NAME

       ALLEGRO_VERTEX_ELEMENT - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro_primitives.h>

              typedef struct ALLEGRO_VERTEX_ELEMENT ALLEGRO_VERTEX_ELEMENT;

DESCRIPTION

       A  small  structure  describing  a certain element of a vertex.  E.g.  the position of the
       vertex, or its color.  These structures are  used  by  the  al_create_vertex_decl(3alleg5)
       function  to  create  the  vertex declaration.  For that they generally occur in an array.
       The last element of such an array should have the attribute field equal to 0,  to  signify
       that  it is the end of the array.  Here is an example code that would create a declaration
       describing the ALLEGRO_VERTEX(3alleg5) structure (passing this as  vertex  declaration  to
       al_draw_prim would be identical to passing NULL):

              /* On compilers without the offsetof keyword you need to obtain the
               * offset with sizeof and make sure to account for packing.
               */
              ALLEGRO_VERTEX_ELEMENT elems[] = {
                 {ALLEGRO_PRIM_POSITION, ALLEGRO_PRIM_FLOAT_3, offsetof(ALLEGRO_VERTEX, x)},
                 {ALLEGRO_PRIM_TEX_COORD_PIXEL, ALLEGRO_PRIM_FLOAT_2, offsetof(ALLEGRO_VERTEX, u)},
                 {ALLEGRO_PRIM_COLOR_ATTR, 0, offsetof(ALLEGRO_VERTEX, color)},
                 {0, 0, 0}
              };
              ALLEGRO_VERTEX_DECL* decl = al_create_vertex_decl(elems, sizeof(ALLEGRO_VERTEX));

       Fields:

       • attribute - A member of the ALLEGRO_PRIM_ATTR(3alleg5) enumeration, specifying what this
         attribute signifies

       • storage - A member of the ALLEGRO_PRIM_STORAGE(3alleg5) enumeration, specifying how this
         attribute is stored

       • offset  -  Offset  in  bytes  from  the beginning of the custom vertex structure.  The C
         function offsetof is very useful here.

SEE ALSO

       al_create_vertex_decl(3alleg5), ALLEGRO_VERTEX_DECL(3alleg5),  ALLEGRO_PRIM_ATTR(3alleg5),
       ALLEGRO_PRIM_STORAGE(3alleg5)