Function gcmouse 

pub fn gcmouse() -> Rule

Mouse movement from GameController in every process.

The Mac driver takes the mouse movement of raw input (WM_INPUT) and DirectInput from GameController’s GCMouse, which reports the device’s own counts. Otherwise that movement is the cursor’s, which macOS has already accelerated and, on a retina display, scaled, so mouselook in a game that reads raw input or DirectInput turns further the faster the hand moves. winemac.drv reads the value through ntdll when it reads its settings, and without one keeps upstream Wine’s behaviour, the cursor’s movement.

It matches every process, like the other defaults. A rule for one game with gcmouse = false gives it the cursor’s movement again: for a game whose sensitivity was tuned to that, a mouse that GameController reports twice, or a regression. A * rule with it does the same for every process.