
+                }
+            }
+        }
+    }
+}
+
 pub fn stroke_paragraph_builder_group_from_text(
     text_content: &TextContent,
     stroke: &Stroke,

render-wasm/src/shapes/text.rs

@@ -2190,6 +2190,16 @@ mod tests {
         );
     }
 
+    #[test]
+    fn horizontal_annotation_uses_the_base_em_not_typographic_leading() {
+        let rect = skia::Rect::from_xywh(0.0, 66.0, 56.0, 90.0);
+
+        assert_eq!(
+            crate::shapes::text_japanese::horizontal_annotation_over_top(rect, 56.0),
+            88.0
+        );
+    }
+
     #[test]
     fn horizontal_warichu_collapses_to_one_builder_position() {
         init_state();

render-wasm/src/shapes/text_japanese.rs

@@ -522,6 +522,18 @@ pub(crate) fn horizontal_span_style(
     })
 }
 
+/// Top of the horizontal base em inside SkParagraph's typographic rectangle.
+/// Its tight rect can include substantial ascender-side padding; anchoring an
+/// over annotation to that rect's top therefore leaves a visible gap above CJK
+/// ink. The em is bottom-aligned to the rect, matching the baseline model used
+/// by the horizontal painter. The ruby showcase needs a 12 px clearance at
+/// 56 px: the original 6 px adjustment still left it 6 px too close to the
+/// kanji. Keep the 3/14-em value proportional at other text sizes.
+pub(crate) fn horizontal_annotation_over_top(rect: skia::Rect, font_size: f32) -> f32 {
+    let font_size = font_size.max(0.0);
+    rect.top.max(rect.bottom - font_size) - font_size * (3.0 / 14.0)
+}
+
 /// Paint horizontal emphasis marks (圏点 / bouten) above their base glyphs.
 /// The base paragraph retains its normal metrics; interlinear collision and
 /// automatic line-gap expansion remain a separate layout policy.
@@ -549,8 +561,26 @@ pub(crate) fn paint_horizontal_emphasis(
         style.set_height_override(true);
         style.set_letter_spacing(0.0);
         let mark_paragraph = warichu_mini_paragraph(&mark.to_string(), &style, f32::MAX);
-        let mark_width = mark_paragraph.longest_line();
-        let mark_height = mark_paragraph.height();
+        let mark_ink = mark_paragraph
+            .get_rects_for_range(
+                0..mark.len_utf16(),
+                RectHeightStyle::Tight,
+                RectWidthStyle::Tight,
+            )
+            .into_iter()
+            .map(|textbox| textbox.rect)
+            .reduce(|mut rect, next| {
+                rect.join(next);
+                rect
+            });
+        let mark_width = mark_ink
+            .as_ref()
+            .map(|rect| rect.width())
+            .unwrap_or_else(|| mark_paragraph.longest_line());
+        let mark_ink_bottom = mark_ink
+            .as_ref()
+            .map(|rect| rect.bottom())
+            .unwrap_or_else(|| mark_paragraph.height());
         for placement in placements
             .iter()
             .filter(|placement| placement.span == range.span && placement.mark == mark)
@@ -564,7 +594,9 @@ pub(crate) fn paint_horizontal_emphasis(
             } else {
                 0.0
             };
-            let mark_y = y + placement.rect.top() - mark_height - ruby_offset;
+            let mark_y = y + horizontal_annotation_over_top(placement.rect, span.font_size)
+                - mark_ink_bottom
+                - ruby_offset;
             mark_paragraph.paint(canvas, (mark_x, mark_y));
         }
     }

render-wasm/src/shapes/text_vertical.rs

@@ -3103,6 +3103,24 @@ fn next_horizontal_ruby_range(
     offset_map.to_shifted(start)..offset_map.to_shifted(*utf16_cursor)
 }
 
+/// Baseline adjustment that attaches a glyph's visible ink edge to its base
+/// strip. Font-wide ascender/descender metrics include leading which makes
+/// horizontal ruby visibly detached for many Japanese faces.
+fn horizontal_ruby_ink_edge(font: &Font, glyph: GlyphId, fallback: f32, over: bool) -> f32 {
+    let mut bounds = [skia::Rect::default()];
+    font.get_bounds(&[glyph], &mut bounds, None);
+    let bound = bounds[0];
+    if bound.right > bound.left && bound.bottom > bound.top {
+        if over {
+            bound.bottom
+        } else {
+            bound.top
+        }
+    } else {
+        fallback
+    }
+}
+
 /// Paint ruby annotations for one horizontally laid-out paragraph. Draw-only:
 /// base rects come from the already laid-out skparagraph
 /// (`get_rects_for_range`), the annotation is shaped at half the span size
@@ -3220,8 +3238,26 @@ pub fn paint_horizontal_ruby(
                 let run = &shaped[*run_index];
                 let (_, metrics) = run.font.metrics();
                 let baseline = match span.ruby_side {
-                    RubySide::Over => y + rect_box.rect.top() - metrics.descent,
-                    RubySide::Under => y + rect_box.rect.bottom() - metrics.ascent,
+                    RubySide::Over => {
+                        y + super::text_japanese::horizontal_annotation_over_top(
+                            rect_box.rect,
+                            span.font_size,
+                        ) - horizontal_ruby_ink_edge(
+                            &run.font,
+                            run.glyphs[*glyph],
+                            metrics.descent,
+                            true,
+                        )
+                    }
+                    RubySide::Under => {
+                        y + rect_box.rect.bottom()
+                            - horizontal_ruby_ink_edge(
+                                &run.font,
+                                run.glyphs[*glyph],
+                                metrics.ascent,
+                                false,
+                            )
+                    }
                 };
                 let mut builder = TextBlobBuilder::new();
                 let (out_glyphs, points) = builder.alloc_run_pos(&run.font, 1, None);
@@ -6551,6 +6587,27 @@ mod tests {
         assert!((shift - metrics_shift).abs() > 0.1);
     }
 
+    #[test]
+    fn horizontal_ruby_attaches_to_visible_glyph_ink() {
+        let layout = layout_content(&make_content(&["a"], 1000.0), 1000.0);
+        let CellKind::Rotated { run } = layout.cells[0].kind else {
+            panic!("expected a rotated run");
+        };
+        let run = &layout.runs[run];
+        let mut bounds = [skia::Rect::default()];
+        run.font.get_bounds(&[run.glyphs[0]], &mut bounds, None);
+
+        assert!(
+            (horizontal_ruby_ink_edge(&run.font, run.glyphs[0], 0.0, true) - bounds[0].bottom)
+                .abs()
+                < f32::EPSILON
+        );
+        assert!(
+            (horizontal_ruby_ink_edge(&run.font, run.glyphs[0], 0.0, false) - bounds[0].top).abs()
+                < f32::EPSILON
+        );
+    }
+
     #[test]
     fn justify_fills_non_last_columns() {
         use std::collections::BTreeMap;