Templates

Generating PDF documents from templates is a common task in software development. Recent developments have made HTML a suitable solution for typesetting and PDF generation.

• Browsers are approaching print-quality typography.
• Open-source browser automation libraries like Puppeteer and Playwright support generating PDFs from HTML.
• Paged.js, a library for designing books with HTML, enables creating paginated content.

Using HTML for templates provides several benefits: HTML is widely known, well-documented, and easily managed through version control systems like git.

Projects

The following projects explore PDF generation using open-source libraries.

• template-renderer: A Node.js proof of concept for generating PDFs from mustache HTML templates using Playwright and mustache.js.
• Example mustache template layouts for email and HTML pagination.
• PDF generation benchmarks: Node.js and C# benchmarks for PDF generation using Puppeteer and Playwright.
• lezer-mustache: A mustache parser for Lezer created for syntax highlighting in CodeMirror editors.
• template-editor: A tool for creating and testing mustache templates that reference each other.
  See this demo.

In these projects, mustache is used as the template language due to its simple syntax and the widespread availability of the mustache template engine. The mustache syntax supports variables, conditionals, repeatable sections, and the inclusion of other templates.

Typesetting with CSS

Browsers provide the following CSS styles for typesetting.

• orphans - minimum number of lines at the bottom of a page
• widows - minimum number of lines at the top of a page
• break-before: avoid-page - avoid page break before a HTML element
• break-after: avoid-page - avoid page break after a HTML element
• text-align: justify - align text to the left and right edges of lines, except at the last line
• hyphens: auto - hyphenate words according to the rules for the language specified with the lang HTML attribute

Open-source libraries

Various open-source libraries are available for template creation, testing, and rendering. These libraries are used in the projects described above.

Paged.js

An open-source library for paginating HTML content for print. This library is created for designing books with HTML.
https://pagedjs.org
https://github.com/pagedjs/pagedjs
https://ashok-khanna.medium.com/beautiful-pdfs-from-html-9a7a3c565404
https://www.adamhyde.net/some-pagedjs-info
License: See project, MIT license at time of writing

Mustache.js

An open-source JavaScript library for rendering mustache templates.
https://github.com/janl/mustache.js
Template language
License: See project, MIT License at time of writing

Stubble

An open-source NuGet package for rendering mustache templates.
https://github.com/StubbleOrg/Stubble
Template language
License: See project, MIT License at time of writing

Playwright

An open-source library that provides control over Chromium, WebKit and Firefox. It is used for automated testing and PDF generation. Playwright is maintained by Microsoft.
https://playwright.dev
License: See project, Apache License 2.0 at time of writing

Puppeteer

An open-source Node.js library that provides control over Chrome or Chromium. It is used for automated testing and PDF generation. Puppeteer is maintained by the Chrome DevTools team.
https://pptr.dev
https://github.com/puppeteer/puppeteer
License: See project, Apache License 2.0 at time of writing

CodeMirror

A text editor for the web specialized in editing code.
https://codemirror.net
https://github.com/codemirror/dev
License: See project, MIT License at time of writing

TinyMCE

An open-source WYSIWYG editor that allows users to create formatted HTML content. This project is funded through sales of a cloud version and advanced plugins.
https://www.tiny.cloud/docs/tinymce/latest
https://www.npmjs.com/package/tinymce
License: See project
Version 6 has an MIT license.
Version 7 has a GPLv2 license.