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layout: Consider vertical alignment of fragments during line breaking.
This makes the line breaker determine the final block positions of each line rather than doing it in a separate pass afterward. Not only does this simplify the code, it makes `vertical-align` and float placement interact properly.
This commit is contained in:
Patrick Walton
parent
04f05349b1
commit
b7c9674044
2 changed files with 171 additions and 275 deletions
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@ -11,7 +11,7 @@ use canvas_traits::CanvasMsg;
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use context::LayoutContext;
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use euclid::{Point2D, Rect, Size2D};
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use floats::ClearType;
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use flow::{self, Flow};
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use flow::{self, Flow, ImmutableFlowUtils};
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use flow_ref::{self, FlowRef};
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use gfx;
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use gfx::display_list::{BLUR_INFLATION_FACTOR, FragmentType, OpaqueNode, StackingContextId};
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@ -38,7 +38,7 @@ use std::sync::{Arc, Mutex};
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use style::computed_values::content::ContentItem;
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use style::computed_values::{border_collapse, clear, display, mix_blend_mode, overflow_wrap};
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use style::computed_values::{overflow_x, position, text_decoration, transform_style};
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use style::computed_values::{white_space, word_break, z_index};
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use style::computed_values::{vertical_align, white_space, word_break, z_index};
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use style::dom::TRestyleDamage;
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use style::logical_geometry::{LogicalMargin, LogicalRect, LogicalSize, WritingMode};
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use style::properties::{ComputedValues, ServoComputedValues};
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@ -2558,6 +2558,24 @@ impl Fragment {
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LayerId::new_of_type(LayerType::OverflowScroll, self.node.id() as usize)
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}
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/// Returns true if any of the inline styles associated with this fragment have
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/// `vertical-align` set to `top` or `bottom`.
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pub fn is_vertically_aligned_to_top_or_bottom(&self) -> bool {
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match self.style.get_box().vertical_align {
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vertical_align::T::top | vertical_align::T::bottom => return true,
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_ => {}
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}
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if let Some(ref inline_context) = self.inline_context {
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for node in &inline_context.nodes {
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match node.style.get_box().vertical_align {
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vertical_align::T::top | vertical_align::T::bottom => return true,
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_ => {}
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}
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}
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}
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false
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}
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pub fn is_text_or_replaced(&self) -> bool {
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match self.specific {
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SpecificFragmentInfo::Generic |
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@ -27,7 +27,7 @@ use range::{Range, RangeIndex};
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use std::cmp::max;
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use std::collections::VecDeque;
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use std::sync::Arc;
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use std::{fmt, isize, mem};
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use std::{fmt, i32, isize, mem};
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use style::computed_values::{display, overflow_x, position, text_align, text_justify};
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use style::computed_values::{text_overflow, vertical_align, white_space};
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use style::logical_geometry::{LogicalRect, LogicalSize, WritingMode};
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@ -419,13 +419,23 @@ impl LineBreaker {
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// block-size. This might not be the case with some weird text fonts.
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fn new_inline_metrics_for_line(&self, new_fragment: &Fragment, layout_context: &LayoutContext)
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-> InlineMetrics {
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self.pending_line.inline_metrics.max(&new_fragment.inline_metrics(layout_context))
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if !new_fragment.is_vertically_aligned_to_top_or_bottom() {
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let fragment_inline_metrics = new_fragment.inline_metrics(layout_context);
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self.pending_line.inline_metrics.max(&fragment_inline_metrics)
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} else {
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self.pending_line.inline_metrics
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}
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}
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fn new_block_size_for_line(&self, new_fragment: &Fragment, layout_context: &LayoutContext)
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-> Au {
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max(self.pending_line.bounds.size.block,
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self.new_inline_metrics_for_line(new_fragment, layout_context).block_size())
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let new_block_size = if new_fragment.is_vertically_aligned_to_top_or_bottom() {
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max(new_fragment.inline_metrics(layout_context).block_size(),
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self.minimum_block_size_above_baseline + self.minimum_depth_below_baseline)
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} else {
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self.new_inline_metrics_for_line(new_fragment, layout_context).block_size()
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};
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max(self.pending_line.bounds.size.block, new_block_size)
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}
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/// Computes the position of a line that has only the provided fragment. Returns the bounding
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@ -856,105 +866,6 @@ impl InlineFlow {
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flow
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}
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/// Returns the distance from the baseline for the logical block-start inline-start corner of
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/// this fragment, taking into account the value of the CSS `vertical-align` property.
