al_get_haptic_autocenter man page
al_get_haptic_autocenter — Allegro 5 API
#include <allegro5/allegro.h> double al_get_haptic_autocenter(ALLEGRO_HAPTIC *hap)
Returns the current automatic centering intensity of the device. Depending on the device automatic centering may ensure that the axes of the device are centered again automatically after playing a haptic effect. The return value can be between 0.0 and 1.0. The value 0.0 means automatic centering is disabled, and 1.0 means automatic centering is enabled at full strength. Any value in between those two extremes means partial automatic centering is enabled. Some platforms do not support partial automatic centering. If that is the case, a value of less than 0.5 means it is turned off, while a value equal to or higher to 0.5 means it is turned on. Can only work if al_get_haptic_capabilities(3) returns a value that has ALLEGRO_HAPTIC_AUTOCENTER(3)ALLEGRO_HAPTIC_CONSTANTS(3) set. If not, this function returns 0.0.
[Unstable API]: Perhaps could be simplified due to limited support for all the exposed features across all of the platforms. Awaiting feedback from users.