servo/components/layout_2020/flow/mod.rs
Martin Robinson 72302e2dae Detect body elements during layout
During layout it is often useful, for various specification reasons, to
know if an element is the `<body>` element of an `<html>` element root. There
are a couple places where a brittle heuristic is used to detect `<body>`
elements. This information is going to be even more important to
properly handle `<html>` elements that inherit their overflow property from
their `<body>` children.

Implementing this properly requires updating the DOM wrapper interface.
This check does reach up to the parent of thread-safe nodes, but this is
essentially the same kind of operation that `parent_style()` does, so is
ostensibly safe.

This change should not change any behavior and is just a preparation
step for properly handle `<body>` overflow.
2023-05-04 10:46:27 +02:00

626 lines
24 KiB
Rust

/* 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/. */
//! Flow layout, also known as block-and-inline layout.
use crate::cell::ArcRefCell;
use crate::context::LayoutContext;
use crate::flow::float::{FloatBox, FloatContext};
use crate::flow::inline::InlineFormattingContext;
use crate::formatting_contexts::{
IndependentFormattingContext, IndependentLayout, NonReplacedFormattingContext,
};
use crate::fragment_tree::BaseFragmentInfo;
use crate::fragments::{
AnonymousFragment, BoxFragment, CollapsedBlockMargins, CollapsedMargin, Fragment,
};
use crate::geom::flow_relative::{Rect, Sides, Vec2};
use crate::positioned::{AbsolutelyPositionedBox, PositioningContext};
use crate::replaced::ReplacedContent;
use crate::sizing::{self, ContentSizes};
use crate::style_ext::{ComputedValuesExt, PaddingBorderMargin};
use crate::ContainingBlock;
use rayon::iter::{IndexedParallelIterator, IntoParallelRefIterator, ParallelIterator};
use rayon_croissant::ParallelIteratorExt;
use servo_arc::Arc;
use style::logical_geometry::WritingMode;
use style::properties::ComputedValues;
use style::values::computed::{Length, LengthOrAuto};
use style::Zero;
mod construct;
pub mod float;
pub mod inline;
mod root;
pub use root::{BoxTree, FragmentTree};
#[derive(Debug, Serialize)]
pub(crate) struct BlockFormattingContext {
pub contents: BlockContainer,
pub contains_floats: bool,
}
#[derive(Debug, Serialize)]
pub(crate) enum BlockContainer {
BlockLevelBoxes(Vec<ArcRefCell<BlockLevelBox>>),
InlineFormattingContext(InlineFormattingContext),
}
#[derive(Debug, Serialize)]
pub(crate) enum BlockLevelBox {
SameFormattingContextBlock {
base_fragment_info: BaseFragmentInfo,
#[serde(skip_serializing)]
style: Arc<ComputedValues>,
contents: BlockContainer,
},
OutOfFlowAbsolutelyPositionedBox(ArcRefCell<AbsolutelyPositionedBox>),
OutOfFlowFloatBox(FloatBox),
Independent(IndependentFormattingContext),
}
struct FlowLayout {
pub fragments: Vec<Fragment>,
pub content_block_size: Length,
pub collapsible_margins_in_children: CollapsedBlockMargins,
}
#[derive(Clone, Copy)]
struct CollapsibleWithParentStartMargin(bool);
impl BlockFormattingContext {
pub(super) fn layout(
&self,
layout_context: &LayoutContext,
positioning_context: &mut PositioningContext,
containing_block: &ContainingBlock,
tree_rank: usize,
) -> IndependentLayout {
let mut float_context;
let float_context = if self.contains_floats {
float_context = FloatContext::new();
Some(&mut float_context)
} else {
None
};
let flow_layout = self.contents.layout(
layout_context,
positioning_context,
containing_block,
tree_rank,
float_context,
CollapsibleWithParentStartMargin(false),
);
assert!(
!flow_layout
.collapsible_margins_in_children
.collapsed_through
);
IndependentLayout {
fragments: flow_layout.fragments,
content_block_size: flow_layout.content_block_size +
flow_layout.collapsible_margins_in_children.end.solve(),
}
}
}
impl BlockContainer {
fn layout(
&self,
layout_context: &LayoutContext,
positioning_context: &mut PositioningContext,
containing_block: &ContainingBlock,
tree_rank: usize,
