From 6bf0a5cb5034a7e684dcc3500e841785237ce2dd Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 19:32:43 +0200
Subject: Adding upstream version 1:115.7.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 servo/components/style/values/specified/calc.rs | 1043 +++++++++++++++++++++++
 1 file changed, 1043 insertions(+)
 create mode 100644 servo/components/style/values/specified/calc.rs

(limited to 'servo/components/style/values/specified/calc.rs')

diff --git a/servo/components/style/values/specified/calc.rs b/servo/components/style/values/specified/calc.rs
new file mode 100644
index 0000000000..7351a61069
--- /dev/null
+++ b/servo/components/style/values/specified/calc.rs
@@ -0,0 +1,1043 @@
+/* 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/. */
+
+//! [Calc expressions][calc].
+//!
+//! [calc]: https://drafts.csswg.org/css-values/#calc-notation
+
+use crate::parser::ParserContext;
+use crate::values::generics::calc as generic;
+use crate::values::generics::calc::{MinMaxOp, ModRemOp, RoundingStrategy, SortKey};
+use crate::values::specified::length::{AbsoluteLength, FontRelativeLength, NoCalcLength};
+use crate::values::specified::length::{ContainerRelativeLength, ViewportPercentageLength};
+use crate::values::specified::{self, Angle, Resolution, Time};
+use crate::values::{CSSFloat, CSSInteger};
+use cssparser::{AngleOrNumber, CowRcStr, NumberOrPercentage, Parser, Token};
+use smallvec::SmallVec;
+use std::cmp;
+use std::fmt::{self, Write};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, StyleParseErrorKind, ToCss};
+
+fn trig_enabled() -> bool {
+    static_prefs::pref!("layout.css.trig.enabled")
+}
+
+fn nan_inf_enabled() -> bool {
+    static_prefs::pref!("layout.css.nan-inf.enabled")
+}
+
+/// The name of the mathematical function that we're parsing.
+#[derive(Clone, Copy, Debug, Parse)]
+pub enum MathFunction {
+    /// `calc()`: https://drafts.csswg.org/css-values-4/#funcdef-calc
+    Calc,
+    /// `min()`: https://drafts.csswg.org/css-values-4/#funcdef-min
+    Min,
+    /// `max()`: https://drafts.csswg.org/css-values-4/#funcdef-max
+    Max,
+    /// `clamp()`: https://drafts.csswg.org/css-values-4/#funcdef-clamp
+    Clamp,
+    /// `round()`: https://drafts.csswg.org/css-values-4/#funcdef-round
+    Round,
+    /// `mod()`: https://drafts.csswg.org/css-values-4/#funcdef-mod
+    Mod,
+    /// `rem()`: https://drafts.csswg.org/css-values-4/#funcdef-rem
+    Rem,
+    /// `sin()`: https://drafts.csswg.org/css-values-4/#funcdef-sin
+    Sin,
+    /// `cos()`: https://drafts.csswg.org/css-values-4/#funcdef-cos
+    Cos,
+    /// `tan()`: https://drafts.csswg.org/css-values-4/#funcdef-tan
+    Tan,
+    /// `asin()`: https://drafts.csswg.org/css-values-4/#funcdef-asin
+    Asin,
+    /// `acos()`: https://drafts.csswg.org/css-values-4/#funcdef-acos
+    Acos,
+    /// `atan()`: https://drafts.csswg.org/css-values-4/#funcdef-atan
+    Atan,
+    /// `atan2()`: https://drafts.csswg.org/css-values-4/#funcdef-atan2
+    Atan2,
+    /// `pow()`: https://drafts.csswg.org/css-values-4/#funcdef-pow
+    Pow,
+    /// `sqrt()`: https://drafts.csswg.org/css-values-4/#funcdef-sqrt
+    Sqrt,
+    /// `hypot()`: https://drafts.csswg.org/css-values-4/#funcdef-hypot
+    Hypot,
+    /// `log()`: https://drafts.csswg.org/css-values-4/#funcdef-log
+    Log,
+    /// `exp()`: https://drafts.csswg.org/css-values-4/#funcdef-exp
+    Exp,
+}
+
+/// A leaf node inside a `Calc` expression's AST.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
+pub enum Leaf {
+    /// `<length>`
+    Length(NoCalcLength),
+    /// `<angle>`
+    Angle(Angle),
+    /// `<time>`
+    Time(Time),
+    /// `<resolution>`
+    Resolution(Resolution),
+    /// `<percentage>`
+    Percentage(CSSFloat),
+    /// `<number>`
+    Number(CSSFloat),
+}
+
+impl Leaf {
+    fn as_length(&self) -> Option<&NoCalcLength> {
+        match *self {
+            Self::Length(ref l) => Some(l),
+            _ => None,
+        }
+    }
+}
+
+impl ToCss for Leaf {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            Self::Length(ref l) => l.to_css(dest),
+            Self::Number(ref n) => n.to_css(dest),
+            Self::Resolution(ref r) => r.to_css(dest),
+            Self::Percentage(p) => crate::values::serialize_percentage(p, dest),
+            Self::Angle(ref a) => a.to_css(dest),
+            Self::Time(ref t) => t.to_css(dest),
+        }
+    }
+}
+
+bitflags! {
+    /// Expected units we allow parsing within a `calc()` expression.
