Skip to content

PDFGENERATION.md

Latest commit

 

History

History
88 lines (60 loc) · 2.7 KB

PDFGENERATION.md

File metadata and controls

88 lines (60 loc) · 2.7 KB

PDF Invoice Generation

The backend generates downloadable PDF invoices using WeasyPrint, an HTML/CSS-to-PDF rendering library. The PDF layout mirrors the frontend invoice preview template exactly.

How it works

  1. The frontend sends GET /api/invoices/{id}/pdf with the auth token.
  2. The backend builds a self-contained HTML document with inline CSS that matches the invoice preview layout (company header, bill-to section, line items table, payment details, tax breakup).
  3. WeasyPrint renders the HTML to a PDF on A4 paper.
  4. The PDF is returned as a streaming download (Content-Disposition: attachment).
  5. The frontend creates a temporary blob URL and triggers the browser download.

API endpoint

GET /api/invoices/{invoice_id}/pdf
Authorization: Bearer <token>

Returns application/pdf with filename invoice_INV-XXXXXX.pdf.

System requirements

WeasyPrint depends on Pango and GLib system libraries for text layout and font rendering.

macOS (local development)

brew install pango

This pulls in all required dependencies (GLib, HarfBuzz, FreeType, Cairo, etc.).

Ubuntu / Debian (Docker, CI)

The Dockerfile already includes the required packages:

apt-get install -y --no-install-recommends \
    libpango-1.0-0 \
    libpangocairo-1.0-0 \
    libpangoft2-1.0-0 \
    libgdk-pixbuf2.0-0 \
    libffi-dev

Alpine Linux

apk add --no-cache pango fontconfig ttf-freefont

Python dependency

Defined in backend/requirements.txt:

weasyprint==63.1

Install in the virtual environment:

cd backend
.venv/bin/pip install -r requirements.txt

Docker

The backend Dockerfile (backend/Dockerfile) already installs the system libraries. No extra steps are needed — just build normally:

docker build -t simple-backend ./backend

Troubleshooting

Problem Solution
OSError: cannot load library 'libgobject-2.0-0' Install Pango system libraries (see above)
OSError: cannot load library 'libpango-1.0-0' Same — brew install pango on macOS
Fonts look wrong or use fallback glyphs Install a font package (ttf-freefont on Alpine, fonts-liberation on Debian)
Currency symbols (₹, €, £) missing Ensure a Unicode-capable font is available on the system
PDF is blank Check WeasyPrint logs for CSS parsing errors — run the backend with LOG_LEVEL=debug

Customising the template

The HTML template is defined in backend/src/api/routes/invoices.py in the _build_invoice_html() function. It uses inline CSS and mirrors the structure of the frontend's previewInvoice modal in frontend/src/pages/InvoicesPage.tsx. To change the PDF layout, edit the HTML/CSS in that function.