Actual Window Manager -

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.

Understanding that it is a construct—a set of compromises between performance, policy, and physics—can make you a better user. When a window lags, you will know: the compositor missed a frame. When focus jumps unexpectedly, you will know: the policy engine made a choice you did not intend. actual window manager

On Linux (Wayland), the kernel's DRM (Direct Rendering Manager) and KMS (Kernel Mode Setting) control the actual display hardware. The compositor talks to DRM via libdrm to flip buffers. On Windows, the DWM talks to the DXGI kernel driver. On macOS, WindowServer talks to the IOKit framebuffer. This is why "actual window manager" is a slippery phrase