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//! Traits for parsing and serializing CSS.
use crate::context::PropertyHandlerContext;
use crate::declaration::{DeclarationBlock, DeclarationList};
use crate::error::{ParserError, PrinterError};
use crate::printer::Printer;
use crate::properties::{Property, PropertyId};
use crate::stylesheet::{ParserOptions, PrinterOptions};
use crate::targets::{Browsers, Targets};
use crate::vendor_prefix::VendorPrefix;
use cssparser::*;
#[cfg(feature = "into_owned")]
pub use static_self::IntoOwned;
/// Trait for things that can be parsed from CSS syntax.
pub trait Parse<'i>: Sized {
/// Parse a value of this type using an existing parser.
fn parse<'t>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i, ParserError<'i>>>;
/// Parse a value from a string.
///
/// (This is a convenience wrapper for `parse` and probably should not be overridden.)
fn parse_string(input: &'i str) -> Result<Self, ParseError<'i, ParserError<'i>>> {
let mut input = ParserInput::new(input);
let mut parser = Parser::new(&mut input);
let result = Self::parse(&mut parser)?;
parser.expect_exhausted()?;
Ok(result)
}
}
/// Trait for things that can be parsed from CSS syntax and require ParserOptions.
pub trait ParseWithOptions<'i>: Sized {
/// Parse a value of this type with the given options.
fn parse_with_options<'t>(
input: &mut Parser<'i, 't>,
options: &ParserOptions<'_, 'i>,
) -> Result<Self, ParseError<'i, ParserError<'i>>>;
/// Parse a value from a string with the given options.
fn parse_string_with_options(
input: &'i str,
options: ParserOptions<'_, 'i>,
) -> Result<Self, ParseError<'i, ParserError<'i>>> {
let mut input = ParserInput::new(input);
let mut parser = Parser::new(&mut input);
Self::parse_with_options(&mut parser, &options)
}
}
impl<'i, T: Parse<'i>> ParseWithOptions<'i> for T {
#[inline]
fn parse_with_options<'t>(
input: &mut Parser<'i, 't>,
_options: &ParserOptions,
) -> Result<Self, ParseError<'i, ParserError<'i>>> {
T::parse(input)
}
}
/// Trait for things the can serialize themselves in CSS syntax.
pub trait ToCss {
/// Serialize `self` in CSS syntax, writing to `dest`.
fn to_css<W>(&self, dest: &mut Printer<W>) -> Result<(), PrinterError>
where
W: std::fmt::Write;
/// Serialize `self` in CSS syntax and return a string.
///
/// (This is a convenience wrapper for `to_css` and probably should not be overridden.)
#[inline]
fn to_css_string(&self, options: PrinterOptions) -> Result<String, PrinterError> {
let mut s = String::new();
let mut printer = Printer::new(&mut s, options);
self.to_css(&mut printer)?;
Ok(s)
}
}
impl<'a, T> ToCss for &'a T
where
T: ToCss + ?Sized,
{
fn to_css<W>(&self, dest: &mut Printer<W>) -> Result<(), PrinterError>
where
W: std::fmt::Write,
{
(*self).to_css(dest)
}
}
pub(crate) trait PropertyHandler<'i>: Sized {
fn handle_property(
&mut self,
property: &Property<'i>,
dest: &mut DeclarationList<'i>,
context: &mut PropertyHandlerContext<'i, '_>,
) -> bool;
fn finalize(&mut self, dest: &mut DeclarationList<'i>, context: &mut PropertyHandlerContext<'i, '_>);
}
pub(crate) mod private {
pub trait TryAdd<T> {
fn try_add(&self, other: &T) -> Option<T>;
}
pub trait AddInternal {
fn add(self, other: Self) -> Self;
}
}
pub(crate) trait FromStandard<T>: Sized {
fn from_standard(val: &T) -> Option<Self>;
}
pub(crate) trait FallbackValues: Sized {
fn get_fallbacks(&mut self, targets: Targets) -> Vec<Self>;
}
/// Trait for shorthand properties.
