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layout: Collect both start and end baselines for fragments (#31230)

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This change starts collecting the starting baseline set for fragments,
which is necessary for some layout modes (flex and tables, namely) as
well as being important for the implementation of `align-items`. In
addition, it converts baseline measurement to use `Au` everywhere.

Co-authored-by: Oriol Brufau <obrufau@igalia.com>
This commit is contained in:
Martin Robinson 2024-02-05 19:06:05 +01:00 • committed by GitHub
parent 28bde741ed
commit 7f13316f24
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GPG key ID: B5690EEEBB952194
10 changed files with 112 additions and 101 deletions
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44
components/layout_2020/flow/line.rs
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@ -40,7 +40,7 @@ pub(super) struct LineMetrics {
pub block_size: Length,
/// The block offset of this line's baseline from [`Self:block_offset`].
pub baseline_block_offset: Length,
pub baseline_block_offset: Au,
}
/// State used when laying out the [`LineItem`]s collected for the line currently being
@ -54,7 +54,7 @@ pub(super) struct LineItemLayoutState<'a> {
/// The block offset of the parent's baseline relative to the block start of the line. This
/// is often the same as [`Self::block_offset_of_parent`], but can be different for the root
/// element.
pub baseline_offset: Length,
pub baseline_offset: Au,
pub ifc_containing_block: &'a ContainingBlock<'a>,
pub positioning_context: &'a mut PositioningContext,
@ -255,7 +255,7 @@ impl TextRunLineItem {
// fallback fonts that use baseline relatve alignment, it might be different.
let mut start_corner = &LogicalVec2 {
inline: state.inline_position,
block: state.baseline_offset - self.font_metrics.ascent.into(),
block: (state.baseline_offset - self.font_metrics.ascent).into(),
} - &state.parent_offset;
if !is_baseline_relative(
self.parent_style
@ -350,7 +350,7 @@ impl InlineBoxLineItem {
inline_position: state.inline_position,
parent_offset: LogicalVec2 {
inline: state.inline_position,
block: block_start_offset,
block: block_start_offset.into(),
},
ifc_containing_block: state.ifc_containing_block,
positioning_context: nested_positioning_context,
@ -388,7 +388,7 @@ impl InlineBoxLineItem {
let mut content_rect = LogicalRect {
start_corner: LogicalVec2 {
inline: state.inline_position,
block: block_start_offset,
block: block_start_offset.into(),
},
size: LogicalVec2 {
inline: nested_state.inline_position - state.inline_position,
@ -405,6 +405,9 @@ impl InlineBoxLineItem {
content_rect.start_corner += &relative_adjustement(&style, state.ifc_containing_block);
}
// NB: There is no need to set a baseline offset for this BoxFragment, because the
// baselines of this InlineFormattingContext is what will propagate to `display:
// inline-block` ancestors.
let mut fragment = BoxFragment::new(
self.base_fragment_info,
self.style.clone(),
@ -414,10 +417,6 @@ impl InlineBoxLineItem {
border,
margin,
None, /* clearance */
// There is no need to set a baseline offset for this BoxFragment, because
// the last baseline of this InlineFormattingContext is what will propagate
// to `display: inline-block` ancestors.
None, /* last_inflow_baseline_offset */
CollapsedBlockMargins::zero(),
);
@ -446,23 +445,19 @@ impl InlineBoxLineItem {
/// Given our font metrics, calculate the space above the baseline we need for our content.
/// Note that this space does not include space for any content in child inline boxes, as
/// they are not included in our content rect.
fn calculate_space_above_baseline(&self) -> Length {
fn calculate_space_above_baseline(&self) -> Au {
let (ascent, descent, line_gap) = (
self.font_metrics.ascent,
self.font_metrics.descent,
self.font_metrics.line_gap,
);
let leading = line_gap - (ascent + descent);
(leading.scale_by(0.5) + ascent).into()
leading.scale_by(0.5) + ascent
}
/// Given the state for a line item layout and the space above the baseline for this inline
/// box, find the block start position relative to the line block start position.
fn calculate_block_start(
&self,
state: &LineItemLayoutState,
space_above_baseline: Length,
) -> Length {
fn calculate_block_start(&self, state: &LineItemLayoutState, space_above_baseline: Au) -> Au {
let vertical_align = self.style.effective_vertical_align_for_inline_layout();
let line_gap = self.font_metrics.line_gap;
@ -470,16 +465,16 @@ impl InlineBoxLineItem {
// baseline, so we need to make it relative to the line block start.
match vertical_align {
GenericVerticalAlign::Keyword(VerticalAlignKeyword::Top) => {
let line_height = line_height(&self.style, &self.font_metrics);
(line_height - line_gap.into()).scale_by(0.5)
let line_height: Au = line_height(&self.style, &self.font_metrics).into();
(line_height - line_gap).scale_by(0.5)
},
GenericVerticalAlign::Keyword(VerticalAlignKeyword::Bottom) => {
let line_height = line_height(&self.style, &self.font_metrics);
let half_leading = (line_height - line_gap.into()).scale_by(0.5);
state.line_metrics.block_size - line_height + half_leading
let line_height: Au = line_height(&self.style, &self.font_metrics).into();
let half_leading = (line_height - line_gap).scale_by(0.5);
Au::from(state.line_metrics.block_size) - line_height + half_leading
},
_ => {
state.line_metrics.baseline_block_offset + Length::from(self.baseline_offset) -
state.line_metrics.baseline_block_offset + self.baseline_offset -
space_above_baseline
},
}
@ -542,9 +537,8 @@ impl AtomicLineItem {
// This covers all baseline-relative vertical alignment.
_ => {
let baseline = line_metrics.baseline_block_offset +
Length::from(self.baseline_offset_in_parent);
baseline - Length::from(self.baseline_offset_in_item)
let baseline = line_metrics.baseline_block_offset + self.baseline_offset_in_parent;
Length::from(baseline - self.baseline_offset_in_item)
},
}
}