1 files changed, 225 insertions, 0 deletions
diff --git a/servo/components/style/values/specified/percentage.rs b/servo/components/style/values/specified/percentage.rs
new file mode 100644
index 0000000000..ccf16d6463
--- /dev/null
+++ b/servo/components/style/values/specified/percentage.rs
@@ -0,0 +1,225 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+//! Specified percentages.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::percentage::Percentage as ComputedPercentage;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics::NonNegative;
+use crate::values::specified::calc::CalcNode;
+use crate::values::specified::Number;
+use crate::values::{normalize, serialize_percentage, CSSFloat};
+use cssparser::{Parser, Token};
+use std::fmt::{self, Write};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, ToCss};
+
+/// A percentage value.
+#[derive(Clone, Copy, Debug, Default, MallocSizeOf, PartialEq, ToShmem)]
+pub struct Percentage {
+    /// The percentage value as a float.
+    ///
+    /// [0 .. 100%] maps to [0.0 .. 1.0]
+    value: CSSFloat,
+    /// If this percentage came from a calc() expression, this tells how
+    /// clamping should be done on the value.
+    calc_clamping_mode: Option<AllowedNumericType>,
+}
+
+impl ToCss for Percentage {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.calc_clamping_mode.is_some() {
+            dest.write_str("calc(")?;
+        }
+
+        serialize_percentage(self.value, dest)?;
+
+        if self.calc_clamping_mode.is_some() {
+            dest.write_char(')')?;
+        }
+        Ok(())
+    }
+}
+
+impl Percentage {
+    /// Creates a percentage from a numeric value.
+    pub(super) fn new_with_clamping_mode(
+        value: CSSFloat,
+        calc_clamping_mode: Option<AllowedNumericType>,
+    ) -> Self {
+        Self {
+            value,
+            calc_clamping_mode,
+        }
+    }
+
+    /// Creates a percentage from a numeric value.
+    pub fn new(value: CSSFloat) -> Self {
+        Self::new_with_clamping_mode(value, None)
+    }
+
+    /// `0%`
+    #[inline]
+    pub fn zero() -> Self {
+        Percentage {
+            value: 0.,
+            calc_clamping_mode: None,
+        }
+    }
+
+    /// `100%`
+    #[inline]
+    pub fn hundred() -> Self {
+        Percentage {
+            value: 1.,
+            calc_clamping_mode: None,
+        }
+    }
+
+    /// Gets the underlying value for this float.
+    pub fn get(&self) -> CSSFloat {
+        self.calc_clamping_mode
+            .map_or(self.value, |mode| mode.clamp(self.value))
+    }
+
+    /// Returns this percentage as a number.
+    pub fn to_number(&self) -> Number {
+        Number::new_with_clamping_mode(self.value, self.calc_clamping_mode)
+    }
+
+    /// Returns the calc() clamping mode for this percentage.
+    pub fn calc_clamping_mode(&self) -> Option<AllowedNumericType> {
+        self.calc_clamping_mode
+    }
+
+    /// Reverses this percentage, preserving calc-ness.
+    ///
+    /// For example: If it was 20%, convert it into 80%.
+    pub fn reverse(&mut self) {
+        let new_value = 1. - self.value;
+        self.value = new_value;
+    }
+
+    /// Parses a specific kind of percentage.
+    pub fn parse_with_clamping_mode<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        num_context: AllowedNumericType,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        match *input.next()? {
+            Token::Percentage { unit_value, .. }
+                if num_context.is_ok(context.parsing_mode, unit_value) =>
+            {
+                Ok(Percentage::new(unit_value))
+            },
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(context, name, location)?;
+                let value = CalcNode::parse_percentage(context, input, function)?;
+                Ok(Percentage {
+                    value,
+                    calc_clamping_mode: Some(num_context),
+                })
+            },
+            ref t => Err(location.new_unexpected_token_error(t.clone())),
+        }
+    }
+
+    /// Parses a percentage token, but rejects it if it's negative.
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+    }
+
+    /// Parses a percentage token, but rejects it if it's negative or more than
+    /// 100%.
+    pub fn parse_zero_to_a_hundred<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::ZeroToOne)
+    }
+
+    /// Clamp to 100% if the value is over 100%.
+    #[inline]
+    pub fn clamp_to_hundred(self) -> Self {
+        Percentage {
+            value: self.value.min(1.),
+            calc_clamping_mode: self.calc_clamping_mode,
+        }
+    }
+}
+
+impl Parse for Percentage {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::All)
+    }
+}
+
+impl ToComputedValue for Percentage {
+    type ComputedValue = ComputedPercentage;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
+        ComputedPercentage(normalize(self.get()))
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Percentage::new(computed.0)
+    }
+}
+
+impl SpecifiedValueInfo for Percentage {}
+
+/// Turns the percentage into a plain float.
+pub trait ToPercentage {
+    /// Returns whether this percentage used to be a calc().
+    fn is_calc(&self) -> bool {
+        false
+    }
+    /// Turns the percentage into a plain float.
+    fn to_percentage(&self) -> CSSFloat;
+}
+
+impl ToPercentage for Percentage {
+    fn is_calc(&self) -> bool {
+        self.calc_clamping_mode.is_some()
+    }
+
+    fn to_percentage(&self) -> CSSFloat {
+        self.get()
+    }
+}
+
+/// A wrapper of Percentage, whose value must be >= 0.
+pub type NonNegativePercentage = NonNegative<Percentage>;
+
+impl Parse for NonNegativePercentage {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(NonNegative(Percentage::parse_non_negative(context, input)?))
+    }
+}
+
+impl NonNegativePercentage {
+    /// Convert to ComputedPercentage, for FontFaceRule size-adjust getter.
+    #[inline]
+    pub fn compute(&self) -> ComputedPercentage {
+        ComputedPercentage(self.0.get())
+    }
+}