/* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at https://mozilla.org/MPL/2.0/. */ use std::cell::OnceCell; use std::mem; use std::vec::IntoIter; use app_units::Au; use atomic_refcell::AtomicRef; use gfx::font::FontMetrics; use gfx::text::glyph::GlyphStore; use gfx::text::text_run::GlyphRun; use log::warn; use serde::Serialize; use servo_arc::Arc; use style::computed_values::white_space::T as WhiteSpace; use style::logical_geometry::WritingMode; use style::properties::ComputedValues; use style::values::computed::Length; use style::values::generics::text::LineHeight; use style::values::specified::text::{TextAlignKeyword, TextDecorationLine}; use style::values::specified::{TextAlignLast, TextJustify}; use style::Zero; use webrender_api::FontInstanceKey; use xi_unicode::{linebreak_property, LineBreakLeafIter}; use super::float::PlacementAmongFloats; use super::CollapsibleWithParentStartMargin; use crate::cell::ArcRefCell; use crate::context::LayoutContext; use crate::flow::float::{FloatBox, SequentialLayoutState}; use crate::flow::FlowLayout; use crate::formatting_contexts::IndependentFormattingContext; use crate::fragment_tree::{ AnonymousFragment, BaseFragmentInfo, BoxFragment, CollapsedBlockMargins, CollapsedMargin, Fragment, HoistedSharedFragment, TextFragment, }; use crate::geom::{LogicalRect, LogicalVec2}; use crate::positioned::{ relative_adjustement, AbsolutelyPositionedBox, PositioningContext, PositioningContextLength, }; use crate::sizing::ContentSizes; use crate::style_ext::{ ComputedValuesExt, Display, DisplayGeneratingBox, DisplayOutside, PaddingBorderMargin, }; use crate::ContainingBlock; // These constants are the xi-unicode line breaking classes that are defined in // `table.rs`. Unfortunately, they are only identified by number. const XI_LINE_BREAKING_CLASS_GL: u8 = 12; const XI_LINE_BREAKING_CLASS_WJ: u8 = 30; const XI_LINE_BREAKING_CLASS_ZWJ: u8 = 40; #[derive(Debug, Serialize)] pub(crate) struct InlineFormattingContext { pub(super) inline_level_boxes: Vec>, pub(super) text_decoration_line: TextDecorationLine, // Whether this IFC contains the 1st formatted line of an element // https://www.w3.org/TR/css-pseudo-4/#first-formatted-line pub(super) has_first_formatted_line: bool, pub(super) contains_floats: bool, /// Whether this IFC being constructed currently ends with whitespace. This is used to /// implement rule 4 of : /// /// > Any collapsible space immediately following another collapsible space—even one /// > outside the boundary of the inline containing that space, provided both spaces are /// > within the same inline formatting context—is collapsed to have zero advance width. /// > (It is invisible, but retains its soft wrap opportunity, if any.) pub(super) ends_with_whitespace: bool, } #[derive(Debug, Serialize)] pub(crate) enum InlineLevelBox { InlineBox(InlineBox), TextRun(TextRun), OutOfFlowAbsolutelyPositionedBox(ArcRefCell), OutOfFlowFloatBox(FloatBox), Atomic(IndependentFormattingContext), } #[derive(Debug, Serialize)] pub(crate) struct InlineBox { pub base_fragment_info: BaseFragmentInfo, #[serde(skip_serializing)] pub style: Arc, pub is_first_fragment: bool, pub is_last_fragment: bool, pub children: Vec>, } /// https://www.w3.org/TR/css-display-3/#css-text-run #[derive(Debug, Serialize)] pub(crate) struct TextRun { pub base_fragment_info: BaseFragmentInfo, #[serde(skip_serializing)] pub parent_style: Arc, pub text: String, pub has_uncollapsible_content: bool, } /// Information about the current line under construction for a particular /// [`InlineFormattingContextState`]. This tracks position and size information while /// [`LineItem`]s are collected and is used as input when those [`LineItem`]s are /// converted into [`Fragment`]s during the final phase of line layout. Note that this /// does not store the [`LineItem`]s themselves, as they are stored as part of the /// nesting state in the [`InlineFormattingContextState`]. struct LineUnderConstruction { /// The position where this line will start once it is laid out. This includes any /// offset from `text-indent`. start_position: LogicalVec2, /// The current inline position in the line being laid out into [`LineItems`] in this /// [`InlineFormattingContext`] independent of the depth in the nesting level. inline_position: Length, /// The maximum block size of all boxes that ended and are in progress in this line. max_block_size: Length, /// Whether any active linebox has added a glyph or atomic element to this line, which /// indicates that the next run that exceeds the line length can cause a line break. has_content: bool, /// Whether or not there are floats that did not fit on the current line. Before /// the [`LineItems`] of this line are laid out, these floats will need to be /// placed directly below this line, but still as children of this line's Fragments. has_floats_waiting_to_be_placed: bool, /// A rectangular area (relative to the containing block / inline formatting /// context boundaries) where we can fit the line box without overlapping floats. /// Note that when this is not empty, its start corner takes precedence over /// [`LineUnderConstruction::start_position`]. placement_among_floats: OnceCell>, /// The LineItems for the current line under construction that have already /// been committed to this line. line_items: Vec, /// The number of justification opportunities in this line. justification_opportunities: usize, } impl LineUnderConstruction { fn new(start_position: LogicalVec2) -> Self { Self { inline_position: start_position.inline.clone(), start_position: start_position, max_block_size: Length::zero(), has_content: false, has_floats_waiting_to_be_placed: false, placement_among_floats: OnceCell::new(), line_items: Vec::new(), justification_opportunities: 0, } } fn line_block_start_considering_placement_among_floats(&self) -> Length { match self.placement_among_floats.get() { Some(placement_among_floats) => placement_among_floats.start_corner.block, None => self.start_position.block, } } fn replace_placement_among_floats(&mut self, new_placement: LogicalRect) { self.placement_among_floats.take(); let _ = self.placement_among_floats.set(new_placement); } /// Trim the trailing whitespace in this line and return the width of the whitespace trimmed. fn trim_trailing_whitespace(&mut self) -> Length { // From : // > 3. A sequence of collapsible spaces at the end of a line is removed, // > as well as any trailing U+1680   OGHAM SPACE MARK whose white-space // > property is normal, nowrap, or pre-line. let mut whitespace_trimmed = Length::zero(); let mut spaces_trimmed = 0; for item in self.line_items.iter_mut().rev() { if !item.trim_whitespace_at_end(&mut whitespace_trimmed, &mut spaces_trimmed) { break; } } self.justification_opportunities -= spaces_trimmed; whitespace_trimmed } } /// The current unbreakable segment under construction for an inline formatting context. /// Items accumulate here until we reach a soft line break opportunity during processing /// of inline content or we reach the end of the formatting context. struct UnbreakableSegmentUnderConstruction { /// The size of this unbreakable segment in both dimension. size: LogicalVec2, /// The LineItems for the segment under construction line_items: Vec, /// The depth in the inline box hierarchy at the start of this segment. This is used /// to prefix this segment when it is pushed to a new line. inline_box_hierarchy_depth: Option, /// Whether any active linebox has added a glyph or atomic element to this line /// segment, which indicates that the next run that exceeds the line length can cause /// a line break. has_content: bool, /// The inline size of any trailing whitespace in this segment. trailing_whitespace_size: Length, /// The number of justification opportunities in this unbreakable segment. justification_opportunities: usize, } impl UnbreakableSegmentUnderConstruction { fn new() -> Self { Self { size: LogicalVec2::zero(), line_items: Vec::new(), inline_box_hierarchy_depth: None, has_content: false, trailing_whitespace_size: Length::zero(), justification_opportunities: 0, } } /// Reset this segment after its contents have been committed to a line. fn reset(&mut self) { assert!