/* 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/. */ //! Support for [custom properties for cascading variables][custom]. //! //! [custom]: https://drafts.csswg.org/css-variables/ use crate::applicable_declarations::CascadePriority; use crate::custom_properties_map::CustomPropertiesMap; use crate::media_queries::Device; use crate::properties::{ CSSWideKeyword, CustomDeclaration, CustomDeclarationValue, LonghandId, LonghandIdSet, VariableDeclaration, }; use crate::properties_and_values::{ registry::PropertyRegistrationData, value::{ AllowComputationallyDependent, ComputedValue as ComputedRegisteredValue, SpecifiedValue as SpecifiedRegisteredValue, }, }; use crate::selector_map::{PrecomputedHashMap, PrecomputedHashSet}; use crate::stylesheets::UrlExtraData; use crate::stylist::Stylist; use crate::values::computed; use crate::values::specified::FontRelativeLength; use crate::Atom; use cssparser::{ CowRcStr, Delimiter, Parser, ParserInput, SourcePosition, Token, TokenSerializationType, }; use selectors::parser::SelectorParseErrorKind; use servo_arc::Arc; use smallvec::SmallVec; use std::borrow::Cow; use std::collections::hash_map::Entry; use std::fmt::{self, Write}; use std::ops::{Index, IndexMut}; use std::{cmp, num}; use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss}; /// The environment from which to get `env` function values. /// /// TODO(emilio): If this becomes a bit more complex we should probably move it /// to the `media_queries` module, or something. #[derive(Debug, MallocSizeOf)] pub struct CssEnvironment; type EnvironmentEvaluator = fn(device: &Device, url_data: &UrlExtraData) -> VariableValue; struct EnvironmentVariable { name: Atom, evaluator: EnvironmentEvaluator, } macro_rules! make_variable { ($name:expr, $evaluator:expr) => {{ EnvironmentVariable { name: $name, evaluator: $evaluator, } }}; } fn get_safearea_inset_top(device: &Device, url_data: &UrlExtraData) -> VariableValue { VariableValue::pixels(device.safe_area_insets().top, url_data) } fn get_safearea_inset_bottom(device: &Device, url_data: &UrlExtraData) -> VariableValue { VariableValue::pixels(device.safe_area_insets().bottom, url_data) } fn get_safearea_inset_left(device: &Device, url_data: &UrlExtraData) -> VariableValue { VariableValue::pixels(device.safe_area_insets().left, url_data) } fn get_safearea_inset_right(device: &Device, url_data: &UrlExtraData) -> VariableValue { VariableValue::pixels(device.safe_area_insets().right, url_data) } fn get_content_preferred_color_scheme(device: &Device, url_data: &UrlExtraData) -> VariableValue { use crate::gecko::media_features::PrefersColorScheme; let prefers_color_scheme = unsafe { crate::gecko_bindings::bindings::Gecko_MediaFeatures_PrefersColorScheme( device.document(), /* use_content = */ true, ) }; VariableValue::ident( match prefers_color_scheme { PrefersColorScheme::Light => "light", PrefersColorScheme::Dark => "dark", }, url_data, ) } fn get_scrollbar_inline_size(device: &Device, url_data: &UrlExtraData) -> VariableValue { VariableValue::pixels(device.scrollbar_inline_size().px(), url_data) } static ENVIRONMENT_VARIABLES: [EnvironmentVariable; 4] = [ make_variable!(atom!("safe-area-inset-top"), get_safearea_inset_top), make_variable!(atom!("safe-area-inset-bottom"), get_safearea_inset_bottom), make_variable!(atom!("safe-area-inset-left"), get_safearea_inset_left), make_variable!(atom!("safe-area-inset-right"), get_safearea_inset_right), ]; macro_rules! lnf_int { ($id:ident) => { unsafe { crate::gecko_bindings::bindings::Gecko_GetLookAndFeelInt( crate::gecko_bindings::bindings::LookAndFeel_IntID::$id as i32, ) } }; } macro_rules! lnf_int_variable { ($atom:expr, $id:ident, $ctor:ident) => {{ fn __eval(_: &Device, url_data: &UrlExtraData) -> VariableValue { VariableValue::$ctor(lnf_int!($id), url_data) } make_variable!($atom, __eval) }}; } static CHROME_ENVIRONMENT_VARIABLES: [EnvironmentVariable; 8] = [ lnf_int_variable!( atom!("-moz-gtk-csd-titlebar-button-spacing"), TitlebarButtonSpacing, int_pixels ), lnf_int_variable!( atom!("-moz-gtk-csd-titlebar-radius"), TitlebarRadius, int_pixels ), lnf_int_variable!( atom!("-moz-gtk-csd-close-button-position"), GTKCSDCloseButtonPosition, integer ), lnf_int_variable!( atom!("-moz-gtk-csd-minimize-button-position"), GTKCSDMinimizeButtonPosition, integer ), lnf_int_variable!( atom!("-moz-gtk-csd-maximize-button-position"), GTKCSDMaximizeButtonPosition, integer ), lnf_int_variable!( atom!("-moz-overlay-scrollbar-fade-duration"), ScrollbarFadeDuration, int_ms ), make_variable!( atom!("-moz-content-preferred-color-scheme"), get_content_preferred_color_scheme ), make_variable!(atom!("scrollbar-inline-size"), get_scrollbar_inline_size), ]; impl CssEnvironment { #[inline] fn get(&self, name: &Atom, device: &Device, url_data: &UrlExtraData) -> Option { if let Some(var) = ENVIRONMENT_VARIABLES.iter().find(|var| var.name == *name) { return Some((var.evaluator)(device, url_data)); } if !url_data.chrome_rules_enabled() { return None; } let var = CHROME_ENVIRONMENT_VARIABLES .iter() .find(|var| var.name == *name)?; Some((var.evaluator)(device, url_data)) } } /// A custom property name is just an `Atom`. /// /// Note that this does not include the `--` prefix pub type Name = Atom; /// Parse a custom property name. /// /// pub fn parse_name(s: &str) -> Result<&str, ()> { if s.starts_with("--") && s.len() > 2 { Ok(&s[2..]) } else { Err(()) } } /// A value for a custom property is just a set of tokens. /// /// We preserve the original CSS for serialization, and also the variable /// references to other custom property names. #[derive(Clone, Debug, MallocSizeOf, ToShmem)] pub struct VariableValue { /// The raw CSS string. pub css: String, /// The url data of the stylesheet where this value came from. pub url_data: UrlExtraData, first_token_type: TokenSerializationType, last_token_type: TokenSerializationType, /// var(), env(), or non-custom property (e.g. through `em`) references. references: References, } trivial_to_computed_value!(VariableValue); // For all purposes, we want values to be considered equal if their css text is equal. impl PartialEq for VariableValue { fn eq(&self, other: &Self) -> bool { self.css == other.css } } impl Eq for VariableValue {} impl ToCss for SpecifiedValue { fn to_css(&self, dest: &mut CssWriter) -> fmt::Result where W: Write, { dest.write_str(&self.css) } } /// A pair of separate CustomPropertiesMaps, split between custom properties /// that have the inherit flag set and those with the flag unset. #[repr(C)] #[derive(Clone, Debug, Default, PartialEq)] pub struct ComputedCustomProperties { /// Map for custom properties with inherit flag set, including non-registered /// ones. pub inherited: CustomPropertiesMap, /// Map for custom properties with inherit flag unset. pub non_inherited: CustomPropertiesMap, } impl ComputedCustomProperties { /// Return whether the inherited and non_inherited maps are none. pub fn is_empty(&self) -> bool { self.inherited.is_empty() && self.non_inherited.is_empty() } /// Return the name and value of the property at specified index, if any. pub fn property_at(&self, index: usize) -> Option<(&Name, &Option)> { // Just expose the custom property items from custom_properties.inherited, followed // by custom property items from custom_properties.non_inherited. self.inherited .get_index(index) .or_else(|| self.non_inherited.get_index(index - self.inherited.len())) } /// Insert