SVG: type written as outlines stacks colour glyphs under their run's paint

As on the canvas: each run's bitmap, COLR and SVG glyphs come before the run's path, so a plain character set over a colour one stays on top.

crates/svg/src/export.rs

@@ -1920,11 +1920,11 @@ impl Writer<'_> {
     }
 
     /// Text as glyph outlines: one compound path per run, painted like the run (gradients span
-    /// the whole text, as on the canvas).
+    /// the whole text), over its colour glyphs, as on the canvas.
     fn text_outlines(&mut self, n: &Node, t: &TextObject) {
         let db = vectorcraft_text::FontDb::global();
         let lay = vectorcraft_text::layout(db, t);
-        let mut runs: Vec<(usize, kurbo::BezPath)> = vec![];
+        let mut runs = vec![kurbo::BezPath::new(); t.runs.len()];
         // Underline and strikethrough bars join their run's outlines; ruby glyphs are painted
         // with the run of the text they annotate.
         let bars = vectorcraft_text::decorations(&lay, db, t);
@@ -1935,9 +1935,8 @@ impl Writer<'_> {
             .chain(lay.ruby.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())),
+            if let Some(bp) = runs.get_mut(run) {
+                bp.extend(outline.iter());
             }
         }
         let id = self.id_attr(n);
@@ -1947,29 +1946,33 @@ impl Writer<'_> {
         // The glyphs stay in text space; the text's transform joins the document's meanwhile.
         let saved = self.xf;
         self.xf = saved * t.xf;
-        for (r, bp) in runs {
-            let Some(run) = t.runs.get(r) else { continue };
-            let pd = PathData::from_bezpath(&bp);
+        for (i, (bp, run)) in runs.iter().zip(&t.runs).enumerate() {
+            // Colour glyphs paint themselves, under their run's paint: bitmap glyphs (emoji) as
+            // their images, COLR and SVG glyphs as their art.
+            for g in lay.glyphs.iter().filter(|g| g.run == i) {
+                if let Some((image, to_text)) = g.placed_image() {
+                    let m = self.matrix(self.xf * to_text);
+                    let href = self.blob_href(&image.blob);
+                    self.line(&format!(
+                        "<image width=\"{}\" height=\"{}\" transform=\"{m}\" preserveAspectRatio=\"none\" xlink:href=\"{}\"/>",
+                        image.width,
+                        image.height,
+                        xml_escape(&href)
+                    ));
+                }
+                if let Some(art) = g.placed_colour(Affine::IDENTITY) {
+                    self.node(&art);
+                }
+            }
+            if bp.elements().is_empty() {
+                continue;
+            }
+            let pd = PathData::from_bezpath(bp);
             // An unnamed id: the pieces carry no id attribute (the group has it).
             let glyphs = Node::path(NodeId(u64::MAX), pd.clone(), run.style.appearance());
             let d = self.path_d(&pd, self.xf);
             self.shape(&glyphs, &d, &[&pd], FillRule::NonZero, Some(lay.bounds));
         }
-        // Colour bitmap glyphs (emoji): their images, which the runs' paint doesn't paint.
-        for (image, to_text) in lay.glyphs.iter().filter_map(|g| g.placed_image()) {
-            let m = self.matrix(self.xf * to_text);
-            let href = self.blob_href(&image.blob);
-            self.line(&format!(
-                "<image width=\"{}\" height=\"{}\" transform=\"{m}\" preserveAspectRatio=\"none\" xlink:href=\"{}\"/>",
-                image.width,
-                image.height,
-                xml_escape(&href)
-            ));
-        }
-        // COLR glyphs: their layers, as art.
-        for art in lay.glyphs.iter().filter_map(|g| g.placed_colour(Affine::IDENTITY)) {
-            self.node(&art);
-        }
         self.xf = saved;
         self.depth -= 1;
         self.line("</g>");

crates/svg/tests/colour_glyphs.rs

@@ -43,14 +43,14 @@ fn embedded_fonts_leave_bitmap_glyphs_to_the_viewer() {
     assert!(out.svg.contains(&format!("{COLOUR_CHAR}F")), "the character stays text");
 }
 
-/// `ch` in the COLR test font (v1 or v0), 24 pt, filled blue.
-fn colr_doc(v1: bool, ch: char) -> Document {
+/// `text` in the COLR test font (v1 or v0), 24 pt, filled blue.
+fn colr_doc(v1: bool, text: impl std::fmt::Display) -> Document {
     use vectorcraft_text::test_fonts::{colr_family, colr_font};
     vectorcraft_text::FontDb::global().add_font(colr_font(v1).unwrap());
     let mut d = Document::new(200.0, 100.0);
     let fill = vectorcraft_doc::color::Paint::solid(vectorcraft_doc::color::Color::rgb8(0, 0, 255));
     let st = CharStyle { font_family: colr_family(v1).into(), size: 24.0, fill, ..CharStyle::default() };
-    let n = Node::new(d.alloc_id(), NodeKind::Text(Box::new(TextObject::point(Point::new(10.0, 50.0), &ch.to_string(), st))));
+    let n = Node::new(d.alloc_id(), NodeKind::Text(Box::new(TextObject::point(Point::new(10.0, 50.0), &text.to_string(), st))));
     let l = d.layers[0].id;
     d.insert(Some(l), 0, n).unwrap();
     d
@@ -82,3 +82,15 @@ fn embedded_fonts_leave_colr_glyphs_to_the_viewer() {
     assert!(out.warnings.iter().any(|w| w.contains("emoji")), "{:?}", out.warnings);
     assert!(out.svg.contains(COLOUR_CHAR), "the character stays text");
 }
+
+/// Outlined text stacks as the canvas paints type: a run's colour glyphs under its paint, so a
+/// plain character set over a colour one stays on top.
+#[test]
+fn outlined_colour_glyphs_stay_under_their_runs_paint() {
+    let outlined = ExportOptions { outline_text: true, ..Default::default() };
+    let svg = export_full(&doc(), &outlined, None).svg;
+    assert!(svg.find("<image ").unwrap() < svg.find("<path").unwrap(), "the emoji, then the run: {svg}");
+    let svg = export_full(&colr_doc(false, format!("{COLOUR_CHAR}F")), &outlined, None).svg;
+    let first = &svg[svg.find("<path").unwrap()..];
+    assert!(first[..first.find('>').unwrap()].contains("f00"), "the red layer first: {svg}");
+}