1 files changed, 50 insertions, 0 deletions
diff --git a/servo/components/style/values/generics/ratio.rs b/servo/components/style/values/generics/ratio.rs
new file mode 100644
index 0000000000..8c66fed602
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+++ b/servo/components/style/values/generics/ratio.rs
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to <ratio>.
+//! https://drafts.csswg.org/css-values/#ratios
+
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// A generic value for the `<ratio>` value.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct Ratio<N>(pub N, pub N);
+
+impl<N> ToCss for Ratio<N>
+where
+    N: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0.to_css(dest)?;
+        // Even though 1 could be omitted, we don't per
+        // https://drafts.csswg.org/css-values-4/#ratio-value:
+        //
+        //     The second <number> is optional, defaulting to 1. However,
+        //     <ratio> is always serialized with both components.
+        //
+        // And for compat reasons, see bug 1669742.
+        //
+        // We serialize with spaces for consistency with all other
+        // slash-delimited things, see
+        // https://github.com/w3c/csswg-drafts/issues/4282
+        dest.write_str(" / ")?;
+        self.1.to_css(dest)?;
+        Ok(())
+    }
+}