Use generics for border-image-slice property

components/style/values/generics/border.rs

@@ -6,6 +6,7 @@
 
 use std::fmt;
 use style_traits::ToCss;
+use values::generics::rect::Rect;
 
 /// A generic value for a single side of a `border-image-width` property.
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
@@ -19,6 +20,16 @@ pub enum BorderImageWidthSide<LengthOrPercentage, Number> {
     Auto,
 }
 
+/// A generic value for the `border-image-slice` property.
+#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+pub struct BorderImageSlice<NumberOrPercentage> {
+    /// The offsets.
+    pub offsets: Rect<NumberOrPercentage>,
+    /// Whether to fill the middle part.
+    pub fill: bool,
+}
+
 impl<L, N> ToCss for BorderImageWidthSide<L, N>
     where L: ToCss, N: ToCss,
 {
@@ -32,3 +43,29 @@ impl<L, N> ToCss for BorderImageWidthSide<L, N>
         }
     }
 }
+
+impl<N> From<N> for BorderImageSlice<N>
+    where N: Clone,
+{
+    #[inline]
+    fn from(value: N) -> Self {
+        Self {
+            offsets: value.into(),
+            fill: false,
+        }
+    }
+}
+
+impl<N> ToCss for BorderImageSlice<N>
+    where N: PartialEq + ToCss,
+{
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
+        where W: fmt::Write
+    {
+        self.offsets.to_css(dest)?;
+        if self.fill {
+            dest.write_str(" fill")?;
+        }
+        Ok(())
+    }
+}