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declaration_block.rs
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declaration_block.rs
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/* 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 http://mozilla.org/MPL/2.0/. */
//! A property declaration block.
#![deny(missing_docs)]
use cssparser::{DeclarationListParser, parse_important};
use cssparser::{Parser, AtRuleParser, DeclarationParser, Delimiter};
use error_reporting::ParseErrorReporter;
use parser::{ParserContext, ParserContextExtraData, log_css_error};
use servo_url::ServoUrl;
use std::boxed::Box as StdBox;
use std::fmt;
use style_traits::ToCss;
use stylesheets::Origin;
use super::*;
/// A declaration [importance][importance].
///
/// [importance]: https://drafts.csswg.org/css-cascade/#importance
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum Importance {
/// Indicates a declaration without `!important`.
Normal,
/// Indicates a declaration with `!important`.
Important,
}
impl Importance {
/// Return whether this is an important declaration.
pub fn important(self) -> bool {
match self {
Importance::Normal => false,
Importance::Important => true,
}
}
}
/// Overridden declarations are skipped.
#[derive(Debug, PartialEq, Clone)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub struct PropertyDeclarationBlock {
/// The group of declarations, along with their importance.
///
/// Only deduplicated declarations appear here.
#[cfg_attr(feature = "servo", ignore_heap_size_of = "#7038")]
pub declarations: Vec<(PropertyDeclaration, Importance)>,
/// The number of entries in `self.declaration` with `Importance::Important`
pub important_count: u32,
}
impl PropertyDeclarationBlock {
/// Returns wheather this block contains any declaration with `!important`.
///
/// This is based on the `important_count` counter,
/// which should be maintained whenever `declarations` is changed.
// FIXME: make fields private and maintain it here in methods?
pub fn any_important(&self) -> bool {
self.important_count > 0
}
/// Returns wheather this block contains any declaration without `!important`.
///
/// This is based on the `important_count` counter,
/// which should be maintained whenever `declarations` is changed.
// FIXME: make fields private and maintain it here in methods?
pub fn any_normal(&self) -> bool {
self.declarations.len() > self.important_count as usize
}
/// Get a declaration for a given property.
///
/// NOTE: This is linear time.
pub fn get(&self, property: PropertyDeclarationId) -> Option< &(PropertyDeclaration, Importance)> {
self.declarations.iter().find(|&&(ref decl, _)| decl.id() == property)
}
/// Find the value of the given property in this block and serialize it
///
/// https://dev.w3.org/csswg/cssom/#dom-cssstyledeclaration-getpropertyvalue
pub fn property_value_to_css<W>(&self, property: &PropertyId, dest: &mut W) -> fmt::Result
where W: fmt::Write,
{
// Step 1: done when parsing a string to PropertyId
// Step 2
match property.as_shorthand() {
Ok(shorthand) => {
// Step 2.1
let mut list = Vec::new();
let mut important_count = 0;
// Step 2.2
for &longhand in shorthand.longhands() {
// Step 2.2.1
let declaration = self.get(PropertyDeclarationId::Longhand(longhand));
// Step 2.2.2 & 2.2.3
match declaration {
Some(&(ref declaration, importance)) => {
list.push(declaration);
if importance.important() {
important_count += 1;
}
},
None => return Ok(()),
}
}
// Step 3.3.2.4
// If there is one or more longhand with important, and one or more
// without important, we don't serialize it as a shorthand.
if important_count > 0 && important_count != list.len() {
return Ok(());
}
// Step 2.3
// We don't print !important when serializing individual properties,
// so we treat this as a normal-importance property
let importance = Importance::Normal;
let appendable_value = shorthand.get_shorthand_appendable_value(list).unwrap();
append_declaration_value(dest, appendable_value, importance, false)
}
Err(longhand_or_custom) => {
if let Some(&(ref value, _importance)) = self.get(longhand_or_custom) {
// Step 3
value.to_css(dest)
} else {
// Step 4
Ok(())
}
}
}
}
/// https://dev.w3.org/csswg/cssom/#dom-cssstyledeclaration-getpropertypriority
pub fn property_priority(&self, property: &PropertyId) -> Importance {
// Step 1: done when parsing a string to PropertyId
// Step 2
match property.as_shorthand() {
Ok(shorthand) => {
// Step 2.1 & 2.2 & 2.3
if shorthand.longhands().iter().all(|&l| {
self.get(PropertyDeclarationId::Longhand(l))
.map_or(false, |&(_, importance)| importance.important())
}) {
Importance::Important
} else {
Importance::Normal
}
}
Err(longhand_or_custom) => {
// Step 3
self.get(longhand_or_custom).map_or(Importance::Normal, |&(_, importance)| importance)
}
}
}
/// Adds or overrides the declaration for a given property in this block,
/// without taking into account any kind of priority.
