Devices with uneven horizontal/vertical resolution are accelerated unevenly. e.g. on the x220t, the touchpad is almost twice as wide as high. The resolution reflects this: Event code 0 (ABS_X) Value 2618 Min 1472 Max 5472 Resolution 75 Event code 1 (ABS_Y) Value 2482 Min 1408 Max 4448 Resolution 129 the acceleration code needs to take this resolution into account to pre-adjust the coordinates. The goal is that a circle on the device reflects a circle on the screen.
commit e18e9d56a8afe0268fcab09a6ef11d359bf0bbd5 Author: Jonas Ådahl <jadahl@gmail.com> Date: Sat May 24 16:53:45 2014 +0200 touchpad: Make anisotropic motion deltas isotropic
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