+    ///
+    /// This is used as a hint for the parser to fast-reject invalid
+    /// expressions. Numbers are always allowed because they multiply other
+    /// units.
+    #[derive(Clone, Copy)]
+    struct CalcUnits: u8 {
+        const LENGTH = 1 << 0;
+        const PERCENTAGE = 1 << 1;
+        const ANGLE = 1 << 2;
+        const TIME = 1 << 3;
+        const RESOLUTION = 1 << 3;
+
+        const LENGTH_PERCENTAGE = Self::LENGTH.bits | Self::PERCENTAGE.bits;
+        // NOTE: When you add to this, make sure to make Atan2 deal with these.
+        const ALL = Self::LENGTH.bits | Self::PERCENTAGE.bits | Self::ANGLE.bits | Self::TIME.bits | Self::RESOLUTION.bits;
+    }
+}
+
+/// A struct to hold a simplified `<length>` or `<percentage>` expression.
+///
+/// In some cases, e.g. DOMMatrix, we support calc(), but reject all the
+/// relative lengths, and to_computed_pixel_length_without_context() handles
+/// this case. Therefore, if you want to add a new field, please make sure this
+/// function work properly.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+#[allow(missing_docs)]
+pub struct CalcLengthPercentage {
+    #[css(skip)]
+    pub clamping_mode: AllowedNumericType,
+    pub node: CalcNode,
+}
+
+impl CalcLengthPercentage {
+    fn same_unit_length_as(a: &Self, b: &Self) -> Option<(CSSFloat, CSSFloat)> {
+        use generic::CalcNodeLeaf;
+
+        debug_assert_eq!(a.clamping_mode, b.clamping_mode);
+        debug_assert_eq!(a.clamping_mode, AllowedNumericType::All);
+
+        let a = a.node.as_leaf()?;
+        let b = b.node.as_leaf()?;
+
+        if a.sort_key() != b.sort_key() {
+            return None;
+        }
+
+        let a = a.as_length()?.unitless_value();
+        let b = b.as_length()?.unitless_value();
+        return Some((a, b));
+    }
+}
+
+impl SpecifiedValueInfo for CalcLengthPercentage {}
+
+impl PartialOrd for Leaf {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        use self::Leaf::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return None;
+        }
+
+        match (self, other) {
+            // NOTE: Percentages can't be compared reasonably here because the
+            // percentage basis might be negative, see bug 1709018.
+            // Conveniently, we only use this for <length-percentage> (for raw
+            // percentages, we go through resolve()).
+            (&Percentage(..), &Percentage(..)) => None,
+            (&Length(ref one), &Length(ref other)) => one.partial_cmp(other),
+            (&Angle(ref one), &Angle(ref other)) => one.degrees().partial_cmp(&other.degrees()),
+            (&Time(ref one), &Time(ref other)) => one.seconds().partial_cmp(&other.seconds()),
+            (&Resolution(ref one), &Resolution(ref other)) => one.dppx().partial_cmp(&other.dppx()),
+            (&Number(ref one), &Number(ref other)) => one.partial_cmp(other),
+            _ => {
+                match *self {
+                    Length(..) | Percentage(..) | Angle(..) | Time(..) | Number(..) |
+                    Resolution(..) => {},
+                }
+                unsafe {
+                    debug_unreachable!("Forgot a branch?");
+                }
+            },
+        }
+    }
+}
+
+impl generic::CalcNodeLeaf for Leaf {
+    fn unitless_value(&self) -> f32 {
+        match *self {
+            Self::Length(ref l) => l.unitless_value(),
+            Self::Percentage(n) | Self::Number(n) => n,
+            Self::Resolution(ref r) => r.dppx(),
+            Self::Angle(ref a) => a.degrees(),
+            Self::Time(ref t) => t.seconds(),
+        }
+    }
+
+    fn sort_key(&self) -> SortKey {
+        match *self {