pub fn set_parsed_declaration(&mut self,
declaration: PropertyDeclaration,
importance: Importance) {
for slot in &mut *self.declarations {
if slot.0.id() == declaration.id() {
match (slot.1, importance) {
(Importance::Normal, Importance::Important) => {
self.important_count += 1;
}
(Importance::Important, Importance::Normal) => {
self.important_count -= 1;
}
_ => {}
}
*slot = (declaration, importance);
return
}
}
self.declarations.push((declaration, importance));
if importance.important() {
self.important_count += 1;
}
}
/// Set the declaration importance for a given property, if found.
pub fn set_importance(&mut self, property: &PropertyId, new_importance: Importance) {
for &mut (ref declaration, ref mut importance) in &mut self.declarations {
if declaration.id().is_or_is_longhand_of(property) {
match (*importance, new_importance) {
(Importance::Normal, Importance::Important) => {
self.important_count += 1;
}
(Importance::Important, Importance::Normal) => {
self.important_count -= 1;
}
_ => {}
}
*importance = new_importance;
}
}
}
/// https://dev.w3.org/csswg/cssom/#dom-cssstyledeclaration-removeproperty
pub fn remove_property(&mut self, property: &PropertyId) {
let important_count = &mut self.important_count;
self.declarations.retain(|&(ref declaration, importance)| {
let remove = declaration.id().is_or_is_longhand_of(property);
if remove && importance.important() {
*important_count -= 1
}
!remove
})
}
/// Take a declaration block known to contain a single property and serialize it.
pub fn single_value_to_css<W>(&self, property: &PropertyId, dest: &mut W) -> fmt::Result
where W: fmt::Write,
{
match property.as_shorthand() {
Err(_longhand_or_custom) => {
if self.declarations.len() == 1 {
self.declarations[0].0.to_css(dest)
} else {
Err(fmt::Error)
}
}
Ok(shorthand) => {
// we use this function because a closure won't be `Clone`
fn get_declaration(dec: &(PropertyDeclaration, Importance))
-> &PropertyDeclaration {
&dec.0
}
if !self.declarations.iter().all(|decl| decl.0.shorthands().contains(&shorthand)) {
return Err(fmt::Error)
}
let iter = self.declarations.iter().map(get_declaration as fn(_) -> _);
match shorthand.get_shorthand_appendable_value(iter) {
Some(AppendableValue::Css(css)) => dest.write_str(css),
Some(AppendableValue::DeclarationsForShorthand(_, decls)) => {
shorthand.longhands_to_css(decls, dest)
}
_ => Ok(())
}
}
}
}
}
impl ToCss for PropertyDeclarationBlock {
// https://drafts.csswg.org/cssom/#serialize-a-css-declaration-block
fn to_css<W>(&self, dest: &mut W) -> fmt::Result
where W: fmt::Write,
{
let mut is_first_serialization = true; // trailing serializations should have a prepended space
// Step 1 -> dest = result list
// Step 2
let mut already_serialized = Vec::new();
// Step 3
for &(ref declaration, importance) in &*self.declarations {
// Step 3.1
let property = declaration.id();
// Step 3.2
if already_serialized.contains(&property) {
continue;
}
// Step 3.3
let shorthands = declaration.shorthands();
if !shorthands.is_empty() {
// Step 3.3.1
let mut longhands = self.declarations.iter()
.filter(|d| !already_serialized.contains(&d.0.id()))
.collect::<Vec<_>>();
// Step 3.3.2
for &shorthand in shorthands {
let properties = shorthand.longhands();
// Substep 2 & 3
let mut current_longhands = Vec::new();
let mut important_count = 0;
for &&(ref longhand, longhand_importance) in longhands.iter() {
if longhand.id().is_longhand_of(shorthand) {
current_longhands.push(longhand);
if longhand_importance.important() {
important_count += 1;
