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style: Don't use a binary tree representation for calc() sums / products.

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Keep a flat list of sum members. Simpify product and division ASAP.

I want to preserve the tree for a bit longer to implement min / max / clamp.
This doesn't do anything for it that we weren't doing already, but it helps to
eventually keep this specified representation and the equivalent computed
representation for <length-percentage> values.

Enable the tests for the comparison functions too, to prevent regressions.

Differential Revision: https://phabricator.services.mozilla.com/D61514
This commit is contained in:
Emilio Cobos Álvarez 2020-02-07 00:40:55 +00:00
parent b038924d44
commit 48eff19ff3
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GPG key ID: E1152D0994E4BF8A
1 changed files with 130 additions and 88 deletions
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218
components/style/values/specified/calc.rs
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@ -13,6 +13,7 @@ use crate::values::specified::length::{AbsoluteLength, FontRelativeLength, NoCal
use crate::values::specified::{Angle, Time};
use crate::values::{CSSFloat, CSSInteger};
use cssparser::{AngleOrNumber, CowRcStr, NumberOrPercentage, Parser, Token};
use smallvec::SmallVec;
use std::fmt::{self, Write};
use style_traits::values::specified::AllowedNumericType;
use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, StyleParseErrorKind, ToCss};
@ -30,6 +31,15 @@ pub enum MathFunction {
Clamp,
}
/// Whether we're a `min` or `max` function.
#[derive(Copy, Clone, Debug)]
pub enum MinMaxOp {
/// `min()`
Min,
/// `max()`
Max,
}
/// A node inside a `Calc` expression's AST.
#[derive(Clone, Debug)]
pub enum CalcNode {
@ -43,18 +53,11 @@ pub enum CalcNode {
Percentage(CSSFloat),
/// `<number>`
Number(CSSFloat),
/// An expression of the form `x + y`
Sum(Box<CalcNode>, Box<CalcNode>),
/// An expression of the form `x - y`
Sub(Box<CalcNode>, Box<CalcNode>),
/// An expression of the form `x * y`
Mul(Box<CalcNode>, Box<CalcNode>),
/// An expression of the form `x / y`
Div(Box<CalcNode>, Box<CalcNode>),
/// A `min()` function.
Min(Box<[CalcNode]>),
/// A `max()` function.
Max(Box<[CalcNode]>),
/// An expression of the form `x + y + ...`. Subtraction is represented by
/// the negated expression of the right hand side.
Sum(Box<[CalcNode]>),
/// A `min()` / `max()` function.
MinMax(Box<[CalcNode]>, MinMaxOp),
/// A `clamp()` function.
Clamp {
/// The minimum value.
@ -183,26 +186,12 @@ macro_rules! impl_generic_to_type {
}
Ok(match *$self {
Self::Sub(ref a, ref b) => $from_float(a.$to_self()?.$to_float() - b.$to_self()?.$to_float()),
Self::Sum(ref a, ref b) => $from_float(a.$to_self()?.$to_float() + b.$to_self()?.$to_float()),
Self::Mul(ref a, ref b) => match a.$to_self() {
Ok(lhs) => {
let rhs = b.to_number()?;
$from_float(lhs.$to_float() * rhs)
},
Err(..) => {
let lhs = a.to_number()?;
let rhs = b.$to_self()?;
$from_float(lhs * rhs.$to_float())
},
},
Self::Div(ref a, ref b) => {
let lhs = a.$to_self()?;
let rhs = b.to_number()?;
if rhs == 0. {
return Err(());
Self::Sum(ref expressions) => {
let mut sum = 0.;
for sub in &**expressions {
sum += sub.$to_self()?.$to_float();
}
$from_float(lhs.$to_float() / rhs)
$from_float(sum)
},
Self::Clamp { ref min, ref center, ref max } => {
let min = min.$to_self()?;
@ -221,25 +210,21 @@ macro_rules! impl_generic_to_type {
}
result
},
Self::Min(ref nodes) => {
let mut min = nodes[0].$to_self()?;
Self::MinMax(ref nodes, op) => {
let mut result = nodes[0].$to_self()?;
for node in nodes.iter().skip(1) {
let candidate = node.$to_self()?;
if candidate.$to_float() < min.$to_float() {
min = candidate;
let candidate_float = candidate.$to_float();
let result_float = result.$to_float();
let candidate_wins = match op {
MinMaxOp::Min => candidate_float < result_float,
MinMaxOp::Max => candidate_float > result_float,
};
if candidate_wins {
result = candidate;
}
}
min
},
Self::Max(ref nodes) => {
let mut max = nodes[0].$to_self()?;
for node in nodes.iter().skip(1) {
let candidate = node.$to_self()?;
if candidate.$to_float() > max.$to_float() {
max = candidate;
}
}
max
result
},
Self::Length(..) |
Self::Angle(..) |
@ -251,6 +236,62 @@ macro_rules! impl_generic_to_type {
}
impl CalcNode {
fn negate(&mut self) {
self.mul_by(-1.);
}
fn mul_by(&mut self, scalar: f32) {
match *self {
Self::Length(ref mut l) => {
// FIXME: For consistency this should probably convert absolute
// lengths into pixels.
*l = *l * scalar;
},
Self::Number(ref mut n) => {
*n *= scalar;
},
