Understanding The X.Org Server's Complex Pointer Acceleration Code

While Peter Hutterer has been involved with the X.Org Server's input code and related projects for the past decade now and has spearheaded the projects around Multi Pointer X, X Input 2, and the Wayland/Xorg-using Libinput libraries, he's still had a tough time grasping the X.Org Server's pointer acceleration code...