Merge pull request #850 from storytold/fix/847-underline-strikethrough

Fix #847: draw Underline and Strikethrough

crates/engine/src/cmd/typecmd.rs

@@ -251,6 +251,13 @@ fn create_outlines(s: &mut Session, _: &Value) -> Result<Value> {
                 node.appearance = st.appearance();
                 children.push(Arc::new(node));
             }
+            // Underline and strikethrough bars become paths of their run's paint too (#847).
+            for (run, bar) in vectorcraft_text::decorations(&lay, vectorcraft_text::FontDb::global(), &t) {
+                let st = t.runs.get(run).map(|r| r.style.clone()).unwrap_or_else(|| t.first_style());
+                let mut node = shape_node(d, PathData::from_bezpath(&bar).transformed(t.xf), None);
+                node.appearance = st.appearance();
+                children.push(Arc::new(node));
+            }
             let (par, idx, _) = d.position(tid).ok_or(EngineError::NoNode(tid))?;
             d.remove(tid)?;
             if children.is_empty() {

crates/pdf/src/export.rs

@@ -1304,6 +1304,9 @@ impl Exporter<'_> {
         let (below, above) = n.appearance.split_contents();
         let all = (!n.appearance.items.is_empty()).then(|| {
             let mut all = layout.to_bezpath();
+            for (_, bar) in vectorcraft_text::decorations(&layout, vectorcraft_text::FontDb::global(), t) {
+                all.extend(bar.iter());
+            }
             all.apply_affine(t.xf);
             to_path(&all).map(|p| (all, p))
         });
@@ -1314,16 +1317,27 @@ impl Exporter<'_> {
         s.push_transform(&xf(t.xf));
         // Real text: the characters' fills as text in embedded fonts.
         let plain = (!self.outline_text).then(|| t.plain_text());
+        let bars = vectorcraft_text::decorations(&layout, vectorcraft_text::FontDb::global(), t);
         for (i, run) in t.runs.iter().enumerate() {
             let mut bp = BezPath::new();
             for g in layout.glyphs.iter().filter(|g| g.run == i) {
                 bp.extend(g.outline.iter());
             }
+            // Underline and strikethrough bars are paths, with real text too (#847).
+            let mut run_bars = BezPath::new();
+            for (_, bar) in bars.iter().filter(|(r, _)| *r == i) {
+                run_bars.extend(bar.iter());
+            }
+            bp.extend(run_bars.iter());
             let fill = &run.style.fill;
             self.overprinting(s, run.style.overprint_fill, fill, |ex, s| {
                 // The outlines left to fill as paths: all of them, or those real text leaves.
                 let outlines = match plain.as_deref().filter(|_| !fill.is_none() && !ex.area_paint(fill)) {
-                    Some(text) => Cow::Owned(ex.glyph_text(s, &layout, i, text, fill)),
+                    Some(text) => {
+                        let mut left = ex.glyph_text(s, &layout, i, text, fill);
+                        left.extend(run_bars.iter());
+                        Cow::Owned(left)
+                    }
                     None => Cow::Borrowed(&bp),
                 };
                 let opaque = (1.0, BlendMode::Normal);

crates/render/src/lib.rs

@@ -1680,6 +1680,13 @@ fn text_geom_snapped(t: &TextObject, snap: Option<Affine>) -> TextGeom {
         cell.apply_affine(Affine::rotate_about(g.angle, g.origin));
         target.extend(cell.iter());
     }
+    // Underline and strikethrough bars, painted as their run's type is (#847).
+    for (run, bar) in vectorcraft_text::decorations(&layout, db, t) {
+        if let Some(r) = runs.get_mut(run) {
+            r.extend(bar.iter());
+        }
+        all.extend(bar.iter());
+    }
     TextGeom { runs, all, bounds: layout.bounds, substituted_fonts, substituted_glyphs, inlines: layout.inlines }
 }
 

