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8299868bd5
This makes the names of flow relative geometry consistent with what is used in the style crate and removes them from a module. With this change it's more obvious what makes these types different from the ones in `euclid`.
1188 lines
48 KiB
Rust
1188 lines
48 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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//! Float layout.
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//!
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//! See CSS 2.1 § 9.5.1: https://www.w3.org/TR/CSS2/visuren.html#float-position
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use std::collections::VecDeque;
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use std::fmt::{Debug, Formatter, Result as FmtResult};
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use std::ops::Range;
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use std::{f32, mem};
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use euclid::num::Zero;
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use serde::Serialize;
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use servo_arc::Arc;
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use style::computed_values::float::T as FloatProperty;
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use style::properties::ComputedValues;
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use style::values::computed::{CSSPixelLength, Clear, Length};
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use style::values::specified::text::TextDecorationLine;
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use crate::context::LayoutContext;
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use crate::dom::NodeExt;
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use crate::dom_traversal::{Contents, NodeAndStyleInfo};
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use crate::formatting_contexts::IndependentFormattingContext;
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use crate::fragment_tree::{BoxFragment, CollapsedBlockMargins, CollapsedMargin, FloatFragment};
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use crate::geom::{LogicalRect, LogicalVec2};
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use crate::positioned::PositioningContext;
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use crate::style_ext::{ComputedValuesExt, DisplayInside, PaddingBorderMargin};
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use crate::ContainingBlock;
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/// A floating box.
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#[derive(Debug, Serialize)]
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pub(crate) struct FloatBox {
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/// The formatting context that makes up the content of this box.
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pub contents: IndependentFormattingContext,
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}
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/// `FloatContext` positions floats relative to the independent block formatting
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/// context which contains the floating elements. The Fragment tree positions
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/// elements relative to their containing blocks. This data structure is used to
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/// help map between these two coordinate systems.
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#[derive(Clone, Copy, Debug)]
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pub struct ContainingBlockPositionInfo {
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/// The distance from the block start of the independent block formatting
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/// context that contains the floats and the block start of the current
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/// containing block, excluding uncollapsed block start margins. Note that
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/// this does not include uncollapsed block start margins because we don't
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/// know the value of collapsed margins until we lay out children.
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pub(crate) block_start: Length,
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/// Any uncollapsed block start margins that we have collected between the
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/// block start of the float containing independent block formatting context
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/// and this containing block, including for this containing block.
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pub(crate) block_start_margins_not_collapsed: CollapsedMargin,
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/// The distance from the inline start position of the float containing
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/// independent formatting context and the inline start of this containing
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/// block.
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pub inline_start: Length,
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/// The offset from the inline start position of the float containing
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/// independent formatting context to the inline end of this containing
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/// block.
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pub inline_end: Length,
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}
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impl ContainingBlockPositionInfo {
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pub fn new_with_inline_offsets(inline_start: Length, inline_end: Length) -> Self {
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Self {
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block_start: Length::zero(),
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block_start_margins_not_collapsed: CollapsedMargin::zero(),
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inline_start,
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inline_end,
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}
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}
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}
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/// This data strucure is used to try to place non-floating content among float content.
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/// This is used primarily to place replaced content and independent formatting contexts
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/// next to floats, as the specifcation dictates.
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pub(crate) struct PlacementAmongFloats<'a> {
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/// The [FloatContext] to use for this placement.
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float_context: &'a FloatContext,
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/// The current bands we are considering for this placement.
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current_bands: VecDeque<FloatBand>,
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/// The next band, needed to know the height of the last band in current_bands.
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next_band: FloatBand,
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/// The size of the object to place.
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object_size: LogicalVec2<Length>,
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/// The minimum position in the block direction for the placement. Objects should not
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/// be placed before this point.
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ceiling: Length,
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/// The inline position where the object would be if there were no floats. The object
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/// can be placed after it due to floats, but not before it.
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min_inline_start: Length,
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/// The maximum inline position that the object can attain when avoiding floats.
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max_inline_end: Length,
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}
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impl<'a> PlacementAmongFloats<'a> {
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pub(crate) fn new(
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float_context: &'a FloatContext,
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ceiling: Length,
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object_size: LogicalVec2<Length>,
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pbm: &PaddingBorderMargin,
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) -> Self {
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assert!(!ceiling.px().is_infinite());
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let mut current_band = float_context.bands.find(ceiling).unwrap();
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current_band.top = ceiling;
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let current_bands = VecDeque::from([current_band]);
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let next_band = float_context.bands.find_next(ceiling).unwrap();
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let min_inline_start = float_context.containing_block_info.inline_start +
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pbm.margin.inline_start.auto_is(Length::zero);
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let max_inline_end = (float_context.containing_block_info.inline_end -
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pbm.margin.inline_end.auto_is(Length::zero))
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.max(min_inline_start + object_size.inline);
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PlacementAmongFloats {
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float_context,
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current_bands,
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next_band,
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object_size,
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ceiling,
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min_inline_start,
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max_inline_end,
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}
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}
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/// The top of the bands under consideration. This is initially the ceiling provided
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/// during creation of this [`PlacementAmongFloats`], but may be larger if the top
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/// band is discarded.
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fn top_of_bands(&self) -> Option<Length> {
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self.current_bands.front().map(|band| band.top)
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}
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/// The height of the bands under consideration.
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fn current_bands_height(&self) -> Length {
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if let Some(top) = self.top_of_bands() {
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self.next_band.top - top
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} else {
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assert!(self.next_band.top.px().is_infinite());
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self.next_band.top
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}
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}
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/// Add a single band to the bands under consideration and calculate the new
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/// [`PlacementAmongFloats::next_band`].
