Separating the Wayland Compositor and Window Manager

Traditional Wayland compositors use a monolithic architecture combining the display server, compositor, and window manager, forcing window manager developers to implement an entire compositor. River 0.4.0 separates the window manager into a standalone program via the stable river-window-management-v1 protocol, granting window managers full control over positioning and keybindings while river handles rendering and low-level plumbing. This design resolves architectural inefficiencies inherited from X11 while avoiding the monolithic coupling of conventional Wayland compositors.