COSMIC desktop makes its debut

Linux hardware vendor System76 started promoting its work on a Rust-based, Wayland desktop environment for its Pop!_OS Ubuntu-derivative distribution almost two years ago. On August 8, the company released an alpha version of the COSMIC desktop environment for users to test out. While it has rough edges and missing features, it is stable enough to get a good feel for what the finished product has in store—and the initial results are promising.

The road to COSMIC

System76 sells Linux laptops, desktops, servers, and other hardware. The company was founded in 2005, and preinstalled Ubuntu as the default operating system on its offerings for many years. In 2017, the company created its Pop!_OS distribution after Canonical discontinued its work on the Unity desktop. Pop!_OS started out using GNOME with just a few tweaks, but over the years the distribution has diverged farther and farther from stock GNOME. In 2018, with the Pop!_OS 18.10 release, the company added its own software "store" called the Pop Shop. The 20.04 LTS release introduced tiling features to the desktop with a GNOME extension called Pop!_OS Shell.

The 21.04 release introduced the "COSMIC" name by using it to describe its customizations to GNOME. The name was initially expanded as "Computer Operating System Main Interface Components", but the company seems to have abandoned that unwieldy backronym, which is probably for the best. Changes in 21.04 included the addition of a dock (a fork of the Dash to Dock extension), trackpad gestures, and other various and sundry modifications.

According to the README for the tiling shell extension, the original plan was to propose integration of the tiling window management features to GNOME upstream. It is unclear if that ever happened, but a recent blog post about building the desktop indicates that it was unsustainable to maintain COSMIC as an extension, since upstream GNOME changes could cause the extension to break. The team also considered forking GNOME, but that would entail "taking on decades of legacy code and adapting it to fit what we want to build". That was ruled out, which left building a custom desktop from the ground up.

COSMIC components

The team working on COSMIC was already familiar with Rust and, according to the blog post, chose to use it for its "readability, stability, and memory safety". The developers chose the iced cross-platform graphical-user-interface (GUI) library, and created their own libraries for text handling, animations, and additional Wayland support. COSMIC uses its own Wayland compositor, which is built on top of the Smithay project. COSMIC's compositor does have XWayland support, so X applications should work just fine on the desktop.

The team has also created a cross-platform libcosmic platform toolkit for applications and applets that is based on iced. According to its documentation, the goal of libcosmic is to "enable the creation of a cross-platform ecosystem of applications that are easy to port from one OS to another". The docs for libcosmic are a work in progress, but interested developers will find a number of examples for creating COSMIC applications in its GitHub repository using the library, as well as an application template.

Desktop impressions

Even though COSMIC is no longer based on GNOME, it still takes a lot of visual cues from GNOME. The default applications and system tools seem to share GNOME's "less is more" approach to toolbars and user-interface elements. For example, COSMIC's file manager has just two navigation buttons (forward and backward), the ability to edit the filesystem path, and (of course) lets users click on directories and files to open them. It has only two file views: grid (thumbnails) or a list view that includes the modification date and size of the file. Other file managers like Mate's Caja or KDE's Dolphin offer several view options, a toolbar full of controls, such as "up" or "home" navigation buttons, and allow users to customize the icons/actions that are presented on the toolbar. Currently that is not possible with COSMIC's default applications.

Some of the desktop's minimalism may be due to the fact that some features are just not implemented yet. One would usually expect, for instance, right-clicking the mouse on the desktop would bring up options to change the background or manage display settings. Right now, right-clicking COSMIC's desktop does nothing. It seems unlikely that will be the case by the time the desktop has a stable release. Still, the overall theme seems to be "keep it simple" when it comes to the user interface.

Simple does not mean that the user can't have it their way, though. Like the GNOME-based iteration of COSMIC, the new desktop environment has a top panel and dock that can be customized to suit most users' preferences. Users can resize and reposition both, add or remove applets (such as the date/time widget, or a button to manage tiling), configure them to automatically hide until they are moused over, and even set light/dark mode for those elements independently of the desktop theme. If a user has a multi-monitor setup, the dock and panel can be set to appear on all monitors or a specific monitor. The settings also have a handy "reset to default" option in case customization gets out of hand. Users can choose to simply turn off the panel and/or dock entirely if desired.

