style: Add support for 'flex-basis:content' in the style system.

Bug: 1105111
Reviewed-by: xidorn
MozReview-Commit-ID: 5WhgHJJ0mDB

components/style/values/computed/flex.rs

@@ -4,8 +4,23 @@
 
 //! Computed types for CSS values related to flexbox.
 
-use values::computed::length::LengthOrPercentage;
 use values::generics::flex::FlexBasis as GenericFlexBasis;
 
+/// The `width` value type.
+#[cfg(feature = "servo")]
+pub type Width = ::values::computed::NonNegativeLengthOrPercentageOrAuto;
+
+/// The `width` value type.
+#[cfg(feature = "gecko")]
+pub type Width = ::values::computed::MozLength;
+
 /// A computed value for the `flex-basis` property.
-pub type FlexBasis = GenericFlexBasis<LengthOrPercentage>;
+pub type FlexBasis = GenericFlexBasis<Width>;
+
+impl FlexBasis {
+    /// `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        GenericFlexBasis::Width(Width::auto())
+    }
+}

components/style/values/computed/length.rs

@@ -427,10 +427,10 @@ impl LengthOrPercentage {
     pub fn clamp_to_non_negative(self) -> Self {
         match self {
             LengthOrPercentage::Length(length) => {
-                LengthOrPercentage::Length(Length::new(length.px().max(0.)))
+                LengthOrPercentage::Length(length.clamp_to_non_negative())
             },
             LengthOrPercentage::Percentage(percentage) => {
-                LengthOrPercentage::Percentage(Percentage(percentage.0.max(0.)))
+                LengthOrPercentage::Percentage(percentage.clamp_to_non_negative())
             },
             _ => self
         }
@@ -511,6 +511,31 @@ impl LengthOrPercentageOrAuto {
     }
 }
 
+/// A wrapper of LengthOrPercentageOrAuto, whose value must be >= 0.
+pub type NonNegativeLengthOrPercentageOrAuto = NonNegative<LengthOrPercentageOrAuto>;
+
+impl NonNegativeLengthOrPercentageOrAuto {
+    /// `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        NonNegative(LengthOrPercentageOrAuto::Auto)
+    }
+}
+
+impl ToAnimatedValue for NonNegativeLengthOrPercentageOrAuto {
+    type AnimatedValue = LengthOrPercentageOrAuto;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        NonNegative(animated.clamp_to_non_negative())
+    }
+}
+
 impl LengthOrPercentageOrAuto {
     /// Returns true if the computed value is absolute 0 or 0%.
     ///
@@ -524,6 +549,15 @@ impl LengthOrPercentageOrAuto {
             Calc(_) | Auto => false
         }
     }
+
+    fn clamp_to_non_negative(self) -> Self {
+        use self::LengthOrPercentageOrAuto::*;
+        match self {
+            Length(l) => Length(l.clamp_to_non_negative()),
+            Percentage(p) => Percentage(p.clamp_to_non_negative()),
+            _ => self,
+        }
+    }
 }
 
 impl ToComputedValue for specified::LengthOrPercentageOrAuto {
@@ -737,6 +771,11 @@ impl CSSPixelLength {
         self.0
     }
 
+    #[inline]
+    fn clamp_to_non_negative(self) -> Self {
+        Self::new(self.px().max(0.))
+    }
+
     /// Return the length with app_unit i32 type.
     #[inline]
     pub fn to_i32_au(&self) -> i32 {

components/style/values/computed/mod.rs

@@ -60,7 +60,8 @@ pub use super::{Auto, Either, None_};
 pub use super::specified::{BorderStyle, TextDecorationLine};
 pub use self::length::{CalcLengthOrPercentage, Length, LengthOrNumber, LengthOrPercentage};
 pub use self::length::{LengthOrPercentageOrAuto, LengthOrPercentageOrNone, MaxLength, MozLength};
-pub use self::length::{CSSPixelLength, ExtremumLength, NonNegativeLength, NonNegativeLengthOrPercentage};
+pub use self::length::{CSSPixelLength, ExtremumLength, NonNegativeLength};
+pub use self::length::{NonNegativeLengthOrPercentage, NonNegativeLengthOrPercentageOrAuto};
 pub use self::list::{ListStyleImage, Quotes};
 #[cfg(feature = "gecko")]
 pub use self::list::ListStyleType;

components/style/values/computed/percentage.rs

@@ -32,6 +32,12 @@ impl Percentage {
     pub fn abs(&self) -> Self {
         Percentage(self.0.abs())
     }
+
+    /// Clamps this percentage to a non-negative percentage.
+    #[inline]
+    pub fn clamp_to_non_negative(self) -> Self {
+        Percentage(self.0.max(0.))
+    }
 }
 
 impl ToCss for Percentage {