Function smooth_svg_lines

crates/plotlars-plotters/src/render/mod.rs:201–210

Post-process SVG to improve line rendering quality: 1. Inject round joins/caps so thick strokes blend smoothly at vertices. 2. Simplify dense polylines (Ramer-Douglas-Peucker) to remove sub-pixel zigzag noise caused by plotters' integer coordinate rounding. No-op for plots without polylines (bar/box/heatmap).

(svg: &mut String)

///
/// No-op for plots without polylines (bar/box/heatmap).
fn smooth_svg_lines(svg: &mut String) {
    if !svg.contains("<polyline ") {
        return;
    }
    *svg = svg.replace(
        "<polyline fill=\"none\"",
        "<polyline stroke-linejoin=\"round\" stroke-linecap=\"round\" fill=\"none\"",
    );
    simplify_svg_polylines(svg);
}

/// Find every `points="..."` attribute in the SVG and, when the polyline has
/// enough vertices, apply Ramer-Douglas-Peucker to remove redundant ones.