servo/components/layout/sizing.rs
Oriol Brufau 4cd7c5196b
layout: Fix block SizeConstraint for replaced elements (#37758)
#37433 didn't handle intrinsic contributions. This patch computes the
correct SizeConstraint to be used as the ConstraintSpace's block size
when computing intrinsic inline sizes.

Testing: Adding new test
Fixes: #37478

Signed-off-by: Oriol Brufau <obrufau@igalia.com>
2025-06-30 12:07:37 +00:00

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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/. */
//! <https://drafts.csswg.org/css-sizing/>
use std::cell::LazyCell;
use std::ops::{Add, AddAssign};
use app_units::Au;
use malloc_size_of_derive::MallocSizeOf;
use style::Zero;
use style::logical_geometry::Direction;
use style::values::computed::LengthPercentage;
use crate::context::LayoutContext;
use crate::geom::{Size, SizeConstraint};
use crate::style_ext::{AspectRatio, Clamp, ComputedValuesExt, ContentBoxSizesAndPBM, LayoutStyle};
use crate::{ConstraintSpace, IndefiniteContainingBlock, LogicalVec2};
#[derive(PartialEq)]
pub(crate) enum IntrinsicSizingMode {
/// Used to refer to a min-content contribution or max-content contribution.
/// This is the size that a box contributes to its containing blocks min-content
/// or max-content size. Note this is based on the outer size of the box,
/// and takes into account the relevant sizing properties of the element.
/// <https://drafts.csswg.org/css-sizing-3/#contributions>
Contribution,
/// Used to refer to a min-content size or max-content size.
/// This is the size based on the contents of an element, without regard for its context.
/// Note this is usually based on the inner (content-box) size of the box,
/// and ignores the relevant sizing properties of the element.
/// <https://drafts.csswg.org/css-sizing-3/#intrinsic>
Size,
}
#[derive(Clone, Copy, Debug, Default, MallocSizeOf)]
pub(crate) struct ContentSizes {
pub min_content: Au,
pub max_content: Au,
}
/// <https://drafts.csswg.org/css-sizing/#intrinsic-sizes>
impl ContentSizes {
pub fn max(&self, other: Self) -> Self {
Self {
min_content: self.min_content.max(other.min_content),
max_content: self.max_content.max(other.max_content),
}
}
pub fn max_assign(&mut self, other: Self) {
*self = self.max(other);
}
pub fn union(&self, other: &Self) -> Self {
Self {
min_content: self.min_content.max(other.min_content),
max_content: self.max_content + other.max_content,
}
}
pub fn map(&self, f: impl Fn(Au) -> Au) -> Self {
Self {
min_content: f(self.min_content),
max_content: f(self.max_content),
}
}
}
impl Zero for ContentSizes {
fn zero() -> Self {
Au::zero().into()
}
fn is_zero(&self) -> bool {
self.min_content.is_zero() && self.max_content.is_zero()
}
}
impl Add for ContentSizes {
type Output = Self;
fn add(self, rhs: Self) -> Self {
Self {
min_content: self.min_content + rhs.min_content,
max_content: self.max_content + rhs.max_content,
}
}
}
impl AddAssign for ContentSizes {
fn add_assign(&mut self, rhs: Self) {
*self = self.add(rhs)
}
}
impl ContentSizes {
/// Clamps the provided amount to be between the min-content and the max-content.
/// This is called "shrink-to-fit" in CSS2, and "fit-content" in CSS Sizing.
/// <https://drafts.csswg.org/css2/visudet.html#shrink-to-fit-float>
/// <https://drafts.csswg.org/css-sizing/#funcdef-width-fit-content>
pub fn shrink_to_fit(&self, available_size: Au) -> Au {
// This formula is slightly different than what the spec says,
// to ensure that the minimum wins for a malformed ContentSize
// whose min_content is larger than its max_content.
available_size.min(self.max_content).max(self.min_content)
}
}
impl From<Au> for ContentSizes {
fn from(size: Au) -> Self {
Self {
min_content: size,
max_content: size,
}
}
}
#[allow(clippy::too_many_arguments)]
pub(crate) fn outer_inline(
layout_style: &LayoutStyle,
containing_block: &IndefiniteContainingBlock,
auto_minimum: &LogicalVec2<Au>,
auto_block_size_stretches_to_containing_block: bool,
is_replaced: bool,
establishes_containing_block: bool,
get_preferred_aspect_ratio: impl FnOnce(&LogicalVec2<Au>) -> Option<AspectRatio>,
get_inline_content_size: impl FnOnce(&ConstraintSpace) -> InlineContentSizesResult,
get_tentative_block_content_size: impl FnOnce(Option<AspectRatio>) -> Option<ContentSizes>,
) -> InlineContentSizesResult {
let ContentBoxSizesAndPBM {
content_box_sizes,
pbm,
mut depends_on_block_constraints,
preferred_size_computes_to_auto,
} = layout_style.content_box_sizes_and_padding_border_margin(containing_block);
let margin = pbm.margin.map(|v| v.auto_is(Au::zero));
let pbm_sums = LogicalVec2 {
block: pbm.padding_border_sums.block + margin.block_sum(),
inline: pbm.padding_border_sums.inline + margin.inline_sum(),
};
let style = layout_style.style();
let is_table = layout_style.is_table();
let content_size = LazyCell::new(|| {
let constraint_space = if establishes_containing_block {
let available_block_size = containing_block
.size
.block
.map(|v| Au::zero().max(v - pbm_sums.block));
let automatic_size = if preferred_size_computes_to_auto.block &&
auto_block_size_stretches_to_containing_block
{
depends_on_block_constraints = true;
Size::Stretch
} else {
Size::FitContent
};
