When we set out to build a new email client, we had a few starting requirements.
First, we felt that email was too important to be lost in a browser tab. For many professionals, an email client will stay open all day every day, often on a dedicated screen. A serious email client should feel native on Windows, Mac, and Linux. That means it should have real windows, its own icon, and the ability to run in the background or offline.
Second, we felt that truly groundbreaking software must embrace creativity and customization. Just like Emacs, Excel, Photoshop, or Minecraft… an email client of the future must be extensible by the end user. There’s no one-size-fits-all solution.
THE SEARCH FOR CROSS-PLATFORM
How do you build a native app that works on Mac, Windows, and Linux? Ten years ago C++ or Java would have been the obvious choice, but Apple has withdrawn direct support for Java and developer mindshare has been moving elsewhere—toward modern web technologies. Today, we knew our best option was the web. But how do you leverage the latest web technologies like ES6 and HTML5 without being chained to the confines of the browser?
The answer lies in Atom, a “hackable” text editor GitHub has been quietly building for the past couple years.
SPLITTING THE ATOM
We’re forking Atom—the hackable text editor—to create a powerful, fast, and flexible mail client.
But this is where we change gears. Atom was designed specifically to be a text editor, and although it’s a great building block, our new email client presents an entirely different set of challenges.
THE NEED FOR SPEED
To feel like a native app, our new mail client needed to be extremely performant. Interface latency—or worse, visually apparent rendering—would expose its web foundation and be a jarring experience for our users. Although performance isn’t an issue for simple websites, we knew our app would grow into a large web application with a huge DOM tree — and modifying the DOM is slow as molasses. Early on, our team built and open sourced a basic mail client in AngularJS, and so we know the woes of a template-powered web framework…
THE FLUX THAT WON THE WEST
When we set out to structure our new mail client, we wanted to use an architecture that would codify best practices of large application development and ideally even prevent poor architectural decisions from being possible. We also wanted to design for extensibility from day one. That meant components of the app should be loosely joined and expose rich interfaces for extension.
To achieve this, we’re using a variant of “Flux” — the pattern for unidirectional data-flow in user interfaces. Flux aims to solve common problems of large MVC applications, enforcing one way data flow through the app and loose coupling between views and business logic. It also mandates use of the “command” pattern: every change in the app triggers a globally declared action. Actions can be dispatched from anywhere in the app, and likewise observed from anywhere. This creates loose couplings between small components, and is therefore a naturally extensible pattern.
There are many other reasons we’re excited about this architecture. Flux keeps business logic out of React components, prevents the brittle intertwining of views and models, and gives our team a concise domain language for one-way data flow and loose coupling.
For example, it’s impossible for a button to directly modify a thread—an action that could cause the interface and local cache to fall out of sync. Instead, the button fires an Action, which triggers business logic in a Store, which modifies the local cache and causes the entire application to receive an update with the new state.
MOVE FAST AND BREAK NOTHING
If you have a large codebase, we believe the only way to quickly ship reliable software is to write tests. Period. People rely on email all day every day, so stability and reliability are hugely important to us. This means we need to write tests — ideally unit tests — for both our core business logic and also our UI components.
PREPARING FOR AN ADVENTURE
We’ve brought together some extraordinary technologies—Electron, React, and Flux — and laid the foundation for something brand new: a powerful and extensible tool for your personal data. Over the next few months, we’ll be sharing more about the architecture of our new client and specific ways we’re making it extensible. Join our mailing list to stay in the loop!