a custom property in the corresponding inherited/non_inherited /// map, depending on whether the inherit flag is set or unset. fn insert( &mut self, registration: &PropertyRegistrationData, name: &Name, value: ComputedRegisteredValue, ) { self.map_mut(registration).insert(name, value) } /// Remove a custom property from the corresponding inherited/non_inherited /// map, depending on whether the inherit flag is set or unset. fn remove(&mut self, registration: &PropertyRegistrationData, name: &Name) { self.map_mut(registration).remove(name); } /// Shrink the capacity of the inherited maps as much as possible. fn shrink_to_fit(&mut self) { self.inherited.shrink_to_fit(); self.non_inherited.shrink_to_fit(); } fn map_mut(&mut self, registration: &PropertyRegistrationData) -> &mut CustomPropertiesMap { if registration.inherits() { &mut self.inherited } else { &mut self.non_inherited } } fn get( &self, registration: &PropertyRegistrationData, name: &Name, ) -> Option<&ComputedRegisteredValue> { if registration.inherits() { self.inherited.get(name) } else { self.non_inherited.get(name) } } } /// Both specified and computed values are VariableValues, the difference is /// whether var() functions are expanded. pub type SpecifiedValue = VariableValue; /// Both specified and computed values are VariableValues, the difference is /// whether var() functions are expanded. pub type ComputedValue = VariableValue; /// Set of flags to non-custom references this custom property makes. #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, MallocSizeOf, ToShmem)] struct NonCustomReferences(u8); bitflags! { impl NonCustomReferences: u8 { /// At least one custom property depends on font-relative units. const FONT_UNITS = 1 << 0; /// At least one custom property depends on root element's font-relative units. const ROOT_FONT_UNITS = 1 << 1; /// At least one custom property depends on line height units. const LH_UNITS = 1 << 2; /// At least one custom property depends on root element's line height units. const ROOT_LH_UNITS = 1 << 3; /// All dependencies not depending on the root element. const NON_ROOT_DEPENDENCIES = Self::FONT_UNITS.bits() | Self::LH_UNITS.bits(); /// All dependencies depending on the root element. const ROOT_DEPENDENCIES = Self::ROOT_FONT_UNITS.bits() | Self::ROOT_LH_UNITS.bits(); } } impl NonCustomReferences { fn for_each(&self, mut f: F) where F: FnMut(SingleNonCustomReference), { for (_, r) in self.iter_names() { let single = match r { Self::FONT_UNITS => SingleNonCustomReference::FontUnits, Self::ROOT_FONT_UNITS => SingleNonCustomReference::RootFontUnits, Self::LH_UNITS => SingleNonCustomReference::LhUnits, Self::ROOT_LH_UNITS => SingleNonCustomReference::RootLhUnits, _ => unreachable!("Unexpected single bit value"), }; f(single); } } fn from_unit(value: &CowRcStr) -> Self { // For registered properties, any reference to font-relative dimensions // make it dependent on font-related properties. // TODO(dshin): When we unit algebra gets implemented and handled - // Is it valid to say that `calc(1em / 2em * 3px)` triggers this? if value.eq_ignore_ascii_case(FontRelativeLength::LH) { return Self::FONT_UNITS | Self::LH_UNITS; } if value.eq_ignore_ascii_case(FontRelativeLength::EM) || value.eq_ignore_ascii_case(FontRelativeLength::EX) || value.eq_ignore_ascii_case(FontRelativeLength::CAP) || value.eq_ignore_ascii_case(FontRelativeLength::CH) || value.eq_ignore_ascii_case(FontRelativeLength::IC) { return Self::FONT_UNITS; } if value.eq_ignore_ascii_case(FontRelativeLength::RLH) { return Self::ROOT_FONT_UNITS | Self::ROOT_LH_UNITS; } if value.eq_ignore_ascii_case(FontRelativeLength::REM) { return Self::ROOT_FONT_UNITS; } Self::empty() } } #[derive(Clone, Copy, Debug, Eq, PartialEq)] enum SingleNonCustomReference { FontUnits = 0, RootFontUnits, LhUnits, RootLhUnits, } struct NonCustomReferenceMap([Option; 4]); impl Default for NonCustomReferenceMap { fn default() -> Self { NonCustomReferenceMap(Default::default()) } } impl Index for NonCustomReferenceMap { type Output = Option; fn index(&self, reference: SingleNonCustomReference) -> &Self::Output { &self.0[reference as usize] } } impl IndexMut for NonCustomReferenceMap { fn index_mut(&mut self, reference: SingleNonCustomReference) -> &mut Self::Output { &mut self.0[reference as usize] } } /// Whether to defer resolving custom properties referencing font relative units. #[derive(Clone, Copy, PartialEq, Eq)] #[allow(missing_docs)] pub enum DeferFontRelativeCustomPropertyResolution { Yes, No, } #[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)] struct VariableFallback { start: num::NonZeroUsize, first_token_type: TokenSerializationType, last_token_type: TokenSerializationType, } #[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)] struct VarOrEnvReference { name: Name, start: usize, end: usize, fallback: Option, prev_token_type: TokenSerializationType, next_token_type: TokenSerializationType, is_var: bool, } /// A struct holding information about the external references to that a custom /// property value may have. #[derive(Clone, Debug, Default, MallocSizeOf, PartialEq, ToShmem)] struct References { refs: Vec, non_custom_references: NonCustomReferences, any_env: bool, any_var: bool, } impl References { fn has_references(&self) -> bool { !self.refs.is_empty() } fn get_non_custom_dependencies(&self, is_root_element: bool) -> NonCustomReferences { let mask = NonCustomReferences::NON_ROOT_DEPENDENCIES; let mask = if is_root_element { mask | NonCustomReferences::ROOT_DEPENDENCIES } else { mask }; self.non_custom_references & mask } } impl VariableValue { fn empty(url_data: &UrlExtraData) -> Self { Self { css: String::new(), last_token_type: Default::default(), first_token_type: Default::default(), url_data: url_data.clone(), references: Default::default(), } } /// Create a new custom property without parsing if the CSS is known to be valid and contain no /// references. pub fn new( css: String, url_data: &UrlExtraData, first_token_type: TokenSerializationType, last_token_type: TokenSerializationType, ) -> Self { Self { css, url_data: url_data.clone(), first_token_type, last_token_type, references: Default::default(), } } fn push<'i>( &mut self, css: &str, css_first_token_type: TokenSerializationType, css_last_token_type: TokenSerializationType, ) -> Result<(), ()> { /// Prevent values from getting terribly big since you can use custom /// properties exponentially. /// /// This number (2MB) is somewhat arbitrary, but silly enough that no /// reasonable page should hit it. We could limit by number of total /// substitutions, but that was very easy to work around in practice /// (just choose a larger initial value and boom). const MAX_VALUE_LENGTH_IN_BYTES: usize = 2 * 1024 * 1024; if self.css.len() + css.len() > MAX_VALUE_LENGTH_IN_BYTES { return Err(()); } // This happens e.g. between two subsequent var() functions: // `var(--a)var(--b)`. // // In that case, css_*_token_type is nonsensical. if css.is_empty() { return Ok(()); } self.first_token_type.set_if_nothing(css_first_token_type); // If self.first_token_type was nothing, // self.last_token_type is also nothing and this will be false: if self .last_token_type .needs_separator_when_before(css_first_token_type) { self.css.push_str("/**/") } self.css.push_str(css); self.last_token_type = css_last_token_type; Ok(()) } /// Parse a custom property value. pub fn parse<'i, 't>( input: &mut Parser<'i, 't>, url_data: &UrlExtraData, ) -> Result> { input.skip_whitespace(); let mut references = References::default(); let mut missing_closing_characters = String::new(); let start_position = input.position(); let (first_token_type, last_token_type) = parse_declaration_value( input, start_position, &mut references, &mut missing_closing_characters, )?; let mut css = input.slice_from(start_position).to_owned(); if !missing_closing_characters.is_empty() { // Unescaped backslash at EOF in a quoted string is ignored. if css.ends_with("\\") && matches!