crates/svg/src/export.rs

@@ -1638,8 +1638,13 @@ impl Writer<'_> {
         let a = self.attrs(&css::transparency(n));
         self.line(&format!("<g{id}{a}>"));
         self.depth += 1;
-        let lay = vectorcraft_text::layout(vectorcraft_text::FontDb::global(), t);
-        let pd = PathData::from_bezpath(&lay.to_bezpath()).transformed(t.xf);
+        let db = vectorcraft_text::FontDb::global();
+        let lay = vectorcraft_text::layout(db, t);
+        let mut all = lay.to_bezpath();
+        for (_, bar) in vectorcraft_text::decorations(&lay, db, t) {
+            all.extend(bar.iter());
+        }
+        let pd = PathData::from_bezpath(&all).transformed(t.xf);
         let d = self.path_d(&pd, self.xf);
         let tb = Some(t.xf.transform_rect_bbox(lay.bounds));
         let (below, above) = n.appearance.split_contents();
@@ -1671,12 +1676,15 @@ impl Writer<'_> {
     /// Text as glyph outlines: one compound path per run, painted like the run (gradients span
     /// the whole text, as on the canvas).
     fn text_outlines(&mut self, n: &Node, t: &TextObject) {
-        let lay = vectorcraft_text::layout(vectorcraft_text::FontDb::global(), t);
+        let db = vectorcraft_text::FontDb::global();
+        let lay = vectorcraft_text::layout(db, t);
         let mut runs: Vec<(usize, kurbo::BezPath)> = vec![];
-        for g in &lay.glyphs {
-            match runs.last_mut() {
-                Some((r, bp)) if *r == g.run => bp.extend(g.outline.iter()),
-                _ => runs.push((g.run, g.outline.clone())),
+        // Underline and strikethrough bars join their run's outlines.
+        let bars = vectorcraft_text::decorations(&lay, db, t);
+        for (run, outline) in lay.glyphs.iter().map(|g| (g.run, &g.outline)).chain(bars.iter().map(|(r, b)| (*r, b))) {
+            match runs.iter_mut().find(|(r, _)| *r == run) {
+                Some((_, bp)) => bp.extend(outline.iter()),
+                None => runs.push((run, outline.clone())),
             }
         }
         let id = self.id_attr(n);

crates/text/src/fontdb.rs

@@ -72,6 +72,10 @@ pub struct FontFace {
     /// values).
     pub(crate) cap_height: f64,
     pub(crate) x_height: f64,
+    /// Underline and strikeout: (offset from the baseline up to the line's top, thickness), in
+    /// font units (the `post` and OS/2 tables', else a common placement).
+    pub(crate) underline: (f64, f64),
+    pub(crate) strikeout: (f64, f64),
     pub(crate) shaper: harfrust::ShaperData,
     /// The axis settings of the variable font's named instance this face is (user units: `wght`
     /// 700); empty for a static face or a variable font's default instance.
@@ -1048,6 +1052,13 @@ fn make_face(bytes: FontBytes, index: u32, spec: FaceStyle, path: Option<std::pa
     let shaper = harfrust::ShaperData::new(&hb);
     let instance =
         (!variations.is_empty()).then(|| harfrust::ShaperInstance::from_variations(&hb, variations.iter().map(|(t, v)| (harfrust::Tag::new(t), *v))));
+    let upem = m.units_per_em.max(1) as f64;
+    let x_height = m.x_height.map(|v| v as f64).filter(|v| *v > 0.0).unwrap_or(m.ascent as f64 * 0.5);
+    let decoration = |d: Option<skrifa::metrics::Decoration>, fallback: (f64, f64)| {
+        d.map(|d| (f64::from(d.offset), f64::from(d.thickness))).filter(|(o, t)| o.is_finite() && *t > 0.0 && t.is_finite()).unwrap_or(fallback)
+    };
+    let underline = decoration(m.underline, (-0.075 * upem, 0.05 * upem));
+    let strikeout = decoration(m.strikeout, (x_height * 0.5 + 0.025 * upem, 0.05 * upem));
     Some(FontFace {
         keys,
         traits,
@@ -1060,11 +1071,13 @@ fn make_face(bytes: FontBytes, index: u32, spec: FaceStyle, path: Option<std::pa
         variations,
         location,
         instance,
-        upem: m.units_per_em.max(1) as f64,
+        upem,
         ascent: m.ascent as f64,
         descent: -(m.descent as f64),
         cap_height: m.cap_height.map(|v| v as f64).filter(|v| *v > 0.0).unwrap_or(m.ascent as f64 * 0.72),
-        x_height: m.x_height.map(|v| v as f64).filter(|v| *v > 0.0).unwrap_or(m.ascent as f64 * 0.5),
+        x_height,
+        underline,
+        strikeout,
         shaper,
         bytes,
         index,

crates/text/src/layout.rs

@@ -146,6 +146,46 @@ pub fn layout(db: &FontDb, t: &TextObject) -> TextLayout {
     layout_with(db, t, &opts)
 }
 
