al_get_haptic_gain - Man Page

#include <allegro5/allegro.h>

double al_get_haptic_gain(ALLEGRO_HAPTIC *hap)

Returns the current gain of the device. Gain is much like volume for sound, it is as if every effect’s intensity is multiplied by it. Gain is a value between 0.0 and 1.0. Only works correctly if al_get_haptic_capabilities(3) returns a value that has ALLEGRO_HAPTIC_GAIN(3)ALLEGRO_HAPTIC_CONSTANTS(3) set. If this is not set, this function will simply return 1.0 and all effects will be played without any gain influence.

5.1.8