(missing_closing_characters.as_bytes()[0], b'"' | b'\'') { css.pop(); } css.push_str(&missing_closing_characters); } css.shrink_to_fit(); references.refs.shrink_to_fit(); Ok(Self { css, url_data: url_data.clone(), first_token_type, last_token_type, references, }) } /// Create VariableValue from an int. fn integer(number: i32, url_data: &UrlExtraData) -> Self { Self::from_token( Token::Number { has_sign: false, value: number as f32, int_value: Some(number), }, url_data, ) } /// Create VariableValue from an int. fn ident(ident: &'static str, url_data: &UrlExtraData) -> Self { Self::from_token(Token::Ident(ident.into()), url_data) } /// Create VariableValue from a float amount of CSS pixels. fn pixels(number: f32, url_data: &UrlExtraData) -> Self { // FIXME (https://github.com/servo/rust-cssparser/issues/266): // No way to get TokenSerializationType::Dimension without creating // Token object. Self::from_token( Token::Dimension { has_sign: false, value: number, int_value: None, unit: CowRcStr::from("px"), }, url_data, ) } /// Create VariableValue from an integer amount of milliseconds. fn int_ms(number: i32, url_data: &UrlExtraData) -> Self { Self::from_token( Token::Dimension { has_sign: false, value: number as f32, int_value: Some(number), unit: CowRcStr::from("ms"), }, url_data, ) } /// Create VariableValue from an integer amount of CSS pixels. fn int_pixels(number: i32, url_data: &UrlExtraData) -> Self { Self::from_token( Token::Dimension { has_sign: false, value: number as f32, int_value: Some(number), unit: CowRcStr::from("px"), }, url_data, ) } fn from_token(token: Token, url_data: &UrlExtraData) -> Self { let token_type = token.serialization_type(); let mut css = token.to_css_string(); css.shrink_to_fit(); VariableValue { css, url_data: url_data.clone(), first_token_type: token_type, last_token_type: token_type, references: Default::default(), } } /// Returns the raw CSS text from this VariableValue pub fn css_text(&self) -> &str { &self.css } /// Returns whether this variable value has any reference to the environment or other /// variables. pub fn has_references(&self) -> bool { self.references.has_references() } } /// fn parse_declaration_value<'i, 't>( input: &mut Parser<'i, 't>, input_start: SourcePosition, references: &mut References, missing_closing_characters: &mut String, ) -> Result<(TokenSerializationType, TokenSerializationType), ParseError<'i>> { input.parse_until_before(Delimiter::Bang | Delimiter::Semicolon, |input| { parse_declaration_value_block(input, input_start, references, missing_closing_characters) }) } /// Like parse_declaration_value, but accept `!` and `;` since they are only invalid at the top level. fn parse_declaration_value_block<'i, 't>( input: &mut Parser<'i, 't>, input_start: SourcePosition, references: &mut References, missing_closing_characters: &mut String, ) -> Result<(TokenSerializationType, TokenSerializationType), ParseError<'i>> { let mut is_first = true; let mut first_token_type = TokenSerializationType::Nothing; let mut last_token_type = TokenSerializationType::Nothing; let mut prev_reference_index: Option = None; loop { let token_start = input.position(); let Ok(token) = input.next_including_whitespace_and_comments() else { break; }; let prev_token_type = last_token_type; let serialization_type = token.serialization_type(); last_token_type = serialization_type; if is_first { first_token_type = last_token_type; is_first = false; } macro_rules! nested { () => { input.parse_nested_block(|input| { parse_declaration_value_block( input, input_start, references, missing_closing_characters, ) })? }; } macro_rules! check_closed { ($closing:expr) => { if !input.slice_from(token_start).ends_with($closing) { missing_closing_characters.push_str($closing) } }; } if let Some(index) = prev_reference_index.take() { references.refs[index].next_token_type = serialization_type; } match *token { Token::Comment(_) => { let token_slice = input.slice_from(token_start); if !token_slice.ends_with("*/") { missing_closing_characters.push_str(if token_slice.ends_with('*') { "/" } else { "*/" }) } }, Token::BadUrl(ref u) => { let e = StyleParseErrorKind::BadUrlInDeclarationValueBlock(u.clone()); return Err(input.new_custom_error(e)); }, Token::BadString(ref s) => { let e = StyleParseErrorKind::BadStringInDeclarationValueBlock(s.clone()); return Err(input.new_custom_error(e)); }, Token::CloseParenthesis => { let e = StyleParseErrorKind::UnbalancedCloseParenthesisInDeclarationValueBlock; return Err(input.new_custom_error(e)); }, Token::CloseSquareBracket => { let e = StyleParseErrorKind::UnbalancedCloseSquareBracketInDeclarationValueBlock; return Err(input.new_custom_error(e)); }, Token::CloseCurlyBracket => { let e = StyleParseErrorKind::UnbalancedCloseCurlyBracketInDeclarationValueBlock; return Err(input.new_custom_error(e)); }, Token::Function(ref name) => { let is_var = name.eq_ignore_ascii_case("var"); if is_var || name.eq_ignore_ascii_case("env") { let our_ref_index = references.refs.len(); let fallback = input.parse_nested_block(|input| { // TODO(emilio): For env() this should be per spec, but no other browser does // that, see https://github.com/w3c/csswg-drafts/issues/3262. let name = input.expect_ident()?; let name = Atom::from(if is_var { match parse_name(name.as_ref()) { Ok(name) => name, Err(()) => { let name = name.clone(); return Err(input.new_custom_error( SelectorParseErrorKind::UnexpectedIdent(name), )); }, } } else { name.as_ref() }); // We want the order of the references to match source order. So we need to reserve our slot // now, _before_ parsing our fallback. Note that we don't care if parsing fails after all, since // if this fails we discard the whole result anyways. let start = token_start.byte_index() - input_start.byte_index(); references.refs.push(VarOrEnvReference { name, start, // To be fixed up after parsing fallback and auto-closing via our_ref_index. end: start, prev_token_type, // To be fixed up (if needed) on the next loop iteration via prev_reference_index. next_token_type: TokenSerializationType::Nothing, // To be fixed up after parsing fallback. fallback: None, is_var, }); let mut fallback = None; if input.try_parse(|input| input.expect_comma()).is_ok() { input.skip_whitespace(); let fallback_start = num::NonZeroUsize::new( input.position().byte_index() - input_start.byte_index(), ) .unwrap(); // NOTE(emilio): Intentionally using parse_declaration_value rather than // parse_declaration_value_block, since that's what parse_fallback used to do. let (first, last) = parse_declaration_value( input, input_start, references, missing_closing_characters, )?; fallback = Some(VariableFallback { start: fallback_start, first_token_type: first, last_token_type: last, }); } else { let state = input.state(); // We still need to consume the rest of the potentially-unclosed // tokens, but make sure to not consume tokens that would otherwise be // invalid, by calling reset(). parse_declaration_value_block( input, input_start, references, missing_closing_characters, )?; input.reset(&state); } Ok(fallback) })?; check_closed!