float_context: Option<&mut FloatContext>,
collapsible_with_parent_start_margin: CollapsibleWithParentStartMargin,
) -> FlowLayout {
match self {
BlockContainer::BlockLevelBoxes(child_boxes) => layout_block_level_children(
layout_context,
positioning_context,
child_boxes,
containing_block,
tree_rank,
float_context,
collapsible_with_parent_start_margin,
),
BlockContainer::InlineFormattingContext(ifc) => ifc.layout(
layout_context,
positioning_context,
containing_block,
tree_rank,
),
}
}
pub(super) fn inline_content_sizes(
&self,
layout_context: &LayoutContext,
writing_mode: WritingMode,
) -> ContentSizes {
match &self {
Self::BlockLevelBoxes(boxes) if layout_context.use_rayon => boxes
.par_iter()
.map(|box_| {
box_.borrow_mut()
.inline_content_sizes(layout_context, writing_mode)
})
.reduce(ContentSizes::zero, ContentSizes::max),
Self::BlockLevelBoxes(boxes) => boxes
.iter()
.map(|box_| {
box_.borrow_mut()
.inline_content_sizes(layout_context, writing_mode)
})
.reduce(ContentSizes::max)
.unwrap_or_else(ContentSizes::zero),
Self::InlineFormattingContext(context) => {
context.inline_content_sizes(layout_context, writing_mode)
},
}
}
}
fn layout_block_level_children(
layout_context: &LayoutContext,
positioning_context: &mut PositioningContext,
child_boxes: &[ArcRefCell<BlockLevelBox>],
containing_block: &ContainingBlock,
tree_rank: usize,
mut float_context: Option<&mut FloatContext>,
collapsible_with_parent_start_margin: CollapsibleWithParentStartMargin,
) -> FlowLayout {
fn place_block_level_fragment(fragment: &mut Fragment, placement_state: &mut PlacementState) {
match fragment {
Fragment::Box(fragment) => {
let fragment_block_margins = &fragment.block_margins_collapsed_with_children;
let fragment_block_size = fragment.padding.block_sum() +
fragment.border.block_sum() +
fragment.content_rect.size.block;
if placement_state.next_in_flow_margin_collapses_with_parent_start_margin {
assert_eq!(placement_state.current_margin.solve(), Length::zero());
placement_state
.start_margin
.adjoin_assign(&fragment_block_margins.start);
if fragment_block_margins.collapsed_through {
placement_state
.start_margin
.adjoin_assign(&fragment_block_margins.end);
return;
}
placement_state.next_in_flow_margin_collapses_with_parent_start_margin = false;
} else {
placement_state
.current_margin
.adjoin_assign(&fragment_block_margins.start);
}
fragment.content_rect.start_corner.block += placement_state.current_margin.solve() +
placement_state.current_block_direction_position;
if fragment_block_margins.collapsed_through {
placement_state
.current_margin
.adjoin_assign(&fragment_block_margins.end);
return;
}
placement_state.current_block_direction_position +=
placement_state.current_margin.solve() + fragment_block_size;
placement_state.current_margin = fragment_block_margins.end;
},
Fragment::AbsoluteOrFixedPositioned(fragment) => {
let offset = Vec2 {
block: placement_state.current_margin.solve() +
placement_state.current_block_direction_position,
inline: Length::new(0.),
};
fragment.borrow_mut().adjust_offsets(offset);
},
Fragment::Anonymous(_) => {},
_ => unreachable!(),
}
}
struct PlacementState {
next_in_flow_margin_collapses_with_parent_start_margin: bool,
start_margin: CollapsedMargin,
current_margin: CollapsedMargin,
current_block_direction_position: Length,
}
let mut placement_state = PlacementState {
next_in_flow_margin_collapses_with_parent_start_margin:
collapsible_with_parent_start_margin.0,
start_margin: CollapsedMargin::zero(),
current_margin: CollapsedMargin::zero(),
current_block_direction_position: Length::zero(),
};
let fragments = positioning_context.adjust_static_positions(tree_rank, |positioning_context| {
if float_context.is_some() || !layout_context.use_rayon {
// Because floats are involved, we do layout for this block formatting context
// in tree order without parallelism. This enables mutable access
// to a `FloatContext` that tracks every float encountered so far (again in tree order).