}
}
}
// Substep 1
/* Assuming that the PropertyDeclarationBlock contains no duplicate entries,
if the current_longhands length is equal to the properties length, it means
that the properties that map to shorthand are present in longhands */
if current_longhands.is_empty() || current_longhands.len() != properties.len() {
continue;
}
// Substep 4
let is_important = important_count > 0;
if is_important && important_count != current_longhands.len() {
continue;
}
let importance = if is_important {
Importance::Important
} else {
Importance::Normal
};
// Substep 5
let was_serialized =
try!(
shorthand.serialize_shorthand_to_buffer(
dest,
current_longhands.iter().cloned(),
&mut is_first_serialization,
importance
)
);
// If serialization occured, Substep 7 & 8 will have been completed
// Substep 6
if !was_serialized {
continue;
}
for current_longhand in current_longhands {
// Substep 9
already_serialized.push(current_longhand.id());
let index_to_remove = longhands.iter().position(|l| l.0 == *current_longhand);
if let Some(index) = index_to_remove {
// Substep 10
longhands.remove(index);
}
}
}
}
// Step 3.3.4
if already_serialized.contains(&property) {
continue;
}
use std::iter::Cloned;
use std::slice;
// Steps 3.3.5, 3.3.6 & 3.3.7
// Need to specify an iterator type here even though it’s unused to work around
// "error: unable to infer enough type information about `_`;
// type annotations or generic parameter binding required [E0282]"
// Use the same type as earlier call to reuse generated code.
try!(append_serialization::<W, Cloned<slice::Iter< &PropertyDeclaration>>, _>(
dest,
&property,
AppendableValue::Declaration(declaration),
importance,
&mut is_first_serialization));
// Step 3.3.8
already_serialized.push(property);
}
// Step 4
Ok(())
}
}
/// A convenient enum to represent different kinds of stuff that can represent a
/// _value_ in the serialization of a property declaration.
pub enum AppendableValue<'a, I>
where I: Iterator<Item=&'a PropertyDeclaration>,
{
/// A given declaration, of which we'll serialize just the value.
Declaration(&'a PropertyDeclaration),
/// A set of declarations for a given shorthand.
///
/// FIXME: This needs more docs, where are the shorthands expanded? We print
/// the property name before-hand, don't we?
DeclarationsForShorthand(ShorthandId, I),
/// A raw CSS string, coming for example from a property with CSS variables.
Css(&'a str)
}
/// Potentially appends whitespace after the first (property: value;) pair.
fn handle_first_serialization<W>(dest: &mut W,
is_first_serialization: &mut bool)
-> fmt::Result
where W: fmt::Write,
{
if !*is_first_serialization {
try!(write!(dest, " "));
} else {
*is_first_serialization = false;
}
Ok(())
}
/// Append a given kind of appendable value to a serialization.
pub fn append_declaration_value<'a, W, I>(dest: &mut W,
appendable_value: AppendableValue<'a, I>,
importance: Importance,
is_overflow_with_name: bool)
-> fmt::Result
where W: fmt::Write,
I: Iterator<Item=&'a PropertyDeclaration>,
{
match appendable_value {
AppendableValue::Css(css) => {
try!(write!(dest, "{}", css))
},
AppendableValue::Declaration(decl) => {
try!(decl.to_css(dest));
},
AppendableValue::DeclarationsForShorthand(shorthand, decls) => {
if is_overflow_with_name {
try!(shorthand.overflow_longhands_to_css(decls, dest));
} else {
try!(shorthand.longhands_to_css(decls, dest));
}
}
}
if importance.important() {
try!(write!(dest, " !important"));
}
Ok(())
}
/// Append a given property and value pair to a serialization.