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fn add_one_band(&mut self) {
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assert!(!self.next_band.top.px().is_infinite());
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self.current_bands.push_back(self.next_band);
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self.next_band = self
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.float_context
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.bands
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.find_next(self.next_band.top)
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.unwrap();
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}
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/// Adds bands to the set of bands under consideration until their block size is at
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/// least large enough to contain the block size of the object being placed.
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fn accumulate_enough_bands_for_block_size(&mut self) {
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while self.current_bands_height() < self.object_size.block {
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self.add_one_band();
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}
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}
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/// Find the start and end of the inline space provided by the current set of bands
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/// under consideration.
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fn calculate_inline_start_and_end(&self) -> (Length, Length) {
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let mut max_inline_start = self.min_inline_start;
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let mut min_inline_end = self.max_inline_end;
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for band in self.current_bands.iter() {
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if let Some(left) = band.left {
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max_inline_start = max_inline_start.max(left);
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}
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if let Some(right) = band.right {
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min_inline_end = min_inline_end.min(right);
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}
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}
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return (max_inline_start, min_inline_end);
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}
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/// Find the total inline size provided by the current set of bands under consideration.
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fn calculate_viable_inline_size(&self) -> Length {
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let (inline_start, inline_end) = self.calculate_inline_start_and_end();
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inline_end - inline_start
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}
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fn try_place_once(&mut self) -> Option<LogicalRect<Length>> {
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assert!(!self.current_bands.is_empty());
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self.accumulate_enough_bands_for_block_size();
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let (inline_start, inline_end) = self.calculate_inline_start_and_end();
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let available_inline_size = inline_end - inline_start;
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if available_inline_size < self.object_size.inline {
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return None;
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}
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let top = self.top_of_bands().unwrap();
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Some(LogicalRect {
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start_corner: LogicalVec2 {
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inline: inline_start,
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block: top,
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},
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size: LogicalVec2 {
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inline: available_inline_size,
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block: self.next_band.top - top,
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},
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})
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}
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/// Checks if we either have bands or we have gone past all of them.
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/// This is an invariant that should hold, otherwise we are in a broken state.
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fn has_bands_or_at_end(&self) -> bool {
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!self.current_bands.is_empty() || self.next_band.top.px().is_infinite()
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}
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fn pop_front_band_ensuring_has_bands_or_at_end(&mut self) {
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self.current_bands.pop_front();
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if !self.has_bands_or_at_end() {
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self.add_one_band();
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}
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}
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/// Run the placement algorithm for this [PlacementAmongFloats].
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pub(crate) fn place(&mut self) -> LogicalRect<Length> {
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debug_assert!(self.has_bands_or_at_end());
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while !self.current_bands.is_empty() {
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if let Some(result) = self.try_place_once() {
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return result;
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}
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self.pop_front_band_ensuring_has_bands_or_at_end();
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}
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debug_assert!(self.has_bands_or_at_end());
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// We could not fit the object in among the floats, so we place it as if it
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// cleared all floats.
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LogicalRect {
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start_corner: LogicalVec2 {
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inline: self.min_inline_start,
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block: self
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.ceiling
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.max(self.float_context.clear_left_position)
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.max(self.float_context.clear_right_position),
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},
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size: LogicalVec2 {
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inline: self.max_inline_end - self.min_inline_start,
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block: Length::new(f32::INFINITY),
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},
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}
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}
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/// After placing an object with `height: auto` (and using the minimum inline and
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/// block size as the object size) and then laying it out, try to fit the object into
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/// the current set of bands, given block size after layout and the available inline
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/// space from the original placement. This will return true if the object fits at the
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/// original placement location or false if the placement and layout must be run again
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/// (with this [PlacementAmongFloats]).
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pub(crate) fn try_to_expand_for_auto_block_size(
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&mut self,
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block_size_after_layout: Length,
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size_from_placement: &LogicalVec2<Length>,
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) -> bool {
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debug_assert!(self.has_bands_or_at_end());
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debug_assert_eq!(size_from_placement.block, self.current_bands_height());
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debug_assert_eq!(
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size_from_placement.inline,
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self.calculate_viable_inline_size()
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);
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// If the object after layout fits into the originally calculated placement, then
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// it fits without any more work.
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if block_size_after_layout <= size_from_placement.block {
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return true;
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}
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// Keep searching until we have found an area with enough height
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// to contain the block after layout.
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let old_num_bands = self.current_bands.len();
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assert!(old_num_bands > 0);
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while self.current_bands_height() < block_size_after_layout {
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self.add_one_band();
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// If the new inline size is narrower, we must stop and run layout again.
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// Normally, a narrower block size means a bigger height, but in some
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// circumstances, such as when aspect ratio is used a narrower inline size
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// can counter-interuitively lead to a smaller block size after layout!
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let available_inline_size = self.calculate_viable_inline_size();
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if available_inline_size < size_from_placement.inline {
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// If the inline size becomes smaller than the minimum inline size, then
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// the current set of bands will never work and we must try removing the
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// first and searching starting from the second.
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if available_inline_size < self.object_size.inline {
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self.next_band = self.current_bands[old_num_bands];
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self.current_bands.truncate(old_num_bands);
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self.pop_front_band_ensuring_has_bands_or_at_end();
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}
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return false;
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}
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}
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true
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}
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}
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/// Data kept during layout about the floats in a given block formatting context.
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///
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/// This is a persistent data structure. Each float has its own private copy of the float context,
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/// although such copies may share portions of the `bands` tree.
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#[derive(Clone, Debug)]
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pub struct FloatContext {
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/// A persistent AA tree of float bands.
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///
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/// This tree is immutable; modification operations return the new tree, which may share nodes
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/// with previous versions of the tree.
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pub bands: FloatBandTree,
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/// The current (logically) vertical position. No new floats may be placed (logically) above
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/// this line.
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pub ceiling: Length,
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/// Details about the position of the containing block relative to the
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/// independent block formatting context that contains all of the floats
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/// this `FloatContext` positions.
