servo/components/layout_2020/flow/mod.rs
2019-12-04 17:24:45 +01:00

751 lines
29 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::context::LayoutContext;
use crate::flow::float::{FloatBox, FloatContext};
use crate::flow::inline::InlineFormattingContext;
use crate::formatting_contexts::{IndependentFormattingContext, IndependentLayout};
use crate::fragments::{AnonymousFragment, BoxFragment, Fragment};
use crate::fragments::{CollapsedBlockMargins, CollapsedMargin};
use crate::geom::flow_relative::{Rect, Sides, Vec2};
use crate::positioned::adjust_static_positions;
use crate::positioned::{AbsolutelyPositionedBox, AbsolutelyPositionedFragment};
use crate::replaced::ReplacedContent;
use crate::style_ext::{ComputedValuesExt, Position};
use crate::{relative_adjustement, ContainingBlock};
use rayon::iter::{IndexedParallelIterator, IntoParallelRefIterator, ParallelIterator};
use rayon_croissant::ParallelIteratorExt;
use servo_arc::Arc;
use style::properties::ComputedValues;
use style::values::computed::{Length, LengthOrAuto, LengthPercentage, LengthPercentageOrAuto};
use style::values::generics::length::MaxSize;
use style::Zero;
mod construct;
mod float;
pub mod inline;
mod root;
pub use root::{BoxTreeRoot, FragmentTreeRoot};
#[derive(Debug)]
pub(crate) struct BlockFormattingContext {
pub contents: BlockContainer,
pub contains_floats: bool,
}
#[derive(Debug)]
pub(crate) enum BlockContainer {
BlockLevelBoxes(Vec<Arc<BlockLevelBox>>),
InlineFormattingContext(InlineFormattingContext),
}
#[derive(Debug)]
pub(crate) enum BlockLevelBox {
SameFormattingContextBlock {
style: Arc<ComputedValues>,
contents: BlockContainer,
},
OutOfFlowAbsolutelyPositionedBox(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<'a>(
&'a self,
layout_context: &LayoutContext,
containing_block: &ContainingBlock,
tree_rank: usize,
absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
) -> 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,
containing_block,
tree_rank,
absolutely_positioned_fragments,
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<'a>(
&'a self,
layout_context: &LayoutContext,
containing_block: &ContainingBlock,
tree_rank: usize,
absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
float_context: Option<&mut FloatContext>,
collapsible_with_parent_start_margin: CollapsibleWithParentStartMargin,
) -> FlowLayout {
match self {
BlockContainer::BlockLevelBoxes(child_boxes) => layout_block_level_children(
layout_context,
child_boxes,
containing_block,
tree_rank,
absolutely_positioned_fragments,
float_context,
collapsible_with_parent_start_margin,
),
BlockContainer::InlineFormattingContext(ifc) => ifc.layout(
layout_context,
containing_block,
tree_rank,
absolutely_positioned_fragments,
),
}
}
}
fn layout_block_level_children<'a>(
layout_context: &LayoutContext,
child_boxes: &'a [Arc<BlockLevelBox>],
containing_block: &ContainingBlock,
tree_rank: usize,
absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
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::Anonymous(fragment) => {
// FIXME(nox): Margin collapsing for hypothetical boxes of
// abspos elements is probably wrong.
assert!(fragment.children.is_empty());
assert_eq!(fragment.rect.size.block, Length::zero());
fragment.rect.start_corner.block +=
placement_state.current_block_direction_position;
},
_ => 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 abspos_so_far = absolutely_positioned_fragments.len();
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 mut fragments: Vec<_>;
if let Some(float_context) = float_context {
// 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).
