The Atom code editor turns 1.0

GitHub recently announced the release of version 1.0 of Atom, its open-source code editor. Functionally, Atom is similar to Emacs, Vim, and many other extensible text editors aimed at developers. But it differs in other respects, starting with the fact that is a local application built on web technology. Naturally enough, Git (and GitHub) support is also integrated, and the size of the GitHub community means that the project already has a large fan base.

Development on Atom started in 2008 as a side project from GitHub co-founder Chris Wanstrath. In 2011, it became an official GitHub project. Although the early incarnations of Atom were an in-browser web application, the recent builds—including the 1.0 release—are packages that can be installed and run locally. Under the hood, however, they incorporate a modified version of the Chromium browser and Node.js. That makes the downloadable bundle on the hefty side: the Debian and RPM packages are around 70 MB. In addition to Linux, Atom runs on Windows and Mac OS X.

Installing and learning one's way around Atom 1.0 is straightforward. The bundle is self-contained, so there are no dependencies to worry about. The editor features built-in syntax highlighting, automatic indentation, a range of available UI color schemes (which can be further modified through a user stylesheet), and customizable keybindings. Hard and soft line wrapping are available, as are settings to display a variety of "invisibles" like white-space characters, carriage returns, and EOL characters.

That said, there are a few niceties in the basic editing functionality that go beyond the bare minimum. For instance, one can open up an HTML preview of Markdown-formatted text with a single keystroke, collapse or expand blocks of code, or "zoom" in and out (by changing the font size) with the mouse wheel. One of the most convenient features, though, is the "command palette." The keystroke Ctrl-Shift-P pops up a modal dialog window that can be used to search for commands. It is akin to command completion in Emacs, but with a live-updating list of matches.

The code for Atom itself is under the MIT license, as is the case with the Atom add-on packages developed at GitHub. There are, however, third-party packages which may be published under different terms. Atom is written in CoffeeScript, as are many of the available add-on packages. And it is the availability of add-on packages that makes Atom particularly noteworthy.

For general-purpose code editing, arguably the most direct competitor to Atom would be Adobe's Brackets or the the Ace editor from Cloud9. All have roots in web development and are written in a JavaScript-like language.

But both Brackets and Ace make a point of aiming for simplicity; one of the design goals for Atom is to provide the same level of extensibility found in Emacs and Vim. Indeed, there are clear similarities with Emacs to be found in Atom. The majority of the functionality found in the default setup is implemented with a suite of more than 70 individual packages. As is the case with Emacs, this architecture allows external packages to make significant changes to how Atom operates.

At the moment, there do not appear to be packages that bring major new, non-editor functionality to Atom (in the manner of the Gnus news-and-email reader for Emacs, to name one example). Although there are a few packages that provide minor new features, such as showing weather information. But there are more than 2,100 packages available, many offering improved support for specific programming languages, better integration with the host OS, and editing conveniences like whole-file overviews, navigation aids, and code-analysis tools. Atom includes a built-in package installer and search tool; each package description includes screenshots (which can be animated), home page links, and more.

It should be noted for the record that a significant percentage of the Atom packages available so far are syntax-highlighting schemes. Such themes are supposed to be packaged and promoted separately from the main package archive, a distinction that does not seem to be enforced. This makes it hard to estimate how many genuinely useful packages are available at the moment, but it is clearly a large number.

The category with the most packages, though, is Git support. Atom comes with basic Git support included. The built-in tools let the user check out branches, track the status of files, and stage and commit changes. Interestingly enough, though, the basic Git functionality does not include pushing a commit, making a pull request, or a number of other features. There is also a set of built-in keybindings that implements a form of GitHub integration, but it relies almost entirely on jumping from the editor to the GitHub site in a separate browser.

For example, there is no built-in way to view git blame information in Atom itself, but the "Alt-g b" key combination will open the corresponding blame-annotated file at GitHub—assuming, that is, that the repository in question is hosted at GitHub. These limitations seem a bit odd, although perhaps users with less allegiance to GitHub will be happy to know that the Atom editor is not tightly bound to one particular service provider.

In any case, there are dozens of third-party Atom packages that extend the editor's Git functionality, starting with the popular git-plus package. Other packages provide enhancements to how diffs are displayed, generate graphs of commit activity, and so on. There are also several popular packages for integration with other services, including Travis CI as well as GitHub competitor Bitbucket. The package-development community is clearly active, and it would appear that GitHub is letting that community have a free rein.

IDE-like functionality is not yet as advanced as version-control support. There are several competing third-party packages for hooking into a compiler, but the vast majority are limited to use with CoffeeScript, LESS, and other web-development languages—in which the "compiler" is more akin to a pre-processor than anything else.

Ultimately, whether or not Atom should find a place on one's desktop (alongside Emacs or Vim, much less replacing them) is an open question. The main selling point seems to be that Atom offers programmer-friendly extensibility in a language that is familiar to more of the "development community" at present. CoffeeScript is, after all, an extension of JavaScript, and there are far more individuals on the web today who have some level of JavaScript experience than there are individuals who have used Common Lisp.

But that is no guarantor of success. Emacs and Vim have remained as popular as they are today because their add-on communities enhance the editors' built-in functionality. Perhaps Atom will attract a sizable community of package developers, but one that never pushes the boundaries beyond somewhat-better Git integration and extensive theming. Whether or not Atom manages to grow beyond those boundaries will determine if it becomes a first-level programmer's editor or remains more of a user-friendly interface to Git and GitHub. Neither is a bad outcome, but they will have distinctly different influence on the development community.