(")"); prev_reference_index = Some(our_ref_index); let reference = &mut references.refs[our_ref_index]; reference.end = input.position().byte_index() - input_start.byte_index() + missing_closing_characters.len(); reference.fallback = fallback; if is_var { references.any_var = true; } else { references.any_env = true; } } else { nested!(); check_closed!(")"); } }, Token::ParenthesisBlock => { nested!(); check_closed!(")"); }, Token::CurlyBracketBlock => { nested!(); check_closed!("}"); }, Token::SquareBracketBlock => { nested!(); check_closed!("]"); }, Token::QuotedString(_) => { let token_slice = input.slice_from(token_start); let quote = &token_slice[..1]; debug_assert!(matches!(quote, "\"" | "'")); if !(token_slice.ends_with(quote) && token_slice.len() > 1) { missing_closing_characters.push_str(quote) } }, Token::Ident(ref value) | Token::AtKeyword(ref value) | Token::Hash(ref value) | Token::IDHash(ref value) | Token::UnquotedUrl(ref value) | Token::Dimension { unit: ref value, .. } => { references .non_custom_references .insert(NonCustomReferences::from_unit(value)); let is_unquoted_url = matches!(token, Token::UnquotedUrl(_)); if value.ends_with("�") && input.slice_from(token_start).ends_with("\\") { // Unescaped backslash at EOF in these contexts is interpreted as U+FFFD // Check the value in case the final backslash was itself escaped. // Serialize as escaped U+FFFD, which is also interpreted as U+FFFD. // (Unescaped U+FFFD would also work, but removing the backslash is annoying.) missing_closing_characters.push_str("�") } if is_unquoted_url { check_closed!(")"); } }, _ => {}, }; } Ok((first_token_type, last_token_type)) } /// A struct that takes care of encapsulating the cascade process for custom properties. pub struct CustomPropertiesBuilder<'a, 'b: 'a> { seen: PrecomputedHashSet<&'a Name>, may_have_cycles: bool, custom_properties: ComputedCustomProperties, reverted: PrecomputedHashMap<&'a Name, (CascadePriority, bool)>, stylist: &'a Stylist, computed_context: &'a mut computed::Context<'b>, references_from_non_custom_properties: NonCustomReferenceMap>, } impl<'a, 'b: 'a> CustomPropertiesBuilder<'a, 'b> { /// Create a new builder, inheriting from a given custom properties map. /// /// We expose this publicly mostly for @keyframe blocks. pub fn new_with_properties( stylist: &'a Stylist, custom_properties: ComputedCustomProperties, computed_context: &'a mut computed::Context<'b>, ) -> Self { Self { seen: PrecomputedHashSet::default(), reverted: Default::default(), may_have_cycles: false, custom_properties, stylist, computed_context, references_from_non_custom_properties: NonCustomReferenceMap::default(), } } /// Create a new builder, inheriting from the right style given context. pub fn new(stylist: &'a Stylist, context: &'a mut computed::Context<'b>) -> Self { let is_root_element = context.is_root_element(); let inherited = context.inherited_custom_properties(); let initial_values = stylist.get_custom_property_initial_values(); let properties = ComputedCustomProperties { inherited: if is_root_element { debug_assert!(inherited.is_empty()); initial_values.inherited.clone() } else { inherited.inherited.clone() }, non_inherited: initial_values.non_inherited.clone(), }; // Reuse flags from computing registered custom properties initial values, such as // whether they depend on viewport units. context .style() .add_flags(stylist.get_custom_property_initial_values_flags()); Self::new_with_properties(stylist, properties, context) } /// Cascade a given custom property declaration. pub fn cascade(&mut self, declaration: &'a CustomDeclaration, priority: CascadePriority) { let CustomDeclaration { ref name, ref value, } = *declaration; if let Some(&(reverted_priority, is_origin_revert)) = self.reverted.get(&name) { if !reverted_priority.allows_when_reverted(&priority, is_origin_revert) { return; } } let was_already_present = !self.seen.insert(name); if was_already_present { return; } if !self.value_may_affect_style(name, value) { return; } let map = &mut self.custom_properties; let registration = self.stylist.get_custom_property_registration(&name); match value { CustomDeclarationValue::Value(unparsed_value) => { let has_custom_property_references = unparsed_value.references.any_var; let registered_length_property = registration.syntax.may_reference_font_relative_length(); // Non-custom dependency is really relevant for registered custom properties // that require computed value of such dependencies. let has_non_custom_dependencies = registered_length_property && !unparsed_value .references .get_non_custom_dependencies(self.computed_context.is_root_element()) .is_empty(); self.may_have_cycles |= has_custom_property_references || has_non_custom_dependencies; // If the variable value has no references to other properties, perform // substitution here instead of forcing a full traversal in `substitute_all` // afterwards. if !has_custom_property_references && !has_non_custom_dependencies { return substitute_references_if_needed_and_apply( name, unparsed_value, map, self.stylist, self.computed_context, ); } let value = ComputedRegisteredValue::universal(Arc::clone(unparsed_value)); map.insert(registration, name, value); }, CustomDeclarationValue::CSSWideKeyword(keyword) => match keyword { CSSWideKeyword::RevertLayer | CSSWideKeyword::Revert => { let origin_revert = matches!(keyword, CSSWideKeyword::Revert); self.seen.remove(name); self.reverted.insert(name, (priority, origin_revert)); }, CSSWideKeyword::Initial => { // For non-inherited custom properties, 'initial' was handled in value_may_affect_style. debug_assert!(registration.inherits(), "Should've been handled earlier"); remove_and_insert_initial_value(name, registration, map); }, CSSWideKeyword::Inherit => { // For inherited custom properties, 'inherit' was handled in value_may_affect_style. debug_assert!(!registration.inherits(), "Should've been handled earlier"); if let Some(inherited_value) = self .computed_context .inherited_custom_properties() .non_inherited .get(name) { map.insert(registration, name, inherited_value.clone()); } }, // handled in value_may_affect_style CSSWideKeyword::Unset => unreachable!