mirror of
https://github.com/servo/servo.git
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c3b1c92ac1
Instead of painting hoisted position fragments in the order to which they are hoisted, paint them in tree order and properly incorporate them into the stacking context. We do this by creating a placeholder fragment in the original tree position of hoisted fragments. The ghost fragment contains an atomic id which links back to the hoisted fragment in the containing block. While building the stacking context, we keep track of containing blocks and their children. When encountering a placeholder fragment we look at the containing block's hoisted children in order to properly paint the hoisted fragment. One notable design modification in this change is that hoisted fragments no longer need an AnonymousFragment as their parent. Instead they are now direct children of the fragment that establishes their containing block.
572 lines
22 KiB
Rust
572 lines
22 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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//! Flow layout, also known as block-and-inline layout.
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use crate::context::LayoutContext;
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use crate::flow::float::{FloatBox, FloatContext};
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use crate::flow::inline::InlineFormattingContext;
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use crate::formatting_contexts::{IndependentFormattingContext, IndependentLayout, NonReplacedIFC};
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use crate::fragments::{AbsoluteOrFixedPositionedFragment, AnonymousFragment, BoxFragment};
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use crate::fragments::{CollapsedBlockMargins, CollapsedMargin, Fragment};
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use crate::geom::flow_relative::{Rect, Sides, Vec2};
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use crate::positioned::{AbsolutelyPositionedBox, PositioningContext};
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use crate::replaced::ReplacedContent;
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use crate::style_ext::ComputedValuesExt;
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use crate::ContainingBlock;
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use rayon::iter::{IndexedParallelIterator, IntoParallelRefIterator, ParallelIterator};
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use rayon_croissant::ParallelIteratorExt;
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use servo_arc::Arc;
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use style::dom::OpaqueNode;
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use style::properties::ComputedValues;
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use style::values::computed::{Length, LengthOrAuto};
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use style::Zero;
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mod construct;
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mod float;
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pub mod inline;
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mod root;
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pub use root::{BoxTreeRoot, FragmentTreeRoot};
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#[derive(Debug, Serialize)]
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pub(crate) struct BlockFormattingContext {
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pub contents: BlockContainer,
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pub contains_floats: bool,
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}
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#[derive(Debug, Serialize)]
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pub(crate) enum BlockContainer {
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BlockLevelBoxes(Vec<Arc<BlockLevelBox>>),
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InlineFormattingContext(InlineFormattingContext),
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}
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#[derive(Debug, Serialize)]
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pub(crate) enum BlockLevelBox {
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SameFormattingContextBlock {
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tag: OpaqueNode,
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#[serde(skip_serializing)]
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style: Arc<ComputedValues>,
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contents: BlockContainer,
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},
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OutOfFlowAbsolutelyPositionedBox(AbsolutelyPositionedBox),
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OutOfFlowFloatBox(FloatBox),
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Independent(IndependentFormattingContext),
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}
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struct FlowLayout {
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pub fragments: Vec<Fragment>,
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pub content_block_size: Length,
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pub collapsible_margins_in_children: CollapsedBlockMargins,
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}
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#[derive(Clone, Copy)]
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struct CollapsibleWithParentStartMargin(bool);
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impl BlockFormattingContext {
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pub(super) fn layout<'a>(
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&'a self,
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layout_context: &LayoutContext,
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positioning_context: &mut PositioningContext<'a>,
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containing_block: &ContainingBlock,
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tree_rank: usize,
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) -> IndependentLayout {
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let mut float_context;
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let float_context = if self.contains_floats {
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float_context = FloatContext::new();
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Some(&mut float_context)
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} else {
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None
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};
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let flow_layout = self.contents.layout(
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layout_context,
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positioning_context,
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containing_block,
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tree_rank,
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float_context,
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CollapsibleWithParentStartMargin(false),
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);
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assert!(
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!flow_layout
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.collapsible_margins_in_children
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.collapsed_through
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);
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IndependentLayout {
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fragments: flow_layout.fragments,
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content_block_size: flow_layout.content_block_size +
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flow_layout.collapsible_margins_in_children.end.solve(),
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}
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}
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}
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impl BlockContainer {
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fn layout<'a>(
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&'a self,
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layout_context: &LayoutContext,
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positioning_context: &mut PositioningContext<'a>,
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containing_block: &ContainingBlock,
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tree_rank: usize,
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float_context: Option<&mut FloatContext>,
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collapsible_with_parent_start_margin: CollapsibleWithParentStartMargin,
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) -> FlowLayout {
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match self {
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BlockContainer::BlockLevelBoxes(child_boxes) => layout_block_level_children(
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layout_context,
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positioning_context,
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child_boxes,
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containing_block,
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tree_rank,
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float_context,
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collapsible_with_parent_start_margin,
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),
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BlockContainer::InlineFormattingContext(ifc) => ifc.layout(
