The Window Is A World Apart
The Window Is A World Apart
The monolithic display server assumes a single pane of glass, shared by all, mediated by a central authority. Plan 9 discards the monolith.
Instead, the graphical subsystem is exposed purely as synthetic files: /dev/draw for pixel compositing, /dev/mouse for events. The window manager, Rio, does not draw windows on a shared screen. It intercepts these files and binds a private, synthetic illusion of them into the namespace of each child process.
To the child program, it is not running in a window. It is the only program running, drawing to the only screen in existence, bounded by its own clip rectangle.
Because Rio itself is just a program reading and writing those same files, it can be run inside itself. A new instance of Rio, launched within a window, simply binds its own synthetic /dev/draw over the one it was given. The result is a fractal isolation: windows within windows, desktops within desktops, each believing itself to be the entirety of the machine.
The boundary is not drawn; it is enforced by the namespace. The window is a world apart.