(), }, } } /// Note a non-custom property with variable reference that may in turn depend on that property. /// e.g. `font-size` depending on a custom property that may be a registered property using `em`. pub fn note_potentially_cyclic_non_custom_dependency( &mut self, id: LonghandId, decl: &VariableDeclaration, ) { // With unit algebra in `calc()`, references aren't limited to `font-size`. // For example, `--foo: 100ex; font-weight: calc(var(--foo) / 1ex);`, // or `--foo: 1em; zoom: calc(var(--foo) * 30px / 2em);` let references = match id { LonghandId::FontSize => { if self.computed_context.is_root_element() { NonCustomReferences::ROOT_FONT_UNITS } else { NonCustomReferences::FONT_UNITS } }, LonghandId::LineHeight => { if self.computed_context.is_root_element() { NonCustomReferences::ROOT_LH_UNITS | NonCustomReferences::ROOT_FONT_UNITS } else { NonCustomReferences::LH_UNITS | NonCustomReferences::FONT_UNITS } }, _ => return, }; let refs = &decl.value.variable_value.references; if !refs.any_var { return; } let variables: Vec = refs .refs .iter() .filter_map(|reference| { if !reference.is_var { return None; } if !self .stylist .get_custom_property_registration(&reference.name) .syntax .may_compute_length() { return None; } Some(reference.name.clone()) }) .collect(); references.for_each(|idx| { let entry = &mut self.references_from_non_custom_properties[idx]; let was_none = entry.is_none(); let v = entry.get_or_insert_with(|| variables.clone()); if was_none { return; } v.extend(variables.clone().into_iter()); }); } fn value_may_affect_style(&self, name: &Name, value: &CustomDeclarationValue) -> bool { let registration = self.stylist.get_custom_property_registration(&name); match *value { CustomDeclarationValue::CSSWideKeyword(CSSWideKeyword::Inherit) => { // For inherited custom properties, explicit 'inherit' means we // can just use any existing value in the inherited // CustomPropertiesMap. if registration.inherits() { return false; } }, CustomDeclarationValue::CSSWideKeyword(CSSWideKeyword::Initial) => { // For non-inherited custom properties, explicit 'initial' means // we can just use any initial value in the registration. if !registration.inherits() { return false; } }, CustomDeclarationValue::CSSWideKeyword(CSSWideKeyword::Unset) => { // Explicit 'unset' means we can either just use any existing // value in the inherited CustomPropertiesMap or the initial // value in the registration. return false; }, _ => {}, } let existing_value = self.custom_properties.get(registration, &name); match (existing_value, value) { (None, &CustomDeclarationValue::CSSWideKeyword(CSSWideKeyword::Initial)) => { debug_assert!(registration.inherits(), "Should've been handled earlier"); // The initial value of a custom property without a // guaranteed-invalid initial value is the same as it // not existing in the map. if registration.initial_value.is_none() { return false; } }, ( Some(existing_value), &CustomDeclarationValue::CSSWideKeyword(CSSWideKeyword::Initial), ) => { debug_assert!(registration.inherits(), "Should've been handled earlier"); // Don't bother overwriting an existing value with the initial value specified in // the registration. if let Some(initial_value) = self .stylist .get_custom_property_initial_values() .get(registration, name) { return existing_value != initial_value; } }, (Some(_), &CustomDeclarationValue::CSSWideKeyword(CSSWideKeyword::Inherit)) => { debug_assert!(!registration.inherits(), "Should've been handled earlier"); // existing_value is the registered initial value. // Don't bother adding it to self.custom_properties.non_inherited // if the key is also absent from self.inherited.non_inherited. if self .computed_context .inherited_custom_properties() .non_inherited .get(name) .is_none() { return false; } }, (Some(existing_value), &CustomDeclarationValue::Value(ref value)) => { // Don't bother overwriting an existing value with the same // specified value. if let Some(existing_value) = existing_value.as_universal() { return existing_value != value; } if let Ok(value) = compute_value( &value.css, &value.url_data, registration, self.computed_context, ) { return existing_value.v != value.v; } }, _ => {}, } true } /// Computes the map of applicable custom properties, as well as /// longhand properties that are now considered invalid-at-compute time. /// The result is saved into the computed context. /// /// If there was any specified property or non-inherited custom property /// with an initial value, we've created a new map and now we /// need to remove any potential cycles (And marking non-custom /// properties), and wrap it in an arc. /// /// Some registered custom properties may require font-related properties /// be resolved to resolve. If these properties are not resolved at this time, /// `defer` should be set to `Yes`, which will leave such custom properties, /// and other properties referencing them, untouched. These properties are /// returned separately, to be resolved by `build_deferred` to fully resolve /// all custom properties after all necessary non-custom properties are resolved. pub fn build( mut self, defer: DeferFontRelativeCustomPropertyResolution, ) -> Option { let mut deferred_custom_properties = None; if self.may_have_cycles { if defer == DeferFontRelativeCustomPropertyResolution::Yes { deferred_custom_properties = Some(ComputedCustomProperties::default()); } let mut invalid_non_custom_properties = LonghandIdSet::default(); substitute_all( &mut self.custom_properties, deferred_custom_properties.as_mut(), &mut invalid_non_custom_properties, &self.seen, &self.references_from_non_custom_properties, self.stylist, self.computed_context, ); self.computed_context.builder.invalid_non_custom_properties = invalid_non_custom_properties; } self.custom_properties.shrink_to_fit(); // Some pages apply a lot of redundant custom properties, see e.g. // bug 1758974 comment 5. Try to detect the case where the values // haven't really changed, and save some memory by reusing the inherited // map in that case. let initial_values = self.stylist.get_custom_property_initial_values(); self.computed_context.builder.custom_properties = ComputedCustomProperties { inherited: if self .computed_context .inherited_custom_properties() .inherited == self.custom_properties.inherited { self.computed_context .inherited_custom_properties() .inherited .clone() } else { self.custom_properties.inherited }, non_inherited: if initial_values.non_inherited == self.custom_properties.non_inherited { initial_values.non_inherited.clone() } else { self.custom_properties.non_inherited }, }; deferred_custom_properties } /// Fully resolve all deferred custom properties, assuming that the incoming context /// has necessary properties resolved. pub fn build_deferred( deferred: ComputedCustomProperties, stylist: &Stylist, computed_context: &mut computed::Context, ) { if deferred.is_empty() { return; } // Guaranteed to not have cycles at this point. let substitute = |deferred: &CustomPropertiesMap, stylist: &Stylist, context: &computed::Context, custom_properties: &mut ComputedCustomProperties| { // Since `CustomPropertiesMap` preserves insertion order, we shouldn't // have to worry about resolving in a wrong order. for (k, v) in deferred.iter() { let Some(v) = v else { continue }; let Some(v) = v.as_universal() else { unreachable!("Computing should have been deferred!") }; substitute_references_if_needed_and_apply( k, v, custom_properties, stylist, context, ); } }; let mut custom_properties = std::mem::take(&mut computed_context.builder.custom_properties); substitute( &deferred.inherited, stylist, computed_context, &mut custom_properties, ); substitute( &deferred.non_inherited, stylist, computed_context, &mut custom_properties, ); computed_context.builder.custom_properties = custom_properties; } } /// Resolve all custom properties to either substituted, invalid, or unset /// (meaning we should use the inherited value). /// /// It does cycle dependencies removal at the same time as substitution. fn substitute_all( custom_properties_map: &mut ComputedCustomProperties, mut deferred_properties_map: Option<&mut ComputedCustomProperties>, invalid_non_custom_properties: &mut LonghandIdSet, seen: &PrecomputedHashSet<&Name>, references_from_non_custom_properties: &NonCustomReferenceMap>, stylist: &Stylist, computed_context: &computed::Context, ) { // The cycle dependencies removal in this function is a variant // of Tarjan's algorithm. It is