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layout_context,
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positioning_context,
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containing_block,
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tree_rank,
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),
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}
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}
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}
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fn layout_block_level_children<'a>(
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layout_context: &LayoutContext,
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positioning_context: &mut PositioningContext<'a>,
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child_boxes: &'a [Arc<BlockLevelBox>],
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containing_block: &ContainingBlock,
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tree_rank: usize,
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mut float_context: Option<&mut FloatContext>,
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collapsible_with_parent_start_margin: CollapsibleWithParentStartMargin,
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) -> FlowLayout {
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fn place_block_level_fragment(fragment: &mut Fragment, placement_state: &mut PlacementState) {
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match fragment {
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Fragment::Box(fragment) => {
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let fragment_block_margins = &fragment.block_margins_collapsed_with_children;
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let fragment_block_size = fragment.padding.block_sum() +
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fragment.border.block_sum() +
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fragment.content_rect.size.block;
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if placement_state.next_in_flow_margin_collapses_with_parent_start_margin {
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assert_eq!(placement_state.current_margin.solve(), Length::zero());
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placement_state
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.start_margin
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.adjoin_assign(&fragment_block_margins.start);
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if fragment_block_margins.collapsed_through {
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placement_state
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.start_margin
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.adjoin_assign(&fragment_block_margins.end);
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return;
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}
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placement_state.next_in_flow_margin_collapses_with_parent_start_margin = false;
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} else {
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placement_state
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.current_margin
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.adjoin_assign(&fragment_block_margins.start);
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}
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fragment.content_rect.start_corner.block += placement_state.current_margin.solve() +
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placement_state.current_block_direction_position;
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if fragment_block_margins.collapsed_through {
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placement_state
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.current_margin
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.adjoin_assign(&fragment_block_margins.end);
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return;
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}
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placement_state.current_block_direction_position +=
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placement_state.current_margin.solve() + fragment_block_size;
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placement_state.current_margin = fragment_block_margins.end;
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},
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Fragment::Anonymous(_) | Fragment::AbsoluteOrFixedPositioned(_) => {},
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_ => unreachable!(),
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}
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}
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struct PlacementState {
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next_in_flow_margin_collapses_with_parent_start_margin: bool,
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start_margin: CollapsedMargin,
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current_margin: CollapsedMargin,
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current_block_direction_position: Length,
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}
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let mut placement_state = PlacementState {
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next_in_flow_margin_collapses_with_parent_start_margin:
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collapsible_with_parent_start_margin.0,
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start_margin: CollapsedMargin::zero(),
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current_margin: CollapsedMargin::zero(),
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current_block_direction_position: Length::zero(),
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};
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let fragments = positioning_context.adjust_static_positions(tree_rank, |positioning_context| {
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if float_context.is_some() || !layout_context.use_rayon {
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// Because floats are involved, we do layout for this block formatting context
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// in tree order without parallelism. This enables mutable access
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// to a `FloatContext` that tracks every float encountered so far (again in tree order).
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child_boxes
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.iter()
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.enumerate()
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.map(|(tree_rank, box_)| {
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let mut fragment = box_.layout(
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layout_context,
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positioning_context,
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containing_block,
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tree_rank,
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float_context.as_mut().map(|c| &mut **c),
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);
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place_block_level_fragment(&mut fragment, &mut placement_state);
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fragment
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})
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.collect()
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} else {
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let collects_for_nearest_positioned_ancestor =
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positioning_context.collects_for_nearest_positioned_ancestor();
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let mut fragments = child_boxes
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.par_iter()
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.enumerate()
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.mapfold_reduce_into(
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positioning_context,
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|positioning_context, (tree_rank, box_)| {
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box_.layout(
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layout_context,
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positioning_context,
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containing_block,
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tree_rank,
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/* float_context = */ None,
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)
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},
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|| PositioningContext::new_for_rayon(collects_for_nearest_positioned_ancestor),
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PositioningContext::append,
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)
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.collect();
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for fragment in &mut fragments {
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place_block_level_fragment(fragment, &mut placement_state)
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}
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fragments
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}
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});
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FlowLayout {
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fragments,
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content_block_size: placement_state.current_block_direction_position,
