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style: Fix style attribute important and revert-layer behavior

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By modeling it as a separate layer that behaves somewhat specially.

See https://github.com/w3c/csswg-drafts/issues/6872.

The remaining revert-layer tests that we fail are because either we
don't implement a feature (like @property) or because it's used in
keyframes (where revert is a bit unspecified and we have existing
issues with it).

Differential Revision: https://phabricator.services.mozilla.com/D133373
This commit is contained in:
Emilio Cobos Álvarez 2023-06-06 17:28:49 +02:00 • committed by Oriol Brufau
parent 5c0f044d39
commit 50510715a2
5 changed files with 67 additions and 31 deletions
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56
components/style/applicable_declarations.rs
View file

@ -45,7 +45,9 @@ pub struct CascadePriority {
#[allow(dead_code)]
fn size_assert() {
#[allow(unsafe_code)]
unsafe { std::mem::transmute::<u32, CascadePriority>(0u32) };
unsafe {
std::mem::transmute::<u32, CascadePriority>(0u32)
};
}
impl PartialOrd for CascadePriority {
@ -57,34 +59,39 @@ impl PartialOrd for CascadePriority {
impl Ord for CascadePriority {
fn cmp(&self, other: &Self) -> std::cmp::Ordering {
self.cascade_level
.cmp(&other.cascade_level)
.then_with(|| {
let ordering = self.layer_order.cmp(&other.layer_order);
// https://drafts.csswg.org/css-cascade-5/#cascade-layering
//
// Cascade layers (like declarations) are ordered by order
// of appearance. When comparing declarations that belong to
// different layers, then for normal rules the declaration
// whose cascade layer is last wins, and for important rules
// the declaration whose cascade layer is first wins.
//
// FIXME: This creates somewhat surprising behavior for the
// style attribute, see
// https://github.com/w3c/csswg-drafts/issues/6872
if self.cascade_level.is_important() {
ordering.reverse()
} else {
ordering
}
})
self.cascade_level.cmp(&other.cascade_level).then_with(|| {
let ordering = self.layer_order.cmp(&other.layer_order);
if ordering == std::cmp::Ordering::Equal {
return ordering;
}
// https://drafts.csswg.org/css-cascade-5/#cascade-layering
//
// Cascade layers (like declarations) are ordered by order
// of appearance. When comparing declarations that belong to
// different layers, then for normal rules the declaration
// whose cascade layer is last wins, and for important rules
// the declaration whose cascade layer is first wins.
//
// But the style attribute layer for some reason is special.
if self.cascade_level.is_important() &&
!self.layer_order.is_style_attribute_layer() &&
!other.layer_order.is_style_attribute_layer()
{
ordering.reverse()
} else {
ordering
}
})
}
}
impl CascadePriority {
/// Construct a new CascadePriority for a given (level, order) pair.
pub fn new(cascade_level: CascadeLevel, layer_order: LayerOrder) -> Self {
Self { cascade_level, layer_order }
Self {
cascade_level,
layer_order,
}
}
/// Returns the layer order.
@ -149,12 +156,13 @@ impl ApplicableDeclarationBlock {
pub fn from_declarations(
declarations: Arc<Locked<PropertyDeclarationBlock>>,
level: CascadeLevel,
layer_order: LayerOrder,
) -> Self {
ApplicableDeclarationBlock {
source: StyleSource::from_declarations(declarations),
source_order: 0,
specificity: 0,
cascade_priority: CascadePriority::new(level, LayerOrder::root()),
cascade_priority: CascadePriority::new(level, layer_order),
}
}