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c02341f6c0
A cubic whose second control point is its end point (as the `y` operator builds, ISO 32000-2 8.5.2.1 Table 58) has a zero derivative at its end. kurbo 0.13.1's offset curve looks for cusps with a root search on the curvature, which grows without bound towards that end; at some widths the search stops on the end point and normalising the zero tangent there gives NaN. vello_common's fill drops any outline with NaN, so the whole stroke vanished (a two-curve `y` path drew nothing at 16, 32 and 63 pt; a PDFBox tracker file lost its 32 pt "XX" outline). The NaN fallback that #4913 added to `flatten::stroke` now also moves such a control point the stroke tolerance towards the previous control point before stroking again (the curve moves by at most 4/9 of the tolerance). Outlines that come back finite take the old path unchanged. The vendor ledger row also gets back #4913's entry, which a merge had dropped. Claude-Session: https://claude.ai/code/session_01Pq7HyCHD1R3rywQBPCHXZA Co-authored-by: mtlcl410 <chuanlin@niar.org.tw> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
62 lines
3.1 KiB
Rust
62 lines
3.1 KiB
Rust
//! A contributor-original synthetic page: a wide stroke of a path built with `y` (the second
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//! control point on the end point, ISO 32000-2 §8.5.2.1 Table 58) was not drawn at all at some widths,
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//! because the stroker put NaN into its outline and the rasterizer dropped the whole path. A file
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//! in the PDFBox issue tracker lost the 32 pt outline of its "XX" this way.
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use pdfcraft_render::{PageRenderer, RenderConfig, RenderRequest};
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use std::sync::Arc;
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/// A one-page 200 × 200 pt PDF drawing `content`, with a cross-reference table.
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fn pdf(content: &str) -> Vec<u8> {
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let objects = [
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"<< /Type /Catalog /Pages 2 0 R >>".to_string(),
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"<< /Type /Pages /Kids [3 0 R] /Count 1 >>".to_string(),
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"<< /Type /Page /Parent 2 0 R /MediaBox [0 0 200 200] /Contents 4 0 R >>".to_string(),
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format!("<< /Length {} >>\nstream\n{content}\nendstream", content.len()),
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];
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let mut bytes = b"%PDF-1.7\n".to_vec();
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let mut offsets = Vec::new();
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for (i, object) in objects.iter().enumerate() {
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offsets.push(bytes.len());
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bytes.extend_from_slice(format!("{} 0 obj\n{object}\nendobj\n", i + 1).as_bytes());
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}
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let xref = bytes.len();
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bytes.extend_from_slice(format!("xref\n0 {}\n0000000000 65535 f \n", objects.len() + 1).as_bytes());
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for offset in offsets {
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bytes.extend_from_slice(format!("{offset:010} 00000 n \n").as_bytes());
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}
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bytes.extend_from_slice(format!("trailer << /Size {} /Root 1 0 R >>\nstartxref\n{xref}\n%%EOF\n", objects.len() + 1).as_bytes());
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bytes
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}
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/// The red channel of the pixel at (`x`, `y`) pt from the top left of `content` rendered at 1×.
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fn red_at(content: &str, x: usize, y: usize) -> u8 {
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let mut renderer = PageRenderer::new(Arc::new(pdf(content)), RenderConfig::default());
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let out = renderer.render(RenderRequest { page: 0, scale: 1.0, ..Default::default() });
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assert!(out.error.is_none(), "{:?}", out.error);
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let at = (y * out.width as usize + x) * 4;
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*out.rgba.get(at).expect("the pixel lies on the page")
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}
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#[test]
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fn a_wide_stroke_of_a_path_with_y_curves_is_drawn() {
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// The path's exact coordinates are the trigger; `cm` moves the point where its two curves
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// meet, (18.9, 236.3), to about (98.9, 99.7) from the top left, inside every stroke width
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// below whatever the caps. The `v` path is the same two curves run backwards, a guard that
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// draws with or without the fix.
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let y = "21.4166 234.5928 m 19.9009 236.0303 18.9478 236.3428 y 19.2603 238.4209 20.8697 238.4209 y S";
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let v = "20.8697 238.4209 m 19.2603 238.4209 18.9478 236.3428 v 19.9009 236.0303 21.4166 234.5928 v S";
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let mut dropped = Vec::new();
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for path in [y, v] {
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for width in [4, 8, 16, 24, 32, 48, 63, 64] {
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for (join, cap) in [(0, 0), (1, 1), (2, 2)] {
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let content = format!("0 1 0 RG {width} w {join} j {cap} J 1 0 0 1 80 -136 cm {path}");
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let red = red_at(&content, 98, 99);
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if red > 64 {
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dropped.push(content);
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}
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}
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}
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}
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assert!(dropped.is_empty(), "strokes not drawn: {dropped:#?}");
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}
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