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style: Will-change should only create stacking contexts / containing blocks / etc if the property it'd change would apply

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As per https://drafts.csswg.org/css-will-change/#will-change.

> If any non-initial value of a property would cause the element to
> generate a containing block for absolutely positioned elements,
> specifying that property in will-change must cause the element to
> generate a containing block for absolutely positioned elements.

But in this case the transform property wouldn't apply to the element so
there's no reason to create a stacking-context.

Differential Revision: https://phabricator.services.mozilla.com/D114121
This commit is contained in:
Oriol Brufau 2023-05-17 00:44:00 +02:00
parent 60867bbe7e
commit 1cc44bd065
6 changed files with 49 additions and 58 deletions
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64
components/style/values/specified/box.rs
View file

@ -6,7 +6,7 @@
use crate::custom_properties::Name as CustomPropertyName;
use crate::parser::{Parse, ParserContext};
use crate::properties::{LonghandId, PropertyDeclarationId, PropertyFlags};
use crate::properties::{LonghandId, PropertyDeclarationId};
use crate::properties::{PropertyId, ShorthandId};
use crate::values::generics::box_::AnimationIterationCount as GenericAnimationIterationCount;
use crate::values::generics::box_::Perspective as GenericPerspective;
@ -1086,44 +1086,54 @@ bitflags! {
/// The change bits that we care about.
#[derive(Default, MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
#[repr(C)]
pub struct WillChangeBits: u8 {
/// Whether the stacking context will change.
const STACKING_CONTEXT = 1 << 0;
/// Whether `transform` will change.
pub struct WillChangeBits: u16 {
/// Whether a property which can create a stacking context **on any
/// box** will change.
const STACKING_CONTEXT_UNCONDITIONAL = 1 << 0;
/// Whether `transform` or related properties will change.
const TRANSFORM = 1 << 1;
/// Whether `scroll-position` will change.
const SCROLL = 1 << 2;
/// Whether `contain` will change.
const CONTAIN = 1 << 3;
/// Whether `opacity` will change.
const OPACITY = 1 << 3;
/// Fixed pos containing block.
const FIXPOS_CB = 1 << 4;
/// Abs pos containing block.
const ABSPOS_CB = 1 << 5;
const OPACITY = 1 << 4;
/// Whether `perspective` will change.
const PERSPECTIVE = 1 << 5;
/// Whether `z-index` will change.
const Z_INDEX = 1 << 6;
/// Whether any property which creates a containing block for non-svg
/// text frames will change.
const FIXPOS_CB_NON_SVG = 1 << 7;
/// Whether the position property will change.
const POSITION = 1 << 8;
}
}
fn change_bits_for_longhand(longhand: LonghandId) -> WillChangeBits {
let mut flags = match longhand {
match longhand {
LonghandId::Opacity => WillChangeBits::OPACITY,
LonghandId::Transform => WillChangeBits::TRANSFORM,
#[cfg(feature = "gecko")]
LonghandId::Translate | LonghandId::Rotate | LonghandId::Scale | LonghandId::OffsetPath => {
WillChangeBits::TRANSFORM
LonghandId::Contain => WillChangeBits::CONTAIN,
LonghandId::Perspective => WillChangeBits::PERSPECTIVE,
LonghandId::Position => {
WillChangeBits::STACKING_CONTEXT_UNCONDITIONAL | WillChangeBits::POSITION
},
LonghandId::ZIndex => WillChangeBits::Z_INDEX,
LonghandId::Transform |
LonghandId::TransformStyle |
LonghandId::Translate |
LonghandId::Rotate |
LonghandId::Scale |
LonghandId::OffsetPath => WillChangeBits::TRANSFORM,
LonghandId::BackdropFilter | LonghandId::Filter => {
WillChangeBits::STACKING_CONTEXT_UNCONDITIONAL | WillChangeBits::FIXPOS_CB_NON_SVG
},
LonghandId::MixBlendMode |
LonghandId::Isolation |
LonghandId::MaskImage |
LonghandId::ClipPath => WillChangeBits::STACKING_CONTEXT_UNCONDITIONAL,
_ => WillChangeBits::empty(),
};
let property_flags = longhand.flags();
if property_flags.contains(PropertyFlags::CREATES_STACKING_CONTEXT) {
flags |= WillChangeBits::STACKING_CONTEXT;
}
if property_flags.contains(PropertyFlags::FIXPOS_CB) {
flags |= WillChangeBits::FIXPOS_CB;
}
if property_flags.contains(PropertyFlags::ABSPOS_CB) {
flags |= WillChangeBits::ABSPOS_CB;
}
flags
}
fn change_bits_for_maybe_property(ident: &str, context: &ParserContext) -> WillChangeBits {