mostly based on the pseudo-code // listed in // https://en.wikipedia.org/w/index.php? // title=Tarjan%27s_strongly_connected_components_algorithm&oldid=801728495 #[derive(Clone, Eq, PartialEq, Debug)] enum VarType { Custom(Name), NonCustom(SingleNonCustomReference), } /// Struct recording necessary information for each variable. #[derive(Debug)] struct VarInfo { /// The name of the variable. It will be taken to save addref /// when the corresponding variable is popped from the stack. /// This also serves as a mark for whether the variable is /// currently in the stack below. var: Option, /// If the variable is in a dependency cycle, lowlink represents /// a smaller index which corresponds to a variable in the same /// strong connected component, which is known to be accessible /// from this variable. It is not necessarily the root, though. lowlink: usize, } /// Context struct for traversing the variable graph, so that we can /// avoid referencing all the fields multiple times. struct Context<'a, 'b: 'a> { /// Number of variables visited. This is used as the order index /// when we visit a new unresolved variable. count: usize, /// The map from custom property name to its order index. index_map: PrecomputedHashMap, /// Mapping from a non-custom dependency to its order index. non_custom_index_map: NonCustomReferenceMap, /// Information of each variable indexed by the order index. var_info: SmallVec<[VarInfo; 5]>, /// The stack of order index of visited variables. It contains /// all unfinished strong connected components. stack: SmallVec<[usize; 5]>, /// References to non-custom properties in this strongly connected component. non_custom_references: NonCustomReferences, map: &'a mut ComputedCustomProperties, /// The stylist is used to get registered properties, and to resolve the environment to /// substitute `env()` variables. stylist: &'a Stylist, /// The computed context is used to get inherited custom /// properties and compute registered custom properties. computed_context: &'a computed::Context<'b>, /// Longhand IDs that became invalid due to dependency cycle(s). invalid_non_custom_properties: &'a mut LonghandIdSet, /// Properties that cannot yet be substituted. deferred_properties: Option<&'a mut ComputedCustomProperties>, } /// This function combines the traversal for cycle removal and value /// substitution. It returns either a signal None if this variable /// has been fully resolved (to either having no reference or being /// marked invalid), or the order index for the given name. /// /// When it returns, the variable corresponds to the name would be /// in one of the following states: /// * It is still in context.stack, which means it is part of an /// potentially incomplete dependency circle. /// * It has been removed from the map. It can be either that the /// substitution failed, or it is inside a dependency circle. /// When this function removes a variable from the map because /// of dependency circle, it would put all variables in the same /// strong connected component to the set together. /// * It doesn't have any reference, because either this variable /// doesn't have reference at all in specified value, or it has /// been completely resolved. /// * There is no such variable at all. fn traverse<'a, 'b>( var: VarType, non_custom_references: &NonCustomReferenceMap>, context: &mut Context<'a, 'b>, ) -> Option { // Some shortcut checks. let (value, should_substitute) = match var { VarType::Custom(ref name) => { let registration = context.stylist.get_custom_property_registration(name); let value = context.map.get(registration, name)?; let value = value.as_universal()?; let non_custom_references = value .references .get_non_custom_dependencies(context.computed_context.is_root_element()); let has_custom_property_reference = value.references.any_var; // Nothing to resolve. if !has_custom_property_reference && non_custom_references.is_empty() { debug_assert!(!value.references.any_env, "Should've been handled earlier"); return None; } // Has this variable been visited? match context.index_map.entry(name.clone()) { Entry::Occupied(entry) => { return Some(*entry.get()); }, Entry::Vacant(entry) => { entry.insert(context.count); }, } context.non_custom_references |= value.as_ref().references.non_custom_references; // Hold a strong reference to the value so that we don't // need to keep reference to context.map. (Some(value.clone()), has_custom_property_reference) }, VarType::NonCustom(ref non_custom) => { let entry = &mut context.non_custom_index_map[*non_custom]; if let Some(v) = entry { return Some(*v); } *entry = Some(context.count); (None, false) }, }; // Add new entry to the information table. let index = context.count; context.count += 1; debug_assert_eq!(index, context.var_info.len()); context.var_info.push(VarInfo { var: Some(var.clone()), lowlink: index, }); context.stack.push(index); let mut self_ref = false; let mut lowlink = index; let visit_link = |var: VarType, context: &mut Context, lowlink: &mut usize, self_ref: &mut bool| { let next_index = match traverse(var, non_custom_references, context) { Some(index) => index, // There is nothing to do if the next variable has been // fully resolved at this point. None => { return; }, }; let next_info = &context.var_info[next_index]; if next_index > index { // The next variable has a larger index than us, so it // must be inserted in the recursive call above. We want // to get its lowlink. *lowlink = cmp::min(*lowlink, next_info.lowlink); } else if next_index == index { *self_ref = true; } else if next_info.var.is_some() { // The next variable has a smaller order index and it is // in the stack, so we are at the same component. *lowlink = cmp::min(*lowlink, next_index); } }; if let Some(ref v) = value.as_ref() { debug_assert!( matches!(var, VarType::Custom(_)), "Non-custom property has references?" ); // Visit other custom properties... // FIXME: Maybe avoid visiting the same var twice if not needed? for next in &v.references.refs { if !next.is_var { continue; } visit_link( VarType::Custom(next.name.clone()), context, &mut lowlink, &mut self_ref, ); } // ... Then non-custom properties. v.references.non_custom_references.for_each(|r| { visit_link(VarType::NonCustom(r), context, &mut lowlink, &mut self_ref); }); } else if let VarType::NonCustom(non_custom) = var { let entry = &non_custom_references[non_custom]; if let Some(deps) = entry.as_ref() { for d in deps { // Visit any reference from this non-custom property to custom properties. visit_link( VarType::Custom(d.clone()), context, &mut lowlink, &mut self_ref, ); } } } context.var_info[index].lowlink = lowlink; if lowlink != index { // This variable is in a loop, but it is not the root of // this strong connected component. We simply return for // now, and the root would remove it from the map. // // This cannot be removed from the map here, because // otherwise the shortcut check at the beginning of this // function would return the wrong value. return Some(index); } // This is the root of a strong-connected component. let mut in_loop = self_ref; let name; let handle_variable_in_loop = |name: &Name, context: &mut Context<'a, 'b>| { if context .non_custom_references .intersects(NonCustomReferences::FONT_UNITS | NonCustomReferences::ROOT_FONT_UNITS) { context .invalid_non_custom_properties .insert(LonghandId::FontSize); } if context .non_custom_references .intersects(NonCustomReferences::LH_UNITS | NonCustomReferences::ROOT_LH_UNITS) { context .invalid_non_custom_properties .insert(LonghandId::LineHeight); } // This variable is in loop. Resolve to invalid. handle_invalid_at_computed_value_time(name, context.map, context.computed_context); }; loop { let var_index = context .stack .pop() .expect("The current variable should still be in stack"); let var_info = &mut context.var_info[var_index]; // We should never visit the variable again, so it's safe // to take the name away, so that we don't do additional // reference count. let var_name = var_info .var .take() .expect("Variable should not be poped from stack twice"); if var_index == index { name = match var_name { VarType::Custom(name) => name, // At the root of this component, and it's a non-custom // reference - we have nothing to substitute, so // it's effectively resolved. VarType::NonCustom(..) => return None, }; break; } if let VarType::Custom(name) = var_name { // Anything here is in a loop which can traverse to the // variable we are handling, so it's invalid at // computed-value time. handle_variable_in_loop(&name, context); } in_loop = true; } // We've gotten to the root of this strongly connected component, so clear // whether or not it involved non-custom references. // It's fine to track it like this, because non-custom properties currently // being tracked can only participate in any loop only once. if in_loop { handle_variable_in_loop(&name, context); context.non_custom_references = NonCustomReferences::default(); return None; } if let Some(ref v) = value { let registration = context.stylist.get_custom_property_registration(&name); let registered_length_property = registration.syntax.may_reference_font_relative_length(); let mut defer = false; if !context.non_custom_references.is_empty() && registered_length_property { if let Some(deferred) = &mut context.deferred_properties { // This property directly depends on a non-custom property, defer resolving it. let deferred_property = ComputedRegisteredValue::universal(Arc::clone(v)); deferred.insert(registration, &name, deferred_property); context.map.remove(registration, &name); defer = true; } } if should_substitute && !defer { for reference in v.references.refs.iter() { if !reference.is_var { continue; } if let Some(deferred) = &mut context.deferred_properties { let registration = context .stylist .get_custom_property_registration(&reference.name); if deferred.get(registration, &reference.name).is_some() { // This property depends on a custom property that depends on a non-custom property, defer. let deferred_property = ComputedRegisteredValue::universal(Arc::clone(v)); deferred.insert(registration, &name, deferred_property); context.map.remove(registration, &name); defer = true; break; } } } if !defer { substitute_references_if_needed_and_apply( &name, v, &mut context.map, context.stylist, context.computed_context, ); } } } context.non_custom_references = NonCustomReferences::default(); // All resolved, so return the signal value. None } // Note that `seen` doesn't contain names inherited from our parent, but // those can't have variable references (since we inherit the computed // variables) so we don't want to spend cycles traversing them anyway. for name in seen { let mut context = Context { count: 0, index_map: PrecomputedHashMap::default(), non_custom_index_map: NonCustomReferenceMap::default(), stack: SmallVec::new(), var_info: SmallVec::new(), map: custom_properties_map, non_custom_references: NonCustomReferences::default(), stylist, computed_context, invalid_non_custom_properties, deferred_properties: deferred_properties_map.as_deref_mut(), }; traverse( VarType::Custom((*name).clone()), references_from_non_custom_properties, &mut context, ); } } // See https://drafts.csswg.org/css-variables-2/#invalid-at-computed-value-time fn handle_invalid_at_computed_value_time( name: &Name, custom_properties: &mut ComputedCustomProperties, computed_context: &computed::Context, ) { let stylist = computed_context.style().stylist.unwrap(); let registration = stylist.get_custom_property_registration(&name); if !registration.syntax.is_universal() { // For the root element, inherited maps are empty. We should just // use the initial value if any, rather than removing the name. if registration.inherits() && !computed_context.is_root_element() { let inherited = computed_context.inherited_custom_properties(); if let Some(value) = inherited.get(registration, name) { custom_properties.insert(registration, name, value.clone()); return; } } else if let Some(ref initial_value) = registration.initial_value { if let Ok(initial_value) = compute_value( &initial_value.css, &initial_value.url_data, registration, computed_context, ) { custom_properties.insert(registration, name, initial_value); return; } } } custom_properties.remove(registration, name); } /// Replace `var()` and `env()` functions in a pre-existing variable value. fn substitute_references_if_needed_and_apply( name: &Name, value: &Arc, custom_properties: &mut ComputedCustomProperties, stylist: &Stylist, computed_context: &computed::Context, ) { let registration = stylist.get_custom_property_registration(&name); if !value.has_references() && registration.syntax.is_universal() { // Trivial path: no references and no need to compute the value, just apply it directly. let computed_value = ComputedRegisteredValue::universal(Arc::clone(value)); custom_properties.insert(registration, name, computed_value); return; } let inherited = computed_context.inherited_custom_properties(); let url_data = &value.url_data; let value = match substitute_internal( value, custom_properties, stylist, registration, computed_context, ) { Ok(v) => v, Err(..) => { handle_invalid_at_computed_value_time(name, custom_properties, computed_context); return; }, } .into_value(url_data); // If variable fallback results in a wide keyword, deal with it now. { let css = value.to_variable_value().css; let mut input = ParserInput::new(&css); let mut input = Parser::new(&mut input); if let Ok(kw) = input.try_parse(CSSWideKeyword::parse) { // TODO: It's unclear what this should do for revert / revert-layer, see // https://github.com/w3c/csswg-drafts/issues/9131. For now treating as unset // seems fine? match ( kw, registration.inherits(), computed_context.is_root_element(), ) { (CSSWideKeyword::Initial, _, _) | (CSSWideKeyword::Revert, false, _) | (CSSWideKeyword::RevertLayer, false, _) | (CSSWideKeyword::Unset, false, _) | (CSSWideKeyword::Revert, true, true) | (CSSWideKeyword::RevertLayer, true, true) | (CSSWideKeyword::Unset, true, true) | (CSSWideKeyword::Inherit, _, true) => { remove_and_insert_initial_value(name, registration, custom_properties); }, (CSSWideKeyword::Revert, true, false) | (CSSWideKeyword::RevertLayer, true, false) | (CSSWideKeyword::Inherit, _, false) | (CSSWideKeyword::Unset, true, false) => { match inherited.get(registration, name) { Some(value) => { custom_properties.insert(registration, name, value.clone()); }, None => { custom_properties.remove(registration, name); }, }; }, } return; } } custom_properties.insert(registration, name, value); } enum Substitution<'a> { Universal(UniversalSubstitution<'a>), Computed(ComputedRegisteredValue), } impl<'a> Default for Substitution<'a> { fn default() -> Self { Self::Universal(UniversalSubstitution::default()) } } #[derive(Default)] struct UniversalSubstitution<'a> { css: Cow<'a, str>, first_token_type: TokenSerializationType, last_token_type: TokenSerializationType, } impl<'a> UniversalSubstitution<'a> { fn from_value(v: VariableValue) -> Self { UniversalSubstitution { css: Cow::from(v.css), first_token_type: v.first_token_type, last_token_type: v.last_token_type, } } } impl<'a> Substitution<'a> { fn new( css: &'a str, first_token_type: TokenSerializationType, last_token_type: TokenSerializationType, ) -> Self { Self::Universal(UniversalSubstitution { css: Cow::Borrowed(css), first_token_type, last_token_type, }) } fn into_universal(self) -> UniversalSubstitution<'a> { match self { Substitution::Universal(substitution) => substitution, Substitution::Computed(computed) => { UniversalSubstitution::from_value(computed.to_variable_value()) }, } } fn from_value(v: VariableValue) -> Self { debug_assert!