+            Self::Number(..) => SortKey::Number,
+            Self::Percentage(..) => SortKey::Percentage,
+            Self::Time(..) => SortKey::Sec,
+            Self::Resolution(..) => SortKey::Dppx,
+            Self::Angle(..) => SortKey::Deg,
+            Self::Length(ref l) => match *l {
+                NoCalcLength::Absolute(..) => SortKey::Px,
+                NoCalcLength::FontRelative(ref relative) => match *relative {
+                    FontRelativeLength::Ch(..) => SortKey::Ch,
+                    FontRelativeLength::Em(..) => SortKey::Em,
+                    FontRelativeLength::Ex(..) => SortKey::Ex,
+                    FontRelativeLength::Cap(..) => SortKey::Cap,
+                    FontRelativeLength::Ic(..) => SortKey::Ic,
+                    FontRelativeLength::Rem(..) => SortKey::Rem,
+                },
+                NoCalcLength::ViewportPercentage(ref vp) => match *vp {
+                    ViewportPercentageLength::Vh(..) => SortKey::Vh,
+                    ViewportPercentageLength::Svh(..) => SortKey::Svh,
+                    ViewportPercentageLength::Lvh(..) => SortKey::Lvh,
+                    ViewportPercentageLength::Dvh(..) => SortKey::Dvh,
+                    ViewportPercentageLength::Vw(..) => SortKey::Vw,
+                    ViewportPercentageLength::Svw(..) => SortKey::Svw,
+                    ViewportPercentageLength::Lvw(..) => SortKey::Lvw,
+                    ViewportPercentageLength::Dvw(..) => SortKey::Dvw,
+                    ViewportPercentageLength::Vmax(..) => SortKey::Vmax,
+                    ViewportPercentageLength::Svmax(..) => SortKey::Svmax,
+                    ViewportPercentageLength::Lvmax(..) => SortKey::Lvmax,
+                    ViewportPercentageLength::Dvmax(..) => SortKey::Dvmax,
+                    ViewportPercentageLength::Vmin(..) => SortKey::Vmin,
+                    ViewportPercentageLength::Svmin(..) => SortKey::Svmin,
+                    ViewportPercentageLength::Lvmin(..) => SortKey::Lvmin,
+                    ViewportPercentageLength::Dvmin(..) => SortKey::Dvmin,
+                    ViewportPercentageLength::Vb(..) => SortKey::Vb,
+                    ViewportPercentageLength::Svb(..) => SortKey::Svb,
+                    ViewportPercentageLength::Lvb(..) => SortKey::Lvb,
+                    ViewportPercentageLength::Dvb(..) => SortKey::Dvb,
+                    ViewportPercentageLength::Vi(..) => SortKey::Vi,
+                    ViewportPercentageLength::Svi(..) => SortKey::Svi,
+                    ViewportPercentageLength::Lvi(..) => SortKey::Lvi,
+                    ViewportPercentageLength::Dvi(..) => SortKey::Dvi,
+                },
+                NoCalcLength::ContainerRelative(ref cq) => match *cq {
+                    ContainerRelativeLength::Cqw(..) => SortKey::Cqw,
+                    ContainerRelativeLength::Cqh(..) => SortKey::Cqh,
+                    ContainerRelativeLength::Cqi(..) => SortKey::Cqi,
+                    ContainerRelativeLength::Cqb(..) => SortKey::Cqb,
+                    ContainerRelativeLength::Cqmin(..) => SortKey::Cqmin,
+                    ContainerRelativeLength::Cqmax(..) => SortKey::Cqmax,
+                },
+                NoCalcLength::ServoCharacterWidth(..) => unreachable!(),
+            },
+        }
+    }
+
+    fn simplify(&mut self) {
+        if let Self::Length(NoCalcLength::Absolute(ref mut abs)) = *self {
+            *abs = AbsoluteLength::Px(abs.to_px());
+        }
+    }
+
+    /// Tries to merge one sum to another, that is, perform `x` + `y`.
+    ///
+    /// Only handles leaf nodes, it's the caller's responsibility to simplify
+    /// them before calling this if needed.
