hardless-render

Receipt renderer for Hardless: turns the ESC/POS command AST from hardless-escpos into what a thermal printer would print.

• HTML (FR-10) at 58 mm (32 columns Font A / 42 Font B) or 80 mm (48 / 64 columns). Alignment, bold, underline, character size, fonts and line wrapping follow the printer.
• Cuts, QR codes, barcodes and raster images (FR-12) are drawn as inline SVG. Unknown commands show as a small visible badge, which can be turned off.
• Plain text (FR-13): to_text lays the receipt out in fixed columns for test assertions, e.g. Total:\s+1,250.
• SVG and PNG (FR-11) with the same layout as the HTML: the same line breaks, columns, alignment, sizes, codes and cuts, drawn in printer dots (576 across 80 mm, 384 across 58 mm). PNG output needs the png feature.
• Safe to embed: all receipt text is HTML- or XML-escaped.
• Sans-IO: builds for wasm32-unknown-unknown (without the png feature).

Usage

use hardless_escpos::parse;
use hardless_render::{render_html, to_text, PaperWidth, RenderOptions};

let ast = parse(b"\x1ba\x01HARDLESS\n\x1ba\x00Total:   1,250\n\x1dV\x00");

// Plain text, 48 columns (80 mm, Font A).
let text = to_text(&ast);
assert!(text.contains("Total:   1,250"));
assert!(text.starts_with("                    HARDLESS")); // centered

// HTML fragment; include STYLESHEET once on the page (or use render_html_document).
let html = render_html(&ast, &RenderOptions { paper: PaperWidth::Mm58, ..Default::default() });
assert!(html.contains("hl-cut"));

// Standalone SVG, one unit per printer dot: 576 dots plus margins for 80 mm.
let svg = hardless_render::render_svg(&ast, &RenderOptions::default());
assert!(svg.contains(r#"width="612""#));

SVG and PNG

render_svg returns a standalone SVG document. Each run of text is stretched to its exact column width (textLength), so columns line up with any monospace font; it asks for Go Mono first, then common system monospace fonts.

render_png (feature png) rasterises that SVG with resvg, one pixel per printer dot, using only the bundled Go Mono font, so a receipt looks the same on every OS and in a container with no fonts. Receipts taller than MAX_PNG_HEIGHT (20,000 dots) are refused rather than allocating hundreds of megabytes.

hardless-render = { version = "0.0.0", features = ["png"] }

Try it on a fixture:

cargo run -p hardless-render --features png --example render -- fixtures/escpos/33-full-receipt.bin 80 png > receipt.png

Bundled font

fonts/ holds Go Mono and Go Mono Bold by Bigelow & Holmes, made for the Go project and licensed under BSD-3-Clause (fonts/LICENSE, also exported as FONT_LICENSE). A binary built with the png feature must ship that notice.

Output reference

License

Apache-2.0