pub fn append_serialization<'a, W, I, N>(dest: &mut W,
property_name: &N,
appendable_value: AppendableValue<'a, I>,
importance: Importance,
is_first_serialization: &mut bool)
-> fmt::Result
where W: fmt::Write,
I: Iterator<Item=&'a PropertyDeclaration>,
N: ToCss,
{
try!(handle_first_serialization(dest, is_first_serialization));
// Overflow does not behave like a normal shorthand. When overflow-x and overflow-y are not of equal
// values, they no longer use the shared property name "overflow" and must be handled differently
if shorthands::is_overflow_shorthand(&appendable_value) {
return append_declaration_value(dest, appendable_value, importance, true);
}
try!(property_name.to_css(dest));
try!(dest.write_char(':'));
// for normal parsed values, add a space between key: and value
match &appendable_value {
&AppendableValue::Css(_) => {
try!(write!(dest, " "))
},
&AppendableValue::Declaration(decl) => {
if !decl.value_is_unparsed() {
// for normal parsed values, add a space between key: and value
try!(write!(dest, " "));
}
},
&AppendableValue::DeclarationsForShorthand(..) => try!(write!(dest, " "))
}
try!(append_declaration_value(dest, appendable_value, importance, false));
write!(dest, ";")
}
/// A helper to parse the style attribute of an element, in order for this to be
/// shared between Servo and Gecko.
pub fn parse_style_attribute(input: &str,
base_url: &ServoUrl,
error_reporter: StdBox<ParseErrorReporter + Send>,
extra_data: ParserContextExtraData)
-> PropertyDeclarationBlock {
let context = ParserContext::new_with_extra_data(Origin::Author, base_url, error_reporter, extra_data);
parse_property_declaration_list(&context, &mut Parser::new(input))
}
/// Parse a given property declaration. Can result in multiple
/// `PropertyDeclaration`s when expanding a shorthand, for example.
pub fn parse_one_declaration(id: PropertyId,
input: &str,
base_url: &ServoUrl,
error_reporter: StdBox<ParseErrorReporter + Send>,
extra_data: ParserContextExtraData)
-> Result<Vec<PropertyDeclaration>, ()> {
let context = ParserContext::new_with_extra_data(Origin::Author, base_url, error_reporter, extra_data);
let mut results = vec![];
match PropertyDeclaration::parse(id, &context, &mut Parser::new(input), &mut results, false) {
PropertyDeclarationParseResult::ValidOrIgnoredDeclaration => Ok(results),
_ => Err(())
}
}
/// A struct to parse property declarations.
struct PropertyDeclarationParser<'a, 'b: 'a> {
context: &'a ParserContext<'b>,
}
/// Default methods reject all at rules.
impl<'a, 'b> AtRuleParser for PropertyDeclarationParser<'a, 'b> {
type Prelude = ();
type AtRule = (Vec<PropertyDeclaration>, Importance);
}
impl<'a, 'b> DeclarationParser for PropertyDeclarationParser<'a, 'b> {
/// A single declaration may be expanded into multiple ones if it's a
/// shorthand for example, so that's why this is a vector.
///
/// TODO(emilio): Seems like there's potentially a bunch of performance work
/// we could do here.
type Declaration = (Vec<PropertyDeclaration>, Importance);
fn parse_value(&mut self, name: &str, input: &mut Parser)
-> Result<(Vec<PropertyDeclaration>, Importance), ()> {
let id = try!(PropertyId::parse(name.into()));
let mut results = vec![];
try!(input.parse_until_before(Delimiter::Bang, |input| {
match PropertyDeclaration::parse(id, self.context, input, &mut results, false) {
PropertyDeclarationParseResult::ValidOrIgnoredDeclaration => Ok(()),
_ => Err(())
}
}));
let importance = match input.try(parse_important) {
Ok(()) => Importance::Important,
Err(()) => Importance::Normal,
};
Ok((results, importance))
}
}
/// Parse a list of property declarations and return a property declaration
/// block.
pub fn parse_property_declaration_list(context: &ParserContext,
input: &mut Parser)
-> PropertyDeclarationBlock {
let mut declarations = Vec::new();
let mut important_count = 0;
let parser = PropertyDeclarationParser {
context: context,
};
let mut iter = DeclarationListParser::new(input, parser);
while let Some(declaration) = iter.next() {
match declaration {
Ok((results, importance)) => {
if importance.important() {
important_count += results.len() as u32;
}
declarations.extend(results.into_iter().map(|d| (d, importance)))
}
Err(range) => {
let pos = range.start;
let message = format!("Unsupported property declaration: '{}'",
iter.input.slice(range));
log_css_error(iter.input, pos, &*message, &context);
}
}
}
let mut block = PropertyDeclarationBlock {
declarations: declarations,
important_count: important_count,
};
super::deduplicate_property_declarations(&mut block);
block
}