+    fn try_sum_in_place(&mut self, other: &Self) -> Result<(), ()> {
+        use self::Leaf::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        match (self, other) {
+            (&mut Number(ref mut one), &Number(ref other)) |
+            (&mut Percentage(ref mut one), &Percentage(ref other)) => {
+                *one += *other;
+            },
+            (&mut Angle(ref mut one), &Angle(ref other)) => {
+                *one = specified::Angle::from_calc(one.degrees() + other.degrees());
+            },
+            (&mut Time(ref mut one), &Time(ref other)) => {
+                *one = specified::Time::from_seconds(one.seconds() + other.seconds());
+            },
+            (&mut Resolution(ref mut one), &Resolution(ref other)) => {
+                *one = specified::Resolution::from_dppx(one.dppx() + other.dppx());
+            },
+            (&mut Length(ref mut one), &Length(ref other)) => {
+                *one = one.try_op(other, std::ops::Add::add)?;
+            },
+            _ => {
+                match *other {
+                    Number(..) | Percentage(..) | Angle(..) | Time(..) | Resolution(..) |
+                    Length(..) => {},
+                }
+                unsafe {
+                    debug_unreachable!();
+                }
+            },
+        }
+
+        Ok(())
+    }
+
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        use self::Leaf::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        match (self, other) {
+            (&Number(one), &Number(other)) => {
+                return Ok(Leaf::Number(op(one, other)));
+            },
+            (&Percentage(one), &Percentage(other)) => {
+                return Ok(Leaf::Percentage(op(one, other)));
+            },
+            (&Angle(ref one), &Angle(ref other)) => {
+                return Ok(Leaf::Angle(specified::Angle::from_calc(op(
+                    one.degrees(),
+                    other.degrees(),
+                ))));
+            },
+            (&Resolution(ref one), &Resolution(ref other)) => {
+                return Ok(Leaf::Resolution(specified::Resolution::from_dppx(op(
+                    one.dppx(),
+                    other.dppx(),
+                ))));
+            },
+            (&Time(ref one), &Time(ref other)) => {
+                return Ok(Leaf::Time(specified::Time::from_seconds(op(
+                    one.seconds(),
+                    other.seconds(),
+                ))));
+            },
+            (&Length(ref one), &Length(ref other)) => {
+                return Ok(Leaf::Length(one.try_op(other, op)?));
+            },
+            _ => {
+                match *other {
+                    Number(..) | Percentage(..) | Angle(..) | Time(..) | Length(..) |
+                    Resolution(..) => {},
+                }
+                unsafe {
+                    debug_unreachable!();
+                }
+            },
+        }
+    }
+
+    fn map(&mut self, mut op: impl FnMut(f32) -> f32) {
+        match self {
+            Leaf::Length(one) => *one = one.map(op),
+            Leaf::Angle(one) => *one = specified::Angle::from_calc(op(one.degrees())),
+            Leaf::Time(one) => *one = specified::Time::from_seconds(op(one.seconds())),
+            Leaf::Resolution(one) => *one = specified::Resolution::from_dppx(op(one.dppx())),
+            Leaf::Percentage(one) => *one = op(*one),
+            Leaf::Number(one) => *one = op(*one),
+        }
+    }
+}
+
+/// A calc node representation for specified values.
+pub type CalcNode = generic::GenericCalcNode<Leaf>;
+
+impl CalcNode {
+    /// Tries to parse a single element in the expression, that is, a
+    /// `<length>`, `<angle>`, `<time>`, `<percentage>`, according to
+    /// `allowed_units`.
+    ///
+    /// May return a "complex" `CalcNode`, in the presence of a parenthesized
+    /// expression, for example.
+    fn parse_one<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        match input.next()? {
+            &Token::Number { value, .. } => Ok(CalcNode::Leaf(Leaf::Number(value))),
+            &Token::Dimension {
+                value, ref unit, ..
+            } => {
+                if allowed_units.intersects(CalcUnits::LENGTH) {
+                    if let Ok(l) = NoCalcLength::parse_dimension(context, value, unit) {
+                        return Ok(CalcNode::Leaf(Leaf::Length(l)));
+                    }
+                }
+                if allowed_units.intersects(CalcUnits::ANGLE) {
+                    if let Ok(a) = Angle::parse_dimension(value, unit, /* from_calc = */ true) {
+                        return Ok(CalcNode::Leaf(Leaf::Angle(a)));
+                    }
+                }
+                if allowed_units.intersects(CalcUnits::TIME) {
+                    if let Ok(t) = Time::parse_dimension(value, unit) {
+                        return Ok(CalcNode::Leaf(Leaf::Time(t)));
+                    }
+                }
+                if allowed_units.intersects(CalcUnits::RESOLUTION) {
+                    if let Ok(t) = Resolution::parse_dimension(value, unit) {
+                        return Ok(CalcNode::Leaf(Leaf::Resolution(t)));
+                    }
+                }
+                return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            },
+            &Token::Percentage { unit_value, .. }
+                if allowed_units.intersects(CalcUnits::PERCENTAGE) =>
+            {
+                Ok(CalcNode::Leaf(Leaf::Percentage(unit_value)))
+            },
+            &Token::ParenthesisBlock => input.parse_nested_block(|input| {
+                CalcNode::parse_argument(context, input, allowed_units)
+            }),
+            &Token::Function(ref name) => {
+                let function = CalcNode::math_function(context, name, location)?;
+                CalcNode::parse(context, input, function, allowed_units)
+            },
+            &Token::Ident(ref ident) => {
+                let number = match_ignore_ascii_case! { &**ident,
+                    "e" if trig_enabled() => std::f32::consts::E,
+                    "pi" if trig_enabled() => std::f32::consts::PI,
+                    "infinity" if nan_inf_enabled() => f32::INFINITY,
+                    "-infinity" if nan_inf_enabled() => f32::NEG_INFINITY,
+                    "nan" if nan_inf_enabled() => f32::NAN,
+                    _ => return Err(location.new_unexpected_token_error(Token::Ident(ident.clone()))),
+                };
+                Ok(CalcNode::Leaf(Leaf::Number(number)))
+            },
+            t => Err(location.new_unexpected_token_error(t.clone())),
+        }
+    }
+
+    /// Parse a top-level `calc` expression, with all nested sub-expressions.