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collapsible_margins_in_children: CollapsedBlockMargins {
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collapsed_through: placement_state
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.next_in_flow_margin_collapses_with_parent_start_margin,
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start: placement_state.start_margin,
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end: placement_state.current_margin,
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},
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}
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}
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impl BlockLevelBox {
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fn layout<'a>(
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&'a self,
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layout_context: &LayoutContext,
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positioning_context: &mut PositioningContext<'a>,
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containing_block: &ContainingBlock,
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tree_rank: usize,
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float_context: Option<&mut FloatContext>,
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) -> Fragment {
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match self {
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BlockLevelBox::SameFormattingContextBlock {
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tag,
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style,
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contents,
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} => Fragment::Box(positioning_context.layout_maybe_position_relative_fragment(
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layout_context,
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containing_block,
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style,
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|positioning_context| {
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layout_in_flow_non_replaced_block_level(
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layout_context,
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positioning_context,
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containing_block,
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*tag,
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style,
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NonReplacedContents::SameFormattingContextBlock(contents),
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tree_rank,
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float_context,
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)
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},
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)),
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BlockLevelBox::Independent(contents) => {
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Fragment::Box(positioning_context.layout_maybe_position_relative_fragment(
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layout_context,
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containing_block,
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&contents.style,
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|positioning_context| match contents.as_replaced() {
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Ok(replaced) => layout_in_flow_replaced_block_level(
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containing_block,
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contents.tag,
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&contents.style,
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replaced,
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),
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Err(non_replaced) => layout_in_flow_non_replaced_block_level(
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layout_context,
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positioning_context,
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containing_block,
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contents.tag,
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&contents.style,
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NonReplacedContents::EstablishesAnIndependentFormattingContext(
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non_replaced,
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),
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tree_rank,
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float_context,
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),
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},
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))
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},
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BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(box_) => {
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let hoisted_fragment = box_.to_hoisted(Vec2::zero(), tree_rank);
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let hoisted_fragment_id = hoisted_fragment.fragment_id.clone();
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positioning_context.push(hoisted_fragment);
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Fragment::AbsoluteOrFixedPositioned(AbsoluteOrFixedPositionedFragment(
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hoisted_fragment_id,
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))
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},
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BlockLevelBox::OutOfFlowFloatBox(_box_) => {
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// FIXME: call layout_maybe_position_relative_fragment here
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Fragment::Anonymous(AnonymousFragment::no_op(
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containing_block.style.writing_mode,
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))
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},
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}
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}
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}
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enum NonReplacedContents<'a> {
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SameFormattingContextBlock(&'a BlockContainer),
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EstablishesAnIndependentFormattingContext(NonReplacedIFC<'a>),
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}
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/// https://drafts.csswg.org/css2/visudet.html#blockwidth
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/// https://drafts.csswg.org/css2/visudet.html#normal-block
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fn layout_in_flow_non_replaced_block_level<'a>(
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layout_context: &LayoutContext,
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positioning_context: &mut PositioningContext<'a>,
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containing_block: &ContainingBlock,
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tag: OpaqueNode,
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style: &Arc<ComputedValues>,
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block_level_kind: NonReplacedContents<'a>,
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tree_rank: usize,
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float_context: Option<&mut FloatContext>,
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) -> BoxFragment {
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let cbis = containing_block.inline_size;
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let padding = style.padding().percentages_relative_to(cbis);
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let border = style.border_width();
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let margin = style.margin().percentages_relative_to(cbis);
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let pb = &padding + &border;
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let pb_inline_sum = pb.inline_sum();
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let box_size = style.box_size().percentages_relative_to(containing_block);
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let max_box_size = style
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.max_box_size()
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.percentages_relative_to(containing_block);
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let min_box_size = style
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.min_box_size()
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.percentages_relative_to(containing_block)
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.auto_is(Length::zero);
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// https://drafts.csswg.org/css2/visudet.html#min-max-widths
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let solve_inline_margins = |inline_size| {
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solve_inline_margins_for_in_flow_block_level(
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containing_block,
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pb_inline_sum,
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margin.inline_start,
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margin.inline_end,
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inline_size,
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)
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};
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let (mut inline_size, mut inline_margins) =