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/// Negative values mean "toward the logical block-start" and positive values mean "toward the
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/// logical block-end".
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///
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/// The extra boolean is set if and only if `largest_block_size_for_top_fragments` and/or
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/// `largest_block_size_for_bottom_fragments` were updated. That is, if the box has a `top` or
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/// `bottom` value for `vertical-align`, true is returned.
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fn distance_from_baseline(fragment: &Fragment,
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ascent: Au,
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parent_text_block_start: Au,
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parent_text_block_end: Au,
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block_size_above_baseline: &mut Au,
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depth_below_baseline: &mut Au,
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largest_block_size_for_top_fragments: &mut Au,
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largest_block_size_for_bottom_fragments: &mut Au,
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layout_context: &LayoutContext)
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-> (Au, bool) {
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let (mut offset_from_baseline, mut largest_size_updated) = (Au(0), false);
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for style in fragment.inline_styles() {
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// Ignore `vertical-align` values for table cells.
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let box_style = style.get_box();
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match box_style.display {
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display::T::inline | display::T::block | display::T::inline_block => {}
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_ => continue,
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}
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match box_style.vertical_align {
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vertical_align::T::baseline => {}
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vertical_align::T::middle => {
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// TODO: x-height value should be used from font info.
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// TODO: Doing nothing here passes our current reftests but doesn't work in
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// all situations. Add vertical align reftests and fix this.
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},
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vertical_align::T::sub => {
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let sub_offset = (parent_text_block_start + parent_text_block_end)
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.scale_by(FONT_SUBSCRIPT_OFFSET_RATIO);
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offset_from_baseline = offset_from_baseline + sub_offset
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},
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vertical_align::T::super_ => {
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let super_offset = (parent_text_block_start + parent_text_block_end)
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.scale_by(FONT_SUPERSCRIPT_OFFSET_RATIO);
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offset_from_baseline = offset_from_baseline - super_offset
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},
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vertical_align::T::text_top => {
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let fragment_block_size = *block_size_above_baseline +
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*depth_below_baseline;
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let prev_depth_below_baseline = *depth_below_baseline;
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*block_size_above_baseline = parent_text_block_start;
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*depth_below_baseline = fragment_block_size - *block_size_above_baseline;
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offset_from_baseline = offset_from_baseline + *depth_below_baseline -
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prev_depth_below_baseline
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},
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vertical_align::T::text_bottom => {
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let fragment_block_size = *block_size_above_baseline +
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*depth_below_baseline;
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let prev_depth_below_baseline = *depth_below_baseline;
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*depth_below_baseline = parent_text_block_end;
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*block_size_above_baseline = fragment_block_size - *depth_below_baseline;
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offset_from_baseline = offset_from_baseline + *depth_below_baseline -
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prev_depth_below_baseline
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},
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vertical_align::T::top => {
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if !largest_size_updated {
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largest_size_updated = true;
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*largest_block_size_for_top_fragments =
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max(*largest_block_size_for_top_fragments,
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*block_size_above_baseline + *depth_below_baseline);
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offset_from_baseline = offset_from_baseline +
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*block_size_above_baseline
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}
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},
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vertical_align::T::bottom => {
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if !largest_size_updated {
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largest_size_updated = true;
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*largest_block_size_for_bottom_fragments =
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max(*largest_block_size_for_bottom_fragments,
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*block_size_above_baseline + *depth_below_baseline);
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offset_from_baseline = offset_from_baseline - *depth_below_baseline
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}
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},
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vertical_align::T::LengthOrPercentage(LengthOrPercentage::Length(length)) => {
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offset_from_baseline = offset_from_baseline - length
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}
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vertical_align::T::LengthOrPercentage(LengthOrPercentage::Percentage(p)) => {
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let line_height = fragment.calculate_line_height(layout_context);
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let percent_offset = line_height.scale_by(p);
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offset_from_baseline = offset_from_baseline - percent_offset
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}
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vertical_align::T::LengthOrPercentage(LengthOrPercentage::Calc(calc)) => {
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let line_height = fragment.calculate_line_height(layout_context);
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let percent_offset = line_height.scale_by(calc.percentage());
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offset_from_baseline = offset_from_baseline - percent_offset - calc.length()
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}
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}
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}
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(offset_from_baseline - ascent, largest_size_updated)
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}
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/// Sets fragment positions in the inline direction based on alignment for one line. This
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/// performs text justification if mandated by the style.