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pub containing_block_info: ContainingBlockPositionInfo,
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/// The (logically) lowest margin edge of the last left float.
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pub clear_left_position: Length,
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/// The (logically) lowest margin edge of the last right float.
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pub clear_right_position: Length,
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}
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impl FloatContext {
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/// Returns a new float context representing a containing block with the given content
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/// inline-size.
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pub fn new(max_inline_size: Length) -> Self {
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let mut bands = FloatBandTree::new();
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bands = bands.insert(FloatBand {
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top: Length::new(-f32::INFINITY),
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left: None,
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right: None,
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});
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bands = bands.insert(FloatBand {
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top: Length::new(f32::INFINITY),
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left: None,
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right: None,
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});
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FloatContext {
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bands,
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ceiling: Length::zero(),
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containing_block_info: ContainingBlockPositionInfo::new_with_inline_offsets(
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Length::zero(),
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max_inline_size,
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),
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clear_left_position: Length::zero(),
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clear_right_position: Length::zero(),
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}
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}
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/// (Logically) lowers the ceiling to at least `new_ceiling` units.
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///
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/// If the ceiling is already logically lower (i.e. larger) than this, does nothing.
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pub fn lower_ceiling(&mut self, new_ceiling: Length) {
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self.ceiling = self.ceiling.max(new_ceiling);
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}
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/// Determines where a float with the given placement would go, but leaves the float context
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/// unmodified. Returns the start corner of its margin box.
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///
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/// This should be used for placing inline elements and block formatting contexts so that they
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/// don't collide with floats.
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pub(crate) fn place_object(
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&self,
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object: &PlacementInfo,
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ceiling: Length,
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) -> LogicalVec2<Length> {
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let ceiling = match object.clear {
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Clear::None => ceiling,
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Clear::Left => ceiling.max(self.clear_left_position),
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Clear::Right => ceiling.max(self.clear_right_position),
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Clear::Both => ceiling
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.max(self.clear_left_position)
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.max(self.clear_right_position),
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};
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// Find the first band this float fits in.
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let mut first_band = self.bands.find(ceiling).unwrap();
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while !first_band.object_fits(&object, &self.containing_block_info) {
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let next_band = self.bands.find_next(first_band.top).unwrap();
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if next_band.top.px().is_infinite() {
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break;
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}
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first_band = next_band;
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}
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// The object fits perfectly here. Place it.
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match object.side {
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FloatSide::Left => {
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let left_object_edge = match first_band.left {
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Some(band_left) => band_left.max(self.containing_block_info.inline_start),
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None => self.containing_block_info.inline_start,
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};
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LogicalVec2 {
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inline: left_object_edge,
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block: first_band.top.max(ceiling),
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}
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},
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FloatSide::Right => {
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let right_object_edge = match first_band.right {
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Some(band_right) => band_right.min(self.containing_block_info.inline_end),
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None => self.containing_block_info.inline_end,
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};
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LogicalVec2 {
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inline: right_object_edge - object.size.inline,
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block: first_band.top.max(ceiling),
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}
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},
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}
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}
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/// Places a new float and adds it to the list. Returns the start corner of its margin box.
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pub fn add_float(&mut self, new_float: &PlacementInfo) -> LogicalVec2<Length> {
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// Place the float.
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let new_float_origin = self.place_object(&new_float, self.ceiling);
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let new_float_extent = match new_float.side {
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FloatSide::Left => new_float_origin.inline + new_float.size.inline,
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FloatSide::Right => new_float_origin.inline,
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};
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let new_float_rect = LogicalRect {
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start_corner: new_float_origin,
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// If this float has a negative margin, we should only consider its non-negative
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// block size contribution when determing where to place it. When the margin is
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// so negative that it's placed completely above the current float ceiling, then
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// we should position it as if it had zero block size.
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size: LogicalVec2 {
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inline: new_float.size.inline.max(CSSPixelLength::zero()),
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block: new_float.size.block.max(CSSPixelLength::zero()),
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},
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};
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// Update clear.
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match new_float.side {
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FloatSide::Left => {
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self.clear_left_position = self
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.clear_left_position
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.max(new_float_rect.max_block_position())
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},
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FloatSide::Right => {
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self.clear_right_position = self
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.clear_right_position
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.max(new_float_rect.max_block_position())
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},
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}
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// Split the first band if necessary.
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let mut first_band = self.bands.find(new_float_rect.start_corner.block).unwrap();
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first_band.top = new_float_rect.start_corner.block;
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self.bands = self.bands.insert(first_band);
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// Split the last band if necessary.
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let mut last_band = self
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.bands
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.find(new_float_rect.max_block_position())
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.unwrap();
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last_band.top = new_float_rect.max_block_position();
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self.bands = self.bands.insert(last_band);
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// Update all bands that contain this float to reflect the new available size.
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let block_range = new_float_rect.start_corner.block..new_float_rect.max_block_position();
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self.bands = self
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.bands
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.set_range(&block_range, new_float.side, new_float_extent);
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// CSS 2.1 § 9.5.1 rule 6: The outer top of a floating box may not be higher than the outer
|
|
// top of any block or floated box generated by an element earlier in the source document.
|
|
self.ceiling = self.ceiling.max(new_float_rect.start_corner.block);
|
|
new_float_rect.start_corner
|
|
}
|
|
}
|
|
|
|
/// Information needed to place an object so that it doesn't collide with existing floats.
|
|
#[derive(Clone, Debug)]
|
|
pub struct PlacementInfo {
|
|
/// The *margin* box size of the object.
|
|
pub size: LogicalVec2<Length>,
|
|
/// Whether the object is (logically) aligned to the left or right.
|
|
pub side: FloatSide,
|
|
/// Which side or sides to clear floats on.
|
|
pub clear: Clear,
|
|
}
|
|
|
|
/// Whether the float is left or right.
