Crate hardless_render 

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

AST node	HTML	SVG / PNG	to_text
Text, line feed, feed	.hl-line per printed line	<text> runs, 30 dots per line (× height)	one line each, aligned with spaces
Cut	.hl-cut (.hl-cut-partial for partial)	dashed line (dotted for partial)	nothing
QR print	inline <svg class="hl-qr">	nested <svg class="hl-qr">	[QR: <data>]
Barcode	inline <svg class="hl-barcode"> plus HRI text if enabled	nested <svg class="hl-barcode"> plus HRI text	[BARCODE <symbology>: <data>]
Raster image	inline <svg class="hl-image">	nested <svg class="hl-image">	[IMAGE <w>x<h>]
Unknown	<span class="hl-unknown"> badge (if show_unknown)	yellow badge with the details as a tooltip	nothing
Drawer pulse, status request, settings	nothing (not printed)	nothing	nothing

License

Apache-2.0

Structs

RenderOptions

Rendering options.

Enums

PaperWidth

Paper roll width.

Constants

FONT_LICENSE

Licence of the bundled Go Mono font (BSD-3-Clause), which the PNG output embeds. Ship it with any binary built with the png feature.

STYLESHEET

Styles for render_html output. Everything is scoped under .hl-receipt; one Font A column is 1ch of the receipt font, so text, codes and images keep the printer’s proportions at any font size. The receipt is white paper in both light and dark themes.

Functions

render_html

Renders an AST to an HTML fragment (<div class="hl-receipt">). Include STYLESHEET once on the page, or use render_html_document.

render_html_document

Renders an AST to a complete HTML document with STYLESHEET, e.g. for GET /devices/:id/jobs/:jobId/render?format=html.

render_svg

Renders an AST to a standalone SVG document with the same layout as crate::render_html.

to_text

Lays out nodes as plain text in fixed columns, as an 80 mm printer with Font A (48 columns) would print them. See to_text_with for other widths.

to_text_with

to_text for a given paper width.