al_get_current_inverse_transform - Allegro 5 API

       Returns  the  inverse  of the current transformation of the target bitmap.  If there is no target bitmap,
       this function returns NULL.

       This is similar  to  calling  al_invert_transform(al_get_current_transform())  but  the  result  of  this
       function is cached.

              Note: Allegro’s transformation inversion functions work correctly only with 2D transformations.

       al_get_current_inverse_transform - Allegro 5 API

       5.1.0

Allegro reference manual                                               al_get_current_inverse_transform(3alleg5)

              #include <allegro5/allegro.h>

              const ALLEGRO_TRANSFORM *al_get_current_inverse_transform(void)