+    ///
+    /// This is in charge of parsing, for example, `2 + 3 * 100%`.
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        // TODO: Do something different based on the function name. In
+        // particular, for non-calc function we need to take a list of
+        // comma-separated arguments and such.
+        input.parse_nested_block(|input| {
+            match function {
+                MathFunction::Calc => Self::parse_argument(context, input, allowed_units),
+                MathFunction::Clamp => {
+                    let min = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let center = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let max = Self::parse_argument(context, input, allowed_units)?;
+                    Ok(Self::Clamp {
+                        min: Box::new(min),
+                        center: Box::new(center),
+                        max: Box::new(max),
+                    })
+                },
+                MathFunction::Round => {
+                    let strategy = input.try_parse(parse_rounding_strategy);
+
+                    // <rounding-strategy> = nearest | up | down | to-zero
+                    // https://drafts.csswg.org/css-values-4/#calc-syntax
+                    fn parse_rounding_strategy<'i, 't>(
+                        input: &mut Parser<'i, 't>,
+                    ) -> Result<RoundingStrategy, ParseError<'i>> {
+                        Ok(try_match_ident_ignore_ascii_case! { input,
+                            "nearest" => RoundingStrategy::Nearest,
+                            "up" => RoundingStrategy::Up,
+                            "down" => RoundingStrategy::Down,
+                            "to-zero" => RoundingStrategy::ToZero,
+                        })
+                    }
+
+                    if strategy.is_ok() {
+                        input.expect_comma()?;
+                    }
+
+                    let value = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let step = Self::parse_argument(context, input, allowed_units)?;
+
+                    Ok(Self::Round {
+                        strategy: strategy.unwrap_or(RoundingStrategy::Nearest),
+                        value: Box::new(value),
+                        step: Box::new(step),
+                    })
+                },
+                MathFunction::Mod | MathFunction::Rem => {
+                    let dividend = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let divisor = Self::parse_argument(context, input, allowed_units)?;
+
+                    let op = match function {
+                        MathFunction::Mod => ModRemOp::Mod,
+                        MathFunction::Rem => ModRemOp::Rem,
+                        _ => unreachable!(),
+                    };
+                    Ok(Self::ModRem {
+                        dividend: Box::new(dividend),
+                        divisor: Box::new(divisor),
+                        op,
+                    })
+                },
+                MathFunction::Min | MathFunction::Max => {
+                    // TODO(emilio): The common case for parse_comma_separated
+                    // is just one element, but for min / max is two, really...
+                    //
+                    // Consider adding an API to cssparser to specify the
+                    // initial vector capacity?
