style: Add computed value ZeroToOneNumber.

Correctly handle clamping to 1 behavior of grayscale(),
invert(), opacity() and sepia().

Differential Revision: https://phabricator.services.mozilla.com/D35509

components/style/values/generics/effects.rs

@@ -52,34 +52,34 @@ pub use self::GenericBoxShadow as BoxShadow;
     ToShmem,
 )]
 #[repr(C, u8)]
-pub enum GenericFilter<Angle, Factor, Length, Shadow, U> {
+pub enum GenericFilter<Angle, NonNegativeFactor, ZeroToOneFactor, Length, Shadow, U> {
     /// `blur(<length>)`
     #[css(function)]
     Blur(Length),
     /// `brightness(<factor>)`
     #[css(function)]
-    Brightness(Factor),
+    Brightness(NonNegativeFactor),
     /// `contrast(<factor>)`
     #[css(function)]
-    Contrast(Factor),
+    Contrast(NonNegativeFactor),
     /// `grayscale(<factor>)`
     #[css(function)]
-    Grayscale(Factor),
+    Grayscale(ZeroToOneFactor),
     /// `hue-rotate(<angle>)`
     #[css(function)]
     HueRotate(Angle),
     /// `invert(<factor>)`
     #[css(function)]
-    Invert(Factor),
+    Invert(ZeroToOneFactor),
     /// `opacity(<factor>)`
     #[css(function)]
-    Opacity(Factor),
+    Opacity(ZeroToOneFactor),
     /// `saturate(<factor>)`
     #[css(function)]
-    Saturate(Factor),
+    Saturate(NonNegativeFactor),
     /// `sepia(<factor>)`
     #[css(function)]
-    Sepia(Factor),
+    Sepia(ZeroToOneFactor),
     /// `drop-shadow(...)`
     #[css(function)]
     DropShadow(Shadow),

components/style/values/generics/mod.rs

@@ -227,6 +227,28 @@ impl<T: Zero> Zero for NonNegative<T> {
 )]
 pub struct GreaterThanOrEqualToOne<T>(pub T);
 
+/// A wrapper of values between zero and one.
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct ZeroToOne<T>(pub T);
+
 /// A clip rect for clip and image-region
 #[allow(missing_docs)]
 #[derive(