By A. N. Ops Published: Interface Quarterly
This is why dragging a window can feel "sticky" under load. The actual window manager is always chasing reality, always a few milliseconds behind. Perhaps the most philosophical duty of the window manager is focus . actual window manager
Your operating system's core understands processes, memory pages, and file descriptors. It does not understand rectangles containing user interfaces. The "window manager" is a userspace fiction—a shared hallucination among applications, the compositor, and your eyes. So, after all this deconstruction, what is an actual window manager? The actual window manager is always chasing reality,
This is why "actual window manager" is a slippery phrase. The manager of pixels is the compositor. The actual manager of input is the event router. The actual manager of window state (minimized, maximized, tiled) is a policy engine. Most systems glue these into one process, but they remain conceptually distinct. Part III: A Brief Taxonomy of Actualities If we take "actual" to mean "the software component(s) that physically control window positioning, stacking, and input routing on a modern graphical system," we find not one answer but a family of them. It does not understand rectangles containing user interfaces
Physically, your monitor is a grid of pixels—millions of tiny lights turning on and off. The graphics card sends a frame buffer: a rectangular array of RGB values. That buffer has no concept of a "window." It has no concept of a "taskbar," a "close button," or a "border."