fragments = child_boxes
.iter()
.enumerate()
.map(|(tree_rank, box_)| {
let mut fragment = box_.layout(
layout_context,
containing_block,
tree_rank,
absolutely_positioned_fragments,
Some(float_context),
);
place_block_level_fragment(&mut fragment, &mut placement_state);
fragment
})
.collect()
} else {
fragments = child_boxes
.par_iter()
.enumerate()
.mapfold_reduce_into(
absolutely_positioned_fragments,
|abspos_fragments, (tree_rank, box_)| {
box_.layout(
layout_context,
containing_block,
tree_rank,
abspos_fragments,
/* float_context = */ None,
)
},
|left_abspos_fragments, mut right_abspos_fragments| {
left_abspos_fragments.append(&mut right_abspos_fragments);
},
)
.collect();
for fragment in &mut fragments {
place_block_level_fragment(fragment, &mut placement_state)
}
}
adjust_static_positions(
&mut absolutely_positioned_fragments[abspos_so_far..],
&mut fragments,
tree_rank,
);
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<'a>(
&'a self,
layout_context: &LayoutContext,
containing_block: &ContainingBlock,
tree_rank: usize,
absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
float_context: Option<&mut FloatContext>,
) -> Fragment {
match self {
BlockLevelBox::SameFormattingContextBlock { style, contents } => {
Fragment::Box(layout_in_flow_non_replaced_block_level(
layout_context,
containing_block,
absolutely_positioned_fragments,
style,
BlockLevelKind::SameFormattingContextBlock,
|containing_block, nested_abspos, collapsible_with_parent_start_margin| {
contents.layout(
layout_context,
containing_block,
tree_rank,
nested_abspos,
float_context,
collapsible_with_parent_start_margin,
)
},
))
},
BlockLevelBox::Independent(contents) => match contents.as_replaced() {
Ok(replaced) => Fragment::Box(layout_in_flow_replaced_block_level(
containing_block,
&contents.style,
replaced,
)),
Err(non_replaced) => Fragment::Box(layout_in_flow_non_replaced_block_level(
layout_context,
containing_block,
absolutely_positioned_fragments,
&contents.style,
BlockLevelKind::EstablishesAnIndependentFormattingContext,
|containing_block, nested_abspos, _| {
let independent_layout = non_replaced.layout(
layout_context,
containing_block,
tree_rank,
nested_abspos,
);
FlowLayout {
fragments: independent_layout.fragments,
content_block_size: independent_layout.content_block_size,
collapsible_margins_in_children: CollapsedBlockMargins::zero(),
}
},
)),
},
BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(box_) => {
absolutely_positioned_fragments.push(box_.layout(Vec2::zero(), tree_rank));
Fragment::Anonymous(AnonymousFragment::no_op(containing_block.mode))
},
BlockLevelBox::OutOfFlowFloatBox(_box_) => {
// TODO
Fragment::Anonymous(AnonymousFragment::no_op(containing_block.mode))
},
}
}
}
#[derive(PartialEq)]
enum BlockLevelKind {
SameFormattingContextBlock,
EstablishesAnIndependentFormattingContext,
}
/// 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<'a>(
layout_context: &LayoutContext,
containing_block: &ContainingBlock,
absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
style: &Arc<ComputedValues>,
block_level_kind: BlockLevelKind,
layout_contents: impl FnOnce(
&ContainingBlock,
&mut Vec<AbsolutelyPositionedFragment<'a>>,
CollapsibleWithParentStartMargin,
) -> FlowLayout,
) -> BoxFragment {
let cbis = containing_block.inline_size;
let padding = style.padding().percentages_relative_to(cbis);
let border = style.border_width();
let margin = style.margin().percentages_relative_to(cbis);
let pb = &padding + &border;
let pb_inline_sum = pb.inline_sum();
let box_size = percent_resolved_box_size(style.box_size(), containing_block);
let max_box_size = percent_resolved_max_box_size(style.max_box_size(), containing_block);
let min_box_size =
percent_resolved_box_size(style.min_box_size(), containing_block).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,
pb_inline_sum,
margin.inline_start,