(self.line_items.is_empty()); // Preserve allocated memory. self.size = LogicalVec2::zero(); self.inline_box_hierarchy_depth = None; self.has_content = false; self.trailing_whitespace_size = Length::zero(); self.justification_opportunities = 0; } /// Push a single line item to this segment. In addition, record the inline box /// hierarchy depth if this is the first segment. The hierarchy depth is used to /// duplicate the necessary `StartInlineBox` tokens if this segment is ultimately /// placed on a new empty line. fn push_line_item(&mut self, line_item: LineItem, inline_box_hierarchy_depth: usize) { if self.line_items.is_empty() { self.inline_box_hierarchy_depth = Some(inline_box_hierarchy_depth); } self.line_items.push(line_item); } /// Trim whitespace from the beginning of this UnbreakbleSegmentUnderConstruction. /// /// From : /// /// > Then, the entire block is rendered. Inlines are laid out, taking bidi /// > reordering into account, and wrapping as specified by the text-wrap /// > property. As each line is laid out, /// > 1. A sequence of collapsible spaces at the beginning of a line is removed. /// /// This prevents whitespace from being added to the beginning of a line. fn trim_leading_whitespace(&mut self) { let mut whitespace_trimmed = Length::zero(); let mut spaces_trimmed = 0; for item in self.line_items.iter_mut() { if !item.trim_whitespace_at_start(&mut whitespace_trimmed, &mut spaces_trimmed) { break; } } self.size.inline -= whitespace_trimmed; self.justification_opportunities -= spaces_trimmed; } /// Prepare this segment for placement on a new and empty line. This happens when the /// segment is too large to fit on the current line and needs to be placed on a new /// one. fn prepare_for_placement_on_empty_line( &mut self, line: &LineUnderConstruction, current_hierarchy_depth: usize, ) { self.trim_leading_whitespace(); // The segment may start in the middle of an already processed inline box. In that // case we need to duplicate the `StartInlineBox` tokens as a prefix of the new // lines. For instance if the following segment is going to be placed on a new line: // // line = [StartInlineBox "every"] // segment = ["good" EndInlineBox "boy"] // // Then the segment must be prefixed with `StartInlineBox` before it is committed // to the empty line. let mut hierarchy_depth = self .inline_box_hierarchy_depth .unwrap_or(current_hierarchy_depth); if hierarchy_depth == 0 { return; } let mut hierarchy = Vec::new(); let mut skip_depth = 0; for item in line.line_items.iter().rev() { match item { // We need to skip over any inline boxes that are not in our hierarchy. If // any inline box ends, we skip until it starts. LineItem::StartInlineBox(_) if skip_depth > 0 => skip_depth -= 1, LineItem::EndInlineBox => skip_depth += 1, // Otherwise copy the inline box to the hierarchy we are collecting. LineItem::StartInlineBox(inline_box) => { let mut cloned_inline_box = inline_box.clone(); cloned_inline_box.is_first_fragment = false; hierarchy.push(LineItem::StartInlineBox(cloned_inline_box)); hierarchy_depth -= 1; if hierarchy_depth == 0 { break; } }, _ => {}, } } let segment_items = mem::take(&mut self.line_items); self.line_items = hierarchy .into_iter() .rev() .chain(segment_items.into_iter()) .collect(); } } struct InlineContainerState { /// Whether or not we have processed any content (an atomic element or text) for /// this inline box on the current line OR any previous line. has_content: bool, /// Indicates whether this nesting level have text decorations in effect. /// From https://drafts.csswg.org/css-text-decor/#line-decoration // "When specified on or propagated to a block container that establishes // an IFC..." text_decoration_line: TextDecorationLine, /// The block size of this inline container maxed with the block sizes of all inline /// container ancestors. This isn't the block size of this container, but if this /// container adds content to a line, this is the block size necessary for that new /// content. nested_block_size: Length, } struct InlineBoxContainerState { /// The container state common to both [`InlineBox`] and the root of the /// [`InlineFormattingContext`]. base: InlineContainerState, /// The style of this inline box. style: Arc, /// The [`BaseFragmentInfo`] of the [`InlineBox`] that this state tracks. base_fragment_info: BaseFragmentInfo, /// The [`PaddingBorderMargin`] of the [`InlineBox`] that this state tracks. pbm: PaddingBorderMargin, /// Whether this is the last fragment of this InlineBox. This may not be the case if /// the InlineBox is split due to an block-in-inline-split and this is not the last of /// that split. is_last_fragment: bool, } struct InlineFormattingContextState<'a, 'b> { positioning_context: &'a mut PositioningContext, containing_block: &'b ContainingBlock<'b>, sequential_layout_state: Option<&'a mut SequentialLayoutState>, layout_context: &'b LayoutContext<'b>, /// A vector of fragment that are laid out. This includes one [`Fragment::Anonymous`] /// per line that is currently laid out plus fragments for all floats, which /// are currently laid out at the top-level of each [`InlineFormattingContext`]. fragments: Vec, /// Information about the line currently being laid out into [`LineItems`]s. current_line: LineUnderConstruction, /// Information about the unbreakable line segment currently being laid out into [`LineItems`]s. current_line_segment: UnbreakableSegmentUnderConstruction, /// After a forced line break (for instance from a `
` element) we wait to actually /// break the line until seeing more content. This allows ongoing inline boxes to finish, /// since in the case where they have no more content they should not be on the next /// line. /// /// For instance: /// /// ``` html /// /// first line
/// /// second line /// ``` /// /// In this case, the `` should not extend to the second line. If we linebreak /// as soon as we encounter the `
` the ``'s ending inline borders would be /// placed on the second line, because we add those borders in /// [`InlineFormattingContextState::finish_inline_box()`]. linebreak_before_new_content: bool, /// The line breaking state for this inline formatting context. linebreaker: Option, /// Whether or not a soft wrap opportunity is queued. Soft wrap opportunities are /// queued after replaced content and they are processed when the next text content /// is encountered. have_deferred_soft_wrap_opportunity: bool, /// Whether or not a soft wrap opportunity should be prevented before the next atomic /// element encountered in the inline formatting context. See /// `char_prevents_soft_wrap_opportunity_when_before_or_after_atomic` for more /// details. prevent_soft_wrap_opportunity_before_next_atomic: bool, /// The currently white-space setting of this line. This is stored on the /// [`InlineFormattingContextState`] because when a soft wrap opportunity is defined /// by the boundary between two characters, the white-space property of their nearest /// common ancestor is used. white_space: WhiteSpace, /// The [`InlineContainerState`] for the container formed by the root of the /// [`InlineFormattingContext`]. root_nesting_level: InlineContainerState, /// A stack of [`InlineBoxContainerState`] that is used to produce [`LineItem`]s either when we /// reach the end of an inline box or when we reach the end of a line. Only at the end /// of the inline box is the state popped from the stack. inline_box_state_stack: Vec, } impl<'a, 'b> InlineFormattingContextState<'a, 'b> { fn current_inline_container_state(&self) -> &InlineContainerState { match self.inline_box_state_stack.last() { Some(inline_box_state) => &inline_box_state.base, None => &self.root_nesting_level, } } fn current_inline_container_state_mut(&mut self) -> &mut InlineContainerState { match self.inline_box_state_stack.last_mut() { Some(inline_box_state) => &mut inline_box_state.base, None => &mut self.root_nesting_level, } } fn current_line_max_block_size(&self) -> Length { self.current_inline_container_state() .nested_block_size .max(self.current_line.max_block_size) } fn propagate_current_nesting_level_white_space_style(&mut self) { let style = match self.inline_box_state_stack.last() { Some(inline_box_state) => &inline_box_state.style, None => self.containing_block.style, }; self.white_space = style.get_inherited_text().white_space; } /// Start laying out a particular [`InlineBox`] into line items. This will push /// a new [`InlineBoxContainerState`] onto [`Self::inline_box_state_stack`]. fn start_inline_box(&mut self, inline_box: &InlineBox) { let (text_decoration_of_parent, nested_block_size_of_parent) = { let parent = self.current_inline_container_state(); (parent.text_decoration_line, parent.nested_block_size) }; let mut inline_box_state = InlineBoxContainerState::new( inline_box, &self.containing_block, text_decoration_of_parent, nested_block_size_of_parent, self.layout_context, inline_box.is_last_fragment, ); if inline_box.is_first_fragment { self.current_line.inline_position += inline_box_state.pbm.padding.inline_start + inline_box_state.pbm.border.inline_start + inline_box_state .pbm .margin .inline_start .auto_is(Length::zero); } let line_item = inline_box_state.layout_into_line_item( self.layout_context, inline_box.is_first_fragment, inline_box.is_last_fragment, ); self.push_line_item_to_unbreakable_segment(LineItem::StartInlineBox(line_item)); self.inline_box_state_stack.push(inline_box_state); } /// Finish laying out a particular [`InlineBox`] into line items. This will add the /// final [`InlineBoxLineItem`] to the state and pop its state off of /// [`Self::inline_box_state_stack`]. fn finish_inline_box(&mut self) { let inline_box_state = match self.inline_box_state_stack.pop() { Some(inline_box_state) => inline_box_state, None => return, // We are at the root. }; self.push_line_item_to_unbreakable_segment(LineItem::EndInlineBox); self.current_line_segment .size .block .max_assign(inline_box_state.base.nested_block_size); // If the inline box that we just finished had any content at all, we want to propagate // the `white-space` property of its parent to future inline children. This is because // when a soft wrap opportunity is defined by the boundary between two elements, the // `white-space` used is that of their nearest common ancestor. if inline_box_state.base.has_content { self.propagate_current_nesting_level_white_space_style(); } if inline_box_state.is_last_fragment { let pbm_end = inline_box_state.pbm.padding.inline_end + inline_box_state.pbm.border.inline_end + inline_box_state.pbm.margin.inline_end.auto_is(Length::zero); self.current_line_segment.size.inline += pbm_end; } } fn finish_last_line(&mut self) { // We are at the end of the IFC, and we need to do a few things to make sure that // the current segment is committed and that the final line is finished. // // A