Use generics for the border-image-width property

components/style/values/generics/border.rs

@@ -0,0 +1,34 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to borders.
+
+use std::fmt;
+use style_traits::ToCss;
+
+/// A generic value for a single side of a `border-image-width` property.
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue)]
+pub enum BorderImageWidthSide<LengthOrPercentage, Number> {
+    /// `<length-or-percentage>`
+    Length(LengthOrPercentage),
+    /// `<number>`
+    Number(Number),
+    /// `auto`
+    Auto,
+}
+
+impl<L, N> ToCss for BorderImageWidthSide<L, N>
+    where L: ToCss, N: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
+        where W: fmt::Write
+    {
+        match *self {
+            BorderImageWidthSide::Length(ref length) => length.to_css(dest),
+            BorderImageWidthSide::Number(ref number) => number.to_css(dest),
+            BorderImageWidthSide::Auto => dest.write_str("auto"),
+        }
+    }
+}