margin.inline_end,
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 = margin.inline_start.auto_is(Length::zero);
let margin_inline_end = margin.inline_end.auto_is(Length::zero);
let margin_inline_sum = margin_inline_start + margin_inline_end;
let inline_size = cbis - pb_inline_sum - margin_inline_sum;
(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: margin.block_start.auto_is(Length::zero),
block_end: 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 = clamp_between_extremums(*block_size, min_box_size.block, max_box_size.block);
}
let containing_block_for_children = ContainingBlock {
inline_size,
block_size,
mode: style.writing_mode(),
};
// https://drafts.csswg.org/css-writing-modes/#orthogonal-flows
assert_eq!(
containing_block.mode, containing_block_for_children.mode,
"Mixed writing modes are not supported yet"
);
let this_start_margin_can_collapse_with_children = CollapsibleWithParentStartMargin(
block_level_kind == BlockLevelKind::SameFormattingContextBlock &&
pb.block_start == Length::zero(),
);
let this_end_margin_can_collapse_with_children = block_size == LengthOrAuto::Auto &&
min_box_size.block == Length::zero() &&
pb.block_end == Length::zero() &&
block_level_kind == BlockLevelKind::SameFormattingContextBlock;
let mut nested_abspos = vec![];
let mut flow_layout = layout_contents(
&containing_block_for_children,
if style.get_box().position == Position::Relative {
&mut nested_abspos
} else {
absolutely_positioned_fragments
},
this_start_margin_can_collapse_with_children,
);
let mut block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
if this_start_margin_can_collapse_with_children.0 {
block_margins_collapsed_with_children
.start
.adjoin_assign(&flow_layout.collapsible_margins_in_children.start);
if flow_layout
.collapsible_margins_in_children
.collapsed_through
{
block_margins_collapsed_with_children
.start
.adjoin_assign(&std::mem::replace(
&mut flow_layout.collapsible_margins_in_children.end,
CollapsedMargin::zero(),
));
}
}
if this_end_margin_can_collapse_with_children {
block_margins_collapsed_with_children
.end
.adjoin_assign(&flow_layout.collapsible_margins_in_children.end);
} else {
flow_layout.content_block_size += flow_layout.collapsible_margins_in_children.end.solve();
}
block_margins_collapsed_with_children.collapsed_through =
this_start_margin_can_collapse_with_children.0 &&
this_end_margin_can_collapse_with_children &&
flow_layout
.collapsible_margins_in_children
.collapsed_through;
let relative_adjustement = relative_adjustement(style, inline_size, block_size);
let block_size = block_size.auto_is(|| {
clamp_between_extremums(
flow_layout.content_block_size,
min_box_size.block,
max_box_size.block,
)
});
let content_rect = Rect {
start_corner: Vec2 {
block: pb.block_start + relative_adjustement.block,
inline: pb.inline_start + relative_adjustement.inline + margin.inline_start,
},
size: Vec2 {
block: block_size,
inline: inline_size,
},
};
if style.get_box().position == Position::Relative {
AbsolutelyPositionedFragment::in_positioned_containing_block(
layout_context,
&nested_abspos,
&mut flow_layout.fragments,
&content_rect.size,
&padding,
containing_block_for_children.mode,
)
}
BoxFragment {
style: style.clone(),
children: flow_layout.fragments,
content_rect,
padding,
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,
style: &Arc<ComputedValues>,
replaced: &ReplacedContent,
) -> BoxFragment {
let cbis = containing_block.inline_size;
let padding = style.padding().percentages_relative_to(cbis);
let border = style.border_width();
let computed_margin = style.margin().percentages_relative_to(cbis);
let pb = &padding + &border;
let mode = style.writing_mode();
// FIXME(nox): We shouldn't pretend we always have a fully known intrinsic size.
let intrinsic_size = replaced.intrinsic_size.size_to_flow_relative(mode);
// FIXME(nox): This can divide by zero.
