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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 https://mozilla.org/MPL/2.0/. */
//! Cascading at-rule types and traits
use crate::stylesheets::Origin;
use std::fmt::{self, Write};
use style_traits::{CssWriter, ToCss};
/// Computes the cascade precedence as according to
/// <http://dev.w3.org/csswg/css-cascade/#cascade-origin>
#[inline]
fn cascade_precendence(origin: Origin, important: bool) -> u8 {
match (origin, important) {
(Origin::UserAgent, true) => 1,
(Origin::User, true) => 2,
(Origin::Author, true) => 3,
(Origin::Author, false) => 4,
(Origin::User, false) => 5,
(Origin::UserAgent, false) => 6,
}
}
/// Cascading rule descriptor implementation.
/// This is only used for at-rules which can cascade. These are @viewport and
/// @page, although we don't currently implement @page as such.
#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
pub struct DescriptorDeclaration<T> {
/// Origin of the declaration
pub origin: Origin,
/// Declaration value
pub descriptor: T,
/// Indicates the presence of a !important property.
pub important: bool,
}
impl<T> DescriptorDeclaration<T> {
#[allow(missing_docs)]
pub fn new(origin: Origin, descriptor: T, important: bool) -> Self {
Self {
origin,
descriptor,
important,
}
}
/// Returns true iff self is equal or higher precedence to the other.
pub fn higher_or_equal_precendence(&self, other: &Self) -> bool {
let self_precedence = cascade_precendence(self.origin, self.important);
let other_precedence = cascade_precendence(other.origin, other.important);
self_precedence <= other_precedence
}
}
impl<T> ToCss for DescriptorDeclaration<T>
where
T: ToCss,
{
fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
where
W: Write,
{
self.descriptor.to_css(dest)?;
if self.important {
dest.write_str(" !important")?;
}
dest.write_char(';')
}
}
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