+                    let arguments = input.parse_comma_separated(|input| {
+                        Self::parse_argument(context, input, allowed_units)
+                    })?;
+
+                    let op = match function {
+                        MathFunction::Min => MinMaxOp::Min,
+                        MathFunction::Max => MinMaxOp::Max,
+                        _ => unreachable!(),
+                    };
+
+                    Ok(Self::MinMax(arguments.into(), op))
+                },
+                MathFunction::Sin | MathFunction::Cos | MathFunction::Tan => {
+                    let a = Self::parse_angle_argument(context, input)?;
+
+                    let number = match function {
+                        MathFunction::Sin => a.sin(),
+                        MathFunction::Cos => a.cos(),
+                        MathFunction::Tan => a.tan(),
+                        _ => unsafe {
+                            debug_unreachable!("We just checked!");
+                        },
+                    };
+
+                    Ok(Self::Leaf(Leaf::Number(number)))
+                },
+                MathFunction::Asin | MathFunction::Acos | MathFunction::Atan => {
+                    let a = Self::parse_number_argument(context, input)?;
+
+                    let radians = match function {
+                        MathFunction::Asin => a.asin(),
+                        MathFunction::Acos => a.acos(),
+                        MathFunction::Atan => a.atan(),
+                        _ => unsafe {
+                            debug_unreachable!("We just checked!");
+                        },
+                    };
+
+                    Ok(Self::Leaf(Leaf::Angle(Angle::from_radians(radians))))
+                },
+                MathFunction::Atan2 => {
+                    let a = Self::parse_argument(context, input, CalcUnits::ALL)?;
+                    input.expect_comma()?;
+                    let b = Self::parse_argument(context, input, CalcUnits::ALL)?;
+
+                    let radians = Self::try_resolve(input, || {
+                        if let Ok(a) = a.to_number() {
+                            let b = b.to_number()?;
+                            return Ok(a.atan2(b));
+                        }
+
+                        if let Ok(a) = a.to_percentage() {
+                            let b = b.to_percentage()?;
+                            return Ok(a.atan2(b));
+                        }
+
+                        if let Ok(a) = a.to_time(None) {
+                            let b = b.to_time(None)?;
+                            return Ok(a.seconds().atan2(b.seconds()));
+                        }
+
+                        if let Ok(a) = a.to_angle() {
+                            let b = b.to_angle()?;
+                            return Ok(a.radians().atan2(b.radians()));
+                        }
+
+                        if let Ok(a) = a.to_resolution() {
+                            let b = b.to_resolution()?;
+                            return Ok(a.dppx().atan2(b.dppx()));
+                        }
+
+                        let a = a.into_length_or_percentage(AllowedNumericType::All)?;
+                        let b = b.into_length_or_percentage(AllowedNumericType::All)?;
+                        let (a, b) = CalcLengthPercentage::same_unit_length_as(&a, &b).ok_or(())?;
+
+                        Ok(a.atan2(b))
+                    })?;
+
+                    Ok(Self::Leaf(Leaf::Angle(Angle::from_radians(radians))))
+                },
+                MathFunction::Pow => {
+                    let a = Self::parse_number_argument(context, input)?;
+                    input.expect_comma()?;
+                    let b = Self::parse_number_argument(context, input)?;
+
+                    let number = a.powf(b);
+
+                    Ok(Self::Leaf(Leaf::Number(number)))
+                },
+                MathFunction::Sqrt => {
+                    let a = Self::parse_number_argument(context, input)?;
+
+                    let number = a.sqrt();
+
+                    Ok(Self::Leaf(Leaf::Number(number)))
+                },
+                MathFunction::Hypot => {
+                    let arguments = input.parse_comma_separated(|input| {
+                        Self::parse_argument(context, input, allowed_units)
+                    })?;
+
+                    Ok(Self::Hypot(arguments.into()))
+                },
+                MathFunction::Log => {
+                    let a = Self::parse_number_argument(context, input)?;
+                    let b = input
+                        .try_parse(|input| {
+                            input.expect_comma()?;
+                            Self::parse_number_argument(context, input)
+                        })
+                        .ok();
+
+                    let number = match b {
+                        Some(b) => a.log(b),
+                        None => a.ln(),
+                    };
+
+                    Ok(Self::Leaf(Leaf::Number(number)))
+                },
+                MathFunction::Exp => {
+                    let a = Self::parse_number_argument(context, input)?;
+
+                    let number = a.exp();
+
+                    Ok(Self::Leaf(Leaf::Number(number)))
+                },
+            }
+        })
+    }
+
+    fn parse_angle_argument<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<CSSFloat, ParseError<'i>> {
+        let argument = Self::parse_argument(context, input, CalcUnits::ANGLE)?;
+        argument
+            .to_number()
+            .or_else(|()| Ok(argument.to_angle()?.radians()))
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    fn parse_number_argument<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<CSSFloat, ParseError<'i>> {
+        Self::parse_argument(context, input, CalcUnits::empty())?
+            .to_number()
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    fn parse_argument<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut sum = SmallVec::<[CalcNode; 1]>::new();
+        sum.push(Self::parse_product(context, input, allowed_units)?);
+
+        loop {
+            let start = input.state();
+            match input.next_including_whitespace() {
+                Ok(&Token::WhiteSpace(_)) => {
+                    if input.is_exhausted() {
+                        break; // allow trailing whitespace
+                    }
+                    match *input.next()? {
+                        Token::Delim('+') => {
+                            sum.push(Self::parse_product(context, input, allowed_units)?);
+                        },
+                        Token::Delim('-') => {
+                            let mut rhs = Self::parse_product(context, input, allowed_units)?;
+                            rhs.negate();
+                            sum.push(rhs);
+                        },
+                        _ => {
+                            input.reset(&start);
+                            break;
+                        },
+                    }
+                },
+                _ => {
+                    input.reset(&start);
+                    break;
+                },
+            }
+        }
+
+        Ok(if sum.len() == 1 {
+            sum.drain(..).next().unwrap()
+        } else {
+            Self::Sum(sum.into_boxed_slice().into())
+        })
+    }
+
+    /// Parse a top-level `calc` expression, and all the products that may
+    /// follow, and stop as soon as a non-product expression is found.