let intrinsic_ratio = intrinsic_size.inline.px() / intrinsic_size.block.px();
let box_size = percent_resolved_box_size(style.box_size(), containing_block);
let min_box_size =
percent_resolved_box_size(style.min_box_size(), containing_block).auto_is(Length::zero);
let max_box_size = percent_resolved_max_box_size(style.max_box_size(), containing_block);
let clamp = |inline_size, block_size| {
(
clamp_between_extremums(inline_size, min_box_size.inline, max_box_size.inline),
clamp_between_extremums(block_size, min_box_size.block, max_box_size.block),
)
};
// https://drafts.csswg.org/css2/visudet.html#min-max-widths
// https://drafts.csswg.org/css2/visudet.html#min-max-heights
let (inline_size, block_size) = match (box_size.inline, box_size.block) {
(LengthOrAuto::LengthPercentage(inline), LengthOrAuto::LengthPercentage(block)) => {
clamp(inline, block)
},
(LengthOrAuto::LengthPercentage(inline), LengthOrAuto::Auto) => {
clamp(inline, inline / intrinsic_ratio)
},
(LengthOrAuto::Auto, LengthOrAuto::LengthPercentage(block)) => {
clamp(block * intrinsic_ratio, block)
},
(LengthOrAuto::Auto, LengthOrAuto::Auto) => {
enum Violation {
None,
Below(Length),
Above(Length),
}
let violation = |size, min_size, mut max_size: Option<Length>| {
if let Some(max) = max_size.as_mut() {
max.max_assign(min_size);
}
if size < min_size {
return Violation::Below(min_size);
}
match max_size {
Some(max_size) if size > max_size => Violation::Above(max_size),
_ => Violation::None,
}
};
match (
violation(
intrinsic_size.inline,
min_box_size.inline,
max_box_size.inline,
),
violation(intrinsic_size.block, min_box_size.block, max_box_size.block),
) {
// Row 1.
(Violation::None, Violation::None) => (intrinsic_size.inline, intrinsic_size.block),
// Row 2.
(Violation::Above(max_inline_size), Violation::None) => {
let block_size = (max_inline_size / intrinsic_ratio).max(min_box_size.block);
(max_inline_size, block_size)
},
// Row 3.
(Violation::Below(min_inline_size), Violation::None) => {
let block_size =
clamp_below_max(min_inline_size / intrinsic_ratio, max_box_size.block);
(min_inline_size, block_size)
},
// Row 4.
(Violation::None, Violation::Above(max_block_size)) => {
let inline_size = (max_block_size * intrinsic_ratio).max(min_box_size.inline);
(inline_size, max_block_size)
},
// Row 5.
(Violation::None, Violation::Below(min_block_size)) => {
let inline_size =
clamp_below_max(min_block_size * intrinsic_ratio, max_box_size.inline);
(inline_size, min_block_size)
},
// Rows 6-7.
(Violation::Above(max_inline_size), Violation::Above(max_block_size)) => {
if max_inline_size.px() / intrinsic_size.inline.px() <=
max_block_size.px() / intrinsic_size.block.px()
{
// Row 6.
let block_size =
(max_inline_size / intrinsic_ratio).max(min_box_size.block);
(max_inline_size, block_size)
} else {
// Row 7.
let inline_size =
(max_block_size * intrinsic_ratio).max(min_box_size.inline);
(inline_size, max_block_size)
}
},
// Rows 8-9.
(Violation::Below(min_inline_size), Violation::Below(min_block_size)) => {
if min_inline_size.px() / intrinsic_size.inline.px() <=
min_block_size.px() / intrinsic_size.block.px()
{
// Row 8.
let inline_size =
clamp_below_max(min_block_size * intrinsic_ratio, max_box_size.inline);
(inline_size, min_block_size)
} else {
// Row 9.
let block_size =
clamp_below_max(min_inline_size / intrinsic_ratio, max_box_size.block);
(min_inline_size, block_size)
}
},
// Row 10.
