8c8c41b05b
The unicode-linebreak crate treats the pipe character '|' as a break opportunity (BA/AL class). This causes ShapeSpan::build to split text like '|>' into separate ShapeWords. When these words are shaped independently, the font shaping engine cannot form ligatures that cross the word boundary. This patch manually checks for the '|>' sequence during segmentation and skips the break opportunity, ensuring they remain in the same shaping run. Added a unit test 'ligature_segmentation' to verify that '|>' remains a single word.
30 lines
1.1 KiB
Rust
30 lines
1.1 KiB
Rust
use cosmic_text::{Attrs, Buffer, FontSystem, Metrics, Shaping};
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#[test]
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fn ligature_segmentation() {
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let mut font_system =
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FontSystem::new_with_locale_and_db("en-US".into(), fontdb::Database::new());
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let font = std::fs::read("fonts/Inter-Regular.ttf").unwrap();
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font_system.db_mut().load_font_data(font);
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let metrics = Metrics::new(14.0, 20.0);
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let mut buffer = Buffer::new(&mut font_system, metrics);
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let mut buffer = buffer.borrow_with(&mut font_system);
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buffer.set_text("|>", &Attrs::new(), Shaping::Advanced, None);
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buffer.shape_until_scroll(false);
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let line = &buffer.lines[0];
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let shape = line.shape_opt().expect("ShapeLine not found");
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let span = &shape.spans[0];
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// The pipe character | is typically a line break opportunity.
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// This test ensures that our patch prevents splitting |> into separate words,
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// which would break ligature formation in fonts that support it.
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assert_eq!(
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span.words.len(),
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1,
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"Expected '|>' to be a single word (preserved for ligature), but found {} words.",
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span.words.len()
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);
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}
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