pub(crate) trait Shorthand<'i>: Sized {
/// Returns a shorthand from the longhand properties defined in the given declaration block.
fn from_longhands(decls: &DeclarationBlock<'i>, vendor_prefix: VendorPrefix) -> Option<(Self, bool)>;
/// Returns a list of longhand property ids for this shorthand.
fn longhands(vendor_prefix: VendorPrefix) -> Vec<PropertyId<'static>>;
/// Returns a longhand property for this shorthand.
fn longhand(&self, property_id: &PropertyId) -> Option<Property<'i>>;
/// Updates this shorthand from a longhand property.
fn set_longhand(&mut self, property: &Property<'i>) -> Result<(), ()>;
}
/// A trait for values that support binary operations.
pub trait Op {
/// Returns the result of the operation in the same type.
fn op<F: FnOnce(f32, f32) -> f32>(&self, rhs: &Self, op: F) -> Self;
/// Returns the result of the operation in a different type.
fn op_to<T, F: FnOnce(f32, f32) -> T>(&self, rhs: &Self, op: F) -> T;
}
macro_rules! impl_op {
($t: ty, $trait: ident $(:: $x: ident)*, $op: ident) => {
impl $trait$(::$x)* for $t {
type Output = $t;
fn $op(self, rhs: Self) -> Self::Output {
self.op(&rhs, $trait$(::$x)*::$op)
}
}
};
}
pub(crate) use impl_op;
use smallvec::SmallVec;
/// A trait for values that potentially support a binary operation (e.g. if they have the same unit).
pub trait TryOp: Sized {
/// Returns the result of the operation in the same type, if possible.
fn try_op<F: FnOnce(f32, f32) -> f32>(&self, rhs: &Self, op: F) -> Option<Self>;
/// Returns the result of the operation in a different type, if possible.
fn try_op_to<T, F: FnOnce(f32, f32) -> T>(&self, rhs: &Self, op: F) -> Option<T>;
}
impl<T: Op> TryOp for T {
fn try_op<F: FnOnce(f32, f32) -> f32>(&self, rhs: &Self, op: F) -> Option<Self> {
Some(self.op(rhs, op))
}
fn try_op_to<U, F: FnOnce(f32, f32) -> U>(&self, rhs: &Self, op: F) -> Option<U> {
Some(self.op_to(rhs, op))
}
}
/// A trait for values that can be mapped by applying a function.
pub trait Map {
/// Returns the result of the operation.
fn map<F: FnOnce(f32) -> f32>(&self, op: F) -> Self;
}
/// A trait for values that can potentially be mapped.
pub trait TryMap: Sized {
/// Returns the result of the operation, if possible.
fn try_map<F: FnOnce(f32) -> f32>(&self, op: F) -> Option<Self>;
}
impl<T: Map> TryMap for T {
fn try_map<F: FnOnce(f32) -> f32>(&self, op: F) -> Option<Self> {
Some(self.map(op))
}
}
/// A trait for values that can return a sign.
pub trait Sign {
/// Returns the sign of the value.
fn sign(&self) -> f32;
/// Returns whether the value is positive.
fn is_sign_positive(&self) -> bool {
f32::is_sign_positive(self.sign())
}
/// Returns whether the value is negative.
fn is_sign_negative(&self) -> bool {
f32::is_sign_negative(self.sign())
}
}
/// A trait for values that can potentially return a sign.
pub trait TrySign {
/// Returns the sign of the value, if possible.
fn try_sign(&self) -> Option<f32>;
/// Returns whether the value is positive. If not possible, returns false.
fn is_sign_positive(&self) -> bool {
self.try_sign().map_or(false, |s| f32::is_sign_positive(s))
}
/// Returns whether the value is negative. If not possible, returns false.
fn is_sign_negative(&self) -> bool {
self.try_sign().map_or(false, |s| f32::is_sign_negative(s))
}
}
impl<T: Sign> TrySign for T {
fn try_sign(&self) -> Option<f32> {
Some(self.sign())
}
}
/// A trait for values that can be zero.
pub trait Zero {
/// Returns the zero value.
fn zero() -> Self;
/// Returns whether the value is zero.