(Violation::Below(min_inline_size), Violation::Above(max_block_size)) => {
(min_inline_size, max_block_size)
},
// Row 11.
(Violation::Above(max_inline_size), Violation::Below(min_block_size)) => {
(max_inline_size, min_block_size)
},
}
},
};
let (margin_inline_start, margin_inline_end) = solve_inline_margins_for_in_flow_block_level(
containing_block,
pb.inline_sum(),
computed_margin.inline_start,
computed_margin.inline_end,
inline_size,
);
let margin = Sides {
inline_start: margin_inline_start,
inline_end: margin_inline_end,
block_start: computed_margin.block_start.auto_is(Length::zero),
block_end: computed_margin.block_end.auto_is(Length::zero),
};
let containing_block_for_children = ContainingBlock {
inline_size,
block_size: LengthOrAuto::LengthPercentage(block_size),
mode,
};
// https://drafts.csswg.org/css-writing-modes/#orthogonal-flows
assert_eq!(
containing_block.mode, containing_block_for_children.mode,
"Mixed writing modes are not supported yet"
);
let independent_layout = replaced.layout(style, &containing_block_for_children);
let relative_adjustement = relative_adjustement(
style,
inline_size,
LengthOrAuto::LengthPercentage(block_size),
);
let content_rect = Rect {
start_corner: Vec2 {
block: pb.block_start + relative_adjustement.block,
inline: pb.inline_start + relative_adjustement.inline + margin.inline_start,
},
size: Vec2 {
block: block_size,
inline: inline_size,
},
};
BoxFragment {
style: style.clone(),
children: independent_layout.fragments,
content_rect,
padding,
border,
block_margins_collapsed_with_children: CollapsedBlockMargins::from_margin(&margin),
margin,
}
}
fn solve_inline_margins_for_in_flow_block_level(
containing_block: &ContainingBlock,
padding_border_inline_sum: Length,
computed_margin_inline_start: LengthOrAuto,
computed_margin_inline_end: LengthOrAuto,
inline_size: Length,
) -> (Length, Length) {
let inline_margins = containing_block.inline_size - padding_border_inline_sum - inline_size;
match (computed_margin_inline_start, computed_margin_inline_end) {
(LengthOrAuto::Auto, LengthOrAuto::Auto) => (inline_margins / 2., inline_margins / 2.),
(LengthOrAuto::Auto, LengthOrAuto::LengthPercentage(end)) => (inline_margins - end, end),
(LengthOrAuto::LengthPercentage(start), _) => (start, inline_margins - start),
}
}
fn clamp_between_extremums(size: Length, min_size: Length, max_size: Option<Length>) -> Length {
clamp_below_max(size, max_size).max(min_size)
}
fn clamp_below_max(size: Length, max_size: Option<Length>) -> Length {
max_size.map_or(size, |max_size| size.min(max_size))
}
fn percent_resolved_box_size(
box_size: Vec2<LengthPercentageOrAuto>,
containing_block: &ContainingBlock,
) -> Vec2<LengthOrAuto> {
Vec2 {
inline: box_size
.inline
.percentage_relative_to(containing_block.inline_size),
block: box_size
.block
.maybe_percentage_relative_to(containing_block.block_size.non_auto()),
}
}
fn percent_resolved_max_box_size(
max_box_size: Vec2<MaxSize<LengthPercentage>>,
containing_block: &ContainingBlock,
) -> Vec2<Option<Length>> {
Vec2 {
inline: match max_box_size.inline {
MaxSize::LengthPercentage(max_inline_size) => {
Some(max_inline_size.percentage_relative_to(containing_block.inline_size))
},
MaxSize::None => None,
},
block: match max_box_size.block {
MaxSize::LengthPercentage(max_block_size) => {
max_block_size.maybe_percentage_relative_to(containing_block.block_size.non_auto())
},
MaxSize::None => None,
},
}
}