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Diffstat (limited to 'servo/components/style/queries/condition.rs')
| -rw-r--r-- | servo/components/style/queries/condition.rs | 365 |
1 files changed, 365 insertions, 0 deletions
diff --git a/servo/components/style/queries/condition.rs b/servo/components/style/queries/condition.rs new file mode 100644 index 0000000000..56822c914a --- /dev/null +++ b/servo/components/style/queries/condition.rs @@ -0,0 +1,365 @@ +/* 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/. */ + +//! A query condition: +//! +//! https://drafts.csswg.org/mediaqueries-4/#typedef-media-condition +//! https://drafts.csswg.org/css-contain-3/#typedef-container-condition + +use super::{FeatureFlags, FeatureType, QueryFeatureExpression}; +use crate::values::computed; +use crate::{error_reporting::ContextualParseError, parser::ParserContext}; +use cssparser::{Parser, Token}; +use std::fmt::{self, Write}; +use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss}; + +/// A binary `and` or `or` operator. +#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, Parse, PartialEq, ToCss, ToShmem)] +#[allow(missing_docs)] +pub enum Operator { + And, + Or, +} + +/// Whether to allow an `or` condition or not during parsing. +#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToCss)] +enum AllowOr { + Yes, + No, +} + +/// https://en.wikipedia.org/wiki/Three-valued_logic#Kleene_and_Priest_logics +#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToCss)] +pub enum KleeneValue { + /// False + False = 0, + /// True + True = 1, + /// Either true or false, but we’re not sure which yet. + Unknown, +} + +impl From<bool> for KleeneValue { + fn from(b: bool) -> Self { + if b { + Self::True + } else { + Self::False + } + } +} + +impl KleeneValue { + /// Turns this Kleene value to a bool, taking the unknown value as an + /// argument. + pub fn to_bool(self, unknown: bool) -> bool { + match self { + Self::True => true, + Self::False => false, + Self::Unknown => unknown, + } + } +} + +impl std::ops::Not for KleeneValue { + type Output = Self; + + fn not(self) -> Self { + match self { + Self::True => Self::False, + Self::False => Self::True, + Self::Unknown => Self::Unknown, + } + } +} + +// Implements the logical and operation. +impl std::ops::BitAnd for KleeneValue { + type Output = Self; + + fn bitand(self, other: Self) -> Self { + if self == Self::False || other == Self::False { + return Self::False; + } + if self == Self::Unknown || other == Self::Unknown { + return Self::Unknown; + } + Self::True + } +} + +// Implements the logical or operation. +impl std::ops::BitOr for KleeneValue { + type Output = Self; + + fn bitor(self, other: Self) -> Self { + if self == Self::True || other == Self::True { + return Self::True; + } + if self == Self::Unknown || other == Self::Unknown { + return Self::Unknown; + } + Self::False + } +} + +impl std::ops::BitOrAssign for KleeneValue { + fn bitor_assign(&mut self, other: Self) { + *self = *self | other; + } +} + +impl std::ops::BitAndAssign for KleeneValue { + fn bitand_assign(&mut self, other: Self) { + *self = *self & other; + } +} + +/// Represents a condition. +#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)] +pub enum QueryCondition { + /// A simple feature expression, implicitly parenthesized. + Feature(QueryFeatureExpression), + /// A negation of a condition. + Not(Box<QueryCondition>), + /// A set of joint operations. + Operation(Box<[QueryCondition]>, Operator), + /// A condition wrapped in parenthesis. + InParens(Box<QueryCondition>), + /// [ <function-token> <any-value>? ) ] | [ ( <any-value>? ) ] + GeneralEnclosed(String), +} + +impl ToCss for QueryCondition { + fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result + where + W: fmt::Write, + { + match *self { + // NOTE(emilio): QueryFeatureExpression already includes the + // parenthesis. + QueryCondition::Feature(ref f) => f.to_css(dest), + QueryCondition::Not(ref c) => { + dest.write_str("not ")?; + c.to_css(dest) + }, + QueryCondition::InParens(ref c) => { + dest.write_char('(')?; + c.to_css(dest)?; + dest.write_char(')') + }, + QueryCondition::Operation(ref list, op) => { + let mut iter = list.iter(); + iter.next().unwrap().to_css(dest)?; + for item in iter { + dest.write_char(' ')?; + op.to_css(dest)?; + dest.write_char(' ')?; + item.to_css(dest)?; + } + Ok(()) + }, + QueryCondition::GeneralEnclosed(ref s) => dest.write_str(&s), + } + } +} + +/// <https://drafts.csswg.org/css-syntax-3/#typedef-any-value> +fn consume_any_value<'i, 't>(input: &mut Parser<'i, 't>) -> Result<(), ParseError<'i>> { + input.expect_no_error_token().map_err(Into::into) +} + +impl QueryCondition { + /// Parse a single condition. + pub fn parse<'i, 't>( + context: &ParserContext, + input: &mut Parser<'i, 't>, + feature_type: FeatureType, + ) -> Result<Self, ParseError<'i>> { + Self::parse_internal(context, input, feature_type, AllowOr::Yes) + } + + fn visit<F>(&self, visitor: &mut F) + where + F: FnMut(&Self), + { + visitor(self); + match *self { + Self::Feature(..) => {}, + Self::GeneralEnclosed(..) => {}, + Self::Not(ref cond) => cond.visit(visitor), + Self::Operation(ref conds, _op) => { + for cond