+    ///
+    /// This should parse correctly:
+    ///
+    /// * `2`
+    /// * `2 * 2`
+    /// * `2 * 2 + 2` (but will leave the `+ 2` unparsed).
+    ///
+    fn parse_product<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut node = Self::parse_one(context, input, allowed_units)?;
+
+        loop {
+            let start = input.state();
+            match input.next() {
+                Ok(&Token::Delim('*')) => {
+                    let rhs = Self::parse_one(context, input, allowed_units)?;
+                    if let Ok(rhs) = rhs.to_number() {
+                        node.mul_by(rhs);
+                    } else if let Ok(number) = node.to_number() {
+                        node = rhs;
+                        node.mul_by(number);
+                    } else {
+                        // One of the two parts of the multiplication has to be
+                        // a number, at least until we implement unit math.
+                        return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                    }
+                },
+                Ok(&Token::Delim('/')) => {
+                    let rhs = Self::parse_one(context, input, allowed_units)?;
+                    // Dividing by units is not ok.
+                    //
+                    // TODO(emilio): Eventually it should be.
+                    let number = match rhs.to_number() {
+                        Ok(n) if n != 0. || nan_inf_enabled() => n,
+                        _ => {
+                            return Err(
+                                input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                            )
+                        },
+                    };
+                    node.mul_by(1. / number);
+                },
+                _ => {
+                    input.reset(&start);
+                    break;
+                },
+            }
+        }
+
+        Ok(node)
+    }
+
+    fn try_resolve<'i, 't, F>(
+        input: &Parser<'i, 't>,
+        closure: F,
+    ) -> Result<CSSFloat, ParseError<'i>>
+    where
+        F: FnOnce() -> Result<CSSFloat, ()>,
+    {
+        closure().map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Tries to simplify this expression into a `<length>` or `<percentage>`
+    /// value.
+    fn into_length_or_percentage(
+        mut self,
+        clamping_mode: AllowedNumericType,
+    ) -> Result<CalcLengthPercentage, ()> {
+        // Keep track of whether there's any invalid member of the calculation,
+        // so as to reject the calculation properly at parse-time.
+        let mut any_invalid = false;
+        self.visit_depth_first(|node| {
+            if let CalcNode::Leaf(ref l) = *node {
+                any_invalid |= !matches!(*l, Leaf::Percentage(..) | Leaf::Length(..));
+            }
+            node.simplify_and_sort_direct_children();
+        });
+
+        if any_invalid {
+            return Err(());
+        }
+
+        Ok(CalcLengthPercentage {
+            clamping_mode,
+            node: self,
+        })
+    }
+
+    /// Tries to simplify this expression into a `<time>` value.
+    fn to_time(&self, clamping_mode: Option<AllowedNumericType>) -> Result<Time, ()> {
+        let seconds = self.resolve(|leaf| match *leaf {
+            Leaf::Time(ref time) => Ok(time.seconds()),
+            _ => Err(()),
+        })?;
+
+        Ok(Time::from_seconds_with_calc_clamping_mode(
+            if nan_inf_enabled() {
+                seconds
+            } else {
+                crate::values::normalize(seconds)
+            },
+            clamping_mode,
+        ))
+    }
+
+    /// Tries to simplify the expression into a `<resolution>` value.
+    fn to_resolution(&self) -> Result<Resolution, ()> {
+        let dppx = self.resolve(|leaf| match *leaf {
+            Leaf::Resolution(ref r) => Ok(r.dppx()),
+            _ => Err(()),
+        })?;
+
+        Ok(Resolution::from_dppx_calc(if nan_inf_enabled() {
+            dppx
+        } else {
+            crate::values::normalize(dppx)
+        }))
+    }
+
+    /// Tries to simplify this expression into an `Angle` value.
+    fn to_angle(&self) -> Result<Angle, ()> {
+        let degrees = self.resolve(|leaf| match *leaf {
+            Leaf::Angle(ref angle) => Ok(angle.degrees()),
+            _ => Err(()),
+        })?;
+        let result = Angle::from_calc(if nan_inf_enabled() {
+            degrees
+        } else {
+            crate::values::normalize(degrees)
+        });
+        Ok(result)
+    }
+
+    /// Tries to simplify this expression into a `<number>` value.
