Reading/Web/PDF Functionality

Introduction
Our current PDF rendering service, the offline content generator, is no-longer maintainable. Simply put, it's breaking down. Originally created by a third party, it currently runs on outdated code which may introduce security vulnerabilities and other major issues in the future. If we're to have the PDF functionality, we unfortunately have to replace it, or we might suddenly find ourselves in a situation where we'd have to take it down without having planned to do so.

Additionally, it does not support a number of rendering requests from the community, the main one being the ability to render tables. We have selected a new service, the electron rendering service, as a suitable replacement. Our next step is to duplicate the functionality provided by OCG using the electron rendering service. Below, we will describe the main portions of the functionality we have identified as necessary. We would like to invite conversation around what is missing or what is superfluous in the provided list. We would also like to highlight over our future plans for PDF rendering to gather initial feedback.

History

 * Rendering PDF articles and books from Wikipedia pages is handled by a service called OCG. When rendering "books" through the book creator, it uses OCG as embedded within the Collection extension. OCG has multiple issues, especially with tables.
 * Multiple issues with OCG are identified, including complaints from the community around OCG's inability to render tables.
 * Rendering of tables ranks as number 9 on the German-speaking Community Technical Wishlist.
 * Wikimedia Deutschland begins on working on a solution for rendering tables in PDF's, and introduces Electron. They do this planning to run it alongside OCG, not to replace it.
 * At the same time as Wikimedia Deutschland is working on the Electron service, the responsible maintainers of the OCG service at the Wikimedia Foundation come to the conclusion that OCG has to be replaced.
 * The WMF Reading Team takes over the responsibility for the long term maintenance of PDF rendering begins plans on implementing table rendering across all projects.
 * The Reading team launches a community consultation for gathering feedback on Electron.
 * The Reading Infrastructure and Web teams begin scoping the working necessary to port OCG functionality over to the Electron service.

Proposal
The following is a proposal for the scope of functionality necessary for PDF rendering:
 * Individual articles will be rendered to PDF using the "Download as PDF" link in the sidebar
 * Multiple articles will be rendered to PDF using the Book Creator tool
 * All articles will contain attribution for text and images
 * All PDF's rendered will be able to print tables
 * Users will be able to customize the layout of their PDF (optional)

Design
The new PDF styles will be designed for increased readability. Based on community feedback and qualitative or quantitative testing, support for a 2-column layout may be built for the book creator and/or for individual PDF's.

Development and Deployment Roadmap
The following is a rough outline of the development and deployment roadmap. It is subject to change.
 * 1) April - May 2017:
 * 2) The Reading team builds back-end support for functionality identified above
 * 3) Communities are consulted on expanding or shrinking proposed functionality
 * 4) Qualitative test performed for styling
 * 5) June - July 2017:
 * 6) New styles implemented
 * 7) First iteration launched on beta
 * 8) Iterations based on consultations and testing
 * 9) August 2017 - September 2017
 * 10) First iteration is launched along with OCG on all projects and performance is compared
 * 11) Additional changes made if necessary
 * 12) October 2017
 * 13) Second iteration launched without OCG on all projects