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improv: ShapeSpan::decoration_spans holds user-level attrs

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Hojjat 2026-02-24 18:05:15 -07:00 • committed by Jeremy Soller
parent e8a6b0cc60
commit 0666ba14b1
3 changed files with 129 additions and 37 deletions
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158
src/shape.rs
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@ -9,7 +9,7 @@ use crate::{
LayoutLine, Metrics, Wrap,
};
#[cfg(not(feature = "std"))]
use alloc::{boxed::Box, format, vec, vec::Vec};
use alloc::{format, vec, vec::Vec};
use alloc::collections::VecDeque;
use core::cmp::{max, min};
@ -237,16 +237,6 @@ fn shape_fallback(
metadata: attrs.metadata,
cache_key_flags: override_fake_italic(attrs.cache_key_flags, font, &attrs),
metrics_opt: attrs.metrics_opt.map(Into::into),
decoration_data: if attrs.text_decoration.has_decoration() {
let (ul_metrics, st_metrics) = decoration_metrics(font);
Some(Box::new(GlyphDecorationData {
text_decoration: attrs.text_decoration,
underline_metrics: ul_metrics,
strikethrough_metrics: st_metrics,
}))
} else {
None
},
});
}
@ -514,8 +504,6 @@ fn shape_skip(
let metrics = swash_font.metrics(&[]);
let glyph_metrics = swash_font.glyph_metrics(&[]).scale(1.0);
let deco_metrics = decoration_metrics(font.as_ref());
let ascent = metrics.ascent / f32::from(metrics.units_per_em);
let descent = metrics.descent / f32::from(metrics.units_per_em);
@ -549,15 +537,6 @@ fn shape_skip(
&attrs,
),
metrics_opt: attrs.metrics_opt.map(Into::into),
decoration_data: if attrs.text_decoration.has_decoration() {
Some(Box::new(GlyphDecorationData {
text_decoration: attrs.text_decoration,
underline_metrics: deco_metrics.0,
strikethrough_metrics: deco_metrics.1,
}))
} else {
None
},
}
}),
);
@ -594,12 +573,10 @@ pub struct ShapeGlyph {
pub metadata: usize,
pub cache_key_flags: CacheKeyFlags,
pub metrics_opt: Option<Metrics>,
/// Decoration data, only allocated when decorations are active
pub decoration_data: Option<Box<GlyphDecorationData>>,
}
impl ShapeGlyph {
fn layout(
const fn layout(
&self,
font_size: f32,
line_height_opt: Option<f32>,
@ -839,6 +816,10 @@ impl ShapeWord {
pub struct ShapeSpan {
pub level: unicode_bidi::Level,
pub words: Vec<ShapeWord>,
/// Decoration data per user-level attr span within this shape span.
/// Each entry maps a byte range to its decoration config and font metrics.
/// Empty when no decorations are active.
pub decoration_spans: Vec<(Range<usize>, GlyphDecorationData)>,
}
impl ShapeSpan {
@ -849,6 +830,7 @@ impl ShapeSpan {
Self {
level: unicode_bidi::Level::ltr(),
words: Vec::default(),
decoration_spans: Vec::new(),
}
}
@ -1037,6 +1019,91 @@ impl ShapeSpan {
self.level = level;
self.words = words;
// Build decoration spans: one entry per user-level attr span that has
// decorations within this shape span's byte range. Font metrics come from
// the primary font (first shaped glyph), following Pango convention.
self.decoration_spans.clear();
// Early-out: skip font lookup and span iteration when no decorations exist.
// For plain text (the common case) this is a single bool check.