|
|
///
|
|
/// See CSS 2.1 § 9.5.1: https://www.w3.org/TR/CSS2/visuren.html#float-position
|
|
#[derive(Clone, Copy, Debug, PartialEq)]
|
|
pub enum FloatSide {
|
|
Left,
|
|
Right,
|
|
}
|
|
|
|
/// Internal data structure that describes a nonoverlapping vertical region in which floats may be
|
|
/// placed. Floats must go between "left edge + `left`" and "right edge - `right`".
|
|
#[derive(Clone, Copy, Debug, PartialEq)]
|
|
pub struct FloatBand {
|
|
/// The logical vertical position of the top of this band.
|
|
pub top: Length,
|
|
/// The distance from the left edge of the block formatting context to the first legal
|
|
/// (logically) horizontal position where floats may be placed. If `None`, there are no floats
|
|
/// to the left; distinguishing between the cases of "a zero-width float is present" and "no
|
|
/// floats at all are present" is necessary to, for example, clear past zero-width floats.
|
|
pub left: Option<Length>,
|
|
/// The distance from the *left* edge of the block formatting context to the first legal
|
|
/// (logically) horizontal position where floats may be placed. If `None`, there are no floats
|
|
/// to the right; distinguishing between the cases of "a zero-width float is present" and "no
|
|
/// floats at all are present" is necessary to, for example, clear past zero-width floats.
|
|
pub right: Option<Length>,
|
|
}
|
|
|
|
impl FloatSide {
|
|
fn from_style(style: &ComputedValues) -> Option<FloatSide> {
|
|
match style.get_box().float {
|
|
FloatProperty::None => None,
|
|
FloatProperty::Left => Some(FloatSide::Left),
|
|
FloatProperty::Right => Some(FloatSide::Right),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl FloatBand {
|
|
/// Determines whether an object fits in a band. Returns true if the object fits.
|
|
fn object_fits(&self, object: &PlacementInfo, walls: &ContainingBlockPositionInfo) -> bool {
|
|
match object.side {
|
|
FloatSide::Left => {
|
|
// Compute a candidate left position for the object.
|
|
let candidate_left = match self.left {
|
|
None => walls.inline_start,
|
|
Some(left) => left.max(walls.inline_start),
|
|
};
|
|
|
|
// If this band has an existing left float in it, then make sure that the object
|
|
// doesn't stick out past the right edge (rule 7).
|
|
if self.left.is_some() && candidate_left + object.size.inline > walls.inline_end {
|
|
return false;
|
|
}
|
|
|
|
// If this band has an existing right float in it, make sure we don't collide with
|
|
// it (rule 3).
|
|
match self.right {
|
|
None => true,
|
|
Some(right) => object.size.inline <= right - candidate_left,
|
|
}
|
|
},
|
|
|
|
FloatSide::Right => {
|
|
// Compute a candidate right position for the object.
|
|
let candidate_right = match self.right {
|
|
None => walls.inline_end,
|
|
Some(right) => right.min(walls.inline_end),
|
|
};
|
|
|
|
// If this band has an existing right float in it, then make sure that the new
|
|
// object doesn't stick out past the left edge (rule 7).
|
|
if self.right.is_some() && candidate_right - object.size.inline < walls.inline_start
|
|
{
|
|
return false;
|
|
}
|
|
|
|
// If this band has an existing left float in it, make sure we don't collide with
|
|
// it (rule 3).
|
|
match self.left {
|
|
None => true,
|
|
Some(left) => object.size.inline <= candidate_right - left,
|
|
}
|
|
},
|
|
}
|
|
}
|
|
}
|
|
|
|
// Float band storage
|
|
|
|
/// A persistent AA tree for float band storage.
|
|
///
|
|
/// Bands here are nonoverlapping, and there is guaranteed to be a band at block-position 0 and
|
|
/// another band at block-position infinity.
|
|
///
|
|
/// AA trees were chosen for simplicity.
|
|
///
|
|
/// See: https://en.wikipedia.org/wiki/AA_tree
|
|
/// https://arxiv.org/pdf/1412.4882.pdf
|
|
#[derive(Clone, Debug)]
|
|
pub struct FloatBandTree {
|
|
pub root: FloatBandLink,
|
|
}
|
|
|
|
/// A single edge (or lack thereof) in the float band tree.
|
|
#[derive(Clone, Debug)]
|
|
pub struct FloatBandLink(pub Option<Arc<FloatBandNode>>);
|
|
|
|
/// A single node in the float band tree.
|
|
#[derive(Clone, Debug)]
|
|
pub struct FloatBandNode {
|
|
/// The actual band.
|
|
pub band: FloatBand,
|
|
/// The left child.
|
|
pub left: FloatBandLink,
|
|
/// The right child.
|
|
pub right: FloatBandLink,
|
|
/// The level, which increases as you go up the tree.
|
|
///
|
|
/// This value is needed for tree balancing.
|
|
pub level: i32,
|
|
}
|
|
|
|
impl FloatBandTree {
|
|
/// Creates a new float band tree.
|
|
pub fn new() -> FloatBandTree {
|
|
FloatBandTree {
|
|
root: FloatBandLink(None),
|
|
}
|
|
}
|
|
|
|
/// Returns the first band whose top is less than or equal to the given `block_position`.
|
|
pub fn find(&self, block_position: Length) -> Option<FloatBand> {
|
|
self.root.find(block_position)
|
|
}
|
|
|
|
/// Returns the first band whose top is strictly greater than to the given `block_position`.
|
|
pub fn find_next(&self, block_position: Length) -> Option<FloatBand> {
|
|
self.root.find_next(block_position)
|
|
}
|
|
|
|
/// Sets the side values of all bands within the given half-open range to be at least
|
|
/// `new_value`.
