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fix(printer): use @page size:auto so thermal receipts print full-size #625

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fix(printer): use @page size:auto so thermal receipts print full-size #625

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22 changes: 19 additions & 3 deletions packages/printer/src/__tests__/print-html.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -32,17 +32,33 @@ describe('buildPrintableReceiptHtml', () => {
expect(html).toContain('<main class="invoice">Hello</main>');
});

it('wraps 80mm thermal output with physical page size and no A4 width rule', () => {
it('defers 80mm thermal output to the printer roll paper via size: auto', () => {
const html = buildPrintableReceiptHtml({
bodyHtml: '<div class="receipt">Thermal</div>',
paperWidth: '80mm',
});

expect(html).toContain('@page { size: 80mm; margin: 0; }');
// Must be `size: auto` — NOT `80mm` (a valid but square 80mm×80mm page) and
// NOT `80mm auto` (invalid `<length> auto`, silently ignored → Letter/A4).
// Both broken forms render the receipt tiny.
expect(html).toContain('@page { size: auto; margin: 0; }');
expect(html).not.toContain('@page { size: 80mm; margin: 0; }');
expect(html).not.toContain('@page { size: 80mm auto; margin: 0; }');
expect(html).not.toContain('body > * { width: 210mm; }');
expect(html).toContain('<div class="receipt">Thermal</div>');
});

it('defers 58mm thermal output to the printer roll paper via size: auto', () => {
const html = buildPrintableReceiptHtml({
bodyHtml: '<div class="receipt">Narrow</div>',
paperWidth: '58mm',
});

expect(html).toContain('@page { size: auto; margin: 0; }');
expect(html).not.toContain('@page { size: 58mm; margin: 0; }');
expect(html).not.toContain('@page { size: 58mm auto; margin: 0; }');
});

it('keeps print mechanics outside user template content', () => {
const html = buildPrintableReceiptHtml({
bodyHtml: '<style>.receipt{padding:24px}</style><div class="receipt">User CSS</div>',
Expand Down Expand Up @@ -71,7 +87,7 @@ describe('prepareSystemPrintHtml', () => {
paperWidth: '80mm',
});

expect(html).toContain('@page { size: 80mm; margin: 0; }');
expect(html).toContain('@page { size: auto; margin: 0; }');
expect(html).toContain('<style>.x{color:red}</style>');
expect(html).toContain('<div>From iframe</div>');
});
Expand Down
12 changes: 11 additions & 1 deletion packages/printer/src/print-html.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,17 @@ export function buildPrintableReceiptHtml({
paperWidth,
}: BuildPrintableReceiptHtmlOptions): string {
const normalizedPaperWidth = normalizeReceiptPaperWidth(paperWidth);
const pageSize = normalizedPaperWidth === 'a4' ? 'A4' : normalizedPaperWidth;
// Thermal receipts defer to the printer's selected roll paper via `size: auto`.
//
// The CSS `@page size` descriptor grammar is `<length>{1,2} | auto | <page-size>`
// — there is no "fixed width, flowing height" form:
// - `80mm auto` is INVALID (length + keyword); browsers ignore it and fall
// back to the default paper (Letter/A4), printing the receipt tiny.
// - `80mm` is valid but makes BOTH dimensions 80mm — an 80mm×80mm square —
// which the print dialog shrinks onto the roll, also printing it tiny.
// `auto` lets the browser use the thermal printer's own paper (e.g. 80×297mm) and
// shrink-fits the content to the roll width, which is what we actually want.
const pageSize = normalizedPaperWidth === 'a4' ? 'A4' : 'auto';
const widthRule = normalizedPaperWidth === 'a4' ? '\nbody > * { width: 210mm; }' : '';

return `<!doctype html>
Expand Down