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fn set_inline_fragment_positions(fragments: &mut InlineFragments,
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@ -1120,13 +1031,12 @@ impl InlineFlow {
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}
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}
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/// Sets final fragment positions in the block direction for one line. Assumes that the
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/// fragment positions were initially set to the distance from the baseline first.
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/// Sets final fragment positions in the block direction for one line.
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fn set_block_fragment_positions(fragments: &mut InlineFragments,
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line: &Line,
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line_distance_from_flow_block_start: Au,
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baseline_distance_from_block_start: Au,
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largest_depth_below_baseline: Au) {
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minimum_block_size_above_baseline: Au,
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minimum_depth_below_baseline: Au,
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layout_context: &LayoutContext) {
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for fragment_index in line.range.each_index() {
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// If any of the inline styles say `top` or `bottom`, adjust the vertical align
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// appropriately.
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@ -1134,42 +1044,63 @@ impl InlineFlow {
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// FIXME(#5624, pcwalton): This passes our current reftests but isn't the right thing
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// to do.
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let fragment = fragments.get_mut(fragment_index.to_usize());
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let mut vertical_align = vertical_align::T::baseline;
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let fragment_inline_metrics = fragment.inline_metrics(layout_context);
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let mut block_start = line.bounds.start.b +
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line.inline_metrics.block_size_above_baseline -
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fragment_inline_metrics.ascent;
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for style in fragment.inline_styles() {
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match (style.get_box().display, style.get_box().vertical_align) {
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(display::T::inline, vertical_align::T::top) |
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(display::T::block, vertical_align::T::top) |
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(display::T::inline_block, vertical_align::T::top) => {
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vertical_align = vertical_align::T::top;
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break
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match style.get_box().vertical_align {
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vertical_align::T::baseline => {}
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vertical_align::T::middle => {}
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vertical_align::T::sub => {
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let sub_offset =
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(minimum_block_size_above_baseline +
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minimum_depth_below_baseline).scale_by(FONT_SUBSCRIPT_OFFSET_RATIO);
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block_start = block_start + sub_offset
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}
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(display::T::inline, vertical_align::T::bottom) |
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(display::T::block, vertical_align::T::bottom) |
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(display::T::inline_block, vertical_align::T::bottom) => {
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vertical_align = vertical_align::T::bottom;
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break
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vertical_align::T::super_ => {
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let super_offset =
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(minimum_block_size_above_baseline +
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minimum_depth_below_baseline).scale_by(FONT_SUPERSCRIPT_OFFSET_RATIO);
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block_start = block_start - super_offset
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}
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vertical_align::T::text_top => {
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block_start = line.bounds.start.b +
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line.inline_metrics.block_size_above_baseline -
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minimum_block_size_above_baseline
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}
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vertical_align::T::text_bottom => {
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block_start = line.bounds.start.b +
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line.inline_metrics.block_size_above_baseline +
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minimum_depth_below_baseline -
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fragment.border_box.size.block
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}
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vertical_align::T::top => {
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block_start = line.bounds.start.b
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}
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vertical_align::T::bottom => {
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block_start = line.bounds.start.b + line.bounds.size.block -
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fragment.border_box.size.block
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}
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vertical_align::T::LengthOrPercentage(LengthOrPercentage::Length(length)) => {
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block_start = block_start - length
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}
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vertical_align::T::LengthOrPercentage(LengthOrPercentage::Percentage(
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percentage)) => {
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let line_height = fragment.calculate_line_height(layout_context);
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let length = line_height.scale_by(percentage);
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block_start = block_start - length
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}
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vertical_align::T::LengthOrPercentage(LengthOrPercentage::Calc(calc)) => {
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let line_height = fragment.calculate_line_height(layout_context);
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let percentage_length = line_height.scale_by(calc.percentage());
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block_start = block_start - percentage_length - calc.length()
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}
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_ => {}
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}
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}
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match vertical_align {
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vertical_align::T::top => {
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fragment.border_box.start.b = fragment.border_box.start.b +
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line_distance_from_flow_block_start
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}
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vertical_align::T::bottom => {
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fragment.border_box.start.b = fragment.border_box.start.b +
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line_distance_from_flow_block_start +
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baseline_distance_from_block_start +
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largest_depth_below_baseline;
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}
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_ => {
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fragment.border_box.start.b = fragment.border_box.start.b +
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line_distance_from_flow_block_start + baseline_distance_from_block_start
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}
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}
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fragment.border_box.start.b = block_start;
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fragment.update_late_computed_block_position_if_necessary();
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}
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}
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@ -1193,31 +1124,88 @@ impl InlineFlow {
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let line_height = text::line_height_from_style(style, &font_metrics);
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let inline_metrics = InlineMetrics::from_font_metrics(&font_metrics, line_height);
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let mut block_size_above_baseline = inline_metrics.block_size_above_baseline;
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let mut depth_below_baseline = inline_metrics.depth_below_baseline;
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let mut block_size_above_baseline = Au(0);
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let mut depth_below_baseline = Au(i32::MIN);
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let mut largest_block_size_for_top_fragments = Au(0);
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let mut largest_block_size_for_bottom_fragments = Au(0);
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// We use `vertical_align::T::baseline` here because `vertical-align` must not apply to
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// the inside of inline blocks.