child_boxes
.iter()
.enumerate()
.map(|(tree_rank, box_)| {
let mut fragment = box_.borrow_mut().layout(
layout_context,
positioning_context,
containing_block,
tree_rank,
float_context.as_mut().map(|c| &mut **c),
);
place_block_level_fragment(&mut fragment, &mut placement_state);
fragment
})
.collect()
} else {
let collects_for_nearest_positioned_ancestor =
positioning_context.collects_for_nearest_positioned_ancestor();
let mut fragments = child_boxes
.par_iter()
.enumerate()
.mapfold_reduce_into(
positioning_context,
|positioning_context, (tree_rank, box_)| {
box_.borrow_mut().layout(
layout_context,
positioning_context,
containing_block,
tree_rank,
/* float_context = */ None,
)
},
|| PositioningContext::new_for_rayon(collects_for_nearest_positioned_ancestor),
PositioningContext::append,
)
.collect();
for fragment in &mut fragments {
place_block_level_fragment(fragment, &mut placement_state)
}
fragments
}
});
FlowLayout {
fragments,
content_block_size: placement_state.current_block_direction_position,
collapsible_margins_in_children: CollapsedBlockMargins {
collapsed_through: placement_state
.next_in_flow_margin_collapses_with_parent_start_margin,
start: placement_state.start_margin,
end: placement_state.current_margin,
},
}
}
impl BlockLevelBox {
fn layout(
&mut self,
layout_context: &LayoutContext,
positioning_context: &mut PositioningContext,
containing_block: &ContainingBlock,
tree_rank: usize,
float_context: Option<&mut FloatContext>,
) -> Fragment {
match self {
BlockLevelBox::SameFormattingContextBlock {
base_fragment_info: tag,
style,
contents,
} => Fragment::Box(positioning_context.layout_maybe_position_relative_fragment(
layout_context,
containing_block,
style,
|positioning_context| {
layout_in_flow_non_replaced_block_level(
layout_context,
positioning_context,
containing_block,
*tag,
style,
NonReplacedContents::SameFormattingContextBlock(contents),
tree_rank,
float_context,
)
},
)),
BlockLevelBox::Independent(independent) => match independent {
IndependentFormattingContext::Replaced(replaced) => {
Fragment::Box(positioning_context.layout_maybe_position_relative_fragment(
layout_context,
containing_block,
&replaced.style,
|_positioning_context| {
layout_in_flow_replaced_block_level(
containing_block,
replaced.base_fragment_info,
&replaced.style,
&replaced.contents,
)
},
))
},
IndependentFormattingContext::NonReplaced(non_replaced) => {
Fragment::Box(positioning_context.layout_maybe_position_relative_fragment(
layout_context,
containing_block,
&non_replaced.style,
|positioning_context| {
layout_in_flow_non_replaced_block_level(
layout_context,
positioning_context,
containing_block,
non_replaced.base_fragment_info,
&non_replaced.style,
NonReplacedContents::EstablishesAnIndependentFormattingContext(
non_replaced,
),
tree_rank,
float_context,
)
},
))
},
},
BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(box_) => {
let hoisted_box = AbsolutelyPositionedBox::to_hoisted(
box_.clone(),
// This is incorrect, however we do not know the
// correct positioning until later, in place_block_level_fragment,
// and this value will be adjusted there
Vec2::zero(),
tree_rank,
containing_block,
);
let hoisted_fragment = hoisted_box.fragment.clone();
positioning_context.push(hoisted_box);
Fragment::AbsoluteOrFixedPositioned(hoisted_fragment)
},
BlockLevelBox::OutOfFlowFloatBox(_box_) => {
// FIXME: call layout_maybe_position_relative_fragment here
Fragment::Anonymous(AnonymousFragment::no_op(
containing_block.style.writing_mode,
))
},
}
}
fn inline_content_sizes(
&mut self,
layout_context: &LayoutContext,
containing_block_writing_mode: WritingMode,
) -> ContentSizes {
match self {
Self::SameFormattingContextBlock {
style, contents, ..