COSMIC's tiling mode is the feature that is likely to be most compelling for users. Tiling is completely optional in COSMIC, and it is off by default. Users who do not like a tiling window manager can just ignore the feature and it will not get in the way. For those who do want it, though, COSMIC's implementation is flexible and user-friendly.

If tiling is turned on, it will attempt to automatically arrange windows on the desktop, but it is easy to adjust and override the automatic placements using the keyboard or mouse. In the extension-based tiling implementation, rearranging windows required a shortcut to start the "adjustment mode" and then use shortcuts to rearrange windows. Now, users only have to use the shift-super-arrow shortcut or just use the mouse to rearrange windows. (The "super" key is the one with the Windows logo on most PC keyboards these days.)

Windows can be stacked as well, by dragging one window on top of another and letting go. This creates a tabbed interface at the top of the window for switching between stacked applications. If a new application window is opened while a stack has focus, then the window will be added to the stacked window automatically. Finally, the tiling mode also supports floating windows. Users can click the title bar and select "Float window" or use the super-g shortcut to toggle the float mode for any window. Using super-f for "float" would have been easier to remember, but that shortcut is used to open a new file manager window. It is possible to change that in the keyboard shortcut settings, though.

For an alpha release, the tiling mode seems quite solid. The one complaint that some users might have is that tiling mode does not seem to work well with multi-monitor setups. In testing, tiling mode could only be activated for one monitor. Other than that, it seemed to work perfectly.

Desktop user-experience folks seem unable to resist the temptation to tinker with the behavior of alt-tab. Historically, one could expect that alt-tab would cycle through windows on the desktop. Now that behavior is desktop-dependent. Sometimes alt-tab does what one would expect, sometimes it cycles through applications instead of windows. In the case of COSMIC, though, it does an unexpected third thing: alt-tab brings up a list of up to eight application windows that the user can cycle through. If there are more than eight windows open, they simply are not displayed. Hopefully this convention will evolve to be more usable before the desktop reaches a stable release. Aside from that one grumble, though, COSMIC is already quite usable when it comes to window-management features.

The desktop only ships with two theme options at the moment, for light mode and dark mode. It also has a settings option to switch between modes automatically at sunset. Users can create and install custom themes as well. For example, Reddit user "Bilu47" posted a link to a set of custom themes that they had created.

The new COSMIC App Store seems more stable and responsive than the Pop Shop included 22.04 LTS. I've run 22.04 on one of my laptops for more than a year, and the Shop can be sluggish at times, and unstable too. Despite being an alpha release, the new App Store has been problem-free for installing, removing, and updating software. It can install applications from the Pop!_OS repositories and Flatpaks from Flathub, and it also lets users install updates. The catalog of software displays applications by category (e.g., "Create", "Work", "Develop", and so on), and includes basic descriptions of the applications. It is missing some information compared to the previous iteration, though, such as the application's homepage and license.

COSMIC supports fractional scaling for displays, including fractions less than 100%. This is an interesting feature for users who might want to squeeze a bit more desktop space out of smaller, lower-resolution screens. The options range from 50% to 200%. The 75% option for a 1920x1080 display produced good results while testing the desktop. The 50% option was too small, but that may have more to do with my eyes than the feature. Younger users may find it perfectly usable. Likewise the larger fractional settings worked well, though the desktop does not rearrange windows correctly within the available space. Increasing the display scaling may result in some windows being partially or completely off screen.

COSMIC $thing

In addition to the desktop environment's components, COSMIC comes with its own file manager, terminal application, and text editor. They all follow the naming convention "COSMIC $thing"—COSMIC Text Editor, COSMIC Files, and COSMIC Terminal. All of the applications are usable, but not quite full-featured enough for daily use. They do, however, provide a good showcase of the libcosmic toolkit for creating applications and applets for the desktop.

