1 files changed, 87 insertions, 0 deletions
diff --git a/rsvg/src/viewbox.rs b/rsvg/src/viewbox.rs
new file mode 100644
index 00000000..e6ad39a9
--- /dev/null
+++ b/rsvg/src/viewbox.rs
@@ -0,0 +1,87 @@
+//! Parser for the `viewBox` attribute.
+
+use cssparser::Parser;
+use std::ops::Deref;
+
+use crate::error::*;
+use crate::parsers::{NumberList, Parse};
+use crate::rect::Rect;
+
+/// Newtype around a [`Rect`], used to represent the `viewBox` attribute.
+///
+/// A `ViewBox` is a new user-space coordinate system mapped onto the rectangle defined by
+/// the current viewport.  See <https://www.w3.org/TR/SVG2/coords.html#ViewBoxAttribute>
+///
+/// `ViewBox` derefs to [`Rect`], so you can use [`Rect`]'s methods and fields directly like
+/// `vbox.x0` or `vbox.width()`.
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub struct ViewBox(Rect);
+
+impl Deref for ViewBox {
+    type Target = Rect;
+
+    fn deref(&self) -> &Rect {
+        &self.0
+    }
+}
+
+impl From<Rect> for ViewBox {
+    fn from(r: Rect) -> ViewBox {
+        ViewBox(r)
+    }
+}
+
+impl Parse for ViewBox {
+    // Parse a viewBox attribute
+    // https://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute
+    //
+    // viewBox: double [,] double [,] double [,] double [,]
+    //
+    // x, y, w, h
+    //
+    // Where w and h must be nonnegative.
+    fn parse<'i>(parser: &mut Parser<'i, '_>) -> Result<ViewBox, ParseError<'i>> {
+        let loc = parser.current_source_location();
+
+        let NumberList::<4, 4>(v) = NumberList::parse(parser)?;
+        let (x, y, width, height) = (v[0], v[1], v[2], v[3]);
+
+        if width >= 0.0 && height >= 0.0 {
+            Ok(ViewBox(Rect::new(x, y, x + width, y + height)))
+        } else {
+            Err(loc.new_custom_error(ValueErrorKind::value_error(
+                "width and height must not be negative",
+            )))
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_valid_viewboxes() {
+        assert_eq!(
+            ViewBox::parse_str("  1 2 3 4").unwrap(),
+            ViewBox(Rect::new(1.0, 2.0, 4.0, 6.0))
+        );
+
+        assert_eq!(
+            ViewBox::parse_str(" -1.5 -2.5e1,34,56e2  ").unwrap(),
+            ViewBox(Rect::new(-1.5, -25.0, 32.5, 5575.0))
+        );
+    }
+
+    #[test]
+    fn parsing_invalid_viewboxes_yields_error() {
+        assert!(ViewBox::parse_str("").is_err());
+        assert!(ViewBox::parse_str(" 1,2,-3,-4 ").is_err());
+        assert!(ViewBox::parse_str("qwerasdfzxcv").is_err());
+        assert!(ViewBox::parse_str(" 1 2 3 4   5").is_err());
+        assert!(ViewBox::parse_str(" 1 2 foo 3 4").is_err());
+
+        // https://gitlab.gnome.org/GNOME/librsvg/issues/344
+        assert!(ViewBox::parse_str("0 0 9E80.7").is_err());
+    }
+}