in conds.iter() { + cond.visit(visitor); + } + }, + Self::InParens(ref cond) => cond.visit(visitor), + } + } + + /// Returns the union of all flags in the expression. This is useful for + /// container queries. + pub fn cumulative_flags(&self) -> FeatureFlags { + let mut result = FeatureFlags::empty(); + self.visit(&mut |condition| { + if let Self::Feature(ref f) = condition { + result.insert(f.feature_flags()) + } + }); + result + } + + /// Parse a single condition, disallowing `or` expressions. + /// + /// To be used from the legacy query syntax. + pub fn parse_disallow_or<'i, 't>( + context: &ParserContext, + input: &mut Parser<'i, 't>, + feature_type: FeatureType, + ) -> Result<Self, ParseError<'i>> { + Self::parse_internal(context, input, feature_type, AllowOr::No) + } + + /// https://drafts.csswg.org/mediaqueries-5/#typedef-media-condition or + /// https://drafts.csswg.org/mediaqueries-5/#typedef-media-condition-without-or + /// (depending on `allow_or`). + fn parse_internal<'i, 't>( + context: &ParserContext, + input: &mut Parser<'i, 't>, + feature_type: FeatureType, + allow_or: AllowOr, + ) -> Result<Self, ParseError<'i>> { + let location = input.current_source_location(); + if input.try_parse(|i| i.expect_ident_matching("not")).is_ok() { + let inner_condition = Self::parse_in_parens(context, input, feature_type)?; + return Ok(QueryCondition::Not(Box::new(inner_condition))); + } + + let first_condition = Self::parse_in_parens(context, input, feature_type)?; + let operator = match input.try_parse(Operator::parse) { + Ok(op) => op, + Err(..) => return Ok(first_condition), + }; + + if allow_or == AllowOr::No && operator == Operator::Or { + return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError)); + } + + let mut conditions = vec![]; + conditions.push(first_condition); + conditions.push(Self::parse_in_parens(context, input, feature_type)?); + + let delim = match operator { + Operator::And => "and", + Operator::Or => "or", + }; + + loop { + if input.try_parse(|i| i.expect_ident_matching(delim)).is_err() { + return Ok(QueryCondition::Operation( + conditions.into_boxed_slice(), + operator, + )); + } + + conditions.push(Self::parse_in_parens(context, input, feature_type)?); + } + } + + fn parse_in_parenthesis_block<'i>( + context: &ParserContext, + input: &mut Parser<'i, '_>, + feature_type: FeatureType, + ) -> Result<Self, ParseError<'i>> { + // Base case. Make sure to preserve this error as it's more generally + // relevant. + let feature_error = match input.try_parse(|input| { + QueryFeatureExpression::parse_in_parenthesis_block(context, input, feature_type) + }) { + Ok(expr) => return Ok(Self::Feature(expr)), + Err(e) => e, + }; + if let Ok(inner) = Self::parse(context, input, feature_type) { + return Ok(Self::InParens(Box::new(inner))); + } + Err(feature_error) + } + + /// Parse a condition in parentheses, or `<general-enclosed>`. + /// + /// https://drafts.csswg.org/mediaqueries/#typedef-media-in-parens + pub fn parse_in_parens<'i, 't>( + context: &ParserContext, + input: &mut Parser<'i, 't>, + feature_type: FeatureType, + ) -> Result<Self, ParseError<'i>> { + input.skip_whitespace(); + let start = input.position(); + let start_location = input.current_source_location(); + match *input.next()? { + Token::ParenthesisBlock => { + let nested = input.try_parse(|input| { + input.parse_nested_block(|input| { + Self::parse_in_parenthesis_block(context, input, feature_type) + }) + }); + match nested { + Ok(nested) => return Ok(nested), + Err(e) => { + // We're about to swallow the error in a `<general-enclosed>` + // condition, so report it while we can. + let loc = e.location; + let error = ContextualParseError::InvalidMediaRule(input.slice_from(start), e); + context.log_css_error(loc, error); + } + } + }, + Token::Function(..) => { + // TODO: handle `style()` queries, etc. + }, + ref t => return Err(start_location.new_unexpected_token_error(t.clone())), + } + input.parse_nested_block(consume_any_value)?; + Ok(Self::GeneralEnclosed(input.slice_from(start).to_owned())) + } + + /// Whether this condition matches the device and quirks mode. + /// https://drafts.csswg.org/mediaqueries/#evaluating + /// https://drafts.csswg.org/mediaqueries/#typedef-general-enclosed + /// Kleene 3-valued logic is adopted here due to the introduction of + /// <general-enclosed>. + pub fn matches(&self, context: &computed::Context) -> KleeneValue { + match *self { + QueryCondition::Feature(ref f) => f.matches(context), + QueryCondition::GeneralEnclosed(_) => KleeneValue::Unknown, + QueryCondition::InParens(ref c) => c.matches(context), + QueryCondition::Not(ref c) => !c.matches(context), + QueryCondition::Operation(ref conditions, op) => { + debug_assert!(!conditions.is_empty(), "We never create an empty op"); + match op { + Operator::And => { + let mut result = KleeneValue::True; + for c in conditions.iter() { + result &= c.matches(context); + if result == KleeneValue::False { + break; + } + } + result + }, + Operator::Or => { + let mut result = KleeneValue::False; + for c in conditions.iter() { + result |= c.matches(context); + if result == KleeneValue::True { + break; + } + } + result + }, + } + }, + } + } +} |