|
|
#[must_use]
|
|
pub fn set_range(
|
|
&self,
|
|
range: &Range<Length>,
|
|
side: FloatSide,
|
|
new_value: Length,
|
|
) -> FloatBandTree {
|
|
FloatBandTree {
|
|
root: FloatBandLink(
|
|
self.root
|
|
.0
|
|
.as_ref()
|
|
.map(|root| root.set_range(range, side, new_value)),
|
|
),
|
|
}
|
|
}
|
|
|
|
/// Inserts a new band into the tree. If the band has the same level as a pre-existing one,
|
|
/// replaces the existing band with the new one.
|
|
#[must_use]
|
|
pub fn insert(&self, band: FloatBand) -> FloatBandTree {
|
|
FloatBandTree {
|
|
root: self.root.insert(band),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl FloatBandNode {
|
|
fn new(band: FloatBand) -> FloatBandNode {
|
|
FloatBandNode {
|
|
band,
|
|
left: FloatBandLink(None),
|
|
right: FloatBandLink(None),
|
|
level: 1,
|
|
}
|
|
}
|
|
|
|
/// Sets the side values of all bands within the given half-open range to be at least
|
|
/// `new_value`.
|
|
fn set_range(
|
|
&self,
|
|
range: &Range<Length>,
|
|
side: FloatSide,
|
|
new_value: Length,
|
|
) -> Arc<FloatBandNode> {
|
|
let mut new_band = self.band.clone();
|
|
if self.band.top >= range.start && self.band.top < range.end {
|
|
match side {
|
|
FloatSide::Left => match new_band.left {
|
|
None => new_band.left = Some(new_value),
|
|
Some(ref mut old_value) => *old_value = old_value.max(new_value),
|
|
},
|
|
FloatSide::Right => match new_band.right {
|
|
None => new_band.right = Some(new_value),
|
|
Some(ref mut old_value) => *old_value = old_value.min(new_value),
|
|
},
|
|
}
|
|
}
|
|
|
|
let new_left = match self.left.0 {
|
|
None => FloatBandLink(None),
|
|
Some(ref old_left) if range.start < new_band.top => {
|
|
FloatBandLink(Some(old_left.set_range(range, side, new_value)))
|
|
},
|
|
Some(ref old_left) => FloatBandLink(Some((*old_left).clone())),
|
|
};
|
|
|
|
let new_right = match self.right.0 {
|
|
None => FloatBandLink(None),
|
|
Some(ref old_right) if range.end > new_band.top => {
|
|
FloatBandLink(Some(old_right.set_range(range, side, new_value)))
|
|
},
|
|
Some(ref old_right) => FloatBandLink(Some((*old_right).clone())),
|
|
};
|
|
|
|
Arc::new(FloatBandNode {
|
|
band: new_band,
|
|
left: new_left,
|
|
right: new_right,
|
|
level: self.level,
|
|
})
|
|
}
|
|
}
|
|
|
|
impl FloatBandLink {
|
|
/// Returns the first band whose top is less than or equal to the given `block_position`.
|
|
fn find(&self, block_position: Length) -> Option<FloatBand> {
|
|
let this = match self.0 {
|
|
None => return None,
|
|
Some(ref node) => node,
|
|
};
|
|
|
|
if block_position < this.band.top {
|
|
return this.left.find(block_position);
|
|
}
|
|
|
|
// It's somewhere in this subtree, but we aren't sure whether it's here or in the right
|
|
// subtree.
|
|
if let Some(band) = this.right.find(block_position) {
|
|
return Some(band);
|
|
}
|
|
|
|
Some(this.band.clone())
|
|
}
|
|
|
|
/// Returns the first band whose top is strictly greater than the given `block_position`.
|
|
fn find_next(&self, block_position: Length) -> Option<FloatBand> {
|
|
let this = match self.0 {
|
|
None => return None,
|
|
Some(ref node) => node,
|
|
};
|
|
|
|
if block_position >= this.band.top {
|
|
return this.right.find_next(block_position);
|
|
}
|
|
|
|
// It's somewhere in this subtree, but we aren't sure whether it's here or in the left
|
|
// subtree.
|
|
if let Some(band) = this.left.find_next(block_position) {
|
|
return Some(band);
|
|
}
|
|
|
|
Some(this.band.clone())
|
|
}
|
|
|
|
/// Inserts a new band into the tree. If the band has the same level as a pre-existing one,
|
|
/// replaces the existing band with the new one.