let any_decoration = attrs_list.defaults().text_decoration.has_decoration()
|| attrs_list.spans_iter().any(|(range, attr_owned)| {
let start = range.start.max(span_range.start);
let end = range.end.min(span_range.end);
start < end && attr_owned.as_attrs().text_decoration.has_decoration()
});
if any_decoration {
// Get font metrics once from the primary glyph of this shape span
let primary_metrics = self
.words
.iter()
.flat_map(|w| w.glyphs.first())
.next()
.and_then(|glyph| {
font_system
.get_font(glyph.font_id, glyph.font_weight)
.map(|font| decoration_metrics(&font))
});
if let Some((ul_metrics, st_metrics)) = primary_metrics {
// Track which sub-ranges of span_range are covered by explicit spans
let mut covered_end = span_range.start;
for (range, attr_owned) in attrs_list.spans_iter() {
// Compute intersection with our shape span's byte range
let start = range.start.max(span_range.start);
let end = range.end.min(span_range.end);
if start >= end {
continue;
}
// Check the gap before this span (covered by defaults)
if covered_end < start {
let default_attrs = attrs_list.defaults();
if default_attrs.text_decoration.has_decoration() {
self.decoration_spans.push((
covered_end..start,
GlyphDecorationData {
text_decoration: default_attrs.text_decoration,
underline_metrics: ul_metrics,
strikethrough_metrics: st_metrics,
},
));
}
}
covered_end = end;
let attrs = attr_owned.as_attrs();
if attrs.text_decoration.has_decoration() {
self.decoration_spans.push((
start..end,
GlyphDecorationData {
text_decoration: attrs.text_decoration,
underline_metrics: ul_metrics,
strikethrough_metrics: st_metrics,
},
));
}
}
// Check trailing gap (covered by defaults)
if covered_end < span_range.end {
let default_attrs = attrs_list.defaults();
if default_attrs.text_decoration.has_decoration() {
self.decoration_spans.push((
covered_end..span_range.end,
GlyphDecorationData {
text_decoration: default_attrs.text_decoration,
underline_metrics: ul_metrics,
strikethrough_metrics: st_metrics,
},
));
}
}
}
}
// Cache buffer for future reuse.
font_system.shape_buffer.words = cached_words;
}
@ -1298,6 +1365,7 @@ impl ShapeLine {
ShapeSpan {
level,
words: vec![word],
decoration_spans: Vec::new(),
}
});
@ -2699,6 +2767,14 @@ impl ShapeLine {
for r in visual_line.ranges[range.clone()].iter() {
let is_ellipsis = r.span == ELLIPSIS_SPAN;
let span_words = self.get_span_words(r.span);
let deco_spans: &[(Range<usize>, GlyphDecorationData)] = if is_ellipsis {
&[]
} else {
&self.spans[r.span].decoration_spans
};
// Cursor into deco_spans — advances forward as glyphs are
// emitted in byte order, giving amortized O(1) lookup.
let mut deco_cursor: usize = 0;
// If ending_glyph is not 0 we need to include glyphs from the ending_word
for i in r.start.word..r.end.word + usize::from(r.end.glyph != 0) {
let word = &span_words[i];
@ -2784,16 +2860,32 @@ impl ShapeLine {
}
glyphs.push(layout_glyph);
// Build decoration spans inline: extend or close+open
// Advance (or reset) the decoration cursor to find
// the span covering this glyph's byte position.
// Resets for RTL/BiDi where byte order reverses.
if deco_cursor < deco_spans.len()
&& glyph.start < deco_spans[deco_cursor].0.start
{
deco_cursor = 0;
}
while deco_cursor < deco_spans.len()
&& deco_spans[deco_cursor].0.end <= glyph.start
{
deco_cursor += 1;
}
let glyph_deco = deco_spans
.get(deco_cursor)
.filter(|(range, _)| glyph.start >= range.start);
let glyph_idx = glyphs.len() - 1;
let cur_deco = glyph.decoration_data.as_deref();
let extends = match (decorations.last(), cur_deco) {
(Some(span), Some(d)) if span.data == *d => true,
_ => false,
};
let extends = matches!(
(decorations.last(), &glyph_deco),
(Some(span), Some((_, d))) if span.data == *d
);
if extends {
decorations.last_mut().unwrap().glyph_range.end = glyph_idx + 1;
} else if let Some(d) = cur_deco {
if let Some(last) = decorations.last_mut() {
last.glyph_range.end = glyph_idx + 1;
}
} else if let Some((_, d)) = glyph_deco {
decorations.push(DecorationSpan {
glyph_range: glyph_idx..glyph_idx + 1,
data: d.clone(),

4
tests/images/text_decoration_bidi.png
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4
tests/images/text_decoration_rtl.png
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@ -1,3 +1,3 @@
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