soft wrap opportunity makes it so the current segment is placed on a new line // if it doesn't fit on the current line under construction. self.process_soft_wrap_opportunity(); // `process_soft_line_wrap_opportunity` does not commit the segment to a line if // there is no line wrapping, so this forces the segment into the current line. self.commit_current_segment_to_line(); // Finally we finish the line itself and convert all of the LineItems into // fragments. self.finish_current_line_and_reset(true /* last_line_or_forced_line_break */); } /// Finish layout of all inline boxes for the current line. This will gather all /// [`LineItem`]s and turn them into [`Fragment`]s, then reset the /// [`InlineFormattingContextState`] preparing it for laying out a new line. fn finish_current_line_and_reset(&mut self, last_line_or_forced_line_break: bool) { let whitespace_trimmed = self.current_line.trim_trailing_whitespace(); let (inline_start_position, justification_adjustment) = self .calculate_current_line_inline_start_and_justification_adjustment( whitespace_trimmed, last_line_or_forced_line_break, ); let block_start_position = self .current_line .line_block_start_considering_placement_among_floats(); let had_inline_advance = self.current_line.inline_position != self.current_line.start_position.inline; let effective_block_advance = if self.current_line.has_content || had_inline_advance || self.linebreak_before_new_content { self.current_line_max_block_size() } else { Length::zero() }; let block_end_position = block_start_position + effective_block_advance; if let Some(sequential_layout_state) = self.sequential_layout_state.as_mut() { // This amount includes both the block size of the line and any extra space // added to move the line down in order to avoid overlapping floats. let increment = block_end_position - self.current_line.start_position.block; sequential_layout_state.advance_block_position(increment); } let mut line_items = std::mem::take(&mut self.current_line.line_items); if self.current_line.has_floats_waiting_to_be_placed { place_pending_floats(self, &mut line_items); } let mut state = LineItemLayoutState { inline_position: inline_start_position, inline_start_of_parent: Length::zero(), ifc_containing_block: self.containing_block, positioning_context: &mut self.positioning_context, line_block_start: block_start_position, justification_adjustment, }; let positioning_context_length = state.positioning_context.len(); let mut saw_end = false; let fragments = layout_line_items( &mut line_items.into_iter(), self.layout_context, &mut state, &mut saw_end, ); let size = LogicalVec2 { inline: self.containing_block.inline_size, block: effective_block_advance, }; // The inline part of this start offset was taken into account when determining // the inline start of the line in `calculate_inline_start_for_current_line` so // we do not need to include it in the `start_corner` of the line's main Fragment. let start_corner = LogicalVec2 { inline: Length::zero(), block: block_start_position, }; let line_had_content = !fragments.is_empty() || state.positioning_context.len() != positioning_context_length; if line_had_content { state .positioning_context .adjust_static_position_of_hoisted_fragments_with_offset( &start_corner, positioning_context_length, ); self.fragments .push(Fragment::Anonymous(AnonymousFragment::new( LogicalRect { start_corner, size }, fragments, self.containing_block.style.writing_mode, ))); } self.current_line = LineUnderConstruction::new(LogicalVec2 { inline: Length::zero(), block: block_end_position, }); } /// Given the amount of whitespace trimmed from the line and taking into consideration /// the `text-align` property, calculate where the line under construction starts in /// the inline axis as well as the adjustment needed for every justification opportunity /// to account for `text-align: justify`. fn calculate_current_line_inline_start_and_justification_adjustment( &self, whitespace_trimmed: Length, last_line_or_forced_line_break: bool, ) -> (Length, Length) { enum TextAlign { Start, Center, End, } let style = self.containing_block.style; let line_left_is_inline_start = style.writing_mode.line_left_is_inline_start(); let mut text_align_keyword = style.clone_text_align(); if last_line_or_forced_line_break { text_align_keyword = match style.clone_text_align_last() { TextAlignLast::Auto if text_align_keyword == TextAlignKeyword::Justify => { TextAlignKeyword::Start }, TextAlignLast::Auto => text_align_keyword, TextAlignLast::Start => TextAlignKeyword::Start, TextAlignLast::End => TextAlignKeyword::End, TextAlignLast::Left => TextAlignKeyword::Left, TextAlignLast::Right => TextAlignKeyword::Right, TextAlignLast::Center => TextAlignKeyword::Center, TextAlignLast::Justify => TextAlignKeyword::Justify, }; } let text_align = match text_align_keyword { TextAlignKeyword::Start => TextAlign::Start, TextAlignKeyword::Center => TextAlign::Center, TextAlignKeyword::End => TextAlign::End, TextAlignKeyword::Left => { if line_left_is_inline_start { TextAlign::Start } else { TextAlign::End } }, TextAlignKeyword::Right => { if line_left_is_inline_start { TextAlign::End } else { TextAlign::Start } }, TextAlignKeyword::Justify => TextAlign::Start, TextAlignKeyword::ServoCenter | TextAlignKeyword::ServoLeft | TextAlignKeyword::ServoRight => { // TODO: Implement these modes which seem to be used by quirks mode. TextAlign::Start }, }; let (line_start, available_space) = match self.current_line.placement_among_floats.get() { Some(placement_among_floats) => ( placement_among_floats.start_corner.inline, placement_among_floats.size.inline, ), None => (Length::zero(), self.containing_block.inline_size), }; // Properly handling text-indent requires that we do not align the text // into the text-indent. // See // "This property specifies the indentation applied to lines of inline content in // a block. The indent is treated as a margin applied to the start edge of the // line box." let text_indent = self.current_line.start_position.inline; let line_length = self.current_line.inline_position - whitespace_trimmed - text_indent; let adjusted_line_start = line_start + match text_align { TextAlign::Start => text_indent, TextAlign::End => (available_space - line_length).max(text_indent), TextAlign::Center => (available_space - line_length + text_indent) / 2., }; // Calculate the justification adjustment. This is simply the remaining space on the line, // dividided by the number of justficiation opportunities that we recorded when building // the line. let num_justification_opportunities = self.current_line.justification_opportunities as f32; let text_justify = self.containing_block.style.clone_text_justify(); let justification_adjustment = match (text_align_keyword, text_justify) { // `text-justify: none` should disable text justification. // TODO: Handle more `text-justify` values. (TextAlignKeyword::Justify, TextJustify::None) => Length::zero(), (TextAlignKeyword::Justify, _) if num_justification_opportunities > 0. => { (available_space - line_length) / num_justification_opportunities }, _ => Length::zero(), }; (adjusted_line_start, justification_adjustment) } fn place_float_fragment(&mut self, fragment: &mut BoxFragment) { let state = self .sequential_layout_state .as_mut() .expect("Tried to lay out a float with no sequential placement state!"); let block_offset_from_containining_block_top = state .current_block_position_including_margins() - state.current_containing_block_offset(); state.place_float_fragment( fragment, CollapsedMargin::zero(), block_offset_from_containining_block_top, ); } /// Place a FloatLineItem. This is done when an unbreakable segment is committed to /// the current line. Placement of FloatLineItems might need to be deferred until the /// line is complete in the case that floats stop fitting on the current line. /// /// When placing floats we do not want to take into account any trailing whitespace on /// the line, because that whitespace will be trimmed in the case that the line is /// broken. Thus this function takes as an argument the new size (without whitespace) of /// the line that these floats are joining. fn place_float_line_item_for_commit_to_line( &mut self, float_item: &mut FloatLineItem, line_inline_size_without_trailing_whitespace: Length, ) { let margin_box = float_item .fragment .border_rect() .inflate(&float_item.fragment.margin); let inline_size = margin_box.size.inline.max(Length::zero()); let available_inline_size = match self.current_line.placement_among_floats.get() { Some(placement_among_floats) => placement_among_floats.size.inline, None => self.containing_block.inline_size, } - line_inline_size_without_trailing_whitespace; // If this float doesn't fit on the current line or a previous float didn't fit on // the current line, we need to place it starting at the next line BUT still as // children of this line's hierarchy of inline boxes (for the purposes of properly // parenting in their stacking contexts). Once all the line content is gathered we // will place them later. let has_content = self.current_line.has_content || self.current_line_segment.has_content; let fits_on_line = !has_content || inline_size <= available_inline_size; let needs_placement_later = self.current_line.has_floats_waiting_to_be_placed || !fits_on_line; if needs_placement_later { self.current_line.has_floats_waiting_to_be_placed = true; } else { self.place_float_fragment(&mut float_item.fragment); float_item.needs_placement = false; } // We've