|
|
fn insert(&self, band: FloatBand) -> FloatBandLink {
|
|
let mut this = match self.0 {
|
|
None => return FloatBandLink(Some(Arc::new(FloatBandNode::new(band)))),
|
|
Some(ref this) => (**this).clone(),
|
|
};
|
|
|
|
if band.top < this.band.top {
|
|
this.left = this.left.insert(band);
|
|
return FloatBandLink(Some(Arc::new(this))).skew().split();
|
|
}
|
|
if band.top > this.band.top {
|
|
this.right = this.right.insert(band);
|
|
return FloatBandLink(Some(Arc::new(this))).skew().split();
|
|
}
|
|
|
|
this.band = band;
|
|
FloatBandLink(Some(Arc::new(this)))
|
|
}
|
|
|
|
/// Corrects tree balance:
|
|
///
|
|
/// T L
|
|
/// / \ / \
|
|
/// L R → A T if level(T) = level(L)
|
|
/// / \ / \
|
|
/// A B B R
|
|
fn skew(&self) -> FloatBandLink {
|
|
if let Some(ref this) = self.0 {
|
|
if let Some(ref left) = this.left.0 {
|
|
if this.level == left.level {
|
|
return FloatBandLink(Some(Arc::new(FloatBandNode {
|
|
level: this.level,
|
|
left: left.left.clone(),
|
|
band: left.band.clone(),
|
|
right: FloatBandLink(Some(Arc::new(FloatBandNode {
|
|
level: this.level,
|
|
left: left.right.clone(),
|
|
band: this.band.clone(),
|
|
right: this.right.clone(),
|
|
}))),
|
|
})));
|
|
}
|
|
}
|
|
}
|
|
|
|
(*self).clone()
|
|
}
|
|
|
|
/// Corrects tree balance:
|
|
///
|
|
/// T R
|
|
/// / \ / \
|
|
/// A R → T X if level(T) = level(X)
|
|
/// / \ / \
|
|
/// B X A B
|
|
fn split(&self) -> FloatBandLink {
|
|
if let Some(ref this) = self.0 {
|
|
if let Some(ref right) = this.right.0 {
|
|
if let Some(ref right_right) = right.right.0 {
|
|
if this.level == right_right.level {
|
|
return FloatBandLink(Some(Arc::new(FloatBandNode {
|
|
level: this.level + 1,
|
|
left: FloatBandLink(Some(Arc::new(FloatBandNode {
|
|
level: this.level,
|
|
left: this.left.clone(),
|
|
band: this.band.clone(),
|
|
right: right.left.clone(),
|
|
}))),
|
|
band: right.band.clone(),
|
|
right: right.right.clone(),
|
|
})));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
(*self).clone()
|
|
}
|
|
}
|
|
|
|
impl Debug for FloatFragment {
|
|
fn fmt(&self, formatter: &mut Formatter) -> FmtResult {
|
|
write!(formatter, "FloatFragment")
|
|
}
|
|
}
|
|
|
|
impl FloatBox {
|
|
/// Creates a new float box.
|
|
pub fn construct<'dom>(
|
|
context: &LayoutContext,
|
|
info: &NodeAndStyleInfo<impl NodeExt<'dom>>,
|
|
display_inside: DisplayInside,
|
|
contents: Contents,
|
|
) -> Self {
|
|
Self {
|
|
contents: IndependentFormattingContext::construct(
|
|
context,
|
|
info,
|
|
display_inside,
|
|
contents,
|
|
// Text decorations are not propagated to any out-of-flow descendants
|
|
TextDecorationLine::NONE,
|
|
),
|
|
}
|
|
}
|
|
|
|
/// Lay out this float box and its children. Note that the position will be relative to
|
|
/// the float containing block formatting context. A later step adjusts the position
|
|
/// to be relative to the containing block.
|
|
pub fn layout(
|
|
&mut self,
|
|
layout_context: &LayoutContext,
|
|
positioning_context: &mut PositioningContext,
|
|
containing_block: &ContainingBlock,
|
|
) -> BoxFragment {
|
|
let style = self.contents.style().clone();
|
|
positioning_context.layout_maybe_position_relative_fragment(
|
|
layout_context,
|
|
containing_block,
|
|
&style,
|
|
|mut positioning_context| {
|
|
// Margin is computed this way regardless of whether the element is replaced
|
|
// or non-replaced.
|
|
let pbm = style.padding_border_margin(containing_block);
|
|
let margin = pbm.margin.auto_is(|| Length::zero());
|
|
let pbm_sums = &(&pbm.padding + &pbm.border) + &margin;
|
|
|
|
let (content_size, children);
|
|
match self.contents {
|
|
IndependentFormattingContext::NonReplaced(ref mut non_replaced) => {
|
|
// Calculate inline size.
|
|
// https://drafts.csswg.org/css2/#float-width
|
|
let box_size = non_replaced.style.content_box_size(&containing_block, &pbm);
|
|
let max_box_size = non_replaced
|
|
.style
|
|
.content_max_box_size(&containing_block, &pbm);
|
|
let min_box_size = non_replaced
|
|
.style
|
|
.content_min_box_size(&containing_block, &pbm)
|
|
.auto_is(Length::zero);
|
|
|
|
let tentative_inline_size = box_size.inline.auto_is(|| {
|
|
let available_size =
|
|
containing_block.inline_size - pbm_sums.inline_sum();
|
|
non_replaced
|
|
.inline_content_sizes(layout_context)
|
|
.shrink_to_fit(available_size)
|
|
});
|
|
let inline_size = tentative_inline_size
|
|
.clamp_between_extremums(min_box_size.inline, max_box_size.inline);
|
|
|
|
// Calculate block size.
|
|
// https://drafts.csswg.org/css2/#block-root-margin
|
|
// FIXME(pcwalton): Is a tree rank of zero correct here?
|
|
let containing_block_for_children = ContainingBlock {
|
|
inline_size,
|
|
block_size: box_size.block,
|
|
style: &non_replaced.style,
|
|
};
|
|
let independent_layout = non_replaced.layout(
|
|
layout_context,
|
|
&mut positioning_context,
|
|
&containing_block_for_children,
|
|
);
|
|
content_size = LogicalVec2 {
|
|
inline: inline_size,
|
|
block: box_size
|
|
.block
|
|
.auto_is(|| independent_layout.content_block_size),
|
|
};
|
|
children = independent_layout.fragments;
|
|
},
|
|
IndependentFormattingContext::Replaced(ref replaced) => {
|
|
// https://drafts.csswg.org/css2/#float-replaced-width
|
|
// https://drafts.csswg.org/css2/#inline-replaced-height
|
|
content_size = replaced.contents.used_size_as_if_inline_element(
|
|
&containing_block,
|
|
&replaced.style,
|
|
None,
|
|
&pbm,
|
|
);
|
|
children = replaced
|
|
.contents
|
|
.make_fragments(&replaced.style, content_size.clone());
|
|
},
|
|
};
|
|
|
|
let content_rect = LogicalRect {
|
|
start_corner: LogicalVec2::zero(),
|
|
size: content_size,
|
|
};
|
|
|
|
BoxFragment::new(
|
|
self.contents.base_fragment_info(),
|
|
style.clone(),
|
|
children,
|
|
content_rect,
|
|
pbm.padding,
|
|
pbm.border,
|
|
margin,
|
|
// Clearance is handled internally by the float placement logic, so there's no need
|
|
// to store it explicitly in the fragment.
|
|
None, // clearance
|
|
CollapsedBlockMargins::zero(),
|
|
)
|
|
},
|
|
)
|
|
}
|
|
}
|
|
|
|
/// Layout state that we maintain when doing sequential traversals of the box tree in document
|
|
/// order.
|
|
///
|
|
/// This data is only needed for float placement and float interaction, and as such is only present
|
|
/// if the current block formatting context contains floats.
|
|
///
|
|
/// All coordinates here are relative to the start of the nearest ancestor block formatting context.
|
|
///
|
|
/// This structure is expected to be cheap to clone, in order to allow for "snapshots" that enable
|
|
/// restarting layout at any point in the tree.
|
|
#[derive(Clone)]
|
|
pub(crate) struct SequentialLayoutState {
|
|
/// Holds all floats in this block formatting context.
|
|
pub(crate) floats: FloatContext,
|
|
/// The (logically) bottom border edge or top padding edge of the last in-flow block. Floats
|
|
/// cannot be placed above this line.
|
|
///
|
|
/// This is often, but not always, the same as the float ceiling. The float ceiling can be lower
|
|
/// than this value because this value is calculated based on in-flow boxes only, while
|
|
/// out-of-flow floats can affect the ceiling as well (see CSS 2.1 § 9.5.1 rule 6).
|
|
pub(crate) bfc_relative_block_position: Length,
|
|
/// Any collapsible margins that we've encountered after `bfc_relative_block_position`.
|
|
pub(crate) current_margin: CollapsedMargin,
|
|
}
|
|
|
|
impl SequentialLayoutState {
|
|
/// Creates a new empty `SequentialLayoutState`.
|
|
pub(crate) fn new(max_inline_size: Length) -> SequentialLayoutState {
|
|
SequentialLayoutState {
|
|
floats: FloatContext::new(max_inline_size),
|
|
current_margin: CollapsedMargin::zero(),
|
|
bfc_relative_block_position: Length::zero(),
|
|
}
|
|
}
|
|
|
|
/// Moves the current block position (logically) down by `block_distance`.
|
|
///
|
|
/// Floats may not be placed higher than the current block position.
|
|
pub(crate) fn advance_block_position(&mut self, block_distance: Length) {
|
|
self.bfc_relative_block_position += block_distance;
|
|
self.floats.lower_ceiling(self.bfc_relative_block_position);
|
|
}
|
|
|
|
/// Replace the entire [ContainingBlockPositionInfo] data structure stored
|
|
/// by this [SequentialLayoutState]. Return the old data structure.
|
|
pub(crate) fn replace_containing_block_position_info(
|
|
&mut self,
|
|
mut position_info: ContainingBlockPositionInfo,
|
|
) -> ContainingBlockPositionInfo {
|
|
mem::swap(&mut position_info, &mut self.floats.containing_block_info);
|
|
position_info
|
|
}
|
|
|
|
/// Return the current block position in the float containing block formatting
|
|
/// context and any uncollapsed block margins.
|
|
pub(crate) fn current_block_position_including_margins(&self) -> Length {
|
|
self.bfc_relative_block_position + self.current_margin.solve()
|
|
}
|
|
|
|
/// Collapses margins, moving the block position down by the collapsed value of `current_margin`
|
|
/// and resetting `current_margin` to zero.
|
|
///
|
|
/// Call this method before laying out children when it is known that the start margin of the
|
|
/// current fragment can't collapse with the margins of any of its children.
|
|
pub(crate) fn collapse_margins(&mut self) {
|
|
self.advance_block_position(self.current_margin.solve());
|
|
self.current_margin = CollapsedMargin::zero();
|
|
}
|
|
|
|
/// Computes the position of the block-start border edge of an element
|
|
/// with the provided `block_start_margin`, assuming no clearance.
|
|
pub(crate) fn position_without_clearance(
|
|
&self,
|
|
block_start_margin: &CollapsedMargin,
|
|
) -> Length {
|
|
// Adjoin `current_margin` and `block_start_margin` since there is no clearance.
|
|
self.bfc_relative_block_position + self.current_margin.adjoin(&block_start_margin).solve()
|
|
}
|
|
|
|
/// Computes the position of the block-start border edge of an element
|
|
/// with the provided `block_start_margin`, assuming a clearance of 0px.
|
|
pub(crate) fn position_with_zero_clearance(
|
|
&self,
|
|
block_start_margin: &CollapsedMargin,
|
|
) -> Length {
|
|
// Clearance prevents `current_margin` and `block_start_margin` from being
|
|
// adjoining, so we need to solve them separately and then sum.
|
|
self.bfc_relative_block_position + self.current_margin.solve() + block_start_margin.solve()
|
|
}
|
|
|
|
/// Returns the block-end outer edge of the lowest float that is to be cleared (if any)
|
|
/// by an element with the provided `clear` and `block_start_margin`.
|
|
pub(crate) fn calculate_clear_position(
|
|
&self,
|
|
clear: Clear,
|
|
block_start_margin: &CollapsedMargin,
|
|
) -> Option<Length> {
|
|
if clear == Clear::None {
|
|
return None;
|
|
}
|
|
|
|
// Calculate the hypothetical position where the element's top border edge
|
|
// would have been if the element's `clear` property had been `none`.
|
|
let hypothetical_block_position = self.position_without_clearance(&block_start_margin);
|
|
|
|
// Check if the hypothetical position is past the relevant floats,
|
|
// in that case we don't need to add clearance.
