style: Add a Zero trait that doesn't require Add, and use it in place of num_traits and IsZeroLength.

Use it to be consistent in InsetRect serialization and storage between Servo and
Gecko.

Differential Revision: https://phabricator.services.mozilla.com/D21493

components/style/values/computed/angle.rs

@@ -6,7 +6,7 @@
 
 use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
 use crate::values::CSSFloat;
-use num_traits::Zero;
+use crate::Zero;
 use std::f64::consts::PI;
 use std::fmt::{self, Write};
 use std::{f32, f64};

components/style/values/computed/border.rs

@@ -14,6 +14,7 @@ use crate::values::generics::border::BorderSpacing as GenericBorderSpacing;
 use crate::values::generics::rect::Rect;
 use crate::values::generics::size::Size2D;
 use crate::values::generics::NonNegative;
+use crate::Zero;
 use app_units::Au;
 
 pub use crate::values::specified::border::BorderImageRepeat;
@@ -75,39 +76,3 @@ impl BorderSpacing {
         Au::from(*self.0.height())
     }
 }
-
-impl BorderCornerRadius {
-    /// Returns `0 0`.
-    pub fn zero() -> Self {
-        GenericBorderCornerRadius(Size2D::new(
-            NonNegativeLengthPercentage::zero(),
-            NonNegativeLengthPercentage::zero(),
-        ))
-    }
-}
-
-impl BorderRadius {
-    /// Returns a `0` border radius.
-    pub fn zero() -> Self {
-        Self {
-            top_left: BorderCornerRadius::zero(),
-            top_right: BorderCornerRadius::zero(),
-            bottom_right: BorderCornerRadius::zero(),
-            bottom_left: BorderCornerRadius::zero(),
-        }
-    }
-
-    /// Returns whether all the values are `0px`.
-    pub fn all_zero(&self) -> bool {
-        fn all(corner: &BorderCornerRadius) -> bool {
-            fn is_zero(l: &NonNegativeLengthPercentage) -> bool {
-                *l == NonNegativeLengthPercentage::zero()
-            }
-            is_zero(corner.0.width()) && is_zero(corner.0.height())
-        }
-        all(&self.top_left) &&
-            all(&self.top_right) &&
-            all(&self.bottom_left) &&
-            all(&self.bottom_right)
-    }
-}

components/style/values/computed/length.rs

@@ -12,11 +12,11 @@ use crate::values::generics::length as generics;
 use crate::values::generics::length::{
     GenericLengthOrNumber, MaxSize as GenericMaxSize, Size as GenericSize,
 };
-use crate::values::generics::transform::IsZeroLength;
 use crate::values::generics::NonNegative;
 use crate::values::specified::length::ViewportPercentageLength;
 use crate::values::specified::length::{AbsoluteLength, FontBaseSize, FontRelativeLength};
 use crate::values::{specified, Auto, CSSFloat, Either, Normal};
+use crate::Zero;
 use app_units::Au;
 use ordered_float::NotNan;
 use std::fmt::{self, Write};
@@ -342,12 +342,6 @@ impl ToComputedValue for specified::CalcLengthPercentage {
 }
 
 impl LengthPercentage {
-    #[inline]
-    #[allow(missing_docs)]
-    pub fn zero() -> LengthPercentage {
-        LengthPercentage::new(Length::new(0.), None)
-    }
-
     /// 1px length value for SVG defaults
     #[inline]
     pub fn one() -> LengthPercentage {
@@ -442,9 +436,13 @@ impl ToComputedValue for specified::LengthPercentage {
     }
 }
 
-impl IsZeroLength for LengthPercentage {
+impl Zero for LengthPercentage {
+    fn zero() -> Self {
+        LengthPercentage::new(Length::zero(), None)
+    }
+
     #[inline]
-    fn is_zero_length(&self) -> bool {
+    fn is_zero(&self) -> bool {
         self.is_definitely_zero()
     }
 }
@@ -453,12 +451,6 @@ impl IsZeroLength for LengthPercentage {
 /// length-percentage or auto.
 macro_rules! computed_length_percentage_or_auto {
     ($inner:ty) => {
-        /// Returns the `0` value.
-        #[inline]
-        pub fn zero() -> Self {
-            generics::LengthPercentageOrAuto::LengthPercentage(<$inner>::zero())
-        }
-
         /// Returns the used value.
         #[inline]
         pub fn to_used_value(&self, percentage_basis: Au) -> Option<Au> {
@@ -547,12 +539,6 @@ impl From<Au> for LengthPercentage {
 }
 