+    fn to_number(&self) -> Result<CSSFloat, ()> {
+        self.resolve(|leaf| match *leaf {
+            Leaf::Number(n) => Ok(n),
+            _ => Err(()),
+        })
+    }
+
+    /// Tries to simplify this expression into a `<percentage>` value.
+    fn to_percentage(&self) -> Result<CSSFloat, ()> {
+        self.resolve(|leaf| match *leaf {
+            Leaf::Percentage(p) => Ok(p),
+            _ => Err(()),
+        })
+    }
+
+    /// Given a function name, and the location from where the token came from,
+    /// return a mathematical function corresponding to that name or an error.
+    #[inline]
+    pub fn math_function<'i>(
+        context: &ParserContext,
+        name: &CowRcStr<'i>,
+        location: cssparser::SourceLocation,
+    ) -> Result<MathFunction, ParseError<'i>> {
+        use self::MathFunction::*;
+
+        let function = match MathFunction::from_ident(&*name) {
+            Ok(f) => f,
+            Err(()) => {
+                return Err(location.new_unexpected_token_error(Token::Function(name.clone())))
+            },
+        };
+
+        let enabled = if context.chrome_rules_enabled() {
+            true
+        } else if matches!(function, Sin | Cos | Tan | Asin | Acos | Atan | Atan2) {
+            trig_enabled()
+        } else if matches!(function, Round) {
+            static_prefs::pref!("layout.css.round.enabled")
+        } else if matches!(function, Mod | Rem) {
+            static_prefs::pref!("layout.css.mod-rem.enabled")
+        } else if matches!(function, Pow | Sqrt | Hypot | Log | Exp) {
+            static_prefs::pref!("layout.css.exp.enabled")
+        } else {
+            true
+        };
+
+        if !enabled {
+            return Err(location.new_unexpected_token_error(Token::Function(name.clone())));
+        }
+
+        Ok(function)
+    }
+
+    /// Convenience parsing function for integers.
+    pub fn parse_integer<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<CSSInteger, ParseError<'i>> {
+        Self::parse_number(context, input, function).map(|n| n.round() as CSSInteger)
+    }
+
+    /// Convenience parsing function for `<length> | <percentage>`.
+    pub fn parse_length_or_percentage<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        clamping_mode: AllowedNumericType,
+        function: MathFunction,
+    ) -> Result<CalcLengthPercentage, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::LENGTH_PERCENTAGE)?
+            .into_length_or_percentage(clamping_mode)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for percentages.
+    pub fn parse_percentage<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<CSSFloat, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::PERCENTAGE)?
+            .to_percentage()
+            .map(crate::values::normalize)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<length>`.
+    pub fn parse_length<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        clamping_mode: AllowedNumericType,
+        function: MathFunction,
+    ) -> Result<CalcLengthPercentage, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::LENGTH)?
+            .into_length_or_percentage(clamping_mode)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<number>`.
+    pub fn parse_number<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<CSSFloat, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::empty())?
+            .to_number()
+            .map(crate::values::normalize)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<angle>`.
+    pub fn parse_angle<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<Angle, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::ANGLE)?
+            .to_angle()
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<time>`.
+    pub fn parse_time<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        clamping_mode: AllowedNumericType,
+        function: MathFunction,
+    ) -> Result<Time, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::TIME)?
+            .to_time(Some(clamping_mode))
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<resolution>`.
+    pub fn parse_resolution<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<Resolution, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::RESOLUTION)?
+            .to_resolution()
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<number>` or `<percentage>`.
+    pub fn parse_number_or_percentage<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<NumberOrPercentage, ParseError<'i>> {
+        let node = Self::parse(context, input, function, CalcUnits::PERCENTAGE)?;
+
+        if let Ok(value) = node.to_number() {
+            return Ok(NumberOrPercentage::Number { value });
+        }
+
+        match node.to_percentage() {
+            Ok(unit_value) => Ok(NumberOrPercentage::Percentage { unit_value }),
+            Err(()) => Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+        }
+    }
+
+    /// Convenience parsing function for `<number>` or `<angle>`.
+    pub fn parse_angle_or_number<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<AngleOrNumber, ParseError<'i>> {
+        let node = Self::parse(context, input, function, CalcUnits::ANGLE)?;
+
+        if let Ok(angle) = node.to_angle() {
+            let degrees = angle.degrees();
+            return Ok(AngleOrNumber::Angle { degrees });
+        }
+
+        match node.to_number() {
+            Ok(value) => Ok(AngleOrNumber::Number { value }),
+            Err(()) => Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+        }
+    }
+}
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