added a new float to the IFC, but this may have actually changed the // position of the current line. In order to determine that we regenerate the // placement among floats for the current line, which may adjust its inline // start position. let new_placement = self.place_line_among_floats(&LogicalVec2 { inline: line_inline_size_without_trailing_whitespace, block: self.current_line.max_block_size, }); self.current_line .replace_placement_among_floats(new_placement); } /// Given a new potential line size for the current line, create a "placement" for that line. /// This tells us whether or not the new potential line will fit in the current block position /// or need to be moved. In addition, the placement rect determines the inline start and end /// of the line if it's used as the final placement among floats. fn place_line_among_floats( &self, potential_line_size: &LogicalVec2, ) -> LogicalRect { let sequential_layout_state = self .sequential_layout_state .as_ref() .expect("Should not have called this function without having floats."); let ifc_offset_in_float_container = LogicalVec2 { inline: sequential_layout_state .floats .containing_block_info .inline_start, block: sequential_layout_state.current_containing_block_offset(), }; let ceiling = self .current_line .line_block_start_considering_placement_among_floats(); let mut placement = PlacementAmongFloats::new( &sequential_layout_state.floats, ceiling + ifc_offset_in_float_container.block, potential_line_size.clone(), &PaddingBorderMargin::zero(), ); let mut placement_rect = placement.place(); placement_rect.start_corner = &placement_rect.start_corner - &ifc_offset_in_float_container; placement_rect } /// Returns true if a new potential line size for the current line would require a line /// break. This takes into account floats and will also update the "placement among /// floats" for this line if the potential line size would not cause a line break. /// Thus, calling this method has side effects and should only be done while in the /// process of laying out line content that is always going to be committed to this /// line or the next. fn new_potential_line_size_causes_line_break( &mut self, potential_line_size: &LogicalVec2, ) -> bool { let available_line_space = if self.sequential_layout_state.is_some() { self.current_line .placement_among_floats .get_or_init(|| self.place_line_among_floats(potential_line_size)) .size .clone() } else { LogicalVec2 { inline: self.containing_block.inline_size, block: Length::new(f32::INFINITY), } }; let inline_would_overflow = potential_line_size.inline > available_line_space.inline; let block_would_overflow = potential_line_size.block > available_line_space.block; // The first content that is added to a line cannot trigger a line break and // the `white-space` propertly can also prevent all line breaking. let can_break = self.current_line.has_content; // If this is the first content on the line and we already have a float placement, // that means that the placement was initialized by a leading float in the IFC. // This placement needs to be updated, because the first line content might push // the block start of the line downward. If there is no float placement, we want // to make one to properly set the block position of the line. if !can_break { // Even if we cannot break, adding content to this line might change its position. // In that case we need to redo our placement among floats. if self.sequential_layout_state.is_some() && (inline_would_overflow || block_would_overflow) { let new_placement = self.place_line_among_floats(potential_line_size); self.current_line .replace_placement_among_floats(new_placement); } return false; } // If the potential line is larger than the containing block we do not even need to consider // floats. We definitely have to do a linebreak. if potential_line_size.inline > self.containing_block.inline_size { return true; } // Not fitting in the block space means that our block size has changed and we had a // placement among floats that is no longer valid. This same placement might just // need to be expanded or perhaps we need to line break. if block_would_overflow { // If we have a limited block size then we are wedging this line between floats. assert!(self.sequential_layout_state.is_some()); let new_placement = self.place_line_among_floats(potential_line_size); if new_placement.start_corner.block != self.current_line .line_block_start_considering_placement_among_floats() { return true; } else { self.current_line .replace_placement_among_floats(new_placement); return false; } } // Otherwise the new potential line size will require a newline if it fits in the // inline space available for this line. This space may be smaller than the // containing block if floats shrink the available inline space. inline_would_overflow } fn defer_forced_line_break(&mut self) { // If this hard line break happens in the middle of an unbreakable segment, there are two // scenarios: // 1. The current portion of the unbreakable segment fits on the current line in which // case we commit it. // 2. The current portion of the unbreakable segment does not fit in which case we // need to put it on a new line *before* actually triggering the hard line break. // // `process_soft_wrap_opportunity` handles both of these cases. self.process_soft_wrap_opportunity(); // Defer the actual line break until we've cleared all ending inline boxes. self.linebreak_before_new_content = true; // We need to ensure that the appropriate space for a linebox is created even if there // was no other content on this line. We mark the line as having content (needing a // advance) and having at least the height associated with this nesting of inline boxes. //self.current_line.has_content = true; self.current_line .max_block_size .max_assign(self.current_line_max_block_size()); } fn possibly_flush_deferred_forced_line_break(&mut self) { if !self.linebreak_before_new_content { return; } self.commit_current_segment_to_line(); self.process_line_break(true /* forced_line_break */); self.linebreak_before_new_content = false; } fn push_line_item_to_unbreakable_segment(&mut self, line_item: LineItem) { self.current_line_segment .push_line_item(line_item, self.inline_box_state_stack.len()); } fn push_glyph_store_to_unbreakable_segment( &mut self, glyph_store: std::sync::Arc, base_fragment_info: BaseFragmentInfo, parent_style: &Arc, font_metrics: &FontMetrics, font_key: FontInstanceKey, ) { let inline_advance = Length::from(glyph_store.total_advance()); let is_non_preserved_whitespace = glyph_store.is_whitespace() && !parent_style .get_inherited_text() .white_space .preserve_spaces(); if is_non_preserved_whitespace { self.current_line_segment.trailing_whitespace_size = inline_advance; } self.current_line_segment.justification_opportunities += glyph_store.total_word_separators() as usize; match self.current_line_segment.line_items.last_mut() { Some(LineItem::TextRun(text_run)) => { debug_assert!(font_key == text_run.font_key); text_run.text.push(glyph_store); self.current_line_segment.size.inline += inline_advance; if !is_non_preserved_whitespace { self.current_line_segment.has_content = true; } return; }, _ => {}, } self.push_content_line_item_to_unbreakable_segment( inline_advance, LineItem::TextRun(TextRunLineItem { text: vec![glyph_store], base_fragment_info: base_fragment_info.into(), parent_style: parent_style.clone(), font_metrics: font_metrics.clone(), font_key, text_decoration_line: self.current_inline_container_state().text_decoration_line, }), !is_non_preserved_whitespace, ); } fn push_content_line_item_to_unbreakable_segment( &mut self, inline_size: Length, line_item: LineItem, counts_as_content: bool, ) { if counts_as_content { self.current_line_segment.has_content = true; } self.current_line_segment.size.inline += inline_size; self.current_line_segment .size .block .max_assign(self.current_inline_container_state().nested_block_size); self.current_line_segment .size .block .max_assign(line_item.block_size()); self.push_line_item_to_unbreakable_segment(line_item); // We need to update the size of the current segment and also propagate the // whitespace setting to the current nesting level. let current_nesting_level = self.current_inline_container_state_mut(); current_nesting_level.has_content = true; self.propagate_current_nesting_level_white_space_style(); } fn process_line_break(&mut self, forced_line_break: bool) { self.current_line_segment .prepare_for_placement_on_empty_line( &self.current_line, self.inline_box_state_stack.len(), ); self.finish_current_line_and_reset(forced_line_break); } /// Process a soft wrap opportunity. This will either commit the current unbreakble /// segment to the current line, if it fits within the containing block and float /// placement boundaries, or do a line break and then commit the segment. fn process_soft_wrap_opportunity(&mut self) { if self.current_line_segment.line_items.is_empty() { return; } if !self.white_space.allow_wrap() { return; } let potential_line_size = LogicalVec2 { inline: self.current_line.inline_position + self.current_line_segment.size.inline - self.current_line_segment.trailing_whitespace_size, block: self .current_line_max_block_size() .max(self.current_line_segment.size.block), }; if self.new_potential_line_size_causes_line_break(&potential_line_size) { self.process_line_break(false /* forced_line_break */); } self.commit_current_segment_to_line(); } /// Commit the current unbrekable segment to the current