Merge #1901: Resolve SVG font-size percentages against the parent font size (@Silvertree2010)

# Conflicts:
#	crates/svg/src/tests.rs

crates/svg/src/lib.rs

@@ -719,7 +719,11 @@ impl<'a, 'i> Parser<'a, 'i> {
         if let Some(c) = d.get("color").and_then(|v| parse_color(v)) {
             st.color = c;
         }
-        if let Some(v) = d.get("font-size").and_then(|v| self.length(v, 'o', st.font_size)) {
+        let font_size = d.get("font-size").and_then(|v| match v.trim().strip_suffix('%') {
+            Some(p) => p.trim().parse::<f64>().ok().map(|p| p / 100.0 * st.font_size),
+            None => self.length(v, 'o', st.font_size),
+        });
+        if let Some(v) = font_size.filter(|v| v.is_finite()) {
             st.font_size = v;
         }
         if let Some(p) = d.get("fill").and_then(|v| self.paint_ref(v)) {

crates/svg/src/tests.rs

@@ -391,3 +391,18 @@ fn matching_work_past_the_budget_errors_without_doing_it() {
     let ok = styled(&format!("{}{{{decls}}}", vec!["circle"; 10_000].join(",")), &[""]);
     assert!(parse(&ok).is_ok());
 }
+
+#[test]
+fn font_size_percentage_resolves_against_the_parent_font_size() {
+    for (body, expected) in [
+        (r#"<g font-size="200%"><rect width="1em" height="1em"/></g>"#, 32.0),
+        (r#"<g font-size="200%"><rect width="2ex" height="1em"/></g>"#, 32.0),
+        (r#"<g font-size="200%"><g font-size="200%"><rect width="1em" height="1em"/></g></g>"#, 64.0),
+    ] {
+        let svg = format!(r#"<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">{body}</svg>"#);
+        let d = parse(svg.as_bytes()).unwrap();
+        let shapes = d.flatten();
+        assert_eq!(shapes.len(), 1);
+        assert!(matches!(shapes[0].2.geom, Geom::Rect { w, .. } if w == expected), "{body}: {:?}", shapes[0].2.geom);
+    }
+}