The compositor

Singularity does not ship its own compositor. It builds on labwc, a lightweight, stacking Wayland compositor based on wlroots, and drives it from the shell. labwc is tracked on a singularity branch with a small set of patches on top of upstream.

Built for labwc today, not married to it

Right now the shell targets labwc, because it is small and capable and let the desktop come together quickly. That is a convenience, not a commitment. The stated goal, and a promise the project has made in the open, is for the shell to be compositor-agnostic: able to run on top of whichever Wayland compositor you bring. Work toward that is already underway, separating the labwc-specific pieces, the config files and the protocols below, behind a clean boundary so the shell does not assume any one compositor. So treat what follows as how it works on labwc today, not as a permanent dependency.

Configuration

The shell writes labwc’s configuration rather than asking you to edit it by hand. The files live under ~/.config/labwc:

• rc.xml holds keybindings, workspaces, and window rules. Keyboard shortcuts set in the desktop are translated into labwc’s key syntax and written here.
• themerc holds the window decoration colors. The shell tints these with your accent so the borders match the rest of the desktop.
• environment.xml holds the keyboard layout.

After writing a change, the shell tells labwc to reload with a reconfigure, so updates take effect without restarting your session.

Talking to the compositor

The shell talks to labwc over Wayland protocols: foreign-toplevel management for the window list and activation, output management for displays, workspaces, gamma control for night light, screencopy for screenshots, and session lock for the lock screen.

A few protocols are specific to Singularity, carried by the branch patches: previews for the app switcher, tiling hints, and the blur used for frosted surfaces.

Shortcuts across the boundary

Because some bindings are handled by the shell and some by labwc, custom keyboard shortcuts are pushed into rc.xml as well. A binding you set behaves the same regardless of which side acts on it.