layout: Move text decoration propagation to stacking context tree construction (#37069)

Text decorations have a special kind of propagation. Instead of
propating these during box tree construction, move propagation to
stacking context tree construction. This will allow for using a very
easy type of incremental layout when text decorations change. For
instance, when a link changes color during hovering over it, we can skip
all of box and fragment tree construction.

In addition, propagation works a bit better now and color and style
properly move down from their originating `Fragment`s.

This introduces three new failures, because now we are drawing the
text-decoration with the correct color in more places, which exposes an
issue we have with text-decorations not being drawn in relation to the
baseline (taking into account `vertical-align`).

Testing: There are tests for these changes.
Fixes #31736.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>
This commit is contained in:
Martin Robinson 2025-05-21 18:38:29 +02:00 committed by GitHub
parent cebb1619ae
commit 9781f1241a
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23 changed files with 152 additions and 142 deletions

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@ -15,7 +15,6 @@ use style::values::generics::box_::{GenericVerticalAlign, VerticalAlignKeyword};
use style::values::generics::font::LineHeight;
use style::values::specified::align::AlignFlags;
use style::values::specified::box_::DisplayOutside;
use style::values::specified::text::TextDecorationLine;
use unicode_bidi::{BidiInfo, Level};
use webrender_api::FontInstanceKey;
@ -572,7 +571,6 @@ impl LineItemLayout<'_, '_> {
font_metrics: text_item.font_metrics,
font_key: text_item.font_key,
glyphs: text_item.text,
text_decoration_line: text_item.text_decoration_line,
justification_adjustment: self.justification_adjustment,
selection_range: text_item.selection_range,
})),
@ -765,7 +763,6 @@ pub(super) struct TextRunLineItem {
pub text: Vec<std::sync::Arc<GlyphStore>>,
pub font_metrics: FontMetrics,
pub font_key: FontInstanceKey,
pub text_decoration_line: TextDecorationLine,
/// The BiDi level of this [`TextRunLineItem`] to enable reordering.
pub bidi_level: Level,
pub selection_range: Option<Range<ByteIndex>>,