GUADEC: Owen Taylor on GNOME Shell

The biggest user-visible piece of GNOME 3 will be the GNOME Shell, which manages the desktop experience. At GUADEC, Owen Taylor updated the assembled GNOME hackers on the current status of GNOME Shell and the work still to be done. He also demonstrated some of the new functionality and compared the Shell with where it was when he presented at the Gran Canaria Desktop Summit (GCDS) in 2009.

Since GCDS, "we wrote code", Taylor said, consisting of some 1362 commits, 1174 of which were code along with 188 translation commits. The project has also added new contributors and four of the top ten contributors since GCDS were new to the project. He was happy to see that those new contributors were not only prolific, but also added "very significant" new features.

In preparing for his talk, Taylor went back to the version from GCDS and was "surprised that it still built". The user interface has been redesigned since then and, in some cases, things have been rewritten three or four times in the interim. He found it interesting that certain features that he thought were there from the start were missing, while others that he thought were newer actually appeared in the year-old version.

The Shell now sports a "sleeker, black look" that fades into the background because it blends into the monitor bezel, he said. The "mess in the upper right hand corner" has been cleaned up, and the task list from last year is gone. In addition, the menus are not GTK-based, but are instead styled with the Shell, giving them a more integrated look.

Switching between applications and workspaces has also undergone some major changes. Alt-Tab now groups all of the windows for an application into a single entry, so that you choose between applications, rather than individual windows. Last year, activities were represented by a grid of workspaces with a dashboard to launch new applications. Now it is "slicker", with a linear view of the workspaces that can be scrolled horizontally to view additional workspaces.

The application browser has switched from a "straight reimplementation from GNOME 2" to a gridded view with fewer categories. Searching has also been integrated into the dashboard. The message tray now slides up from the bottom and you no longer have to dismiss each notification as you did in GNOME 2. It is also integrated with Empathy so that replying to a message no longer requires switching to the application itself—the reply can be typed into the message notification.

The "hot corner"—simply moving the mouse to the upper left corner of the screen—is another new feature. Moving there brings up the activities overview that shows workspaces, places, and recent documents. It's very useful, Taylor said, so much so that "if you go back to GNOME 2, you will keep going to the hot corner".

Looking Glass is an integrated JavaScript console, inspector, and debugger, which acts like "Firebug for the Shell". Taylor did a live demonstration by typing one-line JavaScript expressions into Looking Glass. With that (fairly) simple JavaScript, he was able to change menu titles, scale them to different sizes, and even have them run the scaling as a transition so that the text continuously grew in size.

GNOME Shell is based on the Clutter toolkit, but because "Clutter itself only has four actors that are useful" for the Shell, it uses the Shell toolkit (St) atop Clutter. St is descended from Moblin's MX toolkit, but is more focused on the needs of the Shell. St emphasizes CSS with transitions, property inheritance, shadows, rounded corners, and so on, which make for a "pretty powerful set of capabilities". MX has many more widgets and is more powerful overall. The separate evolution of St and MX is "not a good thing long-term" and the team aims to reunite them at some later point.

Taylor also talked about the development process for GNOME Shell, which is very reliant on code review. The normal GNOME model is "code ownership" he said, but the Shell does "code review of everything". There is no formal structure to the review process, but they get two pairs of eyes on all code changes. The process has its "good parts and not-so-good parts", but overall it works well because it spreads out the knowledge of the code among multiple people in the project. It can lead to bottlenecks, where "patches sit around for a while", but he definitely recommends that development model for other projects.

GNOME Shell is in "good shape" for basic functionality, like window switching and launching applications, Taylor said, though there are still bugs and other things to fix. It makes for a "pretty coherent whole" that can be used on a day-to-day basis. The status area in the upper right hand corner is still a work in progress as is the integration of the Shell with the rest of the system. He pointed to the log out and lock screen dialogs as things that were not yet rendered in the Shell style, and still look like the GNOME 2 versions.

Those changes will come relatively soon, but there are some other things that are a bit further out. The "recently used documents" in the activities overview is just a placeholder right now. There are no customization options for those who want to change the styles or behavior of the Shell. The plan is to add an extension API like Firefox has, but other than some basic infrastructure, that isn't nearly ready. In addition, there is no fall-back support if 3D graphics—required by Clutter—are not available. Some way to fall back to the GNOME 2 look in that case is desired.

Based on the status, it was probably fairly obvious to those in the room that GNOME Shell might not be completely ready for the September release—foreshadowing the next presentation, which was by Vincent Untz and the release team delaying GNOME 3.0. GNOME Shell definitely looks like more than an incremental change to the desktop experience, and Taylor's demo with Looking Glass showed the latent potential for theming and other customization that underlies the Shell. With an additional six months to work on it, focusing on completing a coherent whole, GNOME Shell seems quite likely to impress.