 impl NonNegativeLengthPercentage {
-    /// Get zero value.
-    #[inline]
-    pub fn zero() -> Self {
-        NonNegative(LengthPercentage::zero())
-    }
-
     /// Returns true if the computed value is absolute 0 or 0%.
     #[inline]
     pub fn is_definitely_zero(&self) -> bool {
@@ -656,12 +642,16 @@ impl CSSPixelLength {
     pub fn clamp_to_non_negative(self) -> Self {
         CSSPixelLength::new(self.0.max(0.))
     }
+}
 
-    /// Zero value
-    #[inline]
-    pub fn zero() -> Self {
+impl Zero for CSSPixelLength {
+    fn zero() -> Self {
         CSSPixelLength::new(0.)
     }
+
+    fn is_zero(&self) -> bool {
+        self.px() == 0.
+    }
 }
 
 impl ToCss for CSSPixelLength {
@@ -743,12 +733,6 @@ impl NonNegativeLength {
         NonNegative(Length::new(px.max(0.)))
     }
 
-    /// Return a zero value.
-    #[inline]
-    pub fn zero() -> Self {
-        Self::new(0.)
-    }
-
     /// Return the pixel value of |NonNegativeLength|.
     #[inline]
     pub fn px(&self) -> CSSFloat {

components/style/values/computed/percentage.rs

@@ -7,6 +7,7 @@
 use crate::values::animated::ToAnimatedValue;
 use crate::values::generics::NonNegative;
 use crate::values::{serialize_percentage, CSSFloat};
+use crate::Zero;
 use std::fmt;
 use style_traits::{CssWriter, ToCss};
 
@@ -31,12 +32,6 @@ use style_traits::{CssWriter, ToCss};
 pub struct Percentage(pub CSSFloat);
 
 impl Percentage {
-    /// 0%
-    #[inline]
-    pub fn zero() -> Self {
-        Percentage(0.)
-    }
-
     /// 100%
     #[inline]
     pub fn hundred() -> Self {
@@ -56,6 +51,16 @@ impl Percentage {
     }
 }
 
+impl Zero for Percentage {
+    fn zero() -> Self {
+        Percentage(0.)
+    }
+
+    fn is_zero(&self) -> bool {
+        self.0 == 0.
+    }
+}
+
 impl ToCss for Percentage {
     fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
     where
@@ -69,12 +74,6 @@ impl ToCss for Percentage {
 pub type NonNegativePercentage = NonNegative<Percentage>;
 
 impl NonNegativePercentage {
-    /// 0%
-    #[inline]
-    pub fn zero() -> Self {
-        NonNegative(Percentage::zero())
-    }
-
     /// 100%
     #[inline]
     pub fn hundred() -> Self {

components/style/values/computed/position.rs

@@ -11,6 +11,7 @@ use crate::values::computed::{Integer, LengthPercentage, Percentage};
 use crate::values::generics::position::Position as GenericPosition;
 use crate::values::generics::position::ZIndex as GenericZIndex;
 pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas};
+use crate::Zero;
 use std::fmt::{self, Write};
 use style_traits::{CssWriter, ToCss};
 

components/style/values/computed/svg.rs

@@ -10,6 +10,7 @@ use crate::values::computed::{LengthPercentage, NonNegativeLengthPercentage};
 use crate::values::computed::{NonNegativeNumber, Number, Opacity};
 use crate::values::generics::svg as generic;
 use crate::values::RGBA;
+use crate::Zero;
 
 pub use crate::values::specified::SVGPaintOrder;
 

components/style/values/computed/transform.rs

@@ -9,8 +9,8 @@ use crate::values::animated::transform::{Perspective, Scale3D, Translate3D};
 use crate::values::animated::ToAnimatedZero;
 use crate::values::computed::{Angle, Integer, Length, LengthPercentage, Number, Percentage};
 use crate::values::generics::transform as generic;
+use crate::Zero;
 use euclid::{Transform3D, Vector3D};
-use num_traits::Zero;
 
 pub use crate::values::generics::transform::TransformStyle;