ALLEGRO_RENDER_STATE - Allegro 5 API

       Possible render states which can be set with al_set_render_state(3alleg5):

       ALLEGRO_ALPHA_TEST
              If  this  is  set to 1, the values of ALLEGRO_ALPHA_FUNCTION and ALLEGRO_ALPHA_TEST_VALUE define a
              comparison function which is performed on the alpha component of each pixel.  Only if it evaluates
              to true the pixel is written.  Otherwise no subsequent processing (like depth test or blending) is
              performed.  This can be very useful, for example if a depth buffer is used but  you  do  not  want
              fully transparent pixels to modify it.

       ALLEGRO_ALPHA_FUNCTION
              One of ALLEGRO_RENDER_FUNCTION(3alleg5), only used when ALLEGRO_ALPHA_TEST is 1.

       ALLEGRO_ALPHA_TEST_VALUE
              Only used when ALLEGRO_ALPHA_TEST is 1.  Should be a value of 0 - 255.

       ALLEGRO_WRITE_MASK
              This  determines  how  the framebuffer and depthbuffer are updated whenever a pixel is written (in
              case alpha and/or depth testing is enabled: after all such enabled tests succeed).   Depth  values
              are only written if ALLEGRO_DEPTH_TEST is 1, in addition to the write mask flag being set.

       ALLEGRO_DEPTH_TEST
              If  this  is  set  to  1, compare the depth value of any newly written pixels with the depth value
              already in the buffer, according to ALLEGRO_DEPTH_FUNCTION.  Allegro primitives with no explicit z
              coordinate will write a value of 0 into the depth buffer.

       ALLEGRO_DEPTH_FUNCTION
              One of ALLEGRO_RENDER_FUNCTION(3alleg5), only used when ALLEGRO_DEPTH_TEST is 1.

       ALLEGRO_RENDER_STATE - Allegro 5 API

al_set_render_state(3alleg5), ALLEGRO_RENDER_FUNCTION(3alleg5), ALLEGRO_WRITE_MASK_FLAGS(3alleg5)

Allegro reference manual                                                           ALLEGRO_RENDER_STATE(3alleg5)

       5.1.2

              #include <allegro5/allegro.h>

              typedef enum ALLEGRO_RENDER_STATE {