Self::Angle(ref mut a) => {
*a = Angle::from_calc(a.degrees() * scalar);
},
Self::Time(ref mut t) => {
*t = Time::from_calc(t.seconds() * scalar);
},
Self::Percentage(ref mut p) => {
*p *= scalar;
},
// Multiplication is distributive across this.
Self::Sum(ref mut children) => {
for node in &mut **children {
node.mul_by(scalar);
}
},
// This one is a bit trickier.
Self::MinMax(ref mut children, ref mut op) => {
for node in &mut **children {
node.mul_by(scalar);
}
// For negatives we need to invert the operation.
if scalar < 0. {
*op = match *op {
MinMaxOp::Min => MinMaxOp::Max,
MinMaxOp::Max => MinMaxOp::Min,
}
}
},
// Multiplication is distributive across these.
Self::Clamp { ref mut min, ref mut center, ref mut max } => {
min.mul_by(scalar);
center.mul_by(scalar);
max.mul_by(scalar);
// For negatives we need to swap min / max.
if scalar < 0. {
std::mem::swap(min, max);
}
},
}
}
/// Tries to parse a single element in the expression, that is, a
/// `<length>`, `<angle>`, `<time>`, `<percentage>`, according to
/// `expected_unit`.
@ -354,11 +395,13 @@ impl CalcNode {
Self::parse_argument(context, input, expected_unit)
})?.into_boxed_slice();
Ok(match function {
MathFunction::Min => Self::Min(arguments),
MathFunction::Max => Self::Max(arguments),
let op = match function {
MathFunction::Min => MinMaxOp::Min,
MathFunction::Max => MinMaxOp::Max,
_ => unreachable!(),
})
};
Ok(Self::MinMax(arguments, op))
}
}
})
@ -369,7 +412,8 @@ impl CalcNode {
input: &mut Parser<'i, 't>,
expected_unit: CalcUnit,
) -> Result<Self, ParseError<'i>> {
let mut root = Self::parse_product(context, input, expected_unit)?;
let mut sum = SmallVec::<[CalcNode; 1]>::new();
sum.push(Self::parse_product(context, input, expected_unit)?);
loop {
let start = input.state();
@ -380,14 +424,12 @@ impl CalcNode {
}
match *input.next()? {
Token::Delim('+') => {
let rhs = Self::parse_product(context, input, expected_unit)?;
let new_root = CalcNode::Sum(Box::new(root), Box::new(rhs));
root = new_root;
sum.push(Self::parse_product(context, input, expected_unit)?);
},
Token::Delim('-') => {
let rhs = Self::parse_product(context, input, expected_unit)?;
let new_root = CalcNode::Sub(Box::new(root), Box::new(rhs));
root = new_root;
let mut rhs = Self::parse_product(context, input, expected_unit)?;
rhs.negate();
sum.push(rhs);
},
ref t => {
let t = t.clone();
@ -402,7 +444,11 @@ impl CalcNode {
}
}
Ok(root)
Ok(if sum.len() == 1 {
sum.drain(..).next().unwrap()
} else {
Self::Sum(sum.into_boxed_slice())
})
}
/// Parse a top-level `calc` expression, and all the products that may
@ -419,20 +465,36 @@ impl CalcNode {
input: &mut Parser<'i, 't>,
expected_unit: CalcUnit,
) -> Result<Self, ParseError<'i>> {
let mut root = Self::parse_one(context, input, expected_unit)?;
let mut node = Self::parse_one(context, input, expected_unit)?;
loop {
let start = input.state();
match input.next() {
Ok(&Token::Delim('*')) => {
let rhs = Self::parse_one(context, input, expected_unit)?;
let new_root = CalcNode::Mul(Box::new(root), Box::new(rhs));
root = new_root;
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, expected_unit)?;
let new_root = CalcNode::Div(Box::new(root), Box::new(rhs));
root = new_root;
// Dividing by units is not ok.
//
// TODO(emilio): Eventually it should be.
let number = match rhs.to_number() {
Ok(n) if n != 0. => n,
_ => {
return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
},
};
node.mul_by(1. / number);
},
_ => {
input.reset(&start);
@ -441,7 +503,7 @@ impl CalcNode {
}
}
Ok(root)
Ok(node)
}
/// Tries to simplify this expression into a `<length>` or `<percentage`>
@ -510,32 +572,12 @@ impl CalcNode {
},
NoCalcLength::ServoCharacterWidth(..) => unreachable!(),
},
CalcNode::Sub(ref a, ref b) => {
a.add_length_or_percentage_to(ret, factor)?;
b.add_length_or_percentage_to(ret, factor * -1.0)?;
},
CalcNode::Sum(ref a, ref b) => {
a.add_length_or_percentage_to(ret, factor)?;
b.add_length_or_percentage_to(ret, factor)?;
},
CalcNode::Mul(ref a, ref b) => match b.to_number() {
Ok(rhs) => {
a.add_length_or_percentage_to(ret, factor * rhs)?;
},
Err(..) => {
let lhs = a.to_number()?;
b.add_length_or_percentage_to(ret, factor * lhs)?;
},
},
CalcNode::Div(ref a, ref b) => {
let new_factor = b.to_number()?;
if new_factor == 0. {
return Err(());
CalcNode::Sum(ref children) => {
for child in &**children {
child.add_length_or_percentage_to(ret, factor)?;
}
a.add_length_or_percentage_to(ret, factor / new_factor)?;
},
CalcNode::Max(..) |
CalcNode::Min(..) |
CalcNode::MinMax(..) |
CalcNode::Clamp { .. } => {
// FIXME(emilio): Implement min/max/clamp for length-percentage.
return Err(())