Write your own Wayland compositor: Rendering windows

This installment of a wlroots tutorial begins adding window support to a minimal Wayland compositor. It sets up the XDG shell global so clients can create top-level windows, and explains that top-levels represent the main windows in a hierarchy while popups and dropdowns belong to them. Because the tutorial uses wlroots 0.19, protocol globals are created at versions below the latest available: XDG shell version 6, shared memory version 2, and wl_compositor version 6. It also shows how to generate XDG protocol code with wayland-scanner and inspect the compositor’s advertised globals with wayland-info.

A test with weston-simple-shm exposes the globals clients need to draw: enabling wl_shm alone leads to a crash, and Wayland debug logs help reveal the missing wl_compositor global, which lets clients create surfaces. Once that global is added, the client can create a surface, assign it an XDG top-level role, and commit it; the compositor’s new-toplevel listener then fires. The next step is to track windows in compositor-owned wrapper structures, linking each wrapper into a list and listening for its destruction. Rendering still requires handling the XDG surface’s initial configure handshake: clients provide properties such as title and app identity and suggest a preferred size, while the compositor ultimately determines the size.