Use generics for scroll-snap-points-*

components/style/values/generics/gecko.rs

@@ -0,0 +1,54 @@
+/* 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 legacy Gecko-only properties that should probably be
+//! unshipped at some point in the future.
+
+use std::fmt;
+use style_traits::ToCss;
+
+/// A generic value for scroll snap points.
+#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue)]
+pub enum ScrollSnapPoint<LengthOrPercentage> {
+    /// `none`
+    None,
+    /// `repeat(<length-or-percentage>)`
+    Repeat(LengthOrPercentage)
+}
+
+impl<L> ScrollSnapPoint<L> {
+    /// Returns `none`.
+    #[inline]
+    pub fn none() -> Self {
+        ScrollSnapPoint::None
+    }
+
+    /// Returns the repeat argument, if any.
+    #[inline]
+    pub fn repeated(&self) -> Option<&L> {
+        match *self {
+            ScrollSnapPoint::None => None,
+            ScrollSnapPoint::Repeat(ref length) => Some(length),
+        }
+    }
+}
+
+impl<L> ToCss for ScrollSnapPoint<L>
+where
+    L: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        match *self {
+            ScrollSnapPoint::None => dest.write_str("none"),
+            ScrollSnapPoint::Repeat(ref length) => {
+                dest.write_str("repeat(")?;
+                length.to_css(dest)?;
+                dest.write_str(")")
+            },
+        }
+    }
+}