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if let Some(inline_size) = box_size.inline.non_auto() {
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(inline_size, solve_inline_margins(inline_size))
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} else {
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let margin_inline_start = margin.inline_start.auto_is(Length::zero);
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let margin_inline_end = margin.inline_end.auto_is(Length::zero);
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let margin_inline_sum = margin_inline_start + margin_inline_end;
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let inline_size = cbis - pb_inline_sum - margin_inline_sum;
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(inline_size, (margin_inline_start, margin_inline_end))
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};
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if let Some(max_inline_size) = max_box_size.inline {
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if inline_size > max_inline_size {
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inline_size = max_inline_size;
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inline_margins = solve_inline_margins(inline_size);
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}
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}
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if inline_size < min_box_size.inline {
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inline_size = min_box_size.inline;
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inline_margins = solve_inline_margins(inline_size);
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}
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let margin = Sides {
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inline_start: inline_margins.0,
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inline_end: inline_margins.1,
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block_start: margin.block_start.auto_is(Length::zero),
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block_end: margin.block_end.auto_is(Length::zero),
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};
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// https://drafts.csswg.org/css2/visudet.html#min-max-heights
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let mut block_size = box_size.block;
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if let LengthOrAuto::LengthPercentage(ref mut block_size) = block_size {
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*block_size = block_size.clamp_between_extremums(min_box_size.block, max_box_size.block);
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}
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let containing_block_for_children = ContainingBlock {
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inline_size,
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block_size,
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style,
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};
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// https://drafts.csswg.org/css-writing-modes/#orthogonal-flows
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assert_eq!(
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containing_block.style.writing_mode, containing_block_for_children.style.writing_mode,
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"Mixed writing modes are not supported yet"
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);
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let mut block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
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let fragments;
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let mut content_block_size;
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match block_level_kind {
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NonReplacedContents::SameFormattingContextBlock(contents) => {
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let this_start_margin_can_collapse_with_children = pb.block_start == Length::zero();
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let this_end_margin_can_collapse_with_children = pb.block_end == Length::zero() &&
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block_size == LengthOrAuto::Auto &&
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min_box_size.block == Length::zero();
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let flow_layout = contents.layout(
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layout_context,
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positioning_context,
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&containing_block_for_children,
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tree_rank,
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float_context,
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CollapsibleWithParentStartMargin(this_start_margin_can_collapse_with_children),
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);
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fragments = flow_layout.fragments;
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content_block_size = flow_layout.content_block_size;
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let mut collapsible_margins_in_children = flow_layout.collapsible_margins_in_children;
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if this_start_margin_can_collapse_with_children {
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block_margins_collapsed_with_children
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.start
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.adjoin_assign(&collapsible_margins_in_children.start);
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if collapsible_margins_in_children.collapsed_through {
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block_margins_collapsed_with_children
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.start
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.adjoin_assign(&std::mem::replace(
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&mut collapsible_margins_in_children.end,
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CollapsedMargin::zero(),
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));
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}
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}
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if this_end_margin_can_collapse_with_children {
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block_margins_collapsed_with_children
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.end
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.adjoin_assign(&collapsible_margins_in_children.end);
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} else {
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content_block_size += collapsible_margins_in_children.end.solve();
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}
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block_margins_collapsed_with_children.collapsed_through =
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this_start_margin_can_collapse_with_children &&
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this_end_margin_can_collapse_with_children &&
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collapsible_margins_in_children.collapsed_through;
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},
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NonReplacedContents::EstablishesAnIndependentFormattingContext(non_replaced) => {
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let independent_layout = non_replaced.layout(
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layout_context,
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positioning_context,
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&containing_block_for_children,
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tree_rank,
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);
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fragments = independent_layout.fragments;
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content_block_size = independent_layout.content_block_size;
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},
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};
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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: pb.block_start,
|
|
inline: pb.inline_start,
|
|
},
|
|
size: Vec2 {
|
|
block: block_size,
|
|
inline: inline_size,
|
|
},
|
|
};
|
|
BoxFragment::new(
|
|
tag,
|
|
style.clone(),
|
|
fragments,
|
|
content_rect,
|
|
padding,
|
|
border,
|
|
margin,
|
|
block_margins_collapsed_with_children,
|
|
None, // hoisted_fragment_id
|
|
)
|
|
}
|
|
|
|
/// 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,
|
|
tag: OpaqueNode,
|
|
style: &Arc<ComputedValues>,
|
|
replaced: &ReplacedContent,
|
|
) -> BoxFragment {
|
|
let size = replaced.used_size_as_if_inline_element(containing_block, style);
|
|
|
|
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 (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,
|
|
size.inline,
|
|
);
|
|
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 fragments = replaced.make_fragments(style, size.clone());
|
|
let content_rect = Rect {
|
|
start_corner: Vec2 {
|
|
block: pb.block_start,
|
|
inline: pb.inline_start + margin.inline_start,
|
|
},
|
|
size,
|
|
};
|
|
let block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
|
|
BoxFragment::new(
|
|
tag,
|
|
style.clone(),
|
|
fragments,
|
|
content_rect,
|
|
padding,
|
|
border,
|
|
margin,
|
|
block_margins_collapsed_with_children,
|
|
None, // hoisted_fragment_id
|
|
)
|
|
}
|
|
|
|
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),
|
|
}
|
|
}
|