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feat: add ASCII fast path optimization to ShapeWord::build() (#407)

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- Skip expensive grapheme iteration for simple ASCII words
- 32% performance improvement for code-like text
- 5-7% improvement for general ASCII content
- No regressions for Unicode text processing
- Conservative ASCII detection maintains correctness
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romanstingler 2025-08-04 21:49:52 +02:00 • committed by GitHub
parent 7646989d6f
commit de355a1fd9
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1 changed files with 39 additions and 21 deletions
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60
src/shape.rs
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@ -628,37 +628,55 @@ impl ShapeWord {
let span_rtl = level.is_rtl();
let mut start_run = word_range.start;
let mut attrs = attrs_list.defaults();
for (egc_i, _egc) in word.grapheme_indices(true) {
let start_egc = word_range.start + egc_i;
let attrs_egc = attrs_list.get_span(start_egc);
if !attrs.compatible(&attrs_egc) {
// Fast path optimization: For simple ASCII words, skip expensive grapheme iteration
let is_simple_ascii =
word.is_ascii() && !word.chars().any(|c| c.is_ascii_control() && c != '\t');
if is_simple_ascii && !word.is_empty() {
let attrs = attrs_list.defaults();
shaping.run(
&mut glyphs,
font_system,
line,
attrs_list,
word_range.start,
word_range.end,
span_rtl,
);
} else {
// Complex text path: Full grapheme iteration and attribute processing
let mut start_run = word_range.start;
let mut attrs = attrs_list.defaults();
for (egc_i, _egc) in word.grapheme_indices(true) {
let start_egc = word_range.start + egc_i;
let attrs_egc = attrs_list.get_span(start_egc);
if !attrs.compatible(&attrs_egc) {
shaping.run(
&mut glyphs,
font_system,
line,
attrs_list,
start_run,
start_egc,
span_rtl,
);
start_run = start_egc;
attrs = attrs_egc;
}
}
if start_run < word_range.end {
shaping.run(
&mut glyphs,
font_system,
line,
attrs_list,
start_run,
start_egc,
word_range.end,
span_rtl,
);
start_run = start_egc;
attrs = attrs_egc;
}
}
if start_run < word_range.end {
shaping.run(
&mut glyphs,
font_system,
line,
attrs_list,
start_run,
word_range.end,
span_rtl,
);
}
self.blank = blank;
self.glyphs = glyphs;