} => sizing::outer_inline(style, containing_block_writing_mode, || {
contents.inline_content_sizes(layout_context, style.writing_mode)
}),
Self::Independent(independent) => independent
.outer_inline_content_sizes(layout_context, containing_block_writing_mode),
BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(_) => ContentSizes::zero(),
BlockLevelBox::OutOfFlowFloatBox(_box_) => {
// TODO: Actually implement that.
ContentSizes::zero()
},
}
}
}
enum NonReplacedContents<'a> {
SameFormattingContextBlock(&'a BlockContainer),
EstablishesAnIndependentFormattingContext(&'a NonReplacedFormattingContext),
}
/// https://drafts.csswg.org/css2/visudet.html#blockwidth
/// https://drafts.csswg.org/css2/visudet.html#normal-block
fn layout_in_flow_non_replaced_block_level(
layout_context: &LayoutContext,
positioning_context: &mut PositioningContext,
containing_block: &ContainingBlock,
base_fragment_info: BaseFragmentInfo,
style: &Arc<ComputedValues>,
block_level_kind: NonReplacedContents,
tree_rank: usize,
float_context: Option<&mut FloatContext>,
) -> BoxFragment {
let pbm = style.padding_border_margin(containing_block);
let box_size = style.content_box_size(containing_block, &pbm);
let max_box_size = style.content_max_box_size(containing_block, &pbm);
let min_box_size = style
.content_min_box_size(containing_block, &pbm)
.auto_is(Length::zero);
// https://drafts.csswg.org/css2/visudet.html#min-max-widths
let solve_inline_margins = |inline_size| {
solve_inline_margins_for_in_flow_block_level(containing_block, &pbm, inline_size)
};
let (mut inline_size, mut inline_margins) =
if let Some(inline_size) = box_size.inline.non_auto() {
(inline_size, solve_inline_margins(inline_size))
} else {
let margin_inline_start = pbm.margin.inline_start.auto_is(Length::zero);
let margin_inline_end = pbm.margin.inline_end.auto_is(Length::zero);
let inline_size = containing_block.inline_size -
pbm.padding_border_sums.inline -
margin_inline_start -
margin_inline_end;
(inline_size, (margin_inline_start, margin_inline_end))
};
if let Some(max_inline_size) = max_box_size.inline {
if inline_size > max_inline_size {
inline_size = max_inline_size;
inline_margins = solve_inline_margins(inline_size);
}
}
if inline_size < min_box_size.inline {
inline_size = min_box_size.inline;
inline_margins = solve_inline_margins(inline_size);
}
let margin = Sides {
inline_start: inline_margins.0,
inline_end: inline_margins.1,
block_start: pbm.margin.block_start.auto_is(Length::zero),
block_end: pbm.margin.block_end.auto_is(Length::zero),
};
// https://drafts.csswg.org/css2/visudet.html#min-max-heights
let mut block_size = box_size.block;
if let LengthOrAuto::LengthPercentage(ref mut block_size) = block_size {
*block_size = block_size.clamp_between_extremums(min_box_size.block, max_box_size.block);
}
let containing_block_for_children = ContainingBlock {
inline_size,
block_size,
style,
};
// https://drafts.csswg.org/css-writing-modes/#orthogonal-flows
assert_eq!(
containing_block.style.writing_mode, containing_block_for_children.style.writing_mode,
"Mixed writing modes are not supported yet"
);
let mut block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
let fragments;
let mut content_block_size;
match block_level_kind {
NonReplacedContents::SameFormattingContextBlock(contents) => {
let start_margin_can_collapse_with_children = pbm.padding.block_start == Length::zero() &&
pbm.border.block_start == Length::zero();
let end_margin_can_collapse_with_children = pbm.padding.block_end == Length::zero() &&
pbm.border.block_end == Length::zero() &&
block_size == LengthOrAuto::Auto &&
min_box_size.block == Length::zero();
let flow_layout = contents.layout(
layout_context,
positioning_context,
&containing_block_for_children,
tree_rank,
float_context,
