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layout: Share styles to inline box children via SharedInlineStyles (#36896)

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`TextRun`s use their parent style to render. Previously, these styles
were cloned and stored directly in the box tree `TextRun` and resulting
`TextFragment`s. This presents a problem for incremental layout.
Wrapping the style in another layer of shared ownership and mutability
will allow updating all `TextFragment`s during repaint-only incremental
layout by simply updating the box tree styles of the original text
parents.

This adds a new set of borrows when accessing text styles, but also
makes it so that during box tree block construction
`InlineFormattingContext`s are created lazily and now
`InlineFormattingContextBuilder::finish` consumes the builder, making
the API make a bit more sense. This should also improve performance of
box tree block construction slightly.

Testing: This should not change observable behavior and thus is covered
by existing WPT tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
This commit is contained in:
Martin Robinson 2025-05-12 11:38:50 +02:00 • committed by GitHub
parent db83601b62
commit a0dd2c1beb
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24 changed files with 369 additions and 187 deletions
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30
components/layout/flow/inline/mod.rs
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@ -118,6 +118,7 @@ use super::{
};
use crate::cell::ArcRefCell;
use crate::context::LayoutContext;
use crate::dom_traversal::NodeAndStyleInfo;
use crate::flow::CollapsibleWithParentStartMargin;
use crate::flow::float::{FloatBox, SequentialLayoutState};
use crate::formatting_contexts::{
@ -131,7 +132,7 @@ use crate::geom::{LogicalRect, LogicalVec2, ToLogical};
use crate::positioned::{AbsolutelyPositionedBox, PositioningContext};
use crate::sizing::{ComputeInlineContentSizes, ContentSizes, InlineContentSizesResult};
use crate::style_ext::{ComputedValuesExt, PaddingBorderMargin};
use crate::{ConstraintSpace, ContainingBlock, PropagatedBoxTreeData};
use crate::{ConstraintSpace, ContainingBlock, PropagatedBoxTreeData, SharedStyle};
// From gfxFontConstants.h in Firefox.
static FONT_SUBSCRIPT_OFFSET_RATIO: f32 = 0.20;
@ -173,6 +174,25 @@ pub(crate) struct InlineFormattingContext {
pub(super) has_right_to_left_content: bool,
}
/// [`TextRun`] and `TextFragment`s need a handle on their parent inline box (or inline
/// formatting context root)'s style. In order to implement incremental layout, these are
/// wrapped in [`SharedStyle`]. This allows updating the parent box tree element without
/// updating every single descendant box tree node and fragment.
#[derive(Clone, Debug, MallocSizeOf)]
pub(crate) struct SharedInlineStyles {
pub style: SharedStyle,
pub selected: SharedStyle,
}
impl From<&NodeAndStyleInfo<'_>> for SharedInlineStyles {
fn from(info: &NodeAndStyleInfo) -> Self {
Self {
style: SharedStyle::new(info.style.clone()),
selected: SharedStyle::new(info.get_selected_style()),
}
}
}
/// A collection of data used to cache [`FontMetrics`] in the [`InlineFormattingContext`]
#[derive(Debug, MallocSizeOf)]
pub(crate) struct FontKeyAndMetrics {
@ -1313,7 +1333,7 @@ impl InlineFormattingContextLayout<'_> {
) {
let inline_advance = glyph_store.total_advance();
let flags = if glyph_store.is_whitespace() {
SegmentContentFlags::from(text_run.parent_style.get_inherited_text())
SegmentContentFlags::from(text_run.inline_styles.style.borrow().get_inherited_text())
} else {
SegmentContentFlags::empty()
};
@ -1398,13 +1418,12 @@ impl InlineFormattingContextLayout<'_> {
TextRunLineItem {
text: vec![glyph_store],
base_fragment_info: text_run.base_fragment_info,
parent_style: text_run.parent_style.clone(),
inline_styles: text_run.inline_styles.clone(),
font_metrics,
font_key: ifc_font_info.key,
text_decoration_line: self.current_inline_container_state().text_decoration_line,
bidi_level,
selection_range,
selected_style: text_run.selected_style.clone(),
},
));
}
@ -2363,8 +2382,9 @@ impl<'layout_data> ContentSizesComputation<'layout_data> {
},
InlineItem::TextRun(text_run) => {
let text_run = &*text_run.borrow();
let parent_style = text_run.inline_styles.style.borrow();
for segment in text_run.shaped_text.iter() {
let style_text = text_run.parent_style.get_inherited_text();
let style_text = parent_style.get_inherited_text();
let can_wrap = style_text.text_wrap_mode == TextWrapMode::Wrap;
// TODO: This should take account whether or not the first and last character prevent