From ecc131fc869253161fc827a7be58a33a30938fe2 Mon Sep 17 00:00:00 2001
From: webdevtodayjason <115739170+webdevtodayjason@users.noreply.github.com>
Date: Mon, 12 Oct 2026 17:45:45 +0000
Subject: [PATCH] SVG: percentages in the root <svg> resolve against its own
 width and height

---
 crates/svg/src/lib.rs   |  4 ++++
 crates/svg/src/tests.rs | 22 ++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/crates/svg/src/lib.rs b/crates/svg/src/lib.rs
index 75985fbd..9e24a5b8 100644
--- a/crates/svg/src/lib.rs
+++ b/crates/svg/src/lib.rs
@@ -1147,6 +1147,10 @@ pub fn parse(bytes: &[u8]) -> Result<Doc, Error> {
         }
         None => (pct_or("width", 'x', 300.0), pct_or("height", 'y', 150.0)),
     };
+    // Percentages use the root viewport's user space, even without a viewBox. A size that is not
+    // a finite positive number keeps the 300x150 default, so it cannot produce NaN geometry.
+    let usable = |v: f64, d: f64| if v.is_finite() && v > 0.0 { v } else { d };
+    (p.vw, p.vh) = vb.map_or((usable(dw, 300.0), usable(dh, 150.0)), |(_, w, h)| (w, h));
     let mut rst = st.clone();
     let (opacity, _) = p.cascade(root, &mut rst);
     let mut children = vec![];
diff --git a/crates/svg/src/tests.rs b/crates/svg/src/tests.rs
index 3553205d..e06537e3 100644
--- a/crates/svg/src/tests.rs
+++ b/crates/svg/src/tests.rs
@@ -86,6 +86,28 @@ fn paths_gradients_css_use() {
     assert!(c[0] > 0.9 && c[3] > 0.9, "{c:?}");
 }
 
+#[test]
+fn root_svg_percentages_use_the_document_viewport() {
+    for (attrs, width, height) in [
+        ("width=\"100\" height=\"80\"", 100.0, 80.0),
+        ("width=\"50%\" height=\"200%\"", 150.0, 300.0),
+        ("", 300.0, 150.0),
+        ("width=\"100\" height=\"80\" viewBox=\"0 0 200 160\"", 200.0, 160.0),
+        ("width=\"NaN%\" height=\"1e400\"", 300.0, 150.0),
+    ] {
+        let svg = format!(r#"<svg xmlns="http://www.w3.org/2000/svg" {attrs}><rect x="25%" y="25%" width="50%" height="50%"/></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 { x, y, w, h, .. }
+            if x == width / 4.0 && y == height / 4.0 && w == width / 2.0 && h == height / 2.0),
+            "{attrs}: {:?}",
+            shapes[0].2.geom
+        );
+    }
+}
+
 #[test]
 fn nested_svg_percentages_use_the_nearest_viewport() {
     let d = parse(