CollapsibleWithParentStartMargin(start_margin_can_collapse_with_children),
);
fragments = flow_layout.fragments;
content_block_size = flow_layout.content_block_size;
let mut collapsible_margins_in_children = flow_layout.collapsible_margins_in_children;
if start_margin_can_collapse_with_children {
block_margins_collapsed_with_children
.start
.adjoin_assign(&collapsible_margins_in_children.start);
if collapsible_margins_in_children.collapsed_through {
block_margins_collapsed_with_children
.start
.adjoin_assign(&std::mem::replace(
&mut collapsible_margins_in_children.end,
CollapsedMargin::zero(),
));
}
}
if end_margin_can_collapse_with_children {
block_margins_collapsed_with_children
.end
.adjoin_assign(&collapsible_margins_in_children.end);
} else {
content_block_size += collapsible_margins_in_children.end.solve();
}
block_margins_collapsed_with_children.collapsed_through =
start_margin_can_collapse_with_children &&
end_margin_can_collapse_with_children &&
collapsible_margins_in_children.collapsed_through;
},
NonReplacedContents::EstablishesAnIndependentFormattingContext(non_replaced) => {
let independent_layout = non_replaced.layout(
layout_context,
positioning_context,
&containing_block_for_children,
tree_rank,
);
fragments = independent_layout.fragments;
content_block_size = independent_layout.content_block_size;
},
};
let block_size = block_size.auto_is(|| {
content_block_size.clamp_between_extremums(min_box_size.block, max_box_size.block)
});
let content_rect = Rect {
start_corner: Vec2 {
block: pbm.padding.block_start + pbm.border.block_start,
inline: pbm.padding.inline_start + pbm.border.inline_start + margin.inline_start,
},
size: Vec2 {
block: block_size,
inline: inline_size,
},
};
BoxFragment::new(
base_fragment_info,
style.clone(),
fragments,
content_rect,
pbm.padding,
pbm.border,
margin,
block_margins_collapsed_with_children,
)
}
/// https://drafts.csswg.org/css2/visudet.html#block-replaced-width
/// https://drafts.csswg.org/css2/visudet.html#inline-replaced-width
/// https://drafts.csswg.org/css2/visudet.html#inline-replaced-height
fn layout_in_flow_replaced_block_level<'a>(
containing_block: &ContainingBlock,
base_fragment_info: BaseFragmentInfo,
style: &Arc<ComputedValues>,
replaced: &ReplacedContent,
) -> BoxFragment {
let pbm = style.padding_border_margin(containing_block);
let size = replaced.used_size_as_if_inline_element(containing_block, style, &pbm);
let (margin_inline_start, margin_inline_end) =
solve_inline_margins_for_in_flow_block_level(containing_block, &pbm, size.inline);
let margin = Sides {
inline_start: margin_inline_start,
inline_end: margin_inline_end,
block_start: pbm.margin.block_start.auto_is(Length::zero),
block_end: pbm.margin.block_end.auto_is(Length::zero),
};
let fragments = replaced.make_fragments(style, size.clone());
let content_rect = Rect {
start_corner: Vec2 {
block: pbm.padding.block_start + pbm.border.block_start,
inline: pbm.padding.inline_start + pbm.border.inline_start + margin.inline_start,
},
size,
};
let block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
BoxFragment::new(
base_fragment_info,
style.clone(),
fragments,
content_rect,
pbm.padding,
pbm.border,
margin,
block_margins_collapsed_with_children,
)
}
fn solve_inline_margins_for_in_flow_block_level(
containing_block: &ContainingBlock,
pbm: &PaddingBorderMargin,
inline_size: Length,
) -> (Length, Length) {
let available = containing_block.inline_size - pbm.padding_border_sums.inline - inline_size;
match (pbm.margin.inline_start, pbm.margin.inline_end) {
(LengthOrAuto::Auto, LengthOrAuto::Auto) => (available / 2., available / 2.),
(LengthOrAuto::Auto, LengthOrAuto::LengthPercentage(end)) => (available - end, end),
(LengthOrAuto::LengthPercentage(start), _) => (start, available - start),
}
}