line. In addition, this will /// place all floats in the unbreakable segment and expand the line dimensions. fn commit_current_segment_to_line(&mut self) { if self.current_line_segment.line_items.is_empty() { return; } if !self.current_line.has_content { self.current_line_segment.trim_leading_whitespace(); } self.current_line.inline_position += self.current_line_segment.size.inline; self.current_line.max_block_size = self .current_line_max_block_size() .max(self.current_line_segment.size.block); self.current_line.justification_opportunities += self.current_line_segment.justification_opportunities; let line_inline_size_without_trailing_whitespace = self.current_line.inline_position - self.current_line_segment.trailing_whitespace_size; // Place all floats in this unbreakable segment. let mut segment_items = mem::take(&mut self.current_line_segment.line_items); for item in segment_items.iter_mut() { match item { LineItem::Float(float_item) => { self.place_float_line_item_for_commit_to_line( float_item, line_inline_size_without_trailing_whitespace, ); }, _ => {}, } } // If the current line was never placed among floats, we need to do that now based on the // new size. Calling `new_potential_line_size_causes_line_break()` here triggers the // new line to be positioned among floats. This should never ask for a line // break because it is the first content on the line. if self.current_line.line_items.is_empty() { let will_break = self.new_potential_line_size_causes_line_break(&LogicalVec2 { inline: line_inline_size_without_trailing_whitespace, block: self.current_line_segment.size.block, }); assert!(!will_break); } // Try to merge all TextRuns in the line. let to_skip = match ( self.current_line.line_items.last_mut(), segment_items.first_mut(), ) { ( Some(LineItem::TextRun(last_line_item)), Some(LineItem::TextRun(first_segment_item)), ) => { last_line_item.text.append(&mut first_segment_item.text); 1 }, _ => 0, }; self.current_line .line_items .extend(segment_items.into_iter().skip(to_skip)); self.current_line.has_content |= self.current_line_segment.has_content; self.current_line_segment.reset(); } } impl InlineFormattingContext { pub(super) fn new( text_decoration_line: TextDecorationLine, has_first_formatted_line: bool, ends_with_whitespace: bool, ) -> InlineFormattingContext { InlineFormattingContext { inline_level_boxes: Default::default(), text_decoration_line, has_first_formatted_line, contains_floats: false, ends_with_whitespace, } } // This works on an already-constructed `InlineFormattingContext`, // Which would have to change if/when // `BlockContainer::construct` parallelize their construction. pub(super) fn inline_content_sizes( &self, layout_context: &LayoutContext, containing_block_writing_mode: WritingMode, ) -> ContentSizes { struct Computation<'a> { layout_context: &'a LayoutContext<'a>, containing_block_writing_mode: WritingMode, paragraph: ContentSizes, current_line: ContentSizes, /// Size for whitepsace pending to be added to this line. pending_whitespace: Length, /// Whether or not this IFC has seen any non-whitespace content. had_non_whitespace_content_yet: bool, /// The global linebreaking state. linebreaker: Option, } impl Computation<'_> { fn traverse(&mut self, inline_level_boxes: &[ArcRefCell]) { for inline_level_box in inline_level_boxes { match &mut *inline_level_box.borrow_mut() { InlineLevelBox::InlineBox(inline_box) => { let padding = inline_box.style.padding(self.containing_block_writing_mode); let border = inline_box .style .border_width(self.containing_block_writing_mode); let margin = inline_box.style.margin(self.containing_block_writing_mode); macro_rules! add { ($condition: ident, $side: ident) => { if inline_box.$condition { // For margins and paddings, a cyclic percentage is resolved against zero // for determining intrinsic size contributions. // https://drafts.csswg.org/css-sizing-3/#min-percentage-contribution let zero = Length::zero(); let mut length = padding.$side.percentage_relative_to(zero) + border.$side; if let Some(lp) = margin.$side.non_auto() { length += lp.percentage_relative_to(zero) } self.add_length(length); } }; } add!(is_first_fragment, inline_start); self.traverse(&inline_box.children); add!(is_last_fragment, inline_end); }, InlineLevelBox::TextRun(text_run) => { let result = text_run .break_and_shape(self.layout_context, &mut self.linebreaker); let BreakAndShapeResult { runs, break_at_start, .. } = match result { Ok(result) => result, Err(_) => return, }; if break_at_start { self.line_break_opportunity() } for run in &runs { let advance = Length::from(run.glyph_store.total_advance()); if !run.glyph_store.is_whitespace() { self.had_non_whitespace_content_yet = true; self.current_line.min_content += advance; self.current_line.max_content += self.pending_whitespace + advance; self.pending_whitespace = Length::zero(); } else { // If this run is a forced line break, we *must* break the line // and start measuring from the inline origin once more. if text_run .glyph_run_is_whitespace_ending_with_preserved_newline(run) { self.had_non_whitespace_content_yet = true; self.forced_line_break(); self.current_line = ContentSizes::zero(); continue; } // Discard any leading whitespace in the IFC. This will always be trimmed. if !self.had_non_whitespace_content_yet { continue; } // Wait to take into account other whitespace until we see more content. // Whitespace at the end of the IFC will always be trimmed. self.line_break_opportunity(); self.pending_whitespace += advance; } } }, InlineLevelBox::Atomic(atomic) => { let outer = atomic.outer_inline_content_sizes( self.layout_context, self.containing_block_writing_mode, ); self.current_line.min_content += self.pending_whitespace + outer.min_content; self.current_line.max_content += outer.max_content; self.pending_whitespace = Length::zero(); self.had_non_whitespace_content_yet = true; }, InlineLevelBox::OutOfFlowFloatBox(_) | InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(_) => {}, } } } fn add_length(&mut self, l: Length) { self.current_line.min_content += l; self.current_line.max_content += l; } fn line_break_opportunity(&mut self) { self.paragraph .min_content .max_assign(take(&mut self.current_line.min_content)); } fn forced_line_break(&mut self) { self.line_break_opportunity(); self.paragraph .max_content .max_assign(take(&mut self.current_line.max_content)); } } fn take(x: &mut T) -> T { std::mem::replace(x, T::zero()) } let mut computation = Computation { layout_context, containing_block_writing_mode, paragraph: ContentSizes::zero(), current_line: ContentSizes::zero(), pending_whitespace: Length::zero(), had_non_whitespace_content_yet: false, linebreaker: None, }; computation.traverse(&self.inline_level_boxes); computation.forced_line_break(); computation.paragraph } pub(super) fn layout( &self, layout_context: &LayoutContext, positioning_context: &mut PositioningContext, containing_block: &ContainingBlock, sequential_layout_state: Option<&mut SequentialLayoutState>, collapsible_with_parent_start_margin: CollapsibleWithParentStartMargin, ) -> FlowLayout { let first_line_inline_start = if self.has_first_formatted_line { containing_block .style .get_inherited_text() .text_indent .to_used_value(containing_block.inline_size.into()) .into() } else { Length::zero() }; let mut ifc = InlineFormattingContextState { positioning_context, containing_block, sequential_layout_state, layout_context, fragments: Vec::new(), current_line: LineUnderConstruction::new(LogicalVec2 { inline: first_line_inline_start, block: Length::zero(), }), current_line_segment: UnbreakableSegmentUnderConstruction::new(), linebreak_before_new_content: false, white_space: containing_block.style.get_inherited_text().white_space, linebreaker: None, have_deferred_soft_wrap_opportunity: false, prevent_soft_wrap_opportunity_before_next_atomic: false, root_nesting_level: InlineContainerState { nested_block_size: line_height_from_style(layout_context, &containing_block.style), has_content: false, text_decoration_line: self.text_decoration_line, }, inline_box_state_stack: Vec::new(), }; // FIXME(pcwalton): This assumes that margins never collapse through inline formatting // contexts (i.e. that inline formatting contexts are never empty). Is that right? // FIXME(mrobinson): This should not happen if the IFC collapses through. if let Some(ref mut sequential_layout_state) = ifc.sequential_layout_state { sequential_layout_state.collapse_margins(); // FIXME(mrobinson): Collapse margins in the containing block offsets as well?? } let mut iterator = InlineBoxChildIter::from_formatting_context(self); let mut parent_iterators = Vec::new(); loop { let next = iterator.next(); // Any new box should flush a pending hard line break. if next.is_some() { ifc.possibly_flush_deferred_forced_line_break(); } match next { Some(child) => match &mut *child.borrow_mut() { InlineLevelBox::InlineBox(inline_box) => { ifc.start_inline_box(inline_box); parent_iterators.push(iterator); iterator = InlineBoxChildIter::from_inline_level_box(child.clone()); }, InlineLevelBox::TextRun(run) => { run.layout_into_line_items(layout_context, &mut ifc) }, InlineLevelBox::Atomic(atomic_formatting_context) => { atomic_formatting_context.layout_into_line_items(layout_context, &mut ifc); }, InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(box_) => ifc .push_line_item_to_unbreakable_segment(LineItem::AbsolutelyPositioned( AbsolutelyPositionedLineItem { absolutely_positioned_box: box_.clone(), }, )), InlineLevelBox::OutOfFlowFloatBox(float_box) => { float_box.layout_into_line_items(layout_context, &mut ifc); }, }, None => { match parent_iterators.pop() { // If we have a parent iterator, then we are working on an // InlineBox and we just finished it. Some(parent_iterator) => { ifc.finish_inline_box(); iterator = parent_iterator; continue; }, // If we have no more parents, we are at the end of the root // iterator ie at the end of this InlineFormattingContext. None => break, }; }, } } ifc.finish_last_line(); let mut collapsible_margins_in_children = CollapsedBlockMargins::zero(); let content_block_size = ifc.current_line.start_position.block; collapsible_margins_in_children.collapsed_through = content_block_size == Length::zero() && collapsible_with_parent_start_margin.0; return FlowLayout { fragments: ifc.fragments, content_block_size, collapsible_margins_in_children, }; } /// Return true if this [InlineFormattingContext] is empty for the purposes of ignoring /// during box tree construction. An IFC is empty if it only contains TextRuns with /// completely collapsible whitespace. When that happens it can be ignored completely. pub fn is_empty(&self) -> bool { fn inline_level_boxes_are_empty(boxes: &[ArcRefCell]) -> bool { boxes .iter() .all(|inline_level_box| inline_level_box_is_empty(&*inline_level_box.borrow())) } fn inline_level_box_is_empty(inline_level_box: &InlineLevelBox) -> bool { match inline_level_box { InlineLevelBox::InlineBox(_) => false, InlineLevelBox::TextRun(text_run) => !text_run.has_uncollapsible_content, InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(_) => false, InlineLevelBox::OutOfFlowFloatBox(_) => false, InlineLevelBox::Atomic(_) => false, } } inline_level_boxes_are_empty(&self.inline_level_boxes) } } impl InlineBoxContainerState { fn new( inline_box: &InlineBox, containing_block: &ContainingBlock, text_decoration_of_parent: TextDecorationLine, nested_block_size_of_parent: Length, layout_context: &LayoutContext, is_last_fragment: bool, ) -> Self { let style = inline_box.style.clone(); let text_decoration_line = text_decoration_of_parent | style.clone_text_decoration_line(); Self { base: InlineContainerState { has_content: false, text_decoration_line, nested_block_size: nested_block_size_of_parent .max(line_height_from_style(layout_context, &style)), }, style, base_fragment_info: inline_box.base_fragment_info, pbm: inline_box.style.padding_border_margin(containing_block), is_last_fragment, } } fn layout_into_line_item( &mut self, layout_context: &LayoutContext, is_first_fragment: bool, is_last_fragment_of_ib_split: bool, ) -> InlineBoxLineItem { InlineBoxLineItem { base_fragment_info: self.base_fragment_info, style: self.style.clone(), block_size: line_gap_from_style(layout_context, &self.style), pbm: self.pbm.clone(), is_first_fragment, is_last_fragment_of_ib_split, } } } impl IndependentFormattingContext { fn layout_into_line_items( &mut self, layout_context: &LayoutContext, ifc: &mut InlineFormattingContextState, ) { let style = self.style(); let pbm = style.padding_border_margin(&ifc.containing_block); let margin = pbm.margin.auto_is(Length::zero); let pbm_sums = &(&pbm.padding + &pbm.border) + &margin; let mut child_positioning_context = None; // We need to know the inline size of the atomic before deciding whether to do the line break. let fragment = match self { IndependentFormattingContext::Replaced(replaced) => { let size = replaced.contents.used_size_as_if_inline_element( ifc.containing_block, &replaced.style, None, &pbm, ); let fragments = replaced .contents .make_fragments(&replaced.style, size.clone()); let content_rect = LogicalRect { start_corner: pbm_sums.start_offset(), size, }; BoxFragment::new( replaced.base_fragment_info, replaced.style.clone(), fragments, content_rect, pbm.padding, pbm.border, margin, None, CollapsedBlockMargins::zero(), ) }, IndependentFormattingContext::NonReplaced(non_replaced) => { let box_size = non_replaced .style .content_box_size(&ifc.containing_block, &pbm); let max_box_size = non_replaced .style .content_max_box_size(&ifc.containing_block, &pbm); let min_box_size = non_replaced .style .content_min_box_size(&ifc.containing_block, &pbm) .auto_is(Length::zero); // https://drafts.csswg.org/css2/visudet.html#inlineblock-width let tentative_inline_size = box_size.inline.auto_is(|| { let available_size = ifc.containing_block.inline_size - pbm_sums.inline_sum(); non_replaced .inline_content_sizes(layout_context) .shrink_to_fit(available_size) }); // https://drafts.csswg.org/css2/visudet.html#min-max-widths // In this case “applying the rules above again” with a non-auto inline-size // always results in that size. let inline_size = tentative_inline_size .clamp_between_extremums(min_box_size.inline, max_box_size.inline); let containing_block_for_children = ContainingBlock { inline_size, block_size: box_size.block, style: &non_replaced.style, }; assert_eq!( ifc.containing_block.style.writing_mode, containing_block_for_children.style.writing_mode, "Mixed writing modes are not supported yet" ); // This always collects for the nearest positioned ancestor even if the parent positioning // context doesn't. The thing is we haven't kept track up to this point and there isn't // any harm in keeping the hoisted boxes separate. child_positioning_context = Some(PositioningContext::new_for_subtree( true, /* collects_for_nearest_positioned_ancestor */ )); let independent_layout = non_replaced.layout( layout_context, child_positioning_context.as_mut().unwrap(), &containing_block_for_children, ); // https://drafts.csswg.org/css2/visudet.html#block-root-margin let tentative_block_size = box_size .block .auto_is(|| independent_layout.content_block_size); // https://drafts.csswg.org/css2/visudet.html#min-max-heights // In this case “applying the rules above again” with a non-auto block-size // always results in that size. let block_size = tentative_block_size .clamp_between_extremums(min_box_size.block, max_box_size.block); let content_rect = LogicalRect { start_corner: pbm_sums.start_offset(), size: LogicalVec2 { block: block_size, inline: inline_size, }, }; BoxFragment::new( non_replaced.base_fragment_info, non_replaced.style.clone(), independent_layout.fragments, content_rect, pbm.padding, pbm.border, margin, None, CollapsedBlockMargins::zero(), ) }, }; let soft_wrap_opportunity_prevented = mem::replace( &mut ifc.prevent_soft_wrap_opportunity_before_next_atomic, false, ); if ifc.white_space.allow_wrap() && !soft_wrap_opportunity_prevented { ifc.process_soft_wrap_opportunity(); } let size = &pbm_sums.sum() + &fragment.content_rect.size; ifc.push_content_line_item_to_unbreakable_segment( size.inline, LineItem::Atomic(AtomicLineItem { fragment, size, positioning_context: child_positioning_context, }), true, ); // Defer a soft wrap opportunity for when we next process text content. ifc.have_deferred_soft_wrap_opportunity = true; } } struct BreakAndShapeResult { font_metrics: FontMetrics, font_key: FontInstanceKey, runs: Vec, break_at_start: bool, } impl TextRun { fn break_and_shape( &self, layout_context: &LayoutContext, linebreaker: &mut Option, ) -> Result { use gfx::font::ShapingFlags; use style::computed_values::text_rendering::T as TextRendering; use style::computed_values::word_break::T as WordBreak; let font_style = self.parent_style.clone_font(); let inherited_text_style = self.parent_style.get_inherited_text(); let letter_spacing = if inherited_text_style.letter_spacing.0.px() != 0. { Some(app_units::Au::from(inherited_text_style.letter_spacing.0)) } else { None }; let mut flags = ShapingFlags::empty(); if letter_spacing.is_some() { flags.insert(ShapingFlags::IGNORE_LIGATURES_SHAPING_FLAG); } if inherited_text_style.text_rendering == TextRendering::Optimizespeed { flags.insert(ShapingFlags::IGNORE_LIGATURES_SHAPING_FLAG); flags.insert(ShapingFlags::DISABLE_KERNING_SHAPING_FLAG) } if inherited_text_style.word_break == WordBreak::KeepAll { flags.insert(ShapingFlags::KEEP_ALL_FLAG); } crate::context::with_thread_local_font_context(layout_context, |font_context| { let font_group = font_context.font_group(font_style); let font = match font_group.borrow_mut().first(font_context) { Some(font) => font, None => return Err("Could not find find for TextRun."), }; let mut font = font.borrow_mut(); let word_spacing = &inherited_text_style.word_spacing; let word_spacing = word_spacing .to_length() .map(|l| l.into()) .unwrap_or_else(|| { let space_width = font .glyph_index(' ') .map(|glyph_id| font.glyph_h_advance(glyph_id)) .unwrap_or(gfx::font::LAST_RESORT_GLYPH_ADVANCE); word_spacing.to_used_value(Au::from_f64_px(space_width)) }); let shaping_options = gfx::font::ShapingOptions { letter_spacing, word_spacing, script: unicode_script::Script::Common, flags, }; let (runs, break_at_start) = gfx::text::text_run::TextRun::break_and_shape( &mut font, &self.text, &shaping_options, linebreaker, ); Ok(BreakAndShapeResult { font_metrics: font.metrics.clone(), font_key: font.font_key, runs, break_at_start, }) }) } fn glyph_run_is_whitespace_ending_with_preserved_newline(&self, run: &GlyphRun) -> bool { if !run.glyph_store.is_whitespace() { return false; } if !self .parent_style .get_inherited_text() .white_space .preserve_newlines() { return false; } let last_byte = self.text.as_bytes().get(run.range.end().to_usize() - 1); last_byte == Some(&b'\n') } fn layout_into_line_items( &self, layout_context: &LayoutContext, ifc: &mut InlineFormattingContextState, ) { let result = self.break_and_shape(layout_context, &mut ifc.linebreaker); let BreakAndShapeResult { font_metrics, font_key, runs, break_at_start, } = match result { Ok(result) => result, Err(string) => { warn!