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update_inline_metrics(&inline_metrics,
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style.get_box().display,
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vertical_align::T::baseline,
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&mut block_size_above_baseline,
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&mut depth_below_baseline,
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&mut largest_block_size_for_top_fragments,
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&mut largest_block_size_for_bottom_fragments);
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// According to CSS 2.1 § 10.8, `line-height` of any inline element specifies the minimal
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// height of line boxes within the element.
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for frag in &self.fragments.fragments {
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match frag.inline_context {
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Some(ref inline_context) => {
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for node in &inline_context.nodes {
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let font_style = node.style.get_font_arc();
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let font_metrics = text::font_metrics_for_style(font_context, font_style);
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let line_height = text::line_height_from_style(&*node.style, &font_metrics);
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let inline_metrics = InlineMetrics::from_font_metrics(&font_metrics,
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line_height);
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block_size_above_baseline = max(block_size_above_baseline,
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inline_metrics.block_size_above_baseline);
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depth_below_baseline = max(depth_below_baseline,
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inline_metrics.depth_below_baseline);
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}
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if let Some(ref inline_context) = frag.inline_context {
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for node in &inline_context.nodes {
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let font_style = node.style.get_font_arc();
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let font_metrics = text::font_metrics_for_style(font_context, font_style);
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let line_height = text::line_height_from_style(&*node.style, &font_metrics);
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let inline_metrics = InlineMetrics::from_font_metrics(&font_metrics,
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line_height);
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update_inline_metrics(&inline_metrics,
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node.style.get_box().display,
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node.style.get_box().vertical_align,
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&mut block_size_above_baseline,
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&mut depth_below_baseline,
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&mut largest_block_size_for_top_fragments,
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&mut largest_block_size_for_bottom_fragments);
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}
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None => {}
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}
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}
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(block_size_above_baseline, depth_below_baseline)
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block_size_above_baseline =
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max(block_size_above_baseline,
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largest_block_size_for_bottom_fragments - max(depth_below_baseline, Au(0)));
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depth_below_baseline =
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max(depth_below_baseline,
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largest_block_size_for_top_fragments - block_size_above_baseline);
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return (block_size_above_baseline, depth_below_baseline);
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fn update_inline_metrics(inline_metrics: &InlineMetrics,
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display_value: display::T,
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vertical_align_value: vertical_align::T,
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block_size_above_baseline: &mut Au,
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depth_below_baseline: &mut Au,
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largest_block_size_for_top_fragments: &mut Au,
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largest_block_size_for_bottom_fragments: &mut Au) {
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match (display_value, vertical_align_value) {
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(display::T::inline, vertical_align::T::top) |
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(display::T::block, vertical_align::T::top) |
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(display::T::inline_block, vertical_align::T::top) if
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inline_metrics.block_size_above_baseline >= Au(0) => {
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*largest_block_size_for_top_fragments =
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max(*largest_block_size_for_top_fragments,
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inline_metrics.block_size_above_baseline +
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inline_metrics.depth_below_baseline)
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}
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(display::T::inline, vertical_align::T::bottom) |
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(display::T::block, vertical_align::T::bottom) |
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(display::T::inline_block, vertical_align::T::bottom) if
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inline_metrics.depth_below_baseline >= Au(0) => {
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*largest_block_size_for_bottom_fragments =
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max(*largest_block_size_for_bottom_fragments,
|
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inline_metrics.block_size_above_baseline +
|
||||
inline_metrics.depth_below_baseline)
|
||||
}
|
||||
_ => {
|
||||
*block_size_above_baseline =
|
||||
max(*block_size_above_baseline,
|
||||
inline_metrics.block_size_above_baseline);
|
||||
*depth_below_baseline = max(*depth_below_baseline,
|
||||
inline_metrics.depth_below_baseline);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn update_restyle_damage(&mut self) {
|
||||
|
|
@ -1468,11 +1456,8 @@ impl Flow for InlineFlow {
|
|||
|
||||
|
||||
// Now, go through each line and lay out the fragments inside.