|
|
let clear_position = match clear {
|
|
Clear::None => unreachable!(),
|
|
Clear::Left => self.floats.clear_left_position,
|
|
Clear::Right => self.floats.clear_right_position,
|
|
Clear::Both => self
|
|
.floats
|
|
.clear_left_position
|
|
.max(self.floats.clear_right_position),
|
|
};
|
|
if hypothetical_block_position >= clear_position {
|
|
None
|
|
} else {
|
|
Some(clear_position)
|
|
}
|
|
}
|
|
|
|
/// Returns the amount of clearance (if any) that a block with the given `clear` value
|
|
/// needs to have at `current_block_position_including_margins()`.
|
|
/// `block_start_margin` is the top margin of the block, after collapsing (if possible)
|
|
/// with the margin of its contents. This must not be included in `current_margin`,
|
|
/// since adding clearance will prevent `current_margin` and `block_start_margin`
|
|
/// from collapsing together.
|
|
///
|
|
/// <https://www.w3.org/TR/2011/REC-CSS2-20110607/visuren.html#flow-control>
|
|
pub(crate) fn calculate_clearance(
|
|
&self,
|
|
clear: Clear,
|
|
block_start_margin: &CollapsedMargin,
|
|
) -> Option<Length> {
|
|
return self
|
|
.calculate_clear_position(clear, &block_start_margin)
|
|
.map(|offset| offset - self.position_with_zero_clearance(&block_start_margin));
|
|
}
|
|
|
|
/// A block that is replaced or establishes an independent formatting context can't overlap floats,
|
|
/// it has to be placed next to them, and may get some clearance if there isn't enough space.
|
|
/// Given such a block with the provided 'clear', 'block_start_margin', 'pbm' and 'object_size',
|
|
/// this method finds an area that is big enough and doesn't overlap floats.
|
|
/// It returns a tuple with:
|
|
/// - The clearance amount (if any), which includes both the effect of 'clear'
|
|
/// and the extra space to avoid floats.
|
|
/// - The LogicalRect in which the block can be placed without overlapping floats.
|
|
pub(crate) fn calculate_clearance_and_inline_adjustment(
|
|
&self,
|
|
clear: Clear,
|
|
block_start_margin: &CollapsedMargin,
|
|
pbm: &PaddingBorderMargin,
|
|
object_size: LogicalVec2<Length>,
|
|
) -> (Option<Length>, LogicalRect<Length>) {
|
|
// First compute the clear position required by the 'clear' property.
|
|
// The code below may then add extra clearance when the element can't fit
|
|
// next to floats not covered by 'clear'.
|
|
let clear_position = self.calculate_clear_position(clear, &block_start_margin);
|
|
let ceiling =
|
|
clear_position.unwrap_or_else(|| self.position_without_clearance(&block_start_margin));
|
|
let mut placement = PlacementAmongFloats::new(&self.floats, ceiling, object_size, pbm);
|
|
let placement_rect = placement.place();
|
|
let position = &placement_rect.start_corner;
|
|
let has_clearance = clear_position.is_some() || position.block > ceiling;
|
|
let clearance = if has_clearance {
|
|
Some(position.block - self.position_with_zero_clearance(&block_start_margin))
|
|
} else {
|
|
None
|
|
};
|
|
(clearance, placement_rect)
|
|
}
|
|
|
|
/// Adds a new adjoining margin.
|
|
pub(crate) fn adjoin_assign(&mut self, margin: &CollapsedMargin) {
|
|
self.current_margin.adjoin_assign(margin)
|
|
}
|
|
|
|
/// Get the offset of the current containing block and any uncollapsed margins.
|
|
pub(crate) fn current_containing_block_offset(&self) -> CSSPixelLength {
|
|
self.floats.containing_block_info.block_start +
|
|
self.floats
|
|
.containing_block_info
|
|
.block_start_margins_not_collapsed
|
|
.solve()
|
|
}
|
|
|
|
/// This function places a Fragment that has been created for a FloatBox.
|
|
pub(crate) fn place_float_fragment(
|
|
&mut self,
|
|
box_fragment: &mut BoxFragment,
|
|
margins_collapsing_with_parent_containing_block: CollapsedMargin,
|
|
block_offset_from_containing_block_top: Length,
|
|
) {
|
|
let block_start_of_containing_block_in_bfc = self.floats.containing_block_info.block_start +
|
|
self.floats
|
|
.containing_block_info
|
|
.block_start_margins_not_collapsed
|
|
.adjoin(&margins_collapsing_with_parent_containing_block)
|
|
.solve();
|
|
|
|
self.floats.lower_ceiling(
|
|
block_start_of_containing_block_in_bfc + block_offset_from_containing_block_top,
|
|
);
|
|
|
|
let pbm_sums = &(&box_fragment.padding + &box_fragment.border) + &box_fragment.margin;
|
|
let margin_box_start_corner = self.floats.add_float(&PlacementInfo {
|
|
size: &box_fragment.content_rect.size + &pbm_sums.sum(),
|
|
side: FloatSide::from_style(&box_fragment.style).expect("Float box wasn't floated!"),
|
|
clear: box_fragment.style.get_box().clear,
|
|
});
|
|
|
|
// This is the position of the float in the float-containing block formatting context. We add the
|
|
// existing start corner here because we may have already gotten some relative positioning offset.
|
|
let new_position_in_bfc = &(&margin_box_start_corner + &pbm_sums.start_offset()) +
|
|
&box_fragment.content_rect.start_corner;
|
|
|
|
// This is the position of the float relative to the containing block start.
|
|
let new_position_in_containing_block = LogicalVec2 {
|
|
inline: new_position_in_bfc.inline - self.floats.containing_block_info.inline_start,
|
|
block: new_position_in_bfc.block - block_start_of_containing_block_in_bfc,
|
|
};
|
|
|
|
box_fragment.content_rect.start_corner = new_position_in_containing_block;
|
|
}
|
|
}
|