fn is_zero(&self) -> bool;
}
/// A trait for values that can check if they are compatible with browser targets.
pub trait IsCompatible {
/// Returns whether the value is compatible with all of the given browser targets.
fn is_compatible(&self, browsers: Browsers) -> bool;
}
impl<T: IsCompatible> IsCompatible for SmallVec<[T; 1]> {
fn is_compatible(&self, browsers: Browsers) -> bool {
self.iter().all(|v| v.is_compatible(browsers))
}
}
impl<T: IsCompatible> IsCompatible for Vec<T> {
fn is_compatible(&self, browsers: Browsers) -> bool {
self.iter().all(|v| v.is_compatible(browsers))
}
}
/// A trait to provide parsing of custom at-rules.
///
/// For example, there could be different implementations for top-level at-rules
/// (`@media`, `@font-face`, …)
/// and for page-margin rules inside `@page`.
///
/// Default implementations that reject all at-rules are provided,
/// so that `impl AtRuleParser<(), ()> for ... {}` can be used
/// for using `DeclarationListParser` to parse a declarations list with only qualified rules.
///
/// Note: this trait is copied from cssparser and modified to provide parser options.
pub trait AtRuleParser<'i>: Sized {
/// The intermediate representation of prelude of an at-rule.
type Prelude;
/// The finished representation of an at-rule.
type AtRule;
/// The error type that is included in the ParseError value that can be returned.
type Error: 'i;
/// Parse the prelude of an at-rule with the given `name`.
///
/// Return the representation of the prelude and the type of at-rule,
/// or `Err(())` to ignore the entire at-rule as invalid.
///
/// The prelude is the part after the at-keyword
/// and before the `;` semicolon or `{ /* ... */ }` block.
///
/// At-rule name matching should be case-insensitive in the ASCII range.
/// This can be done with `std::ascii::Ascii::eq_ignore_ascii_case`,
/// or with the `match_ignore_ascii_case!` macro.
///
/// The given `input` is a "delimited" parser
/// that ends wherever the prelude should end.
/// (Before the next semicolon, the next `{`, or the end of the current block.)
fn parse_prelude<'t>(
&mut self,
name: CowRcStr<'i>,
input: &mut Parser<'i, 't>,
options: &ParserOptions<'_, 'i>,
) -> Result<Self::Prelude, ParseError<'i, Self::Error>> {
let _ = name;
let _ = input;
let _ = options;
Err(input.new_error(BasicParseErrorKind::AtRuleInvalid(name)))
}
/// End an at-rule which doesn't have block. Return the finished
/// representation of the at-rule.
///
/// The location passed in is source location of the start of the prelude.
/// `is_nested` indicates whether the rule is nested inside a style rule.
///
/// This is only called when either the `;` semicolon indeed follows the prelude,
/// or parser is at the end of the input.
fn rule_without_block(
&mut self,
prelude: Self::Prelude,
start: &ParserState,
options: &ParserOptions<'_, 'i>,
is_nested: bool,
) -> Result<Self::AtRule, ()> {
let _ = prelude;
let _ = start;
let _ = options;
let _ = is_nested;
Err(())
}
/// Parse the content of a `{ /* ... */ }` block for the body of the at-rule.
///
/// The location passed in is source location of the start of the prelude.
/// `is_nested` indicates whether the rule is nested inside a style rule.
///
/// Return the finished representation of the at-rule
/// as returned by `RuleListParser::next` or `DeclarationListParser::next`,
/// or `Err(())` to ignore the entire at-rule as invalid.
///
/// This is only called when a block was found following the prelude.
fn parse_block<'t>(
&mut self,
prelude: Self::Prelude,
start: &ParserState,
input: &mut Parser<'i, 't>,
options: &ParserOptions<'_, 'i>,
is_nested: bool,
) -> Result<Self::AtRule, ParseError<'i, Self::Error>> {
let _ = prelude;
let _ = start;
let _ = input;
let _ = options;
let _ = is_nested;
Err(input.new_error(BasicParseErrorKind::AtRuleBodyInvalid))
}
}