|
||||
let mut line_distance_from_flow_block_start = Au(0);
|
||||
let line_count = self.lines.len();
|
||||
for line_index in 0..line_count {
|
||||
let line = &mut self.lines[line_index];
|
||||
|
||||
for (line_index, line) in self.lines.iter_mut().enumerate() {
|
||||
// Lay out fragments in the inline direction, and justify them if necessary.
|
||||
InlineFlow::set_inline_fragment_positions(&mut self.fragments,
|
||||
line,
|
||||
|
|
@ -1480,108 +1465,17 @@ impl Flow for InlineFlow {
|
|||
indentation,
|
||||
line_index + 1 == line_count);
|
||||
|
||||
// Set the block-start position of the current line.
|
||||
// `line_height_offset` is updated at the end of the previous loop.
|
||||
line.bounds.start.b = line_distance_from_flow_block_start;
|
||||
|
||||
// Calculate the distance from the baseline to the block-start and block-end of the
|
||||
// line.
|
||||
let mut largest_block_size_above_baseline = self.minimum_block_size_above_baseline;
|
||||
let mut largest_depth_below_baseline = self.minimum_depth_below_baseline;
|
||||
|
||||
// Calculate the largest block-size among fragments with 'top' and 'bottom' values
|
||||
// respectively.
|
||||
let (mut largest_block_size_for_top_fragments,
|
||||
mut largest_block_size_for_bottom_fragments) = (Au(0), Au(0));
|
||||
|
||||
for fragment_index in line.range.each_index() {
|
||||
let fragment = &mut self.fragments.fragments[fragment_index.to_usize()];
|
||||
|
||||
let InlineMetrics {
|
||||
mut block_size_above_baseline,
|
||||
mut depth_below_baseline,
|
||||
ascent
|
||||
} = fragment.inline_metrics(layout_context);
|
||||
|
||||
// To calculate text-top and text-bottom value when `vertical-align` is involved,
|
||||
// we should find the top and bottom of the content area of the parent fragment.
|
||||
// "Content area" is defined in CSS 2.1 § 10.6.1.
|
||||
//
|
||||
// TODO: We should extract em-box info from the font size of the parent and
|
||||
// calculate the distances from the baseline to the block-start and the block-end
|
||||
// of the parent's content area.
|
||||
|
||||
// We should calculate the distance from baseline to the top of parent's content
|
||||
// area. But for now we assume it's the font size.
|
||||
//
|
||||
// CSS 2.1 does not state which font to use. This version of the code uses
|
||||
// the parent's font.
|
||||
|
||||
// Calculate the final block-size above the baseline for this fragment.
|
||||
//
|
||||
// The no-update flag decides whether `largest_block_size_for_top_fragments` and
|
||||
// `largest_block_size_for_bottom_fragments` are to be updated or not. This will be
|
||||
// set if and only if the fragment has `vertical-align` set to `top` or `bottom`.
|
||||
let (distance_from_baseline, no_update_flag) =
|
||||
InlineFlow::distance_from_baseline(
|
||||
fragment,
|
||||
ascent,
|
||||
self.minimum_block_size_above_baseline,
|
||||
self.minimum_depth_below_baseline,
|
||||
&mut block_size_above_baseline,
|
||||
&mut depth_below_baseline,
|
||||
&mut largest_block_size_for_top_fragments,
|
||||
&mut largest_block_size_for_bottom_fragments,
|
||||
layout_context);
|
||||
|
||||
// Unless the current fragment has `vertical-align` set to `top` or `bottom`,
|
||||
// `largest_block_size_above_baseline` and `largest_depth_below_baseline` are
|
||||
// updated.