("Could not render TextRun: {string}"); return; }, }; // We either have a soft wrap opportunity if specified by the breaker or if we are // following replaced content. let have_deferred_soft_wrap_opportunity = mem::replace(&mut ifc.have_deferred_soft_wrap_opportunity, false); let mut break_at_start = break_at_start || have_deferred_soft_wrap_opportunity; if have_deferred_soft_wrap_opportunity { if let Some(first_character) = self.text.chars().nth(0) { break_at_start = break_at_start && !char_prevents_soft_wrap_opportunity_when_before_or_after_atomic( first_character, ) } } if let Some(last_character) = self.text.chars().last() { ifc.prevent_soft_wrap_opportunity_before_next_atomic = char_prevents_soft_wrap_opportunity_when_before_or_after_atomic(last_character); } for (run_index, run) in runs.into_iter().enumerate() { ifc.possibly_flush_deferred_forced_line_break(); // If this whitespace forces a line break, queue up a hard line break the next time we // see any content. We don't line break immediately, because we'd like to finish processing // any ongoing inline boxes before ending the line. if self.glyph_run_is_whitespace_ending_with_preserved_newline(&run) { ifc.defer_forced_line_break(); continue; } // Break before each unbrekable run in this TextRun, except the first unless the // linebreaker was set to break before the first run. if run_index != 0 || break_at_start { ifc.process_soft_wrap_opportunity(); } ifc.push_glyph_store_to_unbreakable_segment( run.glyph_store, self.base_fragment_info, &self.parent_style, &font_metrics, font_key, ); } } } impl FloatBox { fn layout_into_line_items( &mut self, layout_context: &LayoutContext, ifc: &mut InlineFormattingContextState, ) { let fragment = self.layout( layout_context, ifc.positioning_context, ifc.containing_block, ); ifc.push_line_item_to_unbreakable_segment(LineItem::Float(FloatLineItem { fragment, needs_placement: true, })); } } enum InlineBoxChildIter<'box_tree> { InlineFormattingContext(std::slice::Iter<'box_tree, ArcRefCell>), InlineBox { inline_level_box: ArcRefCell, child_index: usize, }, } impl<'box_tree> InlineBoxChildIter<'box_tree> { fn from_formatting_context( inline_formatting_context: &'box_tree InlineFormattingContext, ) -> InlineBoxChildIter<'box_tree> { InlineBoxChildIter::InlineFormattingContext( inline_formatting_context.inline_level_boxes.iter(), ) } fn from_inline_level_box( inline_level_box: ArcRefCell, ) -> InlineBoxChildIter<'box_tree> { InlineBoxChildIter::InlineBox { inline_level_box, child_index: 0, } } } impl<'box_tree> Iterator for InlineBoxChildIter<'box_tree> { type Item = ArcRefCell; fn next(&mut self) -> Option> { match *self { InlineBoxChildIter::InlineFormattingContext(ref mut iter) => iter.next().cloned(), InlineBoxChildIter::InlineBox { ref inline_level_box, ref mut child_index, } => match *inline_level_box.borrow() { InlineLevelBox::InlineBox(ref inline_box) => { if *child_index >= inline_box.children.len() { return None; } let kid = inline_box.children[*child_index].clone(); *child_index += 1; Some(kid) }, _ => unreachable!(), }, } } } /// State used when laying out the [`LineItem`]s collected for the line currently being /// laid out. struct LineItemLayoutState<'a> { inline_position: Length, /// The inline start position of the parent (the inline box that established this state) /// relative to the edge of the containing block of this [`InlineFormattingCotnext`]. inline_start_of_parent: Length, ifc_containing_block: &'a ContainingBlock<'a>, positioning_context: &'a mut PositioningContext, line_block_start: Length, /// The amount of space to add to each justification opportunity in order to implement /// `text-align: justify`. justification_adjustment: Length, } fn layout_line_items( iterator: &mut IntoIter, layout_context: &LayoutContext, state: &mut LineItemLayoutState, saw_end: &mut bool, ) -> Vec { let mut fragments = vec![]; while let Some(item) = iterator.next() { match item { LineItem::TextRun(text_line_item) => { if let Some(fragment) = text_line_item.layout(state) { fragments.push(Fragment::Text(fragment)); } }, LineItem::StartInlineBox(box_line_item) => { if let Some(fragment) = box_line_item.layout(iterator, layout_context, state) { fragments.push(Fragment::Box(fragment)) } }, LineItem::EndInlineBox => { *saw_end = true; break; }, LineItem::Atomic(atomic_line_item) => { fragments.push(Fragment::Box(atomic_line_item.layout(state))); }, LineItem::AbsolutelyPositioned(absolute_line_item) => { fragments.push(Fragment::AbsoluteOrFixedPositioned( absolute_line_item.layout(state), )); }, LineItem::Float(float_line_item) => { fragments.push(Fragment::Float(float_line_item.layout(state))); }, } } fragments } fn place_pending_floats(ifc: &mut InlineFormattingContextState, line_items: &mut Vec) { for item in line_items.into_iter() { match item { LineItem::Float(float_line_item) => { if float_line_item.needs_placement { ifc.place_float_fragment(&mut float_line_item.fragment); } }, _ => {}, } } } enum LineItem { TextRun(TextRunLineItem), StartInlineBox(InlineBoxLineItem), EndInlineBox, Atomic(AtomicLineItem), AbsolutelyPositioned(AbsolutelyPositionedLineItem), Float(FloatLineItem), } impl LineItem { fn trim_whitespace_at_end( &mut self, whitespace_trimmed: &mut Length, spaces_trimmed: &mut usize, ) -> bool { match self { LineItem::TextRun(ref mut item) => { item.trim_whitespace_at_end(whitespace_trimmed, spaces_trimmed) }, LineItem::StartInlineBox(_) => true, LineItem::EndInlineBox => true, LineItem::Atomic(_) => false, LineItem::AbsolutelyPositioned(_) => true, LineItem::Float(_) => true, } } fn trim_whitespace_at_start( &mut self, whitespace_trimmed: &mut Length, spaces_trimmed: &mut usize, ) -> bool { match self { LineItem::TextRun(ref mut item) => { item.trim_whitespace_at_start(whitespace_trimmed, spaces_trimmed) }, LineItem::StartInlineBox(_) => true, LineItem::EndInlineBox => true, LineItem::Atomic(_) => false, LineItem::AbsolutelyPositioned(_) => true, LineItem::Float(_) => true, } } fn block_size(&self) -> Length { match self { LineItem::TextRun(text_run) => text_run.line_height(), LineItem::StartInlineBox(_) => { // TODO(mrobinson): This should get the line height from the font. Length::zero() }, LineItem::EndInlineBox => Length::zero(), LineItem::Atomic(atomic) => atomic.size.block, LineItem::AbsolutelyPositioned(_) => Length::zero(), LineItem::Float(_) => Length::zero(), } } } struct TextRunLineItem { base_fragment_info: BaseFragmentInfo, parent_style: Arc, text: Vec>, font_metrics: FontMetrics, font_key: FontInstanceKey, text_decoration_line: TextDecorationLine, } fn line_height(parent_style: &ComputedValues, font_metrics: &FontMetrics) -> Length { let font_size = parent_style.get_font().font_size.computed_size(); match parent_style.get_inherited_text().line_height { LineHeight::Normal => Length::from(font_metrics.line_gap), LineHeight::Number(number) => font_size * number.0, LineHeight::Length(length) => length.0, } } fn line_gap_from_style(layout_context: &LayoutContext, style: &ComputedValues) -> Length { crate::context::with_thread_local_font_context(layout_context, |font_context| { let font_group = font_context.font_group(style.clone_font()); let font = match font_group.borrow_mut().first(font_context) { Some(font) => font, None => { warn!("Could not find find for TextRun."); return Length::zero(); }, }; let font = font.borrow(); Length::from(font.metrics.line_gap) }) } fn line_height_from_style(layout_context: &LayoutContext, style: &ComputedValues) -> Length { crate::context::with_thread_local_font_context(layout_context, |font_context| { let font_group = font_context.font_group(style.clone_font()); let font = match font_group.borrow_mut().first(font_context) { Some(font) => font, None => { warn!("Could not find find for TextRun."); return Length::zero(); }, }; let font = font.borrow(); line_height(style, &font.metrics) }) } impl TextRunLineItem { fn trim_whitespace_at_end( &mut self, whitespace_trimmed: &mut Length, spaces_trimmed: &mut usize, ) -> bool { if self .parent_style .get_inherited_text() .white_space .preserve_spaces() { return false; } let index_of_last_non_whitespace = self .text .iter() .rev() .position(|glyph| !glyph.is_whitespace()) .map(|offset_from_end| self.text.len() - offset_from_end); let first_whitespace_index = index_of_last_non_whitespace.unwrap_or(0); *spaces_trimmed += self.text.len() - first_whitespace_index; *whitespace_trimmed += self .text .drain(first_whitespace_index..) .map(|glyph| Length::from(glyph.total_advance())) .sum(); // Only keep going if we only encountered whitespace. index_of_last_non_whitespace.is_none() } fn trim_whitespace_at_start( &mut self, whitespace_trimmed: &mut Length, spaces_trimmed: &mut usize, ) -> bool { if self .parent_style .get_inherited_text() .white_space .preserve_spaces() { return false; } let index_of_first_non_whitespace = self .text .iter() .position(|glyph| !glyph.is_whitespace()) .unwrap_or(self.text.len()); *spaces_trimmed += index_of_first_non_whitespace; *whitespace_trimmed += self .text .drain(0..index_of_first_non_whitespace) .map(|glyph| Length::from(glyph.total_advance())) .sum(); // Only keep going if we only encountered whitespace. self.text.is_empty() } fn line_height(&self) -> Length { line_height(&self.parent_style, &self.font_metrics) } fn layout(self, state: &mut LineItemLayoutState) -> Option { if self.text.is_empty() { return None; } let mut number_of_justification_opportunities = 0; let mut inline_advance: Length = self .text .iter() .map(|glyph_store| { number_of_justification_opportunities += glyph_store.total_word_separators(); Length::from(glyph_store.total_advance()) }) .sum(); if !state.justification_adjustment.is_zero() { inline_advance += state.justification_adjustment * number_of_justification_opportunities as f32; } let rect = LogicalRect { start_corner: LogicalVec2 { block: Length::zero(), inline: state.inline_position - state.inline_start_of_parent, }, size: LogicalVec2 { block: self.line_height(), inline: inline_advance, }, }; state.inline_position += inline_advance; Some(TextFragment { base: self.base_fragment_info.into(), parent_style: self.parent_style, rect, font_metrics: self.font_metrics, font_key: self.font_key, glyphs: self.text, text_decoration_line: self.text_decoration_line, justification_adjustment: state.justification_adjustment, }) } } #[derive(Clone)] struct InlineBoxLineItem { base_fragment_info: BaseFragmentInfo, style: Arc, pbm: PaddingBorderMargin, block_size: Length, /// Whether this is the first fragment for this inline box. This means that it's the /// first potentially split box of a block-in-inline-split (or only if there's no /// split) and also the first appearance of this fragment on any line. is_first_fragment: bool, /// Whether this is the last fragment for this inline box. This means that it's the /// last potentially split box of a block-in-inline-split (or the only fragment if /// there's no split). is_last_fragment_of_ib_split: bool, } impl InlineBoxLineItem { fn layout( self, iterator: &mut IntoIter, layout_context: &LayoutContext, state: &mut LineItemLayoutState, ) -> Option { let style = self.style.clone(); let mut padding = self.pbm.padding.clone(); let mut border = self.pbm.border.clone(); let mut margin = self.pbm.margin.auto_is(Length::zero); if !self.is_first_fragment { padding.inline_start = Length::zero(); border.inline_start = Length::zero(); margin.inline_start = Length::zero(); } if !self.is_last_fragment_of_ib_split { padding.inline_end = Length::zero(); border.inline_end = Length::zero(); margin.inline_end = Length::zero(); } let pbm_sums = &(&padding + &border) + &margin; state.inline_position += pbm_sums.inline_start; let mut positioning_context = PositioningContext::new_for_style(&style); let nested_positioning_context = match positioning_context.as_mut() { Some(positioning_context) => positioning_context, None => &mut state.positioning_context, }; let original_nested_positioning_context_length = nested_positioning_context.len(); let mut nested_state = LineItemLayoutState { inline_position: state.inline_position, inline_start_of_parent: state.inline_position, ifc_containing_block: state.ifc_containing_block, positioning_context: nested_positioning_context, line_block_start: state.line_block_start, justification_adjustment: state.justification_adjustment, }; let mut saw_end = false; let fragments = layout_line_items(iterator, layout_context, &mut nested_state, &mut saw_end); // Only add ending padding, border, margin if this is the last fragment of a // potential block-in-inline split and this line included the actual end of this // fragment (it doesn't continue on the next line). if !self.is_last_fragment_of_ib_split || !saw_end { padding.inline_end = Length::zero(); border.inline_end = Length::zero(); margin.inline_end = Length::zero(); } let pbm_sums = &(&padding + &border) + &margin; // If the inline box didn't have any content at all, don't add a Fragment for it. let box_has_padding_border_or_margin = pbm_sums.inline_sum() > Length::zero(); let box_had_absolutes = original_nested_positioning_context_length != nested_state.positioning_context.len(); if !self.is_first_fragment && fragments.is_empty() && !box_has_padding_border_or_margin && !box_had_absolutes { return None; } let mut content_rect = LogicalRect { start_corner: LogicalVec2 { inline: state.inline_position - state.inline_start_of_parent, block: Length::zero(), }, size: LogicalVec2 { inline: nested_state.inline_position - state.inline_position, block: self.block_size, }, }; state.inline_position = nested_state.inline_position + pbm_sums.inline_end; // Relative adjustment should not affect the rest of line layout, so we can // do it right before creating the Fragment. if style.clone_position().is_relative() { content_rect.start_corner += &relative_adjustement(&style, state.ifc_containing_block); } let mut fragment = BoxFragment::new( self.base_fragment_info, self.style.clone(), fragments, content_rect, padding, border, margin, None, CollapsedBlockMargins::zero(), ); if let Some(mut positioning_context) = positioning_context.take() { assert!(original_nested_positioning_context_length == PositioningContextLength::zero()); positioning_context.layout_collected_children(layout_context, &mut fragment); positioning_context.adjust_static_position_of_hoisted_fragments_with_offset( &fragment.content_rect.start_corner, PositioningContextLength::zero(), ); state.positioning_context.append(positioning_context); } else { state .positioning_context .adjust_static_position_of_hoisted_fragments_with_offset( &fragment.content_rect.start_corner, original_nested_positioning_context_length, ); } Some(fragment) } } struct AtomicLineItem { fragment: BoxFragment, size: LogicalVec2, positioning_context: Option, } impl AtomicLineItem { fn layout(mut self, state: &mut LineItemLayoutState) -> BoxFragment { // The initial `start_corner` of the Fragment is the PaddingBorderMargin sum // start offset, which is the sum of the start component of the padding, // border, and margin. Offset that value by the inline start position of the // line layout. self.fragment.content_rect.start_corner.inline += state.inline_position - state.inline_start_of_parent; if self.fragment.style.clone_position().is_relative() { self.fragment.content_rect.start_corner += &relative_adjustement(&self.fragment.style, state.ifc_containing_block); } state.inline_position += self.size.inline; if let Some(mut positioning_context) = self.positioning_context { positioning_context.adjust_static_position_of_hoisted_fragments_with_offset( &self.fragment.content_rect.start_corner, PositioningContextLength::zero(), ); state.positioning_context.append(positioning_context); } self.fragment } } struct AbsolutelyPositionedLineItem { absolutely_positioned_box: ArcRefCell, } impl AbsolutelyPositionedLineItem { fn layout(self, state: &mut LineItemLayoutState) -> ArcRefCell { let box_ = self.absolutely_positioned_box; let style = AtomicRef::map(box_.borrow(), |box_| box_.context.style()); let initial_start_corner = match Display::from(style.get_box().original_display) { Display::GeneratingBox(DisplayGeneratingBox::OutsideInside { outside, inside: _ }) => { LogicalVec2 { inline: match outside { DisplayOutside::Inline => { state.inline_position - state.inline_start_of_parent }, DisplayOutside::Block => Length::zero(), }, block: Length::zero(), } }, Display::GeneratingBox(DisplayGeneratingBox::LayoutInternal(_)) => { unreachable!( "The result of blockification should never be a layout-internal value." ); }, Display::Contents => { panic!("display:contents does not generate an abspos box") }, Display::None => { panic!("display:none does not generate an abspos box") }, }; let hoisted_box = AbsolutelyPositionedBox::to_hoisted( box_.clone(), initial_start_corner, state.ifc_containing_block, ); let hoisted_fragment = hoisted_box.fragment.clone(); state.positioning_context.push(hoisted_box); hoisted_fragment } } struct FloatLineItem { fragment: BoxFragment, /// Whether or not this float Fragment has been placed yet. Fragments that /// do not fit on a line need to be placed after the hypothetical block start /// of the next line. needs_placement: bool, } impl FloatLineItem { fn layout(mut self, state: &mut LineItemLayoutState<'_>) -> BoxFragment { // The `BoxFragment` for this float is positioned relative to the IFC, so we need // to move it to be positioned relative to our parent InlineBox line item. Floats // fragments are children of these InlineBoxes and not children of the inline // formatting context, so that they are parented properly for StackingContext // properties such as opacity & filters. let distance_from_parent_to_ifc = LogicalVec2 { inline: state.inline_start_of_parent, block: state.line_block_start, }; self.fragment.content_rect.start_corner = &self.fragment.content_rect.start_corner - &distance_from_parent_to_ifc; self.fragment } } /// Whether or not this character prevents a soft line wrap opportunity when it /// comes before or after an atomic inline element. /// /// From https://www.w3.org/TR/css-text-3/#line-break-details: /// /// > For Web-compatibility there is a soft wrap opportunity before and after each /// > replaced element or other atomic inline, even when adjacent to a character that /// > would normally suppress them, including U+00A0 NO-BREAK SPACE. However, with /// > the exception of U+00A0 NO-BREAK SPACE, there must be no soft wrap opportunity /// > between atomic inlines and adjacent characters belonging to the Unicode GL, WJ, /// > or ZWJ line breaking classes. fn char_prevents_soft_wrap_opportunity_when_before_or_after_atomic(character: char) -> bool { if character == '\u{00A0}' { return false; } let class = linebreak_property(character); class == XI_LINE_BREAKING_CLASS_GL || class == XI_LINE_BREAKING_CLASS_WJ || class == XI_LINE_BREAKING_CLASS_ZWJ }