+/// The underline and strikethrough bars of `t` laid out as `layout` (#847): per run and line, a
+/// bar from the stretch's first glyph to its last one's advance, placed and sized by the font's
+/// own underline and strikeout metrics through the glyph's transform (so the size, baseline shift
+/// and scaling follow) → (run, bar in text space). Type on a path and vertical type have none yet.
+pub fn decorations(layout: &TextLayout, db: &FontDb, t: &TextObject) -> Vec<(usize, BezPath)> {
+    let mut out = vec![];
+    if layout.on_path || layout.vertical {
+        return out;
+    }
+    let glyphs = &layout.glyphs;
+    let mut i = 0;
+    while let Some(g) = glyphs.get(i) {
+        // The stretch: the glyphs of this run on this line, in a row.
+        let end = glyphs.iter().skip(i).position(|h| h.run != g.run || h.line != g.line).map_or(glyphs.len(), |n| i + n);
+        let stretch = glyphs.get(i..end).unwrap_or_default();
+        i = end.max(i + 1);
+        let Some(style) = t.runs.get(g.run).map(|r| &r.style) else { continue };
+        if !(style.underline || style.strikethrough) {
+            continue;
+        }
+        let Some(face) = db.face_by_id(g.font_id) else { continue };
+        let (x0, x1) = stretch.iter().fold((f64::INFINITY, f64::NEG_INFINITY), |(a, b), h| {
+            let (s, e) = (h.origin.x, h.origin.x + h.advance);
+            (a.min(s).min(e), b.max(s).max(e))
+        });
+        for (on, (offset, thickness)) in [(style.underline, face.underline), (style.strikethrough, face.strikeout)] {
+            if !on {
+                continue;
+            }
+            // Font units run y down in the glyph's transform: the bar's top is at -offset.
+            let (top, bottom) = ((g.xf * Point::new(0.0, -offset)).y, (g.xf * Point::new(0.0, -offset + thickness)).y);
+            let bar = Rect::new(x0, top.min(bottom), x1, top.max(bottom));
+            if bar.width() > 0.0 && bar.height() > 0.0 && bar.width().is_finite() && bar.height().is_finite() {
+                out.push((g.run, bar.to_path(0.1)));
+            }
+        }
+    }
+    out
+}
+
 /// Most layout passes Shrink Text to Fit runs past the first (bisection plus the final pass).
 const SHRINK_PASSES: usize = 11;
 

crates/text/src/lib.rs

@@ -32,7 +32,7 @@ pub use fontdb::{
 };
 pub use hyphen::{hyphenation_exceptions, set_hyphenation_exceptions};
 use kurbo::{Affine, BezPath, Point, Rect, Vec2};
-pub use layout::{layout, layout_with};
+pub use layout::{decorations, layout, layout_with};
 pub use vectorcraft_doc::TextObject;
 
 pub use vectorcraft_doc::{AreaFit, FirstBaseline, VerticalAlign};

crates/text/src/tests.rs

@@ -138,6 +138,29 @@ fn tracking_and_scale() {
     assert!(b.y1 < -4.0, "shifted up: {b:?}");
 }
 
+#[test]
+fn underline_and_strikethrough_bars() {
+    let mut t = point("ab", style(20.0));
+    t.runs = vec![
+        TextRun { text: "ab".into(), style: style(20.0), inline: None },
+        TextRun { text: "cd".into(), style: CharStyle { underline: true, strikethrough: true, ..style(20.0) }, inline: None },
+    ];
+    let l = layout(db(), &t);
+    let bars = decorations(&l, db(), &t);
+    assert_eq!(bars.len(), 2, "one underline and one strikethrough: {bars:?}");
+    assert!(bars.iter().all(|(run, _)| *run == 1), "only the styled run");
+    let (under, strike) = (bars[0].1.bounding_box(), bars[1].1.bounding_box());
+    // The bars span the run's glyphs: from "c" to the end of "d".
+    let (c, d) = (&l.glyphs[2], &l.glyphs[3]);
+    assert!((under.x0 - c.origin.x).abs() < 1e-6 && (under.x1 - d.origin.x - d.advance).abs() < 1e-6, "{under:?}");
+    // y runs down: the underline sits below the baseline, the strikethrough above it, both thin.
+    assert!(under.y0 > 0.0 && under.y1 < 5.0, "{under:?}");
+    assert!(strike.y1 < 0.0 && strike.y0 > -10.0, "{strike:?}");
+    assert!(under.height() < 3.0 && strike.height() < 3.0);
+    // No bars for plain text.
+    assert!(decorations(&layout(db(), &point("ab", style(20.0))), db(), &point("ab", style(20.0))).is_empty());
+}
+
 #[test]
 fn all_caps() {
     let a = width(&point("abc", CharStyle { all_caps: true, ..style(10.0) }));