style: Move font-size-adjust outside of mako

components/style/values/computed/font.rs

@@ -7,7 +7,8 @@
 use app_units::Au;
 use std::fmt;
 use style_traits::ToCss;
-use values::animated::ToAnimatedValue;
+use values::CSSFloat;
+use values::animated::{ToAnimatedValue, ToAnimatedZero};
 use values::computed::{Context, NonNegativeLength, ToComputedValue};
 use values::specified::font as specified;
 use values::specified::length::{FontBaseSize, NoCalcLength};
@@ -212,6 +213,58 @@ impl ToAnimatedValue for FontSize {
     }
 }
 
+#[derive(Animate, Clone, ComputeSquaredDistance, Copy, Debug, MallocSizeOf, PartialEq, ToCss)]
+/// Preserve the readability of text when font fallback occurs
+pub enum FontSizeAdjust {
+    #[animation(error)]
+    /// None variant
+    None,
+    /// Number variant
+    Number(CSSFloat),
+}
+
+impl FontSizeAdjust {
+    #[inline]
+    /// Default value of font-size-adjust
+    pub fn none() -> Self {
+        FontSizeAdjust::None
+    }
+
+    /// Get font-size-adjust with float number
+    pub fn from_gecko_adjust(gecko: f32) -> Self {
+        if gecko == -1.0 {
+            FontSizeAdjust::None
+        } else {
+            FontSizeAdjust::Number(gecko)
+        }
+    }
+}
+
+impl ToAnimatedZero for FontSizeAdjust {
+    #[inline]
+    // FIXME(emilio): why?
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+impl ToAnimatedValue for FontSizeAdjust {
+    type AnimatedValue = Self;
+
+    #[inline]
+    fn to_animated_value(self) -> Self {
+        self
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        match animated {
+            FontSizeAdjust::Number(number) => FontSizeAdjust::Number(number.max(0.)),
+            _ => animated
+        }
+    }
+}
+
 impl ToComputedValue for specified::MozScriptMinSize {
     type ComputedValue = MozScriptMinSize;
 

components/style/values/computed/mod.rs

@@ -36,7 +36,7 @@ pub use self::angle::Angle;
 pub use self::background::{BackgroundSize, BackgroundRepeat};
 pub use self::border::{BorderImageSlice, BorderImageWidth, BorderImageSideWidth};
 pub use self::border::{BorderRadius, BorderCornerRadius, BorderSpacing};
-pub use self::font::{FontSize, FontWeight, MozScriptLevel, MozScriptMinSize, XTextZoom};
+pub use self::font::{FontSize, FontSizeAdjust, FontWeight, MozScriptLevel, MozScriptMinSize, XTextZoom};
 pub use self::box_::{AnimationIterationCount, AnimationName, ScrollSnapType, VerticalAlign};
 pub use self::color::{Color, ColorPropertyValue, RGBAColor};
 pub use self::effects::{BoxShadow, Filter, SimpleShadow};

components/style/values/specified/font.rs

@@ -13,7 +13,7 @@ use properties::longhands::system_font::SystemFont;
 use std::fmt;
 use style_traits::{ToCss, StyleParseErrorKind, ParseError};
 use values::computed::{font as computed, Context, Length, NonNegativeLength, ToComputedValue};
-use values::specified::{AllowQuirks, LengthOrPercentage, NoCalcLength};
+use values::specified::{AllowQuirks, LengthOrPercentage, NoCalcLength, Number};
 use values::specified::length::{AU_PER_PT, AU_PER_PX, FontBaseSize};
 
 const DEFAULT_SCRIPT_MIN_SIZE_PT: u32 = 8;
@@ -151,6 +151,76 @@ impl From<LengthOrPercentage> for FontSize {
     }
 }
 
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss)]
+/// Preserve the readability of text when font fallback occurs
+pub enum FontSizeAdjust {
+    /// None variant
+    None,
+    /// Number variant
+    Number(Number),
+    /// system font
+    System(SystemFont),
+}
+
+impl FontSizeAdjust {
+    #[inline]
+    /// Default value of font-size-adjust
+    pub fn none() -> Self {
+        FontSizeAdjust::None
+    }
+
+    /// Get font-size-adjust with SystemFont
+    pub fn system_font(f: SystemFont) -> Self {
+        FontSizeAdjust::System(f)
+    }
+
+    /// Get SystemFont variant
+    pub fn get_system(&self) -> Option<SystemFont> {
+        if let FontSizeAdjust::System(s) = *self {
+            Some(s)
+        } else {
+            None
+        }
+    }
+}
+
+impl ToComputedValue for FontSizeAdjust {
+    type ComputedValue = computed::FontSizeAdjust;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            FontSizeAdjust::None => computed::FontSizeAdjust::None,
+            FontSizeAdjust::Number(ref n) => computed::FontSizeAdjust::Number(n.to_computed_value(context)),
+            FontSizeAdjust::System(_) => {
+                #[cfg(feature = "gecko")] {
+                    context.cached_system_font.as_ref().unwrap().font_size_adjust
+                }
+                #[cfg(feature = "servo")] {
+                    unreachable!()
+                }
+            }
+        }
+    }
+
+    fn from_computed_value(computed: &computed::FontSizeAdjust) -> Self {
+        match *computed {
+            computed::FontSizeAdjust::None => FontSizeAdjust::None,
+            computed::FontSizeAdjust::Number(ref v) => FontSizeAdjust::Number(Number::from_computed_value(v)),
+        }
+    }
+}
+
+impl Parse for FontSizeAdjust {
+    /// none | <number>
+    fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Result<FontSizeAdjust, ParseError<'i>> {
+        if input.try(|input| input.expect_ident_matching("none")).is_ok() {
+            return Ok(FontSizeAdjust::None);
+        }
+
+        Ok(FontSizeAdjust::Number(Number::parse_non_negative(context, input)?))
+    }
+}
+
 /// CSS font keywords
 #[derive(Animate, ComputeSquaredDistance, MallocSizeOf, ToAnimatedValue, ToAnimatedZero)]
 #[derive(Clone, Copy, Debug, PartialEq)]

components/style/values/specified/mod.rs

@@ -30,7 +30,7 @@ pub use self::align::{AlignItems, AlignJustifyContent, AlignJustifySelf, Justify
 pub use self::background::{BackgroundRepeat, BackgroundSize};
 pub use self::border::{BorderCornerRadius, BorderImageSlice, BorderImageWidth};
 pub use self::border::{BorderImageSideWidth, BorderRadius, BorderSideWidth, BorderSpacing};
-pub use self::font::{FontSize, FontWeight, MozScriptLevel, MozScriptMinSize, XTextZoom};
+pub use self::font::{FontSize, FontSizeAdjust, FontWeight, MozScriptLevel, MozScriptMinSize, XTextZoom};
 pub use self::box_::{AnimationIterationCount, AnimationName, ScrollSnapType, VerticalAlign};
 pub use self::color::{Color, ColorPropertyValue, RGBAColor};
 pub use self::effects::{BoxShadow, Filter, SimpleShadow};