let aspect_ratio = get_preferred_aspect_ratio(&pbm.padding_border_sums);
let block_size =
if let Some(block_content_size) = get_tentative_block_content_size(aspect_ratio) {
SizeConstraint::Definite(content_box_sizes.block.resolve(
Direction::Block,
automatic_size,
|| auto_minimum.block,
available_block_size,
|| block_content_size,
is_table,
))
} else {
content_box_sizes.block.resolve_extrinsic(
automatic_size,
auto_minimum.block,
available_block_size,
)
};
ConstraintSpace::new(block_size, style.writing_mode, aspect_ratio)
} else {
// This assumes that there is no preferred aspect ratio, or that there is no
// block size constraint to be transferred so the ratio is irrelevant.
// We only get into here for anonymous blocks, for which the assumption holds.
ConstraintSpace::new(
containing_block.size.block.into(),
containing_block.writing_mode,
None,
)
};
get_inline_content_size(&constraint_space)
});
let resolve_non_initial = |inline_size, stretch_values| {
Some(match inline_size {
Size::Initial => return None,
Size::Numeric(numeric) => (numeric, numeric, false),
Size::MinContent => (
content_size.sizes.min_content,
content_size.sizes.min_content,
content_size.depends_on_block_constraints,
),
Size::MaxContent => (
content_size.sizes.max_content,
content_size.sizes.max_content,
content_size.depends_on_block_constraints,
),
Size::FitContent => (
content_size.sizes.min_content,
content_size.sizes.max_content,
content_size.depends_on_block_constraints,
),
Size::FitContentFunction(size) => {
let size = content_size.sizes.shrink_to_fit(size);
(size, size, content_size.depends_on_block_constraints)
},
Size::Stretch => return stretch_values,
})
};
let (mut preferred_min_content, preferred_max_content, preferred_depends_on_block_constraints) =
resolve_non_initial(content_box_sizes.inline.preferred, None)
.unwrap_or_else(|| resolve_non_initial(Size::FitContent, None).unwrap());
let (mut min_min_content, mut min_max_content, mut min_depends_on_block_constraints) =
resolve_non_initial(
content_box_sizes.inline.min,
Some((Au::zero(), Au::zero(), false)),
)
.unwrap_or((auto_minimum.inline, auto_minimum.inline, false));
let (mut max_min_content, max_max_content, max_depends_on_block_constraints) =
resolve_non_initial(content_box_sizes.inline.max, None)
.map(|(min_content, max_content, depends_on_block_constraints)| {
(
Some(min_content),
Some(max_content),
depends_on_block_constraints,
)
})
.unwrap_or_default();
// https://drafts.csswg.org/css-sizing-3/#replaced-percentage-min-contribution
// > If the box is replaced, a cyclic percentage in the value of any max size property
// > or preferred size property (width/max-width/height/max-height), is resolved against
// > zero when calculating the min-content contribution in the corresponding axis.
//
// This means that e.g. the min-content contribution of `width: calc(100% + 100px)`
// should be 100px, but it's just zero on other browsers, so we do the same.
if is_replaced {
let has_percentage = |size: Size<LengthPercentage>| {
// We need a comment here to avoid breaking `./mach test-tidy`.
matches!(size, Size::Numeric(numeric) if numeric.has_percentage())
};
if content_box_sizes.inline.preferred.is_initial() &&
has_percentage(style.box_size(containing_block.writing_mode).inline)
{
preferred_min_content = Au::zero();
}
if content_box_sizes.inline.max.is_initial() &&
has_percentage(style.max_box_size(containing_block.writing_mode).inline)
{
max_min_content = Some(Au::zero());
}
}
// Regardless of their sizing properties, tables are always forced to be at least
// as big as their min-content size, so floor the minimums.
if is_table {
min_min_content.max_assign(content_size.sizes.min_content);
min_max_content.max_assign(content_size.sizes.min_content);
min_depends_on_block_constraints |= content_size.depends_on_block_constraints;
}
InlineContentSizesResult {
sizes: ContentSizes {
min_content: preferred_min_content
.clamp_between_extremums(min_min_content, max_min_content) +
pbm_sums.inline,
max_content: preferred_max_content
.clamp_between_extremums(min_max_content, max_max_content) +
pbm_sums.inline,
},
depends_on_block_constraints: depends_on_block_constraints &&
(preferred_depends_on_block_constraints ||
min_depends_on_block_constraints ||
max_depends_on_block_constraints),
}
}
#[derive(Clone, Copy, Debug, MallocSizeOf)]
pub(crate) struct InlineContentSizesResult {
pub sizes: ContentSizes,
pub depends_on_block_constraints: bool,
}
pub(crate) trait ComputeInlineContentSizes {
fn compute_inline_content_sizes(
&self,
layout_context: &LayoutContext,
constraint_space: &ConstraintSpace,
) -> InlineContentSizesResult;
/// Returns the same result as [`Self::compute_inline_content_sizes()`], but adjusted
/// to floor the max-content size by the min-content size.
/// This is being discussed in <https://github.com/w3c/csswg-drafts/issues/12076>.
fn compute_inline_content_sizes_with_fixup(
&self,
layout_context: &LayoutContext,
constraint_space: &ConstraintSpace,
) -> InlineContentSizesResult {
let mut result = self.compute_inline_content_sizes(layout_context, constraint_space);
let sizes = &mut result.sizes;
sizes.max_content.max_assign(sizes.min_content);
result
}
}