( !v.has_references(), "Computed values shouldn't have references" ); let substitution = UniversalSubstitution::from_value(v); Self::Universal(substitution) } fn into_value(self, url_data: &UrlExtraData) -> ComputedRegisteredValue { match self { Substitution::Universal(substitution) => { let value = Arc::new(VariableValue { css: substitution.css.into_owned(), first_token_type: substitution.first_token_type, last_token_type: substitution.last_token_type, url_data: url_data.clone(), references: Default::default(), }); ComputedRegisteredValue::universal(value) }, Substitution::Computed(computed) => computed, } } } fn compute_value( css: &str, url_data: &UrlExtraData, registration: &PropertyRegistrationData, computed_context: &computed::Context, ) -> Result { debug_assert!(!registration.syntax.is_universal()); let mut input = ParserInput::new(&css); let mut input = Parser::new(&mut input); SpecifiedRegisteredValue::compute( &mut input, registration, url_data, computed_context, AllowComputationallyDependent::Yes, ) } /// Removes the named registered custom property and inserts its uncomputed initial value. fn remove_and_insert_initial_value( name: &Name, registration: &PropertyRegistrationData, custom_properties: &mut ComputedCustomProperties, ) { custom_properties.remove(registration, name); if let Some(ref initial_value) = registration.initial_value { let value = ComputedRegisteredValue::universal(Arc::clone(initial_value)); custom_properties.insert(registration, name, value); } } fn do_substitute_chunk<'a>( css: &'a str, start: usize, end: usize, first_token_type: TokenSerializationType, last_token_type: TokenSerializationType, url_data: &UrlExtraData, custom_properties: &'a ComputedCustomProperties, registration: &PropertyRegistrationData, stylist: &Stylist, computed_context: &computed::Context, references: &mut std::iter::Peekable>, ) -> Result, ()> { if start == end { // Empty string. Easy. return Ok(Substitution::default()); } // Easy case: no references involved. if references .peek() .map_or(true, |reference| reference.end > end) { let result = &css[start..end]; if !registration.syntax.is_universal() { let computed_value = compute_value(result, url_data, registration, computed_context)?; return Ok(Substitution::Computed(computed_value)); } return Ok(Substitution::new(result, first_token_type, last_token_type)); } let mut substituted = ComputedValue::empty(url_data); let mut next_token_type = first_token_type; let mut cur_pos = start; while let Some(reference) = references.next_if(|reference| reference.end <= end) { if reference.start != cur_pos { substituted.push( &css[cur_pos..reference.start], next_token_type, reference.prev_token_type, )?; } let substitution = substitute_one_reference( css, url_data, custom_properties, reference, stylist, computed_context, references, )?; // Optimize the property: var(--...) case to avoid allocating at all. if reference.start == start && reference.end == end && registration.syntax.is_universal() { return Ok(substitution); } let substitution = substitution.into_universal(); substituted.push( &substitution.css, substitution.first_token_type, substitution.last_token_type, )?; next_token_type = reference.next_token_type; cur_pos = reference.end; } // Push the rest of the value if needed. if cur_pos != end { substituted.push(&css[cur_pos..end], next_token_type, last_token_type)?; } if !registration.syntax.is_universal() { let computed_value = compute_value(&substituted.css, url_data, registration, computed_context)?; return Ok(Substitution::Computed(computed_value)); } Ok(Substitution::from_value(substituted)) } fn substitute_one_reference<'a>( css: &'a str, url_data: &UrlExtraData, custom_properties: &'a ComputedCustomProperties, reference: &VarOrEnvReference, stylist: &Stylist, computed_context: &computed::Context, references: &mut std::iter::Peekable>, ) -> Result, ()> { let registration; if reference.is_var { registration = stylist.get_custom_property_registration(&reference.name); if let Some(v) = custom_properties.get(registration, &reference.name) { #[cfg(debug_assertions)] debug_assert!(v.is_parsed(registration), "Should be already computed"); if registration.syntax.is_universal() { // Skip references that are inside the outer variable (in fallback for example). while references .next_if(|next_ref| next_ref.end <= reference.end) .is_some() {} } else { // We need to validate the fallback if any, since invalid fallback should // invalidate the whole variable. if let Some(ref fallback) = reference.fallback { let _ = do_substitute_chunk( css, fallback.start.get(), reference.end - 1, // Don't include the closing parenthesis. fallback.first_token_type, fallback.last_token_type, url_data, custom_properties, registration, stylist, computed_context, references, )?; } } return Ok(Substitution::Computed(v.clone())); } } else { registration = PropertyRegistrationData::unregistered(); let device = stylist.device(); if let Some(v) = device.environment().get(&reference.name, device, url_data) { while references .next_if(|next_ref| next_ref.end <= reference.end) .is_some() {} return Ok(Substitution::from_value(v)); } } let Some(ref fallback) = reference.fallback else { return Err(()); }; do_substitute_chunk( css, fallback.start.get(), reference.end - 1, // Skip the closing parenthesis of the reference value. fallback.first_token_type, fallback.last_token_type, url_data, custom_properties, registration, stylist, computed_context, references, ) } /// Replace `var()` and `env()` functions. Return `Err(..)` for invalid at computed time. fn substitute_internal<'a>( variable_value: &'a VariableValue, custom_properties: &'a ComputedCustomProperties, stylist: &Stylist, registration: &PropertyRegistrationData, computed_context: &computed::Context, ) -> Result, ()> { let mut refs = variable_value.references.refs.iter().peekable(); do_substitute_chunk( &variable_value.css, /* start = */ 0, /* end = */ variable_value.css.len(), variable_value.first_token_type, variable_value.last_token_type, &variable_value.url_data, custom_properties, registration, stylist, computed_context, &mut refs, ) } /// Replace var() and env() functions, returning the resulting CSS string. pub fn substitute<'a>( variable_value: &'a VariableValue, custom_properties: &'a ComputedCustomProperties, stylist: &Stylist, computed_context: &computed::Context, ) -> Result, ()> { debug_assert!(variable_value.has_references()); let v = substitute_internal( variable_value, custom_properties, stylist, PropertyRegistrationData::unregistered(), computed_context, )?; let v = v.into_universal(); Ok(v.css) }