COSMIC's sample applications only have three top-level menu choices: File, Edit, and View. This means that users may not find things, such as settings, where they would normally expect to find them. COSMIC's homegrown applications also have a somewhat novel way of displaying settings and other secondary pages. Instead of opening a new window or a dialog for settings, etc., applications have a side panel that opens on the right-hand side of the window as seen in the screenshot to the left.

The terminal and text editor applications are fine for light use, but probably will not win over users who already have a favorite editor or terminal application. The file manager would need a few additional features to be suitable for daily use, such as the ability to choose from any installed application to open a file. Right now, selecting "Open with" for a file only displays a list of applications that COSMIC thinks are suitable for the file.

Users can set the color scheme for applications independently of the desktop, so even if the desktop is set to a light theme, one might choose to use the dark theme for the terminal application. This would also be useful when using COSMIC applications with another desktop environment, since they do not inherit their color scheme from GNOME, KDE, or other desktop environments.

Fragmentation

On the topic of running applications on different desktop environments: testing COSMIC as my primary desktop for more than a week really emphasized just how inconsistent the Linux desktop user-interface experience can be. Using Firefox, Claws Mail, Emacs, and other applications alongside native COSMIC applications, GNOME applications, and a few KDE applications, means having a bunch of inconsistent menu types, application title bars, and so forth. Claws Mail, for example, did not inherit the minimize and maximize title bar buttons in COSMIC, nor did Firefox. Some applications use COSMIC's native file dialog when opening files, while Emacs and the Kate text editor use different file choosers. The list of small, but real, incompatibilities is lengthy.

As a person who has been using Linux since the 1990s, I've grown accustomed to this and it is generally nothing more than a mild annoyance, if that. For users new to Linux, which would include much of System76's target audience, it is likely more confusing. This, of course, is not System76's fault or problem to solve alone, but the introduction of yet-another-desktop does exacerbate the fragmentation problem. The company is not wrong in creating COSMIC, by any means, but more unity (pun somewhat intended) on the Linux desktop would be a good thing for appealing to new users. Short of dropping all of the open-source-desktop teams into an arena and making them sort out their differences Highlander style, though, there doesn't seem to be a solution to the fragmentation problem.

Getting COSMIC

ISOs for Pop!_OS 24.04 LTS alpha are available in two flavors: one for systems with NVIDIA graphics chipsets (which includes the proprietary NVIDIA drivers), and one for systems with Intel or AMD graphics. If the system has hybrid graphics with Intel/NVIDIA, choose the NVIDIA ISO. There is a Raspberry Pi version of Pop!_OS for the current stable release, but so far there is no alpha ISO for Raspberry Pi.

The company has been open about wanting to see COSMIC adopted by other Linux distributions, and the desktop is already packaged for a number of them. There are instructions for installing COSMIC on Arch, Fedora, NixOS, or Serpent OS. OpenSUSE is listed as "coming soon" on the landing page for COSMIC, and Redox OS (which LWN covered in June) already includes some COSMIC components. One note for users who try out the desktop on another distribution: the packages may be behind those available for Pop!_OS.

Users should temper their expectations before installing and testing COSMIC. It is reasonably stable for an alpha release, but it does have plenty of minor bugs, usability paper cuts, and enough instability that it's a bad bet for a production system. It has problems waking from the suspend state, as just one example. This is a known problem, so it is likely to be fixed soon, but it is no fun having to restart a laptop every time its lid closed.

A smaller, fixable, issue is that it's necessary to set the system time zone manually using timedatectl or similar:

    $ sudo timedatectl set-timezone 'America/Denver'

All of those problems, of course, are to be expected from an alpha-quality release. Users who would like to test COSMIC and give feedback are encouraged to join the Pop!_OS Mattermost server. Note that this requires setting up an account on the server.

Grumbles about desktop fragmentation aside, COSMIC is an ambitious project and shows a lot of promise. It also has a great deal of maturing to do before it will be suitable for daily use, but it has made significant progress in just two years. Watching it evolve, and seeing whether users and developers take to it, should be interesting.