|
||||
if !no_update_flag {
|
||||
largest_block_size_above_baseline = max(block_size_above_baseline,
|
||||
largest_block_size_above_baseline);
|
||||
largest_depth_below_baseline = max(depth_below_baseline,
|
||||
largest_depth_below_baseline);
|
||||
}
|
||||
|
||||
// Temporarily use `fragment.border_box.start.b` to mean "the distance from the
|
||||
// baseline". We will assign the real value later.
|
||||
fragment.border_box.start.b = distance_from_baseline
|
||||
}
|
||||
|
||||
// Calculate the distance from the baseline to the top of the largest fragment with a
|
||||
// value for `bottom`. Then, if necessary, update `largest_block-size_above_baseline`.
|
||||
largest_block_size_above_baseline =
|
||||
max(largest_block_size_above_baseline,
|
||||
largest_block_size_for_bottom_fragments - largest_depth_below_baseline);
|
||||
|
||||
// Calculate the distance from baseline to the bottom of the largest fragment with a
|
||||
// value for `top`. Then, if necessary, update `largest_depth_below_baseline`.
|
||||
largest_depth_below_baseline =
|
||||
max(largest_depth_below_baseline,
|
||||
largest_block_size_for_top_fragments - largest_block_size_above_baseline);
|
||||
|
||||
// Now, the distance from the logical block-start of the line to the baseline can be
|
||||
// computed as `largest_block-size_above_baseline`.
|
||||
let baseline_distance_from_block_start = largest_block_size_above_baseline;
|
||||
|
||||
// Compute the final positions in the block direction of each fragment. Recall that
|
||||
// `fragment.border_box.start.b` was set to the distance from the baseline above.
|
||||
// Compute the final positions in the block direction of each fragment.
|
||||
InlineFlow::set_block_fragment_positions(&mut self.fragments,
|
||||
line,
|
||||
line_distance_from_flow_block_start,
|
||||
baseline_distance_from_block_start,
|
||||
largest_depth_below_baseline);
|
||||
self.minimum_block_size_above_baseline,
|
||||
self.minimum_depth_below_baseline,
|
||||
layout_context);
|
||||
|
||||
// This is used to set the block-start position of the next line in the next loop.
|
||||
line.bounds.size.block = largest_block_size_above_baseline +
|
||||
largest_depth_below_baseline;
|
||||
line_distance_from_flow_block_start = line_distance_from_flow_block_start +
|
||||
line.bounds.size.block;
|
||||
|
||||
// We're no longer on the first line, so set indentation to zero.
|
||||
// This is used to set the block-start position of the next line in the next iteration
|
||||
// of the loop. We're no longer on the first line, so set indentation to zero.
|
||||
indentation = Au(0)
|
||||
} // End of `lines.iter_mut()` loop.
|
||||
}
|
||||
|
||||
// Assign block sizes for any inline-block descendants.
|
||||
let thread_id = self.base.thread_id;
|
||||
|
|
@ -1968,22 +1862,6 @@ impl InlineMetrics {
|
|||
}
|
||||
}
|
||||
|
||||
/// Calculates inline metrics from font metrics and line block-size per CSS 2.1 § 10.8.1.
|
||||
#[inline]
|
||||
pub fn from_block_height(font_metrics: &FontMetrics,
|
||||
block_height: Au,
|
||||
block_start_margin: Au,
|
||||
block_end_margin: Au)
|
||||
-> InlineMetrics {
|
||||
let leading = block_height + block_start_margin + block_end_margin -
|
||||
(font_metrics.ascent + font_metrics.descent);
|
||||
InlineMetrics {
|
||||
block_size_above_baseline: font_metrics.ascent + leading.scale_by(0.5),
|
||||
depth_below_baseline: font_metrics.descent + leading.scale_by(0.5),
|
||||
ascent: font_metrics.ascent + leading.scale_by(0.5) - block_start_margin,
|
||||
}
|
||||
}
|
||||
|
||||
pub fn block_size(&self) -> Au {
|
||||
self.block_size_above_baseline + self.depth_below_baseline
|
||||
}
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue